Electrochemical synthesis of hexagonal hollow ZnO nanostructures

[EN] A simple and controllable one-step electrodeposition process is proposed in order to obtain ZnO nanotubes. Zinc oxide thin films were grown on fluorine-doped tin oxide by electrodeposition from an aqueous electrolyte containing zinc nitrate and potassium nitrate. Generally, in aqueous electrolytes ZnO is electrochemically deposited in the form of hexagonal nanocolumns. These nanocolumns grow perpendicularly to the substrate until reaching a maximum height of about 2 µm and then the perpendicular growth vanishes and the solid nanocolumns develop to hexagonal hollow structures. Several characteristics of the electrodeposited films such as thickness, morphology and crystalline structure were obtained as a function of the deposited charge. The evolution of the morphology of the electrodeposited layers as a function of time was monitored by Scanning Electron Microscopy. X-Ray Diffraction confirms that hexagonal nanotubes are preferentially oriented along the (002) direction.This work was supported by CONICYT (project 3130451), Ministerio de Economía y Competitividad (project ENE2013-46624-C4-4-R) and European Commission through NanoCISproject FP7-PEOPLE-2010-IRSES (ref. 269279).Abellan Rubio, MA.; Moya Forero, MM.; Marí, B. (2015). Electrochemical synthesis of hexagonal hollow ZnO nanostructures. International journal of current research. 7(3):13241-13245. http://hdl.handle.net/10251/81663S13241132457

Nanostructured hybrid ZnO thin films for energy conversion

We report on hybrid films based on ZnO/organic dye prepared by electrodeposition using tetrasulfonated copper phthalocyanines (TS-CuPc) and Eosin-Y (EoY). Both the morphology and porosity of hybrid ZnO films are highly dependent on the type of dyes used in the synthesis. High photosensitivity was observed for ZnO/EoY films, while a very weak photoresponse was obtained for ZnO/TS-CuPc films. Despite a higher absorption coefficient of TSCuPc than EoY, in ZnO/EoY hybrid films, the excited photoelectrons between the EoY levels can be extracted through ZnO, and the porosity of ZnO/EoY can also be controlled. © 2011 Moya et al.This study was supported by the Spanish Government through MCINN grant MAT2009-14625-C03-03, the Generalitat Valenciana through programme PROMETEO/2009/063, and the Fundacao para a Ciencia e a Tecnologia (Portugal). Thanks are due to Susie Pannell for critically reading the manuscript and providing invaluable suggestions.Moya Forero, MM.; ANURA SAMANTILLEKE; Mollar García, MA.; Marí Soucase, B. (2011). Nanostructured hybrid ZnO thin films for energy conversion. Nanoscale Research Letters. 6:384-389. https://doi.org/10.1186/1556-276X-6-384S3843896ZHENG, H., PAN, Y., & XIANG, X. (2007). Oxidation of acidic dye Eosin Y by the solar photo-Fenton processes. Journal of Hazardous Materials, 141(3), 457-464. doi:10.1016/j.jhazmat.2006.12.018Qazi, S. J. S., Rennie, A. R., Cockcroft, J. K., & Vickers, M. (2009). Use of wide-angle X-ray diffraction to measure shape and size of dispersed colloidal particles. Journal of Colloid and Interface Science, 338(1), 105-110. doi:10.1016/j.jcis.2009.06.00

PREPARACIÓN ELECTROQUÍMICA DE CAPAS NANOESTRUCTURADAS DE ZnO PARA APLICACIONES FOTOVOLTAICA

En esta tesis se centra en el estudio de capas delgadas basadas en óxido de zinc (ZnO) para aplicaciones fotovoltaicas, en concreto células solares sensibilizadas con colorante (DSSC). Se optimizaron los parámetros de crecimiento de estas nanoestructuras hibridas depositadas mediante la técnica de electrodeposición catódica para posteriormente desarrollar un dispositivo eficiente para la conversión de la luz. OBJETIVOS Los objetivos principales de la tesis son: - Establecer las condiciones de crecimiento de las películas híbridas de ZnO/colorante mediante su estudio morfológico, estructural, óptico y eléctrico. - Verificar la incorporación de diferentes colorantes como Eosin-Y, Fthalociania de cobre (Ts-CuPc) y N719 en la estructura del ZnO. - Implementación de una celda DSCC basada en estas películas híbridas para la conversión de la energía mediante el cálculo de eficiencia. ELEMENTOS DE LA METODOLOGÍA La técnica de depósito utilizada para la obtención de estos materiales híbridos es la electrodeposición catódica. Para el estudio y la optimización de estas películas se utilizaron diferentes técnicas de caracterización física mediante SEM, AFM, XRD, transmitancia, fotocorriente, etc. Y finalmente, estas películas se integraron en dispositivos DSSC. RESULTADOS LOGRADOS Los resultados obtenidos fueron los siguientes: - Optimización y caracterización del crecimiento de la película delgada de ZnO. Se observo que la estructura hexagonal del ZnO es modificable y altamente dependiente de la concentración tanto de los precursores como del disolvente en la disolución. Las películas con mejores propiedades cristalinas se obtuvieron a una temperatura de depósito de 80°C y a un potencial de -0,9 V. - Optimización y caracterización del crecimiento de películas delgadas de ZnO/híbridas usando distintos colorantes: Eosin-Y, Ts-CuPc y N719. Las propiedades eléctricas y físicas se pueden modificar variando las concentraciones de los colorantes. En el caso delMoya Forero, MM. (2012). PREPARACIÓN ELECTROQUÍMICA DE CAPAS NANOESTRUCTURADAS DE ZnO PARA APLICACIONES FOTOVOLTAICA [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/17322Palanci

