水热合成法制备纳米α-Fe_2O_3粉体及光催化性能研究

以氯化铁和三乙烯四胺为原料,采用水热合成法制备了纳米α-Fe2O3。对样品进行了XRD、FT-IR、TEM表征分析,并研究了其光催化性能。研究结果表明,随着Fe Cl3与C6H18N4摩尔比的增大,纳米颗粒先增大后减小,当n(Fe Cl3)∶n(C6H18N4)=1∶1,样品为结晶度较好的50~80 nm的近方形颗粒,且分散性较好。当n(Fe Cl3)∶n(C6H18N4)=2∶1,样品颗粒最小,光催化性能最好。随着水热反应时间延长,样品颗粒尺寸减小,当水热反应0.5 h时,样品为形貌不规则、界面不清晰、有毛绒状物质附着的60~70 nm的圆形颗粒,有团聚,结晶度较差。当水热反应1 h时,样品为粒径65 nm左右的近方形均匀块状颗粒,且分散性较好,结晶度较高。继续延长水热反应时间,样品形貌变化且颗粒减小,光催化性能逐渐增强。     

离子液体辅助合成AuPd纳米海绵及催化性能

在功能化离子液体氯化1-羟乙基-3-甲基咪唑([HEmim]Cl)辅助下, 在室温水溶液中一步快速合成了具有多孔海绵状结构的AuPd纳米材料. 通过场发射扫描电子显微镜(FESEM)、 透射电子显微镜(TEM)、 X射线能谱(EDX)和X射线衍射分析(XRD)等对该材料进行了表征. 结果表明, AuPd纳米海绵为合金结构, 由表面粗糙的纳米颗粒聚集熔接而成. 采用不同摩尔比(3∶1, 1∶1或1∶3)的前驱物HAuCl₄和Na₂PdCl₄均可制备出海绵状AuPd合金结构. 离子液体对AuPd纳米海绵状结构的形成起关键作用. 在对硝基苯酚还原反应中, 不同组成的AuPd纳米海绵均表现出比商用Pd/C催化剂更优异的性能. 其中, Au₁Pd₃纳米海绵具有最高的催化活性, 反应在98 s内即可完成, 反应速率常数为0.0143 s ^-1, 是商用Pd/C的2.3倍. 该方法也可用于制备其它双金属(如PdCu, PtCu等)和多金属纳米海绵.     

氧化银纳米线在官能化二氧化硅颗粒表面的自组装合成

在碱性水醇溶液中, 硝酸银与用3-(2-氨乙基氨丙基)三甲氧基硅烷[N-(2-aminoethyl)-3-aminopropyl-trimethoxy- silane, AMPTS]表面修饰后的二氧化硅胶体颗粒相互作用, 发现所生成的氧化银纳米颗粒可以在二氧化硅颗粒表面自组装为氧化银纳米线. 通过调变反应物中Ag/Si摩尔比, 可对氧化银纳米线的形貌进行调控. 在较小的Ag/Si摩尔比下, 可以得到结构均匀、直径约为50 nm、长度几十微米的氧化银纳米线. 随Ag/Si摩尔比增大, 得到的氧化银纳米线逐渐变短变粗, 且结构变得不均匀. 高分辨透射电镜(HRTEM)显示, 所有的氧化银纳米线均由直径10～20 nm的氧化银颗粒定向堆积而得. 利用透射电镜(TEM)对氧化银纳米线的形成过程进行了观察, 并对氧化银颗粒形成及组装机理进行了探讨.     

SnO2纳米粒子-花生酸LB膜有序组合体的研究

采用胶体化学法制备了稳定的SnO2纳米粒子（nanoparticleNP）水溶胶，用膜天平和原位布儒斯特角显微镜（BAM）考察了经典成膜材料花生酸（AA）在此水溶胶气-液界面的成膜性，并用LB膜技术在不同基底上制得了单层和多层AA-Sno2NP复合LB膜，通过TEM、小角X-ray、IR和UV-VIS光谱，进一步考察了该有序组装体的结构和周期性，以及组装作中Sno2纳米粒子的形貌、粒度分布和表面聚集状态.结果表明，用这种方法能够制得粒度分布均匀、农致密的Sno2纳米粒子复合LB膜，并且多层复合膜具有良好的周期性.     

