Staff directory Belén Ballesteros Pérez

Belén Ballesteros Pérez

CSIC Research Scientist and Unit Leader
belen.ballesteros(ELIMINAR)@icn2.cat
Electron Microscopy Unit

ORCID: 0000-0002-1958-8911
Researcher ID: B-1167-2010

Publications

2024

Spin-Orbit Torques and Magnetization Switching in (Bi,Sb)₂Te₃/Fe₃GeTe₂ Heterostructures Grown by Molecular Beam Epitaxy
Guillet, Thomas; Galceran, Regina; Sierra, Juan F; Belarre, Francisco J; Ballesteros, Belen; Costache, Marius V; Dosenovic, Djordje; Okuno, Hanako; Marty, Alain; Jamet, Matthieu; Bonell, Frederic; Valenzuela, Sergio O Nano Letters; 24 (3): 822 - 828. 2024. 10.1021/acs.nanolett.3c03291.
Surface two-dimensional hole gas in Si doped β-Ga2O3 thin film
Chikoidze, Ekaterine; Leach, Jacob; Chi, Zeyu; von Bardeleben, Jurgen; Ballesteros, Belen; Goncalves, Anne-Marie; Tchelidze, Tamar; Dumont, Yves; Perez-Tomas, Amador Journal Of Alloys And Compounds; 971: 172713. 2024. 10.1016/j.jallcom.2023.172713.

2023

Lithium halide filled carbon nanocapsules: Paving the way towards lithium neutron capture therapy (LiNCT)
Goncalves, G; Sandoval, S; Llenas, M; Ballesteros, B; Da Ros, T; Bortolussi, S; Cansolino, L; Ferrari, C; Postuma, I; Protti, N; Melle-Franco, M; Altieri, S; Tobias-Rossell, G Carbon; 208: 148 - 159. 2023. 10.1016/j.carbon.2023.03.034. IF: 10.900

2022

Functionalization of filled radioactive multi-walled carbon nanocapsules by arylation reaction forin vivodelivery of radio-therapy
Gajewska A., Wang J.T., Klippstein R., Martincic M., Pach E., Feldman R., Saccavini J.-C., Tobias G., Ballesteros B., Al-Jamal K.T., Da Ros T. Journal of Materials Chemistry B; 10 (1): 47 - 56. 2022. 10.1039/d1tb02195h. IF: 6.331

Functionalized multi-walled carbon nanotubes (MWCNTs) containing radioactive salts are proposed as a potential system for radioactivity delivery. MWCNTs are loaded with isotopically enriched 152-samarium chloride (152SmCl3), the ends of the MWCNTs are sealed by high temperature treatment, and the encapsulated152Sm is neutron activated to radioactive153Sm. The external walls of the radioactive nanocapsules are functionalized through arylation reaction, to introduce hydrophilic chains and increase the water dispersibility of CNTs. The organ biodistribution profiles of the nanocapsules up to 24 h are assessed in naïve mice and different tumor modelsin vivo. By quantitative γ-counting,153SmCl3@MWCNTs-NH2exhibite high accumulation in organs without leakage of the internal radioactive material to the bloodstream. In the treated mice, highest uptake is detected in the lung followed by the liver and spleen. Presence of tumors in brain or lung does not increase percentage accumulation of153SmCl3@MWCNTs-NH2in the respective organs, suggesting the absence of the enhanced permeation and retention effect. This study presents a chemical functionalization protocol that is rapid (∼one hour) and can be applied to filled radioactive multi-walled carbon nanocapsules to improve their water dispersibility for systemic administration for their use in targeted radiotherapy. © The Royal Society of Chemistry 2021.

View abstract
Rational design of MXene/activated carbon/polyoxometalate triple hybrid electrodes with enhanced capacitance for organic-electrolyte supercapacitors
Zhu J.-J., Hemesh A., Biendicho J.J., Martinez-Soria L., Rueda-Garcia D., Morante J.R., Ballesteros B., Gomez-Romero P. Journal of Colloid and Interface Science; 623: 947 - 961. 2022. 10.1016/j.jcis.2022.04.170.

We report a triple hybrid electrode (MXene/activated carbon (AC)/polyoxometalates (POMs)) combining the merits of three materials: MXene (high volumetric capacitance), AC (high gravimetric capacitance) and Phosphotungstate (fast redox). Phosphotungstic acid (HPW12) and tetraethylammonium phosphotungstate (TEAPW12) were the two POMs used to prepare MXene/AC/POMs triple hybrids. MXene/AC/TEAPW12 outperformed MXene/AC/HPW12 in 1 M tetraethylammonium tetrafluoroborate (TEABF4)/acetonitrile. Nano-dispersion of POMs facilitates charge storage through surface capacitive processes (91% at 2 mV s−1). MXene/AC/TEAPW12 delivered significantly higher gravimetric capacitance (87F g−1 at 1 mV s−1) than MXene (40F g−1 at 1 mV s−1) in the same organic electrolyte, without sacrificing much volumetric capacitance (less than 10%). The gravimetric capacitance of the triple hybrid was similar to that of MXene/AC, whereas its volumetric capacitance was 1.5 times higher. Replacing TEA cations with 1-ethyl-3-methylimidazolium cations (EMIM+), the capacitance improved by 21%. Coupled with AC positive electrodes in an asymmetric cell, MXene/AC/TEAPW12 delivered 4.6 times higher gravimetric energy density and 3.5 times higher volumetric energy density than a similar MXene asymmetric cell at relatively high-power densities. This study proves that MXene/AC/TEAPW12 combines the merits and compensates for the demerits of each component and is a promising electrode material for organic-electrolyte supercapacitors. © 2022 The Author(s)

View abstract
Role of pO2 and film microstructure on the memristive properties of La2NiO4+δ/LaNiO3−δ bilayers
Maas K., Wulles C., Caicedo Roque J.M., Ballesteros B., Lafarge V., Santiso J., Burriel M. Journal of Materials Chemistry A; 10 (12): 6523 - 6530. 2022. 10.1039/d1ta10296f. IF: 12.732

LaNiO3/La2NiO4 bilayers deposited at varying pO2 conditions resulted in remarkable differences in film microstructure and cell parameters, directly affecting the electrical behaviour of Pt/LaNiO3/La2NiO4/Pt devices. The devices deposited at low pO2 showed the largest memristance. We propose this is due to the formation of a p-type Schottky contact between LaNiO3 and La2NiO4, where the extent of its carrier depletion width can be modulated by the electric-field induced drift of interstitial oxygen ions acting as mobile acceptor dopants in La2NiO4 © 2022 The Royal Society of Chemistry

View abstract
Structural peculiarities of e-Fe2O3/GaN epitaxial layers unveiled by high-resolution transmission electron microscopy and neutron reflectometry
Suturin, SM; Dvortsova, PA; Snigirev, LA; Ukleev, VA; Hanashima, T; Rosado, M; Ballesteros, B Materials Today Communications; 33 2022. 10.1016/j.mtcomm.2022.104412. IF: 3.662

2021

Fabrication and characterization of large-area suspended MoSe2 crystals down to the monolayer
Varghese S., Reig D.S., Mehew J.D., Block A., El Sachat A., Chávez-Ángel E., Sledzinska M., Ballesteros B., Sotomayor Torres C.M., Tielrooij K.-J. JPhys Materials; 4 (4, 046001) 2021. 10.1088/2515-7639/ac2060. IF: 0.000

Many layered materials, such as graphene and transition metal dichalcogenides, can be exfoliated down to atomic or molecular monolayers. These materials exhibit exciting material properties that can be exploited for several promising device concepts. Thinner materials lead to an increased surface-to-volume ratio, with mono- and bi-layers being basically pure surfaces. Thin crystals containing more than two layers also often behave as an all-surface material, depending on the physical property of interest. As a result, flakes of layered materials are typically highly sensitive to their environment, which is undesirable for a broad range of studies and potential devices. Material systems based on suspended flakes overcome this issue, yet often require complex fabrication procedures. Here, we demonstrate the relatively straightforward fabrication of exfoliated MoSe2 flakes down to the monolayer, suspended over unprecedentedly large holes with a diameter of 15 µm. We describe our fabrication methods in detail, present characterization measurements of the fabricated structures, and, finally, exploit these suspended flakes for accurate optical absorption measurements. © 2021 The Author(s).

View abstract
Gadolinium-Incorporated Carbon Nanodots for T1-Weighted Magnetic Resonance Imaging
Ji D.-K., Reina G., Liang H., Zhang D., Guo S., Ballesteros B., Ménard-Moyon C., Li J., Bianco A. ACS Applied Nano Materials; 4 (2): 1467 - 1477. 2021. 10.1021/acsanm.0c02993. IF: 5.097

The design and development of contrast agents for magnetic resonance imaging (MRI) with improved chemical stability and higher contrasting capability for clinical translation compared to conventional contrast agents are still of great interest. In this study, a facile and universal approach was explored for controllable functionalization of red-emissive carbon nanodots (RCNDs) with diethylenetriaminepentaacetic anhydride (DTPA) for chelation of gadolinium. A series of accurate characterizations were used to control each step of the synthesis. The functionalization did not alter the band gap of the carbon nanodots, preserving their inherent far-red fluorescence. The as-prepared RCND-DTPA-Gd displayed a high colloidal stability with negligible Gd leakage. The nanodots also showed a better magnetic resonance relaxivity than commercial MRI agents. RCND-DTPA-Gd had good biocompatibility in vivo even at high doses. The systemically injected RCND-DTPA-Gd were found to be efficiently excreted through the renal route, a feature that further minimizes the potential toxicity risks. All these properties suggest that carbon nanodots can be well designed as efficient carriers of Gd, resulting in potential clinical tools as dual MRI/fluorescence functional probes for imaging applications. The approach described here could pave the pathway to a flexible strategy for the controllable functionalization of small-sized nanoparticles including carbon dots, rendering them more versatile. This work is expected to promote the future translation of carbon nanodots into clinical trials. © 2021 American Chemical Society. All rights reserved.

