磁性纳米四氧化三铁在生物医学中的应用

近年来,由于磁性纳米粒子在实际应用中发挥越来越重要的作用,有关磁性纳米粒子的应用受到科学界广泛关注,特别是生物医学领域。由于磁性纳米Fe_3O_4粒子制作简单且晶体对细胞无毒,在生物医药领域大量应用,磁性纳米Fe_3O_4粒子主要通过表面包覆成为免疫磁性微球进行使用。简述了磁性纳米Fe_3O_4粒子的制备方法,重点综述了近些年磁性纳米Fe_3O_4粒子在生物医学上的应用,包括磁共振成像技术、磁分离技术、靶向药物载体技术、肿瘤热疗技术、造影剂技术,并且阐述了磁性纳米Fe_3O_4粒子的发展前景。     

蔗糖/水体系磁性聚苯乙烯微球的制备及其表征

以氧化法制备Fe_3O_4磁流体,首次采用蔗糖水溶液为分散介质,以聚乙烯醇为稳定剂,偶氮二异丁腈为引发剂,悬浮聚合法合成了磁性聚苯乙烯微球.该蔗糖水反应体系对环境无污染且后处理简单.考察了蔗糖、苯乙烯(St)、Fe_3O_4磁流体、稳定剂、引发剂的含量等条件对微球的粒径及其分布的影响.所合成的磁性聚苯乙烯微球具有核壳型结构,有较强的磁响应性能,球形和分散度良好,粒径为80～85μm.采用红外光谱、振动样品磁强计和光学显微镜对磁性聚苯乙烯微球进行了表征.     

磁性荧光双功能纳米材料Fe_3O_4/CS@CQDs的制备与表征

以化学共沉淀法制备出Fe_3O_4磁性纳米粒子,通过壳聚糖(CS)修饰制备得Fe_3O_4/CS磁性微球,再将Fe_3O_4/CS磁性微球与表面富含羧基的碳量子点(CQDs)连接,合成了以碳量子点为荧光材料的磁性荧光双功能纳米微球Fe_3O_4/CS@CQDs。经过红外光谱仪(FT-IR)、X射线衍射仪(XRD)、荧光分光光度计、振动样品磁强计(VSM)、荧光显微镜及透射电子显微镜(TEM)对该纳米材料表征。结果表明:双功能纳米微球Fe_3O_4/CS@CQDs饱和磁化强度达到13.66emu/g,分散性良好,粒径约为45nm,具有良好的荧光性能及磁响应性,有望取代以半导体量子点作为荧光材料的磁性复合材料,在生物医学等方面得到广泛应用。     

Fe3O4/SiO2/PS的制备及对有机染料分子的吸附性能

采用乳液聚合法在Fe_3O_4@SiO_2纳米粒子表面引发苯乙烯单体聚合,制备了聚苯乙烯修饰的Fe_3O_4@SiO_2磁性复合微球(Fe_3O_4@SiO_2@PS),研究了其对甲基橙(MO)和亚甲基蓝(MB)的吸附性能。用透射电镜和扫描电镜对所制得样品进行了形貌表征。结果表明,复合材料中的Fe_3O_4粒径分布在150～220 nm范围内,粒径分布较均匀、分散性良好;用振动样品磁强计对样品的磁性能进行表征,Fe_3O_4@SiO_2@PS复合粒子具有超顺磁性和较好的磁响应性;采用X射线衍射仪、傅里叶变换红外光谱仪、热重分析仪分析了复合粒子的结构和组成,用紫外-可见分光光度计测定有机染料分子的浓度,从而计算吸附量。Fe_3O_4@SiO_2@PS复合粒子对甲基橙和亚甲基蓝具有良好的吸附性能,在2 h达到吸附平衡,MO和MB单位平衡吸附量分别为94.5 mg/g、167.8 mg/g;该磁性吸附剂吸附染料分子后,可以用乙醇进行解吸附,在保持原始最大吸附量的81%下,可重复使用4次。     

海藻酸钠修饰磁性纳米粒子驱动液及其正渗透分离性能

通过微乳液共混沉淀法制备了海藻酸钠(SA)修饰的Fe_3O_4磁性纳米粒子Fe_3O_4-SA,该粒子具有良好的分散性和磁响应性.采用红外、透射电镜、磁滞回线和热失重等对磁性纳米粒子的结构和性能进行表征,同时对该磁性纳米粒子与去离子水的混合液作为驱动液时的正渗透(FO)分离性能进行了测试.结果表明,SA成功包覆在Fe_3O_4粒子表面,粒子的粒径约为20 nm,80 g/L的Fe_3O_4-SA磁性纳米粒子与去离子水的混合液渗透压达到1 270 mOSM/L,以此混合液作为FO过程的驱动液时,渗透通量可以达到2.04 L/(m~2·h),并且该驱动液具有较低的反向溶质通量,当驱动液质量浓度为80 g/L时,反向溶质通量约为0.04 g/(m~2·h),大大低于NaCl和SA的反向溶质通量,这说明该驱动液具有较好的FO分离性能.     

