Staff directory
Belén Ballesteros Pérez
CSIC Research Scientist and Unit Leader
belen.ballesteros(ELIMINAR)@icn2.cat
Electron Microscopy Unit
- ORCID: 0000-0002-1958-8911
Publications
2017
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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
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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.
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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.
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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
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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.
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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
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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.
2016
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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).
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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.
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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.
2015
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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-NH
3 +) 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.