金属纳米颗粒增强太阳能电池光吸收效应研究

采用Mie理论,对球形纳米金属颗粒进行数值计算,研究了金属纳米颗粒在发生表面等离激元共振时表现出的散射效应.改变金属材料类型或者颗粒尺寸大小,金属纳米球的散射效率均发生不同程度的变化.这一现象表明:金属纳米颗粒的散射效应受材料类型和尺寸大小的影响显著.计算结果表明,半径为100nm的Ag纳米颗粒在发生表面等离激元共振时,散射效率最高,吸收效应最弱.     

纳米ZnS的合成与表征

将通过直接沉淀法得到的纳米ZnS再经过水溶剂热处理,使其晶化.XRD及TEM结果显示ZnS是立方闪锌矿结构,为8-15nm的球状颗粒.水溶剂热晶化后,颗粒的大小、分散性、均匀度、晶化度均提高,表面活性剂的存在对颗粒的性质有影响.     

单分散水性硫普罗宁包覆金纳米粒子可控制备

利用紫外-可见光谱（UV-vis）、X衍射（X-ray Diffraction,XRD）和透射电子显微镜（Transmission Electron Microscope,TEM）等研究小尺寸水溶性金纳米粒子的可控制备.在乙酸和甲醇（体积比为1：6）的混合系统中,通过NaBH4对三水氯金酸还原,将硫普罗宁分子包覆到金纳米粒子表面,得到尺寸可控、稳定的硫普罗宁包覆的金纳米粒子水溶胶.通过控制金与硫普罗宁的摩尔比（Au/S比）,金纳米粒子的尺寸能够在2~8nm范围内得到有效控制.本文中,当Au/S比分别为1：3,1：1和3：1时,所合成的金纳米粒子的尺寸分别为（2.8±0.3）,（4.0±0.3）,（6.1±0.4）nm.     

ZnS/PbS核壳结构微球的制备和表征

用简单两步法制备ZnS/PbS核壳结构复合微球,采用SEM、EDS、TEM、XRD、FT-IR和固体紫外等测试手段对核壳结构复合微球样品进行性能表征,发现所得复合微球由ZnS核和PbS壳构成,其平均粒径约为8μm;而且具有中空结构的ZnS微球表面被很多细小的PbS颗粒包覆形成核壳结构。UV-vis表明ZnS/PbS核壳结构复合微球在紫外-可见光区都有良好的吸收,说明其在光电器件领域中将会有很好的发展前景。另外,还探讨了复合微球形成的机理。     

咪唑类离子液体在金纳米粒子表面结构性质的模拟研究

采用分子动力学(Molecular Dynamics,MD)模拟方法,研究了1-丁基-3-甲基咪唑四氟硼酸盐([BMIM][BF₄])离子液体在不同尺寸的金纳米粒子表面的结构性质.计算结果在分子水平上揭示了咪唑类离子液体在Au纳米粒子表面的结构特征与纳米粒子尺寸密切相关.通过分析,发现阳离子中的烷基侧链在小尺寸Au₁₃纳米粒子表面聚集的最多,然而阳离子中的咪唑环则在大尺寸Au₃₀₉纳米粒子表面聚集的最多.同时,取向分布也表明阳离子中的咪唑环倾向于分布在大尺寸Au₃₀₉纳米粒子周围而不是小尺寸Au₁₃纳米粒子.进一步的能量分析表明,阳离子中的烷基侧链与小尺寸的Au₁₃纳米粒子相互作用能要强于阳离子中的咪唑环,而Au₃₀₉纳米粒子则与咪唑环的相互作用能最强.此外,无论是对于小尺寸的Au₁₃纳米粒子还是大尺寸的Au₃₀₉纳米粒子,阴离子的相互作用能都是最小的.这预示着阴离子对于Au纳米粒子表面结构性质是典型的间接作用.     

