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This paper presents a study on the crystallization and growth mechanism of selenium nanowires induced by silver nanoparticles at ambient conditions with special reference to the effects of factors such as the shapes and size of silver nanoparticles, the induced reaction time, and the molar ratio of Ag0 to SeO 3 2− ions. The synthesis approach is conducted with no need of any stabilizers, and with no sonochemical process and/or templates. It is found that whether silver spherical particles or colloids can lead to the formation of nanowires with average diameter of 25 nm and lengths up to a few micrometers, and silver nanoplates lead to the formation of flat Se nanostructures. In particular, Au, Cu, Pt, and Pd particles cannot induce the growth of selenium nanowires in aqueous solution at room temperature. The results indicate that silver particles play a critical role in determining the growth of selenium nanowires. The lattice match between hexagonal-Se and orthorhombic- or trigonal-Ag2Se particles is the major driving force in the growth of such nanostructures. The findings would be useful for design and construction of heterogeneous nanostructures with similar lattice parameter(s).

The detailed structure of a dispersed nanoparticle suspension has been studied by transmission electron microscopy and dynamic light scattering for comparison with an off-lattice gas computer model. For low adhesion between particles, the structure of the suspension is shown to be a “gas with clusters” phase of particles comprising aggregates ranging from singlets, doublets, triplets, etc. to 16-plets in a continuous distribution. Further increasing the adhesion between the particles reduces the number of singlets and causes larger aggregates to form, without precipitation, as some condensed phase appears in the gas. This phase appears as metastable clumps, which do not grow rapidly until adhesion is raised. Then, at high adhesion, flocculation occurs with aggregates growing with time and a large reduction in the number of singlets. Experiments on monosize 62-nm-diameter hematite particles in water confirm this behaviour. An off-lattice computational model based on a square well adhesion potential qualita...

A new synthesis method, induced by silver nanoparticles, has been developed for generating trigonal-selenium (t-Se) nanowires in aqueous solution at room temperature (RT). By this method, single-crystalline t-Se nanowires capped tips were successfully synthesized with uniform diameter of ∼23 nm and length over hundreds of nanometers. This method exhibits some advantages in fabricating t-Se nanostructures, including no need to use stabilizers and sonichemical process, avoidance of toxic reducing agents (e.g. NaBH4 ,N 2H4), and all operations being proceeded in aqueous media and at RT; particularly it can successfully achieve the transformation from amorphous α-Se to crystalline t-Se in aqueous solution. The as-synthesized nanowires display highly crystalline quality and high aspect ratios. They would be potentially applied in photoconductors, anisotropic thermo-conductors, and nonlinear optical responses. This method would be useful for generating one-dimensional nanostructures with similar lattice parameter(s). © 2006 Elsevier B.V. All rights reserved.

The structural and optical stability of nanoparticles directly influences their applications. The shape evolution of silver nanoplates synthesized in the presence of bis(2-ethylhexyl) sulfosuccinate (AOT) could be effectively frozen using thiols in aqueous solution. These thiols (e.g., 1-hexanethiol, 1-octanethiol, 1-dodecanethiol, and 1-hexadecanethiol) exhibit stronger surface affinity on the silver crystalline surfaces. This is evidenced from both the unchanged shape/size of nanoplates and their unshifted plasmon resonances in optical absorption. To quantitatively explain the thiol-frozen shape evolution mechanism of silver nanoplates at molecular scale, molecular dynamics simulation was performed. The results show that these thiols exhibit larger interaction energies than AOT molecules on the silver atomic surfaces and hence freeze the shape evolution of silver nanoparticles. This thiol-frozen strategy would not only be useful for stabilizing nanoparticles but would also allow the introduction of a wide range of surface chemical functionalities to the nanoparticles for potential applications in nanosensors.

Gold nanorods and their core-shell nanocomposites have been widely studied because of their well-defined anisotropy and unique optical properties and applications. This study demonstrates a facile hydrothermal synthesis strategy for generating carbon coating on gold nanorods (AuNRs@C) under mild conditions (

The TEM image of V 2 O 5 as a reactant is displayed in Fig. S1. The effects of SDS/V molar ratio on the morphology of the as-prepared nanobelts is shown in Fig. S2. Fig. S3 shows the stability of Ag0.35V2O5 nanostructure by calcining the material at 400 °C for 10 hours in air. Fig. S4 shows the response/revovery time for this material. The details can be seen in Supporting Information.

