Structural and electronic properties of phosphino(oligothiophene) gold(I) complexes

A series of gold(I) complexes containing phosphino(oligothiophene) ligands of varying conjugation length has been prepared. Solid state crystal structures of (PT3)AuCl (PT3 = 5-diphenylphosphino-2,2':5',2' '-terthiophene) and AuCl(PTP)AuCl (PTP = 2,5-diphenylphosphinothiophene) have been obtained. The complex AuCl(PTP)AuCl crystallizes as a dimer with two intermolecular Au-Au contacts. Variable temperature NMR spectroscopy is used to demonstrate the presence of aurophilic interactions in solution for AuI(PTP)AuI. Dual emission is observed for AuCl(PTP)AuCl in solution and is attributed to emission from both monomer and dimer. In the solid state, dimer emission is dominant. The iodo analogue, AuI(PTP)AuI, shows only low energy dimer emission in both solution and the solid state. Compounds in which the ligands contain longer bridges (either bithienyl or terthienyl) show absorption and emission bands due to the pi-pi* transition only, both in solution and the solid state.     

线型和星型平面噻吩类低聚物衍生物分子结构及光电性质研究

运用密度泛函DFT B3LYP／6-31G(d)方法对线型(a)和星型(b)平面噻吩类低聚物衍生物分别进行了几何构型优化,并采用含时密度泛函TD-DFT B3LYP／6-31G(d)方法计算了其紫外吸收光谱．计算结果表明:用TD-DFT．方法计算体系的紫外吸收光谱值与实验数据吻合;通过对噻吩类低聚物衍生物分子几何结构和前线分子轨道能级的分析,并从理论上解释了线型(a)和星型(b)衍生物光谱性质的差异:后者与前者相比较吸收光谱发生红移,这是由于星型结构使其相应HOMO能级升高,电离能(IP)降低,成为很好的电子给体和空穴传输材料．     

Construction of a network structure composed of gold nanoparticles and spin-polarized molecular wires and its conducting and magnetic properties

This is the first demonstration of the negative magneto-resistance in the networked gold nano-particles connected with spin-polarized molecular wires. It is a direct proof for the communication between tunneling electrons migrating among nano-particles through the molecular wires and localized spins residing on them.     

Formation of gold nanoparticles in microreactor composed of helical peptide assembly in water

A novel microreactor was prepared by self-assembly of an amphiphilic block copolymer composed of a hydrophobic helical peptide unit with a naphthyl group at the C terminal and a hydrophilic poly(ethylene glycol) unit. The copolymer formed a self-assembly in water, taking a vesicular structure. Noticeably, when the copolymer was dispersed in an Au(3+) aqueous solution, gold nanoparticles were formed without addition of any reducing reagent. The naphthyl groups, which are located at the inner surface of the vesicular assembly, promoted the reduction of Au(3+) ions with accompanying pH decrease.     

Electrophoretic properties of DNA-modified colloidal gold nanoparticles

Oligonucleotide-modified gold nanoparticles are used in various kinds of colorimetric DNA targeting biosensors and nanoparticle assembly techniques. Herein we focus on how the size of 13 nm gold colloids changes upon DNA modification. We have performed a series of electrophoresis experiments of particles modified both thiol specifically and nonspecifically with single- and double-stranded oligonucleotides of different lengths (12- and 25-mers). Both unmodified and DNA-modified particles migrated at constant velocity in different concentrations of Metaphor agarose gels. Linear Ferguson plots were obtained for all samples, and on the basis of the Ogston model approach, we present how the particle size increases in different amounts depending on the oligonucleotide length, secondary structure, and type of modification (specific or nonspecific). Thiol specifically modified particles obtain a thicker DNA layer since the oligonucleotides are only anchored to the particle in one end and thus stand up from the surface more compared to nonspecifically modified ones, where the oligonucleotides tend to lay more or less flat on the surface with multiple adsorption points. However the thickness of the DNA layer for the thiol specifically modified particles is smaller than the length of a corresponding stretched oligonucleotide, suggesting a flexibility of the thiol-bound strands allowing them to tilt relative to the particle surface.     

Synthesis and properties of tadpole-shaped gold nanoparticles

In this communication, gold nanoparticles with a tadpole shape were synthesized by a simple aqueous-phase chemical method. The unusual three-dimensional and crystallized structures were demonstrated by TEM, AFM, and HRTEM methods. The SEM and UV-visible absorption measurements and electrophoresis experiments revealed that the tadpoles had novel optical and electrical properties. These attractive structures and properties are expected to find uses in many fields such as electrics, optics, electrochemistry, and biological sensing.     

