Control of dispersion-aggregation of nanoparticles by illumination

通过照明控制纳米颗粒的分散聚集

基本信息

批准号：
06453058
负责人：
KIMURA Keisaku
金额：
$ 3.84万
依托单位：
Himeji Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1994
资助国家：
日本
起止时间：
1994 至 1995
项目状态：
已结题

项目摘要

Gold nanometer-sized particles were prepared by the gas flow-solution trap method. The dispersing solvent is 2-propanol and average size of starting particles is 8nm. On irradiation of an Ar-ion laser, the color of dispersion has changed from wine red to dark blue otherwise wine red for more than years. It was shown that dispersed particles agglomerated into fractal cluster in concurrent with the spectral change of increase in 750 nm band and decrease in 523nm plasmon band.The change of dispersion by the illumination of light resembles to the effect of the addition of salt. The stability of dispersion is most sensitive to the concentration of electrolyte in the dispersion because ions affect the Debye length around the particle sphere. Sudden coagulation started at the instant of addition of NaCl solution. That is, the initial peak maximum at 520 nm shifted toward red wavelength region upon increasing concentration of salt. This tendency is similar to the photocoagulation.Following the standard theory of colloids, the stability of sols is governed by balancing between van der Waals attraction and Coulombic repulsion of charged particles. It is obvious that the coagulation proceeds with the visible light energy. At Mie resonance frequency, the free electron-system in a metallic particle feels forced vibration at the resonance frequency causing large dipole oscillation. This large oscillation induced interparticle attractive force among the same particle likewise in the normal van der Waals force. As a result, the interaction is a function of the square of size of particles and the power of a field. The interaction energy has its maximum at about 20 nm and gradually decay for a larger size. Hence the system has to be a mesoscopic scale for a large enhancement to be observed.

通过气体流量陷阱法制备金纳米尺寸的颗粒。分散溶剂是2-丙醇，起始颗粒的平均大小为8nm。在辐照AR-ION激光器后，分散颜色已从红色红色变为深蓝色，否则葡萄酒红色已有多年了。结果表明，分散的颗粒与750 nm频段的频谱变化并在523nm等离子体带中降低。色散的稳定性对分散体中电解质的浓度最敏感，因为离子会影响粒子球周围的debye长度。突然的凝血始于添加NaCl溶液的瞬间。也就是说，在增加盐浓度时，在520 nm处的初始峰值最大值向红色波长区域转移。这种趋势类似于光凝性。遵循胶体的标准理论，溶胶的稳定性受范德华吸引力与带电颗粒的库仑拒绝之间的平衡来控制。显然，凝血以可见的光能进行。在MIE共振频率下，金属粒子中的自由电子系统在共振频率下感到振动，从而导致大偶极振荡。这种较大的振荡在正常的范德华力中同样会引起同一粒子之间的颗粒间吸引力。结果，相互作用是粒子大小和场的功率的函数。相互作用能的最大值约为20 nm，并且逐渐衰减更大的尺寸。因此，该系统必须是介观量表，才能观察到很大的增强。