Synthesis and shape control of CuInS(2) nanoparticles

Cu(2)S-CuInS(2) hybrid nanostructures as well as pure CuInS(2) (CIS) nanocrystals were synthesized by methods of colloidal chemistry. The structure, the shape and the composition of these nanomaterials were investigated with transmission electron microscopy (TEM), powder X-ray diffraction (XRD) and energy dispersive X-ray analysis (EDX). By changing the reaction conditions, CuInS(2) nanorods with different aspect ratio, dimeric nanorods as well as hexagonal discs and P-shaped particles could be synthesized. Under our reaction conditions, CIS nanoparticles crystallize in the hexagonal wurtzite structure, as confirmed by Rietveld analysis of the X-ray diffraction patterns. The formation of Cu(2)S-CuInS(2) hybrid nanostructures turned out to be an essential intermediate step in the growth of CIS nanoparticles, the copper sulphide part of the hybrid material playing an important role in the shape control of the CIS nanocrystals. By a treatment of Cu(2)S-CuInS(2) with 1,10-phenanthroline, Cu(2)S parts of the hybrid nanostructures could be removed, and pure CIS nanoparticles with shapes not accessible with other methods can be obtained. Our synthetic procedure turned out to be suitable to synthesize also other compounds, like CuInS(2)-ZnS alloys, and to modify, in this way, the optical properties of the nanocrystals.     

Simple reductant concentration-dependent shape control of polyhedral gold nanoparticles and their plasmonic properties

We report a facile seed-mediated method for the synthesis of monodisperse polyhedral gold nanoparticles, with systematic shape evolution from octahedral to trisoctahedral structures. The control over the particle growth process was achieved simply by changing the concentration of the reductant in the growth solution, in the presence of small spherical seed nanoparticles. By progressively increasing the concentration of the reductant used in the growth solution (ascorbic acid), while keeping the amount and type of added surfactant constant, the morphology of the gold nanoparticles was varied from octahedral to truncated octahedral, cuboctahedral, truncated cubic, cubic, and finally trisoctahedral structures. These nanoparticles were monodisperse in size, possessed similar volumes, and were naturally oriented so that their larger crystal planes were face down on quartz substrates when deposited from the solution. By adjusting the volume of gold seed nanoparticle solution added to a growth solution, the size of the simplest gold nanoparticles (with a highly symmetric cubic morphology) could be tuned from 50 ± 2.1 to 112 ± 11 nm. When other seed nanoparticles were used, the size of the cubic Au nanoparticles reached 169 ± 7.0 nm. The nanoparticle growth mechanism and the plasmonic properties of the resulting polyhedral nanoparticles are discussed in this paper.     

SnS2纳米花/石墨烯纳米复合物的一步法合成及其增强的锂离子存储性能

SnS₂ is considered as an attractive anode material to substitute commercial graphite anodes of lithium-ion batteries due to its high specific capacity of 645 mAh·g^-1 as well as low cost. Nevertheless, it suffers poor large volume expansion during the lithiation/delithiation processes, leading to the loss of electrical contact and rapid capacity fading. Herein, by using a facile one-step solvothermal method, SnS₂ nanoflower/graphene nanocomposites (SnS₂ NF/GNs) were prepared, where flower-like SnS₂ hierarchical nanostructures consisting of ultrathin nanoplates, are tightly enwrapped in graphene nanosheets. As anode materials for lithium-ion batteries, the SnS₂ NF/GNs electrode exhibit superior electrochemical performance, with a reversible capacity of 523 mAh·g^-1 after 200 charge-discharge cycles. The enhanced Li storage performance was attributed to the synergistic effect of SnS₂ and graphene. The SnS₂ NF can effectively accommodate the volume change and shorten Li⁺ diffusion distance, while graphene nanosheets can further alleviate the volume expansion of SnS₂ and improve the electronic conductivity.     

Shock-absorbing and failure mechanisms of WS2 and MoS2 nanoparticles with fullerene-like structures under shock wave pressure

The excellent shock-absorbing performance of WS2 and MoS2 nanoparticles with inorganic fullerene-like structures (IFs) under very high shock wave pressures of 25 GPa is described. The combined techniques of X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, thermal analysis, and transmission electron microscopy have been used to evaluate the diverse, intriguing features of shock recovered IFs, of interest for their tribological applications, thereby allowing improved understanding of their antishock behavior and structure-property relationships. Two possible failure mechanisms are proposed and discussed. The supershock-absorbing ability of the IF-WS2 enables them to survive pressures up to 25 GPa accompanied with concurrent temperatures of up to 1000 degrees C without any significant structural degradation or phase change making them probably the strongest cage molecules now known.     

Inclusion-water-cluster in a three-dimensional superlattice of gold nanoparticles

Three-dimensional particle crystals made of dicarboxylic thiolate (MSA)-stabilized gold nanoparticles were formed at an air/water interface. FTIR spectra of this supracrystal showed that three well-resolved peaks existed from 3400 to 3550 cm-1 just falling in a region of OH stretching vibrational mode. Precise analysis showed that all these peaks originated from the water cluster included in the interstice of a particle crystal.     