This work reports a newly developed synthesis method, i.e., a self-seeding coreduction method, for shape control of silver nanoparticles such as triangular nanoplates and circular nanodiscs. By this method, high surface-to-volume silver nanoplates (~2.3 nm in thickness) were successfully generated. The distinct advantages of this method include no need to add external seeds, no need to use organic solvents that are environmentally unfriendly, being able to perform at room temperature, and synergetic use of a few reducing agents for better growth control of two-dimensional nanostructures. In particular, molecular dynamics simulation is used to quantify the interaction energies between surfactant molecules and different facets of silver crystal. Such molecular information, together with measurements using x-ray diffraction (XRD), transmission electron microscopy (TEM), atomic force microscopy (AFM) and ultraviolet–visible (UV–vis) spectroscopy, has proven to be useful in understanding the growth mechanisms of silver nanoplates.

In the present work, nanowires of trigonal selenium ( t -Se) were reacted with Ru(acac) 3 and Pd(acac) 2 (or PdCl 2 ) to generate RuSe 2 and Pd 17 Se 15 on the surface of each t -Se nanowire as a uniform, conformal sheath. The unreacted cores of selenium could be evaporated by heating the as-synthesized Se@RuSe 2 and Se@Pd 17 Se 15 nanocables to yield selenide nanotubes with their typical wall-thickness around 6 nm. This template-engaged approach allowed for the production of both nanocables and nanotubes in a relatively large scale, and is believed to be able to get extended to synthesize other chalcogenides as tubular nanostructures.

A solution-phase, precursor method has been demonstrated for the large-scale synthesis of single crystalline nanowires of lead with uniform diameters in the range 50−90 nm and lengths up to several...

This paper describes a vapor-phase approach to the facial synthesis of cupric oxide (CuO) nanowires supported on the surfaces of various copper substrates that include grids, foils, and wires. A typical procedure simply involved the thermal oxidation of these substrates in air and within the temperature range from 400 to 700 °C. Electron microscopic studies indicated that these nanowires had a controllable diameter in the range of 30−100 nm with lengths of up to 15 μm by varying the temperature and growth time. Electron diffraction and high-resolution TEM studies implied that each CuO nanowire was a bicrystal divided by a (111) twin plane in its middle along the longitudinal axis. A possible mechanism was also proposed to account for the growth of these CuO nanowires.

Submicrometer hollow CuS, CdS, and NiS spheres with diameters between 400 and 1300 nm were successfully prepared through an interface-mineralizing reaction in a NH3·H2O–CS2 solution at low temperature. Several techniques were applied to characterize the interesting self-assembled structures. The compositions of the prepared CuS, CdS, and NiS materials were confirmed by X-ray powder diffraction (XRD), the surface atomic ratios and the valence state of ions were examined by X-ray photoelectron energy spectroscopy (XPS), and the morphologies of products by transmission electron microscope (TEM). The optical properties, including absorption and emission, were recorded by UV–vis absorption and fluorescence spectroscopy, respectively. In this approach, ethylenediamine (en) was substituted by aqueous ammonia (NH3·H2O) to avoid violent reactions with carbon disulfide (CS2). The main advantage to this approach is that both ammonia and CS2 played multi-functional roles in the assembly of hollow-sphere structures. The reaction sources themselves (CS2) served as the reaction template and required no other templates to support it. The proposed interface-mineralizing mechanism is discussed, and the hollow-sphere structures obtained are envisioned to have applications in area of materials science.Key words: hollow-sphere structure, NH3·H2O–CS2, metal sulfides

Vanadium oxides are known for their multioxidation states and diverse crystalline structures. Owing to their excellent interactions with molecules or ions, outstanding catalytic activities, and/or strong electron–electron correlations, nanostructured vanadium oxides have been extensively studied for energy conversion in the recent years. Here is a review of the recent advances in the development of nanostructured vanadium oxides and their applications. The synthesis strategies and structural properties of various vanadium oxide nanostructures, including vanadium dioxide (VO2), vanadium pentoxide (V2O5), and others, are summarized. The applications of vanadium oxides in energy conversion are discussed, focusing on three important types of energy sources: chemical energy (LIBs, pseudocapacitors and fuel cells), solar energy (photovoltaics and photocatalytic hydrogen evolutions), and heat (thermoelectric generation). Finally, conclusion with our remarks on the prospects of nanostructured vanadium oxides in energy conversion are provided.

