EuF3-NaYF4纳米晶/PNIPAm三元复合凝胶的荧光温敏行为与影响机制

分别采用水热法制备EuF3与NaYF4纳米晶, 与N-异丙基丙烯酰胺（NIPAm）混合后进行自由基聚合, 一步法合成EuF3-NaYF4纳米晶/聚N-异丙基丙烯酰胺（PNIPAm）三元复合凝胶。 对纳米晶与复合凝胶的结构与荧光性能进行了表征。 重点研究了三元复合凝胶的荧光温敏行为, 并对其影响机制进行了探讨。 结果表明, EuF3与NaYF4纳米晶在PNIPAm凝胶基体中的体相掺杂, 同样产生了明显的能量传递。 两种纳米晶相对含量的变化, 对复合凝胶的荧光温敏性能有重要影响。     

单分散CdS纳米晶/PNIPAM复合水凝胶的制备及其温敏荧光特性

采用液体-固体-溶液法(LSS)制备单分散CdS纳米晶;通过自由基聚合制备单分散CdS纳米晶/聚N-异丙基丙烯酰胺(CdS/PNIPAM)复合温敏水凝胶.采用HRTEM、XRD、FTIR、DSC、PL等对CdS纳米晶、CdS/PNIPAM温敏复合凝胶的微观结构与性能进行了表征,变温荧光光谱研究了温度对凝胶荧光性能的影响.结果表明,CdS纳米晶粒径约为2.8 nm,单分散性良好;复合凝胶的荧光发射强度与环境温度存在一定的关联性,且呈可逆性.     

一锅法制备YF_3:Yb~(3+)-Er~(3+)纳米晶复合PNIPAm-co-PAA纳凝胶及其荧光温敏行为

采用巯基乙胺为配体,以硝酸铒(Er(NO3)3),硝酸镱(Yb(NO3)3),硝酸钇(Y(NO3)3)和氟化铵(NH4F)为原料,水热法制备表面含NH2基团的活性YF3:Yb3+-Er3+纳米晶;以过硫酸钾(K2S2O8)为引发剂,借助1-乙基-(3-二甲基氨基丙基)碳酰二亚胺(EDC)与N-羟基丁二酰亚胺(NHS)的偶联反应,在活性纳米晶存在下,进行N-异丙基丙烯酰胺(NIPAm),N,N'-亚甲基双丙烯酰胺(BIS)与丙烯酸的自由基共聚合,一锅法制备了YF3:Yb3+-Er3+/PNIPAm-co-PAA荧光温敏纳凝胶.对制备的纳米晶及纳凝胶的结构与荧光性能进行了表征.结果表明,纳米晶的粒径为6~10 nm,呈单分散分布;纳凝胶的粒径呈多分散分布,粒径主要分布在100~300 nm.PL光谱分析表明,活性YF3:Yb3+-Er3+纳米晶的4F7/2→4I15/2跃迁,在483和496 nm处产生明显的能级劈裂;纳凝胶中,该能级劈裂依然存在,但随温度升高发生耦合;环境温度对纳凝胶的上转换发光强度产生明显影响.     

上转换荧光响应性复合纳米凝胶的制备及荧光能量传递行为

采用水热法合成NaYF₄∶Yb³⁺,Er³⁺稀土纳米晶, 再经3-苄基三硫代碳酸酯基丙酸(BSPA)修饰, 制得功能化纳米晶体; 以罗丹明6G(R6G)为母体荧光染料, 经一系列反应合成了乙烯基功能化单体罗丹明6G酰基邻羧基苯甲肼腙(R6GHA); 将功能化纳米晶体与R6GHA构成荧光共振能量传递(FRET)的“给体/受体”对, 通过可逆加成断裂链转移(RAFT)聚合和“点击化学”反应, 合成具有多重响应性复合荧光纳米凝胶NaYF₄∶Yb³⁺,Er³⁺/PNIPAm-co-R6GHA. 采用TEM, XRD, FTIR和DSC对产物的微观结构进行了表征; 采用上转换荧光光谱(PL)研究了该复合纳米凝胶对pH值、 环境温度和不同金属离子的荧光响应行为, 并对相关机理进行了探讨. 结果表明, 环境温度变化对复合纳米凝胶的荧光发射具有显著影响, 且该复合纳米凝胶对Hg²⁺具有选择性荧光响应; 在H⁺或Hg²⁺作用下, 复合纳米凝胶中纳米晶和R6GHA之间会发生荧光共振能量传递; 通过纳米凝胶中纳米晶与R6GHA特征荧光发射峰比率的变化, 实现对Hg²⁺的检测.     

