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Hierarchical three-dimensional nanosheet-assembled vanadium pentoxide (V2O5) microflowers are successfully synthesized by a hydrothermal method, followed by a high-temperature sintering treatment. Several advanced techniques are used to characterize the morphology and composition of the resulting nanostructures, such as TEM, HRTEM, SEM, XRD, and BET. The HRTEM image shows that the microflowers are assembled from the nanosheets with highly exposed {010} facets, as confirmed by selected area electron diffraction (SAED). According to N2 sorption isothermal studies, the as-prepared V2O5 microflowers show high specific surface area of 61.5 m2 g−1. The formation of the microflowers with assistance of NaHCO3, which may play a critical role in the self-assembly process, may be attributed to a “reproduction mechanism”. The gas sensing performances of both the V2O5 microflowers and the V2O5 nanosheets were evaluated towards several volatile organic compounds (VOCs), such as 1-butylamine, ethanol, acetone, and formaldehyde. The results show that the flower-like structure exhibits a superior sensing response and selectivity towards amines compared to that of the sheet-like structure at an optimum working temperature of ∼300 °C. The high selectivity towards 1-butylamine can be ascribed to the selective oxidation mechanism. This work will help explore vanadium oxides as gas sensors toward volatile organic compounds with high performance.

Vanadium dioxide (VO2) is one of the best candidates for thermochromic smart windows, which undergoes a metal–insulator transition at a critical temperature (Tc) of ∼68 °C, accompanied with a huge transmittance contrast in the near-infrared range. However, the application of VO2-based smart windows is limited by the poor luminous transmittance (Tlum) and low solar modulation efficiency (ΔTsol). Besides, the intrinsic yellow–brown color of the VO2 film does not change before and after the phase transition, which is not satisfactory. In order to solve the above-mentioned issues, a photochromic material [6-nitro-1′,3′,3′-trimethylspiro-[2H-1-benzopyran-2,2′-indoline] (spiropyran)] has been employed to combine with VO2 nanoparticles to form a hybrid composite film. This newly designed nanostructure demonstrates exemplary solar modulation efficiency (ΔTsol = 23.58%) along with color change from yellow to pink as the light sources change. Moreover, this hybrid composite could block ultraviolet radiation, a crucial index to evaluate the performance of the VO2-based smart windows, which will be promising for industrial applications.

The one-step epoxidation of allyl chloride has always been a great challenge for the industrial production. The key of this technology is to find efficient and friendly catalyst. In this paper, three structurally related quaternary ammonium modified polyoxophosphotungstates were synthesized by green and facile method. Among them, [C16H33(CH3)3N]3PW4O24 and [π-C5H5NC16H33]3PW4O24 are reaction-controlled phase transfer catalyst (RPTC) and [(C18H37)2(CH3)2N]3PW4O24 is temperature-controlled phase transfer catalyst (TPTC). All three catalysts could achieve the epoxidation of allyl chloride with equimolar H2O2 under solvent-free and mild conditions. Moreover, the catalysts exhibited excellent catalytic performance and reusability. The catalytic mechanism was explored by FT-IR spectroscopy. The results of kinetic experiments show that the chain length of alkanes and heterocyclic structure of cations have a great influence on the catalytic activity of the catalysts.

This study demonstrates the synthesis of self-assembled hexagonal WO3 nanowire bundles, with both ordered and random structures in the presence of SO42− ions, by a simple but efficient solvent-thermal method. The as-synthesized products are composed of hierarchical bundles with assembled ultrathin nanowire subunits. The growth and assembly mechanisms, regarding WO3 nanowire bundles, may be elucidated through oriented attachment or Ostwald ripening growth, based on a synergistic effect from both oxalic acid and ethylene glycol in dehydrating WO3·xH2O to WO3 nanocrystals and in controlling segregation behavior, along with high surface areas (18.4 m2 g-1 for ordered structures while 11.6 m2 g-1 disordered ones), which makes WO3 bundles great potential for gas sensing. To further enhance gas sensing, gold nanoparticles were chosen to deposit on the surface of WO3 nanowire bundles by acting with amino groups linked with WO3 bundles in the HAuCl4 solution with further oxidation. The Au-WO3 composites were examined towards various reducing gases, with exemplary sensitivities of (S = 127, 82), (S = 72, 52) towards n-butanol and acetone, respectively. The sensing mechanisms of such WO3 bundle structures are further understood in detail. This work will make the unique WO3 bundle nanostructures highly potential for gas sensing applications.