The sensitivity of a metal oxide gas sensor is strongly dependent on the nature of the crystal surface exposed to the gas species. In this study, two types of zinc oxide (ZnO) nanostructures: nanoplates and nanorods with exposed (0001) and (10̄10) crystal surfaces, respectively, were synthesized through facile solvothermal methods. The gas-sensing results show that sensitivity of the ZnO nanoplates toward ethanol is two times higher than that of the ZnO nanorods, at an optimum operating temperature of 300 °C. This could be attributed to the higher surface area and the exposed (0001) crystal surfaces. DFT (Density Functional Theory) simulations were carried out to study the adsorption of ethanol on the ZnO crystal planes such as (0001), (10̄10), and (11̄20) with adsorbed O(-) ions. The results reveal that the exposed (0001) planes of the ZnO nanoplates promote better ethanol adsorption by interacting with the surface oxygen p (O2p) orbitals and stretching the O-H bond to lower the adsorption energy, leading to the sensitivity enhancement of the nanoplates. These findings will be useful for the fabrication of metal oxide nanostructures with specifically exposed crystal surfaces for improved gas-sensing and/or catalytic performance.

Nanocrystallites of nonstoichiometric copper selenide (Cu(2-x)Se) and stoichiometric copper selenides (beta-CuSe and Cu(3)Se(2)) were synthesized in different solutions via sonochemical irradiation at room temperature. The influence of solvents, surfactants, and ultrasonic irradiation on the morphology and phase of products has been investigated. The morphological difference of the products was mainly affected by the solvents and surfactants, which can self-aggregate into lamellar structures or microemulsions, and then these unique structures can act as both supramolecular template and microreactor to direct the growth of copper selenides. On the other hand, it was also found that the sonochemical irradiation and solvents played an important role in the formation of different phases of copper selenides. The proposed formation mechanism of copper selenides is discussed.

By using a novel method denoted the “Scission–template–transportation” route, CdIn2S4 nanorods with stoichiometric composition and high quality can be prepared in an ethylenediamine–ethanol mixed solvent at a relatively low temperature. Transmission electron microscopy images showed that the product from the 1∶1 mixed solvent was rod-like with an average size of 25 × 700 nm. Ethylenediamine serves as the nucleophile for the formation of the inorganic [Cd2S2] core by scission of the thione groups of cadmium bis(diethyldithiocarbanate) [Cd(DDTC)2]2 while ethanol acts as the transportation reagent for InCl3 in the process. These factors are both conducive to the growth of CdIn2S4 nanorods. The reaction proceeds through one-dimensional [CdS]n clusters, which act as intermediate templates for the subsequent growth of CdIn2S4 nanorods. Through adjusting the ethylenediamine∶ethanol ratio, the size of the CdIn2S4 nanorods can be easily controlled. The products were also investigated by X-ray powder diffraction, X-ray photoelectron spectroscopy and ICP elemental analysis.

Low-dimensional iron chalcogenide Fe7S8 and FeSe2 microcrystals and FeTe2 bulk single crystals were synthesized via the reactions of FeCl3 with S or Se or Te powders in hydrazine hydrate solution (85%, v/v) at 140 °C for 36 h. The products were characterized by means of X-ray powder diffraction, rocking curve, transmission electron microscopy, electron diffraction, and scanning electron microscopy techniques. In the reaction process, hydrazine hydrate can coreduce Fe3+ and elemental chalcogen to Fe2+ and chalcogen anions, respectively, the combination of which can lead to the reaction proceeding completely. The morphologies of the products are affected by the temperature, pressure, and pH values. Moreover, a suitable speed of decreasing the temperature and proper supersaturation are two important factors in the formation of single-crystal FeTe2. Mossbauer spectra show the magnetism of Fe7S8 and nonmagnetic properties for FeSe2 and FeTe2 at room temperature.

In this paper, we report a safe method for the preparation of transition metal arsenides. At room temperature, well-crystallized and monodispersed arsenides particles were successfully obtained under high-intensity ultrasonic irradiation for 4 h from the reaction of transition metal chlorides, arsenic (which is the least toxic arsenic feedstock) and zinc in ethanol. Characterization by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), electron diffraction (ED), and X-ray photoelectron spectroscopy (XPS) shows that the product powders consist of nanosize particles. The ultrasonic irradiation and the solvent are both important in the formation of the product.