NdFeO3纳米晶的合成及气敏性能

以Nd2O3,Fe(NO3)3·9H2O,硝酸(1∶1)为原料,在柠檬酸体系中用溶胶凝胶法合成了具有钙钛矿结构的稀土复合氧化物NdFeO3;用XRD和TEM对产物的组成、颗粒大小、形貌进行了表征;结果表明:产物为纳米颗粒,平均粒径为28nm左右,且颗粒均匀。还采用静态配气法测试了材料的气敏性能,发现NdFeO3对H2S有很高的灵敏度,且抗干扰能力强,有较好的工业应用前景。     

PAn-PEG-PAn三嵌段共聚物的合成和表征

在合成α,ω-双(对氨基苯基)聚乙二醇(BAPPEG)的基础上, 用化学氧化共聚法制备了PAn-PEG-PAn三嵌段共聚物. 研究了共聚时苯胺(An)与BAPPEG摩尔比(r)对共聚物的化学组成、UV-Vis谱图、热稳定性和在水溶液中的自组装特性的影响. 结果表明：随着r的增加, 共聚物中PAn链段的含量增大；其UV-Vis谱图中对应PAn链段的吸收峰出现红移, 且红移的程度增加； 热稳定性提高. 三嵌段共聚物在水中表现出自组装特性： 随着r的增加, 先形成粒径约为90 nm的PAn链段/PEG链段球型核壳胶束, 然后形成长为400～800 nm, 直径约为30 nm的棒状结构, 和棒状结构聚集形成的网状结构, 最后又变成球型胶束.     

金纳米粒子组装体的连续离散型纳米结构控制

采用柠檬酸钠还原氯金酸的方法,制备出粒径均一的金纳米粒子(AuNPs),通过加入二水合双(对-磺酰苯基)苯基膦化二钾盐(BSPP),增强了AuNPs体系的分散性与稳定性.选用直径为15和40nm的AuNPs,用不同序列巯基修饰的单链DNA连接到其表面,通过DNA链的杂交,形成不同结构的金纳米粒子组装体.通过改变加入DNA延长连接单元的比例,可以控制金纳米粒子组装体具有连续离散型的1∶1,2∶1和3∶1纳米结构.     

高比表面积纳米结构Ce0.7Zr0.3O2固溶体的模板组装

介绍了模板剂结构诱导下均相沉淀法组装纳米结构Ce0.7Zr0.3O2工艺方法, CTAB为0.02 mol, Ce(NO3)3 6H2O和Zr(NO3)4 5H2O总量为0.01 mol(Ce∶Zr为7∶3), (NH2)2CO为0.44 mol反应108 h可获得肩峰较宽、较纯的铈锆固溶体晶体相, 颗粒粒径在10～20 nm、孔径在2～4 nm、比表面积达178.57 m2*g-1. 高温焙烧及N2吸附分析表明, 样品具有良好热稳定性及吸附催化活性.     

凝胶燃烧法合成5V级正极材料LiNi_(0.5)Mn_(1.5)O_4及其高倍率放电性能

采用聚乙烯吡咯烷酮(PVP)作为络合剂和燃料以凝胶燃烧法制备了具有优异高倍率放电性能的亚微米LiNi0.5Mn1.5O4材料.用热重/差热分析(TG/DTA)研究了凝胶的燃烧过程,用X射线衍射(XRD)、扫描电镜(SEM)和循环伏安(CV)研究了LiNi0.5Mn1.5O4材料的结构和形貌.结果表明材料为结晶良好的纯尖晶石相结构,由5μm左右的二次颗粒组成,颗粒大小分布均匀,一次晶粒发育良好,粒径在500nm左右.充放电测试表明材料的倍率性能和循环性能十分优异.在3.5至4.9V进行充放电测试,0.5C、1C、4C、8C和10C倍率下放电容量分别为131.9、127.6、123.4、118.4和113.7mAh·g-1.在10C大倍率放电条件下循环100、500和1000次的容量保持率分别为91.4%、80.9%和73.5%.     