View abstract
Graphene oxide prevents lateral amygdala dysfunctional synaptic plasticity and reverts long lasting anxiety behavior in rats
Franceschi Biagioni A., Cellot G., Pati E., Lozano N., Ballesteros B., Casani R., Coimbra N.C., Kostarelos K., Ballerini L. Biomaterials; 271 (120749) 2021. 10.1016/j.biomaterials.2021.120749. IF: 12.479

Engineered small graphene oxide (s-GO) sheets were previously shown to reversibly down-regulate glutamatergic synapses in the hippocampus of juvenile rats, disclosing an unexpected translational potential of these nanomaterials to target selective synapses in vivo. Synapses are anatomical specializations acting in the Central Nervous System (CNS) as functional interfaces among neurons. Dynamic changes in synaptic function, named synaptic plasticity, are crucial to learning and memory. More recently, pathological mechanisms involving dysfunctional synaptic plasticity were implicated in several brain diseases, from dementia to anxiety disorders. Hyper-excitability of glutamatergic neurons in the lateral nucleus of the amygdala complex (LA) is substantially involved in the storage of aversive memory induced by stressful events enabling post-traumatic stress disorder (PTSD). Here we translated in PTSD animal model the ability of s-GO, when stereotaxically administered to hamper LA glutamatergic transmission and to prevent the behavioral response featured in long-term aversive memory. We propose that s-GO, by interference with glutamatergic plasticity, impair LA-dependent memory retrieval related to PTSD. © 2021 The Authors

View abstract
Graphene quantum dots: From efficient preparation to safe renal excretion
Hadad C., González-Domínguez J.M., Armelloni S., Mattinzoli D., Ikehata M., Istif A., Ostric A., Cellesi F., Alfieri C.M., Messa P., Ballesteros B., Da Ros T. Nano Research; 14 (3): 674 - 683. 2021. 10.1007/s12274-020-3096-y. IF: 8.897

Carbon nanomaterials offer excellent prospects as therapeutic agents, and among them, graphene quantum dots (GQDs) have gained considerable interest thanks to their aqueous solubility and intrinsic fluorescence, which enable their possible use in theranostic approaches, if their biocompatibility and favorable pharmacokinetic are confirmed. We prepared ultra-small GQDs using an alternative, reproducible, top-down synthesis starting from graphene oxide with a nearly 100% conversion. The materials were tested to assess their safety, demonstrating good biocompatibility and ability in passing the ultrafiltration barrier using an in vitro model. This leads to renal excretion without affecting the kidneys. Moreover, we studied the GQDs in vivo biodistribution confirming their efficient renal clearance, and we demonstrated that the internalization mechanism into podocytes is caveolae-mediated. Therefore, considering the reported characteristics, it appears possible to vehiculate compounds to kidneys by means of GQDs, overcoming problems related to lysosomal degradation. [Figure not available: see fulltext.]. © 2020, The Author(s).

View abstract
Heat-up colloidal synthesis of shape-controlled cu-se-s nanostructures—role of precursor and surfactant reactivity and performance in n2 electroreduction
Mourdikoudis S., Antonaropoulos G., Antonatos N., Rosado M., Storozhuk L., Takahashi M., Maenosono S., Luxa J., Sofer Z., Ballesteros B., Thanh N.T.K., Lappas A. Nanomaterials; 11 (12, 3369) 2021. 10.3390/nano11123369. IF: 5.076

Copper selenide-sulfide nanostructures were synthesized using metal-organic chemical routes in the presence of Cu-and Se-precursors as well as S-containing compounds. Our goal was first to examine if the initial Cu/Se 1:1 molar proportion in the starting reagents would always lead to equiatomic composition in the final product, depending on other synthesis parameters which affect the reagents reactivity. Such reaction conditions were the types of precursors, surfactants and other reagents, as well as the synthesis temperature. The use of ‘hot-injection’ processes was avoided, focusing on ‘non-injection’ ones; that is, only heat-up protocols were employed, which have the advantage of simple operation and scalability. All reagents were mixed at room temperature followed by further heating to a selected high temperature. It was found that for samples with particles of bigger size and anisotropic shape the CuSe composition was favored, whereas particles with smaller size and spherical shape possessed a Cu2−xSe phase, especially when no sulfur was present. Apart from elemental Se, Al2Se3 was used as an efficient selenium source for the first time for the acquisition of copper selenide nanostructures. The use of dodecanethiol in the presence of trioctylphosphine and elemental Se promoted the incorporation of sulfur in the materials crystal lattice, leading to Cu-Se-S compositions. A variety of techniques were used to characterize the formed nanomaterials such as XRD, TEM, HRTEM, STEM-EDX, AFM and UV-Vis-NIR. Promising results, especially for thin anisotropic nanoplates for use as electrocatalysts in nitrogen reduction reaction (NRR), were obtained. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.

View abstract
Shedding plasma membrane vesicles induced by graphene oxide nanoflakes in brain cultured astrocytes
Musto M., Parisse P., Pachetti M., Memo C., Di Mauro G., Ballesteros B., Lozano N., Kostarelos K., Casalis L., Ballerini L. Carbon; 176: 458 - 469. 2021. 10.1016/j.carbon.2021.01.142. IF: 9.594

Microvesicles (MVs) generated and released by astrocytes, the brain prevalent cells, crucially contribute to intercellular communication, representing key vectorized systems able to spread and actively transfer signaling molecules from astrocytes to neurons, ultimately modulating target cell functions. The increasing clinical relevance of these signaling systems requires a deeper understanding of MV features, currently limited by both their nanoscale dimensions and the low rate of their constituent release. Hence, to investigate the features of such glial signals, nanotechnology-based approaches and the applications of unconventional, cost-effective tools in generating MVs are needed. Here, small graphene oxide (s-GO) nanoflakes are used to boost MVs shedding from astrocytes in cultures and s-GO generated MVs are compared with those generated by a natural stimulant, namely ATP, by atomic force microscopy, light scattering, attenuated total reflection–fourier transform infra-red and ultraviolet resonance Raman spectroscopy. We also report the ability of both types of MVs, upon acute and transient exposure of patch clamped cultured neurons, to modulate basal synaptic transmission, inducing a stable increase in synaptic activity accompanied by changes in neuronal plasma membrane elastic features. © 2021 The Author(s)

View abstract
Superelasticity preservation in dissimilar joint of NiTi shape memory alloy to biomedical PtIr
Shamsolhodaei A., Oliveira J.P., Panton B., Ballesteros B., Schell N., Zhou Y.N. Materialia; 16 (101090) 2021. 10.1016/j.mtla.2021.101090. IF: 0.000

Laser microwelding was used to join, for the first time, superelastic NiTi to biomedical PtIr which can be used in multicomponent biomedical devices. By process optimization, it was possible to control the formation of the B2 NiTiPt phase, with no intermetallic compounds being formed. The NiTiPt phase inside the fusion zone had a strong metallurgical bonding with the NiTi base material due to the smooth transition of its grain orientation towards 〈111〉 B2 NiTi. The major finding of the present work is the preservation of the NiTi superelastic response in the welded joint as evidenced by the load/unloading cycling up to 6% strain, significantly higher than typically required for biomedical applications. © 2021

View abstract
Tailoring the Architecture of Cationic Polymer Brush-Modified Carbon Nanotubes for Efficient siRNA Delivery in Cancer Immunotherapy
Li D., Ahmed M., Khan A., Xu L., Walters A.A., Ballesteros B., Al-Jamal K.T. ACS Applied Materials and Interfaces; 13 (26): 30284 - 30294. 2021. 10.1021/acsami.1c02627. IF: 9.229

The facile and controlled fabrication of homogeneously grafted cationic polymers on carbon nanotubes (CNTs) remains poorly investigated, which further hinders the understanding of interactions between functionalized CNTs with different nucleic acids and the rational design of appropriate gene delivery vehicles. Herein, we describe the controlled grafting of cationic poly(2-dimethylaminoethylmethacrylate) brushes on CNTs via surface-initiated atom transfer radical polymerization integrated with mussel-inspired polydopamine chemistry. The binding of nucleic acids with different brush-CNT hybrids discloses the highly architectural-dependent behavior with dense short brush-coated CNTs displaying the highest binding among all the other hybrids, namely, dense long, sparse long, and sparse short brush-coated CNTs. Additionally, different chemistries of the brush coatings were shown to influence the biocompatibility, cellular uptake, and silencing efficiency in vitro. This platform provides great flexibility for the design of polymer brush-CNT hybrids with precise control over their structure-activity relationship for the rational design of nucleic acid delivery systems. © 2021 American Chemical Society. All rights reserved.

View abstract
The role of temperature on the degree of end-closing and filling of single-walled carbon nanotubes
Kierkowicz M., Pach E., Fraile J., Domingo C., Ballesteros B., Tobias G. Nanomaterials; 11 (12, 3365) 2021. 10.3390/nano11123365. IF: 5.076

Carbon nanotubes (CNTs), owing to their high surface area-to-volume ratio and hollow core, can be employed as hosts for adsorbed and/or encapsulated molecules. At high temperatures, the ends of CNTs close spontaneously, which is relevant for several applications, including catalysis, gas storage, and biomedical imaging and therapy. This study highlights the influence of the annealing temperature in the range between 400 and 1100◦C on the structure and morphology of single-walled CNTs. The nitrogen adsorption and density functional theory calculations indicate that the fraction of end-closed CNTs increases with temperature. Raman spectroscopy reveals that the thermal treatment does not alter the tubular structure. Insight is also provided into the efficacy of CNTs filling from the molten phase, depending on the annealing temperature. The CNTs are filled with europium (III) chloride and analyzed by using electron microscopy (scanning electron microscopy and highresolution transmission electron microscopy) and energy-dispersive X-ray spectroscopy, confirming the presence of filling and closed ends. The filling yield increases with temperature, as determined by thermogravimetric analysis. The obtained results show that the apparent surface area of CNTs, fraction of closed ends, and amount of encapsulated payload can be tailored via annealing. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.

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2020

Charge transfer in steam purified arc discharge single walled carbon nanotubes filled with lutetium halides
Santidrián A., Kierkowicz M., Pach E., Darvasiová D., Ballesteros B., Tobias G., Kalbáč M. Physical Chemistry Chemical Physics; 22 (18): 10063 - 10075. 2020. 10.1039/d0cp01408g. IF: 3.430

In the present work, the effect of doping on electronic properties in bulk purified and filled arc-discharge single-walled carbon nanotubes samples is studied for the first time by in situ Raman spectroelectrochemical method. A major challenge to turn the potential of SWCNTs into customer applications is to reduce or eliminate their contaminants by means of purification techniques. Besides, the endohedral functionalization of SWCNTs with organic and inorganic materials (i.e. metal halides) allows the development of tailored functional hybrids. Here, we report the purification and endohedral functionalization of SWCNTs with doping affecting the SWCNTs. Steam-purified SWCNTs have been filled with selected lutetium(iii) halides, LuCl3, LuBr3, LuI3, and sealed using high-temperature treatment, yielding closed-ended SWCNTs with the filling material confined in the inner cavity. The purified SWCNTs were studied using TGA, EDX, STEM and Raman spectroscopy. The lutetium(iii) halide-filled SWCNTs (LuX3@SWCNTs) were characterized using STEM, EDX, Raman spectroscopy and in situ Raman spectroelectrochemistry. It was found that there is a charge transfer between the SWCNTs and the encapsulated LuX3 (X = Cl, Br, I). The obtained data testify to the acceptor doping effect of lutetium(iii) halides incorporated into the SWCNT channels, which is accompanied by the charge transfer from nanotube walls to the introduced substances. © 2020 the Owner Societies.

