Fe3O4/CdTe磁性荧光纳米复合物的逐步杂凝聚法合成及其表征

采用逐步杂凝聚法合成了Fe3O4/CdTe磁性荧光纳米复合物.以化学共沉淀法制备Fe3O4纳米颗粒,经油酸修饰后分散在表面活性剂中形成磁流体.CdTe量子点以巯基乙酸为稳定剂制得.最后以聚乙烯亚胺(PEI)为联接剂,成功制备了Fe3 O4 /CdTe磁性荧光双功能纳米复合物颗粒.该复合物颗粒平均尺寸为(30±5)nm,荧光产率为0.186,饱和磁化强度为15.745emu/g,该纳米粒子既具有优异的荧光特性,也具有较强的超顺磁性.     

Fe_3O_4/CA@CdSe/CdS磁性荧光纳米复合材料的制备及表征

采用共沉淀法制备出Fe3O4,使磁性颗粒表面羟基化,通过柠檬酸(CA)修饰制备得Fe3O4/CA。量子点CdSe/CdS是用三步法合成得到,并用巯基乙酸进行改性,再通过乙二胺偶联剂的作用,将量子点CdSe/CdS和Fe3O4连接。该微粒经过荧光分光光度计、荧光显微镜、透射电子显微镜(TEM)、能谱(EDS)和振动样品磁强计(VSM)的表征。结果表明:通过乙二胺的桥梁作用(静电吸附和氢键作用),量子点CdSe/CdS成功连接到了Fe3O4/CA表面,得到了磁性荧光双功能材料,该材料在药物分离、可视化,靶向治疗等方面的应用都具有很大潜力。     

Fe_3O_4/PMIDA/Tris@CdSe/CdS制备磁性荧光双功能材料及其表征

采用化学共沉淀法,制备出Fe3O4磁性纳米颗粒,先后用四甲基氢氧化铵(TMAOH)、双甘膦(PMIDA)对Fe3O4磁性纳米颗粒表面进行修饰,产物记为C1。加入氨丁三醇(Tris)对C1进行修饰,产物记为C2。运用油相合成的方法制备CdSe/CdS量子点,再用巯基乙酸将其转成水相,得到具有良好水溶性和较好稳定性的产物。将修饰后的磁性颗粒与量子点进行连接,制得磁性荧光双功能材料,并对结构和性能进行表征,结果表明经Tris修饰后,双功能材料的荧光性能得到了显著地提高。首次用Tris对产物的性质进行改进,具有一定的科学研究价值。     

Fe_3O_4/OA/PANI@CdSe/CdS磁性荧光纳米复合物的制备及其表征

由共沉淀法制备出表面羟基化的Fe3O4,并用油酸(OA)进行了修饰。通过新颖简便的微悬浮方法制备出聚苯胺包裹的Fe3O4/OA/PANI。用三步法合成出具有良好的荧光性能的量子点CdSe/CdS。通过EDC交联剂的作用,将量子点CdSe/CdS和Fe3O4连接。该微粒经过透射电子显微镜(TEM)、能谱(EDS)、荧光分光光度计、荧光显微镜和振动样品磁强计(VSM)的表征。结果表明:通过PANI的桥梁作用(静电吸附和氢键作用),量子点CdSe/CdS成功连接到了Fe3O4/OA/PANI表面,得到了磁性荧光复合材料,该材料在药物传递、靶向治疗的应用上都具有很大潜力。     

磁性/荧光双功能纳米颗粒的制备及性能研究

通过对Fe3O4纳米颗粒的SiO2包覆和表面胺基化修饰,成功地将CdSe量子点（QDs）均匀地包覆在Fe3O4纳米粒子表面,制备了稳定的、具有磁性/荧光双功能的纳米颗粒,结果表明,所制备的纳米颗粒具有良好的分散性、优异的磁响应特性和荧光发射性能,为制备该类双功能纳米材料,拓宽其应用领域提供了新的途径。     

