金纳米颗粒的自组装修饰及其生物学效应

为了探究金纳米颗粒(Au NP)s的表面自组装亲疏水性修饰及其生物学效应,通过自组装技术制备SH-(CH2)11OH和SH-(CH2)11CH3不同配比修饰的Au NPs,并用透射电子显微镜(TEM)、纳米粒度仪和傅里叶变换红外光谱(FT-IR)检测修饰后的表面形貌与结构特征。用体视显微镜观察Au NPs修饰后对斑马鱼胚胎/幼鱼表型的影响。用MMT、NO含量试剂盒、总抗氧化能力(T-AOC)试剂盒检测Au NPs修饰后对人脐静脉内皮细胞(HUVECs)毒性和功能指标的影响。利用电感耦合等离子体发射光谱和TEM检测Au NPs修饰后被HUVECs摄入情况。结果表明,用SH-(CH2)11OH修饰比用SH-(CH2)11CH3修饰的Au NPs毒性大,当修饰Au NPs的SH-(CH2)11OH和SH-(CH2)11CH3配比为50:50时毒性最小。     

Equilibrium and stability of phase-separating Au–Pt nanoparticles

We report on a theoretical and experimental investigation of Au–Pt nanoparticles (NPs). The Au–Pt miscibility gap is theoretically reevaluated for NPs of various sizes. The model includes a composition-dependent surface energy evaluated by considering surface segregation. Using precise quantitative energy-dispersive X-ray spectroscopy (EDXS) and high-resolution electron microscopy (HREM), the structural evolution of ∼20 nm Au(core)–Pt(shell) NPs upon annealing at various temperatures (300–800 °C) is studied. At low temperatures, only interdiffusion occurs between the core and the shell, while above ∼600 °C, the NPs evolve into Au- and Pt-rich crystals, separated by an interface. At these temperatures, the Au solubility in the Pt-rich phase is found to be 5–10% higher than the bulk phase diagram and agrees qualitatively with the theoretical model. Based on the EDXS and HREM results, the nature of the interface separating the Au- and Pt-rich phases within a NP is discussed and an estimate of its energy is obtained.     

Surface functionalization of single-walled carbon nanombes using metal nanoparticles

Surface functionalization of suspended single-walled carbon nanotubes (SWNTs) using metal (Au) nanoparticles (NPs) is reported. SWNTs are grown on three-dimensionally patterned substrates by thermal chemical vapor deposition and successfully functionalized with Au NPs. Ethylendiamine is mainly used to functionalize SWNTs surface with amino groups before introducing Au NPs. From Raman scattering spectroscopy of the Au-functionalized suspended SWNTs, enhanced Raman scattering properties are obtained. The results suggest that the attached Au NPs may contribute to the enhancement of resonant phenomena. By measuring the electric properties after each functionalization process, it is found that Au NPs act as electron acceptor to the amine functionalized SWNTs.     

Nanoscale photoluminescence of light-emitting poly (3-methylthiophene) nanotubes hybridized with Au nanoparticles

We reported on the fabrication and nanoscale luminescence characteristics of the hybrid nanotubes (NTs) of light-emitting poly (3-methylthiophene) (P3MT) NT with gold (Au) nanoparticles (NPs) (P3MT/Au-NPs). After hybridizing the Au-NPs onto the surface of P3MT NTs, the light-emitting color of P3MT NTs was dramatically changed from a green to a bright red. From laser confocal microscope photoluminescence (PL) experiments for an isolated single strand of the NTs, we observed a ～220 times enhancement of the PL peak intensity for the hybrid NT of P3MT/Au-NPs compared to that of the P3MT single NT. The enhancement PL efficiency of the hybrid NT of P3MT/Au-NPs can be explained in terms of a surface plasmon resonance (SPR) and nanoscale local electric field enhancement effects.     