Liquid marbles to separate wetting (silver nanowires) from non-wetting (graphite and talcum) particles is described here. Two types of liquid marbles are formed by coating the dry mixture test material on pendant or sessile drops. The silver nanowire particles are separated from the graphite or talcum shell by entering into the liquid core of the marbles. The liquid core is extracted into capillary tubes where the presence of silver nanoparticles was confirmed by a blue to colourless change arising from silver-mediated catalytic reduction of methylene blue and sodium borohydride solution. The use of an inclined rotating surface to coat the pendant drop was found to create liquid marbles in a more controllable manner. A platform tilt angle of 15o followed by rotation was found to provide more uniform albeit only partially coating the bottom of the pendant drop.

Tungsten oxides (stoichiometric and non-stoichiometric) have gained extensive research interests because of promising physicochemical properties and diverse applications. Ultrathin walled tungsten oxide (WO3) nanotubes have been fabricated by hydrothermal route in the presence of both K2SO4 and citric acid under mild conditions. WO3 nanocrystals randomly assembled into ultrathin layered structures with highly peaked end which are then interwoven into nanotubes (diameter of 10−15 nm, wall thickness of 1−2 nm, width of 21 nm), because of Ostwald Ripening growth kinetics. Non-stoichiometric WO3-x nanowires (diameter 10−15 nm) were also synthesized using K2SO4 in the absence of organic ligand. The Brunauer–Emmett–Teller (BET) surface area for h-WO3 nanotubes was 71.95 m2 g−1 higher than WO3-x nanowires (51.83 m2 g−1), WO3 nanowires (42.70 m2 g−1) and nanorods (24.60 m2 g−1). Photoluminescence (PL) spectra show that the h-WO3 nanotubes and WO3-x nanowires have more crystal defects and oxygen vacancies. Time-dependent experiments were conducted and the plausible growth mechanism of h-WO3 nanotubes was proposed. The WO3 nanostructures with different morphologies were used as gas sensors that could detect acetone and ethanol with superior sensing performance (Ra/Rg for WO3 nanotubes = 32 & 26, respectively) under mild conditions, notably attributed to the ultrathin wall with high surface areas, crystal defects and oxygen vacancies.

This work reports a facile and efficient seed-mediated method for the synthesis of dendritic platinum (Pt) nanoparticles (NPs) at low temperatures of 55–60 °C in water, using L-ascorbic acid as a reducing agent and sodium citrate as a capping agent.It is found that the dendritic Pt NPs (10–150 nm) are composed of tiny Pt nanocrystals, which nucleate and grow through the introduced smaller Pt seeds with diameters of 3–5 nm. Further investigation shows that the dendritic Pt nanostructures display excellent catalytic performance in an aqueous-phase aromatic ketone hydrogenation reaction, including: (i) acetophenone conversion rate of > 90%, with smaller dendritic Pt NPs (10–46 nm) offering a higher conversion efficiency; (ii) high chemoselectivity toward carbonyl group (90.6%–91.5%), e.g., the selectivity to 1-phenylethanol is ∼90.1% with nearly 100% acetophenone conversion for 10 nm dendritic Pt NPs within 60 min, under mild reaction conditions (20 °C, 1.5 bar H 2 pressure, and 1.5 mol% catalyst). The high catalytic activity, selectivity and stability of the dendritic Pt nanostructures under the organic solvent-free conditions make them promising for many potential applications in green catalytic conversion of hydrophilic biomass derived compounds.

Nano-sized ZnTiTa2O8 powders with ixiolite structure, with particle sizes ranging from 10 nm to 30 nm, were synthesized by thermal decomposition at 950 °C. The precursors were obtained by aqueous sol–gel and the compacted and sintered ceramics with nearly full density were obtained through subsequent heat treatment. The microstructure and electrical performance were characterized by field emission scanning electron microscopy, x-ray diffraction, and microwave dielectric measurements. All the samples prepared in the range 950–1150 °C exhibit single ixiolite phase and relative density between ~87% and ~94%. The variation of permittivity and Q·ƒ value agreed with that of the relative density. Pure ZnTiTa2O8 ceramic sintered at 1050 °C for 4 h exhibited good microwave dielectric properties with a permittivity of 35.7, Q·ƒ value of 57,550 GHz, and the temperature coefficient of resonant frequency of about −24.7 ppm/°C. The relatively low sintering temperature and excellent dielectric properties in the microwave range would make these ceramics promising for applications in electronics.

This study demonstrates a facile but efficient hydrothermal method for the direct synthesis of both carbonaceous silver (Ag@C core-shell) nanocables and carbonaceous nanotubes under mild conditions (

This study reports facile hydrothermal strategies for the synthesis of novel ternary α-Fe 2 O 3 –ZnO–Au nanocomposites under mild conditions, through further surface coating of ZnO and Au nanoparticles (NPs) on α-Fe 2 O 3 nanorods. The ternary α-Fe 2 O 3 –ZnO–Au nanocomposites are found to show (1) higher sensitivity/responses ( S ) of 113 and 57 toward 100-ppm n -butanol and acetone, respectively compared to single α-Fe 2 O 3 ( S = 11.7, 9.1 for n -butanol, acetone) and binary α-Fe 2 O 3 -ZnO ( S = 54.4, 28 for n -butanol, acetone) sensing materials, and (2) lower optimum operating temperature, i.e., 225 °C. The enhanced sensitivity could be attributed to the chemical sensitization effect induced by the Au NPs, and the existence of conjugated depletion layers in the nanocomposites which promote a greater drop in resistance upon exposure to the gas. These results will be useful for future design of iron oxide-based ternary nanocomposites as gas-sensing materials with high sensitivity, selectivity and stability.