View abstract
Differential properties and effects of fluorescent carbon nanoparticles towards intestinal theranostics
Vallan L., Hernández-Ferrer J., Grasa L., González-Domínguez J.M., Martínez M.T., Ballesteros B., Urriolabeitia E.P., Ansón-Casaos A., Benito A.M., Maser W.K. Colloids and Surfaces B: Biointerfaces; 185 (110612) 2020. 10.1016/j.colsurfb.2019.110612. IF: 4.389

Given the potential applications of fluorescent carbon nanoparticles in biomedicine, the relationship between their chemical structure, optical properties and biocompatibility has to be investigated in detail. In this work, different types of fluorescent carbon nanoparticles are synthesized by acid treatment, sonochemical treatment, electrochemical cleavage and polycondensation. The particle size ranges from 1 to 6 nm, depending on the synthesis method. Nanoparticles that were prepared by acid or sonochemical treatments from graphite keep a crystalline core and can be classified as graphene quantum dots. The electrochemically produced nanoparticles do not clearly show the graphene core, but it is made of heterogeneous aromatic structures with limited size. The polycondensation nanoparticles do not have C[dbnd]C double bonds. The type of functional groups on the carbon backbone and the optical properties, both absorbance and photoluminescence, strongly depend on the nanoparticle origin. The selected types of nanoparticles are compatible with human intestinal cells, while three of them also show activity against colon cancer cells. The widely different properties of the nanoparticle types need to be considered for their use as diagnosis markers and therapeutic vehicles, specifically in the digestive system. © 2019 Elsevier B.V.

View abstract
Large thermoelectric power variations in epitaxial thin films of layered perovskite GdBaCo2O5.5±δwith a different preferred orientation and strain
Chatterjee A., Chavez-Angel E., Ballesteros B., Caicedo J.M., Padilla-Pantoja J., Leborán V., Sotomayor Torres C.M., Rivadulla F., Santiso J. Journal of Materials Chemistry A; 8 (38): 19975 - 19983. 2020. 10.1039/d0ta04781c. IF: 11.301

This work describes the growth of thin epitaxial films of the layered perovskite material GdBaCo2O5.5±δ(GBCO) on different single crystal substrates SrTiO3(STO), (LaAlO3)0.3(Sr2TaAlO6)0.7(LSAT) and LaAlO3(LAO) as an approach to study changes in the thermoelectric properties by means of the induced epitaxial strain. In addition to strain changes, the films grow with considerably different preferred orientations and domain microstructures: GBCO films on STO are purelyc-axis oriented (c⊥) with an average 0.18% in-plane tensile strain; GBCO on LSAT is composed of domains with a mixed orientation (c‖andc⊥) with an average 0.71% in-plane compressive strain; while on LAO it isb-axis oriented (c‖) with an average 0.89% in-plane compressive strain. These differences result in important cell volume changes, as well as in the orthorhombicity of thea-bplane of the GBCO structure, which in turn induce a change in the sign and temperature dependence of the thermopower, while the electrical conductivity remains almost unchanged. In general, compressively strained films show negativeSthermopower (n-type) while tensile strained films show a positiveS(p-type) at low temperatures, probing the adaptive nature of the GdBaCo2O5.5±δcompound. These results point to the spontaneous generation of oxygen vacancies to partially accommodate the epitaxial stress as the main cause for this effect. © The Royal Society of Chemistry 2020.

View abstract
Multi-approach analysis to assess the chromium(III) immobilization by Ochrobactrum anthropi DE2010
Villagrasa E., Ballesteros B., Obiol A., Millach L., Esteve I., Solé A. Chemosphere; 238 (124663) 2020. 10.1016/j.chemosphere.2019.124663. IF: 5.778

Ochrobactrum anthropi DE2010 is a microorganism isolated from Ebro Delta microbial mats and able to resist high doses of chromium(III) due to its capacity to tolerate, absorb and accumulate this metal. The effect of this pollutant on O. anthropi DE2010 has been studied assessing changes in viability and biomass, sorption yields and removal efficiencies. Furthermore, and for the first time, its capacity for immobilizing Cr(III) from culture media was tested by a combination of High Angle Annular Dark Field (HAADF) Scanning Transmission Electron Microscopy (STEM) imaging coupled to Energy Dispersive X-ray spectroscopy (EDX). The results showed that O. anthropi DE2010 was grown optimally at 0–2 mM Cr(III). On the other hand, from 2 to 10 mM Cr(III) microbial plate counts, growth rates, cell viability, and biomass decreased while extracellular polymeric substances (EPS) production increases. Furthermore, this bacterium had a great ability to remove Cr(III) at 10 mM (q = 950.00 mg g−1) immobilizing it mostly in bright polyphosphate inclusions and secondarily on the cellular surface at the EPS level. Based on these results, O. anthropi DE2010 could be considered as a potential agent for bioremediation in Cr(III) contaminated environments. © 2019 Elsevier Ltd

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Neutron Activated 153Sm Sealed in Carbon Nanocapsules for in Vivo Imaging and Tumor Radiotherapy
Wang J.T.-W., Klippstein R., Martincic M., Pach E., Feldman R., Šefl M., Michel Y., Asker D., Sosabowski J.K., Kalbac M., Da Ros T., Ménard-Moyon C., Bianco A., Kyriakou I., Emfietzoglou D., Saccavini J.-C., Ballesteros B., Al-Jamal K.T., Tobias G. ACS Nano; 14 (1): 129 - 141. 2020. 10.1021/acsnano.9b04898. IF: 14.588

Radiation therapy along with chemotherapy and surgery remain the main cancer treatments. Radiotherapy can be applied to patients externally (external beam radiotherapy) or internally (brachytherapy and radioisotope therapy). Previously, nanoencapsulation of radioactive crystals within carbon nanotubes, followed by end-closing, resulted in the formation of nanocapsules that allowed ultrasensitive imaging in healthy mice. Herein we report on the preparation of nanocapsules initially sealing "cold" isotopically enriched samarium (152Sm), which can then be activated on demand to their "hot" radioactive form (153Sm) by neutron irradiation. The use of "cold" isotopes avoids the need for radioactive facilities during the preparation of the nanocapsules, reduces radiation exposure to personnel, prevents the generation of nuclear waste, and evades the time constraints imposed by the decay of radionuclides. A very high specific radioactivity is achieved by neutron irradiation (up to 11.37 GBq/mg), making the "hot" nanocapsules useful not only for in vivo imaging but also therapeutically effective against lung cancer metastases after intravenous injection. The high in vivo stability of the radioactive payload, selective toxicity to cancerous tissues, and the elegant preparation method offer a paradigm for application of nanomaterials in radiotherapy. Copyright © 2019 American Chemical Society.

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Neutron-irradiated antibody-functionalised carbon nanocapsules for targeted cancer radiotherapy
Wang J.T.-W., Spinato C., Klippstein R., Costa P.M., Martincic M., Pach E., Ruiz de Garibay A.P., Ménard-Moyon C., Feldman R., Michel Y., Šefl M., Kyriakou I., Emfietzoglou D., Saccavini J.-C., Ballesteros B., Tobias G., Bianco A., Al-Jamal K.T. Carbon; 162: 410 - 422. 2020. 10.1016/j.carbon.2020.02.060. IF: 8.821

Radiotherapy is a cancer treatment utilising high doses of ionizing radiation to destroy cancer cells. Our team has pioneered neutron activation of 152Sm, filled and sealed into single-walled (SWCNTs) and multi-walled carbon nanotubes (MWCNTs), to create stable and high-dose radioactive carbon nanocapsules for cancer radiotherapy. In this work, MWCNTs filled with enriched 152SmCl3 (Sm@MWCNTs) were sealed and irradiated, followed by surface functionalisation with an epidermal growth factor receptor (EGFR)-targeting antibody. Characterisation of functionalised Sm@MWCNTs was carried out using thermogravimetric analysis, gel electrophoresis and transmission electron microscopy. The organ biodistribution of the radioactive functionalised 153Sm@MWCNTs and therapeutic efficacy were studied in an experimental melanoma lung metastatic tumour model in mice after intravenous injection. Quantitative biodistribution analyses showed high accumulation of 153Sm@MWCNT-Ab in lung. Significant tumour growth reduction was induced by both treatments of 153Sm@MWCNTs functionalised with or without the antibody after a single intravenous injection. Although EGFR targeting showed no improvement in therapeutic efficacy, reduced spleen toxicity and normal haematological profiles were obtained for both functionalised derivatives. The current study demonstrated the possibility of performing chemical functionalisation and antibody conjugation on radioactive nanocapsules post-irradiation for the preparation of targeted radiopharmaceuticals. © 2020 Elsevier Ltd

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P-Type Ultrawide-Band-Gap Spinel ZnGa2O4: New Perspectives for Energy Electronics
Chikoidze E., Sartel C., Madaci I., Mohamed H., Vilar C., Ballesteros B., Belarre F., Del Corro E., Vales-Castro P., Sauthier G., Li L., Jennings M., Sallet V., Dumont Y., Pérez-Tomás A. Crystal Growth and Design; 20 (4): 2535 - 2546. 2020. 10.1021/acs.cgd.9b01669. IF: 4.089

The family of spinel compounds is a large and important class of multifunctional materials of general formulation AB2X4 with many advanced applications in energy and optoelectronic areas such as fuel cells, batteries, catalysis, photonics, spintronics, and thermoelectricity. In this work, it is demonstrated that the ternary ultrawide-band-gap (∼5 eV) spinel zinc gallate (ZnGa2O4) arguably is the native p-type ternary oxide semiconductor with the largest Eg value (in comparison with the recently discovered binary p-type monoclinic β-Ga2O3 oxide). For nominally undoped ZnGa2O4 the high-temperature Hall effect hole concentration was determined to be as large as p = 2 × 1015 cm-3, while hole mobilities were found to be μh = 7-10 cm2/(V s) (in the 680-850 K temperature range). An acceptor-like small Fermi level was further corroborated by X-ray spectroscopy and by density functional theory calculations. Our findings, as an important step toward p-type doping, opens up further perspectives for ultrawide-band-gap bipolar spinel electronics and further promotes ultrawide-band-gap ternary oxides such as ZnGa2O4 to the forefront of the quest of the next generation of semiconductor materials for more efficient energy optoelectronics and power electronics. Copyright © 2020 American Chemical Society.