Sensing behavior of silica-coated Au nanoparticles towards nitrobenzene

In the present work, we report silica-stabilized gold nanoparticles (SiO₂/Au NPs) as a wide-range sensitive sensing material towards nitrobenzene (NB). Surface hydroxyl groups of silica selectively form Meisenheimer complex with electron-deficient aromatic ring of NB and facilitate its immobilization and subsequent catalytic reduction by Au cores. Silica-coated Au NPs were synthesized and characterized for their chemical, morphological, structural, and optical properties. SiO₂/Au NPs-modified electrodes were characterized with impedometric and cyclic voltammetric electrochemical techniques. SiO₂/Au NPs are found to have a higher optical detection window of range, 0.1 M to 1 μM and a lower electrochemical detection window of range, 10⁻⁴ to 2.5 × 10⁻² mM with a detection limit of 12.3 ppb. A significant enhancement in cathodic peak current, C ₁, and sensitivity (102 μA/mM) was observed with modified electrode relative to bare and silica-modified electrodes. The I _P was found to be linearly co-related to NB concentration (R ² = 0.985). The interference of cationic and anionic species on sensor sensitivity was also studied. Selectivity in the present sensing system may be further improved by modifying silica with specific functional moieties.     

Evolution of the microstructure,chemical composition and magnetic behaviour during the synthesis of alkanethiol-capped gold nanoparticles

In the present paper, we show an exhaustive microstructural characterization of thiol-capped gold nanoparticles (NPs) with two different average particle sizes. These samples are compared with the polymer-like Au(I) phase formed as a precursor during the synthesis of the thiol-capped gold NPs. The set of analysed samples shows different microstructures at the nanoscale with different proportions of Au atoms bonded either to S or to Au atoms. It has been experimentally shown that the presence of a ferromagnetic-like behaviour is associated to the formation of NPs with simultaneous presence of Au–Au and Au–S bonds. In order to explain such magnetic behaviour a possible model is proposed based on the spin–orbit coupling so that localized charges and/or spins (Au–S bonds) can trap conduction electrons (Au–Au bonds) in orbits.     

金纳米粒子在云母表面组装行为的研究

在超声场作用下,以氯金酸为前驱物,经柠檬酸钠和单宁酸还原,在云母基底上组装分散均匀的金纳米粒子单层膜。利用扫描探针显微镜、扫描电子显微镜和X射线衍射等技术对制备的金胶体进行表征。结果表明：超声场分布和超声功率对金纳米粒子形貌影响较大,驻波场下制备的金粒子为纺锤形,而且随超声波功率的增大,纺锤形金粒子的平均长径比减小;而在扩散场中得到单分散的球形金纳米颗粒,XRD和SEM测试表明金的平均晶粒尺寸为25 nm。金纳米粒子在处理前后的云母表面均能组装成膜,但在处理后的云母表面覆盖度更大     

Superparamagnetic CoFe_2O_4@Au with High Specific Absorption Rate and Intrinsic Loss Power for Magnetic Fluid Hyperthermia Applications

CoFe_2O_4 nanoparticles(NPs) and surface modified with gold(Au) have been synthesized by a thermal decomposition method. The obtained NPs and formation of CoFe_2O_4@Au core–shell(CS) were confirmed by characterizing their structural and optical properties using X-ray powder diffraction(XRD) patterns, Fourier transform infrared spectroscopy,Raman spectroscopy, UV–Visible and photoluminescence studies. Morphological and compositional studies were carried out using high-resolution transmission electron microscopy and energy-dispersive X-ray spectroscopy, while the magnetic properties were determined using alternating gradient magnetometer and Mossbauer to define the magneto-structural effects of shell formation on the core NPs. Induction heating properties of CoFe_2O_4 and CoFe_2O_4@Au CS magnetic nanoparticles(MNPs) have been investigated and correlated with magneto-structural properties. Specific absorption rate and intrinsic loss power were calculated for these MNPs within the human tolerable range of frequency and amplitude,suggesting their potential in magnetic fluid hyperthermia therapy for possible cancer treatment.     