Synthesis of iron nanoparticles: Size effects, shape control and organisation

Hydrogenation of bis(ditrimethylsilyl)amido iron complex, [Fe{N(SiMe₃)₂}₂], provides iron nanoparticles (NPs) which have been stabilised either by an organic polymer matrix or mixtures of long chain acid and amine ligands leading respectively to spherical nanoparticles of 1.8 nm size or nanocubes with edges of 7.2 or 8.4 nm. The 1.8 nm size NPs are magnetically independent. Their magnetisation is shown to be identical to that of clusters of the same size prepared and measured in UHV conditions, i.e. strongly increased as compared to bulk value. These NPs have been structurally characterised and display an original structure different from the classical bcc and fcc structures encountered in bulk iron. On the reverse iron nanocubes display a bcc structure and magnetic properties similar to those of bulk iron within experimental errors, in agreement with their larger size. These cubes crystallise into 3D superstructures.     

Advances in the synthesis of inorganic nanotubes and fullerene-like nanoparticles

In analogy to graphite, nanoparticles of inorganic compounds with lamellar two-dimensional structure, such as MoS(2), are not stable against folding, and can adopt nanotubular and fullerene-like structures, nicknamed inorganic fullerenes or IF. Various applications for such nanomaterials were proposed. For instance, IF-WS(2) nanoparticles were shown to have beneficial effects as solid lubricants and as part of tribological surfaces. Further applications of IF for high-tensile-strength fibers, hydrogen storage, rechargeable batteries, catalysis, and in nanotechnology are being contemplated. This Minireview highlights some of the latest developments in the synthesis of inorganic nanotubes and fullerene-like structures. Some structural aspects and properties of IF, which are distinct from the bulk materials, are briefly discussed.     

Magnetic nanoparticles with hybrid shape

Co₅₀Ni₅₀ particles with very unusual shapes, resembling dumbbells or diabolos, are obtained by reducing mixtures of cobalt and nickel acetates in sodium hydroxide solution in 1,2-propane diol. These particles consist of a central column richer in cobalt than the overall composition, capped with two terminal platelets that are richer in nickel. These hybrid shapes are the result of a two-step growth mechanism due to a difference in reactivity of the two metal ions. The sodium hydroxide concentration controls the length and diameter of the column, in the ranges 50–250 nm and 5–15 nm, respectively, and the diameter of the platelets in the range 25–50 nm. The X-ray diffraction patterns show a mixture of hcp and fcc phases in various proportions depending on the particle shape. High-resolution electron microscopy shows that the hcp phase is located mainly in the central column and the fcc phase mainly in the terminal platelets. The particles are ferromagnetic at room temperature. When the volume fraction of the central column is high enough and the hcp phase is predominant and not much faulted, high coercivity (up to 1900 Oe) is observed.     

Introducing sulfur vacancies and in-plane SnS2/SnO2 heterojunction in SnS2 nanosheets to promote photocatalytic activity

Due to the relatively sluggish charge carrier separation in metal sulfides, the photocatalytic activity of them is still far lower than expected. Herein, sulfur vacancies and in-plane SnS₂/SnO₂ heterojunction were successfully introduced into the SnS₂ nanosheets through high energy ball-milling. These defective structures were studied by the electron paramagnetic resonance, Raman spectra, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscope analyses. The sulfur vacancies and in-plane heterojunctions strongly accelerate the separation of photoexcited electron-hole pairs, as confirmed by the photoluminescence emission spectra and time-resolved photoluminescence decay spectra. The introduction of sulfur vacancies and in-plane heterojunction in SnS₂ nanosheets results in roughly six times higher photodegrading rate for methyl orange and four times higher photocatalytic reduction rate of Cr⁶⁺ than those of pure SnS₂ nanosheets.     

Synthesis and characterization of polyhedral Pt nanoparticles: their catalytic property, surface attachment, self-aggregation and assembly

In this paper, we presented the preparation procedure of Pt nanoparticles with the well-controlled polyhedral morphology and size by a modified polyol method using AgNO(3) in accordance with the reduction of H(2)PtCl(6) in EG at high temperature around 160°C. The methods of UV-vis spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), and high resolution (HR) TEM measurements were used to characterize their surface morphology, size, and crystal structure. We have observed that the polyhedral Pt nanoparticles of sharp edges and corners were produced in the preferential homogenous growth as well as the formation of porous and large Pt particles by self-aggregation and assembly originating from as-prepared polyhedral Pt nanoparticles. It is most impressive to find that the arrangement of Pt nanoparticles was observed in their surface attachments, self-aggregation, random and directed surface self-assembly by the bottom-up approach. Their high electrocatalytic activity for methanol oxidation was predicted. The findings and results showed that the polyhedral Pt nanoparticle-based catalysts exhibited the high electrocatalytic activity for their potential applications in developing the efficient Pt-based catalysts for direct methanol fuel cells.     