Selectively-absorbing nanofluids were synthesized and evaluated for spectrum splitting PV/T collector applications. Core-shell silver-silica (Ag-SiO2) nanodiscs and multi-walled carbon nanotubes (MWCNTs) were suspended in water at varying dilutions and then tested as an optical filter placed between a light source and silicon solar cell. A concentrated Ag-SiO2 solution diluted with an aqueous MWCNT solution yielded higher thermal efficiencies than when diluted by the same volume of water. However, AgSiO2-MWCNT mixtures yielded a lower electrical output than aqueous AgSiO2 dilutions due to the non-selective absorption of MWCNTs. The most concentrated Ag-SiO2 nanofluid (0.026wt%) yielded a peak thermal efficiency of 65%, to deliver the greatest combined efficiency of ∼72%.

Vanadium dioxide/titanium nitride (VO

The authors describe a novel recyclable substrate for highly sensitive surface-enhanced Raman scattering (SERS) studies. It consists of gold nanorods (AuNRs) self-assembled on a TiO2 film and combines the high SERS enhancement of assembled AuNRs with the self-cleaning property of the TiO2 film. It overcomes limitations of conventional SERS substrates such as limited sensitivity, high costs, and poor recyclability. The packing density of the AuNRs on the TiO2 film can be well adjusted, and therefore the SERS enhancement factor of the substrates can be tuned. For the optimized substrate, the SERS enhancement factor is as high as 5.4 × 1010 (Raman laser at 782 nm with 10% of 1.15 mW). This indicates extremely high sensitivity and is promising in terms of single molecule detection. Raman mapping experiments showed the SERS signal to be homogeneously distributed over the whole surface, with a maximal deviation of 3.5%. The SERS activity of this substrate can be restored by degradation of the probe molecules through TiO2 photocatalysis under UV irradiation. In our perception, these findings open a new venue for developing ultra-sensitive and recyclable SERS substrates.

Gold nanorods (AuNRs) have attracted high attention because of their multifunctions and potential applications in optical, electronic, catalytic and biomedical areas. This study demonstrates a key role of silver (Ag) atoms/clusters, experimentally and theoretically, in the formation and growth of AuNRs. It was found that the addition of silver salt (silver nitrate) can preferably deposit on certain Au crystalline {100} and/or {110} facets to affect the stacking of Au atoms when form and grow to AuNRs in the reported reaction system, resulting in slower atomic stacking on these two {100} and {110} facets but regular growth on the {111} facets. If no use of silver salt(s), gold nanospheres rather than nanorods were obtained in such a reaction system. It was found, by theoretical simulations (molecular dynamic method, MD), that Ag atoms can be oxidized to Ag+ ions by AuCl4 − ions and exist in a short lifetime, which finally diffuses out from the Au crystal structure. The findings would be useful for better understanding the role of Ag in the formation and growth of AuNRs with crystal facet control, which will be beneficial for catalytic and gas sensing applications that often require highly exposed crystalline facets.

One-dimensional silver vanadate (Ag2V4O11) nanostructures have been prepared by a facile hydrothermal method with no any additives under mild conditions. The pertinent variables for generating such nanostructures were investigated, and found that the composition and crystallinity of Ag2V4O11 could be controlled, e.g., by adjusting solution pH (pH = 1) benefiting for the crystallinity of Ag2V4O11 nanobelts. These nanostructures have high surface-to-volume ratios and could be explored for gas sensing materials. The gas sensing performances of such nanomaterials were tested, and found that the Ag2V4O11 nanobelts showed a relatively high sensitivity towards amine(s), with a low detection limit (5 ppm) and quite good selectivity of amines to ammonia at an optimized working temperature of ∼260 °C. The possible sensing mechanism was finally discussed. This study may offer a promising approach to prepare sensing materials towards detecting and monitoring organic amines for practice applications.