Fe_3O_4/PAA/ATP纳米复合磁性微凝胶吸附剂对Pb(Ⅱ)吸附动力学和吸附热力学研究

用γ-甲基丙烯酰氧基丙基三甲氧基硅烷(KH-570)对纳米Fe_3O_4磁性粒子和凹凸棒黏土纳米棒晶进行表面改性,通过KH-570的桥接,在纳米Fe_3O_4磁性粒子和凹凸棒纳米棒晶的表面原位接枝聚合丙烯酸单体,制备Fe_3O_4/PAA/ATP纳米复合磁性微凝胶。将该复合微凝胶用作吸附剂,处理水体中的Pb(Ⅱ),研究其对Pb(Ⅱ)的吸附动力学和吸附热力学。     

Ag∶InP/ZnSe纳米晶的合成与生物成像

采用高温热注入法,以P[N(CH_3)_2]_3为磷源合成了具有近红外荧光的Ag∶InP/ZnSe纳米晶.采用紫外-可见-近红外吸收光谱(UV-Vis-NIR)、荧光光谱、透射电子显微镜(TEM)、X射线衍射(XRD)等对产物的结构和光学性质进行了表征,并分析了Ag掺杂浓度和温度对InP纳米晶荧光性能的影响.通过调节Ag掺杂浓度和反应温度,发现当Ag掺杂量为6%,反应温度为200℃时,Ag∶InP纳米晶的发光效率最高.将制备的Ag∶InP的表面包覆ZnSe,粒子的荧光效率从原来的20%提高到45%.将具有近红外荧光的Ag∶InP/ZnSe纳米晶应用于细胞成像,结果表明制备的荧光纳米晶在细胞成像中清晰可见且毒性较低.     

功能化ZnxCd1-xS纳米晶的制备及其光学性能的研究

以氯化锌、氯化镉和硫化钠为原料，采用巯基乙醇为表面修饰剂，H₂O/DMF为溶剂，制得未团聚且分散均匀的纳米晶溶液，同时得到表面富含羟基基团不同锌镉组成的复合Zn_xCd_1-xS纳米晶。利用FTIR、EDS、UV-Vis、XRD、荧光光谱(PL)考察了复合纳米晶结构和光学性能的关系，并利用紫外灯摄像技术对Zn_xCd_1-xS纳米晶的光致发光性能进行     

Mg2 FeH6 纳米晶的制备及储氢性能

在室温和氩气气氛下, 以MgH2 和纳米Fe为原料, 采用机械合金化(球磨法)制备了Mg2FeH6纳米晶. 考察了球磨参数(时间、 转速)对产物的影响, 对所制备的Mg2FeH6 纳米晶的组成、 结构和形貌进行了表征, 并对其储氢性能进行了测试. 结果表明, 所制备的Mg2FeH6纳米晶为立方结构, 纯度较高(91.4%), 其晶粒尺寸较小, 约为10~30 nm, 但团聚现象较为严重. Mg2FeH6纳米晶具有较低的活化能和较好的吸放氢动力学性能, 其放氢的脱附焓和脱附熵分别为(-42.8±2) kJ/mol和(-72.0±3) J/(mol·K). 在503 K和6 kPa的氢气压力下, Mg2FeH6纳米晶在70 min内放氢量达到2.5%(质量分数); 在2 MPa的氢气压力下, 上述放氢产物具有较快的起始吸氢速率.     

Study of nucleation and growth in the organometallic synthesis of magnetic alloy nanocrystals: the role of nucleation rate in size control of CoPt3 nanocrystals

High quality CoPt(3) nanocrystals were synthesized via simultaneous reduction of platinum acetylacetonate and thermodecomposition of cobalt carbonyl in the presence of 1-adamantanecarboxylic acid and hexadecylamine as stabilizing agents. The high flexibility and reproducibility of the synthesis allows us to consider CoPt(3) nanocrystals as a model system for the hot organometallic synthesis of metal nanoparticles. Different experimental conditions (reaction temperature, concentration of stabilizing agents, ratio between cobalt and platinum precursors, etc.) have been investigated to reveal the processes governing the formation of the metal alloy nanocrystals. It was found that CoPt(3) nanocrystals nucleate and grow up to their final size at an early stage of the synthesis with no Ostwald ripening observed upon further heating. In this case, the nanocrystal size can be controlled only via proper balance between the rates for nucleation and for growth from the molecular precursors. Thus, the size of CoPt(3) nanocrystals can be precisely tuned from approximately 3 nm up to approximately 18 nm in a predictable and reproducible way. The mechanism of homogeneous nucleation, evolution of the nanocrystal ensemble in the absence of Ostwald ripening, nanocrystal faceting, and size-dependent magnetic properties are investigated and discussed on the example of CoPt(3) magnetic alloy nanocrystals. The developed approach was found to be applicable to other systems, e.g., FePt and CoPd(2) magnetic alloy nanocrystals.     

