Microwave-Assisted Green Synthesis of Gold Nanoparticles Using Olibanum Gum (Boswellia serrate) and its Catalytic Reduction of 4-Nitrophenol and Hexacyanoferrate (III) by Sodium Borohydride

In this work we report straightforward, an economically viable, one-step microwave-assisted green synthesis of well stabilized gold nanoparticles (AuNPs) by reducing chloroauric acid with natural water soluble olibanum gum (Boswellia serrate). The olibanum gum acts as a dual role of reducing and capping agent for synthesis of AuNPs. The formation of AuNPs was confirmed using UV–Vis spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy and electron diffraction. The results indicated that the synthesized NPs were well dispersed and spherical in shape had an average diameter of 3 ± 2 nm. The reaction parameters significantly affected the formation of NPs, as the concentration of gum and irradiation time increases the formation of NPs particles increases and size of particles are reduced. In addition, it has been shown that these olibanum gum capped AuNPs functioned as effective homogeneous catalyst for the reduction of two model reactions hexacyanoferrate(III) and 4-nitrophenol by sodium borohydride. The kinetic investigations were carried out at different amount of AuNPs and different temperatures.     

Facile <Emphasis Type="Italic">Aglaia elaeagnoidea</Emphasis> Mediated Synthesis of Silver and Gold Nanoparticles: Antioxidant and Catalysis Properties

A facile and green route for the synthesis of metallic nanoparticles is of significant intriguing, as it provides simple, rapid, clean, nontoxic, easily available, energy-efficient, cost-effective fabrication method. We reported environmentally benign and unexplored plant Aglaia elaeagnoidea flower extract for the synthesis of spherical and crystalline silver (Ag) and gold (Au) nanoparticles with an excellent robustness against agglomeration. The resultant nanoparticles were characterized using UV–Vis spec., FTIR, XRD, FESEM, EDAX, and TEM techniques. The uniqueness of our method lies in fast synthesis (10 min for Ag NPs) and ultra rapid homogeneous and heterogeneous complete degradation of Methylene Blue and Congo Red within few seconds using the synthesized Ag and Au NPs as the catalyst, respectively. Whereas more than 90% conversion of 4-Nitrophenol to 4-Aminophenol within few minutes for homogenous and few seconds for heterogeneous method using Ag and Au NPs were obtained. Hence, the results of this study demonstrate the possible application of biosynthesized of Ag and Au NPs as nanocatalyst in waste water treatment.     

Facile preparation of Au nanoparticles mediated by Foeniculum Vulgare aqueous extract and investigation of the anti-human breast carcinoma effects

This experiment evaluated antioxidant, anti-human breast cancer activities, and cytotoxicity effects of green synthesis of Au nanoparticles (AuNPs) containing Foeniculum Vulgare aqueous extract. Mixing Foeniculum Vulgare aqueous with Au chloride solution produced Au nanoparticles. The characteristics of Au nanoparticles determined using Fourier Transformed Infrared Spectroscopy (FT‐IR), Transmission Electron Microscopy (TEM), UV–Visible Spectroscopy (UV–Vis), and Field Emission Scanning Electron Microscopy (FE‐SEM). To check the cytotoxicity and anti-breast cancer effects of Au chloride, Foeniculum Vulgare aqueous extract, and AuNPs on common breast cancer cell lines i.e., ZR-75-30, T47D, and HCC1187 was used MTT assay. AuNPs showed no cytotoxicity and the most effective anti-breast cancer features compared to other items that were tested. They had no cytotoxic effects on normal cell line (HUVEC) and had very low cell viability, high anti-breast cancer activities dose-dependently against ZR-75-30, T47D, and HCC1187 cell lines. In the presence of butylated hydroxytoluene as the positive control, the DPPH test was used to evaluate the antioxidant features of Au chloride, Foeniculum Vulgare aqueous extract, and Au nanoparticles. AuNPs showed the best antioxidant properties compared to other items that were tested. Perhaps remarkable anti-human breast cancer activities of Au nanoparticles synthesized by Foeniculum Vulgare aqueous extract due to its antioxidant properties. After clinical trial and confirmation of results, this formulation can be used as an effective drug to treat breast cancer.     

