III-Vsemiconductor nanocrystals rarely exist as spherical inclusions inside glasses, due to difficulties during their preparation, such as high toxic reagents or fast oxidation under usual glass technology temperature...III-Vsemiconductor nanocrystals rarely exist as spherical inclusions inside glasses, due to difficulties during their preparation, such as high toxic reagents or fast oxidation under usual glass technology temperatures. In this article a sol-gel method for synthesis of InP nanocrystals embedded in silica glasses was described. Gels were synthesized by hydrolysis of a complex solution of Si(OC 2 H 5 ) 4 , InCl 3 4H 2 O and PO(OC 2 H 5 ) 3 . Then, the gels were heated at 600 o C in the presence of H 2 gas to form fine cubic InP crystallites. Raman spectrum showed InP longitudinal-optic mode (342cm -1 ) and transverse-optic mode (303cm -1 ). The size of InP nanocrystals was found to be from 2 to 8 nm in diameter by transmission electron microscopy. A strong photoluminescence with peaks at, 606, 730nm 856 nm was observed from 3InP/100SiO 2 nanocompositions. The temperature-and excitation power-dependent PL spectra from the nanocomposition are measured in order to confirm the origin of the PL spectra. These behaviors of the three peaks emissions suggest that 606, 733, and 856 nm emissions do not have the same origin. The PL with peak at 856nm arise from the cubic InP nanocrystallites embedded in the SiO 2 gel glasses. The 605 and 732 nm emissions may arise from the SiO 2 gel glass matrix or the interface between the InP crystallite core and SiO2 glass matrix.展开更多
A new citrate acid-hydrazine sol-gel route for preparation of Co3O4 nanoparticles has been developed. Co3O4 nanoparticles with different particle-sizes and morphology were prepared at different heat-treatment temperat...A new citrate acid-hydrazine sol-gel route for preparation of Co3O4 nanoparticles has been developed. Co3O4 nanoparticles with different particle-sizes and morphology were prepared at different heat-treatment temperatures and the pure cubic nanocrystals of Co3O4 were obtained at 600℃. The synthesis process was monitored by infrared spectroscopy (IR), thermal gravimetric and differential thermal analysis (TG-DTA). The structure and morphology of Co3O4 nanocrystals were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and X-ray-photoelectron spectroscopy (XPS). The infrared absorption bands blue-shifted with particle size decreasing, which could be attributed to increasing surface effect. XPS results showed that predominant species at surface layers of Co3O4 nanocrystals are octahedral Co (Ⅲ).展开更多
New Ge/SiO_2 glasses have been synthesized by heating the GeO_2/SiO_2 dry gels under H_2gas at 700℃. The resulting fluorescence spectra show that this kind of Ge/SiO_2 glasses emit strongphotoluminescence at 392 nm (...New Ge/SiO_2 glasses have been synthesized by heating the GeO_2/SiO_2 dry gels under H_2gas at 700℃. The resulting fluorescence spectra show that this kind of Ge/SiO_2 glasses emit strongphotoluminescence at 392 nm (3.12 eV), medium strong photoluminescence at 600 nm (2.05 eV)and weak photoluminescence at 770 nm (1.60 eV) respectively. Possible photoluminescencemechanisms are also discussed based on the results of X-ray diffraction (XRD) and X-rayphotoelectron spectra(XPS).展开更多
（N, F）-codoped anatase TiO2 nanocrystals with active visible light response were prepared by using a simple sol-gel approach. X-ray photoelectron spectroscopy measurements suggested that the substitutional N and F s...（N, F）-codoped anatase TiO2 nanocrystals with active visible light response were prepared by using a simple sol-gel approach. X-ray photoelectron spectroscopy measurements suggested that the substitutional N and F species replaced the lattice oxygen atoms in TiO2 nanocrystals. Such nanocrystals showed strong absorption from 400 to 550 nm, which was mainly induced by nitrogen doping. The phase transformation from anatase to rutile was hindered by fluorine doping at high calcination temperatures, which was verified by XRD patterns. The N2 adsorption-desorption isotherms revealed the absence of mesopores in these nanocrystals. The （N, F）- codoped TiO2 nanocrystals showed satisfying photocatalytic activity on the photo-degradation of methylene blue under visible light.展开更多
