Staff directory Lorenzo Vallan

Publications

2021

  • Functionalized carbon dots on TiO2 for perovskite photovoltaics and stable photoanodes for water splitting

    Ansón-Casaos A., Hernández-Ferrer J., Vallan L., Xie H., Lira-Cantú M., Benito A.M., Maser W.K. International Journal of Hydrogen Energy; 46 (22): 12180 - 12191. 2021. 10.1016/j.ijhydene.2020.03.077. IF: 5.816

    Various types of fluorescent carbon nanoparticles, often called carbon dots (CDs), are synthesized by different polycondensation methods: microwave irradiation, hydrothermal conditions or solution chemistry at ambient temperature with subsequent chemical functionalization. The CDs are deposited on TiO2 films to be probed as electron transport layers in perovskite photovoltaics and the anode for photoelectrochemical water splitting. Nitrogen CDs, which do not contain oxygen, lead to an increase of around 50 mV in the open circuit voltage of perovskite solar cells. All the CD types produce an improved photocurrent in water splitting, particularly CDs that are functionalized with thiol groups and butyl chains. It is demonstrated that the modified electrode is stable under continuous operation. Other electrochemical characteristics of the electrode, such as the voltammogram shape, onset potentials and open circuit potentials, remain nearly unchanged upon the deposition of CDs. Only the incident photon to current conversion efficiency improves clearly, extending the absorption range by around 20 nm towards longer wavelengths. This study provides new data about mechanisms and electrode arrangements for improving the performance of n-type semiconductors in photovoltaic cells and photoelectrochemical hydrogen production. © 2020 Hydrogen Energy Publications LLC


2020

  • 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.