CS2-stabilized silver nanoparticles of ∼6 nm in diameter are prepared in aqueous solution via chemical reduction of Ag+ ions by KBH4 in the presence of CS2. The product is proven to be Ag by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and electron diffraction (ED) patterns. In the UV−visible spectra, an intense surface plasmon is built up at 350−500 nm, and it is centered at 395 nm after the reduction of Ag+ ions. This can be assigned to a reaction product of Ag with CS2 because of the strong affinity of S on the surface of Ag particles. The silver nanoparticles in the presence of CS2 remain stable for months at room temperature. It is also found that the absorption band in the range 300−350 nm increases, is centered at 325 nm, and depends on the concentration of CS2, which maybe a derivative (CS or CnSm of CS2). Again the catalytic reduction of a dye, 2,7-dichlorofluorescein (DCF), in the presence of CS2-stabilized silver particles is investigated.

Semiconductor ZnS nanowires were synthesized by a direct templating route in an inverted hexagonal liquid crystal formed by oligo(ethylene oxide)oleyl ether amphiphiles, n-hexane, n-hexanol/i-propa...

The phase-pure III-V binary antimonide (InSb) was first prepared through a novel solution route at a temperature of 200°C: [Formula: see text] Mean crystallite dimensions of 40 nm were determined from X-ray powder diffraction. Transmission electron microscopy images showed that the spherical grains with a diameter of 40-60 nm and the rodlike grains with a size of 120 × 1500 nm coexisted in the same product. The reaction proceeds with indium as the intermediate and a solution-liquid-solid mechanism is proposed for the one-dimensional growth.Key words: indium antimonide, nanorod, phase-pure, solvothermal, solution-liquid-solid mechanism.

Nanocrystalline Ag2E (E = S, Se, or Te) was interface self-assembled in-situ in the heterogeneous microphase via the reaction of aqueous AgNO3 and RE (R = PPh3, PBu3, PCy3 or Py; E = S, Se, or Te) toluene solution at room temperature. Chalcogen directional transfer agents RE were prepared by refluxing in toluene solution for 12 h. The compositions of as-prepared products were characterized by X-ray powder diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The atomic ratios of Ag to S, Se or Te, measured by inductively coupled plasma (ICP) spectroscopy, were 1.98∶1, 2.08∶1 and 2.13∶1, respectively. The morphologies of products were confirmed by transmission electron microscopy (TEM). UV-Visible spectroscopy was used to record the absorption of Ag2E nanocrystallites after removal of the passivated molecules at high temperature (>500 °C). The thermal stability of Ag2E particles passivated by RE (R = PPh3, PBu3, PCy3 or Py) molecules was studied using thermal gravimetric analysis (TGA). The possible mechanism of nanocrystalline silver chalcogenide self-assembly is discussed.

A very mild synthesis of nanocrystalline γ-NiSb via a novel solvothermal coordination-reduction process is reported here. The reaction of the mixture of NiCl2, antimony, and KBH4 was carried out in ethylenediamine (en) at 140°C for 24 h. X-ray powder diffraction and transmission electron microscope images show that the products are hexagonal γ-NiSb phase and well crystallized with an average size of about 15 nm. The reaction proceeds through a metallic nickel intermediate. The morphology of the products was influenced markedly by the solvents, and a dendritic crystal of NiSb was obtained in diethylamine. The products were also investigated by UV/vis absorption, photoluminescence, X-ray photoelectron spectra, and Fourier-transform IR.

Nanocrystallites of non-stoichiometric copper sulfides were synthesized via the reaction between [Cu(NH3)4]2+ and thiourea in sealed autoclaves at the low temperature of 60°C for 3 h. Thiourea played a key role in the process of Cu9S8 nanocrystal formation. Through adjusting the redox atmosphere, Cu7S4 and CuS were obtained from the freshly formed Cu9S8 nanocrystals. The products were characterized by means of X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), FT-IR spectroscopy and transmission electron microscopy (TEM) techniques. The Cu ∶ S atomic ratios for Cu9S8 and Cu7S4 were 9 ∶ 8.08 and 7 ∶ 4.05, respectively, analyzed by inductively coupled plasma (ICP) spectroscopy. The possible mechanism of phase transformation among copper sulfides (Cu9S8, CuS, and Cu7S4) was discussed. The optical properties of the products were also recorded by means of UV–vis absorption, and photoluminescence spectroscopy.

The microstructural characteristics of primary amine N1923/n-heptane/alcohol/water reverse micelles have been investigated by means of the dilution method and FT-IR spectroscopic and TEM techniques...

