Physico-Chemical Effects on the Scale-Up of Ag Photodeposition on TiO2 Nanoparticles

Abstract

We have previously demonstrated that TiO 2 nanoparticles can be functionalized by photodeposition with silver or gold particles in the 1-2 nm range presumed to be desirable for catalysis applications. However, the preparation of these samples directly on microscope grids, while conducive to particle size determinations, did not produce sufficient materials for reaction studies. We report here scale-up techniques designed to produce greater quantities of material for testing, while maintaining characteristics that contribute to uniformity in the deposition process. For the scale-up process, an irradiation source with highly uniform intensity is necessary to generate Ag/TiO 2 samples with consistent Ag loading. In addition, control of the precursor concentration is also required to produce Ag/ TiO 2 samples with high Ag loading and narrow Ag size distribution. The optimum conditions for the scale-up process found in this study involved Ag photodeposition from a 5 9 10 -3 M AgNO 3 solution using a high pressure Hg lamp at 366 nm for 60 s. Under these reaction conditions, the size of Ag particles determined by TEM and HAADF-STEM imaging was within 1-2 nm and the Ag loading was *3.2 wt%. Achievement of this level of uniformity required control of the uniformity of illumination, as well as of the solution concentration and irradiation conditions. Higher solution concentrations and higher power led to the growth of larger (ca. 10 nm) silver particles. In contrast, the loading and size distribution of the Ag particles photodeposited were remarkably insensitive to the source and morphology of the TiO 2 nanoparticles utilized. No Ag peak was resolved in the XRD patterns for Ag/TiO 2 samples obtained from the optimized scale-up process, corroborating the size range determination of the Ag nanoparticles. XPS showed that the Ag particles in all cases were metallic Ag.

Sulfur Dioxide Adsorption on ZnO Nanoparticles and Nanorods

“…This suggests potentially a greater defect site density for the smallest nanorods, but for the nanoparticles the data suggest the defect site density is independent of size. This is a similar conclusion derived by studies of Barteau and co-workers for TiO 2 nanoparticles. − Additionally, particle size due to coarsening as a result of heating to remove surface organics may play a role in the behavior of these nanomaterials and their surface chemistry with sulfur dioxide.…”

Photocatalytic Method for the Simultaneous Synthesis and Immobilization of Ag Nanoparticles onto Solid Substrates

“…The photocatalytic deposition relies on a solid photocatalyst framework that is exposed to a metal precursor solution and irradiated by a luminous source of appropriate wavelength. − Although the chasing for photocatalysts that work in the visible range never ends, TiO 2 , which is the most effective photocatalyst so far, works properly only in the UV range . Indeed, the scientific literature since the 1970’s provides many examples of photocatalytic formation and/or immobilization of AgNPs onto TiO 2 NPs. − …”

Study of the composition and structure of titanium dioxide based coatings deposited by the method of reactive magnetic sputtering

“…Спектр применения технологий осаждения пленок ди-оксида титана очень широк: от медицины до различных областей техники, в том числе в антиотражающих по-крытиях и диффузионных барьерах [1]. Диоксид тита-на из-за его высокой фотокаталитической активности используют для очищения от вредных органически сложных соединений.…”

“…, принадлежащие дважды вырожден-ным модам оптических фононов, -обозначаются они как E g (1), E g (2) и E g (3) и два пика, принадлежащие невы-рожденным модам оптических фононов, обозначаемых как 2 B 1g пика (390 см −1 и 520 см −1 ). Линии рамановского рассеяния для образцов диоксида титана сильно ушире-ны.…”