View abstract

2019

In vivo behaviour of glyco-NaI@SWCNT ‘nanobottles’
De Munari S., Sandoval S., Pach E., Ballesteros B., Tobias G., Anthony D.C., Davis B.G. Inorganica Chimica Acta; 495 (118933) 2019. 10.1016/j.ica.2019.05.032. IF: 2.433

Carbon nanotubes are appealing imaging and therapeutic systems. Their structure allows not only a useful display of molecules on their outer surface but at the same time the protection of encapsulated cargoes. Despite the interest they have provoked in the scientific community, their applications have not yet been fully realised due to the limited knowledge we possess concerning their physiological behaviour. Previously, we have shown that the encapsulation of radionuclide in the inner space of glycan-functionalized single-walled carbon nanotubes (glyco-X@SWCNT) redirected in vivo distribution of radioactivity from the thyroid to the lungs. Here we test the roles played by such glycans attached to carbon nanotubes in controlling sites of accumulation using nanotubes carrying both ‘cold’ and ‘hot’ salt cargoes decorated with two different mammalian carbohydrates, N-acetyl-D-glucosamine (GlcNAc) or galactose (Gal)-capped disaccharide lactose (Gal–Glc). This distinct variation of the terminal glycan displayed between two types of glycan ligands with very different in vivo receptors, coupled with altered sites of administration, suggest that distribution in mammals is likely controlled by physiological mechanisms that may include accumulation in the first capillary bed they encounter and not by glycan-receptor interaction and that the primary role of glycan is in aiding the dispersibility of the CNTs. © 2019

View abstract
Microwave-assisted synthesis of SPION-reduced graphene oxide hybrids for magnetic resonance imaging (MRI)
Llenas M., Sandoval S., Costa P.M., Oró-Solé J., Lope-Piedrafita S., Ballesteros B., Al-Jamal K.T., Tobias G. Nanomaterials; 9 (10, 1364) 2019. 10.3390/nano9101364. IF: 4.034

Magnetic resonance imaging (MRI) is a useful tool for disease diagnosis and treatment monitoring. Superparamagnetic iron oxide nanoparticles (SPION) show good performance as transverse relaxation (T2) contrast agents, thus facilitating the interpretation of the acquired images. Attachment of SPION onto nanocarriers prevents their agglomeration, improving the circulation time and efficiency. Graphene derivatives, such as graphene oxide (GO) and reduced graphene oxide (RGO), are appealing nanocarriers since they have both high surface area and functional moieties that make them ideal substrates for the attachment of nanoparticles. We have employed a fast, simple and environmentally friendly microwave-assisted approach for the synthesis of SPION-RGO hybrids. Different iron precursor/GO ratios were used leading to SPION, with a median diameter of 7.1 nm, homogeneously distributed along the RGO surface. Good relaxivity (r2*) values were obtained in MRI studies and no significant toxicity was detected within in vitro tests following GL261 glioma and J774 macrophage-like cells for 24 h with SPION-RGO, demonstrating the applicability of the hybrids as T2-weighted MRI contrast agents. © 2019 by the authors. Licensee MDPI, Basel, Switzerland.

View abstract
Non-cytotoxic carbon nanocapsules synthesized via one-pot filling and end-closing of multi-walled carbon nanotubes
Martincic M., Vranic S., Pach E., Sandoval S., Ballesteros B., Kostarelos K., Tobias G. Carbon; 141: 782 - 793. 2019. 10.1016/j.carbon.2018.10.006. IF: 7.466

Filled carbon nanotubes (CNTs) find application in a variety of fields that expand from sensors to supercapacitors going through targeted therapies. Bulk filling of CNTs in general results in samples that contain a large amount of non-encapsulated material external to the CNTs. The presence of external material can dominate the properties of the resulting hybrids and can also induce side effects when employed in the biomedical field. Unless the encapsulated payloads have a strong interaction with the inner CNT walls, an additional step is required to block the ends of the CNTs thus allowing the selective removal of the non-encapsulated compounds while preserving the inner cargo. Herein we present a fast, easy and versatile approach that allows both filling (NaI, KI, BaI2, GdCl3 and SmCl3) and end-closing of multi-walled CNTs in a single-step, forming “carbon nanocapsules”. Remarkably the encapsulation of GdCl3 and SmCl3 leads to the formation of tubular van der Waals heterostructures. The prepared nanocapsules are efficiently internalized by cells without inducing cytotoxicity, thus presenting a safe tool for the delivery of therapeutic and dianostic agents to cells. The synergies of novel carbon and inorganic hybrid materials can be explored using the present approach. © 2018 Elsevier Ltd

View abstract

2018

An in operando study of chemical expansion and oxygen surface exchange rates in epitaxial GdBaCo2O5.5 electrodes in a solid-state electrochemical cell by time-resolved X-ray diffraction
Chatterjee A., Caicedo J.M., Ballesteros B., Santiso J. Journal of Materials Chemistry A; 6 (26): 12430 - 12439. 2018. 10.1039/c8ta02790k. IF: 9.931

This report explores the fundamental characteristics of epitaxial thin films of a mixed ionic electronic conducting GdBaCo2O5.5±δ (GBCO) material with a layered perovskite structure, relevant for use as an active electrode for the oxygen reduction and evolution reactions in electrochemical devices. Time-resolved X-ray diffraction in combination with voltage step chrono-amperometric measurements in a solid state electrochemical cell provides a deeper insight into the chemical expansion mechanism in the GBCO electrode. The chemical expansion coefficient along the c-axis, αc, shows a negative value upon the compound oxidation contrary to standard perovskite materials with disordered oxygen vacancies. Chemical expansion also shows a remarkable asymmetry from αc = -0.037 to -0.014 at δ < 0 and δ > 0, respectively. This change in chemical expansion is an indication of a different mechanism of the structural changes associated with the variable Co cation oxidation state from Co2+ → Co3+ → Co4+. Since redox reactions are dominated by oxygen surface exchange between the GBCO electrode and gas atmosphere, monitoring the time response of the structural changes allows for direct determination of oxygen reduction and evolution reaction kinetics. The reaction kinetics are progressively slowed down upon reduction in the δ < 0 oxygen stoichiometry region, while they maintain a high catalytic activity in the δ > 0 region, in agreement with the structural changes and the electronic carrier delocalization when crossing δ = 0. This work validates the time-resolved XRD technique for fast and reversible measurements of electrode activity in a wide range of oxygen non-stoichiometry in a solid-state electrochemical cell operating under realistic working conditions. © 2018 The Royal Society of Chemistry.

View abstract
Comparative study of shortening and cutting strategies of single-walled and multi-walled carbon nanotubes assessed by scanning electron microscopy
Kierkowicz M., Pach E., Santidrián A., Sandoval S., Gonçalves G., Tobías-Rossell E., Kalbáč M., Ballesteros B., Tobias G. Carbon; 139: 922 - 932. 2018. 10.1016/j.carbon.2018.06.021. IF: 7.082

Short carbon nanotubes (CNTs) are desired for a variety of applications. As a consequence, several strategies have been reported to cut and shorten the length of as-produced CNTs via chemical and physical routes. The efficiency of a given strategy largely depends on the physico-chemical characteristics of the CNTs employed. In order to be able to directly compare the advantages and disadvantages of commonly used protocols, a single batch of chemical vapor deposition single-walled CNTs (SWCNTs) and a batch of multi-walled CNTs (MWCNTs) were subjected to four cutting/shortening strategies, namely acid cutting, piranha treatment, steam shortening and ball milling. The length distribution was assessed by means of scanning electron microscopy. Sample purity and CNT wall structure were determined by Raman spectroscopy, thermogravimetric analysis and magnetic measurements. Within the employed experimental conditions, piranha treatment turned out to be the most efficient to achieve short SWCNTs with a narrow length distribution in a good yield, whereas a mixture of sulfuric/nitric acid was preferred in the case of MWCNTs. A subsequent short steam treatment allowed to remove functional groups present in the samples, leading to median length distributions of 266 nm and 225 nm for SWCNTs and MWCNTs respectively after the combined protocols. © 2018 Elsevier Ltd

View abstract
Determination of the length of single-walled carbon nanotubes by scanning electron microscopy
Sandoval S., Kierkowicz M., Pach E., Ballesteros B., Tobias G. MethodsX; 5: 1465 - 1472. 2018. 10.1016/j.mex.2018.11.004.

A methodology is presented to determine the length of well individualized single-walled carbon nanotubes (SWCNTs) by means of scanning electron microscopy (SEM). Accurate measurements on wide areas of the sample can be achieved in an easy, fast and trustworthy manner. We have tested several supports and solvents to optimize the dispersion of SWCNTs, as well as the SEM imaging conditions. The optimal methodology goes via dispersion of the sample in ortho-dichlorobenzene, deposition onto a continuous carbon film supported on a copper TEM grid, and SEM imaging at 2 kV in secondary electrons mode using a through-in-lens detector. • Individualization of SWCNTs is achieved by dispersion of SWCNTs in ortho-dichlorobenzene and deposition onto TEM grids• Individual SWCNTs are imaged by SEM• Length determination by SEM is as precise as AFM © 2018 The Author(s)

View abstract
Encapsulation of cationic iridium(iii) tetrazole complexes into a silica matrix: Synthesis, characterization and optical properties
Zanoni I., Fiorini V., Rosado M., Ballesteros B., Androulidaki M., Blosi M., Ortelli S., Stagni S., Dondi M., Costa A.L. New Journal of Chemistry; 42 (12): 9635 - 9644. 2018. 10.1039/c8nj01514g. IF: 3.201

Herein we report the easy incorporation of brightly phosphorescent cationic iridium(iii) tetrazole complexes into a silica based matrix via an easily scalable colloidal process. For this purpose, two cationic Ir(iii) emitters bearing 5-aryl tetrazole ligands (R-CN4) were selected: blue [F2IrPTZ-Me]+ (C^N = F2ppy; N^N = PTZ-Me-2-(2-methyl-2H-tetrazol-5-yl)pyridine) and red [IrQTZ-Me]+ (C^N = ppy; N^N = QTZ-Me-2-(2-methyl-2H-tetrazol-5-yl)quinoline). The cationic complexes were readily adsorbed to negatively charged silica nanoparticles and trapped in the sol-gel matrix. The sol-to-solid phase transfer was performed by using an innovative spray-freeze-drying technique, leading to the formation of phosphorescent solid micro-granules. The structural and optical characterisation of the Ir(iii) complexes together with SiO2 nanoparticles, nanosols (Ir@SiO2) and powders (Ir@SiO2 powders), revealed how the presence of the Ir(iii)-based complexes did not alter the morphology of the colloidal silica or granulated phases. Moreover, the silica matrix did not interfere with the optical properties of the embedded complexes. The distribution of [F2IrPTZ-Me]+ and [IrQTZ-Me]+ in the spray-freeze-dried powders was qualitatively evaluated by fluorescence microscopy, revealing how the luminescent particles were homogeneously dispersed all over the silica matrix. Interestingly, in aqueous solution the release of complex [F2IrPTZ-Me]+ from the corresponding Ir@SiO2 powder is almost negligible, therefore suggesting that a strong interaction occurs between the host-silica matrix and the Ir(iii) guest complex. © 2018 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.

