Green synthesis of biocompatible gold nanoparticles using Fagopyrum esculentum leaf extract

This report describes the use of ethnolic extract of Fagopyrum esculentum leaves for the synthesis of gold nanoparticles. UV-visible spectroscopy analysis indicated the successful formation of gold nanoparticles. The synthesized nanoparticles were characterized by transmission electron microscopy (TEM), high resolution TEM (HRTEM) and were found to be spherical, hexagonal and triangular in shape with an average size of 8.3 nm. The crystalline nature of the gold nanoparticles was confirmed from X-ray diffraction (XRD) and selected-area electron diffraction (SAED) patterns. Fourier transform infrared (FT-IR) and energy-dispersive X-ray analysis (EDX) suggested the presence of organic biomolecules on the surface of the gold nanoparticles. Cytotoxicity tests against human HeLa, MCF-7 and IMR-32 cancer cell lines revealed that the gold nanoparticles were non-toxic and thus have potential for use in various biomedical applications.     

Biogenic materialization using pear extract intended for the synthesis and design of ordered gold nanostructures

We report a facile, green, and biomimetic reduction route coupled with the synthesis and biomolecular-based well-defined self-assembly of gold nanoparticles (AuNPs), without using any organic solvents or any toxic reducing or capping agents. To demonstrate the potential use of pear phytochemicals for the materialization of AuNPs, we propose that the available biomolecules appending on the AuNPs surface and subsequently observed their importance in assembly designs. The spatial array of AuNPs was investigated precisely by using a high-resolution transmission electron microscopy. This method offered biomolecular capping of the AuNPs during and after synthesis and thus provides a promising alternative for nanosurface engineering. The peptide and other biomolecule-based coatings on the AuNPs are applicable for their stability and healthy capping. The hybrid “biomolecular-inorganic” system will be suitable for safe application in medical and diagnostic fields.     

One-step high-yield aqueous synthesis of size-tunable multispiked gold nanoparticles

Multispiked gold nanoparticles are required in large quantities for many fundamental studies and applications like (bio)sensing, but their preparation in high yield by the bottom-up chemical synthetic method is challenging. A water-based, non-'seed-mediated', straightforward method for the synthesis of gold nanoparticles with well-developed surface spikes is reported here. The yield of multispiked gold particles is very high (>90%). The method allows the tuning of the number and size of the spikes and the overall size of the particles, and hence the localized surface plasmon resonances of the particles over the broad spectral range in the visible and near-infrared. A mechanism for the evolution of twinned, sharp-tipped surface protrusions has been proposed based on systematic spectrophotometric and transmission electron microscopic studies, which were employed to elucidate the morphological features, structure, chemical composition, and optical properties of the multispiked gold nanoparticles.     

One-step synthesis of highly reactive g-C3N4

Journal of Materials Science: Materials in Electronics - Graphitic carbon nitride (g-C3N4) with well-controlled properties are the key for photocatalysis water splitting and organic pollutant...     

One-step synthesis of star-like gold nanoparticles for surface enhanced Raman spectroscopy

In this paper we present a new protocol for the synthesis of Star-Like Gold Nanoparticles (SGNs) by a simple one-step, room temperature procedure not involving the use of seeds or surfactants, that can be performed in seconds in any laboratory without the need of special technologies. These particles exhibited excellent properties for Surface Enhanced Raman Spectroscopy (SERS) and, when compared with spherical nanoparticles with similar size and concentration, showed enhancing factors from 10 to 50 times higher depending on the dye and on the wavelength employed. SGNs could be used directly in suspension as single, non-aggregating particles and were shown to be active in a remarkably broad range of the light spectrum from green to near infrared. Moreover, SGNs were adsorbed on the surface of a silicon slide to prepare SERS active solid substrate. Despite the fact that the surface of the solid substrate was not perfectly homogeneous, the signals recorded from different positions acquired through DuoScan averaging mode show excellent reproducibility, demonstrating how this simple and cheap protocol can be applied in order to generate reliable and homogeneous SERS substrates.     

