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...     

Facile green synthesis of gold nanoparticles using leaf extract of antidiabetic potent Cassia auriculata

A simple biological method for the synthesis of gold nanoparticles (AuNPs) using Cassia auriculata aqueous leaf extract has been carried out in the present study. The reduction of auric chloride led to the formation of AuNPs within 10 min at room temperature (28°C), suggesting a higher reaction rate than chemical methods involved in the synthesis. The size, shape and elemental analysis were carried out using X-ray diffraction, TEM, SEM-EDAX, FT-IR and visible absorption spectroscopy. Stable, triangular and spherical crystalline AuNPs with well-defined dimensions of average size of 15-25 nm were synthesized using C. auriculata. Effect of pH was also studied to check the stability of AuNPs. The main aim of the investigation is to synthesize AuNPs using antidiabetic potent medicinal plant. The stabilizing and reducing molecules of nanoparticles may promote anti-hyperglycemic if tested further.     

聚甲基丙烯酸钠辅助的金纳米颗粒的绿色制备

利用聚甲基丙烯酸钠的弱还原性和螯合作用,建立了一种水溶性金纳米颗粒合成的新方法.借助紫外可见分光光度计和透射电子显微镜对金纳米颗粒进行了表征,初步讨论了反应物浓度以及反应温度对产物的影响.     

Pistacia integerrima gall extract mediated green synthesis of gold nanoparticles and their biological activities

This paper reports a rapid, facile and one-pot synthesis of environmentally safe gold nanoparticles capped and stabilized with galls extract of Pistacia integerrima. The aqueous gold ions when exposed to P. integerrima galls extract were rapidly reduced as evident from abrupt color change to ruby red, suggesting the biosynthesis of gold nanoparticles (Au-NPs) which were further characterized by UV–Vis spectroscopy, Fourier transform infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM). Their stability was evaluated against varying pH and different volumes of sodium chloride (NaCl) as well as at a range of temperature (20–80 °C). Au-NPs were tested for enzyme inhibition, antibacterial, antifungal, antinociceptive, muscle relaxant and sedative activities. The UV–Vis spectra of the gold nanoparticles gave surface plasmon resonance at 540 nm while the SEM analysis revealed the particle size in the range of 20–200 nm. FTIR spectra confirmed the involvement of amines, amide groups and alcohols in capping and reduction of gold nanoparticles. Au-NPs showed remarkable stability in different NaCl and pH solutions as well as at elevated temperature. Au-NPs have good antifungal activity and possessed antinociceptive and muscle relaxant properties as observed from their zone of inhibition and significant attenuation of acetic acid induced writhing and reduction of time spent on the rota rod respectively. These results concluded that the gall extract of P. integerrima is a very good bioreductant for the synthesis of gold nanoparticles that have potential for various biomedical and pharmaceutical applications.     

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).     

TEMPO-mediated, room temperature synthesis of pure CoO nanoparticles

Treatment of dicobalt octacarbonyl with TEMPO in THF at room temperature, in the presence of oleic acid as the sole additive, leads to the formation of monodisperse nanoparticles (ca. 3.0 nm diameter) of CoO; the particles agglomerate in solution at room temperature into aggregates, and this property has been used for the controlled preparation of hybrid materials.     

An efficient one-pot synthesis of polyhydroquinolines at room temperature using HY-zeolite

An efficient one-pot synthesis of polyhydroquinolines by four-component coupling reactions of aldehydes, ethyl acetoacetate, dimedone and ammonium acetate in the presence of HY-zeolite at ambient temperature has been achieved. The conversions took shorter times to form the products in excellent yields. HY-zeolite can be recovered and reused.     

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.     

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.     

Rapid elongation of CdS nanowire at room temperature

The CdS nanowires synthesized by solvothermal route are rapidly elongated in the presence of the ethylenediamine by ultrosonication method at room temperature. Transmission electron microscopy (TEM) analysis reveals that the influential factors on the rapid elongate process are the concentration of ethylenediamine and duration of the ultrosonication reaction. The elongated CdS nanowires are further characterized by UV–vis absorption spectra, which has no apparent difference in the position of the maximum absorption peak comparing with the starting CdS nanowires synthesized by solvothermal method. A mechanism of oriented attachment is proposed to explain the phenomena based on a series of experimental results.     

Murraya Koenigii leaf-assisted rapid green synthesis of silver and gold nanoparticles

A facile bottom-up 'green' and rapid synthetic route using Murraya Koenigii leaf extract as reducing and stabilizing agent produced silver nanoparticles at ambient conditions and gold nanoparticles at 373 K. The nanoparticles were characterized using UV-vis, transmission electron microscopy (TEM), X-ray diffraction (XRD) and FTIR analysis. This method allows the synthesis of well-dispersed silver and gold nanoparticles having size ～10 nm and ～20 nm, respectively. Silver nanoparticles with size ～10 nm having symmetric SPR band centered at 411 nm is obtained within 5 min of addition of the extract to the solution of AgNO3 at room temperature. Nearly spherical gold nanoparticles having size ～20 nm with SPR at 532 nm is obtained on adding the leaf extract to the boiling solution of HAuCl4. Crystallinity of the nanoparticles is confirmed from the high-resolution TEM images, selected area electron diffraction (SAED) and XRD patterns. From the FTIR spectra it is found that the biomolecules responsible for capping are different in gold and silver nanoparticles. A comparison of the present work with the author's earlier reports on biosynthesis is also included.     