This study represents that a facile and efficient hydrothermal method has been developed for the synthesis of sodium vanadium oxide (Na2V6O16·3H2O) nanobelts with lengths varying from hundreds of nanometres up to a few micrometres, and widths ranging from 80 to 250 nm. These Na2V6O16·3H2O nanobelts transform into Na1.08V3O8 nanorods by calcination at 350 ◦ C for 3 h and this results in a slight shrinkage. This material has been characterized and examined in terms of its gas sensing properties and it was found that the Na1.08V3O8 nanorods exhibit a good sensitivity towards alcohol(s), and acetone at the optimized operating temperature of 260 ◦C. The as-prepared Na1.08V3O8 nanorods displayed a higher sensitivity towards ethanol than pure V2O5 nanobelts and metal oxide-coated/doped V2O5 nanobelts, as a result of the existence of extra Na+ ions and the decreased electronegativity of V ions that can enhance the gas molecule adsorption and hence the sensing performance. Density functional theory (DFT) simulation has also been carried out to understand the sensing mechanism. This study would be useful for developing sodium vanadium oxide nanostructures as potential gas sensor materials. © 2014 Published by Elsevier B.V.

This study demonstrates a facile and efficient hydrothermal method to prepare spindle titanate (Li4Ti5O12 denoted as LTO) and/or carbon-LTO nanocomposites (C-LTO), in which the LTO or C-LTO microspheres have diameters of a few micrometers, composed of numerous nanosheets with thickness of ~30 nm and edge length of hundreds of nanometers. The morphology and size control of these nanoparticles could be achieved by varying experimental parameters including concentration of titanium butoxide, lithium hydroxide, and cetyltrimethylammonium bromide, as well as reaction temperature and time. These micro-nanostructures were characterized by several advanced techniques, such as transmission electron microscopy, scanning electron microscopy, X-ray diffraction, energy dispersive spectroscopic analysis, surface area, and electrochemical measurements. The LTO and C-LTO microstructures were examined in the charge–discharge capacity at a rate of 50 C, as well as the stability after 100 cycles at a rate of 10 C. The excellent capability may be attributed to good conductivity, large surface area, and stable assembly structure of such micro-nanostructures, which could be explored as a promising anode material for lithium-ion batteries.

This paper reports a newly developed solvothermal strategy for the synthesis of ZnO-decorated α-Fe2O3 nanorods based on the reaction of α-Fe2O3 nanorods with zinc sulfate and urea in autoclaves at 180 °C. The resulting nanocomposites consist of porous α-Fe2O3 nanorods with diameters of 100–200 nm and a surface decorated with small ZnO nanoparticles (10–20 nm). The ZnO NPs are found to grow epitaxially on {110} planes of α-Fe2O3, forming an interfacial orientation relationship of (100)ZnO/(110)α-Fe2O3. The addition of ZnO is found to shift the Fe 2p peak position in the α-Fe2O3/ZnO nanocomposites to higher binding energies due to the formation of the α-Fe2O3/ZnO heterojunction interface. The gas-sensing results show that the ZnO-decorated α-Fe2O3 nanorods exhibit excellent sensitivity, selectivity, and stability toward n-butanol gas at a low optimum temperature of 225 °C. In particular, they show higher sensitivity compared to pure α-Fe2O3 (4 times higher) and ZnO nanorods (2.5 times higher), respectively, along with faster response times. The significant enhancement in sensitivity may be attributed to the chemical and electronic sensitization induced by the ZnO nanoparticles deposited on the surfaces of the α-Fe2O3 nanorods. The findings reported in this study will be useful for the design and construction of surface modified-metal oxide nanostructures with enhanced gas-sensing performance.

Correction for ‘Advances on tungsten oxide based photochromic materials: strategies to improve their photochromic properties’ by Shufen Wang et al., J. Mater. Chem. C, 2018, 6, 191–212.

Zinc oxide single crystals with a high percentage of exposed { 4 2 ¯ 2 ¯ 3 ¯ } reactive facet were prepared by a facile hydrothermal route. X-ray diffraction, field emission scanning electron microscopy, and high resolution transmission microscopy confirmed the faceted single crystal structure. Through the density functional theory (DFT) calculations, it is validated that the { 4 2 ¯ 2 ¯ 3 ¯ } surface of ZnO crystals has high surface energy. When used as a sensing material in gas sensors, ZnO crystals with dominating exposed { 4 2 ¯ 2 ¯ 3 ¯ } planes exhibited a superior sensitivity toward toxic and flammable gases.

This study demonstrates a novel approach for rapid synthesis of silver (Ag) nanowires induced by vanadium trioxide (V 2 O 3 ) particles in aqueous solution at room temperature. Silver nanowires have an average diameter of 20 nm and length up to a few micrometers by parametric optimization. The micro-structure of the silver nanowires was characterized by TEM, HRTEM, SEM, and XRD techniques. The optical property of the as-prepared product was measured by ultraviolet–visible (UV–vis) spectroscopy. The possible growth mechanism of Ag nanowires via oriented attachment of Ag nanocrystals was discussed. The present approach shows several unique features such as rapid (a few minutes), reproducible and high-yield reaction with no need of any modifiers. V 2 O 3 rods were reported for the first time to be used for synthesis of silver nanowires, playing multiple roles as reducing agent, template, and catalyst. The silver nanowires produced are promising for optical applications (e.g., SERS) due to their rough surface.

