Electron under visible light illumination

Based on their experimental results concerning ethanol and methanol photooxidation by Au/Ti02 composites under visible-light illumination, Tatsuma et al. (Tian and Tatsuma 2005) proposed a plasmon-induced charge separation scheme. They observed a surprising phenomenon, in which the photoelectrons were excited from Au nanoparticles and transferred to the CB of Ti02 (Wood et al. 2001 Subramanian et al. 2004). Meanwhile, the oxidized Au species accepted electrons from the donor molecules present in the solution to recover the charge balance. The process is illustrated in Fig. 16.23. 

Zhao et al. (2002) studied the photodestruction of sulforhodamine-B in Pt/Ti02 suspension under visible light illumination. The electrons excited from dye molecules were accepted by Pt islands. The accumulated electrons then react with 02 to form 02- and subsequently OH, which ultimately caused the self-destruction of the dye molecules. Photocatalytic destruction of oxalic acid (Iliev et al. 2006) and H2 generation (Sreethawong et al. 2006) from aqueous methanol solution were also promoted by platinizing Ti02. Under anoxic conditions, products from... 

An O2 molecule attached to the oxygen vacancy site (b) forms a peroxide 02 ion by coordination with the two ions, in accord with theoretical studies [113]. When one electron is transferred from 02 to one of the two oxidized ions by visible-light illumination, the corresponding O—coordination is broken, and a pair of 02 (B) and species are concomitantly formed as observed. On the other hand, adsorption of O2 at the five-coordinate site (a) may generate 02 (A) by one-electron transfer from to the adsorbed O2 molecule. The paramagnetic 02 (A) species appears to be inactive under visible-light illumination. 

Some dyes having visible light sensitivity can be used in photocatalytic systems as suitable materials to catch most of the energy available from sunlight. Under visible light illumination, the excited dyes can inject electrons into the CB of semiconductors to initiate the photocatalytic reactions (Latorre-Sanchez et al., 2012 Li et al., 2011). 

Illumination experiments with varying wavelength show that the observed electron transfer under visible light is caused by the formation of a charge transfer complex between the chlorophenol molecules and surface holes (Figure 4.13). This complex is found only with mixed-phase P25. Electrons are injected from the... 

In the late nineteenth century, as physics progressed rapidly, J. J. Thomson discovered the electron the invention of the electron microscope followed several decades later. Because the wavelength of the electron is shorter than the wavelength of visible light, much smaller objects can be resolved if they are illuminated with electrons. Electron microscopy has a number of practical difficulties, not least of which is the tendency of the electron beam to fry the sample. But ways were found to get around the problems, and after World War II electron microscopy came into its own. New subcellular structures were discovered Holes were seen in the nucleus, and double membranes detected around mitochondria (a cell s power plants). The same cell that looked so simple under a light microscope now looked much different. The same wonder that the early light microscopists felt when they saw the detailed structure of insects was again felt by twentieth-century scientists when they saw the complexities of the cell. 

---