View abstract
Epoxidation of carbon nanocapsules: Decoration of single-walled carbon nanotubes filled with metal halides
D’Accolti L., Gajewska A., Kierkowicz M., Martincic M., Nacci A., Sandoval S., Ballesteros B., Tobias G., Da Ros T., Fusco C. Nanomaterials; 8 (3, 137) 2018. 10.3390/nano8030137. IF: 3.504

Methyl(trifluoromethyl)dioxirane (TFDO) can be used for the oxyfunctionalization of SWCNTs filled with NaI and LuCl3 under mild conditions. The chosen metal halides are of interest for theranostics, both for imaging and therapy when in their radioactive form. The applied functionalization methodology does not require metal catalyst, preserves the integrity of the nanotubes during treatment, avoiding the release of the filling material. In this way, epoxidation can be considered as an efficient methodology for the functionalization of carbon nanocapsules, where the traditional harsh oxidation conditions by acids are not applicable. © 2018 2018 by the authors. Licensee MDPI, Basel, Switzerland.

View abstract
Facile synthesis of nanoparticles of the molecule-based superconductor κ-(BEDT-TTF)2Cu(NCS)2 [Synthèse aisée de nanoparticules du supraconducteur moléculaire κ-(BEDT-TTF)2Cu(NCS)2]
Cormary B., Faulmann C., de Caro D., Valade L., de Caro P., Ballesteros B., Fraxedas J. Comptes Rendus Chimie; 21 (9): 809 - 813. 2018. 10.1016/j.crci.2018.07.006. IF: 1.877

Well-dispersed roughly spherical nano-objects of the molecule-based superconductor κ-(BEDT-TTF)2Cu(NCS)2 have been prepared in an organic solution by using an easy synthetic route. Long alkyl-chain aconitate esters have been used as growth controlling agents. Nano-objects exhibiting sizes in the 35–120 nm range are made of aggregated individual smaller nanoparticles ranging from 3 to 10 nm. Nanoparticle powders have been studied by X-ray diffraction, high resolution electron microscopy and atomic force microscopy in the conductivity mode. © 2018 Académie des sciences

View abstract
Optimisation of growth parameters to obtain epitaxial Y-doped BaZrO3 proton conducting thin films
Magrasó A., Ballesteros B., Rodríguez-Lamas R., Sunding M.F., Santiso J. Solid State Ionics; 314: 9 - 16. 2018. 10.1016/j.ssi.2017.11.002. IF: 2.751

We hereby report developments on the fabrication and characterization of epitaxial thin films of proton conducting Y-doped BaZrO3 (BZY) by pulsed laser deposition (PLD) on different single crystal substrates (MgO, GdScO3, SrTiO3, NdGaO3, LaAlO3 and sapphire) using Ni-free and 1% Ni-containing targets. Pure, high crystal quality epitaxial films of BZY are obtained on MgO and on perovskite-type substrates, despite the large lattice mismatch. The deposition conditions influence the morphology, cell parameters and chemical composition of the film, the oxygen partial pressure during film growth being the most determining. Film characterization was carried out using X-ray diffraction, transmission electron and atomic force microscopies, wavelength dispersive X-ray spectroscopy and angle-resolved X-ray photoelectron spectroscopy. All films show a slight tetragonal distortion that is not directly related to the substrate-induced strain. The proton conductivity of the films depends on deposition conditions and film thickness, and for the optimised conditions its total conductivity is slightly higher than the bulk conductivity of the target material (3 mS/cm at 600 °C, in wet 5% H2/Ar). The conductivities are, however, more than one order of magnitude lower than the highest reported in literature and possible reasoning is elucidated in terms of local and extended defects in the films. © 2017 Elsevier B.V.

View abstract
Protein-Corona-by-Design in 2D: A Reliable Platform to Decode Bio–Nano Interactions for the Next-Generation Quality-by-Design Nanomedicines
Mei K.-C., Ghazaryan A., Teoh E.Z., Summers H.D., Li Y., Ballesteros B., Piasecka J., Walters A., Hider R.C., Mailänder V., Al-Jamal K.T. Advanced Materials; 30 (40, 1802732) 2018. 10.1002/adma.201802732. IF: 21.950

Hard corona (HC) protein, i.e., the environmental proteins of the biological medium that are bound to a nanosurface, is known to affect the biological fate of a nanomedicine. Due to the size, curvature, and specific surface area (SSA) 3-factor interactions inherited in the traditional 3D nanoparticle, HC-dependent bio–nano interactions are often poorly probed and interpreted. Here, the first HC-by-design case study in 2D is demonstrated that sequentially and linearly changes the HC quantity using functionalized graphene oxide (GO) nanosheets. The HC quantity and HC quality are analyzed using NanoDrop and label-free liquid chromatography–mass spectrometry (LC-MS) followed by principal component analysis (PCA). Cellular responses (uptake and cytotoxicity in J774 cell model) are compared using imaging cytometry and the modified lactate dehydrogenase assays, respectively. Cellular uptake linearly and solely correlates with HC quantity (R2 = 0.99634). The nanotoxicity, analyzed by retrospective design of experiment (DoE), is found to be dependent on the nanomaterial uptake (primary), HC composition (secondary), and nanomaterial exposure dose (tertiary). This unique 2D design eliminates the size–curvature–SSA multifactor interactions and can serve as a reliable screening platform to uncover HC-dependent bio–nano interactions to enable the next-generation quality-by-design (QbD) nanomedicines for better clinical translation. © 2018 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

View abstract
Selective Laser-Assisted Synthesis of Tubular van der Waals Heterostructures of Single-Layered PbI2 within Carbon Nanotubes Exhibiting Carrier Photogeneration
Sandoval S., Kepić D., Pérez Del Pino Á., György E., Gómez A., Pfannmoeller M., Tendeloo G.V., Ballesteros B., Tobias G. ACS Nano; 12 (7): 6648 - 6656. 2018. 10.1021/acsnano.8b01638. IF: 13.709

The electronic and optical properties of two-dimensional layered materials allow the miniaturization of nanoelectronic and optoelectronic devices in a competitive manner. Even larger opportunities arise when two or more layers of different materials are combined. Here, we report on an ultrafast energy efficient strategy, using laser irradiation, which allows bulk synthesis of crystalline single-layered lead iodide in the cavities of carbon nanotubes by forming cylindrical van der Waals heterostructures. In contrast to the filling of van der Waals solids into carbon nanotubes by conventional thermal annealing, which favors the formation of inorganic nanowires, the present strategy is highly selective toward the growth of monolayers forming lead iodide nanotubes. The irradiated bulk material bearing the nanotubes reveals a decrease of the resistivity as well as a significant increase in the current flow upon illumination. Both effects are attributed to the presence of single-walled lead iodide nanotubes in the cavities of carbon nanotubes, which dominate the properties of the whole matrix. The present study brings in a simple, ultrafast and energy efficient strategy for the tailored synthesis of rolled-up single-layers of lead iodide (i.e., single-walled PbI2 nanotubes), which we believe could be expanded to other two-dimensional (2D) van der Waals solids. In fact, initial tests with ZnI2 already reveal the formation of single-walled ZnI2 nanotubes, thus proving the versatility of the approach. © 2018 American Chemical Society.

View abstract

2017

Encapsulation of two-dimensional materials inside carbon nanotubes: Towards an enhanced synthesis of single-layered metal halides
Sandoval S., Pach E., Ballesteros B., Tobias G. Carbon; 123: 129 - 134. 2017. 10.1016/j.carbon.2017.07.031. IF: 6.337

The unique properties of two-dimensional (2D) nanomaterials make them highly attractive for a wide range of applications. As a consequence, several top-down and bottom up approaches are being explored to isolate or synthesize single-layers of 2D materials in a reliable manner. Here we report on the synthesis of individual layers of several 2D van der Waals solids, namely CeI3, CeCl3, TbCl3 and ZnI2 by template-assisted growth using carbon nanotubes as directing agents, thus proving the versatility of this approach. Once confined, the metal halides can adopt different structures including single-layered metal halide nanotubes, which formation is greatly enhanced by increasing the temperature of synthesis. This opens up a new strategy for the isolation of individual layers of a wide variety of metal halides, a family of 2D materials that has been barely explored. © 2017 Elsevier Ltd

View abstract
Evaluation of the immunological profile of antibody-functionalized metal-filled single-walled carbon nanocapsules for targeted radiotherapy
Perez Ruiz De Garibay A., Spinato C., Klippstein R., Bourgognon M., Martincic M., Pach E., Ballesteros B., Ménard-Moyon C., Al-Jamal K.T., Tobias G., Bianco A. Scientific Reports; 7 ( 42605) 2017. 10.1038/srep42605. IF: 4.259

This study investigates the immune responses induced by metal-filled single-walled carbon nanotubes (SWCNT) under in vitro, ex vivo and in vivo settings. Either empty amino-functionalized CNTs [SWCNT-NH 2 (1)] or samarium chloride-filled amino-functionalized CNTs with [SmCl 3 @SWCNT-mAb (3)] or without [SmCl 3 @SWCNT-NH 2 (2)] Cetuximab functionalization were tested. Conjugates were added to RAW 264.7 or PBMC cells in a range of 1 μg/ml to 100 μg/ml for 24 h. Cell viability and IL-6/TNFα production were determined by flow cytometry and ELISA. Additionally, the effect of SWCNTs on the number of T lymphocytes, B lymphocytes and monocytes within the PBMC subpopulations was evaluated by immunostaining and flow cytometry. The effect on monocyte number in living mice was assessed after tail vein injection (150 μg of each conjugate per mouse) at 1, 7 and 13 days post-injection. Overall, our study showed that all the conjugates had no significant effect on cell viability of RAW 264.7 but conjugates 1 and 3 led to a slight increase in IL-6/TNFα. All the conjugates resulted in significant reduction in monocyte/macrophage cell numbers within PBMCs in a dose-dependent manner. Interestingly, monocyte depletion was not observed in vivo, suggesting their suitability for future testing in the field of targeted radiotherapy in mice. © The Author(s) 2017.

View abstract
Filling Single-Walled Carbon Nanotubes with Lutetium Chloride: A Sustainable Production of Nanocapsules Free of Nonencapsulated Material
Kierkowicz M., González-Domínguez J.M., Pach E., Sandoval S., Ballesteros B., Da Ros T., Tobias G. ACS Sustainable Chemistry and Engineering; 5 (3): 2501 - 2508. 2017. 10.1021/acssuschemeng.6b02850. IF: 5.951

Filled carbon nanotubes are of interest for a wide variety of applications ranging from sensors to magnetoelectronic devices and going through the development of smart contrast and therapeutic agents in the biomedical field. In general, regardless of the method employed, bulk filling of carbon nanotubes results in the presence of a large amount of external nonencapsulated material. Therefore, further processing is needed to achieve a sample in which the selected payload is present only in the inner cavities of the nanotubes. Here, we report on a straightforward approach that allows the removal of nonencapsulated compounds in a time efficient and environmentally friendly manner, using water as a "green" solvent, while minimizing the residual waste. The results presented herein pave the way toward the production of large amounts of high-quality closed-ended filled nanotubes, also referred to as carbon nanocapsules, readily utilizable in the foreseen applications. © 2017 American Chemical Society.

