Colloidal suspension of CdS

Fig. 9.7. Dark current as a function of applied electrode potential at a range of rotation speeds for a 5 mol m-J colloidal suspension of CdS ( ), 4s-, ( ), 16s-1, (A), 36s-1.

Fig. 9.8. Typical plot of mass transport limited dark current (iD)i. versus at 1,2 for a 5 mol itT colloidal suspension of CdS. Electrode radius = 2x lO-3 m.

The colloidal suspensions of Cd-Se quantum dots of increasing size from left to right are shown in Figure 1. 

Steady state photoelectrochemical behaviour of colloidal CdS For the purposes of the studies reported here, the photocurrent was taken to be the total current recorded at the ORDE from an illuminated colloidal dispersion of CdS minus the current recorded under identical condition from the same dispersion in the dark. In both studies, the photocurrents generated by CdS particles illuminated at the ORDE exhibited a wavelength dependence (action spectrum) identical to the absorption spectrum of colloidal and bulk CdS [166,168], unambiguously indicating that the observed photocurrent is due entirely to ultra-band gap photoexcited conduction band electrons. However, it should be noted that, unless stated otherwise (e.g. the action spectrum experiments), the particle suspensions of both studies were usually irradiated with white light from a 250 W quartz iodine projector lamp to maximise the photocurrents observed. 

Nanoparticles are particles with diameters smaller than 100 nm [16]. Examples include colloidal suspensions, particles of metals (An), and semiconductors (CdS, Xi02). Their properties differ from those of the corresponding bulk making them attractive for novel technological applications. Giant molecules and proteins can also be included in this category. 

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