A general approach for transferring hydrophobic nanocrystals into water

Hydrophobic inorganic nanocrystals have been transferred from organic solvent to aqueous solution through a robust and general ligand exchange procedure. Polyelectrolytes such as poly(acrylic acid) and poly(allylamine) are used to replace the original hydrophobic ligands on the surface of nanocrystals at an elevated temperature in a glycol solvent and eventually render the nanocrystals highly water soluble. The physical properties of the nanocrystals, such as superparamagnetism, photocatalytic activity, and photoluminescence, are maintained or improved after ligand exchange.     

A facile and general approach to polynary semiconductor nanocrystals via a modified two-phase method

Cu(2)ZnSnS(4) nanocrystals were synthesized through a modified two-phase method and characterized with transmission electron microscopy (TEM), powder x-ray diffraction (XRD) and UV-vis spectroscopy. Inorganic metal salts were dissolved in the polar solvent triethylene glycol (TEG) and then transferred into the non-polar solvent 1-octadecene (ODE) by forming metal complexes between metal ions and octadecylamine (ODA). Since nucleation and growth occur in the single phase of the ODE solution, nanocrystals could be produced with qualities similar to those obtained through the hot-injection route. Balancing the reactivity of the metal precursors is a key factor in producing nanocrystals of a single crystalline phase. We found that increasing the reaction temperature increases the reactivity of each of the metal precursors by differing amounts, thus providing the necessary flexibility for obtaining a balanced reactivity that produces the desired product. The versatility of this synthesis strategy was demonstrated by extending it to the production of other polynary nanocrystals such as binary (CuS), ternary (CuInS(2)) and pentanary (Cu(2 - x)Ag(x)ZnSnS(4)) nanocrystals. This method is considered as a green synthesis route due to the use of inorganic metal salts as precursors, smaller amounts of coordinating solvent, shorter reaction time and simpler post-reaction treatment.     

Solubility enhancement of miconazole nitrate: binary and ternary mixture approach

Context: Enhancement of aqueous solubility of very slightly soluble Miconazole Nitrate (MN) is required to widen its application from topical formulation to oral/mucoadhesive formulations.

Objective: Aim of the present investigation was to enhance the aqueous solubility of MN using binary and ternary mixture approach.

Materials and methods: Binary mixtures such as solvent deposition, inclusion complexation and solid dispersion were adopted to enhance solubility using different polymers like lactose, beta-cyclodextrin (β-CD) and polyethylene-glycol 6000 (PEG 6000), respectively. Batches of binary mixtures with highest solubility enhancement potentials were further mixed to form ternary mixture by a simple kneading method. Drug polymer interaction and mixture morphology was studied using the Fourier transform infrared spectroscopy and the scanning electron microscopy, respectively along with their saturation solubility studies and drug release.

Results: An excellent solubility enhancement, i.e. up to 72 folds and 316 folds of MN was seen by binary and ternary mixture, respectively. Up to 99.5% drug was released in 2?h from the mixtures of MN and polymers.

Discussion: Results revealed that solubility enhancement by binary mixtures is achieved due to surface modification and by increasing wettability of MN. Tremendous increase in solubility of MN by ternary mixture could possibly be due to blending of water soluble polymers, i.e. lactose and PEG 6000 with β-CD which was found to enhance the solubilizing nature of β-CD.

Conclusion: Owing to the excellent solubility enhancement potential of ternary mixtures in enhancing MN solubility from 110.4?μg/ml to 57?640.0?μg/ml, ternary mixture approach could prove to be promising in the development of oral/mucoadhesive formulations.     

A mechanochemical approach to manufacturing bamboo cellulose nanocrystals

Bamboo cellulose nanocrystals (BCNC) were manufactured via a mechanochemical approach with the dissolving action of phosphoric acid on cellulose. The effects of phosphoric acid concentration, reaction time, reaction temperature, and ultrasonication time on the yield of BCNC were investigated. Micromorphology and microstructure of BCNC were studied using scanning electron microscopy and transmission electron microscopy. Results showed that BCNC were short rod-like particles with 100–200 nm in length and 15–30 nm in width, forming an interconnected network structure. X-ray diffraction results indicated that the crystalline structure of BCNC transformed from cellulose I to cellulose II, compared to cellulose pulp, with the crystallinity index declining from 66.44 to 59.62 %. The thermal properties of BCNC were investigated by thermogravimetric analysis and revealed that BCNC exhibited lower thermal stability compared to cellulose pulp. This research work provides a low-cost approach and mild operating conditions to manufacturing BCNC.     

A low temperature composite-hydroxide approach to NiO nanocrystals

Nanocrystalline NiO has been successfully synthesized via a low temperature molten composite hydroxide route using nickel chloride hydrate as nickel source. The as-obtained oxide nanocrystals were characterized by X-ray powder diffraction and transmission electronic microscopy. It is found that the ratio of reagent to molten solvent has a great influence on the quality of the products. The effect of temperature and time was also investigated. The present route may have a good prospect to prepare many functional nanomaterials.     

