One-step synthesis of stoichiometrically defined metal oxide nanoparticles at room temperature

A great variety of metal oxide nanoparticles have been readily synthesized by using alkali metal oxides, M(2)O (M is Na or Li) and soluble metal salts (metal chlorides) in polar organic solutions, for example, methanol and ethanol, at room temperature. The oxidation states of the metals in the resulting metal oxides (Cu(2)O, CuO, ZnO, Al(2)O(3), Fe(2)O(3), Bi(2)O(3), TiO(2), SnO(2), CeO(2), Nb(2)O(5), WO(3), and CoFe(2)O(4)) range from 1 to 6 and remain invariable through the reactions where good control of stoichiometry is achieved. Metal oxide nanoparticles are 1-30 nm and have good monodispersivity and displayed comparable optical spectra. These syntheses are based on a general ion reaction pathway during which the precipitate occurs when O(2-) ions meet metal cations (M(n+)) in anhydrous solution and the reaction equation is M(n+) + n/2 O(2-) --> MO(n/2) (n=1-6).     

Rapid green synthesis of gold nanoparticles using Rosa hybrida petal extract at room temperature

This study reports a green method for the synthesis of gold nanoparticles using the aqueous extract of rose petals. The effects of gold salt concentration, extract concentration and extract quantity were investigated on nanoparticles synthesis. Gold nanoparticles were characterized with different techniques such as UV-vis spectroscopy, FT-IR spectroscopy, X-ray diffraction, energy dispersive X-ray spectroscopy, dynamic light scattering and transmission electron microscopy. Transmission electron microscopy experiments showed that these nanoparticles are formed with various shapes. FT-IR spectroscopy revealed that gold nanoparticles were functionalized with biomolecules that have primary amine group (-NH2), carbonyl group, -OH groups and other stabilizing functional groups. X-ray diffraction pattern showed high purity and face centered cubic structure of gold nanoparticles. Dynamic light scattering technique was used for particle size measurement, and it was found to be about 10nm. The rate of the reaction was high and it was completed within 5 min.     

Facile synthesis of PbTe nanoparticles and thin films in alkaline aqueous solution at room temperature

A novel, simple, and cost-effective route to PbTe nanoparticles and films is reported in this paper. The PbTe nanoparticles and films are fabricated by a chemical bath method, at room temperature and ambient pressure, using conventional chemicals as starting materials. The average grain size of the nanoparticles collected at the bottom of the bath is ∼25 nm. The film deposited on glass substrate is dense, smooth, and uniform with silver gray metallic luster. The film exhibits p-type conduction and has a moderate Seebeck coefficient value (∼147 μV K⁻¹) and low electrical conductivity (∼0.017 S cm⁻¹). The formation mechanism of the PbTe nanoparticles and films is proposed.     

Photodegradation of 2-nitrophenol catalyzed by CoO, CoS and CoO/CoS nanoparticles

The nanoparticles of CoO, CoS and CoO/CoS composite are synthesized using precipitation method. The X-ray diffraction, UV–Vis absorption spectroscopy, energy dispersive X-ray spectroscopy, scanning electron microscopy and FT-IR spectroscopy are used to characterize the prepared nanoparticles. The EDX analysis shows the formation of CoO_0.67S_0.33 composite. The XRD pattern indicates the hexagonal structure for nanocomposite. The formation of Co–O and Co–S bonds is confirmed by FT-IR spectra. The band-gap energies of 2.97, 3.06 and 2.91 eV are obtained from UV–Vis spectra of CoO, CoS and CoO/CoS nanoparticles, respectively. The results of photodegradation of 2-nitrophenol show that the photoreactivity order of nanocatalysts is CoO/CoS > CoO > CoS. The pseudo first-order kinetic rate constants of 6.4 × 10^?3, 4.3 × 10^?3 and 12.2 × 10^?3 min^?1 are obtained for CoO, CoS and CoO/CoS nanoparticles, respectively, at photodegradation reaction conditions of pH 10, 30 mg/L of 2-NP and 1.3 g/L of the catalyst. The proposed nanocomposite shows an acceptable reusability and stability against photocorrosion in four-cycle photodegradation experiments.     

Reversible photoswitching of ferromagnetic FePt nanoparticles at room temperature

There has been a great interest in developing photoswitchable magnetic materials because of their possible applications for future high-density information storage media. In fact, however, the examples reported so far did not show ferromagnetic behavior at room temperature. From the viewpoint of their practical application to magnetic recording systems, the ability to fix their magnetic moments such that they still exhibit room-temperature ferromagnetism is an absolute requirement. Here, we have designed reversible photoswitchable ferromagnetic FePt nanoparticles whose surfaces were coated with azobenzene-derivatized ligands. On the surfaces of core particles, reversible photoisomerization of azobenzene in the solid state was realized by using spacer ligands that provide sufficient free volume. These photoisomerizations brought about changes in the electrostatic field around the core-FePt nanoparticles. As a result, we have succeeded in controlling the magnetic properties of these ferromagnetic composite nanoparticles by alternating the photoillumination in the solid state at room temperature.     