Green synthesis of biocompatible carbon dots using aqueous extract of Trapa bispinosa peel

We are reporting highly economical plant based method for the production of luminescent water soluble carbon dots (C-dot) using Indian water plant Trapa bispinosa peel extract without adding any external oxidizing agent at 90 °C. C-dots ranging from 5 to 10 nm were found in the solution with a prominent green fluorescence under UV-light (λ_ex = 365 nm). UV–vis spectra recorded at different time intervals (30–120 min) displayed signature absorption of C-dots between 400 and 600 nm. Fluorescence spectra of the dispersion after 120 min of synthesis exhibited characteristic emission peaks of C-dots when excited at 350, 400, 450 and 500 nm. C-dots were further analyzed using X-ray diffraction (XRD), Raman Spectroscopy and Thermo-Gravimetric Analysis (TGA). Structure of the C-dots was found to be turbostratic when studied using XRD. C-dots synthesized by our method were found to be exceptionally biocompatible against MDCK cells.     

One-step synthesis and characterisation of chitosan-mediated micro-sized gold nanoplates through a thermal process

Most of the synthesising methods of gold nanoplates reported to date rely heavily on the use of chemical reducing agents such as N, N-dimethylformamide, sodium borohydride or other organic compounds. All of these chemicals are highly reactive and may pose potential biological risks. A simple, convenient and economical route for the mass synthesis of single-crystalline, micro-sized, polygonal gold nanoplates using chitosan as a reducing/capping agent is reported. The nanoplates possess well-defined shapes with sharp edges confirmed by scanning electron microscopy. The gold nanoplates are single crystals bound primarily by (1 1 1) lattice planes, as revealed by both selected area electron diffraction and powder X-ray diffraction. These large gold nanoplates had strong absorption in the near-infrared region. The concentration and molecular weight of chitosan are important factors for the morphology and size control of the final product. This facile approach may be extended to the synthesis of some other metal nanostructures.     

One-step preparation of gold nanoparticles with different size distribution

Gold nanoparticles with different size distributions have been prepared through a one-step route, carried out by mixing 3-thiophenemalonic acid and HAuCl₄ aqueous solutions without the additional step of introducing other reducing agents and protective agents. The growth of such gold nanoparticles follows the Ostwald ripening growth mechanism.     

Size controlled synthesis of biocompatible gold nanoparticles and their activity in the oxidation of NADH

Size and shape controlled synthesis remains a major bottleneck in the research on nanoparticles even after the development of different methods for their preparation. By tuning the size and shape of a nanoparticle, the intrinsic properties of the nanoparticle can be controlled leading tremendous potential applications in different fields of science and technology. We describe a facile route for the one pot synthesis of gold nanoparticles in water using monosodium glutamate as the reducing and stabilizing agent in the absence of seed particles. The particle diameter can be easily controlled by varying the pH of the reaction medium. Nanoparticles were characterized using scanning electron microscopy, UV-vis absorption spectroscopy, cyclic voltammetry, and dynamic light scattering. Zeta potential measurements were made to compare the stability of the different nanoparticles. The results suggest that lower pH favours a nucleation rate giving rise to smaller particles and higher pH favours a growth rate leading to the formation of larger particles. The synthesized nanoparticles are found to be stable and biocompatible. The nanoparticles synthesized at high pH exhibited a good electrocatalytic activity towards oxidation of nicotinamide adenine dinucleotide (NADH).     

Hydrothermal synthesis of biocompatible whiskers

The preparation of non-toxic and biocompatible fibres or whiskers is one of the most urgent tasks today, because most of the fibrous materials which have been used (including asbestos which has been used for many years) are thought to be biohazardous. Whiskers of hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂HAp), which is expected to be one of the best biocompatible materials, have been successfully synthesized by hydrothermal treatments of beta-tricalcium phosphate (beta-Ca₃(PO₄)₂: beta-TCP) with citric acid. These whiskers were single crystals, elongated along the c-axis, with a length of 20–30 m and a width of 0.1–1 m. They were slightly calcium deficient (Ca/P molar ratio = 1.63) and they contained a trace of CO ₃ ^2– in their structure.     

Low pressure annealing of gold nanostructures

Ultra-thin Au films sputtered on glass substrates were investigated. The samples were annealed in air and in an evacuated chamber. The dependence of the annealing process on ambient pressure during thermal treatment was studied. The thermally-induced changes in surface morphology were followed by atomic force microscopy. The changes have a great impact on dielectric, optical and physical properties of the prepared structures. UV–Vis absorption spectra were used to investigate optical parameters and showed the semiconducting characteristic of intrinsic Au clusters. It was found that reduced ambient pressure stabilizes the continuous structure of the thin gold film during the annealing process.     