TiO2纳米颗粒胶体活化系统设计及流场仿真分析

紫外光(UV)诱导纳米颗粒胶体射流加工可实现硬脆晶体材料亚纳米级超光滑表面的加工,根据其材料去除原理可知,伴随抛光过程的进行,胶体中TiO₂纳米颗粒表面会吸附一层工件表面的被去除原子,从而影响TiO₂纳米颗粒胶体的活性和光催化性.为了实现TiO₂纳米颗粒胶体的循环使用,基于O₃/UV高级氧化法对使用后的TiO₂纳米颗粒胶体再活化机理进行了研究,同时结合紫外光诱导纳米颗粒胶体射流加工系统设计了TiO₂纳米颗粒胶体活化系统,对系统内的再活化反应室结构进行了流体动力学仿真,仿真结果表明其结构设计满足TiO₂纳米颗粒胶体的活化要求.     

变形六方ZnS纳米晶的固相合成及其荧光特性

以硫化钠与醋酸锌为原料，采用改进的室温（湿）固相合成法制备硫化锌纳米晶，用TEM，XRD，UV，PL等方法研究了硫化锌纳米晶粒径、结构与荧光特性。结果表明，硫化锌纳米晶平均粒径约4.0nm，为六方结构。所制备的样品在400－450nm波段出现强荧光发射，并有光谱分裂现象。光谱分裂的原因可能是乙醇对纳米微粒的表面修饰作用、微量杂质的影响以及小尺寸效应的结果。     

Pt纳米颗粒几何特征与结构稳定性的原子尺度研究

基于金属纳米颗粒的几何特征及其幻数结构构建了一系列不同粒径和形貌的Pt纳米颗粒,利用改进分析型嵌入原子势与淬火分子动力学模拟研究了其结构稳定性。一方面揭示了各表面位比例、比表面积、平均配位数与粒径、形貌的定量关系;另一方面预测了晶体结构Pt纳米颗粒的平均原子结合能与颗粒尺寸的线性关联;二十面体形貌具有最密排的表面,尺寸较小时表面能的贡献使之成为首选结构,但大尺寸时应变能使之最不稳定;由于应变能的释放,晶态截切多面体小颗粒的稳定性与二十面体相仿,尺寸增大时具有最高稳定性。     

Suppression of crystal nucleation in polydisperse colloids due to increase of the surface free energy

The formation of small crystallites is governed by two competing factors: the free energy gained upon transferring constituent atoms, molecules or colloidal particles from the metastable liquid to the more stable solid, and the free energy needed to create the surface area of the crystallite. Because the ratio of surface area to bulk is large for small particles, small crystallites dissolve spontaneously under conditions where larger crystallites are stable and macroscopic crystal growth occurs only if spontaneously formed crystallites exceed a critical minimum size. On theoretical grounds, the probability of forming such critical crystal nuclei is expected to increase rapidly with supersaturation. However, experiments show that the rate of crystal nucleation in many systems goes through a maximum as the supersaturation is increased. It is commonly assumed that the nucleation rate peaks because, even though the probability of forming critical nuclei increases with increasing concentration, the rate of growth of such nuclei decreases. Here we report simulations of crystal nucleation in suspensions of colloidal spheres with varying size distributions that show that the probability that critical nuclei will form itself goes through a maximum as the supersaturation is increased. We find that this effect, which is strongest for systems with the broadest particle size distribution, results from an increase with supersaturation of the solid-liquid interfacial free energy. The magnitude of this effect suggests that vitrification at high supersaturations should yield colloidal glasses that are truly amorphous, rather than nano-crystalline.     

