The Effect of the Adsorption of Substituted Phenols on the Dark and Photoconductivity of Zinc Oxide

Abstract

One of the most active areas of present day research is in the area of heterogeneous catalysis. These studies are usually directed toward characterizing the changes which take place in the absorbate (that which is absorbed), or characterizing the changes which take place in the catalysis. The study of an absorbate on the surface of a catalysis is usually carried out using spectroscopic methods (1-3). Eischens (1) has studied the infrared spectrum of hydrogen chemisorbed on zinc oxide and has found evidence of new bands at 2.86u and 5.85u, which were proposed to be due to the oxygen-hydrogen stretching vibration of the OH group and the zinc-hydrogen stretching vibration of the ZnH or (ZnH)+ group, respectively. Zeitlin (2) has done work with o-nitrophenol adsorbed on alkaline earth oxides. A bathochromic shift in the UV maxima of o-nitrophenol was found. Terenin (3) reviews the work being done in the area of spectral studies of adsorbed molecules. The study of the changes that occur in the catalysis are being carried out by many investigators. One of the catalysis under study by these investigators is zinc oxide (4-22). Pure zinc oxide is a non-conductor; however, through various heating procedures zinc oxide may be transformed into a semiconductor that also shows varying degrees of photoconductivity. It has been shown that the electrical conductivity properties of zinc oxide is a function of the type and amount of gas molecules adsorbed on the zinc oxide surface (4,6,8,10,13,15,17). This present study attempts to characterize the effects the adsorption of substituted phenols have on the dark- and photoconductivity of pressed powder samples of zinc oxide.