Kasem K Kasem
Articles written in Bulletin of Materials Science
Volume 31 Issue 7 December 2008 pp 925-929 Nanomatter
Colloidal Cu2O solutions were used to explore photonic activities at the semiconductor/electrolyte interface. Fluorescence spectroscopic studies were performed on Cu2O colloidal particles modified with some conjugated organic monomers such as 2-amino-phenyl pyrrole (2-APPy), tri-phenyl amine (TPA), or 2-thionyl pyrrole (2-Th-Py) to investigate the quantum absorbance efficiency at this inorganic/organic interface (IOI). Our study shows that colloidal 𝑝-type Cu2O possesses a bandgap with direct transition of ≈ 2.2 eV and indirect transition of 1.85 eV. The recorded rates of charge injection into colloidal Cu2O, 𝑘ct, were 2.31 × 109 s-1, 5.05 × 108 s-1, and 7.22 × 108 s-1 for 2-APPy, TPA and 2-Th-Py, respectively. The studied systems show more stability in colloidal form than in thin solid form. Results were interpreted using the optical and electrical parameters of the organic monomer such as ionization potential (IP), electron affinity (EA) and energy bandgap (Eg), and the barrier height at the IOI interface. Stability of the colloidal system is attributed to the physical dimensions of the photoactive system. The nano-colloidal particle offers a condition where its size is less than √𝐷𝑡.
Volume 38 Issue 2 April 2015 pp 303-308
Photoproduction of hydrogen was achieved by photolysis of aqueous suspensions of mixed TiO2/V2O5 or CdS/ZnS semiconductor (SC) nanoparticle in phosphate buffers containing [Fe(CN)6]4−. Manipulations of the band structure of the SC materials took place by either combining oxides/sulphides in binary mixtures or by modification of the SC surface with an organic semiconductor. Studies show that the bandgap of these mixed materials varied monotonically with the percent composition of the mixture. Furthermore, results show that maximum generation of hydrated electrons by [Fe(CN)6]4− occurred at pH 6. Mixtures of CdS/ZnS showed greater photoactivity than metal oxides TiO2/V2O5. On the other hand, surface-modified CdS or TiO2 gave much better photoreduction than the high percentage composite mixtures. The aqueous nanosystems used in these studies sustained their stability as indicated by the reproducibility of their photocatalytic activities.
Volume 43, 2020
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