This study reports a facile and efficient one-step hydrothermal method for the synthesis of zinc oxide (ZnO) nanoflakes with exposed ZnO(1010) surfaces. The as-prepared nanoflakes exhibit excellent sensitivity, selectivity, and stability toward volatile n-butanol gas at the optimized operating temperature of 330 °C. The gas-sensing results further indicate that the chemisorbed oxygen species on the surfaces of the ZnO nanoflakes are dominated by O2– rather than O– ions at 330 °C. The molecular dynamics (MD) method was also employed to understand the underlying fundamentals through simulating the adsorption of different gas molecules onto various ZnO crystal surfaces, such as (1010), (1120), and (0001). The simulation results confirm the enhancing effect of the exposed (1010) surfaces toward n-butanol gas molecules because of their lower diffusion coefficient on (1010) compared to those on (1120) and (0001) surfaces. The findings will provide new physical insights into the adsorption behaviors of vol...

The adsorption of water, oxygen, ethanol, and acetic acid onto the SnO2(110) surface was studied using molecular dynamics (MD) simulations. It was found that the atomic arrangement of metal oxide surfaces can play a crucial role in the adsorption and weakening of molecular bonds. The Obridge of this particular metal oxide surface exhibits extraordinary properties that can attract the O–H group of water and ethanol molecules. Moreover, the temperature is also an important factor where it supplies the extra energy required for extreme bond stretching, particularly with the O–H group. However, this will also reduce the performance where the molecules are more likely to diffuse and cannot adsorb onto the surface of SnO2. Other metal oxides (e.g., ZnO and Fe2O3) were also simulated to compare their adsorption behaviors. To verify the MD results, the adsorption and bond stretching behavior of ethanol on the SnO2(110) is compared with the results generated by density functional theory (DFT) simulation. The simul...

This study demonstrates a facile but effective method to construct glucose coated magnetic Fe3O4 nanoparticles for drug delivery through a glycothermal method (100–200 °C). In this process, magnetic Fe3O4 nanoparticles were firstly prepared via a glycothermal reaction of Fe (III) salts (e.g., FeCl3·6H2O) in ethylene glycol. Second, the polymerized glucose was used as a carbon layer to coat on the surface of Fe3O4 nanoparticles. The polymerized glucose layer is biocompatible and can provide functional –OH groups for interaction with biomolecules that contain –COOH, –SH, and –NH2 groups. The particle characteristics (morphology, size, surface property) were identified by various techniques such as transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, and ultraviolet visible (UV–vis) spectrum. Finally, the polymerized-glucose coated magnetic Fe3O4 nanocomposites were used in drug delivery test at ambient conditions, and the loading or release performance of aspirin was assessed by using UV–vis spectroscopy. The influence of pH and ionic strength on the adsorption capacity has also been investigated. The findings in this study will be useful for engineering iron oxide nanoparticles for potential drug delivery applications.

The emergence of metal-organic frameworks (MOFs) as a new class of crystalline porous materials is attracting considerable attention in many fields such as catalysis, energy storage and conversion, sensors, and environmental remediation due to their controllable composition, structure and pore size. MOFs are versatile precursors for the preparation of various forms of nanomaterials as well as new multifunctional nanocomposites/hybrids, which exhibit superior functional properties compared to the individual components assembling the composites. This review provides an overview of recent developments achieved in the fabrication of porous MOF-derived nanostructures including carbons, metal oxides, metal chalcogenides (metal sulfides and selenides), metal carbides, metal phosphides and their composites. Finally, the challenges and future trends and prospects associated with the development of MOF-derived nanomaterials are also examined.

Binary 1D nanowires consisting of both SnO2 nanoparticles and Au nanorods are fabricated through a "substrate-particle solution template" assembling method, which shows highly enhanced gas sensitivity toward acetone under ambient conditions.

This study presents a comprehensive theoretical and experimental study on the deposition mechanism of precious metal nanoparticles (e.g., Au, Pt, Ag, and Pd) onto iron oxides (e.g., α-FeOOH, α-Fe2O3, and Fe3O4), which can be generated through a hydrothermal synthesis at ambient conditions. By using molecular dynamics (MD) method, the surface interaction energy between metal nanoparticle and iron oxide surface can be quantified. The analysis shows that the total potential energy of the metal nanoparticles decreases significantly when the metal particles are deposited onto porous or defected sites. The interaction is heavily dependent on nanoparticle size, elemental species, and surface structure of the iron oxide (porous or defects). The van der Waals force was found to play a dominant role in the deposition process. The MD simulation shows that the gases (e.g., CO, propene) on such nanocomposites have a lower diffusion coefficient at the Au/Fe2O3 surface and hence enhance catalytic activity, which may hel...

