复合磁性纳米NiFe2O4的制备及光谱特性

用微乳液化学剪裁方法制备了明胶包裹的复合纳米NiFe2 O4 。将明胶和亚铁盐以及镍盐制成凝胶 ,使该凝胶状反应物在微乳液的胶束中剪裁成微粒 ,再被还原 化合 成核长大。生成的微粒处于明胶蛋白分子的包裹之中。用XRD ,TEM ,EDS ,IR等测试表明 :微粒为明胶包裹球形纳米微粒。微球的平均粒径为 10～10 0nm ,单个微粒的粒径 3 3～ 4 6nm。每个复合微球中约有 3～ 2 2个NiFe2 O4 粒子。NiFe2 O4 复合微粉的比饱和磁化强度σs=36 31× 10 3 4π(A·m- 1 ·g- 1 ) ,矫顽力Hc=6 75 0A·m- 1 ,剩磁Br=4 39× 10 3 4π(A·m- 1 ·g- 1 )。     

三硼酸铯和硼酸铯锂晶体的晶格振动光谱研究

本文对新型非线性光学晶体三硼酸铯（ＣｓＢ３Ｏ５∶ＣＢＯ）和硼酸铯锂（ＣｓＬｉＢ６Ｏ１０∶ＣＬＢＯ）进行了晶格振动光谱研究。首先对两种晶体的基本晶格振动模进行了对称性分类,记录了两种晶体低温下的拉曼光谱和室温下的红外反射光谱,对晶体的晶格振动模进行了认定,将振动模归属于平面六元环（Ｂ３Ｏ６）和四面体（ＢＯ４）。然后比较了ＣＢＯ,ＣＬＢＯ和ＬＢＯ（ＬｉＢ３Ｏ５）三种晶体的晶格振动光谱,讨论了阳离子对振动光谱的影响。另外,还讨论了硼酸盐晶体晶格振动模ＬＯ ＴＯ分裂的大小与晶体非线性光学系数之间的关系。     

掺杂的Bi4Ge3O12晶体的近红外发光性能

生长了Mg、Ca离子掺杂(提拉法)和Cl离子掺杂(坩埚下降法)的Bi₄Ge₃O₁₂(BGO)晶体,测试了晶体样品的吸收谱、光致发光谱和发光衰减时间等。这些掺杂的BGO晶体的可见光发光比纯BGO有所减弱,但在808 nm和980 nm激光二极管(LD)激发下出现了纯BGO几乎没有的近红外发光,归因于改变了能级的Bi离子或可能出现的低价态Bi离子。掺杂对近红外发光的影响跟掺杂离子价态有关,同价态的掺杂离子对近红外发光的影响相差不大。     

O_2在Si掺杂石墨烯上吸附与活化

采用包含色散力校正的密度泛函理论方法(DFT-D)研究了O2在Si掺杂石墨烯(Si-Gra)上吸附与活化.研究结果表明:1)与纯净石墨烯相比,Si掺杂极大的增强了石墨烯对O2的吸附能力.O2的最稳定吸附构型是以Side-on模式吸附在掺杂的Si的顶位,形成O-Si-O三元环.次稳定吸附构型是与Si及近邻的一个C形成O-Si-C-O四元环结构.两个吸附构型对应的吸附能分别为-2.40和-1.93eV;2)O2有两种分解路径:直接分解路径(势垒为0.53eV)和整体扩散后的分解路径(势垒为0.81eV);3)分解之后的两个O原子分别吸附在Si的顶位和相邻碳环的两个碳原子的桥位;4)电子结构分析表明吸附的O2从Si-Gra获得较多电荷,从而被活化.总之,Si-Gra具有较强的催化氧气还原能力,是一种潜在的良好的非金属氧还原催化剂.     

Gd~(3+),Tm~(3+)和Yb~(3+)掺杂的Y_2O_3微晶中Gd~(3+)离子的紫外上转换发光及其增强的研究

采用均相沉淀法制备了Y(OH)3微米颗粒,经1 100℃焙烧后制备出具有上转换发光性质的Yb3+-Tm3+-Gd3+共掺的Y2O3微米晶体,讨论了Yb3+-Tm3+-Gd3+在Y2O3中能量传递过程及壳层对发光强度的影响。980 nm近红外光激发下的上转换光谱表明,在Yb3+-Tm3+-Gd3+共掺Y2O3体系中,核-壳结构大幅提高了Gd3+离子和Tm3+离子的上转换发光强度,尤其是样品在紫外发光部分的增强相比于可见和红外光部分更为明显。同时,通过研究Tm3+和Gd3+在不同波段的发光强度与泵浦功率的关系探讨了氧化物中上转换发光的机制。     

