Thus, our results showed that it may be possible to achieve better size distribution control of the nanoparticles and good dispersity by selecting the appropriate reductant and stabilizer from various biological materials. In conclusion, the AuNPs formed in the KGM solution could be stabilized by a combination of gold-hydroxyl interaction and the steric stabilization owing to the molecular-scale entanglement of the polysaccharide. Catalytic properties Transition metal nanoparticles are attractive to use as catalysts due to their high surface-to-volume ratio compared to bulk catalytic materials. To date, the use of metal nanoparticles synthesized with polysaccharide

is very limited. Here, our TEM images above showed that the gold nanoparticles are nearly spherical in shape and are composed of numerous (100) and (111) planes with corners and edges at the interfaces of these facets. Hence, the as-prepared gold nanoparticles are expected learn more to be catalytically active. To investigate their catalytic activity, the reduction of 4-NP to 4-AP by NaBH4 was selected as a model system. It is well known that the absorption spectrum of a mixture of 4-NP and NaBH4 shows an absorption peak at 400 nm corresponding to the formation of an intermediate 4-nitrophenolate ion. Thus, the reaction process can be monitored by CB-839 monitoring the changes find protocol in the absorption

spectra of the 4-nitrophenolate ion at 400 nm. In a control experiment without AuNP addition, the absorbance at 400 nm did not change with time, indicating that no reduction of 4-NP occurred in the absence of AuNPs. Immediately after addition

of nanoparticles, there was a remarkable decrease in the intensity of the absorption peak at 400 nm, and at the same Edoxaban time, a new peak at 298 nm appeared indicating the formation of reduction product, 4-AP. Figure  8a shows time-dependent absorption spectra of the reduction with the obtained gold nanoparticles. The results showed that the KGM-capped gold nanoparticles can successfully catalyze the reduction reaction. It could be observed that the reaction was almost completed within 600 s in the presence of NaBH4 (Figure  8a). Since the concentration of sodium borohydride far exceeds the concentration of 4-NP, the reduction rate can be assumed to be independent of the borohydride concentration. In this context, a pseudo-first-order rate could be used to evaluate the kinetic reaction rate of the current catalytic reaction. Figure  8b shows the plot of ln A t /A 0 and A t /A 0 versus time. ln A t /A 0 decreased linearly with reaction time, indicating that the reduction reaction follows first-order kinetics. The first-order rate constant was calculated to be 6.03 × 10-3 s-1, and this value shows that the AuNPs prepared here with KGM possess better catalytic activity compared to other polysaccharides and some extracts (Table  1).