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采用光诱导法制备片状三角形纳米银粒子,利用紫外-可见光分光光度计(UV-Vis)和透射电子显微镜(TEM)对处于不同生长阶段和不同光源辐照的纳米银胶体进行光谱和形貌表征,并对光诱导机制、纳米银的生长机制和柠檬酸钠对形貌诱导的影响作了详细解释。结果表明,高压钠灯能够激发晶核的表面等离子体共振(SPR),促使晶核生长并转变为片状三角形,偶极子共振较强时倾向于形成尖角的三角形结构,面内四极子共振较强时倾向于形成截角的三角形结构。纳米粒子的这一生长过程实质上是一系列银的氧化还原沉积过程,符合奥斯特瓦尔德熟化机制。柠檬酸钠在高压钠灯的辅助下能够有效诱导球形向片状三角形转变,当5 mmol·L~(-1)20 mmol·L~(-1)时,该吸收峰则逐渐发生缓慢红移,并且该吸收峰的强度随着柠檬酸钠浓度的增加而不断增大。当柠檬酸钠浓度低至1 mmol·L~(-1)时,胶体溶液中只含有平均粒径为(25±5)nm的球形粒子。柠檬酸钠通过物理吸附对纳米粒子的表面进行修饰,阻止晶核沿纵向方向生长,保持纳米粒子呈相对扁平的结构。
Flake triangular nano-silver particles were prepared by light-induced method. The spectra and morphologies of the nano-silver colloids were observed by UV-Vis and TEM. The mechanism of photoinduced mechanism, the growth mechanism of nanosilver and the effect of sodium citrate on morphology induction were explained in detail. The results show that high pressure sodium lamp can excite the surface plasmon resonance (SPR) of nuclei and promote the growth of nuclei and transform into flaky triangle. When the dipole resonance is strong, it tends to form a sharp triangular structure. The in-plane quadrupole Strong resonance tends to form a truncated triangular structure. This growth of nanoparticles is essentially a series of silver redox deposition process, in line with the Ostwald ripening mechanism. Sodium citrate can effectively induce spherical to flaky triangular transformation with the help of high pressure sodium lamp and at 700 nm at 5 mmol·L -1 <20 mmol·L -1 TSC Of the dipole resonance absorption peak first appeared a slow blue shift first; when CTSC> 20 mmol·L -1, the absorption peak gradually slow red shift, and the intensity of the absorption peak with the sodium citrate Increasing concentration and increasing. When the sodium citrate concentration was as low as 1 mmol·L -1, the colloidal solution contained only spherical particles with an average diameter of (25 ± 5) nm. Sodium citrate modified the surface of the nanoparticles by physical adsorption to prevent the crystal nuclei from growing in the longitudinal direction and keeping the nanoparticles in a relatively flat structure.