Gold‐Aryl nanoparticles coated with polyelectrolytes for adsorption and protection of DNA against nuclease degradation

Binding DNA on nanoparticles was pursued to form nanoplatform for formation of non‐viral gene system. Carboxyl derivatized gold‐aryl nanoparticles can bind with biodegradable cationic polyelectrolytes such as polydiallyldimethylammonium chloride (PDADMAC). In our study, we used gold‐aryl nanoparticles (AuNPs) treated with PDADMAC to form conjugates with non‐thiol or non‐disulfide modified oligonucleotide DNA. Both AuNPs‐DNA and PDADMAC‐AuNPs‐DNA biomaterials were characterized using UV–Vis, dynamic light scattering (DLS), atomic force microscopy (AFM), transmission electron microscopy (TEM) and agarose gel electrophoresis. UV–Vis showed a red shift in the plasmon peak as compared with unconjugated AuNPs. DLS measurements also showed difference in the size of AuNPs‐DNA and PDADMAC‐AuNPs‐DNA. AFM and TEM results showed proper conjugation of DNA with AuNPs. Gel electrophoresis proved the presence of interaction between PDADMAC‐AuNPs and negatively charged DNA. The binding of DNA in the described bioconjugate enhanced its protection against nuclease degradation and prolonged its presence in the digestive environment of DNase‐I. From the results we expect that these biomaterials can be used in nanomedicine with emphasis on non‐viral gene system.     

Study of Aggregation of Gold Nanoparticles in Chitosan

In this work it is reported the synthesis of gold nanoparticles supported in situ in chitosan by solvated metal atom dispersion technique in order to study the inclusion of Au nanoparticles in the biopolymer matrix. To study their aggregation along time and compare with the synthesis of Au/2-propanol colloid by chemical liquid deposition technique. Studies of Au nanoparticles aggregation along time, supported nanoparticles and colloidal nanoparticles morphology were also carried out. The characterization of Au nanoparticles was performed by transmission electron microscopy, field-emission and scanning electron microscopy, infrared spectroscopy, X-ray diffraction, light scattering and ultraviolet–visible spectroscopy. Metal colloid showed fractal agglomeration type and delay time after the synthesis, the agglomeration size increased to flocculate. Au nanoparticles supported in chitosan showed the same shape as colloids and fractal aggregation was mostly distributed on the matrix.     

A glassy carbon electrode modified with graphene, gold nanoparticles and chitosan for ultrasensitive determination of lead(II)

We have modified a glassy carbon electrode by single-step electrodeposition of graphene (GR), gold nanoparticles (AgNPs), and chitosan (CS) directly from a solution containing graphene oxide, tetrachloroauric acid, and chitosan. The surface and electrochemical properties of the film-modified electrode were investigated by SEM and TEM images. The AuNPs have a diameter of about 20 nm and are uniformly dispersed in the matrix. Combining the advantages of GR (i.e., high surface area and conductivity), of AuNPs (excellent electrical conductivity) and CS (excellent film-forming ability and good water permeability), the hybrid film effectively enhances electron-transfer and promotes the response to lead(II) ion. Under the optimum conditions, a linear relationship exists between electrical current and the concentration of lead (II) ion in the range between 0.5 to 100 μg?L-1, with a detection limit of 1 ng?L-1 (at an SNR of 3). The electrode was successfully applied to the detection of lead(II) in spiked samples of river water.

Calix[4]arene‐Functionalised Silver Nanoparticles as Hosts for Pyridinium‐Loaded Gold Nanoparticles as Guests

A series of lipophilic gold nanoparticles (AuNPs) circa 5 nm in diameter and having a mixed organic layer consisting of 1‐dodecanethiol and 1‐(11‐mercaptoundecyl) pyridinium bromide was synthesised by reacting tetraoctylammonium bromide stabilised AuNPs in toluene with different mixtures of the two thiolate ligands. A bidentate ω‐alkylthiolate calix[4]arene derivative was instead used as a functional protecting layer on AgNPs of approximately 3 nm. The functionalised nanoparticles were characterised by transmission electron microscopy (TEM), and by UV/Vis and X‐ray photoelectron spectroscopy (XPS). Recognition of the pyridinium moieties loaded on the AuNPs by the calix[4]arene units immobilised on the AgNPs was demonstrated in solution of weakly polar solvents by UV/Vis titrations and DLS measurements. The extent of Au‐AgNPs aggregation, shown through the low‐energy shift of their surface plasmon bands (SPB), was strongly dependent on the loading of the pyridinium moieties present in the organic layer of the AuNPs. Extensive aggregation between dodecanethiol‐capped AuNPs and the Ag calix[4]arene‐functionalised NPs was also promoted by the action of a simple N‐octyl pyridinium difunctional supramolecular linker. This linker can interdigitate through its long fatty tail in the organic layer of the dodecanethiol‐capped AuNPs, and simultaneously interact through its pyridinium moiety with the calix[4]arene units at the surface of the modified AgNPs.     