单源前体合成水溶性的CdS和ZnS纳米晶

0引言量子点(QuantumDots)一般指半径小于或接近玻尔激子半径的半导体纳米晶颗粒。和有机染料分子相比,无机半导体纳米晶的带隙宽度可通过简单     

Colloidal gallium indium oxide nanocrystals: a multifunctional light-emitting phosphor broadly tunable by alloy composition

We demonstrate compositionally tunable photoluminescence in complex transparent conducting oxide nanocrystals. Alloyed gallium indium oxide (GIO) nanocrystals with variable crystal structures are prepared by a colloidal method throughout the full composition range and studied by different structural and spectroscopic methods, including photoluminescence and X-ray absorption. The structures and sizes of the GIO nanocrystals can be simultaneously controlled, owing to the difference in the growth kinetics of In(2)O(3) and Ga(2)O(3) nanocrystals and the polymorphic nature of both materials. Using the synthesized nanocrystal series, we demonstrate the structural and compositional dependences of the photoluminescence of GIO nanocrystals. These dependences, induced by the interactions between specific defect sites acting as electron donors and acceptors, are used to achieve broad emission tunability in the visible spectral range at room temperature. The nature of the photoluminescence is identified as donor-acceptor pair recombination and changes with increasing indium content owing to the changes in the energy states of, and interactions between, donors and acceptors. Structural analysis of GIO nanocrystals by extended X-ray absorption fine structure spectroscopy reveals that In(3+) occupies only octahedral, rather than tetrahedral, sites in the spinel-type γ-Ga(2)O(3) nanocrystal host lattice, until reaching the substitutional incorporation limit of ca. 25%. The emission decay dynamics is also strongly influenced by the nanocrystal structure and composition. The oxygen vacancy defects, responsible for the observed photoluminescence properties, are also implicated in other functional properties, particularly conductivity, enabling the application of colloidal GIO nanocrystals as integrated optoelectronic materials.     

Room-temperature Wurtzite ZnS nanocrystal growth on Zn finger-like peptide nanotubes by controlling their unfolding peptide structures

ZnS nanocrystal, a class of wide-gap semiconductors, has shown interesting optical, electrical, and optoelectric properties via quantum confinement. For those applications, phase controls of ZnS nanocrystals and nanowires were critical to tune their physical properties to the appropriate ones. The wurtzite ZnS nanocrystal growth at room temperature is the useful fabrication; however, the most stable ZnS structure in nanoscale is the zinc blende (cubic) structure, and scientists have just begun exploring the room-temperature synthesis of the wurtzite (hexagonal) structure of ZnS nanocrystals. In this report, we applied the Zn finger-like peptides as templates to control the phase of ZnS nanocrystals to the wurtzite structure at room temperature. The peptide nanotubes, consisting of a 20 amino acids (VAL-CYS-ALA-THR-CYS-GLU-GLN-ILE-ALA-ASP-SER-GLN-HIS-ARG-SER-HIS-ARG-GLN-MET-VAL, M1 peptide) synthesized based on the peptide motif of the Influenza Virus Matrix Protein M1, could grow the wurtzite ZnS nanocrystals on the nanotube templates in solution. In the M1 protein, the unfolding process of the helical peptide motif via pH change creates a linker region between N- and C-terminated helical domains that contains a Zn finger-like Cys2His2 motif. Because the higher pH increases the uptake of Zn ions in the Cys2His2 motif of the M1 peptide by unfolding more helical domains, the pH change can essentially control the size and the number of the nucleation sites in the M1 peptides to grow ZnS nanocrystals with desired phases. Here we optimized the nucleation sites in the M1 peptides by unfolding them via pH change to obtain highly monodisperse and crystalline wurtzite ZnS nanocrystals on the template nanotubes at room temperature. This type of peptide-induced biomineralization technique will provide a clean and reproducible method to produce semiconductor nanotubes due to its efficient nanocrystal formation, and the band gaps of resulting nanotubes can also be tuned simply by phase control of ZnS nanocrystal coatings via the optimization of the unfolding peptide structures.     

