Synthesis Of SnO₂ And ZnS:Mn Quantum Dots Embedded In Silica Glass Via SPS And Its Optical Properties Research

Semiconductor quantum dots have attracted a lot of attention due to their unique optical and electronic properties.But the heavy metal contained in Cd and Pb quantum dots will cause environment pollution and is harmful to the human body,so cannot be applied in biological fields.The preparation of non-toxic and harmless quantum dots is more worthy of attention and study.In addition,the effective storage and application of quantum dots have been the focus of research,so it is also a hot point to find a more effective method to preserve quantum dots.Due to the quantum size effect,surface effect,dielectric confinement effect,the quantum dots display unique physical and chemical properties,especially the size-dependent optical properties,which is a research hot issue been used in optical devices.However,nanocrystals possess large surface area,high activity and poor stability,hindering the direct use of quantum dots.When the glass used as a substrate,it has a range of characteristics different from other solid laser host materials,which attracts much attention of the researchers.The optical properties of nanocrystals semiconductors have been extensively researched in recent years.When the particle size of a semiconductor becomes comparable to the Bohr radius of exciton,the ratio of surface atoms to those in the interior increases observably,resulting that the surface properties play an important role in the properties of the material.Among various kinds of semiconductor materials,SnO₂ is stable with a large n-type band gap?Eg=3.6eV at 300K?,a low electron affinity and a large excitonic binding energy level?130 meV?,which has been widely used as a gas sensor material and also investigated to be used in transparent heating elements,electrode materials,solar cells,resistors,antistatic coating and special coating for energy-conserving �low-emissivity� windows.Furthermore,among various inorganic semiconductor nanocrystals,zinc chalcogenide-based colloidal quantum dots have been a class of the main components of luminescent materials.The main advantages of zinc chalcogenides are their wide bandgap,low toxicity?cadmium-and lead-free?,easy synthesis with potential scalability of production,and availability of metal-ion doping.Mn-doped ZnS and Mn-doped ZnSe quantum dots have been used for tunable or white light emission machines,as well as zinc chalcogenides with core/shell and core/shell/shell structures have been synthesized and investigated.However,due to the luminescent instability of ZnS quantum dots,it is more meaningful to study the ZnS:Mn quantum dots with stable doping characteristic peak.In this article,the quantum dots with controllable size,stable concentration and narrow distribution which prepared through the combination of SnO₂ and ZnS:Mn quantum dots with high quality synthsized by chemical approaches and SBA-15 via spark plasma sintering?SPS?technology?Powder could avoid being melted directly solidified into glass at a low temperature and without annealing process.?.The SnO₂ and ZnS:Mn quantum dots with high quality synthesized by hydrothermal method and hot injection method respectively.Then,the synthesized SnO₂ and ZnS:Mn quantum dots were composited into mesoporous silica powder?SBA-15?to get SnO₂/SBA-15 and ZnS:Mn/SBA-15 compound powder.Finally,the compound powder of SnO₂,ZnS:Mn was sintered into quantum dots glass through SPS technology.Moreover,this article will briefly describe the luminescent properties of quantum dots,as well as the main preparation method including the advantages and disadvantages.What's more,this paper will introduce several common kinds of quantum dots glass from the category of the quantum dots doped glass systems,mechanism of the luminescence and the spectra characteristics.In addition,this dissertation will mainly introduce the application prospects of the quantum dots glass,and will focus on the principle,advantage and research status of spark plasma sintering in recent years.First of all,the SBA-15 of high quality was prepared by soft template approach.The Vickers hardness of quartz glass was 6.72 GPa.Subsequently,apply chemical methods for the preparation of SnO₂ and ZnS:Mn quantum dots.Firstly,the SnO₂ quantum dots with good crystallinity of tetragonal structure were obtained by hydrothermal method.With the increasing synthetic p H value,the particles' crystal form were gradually transformed from the ball into rod and the crystal form were also more and more complete,the size of the particle were under 60 nm.The spectral analysis showed that the photoluminescence peak were located at 400 nm,469nm and 536 nm respectively.Secondly,the ZnS:Mn quantum dots with good crystallinity of wurtzite structure were prepared by hot injection method.The average particle size was about 4.3nm according to the Scherrer formula.The analysis of spectral showed an intrinsic luminescence peak at 470 nm and a defect luminescence peak at 580 nm respectively.Finally,the quantum dots glass was obtained by SPS the SnO₂/SBA-15 and ZnS:Mn/SBA-15 compound powder.The luminescent properties of the SnO₂-QDs were enhanced,and the good crystallinity of SnO₂ QDs was also maintained after the SnO₂-QDs glasses obtained.The SnO₂-QDs glass had a photoluminescence peak at 397 nm,and when the contained concentration was 1wt%,the intensity of the luminescence intensity reached the maximum.The Vickers microhardness of SnO₂-QDs glasses was gradually reduced with the increasing compound concentration of quantum dots.At the same time,the ZnS:Mn-QDs glasses with excellent luminescent properties and good crystallinity were obtained.The photoluminescence peak at 580 nm of ZnS:Mn-QDs glasses was greatly enhanced while the intrinsic luminescence peak at 470 nm was disappeared.The Vickers microhardness of the ZnS:Mn-QDs glasses were also gradually reduced with the increasing compound concentration.After SPS sintering,the luminescence properties of QDs were enhanced with a certain extent,and the position of the emission peak was also unified.In this manuscript,SnO₂-QDs and ZnS:Mn-QDs glasses were successfully prepared and the problems of uncontrollable concentration,wide particle size distribution and low luminous intensity were solved through combining SPS sintering technology with the SnO₂ and ZnS:Mn quantum dots of high quanlity synthsized by different chemical methods which created a new research direction for the preservation stability and application of quantum dots.