Quantum plasmon resonances of individual metallic nanoparticles

The plasmon resonances of metallic nanoparticles have received considerable attention for their applications in nanophotonics, biology, sensing, spectroscopy and solar energy harvesting. Although thoroughly characterized for spheres larger than ten nanometres in diameter, the plasmonic properties of particles in the quantum size regime have been historically difficult to describe owing to weak optical scattering, metal-ligand interactions, and inhomogeneity in ensemble measurements. Such difficulties have precluded probing and controlling the plasmonic properties of quantum-sized particles in many natural and engineered processes, notably catalysis. Here we investigate the plasmon resonances of individual ligand-free silver nanoparticles using aberration-corrected transmission electron microscope (TEM) imaging and monochromated scanning TEM electron energy-loss spectroscopy (EELS). This technique allows direct correlation between a particle's geometry and its plasmon resonance. As the nanoparticle diameter decreases from 20 nanometres to less than two nanometres, the plasmon resonance shifts to higher energy by 0.5 electronvolts, a substantial deviation from classical predictions. We present an analytical quantum mechanical model that describes this shift due to a change in particle permittivity. Our results highlight the quantum plasmonic properties of small metallic nanospheres, with direct application to understanding and exploiting catalytically active and biologically relevant nanoparticles.     

纳米颗粒表面修饰对纳米流体粘度的影响

纳米流体的黏度受流体温度、纳米颗粒粒径、纳米颗粒浓度等多方面的影响。在前人的研究中,黏度随流体温度的增加而减小,随纳米颗粒粒径的增加而减小,随纳米颗粒浓度的增加而增大,但黏度随纳米颗粒浓度的增大程度不同。通过总结大量不同情况下纳米流体的黏度数据,分析纳米流体黏度随纳米颗粒浓度的增加与纳米颗粒表面性质的关系。分析结果表明:纳米颗粒的添加增加基础流体的黏度;且亲水型纳米颗粒比疏水型纳米颗粒与水形成的纳米流体的黏度高。通过对纳米颗粒表面性质的修饰,可以控制纳米流体黏度的变化,从而影响流体输送过程中的能耗。     

金纳米微粒晶格畸变和结合能的尺寸形状效应

利用紧束缚分子动力学的方法,模拟了球形和立方体金纳米微粒的最近邻原子间距以及结合能. 研究表明,原子数为108, 256的立方体纳米微粒的稳定结构是非晶态,而其他尺寸的球形和立方体形微粒则是面心立方结构. 对于晶态结构,在一定的形状下,金纳米微粒的最近邻原子间距以及结合能随着微粒尺寸的减小而降低;而在微粒原子数一定时,球形金纳米微粒的最近邻原子间距以及结合能的变化量分别要小于立方体形微粒的相应变化量. 由于晶体-非晶转变对于最近邻原子间距的影响非常明显,因此最近邻原子间距可以作为晶态和非晶态纳米微粒的一个判据. 通过线性拟合模拟数据, 定量地给出了形状对于最邻近原子间距变化量的贡献为总变化量的2%,而对于结合能的贡献为总变化量的15%. 本文模拟的最近邻原子间距的数值与文献上报道的实验结果符合得很好.     

A novel nonviral nanoparticle gene vector: Poly-L-lysine-silica nanoparticles

DNA delivery is a core technology for gene structure and function research as well as clinical settings. The ability to safely and efficiently targeted transfer foreign DNA into cells is a fundamental goal in biotechnology. With the development of nanobiotechnology, nanoparticle gene vectors brought about new hope to reach the goal. In our research, silica nanoparticles (SiNP) were synthesized first in a microemulsion system polyoxyethylene nonylphenyl ether (OP-10)/cyclohexane/ammonium hydroxide, at the same time the effects of SiNP size and its distribution were elucidated by orthogonal analysis; then poly-L-lysine (PLL) was linked on the surface of SiNP by nanoparticle surface energy and electrostatically binding; lastly a novel complex nanomateial—poly-L-lysine-silica nanoparticles (PLL-SiNP) was prepared. The analysis of plasmid DNA binding and DNase I enzymatic degradation discovered that PLL-SiNP could bind DNA, and protect it against enzymatic degradation. Cell transfection showed that PLL-SiNP could efficiently transfer PEGFPC-2 plasmid DNA into HNE1 cell line. These results indicated that PLL-SiNP was a novel nonviral nanoparticle gene vector, and would probably play an important role in gene structure and function research as well as gene therapy.     