改性Fe3O4纳米粒子在磁性复合超滤膜中的应用

为解决Fe3O4纳米粒子在磁性复合超滤膜中发生团聚和分布不均匀的问题,文中以市售20nm的Fe3O4粒子为对照,添加自制的改性Fe3O4纳米粒子制备出Fe3O4-聚砜(PSF)磁性复合超滤膜(改性复合超滤膜)。经扫描电镜观察膜表面形貌、能谱仪扫描复合膜中Fe元素分布以及铸膜液中Fe3O4纳米粒子分布情况分析和复合膜孔径分布测试后表明,改性后复合超滤膜中纳米粒子的分布较改性前更为均匀,且未出现粒子团聚现象,改性效果明显。由改性前后的复合膜在不同磁场下对聚乙二醇6000和10000的截留率呈现几乎相同的变化趋势可知,添加改性粒子并未改变磁性复合膜的分离特性。     

磁性羧甲基化壳聚糖纳米粒子的制备与表征

以化学共沉淀法制备了Fe3O4纳米粒子,壳聚糖经羧甲基化改性后接枝在Fe3O4颗粒表面,得到了磁性羧甲基化壳聚糖(Fe3O4/CMC)纳米粒子.利用透射电镜(TEM)、X射线衍射(XRD)、傅立叶红外光谱(FT-IR)及磁性测试对产物进行了表征.TEM表明Fe3O4纳米粒子被CMC包覆,粒径约10 nm;XRD分析表明复合纳米粒子中磁性物质为Fe3O4;FT-IR表明壳聚糖发生羧甲基反应以及在Fe3O4表面的接枝反应.Fe3O4/CMC纳米粒子具有超顺磁性,比饱和磁化强度25.73 emu/g,有良好的磁稳定性.     

双功能磁性荧光纳米复合物Fe_3O_4/MPTS@CdSe/CdS的制备及其表征

在水相中,采用化学共沉淀法以FeCl_3·6H_2O和FeSO_4·7H_2O为原料合成超顺磁性Fe_3O_4纳米粒子,将磁性纳米粒子加入到正硅酸乙酯(TEOS)的醇水体系中,使磁性纳米粒子表面生成一层无定型SiO_2包覆层,再以3-(甲基丙烯酰氧)丙基三甲氧基硅烷(MPTS)对其进行修饰,使磁性纳米粒子表面接入丰富的功能双键,与巯基乙酸、乙二胺修饰后的CdSe/CdS量子点连接,得到磁性荧光双功能纳米微球,并对其进行结构表征和性能测试。结果表明,合成的磁性纳米粒子粒径约为40nm,荧光强度约为450a.u.,饱和磁化强度为32.2emu/g。这种合成简便的磁性荧光双功能纳米材料有望在靶向治疗、免疫检测、细胞的分离和催化等领域得到广泛应用。     

静电纺丝法制备PAN/Fe3O4磁性纳米纤维

采用化学共沉淀法制备纳米四氧化三铁,选用曲拉通X-100为分散剂,利用静电纺丝法制备PAN/Fe3O4磁性纳米复合材料。X射线衍射仪(XRD)验证了四氧化三铁在复合纳米纤维中的存在。同时使用扫描电镜(SEM)和透射电镜(TEM)对复合纳米纤维的微观形貌和Fe3O4在纤维中的分布进行了观察,利用热重(TGA)对纳米复合材料的热稳定性进行分析;通过磁性实验分析了纳米复合材料的磁性性能。结果表明,所制备PAN/Fe3O4磁性纳米纤维成型良好,且Fe3O4磁性颗粒在纤维中分散均匀,其与PAN是物理复合。纳米复合材料具有一定磁性,并可由磁性颗粒的加入量进行控制。     