三条两亲性多肽的自组装行为及酸敏特性

通过固相合成法制备了三条疏水端不同的两亲性多肽VVVVVVKKGRGDS (AP1)、C₁₂KKGRGDS(AP2)、FAFAFAKKGRGDS (AP3). 自组装行为研究表明, 三条多肽在中性条件下(pH 7.0)均能形成球形纳米胶束, 透射电子显微镜(TEM)检测其粒径为~30 nm, 动态光散射(DLS)测试其粒径分布均一. 当pH下降为5.0时,肽链AP1的胶束结构被破坏, TEM视野中没有发现任何自组装体, 而肽链AP2和AP3的胶束结构在pH 5.0时依然存在, 但AP2的纳米粒子之间明显发生了部分聚集, 表现为团聚样分布, AP3组装体的粒径明显增大, 形貌变得不规则. DLS测试结果显示, 当pH下降到5.0时, 肽链AP1在1-1000 nm范围内没有出现吸收峰, AP2呈多峰分布, AP3呈宽单峰分布. DLS的测试结果很好地印证了TEM的测试结果. 为了探究三条多肽组装性能不同的二级结构因素, 我们对AP1、AP2和AP3进行了圆二色谱(CD)和傅里叶变换红外(FT-IR)光谱测试. 结果表明, 三条多肽在中性条件下二级结构中均存在一定含量的β-折叠, 当pH下降到5.0 时, AP1 结构中的β-折叠成分显著下降, 出现部分无规卷曲. AP2和AP3的β-折叠成分虽有变化, 但其CD主峰依然存在. 以姜黄素作为模型药物, 进一步确认AP1 载药胶束的释药行为也具有优良的酸敏感特性. AP1、AP2 和AP3 在酸性条件下自组装行为的不同, 表明调控两亲性多肽的疏水端组成有可能是调控多肽自组装性能的有效手段. AP1组装体有望成为理想的pH响应性载体材料.     

Synthesis of cadmium sulphide in pure and mixed Langmuir-Blodgett films of n -octadecylsuccinic acid

Cadmium sulphide (CdS) nanoparticles were grown by the reaction of sodium sulphide (Na₂S) with Langmuir-Blodgett (LB) films of cadmium salts ofn-octadecylsuccinic acid (ODSU) and with LB films of ODSU in mixtures of octadecylamine and octadecyl alcohol. The results indicate that heterogeneous nucleation and aggregation in the pure ODSU LB films due to processes like Ostwald ripening are destabilized by the presence of the long-chain amine and alcohol in mixed systems. CdS nanoparticles in the LB films were monitored by UV-visible absorption spectra, which allow an estimation of the size of the particles. The morphology, size and nature of the nanocrystallites formed depend on whether the sulphidation was done on the pure film or in the mixed films. It is seen that particles of size around 1.6 nm were formed in ODSU/octadecylalcohol and ODSU/ octadecylamine mixed LB films while in pure ODSU films the size was about 2.7 nm. These films showed typical needle-shaped structures, as observed by the optical microscopic technique. Mean size and morphology were confirmed by transmission and scanning electron microscopy, while selective area electron diffraction patterns showed six-fold symmetry and indicated that the CdS crystals grow epitaxially with respect to the monolayer. Further, the crystallisation enhanced in the mixed LB films showed a characteristic zinc oxide (Wurtzite) structure compared with the pure ODSU matrix.     

Thermal behavior of H-aggregate in a mixed Langmuir-Blodgett film of merocyanine dye, arachidic acid, and n-octadecane ternary system investigated by UV-visible and IR absorption spectroscopy

We have investigated the thermal behavior of H-aggregate in a mixed Langmuir-Blodgett (LB) film of the merocyanine dye (MS18)-arachidic acid (C20)- n-octadecane (AL18) ternary system by means of UV-visible and IR absorption spectroscopy in the range from 25 to 250 degrees C with a continuous scan. The results of both UV-visible and IR spectra indicate that the temperature-dependent variation in MS 18 aggregation state is linked not only with the degree of intramolecular charge transfer and the behavior of packing, orientation, conformation, and thermal mobility of the MS18 hydrocarbon chain but also with the presence and absence of AL18. The H-aggregate dissociates from 25 up to 50 degrees C, which is caused by the AL18 evaporation from the mixed LB film and the increment of thermal mobility of the MS18 hydrocarbon chain. From 110 to 160 degrees C, blue-shifted bands, attributed to the oligomeric MS18 aggregation, appear near 515 nm in the MS18-C 20-AL18 ternary system as well. The temperature at which the 515 nm band occurs is identical for both present ternary system and previously investigated MS18-deuterated arachidic acid (C20- d) binary system, and it is in good agreement with the melting point (110 degrees C) of cadmium arachidate (CdC20). Therefore, it is indicated that the driving force which induces the 515 nm band comes from the melting phenomenon of CdC20 molecules which are phase-separated from MS 18 molecules in as-deposited LB films.     

