-Eosin is an organic water soluble bright red dye used in many applications in biological science, medical science, textile dying, ink manufacturing, etc. Its reduced form is colourless and hence its reduction can be monitored by following the decrease in its absorption peak intensity. Eosin absorbs green light and therefore decrease in eosin absorbance was followed at 535 nm wavelength near its absorption maximum. In the absence of catalysts, one does not observe, in the experimental time scale, the reduction of eosin in aqueous solution by sodium borohydride. However, the rate of reduction reaction becomes appreciably faster in the presence of gold particles. Gold particles here act as catalysts. Depending on the catalysing particle size and concentration (Table 1), the rate of reduction reaction varies though all the sets of particles prepared here have the same quantity of total gold (1×10-4 M).
+Eosin is an organic water soluble bright red dye used in many applications in biological science, medical science, textile dying, ink manufacturing, etc. Its reduced form is colourless and hence its reduction can be monitored by following the decrease in its absorption peak intensity. Eosin absorbs green light and therefore decrease in eosin absorbance was followed at 535 nm wavelength near its absorption maximum. In the absence of catalysts, one does not observe, in the experimental time scale, the reduction of eosin in aqueous solution by sodium borohydride. However, the rate of reduction reaction becomes appreciably faster in the presence of gold particles. Gold particles here act as catalysts. Depending on the catalysing particle size and concentration (Table 1), the rate of reduction reaction varies though all the sets of particles prepared here have the same quantity of total gold (1×10-4 M).A pseudo-first order kinetics with respect to eosin, i.e., log (At - AAu) vs. time could be used in this case, where At stands for absorbance at any time t and AAu stands for absorbance of aqueous gold particle system before the addition of dye. Thus one can determine the values of pseudo-first-order rate constants (k) and corresponding correlation coefficients from these plots.