A thcile one-step sol-gel method was used to prepare CdTe nanocrystals（NCs） doped silica microspheres with luxuriant thiol group on their surface using 3-mercaptopropyl trimethoxysilane（MPTMS） as organosilane in t...A thcile one-step sol-gel method was used to prepare CdTe nanocrystals（NCs） doped silica microspheres with luxuriant thiol group on their surface using 3-mercaptopropyl trimethoxysilane（MPTMS） as organosilane in the aqueous solution. As the ligand and organosilane, MPTMS ensured the doping efficiency of CdTe NCs by ligand exchange and a large thiol group exposed to the solution to activate the surface of silica microspheres. The remodeled sol-gel process was performed at a lower temperature, which protected the thiol groups from degradation. Meanwhile, the particle size and size distribution can be controlled by varying synthesis conditions, such as the stirring rate and the reaction temperature. This user-friendly method provides a plattbrm tbr immobilization of chemical groups such as carboxyl for combination of bioactive and diagnostic molecules at the surface of CdTe NCs doped silica micro- spheres through thiol-ene chemistry for high-throughput microarrays.展开更多
Pb_ 1-xLa_xTi_ 1-x/4O_3 nanocrystals with different amounts of lanthanum were prepared by modified sol-gel method and detected by FT-Raman spectra at 288 and 378 K, respectively. The improved synthetic technique used ...Pb_ 1-xLa_xTi_ 1-x/4O_3 nanocrystals with different amounts of lanthanum were prepared by modified sol-gel method and detected by FT-Raman spectra at 288 and 378 K, respectively. The improved synthetic technique used in this paper could obtain nanocrystals with apparently promoted synthetic speed from a few days to several hours (4 times faster of hydrolytic process than that of traditional sol-gel method and reduced preparation period of gel from 24 h to several hours) at relatively lower temperature by hydrolysis of sol to gel through adding methyl alcohol/water solution into sol under vigorous stirring and annealed the fresh gel directly. The effects of lanthanum′s amount, annealed temperature and nanocrystals′ grain size of Pb_ 0.9La_ 0.1Ti_ 0.975O_3 nanocrystals on frequency, shape and width of the phonon peak were also discussed in detail.展开更多
In present work, the optical and structural properties of silica sol-gel glasses and glass-ceramic materials singly- and dou- bly-doped with Eu3＋ and Gd3＋ ions were investigated. The optical properties of studied sy...In present work, the optical and structural properties of silica sol-gel glasses and glass-ceramic materials singly- and dou- bly-doped with Eu3＋ and Gd3＋ ions were investigated. The optical properties of studied systems were determined based on absorption, excitation and emission spectra as well as luminescence decay analysis. Conducted studies clearly indicated a significant enhance- ment of visible emission originated from Eu3＋ ions as a result of changing the excitation mechanism, via Gd3＋Eu3＋ energy transfer. The luminescence intensity R-ratio was analyzed before and after heat-treatment process upon excitation at λex=393 nm and λex=273 nm. Moreover, the influence of excitation wavelength on luminescence decay time of the 5D0 excited state was also analyzed. The GdS＋-Eu3＋ energy transfer efficiencies for precursor and annealed samples were calculated based on luminescence lifetime of the 6p7/2 level of Gd3＋ ions. The X-ray diffraction measurements were conducted to verify the nature of obtained sol-gel materials. In re- sult, the formation of orthorhombic GdF3 nanocrystal phase dispersed in amorphous silica glass host was identified after annealing. Obtained results clearly indicated an incorporation of Eu3＋ activators into formed GdF3 nanocrystals. Thus, conducted heat-treatment process led to considerable changes in surrounding environment around Eu3＋ ions. Actually, it was found that en- ergy transfer phenomenon and heat-treatment process were responsible for significant improvement of Eu3＋ luminescence in stud- ied sol-gel samples.展开更多
