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Preparation Of PbS QDs Embedded In Glass By SPS And Its Luminescent Property Study

Posted on:2014-11-04Degree:MasterType:Thesis
Country:ChinaCandidate:X W YuFull Text:PDF
GTID:2271330482472765Subject:Materials Physics and Chemistry
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Lead sulfide(PbS) quantum dots(QDs) have lots of potential applications in the fields of laser device, infrared detector and optical switch,etc,Compared with other IV-VI QDs, PbS QDs have excellent tunable luminescent properties in NIR region depending on sizes, small band gap energy( Eg=0.41eV) and large exciton Bohr radius of 18 nm . Melting-quenching and sol-gel method are commonly methods in preparating semiconductor quantum dots embedded in glass. However, many problems are difficult to overcome, such as wide particle size distribution, low QDs concentration and many defects and vacancies.Chemical synthesis can prepare micro-controlled quantum dots- Spark Plasma Sintering(SPS) technology is used to compact powder without melt at comparably low temperatures in a very fast manner,thus suppressing the growth of particles and obtaining high density bulk material. We hope that luminescent glass with size-controllable and uniform distribution QDs could be prepared and it has stable concentration and integrated advantages of both QDs and glass. We synthesized amorphous silica materials(SBA-15) with well-ordered hexagonal mesoporous structure. PbS QDs were prepared through a two-phase approach and an aqueous method respectively. Composith powder was sintered into glass by SPS. The main content of this thesis is as follows:Firstly, SBA-15 powders were prepared at 130℃ for 72 h,and the pore size and BET of as-synthesized powders is about 30 mn and 790m2/g, respectively. The powders were heated to the fmal sintering temperature(1080℃) using a heating rate of 100℃/min and an uniaxial pressure of 50 MPa. Modified Small Punch(MSP)strength and Vickers microhardness of the SPS-sintered transparent glass sample at room temperature reached 60 MPa and 7.8GPa, respectively. UV-Vis spectra showed a transmittance is more than 82%.Secondly, we have investigated tile absorption and luminescent properties of QDs prepared by two methods. The results showed that the absorption shoulder of oil soluble PbS QDs was at 580 nm and water soluble PbS QDs was at 600-700 nm. And the emission peaks in the photoluminescence spectra were at 760 nm and 970 mn,respectively. XRD analysis confirmed that the PbS QDs were cubic phase. TEM results showed that the sizes of both types of PbS QDs were smaller than the exciton Bohr radius (18nm).In addition, quantum dots were dispersed into SBA-15 powder by using intermittent ultrasonication and mechanical stirring. Composite powders were obtained after Ar/H2 atmosphere heat treatment. Quantum dots maintained the original size, structure and morphology in the composite powders, except that a few large particles occurred.Finally, the composite powders were heated to the final sintering temperature (1080℃)using a heating rate of 100℃/min and a uniaxial pressure of 50 MPa. The glass contained oil soluble PbS QDs had an emission peak in 915nm. The glass contained 3wt%oil soluble PbS QDs had the strongest emission peak. UV-Vis spectra showed a transmittance lower than 45%. Modified Small Punch (MSP) strength and Vickers microhardness of this glass reached 35MPa and 7.4GPa, respectively. However, the glass contained water soluble PbS QDs had weak luminescence properties and its emission peak was at 990nm. The strength was also very low.In summary, through a combination of chemical synthesis and SPS sintering technology, we have successfully prepared luminescent glass embedded with QDs. Problems in semiconductor quantum dot glass were preliminarily solved.
Keywords/Search Tags:luminescent glass, quantum dots, SBA-15, near infrared luminescence, spark plasma sintering
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