One-pot, large-scale synthesis of SnO2 nanotubes at room temperature

SnO(2) nanotubes were synthesized via a one-pot redox route at room temperature, in which the Kirkendall effect is definitely responsible for the formation of hollow structures.     

Peptide synthesis in room temperature ionic liquids

We demonstrate that chemical peptide coupling using modern coupling agents is efficient in rt ionic liquids. This new approach presents some advantages, especially in the case of hindered amino acids, which are not easy to couple under standard conditions, since high purities for the crude peptides were observed with respect to coupling in classical solvents.     

A novel one step synthesis of silver nanoparticles using room temperature ionic liquid and their biocidal activity

This article reports the synthesis of silver Nan particles (SNPs) using 1-(dodecyl) 2 amino-pyridinium bromide ionic liquid. This is a new one phase method for the synthesis of uniform monodispersed crystalline silver nanoparticles in a water-ionic liquid system. In this work, the functionalized room temperature IL acts as stabilizing agent and solvent. Hydrazine hydrate acts as reducing agent. To the best of our knowledge, there is no report of the synthesis of metal nanoparticles using this ionic liquid. The synthesis of silver nanoparticles is very primarily studied by UV-Visible spectroscopic analysis. The TEM and particle size distribution was used to study morphology and size of the particles. The charge on synthesized SNPs was determined by Zeta potential. The silver nanoparticles have been known to have inhibitory and bactericidal effect. The investigation of antibacterial activities of ionic liquid stabilized silver nanoparticles was performed by measurement of the minimum inhibitory concentration.     

Green synthesis of water-dispersible silver nanoparticles at room temperature using green carambola (star fruit) extract

Journal of Sol-Gel Science and Technology - Silver nanoparticles (AgNPs) dispersible in water were synthesized at room temperature in the presence of carambola fruit extract at different pH. The...     

Observation of enhanced room temperature multiferroicity in nanoparticles BiFeO3

Impurity free monophasic rhombohedral BiFeO₃ (BFO) nanoparticles are synthesized by sol?Cgel method. Effect of processing technique and particle size are found to influence the dielectric, ferroelectric, magnetic and leakage behavior of BFO ceramic prepared by sol?Cgel as well as conventional solid state reaction route. From XRD analysis it is observed that bulk BFO sample showed rhombohedral structure (R3c) along with other impurity phases, which become suppressed with the decrease of particles size to few nanometers. The dielectric behavior and leakage current characteristic of the samples were improved significantly in nanoparticles of BFO. Ferroelectric hysteresis loops of sintered bulk BFO ceramic is found to change its shape from semi elliptical lossy P?CE features to a typical ferroelectric feature with improved remnant and saturation polarization value for the particle size down to nanometer scale. Furthermore, BFO nanoparticles also showed a good ferromagnetic M?CH hysteresis loop with enhanced saturation magnetization value of 0.138?emu/mg.     

Low temperature synthesis of zinc ferrite nanoparticles

Zinc ferrite (ZnFe₂O₄) nanocrystalline powder materials with various particle sizes were prepared by a unique solid-state combustion method. Phase purity of ZnFe₂O₄ was confirmed by X-ray diffraction studies. High resolution transmission electron microscopic analysis and selected area diffraction pattern also confirmed the correct crystalline phase formation. Particle size was determined from both the transmission electron microscopic images and also from the XRD peak broadening analysis. Oxidation states of different elements present in ZnFe₂O₄ were determined by X-ray photoelectron spectroscopy. Frequency dependent dielectric constant and a.c. conductivity were measured as a function of particle size and both of them were found to decrease with decreasing particle size. These studies indicated that good quality zinc ferrite nanocrystalline powdered materials can be synthesized at low temperature.     

Room temperature synthesis of surface-functionalised boron nanoparticles

Capped boron nanoparticles have been synthesized at room temperature by a simple route that does not involve the use of flammable boranes.     

Nickel-catalyzed synthesis of aryl trifluoromethyl sulfides at room temperature

Inexpensive nickel-bipyridine complexes were found to be active for the trifluoromethylthiolation of aryl iodides and aryl bromides at room temperature using the convenient [NMe(4)][SCF(3)] reagent.     