Gold nanospheres (GNSs), biocompatible nanoparticles that can be designed to absorb visible and near-infrared light, have shown great potential in induced thermal treatment of cancer cells via Plasmonic Photothermal Therapy (PPTT) [3]. In this study, light induced heating of a water-based dispersion of 20 nm diameter GNSs was investigated at their plasmon resonance wavelength (λ = 520 nm). Temperature changes of the solution at the point of light irradiation were measured experimentally. A heat transfer model was used to verify the experimental data. The effect of two key parameters, light intensity and particle concentration, on the solution’s temperature was investigated. The experimental results showed a significant temperature rise of the GNS solution compared to de-ionized water. The temperature rise of GNS solution was linearly proportional to the concentration of GNS (from 0.25–1.0 C, C = 1×1013 particles per ml) and the light intensity (from 0.25 to 0.5 W cm−2). The experimental data matches the modeling results adequately. Overall, it can be concluded that the hyperthermic ablation of cancer cells via GNS can be achieved by controlled by the light intensity and GNS concentration. A novel component of this study is that a high power lamp source was used instead of a high power laser. This means that only low cost components were used in the current experimental set-up. Moreover, by using suitable filters and white light from the high power lamp source, it is possible to obtain light in many wavelength bands for the study of other nanoparticles with different plasmon wavelength ranges. The current results represtent just one example in this versatile experimental set-up developed. It should be noted, however, the plasmon resonance wavelength used in this study is not within the therapeutic window (750–1300 nm) [13]. Therefore, the GNSs used in this experiment are only applicable to the surface induced thermal treatment of cancer cells, for instance, in the skin.Copyright © 2013 by ASME

In this experimental study, a filtered white light is used to induce heating in water-based dispersions of 20 nm diameter gold nanospheres (GNSs)—enabling a low-cost form of plasmonic photothermal heating. The resulting temperature fields were measured using an infrared (IR) camera. The effect of incident radiative flux (ranging from 0.38 to 0.77 W·cm−2) and particle concentration (ranging from 0.25–1.0 × 1013 particles per mL) on the solution's temperature were investigated. The experimental results indicate that surface heat treatments via GNSs can be achieved through complementary tuning of GNS solutions and filtered light.

Nanoparticles have garnered significant interest because of their ability to enhance greatly the optical properties of the base fluid in which they are suspended. The optical properties of nanoparticles are sensitive to the materials used, as well as to the host medium. Most fluids exhibit refractive indices that are highly temperature-dependent, resulting in nanoparticle suspensions which also exhibit temperature-dependent optical properties. Previous work has shown that temperature increases result in decreased absorption in nanoparticle suspensions. Here, we expand previous work to include core–shell particles due to the potential spectral shifts in optical properties that will arise from the base fluid with temperature changes and the role of agglomeration under temperature cycling through both experimental and numerical efforts. Thermal cycling tests for silica and gold, the constituents of the core–shell nanoparticles used in this study, were tested to determine the extent of particle agglomeration resulting from up to 200 accelerated heating cycles. Optical properties were recorded after heating two base fluids (water and ethylene glycol) with multiple surfactants for silver nanospheres and silica–gold core–shell nanoparticles. It was found that the temperature results in a small increase in the transmittance for both particle types and a blue shift in the spectral transmittance for core–shell nanoparticles. Further, the coupling effect of temperature and agglomeration played a significant role in determining both the spectral properties—particularly the resulting transmittance—of the silver nanoparticle suspensions.

Nanofluids have been increasingly used in a wide range of thermal applications. Although these applications can benefit greatly from investigating the behavior of nanoparticles under different heating scenarios, there is a lack of experiments that can achieve this. To overcome this challenge, an optical “pump–probe”-type experiment is suggested in this paper. In experiments of this type, a set of “pumping” nanoparticles are specifically selected to absorb laser radiation. These particles represent a flexible tool for volumetric heating. A second set of “probing” nanoparticles can be tailored to scatter a separate optical probing signal. This work presents a selection procedure for nanoparticles of both types. The selection procedure is then demonstrated for a specific example where the pump and probe wavelengths are of 980 and 532 nm, respectively. Gold nanorods with diameters of 10 and a length of 58 nm are selected as the “most suitable” absorbing particles, while silver nanospheres with a diameter of 110 nm are selected as the “most suitable” scattering particles. These particles are synthesized and shown to experimentally match the desired optical properties. Overall, this paper proposes and demonstrates an approach by which it is possible to design and fabricate particles for a wide range of optical studies in semi-transparent nanofluids.

