Nanocomposites and nanomaterials

The medium influence on the luminescence intensity of SnO2 nanoparticles ensembles in a porous silicate glass matrix 
Doycho I.K., Filevska L.M., Gevelyuk S.A., Grinevich V.S.
Odessa I.I. Mechnikov National University, Dvoryanskaya str.,2, Odessa-65082, Ukraine

E-mail: lfilevska@gmail.com 

Tin dioxide nanoscale forms, besides their stability in most of aggressive media, and high gas sensitivity, appear luminescence in the visible range. This makes the material promising for the creation of contactless sensors of various composition environments.
The aim of this study is to elucidate the medium influence (with alkaline and acid components) on the luminescence of SnO2 nanoparticles ensembles in a porous silicate glass matrix. The ensembles were formed by impregnating glass samples with alcohol solutions of SnCl4 of various concentrations, followed by thermosynthesis of SnO2 directly in the pores. The obtained ensembles’ samples of tin dioxide nanoparticles being in media with NH4OH and HCl vapors showed number of photoluminescence characteristic dependences on the composition of the environment.
In an alkaline medium, the luminescence intensity decreased by more than half in the interval of 10-20 sec. In an acidic medium, the same samples’ luminescence intensity also decreased, but, by only 5% in tens of minutes. The luminescence kinetics changes for SnO2 nanoparticles ensembles obtained at SnCl4 concentrations of 5 %, 7.5 %, 12.5 %, and 25 % were considered during the first minute after placing the samples in alkaline and acidic media. The proposed behavior models for the luminescence of samples in alkaline and acidic media are based on the nature of ammonia and hydrogen chloride vapors interaction with nanoparticles’ surfaces in ensembles. A sharp photolumiscence intensity decrease in an alkaline medium is explained by the unstable ammonia complexes SnO2[NH3] formation. When, in acidic environments such complexes are not formed.
Complete self relaxation to the initial luminescence intensity values of the SnO2 nanoparticles ensembles within 10-12 hours after extraction from the aggressive medium allows using them as reliable active elements of a luminescent ammonia sensor.
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