View abstract
Functionalization of Polypyrrole Nanopipes with Redox-Active Polyoxometalates for High Energy Density Supercapacitors
Dubal D.P., Ballesteros B., Mohite A.A., Gómez-Romero P. ChemSusChem; 10 (4): 731 - 737. 2017. 10.1002/cssc.201601610. IF: 7.226

Hybrid materials are very attractive for the fabrication of high-performance supercapacitors. Here, we have explored organic–inorganic hybrid materials based on open-end porous 1 D polypyrrole nanopipes (PPy-NPipes) and heteropolyoxometalates (phosphotungstate ([PW12O40]3−, PW12) or phosphomolybdate ([PMo12O40]3−, PMo12)) that display excellent areal capacitances. Two different hybrid materials (PMo12@PPy and PW12@PPy) were effectively synthesized and used for symmetric supercapacitors. The anchoring of the inorganic nanoclusters onto the conducting polymer nanopipes led to electrodes that stood up to our best expectations exhibiting outstanding areal capacitances that are almost 1.5 to 2 fold higher than that of pristine PPy-NPipes. In addition, symmetric cells based on PMo12@PPy and PW12@PPy hybrid electrodes were fabricated and showed significant improvement in cell performance with very high volumetric capacitances in the range of 6.3–6.8 F cm−3(considering the volume of whole device). Indeed, they provide extended potential windows in acidic electrolytes (up to 1.5 V) which led to ultrahigh energy densities of 1.5 and 2.2 mWh cm−3for PMo12@PPy and PW12@PPy cells, respectively. Thus, these unique organic-inorganic hybrid symmetric cells displayed extraordinary electrochemical performances far exceeding those of more complex asymmetric systems. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

View abstract
Multi-scale analysis of the diffusion barrier layer of gadolinia-doped ceria in a solid oxide fuel cell operated in a stack for 3000 h
Morales M., Miguel-Pérez V., Tarancón A., Slodczyk A., Torrell M., Ballesteros B., Ouweltjes J.P., Bassat J.M., Montinaro D., Morata A. Journal of Power Sources; 344: 141 - 151. 2017. 10.1016/j.jpowsour.2017.01.109. IF: 6.395

The state-of-the-art materials for SOFCs are yttria-stabilized zirconia as electrolyte and lanthanum strontium cobalt ferrite as cathode. However, the formation of insulating phases between them requires the use of diffusion barriers, typically made of gadolinia doped ceria. The study of the stability of this layer during the fabrication and in operando is currently one of the major goals of the SOFC industry. In this work, the cation inter-diffusion at the cathode/barrier layer/electrolyte region is analysed for an anode-supported cell industrially fabricated by conventional techniques, assembled in a short-stack and tested under real operation conditions for 3000 h. A comprehensive study of this cell, and an equivalent non-operated one, is performed in order to understand the inter-diffusion mechanisms with possible effects on the final performance. The analyses evidence that the cation diffusion is occurring during the fabrication process. Despite the significant diffusion of Ce,Gd, Zr, Y and Sr cations, the formation of typically reported CGO-YSZ solid solution is not observed while the presence of isolated grains of SrZrO3is proved. All in all, this study presents new insights into the stability of the typically employed diffusion barriers for solid oxide cells that will guide future strategies to improve their performance and durability. © 2017 Elsevier B.V.

View abstract
Nanosecond Laser-Assisted Nitrogen Doping of Graphene Oxide Dispersions
Kepić D., Sandoval S., Pino Á.P.D., György E., Cabana L., Ballesteros B., Tobias G. ChemPhysChem; 18 (8): 935 - 941. 2017. 10.1002/cphc.201601256. IF: 3.075

N-doped reduced graphene oxide (RGO) has been prepared in bulk form by laser irradiation of graphene oxide (GO) dispersed in an aqueous solution of ammonia. A pulsed Nd:YAG laser with emission wavelengths in the infrared (IR) 1064 nm, visible (Vis) 532 nm, and ultraviolet (UV) 266 nm spectral regions was employed for the preparation of the N-doped RGO samples. Regardless of the laser energy employed, the resulting material presents a higher fraction of pyrrolic nitrogen compared to nitrogen atoms in pyridinic and graphitic coordination. Noticeably, whereas increasing the laser fluence of UV and Vis wavelengths results in an increase in the total amount of nitrogen, up to 4.9 at. % (UV wavelength at 60 mJ cm−2 fluence), the opposite trend is observed when the GO is irradiated in ammonia solution through IR processing. The proposed laser-based methodology allows the bulk synthesis of N-doped reduced graphene oxide in a simple, fast, and cost efficient manner. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

View abstract
Raman antenna effect from exciton-phonon coupling in organic semiconducting nanobelts
Wang M., Gong Y., Alzina F., Svoboda O., Ballesteros B., Sotomayor Torres C.M., Xiao S., Zhang Z., He J. Nanoscale; 9 (48): 19328 - 19336. 2017. 10.1039/c7nr07212k. IF: 7.367

The highly anisotropic interactions in organic semiconductors together with the soft character of organic materials lead to strong coupling between nuclear vibrations and exciton dynamics, which potentially results in anomalous electrical, optical and optoelectrical properties. Here, we report on the Raman antenna effect from organic semiconducting nanobelts 6,13-dichloropentacene (DCP), resulting from the coupling of molecular excitons and intramolecular phonons. The highly ordered crystalline structure in DCP nanobelts enables the precise polarization-resolved spectroscopic measurement. The angle-dependent Raman spectroscopy under resonant excitation shows that all Raman modes from the skeletal vibrations of DCP molecule act like a nearly perfect dipole antenna IRaman ∝ cos4(θ - 90), with almost zero (maximum) Raman scattering parallel (perpendicular) to the nanobelt's long-axis. The Raman antenna effect in DCP nanobelt is originated from the coupling between molecular skeletal vibrations and intramolecular exciton and the confinement of intermolecular excitons. It dramatically enhances the Raman polarization ratio (ρ =I∥/I⊥ > 25) and amplifies the anisotropy of the angle-dependent Raman scattering (κRaman = Imax/Imin > 12) of DCP nanobelts. These findings have crucial implications for fundamental understanding on the exciton-phonon coupling and its effects on the optical properties of organic semiconductors. © 2017 The Royal Society of Chemistry.

View abstract

2016

Carbon nanotubes allow capture of krypton, barium and lead for multichannel biological X-ray fluorescence imaging
Serpell C.J., Rutte R.N., Geraki K., Pach E., Martincic M., Kierkowicz M., De Munari S., Wals K., Raj R., Ballesteros B., Tobias G., Anthony D.C., Davis B.G. Nature Communications; 7 ( 13118) 2016. 10.1038/ncomms13118. IF: 11.329

The desire to study biology in situ has been aided by many imaging techniques. Among these, X-ray fluorescence (XRF) mapping permits observation of elemental distributions in a multichannel manner. However, XRF imaging is underused, in part, because of the difficulty in interpreting maps without an underlying cellular 'blueprint'; this could be supplied using contrast agents. Carbon nanotubes (CNTs) can be filled with a wide range of inorganic materials, and thus can be used as 'contrast agents' if biologically absent elements are encapsulated. Here we show that sealed single-walled CNTs filled with lead, barium and even krypton can be produced, and externally decorated with peptides to provide affinity for sub-cellular targets. The agents are able to highlight specific organelles in multiplexed XRF mapping, and are, in principle, a general and versatile tool for this, and other modes of biological imaging. © 2016 The Author(s).

View abstract
Design of antibody-functionalized carbon nanotubes filled with radioactivable metals towards a targeted anticancer therapy
Spinato C., Perez Ruiz De Garibay A., Kierkowicz M., Pach E., Martincic M., Klippstein R., Bourgognon M., Wang J.T.-W., Ménard-Moyon C., Al-Jamal K.T., Ballesteros B., Tobias G., Bianco A. Nanoscale; 8 (25): 12626 - 12638. 2016. 10.1039/c5nr07923c. IF: 7.760

In the present work we have devised the synthesis of a novel promising carbon nanotube carrier for the targeted delivery of radioactivity, through a combination of endohedral and exohedral functionalization. Steam-purified single-walled carbon nanotubes (SWCNTs) have been initially filled with radioactive analogues (i.e. metal halides) and sealed by high temperature treatment, affording closed-ended CNTs with the filling material confined in the inner cavity. The external functionalization of these filled CNTs was then achieved by nitrene cycloaddition and followed by the derivatization with a monoclonal antibody (Cetuximab) targeting the epidermal growth factor receptor (EGFR), overexpressed by several cancer cells. The targeting efficiency of the so-obtained conjugate was evaluated by immunostaining with a secondary antibody and by incubation of the CNTs with EGFR positive cells (U87-EGFR+), followed by flow cytometry, confocal microscopy or elemental analyses. We demonstrated that our filled and functionalized CNTs can internalize more efficiently in EGFR positive cancer cells. © The Royal Society of Chemistry 2016.

View abstract
Gadolinium-functionalised multi-walled carbon nanotubes as a T1 contrast agent for MRI cell labelling and tracking
Servant A., Jacobs I., Bussy C., Fabbro C., Da Ros T., Pach E., Ballesteros B., Prato M., Nicolay K., Kostarelos K. Carbon; 97: 126 - 133. 2016. 10.1016/j.carbon.2015.08.051. IF: 6.198

The development of efficient contrast agents for cell labelling coupled with powerful medical imaging techniques is of great interest for monitoring cell trafficking with potential clinical applications such as organ repair and regenerative medicine. In this paper, functionalised multi-walled carbon nanotubes (MWNTs) were engineered for cell labelling in T1-weighted MRI applications. These sophisticated constructs were covalently functionalised with the gadolinium (Gd) chelating agent, diethylene triamine pentaacetic acid (DTPA), enabling tight attachment of Gd atoms onto the nanotube surface. The resulting Gd-labelled MWNTs were found to be stable over 2 weeks in water and mouse serum and high payload of Gd atoms could be loaded onto the nanotubes. The r1 relaxivity of the Gd-MWNTs was a 3-fold higher than of the clinically approved T1 contrast agent Magnevist at a magnetic field strength of 7T. The contrast efficiency, expressed as the r1 relaxivity, of the Gd-MWNTs in Human Umbilical Vein Endothelial cells (HUVEC) was investigated at 7T and was found to be around 6.6 mM-1 s-1. There was no reduction of the contrast efficiency after internalisation in HUVECs, which was imparted to the ability of carbon nanotubes to translocate the cell membrane. © 2015 The Authors. Published by Elsevier Ltd.

