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1.
Using La2(SO4)3 and the active carbon powder as reactants, La2O2S∶Mn2+ red phosphor was synthesized by microwave radiation method. The phosphor was characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), laser-diffraction size analyzer and fluorospectrophotometer. The XRD analysis showed that the phosphor was pure phase La2O2S. The phosphor of La2O2S∶Mn2+ showed hexagonal crystal structure with diverse shapes, such as spherical and rod, with average particle size of 10.22 μm. The emission and excitation spectra of the phosphor were determined by fluorospectrophotometer and the results showed that the excitation spectrum of the phosphor under 600 nm emission wavelength was excitation bands between 250 nm and 350 nm with a peak value of 303 nm. Then ,when exicited under UV 303 nm, the phosphor showed broad band emission of 550~700 nm with a peak at 607 nm. In addition, the optimal effects were obtained for the phosphor preparation when the concentration of the activator Mn2+ was xMn=0.01, the ratio of C and O (nC / nO) in the reactants was 0.6∶1, and the time of reaction was about 1 h. La2O2S∶Mn2+ has strong absorption of UV spectrum and can emit bright red light.  相似文献   

2.
水溶性荧光CdSe量子点的合成及其在指纹显现中的应用   总被引:4,自引:0,他引:4  
Water-soluble fluorescent CdSe quantum dots(QDs) were synthesized by using Se、Na2SO3 and CdCl2 as precursors and mercaptoacetic acid(TGA) as modifier. The effects of refluxing time and initial pH values of the reaction on the particle size and fluorescence intensity of CdSe QDs were studied. The XRD、HRTEM and fluorescent spectroscopy were employed to characterize these samples. It is found that CdSe QDs with crystalline size of 2~3 nm are homogeneously distributed in the organic matrix. The maximum fluorescence absorption and emission peak of CdSe QDs solution are at 450 nm and 562 nm, respectively. The fingerprint details on the surface of smooth objects were clearly developed with CdSe QDs solution under irradiation of UV lights.  相似文献   

3.
球形Gd2O3∶Eu纳米发光材料的制备   总被引:1,自引:0,他引:1  
Spherical nanometer Gd2O3∶Eu luminescent materials were prepared by homogeneous precipitation method, and the properties were studied also. TG, FTIR and XRD analysis showed that the precursor was carbonate, the cubic Gd2O3was obtained after calcination. TEM photographs indicated that the samples were spherical and well dispersed with nanometer and submicrometer size of 200~300 nm which is the nanoparticles’ aggregate. The mechanics of agglomerating growth is also discussed. ED photograph showed that the particle was crystalline. The PL analysis exhibited that CTB band of nanometer Gd2O3∶Eu was of 17 nm red shift to bulk materials, and the emission peak was broadened due to the surface and interface effect of nanocrystals.  相似文献   

4.
The spheric La2O3∶Eu nanocrystals were prepared using NH3·H2O-NH4HCO3 mixture as precipitant. The material was characterized by FTIR, XRD and TEM techniques. The luminescence properties of Eu3+ in spheric La2O3 were measured by three dimension spectra, emission and excitation spectra. The results indicate that the La2O3∶Eu nanocrystals are in hexagonal phase by annealing at 800 ℃, the crystal size is about 30 nm. The maximum emission and excitation wavelength were determined by three dimensional spectroscopy to be at 591 nm and 394 nm, respectively. In emission spectrum the band at 591 nm and 612 nm are corresponding to 5D0-7F1 and 5D0-7F2 transition of Eu3+ ions. With increasing in annealing temperature the differences of intensity of the two transitions are increased. This phenomenon shows that the luminescence intensity of La2O3∶Eu nanocrystals can be tuned by changing annealing temperature.  相似文献   

5.
二硫代乙二酰胺合镍在硫化镉纳米晶表面的逐层配位组装   总被引:1,自引:0,他引:1  
CdS nanocrystals, which were surface modified by poly (nickel dithioxamide) [Ni(DTO)]n, were prepared and characterized. TEM image showed that the shape and the outward aspect of the modified CdS sample were essentially the same as those of the original material and no impurities were found. The characteristic IR peaks at 1 513cm-1 and 870 cm-1 confirmed the success in assembling [Ni(DTO)]n on the surface of CdS. For XPS spectra, the characteristic bands of Ni2p3/2 and Ni2p1/2 appeared at 856 eV and 877 eV indicating the nickel in Ni(Ⅱ) oxidation state. The solid state electronic spectra showed the improvement in surface energy gap, which was changed from 2.38 eV to below 1.91 eV.  相似文献   

6.
A phosphor, Ba0.97Al2Si2O8∶Eu2+, was synthesized by high temperature solid-phase method at different temperatures. The samples were characterized by TG/DTA, XRD and fluorescence spectroscopy. The results show that the main phase for host of these luminescence materials is barium feldspar BaAl2Si2O8∶Eu2+ and there is a transition from hexagonal crystal system to monoclinic crystal system in the process of the sintering of barium feldspar. The luminescent phenomen of barium feldspar with hexagonal structure can not be observed under the excitation of ultraviolet lamp of 365 nm while the barium feldspar with monoclinic structure has excellent luminescence properties. The excitation spectra of all these samples show broad band spectra ranging from 250~390 nm with peak at λex of 357 nm,which indicates that these samples can be effectively excited by near ultraviolet ; the emission spectra range from 380~600 nm with peak at λem of 433 nm. The luminescent intensity increases then decreases with the concentration of doping Eu2+ ions. When the concentration of dopants is 2.5mol%, the luminescent intensity reaches the maximum value. When the concentration of Eu2+ ions changes from 0.5mol% to 2.5mol%, the emission peak has a red shift from 427 nm to 440 nm.  相似文献   

