Biopolymer-assisted self-assembly of ZnO nanoarchitectures from nanorods

We have investigated three-dimensional (3-D) architectures–microspheres and radial structures–based on biopolymer-assisted self-assembly from one-dimensional ZnO nanorods. The developed method is simple, rapid and cost-effective and can be used for self-assembly of different complex superstructures. A possible model of 3-D architectures self-assembled with biopolymer assistance is presented using minimum energy considerations. Scanning electron microscopy, X-ray diffraction, energy dispersive X-ray spectroscopy, transmission electron microscopy, micro–Raman spectroscopy and cathode luminescence investigations show that the novel 3-D architectures are built from high-purity ZnO nanorods with a wurtzite structure. The resulting radial structures show an intense ultraviolet (UV) cathode luminescence emission suggesting applications as UV light emitting diodes or lasers. Their structural characteristics endow them with a broad area of applications and offer a possibility to be used as fundamental low-dimensional building units. These building units open opportunities for the self-assembly of multifunctional nanostructured systems with applications in bioscience and nanomedicine, electronics and photonics.     

Synthesis and self-assembly of magnetic nanoparticles

We report the synthesis and self-assembly of different shapes and sizes of FePt nanoparticles. Our study shows that surfactants and solvent play an important role in the synthesis of different shapes and sizes of FePt nanoparticles. Higher boiling point solvents lead to the formation of spherical nanoparticles and low boiling point solvents form cubic nanoparticles. Our studies also indicate that self-assembly of FePt nanoparticles on substrates is a complex process that is sensitive to the concentration of excess surfactant in the nanoparticle solution.     

Reshaping elastic nanotubes via self-assembly of surface-adhesive nanoparticles

Elastic sheets with macroscopic dimensions are easy to deform by bending and stretching. Yet shaping nanometric sheets by mechanical manipulation is hard. Here we show that nanoparticle self-assembly could be used to this end. We demonstrate that spherical nanoparticles adhering to the outer surface of an elastic nanotube can self-assemble into linear structures: rings or helices on stretchable nanotubes, and axial strings on nanotubes with high rigidity to stretching. These self-assembled structures are inextricably linked to a variety of deformed nanotube profiles, which can be controlled by tuning the concentration of nanoparticles, the nanoparticle-nanotube diameter ratio and the elastic properties of the nanotube. Our results open the possibility of designing nanoparticle-laden tubular nanostructures with tailored shapes, for potential applications in materials science and nanomedicine.     

Mechanism for rapid self-assembly of block copolymer nanoparticles

Amphiphilic block copolymers in solution spontaneously self-assemble when the solvent quality for one block is selectively decreased. We demonstrate that, for supersaturation ratio changes [d(S)/dt] over 10(5) per second from equilibrium, nanoparticles are obtained with a formation mechanism and size dependent on the jumping rate and magnitude. The threshold rate for homogeneous precipitation is determined by the induction time of a particle, equivalent to the diffusion limited fusion of copolymer chains to form a corona of overlapping soluble brushes. Via determination of the induction time with a novel confined impinging jets mixer and use of a scaling relation, the interfacial free energy of a block copolymer nanoparticle was measured for the first time.     

Colloid electrostatic self-assembly synthesis of SnO2/graphene nanocomposite for supercapacitors

Journal of Nanoparticle Research - Most anticancer drugs cannot kill cancer stem cells (CSCs) effectively, which lead to the failure of anticancer chemotherapy, such as relapse and metastasis. In...     

Solvent and surfactant effect on the self-assembly and luminescence properties of ZrO2:Eu3+ nanoparticles

ZrO₂:Eu³⁺ nanocrystals ranging from 17 to 43 nm were prepared by the facile precipitation method with a hydrothermal process. The crystallite size was strongly influenced by the solvent composition and enhanced with the presence of surfactant. The use of ethanol combined with surfactant stabilizes 50 wt% of the monoclinic phase, while the use of water only results in 100 wt% tetragonal phase. 80% of nanobelts were obtained preparing the sample with ethanol and surfactant as a results of the self-assembly of nanoparticles. The photoluminescence emission peak centered at 606 nm dominates the emission band for nanobelts, while for nanoparticles it is dominated by a peak centered at 612 nm. Such differences were explained in terms of the site symmetry occupying Eu³⁺ in the host that in turn depends on the crystalline phase. Changes in the intensity ratio I(612 nm)/I(606 nm) is proposed as a tool to analyzing changes in the monoclinic/tetragonal phase composition. The calculated asymmetry ratio R=⁷F₂/⁷F₁～1.2 suggest a high degree of crystallinity of the prepared samples.     