Fe_3O_4水基磁性液体的制备及性能研究

采用化学共沉法制备磁粒子Fe_3O_4,选用表面活性剂油酸进行一次包覆,乳化剂OP(烷基酚聚氧乙烯醚)进行二次包覆制备出稳定的水基磁性液体。利用XRD和TEM分析了样品的结构、形貌及粒径;运用VSM技术研究了样品磁性能;重点考察了油酸和OP用量对水基磁性液体稳定性的影响。结果表明,所制备的Fe_3O_4粒子为球形,颗粒的粒径较均匀细小,在10nm左右;磁性液体显示超顺磁性,饱和磁化强度M_s=54.636A·m~2/kg;油酸和OP用量对磁性液体的稳定性有重要影响,当n(Fe_O_4):n(油酸):n(OP)=5:2:4时,磁性液体的稳定性能最好。     

P(St-co-AA)与 Fe3O4纳米粒自组装制备高分子磁微球

用微乳液聚合法制备了粒径均匀的聚苯乙烯-丙烯酸高分子微球P(St-co-AA),与共沉淀法所制纳米Fe3O4通过静电作用,使两种微球自组装成高磁含量的磁性微球[Fe3O4/P(St-co-AA)].采用XRD、TEM、SEM、IR等对样品进行表征,采用VSM对样品进行磁性能测试.结果表明P(St-co-AA)平均粒径约为70nm,表面含有羧基;所得磁粉为Fe3O4单相,平均粒径约为10nm.磁性能测试表明,当外加磁场为1.5×106/π(A/m)时,磁化强度达到饱和,饱和磁化强度为69A·m2·kg-1;自组装所制高分子磁性微球为球形,平均粒径约800nm,磁粉含量为15.8%.研究表明,pH值、搅拌等对复合磁性微球的形成有重要影响.     

碳量子点磁性纳米复合材料的制备与表征

采用一步法在高压反应釜中合成了粒径均一、荧光性能优异的碳量子点(CQDs)。再以化学共沉淀法制备纳米Fe_3O_4粒子,通过聚多巴胺(PDA)修饰制备得Fe_3O_4/PDA。本实验首次以PDA为桥梁,将Fe_3O_4纳米颗粒与CQDs连接,合成了以CQDs为荧光材料的多功能复合微球Fe_3O_4/PDA@CQDs。经过傅里叶变换红外光谱仪、X射线衍射、振动样品磁强计、透射电子显微镜及荧光分光光度计等对该纳米复合物表征。结果表明:CQDs粒径约10nm,连接后的复合纳米粒子粒径在40nm左右,分散性良好且兼具优异的磁响应性和荧光发光性能。该复合微球无毒且生物相容性高,可以取代半导体量子点磁性纳米复合材料并广泛应用于药物分离、可视化和靶向治疗等生命科学领域。     

聚苯乙烯-SiO2/NiFe2O4磁性微球的制备与表征

以NiFe2O4纳米粒子作磁性载体、苯乙烯(ST)、正硅酸乙酯(TEOS)为原料,KH-570为交联剂,采用乳液聚合法制备了聚苯乙烯-SiO2/NiFe2O4磁性微球材料。通过VSM、FT-IR、SEM、TG-DTA、溶剂抽提等方法对磁性微球材料进行了测试。制备的NiFe2O4粒子为面心立方结构,NiFe2O4纳米颗粒及聚苯乙烯-SiO2/NiFe2O4磁性微球具有超顺磁性。聚苯乙烯-SiO2/NiFe2O4磁性微球以SiO2/NiFe2O4为核、PS为壳,通过KH-570接枝到SiO2/NiFe2O4上,核壳间以共价键相接的包覆型纳米粒子,平均直径为100nm左右,具有良好的热稳定性和耐溶剂性能。热重(TG)分析表明,磁性聚苯乙烯微球磁性物质质量分数为28.8%。     

