A high-pressure study of PbCO3 by XRD and Raman spectroscopy

The pressure-induced phase transitions of PbCO3 are studied using synchrotron radiation in a diamond anvil cell at room temperature. The XRD measurement indicates that PbCO3 with an initial phase of aragonite-type structure undergoes two phase transitions at ～7.8GPa and ～15.7GPa respectively. The higher-pressure phase appearing at ～ 15.7GPa is stable up to 51.8GPa. The two phase transitions are further confirmed by Raman scattering up to 23.3GPa. During the decompression process, the high-pressure phases of PbCO3 are gradually recovered to the starting aragonite-type structure, but exhibit some hysteresis. The bulk modulus B0 of the aragonite-type structure is obtained to be 63±(3) GPa by fitting the volume-pressure data to the Birch-Murnaghan equation of states with B0 fixed to 4.     

高效荧光碳点的制备及其对金属离子的检测研究

采用氮和硫元素共掺杂的水热法合成了一种发蓝光的碳点.经过一系列的光学和微观结构表征分析,发现氮和硫元素可以通过杂原子掺杂和表面官能团的形式充分参与到碳点中,这决定了所制备的蓝光碳点拥有最高54.27%的量子产率.由于其高效荧光,该碳点可以用作传感探头检测金属离子,且对Ag+和Fe3+具有高灵敏度和选择性,通过Stern-Volmer方程拟合发现,随着离子浓度的变化,两种金属离子不同的淬灭机制和检测极限为在实践中有效检测和区分Ag+和Fe3+提供了一种可行的新方法.     

Bi1-xYbxFeO3的结构相变与磁性

用溶胶-凝胶法制备了Bi_1-xYb_xFeO₃(0≤x≤0.2)粉晶样品,并用X射线衍射光谱和拉曼光谱对其结构进行了研究. 结果表明, 在x=0.1～0.125, 发生了结构相变, 由菱形R3c结构变为正交Pnma结构,对应的应该是从铁电相到顺电相的转变. 在结构相变边界,磁化强度达到最大值. 其原因是在低浓度掺杂区域,随着Yb³⁺的掺杂浓度的增大,BiFeO₃的自旋螺旋结构受到抑制,部分未被抵消的磁矩被释放出来,到了相变边界,自旋螺旋结构受到的抑制达到最大,磁矩被完全释放出来. 随着x的继续增大,磁化强度开始逐渐减小,这是由于逐渐形成了良好的反铁磁序排列.     

晶相对碳点多色发光的调制及其在白光发光二极管器件中的应用

报道了一种以邻苯二甲酸前体结晶作为基质包覆碳点制备固态荧光材料的方法。通过改变溶剂,微波合成分别发射蓝色和绿色荧光的晶态碳点。详细的结构和光谱表征后发现,在形成碳点的同时,由邻苯二甲酸前体结晶在碳点的周围生长了晶态基质,该基质对碳点的分散作用有效阻断了碳点的聚集,从而阻止了碳点荧光猝灭的发生。并且,晶态基质结构的变化导致了碳点碳核和基质界面处吡啶氮类基团增多,从而致使该碳点发光颜色变化。鉴于其优异的发光性能,所制备晶态碳点用于封装白光发光二极管器件(WLED)。通过与商用荧光粉相结合,蓝色光碳点封装的WLED在色度坐标为(0.37,0.36)时获得了相关色温4 061 K、显色指数88.4的暖白光。而绿色光碳点封装的WLED在色度坐标为(0.36,0.34)时获得了相关色温44 678 K、显色指数85的暖白光。优异的光度学参数赋予这些荧光纳米材料在光电领域潜在的应用价值。     

邻苯二甲酸结晶诱导荧光碳点制备及其在白光发光二极管中的应用

通过简单的方法获得基于碳纳米点的固态荧光材料,实现该类材料在光电器件领域的应用研究有着重要的意义.然而,由于聚集诱导猝灭效应的存在,合成该类材料仍面临着严峻的挑战.本文报道了一种简单热解合成硫(S)和氮(N)共掺杂荧光碳点晶态材料的方法.优化制备条件后,获得的材料能发出耀眼的橙红色荧光,这是由于在形成碳点的同时,碳点的...     

High-pressure structural properties of tetramethylsilane

High-pressure structural properties of tetramethylsilane are investigated by synchrotron powder x-ray diffraction at pressures up to 31.1 GPa and room temperature. A phase with the space group of Pnma is found to appear at 4.2 GPa. Upon compression, the compound transforms to two following phases: the phase with space groups of P2_1/c at 9.9 GPa and the phase with P2/m at 18.2 GPa successively via a transitional phase. The unique structural character of P2_1/c supports the phase stability of tetramethylsilane without possible decomposition upon heavy compression. The appearance of the P2/m phase suggests the possible realization of metallization for this material at higher pressure.     

基于光谱测试的纯净金刚石品质与缺陷研究

本文利用低温拉曼与光致发光光谱对纯净金刚石晶片的结晶质量、晶体应力分布进行表征分析,并结合电子辐照和快速退火对晶片的杂质缺陷结构开展研究。通过拉曼光谱对金刚石特征峰的表征分析发现,由于金刚石生长机制以及晶片的切割、抛光等因素影响,晶片的边缘与表面应力分布较高。光致发光光谱中的零声子线具有明显的温度依赖性,根据Jahn-Teller效应与电子-声子耦合理论阐明了测试温度变化引起中性单空位缺陷零声子线分裂与红移的机理。对晶片做电子辐照与退火调控处理后,晶片中氮-空位(NV)缺陷显著增多,表明在纯净晶片中氮主要以替代位氮杂质的形式存在。     

Phase transitions in a hydrogen-rich compound：tetramethylsilane

High-pressure behavior of tetramethylsilane is investigated by synchrotron powder X-ray diffraction and Raman scattering at pressures up to 30 GPa and room temperature. Our results reveal the analogous phase transitions, though slight hysteresis for the certain phases. A new phase is found to appear at 4.2 GPa due to the disappeared Raman mode. These findings offer the possibility to understand the evolution of the H-H bonding with pressure in such hydrogen-rich compounds.