Optimization of the ultrasound-assisted synthesis of allyl 1-naphthyl ether using response surface methodology

Allyl 1-naphthyl ethers are useful compounds for different purposes, but reported methods to synthesize them require long reaction times. In this work, we have obtained allyl 1-naphthyl ether in good yield using ultrasonic-assisted methodology in a 1-h reaction. A central composite design was used to obtain a statistical model and a response surface (p < 0.05; R(2) = 0.970; R(adj)(2) = 0.949; R(pred)(2) = 0.818) that can predict the optimal conditions to maximize the yield, validated experimentally. (C) 2010 Elsevier B.V. All rights reserved.

Ultrasound-assisted synthesis of aliphatic acid esters at room temperature

This work describes the ultrasound-assisted synthesis of saturated aliphatic esters from synthetic aliphatic acids and either methanol or ethanol. The products were isolated in good yields after short reaction times under mild conditions. (C) 2011 Elsevier BM. All rights reserved.

Ultrasound-assisted green synthesis of nanocrystalline ZnO in the ionic liquid [hmim][NTf2]

For the first time, zinc oxide nanoparticles have been synthesized by the sonochemical method in an ionic liquid, 1-hexyl-3-methylimidazolium his (trifluoromethylsulfonyl) imide, liquid [hmim][NTf2] as a solvent. The morphology and structure of ZnO nanoparticles have been characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). A possible mechanism is proposed to explain the formation of ZnO nanostructures. (C) 2008 Elsevier B.V. All rights reserved.

Effects of Ultrasound Irradiation on the Synthesis of Metal Oxide Nanostructures

High intensity ultrasound can be used for the production of novel nanomaterials, including metal oxides. According to previous works in this field, the most notable effects are consequence of acoustic cavitation. In this context, we have studied the preparation of different materials in the presence of ultrasound, including N-doped TiO2 nanopowder, NiTiO3 nanorods and MnOx thin films. Ultrasound did not show a significant effect in all the cases. Exclusively for NiTiO3 nanorods a reduction of the final particle size occurs upon ultrasonic irradiation. From these results, it can be concluded that the ultrasound irradiation does not always play a key role during the synthesis of metal oxides. The effects seem to be particularly relevant in those cases where mass transport is highly hindered and in those procedures that require the rupture of nanoparticle aggregates to obtain a homogenous dispersion.

Rapid microwave-assisted synthesis of Mn3O4–graphene nanocomposite and its lithium storage properties

A nanocomposite of Mn3O4 wrapped in graphene sheets (GSs) was successfully synthesized via a facile, effective, energy-saving, and scalable microwave hydrothermal technique. The morphology and microstructures of the fabricated GS–Mn3O4 nanocomposite were characterized using various techniques. The results indicate that the particle size of the Mn3O4 particles in the nanocomposite markedly decreased to nearly 20 nm, significantly smaller than that for the bare Mn3O4. Electrochemical measurements demonstrated a high specific capacity of more than 900 mA h g−1 at 40 mA g−1, and excellent cycling stability with no capacity decay can be observed up to 50 cycles. All of these properties are also interpreted by experimental studies and theoretical calculations.

Single-step, catalyst-free plasma-assisted synthesis and growth mechanism of single-crystalline aluminum nitride nanorods

Synthesis of one-dimensional AlN nanostructures commonly requires high process temperatures (>900 °C), metal catalyst, and hazardous gas/powder precursors. We report on a simple, single-step, catalyst-free, plasma-assisted growth of dense patterns of size-uniform single-crystalline AlN nanorods at a low substrate temperature (∼650 °C) without any catalyst or hazardous precursors. This unusual growth mechanism is based on highly effective plasma dissociation of N2 molecules, localized species precipitation on AlN islands, and reduced diffusion on the nitrogen-rich surface. This approach can also be used to produce other high-aspect-ratio oxide and nitride nanostructures for applications in energy conversion, sensing, and optoelectronics. © 2010 American Institute of Physics.

