Synthesis Of Pb(Cd)S Quantum Dots Embedded In Silica Glass Via SPS And Its Performance Study

Semiconductor Quantum dots (QDs) have attracted tremendous attention due to their uniquesize-dependent optoelectronic properties. PbS could obtain a stronger quantum confinement effectunder larger particle size, owing to its relatively narrow band gap energies (0.41eV at300K) andlarge excitation Bohr radius (20nm) from the corresponding bulk materials. The photoluminescence(PL) spectra of PbS QDs can be tuned from near-infrared to visible wavelength region by alteringthe particle size. As a result, PbS QDs have a widely range of applications in the fields of biology(biological labeling, targeted drug, etc), energy (solar cells), optics (laser, infrared detector,non-linear optics and optical switches, etc), etc. The CdS quantum dot is a typical II-Vl compoundsand wide bandgap semiconductor materials. It has great potential in the applications of solar-energyconversion, non-linear optics, photoelectrochemistry, photocatalysis, biological labeling and LEDs,etc. Therefore, it is great significance to reserach about PbS-QDs and CdS-QDs materials.In this paper, the controllable size, narrow distribution and stable concentration quantum dotsglasses which prepared by combining with the chemical synthesis of high quality PbS, CdS quantumdots and the spark plasma sintering (SPS) technology (Powder could not be melting directlysolidified into glass at a low temperature.). The high quality of PbS and CdS quantum dots weresynthesized via two-phase method, in situ polymerization and aqueous phase approach. Then, thesynthesized of PbS, CdS quantum dots were composited into mesoporous silica powder (SBA-15) toget PbS/SBA-15and CdS/SBA-15compound powder. Finally, the compound powder of PbS, CdSquantum dots glass was sintered SPS technology.First of all, the high quality SBA-15was prepared by a soft template. The synthesis SBA-15byfollowing approach: the reagents were under40℃for24h in oil bath, the hydrothermal blast oven was under130℃for72h. The sintering process of quartz glass by following: the SBA-15powderswere heated to the final sintering temperature (1080℃) under increased rate of100℃/min, anuniaxial pressure of50MPa and hold time about4min. The Vickers hardness of quartz glass was6.72GPa.Secondly, the synthesis of PbS and CdS quantum dots. Firstly, the cubic structure, wellcrystallized and narrow size distribution (the average particle size was4nm) of oil-soluble PbS-QDswas synthesized by two-approach. The monodispersed PbS-QDs have an absorption andphotoluminescence peak at570nm and736nm, respectively. Then, the colloidal PbS-QDs with thenarrow size distribution (the average particle size was3nm) and desirable monodispersed weresynthesized via a facile two-phase approach. The well crystallized of PbS-QDs have an absorptionand photoluminescence peak at290nm and430nm, respectively. Thirdly, PbS-QDs were preparedby in-situ polymerization method. The obtained PbS-QDs have a photoluminescence peak at970nmand the particle size was10nm calculated by Scherer’s formula. Fourthly, the water-solublePbS-QDs were synthesized via a facile approach. The as-prepared PbS-QDs have an absorption andphotoluminescence peak at800nm and960nm, respectively, and the average particle size was3.3nm calculated by Scherer’s formula. Fifthly, the water-soluble CdS-QDs were synthesized by using asingle-source organometallic precursor. The average particle size of cubic CdS-QDs was3.5nm. Theas-synthesized CdS-QDs have an absorption and photoluminescence peak at445nm and470nm,respectively.Then, the as-synthesized quantum dots were composited into SBA-15powder.PbS-QDs/SBA-15compound powder which mixed the oil-soluble PbS-QDs into SBA-15powderthen removing residual organic matter with high purity Ar gas protected in a tube furnace at differentheat treatment temperatures. As to the in-situ polymerization prepared PbS/SBA-15compoundpowder was calcinated to remove (3-thiolpropyl)-trimethoxysilane (SH) protected by Ar/H2gas inthe tube furnace calcination. The compound powder of CdS/SBA-15which CdS-QDs were directlymixed into SBA-15powder without purificating and stiring about5h. Then, the pure CdS/SBA-15compound powder was got by using a rotary evaporator to removed ethanol and thiourea.Finally, quantum dots silica glasses were obtained by sintering the PbS/SBA-15andCdS/SBA-15compound powder. The well distribution and monodispersed PbS-QDs glasses wereobtained by using SPS sintering technology, and the particle size of PbS-QDs was about8nm. Theglasses have a photoluminescence peak at789nm, and the intensity of emission reached maximumwhen the contained was3wt%. The Vickers microhardness of PbS-QDs glasses were graduallyreduced when the composite concentration increased. The well crystallized and desirablemonodispersed CdS-QDs glasses were obtained by using SPS sintering technology, and the particlesize of CdS-QDs was about5nm. It was great breakthrough that the CdS-QDs glasses have a quitenarrow photoluminescence peak at about510nm and full width at half maximum (FWHM) was less than25nm. The Vickers microhardness of CdS-QDs glasses were gradually reduced when theembedded concentration increased.In this manuscript, we have successful obtained quantum dot glasses via combining chemicalsynthesis of high-quality quantum dots with SPS sintering technology. The challenge, which thewide particle size distribution, uncontrolled concentration and low luminous intensity, is solved. It isnew ideas to assemble quantum dots glass with corresponding LED chip for high temperature andhigh power QDs-LED.