Skin formation in drying a film of soft matter solutions:Application of solute based Lagrangian scheme

When a film of soft matter solutions is being dried, a skin layer often forms at its surface, which is a gel-like elastic phase made of concentrated soft matter solutions. We study the dynamics of this process by using the solute based Lagrangian scheme which was proposed by us recently. In this scheme, the process of the gelation(i.e., the change from sol to gel) can be naturally incorporated in the diffusion equation. Effects of the elasticity of the skin phase, the evaporation rate of the solvents, and the initial concentration of the solutions are discussed. Moreover, the condition for the skin formation is provided.     

长余辉发光玻璃SrAl2O4∶Dy, Eu的制备与发光性能研究

在低熔点破璃中掺杂一定量的长余辉发光粉制备了性能优良的长余辉发光玻璃。在保证发光玻璃均匀透明的基础上，发光性能随发光粉掺杂量的增加而增强，尽量降低假烧温度和减少保温时间可以保持良好的发光性能，在还原气氛制备的发光玻璃性能优于在空气中制备的。煅烧工艺对发光玻璃的微观结构有显著的影响。     

A density functional theory study on the adsorption of CO and O₂ on Cu-terminated Cu₂O（111） surface

The adsorptions of CO and O2 molecules individually on the stoichiometric Cu-terminated Cu2O(111) surface are investigated by first-principles calculations on the basis of the density functional theory.The calculated results indicate that the CO molecule preferably coordinates to the Cu2 site through its C atom with an adsorption energy of -1.69 eV,whereas the O2 molecule is most stably adsorbed in a tilt type with one O atom coordinating to the Cu2 site and the other O atom coordinating to the Cu1 site,and has an adsorption energy of -1.97 eV.From the analysis of density of states,it is observed that Cu 3d transfers electrons to 2π orbital of the CO molecule and the highest occupied 5σ orbital of the CO molecule transfers electrons to the substrate.The sharp band of Cu 4s is delocalized when compared to that before the CO molecule adsorption,and overlaps substantially with bands of the adsorbed CO molecule.There is a broadening of the 2π orbital of the O2 molecule because of its overlapping with the Cu 3d orbital,indicating that strong 3d-2π interactions are involved in the chemisorption of the O2 molecule on the surface.     

CBP有机薄膜对MEH-PPV聚合物发光二极管性能的影响

以聚合物发光材料MEH-PPV为发光层的聚合物发光二极管的ITO阳极与发光层之间,加入一层溶解于氯仿中的有机小分子CBP,能显著改善发光器件的电流特性。在电压较低的时候能提高电流,在电压较高的时候能抑制电流,从而增加工作电压范围。此外,器件的电流效率也能得到显著的提高。实验结果表明,加入CBP层后,在低电压时,CBP层能够减缓空穴注入到发光层中,将其限制在CBP层,从而在器件中形成一个内电场,有助于电子的传输,降低开启电压,提高发光亮度。在电压较高时,CBP作为电子阻挡层,能阻挡电子漏泄到阳极,从而使在复合区的空穴与少数载流子电子的复合效率提高,改善器件的性能。     

聚甲基丙烯酸甲酯包覆(CH3NH3)PbBr3纳米晶静电纺丝膜的制备及对氨气的荧光传感

采用原位合成法制备了聚甲基丙烯酸甲酯包覆MAPbBr₃纳米晶(MAPbBr₃@PMMA,MA=甲铵离子)静电纺丝膜。当氨气(NH₃)通入MAPbBr₃@PMMA纤维膜时与MAPbBr₃中的MA发生取代,能显著降低MAPbBr₃@PMMA纤维的荧光强度,以此构建了基于MAPbBr₃@PMMA纤维荧光猝灭的NH₃传感器。通过扫描电镜、透射电镜、粉末X射线衍射和红外对静电纺丝膜的形貌和结构进行表征,通过紫外可见光谱、荧光光谱对其光学特性进行表征。结果表明,传感器的荧光强度与NH₃浓度在8~90 mg·L^-1之间呈现出良好的线性关系(r=0.995 9),NH₃的检出限低(3 mg·L^-1),且具有良好的重现性和选择性。在实际样品气体的测定中,加标回收率为92.2%~102.1%,相对标准偏差(RSD)为1.8%~3.2%。     