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Highly Dispersible and Stable Anionic Boron Cluster-Graphene Oxide Nanohybrids
Cabrera-González J., Cabana L., Ballesteros B., Tobias G., Núñez R. Chemistry - A European Journal; 22 (15): 5096 - 5101. 2016. 10.1002/chem.201505044. IF: 5.771

An efficient process to produce boron cluster-graphene oxide nanohybrids that are highly dispersible in water and organic solvents is established for the first time. Dispersions of these nanohybrid materials in water were extraordinarily stable after one month. Characterization of hybrids after grafting of appropriate cobaltabisdicarbollide and closo-dodecaborate derivatives onto the surface of graphene oxide (GO) was done by FT-IR, XPS, and UV/Vis. Thermogravimetric analysis (TGA) clearly shows a higher thermal stability for the modified-GO nanohybrids compared to the parent GO. Of particular note, elemental mapping by energy-filtered transmission electron microscopy (EFTEM) reveals that a uniform decoration of the graphene oxide surface with the boron clusters is achieved under the reported conditions. Therefore, the resulting nanohybrid systems show exceptional physico-chemical and thermal properties, paving the way for an enhanced processability and further expanding the range of application for graphene-based materials. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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Synthesis of dry SmCl3from Sm2O3revisited. Implications for the encapsulation of samarium compounds into carbon nanotubes
Martincic M., Frontera C., Pach E., Ballesteros B., Tobias G. Polyhedron; 116: 116 - 121. 2016. 10.1016/j.poly.2016.03.045. IF: 2.108

Samarium is a rare-earth metal with several applications in materials science. It is used in organic chemistry as a reducing agent and it is the active payload in samarium-153 lexidronam, a drug being used for palliative treatment of bone metastases. Recently, the encapsulation of samarium compounds into the cavities of carbon nanotubes has attracted interest for the development of the next generation of radiopharmaceuticals. In the present study, we explore different routes to afford the encapsulation of samarium based materials into single-walled carbon nanotubes. Anhydrous samarium(III) chloride, despite being highly hygroscopic, raises as an excellent candidate to achieve a high filling efficiency. We provide a protocol that allows the synthesis of anhydrous samarium(III) chloride starting from samarium(III) oxide in a fast and simple manner. Synchrotron X-ray powder diffraction confirmed the crystallinity and purity of the synthesized SmCl3. © 2016 Elsevier Ltd

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Synthesis, characterization, and thermoelectric properties of superconducting (BEDT-TTF)2I3 nanoparticles
Chtioui-Gay I., Faulmann C., De Caro D., Jacob K., Valade L., De Caro P., Fraxedas J., Ballesteros B., Steven E., Choi E.S., Lee M., Benjamin S.M., Yvenou E., Simonato J.-P., Carella A. Journal of Materials Chemistry C; 4 (31): 7449 - 7454. 2016. 10.1039/c6tc01378c. IF: 5.066

The synthesis of (BEDT-TTF)2I3 in the presence of two neutral amphiphilic molecules [N-octylfurfurylimine and 1-octanamine, N-(2-thienylmethylene)] leads to single and aggregated nanoparticles of 2 to 6 nm size. The samples contain highly crystalline nanoparticles of the βCO-(BEDT-TTF)2I3 phase, confirmed by XRD. Temperature dependent resistance and magnetic susceptibility studies evidence the superconducting transition characteristics of the βCO-(BEDT-TTF)2I3 phase. The I-V curve of a single nanoparticle aggregate, measured using AFM, exhibits an expected semiconductor-like behaviour. Thermoelectric studies led to a ZT of 1.47 × 10-3 at 300 K. © The Royal Society of Chemistry 2016.

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2015

Cationic Liposome- Multi-Walled Carbon Nanotubes Hybrids for Dual siPLK1 and Doxorubicin Delivery in Vitro
Pereira S., Lee J., Rubio N., Hassan H.A.F.M., Suffian I.B.M., Wang J.T.W., Klippstein R., Ballesteros B., Al-Jamal W.T., Al-Jamal K.T. Pharmaceutical Research; 32 (10): 3293 - 3308. 2015. 10.1007/s11095-015-1707-1. IF: 3.420

Purpose: To formulate f-MWNTs-cationic liposome hybrids for the simultaneous delivery of siPLK1 and doxorubicin to cancer cells. Method: f-MWNTs-cationic liposome hybrids were prepared by the thin film hydration method where the lipid film was hydrated with 100 μg/ml or 1 mg/ml of ox-MWNTs-NH3 + or MWNTs-NH3 + in 5% dextrose. siRNA complexation and protection ability was determined by agarose gel electrophoresis. f-MWNTs and liposome interaction was evaluated using Nile Red (NR) fluorescence spectroscopy. Cellular uptake in A549 cells was assessed by flow cytometry. Silencing of target proteins was determined by Luciferase and MTT assays. Sub-G1 analysis was performed to evaluate apoptosis following co-delivery of siPLK1 and Doxorubicin (Dox). Results: Zeta potential and siRNA complexation profile obtained for all hybrids were comparable to those achieved with cationic liposomes. ox-MWNTs-NH3 + showed greater extent of interaction with cationic liposomes compared to MWNTs-NH3 +. ox-MWNTs-NH3 + was able to protect siRNA from nuclease-mediated degradation. Enhanced cellular uptake of both the carrier and loaded siRNA in A549 cell, were observed for this hybrid compared to the liposomal carrier. A synergistic pro-apoptotic effect was obtained when siPLK1 silencing was combined with doxorubicin treatment for the hybrid:siRNA complexes compared to the lipoplexes, in A549 cells in vitro. Conclusions: f-MWNTs-cationic liposome hybrid designed in this study can serve as a potential vehicle for the co-delivery of siRNA and cytotoxic drugs to cancer cells in vitro. © 2015 The Author(s).

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Quantitative monitoring of the removal of non-encapsulated material external to filled carbon nanotube samples
Martincic M., Pach E., Ballesteros B., Tobias G. Physical Chemistry Chemical Physics; 17 (47): 31662 - 31669. 2015. 10.1039/c5cp04664e. IF: 4.493

The endohedral functionalization of carbon nanotubes with both organic and inorganic materials allows the development of tailored functional hybrids whose properties benefit from the synergistic effects of the constituent compounds. Bulk filling of carbon nanotubes (CNTs) results in samples that contain a large amount of non-encapsulated material external to the CNTs. The presence of the external material is detrimental to the processing and application of the resulting hybrids. Here we introduce the use of UV-Vis spectroscopy to monitor the cleaning process, i.e. the elimination of non-encapsulated compounds. Chrome azurol S has been employed to assess the bulk removal of external samarium(iii) chloride from filled single-walled carbon nanotubes. Chrome azurol S is of interest since it can be used to quantify a large variety of materials in a fast, accurate and reliable manner. The parameters that control the cleaning process have been optimized, including the time, temperature, volume and sonication, to achieve a fast and complete removal of the external material. © 2015 the Owner Societies.

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Spin density wave and superconducting properties of nanoparticle organic conductor assemblies
Winter L.E., Steven E., Brooks J.S., Benjamin S., Park J.-H., De Caro D., Faulmann C., Valade L., Jacob K., Chtioui I., Ballesteros B., Fraxedas J. Physical Review B - Condensed Matter and Materials Physics; 91 (3, 035437) 2015. 10.1103/PhysRevB.91.035437. IF: 3.736

The magnetic susceptibilities of nanoparticle assemblies of two Bechgaard salts (TMTSF)2PF6 and (TMTSF)2ClO4, have been studied vs temperature and magnetic field. In the bulk these materials exhibit a spin density wave formation (TSDW=12K) and superconductivity (Tc=1.2K), respectively. We show from inductive (susceptibility) measurements that the nanoparticle assemblies exhibit ground-state phase transitions similar to those of randomly oriented polycrystalline samples of the parent materials. Resistivity and diamagnetic shielding measurements yield additional information on the functional nanoparticle structure in terms of stoichiometric and nonstoichiometric composition. © 2015 American Physical Society.

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The interaction of carbon nanotubes with an in vitro blood-brain barrier model and mouse brain in vivo
Kafa H., Wang J.T.W., Rubio N., Venner K., Anderson G., Pach E., Ballesteros B., Preston J.E., Abbott N.J., Al-Jamal K.T. Biomaterials; 53: 437 - 452. 2015. 10.1016/j.biomaterials.2015.02.083. IF: 8.557

Carbon nanotubes (CNTs) are a novel nanocarriers with interesting physical and chemical properties. Here we investigate the ability of amino-functionalized multi-walled carbon nanotubes (MWNTs-NH3+) to cross the Blood-Brain Barrier (BBB) invitro using a co-culture BBB model comprising primary porcine brain endothelial cells (PBEC) and primary rat astrocytes, and invivo following a systemic administration of radiolabelled f-MWNTs. Transmission Electron microscopy (TEM) confirmed that MWNTs-NH3+ crossed the PBEC monolayer via energy-dependent transcytosis. MWNTs-NH3+ were observed within endocytic vesicles and multi-vesicular bodies after 4 and 24h. A complete crossing of the invitro BBB model was observed after 48h, which was further confirmed by the presence of MWNTs-NH3+ within the astrocytes. MWNT-NH3+ that crossed the PBEC layer was quantitatively assessed using radioactive tracers. A maximum transport of 13.0±1.1% after 72h was achieved using the co-culture model. f-MWNT exhibited significant brain uptake (1.1±0.3% injected dose/g) at 5min after intravenous injection in mice, after whole body perfusion with heparinized saline. Capillary depletion confirmed presence of f-MWNT in both brain capillaries and parenchyma fractions. These results could pave the way for use of CNTs as nanocarriers for delivery of drugs and biologics to the brain, after systemic administration. © 2015 The Authors.

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Vertically Aligned ZnO/Inx S y Core-Shell Nanorods for High Efficient Dye-Sensitized Solar Cells
Gonzalez-Valls I., Ballesteros B., Lira-Cantu M. Nano; 10 (7, 1550103) 2015. 10.1142/S1793292015501039. IF: 1.090

Innovative vertically aligned ZnO/InxSy nanorod (NR) electrodes were prepared by successive ion layer adsorption and reaction (SILAR) technique. The InxSy shell layer was deposited on top of ZnO NR electrodes of two different lengths, ~1.6 μm and ~3.2 μm. Two sulfur contents on the InxSy shell layer with different layer thicknesses were analyzed. These electrodes were fully characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction spectroscopy (XRD), Energy-dispersive x-ray spectroscopy (EDS), Infrared spectroscopy (FT-IR), x-ray photoelectron spectroscopy (XPS) and ultraviolet photoemission spectroscopy (UPS) and then applied in dye-sensitized solar cells (DSC). Power conversion efficiency of 2.32% was observed when a low-sulfur content InxSy shell layer was applied in comparison to the stoichiometric In2S3 shell layer (0.21%) or the bare ZnO NRs (0.87%). In the case of low sulfur content, a shell layer of In(OH)xSy or/and In(OH)3 is formed as observed by the presence of-OH observed by FTIR analyses. The presence of higher amounts of hydroxide groups modifies the bandgap and work function of the InxSy shell and facilitates dye adsorption, increasing the final solar cell performance. © 2015 World Scientific Publishing Company. © 2015 World Scientific Publishing Company.