Mn改性CdSe/CdS制备磁性荧光双功能材料及性能表征

以共沉淀法制备出表面羟基化的四氧化三铁(Fe_3O_4)磁性颗粒,通过柠檬酸(CA)修饰制备出Fe_3O_4/CA。三步法合成出具有较好荧光性能的CdSe(硒化镉)/CdS(硫化镉)量子点,并经锰(Mn)元素改性,使其具备更好的荧光特性。巯基乙酸(C_2H_4O_2S)为改性后量子点提供连接基团,经乙二胺(C_2H_8N_2)与Fe_3O_4/CA相连接。该材料经荧光分光光度计、荧光显微镜、透射电子显微镜(TEM)和振动样品磁强计(VSM)的表征。结果表明:通过乙二胺的连接(静电吸附及氢键作用),经Mn改性后的CdSe/CdS量子点成功与Fe_3O_4/CA连接,形成了具备磁性荧光双功能的复合材料,饱和磁化强度达到28.86emu/g,其优秀的磁性荧光性能在药物分离、靶向治疗等方面具有很高的应用价值。     

Structural and optical properties of AlxOy/Pt/AlxOy multilayer absorber

We report on the microstructure and optical properties of Al_xO_y–Pt–Al_xO_y interference-type multilayer films, deposited by electron beam (e-beam) deposition onto corning 1737 glass, silicon (1 1 1) and copper substrates. The structural properties were investigated by Rutherford backscattering spectrometry, X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy and atomic force microscopy. The optical properties were extracted from specular reflection/transmission, diffuse reflectance and emissometer measurements. The stratification of the coatings consists of a semi-transparent middle Pt layer sandwiched between two layers of Al_xO_y. The top and bottom Al_xO_y layers were non-stoichiometric with no crystalline phases present. The Pt layer is in the fcc crystalline phase with a broad size distribution and spheroidal shape in and between the rims of Al_xO_y. The surface roughness of the stack was found to be comparable to the inter-particle distance. The optical calculations confirm a high solar absorptance of ∼0.94 and a low thermal emittance of ∼0.06 for the multilayer stack, which is attributed not only to the optimized nature of the multilayer interference stacks, but also to the specific surface morphology and texture of the coatings. These optical characteristics validate the spectral selectivity of the Al_xO_y–Pt–Al_xO_y interference-type multilayer stack for use in high temperature solar-thermal applications.     

Optimization of AlxOy/Pt/AlxOy multilayer spectrally selective coatings for solar-thermal applications

Spectrally selective Al_xO_y/Pt/Al_xO_y multilayer absorber coatings were deposited onto corning 1737 glass, Si (111) and copper substrates using electron beam (e-beam) vacuum evaporator at room temperature. The employment of ellipsometric measurements and optical simulation was proposed as an effective method to optimize and deposit multilayer solar absorber coatings. The optical constants (n and k) measured using spectroscopic ellipsometry, showed that both Al_xO_y layers, which used in the coatings, were dielectric in nature and the Pt layer was semi-transparent. The optimized multilayer coatings exhibited high solar absorptance α ∼ 0.94 ± 0.01 and low thermal emittance ? ∼ 0.06 ± 0.01 at 82 °C. The Rutherford backscattering spectroscopy (RBS) data of Al_xO_y/Pt/Al_xO_y multilayer absorber indicated the Al_xO_y layers present in the coating were nearly stoichiometry. The scanning electron microscope analysis (SEM) result indicated that the average diameter and inter-particles distance of Pt grains were statistically about 146 ± 0.17 nm and 6-10 ± 0.2 nm respectively.     

Interfacial microstructure of NiSix/HfO2/SiOx/Si gate stacks

Integration of NiSi_x based fully silicided metal gates with HfO₂ high-k gate dielectrics offers promise for further scaling of complementary metal-oxide- semiconductor devices. A combination of high resolution transmission electron microscopy and small probe electron energy loss spectroscopy (EELS) and energy dispersive X-ray analysis has been applied to study interfacial reactions in the undoped gate stack. NiSi was found to be polycrystalline with the grain size decreasing from top to bottom of NiSi_x film. Ni content varies near the NiSi/HfO_x interface whereby both Ni-rich and monosilicide phases were observed. Spatially non-uniform distribution of oxygen along NiSi_x/HfO₂ interface was observed by dark field Scanning Transmission Electron Microscopy and EELS. Interfacial roughness of NiSi_x/HfO_x was found higher than that of poly-Si/HfO₂, likely due to compositional non-uniformity of NiSi_x. No intermixing between Hf, Ni and Si beyond interfacial roughness was observed.     

