The Synthesis Of Gold Nanorod With Binary Surfactants And Its Applications

Due to the tunable surface plasmon resonance(Longditudinal surface plasmon resonance,LSPR)peaks in near infrared region(NIR),gold nanorod(AuNR)has received extensive attention and research for its optical applications in numerous fields.Although seed-mediated growth method is the most popular one using cetyltrimethyl ammonium bromide(CTAB)as the cationic surfactant,even a trace amount of iodine impurities may result in the failure or low yield of AuNR.By introducing of the anionic surfactant sodium dodecyl benzene sulfonate(SDBS)into the growth solution of seed-mediated growth method,we obtain the cationic and anionic binary surfactants system.UV-Visible-NIR absorption spectroscopy(UV-Vis-NIR)and transmission electron microscope(TEM)were employed to investigate the morphology evolution of gold nanoparticles in the binary surfactants with different ratio.The system was verified to overcome the negative effects resultingfrom iodide ions.The possible reason is that binary surfactants play a more powerful protection that the reaction rate is greatly decreased so as to minimize the negative effects of iodide ions.Both of the conversion and morphology selectivity are above 95%under the optimum conditions.The endurance against iodide is enhanced with the increase of the CTAB/SDBS ratio,up to 30μM I~-with ratio of 0.025M/0.01M.The effects of the factors such as silver ion,ascorbic acid,pH,seed,temperature,concentration of surfactant have also been discussed comprehensively.It indicated that AuNR with broad LSPR peak and size can be synthesized vis adjusting pH vaule and seed.The role of binary surfactants serves both as template and stabilizer is confirmed by controlling temperature and concentration of growth solution.Moreover,other saturated anionic(SDS)can be selected as long as fulfill requirement of the solubility.Chiral anionic surfactant was utilized to prepare asymmetric gold nanorods,and it confirmed that the surfactants in the growth solution served as a template to guide the growth AuNR was confirmed.By replacing CTAB covered on AuNR with chitosan,the cytotoxicity of AuNR was prove to be eliminated by MTT(methyl-thiotetrazole)and its effects on microstructure of cells were further investigated with TEM.The use of near-infrared laser was applied to explore photothermal conversion efficiency of AuNR with different longitudinal plasma surface resonance peak,AuNR matched with the laser wavelength was found to be the most efficient one and the photothermal conversion efficiency reduced as the size of AuNR getting bigger.Using breast cancer cells(MCF-7)as a model,the efficacy of the photothermal therapy with gold nanorods got better as the concentration of AuNR and irradiation time increased by MTT assay and fluorescence microscopy staining results.