Synthesis of TiO2 nanoparticles using microorganisms

A low-cost green and reproducible microbes (Lactobacillus sp. and Sachharomyces cerevisae) mediated biosynthesis of TiO₂ nanoparticles is reported. The synthesis is performed akin to room temperature in the laboratory ambience. X-ray and transmission electron microscopy analyses are performed to ascertain the formation of TiO₂ nanoparticles. Individual nanoparticles as well as a few aggregate having the size of 8–35 nm are found. Concentric Scherrer rings in the selected area electron diffraction pattern indicated that the nanoparticles are having all possible orientations. A possible involved mechanism for the biosynthesis of nano-TiO₂ has also been proposed in which pH as well as partial pressure of gaseous hydrogen (rH₂) or redox potential of the culture solution seems to play an important role in the process.     

Synthesis of self-assembled 3D flowerlike SnS2 nanostructures with enhanced lithium ion storage property

In this work, we reported a facile ethanol solvothermal approach to fabricate highly dispersive 3D flowerlike SnS₂ architectures. The effects of synthetic conditions, such as the solvent system and the concentration of thiourea, on the morphology of the products were investigated. A possible growth mechanism for the formation of 3D flowerlike architectures was preliminarily propounded on the basis of the evolution of the structure and the morphology with increasing the reaction time. As anode materials of rechargeable Li-ion batteries, the as-prepared flowerlike SnS₂ structures exhibited exceptional good electrochemical properties, which revealed a higher reversible capacity about 502 mA h g^?1 and more stable cyclic retention at 50th cycle than the as-prepared SnS₂ nanoplates. The reasons for the improved electrochemical performance of the flowerlike structures have been proposed. All the results demonstrated that they were potential anode materials in Li-ion batteries.     

Synthesis of spherical silver nanoparticles by digestive ripening, stabilization with various agents, and their 3-D and 2-D superlattice formation

Capped nanoparticles of silver were synthesized via the solvated metal atom dispersion (SMAD) technique followed by a digestive ripening procedure producing gram quantities of monodisperse spherical nanoparticles. This shows for the first time that a digestive ripening protocol is possible for an element other than gold. The particle size and optical spectra were found to be dependent on the capping agent used. Particles capped with dodecane thiol had a mean diameter of 6.6+/-1 nm, while trioctyl phosphine capped particles were 6.0+/-2 nm determined via TEM microscopy. These particles were found to organize into two- and three-dimensional superlattices with a well defined geometry through self-assembly in a liquid solution, that was dictated by the ligand used resulting in a triangular or circular lattice.     

First-principles studies of SnS2 nanotubes: a potential semiconductor nanowire

First principles calculations are used to predict the stability and electronic structures of SnS(2) nanotubes. Optimization of several structures and their corresponding strain energies confirm the stability of SnS(2) nanotube structures. Band structure calculations show that SnS(2) nanotubes could have moderate band gaps regardless of their chirality. It suggests that SnS(2) nanotubes would be well-suited to use as semiconductor wires in nanoelectronic devices if they are synthesized. Adsorption of NH(3) onto SnS(2) is also investigated and discussed with regard to potential sensor application.     

Electronic states of SnS and SnS+: a configuration interaction study

Ab initio based multireference configuration interaction calculations are carried out for SnS and its monopositive ion using effective core potentials. Potential energy curves and spectroscopic constants of the low-lying states of SnS and SnS+ are computed. The ground-state dissociation energies of the neutral and ionic species are about 4.71 and 2.86 eV, respectively which compare well with the available thermochemical data. The effect of d-electron correlation on the spectroscopic constants of a few low-lying states has been studied. The spin-orbit interaction has also been included to investigate its effect on the spectroscopic properties of both SnS and SnS+. Dipole moment and transition moment curves are also constructed as a function of the bond length. Transition probabilities of some dipole-allowed and spin-forbidden transitions are studied. Radiative lifetimes of a few low-lying states are estimated. The E1sigma+-X1sigma+ transition of SnS is predicted to be the strongest one. The components of the A2sigma(+)(1/2)-X2(2)pi(1/2) transition with parallel and perpendicular polarization are separately analyzed. The vertical ionization energies of the ground-state SnS to the ground and low-lying excited states of the monopositive ion are calculated.     

Synthesis of vertically aligned carbon nanotube arrays on polyhedral Fe/Al2O3 catalysts

Polyhedral Fe/Al(2)O(3) catalysts prepared by an impregnation method were used for the synthesis of vertically aligned carbon nanotube (CNT) arrays from the pyrolysis of ethylene at 800 °C.     

Lattice Distortion in Hollow Multi-Shelled Structures for Efficient Visible-Light CO2 Reduction with a SnS2/SnO2 Junction

Precise control of the micro-/nanostructures of nanomaterials, such as hollow multi-shelled structures (HoMSs), has shown its great advantages in various applications. Now, the crystal structure of building blocks of HoMSs are controlled by introducing the lattice distortion in HoMSs, for the first time. The lattice distortion located at the nanoscale interface of SnS₂/SnO₂ can provide additional active sites, which not only provide the catalytic activity under visible light but also improve the separation of photoexcited electron–hole pairs. Combined with the efficient light utilization, the natural advantage of HoMSs, a record catalytic activity was achieved in solid–gas system for CO₂ reduction, with an excellent stability and 100 % CO selectivity without using any sensitizers or noble metals.