Tc trend in high-Tc superconductors

In our previous works, we have shown that most existing ceramic superconductors can be considered to be built of superconductor-semiconductor composite and we have estimated the change in phonon spectrum of the intrinsic superconductor unit if a semiconductor unit is attached to it. Moreover, the proximity effect under the size quantization condition has been examined in the superconductor-semiconductor composite. Each of the stated effects by itself could causeT _c enhancement in general as more semiconductor blocks are added to the system. We extend our study in this paper to analyze the combined actions of phonon spectral change and proximity effect without size quantization condition onT _c variation in members of the Tl₁ series of high-T _c superconductors. Our results indicate that an optimumT _c is obtained if the stated effects are included in the idealized unit cells of the superconductors made up of a superconductor-semiconductor array.     

Anomalous Hall Effect in Sn1?x?yMnxEuyTe and Sn1?x?yMnxEryTe Mixed Crystals

The Anomalous Hall Effect (AHE) was investigated in IV–VI ferromagnetic semimagnetic semiconductors of Sn_1–x Mn _x Te codoped with either Eu or Er. The analysis of experimental data is as follows. Hall resistivity and magnetization showed that AHE coefficient R _s depends on temperature and its value decreases with thetemperature increase. We observe that above ferromagnet–paramagnet transition temperature R _s changes sign. We discuss the possible physical mechanisms responsible for observed temperature dependence of R _s , particularly change of the sign.     

Synthesis of a new perovskite Pb(Li14Nb34)O3

A high-pressure technique was adopted to obtain perovskite-type $\text{Pb(Li}{}_{\mathrm{<mtext>1</mtext><mtext>4</mtext>}}\text{Nb}{}_{\mathrm{<mtext>3</mtext><mtext>4</mtext>}}\text{)}\text{O}{}_3$. A new perovskite $\text{Pb(Li}{}_{\mathrm{<mtext>1</mtext><mtext>4</mtext>}}\text{Nb}{}_{\mathrm{<mtext>3</mtext><mtext>4</mtext>}}\text{)}\text{O}{}_3$ was characterized to have a cubic symmetry with $\text{a}{}_{\mathrm{<mtext>o</mtext>}}\text{= 4.069}\text{A}\text{?}$; Li and Nb ions in the B-site of perovskite lattice may be in a random arrangement.     

Bulk crystalline BaPb34Bi14O3: A ceramic superconductor

The preparation conditions of the high T_C ceramic superconductor Ba(Pb,Bi)O₃ is correlated with the superconducting transition. Transition onsets of all materials are similar, but transition widths and transition completeness is strongly dependent on firing temperature. Only materials prepared over a narrow temperature range, resulting in a nearly ideal weight loss, have a complete and narrow transition.     

Electrostriction in Pb (Zn13Nb23)O3

The electrostriction in $\text{Pb (Zn}{}_{\mathrm{<mtext>1</mtext><mtext>3</mtext>}}\text{Nb}{}_{\mathrm{<mtext>2</mtext><mtext>3</mtext>}}\text{)}\text{O}{}_3$ crystals has been investigated using a strain gauge method. In the ferroelectric phase below 140 C, the strain vs the electric field shows a hysteresis, which is ascribed to the effect of ferroelectric domains. A quadratic relation holds between the strain x and the electric polarization P as x = QP² above about 170 C in the paraelectric phase. Values of the electrostrictive Q coefficients are determined from the measurements near 190 C, as Q₁₁ = 1.6·10^?2m⁴/C², Q₁₂ = ?0.86·10^?2m⁴/C², and Q₄₄ = 0.85·10^?2m⁴/C².     

Effect of pressure onTc in La2-xBaxCuO4 withx=0.125

The superconducting transition temperature,T _c , of La_2–x Ba _x CuO₄ has been measured under high pressure up to 8 GPa.T _c is found to change drastically at the pressure where the structural phase transition takes place. This finding clearly indicates that there exists an intimate relation between the crystal structure and superconductivity.