PDF Publication Title:
Text from PDF Page: 007
Figure 5. The different steps that occurred in the preparation of Au NPs. on the synthesis of Au NPs. The effect of the pH on the synthesis was established by a UV-visible spectropho- tometer. The authors have found that at high pH, curcu- min reacted totally since the absorption peak of curcumin was absent and a peak around 550 nm, relative to the Au NPs, was obtained. Nevertheless, at pH 4, 7, and 10, the absorption peak of curcumin at 425 nm was remarkable as obtained in the UV-visible spectra. This study proved the role of curcumin at high pH as an electron donor, inducing the reduction of Au3+ to Au0. Meaning that, at low pH, the curcumin is kept unreacted and inhibits the formation of Au NPs (Figure 6). Nonetheless, El Kurdi et al. have confirmed the role of curcumin as a reducing agent in acidic, neutral, and basic media in the presence of cetyltrimethylammonium bromide (CTAB) (65). The authors have tested the ability of curcumin to reduce Au3+ to Au0 at pH 4, 7, 8, 9, 11, and 13. In contrast to the results obtained with Al by Shehab et al., Au NPs were obtained at all pHs. However, different shapes and sizes were obtained. Using curcu- min as a reducing agent and cetyltrimethylammonium bromide as a stabilizing agent has enhanced the pro- duction of Au NPs at different pHs. The authors have verified the production of gold nanoparticles through the color change of the solution. In fact, after 24 h and at 45°C, the solution turned from orange to brown at pH 4, 7, 8, 9, and 11. Hence, the big difference was occurred at pH 13, when the solution color turned from orange to dark red. This difference in the color was attributed to the different shapes obtained, where at pH 13 nanoparticles in nanowires shape were obtained, and for the other pH, spherical nanoparticles were formed. This difference in the results between Al Shehab et al. and El Kurdi et al. could be attributed to the type of sur- factant present in the solution. Therefore, the study established by El Kurdi et al. enhances the activity of cur- cumin as a reducing agent in acidic, neutral, and basic media. Moreover, additional work was done by Moussawi et al. aims to produce Au NPs using CTAB and curcumin at pH equal to 9.2 (66). In this work, the authors have proved the role of curcumin as a secondary reducing agent to improve the gold nanoparticles formation in a rod shape. It was found that when adding curcumin and silver nitrate to CTAB capped Au NPs seed, nanorods in high yield were formed. According to Moussawi et al., the above procedure was simple, decreased the suscep- tibility of impurities, and enhances the reproducibility of the product distribution. However, nanorods were GREEN CHEMISTRY LETTERS AND REVIEWS 479 Figure 6. Effect of pH on curcumin reaction to reduce Au3+ to Au0.PDF Image | Curcumin as a novel agent for metallic nanoparticles
PDF Search Title:
Curcumin as a novel agent for metallic nanoparticlesOriginal File Name Searched:
Curcumin-nanoparticles.pdfDIY PDF Search: Google It | Yahoo | Bing
CO2 Organic Rankine Cycle Experimenter Platform The supercritical CO2 phase change system is both a heat pump and organic rankine cycle which can be used for those purposes and as a supercritical extractor for advanced subcritical and supercritical extraction technology. Uses include producing nanoparticles, precious metal CO2 extraction, lithium battery recycling, and other applications... More Info
Heat Pumps CO2 ORC Heat Pump System Platform More Info
CONTACT TEL: 608-238-6001 Email: greg@infinityturbine.com (Standard Web Page)