Articles written in Journal of Chemical Sciences

    • CdSe-SnO2 coupled semiconductor thin films: Electrochemical and photoelectrochemical studies

      Chouhaid Nasr Surat Hotchandani Prashant V Kamat

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      The coupled OTE/SnO2/CdSe electrodes have been prepared by sequential deposition of SnO2 and CdSe colloidal films onto an optically transparent electrode (OTE), and their electrochemical and photoelectrochemical properties have been studied. It is observed that coupling SnO2 film with CdSe particles has extended its photoresponse into the visible. The incident photon-to-photocurrent conversion efficiency (IPCE) for CdSe film which is doubled when coupled with SnO2 film, shows a better charge separation in the coupled film. The cyclic voltammetric results of [Fe(CN)6]3−/4− with OTE, OTE/CdSe and OTE/SnO2/CdSe electrodes suggest that the coupling of CdSe with SnO2 creates an energy barrier that hinders electron flow from SnO2 to CdSe and into the electrolyte. Photocurrent stability of the cell employing OTE/SnO2/CdSe electrode has been improved by increasing the thickness of SnO2 particulate film. The photoelectrochemical performance of the cell has been evaluated and a net conversion efficiency of 2.25% has been obtained

    • Capped semiconductor colloids: Synthesis and photochemistry of CdS capped SnO2 nanocrystallites

      Robert Kennedy Ignacio Martini Greg Hartland Prashant V Kamat

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      Cds-capped SnO2 (CdS@SnO2) and SiO2 (CdS@SiO2) colloids of 50–80 Å in diameter have been prepared in aqueous medium. Significant quenching of CdS emission is observed in the CdS@SnO2 system as the electrons are injected from the excited CdS shell into the SnO2 core. Photoinduced charge separation in this system also results in transient bleaching in the 450 nm region. Picosecond laser flash photolysis studies of composite semiconductor nanoclusters that highlight the effect of the metal oxide core on the photophysical properties of the outer CdS shell are described.

    • Glutathione-capped gold nanoclusters: photoinduced energy transfer and singlet oxygen generation


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      Glutathione-capped gold clusters prepared in an aqueous medium are known to exhibit excellent photosensitizing properties. We have now successfully transferred these gold clusters in an organic medium while retaining all the characteristic excited state properties. These gold clusters can be further modified with organic ligands such as 2-Phenylethanethiol (PET). The gold clusters in organic medium exhibit enhanced emission yield (Φf=0.15) compared to that in an aqueous medium (Φf=0.08). The excited state lifetimesof 3.7 μs (untreated) and 1.5 μs (PET treated) in toluene are also greater than the lifetime observed in aqueous solution (0.77 μs). By employing laser flash photolysis we are able to induce triplet energy transfer to β-carotene and oxygen. A singlet oxygen generation with the efficiency of 13% was observed in these experiments. The excited state properties of glutathione-capped gold clusters further shows its importance as a photosensitizer in light energy conversion and biomedical applications.

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