A new synthetic approach has been developed to prepare silver@titanium dioxide (Ag@TiO2) core-shell nanostructures with controllable size, shape, crystal phase and function at ambient conditions (e.g. in water, ≤100 ° C). This approach shows a few unique features, including short reaction time (a few minutes) for forming core-shell nanostructures, no requirement of high temperature calcinations for generating TiO2 (e.g. at ~100 ° C in our case), tunable TiO2 shell thickness, high yield and good reproducibility. The experimental results show that the Ag@TiO2 core-shell nanostructures exhibit excellent photocatalytic activity compared to the commercial TiO2 (P25) and Ag-doped TiO2 nanocomposite in the degradation of organic dye molecules (e.g. methyl orange) with ultraviolet (UV) irradiation. This could be attributed to the large surface area of TiO2 nanoparticles for maximum harvesting of UV light, mixed anatase and rutile crystalline phases in the TiO2 shell and the effective charge separation between Ag and TiO2 that can reduce the possible recombination of electron-hole (e(-)-h(+)) pairs within TiO2 generated under UV radiation. To further understand the charge separation situation within Ag-TiO2 composites, theoretical simulation (e.g. density functional theory, DFT) was employed in this study. The DFT simulation results indicate that for the Ag@TiO2 core-shell nanostructures, photo-generated electrons transfer readily from the external TiO2 layer to the internal Ag layer with heavy accumulation compared to those doping Ag on TiO2 surfaces, which may reduce the recombination of e(-)-h(+) pairs and thus enhance the photocatalytic efficiency. The findings may open a new strategy to synthesize TiO2-based photocatalysts with highly enhanced efficiency for environmental remediation applications.

This study reports a facile hydrothermal approach for the synthesis of shape-controlled FeVO4·1.1H2O nanorods and the subsequent conversion into FeVO4 nanorods upon calcination at 500 °C for 2 h. The lengths of the synthesized FeVO4 nanorods vary from 0.7–3.5 μm, with the widths ranging from 70–270 nm. The proposed synthesis strategy does not involve the use of surfactants and requires only a very short reaction time, which is highly beneficial for the scale-up preparation. The anions of the Fe precursor are found to directly influence the shape and composition of the resultant hydrated FeVO4 products, due to the differences in their ionic strength and their abilities to intercalate into the layered structure of FeVO4·1.1H2O. The Cl− ions are particularly useful in limiting the growth of the nanorods in the lateral direction without being strongly intercalated into the layered structure. The porous FeVO4 nanorods exhibit higher selectivity and sensitivity toward n-butanol compared to FeVO4 nanoparticles, due to the high surface area and porosity. The findings demonstrate for the first time the potential of nanosized FeVO4 as a sensor material for the detection of volatile gases.

This study reports a simple but effective glycothermal method for synthesis of urchin-like vanadium pentoxide (V2O5) nanostructures for gas sensing. By this method, the V2O5 nanostructure was prepared by two steps, involving preparation of precursor, followed by calcinations. The as-prepared precursor particles were rods (200 nm×1 μm) and could assemble into microspheres or urchin-like structures with a diameter of ~3 μm. The V2O5 nanoparticles were tested for sensing isopropanol. The microurchin structures show higher gas sensing performance than the nanorods.

Silver-gold (Ag-Au) bimetallic nanowires were controllably synthesized by a newly developed wet-chemical method at room temperature. The Ag nanowires and Au nanoparticles were sequentially formed by reduction with vanadium oxide (V2O3) nanoparticles so as to form Ag-Au bimetal, in which the Ag nanowires show a diameter of ~20 nm and length up to 10 μm. A few unique features were noted in our new approach: it was rapid (within a few minutes), controllable in shape and size, reproducible, and there was no need for any surface modifiers. The formation and growth mechanisms of these Ag-Au bimetallic nanostructures driven by lattice match and a unique reducing agent (V2O3) have been proposed in this study. Moreover, the application of such bimetallic nanoparticles for catalytic reduction of 4-nitrophenol to 4-aminophenol was performed, and they exhibit catalytic properties superior to those of the Ag nanowires, Au nanoparticles, and Ag-Pd bimetallic nanostructures prepared under the reported conditions. These Ag-Au bimetallic nanoparticles have potential to be highly efficient catalysts for the reduction of 4-nitrophenol. This study may lead to new path for the generation of other bimetallic nanostructures with excellent catalytic efficiency.

Sensitive and selective detection strategies for toxic heavy metal ions, which are rapid, cheap and applicable to environmental and biological fields, are of significant importance. As a result of specific interaction between thiol(s) used as ligands and heavy metal ions, the photoluminescence intensity of quantum dots (QDs) in PBS buffer solution was quenched and the aggregation of QDs was formed at the same time. Herein, we present water-soluble, low toxic QDs, ZnSe/ZnS, which were applied for ultrasensitive Hg(2+) ion detection with a low detection limit (2.5 nM). In addition, a model has been proposed to explain the aggregation of QDs in the presence of heavy metal ions such as Hg(2+) ions.