A highly sensitive and selective gas-sensing material based on gold (Au)-functionalized tungsten oxide (WO3) composite nanofibers (NFs) has been fabricated under mild conditions by electrospinning (ES). Au nanoparticles (NPs)-decorated WO3 composite NFs were obtained by ES of the tungsten precursor (ammonium metatungstate hydrate) (AMT) and polyvinyl alcohol (PVA) solution followed by a two-step annealing treatment. The chemical and structural characterizations of the resulting composite nanofibers have been performed with various techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM) and inductively coupled plasma optical emission spectrometry (ICP-OES). The gas-sensing properties of the WO3–Au composite NFs with different Au contents (0.01 M and 0.1 M) toward volatile organic compounds (VOCs) (such as n-butanol) have been studied. A discussion concerning the role of Au content and the operating temperature is given to optimize the sensitivity, the dynamic response–recovery behaviors and consequently the efficiency of the WO3–Au composite sensor.

The deposition of gold nanoparticles on the magnetite (Fe(3)O(4)) surface is demonstrated through a molecular dynamics method. The simulated results show that an intermediate layer composed by such as a surfactant, polymer, or silica plays a key role in the formation of core/shell Fe(3)O(4)/Au nanostructures. The functional groups of the intermediate layer are crucial factors in depositing gold onto the Fe(3)O(4) surface via nonbonding interactions, in which the van der Waals and columbic forces will determine the strength of interaction toward the gold and iron oxide. Such interactions can affect the stability of the metal-coated nanocomposites and hence the functional properties. The nanocomposite is further investigated on the surface adsorption of amino acids (e.g., cysteine), which may be useful for functional exploration in biomedical applications.

This study demonstrates a facile but effective polyol-thermal reaction method for the synthesis of silver nanowires in autoclaves (160–180 °C). By this approach, the generated silver nanowires show an average diameter of ~40 nm and length up to tens of micrometers with a high yield and potential for large-scale production. To achieve shape- and size-controlled Ag nanowires, several experimental parameters were investigated and optimized, including surface controller(s), molar ratio of surfactant(s) to silver ions, temperature, and concentration of reactants. The structure and composition of silver nanowires were characterized by transmission electron microscopy (TEM), high-resolution TEM (HRTEM), scanning electron microscopy (SEM), and X-ray diffraction (XRD) techniques. In particular, the twinned crystal structure observed in both spherical particles and nanowires was analyzed by HRTEM technique, and the possible formation and growth mechanisms were discussed. The optical property of the as-prepared product was measured by ultraviolet–visible (UV–vis) spectroscopy. The sensing detection of metal ions (e.g., Hg2+) using the obtained silver nanowires in aqueous media was finally investigated.

This study demonstrates the details on the twinned structure and growth process of V-shaped silver nanowires with different bending angles (e.g., 90°, 120°, and 135°) confirmed by high-resolution transmission electron microscopy (HRTEM). These nanowires could be synthesized by a facile but effective polyol−thermal reaction method in autoclaves (160−180 °C). The nearly uniform-size silver nanowires show an average diameter of ∼45 nm and length up to tens of micrometers. The microstructure and optical properties of the silver nanowires were characterized by various advanced techniques, including TEM, HRTEM, scanning electron microscopy (SEM), and ultraviolet−visible (UV−vis) spectroscopy. The twinned structure can occur in both silver spherical particles and nanowires, confirmed by HRTEM analysis and also simulated by molecular dynamics methods. The growth of V-shaped nanowires by two possible means was particularly investigated: (i) crystal lattice match-induced end-to-end or end-to-side fusion of two nano...

This study employs molecular dynamics (MD) method to fundamentally understand the growth mechanism of one-dimensional goethite (α-FeOOH) nanostructure, which can be generated by a simple hydrochemical method assisted by the surfactant of cetyltrimethylammonium bromide (CTAB) under mild conditions. In this approach, various surfactants were investigated for testing their effectiveness during the formation and growth into nanorods, further confirmed by the calculation of the interaction energies between goethite surfaces with surfactant molecules. It was found that the efficient surfactant/additive prefers to interact with the (xy0), i.e., (100), (010) and (110), but weakly on the (xy1), i.e., (101), (011) and (001) surfaces. The results can be used to explain the formation and growth mechanism of goethite nanorods. The interactions were found to be highly dependent on the electrostatic energy of the functional groups in the molecule which allow the strong interaction on a certain goethite surface. The findings can provide quantitative information for understanding nanoparticle growth, and useful for optimizing surface acting agents (surfactants or polymers) for shape control of nanoparticles with desirable functional properties.

