不同形貌Pt纳米颗粒有序阵列的可控制备及其光学特性*

Controllable Fabrication of Pt Nanoparticle Array with Various Morphology and Its Optical Properties*

摘要:

基于目前湿化学法制备铂纳米颗粒存在颗粒形貌难以自由调控、含有表面活性剂及易于团聚等问题,发展了以单层胶体晶体为模板,采用磁控溅射技术沉积一层铂膜,通过改变退火温度可控制备具有不同形貌铂纳米颗粒阵列的方法。当退火温度为300℃,500℃,700℃ 和 900℃时,分别获得了 “帽状”,“杯状”,“米粒状”和“球形”的铂纳米颗粒阵列。此法操作简单、无污染,为各向异性纳米颗粒阵列的制备提供了一种新的思路。进一步研究了不同形貌纳米颗粒阵列的消光光谱。结果表明,样品的消光光谱随着纳米颗粒形貌的变化发生相应的偏移。“帽状”,“杯状”和“米粒状” Pt纳米颗粒的横向局域表面等离子体共振峰从487 nm蓝移至453 nm,而纵向局域表面等离子体共振峰从1201 nm蓝移至898 nm。实现了横向和纵向局域表面等离子体共振峰分别在可见光和近红外较宽波段内移动。这些由各向异性的纳米颗粒产生的光学性质可以使其在热疗、生化传感、光学成像等领域具有重要应用。

Abstract:

An interesting and simple strategy to prepare Pt nanoparticle arrays with different morphologies on a substrate was developed by using monolayer colloidal crystal as a template, followed by depositing a layer of Pt film and annealing at different temperatures. Hat-shaped, cup-shaped, rice-shaped and sphere-shaped Pt nanoparticle array were obtained after annealing the PS template with Pt shell at 300℃, 500℃, 700℃ and 900℃, respectively. Their extinction spectra presented two obvious peaks, assigning to transverse and longitudinal localized surface plasmon resonances of the Pt nanoparticles. The transverse and longitudinal localized surface plasmon resonances peaks both blue shifted when geometrical morphology changed from hat-shaped to cup-shaped, and then to rice-shaped due to increasing annealing temperature. The transverse localized surface plasmon resonances peaks blue shifted from 487 nm to 453 nm, and longitudinal localized surface plasmon resonances peaks blue shifted from 1201 nm to 898 nm. With strong absorption in near infrared, the hat-shaped, cup-shaped and rice-shaped Pt nanoparticles array may be suitable for thermotherapy application. However, in the curves of extinction spectra of the hat-shaped, cup-shaped and rice-shaped Pt nanoparticle arrays, the Bragg diffraction peaks were not very obvious. This may be attributed to overlap of their localized surface plasmon resonance peaks and diffraction peaks or absorbance of Pt nanoparticles is too high, resulting in diffraction peak too weak to be detected. Compared with hat-shaped, cup-shaped and rice-shaped Pt nanoparticle array, in the curve of extinction spectra of sphere-shaped Pt nanoparticle array, there was only one localized surface plasmon resonance peak because of its symmetrical nanostructure. But it presented a peak at 635 nm, which is assigned to Bragg diffraction of the highly ordered structure of the Pt nanosphere array. In a word, this controlling annealing temperature strategy is simple and could be potentially extended to prepare novel anisotropic nanostructures for other materials, which is difficult to be synthesized via conventional wet chemical method. And this method would promote more research efforts in developing new methods to fabricate asymmetrical nanostructures. Additionally, these novel properties originating from the anisotropic nanostructures may open up new applications in many fields.