One-step synthesis of N,P co-doped porous carbon electrocatalyst for highly efficient nitrogen fixation

Heteroatom-doped porous carbon has attracted many researchers'interests owing to their hierarchical porous and more active sites for nitrogen reduction reaction...     

One-step synthesis of MoO3 and MoO3-x nanostructures by condensation in gas: effect of the carrier gas

MoO3 and MoO3-x nanostructures were grown in a simple one-step process by direct evaporation of MoO3 pellets from a tungsten resistive source in presence of helium or hydrogen at pressures from 100 to 1200 Pa. This method uses no templates, catalysts or oxidizing agents. It leads to one dimensional (1-D) crystalline nanostructures mixed with amorphous material in variable ratios. Amorphous structures grew preferentially when hydrogen was used as carrier gas while crystalline material predominated when helium was used. In fact, only crystalline structures were found when the evaporation was carried out under a helium pressure of 600 Pa with source temperatures between 763 and 910 degrees C. Hydrated MoO3 phases with different water concentrations were preferentially formed using hydrogen. X-ray photoelectron spectroscopy detected only molybdenum in its +6 oxidation state in the samples grown under helium, exhibiting the same chemical composition of the source material. Molybdenum in its +6 as well as its +5 oxidation states was detected in the samples obtained under hydrogen at 600 Pa. Hydroxyl groups were identified in samples grown using both gases. The effect of the helium pressure on the growth kinetics and crystallinity of the samples is discussed according to the kinetics conditions (supersaturation, evaporation, cooling and convection rates) driving to the formation of nanostructures in the inert-gas condensation. Finally, the effect of hydrogen on the growth of MoO3 is discussed.     

One-step synthesis of novel snowflake-like Si-O/Si-C nanostructures on 3D graphene/Cu foam by chemical vapor deposition

The recent development of synthesis processes for three-dimensional (3D) graphene-based structures has tended to focus on continuous improvement of porous nanostructures, doping modification during thin-film fabrication, and mechanisms for building 3D architectures. Here, we synthesized novel snowflake-like Si-O/Si-C nanostructures on 3D graphene/Cu foam by one-step low-pressure chemical vapor deposition (CVD). Through systematic micromorphological characterization, it was determined that the formation mechanism of the nanostructures involved the melting of the Cu foam surface and the subsequent condensation of the resulting vapor, 3D growth of graphene through catalysis in the presence of Cu, and finally, nucleation of the Si-O/Si-C nanostructure in the carbon-rich atmosphere. Thus, by tuning the growth temperature and duration, it should be possible to control the nucleation and evolution of such snowflake-like nanostructures with precision. Electrochemical measurements indicated that the snowflake-like nanostructures showed excellent performance as a material for energy storage. The highest specific capacitance of the Si-O/Si-C nanostructures was ～963.2 mF/cm² at a scan rate of 1 mV/s. Further, even after 20,000 sequential cycles, the electrode retained 94.4% of its capacitance.

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Green synthesis of gold nanoparticles using ethanolic leaf extract of Centella asiatica

Here, we report a novel use of the ethanolic leaf extract of Centella asiatica to produce gold nanoparticles by reduction of AuCl₄⁻ ions. The phytochemicals present in the leaf extract served as effective reducing and capping agent. The gold nanoparticles obtained were characterized by UV-visible spectra, transmission electron microscopy (TEM) and X-ray diffraction (XRD). TEM studies showed the particles to be of various shapes and sizes. Selected-area electron diffraction (SAED) pattern and high-resolution TEM image confirmed a fcc phase and high crystallinity of the particles. The XRD patterns showed a (1 1 1) preferential orientation of the gold nanoparticles. Fourier transform infra-red spectroscopy (FTIR) measurements showed the GNPs having a coating of phenolic compounds indicating a possible role of biomolecules responsible for capping and efficient stabilization of the gold nanoparticles. As no synthetic reagents were used in this method, the synthesized gold nanoparticles have potential for application in bio-molecular imaging and therapy.