介孔二氧化硅SBA - 15和Pt/SBA - 15振动光谱的结构敏感性

Structure sensitivity of vibrational spectra of mesoporous silica SBA-15 and Pt/SBA-15.

作者信息

Borodko Yuri, Ager Iii Joel W, Marti G Edward, Song H, Niesz Krisztian, Somorjai Gabor A

机构信息

Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.

出版信息

J Phys Chem B. 2005 Sep 22;109(37):17386-90. doi: 10.1021/jp051801x.

DOI:10.1021/jp051801x

PMID:16853222

Abstract

The vibrational properties of mesoporous silica (SBA-15) were investigated by deep ultraviolet (UV) Raman and infrared spectroscopies with and without the presence of platinum nanoparticles in the mesopores that were incorporated by sonication. Raman and IR spectral line assignments were made by comparison to amorphous silicas. This procedure permitted identification of vibrations of longitudinal (LO) and transverse (TO) optical lattice modes, the presence of Si-OH, and vibrational modes associated with the presence of three-, four-, and six-membered siloxane rings. Hydraulic pressing of the mesoporous silica with pressure in the range 3-7 tons cm(-2) destroys the X-ray diffraction pattern and strongly decreases the Raman peak (D2) associated with three-membered rings at the surface. In the presence of platinum nanoparticles in the silica mesopores, a peak attributed to a Pt-O stretching vibration appears at between 530 and 580 cm(-1) in the UV-Raman spectrum, which can be used to monitor the presence of the platinum particles and their interaction with the support. The D2 feature in the UV-Raman spectra also decreases with increasing Pt loading, which is attributed to interactions of the Pt nanoparticles with the silica surface.

摘要

通过深紫外（UV）拉曼光谱和红外光谱研究了介孔二氧化硅（SBA - 15）的振动特性，介孔中通过超声处理引入了铂纳米颗粒，研究了有无铂纳米颗粒时的情况。通过与无定形二氧化硅比较进行拉曼和红外光谱谱线归属。该过程能够识别纵向（LO）和横向（TO）光学晶格模式的振动、Si - OH的存在以及与三元、四元和六元硅氧烷环存在相关的振动模式。在3 - 7吨厘米⁻²范围内对介孔二氧化硅进行液压压制会破坏X射线衍射图案，并强烈降低与表面三元环相关的拉曼峰（D2）。在二氧化硅介孔中存在铂纳米颗粒时，在紫外拉曼光谱中530至580厘米⁻¹之间出现一个归因于Pt - O伸缩振动的峰，可用于监测铂颗粒的存在及其与载体的相互作用。紫外拉曼光谱中的D2特征也随着铂负载量的增加而降低，这归因于铂纳米颗粒与二氧化硅表面的相互作用。