水溶性荧光黄掺杂硅溶胶的性能

采用溶胶-凝胶法将水溶性荧光黄染料掺杂到硅溶胶中,制备出荧光溶胶,研究了二氧化硅用量和染料用量对荧光溶胶的黏度、表面张力、相对荧光强度、紫外-可见吸收光谱等性能的影响。实验结果表明:随着二氧化硅用量的增加,荧光溶胶的黏度逐渐增加,表面张力逐渐减小。荧光溶胶的相对荧光强度和吸光度与荧光染液的相近;随着荧光染料用量的增加,荧光溶胶的相对荧光强度逐渐增加。当染料质量分数超过0.6%后,荧光溶胶的相对荧光强度开始有下降的趋势。

LED用YAG:Ce^(3+)荧光粉包覆SiO_2膜的研究

选用热稳定性好、无色透明的SiO2为包覆物,采用溶胶法,以正硅酸乙酯(TEOS)为硅源,对YAG:Ce3+荧光粉的表面进行SiO2膜的包覆研究,以解决LED荧光粉在使用过程中突出的热劣化问题。采用X射线衍射(XRD),扫描电子显微镜(SEM),透射电子显微镜(TEM)和荧光光谱(FS)等对包膜前后的YAG:Ce3+荧光粉的晶体结构、表面形貌、发光性能等进行表征和分析。结果表明,YAG:Ce3+荧光粉表面上包覆了一层均匀且致密的氧化硅膜层,且对包膜后的YAG:Ce3+荧光粉的发光性能基本没有影响,包覆效果较好。

The Element Size-Spectrum Distribution of Atmospheric Aerosol in Strong Autumn Winds over Beijing

Atmospheric aerosol samples collected in Beijing during 17-21 September 2004 were analyzed using the proton-induced X-ray emissions (PIXE) method,yielding concentrations of 20 elements.Analyzing the aerosol element size-spectrum distribution,enrichment factor (EF) and source over Beijing showed that under strong wind weather conditions,there were double peak distributions in the element size-spectra of Cu,S,K,Mn,As,Br,and Pb:one in fine mode and another in coarse mode.The peak in fine mode resulted from local emissions related to human activities,while the peak in coarse mode was caused by long range transport.The EF values of elements Ni,Cu,Zn,As,Se,Br,and Pb were relatively high,suggesting an evident characteristic polluted by regional aerosol.Results from factor analysis indicated that soil dust,coal-burning,industry and vehicle emissions contributed considerably to the autumn aerosol pollution in Beijing.

SOL-GEL SYNTHESIS AND LUMINESCENCE OF GREEN LIGHT EMITTING PHOSPHORS ZN_2SIO4/MN^(2+)

Mn^2＋ doped Zn2SiO4 phosphors were synthesized by sol-gel method, and the influence of zinc source, Mn^2＋ dopant concentration and annealing temperature were investigated. Results show that zinc nitrate based precursor with strong green emission intensities is better than zinc acetate based precursor. The intensity of green light emission reaches a peak at 254 nm when the Mn^2＋ dopant concentration is about 5%（ molar percentage）. Structural details of the phosphors were examined through X-ray diffractometry, thermogravimetric and differential thermal analysis. The result indicates that they are both rhombohedral structures, which remain amorphous below 700 ℃ and crystallize completely around 1000 ℃. The luminescent properties of Zn2SiO4/Mn^2＋ phosphors were characterized by excitation and emission spectra.

Preparation and luminescence properties of europium complex with α-naphthylacetic acid incorporated in silica matrix by sol-gel method

Europium ternary complex of Eu(NNA) 3(NNA=α-naphthylacetic acid) was embedded in silica matrix at different ratios by sol-gel method. The luminescence properties of silica composites were studied by comparing them with those of corresponding pure complex by means of excitation, emission spectra and lifetimes. The fluorescence lifetime was prolonged when the pure complex was incorporated in silica matrix. The relative fluorescence intensity and fluorescence lifetimes increased simultaneously with the increase of (Eu(NNA) 3.)

FLUORESCENCE STUDIES ON MORPHOLOGICAL CHANGE OF ST/DVB CROSSLINKED GELS DURING CHLOROMETHYLATION

The morphological change of St/DVB crosslinked gels during chloromethylation wasstudied by fluorescence spectroscopy using St/DVB crosslinked and hypercrosslinked gels as controlsamples. It has been found that with increase of chlorine content, the excimer emission band (~325nm)approaches to vanish, while the intensity of multi-ring aggregate emission band (~420nm) quicklyreaches a maximum, and then decreases sharply accompanied by appearance ofa new broad bandcentred at ca 488nm which roughly coincides with the typical emission band of hypercrossllinkedSt/DVB gels. Mearwhile, the result of IR measurement suggests that methylene bridge between phenylrings forms and increases with chloromethylation process. These results are explained in terms ofaside reaction of post-crosslinking, which densifies the loosely crosslinked networks and undoes thedensely entangled microgel nuclei. As a result, the morphology of the crosslinked gels becom es morehomogeneous with chloromethylation.

介孔LaVO4：Eu3＋的制备和荧光性能

以硝酸镧(La(NO3)3·6H2O)、硝酸铕(Eu(NO3)3·6H2O)、偏钒酸铵(NH4VO3)为原料,以十六烷基三甲基溴化铵(CTAB)为模板剂,用研磨-溶胶-凝胶法制备了三维蚯蚓状LaVO4:Eu3+介孔材料,并用XRD、XPS、TEM、BET、IR、FL等手段表征了材料的结构、形貌、比表面积、孔径分布及荧光性能。结果表明,在673 K焙烧所得的样品是四方锆石型结构的介孔材料,其比表面积达179.5 m2/g,平均孔径为2.56 nm,孔容积为0.115 m3/g,晶粒尺寸6.38 nm,表现出很强的红光发射(5D0→7F2)。适当提高焙烧温度能提高样品的红光发射,但焙烧温度过高(≥1273 K)则破坏材料介孔结构并使其荧光强度急剧降低。