Synthesis and Photocatalytic Properties of High-Surface-Area Mesoporous TiO 2 Nanoparticle Assemblies
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Synthesis and Photocatalytic Properties of High-Surface-Area Mesoporous TiO2 Nanoparticle Assemblies Ioannis Tamiolakis1, Ioannis N. Lykakis2 and Gerasimos S. Armatas*1 Department of Materials Science and Technology, University of Crete, Heraklion 71003, Greece 2 Department of Chemistry, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece. 1
ABSTRACT Mesoporous TiO2 nanoparticle assemblies have been synthesized via a surfactant-assisted aggregating process. The products feature a three-dimensional network of interconnected anatase-TiO2 NPs with large internal BET surface area (ca. 142–152 m2g-1) and uniform pores (ca. 7–8 nm). Preliminary catalytic experiments indicated that these mesophases exhibit excellent catalytic activity in UV-visible light oxidation of 1-phenylethanol with molecular oxygen. INTRODUCTION The self-assembly of nanoparticles (NPs) into a well-defined porous nanostructure is one of the greatest challenges in materials chemistry. Although individual metal oxide nanoparticles feature unique catalytic, magnetic and electronic properties, their low surface area and tendency for clustering limit the applicability of these nanomaterials, especially in adsorption and catalysis. Three-dimensional assemblies of nanoparticles with large internal surface area and open-pore structure promise a different kind of porous materials with advantageous characteristics. These materials are expected to achieve excellent catalytic and optoelectronic properties and yet possess additional characteristics such as size-selective adsorption and molecular recognition of substrate. Among the simple metal oxides, titanium dioxide (TiO2) has been predominantly used for photocatalytic, photovoltaic, and electrochromic applications because of its inherent superior photocatalytic and opto-electronic properties [1]. Recent efforts to improve photoactivity of TiO2–based materials have been focused on synthesis of nanometer-sized TiO2 particles, which possess high crystallinity and large surface area [2]. The surfactant-assisted templating of inorganic species provides a simple and effective method for producing mesoporous ensembles of nanoparticles. In this context, several organic amphiphilic molecules, like charged small molecules and block copolymers, have been employed as templates to direct the assembly of Ti molecular compounds (TiCl4, Ti(OR)4, etc.) or pre-synthesized TiO2 nanocrystals into various nanoscale architectures [3]. Interestingly, modulation of the interactions between inorganic species and surfactant molecules provides a way of controlling the morphology and pore geometry of resulting structures. These materials show enhanced photocatalytic activity and Listorage capability granted by the nanoscopic framework components [4]. Although significant progress in this area has been achieved, developing high-surface-area mesoporous assemblies from well crystalline TiO2 NPs is a worthwhile goal.
Herein, we report the synthesis of high surface area, high crystalline, nanostructured anatase-titania via a su
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