Bimetallic nano-structured glucose sensing electrode composed of copper atoms deposited on gold nanoparticles

We describe the preparation and sensing capabilities of a bimetallic electrode consisting of copper atoms deposited on gold nanoparticles (GNPs). The electrode was obtained by first constructing a GNP template on the surface of a glassy carbon electrode by exploiting the hydrogen-bonding interactions between pyridine groups on the surface of the GNPs and the carboxy groups of poly(acrylic acid). GNPs (60?nm in diameter) were homogeneously and densely deposited in the template (as revealed by scanning electron microscopy). The electro-deposition of copper ad-atoms on GNPs occurred at an underpotential and was proven by electrochemical techniques. The presence of GNPs in the template accelerated the deposition at low potential due to its beneficial effect on the rate of electron transfer. The new electrode was studied for its response to glucose. Highly stable and reproducible catalytic activity towards glucose oxidation is observed and attributed to the synergistic catalytic effect of the copper atoms on the surface of the GNPs. The detection limit is as low as 50?nM (at a signal-to-noise ratio of 3), and the response is between 200?nM and 10?mM of glucose.

Hybrids of silver nanoparticles with amphiphilic hyperbranched macromolecules exhibiting antimicrobial properties

Hybrids of silver particles of 1 to 2 nm in size with highly branched amphiphilically modified polyethyleneimines adhere effectively to polar substrates providing environmentally friendly antimicrobial coatings.     

Blue-to-red chromatic sensor composed of gold nanoparticles conjugated with thermoresponsive copolymer for Thiol sensing

We describe the first determination of thiol compounds with gold nanocomposites composed of gold nanoparticles and thermoresponsive copolymers having polyamino groups. The gold nanocomposites, which are used as a chromatic sensor, reveal chromatic change from blue to red with thermal stimuli, heating followed by cooling the solution. The blue-to-red chromatic change results from disassembly of the gold nanocomposites, which arises from shrinkage of the thermoresponsive copolymers bound to the gold nanoparticle surfaces due to the phase transition induced by thermal stimuli. The disassembly is inhibited by addition of thiol compounds through displacement of the adhered thermoresponsive copolymers. The detached copolymers no longer influence morphological change of the gold nanocomposites. Corresponding with increase of concentration of the thiol compounds, a solution of the gold nanocomposites after the thermal stimuli shows chromatic change, which was quantified with the a* value in L*a*b* chromatic coordinates. A linear relationship between the a* value and concentration of cysteine, examined as a bio-important thiol, is obtained below 7x10(-6) mol dm(-3), estimating a detection limit defined as 3sigma of the blank to be 2.8x10(-7) mol dm(-3). The chromatic sensor of the gold nanocomposites is applied to the determination of cysteine in commercial supplements containing ascorbic acid, which seriously interferes with redox-based determination of cysteine. Analytical results obtained with the chromatic sensor are identical to those obtained with HPLC.     

半乳糖保护的Au纳米颗粒的制备及性能研究

通过一种简易的方法,利用D-半乳糖胺和氯金酸制备出了能够用于肝癌细胞靶向识别的Au纳米颗粒探针.该纳米颗粒形貌和尺寸均一并且生物相容性良好.通过改变反应体系的pH能够对Au纳米颗粒的尺寸进行调控.此外,这种新型的纳米颗粒对RCA120还具有超高的检测灵敏度,实验结果显示其检测限度可以达到2μg·L^-1.     

Molecular engineering of photoresponsive three-dimensional DNA nanostructures

This study demonstrates the use of azobenzene-incorporated DNA as a control agent to precisely monitor three-dimensional DNA nanostructures. The shape of a DNA tetrahedron can be controlled by alternate irradiations with different wavelengths of light.     

Silver carbonate nanoparticles stabilised over alumina nanoneedles exhibiting potent antibacterial properties

A simple method of preparing Ag(2)CO(3) nanoparticles utilising high area gamma-alumina nanoneedles has been developed; these are promising antimicrobial agents against diverse bacterial strains.     

Electronic and surface properties of PbS nanoparticles exhibiting efficient multiple exciton generation

Ultrafast transient absorption measurements have been used to study multiple exciton generation in solutions of PbS nanoparticles vigorously stirred to avoid the effects of photocharging. The threshold and slope efficiency of multiple exciton generation are found to be 2.5 ± 0.2 ×E(g) and 0.34 ± 0.08, respectively. Photoemission measurements as a function of nanoparticle size and ageing show that the position of the valence band maximum is pinned by surface effects, and that a thick layer of surface oxide is rapidly formed at the nanoparticle surfaces on exposure to air.     