基础物理实验课后的思考

物理实验课的课后讨论需要引起重视,同时这是尊重和提高学生的自主创新能力的必要途径。提出物理实验课课后开设讨论答疑课的必要性和重要性。阐述了开设实验课后讨论答疑课可以采取的方式和方法,目的是实现学生与教师的综合素质在学与教的过程中相互促进与相互提高。     

聚甲基丙烯酸甲酯包覆(CH3NH3) PbBr3纳米晶静电纺丝膜的制备及对氨气的荧光传感

采用原位合成法制备了聚甲基丙烯酸甲酯包覆MAPbBr₃纳米晶（MAPbBr₃@PMMA,MA=甲铵离子）静电纺丝膜。当氨气（NH₃）通入MAPbBr₃@PMMA纤维膜时与MAPbBr₃中的MA发生取代,能显著降低MAPbBr₃@PMMA纤维的荧光强度,以此构建了基于MAPbBr₃@PMMA纤维荧光猝灭的NH₃传感器。通过扫描电镜、透射电镜、粉末X射线衍射和红外对静电纺丝膜的形貌和结构进行表征,通过紫外可见光谱、荧光光谱对其光学特性进行表征。结果表明,传感器的荧光强度与NH₃浓度在8~90 mg·L^-1之间呈现出良好的线性关系（r=0.995 9）,NH₃的检出限低（3 mg·L^-1）,且具有良好的重现性和选择性。在实际样品气体的测定中,加标回收率为92.2%~102.1%,相对标准偏差（RSD）为1.8%~3.2%。     

Crystal Structure and Judd–Ofelt Analysis of Er~(3+) Doped LuAl_3(BO_3)_4 Crystal

Single crystal Er:LuAl_3(BO_3)(Er:Lu AB) is successfully grown using the top-seeded solution growth method with a K_2Mo_3O_(10) flux. The cell parameters of the grown crystal are estimated by an x-ray single crystal diffactometor and x-ray powder diffraction analysis. The result indicates that it still belongs to the space group R32. The obtained unit-cell parameters are a= 9.2793(19) ?, c= 7.210(3) ?, V= 537.65(27) ?~3, and Z=3.The absorption spectrum is measured at room temperature. The spectroscopy properties are investigated based on the Judd–Ofelt(J-O) theory, and the effective J-O parameters were calculated to be Ω_2=8.33×10~(-20),Ω_4=3.83×10~(-20), and Ω_6 =3.55×10~(-20). The emission spectra of Er:LuAB crystal at room temperature are also studied and the ~4I_(11/2)→~4I_(13/2) fluorescence around 3170 nm is observed. The emission cross section calculated by the F-L formula is 8.6×10~(-20) cm~2. These results suggest that the Er:LuAB crystal may be a promising ~3 μm laser material.     

Er∶LaAl3(BO3)4晶体的生长和光谱性质研究

采用助熔剂法生长了Er: LaAl3(BO3)4晶体.LaAl3(BO3)4晶体属正交晶系,晶胞参数a=0.93586(4) nm,b=0.79904(3) nm,c=0.43626 (6) nm,V=0.34595 nm3.测量了晶体在室温的吸收光谱和荧光光谱.该晶体吸收光谱能级丰富;在1533 nm波长处有较强的荧光光谱,对应于4I13/2→4I15/2的能级跃迁;晶体的荧光寿命为2.72ms.研究了晶体的热学性质,室温时的比热容大约为0.595 J/g·℃.     

不同制备条件对Zn2SiO4∶Mn2+粉末发光性能的影响

利用溶胶-凝胶法制备了Zn2SiO4∶Mn2 粉末,探讨了体系pH值、热处理温度、煅烧气氛对材料结构和发光性能的影响。利用X射线衍射(XRD)、扫描电子显微镜(SEM)、光致发光(PL)谱等分析手段对Zn2SiO4∶Mn2 粉末的结构、颗粒大小、形貌、发光性能进行了表征。结果表明:溶胶的pH值影响制备的粉体的结晶性和颗粒大小,当溶胶pH值为4.34时,体系水解缩聚反应充分,所得荧光粉的光致发光强度最强;煅烧气氛显著影响荧光粉的发光强度,前驱体在N2(90%) H2(10%)的还原气氛下煅烧得到的发光粉发光强度最强;最佳热处理温度为900℃。