A novel approach to synthesis of high-dispersed anatase titania nanocrystals

A novel approach was employed in the synthesis of high-dispersed anatase titania (TiO₂) nanocrystals by sol–gel process with NH₄NO₃ (AN) as solid substrates. Further calcination was conducted after the hydrous TiO₂ nanoparticles were adsorbed onto the surface of AN particles. The products were investigated by TGA, XRD, and TEM. The results indicated that AN was melting and decomposing during the calcining process, which was very important to inhibit the agglomeration of anatase TiO₂ nanocrystals. The highly dispersed anatase TiO₂ nanocrystals were in needle-shape having lengths about 16–20 nm and diameter of 6–9 nm.     

A general approach to monodisperse perovskite microspheres

BaTiO₃, PbTiO₃, SrTiO₃, and Pb(Zr,Ti)O₃ microspheres with uniform size and narrow size distribution have been successfully synthesized by a novel hydrothermal and annealing approach. In this approach, the chemical reaction and crystallization process of the ABO₃ perovskite oxides were separated in two steps. Spherical particles containing the B-site ions were obtained first via a controlled hydrolysis and aging process. Then, during hydrothermal treatment, the A-site ions were incorporated in situ into the microspheres to form amorphous perovskite microspheres. The particles were further crystallized with preserved spherical morphology under subsequent annealing treatment. The BET surface areas of the TiO₂ gel particles, the amorphous PbTiO₃ and the as-annealed PbTiO₃ microspheres were 245.7 m²/g, 41.67 m²/g and 4.53 m²/g, respectively, showing a significant change of the surface feature in the preparation process. This approach also allowed the microspheres diameters to be manipulated from 100 nm to 1500 nm in a controlled manner. Most of the microspheres were composed by closely packed nano-sized particles. Furthermore, the Pb(Zr,Ti)O₃ microspheres with an average diameter of 200 nm exhibited single crystal features, indicating highly oriented growth in the crystallization process. The microspheres were very stable, and still maintained spherical shape after higher temperature calcination.     

A first-principles thermodynamic approach to ordering in binary alloys

The communication reviews the augmented space based approaches to thermodynamics and ordering of binary alloys. We give several examples of metallic alloys to illustrate our methodology.     

A hybrid approach to multi-scale modelling of cancer

In this paper, we review multi-scale models of solid tumour growth and discuss a middle-out framework that tracks individual cells. By focusing on the cellular dynamics of a healthy colorectal crypt and its invasion by mutant, cancerous cells, we compare a cell-centre, a cell-vertex and a continuum model of cell proliferation and movement. All models reproduce the basic features of a healthy crypt: cells proliferate near the crypt base, they migrate upwards and are sloughed off near the top. The models are used to establish conditions under which mutant cells are able to colonize the crypt either by top-down or by bottom-up invasion. While the continuum model is quicker and easier to implement, it can be difficult to relate system parameters to measurable biophysical quantities. Conversely, the greater detail inherent in the multi-scale models means that experimentally derived parameters can be incorporated and, therefore, these models offer greater scope for understanding normal and diseased crypts, for testing and identifying new therapeutic targets and for predicting their impacts.     

A hybrid GA-simulation approach to improve JIT systems

This study presents a hybrid approach involving genetic algorithms (GAs) as an optimisation search technique and a simulation model, representing the dynamic behaviour of a system and its limitations, to improve an existing just-in-time (JIT) manufacturing system. To achieve the objective, first, the existing system is modelled and simulated (by considering the system's limitations and its dynamic behaviour). Second, the integrated simulation model is tested and validated by analysis of variance. Third, the hybrid GA-simulation approach is used in an interactive manner to determine the optimal/near-optimal number of kanban cards in different stations of the existing JIT system. The presented hybrid approach is tested and applied to an auto industry production line. Furthermore, it is compared with the practical JIT through analysis of variance (ANOVA) and the results show improvements in the average daily production rate, the average resource utilisation and the average cycle time but some deterioration in the average queue length and in-process inventory is inevitable.     

The rare-earth doping of binary and ternary chalcogenides

Experimental evidence on the rare-earth doping of the IIVI compounds and a knowledge of the rare-earth chalcogenide structures is used to suggest a set of principles with which to predict the ultimate doping limit for the binary and ternary chalcogenides. The validity of these rules is tested by experiment.     

Superconductivity of some binary and ternary transition-metal borides

Superconducting transition temperatures of some binary transition-metal borides and a new series of ternary transition-metal borides are reported. The variation of T_C vs electron/atom ratio and the crystal chemical behavior of the borides in relation to their superconducting behavior are discussed.     