稀土螯合物发光体LB膜的研究(I)

稀土有机配合物的发光研究近年来取得了可喜的近展.铕(Ⅲ)、铽(Ⅲ)、钐(Ⅲ)与β-二酮(β-dik),三正辛基氧化膦(TOPO)所形成的螯合物,以及它们的硝酸盐与邻菲咯啉(Phen)所形成的螯合物都是高光效的发光体,有广阔的应用前景,在某些方面已获得应用.如能把这些具有发光功能的稀土螯合物组装成有序的分子组合体,则很可能在分子光学技术,光电子技术等领域发挥重要作用.如何组装?本文用LB 膜技术,通过交替成膜或混     

Dis-aggregation of an insoluble porphyrin in a calixarene matrix: characterization of aggregate modes by extended dipole model

In this paper, the different aggregation modes of a water-insoluble porphyrin (EHO) mixed with an amphiphilic calix[8]arene (C8A), at the air-water interface and in Langmuir-Blodgett (LB) film form, are analyzed as a function of the mixed composition. The strategy used to control the EHO aggregation has consisted of preparing mixed thin films containing EHO and C8A, in different ratios, at the air-water interface. Therefore, the increase of the C8A molar ratio in the mixed film diminishes the aggregation of the EHO molecules, although such an effect must be exclusively related to the dilution of the porphyrin. The reflection spectra of the mixed C8A-EHO films registered at the air-water interface, show a complex Soret band exhibiting splitting, hypochromicity and broadening features. Also, during the transfer process at high surface pressure, it has been shown that the EHO molecules are ejected from the C8A monolayer and only a fraction of porphyrin is transferred to the solid support, in spite of a complete transfer for the C8A matrix. The complex structure of the reflection spectra at the air-water interface, as well as the polarization dependence of the absorption spectra for the mixed LB films, indicate the existence of four different arrangements for the EHO hosted in the C8A matrix. The aggregate formation is governed by two factors: the attraction between the porphyrin rings which minimizes their separation, and the alkyl chain interactions, that is, hydrophobic effect and/or steric hindrance which determine and restrict the possible aggregation structures. By using the extended dipole model, the assignment of the spectral peaks observed to different EHO aggregates is shown.     

Fabrication and properties of fullerodendron thin films

Thin films of fullerodendron (C(60)(Gn-COOMe) (n = 0.5, 1.5, 2.5)), which was synthesized from fullerene and anthracenyl poly(amido amine) dendron with methyl ester terminals and different generations (G), were fabricated by the Langmuir-Blodgett (LB) and adsorption techniques. It was characterized by X-ray reflectometry that the LB films possessed well-ordered structure, although the adsorption method led to random orientation of molecules. As to C(60)(G0.5-COOMe) and C(60)(G1.5-COOMe), the LB films took a four-layer structure consisting of a double layer of molecules, and fullerene moieties exist in the interior of the LB films. On the other hand, C(60)(G2.5-COOMe) led to a two-layer structure in which the fullerene moieties were at the air side and the dendron moieties were at the substrate side. With increasing generation of dendron, the monolayer formation ability at the air/water interface as amphiphilic molecule strengthens and the amphiphilic property becomes superior to the fullerene-fullerene attractive interaction that prevents the monolayer formation. Furthermore, in the case of C(60)(G0.5-COOMe) and C(60)(G1.5-COOMe), the reduction peak in cyclic voltammetry of the LB film remained even after UV light irradiation. On the contrary, the peak of the C(60)(G2.5-COOMe) LB film disappeared, indicating that molecular arrangement in the films affects electrochemical properties.     

种子生长法制备Au-Ag纳米花

以金纳米花为种子,抗坏血酸和硝酸银混合物作为生长溶液制备了Au-Ag纳米花.当Ag/Au的摩尔比从0增加到0.3时,银可以在Au种子表面沉积,得到的Au-Ag纳米花光谱在592～518 nm之间连续可调,同时纳米花的枝长逐渐减小;而当Ag/Au摩尔比大于0.3时,还原的银出现自成核现象.与Au纳米花相比,Au-Ag纳米花体现出了更好的Raman增强活性.     