7.
TiO2纳米管负载Ag、Au、Pt纳米粒子的微波合成与表征(英)   总被引:8,自引:0,他引:8  
TiO2 nanotubes were prepared under normal pressure at a temperature of 120 ℃. Ag, Au, Pt nanoparticles supported on TiO2 nanotubes were prepared by microwave assisted heating polyol process. TEM images showed that microwave prepared Ag, Au, Pt nanoparticles supported on TiO2 nanotubes were small and well dispersed on the surface of the TiO2 nanotubes. UV-Vis absorption spectra showed that the absorbance of Ag/TiO2 nanotubes and Au/TiO2 nanotubes in the visible light range increased greatly compared to the single titania nanotubes.  相似文献   

8.
The structure default of kaolinites was characterized with 1H MAS NMR and Raman spectra. Although the HI indexes of Suzhou and Maoming kaolinite are similar, their 1H MAS NMR and Raman spectra are very different. 1H MAS NMR showed that the hydroxyl proton chemical shifts of Suzhou kaolinite are in the higher field and with larger different between the inner surface hydroxyls protons and inner hydroxyls proton chemical shifts than Maoming kaolinite. Raman spectra showed that the surface hydroxyls stretching vibration bands of Suzhou kaolinite are in the high frequency region, and the half height widths of the bands are 7.0~14 cm-1. The area ratio Sz/(Sz+SA), where SZ and SA are the areas of bands 3685 cm-1 and 3695 cm-1 respectively, is 0.23. But the surface hydroxyls stretching vibration bands of Maoming kaolinite are in the low frequency region, and the half height widths of the bands are 8.9~15.1 cm-1. The area ratio Sz/(Sz+SA) is 0.77. Those data proved that Suzhou kaolinite has lower structure default than Maoming kaolinite and 1H MAS NMR and Raman spectra are effective method for study of kaolinite structure default.  相似文献   

9.
自激活白光发射Ba2TiP2O9发光材料的发光特性   总被引:2,自引:0,他引:2  
The Ba2TiP2O9 phosphor was synthesized via the conventional high-temperature solid-state method. The Ba2TiP2O9 phosphor showed high luminance white-light emitting when excited under 254 nm radiation. Furthermore, obvious long-lasting phosphorescence could be observed when the UV excitation source had been removed. XRD and photoluminescence (PL) spectra as well as the luminance decay were used to characterize the synthesized phosphor. The results of XRD indicated that the products obtained under 1 100 ℃ for 3 h had a good crystallization. Both the PL spectra and luminance decay measurement revealed that this kind of phosphors was a new kind of white-light-emitting phosphor. The thermoluminescence properties have also been investigated. The energy level of the 352 K and 493 K TL peaks have also been calculated and found that their energy level values were 0.35 eV and 1.08 eV, respectively. The 352 K TL peak is responsible for the origin of the long-lasting phosphorescence.  相似文献   

10.
N 掺杂TiO2光催化剂的制备及其可见光活性研究   总被引:15,自引:0,他引:15  
A visible-light-active photocatalyst was prepared by calcination of the hydrolysis product of tetrabutyl titanate with ammonia as precipitant. The photocatalyst was characterized by X-ray diffraction (XRD), UV-Vis diffuse reflection spectra (DRS), thermal gravimetric-differential thermal analysis (TG-DTA), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM). The color of the photocatalyst was yellow and could absorb light wavelength under 550 nm as measured by DRS. The catalyst calcined at higher temperature will give lower absorbance for visible light. Structures of the sample were characterized mainly to be anatase by XRD except for the sample calcined at 700 ℃ which gave mixtures of anatase and rutile. TG-DTA results showed that temperature for anatase formation was 415 ℃. XPS results showed that doped-nitrogen was presented in the sample, they are important to show visible-light absorbency. The photocatalytic activities were evaluated using methyl orange and phenol as model pollutants, the results showed that over 90% of phenol could be degraded under visible light using N/TiO2 as the catalyst after 4 hours reaction. Almost the same activity was found for the TiO2 photocatalyst calcined at different temperature under sunlight but activities were different when the treatment was under UV light.  相似文献   

11.
In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.  相似文献   

12.
KMnO4-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.  相似文献   

13.
The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.  相似文献   

14.
Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.  相似文献   

15.
A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.  相似文献   

16.
The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp3)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp2)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp2)?H and aliphatic 1,5- and 1,6-C(sp3)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp3)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp2)?H insertion.  相似文献   

17.
The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.  相似文献   

18.
An efficient approach to the synthesis of highly congested di, penta and hexacyclic pyrazoles as well as imidazole fragment containing novel heterocyclic molecule has been developed through a carbanion induced transformation of suitably functionalized 2H-pyran-2-ones, benzo[h]chromene and thiochromeno[4,3-b]pyrans. Due to the presence of fluorescence, we report their prime application metal sensor as off/on switching in ferric ions.  相似文献   

19.
N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).  相似文献   

20.
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