Facile route to tin oxide containing mesoporous silica composites with room-temperature photoluminescence
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In this paper, we report a facile route, the tin vapor treatment method, to prepare tin oxide containing mesoporous silica composites (TOMS), which display room-temperature photoluminescence (RT-PL). Among them, TOMS-1 and TOMS-2 were synthesized from mesoporous silica SBA-15 and KIT-6, respectively. They are composed of amorphous SiO2 and tin oxide species and they display strong emission near ultraviolet (UV) when excited by UV light. By increasing the preparation temperature, their Sn content can be increased and subsequently their photoluminescence (PL) intensities can be greatly enhanced. Besides, their PL properties are revealed to be closely related to 2-fold-coordinated tin oxygen-deficient centers.
I. INTRODUCTION
Porous materials with luminescence properties are of great interest both from scientific and technological points of view. Notable examples, such as the porous Si,1,2 porous SiC,3,4 and zeolite-based materials, which contain functional guest inclusions in their micropores,5 are well known because some of them have been commercially applied in solar cells, optoelectronic devices, and laser devices.6–9 In recent decades, with the discovery and development of ordered mesoporous materials, much attention has been paid to their optical applications.10 Many mesoporous materials with luminescence properties have been synthesized by the inclusion of dyes,11,12 polymers, organometallic compounds, or nanocrystals of semiconductor in their mesopores,13–18 or by incorporation of rare-earth ions or semiconductors in their walls.19–22 Besides, to produce defects such as oxygen vacancies is also a feasible method to bring on the photoluminescence (PL).23–26 For example it is found that after rapid thermal annealing, the PL intensity of MCM-41 or MCM-48 was greatly enhanced, which has been ascribed to the generation of oxygen-related defects according to the surface properties.23,24 Recently, we found that after post-treatment with phosphoric acid, mesoporous zirconia showed strong room-temperature violet-blue luminescence, which was also closely related to the oxygen-related vacancies or defects.27
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Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2006.0075 J. Mater. Res., Vol. 21, No. 3, Mar 2006
SnO2 is an n-type semiconductor with wide energy gap (∼3.62 eV).28 Because of its outstanding electrical, optical, and electrochemical properties, SnO2 is extensively used in many fields such as gas sensors, solar cells, catalytic supports, and transparent electrodes for flat panel displays and other applications. Although bulk SnO2 has no PL properties at room temperature, it has been reported that nanocrystalline SnO2 thin film29–32 and SnO2 nanoparticles demonstrate room-temperature PL properties.33,34 However, few published works have documented the synthesis of tin oxide containing mesoporous silica with PL properties. In this paper, we demonstrate for the first time a new and general synthetic route, the tin vapor treatment method, to prepare tin oxide containing me
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