Polyacrylic Acid Assisted Synthesis of Cu2ZnSnS4 by Hydrothermal Method

Pure phase Cu2ZnSnS4 (CZTS) nanoparticles were successfully synthesized via polyacrylic acid (PAA) assisted one-pot hydrothermal route. The morphology, crystal structure, composition and optical properties as well as the photoactivity of the as-synthesized CZTS nanoparticles were characterized by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectrometer, UV-visible absorption spectroscopy and photoelectrochemical measurement. The influence of various synthetic conditions, such as the reaction temperature, reaction duration and the amount of PAA in the precursor solution on the formation of CZTS compound was systematically investigated. The results have shown that the crystal phase, morphology and particle size of CZTS can be tailored by controlling the reaction conditions. The formation mechanism of CZTS in the hydrothermal reaction has been proposed based on the investigation of time-dependent phase evolution of CZTS which showed that metal sulfides (e.g., Cu2S, SnS2 and ZnS) were formed firstly during the hydrothermal reaction before forming CZTS compound through nucleation. The band gap of the as-synthesized CZTS nanoparticles is 1.49 eV. The thin film electrode based on the synthesized CZTS nanoparticles in a three-electrode photoelectrochemical cell generated pronounced photocurrent under illumination provided by a red light-emitting diode (LED, 627 nm), indicating the photoactivity of the semiconductor material.

Ultrasound-assisted surface engineering of pharmaceutical powders

Effective processing of powdered particles can facilitate powder handling and result in better drug product performance, which is of great importance in the pharmaceutical industry where the majority of active pharmaceutical ingredients (APIs) are delivered as solid dosage forms. The purpose of this work was to develop a new ultrasound-assisted method for particle surface modification and thin-coating of pharmaceutical powders. The ultrasound was used to produce an aqueous mist with or without a coating agent. By using the proposed technique, it was possible to decrease the interparticular interactions and improve rheological properties of poorly-flowing water-soluble powders by aqueous smoothing of the rough surfaces of irregular particles. In turn, hydrophilic polymer thin-coating of a hydrophobic substance diminished the triboelectrostatic charge transfer and improved the flowability of highly cohesive powder. To determine the coating efficiency of the technique, the bioactive molecule β-galactosidase was layered onto the surface of powdered lactose particles. Enzyme-treated materials were analysed by assaying the quantity of the reaction product generated during enzymatic cleavage of the milk sugar. A near-linear increase in the thickness of the drug layer was obtained during progressive treatment. Using the enzyme coating procedure, it was confirmed that the ultrasound-assisted technique is suitable for processing labile protein materials. In addition, this pre-treatment of milk sugar could be used to improve utilization of lactose-containing formulations for populations suffering from severe lactose intolerance. Furthermore, the applicability of the thin-coating technique for improving homogeneity of low-dose solid dosage forms was shown. The carrier particles coated with API gave rise to uniform distribution of the drug within the powder. The mixture remained homogeneous during further tabletting, whereas the reference physical powder mixture was subject to segregation. In conclusion, ultrasound-assisted surface engineering of pharmaceutical powders can be effective technology for improving formulation and performance of solid dosage forms such as dry powder inhalers (DPI) and direct compression products.

Microwave-Assisted Synthesis of NiO Nanoparticles

NiO has been synthesized by microwave-induced chemical synthesis route using metalorganic complex of nickel in a domestic-type microwave oven (2.45 GHz). A novel metalorganic complex of nickel, viz., a beta-ketoester of nickel, synthesized and characterized as apart of this work, was employed as the precursor material. We varied the experimental parameters, such as the choice of solvent and microwave power, to obtain nanoparticles of NiO. The NiO nanoparticles were characterized by XRD, SEM, and TEM. The particle size of the NiO was found to vary from 7-40 nm. The magnetic behavior of the nanoparticles of NiO was examined with a vibrating sample magnetometer, revealing that as the particle size diminishes, the magnetic ordering in NiO changes, leading to a small, measurable coercivity.

