质子酸功能化离子液体中银纳米颗粒的制备及其光学性能研究

Preparation of Silver Nanoparticles in Brnsted Acidic Ionic Liquid and Its Optical Properties

以质子酸功能化离子液体1-丁基-3-甲基咪唑磷酸二氢盐([Bmim]H2PO4)为反应介质和表面活性剂,采用简单的化学还原法制备了具有形状各向异性的块状银纳米颗粒。通过X射线衍射(XRD)、扫描电镜(SEM)、紫外-可见(UV-Vis)吸收光谱等一系列手段对其结构、形貌及光吸收特性进行了表征。结果表明,所制备的银纳米块具有立方结构,其平均横向尺寸约为30 nm,在硅片上自组装形成密堆积结构的多层膜。以1,2-二(4-吡啶基)乙烯(BPE)作为探针分子,研究所制备银纳米颗粒的表面增强拉曼散射(SERS)活性。结果表明所制的银纳米颗粒是较好的SERS基底,具有良好的增强效果,痕检能力及稳定性。对BPE分子的最低检测浓度可低至10-9mol.L-1,而且保存了90天后,其检测灵敏度没有显著的降低。

The use of room-temperature ionic liquids （RTILs） as green media for preparation of nanomaterials is very attractive. Herein, anisotropic silver nanoparticles were synthesized via chemical reduction silver nitrate with sodium hypophosphite, employing brФnsted acidic functionalized ionic liquid; Ag nanoparticles; Anisotropy; SERSnsted acidic functionalized ionic liquid 1-butyl-3-methyl-imidazolium dihydrogen phosphate （[bmim] H2PO4 ）, which acted both as reaction medium and as a capping/shape-directing agent. The structure, morphology and optical absorption properties of anisotropic silver nanopartieles were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, and UV-Visible （UV-Vis） absorption spectra. The XRD patterns revealed that the crystal was cubic structure for anisotropic silver nanoparticles. The SEM image indicated that the anisotropic silver nanoparticles were block-like with average lateral dimensions of about 30 nm, and they were self-assembled into two-dimensional disordered multilayer on the silico, n warer, and the particles appeared to be closely packed. The UV-Vis absorption spectrum exhibited a strong absorption peak around 438 nm and a weak peak at 353 nm, which came from dipole and quadrupole oscillation resonance, indicating the formation of non-spherical silver nanoparticles. The surface-enhanced Raman scattering （SERS） active of the anisotropic silver nanoparticles were investigated using trans-1,2-bis（4-pyridyl）-ethylene （BPE） as probe molecule. The results indicate that self-assembled silver film of anisotropic silver nanoparticles on the silicon wafer is excellent substrate for SERS measurements, demonstrating significant enhancement, trace detection capability, and good stability. The minimum analytic concentration was 10 9 mol ·L^-1 for trans-1,2-his （4-pyridyl）-ethylene （BPE） molecules. It was also found that silver film stored for 90 days in air shows no significant degradation in its sensitivity.