Semiconductor Oxide Nanocrystals Doped Nanoporous Silica Glasses And Their Applications

Nanocrystals and rare earth ions doped glasses exhibit unique optoelectronic properties such as fluorescence,nonlinearity,and electrical conductivity,which are widely used in laser,lighting,and sensing fields.Uniform distribution of semiconductor oxide nanocrystals can effectively promote the luminescence properties of rare earth ions doped glasses.However,precisely controlling the size and distribution of semiconductor oxide nanocrystals in glasses is a challenging problem.In this paper,we synthesized semiconductor oxide nanocrystals and rare earth ions single-doped and co-doped glasses with nanoporous silica glass matrix via a solution doping method.The corresponding fluorescence enhancement properties were studied.The mechanism of enhancement was explored.Finally,we applied these hybrids for ion detection and temperature sensing.At the beginning of this thesis,we introduced nanoporous silica glasses,several typical semiconductor oxide nanomaterials,rare earth ions and their applications in sensing.Subsequently,the development of semiconductor oxide and rare earth co-doped glasses was summarized in detail.Thesis consists of three main parts:preparation of indium oxide（In₂O₃）,tin oxide（SnO₂）and indium tin oxide（ITO）semiconductor oxide nanocrystal single-doped glasses;study on the fluorescence enhancement properties of rare earth ions and semiconductor oxide nanocrystals co-doped glasses;the application of these composite glass systems in metal ion probes and temperature sensing.In the preparation of semiconductor oxide nanocrystals doped glasses,indium oxide（In₂O₃）,tin oxide（SnO₂）and indium tin oxide（ITO）semiconductor oxides doped glasses were prepared by solution doping method using nanoporous silica glasses as matrix.Data showed that the nanocrystals were well crystallized and evenly distributed,with particle size 5-40 nm.It is easy to regulate the distribution and size of the nanocrystals by the uniformly distributed nanopores in the glass,which proposes a feasible solution to crystal clusters and uncontrollable growth in glasses.The upconversion photoluminescence（UCPL）properties of Er³⁺/Yb³⁺ions and ITO nanocrystals co-doped silica glasses were studied in detail.When the doping concentration of ITO nanocrystals is 0.4mol/L,the UCPL effect of co-doped glass is optimal and the maximum enhancement factors are obtained,which are 12.34（519 nm）,10.29（541 nm）,22.68（651 nm）and 14.96（666 nm）,respectively.At the same time,the fluorescence properties of SnO₂,In₂O₃ and ITO nanocrystals and Eu ions co-doped silica glasses were investigated.When the doping concentration of SnO₂ nanocrystals is0.4mol/L,the ⁵D₀-⁷F₁ transition corresponding to Eu³⁺,ie,the fluorescence intensities at588nm,593nm and 598nm are 116,95 and 43 times higher than that of undoped glasses,respectively.The results indicate that nanocrystals can effectively enhance the fluorescence properties of rare earth ions doped glasses.The possible mechanism of energy transfer behavior between rare earth ions and nanocrystals was explored in detail by absorption spectroscopy,fluorescence lifetime curves and fluorescence excitation spectroscopy.Finally,the sensing properties of Eu³⁺and SnO₂ nanocrystal co-doped glasses on Fe³⁺ions in aqueous solution were investigated.The results show that the detection limit of the composite system for Fe³⁺ions is 7.54 nmol/L,which has good selectivity,resistance to metal cations and anion interference.Moreover,the temperature sensing characteristics of Eu²⁺/Eu³⁺,Tb³⁺,and SnO₂ nanocrystal co-doped glasses based on fluorescence peak ratio in the range of 298-773K were further investigated.The results show that the material has good fluorescence temperature sensing characteristics in the high temperature range.