LSPR Regulation And Application Of Tungsten Bronze Nanocrystalline Sn_xWO₃

The localized surface plasmon resonance（LSPR）effect has been favored by scientists for its unique response properties to light,and the effect has potential in many fields,such as photocatalysis,improved sensor sensitivity,bio-detection,and improved solar cell efficiency.Recent studies have shown an increasing interest in the LSPR effect of semiconductor nanocrystals.Because the LSPR absorption of precious metals（Au,Ag,etc.）is generally in the visible region,the LSPR absorption peak of semiconductor nanocrystals is mainly in the near-infrared region,pointing the way for optical applications of plasmon in the near-infrared region.Although some progress has known and applied of LSPR effects in semiconductor nanocrystals,the correlation between LSPR properties and their material composition,structure and morphology are still under study,and the ways and mechanisms of LSPR to improve the performance of optical applications need to be further explored.Therefore,the development and utilization of new semiconductor nanocrystals with significant LSPR effect is of great scientific significance and application value.The LSPR effect of semiconductor nanocrystals is mainly due to the collective oscillation of free carriers induced by doping or crystal defects.By changing the doping element type and doping ratio,the LSPR characteristics of semiconductor nanocrystals can be effectively regulated to obtain the target absorption peak position and absorption intensity,and then realize the full utilization of light energy in the near-infrared region.Most existing research is based on M as a monovalent alkali metal ion.Nanocrystals,such as Cs_xWO₃.The synthesis of tungsten bronze nanocrystals with high valence ion doping and the modulation of their LSPR effect and applications have not been reported.In this thesis,different series of Sn_xWO₃ semiconductor nanocrystal was prepared and synthesized,and the relationship between the LSPR performance of the materials and their preparation conditions,structure and morphology and the corresponding mechanism were investigated in detail,and preliminary attempts were made to apply the materials in enhancing rare-earth upconversion luminescence and near-infrared shielding performance.Based on the above,the following two main parts of work are done in this paper.（1）Firstly,the tungsten bronze nanocrystalline Sn_xWO₃ with significant LSPR effect was obtained by using different Sn precursors and regulated NH₄F.Sn_xWO₃ nanocrystals with different crystal phases and morphologies（SWO-Cl,SWO-SO₄,SWO-OX）were obtained using the solvother one-pot method and different Sn precursors,and NH₄F was added to promote the further growth of nanocrystals,and Vis-NIR absorption showed that the three series of samples had different LSPR absorption characteristics in the near-infrared region.Combined with the characterization and analysis of XRD,SEM,TEM and XPS,the mechanism affecting the absorption characteristics of Sn_xWO₃ nanocrystalline LSPR was explained:the type of acid root provided by different Sn precursors was an important factor affecting the phase,morphology and absorption performance of Sn_xWO₃ nanocrystalline crystals.The different valence states of Sn ion and the strong reducibility of oxalic acid make SWO-OX had the most significant LSPR characteristics,represented by SWO-OX,which had the strongest LSPR absorption,and prepare Glass/Sn_xWO₃/PMMA/Na YF₄:Yb³⁺,Er³⁺layered structures for enhanced upconversion luminescence.Compared with Glass/Na YF₄:Yb³⁺,Er³⁺,the layered structure fluorescence was enhanced significantly.The analysis of fluorescence life test showed that the fluorescence enhancement was mainly due to the LSPR effect of tungsten bronze nanocrystals Sn_xWO₃coincided with the excitation fields of Na YF₄:Yb³⁺,Er³⁺,and the coupling of the two produced a strong local electromagnetic field resulting in significant upconversion luminescence enhancement.（2）Combined with the work of the first part,Mo ions with similar ion radii and properties to W ions were selected to replace W ions into the lattice of tungsten bronze nanocrystals Sn_xWO₃ to further improve the LSPR effect in the near-infrared region.Using Sn Cl₄,Sn SO₄,Sn C₂O₄ as precursors to Sn,doping different concentrations of Mo ions,the best doping concentrations in 0.03 and 0.04,and obtaining tungsten bronze nanocrystals Sn_xWO₃ with different crystal phases and different morphologies.We selected three kinds of best absorbed samples for thermal insulation test,the thermal insulation performance of the three nanocrystals was SWMO-OX-0.04>SWMO-SO₄-0.03>SWMO-Cl-0.03,Among them,the light temperature difference of SWMO-OX-0.04 nanocrystals is 18.8°C,which is 25.8°C compared with the temperature difference of blank quartz glass sheets,and the overall decrease is 7°C.The tungsten bronze nanocrystalline Sn_xWO₃ prepared in this experiment has high visible light transmittance and near-infrared light shielding performance,which achieves the effect of energy saving and environmental protection.