A new method for the synthesis of CdS nanocrystals in polymer-impregnated sol-gel matrix was（described）.The CdS nanocrystals were prepared by simply passing H2S in polymer/silica sol-gel composite matrix formed by t...A new method for the synthesis of CdS nanocrystals in polymer-impregnated sol-gel matrix was（described）.The CdS nanocrystals were prepared by simply passing H2S in polymer/silica sol-gel composite matrix formed by the in situ polymerization of tetraethoxysilane in Cd2+ containing polymer microgel.The synthesized CdS nanocomposite were characterized by means of X-ray diffraction（XRD）,UV-Vis spectroscopy and TEM.X-ray diffraction and TEM results show that hexagonal CdS nanocrystals are well dispersed in polymer/silica composite matrix.The results of UV-Vis spectroscopy demonstrate that the size of CdS nanocrystals can be adjusted from 1.0 nm to 2.4 nm by changing the amount of H2S.展开更多
文摘III-Vsemiconductor nanocrystals rarely exist as spherical inclusions inside glasses, due to difficulties during their preparation, such as high toxic reagents or fast oxidation under usual glass technology temperatures. In this article a sol-gel method for synthesis of InP nanocrystals embedded in silica glasses was described. Gels were synthesized by hydrolysis of a complex solution of Si(OC 2 H 5 ) 4 , InCl 3 4H 2 O and PO(OC 2 H 5 ) 3 . Then, the gels were heated at 600 o C in the presence of H 2 gas to form fine cubic InP crystallites. Raman spectrum showed InP longitudinal-optic mode (342cm -1 ) and transverse-optic mode (303cm -1 ). The size of InP nanocrystals was found to be from 2 to 8 nm in diameter by transmission electron microscopy. A strong photoluminescence with peaks at, 606, 730nm 856 nm was observed from 3InP/100SiO 2 nanocompositions. The temperature-and excitation power-dependent PL spectra from the nanocomposition are measured in order to confirm the origin of the PL spectra. These behaviors of the three peaks emissions suggest that 606, 733, and 856 nm emissions do not have the same origin. The PL with peak at 856nm arise from the cubic InP nanocrystallites embedded in the SiO 2 gel glasses. The 605 and 732 nm emissions may arise from the SiO 2 gel glass matrix or the interface between the InP crystallite core and SiO2 glass matrix.
基金This work was financially supported by the Program of International Cooperation of Science & Technology between China and Ukraine (No. 043-05)the Joint Program between the Educational Committee and Economic Trade Committee of Gansu Provience (No. CX-
文摘A new citrate acid-hydrazine sol-gel route for preparation of Co3O4 nanoparticles has been developed. Co3O4 nanoparticles with different particle-sizes and morphology were prepared at different heat-treatment temperatures and the pure cubic nanocrystals of Co3O4 were obtained at 600℃. The synthesis process was monitored by infrared spectroscopy (IR), thermal gravimetric and differential thermal analysis (TG-DTA). The structure and morphology of Co3O4 nanocrystals were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and X-ray-photoelectron spectroscopy (XPS). The infrared absorption bands blue-shifted with particle size decreasing, which could be attributed to increasing surface effect. XPS results showed that predominant species at surface layers of Co3O4 nanocrystals are octahedral Co (Ⅲ).
文摘New Ge/SiO_2 glasses have been synthesized by heating the GeO_2/SiO_2 dry gels under H_2gas at 700℃. The resulting fluorescence spectra show that this kind of Ge/SiO_2 glasses emit strongphotoluminescence at 392 nm (3.12 eV), medium strong photoluminescence at 600 nm (2.05 eV)and weak photoluminescence at 770 nm (1.60 eV) respectively. Possible photoluminescencemechanisms are also discussed based on the results of X-ray diffraction (XRD) and X-rayphotoelectron spectra(XPS).
基金supported by the Excellent Young Teachers Program of MOEKey Project of Shanghai Science and Technology Committee (No. 06DZ05025),China
文摘（N, F）-codoped anatase TiO2 nanocrystals with active visible light response were prepared by using a simple sol-gel approach. X-ray photoelectron spectroscopy measurements suggested that the substitutional N and F species replaced the lattice oxygen atoms in TiO2 nanocrystals. Such nanocrystals showed strong absorption from 400 to 550 nm, which was mainly induced by nitrogen doping. The phase transformation from anatase to rutile was hindered by fluorine doping at high calcination temperatures, which was verified by XRD patterns. The N2 adsorption-desorption isotherms revealed the absence of mesopores in these nanocrystals. The （N, F）- codoped TiO2 nanocrystals showed satisfying photocatalytic activity on the photo-degradation of methylene blue under visible light.