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.     

A green synthesis of palladium nanoparticles by Sapindus mukorossi seed extract and use in efficient room temperature Suzuki–Miyaura cross‐coupling reaction

A simple and green method for the synthesis of palladium nanoparticles using an aqueous extract of Sapindus mukorossi seed has been demonstrated. The synthesized nanoparticles were characterized using UV–visible spectroscopy, powxder X‐ray diffraction, energy‐dispersive X‐ray analysis and transmission electron microscopy. The nanocatalyst was successfully utilized in an efficient Suzuki–Miyaura cross‐coupling reaction at room temperature.     

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.     

Biosynthesis of iron and silver nanoparticles at room temperature using aqueous sorghum bran extracts

Iron and silver nanoparticles were synthesized using a rapid, single step, and completely green biosynthetic method employing aqueous sorghum extracts as both the reducing and capping agent. Silver ions were rapidly reduced by the aqueous sorghum bran extracts, leading to the formation of highly crystalline silver nanoparticles with an average diameter of 10 nm. The diffraction peaks were indexed to the face-centered cubic (fcc) phase of silver. The absorption spectra of colloidal silver nanoparticles showed a surface plasmon resonance (SPR) peak centered at a wavelength of 390 nm. Amorphous iron nanoparticles with an average diameter of 50 nm were formed instantaneously under ambient conditions. The reactivity of iron nanoparticles was tested by the H(2)O(2)-catalyzed degradation of bromothymol blue as a model organic contaminant.     

Visible light driven amide synthesis in water at room temperature from Thioacid and amine using CdS nanoparticles as heterogeneous Photocatalyst

Highly efficient photocatalytic thioacid mediated amide synthesis at room temperature using CdS nanoparticles as photocatalyst was observed under a household 30 W CFL in water. The operationally mild reaction was tolerant to a number of functional group substitutions on amine and could be scaled up to gram. This heterogeneous photocatalyst was extremely stable and could easily be recovered by simple centrifugation for at least six recycling reactions without any significant loss of catalytic performance. The possible reaction mechanism for the photocatalytic thioacid mediated amide synthesis over the CdS semiconductor has also been proposed on the basis of experimental observations.     

Alloy formation at the deposition of palladium on gold at room temperature

Palladium is shown to be deposited underpotentially on gold electrodes in 1 M H₂OSO₄. The deposit forms an alloy according to a t^1/2 law. The rate of alloy formation is strongly dependent on the potential. The diffusion coefficient is about 10^?16 cm² s^?1. This value is discussed in comparison with earlier measurements on gold-palladium alloys at higher temperatures.     

A green approach for the synthesis of 2‐oxazolidinones using gold(I) complex immobilized on KCC‐1 as nanocatalyst at room temperature

A novel gold(I)‐containing ionic liquid‐based KCC‐1 catalyst was applied for the cyclization of propargylic amines with CO₂ to provide 2‐oxazolidinones. High catalytic activity and ease of recovery from the reaction mixture using an external magnet, and several recycle runs without significant loss in performance are additional eco‐friendly attributes of this catalytic system. Copyright © 2016 John Wiley & Sons, Ltd.     

Green synthesis of well-dispersed gold nanoparticles using Macrotyloma uniflorum

The synthesis of metal nanoparticles of different sizes, shapes, chemical composition and controlled monodispersity is an important area of research in nanotechnology because of their interesting physical properties and technological applications. Present work describes an eco-friendly method for the synthesis of spherical gold nanoparticles using aqueous extract of Macrotyloma uniflorum. The effects of quantity of extract, temperature and pH on the formation of nanoparticles are studied. The nanoparticles are characterized by UV-visible spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD) and FTIR analysis. The high crystallinity of nanoparticles with fcc phase is evident from HRTEM images, SAED and XRD patterns. Synthesized nanoparticles have size in the range 14-17nm. FTIR spectrum indicates the presence of different functional groups present in the bio-molecule capping the nanoparticles. The possible mechanism leading to the formation of gold nanoparticles is suggested.     

Size-tunable green synthesis of platinum nanoparticles using chlorogenic acid

A facile green synthesis of platinum nanoparticles (PtNPs) using chlorogenic acid (CGA) as a reducing agent and stabilizing agent has been reported here for the first time to the knowledge of the authors. Well-dispersed PtNPs are synthesized in spherical shapes and are tuned in size by simply changing the molar ratio of H₂PtCl₆ to CGA, with the same salt, temperature and solvent. The average sizes of the particles were 16.9 ± 4.7, 13.3 ± 4.0, 10.8 ± 3.4, and 7.5 ± 2.3 nm, respectively, corresponding to molar ratios of the initial H₂PtCl₆/CGA of 1:1, 1:2, 1:3 and 1:4 and decreased with an increase in CGA concentration. Transmission electron microscope; energy-dispersive spectrometer; UV–visible absorption spectra (UV–Vis); and Fourier transmission infrared spectra were used to characterize the PtNPs. Additionally, the advantage of CGA for possible synergistic biological activity was studied through the in vitro antioxidant activity of PtNPs by CGA for capture of free radicals. Our results indicate that CGA is an excellent reducing and stabilizing agent in green synthesis of PtNPs, and these size-tunable PtNPs can provide potential applications in the field of biomedicines.

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