Nanospherical Surface‐Supported Seeded Growth of Au Nanowires: Investigation on a New Growth Mechanism and High‐Performance Hydrogen Peroxide Sensors

In this paper, a novel strategy with a new growth mechanism for fast and large‐scale growth of Au long nanowires on high‐curvature SiO₂ nanospherical surfaces has been developed. The synthesis includes three steps, i.e., amino modification of SiO₂ nanospheres, Au seed loading on aminated SiO₂ nanospheres and subsequently, Au seed‐mediated nanowire growth on SiO₂ nanospheres. The prepared Au nanowires (Au NWs) (exhibit long length, high aspect ratio, and good flexibility, and can naturally form the dense nanowire film, which is promising as a stable conductive electrode. In addition, the effect of synthetic conditions such as reactant feeding order, Au seeds and SiO₂@Au seeds on the morphology of Au nanostructures (nanowires, nanoteeth, and nanoflowers) has been investigated. It is found that Au seeds and high‐curvature SiO₂ nanospherical surfaces are necessary conditions for the successful preparation of Au NWs and nanowire films. The different growth mechanisms for Au NWs and nanoteeth have been proposed and discussed. Moreover, the novel nonenzymatic H₂O₂ sensor based on Au NWs exhibits much enhanced performance such as higher sensitivity, stability, and selectivity, wider linear range and lower detection limit, compared with that of Au nanoparticles‐based H₂O₂ sensor.     

铕激活的铝酸锶镁的合成及发光特性

研究了二价铕激活的Sr1-nMgnAl2O4的合成、发光性质以及基质组分Sr/Mg摩尔比与荧光性质的关系，并对其余辉及衰减进行了测定。     

New experimental evidence of the structural modification in single crystal Bi2Sr2CaCu2Oy by X-ray diffraction observation

The variations of the high angle 00 peak-shape by means of X-ray l scans of the 00l fundamental reflections were investigated in detail for a highly oriented Bi₂Sr₂CaCu₂O_y (Bi2212) crystal with sufficiently small intrinsic mosaicity and the same crystal annealed in air at 250, 300, 400, 600, and 750°C for 20 h in consequence. For the first time, we observed a new additional reflection almost overlapped original 00l fundamental reflection at annealing temperature below 400°C by X-ray diffraction measurement, which shows that there coexisted two sets of lattice periodicity in the c-direction of the annealed crystal. The new additional reflection appeared at 250°C and disappeared at 400°C. Its intensity was increased at 300°C. The measurements of the AC susceptibility, c-axis parameter and full width at half maximum (FWHM) of the 00 peaks showed that the new additional reflection was associated with the oxygen diffusion in CuO₂ planes and the changes of strain field. The results provide the new experimental evidence that the structural distortion is more sensitive to the oxygen diffusion in CuO₂ planes than to that in Bi–O layers.     

Effect of Li2O doping on electrical properties of CoFe2O4

The solid–solid interactions between cobalt and ferric oxides to produce CoFe₂O₄ were followed up using XRD investigation. The effect of Li₂O-doping on the ferrite formation was also studied. The electrical and dielectric parameters of pure and doped mixed solids precalcined at 1273 K were measured using d.c and a.c instruments.The dopant concentration was varied between 0.5 and 6 mol% Li₂O. The results obtained revealed that Li₂O doping much enhanced the ferrite formation due to an increase in the mobility of the reacting species.

The addition of the smallest amount of Li₂O (0.5 mol%) resulted in measurable variations in the electrical constants (ρ, E_a, ′, ″ and tan δ). Resistivity increased upon increasing the dopant concentration up to 1.5 mol% exceeding the values measured for the undoped sample. Furthermore, the presence of 6 mol% Li₂O brought about a significant decrease of electrical resistivity. Also, the activation energy decreased with increasing the dopant concentration. The dielectric constant behaves according to ε=const. 1/ρ^1/2.

The Li₂O-doping modified the values of different dielectric constants, the change in these constants was found to be strongly dependent on the amount of Li₂O added.These results have been discussed in terms of the potentiality of Li₂O in increasing the mobility of the reacting species involved in the ferrite formation.     

CO2激光局域热固定光折变全息的一种新方法

提出用ＣＯ２激光加热后记录固定的方案对ＬｉＮｂＯ３晶体中的全息进行实时实地局域热固定。通过加载绝热体,利用连续激光加热晶体全部范围至接近２００℃,停止加热开始记录,到该区域温度降屋１００℃时,将固定一个体全息。文中给出了热传导模型及其数值解。由得到的初步结果参数进行了一系列实验。实验结果显示,管种方案可成功地对光折变全息进行实时实时局域热固定,并且具有温度更均匀的特点,所固定的全息质量有较大改善。