One-step synthesis of highly water-dispersible Mn(3)O(4) nanocrystals

Highly water-dispersible Mn(3)O(4) nanocrystals with well-controlled size, size distribution and high crystallinity have been successfully synthesized through a modified polyol process. Poly(acrylic acid) is used as the capping agent, conferring upon the particles high water-dispersion, of which the carboxylate groups partially bind to the nanocrystal surface and the uncoordinated carboxylate groups extend into water. The water-dispersible Mn(3)O(4) nanocrystals can be further transferred to nonpolar solvent by linking oleylamine molecules through electrostatic interaction. The as-prepared Mn(3)O(4) nanocrystals exhibit ferromagnetic behavior at low temperature and weak paramagnetic behavior at room temperature. The Curie-Weiss temperature and the blocking temperature are 40 K and 32 K, respectively.     

溶胶－凝胶法制备镶嵌在SiO2玻璃中的InAs纳米晶

以As2O3,InCl3·4H2O和正硅酸乙酯为原料,通过水解、缩聚制备了xIn2O3-xAs2O3-100SiO2(x=0.5～7.5)凝胶,在氧气中加热到450℃对凝胶热处理使其转化成凝胶玻璃,再在200～500℃与氢气反应,结果在SiO2凝胶玻璃中形成了立方相InAs,利用XRD测试了InAs纳米颗粒的大小、发现随着反应温度的升高及掺杂量的增加,InAs纳米颗粒粒径从6增大到29nm,电子衍射表明凝胶玻璃中的InAs纳米颗粒为多晶结构。     

Constraints in post-synthesis ligand exchange for hybrid organic (MEH-PPV)–inorganic (CdSe) nanocomposites

For an optimum charge/energy transfer performance of hybrid organic–inorganic colloidal nanocrystals for applications such as photonic devices and solar cells, the determining factors are the distance between the nanocrystal and polymer which greatly depends upon nanocrystal size/nanocrystal ligands. Short chain ligands are preferred to ensure a close contact between the donor and acceptor as a result of the tunnelling probability of the charges and the insulating nature of long alkyl chain molecules. Short distances increase the probability for tunnelling to occur as compared to long distances induced by long alkyl chains of bulky ligands which inhibit tunnelling altogether. The ligands on the as-synthesized nanocrystals can be exchanged for various other ligands to achieve desirable charge/energy transfer properties depending on the bond strength of the ligand on the nanocrystal compared to the replacement ligand. In this work, the constraints involved in post-synthesis ligand exchange process have been evaluated, and these factors have been tuned via wet chemistry to tailor the hybrid material properties via appropriate selection of the nanocrystal capping ligands. It has been found that both oleic acid and oleylamine (OLA)-capped cadmium selenide (CdSe) quantum dots (QDs) as compared with trioctylphosphine oxide (TOPO)-passivated CdSe QDs are of high quality, and they provide better steric stability against coagulation, homogeneity, and photostability to their respective polymer:CdSe nanocomposites. CdSe QDs particularly with OLA capping have relatively smaller surface energies, and thus, lesser quenching capabilities show dominance of photoinduced Forster energy transfer between donors (polymer) and acceptors (CdSe nanocrystals) as compared to charge transfer mechanism as observed in polymer:CdSe (TOPO) composites. It is conjectured that size quantization effects, stereochemical compatibility of ligands (TOPO, oleic acid, and oleyl amine), and polymer MEH-PPV stability greatly influence the photophysics and photochemistry of hybrid polymer–semiconductor nanocomposites.     

One-step synthesis of highly water-soluble magnetite colloidal nanocrystals

A high-temperature solution-phase hydrolysis approach has been developed for the synthesis of colloidal magnetite nanocrystals with well-controlled size and size distribution, high crystallinity, and high water solubility. The synthesis was accomplished by the hydrolysis and reduction of iron(III) cations in diethylene glycol with a rapidly injected solution of sodium hydroxide at an elevated temperature. The high reaction temperature allows for control over size and size distribution and yields highly crystalline products. The superior water solubility is achieved by using a polyelectrolyte, that is, poly(acrylic acid) as the capping agent, the carboxylate groups of which partially bind to the nanocrystal surface and partially extend into the surrounding water. The direct synthesis of water-soluble nanocrystals eliminates the need for additional surface modification steps which are usually required for treating hydrophobic nanocrystals produced in nonpolar solvents through the widely recognized pyrolysis route. The abundant carboxylate groups on the nanocrystal surface allow further modifications, such as bioconjugation, as demonstrated by linking cysteamine to the particle surface. The monodisperse, highly water-soluble, superparamagnetic, and biocompatible magnetite nanocrystals should find immediate important biomedical applications.