Rapid room temperature synthesis of electrocatalytically active Au nanostructures

We describe a facile route for the one-pot room temperature synthesis of anisotropic Au nanostructures in aqueous solution in the absence of seeds or surfactants and their electrocatalytic activity. The Au nanostructures were synthesized using piperazine derivatives 1-(2-hydroxyethyl)piperazine and 1,4-Bis(2-hydroxyethyl)piperazine as reducing agents. The Au nanostructures were characterized by spectral, transmission electron microscopic (TEM), X-ray diffraction and electrochemical measurements. The absorption spectrum of colloidal nanoparticles displays two bands ~580 and ~930 nm, corresponding to the dipole and quadrupole plasmon resonance, respectively. TEM measurements show that the Au nanostructures have penta-twined polyhedral shape with an average size of 52 nm. X-ray and selected area electron diffraction patterns reveal the existence of face centered cubic nanocrystalline Au. The concentration of Au(III) controls the stability of the nanoparticles. The nanoparticles were immobilized on 3-D silicate network pre-assembled on a conducting support to examine their electrocatalytic activity. The nanoparticle-based electrochemical interface was characterized by spectral, voltammetric and impedance measurements. The nanoparticle shows high catalytic activity in the oxidation of NADH and reduction of oxygen. Unique inverted 'V' shape voltammogram was obtained for the oxidation of NADH at less positive potential. The nanoparticle-based interface favors two-step four-electron reduction of oxygen to water in neutral pH. Significant decrease in the overpotential for the oxidation of NADH and reduction of oxygen with respect to the polycrystalline Au electrode was observed. The electrocatalytic performance of the polyhedral nanoparticle is compared with the conventional citrate stabilized spherical nanoparticles.     

Shape-controllable synthesis of dendritic silver nanostructures at room temperature

In this communication, we demonstrated a simple chemical approach for preparing dendritic silver nanostructures by mixing AgNO₃ aqueous and o-phenylenediamine in the presence of NaCl solutions at room temperature. o-Phenylenediamine was found to act as a stabilizer as well as a reduction agent. Asformed silver dendrites were examined by scanning electron microscopy, energy dispersive spectrometry, X-ray diffraction, and Fourier transform infrared spectroscopy techniques. We found that the concentration of NaCl strongly influenced the shape of silver structures. The forming AgCl serve as efficient etchant and also produces single-crystal seeds. The possible formation mechanism is also discussed.     

Surfactant-assisted synthesis,characterizations, and room temperature ammonia sensing mechanism of nanocrystalline CuO

CuO nanocrystalline powder has been synthesized by a sol?gel auto combustion route with cetyltrimethylammonium bromide (CTAB) as cationic surfactant, and sodium dodecyl sulphate (SDS) as anionic surfactant. The powder samples are characterized by TGA/DTA, XRD, FESEM, and TEM techniques. Thermal analysis of the dried gel samples shows that addition of surfactant in the precursor increases the heat of reaction, which is evolved in the decomposition of metal citrate complex. The CTAB and SDS addition in the reaction mixture lowers the average crystallite size to few tens of nanometer. Surfactant doping in precursor causes a variation in lattice strain and changes to its type to compressive. CuO nanoparticles are bound together into facets–like weakly aggregated clusters, as indicated by FESEM images. TEM micrographs indicate the porous, nearly spherical particles having crystallite size around 7 and 18 nm for CTAB and SDS surfactant assisted CuO samples respectively. CuO nanoparticles assembled as thick film have been tested for their response to 100 ppm ammonia gas at room temperature. Cationic surfactant assisted sample shows maximum response to ammonia as compared to anionic surfactant. The CTAB assisted sensor shows almost completes recovery in 500 s whereas SDS assisted sample shows 75% recovery in the same time. The ammonia response of the films obeys the Elovich equation. The response rate of sensor is found to be maximum for CTAB assisted CuO films as compared to other samples. The kinetics of the response reaction shows that the ionic surfactants assisted CuO follows second order reaction kinetics.     

Preparation and characterization of polyvinyl alcohol-capped CdSe nanoparticles at room temperature

Polyvinyl alcohol (PVA)-capped CdSe nanoparticles were successfully prepared by a one-step solution growth technique at room temperature and ambient pressure. X-ray diffraction, transmission electron microscopy, infrared spectra, and X-ray photoelectron spectra were used to characterize the final product. The as-prepared CdSe nanocrystals were well dispersed and uniform in shape and the diameter of the particles was confined within 8 nm. Ultraviolet-visible absorption spectra were used to study the confined growth process of PVA-capped CdSe nanoparticles. Photoluminescence measurement showed the near band-edge luminescence of the final product.     

The design and investigation of room temperature thermotropic nematic gold nanoparticles

Nematic gold nanoparticles, covered with a monolayer of calamitic mesogens and short hydrocarbon chains, have been synthesized and investigated. The materials are chemically stable and exhibit nematic phase behavior at room temperature.     

Microwave-assisted one-step hydrothermal synthesis of pure iron oxide nanoparticles: magnetite, maghemite and hematite

A simple, rapid, one-step synthesis way of pure iron oxide nanoparticles: magnetite (Fe₃O₄), maghemite (γ-Fe₂O₃) and hematite (α-Fe₂O₃) was investigated. Nanoparticles were prepared by microwave synthesis, from ethanol/water solutions of chloride salts of iron (FeCl₂ and FeCl₃) in the presence of sodium hydroxide NaOH. X-ray powder diffraction (XRD), Transmission Electron Microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) were used to characterize these nanoparticles.