Synthesis of oligo(para-phenylenevinylene) methyl thiols for self-assembled monolayers on gold surfaces

All-trans oligo(para-phenylenevinylene) (OPV) methyl thiols of a two-ring phenylene-vinylene dimer and a three-ring trimer have been synthesized to prepare self-assembled monolayers (SMS) onto an Au(1 1 1) surface. The molecular level morphologies of the monolayers prepared on Au surfaces were probed by scanning tunneling microscopy (STM) or atomic force microscopy (AFM). The soluble dimer formed a highly ordered structure lying down on the Au surfaces. The molecules of trimer stand slantwise on the Au surfaces, but the structure of monolayers is less ordered. Another longer OPV methyl thioacetate, a slightly soluble four-ring tetramer, has also been synthesized. Although it was difficult for aggregative molecules of the longer OPV to self-assemble on Au, we could successfully insert the tetramer into tetradecane-1-thiol monolayers on Au surfaces by an exchange reaction. The mixture monolayer showed that the isolated tetramer was adsorbed almost vertically on the Au surfaces.     

Enhancement of the photocurrent generation in dye-sensitized solar cell based on electrospun TiO2 electrode by surface treatment

We investigated the dye-sensitized solar cell (DSSC) using TiO₂ electrode electrospun directly onto the substrate from a mixture of titanium propoxide and poly(vinyl acetate) in dimethyl formamide (DMF). The electrospun electrode could be penetrated efficiently by a viscous polymer gel electrolyte because of porous structure. The energy conversion efficiency obtained from the DSSC with poly(vinylidenefluoride-co-hexafluoropropylene) (PVDF-HFP) gel electrolyte was over 90% of that obtained from liquid electrolyte. In order to improve the short-circuit photocurrent, we treated the electrospun TiO₂ electrode with TiCl₄ aqueous solution. The rutile crystal was grown epitaxially on anatase TiO₂ fibers. An additional TiO₂ layer increased the volume fraction of active materials resulting in an increase of sensitizer adsorption. The incident photon-to-current conversion efficiency (IPCE) of TiCl₄-treated electrode was higher than the untreated. In particular, the contribution from TiO₂ increases after the surface treatment due to an increase in packing density. The photocurrent of the DSSC with electrospun TiO₂ electrode was enhanced more than 30% after TiCl₄ treatment.     

A Novel Approach to Prepare Gold Nanoparticles/ Polyacrylamide Composite Nanofibers

在溶液内,利用聚丙烯酰胺为还原剂制备出了聚丙烯酰胺保护下的Au纳米粒子。聚丙烯酰胺起到双重作用,它是制备金纳米粒子的还原剂;另外,它也是一种很好的金纳米粒子的稳定剂。紫外-可见光谱测试证实了溶液内金纳米粒子的存在,透射电镜观察到制得的纳米纤维内含有金纳米粒子。这种新的路线对于制备其他功能性复合纤维有很好的借鉴作用。     

Fabrication and characteristics of spindle Fe2O3@Au core/shell particles

The fabrication and characteristics of spindle Fe2O3@Au core/shell particle were investigated, and the effect of the core/shell nanoparticles as the surface enhanced Raman spectroscopy (SERS)-active substrates was studied. By using the seed-catalyzed reduction technique, anisotropic Fe2O3@Au core/shell particles with spindle morphology were successfully prepared. The Fe2O3 particles with spindle morphology were initially prepared as original cores. The Au nanoparticles of 2 nm were attached onto the Fe2O3 particles through organosilane molecules. Uniform Au shell formed onto Fe2O3 core modified by Au nanoparticles through the in-situ reduction of HAuCl4. The shell thickness was controlled through regulating the concentration of HAuCl4 solution. The results of TEM, XRD and UV-vis characterization show that the core/shell particles with the original shape of the Fe2O3 particles are obtained and these surfaces are covered by Au shell completely. The surface enhanced Raman spectrum of the probe molecules adsorbed on these core/shell substrates is strong and the intensity is enhanced with the increase of the thickness of Au shell or the aspect ratio of particles. The spindle Fe2O3@Au core/shell particles exhibit optimum (SERS) activity.     