This study demonstrates a facile but effective glycothermal method to synthesize vanadium oxide nanostructures for gas sensing detection. In this method, sodium orthovanadate was first dispersed and heated in ethylene glycol at 120-180 °C for a few hours, and then the precipitates were collected, rinsed, and sintered at high temperatures (e.g., 600°C) for V 2O 5 in air and V 2O 3 in nitrogen, respectively. The as-prepared vanadium oxide particles are nanorods (200 nm × 1 μm) and can assemble into microspheres or urchin-like structures with a diameter of ~3 μm. The experimental parameters (temperature, time, and surfactants) and the formation mechanisms were investigated by various advanced techniques, such as transmission electron microscope, scanning electron microscope, X-ray diffraction, Fourier transform infrared spectroscopy, and thermo-gravimetric analysis. Finally, the V 2O 5 nanoparticles were tested for sensing detection of gas species of acetone, isopropanol, and ammonia. The microurchin structures show higher sensing performance than the nanorods. Graphical Abstract: [Figure not available: see fulltext.] © 2012 Springer Science+Business Media B.V.

This study demonstrates a facile and effective method to generate mono-dispersed titanium dioxide spheres at ambient conditions. The size of the colloids can be controlled from 60 to 500 nm by optimizing experimental parameters (e.g., concentration, time, and temperature). Anatase TiO 2 can be obtained through titanium glycolate colloids generated in acetone via two ways: water boiling approach and calcination at a high temperature of 500 °C. Particle characteristics (shape, size, and size distribution) were measured by advanced techniques, including transmission electron microscope (TEM), thermo-gravimetric analysis (TGA), UV/Vis absorption spectrum, nitrogen gas adsorption and desorption isotherms Brunauer–Emmett–Teller (BET) surface area measurement, and X-ray diffraction technique (XRD). The possible mechanism of nucleation and growth of such colloids was discussed. The role of acetone in the formation and growth of titanium glycolate colloids was also investigated by Fourier transform infrared (FT-IR) spectroscopy. Finally, the photocatalysis performance of such anatase TiO 2 particles was tested and proved to be efficient in degradation of organic dyes (e.g., phenolphthalein and methly orange).

Iron oxide has many phases, including 16 pure phases (e.g., FeO, Fe3O4), 5 polymorphs of FeOOH (e.g., -FeOOH, -FeOOH) and 4 kinds of Fe2O3 (e.g., -Fe2O3, -Fe2O3). Because of their unique properties (optical, electronic, magnetic), they have found many applications in the areas of catalysts, magnetic recording, sorbents, pigments, flocculants, coatings, gas sensors, lubrications, and biomedical applications (e.g., magnetic resonance imaging, drug delivery and therapy).

The Avrami's kinetics was known to be the best theory to describe Bi-2223 crystals growth. Whereas, it cannot explain the fact that maximum product volume appearing at optimum sintering time during synthesis Bi-2223 crystal. Meanwhile, the Avrami's equation can also be used to determine the activation energy of Bi-2223 crystal growth; unfortunately, the determined activation energy, E, had dispersion as much as hard to be accepted by researchers themselves. To solve those problems, we studied and developed Avrami's kinetics and obtained a developed Avrami's kinetics equation in this research. With the developed Avrami equation, the index of growth, n, and E of Bi-2223 crystals were determined, including the periods of Bi-2223 crystals growing and decomposing. The n and E for Bi-2223 crystals were changing during synthesis period, values of which can be positive, zero or negative for different reaction periods. And the negative E and n were no reports to be found before, which caused by the decomposition of the product. The developed kinetics can describe a phase transformation system that with metastable or stable product. The developed kinetics theory, as a universal theoretical tool, is expected to be widely applied in the science and engineering multidisciplines and their related interdisciplines.

This study demonstrates a facile but efficient approach to deposit metallic (gold) nanoparticles on β-FeOOH nanorods to obtain Au/β-FeOOH nanocomposites without the assistance of any polymers or surfactants at ambient conditions. In this method, a strong reducing agent (NaBH4) can be used to extensively produce Au nanoparticles, converting β-FeOOH into Fe3O4 and depositing gold particles onto magnetic Fe3O4 simultaneously. The microstructure, composition, and chemical properties of the obtained nanocomposites are characterized by various advanced techniques, including transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and UV–vis spectroscopy. Moreover, the Au/β-FeOOH nanocomposite can be used to detect trace melamine using UV spectrum in the ultraviolet wavelength range (190–260 nm), in which the nanocomposites show a higher sensitivity toward melamine due to the promotion of symmetry-forbidden bands (n → π*) of melamine molecules and also avoid the disturbance of commercial products containing solid colloids or food colorings that distort visual spectrum during the detection of chemical sensing. The deposition mechanisms and their sensing detection toward melamine are discussed.