层层自组装法制备碳包覆的Fe_3O_4碳量子点磁性荧光双功能材料

通过化学共沉淀法制备Fe_3O_4磁性纳米颗粒,在其表面包覆碳层,形成Fe_3O_4@C磁性微球,采用层层自组装法将聚二烯丙基二甲基氯化铵(PDDA)修饰到微球表面。将该微球与表面富含羧基的碳量子点(CQDS)连接,得到碳包覆的Fe_3O_4@CQDS(Fe_3O_4@C@CQDS)磁性荧光双功能复合微球。通过X射线衍射(XRD)、振动样品磁强计(VSM)、扫描电子显微镜(SEM)、荧光分光光度计和荧光显微镜等表征手段对该复合微球进行结构表征以及性能测试。结果表明:复合微球粒径约为50nm,饱和磁强度为23.39emu/g,这种性能优异的磁性荧光双功能复合微球有望在生命科学领域得到广泛应用。     

Ferrimagnetic and semiconducting CaCu3Fe2Sb2O12 by first principles

CaCu₃Fe₂Sb₂O₁₂ is mechanically stable, thermodynamically stable at pressures above 18 GPa. Both GGA and GGA + U methods predict that it is a ferrimagnetic semiconductor with Fe³⁺ in high spin state (S = 5/2). The coupling of Fe–Cu is antiferromagnetic, while that of Cu–Cu is ferromagnetic. The calculated total spin moment is 6.17 μ_B.     

Effect of Ca Substitution on the Superconductivity of La2.5Y0.5CaBa3(Cu0.88Fe0.12)7Oz

The structural and superconducting properties of single-phase La_2.5–y Y_0.5Ca_1+y Ba₃ (Cu_0.88Fe_0.12)₇O _z (LYCaBCuFe) (y= 0.0–1.0) compounds with triple perovskite structure are investigated using X-ray diffraction, resistivity, a.c. susceptibility, and oxygen content measurements. Increasing Ca substitution for La resulted in a decrease in unit cell axes and volume. T _c ^R=0 shows a marginal increase from 31 K to 37 K for y = 0.0–0.21 and thereafter it decreases with increasing y leading to zero T _c ^R=0 at y 0.84. This shows that the suppression of T _c from 80 K to 31 K by Fe doping at x = 0.12 La_2.5Y_0.5CaBa₃(Cu_1–x Fe _x )₇O _z cannot be compensated by appropriate hole doping with Ca in LaYCaBCuFe.     

纳米Fe3O4及Fe3O4-SrFe12O19吸波复合材料的制备及性能

采用共沉淀法成功制备出具有超顺磁性的纳米Fe₃O₄, 并将Fe₃O₄与SrFe₁₂O₁₉复合制成复合吸波材料Fe₃O₄-SrFe₁₂O₁₉, 利用X射线衍射仪(XRD)、透射电镜(TEM)、振动样品磁强计(VSM)和矢量网络分析仪(PNA)对产物的物相、显微结构、磁性能和吸波性能进行了表征与分析。结果表明, 当Fe₃O₄与SrFe₁₂O₁₉质量比为1∶0.3时, Fe₃O₄-SrFe₁₂O₁₉饱和磁化强度为11.1 emu·g^-1, 矫顽力0.86 Oe, 剩余磁化强度0.08 emu·g^-1, 其吸波性能最佳, 最大吸收峰值为-17.7 dB,-5 dB频宽为1.3 GHz, 较Fe₃O₄和 SrFe₁₂O₁₉的最大吸收峰值分别提高247%和185%, 频带分别拓宽1.12 GHz和0.40 GHz。     

Anisotropy in the resistive superconducting transition under magnetic fields in single crystal Pb2Sr2Ho0.5Ca0.5Cu3O8

Anisotropie properties of the single crystal Pb₂Sr₂Ho_0.5Ca_0.5Cu₃O₈ have been investigated by measuring the electrical resistivity in theab-plane _ab (H, ,T), which depends on the angle between theab-plane and the magnetic-field direction, in various constant fieldsH perpendicular to the current direction. All the angle-dependent values of _ab (H, ,T) at a constant temperature are scaled to be on one curve as a function of reduced field. The anisotropic parameter (m _c ^* /m _ab ^* )^1/2 is estimated as 12–13, which is larger than that of YBa₂Cu₃O₇ and much smaller than that of Bi₂Sr₂CaCu₂O₈. It has been concluded that the anisotropy does not always depend on the thickness of the blocking layer but seems to depend on the overlap of the electronic wave functions along thec-axis. Anisotropy in the pinning potential has also been discussed from the resistive tail in the temperature dependence of _ab (H,,T).     