Breathing mode dynamics and elastic properties of gold nanoparticles

We present calculations of the bulk modulus, heat capacity, and the period of the breathing mode for spherical nanoparticles following excitation by ultrafast laser pulses. The bulk modulus and heat capacities both exhibit clear transitions upon bulk melting of the particles. Equilibrium calculations of the heat capacity show that the melting transition is sharper and occurs at a lower temperature than one would observe from an ultrafast experiment. We also observe an intriguing splitting in the low-frequency spectra of the nanoparticles and analyze this splitting in terms of Lamb's classical theory of elastic spheres. We conclude that the particles either (1) melt during the observation period following laser excitation or (2) melt an outer shell while maintaining a crystalline core. Both mechanisms for melting are commensurate with our observations.     

Quantitatively modeling the equilibrium properties of thiol-decorated gold nanoparticles

We employ a molecular mean-field theory to quantitatively understand the sizes, surfactant surface coverage, and size fluctuations of gold nanocrystals decorated with thiol surfactants of different chain lengths. Our model assumes that surfactant-coated nanoparticles are equilibrium structures. We find that packing constraints experienced by the surfactant tails are less significant for more curved (smaller) particles. This effect enables us to rationalize the experimental observations/deductions that the thiol coverage per unit area increases with decreasing particle size. The reduction of surface coverage with increasing size also explains the fact that size polydispersity increases with increasing nanoparticle size. We find that increasing the length of the surfactants results in larger nanoparticles.     

Antioxidant properties of gold nanoparticles studied by ESR spectroscopy

The Au-containing nanocomposites were synthesized by UV irradiation followed by the thermal treatment of chitosan oligomer solutions doped by HAuCl₄. The size of the formed gold nanoparticles depends on the concentration of the dopant, which is proved by UV—Vis absorption spectroscopy and small-angle X-ray scattering (SAXS). The antioxidant activity of the gold nanoparticles with respect to hydroxy radicals significantly depends on the specific surface of the particles, which was found using the secondary radical spin-trapping technique. The change in the ^·OH radical concentration was monitored by the intensity of the ESR signal of the adduct of the spin trap (α-phenyl-N-tert-butylnitrone) with the Me^·radicals formed in the reaction of ^·OH with DMSO. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 509–512, March, 2008.     

Fast protein detection using absorption properties of gold nanoparticles

In this study we describe the use of gold nanoparticles as a fast detection system for the sensitive analysis of proteins. The immunological method allows for protein analysis at the nanogram level, as required for clinical diagnosis. Initially a test protein is used for the development of the assay. The system is subsequently adopted for alpha-fetoprotein, which is a relevant tumor marker. This work demonstrates that antibody functionalized gold nanoparticles can be used for the detection of proteins by forming gold nanoparticle aggregates. The influence of the size of the gold nanoparticles on the sensitivity of the assay is investigated in the range from 20-60 nm particles; the larger particles show here the highest relative changes. The formation of antigen-gold nanoparticle aggregates is detected by an increase in hydrodynamic diameter by dynamic light scattering (DLS). UV/Vis spectroscopy also allows assay monitoring by quantifying the red shift of the plasmon resonance wavelength. Alpha-fetoprotein can be analysed in the concentration range of 0.1-0.4 μg ml(-1). The influence of pH, ionic strength and ratio of sample to Au-NP solution is studied. With this method, the protein AFP can be rapidly detected as demanded for clinical diagnosis.     

Catalytic properties of supported gold nanoparticles in organic syntheses

Gold nanoparticles exhibit unique properties due to their ability to form aggregates of atoms of diverse morphology shapes and sizes of which depend, to a considerable extent, on specific features of the nearest environment. The nature of gold nanoparticles varies in a wide range: from the particles with pronounced Lewis acidic properties to the negatively charged particles bearing a formal zero-valence charge. The most examples of new reactions catalyzed by gold nanoparticles include unsaturated compounds and strong nucleophiles (such as amines) as substrates. This short review provides a digest of the catalytic properties of gold nanoparticles. The main attention is paid to the possible role of certain forms of the metal in catalytic reactions. Of special interest are reactions in which effects of synergism of gold and other active species or second metals present in the catalyst are revealed or a size effect is established.     

Synthesis and characterization of nanoheterostructures based on oligothiophene functionalized Ru nanoparticles

Monodisperse ruthenium nanoparticles functionalized by electroactive oligothiophenes have been prepared and characterized. Using TEM, UV-visible and FTIR we established that the organization of these nanoparticles into nanospheres can be directly controlled via modulation of the pi-pi interaction between the organic components adsorbed on the surface. This finding also shows that the self-assembled nanoheterostructures may be switched from monodisperse nanoparticles to ordered nanospheres by tuning the pH.     

Preparation and electrocatalytic properties of gold nanoparticles loaded carbon nanotubes

Here, we report a new method of preparation of gold nanoparticles loaded carbon nanotubes (Au/CNTs) and the eleltrocatalystic properties of the obtained Au/CNTs as composite catalyst. This method shows advantages as it is easy to wash sodium citrate and the particle size of Au nanoparticles could by controlled by pH.