This study demonstrates a facile approach for one-step synthesis and self-assembly of silver nanoparticles at ambient conditions. It was found that pyrogallol acid (PYA) can play multiple roles in the proposed synthesis, including a reducing agent, a stabilizer, and a linking agent for assembly. Silver ions can be readily reduced by PYA at room temperature due to its powerful reducing capability. The capability in shape and size control can be evidenced by TEM images. A third function of PYA in this case is to link the generated silver particles into chains through the action of hydrogen bonding, which leads to a new plasmon resonance emerges in the longer wavelength region centered at approximately 650 nm. These results may be useful for shape-controlled synthesis and self-assembly of other metallic nanoparticles. The self-assembly structures would be imposed more functional applications in the areas of optics, plasmonics, biomedicine labeling and ionic sensing.

This study demonstrates a facile surfactant-directed approach to prepare goethite (α-FeOOH) nanorods in aqueous solution at room temperature. The obtained α-FeOOH nanorods have a diameter of ∼20 nm and length up to 300 nm. Various experimental parameters have been investigated, such as surfactants, solution pH, and reaction temperature. It is observed that the surfactant, cetyltrimethylammonium bromide (CTAB), plays a key role in the growth of goethite nanorods at ambient conditions. The final product can be purified using diluted hydrochloric acid (HCl) to remove particles of other shapes. Molecular dynamics (MD) method is used to understand the underlying principles governing particle growth through the analysis of the interaction energies between crystal surfaces and surfactant molecules. The simulation results indicate that CTAB can strongly interact with {100}, {010}, and {110} planes, which benefits the growth of nanorods along [001] direction. Such simulations can provide useful information for the synthesis and shape control of other metal oxide materials.

Precious metallic nanoparticles have attracted considerable attention because of their unique properties (optical, electronic, and chemical properties) and potential applications in many areas such as optical probes, biochemical sensors, and surface enhanced Raman Spectrum. Despite many successes in synthesis of anisotropic nanoparticles (rods, plates), some limitations still exist in generating monodispersed silver nanoparticles. This study intends to elucidate the influence of crystalline seeds on the shape, size, and size distribution of nanoparticles through a seed-mediated method. The crystalline seeds can be modified by using different ways, such as heating treatment and oxidative etching. The shape and size of the generated particles will be characterized by TEM, and the particle formation and growth is tracked by UV-vis spectrometry. The findings would be useful for the shape-controlled synthesis of metal nanoparticles for desired functional properties.

Goethite (α-FeOOH) nanorods could be prepared by a surfactant directed approach in aqueous solution at ambient conditions. In this approach, it is observed that the surfactants (e.g, cetyltrimethylammonium bromide (CTAB) and tetraethylamine chloride (TEAC)) play a key role in the growth of goethite nanorods under the reported conditions. The molecular dynamics (MD) method is used to understand the underlying principle governing particle formation and growth through the analysis of the interaction energies between the crystal surfaces and the surfactant molecules. The findings will be useful for understanding the growth mechanism of anisotropic particles and their surface coatings with heterogeneous materials for desired functional properties.

Vanadium dioxide/titanium nitride (VO2 /TiN) smart coatings are prepared by hybridizing thermochromic VO2 with plasmonic TiN nanoparticles. The VO2 /TiN coatings can control infrared (IR) radiation dynamically in accordance with the ambient temperature and illumination intensity. It blocks IR light under strong illumination at 28 °C but is IR transparent under weak irradiation conditions or at a low temperature of 20 °C. The VO2 /TiN coatings exhibit a good integral visible transmittance of up to 51% and excellent IR switching efficiency of 48% at 2000 nm. These unique advantages make VO2 /TiN promising as smart energy-saving windows.

The flux pinning potential energy of silver (Ag) sheathed high-Tc Bi-2223 tapes determined from measured current densities, J(T,H), is reported in this paper. Measurements of the transport current density, J, of the Ag sheathed Bi-2223 tapes were performed with an applied magnetic field directions parallel (H‖ab) and perpendicular (H‖c) to the tape’s board surface from 0 to 3 T, at temperatures from 23 to 77 K. To obtain the pinning potential energy of the Bi-2223 superconductor, an empirical scaling of J(T,H) is introduced in this study. Under the flux dynamics, the effective pinning energy, Ueff(T,H,J), can be formulated using the measured current density, J(T,H). Furthermore, the pinning potential energies, U(T,H), for both H‖ab and H‖c were quantitatively determined by the scaling of J(T,H). The two energies, U(T,H), exhibit as a function that is inversely proportional to both temperature and logarithmic magnetic field. The magnitude of U(T,H) for H‖ab is three or more times larger than that for H‖c under the considered conditions. The U(T,H) is sensitive to the temperature, but insensitive to the magnetic field. This characteristic of insensitiveness towards magnetic field is an advantage for applications on the conditions of high current density, high magnetic field, and low temperature.

