Improving the Efficiency of Photocatalytic Transformations

It has been shown that the photocatalytic electron transfer processes at the semiconductor interface can be greatly enhanced by depositing a noble metal on the semiconductor particle [175-179]. The photogenerated holes are capable of oxidizing thiocyanate ions at the semiconductor interface [180]. The thiocyanate radicals ((SCN)2 ) generated in the photocatalytic oxidation can be conveniently monitored from its absorbance at 480 run [180-183]. 

By employing a 337 nm pulsed laser as the excitation source for exciting Ti02 colloids and initiating the redox reactions at the interface one can monitor the interfacial hole transfer process (reactions (1) and (2)). 

On the other hand, when low concentrations of metal are used to cap the semiconductor core we can expect the outer layer to be discontinuous. Such a configuration of core shell particles (i.e. small metal islands deposited on the Ti02 core) provides a favorable geometry for facilitating the interfacial charge transfer under UV irradiation. It should be noted that, a new band appears at 390 nm in the case of Ti02/Au nanoparticles as the transient absorption corresponding to (SCN)2  

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