Thermal behavior of J-aggregates in mixed Langmuir-Blodgett films composed of merocyanine dye and deuterated arachidic acid investigated by UV-visible and infrared absorption spectroscopy

We have investigated the thermal behavior of J-aggregates in the mixed Langmuir-Blodgett (LB) films composed of the merocyanine dye (MS18)-deuterated arachidic acid (C20-d) binary system in the temperature range from 25 to 250 degrees C by means of UV-visible and IR transmission absorption spectroscopy. The temperature-dependent variations in both UV-visible and IR absorption spectra indicate that the MS18 aggregation states are linked with the MS18 intramolecular charge transfer and the behavior of the packing, orientation, conformation, and thermal mobility of the MS18 hydrocarbon chain. The J-aggregate formed at 25 degrees C in the mixed LB films dissociates in the temperature range from 25 to 110 degrees C, which is mainly ascribed to the increase in the thermal mobility of MS18 hydrocarbon chain and the dissociation of the chelation by a cadmium ion to the MS18 keto group. A thermally induced blue-shifted band appears at around 515 nm from 110 to 160 degrees C. This band is attributed to oligomeric aggregation with side-by-side alignment of the MS18 transition dipole moments on the basis of the shift to a higher-energy side, broadening, and temporary increment of the MS18 intramolecular charge transfer of the band. Consequently, the appearance of the thermally induced blue-shifted band indicates the possibility that the MS18 aggregation states can be controlled from the red shift to the blue shift by the annealing method adopted in the present study.     

Raman spectroscopic investigation of the single-monolayer Langmuir-Blodgett film of C16NaphOH and C10AzoNaphC4N-SDS

Raman spectra were measured for Langmuir-Blodgett (LB) films of C(16)NaphOH and C(10)AzoNaphC(4)N-SDS on Calcium Fluorite substrate for the first time. In order to find out favorable excitation condition, Raman spectra of the single and multi-monolayer LB films excited at different lines at 244, 514, 633 and 778 nm are recorded and compared in the present study. Raman spectrum of the monolayer LB film of C(16)NaphOH excited by 244 nm demonstrate that excellent signal to noise is achieved even for one monolayer LB film with an extremely short integrating time as 60 s because of being resonantly enhanced, while no meaningful spectra were recorded under the same condition for the monolayer LB film of C(10)AzoNaphC(4)N-SDS because of burning. Using a HeNe 633 nm excitation the problem with strong substrate fluorescence was partially solved, since under these conditions this fluorescence is mainly outside the fingerprint region of the LB film molecules (1000-2000 cm(-1)). Therefore by using the HeNe laser excitation, Raman spectra with high signal to noise ratio of LB films of C(16)NaphOH were collected and shown in this paper. These findings stress again the necessity to define an appropriate Raman system for this special application of LB film diagnosis.     

四(十六烷硫基)四硫富瓦烯/硬脂酸混合LB膜的结构研究

我们考察了四(十六烷硫基)四硫富瓦烯/硬脂酸(THT-TTF:SA=1:n)在气-液界面的聚集状态及在LB膜中的排列,当n=1时,THT-TTF分子在气-液界面形成了双分子膜;当n>6时,THT-TTF分子形成了单分子膜;1相似文献   

Spectroscopic and optical characterization of porphyrin chromophores incorporated into ultrathin polyimide films

Polyamic acid (PAA) containing free-base porphyrin and zinc(II) porphyrin chromophores was synthesized by copolymerization of diphenylether-type tetracarboxylic dianhydride and diamines. The monolayer of the alkylamine salts of PAA (PAASs) at the air/water interface was deposited on solid substrates by the Langmuir-Blodgett (LB) technique. The PAAS LB films thus obtained were converted to polyimide (PI) LB films by chemical treatment. The fluorescence of porphyrin moieties in the PI LB film was observed, because of the weak electron-accepting properties of the diphenylether unit. Therefore, the photophysically important processes, such as photoinduced electron transfer, excitation energy transfer, and excitation energy migration could be investigated in relation to the layered nanostructures of the ultrathin PI films. The fluorescence spectrum suggested that the aggregation of porphyrin moieties in the PI LB films was effectively prevented by the use of polymeric films. The surface plasmon (SP) measurement showed that the thickness of the monolayers was 0.9-1.0 nm for PAAS films and 0.32-0.40 nm on average for PI LB films. The absorption dichroism of the Soret band of porphyrin indicated that porphyrin moieties in the PAAS and PI LB films are oriented in parallel with the substrate. These results showed that the orientation and the spatial distribution of porphyrin units can be efficiently regulated in the PI LB films in a nanometer dimension.