DNA模板纳米粒子自组装及其在纳米电子器件中的可能应用

以生物分子为模板进行的纳米粒子白组装之所以受到人们的广泛关注，主要是追求其在纳米电子器件的成功应用。文章结合近年来国内外研究工作和本实验室小组成员的一些相关工作，综述了DNA模板的无机纳米粒子白组装形成有序纳米结构及其在纳米电子器件上应用的研究进展，讨论了此种组装技术的局限性并展望其发展前景．     

Effect of dielectrophoretic force in the self-assembly process of electrosprayed nanoparticles

In this work the effect of the dielectrophoretic force (DEP) in the self-assembly process of nanoparticles electrosprayed onto a substrate, is examined. DEP force is originated by the electric field created by the electrospray gun and by the distortion of the field created by the effective dipole of each nanoparticle. It is also shown that the modulus of this force is large when the distance between particles is few times its diameter, provided the medium is wet and the electric field is not switched off.The directional nature of DEP In this wet phase, is shown to chain nanoparticles aligned with the main electric field direction. Although there is a repulsive force between chains in the orthogonal direction to the field, it is minimum when the beads align with the voids in the nearby chains.DEP is a dominant force in the close distances of nanoparticles compared to double layer, van der Waals, electrophoretic retardation, weight and buoyancy.     

Electrostatic self-assembly of Fe3O4 nanoparticles on carbon nanotubes

Carbon nanotubes (CNTs)-based magnetic nanocomposites can find numerous applications in nanotechnology, integrated functional system, and in medicine owing to their great potentialities. Herein, densely distributed magnetic Fe₃O₄ nanoparticles were successfully attached onto the convex surfaces of carbon nanotubes (CNTs) by an in situ polyol-medium solvothermal method via non-covalent functionalization of CNTs with cationic surfactant, cetyltrimethylammonium bromide (CTAB), and anionic polyelectrolyte, poly(sodium 4-styrenesulfonate) (PSS), through the polymer-wrapping technique, in which the negatively charged PSS-grafted CNTs can be used as primer for efficiently adsorption of positively metal ions on the basis of electrostatic attraction. X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) analysis have been used to study the formation of Fe₃O₄/CNTs. The Fe₃O₄/CNTs nanocomposites were proved to be superparamagnetic with saturation magnetization of 43.5 emu g^?1. A mechanism scheme was proposed to illustrate the formation process of the magnetic nanocomposites.     

Study of DNA coated nanoparticles as possible programmable self-assembly building blocks

Nanoparticles coated with single stranded DNA have been shown to efficiently hybridize to targets of complementary DNA. This property might be used to implement programmable (or algorithmic) self-assembly to build nanoparticle structures. However, we argue that a DNA coated nanoparticle by itself cannot be used as a programmable self-assembly building block since it does not have directed bonds. A general scheme for assembling and purifying nanoparticle eight-mers with eight geometrically well-directed bonds is presented together with some preliminary experimental work.     

Thermal conduction of one-dimensional carbon nanomaterials and nanoarchitectures

This review summarizes the current studies of the thermal transport properties of one-dimensional(1D) carbon nanomaterials and nanoarchitectures. Considering different hybridization states of carbon, emphases are laid on a variety of 1D carbon nanomaterials, such as diamond nanothreads, penta-graphene nanotubes, supernanotubes, and carbyne. Based on experimental measurements and simulation/calculation results, we discuss the dependence of the thermal conductivity of these 1D carbon nanomaterials on a wide range of factors, including the size effect, temperature influence, strain effect, and others. This review provides an overall understanding of the thermal transport properties of 1D carbon nanomaterials and nanoarchitectures, which paves the way for effective thermal management at nanoscale.     

Radiation-induced synthesis of RuO2 nanoparticles by thermal decomposition of Ru-tris-acetylacetonate

Pure-phase RuO₂ nanoparticles were obtained by thermal decomposition of unirradiated and γ-irradiated Ru-tris-acetylacetonate precursors. Several influencing factors including absorbed dose, calcination times and temperatures and addition of surfactants were thoroughly investigated. The newly synthesized RuO₂ nanoparticles were characterized by X-ray diffraction, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. The results showed that the best conditions for the preparation of mono-dispersed RuO₂ nanoparticles were achieved by calcinations of unirradiated Ru-tris-acetylacetonate for 6 h at 600°C. For γ-irradiated Ru-tris-acetylacetonate with 10² Gy total γ-ray doses, the optimal conditions for RuO₂ preparation were calcination for 2 h at 200°C. Thermal stability of RuO₂ nanoparticles was studied using thermogravimetric (TG) and differential thermal analysis (DTA) techniques, and the results were evaluated and discussed.     

Nickel nanoparticles deposited into an activated porous carbon: synthesis,microstructure and magnetic properties

Activated carbons (AC) are commonly used as efficient adsorbents to remove contaminants. The incorporation of a magnetic material into the AC could greatly enhance its manipulation through magnetic separation. However, the composite material will need to have sufficiently saturated magnetization, and as low as possible coercivity to be easily attracted by commercial permanent magnets. In this letter we report on the correlation between microstructure and magnetic behaviour of Ni nanoparticles (NPs) embedded in an amorphous activated porous carbon (Ni–AC). The Ni–AC powders have been synthesized by means of an easy and low‐cost procedure. The addition of sucrose during the preparation process provides effective protection in acid media. This Ni–AC composite has a microstructure composed of crystalline NPs with diameters in the range of 7–25 nm, and exhibits superparamagnetic behaviour at room temperature, with saturation magnetization values around 3 A m² kg^–1 under applied magnetic fields of 200 mT. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Chemical vapor synthesis of fluorine-doped SnO2 (FTO) nanoparticles

Journal of Nanoparticle Research - The synthesis and properties of nanocrystalline SnO2 particles and the effects of doping with fluorine are reported in this work. Simultaneous thermal...     