Microstructures and ion-irradiation behaviour of friction stir welded 12Cr-ODS steel

12Cr oxide dispersion strengthened steel was successfully joined by friction stir welding (FSW), and the joints were irradiated with 3?MeV Au ions at 500°C. The morphology of grains, dislocations, sizes and distributions of nano-sized oxide particles (NPs) in different zones of the FSW joints were analysed. It was found severe plastic deformation occurred and fine equixed grains were formed in stir zone (SZ). The NPs coarsen obviously in thermal-mechanically affected zone (TMAZ) on advancing side (AS) due to the relative movements of plastic materials with high-velocity gradient. The size distributions of the NPs in base metal (BM), heat affected zone (HAZ) and RS-TMAZ are concentrated in a smaller range than those in SZ and AS-TMAZ. Finer grains and high density of dislocations result in hardness increasing obviously in SZ. Irradiation introduced higher hardening in HAZ because of its less grain boundaries and dislocation density compared with SZ and BM.     

Ag/Au-decorated Fe3O4/SiO2 composite nanospheres for catalytic applications

Noble metal particles in nanoscale (Au, Ag, Pt, etc.) have attracted intensive research interest due to their promising catalysis properties. However, the practical applications of these nanoparticle catalysts are always jeopardized by two problems. One is the difficulty in recovering the used nanoparticles and the other arises from the low catalytic efficiency due to the aggregation of the nanoparticles. In this work, Ag/Au nanoparticles were distributed onto spherical superparamagnetic carriers (SSCNs), which were fabricated through a facile oil-in-DEG emulsion route. The Ag/Au nanoparticles were attached onto the SSCNs by two steps. The Au seeds were attached onto the silica surface through electrostatic attraction first, and the Ag nanoparticles were grown on the basis of the Au seeds. The obtained Ag/Au–SSCN composite nanospheres demonstrated promising catalytic properties, which could also be recycled very easily by using a magnet.     

The combination effects of trivalent gold ions and gold nanoparticles with different antibiotics against resistant Pseudomonas aeruginosa

Despite much success in drug design and development, Pseudomonas aeruginosa is still considered as one of the most problematic bacteria due to its ability to develop mutational resistance against a variety of antibiotics. In search for new strategies to enhance antibacterial activity of antibiotics, in this work, the combination effect of gold materials including trivalent gold ions (Au³⁺) and gold nanoparticles (Au NPs) with 14 different antibiotics was investigated against the clinical isolates of P. aeruginosa, Staphylococcus aureus and Escherichia coli. Disk diffusion assay was carried out, and test strains were treated with the sub-inhibitory contents of gold nanomaterial. Results showed that Au NPs did not increase the antibacterial effect of antibiotics at tested concentration (40 μg/disc). However, the susceptibility of resistant P. aeruginosa increased in the presence of Au³⁺ and methicillin, erythromycin, vancomycin, penicillin G, clindamycin and nalidixic acid, up to 147 %. As an individual experiment, the same group of antibiotics was tested for their activity against clinical isolates of S. aureus, E. coli and a different resistant strain of P. aeruginosa in the presence of sub-inhibitory contents of Au³⁺, where Au³⁺ increased the susceptibility of test strains to methicillin, erythromycin, vancomycin, penicillin G, clindamycin and nalidixic acid. Our finding suggested that using the combination of sub-inhibitory concentrations of Au³⁺ and methicillin, erythromycin, nalidixic acid or vancomycin may be a promising new strategy for the treatment of highly resistant P. aeruginosa infections.     

Unique structural features and electrical properties of electrospun conjugated polymer poly(3-hexylthiophene) (P3HT) fibers

This study examines and compares the internal structure conjugated polymeric fibers fabricated by electrospinning with cast films. Despite rigidity of polymer chain and the inability of its molecular chains to entangle to form viscoelastic jets, regioregular poly(hexyl-3-thiophene) (P3HT) exhibited the remarkable capability to be electrospun when the solution was subjected to gelation. In order to investigate the influence of additional mechanical stretching on the fibers, P3HT was electrospun with the aid of a rotating disc collector. Structure of electrospun fibers was probed via characterization techniques such as differential scanning calorimetry (DSC), Fourier transform infrared and photoluminescence (PL) spectroscopies. The findings indicated internal structural modifications developed within P3HT fibers, as a consequence of additional mechanical stretching induced by the rotating collector. Polarized FTIR and PL spectroscopies suggested that the molecular chains were aligned along the fiber axis. Electrical conductivity of iodine doped P3HT electrospun fibers was between 3 × 10³ S/m and 6 × 10³ S/m.     

