Gharibshahi Elham, Saion Elias, Ashraf Ahmadreza, Gharibshahi Leila
Department of Physics, Faculty of Science, University of Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia; Department of Physics and Astronomy, University of Texas at San Antonio, One UTSA Circle, San Antonio, TX 78249, USA.
Department of Physics, Faculty of Science, University of Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia.
Appl Radiat Isot. 2017 Dec;130:211-217. doi: 10.1016/j.apradiso.2017.09.012. Epub 2017 Sep 9.
Gamma radiolytic synthesis was used to produce size-controlled spherical platinum nanoparticles from an aqueous solution containing platinum tetraammine and polyvinyl pyrrolidone. The structural characterizations were performed using X-ray diffraction, and transmission electron microscopy. The transmission electron microscopy was used to determine the average particle diameter, which decreased from 4.4nm at 80kGy to 2.8nm at 120kGy. The UV-visible absorption spectrum was measured and found that platinum nanoparticles exhibit two steady absorption maxima in UV regions due to plasmonic excitation of conduction electrons, which blue shifted to lower wavelengths with a decrease in particle size. We consider the conduction electrons of platinum nanoparticles to follow Thomas-Fermi-Dirac-Weizsacker atomic model that they are not entirely free but weakly bounded to particles at lower-energy states {n = 5, l = 2 or 5d} and {n = 6, l = 0 or 6s}, which upon receiving UV photon energy the electrons make intra-band quantum excitations to higher-energy states allowed by the principles of quantum number that results the absorption maxima. We found an excellent agreement between the experimental and theoretical results, which suggest that the optical absorption of metal nanoparticles could be fundamentally described by a quantum mechanical interpretation, which could be more relevant to photo-catalysis and heterogeneous catalysis.
利用伽马辐射分解合成法，从含有四氨合铂和聚乙烯吡咯烷酮的水溶液中制备出尺寸可控的球形铂纳米颗粒。使用X射线衍射和透射电子显微镜进行结构表征。透射电子显微镜用于确定平均粒径，其从80kGy时的4.4nm降至120kGy时的2.8nm。测量了紫外可见吸收光谱，发现由于传导电子的等离子体激发，铂纳米颗粒在紫外区域呈现出两个稳定的吸收最大值，随着粒径减小，吸收峰蓝移至更低波长。我们认为铂纳米颗粒的传导电子遵循托马斯 - 费米 - 狄拉克 - 魏茨泽克原子模型，即它们并非完全自由，而是在低能态{n = 5, l = 2或5d}和{n = 6, l = 0或6s}时与颗粒弱结合，当吸收紫外光子能量时，电子进行带内量子激发，跃迁到量子数原理允许的高能态，从而产生吸收最大值。我们发现实验结果与理论结果高度吻合，这表明金属纳米颗粒的光吸收可以从根本上用量子力学解释来描述，这可能与光催化和多相催化更相关。