基金Supported by the National Program on Key Research ＆ Development Program Sub-project, China（No.2016YFC0800901- Z01 ） and the National Natural Science Foundation o f China（Nos.21271082, 21301066, 21371068, 21401073）.
文摘A thcile one-step sol-gel method was used to prepare CdTe nanocrystals（NCs） doped silica microspheres with luxuriant thiol group on their surface using 3-mercaptopropyl trimethoxysilane（MPTMS） as organosilane in the aqueous solution. As the ligand and organosilane, MPTMS ensured the doping efficiency of CdTe NCs by ligand exchange and a large thiol group exposed to the solution to activate the surface of silica microspheres. The remodeled sol-gel process was performed at a lower temperature, which protected the thiol groups from degradation. Meanwhile, the particle size and size distribution can be controlled by varying synthesis conditions, such as the stirring rate and the reaction temperature. This user-friendly method provides a plattbrm tbr immobilization of chemical groups such as carboxyl for combination of bioactive and diagnostic molecules at the surface of CdTe NCs doped silica micro- spheres through thiol-ene chemistry for high-throughput microarrays.
文摘Pb_ 1-xLa_xTi_ 1-x/4O_3 nanocrystals with different amounts of lanthanum were prepared by modified sol-gel method and detected by FT-Raman spectra at 288 and 378 K, respectively. The improved synthetic technique used in this paper could obtain nanocrystals with apparently promoted synthetic speed from a few days to several hours (4 times faster of hydrolytic process than that of traditional sol-gel method and reduced preparation period of gel from 24 h to several hours) at relatively lower temperature by hydrolysis of sol to gel through adding methyl alcohol/water solution into sol under vigorous stirring and annealed the fresh gel directly. The effects of lanthanum′s amount, annealed temperature and nanocrystals′ grain size of Pb_ 0.9La_ 0.1Ti_ 0.975O_3 nanocrystals on frequency, shape and width of the phonon peak were also discussed in detail.
文摘In present work, the optical and structural properties of silica sol-gel glasses and glass-ceramic materials singly- and dou- bly-doped with Eu3＋ and Gd3＋ ions were investigated. The optical properties of studied systems were determined based on absorption, excitation and emission spectra as well as luminescence decay analysis. Conducted studies clearly indicated a significant enhance- ment of visible emission originated from Eu3＋ ions as a result of changing the excitation mechanism, via Gd3＋Eu3＋ energy transfer. The luminescence intensity R-ratio was analyzed before and after heat-treatment process upon excitation at λex=393 nm and λex=273 nm. Moreover, the influence of excitation wavelength on luminescence decay time of the 5D0 excited state was also analyzed. The GdS＋-Eu3＋ energy transfer efficiencies for precursor and annealed samples were calculated based on luminescence lifetime of the 6p7/2 level of Gd3＋ ions. The X-ray diffraction measurements were conducted to verify the nature of obtained sol-gel materials. In re- sult, the formation of orthorhombic GdF3 nanocrystal phase dispersed in amorphous silica glass host was identified after annealing. Obtained results clearly indicated an incorporation of Eu3＋ activators into formed GdF3 nanocrystals. Thus, conducted heat-treatment process led to considerable changes in surrounding environment around Eu3＋ ions. Actually, it was found that en- ergy transfer phenomenon and heat-treatment process were responsible for significant improvement of Eu3＋ luminescence in stud- ied sol-gel samples.
文摘A new method for the synthesis of CdS nanocrystals in polymer-impregnated sol-gel matrix was（described）.The CdS nanocrystals were prepared by simply passing H2S in polymer/silica sol-gel composite matrix formed by the in situ polymerization of tetraethoxysilane in Cd2+ containing polymer microgel.The synthesized CdS nanocomposite were characterized by means of X-ray diffraction（XRD）,UV-Vis spectroscopy and TEM.X-ray diffraction and TEM results show that hexagonal CdS nanocrystals are well dispersed in polymer/silica composite matrix.The results of UV-Vis spectroscopy demonstrate that the size of CdS nanocrystals can be adjusted from 1.0 nm to 2.4 nm by changing the amount of H2S.