CocorePdshell/C核壳型纳米粒子电催化氧还原性能

应用胶体粒子模板法制备不同壳层厚度的CocorePdshell纳米电催化剂。TEM、XRD和EDS证实,CocorePdshell纳米粒子基本为球形,面心立方晶型(fcc)Pd成功包覆在纳米金属Co的表面,其中,Co1Pd2纳米粒子平均直径约10 nm且粒径分布较窄。动电位、交流阻抗、循环伏安及原位傅里叶变换红外反射光谱等电化学测试结果表明:与Pd/C相比,CocorePdshell/C纳米粒子对氧还原反应(ORR)的活性有明显的提高,甚至接近于Pt/C;抗甲醇能力非常优异,对甲醇氧化几乎无活性;不同壳层厚度催化剂中,以Co1Pd2/C催化剂的活性最高,在0.5 mol/L H2SO4中氧还原峰电流密度可达175.5 mA/mg,比Pt/C的要高出20 mA/mg。     

Green synthesized ZnO nanoparticles against bacterial and fungal pathogens

Zinc oxide nanoparticles are known to be one of the multifunctional inorganic nanoparticles with effective antibacterial activity. This study aims to determine the antimicrobial efficacy of green and chemical synthesized ZnO nanoparticle against various bacterial and fungal pathogens. Various microbiological tests were performed using varying concentrations of green and chemical ZnO NPs with sizes 40 and 25 nm respectively. Results prove that green ZnO nanoparticles show more enhanced biocidal activity against various pathogens when compared to chemical ZnO nanoparticles. Also effectiveness of nanoparticles increases with increasing particle dose, treatment time and synthesis method. In addition, the current study has clearly demonstrated that the particle size variation and surface area to volume ratio of green ZnO nanoparticle are responsible for significant higher antimicrobial activity. From the results obtained it is suggested that green ZnO NPs could be used effectively in agricultural and food safety applications and also can address future medical concerns.     

Pt/纳米TiO2-CNT复合电极的制备及对甲醇的电催化氧化

通过电合成前驱体Ti(OEt)4直接水解法和在恒电位-0.05V (vs. SCE)电沉积法制备Pt/nano TiO2-CNT电极.透射电镜 (TEM) 和X射线衍射 (XRD) 分析结果表明, 锐钛矿型纳米TiO2粒子(粒径5-10nm) 和碳纳米管结合形成网状结构, Pt纳米粒子(粒径8-15 nm)均匀地分散在纳米TiO2/碳纳米管复合膜表面.通过循环伏安和计时电流测试表明, Pt/ nano TiO2-CNT电极具有高活性表面, 同时对甲醇的电化学氧化具有高催化活性和稳定性,Pt载量为0.24mg/cm2时, 常温常压下甲醇的氧化峰电流达到260mA/cm2.     

添加纳米粒子对脂肪酶交联酶聚集体活性及结构的影响

将纳米TiO2、纳米MgO和纳米Cu分别引入假丝酵母脂肪酶（Candida sp. 1619）的交联酶聚集体（CLEAs）制备过程，获得相应的纳米粒子-CLEAs，采用傅里叶变换红外光谱仪(FTIR)、扫描电子显微镜(SEM)、激光粒度分析仪(SLP)等分析了纳米粒子对CLEAs活性和结构的影响。结果表明与未加纳米粒子的CLEAs相比，适量纳米TiO2的加入可提高CLEAs的酶活，最大增加15.2%；而不管添加浓度大小，纳米MgO、纳米Cu对CLEAs酶活均有抑制作用，酶活下降63.7%~97.9%。SEM、SLP分析结果表明，与未添加纳米粒子时相比，加入纳米TiO2的CLEAs粒径变小，粒度较均匀，孔道增加；而纳米MgO-CLEAs和纳米Cu-CLEAs则出现粒度不均匀性增加、粒径范围扩大、孔道减少的现象。FTIR分析结果表明，加入3种纳米粒子后CLEAs二级结构中有序结构（α-螺旋、β-折叠）/无序结构（β-转角、无规则卷曲）值显著提高，顺序为纳米TiO2-CLEAs（0.55）>纳米MgO-CLEAs（0.43）>纳米Cu-CLEAs（0.35）>CLEAs（0.28），这与纳米粒子-CLEAs酶活顺序不一致，表明纳米粒子可能还存在其他影响CLEAs酶活的途径。     