This work presents a review of the recent advances on the low-dimensional (LD) silver nanostructures (e.g., one-dimensional nanorods and nanowires, and two-dimensional nanoplates and nanodisks). First, the methods, either physical or chemical, for the synthesis of silver LD nanostructures are introduced. Then, the use is discussed of advanced experimental techniques (e.g., transmission electron microscope, high-resolution transmission electron microscope, scanning electron microscope, atomic force microscope, ultraviolet-visible and Raman spectra) and theoretical techniques at different time and length scales from quantum mechanics (e.g., ab initio simulation and density function theory) to molecular dynamics method for understanding the principles of governing particle growth, as well as discrete dipolar approximate method for understanding the optical properties of different shapes and sizes of silver LD nanostructures. Subsequently, the functional applications of the LD silver nanostructures in different areas such optical, electronic, and sensing, particularly for those related to surface plasma resonance are summarized based on the recent findings. Finally, some perspectives and comments for future investigation of silver nanostructures are also briefly discussed.

This study presents the role of reaction temperature in the formation and growth of silver nanoparticles through a synergetic reduction approach using two or three reducing agents simultaneously. By this approach, the shape-/size-controlled silver nanoparticles (plates and spheres) can be generated under mild conditions. It was found that the reaction temperature could play a key role in particle growth and shape/size control, especially for silver nanoplates. These nanoplates could exhibit an intensive surface plasmon resonance in the wavelength range of 700–1,400 nm in the UV–vis spectrum depending upon their shapes and sizes, which make them useful for optical applications, such as optical probes, ionic sensing, and biochemical sensors. A detailed analysis conducted in this study clearly shows that the reaction temperature can greatly influence reaction rate, and hence the particle characteristics. The findings would be useful for optimization of experimental parameters for shape-controlled synthesis of other metallic nanoparticles (e.g., Au, Cu, Pt, and Pd) with desirable functional properties.

Nanocrystalline FeAs, CoAs and NiAs were prepared by keeping the mixture of FeCl3, CoCl2 or NiCl2 with arsenic and KBH4 in ethylenediamine (en) at 100 °C for 4 h, respectively. X-Ray powder diffraction (XRD) patterns and transmission electron microscope (TEM) images show that the products are orthorhombic FeAs, CoAs and hexagonal NiAs, respectively, and all are well crystalline in nanometers.

Nanocrystallites of nonstoichiometric copper selenide (Cu(2-x)Se) and stoichiometric copper selenides (beta-CuSe and Cu(3)Se(2)) were synthesized in different solutions via sonochemical irradiation at room temperature. The influence of solvents, surfactants, and ultrasonic irradiation on the morphology and phase of products has been investigated. The morphological difference of the products was mainly affected by the solvents and surfactants, which can self-aggregate into lamellar structures or microemulsions, and then these unique structures can act as both supramolecular template and microreactor to direct the growth of copper selenides. On the other hand, it was also found that the sonochemical irradiation and solvents played an important role in the formation of different phases of copper selenides. The proposed formation mechanism of copper selenides is discussed.

A novel solvent-relief-self-seeding (SRSS) process was applied to grow bulk polygonal tubular single crystals of Sb2E3 (E = S, Se), using SbCl3 and chalcogen elements E (E = S, Se) as the raw materials at 180 °C for 7 days in ethanol solution. The products were characterized by various techniques, including X-ray powder diffraction (XRD), scanning electronic microscope (SEM), transmission electronic microscope (TEM), electronic diffraction (ED), and X-ray photoelectron spectra (XPS). The calculated electrical resistivities of the tubular single crystals in the range 20−320 K were of the order of 105−106 Ω cm for Sb2S3 and 103−104 Ω cm for Sb2Se3, respectively. The studies of the optical properties revealed that the materials formed had a band gap of 1.72 eV for Sb2S3 and 1.82 eV for Sb2Se3, respectively. The optimal reaction conditions for the growth of bulk tubular single crystals were that the temperature was not lower than 180 °C and the reaction time was not shorter than 7 days. The possible growth me...