Iron oxide and metal doped iron oxide nanocomposites have found attractive and versatile applications in many research areas such as catalysts, sensors, and biomedicine. This work reports a surfactant-free hydrolysis approach for the synthesis of hematite (α-Fe2O3) and Pd doped α-Fe2O3 nanoparticles with low-temperature catalytic activity. By this method, iron oxide rod-like nanoparticles were achieved by hydrolysis of ferric chloride salt with dilute HCl at a temperature of 100 °C. The Pd/iron oxide nanocomposites were obtained by adding citric acid into a mixture of iron oxide nanoparticles and palladium precursor (Pd(CH3CN)2Cl2) under a reflux heating at 90 °C for 2 h. This method is featured as no use of any surfactants and templates, and no requirement of high-temperature thermal decomposition that are usually required for shape/size control in polar or nonpolar solvents. More importantly, it was found that the Pd/α-Fe2O3 nanocomposites exhibited high low-temperature catalytic activity in carbon monoxide (CO) oxidation.

This study reports a facile hydrothermal method for the synthesis of monodispersed hematite (α-Fe2O3) nanodiscs under mild conditions. The method has features such as no use of surfactants, no toxic precursors, and no requirements of high-temperature decomposition of iron precursors in non-polar solvents. By this method, α-Fe2O3 nanodiscs were achieved with diameter of 50 ± 10 nm and thickness of ~6.5 nm by the hydrolysis of ferric chloride. The particle characteristics (e.g., shape, size, and distribution) and functional properties (e.g., magnetic and catalytic properties) were investigated by various advanced techniques, including TEM, AFM, XRD, BET, and SQUID. Such nanodiscs were proved to show unique magnetic properties, i.e., superparamagnetic property at a low temperature (e.g., 20 K) but ferromagnetic property at a room temperature (~300 K). They also exhibit low-temperature (

This work reports a newly developed two-step hydrothermal method for the synthesis of monodispersed colloidal carbon spheres (CCS) under mild conditions. Using this approach, monodispersed CCS with diameters ranging from 160 to 400 nm were synthesized with a standard deviation around 8%. The monomer concentration ranging from 0.1 to 0.4 M is in favor of generation of narrower size distribution of CCS. The particle characteristics (e.g., shape, size, and distribution) and chemical stability were then characterized by using various techniques, including scanning electron microscopy (SEM), FT-IR spectrum analysis, and thermalgravity analysis (TGA). The possible nucleation and growth mechanism of colloidal carbon spheres were also discussed. The findings would be useful for the synthesis of more monodispersed nanoparticles and for the functional assembly.

This paper reports a facile synthesis method for shape control of gold nanoparticles by treating an aqueous solution of chloroauric acid with sodium citrate and poly(vinyl pyrrolidone) (PVP). By such an environmentally friendly method, gold nanoparticles were prepared with different morphologies including spheres, rods, and worm-like nanoparticles. Two possible growth mechanisms were proposed in the formation of wormlike particles: from spherical colloids to nanorods, and from nanorods to worm-like particles by stacking faults or by rods conjunction. It was found that the PVP plays a key role in the formation of nanostructures by acting as reducing agent, stabilizer, and surface capping agent. Density function theory (DFT) is applied to quantify the binding energies of PVP with different gold crystal surfaces (i.e., 100, 110, and 111). Such a DFT approach, facilitated by transmission electron microscopy and ultraviolet−visible spectroscopy characterizations, will be useful for fundamental understanding of...

The spectrally- and polarization-resolved absorption cross-sections of a single gold nanorod have been investigated using the spatial modulation spectroscopy technique. The ensemble of its optical features, that is, longitudinal and transverse surface plasmon resonances and interband absorption, has been quantitatively characterized. The results are compared with numerical simulations using the discrete dipole approximation and the finite element method, yielding information on the investigated nanorod size and shape.

This paper demonstrates a simple sensing method to detect inorganic anions by silver nanoplates (edge length of approximately 70 nm and thickness of approximately 2 nm) in aqueous solution. By this method, the solution system containing silver nanoplates shows a high sensitivity on the order of 1 x 10(-6) M in detecting halides, phosphate, and thiocyanate ions in water at room temperature. The sensitivity could be identified by the shift in the surface plasmon resonance (SPR) band in UV-vis spectrum. The selectivity of such a sensing system toward various anions was also studied, and it was found that this sensing system could distinguish individual anions (e.g., Cl-, Br-, I-, H2PO4-, and SCN-) from other anions (e.g., F-, SO42-, CH3COO-, NO3-, and ClO4-) and inorganic cations (e.g., Zn2+, Cd2+, and Cu2+) under the given conditions. The sensing mechanism was also analyzed. It was proposed that the particle surface electron charging, which is mainly determined by the interaction tendency between silver atoms and various inorganic anions in water, is responsible for the shift in the SPR observed. The need for further studies was finally discussed, particularly for systems composed of mixed anions.