Theoretical investigation of Ag_n@(ZnS)_(42)(n=6-16) using first principles:Structural,electronic and optical properties

Ag@ZnS nanoparticles display enhanced photocatalytic efficiency and good photoelectric properties compared to their single-component counterparts in the process of forming a core-shell structure using an Ag cluster as the inner core of a ZnS outer shell.In this study,first-principles calculations were used to investigate the structural,electronic,and optical properties of Ag_n@(ZnS)_(42)(n=6-16)core-shell nanocomposites.The calculated results show significant even-odd oscillations in the structural stability,that is,Ag@ZnS nanostructures with an even number of Ag_n core atoms are relatively more stable than those with an odd number of core atoms.The secondorder differences in the total energies(Δ_2E)and the core-shell interaction energy E_(cs) indicate that a Ag_(12)@(ZnS)_(42)nanostructure is the most stable configuration.A significant red shift was found in Ag_n@(ZnS)_(42)nanoparticles in the absorption spectrum compared with a(ZnS)_(48) nanostructure,which is likely attributed to the strong electron interactions between the Ag core and the ZnS shell.     

柴油发动机尾气纳米颗粒演变的TEMOM-LES模型

 中国雾霾主要成因是包括柴油发动机在内的污染源排放导致的二次颗粒物, 本文针对柴油发动机尾气排放的颗粒物进行研究, 主要关注极大数目微纳米颗粒的综合效应导致的颗粒参数的变化, 次了解根据不同柴油含硫标准下产生的颗粒物的分布情况。通过把针对尺度谱演变问题的泰勒展开矩方法(TEMOM)和大涡模拟方法(LES)技术进行结合, 研究了排气管附近柴油二次颗粒物的演变过程, 并在相同流动工况条件下, 对加拿大、新加坡、欧盟、美国、俄罗斯、中国和日本不同国家和地区不同柴油含硫标准所导致的二次颗粒物的总颗粒数浓度、总体积浓度和颗粒大小进行了对比研究。结果显示, 颗粒物在近排气管处主要分布在射流剪切层, 颗粒数浓度和颗粒物直径的最大值在距离喷嘴0.6 m 附近产生, 在射流下游, 射流与下游空气混合稀释效应明显, 颗粒数浓度和颗粒直径趋于一稳定值。通过研究时间平均颗粒场的分布发现, 低燃硫量柴油尾气产生的颗粒数浓度比高燃硫量产生的颗粒数浓度低4 个数量级, 产生的颗粒体积浓度最大相差6 个数量级。     

添加纳米二氧化硅的菜籽油润滑行为

采用溶胶-凝胶法,以正硅酸乙酯为原料制备了纳米二氧化硅微粒,通过透射电子显微镜对其结构进行了表征,利用四球摩擦磨损试验机测定了添加不同含量纳米二氧化硅菜籽油润滑剂摩擦学性能,采用扫描电子显微镜和能量散射谱仪观察分析了磨损表面形貌及表面元素组成.结果表明:所制备的纳米二氧化硅是粒径为50 nm球形微粒,具有很高的表面能和表面活性,具有无定形结构;纳米二氧化硅作为菜籽油添加剂能显著提高菜籽油的PB和PD值,添加量为2.5%时的润滑剂性能最好,相对应的钢球磨斑直径最小.