A hybrid approach to machine-tool selection through AHP and simulation

The selection process of a machine tool has been a critical issue for companies for years, because the improper selection of a machine tool might cause many problems having a negative effect on productivity, precision, flexibility, and a company's responsive manufacturing capabilities. Therefore, in this paper, to determine the best machine tool satisfying the needs and expectations of a manufacturing organization among a set of possible alternatives in the market, a hybrid approach is proposed, which integrates an analytic hierarchy process (AHP) with simulation techniques. The AHP as one of the most commonly used multiple criteria decision-making methods is used to narrow down all possible machine tool alternatives in the market by eliminating those whose scores (or weights) are smaller than a determined value obtained under certain circumstances. Then, a simulation generator is used first to automatically model a manufacturing organization, where the ultimate machine tool will be used, and second to try each alternative remaining from the AHP as a scenario on the generated model. Finally, the final alternative is selected by using the unit investment cost ratio, which is calculated by dividing the investment cost per year of each alternative by the additional number of produced units obtained from the simulation experiment of the relevant alternative.     

A general approach to conservation laws in viscoelasticity

Summary The equation of motion and the associated Lagrangian density of a linear viscoelastic solid are considered in terms of the Laplace transform of the displacement vector. A generalized form of Noether's theorem is applied where invariance is meant up to a divergence. Then a systematic approach is developed which allows the derivation of conservation laws with non-vanishing densities. As a preliminary application, new conservation laws are found and previous results are recovered.     

A general combustion approach to multipod ZnO and its characterization

By a general approach of combustion oxidation at high temperature, multipod ZnO was synthesized without any catalysts or additives. The morphology and optical properties of the multipod ZnO were studied in detail. The growth mechanism was discussed preliminarily. An ultraviolet (UV) emission peak at 374 nm and a broad green emission peak centered at 502 nm are observed in photoluminescence spectrum of the multipod ZnO. The multipod structure exhibits significant enhancement of UV emission intensity and green light emission intensity compared with the tetrapod structure, which are attributed to less structural defects and increased surface area respectively. Furthermore, compared with nano-particle and micro-particle ZnO, UV emission peak of multipod ZnO appears a slight blue shift. Due to slim tips of the legs, quantum size effect cause a slight blue shift of UV emission peak. We believe that these optical properties of the multipod structure have extensive applications in nanoscale optical devices.     

Shaping binary metal nanocrystals through epitaxial seeded growth

Morphological control of nanocrystals has become increasingly important, as many of their physical and chemical properties are highly shape dependent. Nanocrystal shape control for both single- and multiple-material systems, however, remains empirical and challenging. New methods need to be explored for the rational synthetic design of heterostructures with controlled morphology. Overgrowth of a different material on well-faceted seeds, for example, allows for the use of the defined seed morphology to control nucleation and growth of the secondary structure. Here, we have used highly faceted cubic Pt seeds to direct the epitaxial overgrowth of a secondary metal. We demonstrate this concept with lattice-matched Pd to produce conformal shape-controlled core-shell particles, and then extend it to lattice-mismatched Au to give anisotropic growth. Seeding with faceted nanocrystals may have significant potential towards the development of shape-controlled heterostructures with defined interfaces.     

Application of spark plasma sintering to the fabrication of binary and ternary skutterudites

Spark plasma sintering (SPS) synthesis of CoSb₃ and LaFe₄Sb₁₂ from ball-milled elemental metal powders has been performed obtaining samples with high relative densities (∼99%). Fracture behaviour, the microstructure and mechanical properties were studied. From ultrasound and nano-indentation measurements, Young's moduli of 148 GPa for CoSb₃ and 141 GPa for LaFe₄Sb₁₂ were deduced. SPS has been also applied to compact alkali metal and alkaline-earth metal iron antimonides with filled skutterudite structure.     

Magnetostriction of binary and ternary Fe–Ga alloys

This article will review the development of the Fe–Ga (Galfenol) alloy system for magnetostriction applications including work on substitutional ternary alloying additions for magnetic property enhancement. A majority of the alloying addition research has focused on substitutional ternary elements in Bridgman grown single crystals with the intent of improving the magnetostrictive capability of the Galfenol system. Single crystals provide the ideal vehicle to assess the effectiveness of the addition on the magnetostrictive properties by eliminating grain boundary effects, orientation variations, and grain-to-grain interactions that occur when polycrystals respond to applied magnetic fields. In almost all cases, ternary additions of transition metal elements have decreased the magnetostriction values from the binary Fe–Ga alloy. Most of the ternary additions are known to stabilize the D0₃ chemical order and could be a primary contribution to the observed reduction in magnetostriction. In contrast, both Sn and Al are found to substitute chemically for Ga. For Sn additions, whose solubility is limited, no reduction in magnetostriction strains are observed when compared to the equivalent binary alloy composition. Aluminum additions, whose effect on the magnetoelastic coupling on Fe is similar to Ga, result in a rule of mixture relationship. The reviewed research suggests that phase stabilization of the disordered bcc structure is a key component to increase the magnetostriction of Fe–Ga alloys.