不同壳层厚度Au@SiO_2的表面增强拉曼效应

通过电偶置换反应制备了尺寸在30~35 nm的结晶性良好的Au纳米颗粒,并成功在其表面包覆了不同厚度的Si O2壳层,利用TEM、HRTEM和UV-Vis对样品的结构和形貌进行了表征,并以罗丹明6G(R6G)为探针分子,对Au@SiO_2复合粒子的表面增强拉曼散射(SERS)效应进行了研究。结果显示,相对于Au纳米颗粒,Au@SiO_2复合粒子显著提高了拉曼信号的质量和检测的灵敏度,且Si O2壳层厚度对其SRES效应影响显著,壳层厚度为2 nm的复合粒子对R6G分子的检测极限可达10~(-7)mol/L。     

树枝状硅钛杂化纳米球负载金纳米颗粒催化性能研究

树枝状纳米球独特的三维中心辐射状孔道结构使其具有出色的比表面积和孔体积。客体物质可负载于多级孔道内,形成新型的载体/递送/反应平台。本研究设计构筑了一类具有高稳定性的多功能复合材料——树枝状硅钛杂化纳米球负载金纳米颗粒催化剂。使其经过系列化学反应及改性过程,树枝状硅钛杂化纳米球依旧保持中心辐射状纹理结构,孔道内成功负载了锐钛矿二氧化钛和超细金纳米粒子。结果表明,相较于树枝状二氧化硅纳米球负载金纳米颗粒材料(对比样),设计合成的催化剂展现出更加优越的多功能催化性能。在模拟太阳光下,其光解水产氢量为210.01μmol·g^-1,约为对比样的10倍。无光条件下,其降解对硝基苯酚的表观动力学常数为2.150×10^-3 s^-1,约是对比样(0.111×10^-3 s^-1)的19倍。     

Characterization of zinc oxide nanoparticles synthesized by polymer assisted deposition method

Zinc oxide nanoparticles (ZNPs) are synthesized onto glass substrates by employing simple and low cost solution based modified polymer assisted deposition (PAD) method. Trionx100 is used as a capping agent and zinc acetate as the zinc source. TritonX100 concentration is varied from 0.02 to 0.45 M for the synthesis of pure ZnO NPs. TG-DTA analysis was employed to determine the decomposition temperature of TritonX100 and zinc acetate, which lead to the formation of ZnO. The films were further characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and high-resolution transmission electron microscope (HR-TEM), Fourier transforms infrared spectroscopy (FT-IR) and room temperature photoluminescence (PL). The results indicate that the synthesized nanoparticles (NPs) exhibits the room temperature PL with two emission peaks, one corresponding to ZnO band edge emission and the other one to point defect states created due to oxygen deficiency. The first peak undergoes blue-shift due to change in NPs size while there is no shift in the second peak. Nevertheless, with increase in TritonX100 concentration the peak intensity of defect peak decreases, indicating that the highly pure NPs have been successfully synthesized by PAD method.     

核-壳结构Ag-Au纳米颗粒合金化行为的分子动力学

利用分子动力学方法和改进分析型嵌入原子势函数模拟了核-壳结构Ag-Au纳米颗粒的合金化行为,从原子扩散、微观结构演变以及合金化程度等方面对比分析了壳层厚度对合金化行为的影响。结果表明,壳层较薄时,核-壳界面处原子扩散现象显著,内核表现出多面体形貌,表层Au、Ag原子完全混合。壳层较厚时,表面原子以扩散为主,整个颗粒表面为多面体结构,但内核保持初始球状结构。通过层错生长方式使形貌发生了改变。壳层越薄,体系合金化程度越高