Microstructural study of YBa2Cu3O7/SrTiO3/YBa2Cu3O7 heteroepitaxial trilayer films grown on (100) SrTiO3 substrates

Detailed transmission electron microscopic study has been carried out on heteroepitaxial YBa₂Cu₃O₇/SrTiO₃/YBa₂Cu₃O₇ trilayer thin films grown on (100)SrTiO₃ substrates prepared by DC and RF magnetron sputtering. The microstructural results showed the existence of somea-axis-oriented YBCO grains 20–90 nm wide in thec-axis-oriented YBCO matrix. Some of thea-axis grains in the lower YBCO thin film layer have protruded into the above SrTiO₃ layer, which may cause short circuit between the two YBCO superconducting layers. This is unsuitable for the application of trilayer thin films for microelectronic devices. The defects on the surface of the substrates would also influence the growth quality of the YBCO thin films.     

Ba2Ti9O20-Ba1.85Sm4.1Ti9O24 layered dielectric resonators with adjustable effective dielectric constant

The layered dielectric resonator structures composed of Ba₂Ti₉O₂₀ (BTO) and Ba_1.85Sm_4.1Ti₉O₂₄ (BSTO) ceramic pellets were introduced to design new microwave dielectric materials with adjustable dielectric constant between 50 and 70. Good combination of microwave dielectric properties (?_r,eff = 50 ~ 70, Qf = 11,700-19,100 GHz and τ_f = − 4.3 to − 1.5 ppm/°C) was obtained by the present approach, and such combination could be optimized by adjusting the volume fraction of BSTO and stacking scheme. For practical applications, the BTO and BSTO layers could be bonded by low-loss adhesive, and the effects of the adhesive on the microwave dielectric properties were limited.     

Raman scattering studies of ultrathin-layer YBa2Cu3O7/PrBa2Cu3O7 superlattices

We present Raman scattering studies ofc-oriented ultrathin-layer superconducting (YBa₂Cu₃O₇) _m /(PrBa₂Cu₃O₇) _n superlattices. For the superlattice with (m=2,n=1) sequence, Raman spectra reveal a new line in the spectral region around 320 cm^–1. It is interpreted as a mode representing a combination of IR optical phonons of the Y-sublayers with an admixture of aB _1g type Raman active vibration in the Pr sublayers. This new line, which is similar to those from the interior of the Brillouin zone of the original lattice, does not exhibit superconductivity-induced self-energy effects, although its counterpart in the pure substance does. No additional line is found in the (m=1,n=2) superlattice in the same region, supporting our interpretation for the (m=2,n=1) sample.     

Development of random access memory in Nd0.7Ca0.3MnO3/YBa2Cu3O7 heterostructure

The effects of electrode on the resistive switching in Nd_0.7Ca_0.3MnO₃(NCMO)/YBa₂Cu₃O₇(YBCO) heterostructure are investigated at room temperature. For Cu/NCMO/YBCO, resistance can be switched on-and-off from a high- to low-resistance state at a steady ratio of 25% with a pulsed-voltage of ± 3 V. On the other hand, a giant resistance-change as large as 1350% is observed with ± 5 V for Ag/NCMO/YBCO with a fast decay down to 550%. Our experimental results show clear evidences that the nature of interfaces can be modified by the electric field and it dictates the resistive switching behavior of these heterostructure devices, which are the potential candidates for the random access memory.     

Vortex motion in coupled DyBa2Cu3O7/(Y0.6Pr0.4)Ba2Cu3O7 heterostructures

Multilayer structures containing 24 Å thick DyBa₂Cu₃O₇ layers, separated by 96 Å of an (Y_0.6Pr_0.4)Ba₂Cu₃O₇ alloy, are studied to investigate the effect of coupling on vortex dynamics. With the magnetic field perpendicular to theab plane, and as a function of the number of superconducting layers in the structure, we find that the activation energy for flux motion increases, first linearly, and then saturates. This linear increase is taken as evidence that pancake vortices belonging to different DyBa₂Cu₃O₇ layers are stacked and have a coupled motion. Above a characteristic number of superconducting layers,N _c , shear of the vortex structures becomes important and the thermally activated process only displaces a stack ofN _c pancake vortices, meaning that the vortex lattice is turning three dimensional. In these structures we findN _c to be 2 to 3.