Elastic property estimation using Ultrasound Assisted Optical Elastography through Remote Palpation - A simulation study - art. no. 61640Q

We propose an effective elastography technique in which an acoustic radiation force is used for remote palpation to generate localized tissue displacements, which are directly correlated to localized variations of tissue stiffness and are measured using a light probe in the same direction of ultrasound propagation. The experimental geometry has provision to input light beam along the ultrasound propagation direction, and hence it can be prealigned to ensure proper interception of the focal region by the light beam. Tissue-mimicking phantoms with homogeneous and isotropic mechanical properties of normal and malignant breast tissue are considered for the study. Each phantom is insonified by a focusing ultrasound transducer (1 MHz). The focal volume of the transducer and the ultrasound radiation force in the region are estimated through solving acoustic wave propagation through medium assuming average acoustic properties. The forward elastography problem is solved for the region of insonification assuming the Lame's parameters and Poisson's ratio, under Dirichlet boundary conditions which gives a distribution of displacement vectors. The direction of displacement, though presented spatial variation, is predominantly towards the ultrasound propagation direction. Using Monte Carlo (MC) simulation we have traced the photons through the phantom and collected the photons arriving at the detector on the boundary of the object in the direction of ultrasound. The intensity correlations are then computed from detected photons. The intensity correlation function computed through MC simulation showed a modulation whose strength is found to be proportional to the amplitude of displacement and inversely related to the storage (elastic) modulus. It is observed that when the storage modulus in the focal region is increased the computed displacement magnitude, as indicated by the depth of modulation in the intensity autocorrelation, decreased and the trend is approximately exponential.

Hydrogel-assisted synthesis of nanotubes and nanorods of US, ZnS and CuS, showing some evidence for oriented attachment

By carrying out the reaction of appropriate metal compounds with Na2S in the presence of a tripodal cholamide-based hydrogel, nanotubes and nanorods of CdS, ZnS and CuS have been obtained. The nanostructures have been characterized by transmission electron microscopy and spectroscopic techniques. Evidence is presented for the assembly of short nanorods to form one-dimensional chains.

Microwave Assisted Synthesis of Nanostructured Titanium Dioxide with High Photocatalytic Activity

TiO2 (anatase) was synthesized using a microwave-irradiation-assisted chemical method. The reaction conditions were varied to obtain unique nanostructures of TiO2 comprising nanometric spheres giving the materials a very porous morphology. The oxide was characterized by X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy, and thermogravimetric analysis (TGA). The specific surface area and porosity were quantified by the BET method, and the degradation of dyes was carried out using these materials. The photocatalytic activity of the nanometric TiO2 was significantly higher than that of commercially available TiO2 (Degussa P25) for the degradation of the dyes.

Microwave assisted synthesis and UV-Vis spectroscopic studies of silver nanoparticles synthesized using vanillin as a reducing agent

The present investigation explores the adaptability of a microwave assisted route to obtain silver nanoparticles by the reduction of AgNO3 with vanillin, an environmentally benign material. Anionic surfactants such as AOT and SDS were used separately for encapsulating AgNPs and their role was compared. The UV-Visible absorption spectra present a broad SPR band consisting of two peaks suggesting the formation of silver nanoparticle with bimodal size distribution. The TEM image shows particles with spherical and hexagonal morphologies which confirms the results of UV-Vis studies. The anisotropy in the particle morphology can be attributed to the surface oxidation which in turn produces Ag@Ag2O core-shell nanostructures. Thus an intriguing feature of this system is that the obtained colloid is a mixture of AgNPs with and without Ag2O layers. Studies on the influence of pH on the stability of the synthesized nanoparticles revealed that the presence of excess Ag2O layers has a profound influence on it. Ag2O layers can be removed from AgNPs' surface by changing the solution pH to the acidic regime. The present study attests the enhanced ability of AOT in stabilizing the AgNPs in aqueous media. (C) 2011 Elsevier B.V. All rights reserved.

Rapid microwave assisted synthesis of hydroxyapatite

A fast, efficient and novel method of preparation of hydroxyapatite using microwaves has been described.

Microwave Assisted Synthesis and Antimicrobial Study of Schiff Base Vanadium(IV) Complexes of Phenyl Esters of Amino Acids

Schiff base vanadium(IV) complexes of phenyl esters of the two acidic amino acids, i.e., aspartic and glutamic acid, were synthesized. The phenyl esters of these amino acids were synthesized by conventional method whereas the Schiff base vanadium(IV) complexes were synthesized using microwave irradiation. The complexes were characterized by spectroscopic tools such as IR, 1H NMR, mass (ES), ESR, and UV visible spectroscopy. All the complexes were studied for antibacterial and antifungal activity and found to be moderately active.