Rapid synthesis and size control of CuInS2 semi-conductor nanoparticles using microwave irradiation

The properties of CuInS₂ semi-conductor nanoparticles make them attractive materials for use in next-generation photovoltaics. We have prepared CuInS₂ nanoparticles from single source precursors via microwave irradiation. Microwave irradiation methods have allowed us to increase the efficiency of preparation of these materials by providing uniform heating and rapid reaction times. The synergistic effect of varying thiol capping ligand concentrations as well as reaction temperatures and times resulted in fine control of nanoparticle growth in the 3–5 nm size range. Investigation of the photophysical properties of the colloidal nanoparticles were performed using electronic absorption and luminescence emission spectroscopy. Qualitative nanoparticles sizes were determined from the photoluminescence (PLE) data and compared to HRTEM images.

The characteristics of lysine-mediated self-assembly of gold nanoparticles on the ITO glass

In this study, lysine was investigated as a cross-linker to induce the self-assembly of gold nanoparticles (GNPs) with the variation of solution pH, dosage amounts of lysine, and GNP size. Lysine molecules at acidic pH ranges induced the aggregation of Au colloids via α, ?-amine mediated self-assembly of GNPs, consequently leading to the generation of secondary peak at longer wavelength for aggregated GNPs. At intermediate and basic pH ranges, however, the ionization of carboxylic acid groups in lysine hindered the cross-linking between Au colloids with the consequent disappearance of secondary peak. For the array of small Au colloids (ca. 43 nm), lysine induced heavily-aggregated GNPs on the ITO glass at strongly acidic condition (pH2～3) through its molecular bridging effect. For the array of large Au colloids (ca.70 nm), lysine produced one-dimensional assembly of GNPs on the ITO glass at slightly acidic condition (at pH4.7) through zwitterions-mediated interactions.     

Ion synthesis and laser annealing of Cu nanoparticles in Al2O3

Al₂O₃ samples with Cu nanoparticles, synthesised by ion implantation at 40 keV with a dose of 1×10¹⁷ ion/cm² and a current density from 2.5 to 12.5 μA/cm², were annealed using ten pulses from a KrF excimer laser with a single pulse fluence of 0.3 J/cm². The copper depth distribution, formation and modification of metal nanoparticles under the ion implantation and laser treatment were studied by Rutherford backscattering (RBS), energy dispersive X-ray (EDX) analysis, atomic force microscopy (AFM) and optical spectroscopy. It was found that laser annealing leads to a reduction in the nanoparticle size without diffusion of metal atoms into the bulk. The change in particle size and the possibility for oxidation of the copper particles are examined in the framework of Mie theory. Calculations presented show that under excimer laser treatment, Cu nanoparticles are more likely to be reduced in size than to undergo oxidation. Received: 19 April 2001 / Accepted: 7 November 2001 / Published online: 23 January 2002     

液相法制备金属纳米粒子

液相法是在均相溶液中，利用各种途径引发化学反应，通过均相或异相成核及随后的扩散生长而制备出粒径分布窄且表面功能化的纳米尺度材料．介绍了液-液两相法、反相胶束、高温液相法等制备单分散金属纳米粒子的方法和高温液相法制备金属纳米粒子的影响因素，以及近年来在金属纳米粒子的制备和性能研究上的进展，尤其是Co等多种磁性纳米粒子的制备、磁性研究．     

Size-tuneable synthesis of nickel nanoparticles

A facile method is described for synthesising nickel nanoparticles via the thermal decomposition of an organometallic precursor in the presence of excess n-trioctylphosphine as a capping ligand. For the first time, alkylamines with different chain lengths were employed as size-limiting agents in this synthesis. A direct correlation is demonstrated between the size of the alkylamine ligands used and the mean diameter of the nickel nanoparticles obtained. The use of bulky oleylamine as a size-limiting agent over a reaction period of 30 min led to the growth of nickel nanoparticles with a mean diameter of 2.8 ± 0.9 nm. The employment of less bulky N,N-dimethylhexadecylamine groups led to the growth of nickel nanoparticles with a mean diameter of 4.4 ± 0.9 nm. By increasing the reaction time from 30 to 240 min, while employing oleylamine as the size-limiting agent, the mean diameter of the nickel nanoparticles was increased from 2.8 ± 0.9 to 5.1 ± 0.7 nm. Decreasing the amount of capping ligand present in the reaction system allowed further growth of the nickel nanoparticles to 17.8 ± 1.3 nm. The size, structure and morphology of the nanoparticles synthesised were characterised by transmission electron microscopy and powder X-ray diffraction; while magnetic measurements indicated that the particles were superparamagnetic in nature.