Additive-free Noble Metal Nanoparticles: The Synthesis And Applications

Metal nanoparticles have been extensively explored due to their unique physical and chemical properties. Among the various metal nanoparticles, noble metal nanoparticles have attracted significant attention because of their fascinating performance. For example, noble metal nanoparticles have been widely studied in the fields of catalysis, electronics and spectroscopy etc. Nowadays, ―green chemistry‖ has attracted more and more attentions along with development of economy and society. Green and environmental friendly synthetic methods are more coincident with the requirements of the public. Chemical reduction is the conventional route to synthesize noble metal nanoparticles, however, the synthetic process can’t dispense with the extra addition of additives. To meet the command of green chemistry, we employed additive-free irradiation method to fabricate noble metal nanoparticles and investigated their applications. The main research work are as follows:(a) Additive-free gold nanoparticles were successfully synthesized through gamma ray irradiation in aqueous solution using HAu Cl4 as precursor. The obtained gold nanoparticles were characterized by SEM, XRD and UV-vis spectrophotometer, and the size and morphology of gold nanoparticles were optimized by regulating the concentration of HAu Cl4 and the dose of irradiation. The electrocatalytic performance of gold nanoparticles for the detection of glucose and dopamine were demonstrated, and the experiment results showed that the obtained gold nanoparticles modified glass carbon electrode displayed superior electrochemical property, which exhibited high sensitivity and excellent stability and reproducibility.(b) Silver nanoparticles were synthesized in the same way of gamma irradiation from Ag NO3 aqueous solution. The surface enhanced Raman scattering activity of obtained gold and silver nanoparticles were investigated simultaneously. Firstly, SERS substrate were fabricated with the gold and silver nanoparticles respectively. Then, rodamine 6G was employed as probe molecules and Raman spectra were collected in liquid test way. The results displayed that the detection limit of gold and silver nanoparticles were 1 × 10-7 M and 1 × 10-9 M, respectively. The substrates not only had high sensitivity,but also showed excellent stability and reproducibility. For the random100 points, all points exhibited clear SERS signals of rodamine 6G and the relative standard deviation of the intensities of main characteristic peaks were less than 20%.(c) In situ SERS detection from siver nanoparticles obtaind from the irradiation of silver oxide nanoparticles were investigated. First, silver oxide nanoparticles were synthesized from wet chemical routes. Then, self assembly method was used for the fabrication of SERS substrate. Last, Raman spectra were collected employing rodamine 6G and 4-mercaptobenzoic acid as probe molecules. Obviously, the Raman spectra of guest molecules became more evident and the intensities of characteristic peaks increased with the accumulation of time, and the peaks changed to be stable when the time accumulated to a certain degree. SERS mapping was conducted after time accumulation, which further demonstrated the uniformity of the substrate.The above results show that the noble metal nanoparticles obtaied through irradiation methods reveal superior electrochemical property as well as excellent SERS activity. As a green and environmental friendly route, irradiation synthesis is promising to fabricate additive-free materials with a wide range of applications.