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2014

Covalent functionalization of multi-walled carbon nanotubes with a gadolinium chelate for efficient T1-weighted magnetic resonance imaging
Marangon, I.; Ménard-Moyon, C.; Kolosnjaj-Tabi, J.; Béoutis, M.L.; Lartigue, L.; Alloyeau, D.; Pach, E.; Ballesteros, B.; Autret, G.; Ninjbadgar, T.; Brougham, D.F.; Bianco, A.; Gazeau, F. Advanced Functional Materials; 24 (45): 7173 - 7186. 2014. 10.1002/adfm.201402234. IF: 10.439
Fieldlike and antidamping spin-orbit torques in as-grown and annealed Ta/CoFeB/MgO layers
Avci, C.O.; Garello, K.; Nistor, C.; Godey, S.; Ballesteros, B.; Mugarza, A.; Barla, A.; Valvidares, M.; Pellegrin, E.; Ghosh, A.; Miron, I.M.; Boulle, O.; Auffret, S.; Gaudin, G.; Gambardella, P. Physical Review B - Condensed Matter and Materials Physics; 89: 21 - 214419. 2014. 10.1103/PhysRevB.89.214419. IF: 3.664
Four Molecular Superconductors Isolated as Nanoparticles
de Caro, D; Faulmann, C; Valade, L; Jacob, K; Chtioui, I; Foulal, S; de Caro, P; Bergez-Lacoste, M; Fraxedas, J; Ballesteros, B; Brooks, J.S.; Steven, E; Winter, L.E. European Journal of Inorganic Chemistry; 2014 (24): 4010 - 4016. 2014. 10.1002/ejic.201402007. IF: 2.965
Production of water-soluble few-layer graphene mesosheets by dry milling with hydrophobic drug
Rubio, N.; Serra-Maia, R.; Kafa, H.; Mei, K.-C.; Al-Jamal, K.T.; Luckhurst, W.; Zloh, M.; Festy, F.; Richardson, J.P.; Naglik, J.R.; Pach, E.; Ballesteros, B. Langmuir : the ACS journal of surfaces and colloids; 30 (49): 14999 - 15008. 2014. 10.1021/la5038475. IF: 4.384
Synthesis of PbI2 single-layered inorganic nanotubes encapsulated within carbon nanotubes
Cabana, L.; Ballesteros, B.; Batista, E.; Magén, C.; Arenal, R.; Orõ-Solé, J.; Rurali, R.; Tobias, G. Advanced Materials; 26 (13): 2016 - 2021. 2014. 10.1002/adma.201305169. IF: 15.409
Ultraviolet pulsed laser irradiation of multi-walled carbon nanotubes in nitrogen atmosphere
Pérez Del Pino, Á.; György, E.; Cabana, L.; Ballesteros, B.; Tobias, G. Journal of Applied Physics; 2014. 10.1063/1.4864776. IF: 2.185

2013

Effect of laser radiation on multi-wall carbon nanotubes: Study of shell structure and immobilization process
György, E.; Pérez Del Pino, A.; Roqueta, J.; Ballesteros, B.; Cabana, L.; Tobias, G. Journal of Nanoparticle Research; 15 2013. 10.1007/s11051-013-1852-6. IF: 2.175
Fractal porosity in metals synthesized by a simple combustion reaction
Gómez-Romero, P.; Fraile, J.; Ballesteros, B. RSC Advances; 3: 2351 - 2354. 2013. 10.1039/c2ra22441k. IF: 2.562
Magnetization reversal behaviour of planar nanowire arrays of Fe
Arora, S.K.; ODowd, B.J.; Thakur, P.; Brookes, N.B.; Ballesteros, B.; Gambardella, P.; Shvets, I.V. Current Nanoscience; 9 (5): 609 - 614. 2013. 10.2174/15734137113099990069. IF: 1.356
Observation of out-of-plane unidirectional anisotropy in MgO-capped planar nanowire arrays of Fe
Arora, S.K.; ODowd, B.J.; Polishchuk, D.M.; Tovstolytkin, A.I.; Thakur, P.; Brookes, N.B.; Ballesteros, B.; Gambardella, P.; Shvets, I.V. Journal of Applied Physics; 114 (13) 2013. 10.1063/1.4823514. IF: 2.210

2012

Deposition of functionalized single wall carbon nanotubes through matrix assisted pulsed laser evaporation
Pérez Del Pino, Á.; György, E.; Cabana, L.; Ballesteros, B.; Tobias, G. Carbon; 50: 4450 - 4458. 2012. 10.1016/j.carbon.2012.05.023.
Magnetic properties of planar nanowire arrays of Co fabricated on oxidized step-bunched silicon templates
Arora, S.K. ; O'Dowd, B.J.; Ballesteros, B.; Gambardella, P. ; Shvets, I.V. Nanotechnology; 23: 235702. 2012. .
Structural and magnetic properties of planar nanowire arrays of Co grown on oxidized vicinal silicon (111) templates
Arora, S.K.; O'Dowd, B.J.; Nistor, C.; Balashov, T.; Ballesteros, B. ; Lodi Rizzini, A.; Kavich, J.J.; Dhesi, S.S.; Gambardella, P. ; Shvets, I.V. Journal of Applied Physics; 111: 07E342. 2012. .
Synthesis and characterization of CdSe/ZnS core-shell quantum dots immobilized on solid substrates through laser irradiation
GyÃ¶rgy, E.; PÃ©rez Del Pino, A.; Roqueta, J.; Ballesteros, B.; Miguel, A.S.; Maycock, C.; Oliva, A.G. Physica Status Solidi (A) Applications and Materials; 209: 2201 - 2207. 2012. 10.1002/pssa.201127749.

2011

Heteroepitaxial orientation control of YSZ thin films by selective growth on SrO-, TiO2-terminated SrTiO3 crystal surfaces
Cavallaro, A.; Ballesteros, B.; Bachelet, R.; Santiso, J. CrystEngComm; 13: 1625 - 1631. 2011. 10.1039/c0ce00606h.
One-dimensional composites based on single walled carbon nanotubes and poly(o-phenylenediamine)
Baibarac, M.; Baltog, I.; Scocioreanu, M.; Ballesteros, B.; Mevellec, J.Y.; Lefrant, S. Synthetic Metals; 161: 2344 - 2354. 2011. 10.1016/j.synthmet.2011.09.001.
Orbital moment anisotropy of Pt/Co/AlOx heterostructures with strong Rashba interaction
Nistor, C.; Balashov, T. ; Kavich, J. J.; Lodi Rizzini, A. ; Ballesteros, B. ; Gaudin, G. ; Auffret, S.; Rodmacq, B.; Dhesi, S.S.; Gambardella, P. Physical Review B; 2011. .
Polymer electrolyte membrane fuel cells | Pilas de combustible de membrana polimérica
Asensio, J.A.; Peña, J.; Pérez-Coll, D.; Ruiz-Morales, J.C.; Marrero-Lopez, D.; Nuñez, P.; Ballesteros, B.; Canales-Vazquez, J.; Borrós, S.; Gómez-Romero, P. Afinidad; 68: 246 - 258. 2011. .
Sidewall functionalisation of carbon nanotubes by addition of diarylcarbene derivatives
Luksirikul, P.; Ballesteros, B.; Tobias, G.; Moloney, M.G.; Green, M.L.H. Journal of Materials Chemistry; 21: 19080 - 19085. 2011. 10.1039/c1jm13783b.
Synthesis and laser immobilization onto solid substrates of CdSe/ZnS core-shell quantum dots
György, E.; Pino, A.P.D.; Roqueta, J.; Ballesteros, B.; Miguel, A.S.; Maycock, C.D.; Oliva, A.G. Journal of Physical Chemistry C; 115: 15210 - 15216. 2011. 10.1021/jp203051b.
Synthesis and stabilization of subnanometric gold oxide nanoparticles on multiwalled carbon nanotubes and their catalytic activity
Alves, L.; Ballesteros, B.; Boronat, M.; Cabrero-Antonino, J.R.; Concepción, P.; Corma, A.; Correa-Duarte, M.A.; Mendoza, E. Journal of the American Chemical Society; 133: 10251 - 10261. 2011. 10.1021/ja202862k.
Synthesis conditions, light intensity and temperature effect on the performance of ZnO nanorods-based dye sensitized solar cells
Gonzalez-Valls, I.; Yu, Y.; Ballesteros, B.; Oro, J.; Lira-Cantu, M. Journal of Power Sources; 196: 6609 - 6621. 2011. 10.1016/j.jpowsour.2011.03.063.
Zinc oxide/carboxylic acid lamellar structures
Segovia, M.; Lemus, K.; Moreno, M.; Ana, M.A.S.; González, G.; Ballesteros, B.; Sotomayor, C.; Benavente, E. Materials Research Bulletin; 46: 2191 - 2195. 2011. 10.1016/j.materresbull.2011.06.040.

2010

Carbon nanocapsules: Blocking materials inside carbon nanotubes
Tobias, G.; Ballesteros, B.; Green, M.L.H. Physica Status Solidi (C) Current Topics in Solid State Physics; 7: 2739 - 2742. 2010. 10.1002/pssc.200983823.
Filled and glycosylated carbon nanotubes for in vivo radioemitter localization and imaging
You Hong, S.; Tobias, G.; Al-Jamal, K.T.; Ballesteros, B.; Ali-Boucetta, H.; Lozano-Perez, S.; Nellist, P.D.; Sim, R.B.; Finucane, C.; Mather, S.J.; Green, M.L.H.; Kostarelos, K.; Davis, B.G. Nature Materials; 2010. .
pH-triggered release of materials from single-walled carbon nanotubes using dimethylamino-functionalized fullerenes as removable "corks"
Luksirikul, P.; Ballesteros, B.; Tobias, G.; Moloney, M.G.; Green, M.L.H. Carbon; 48: 1912 - 1917. 2010. 10.1016/j.carbon.2010.01.053.

2009

Steam purification for the removal of graphitic shells coating catalytic particles and the shortening of single-walled carbon nanotubes
B. Ballesteros; G. Tobias; L. Shao; E. Pellicer; E. Mendoza; M.L.H. Green Small; 4: 1501 - 1506. 2009. 10.1002/smll.200701283.

2006

Ionic and electronic conductivity of 5% Ca-Doped GdNbO4
Haugsrud, R.; Ballesteros, B.; Lira-Cantú, M.; Norby, T. Journal of the Electrochemical Society; 153: J87 - J90. 2006. 10.1149/1.2203933.