Electrodeposition of hybrid ZnO/organic dye films

[EN] The viability of the electrodeposition as a suitable technique for preparing new porous hybrid materials has been tested in this paper. Hybrid ZnO films with two different organic dyes: Eosin-Y and Tetrasulphonated-Cu-phtalocyanine were prepared. Their physical and chemical properties as well as their dependence on the growth conditions were investigated. It is found that the type of dye has a big influence on the morphology and porosity of hybrid films. Open and connected pores are created in hybrid ZnO/Eosin-Y films while both open and closed pores coexist in hybrid ZnO/Tetrasulfonated-Cu-phthalocyanine. As one of the promising applications of hybrid materials is photovoltaic conversion of sunlight, photoelectrochemical characterization of hybrid films is also reported. Photocurrent generation owing to both contributions ZnO and Eosin-Y is observed in ZnO/Eosin-Y films but no photocurrent has been observed in ZnO/Tetrasulfonated-Cu-phthalocyanine films. SEM micrographs of hybrid ZnO films grown in aqueous bath; (Left) ZnO/Eosin-Y films grown at 70 degrees C, -0.9 V (Right) ZnO/Ts-CuPc films grown at 70 degrees C, -0.9 V.Moya Forero, MM.; Marí Soucase, B.; Mollar García, MA. (2011). Electrodeposition of hybrid ZnO/organic dye films. Physica status solidi (b). 8(6):1744-1748. doi:10.1002/j.tsf.201000095S174417488

Characterization and photoluminescence properties of some CaO, SrO and CaSrO2 phosphors co-doped with Eu3+ and alkali metal ions

CaO:Eu3+, M+ (Li+ or Na+ or K+ ), SrO:Eu3+and CaSrO2:Eu3+ powders were prepared by combustion synthesis method and the samples were further heated to 1000 C to improve the crystallinity of the materials. The structure and morphology of materials were examined by X-ray diffraction and scanning electron microscopy. The morphology of CaO:Eu3+ and co-doped with alkali metal ions powders was very similar. Small and coagulated particles of nearly cubical shapes with small size distribution having smooth and regular surface were formed. The surface morphology of SrO and CaSrO2 materials was not smooth and coagulated particles of irregular shapes with different sizes were observed. The characteristic emissions of Eu3+ had strong emission at 614 and 620 nm for 5 D0 ? 7 F2 with other weak transitions observed at 580, 592, 654, 705 nm for 5 D0 ? 7 Fn transitions where n = 0, 1, 3, 4 respectively in all host lattices. Photoluminescence intensity followed the order as in CaO > CaSrO2 > SrO lattices. A remarkable increase of photoluminescence intensity was observed by the co-doping of alkali metal ions particularly K+ ions in CaO:Eu3+.This work was supported by Spanish Government through MCINN Grant MAT2009-14625-C03-03. K.C. Singh acknowledges MEC for financial support (SAB2010-0019).Marí Soucase, B.; Singh, KC.; Moya Forero, MM.; Singh, I.; Om, H.; Chand, S. (2012). Characterization and photoluminescence properties of some CaO, SrO and CaSrO2 phosphors co-doped with Eu3+ and alkali metal ions. Optical Materials. 34:1267-1271. https://doi.org/10.1016/j.optmat.2012.01.032S126712713

Growth mechanism and morphology of ZnO/Eosin-Y hybrid films

Thin hybrid films of ZnO/eosin-Y were prepared by electrodeposition at -0.8 and -0.9 V in aqueous and non-aqueous baths at temperatures ranging from 40 to 90 °C with dye concentrations of 100 and 400 µmol·L-1 . The films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), and absorption spectroscopy. The films prepared in a non-aqueous bath were non-porous and did not adsorb dye molecules on their surface. However, the films grown in aqueous media were porous in nature and adsorbed dye during the deposition of ZnO. Preferential growth of the film along the (002) face was observed, and the highest crystallinity was achieved when the film was deposited at 60 °C. The maximum absorption was achieved for the films grown at 60 to 70 °C, a deposition potential of -0.9 V, and a dye concentration of 100 µmol·L-1 .The project was supported by the Spanish Government through MCINN Grant (MAT2009-14625-C03-03) and MEC Financial Fund (SAB2010-0019) for Singh, K.C.Marí Soucase, B.; Singh, KC.; Mollar García, MA.; Moya Forero, MM.; Rana, R. (2012). Growth mechanism and morphology of ZnO/Eosin-Y hybrid films. Wuli Xuebao. 28(1):251-256. https://doi.org/10.3866/PKU.WHXB201228251S25125628