Water‐Soluble Gold Nanoparticles: From Catalytic Selective Nitroarene Reduction in Water to Refractive Index Sensing

Water‐soluble gold nanoparticles (Au NPs) stabilized by a nitrogen‐rich poly(ethylene glycol) (PEG)‐tagged substrate have been prepared by reduction of HAuCl₄ with NaBH₄ in water at room temperature. The morphology and size of the nanoparticles can be controlled by simply varying the gold/stabilizer ratio. The nanoparticles have been fully characterized by TEM, high‐resolution (HR) TEM, electron diffraction (ED), energy‐dispersive X‐ray spectroscopy (EDS), UV/Vis, powder XRD, and elemental analysis. The material is efficient as a recyclable catalyst for the selective reduction of nitroarenes with NaBH₄ to yield the corresponding anilines in water at room temperature. Furthermore, the potential ability of the Au NPs as a refractive index sensor owing to their localized surface plasmon resonance (LSPR) effect has also been assessed.     

Spectrophotometric and physicochemical investigations of Congo,alizarin red dyes and BSA interactions with Au,Ag and Au/Ag mix nanoparticles,and their antimicrobial activities

Individual and mix metal nanoparticles of Ag and Au have been prepared by the reducing method where citrate was used as reducing/stabilizing agent. The prepared NPs were characterized with UV/Visible and transmission electron microscopic (TEM) tools. The characteristic peak in UV/Visible at 525, 444 and 531 nm for Au, Ag and Ag/Au mix NPs respectively, gave primary confirmation of prepared NPs. TEM analysis showed the size of nanoparticles as 44.04, 19.78 and 30.93 nm for Ag, Au and Ag/Au mix NPs respectively. Congo and alizarin red dye interactions studies have been performed with prepared NPs to see the removal of the pollutants from water. Congo dye has shown weaker interaction as compared to alizarin due to structural symmetry. Amongst all, the AgNPs have shown maximum 67% and 75% interactions with Congo red and alizarin respectively due to high negative charges on the surface. The Au, Ag and Au/Ag mix NPs have shown stronger interaction with bovine serum albumin (BSA) protein up to 51, 59, 55% respectively, estimated through UV/Vis and physicochemical analysis. The biological evaluations of the prepared NPs have shown their antibacterial activity against Gram + ve and –ve species showing up to 9 cm zone of inhibition. The BSA interaction and antibacterial activity of NPs reveal the importance of NPs in medicinal field.     

Bimetallic nanoparticles as a novel chemiresistor coating

Here, we describe the chemiresistive sensing of some volatile organic compounds with a novel film of chemically synthesized Au–Pt bimetallic nanoparticles (NPs) stabilized with 11-mercaptoundecanoic acid. The chemiresistive sensing properties were measured over a concentration range of 1.4–250 mg L^?1 for methanol, ethanol, ethyl acetate and acetone vapours and the responses were compared with Au and Pt monometallic nanoparticles. It is observed that the sensitivity of bimetallic nanoparticles is increased about 60 % in exposure to methanol and ethanol vapours, but there are no changes in the sensitivity to the other tested vapours. In addition, the detection limit is improved about 80–100 % for all tested vapours in bimetallic nanoparticles compared to AuNPs and 20–30 % compared to PtNPs.     

Biosynthesis of Au nanoparticles using olive leaf extract: 1st Nano Updates

The biological synthesis of gold nanoparticles (AuNPs) of various shapes (triangle, hexagonal, and spherical) using hot water olive leaf extracts as reducing agent is reported. The size and the shape of Au nanoparticles are modulated by varying the ratio of metal salt and extract in the reaction medium. Only 20 min were required for the conversion into gold nanoparticles at room temperature, suggesting a reaction rate higher or comparable to those of nanoparticles synthesis by chemical methods. The variation of the pH of the reaction medium gives AuNPs nanoparticles of different shapes. The nanoparticles obtained are characterized by UV–Vis spectroscopy, photoluminescence, transmission electron microscopy (TEM), X-ray diffraction (XRD), FTIR spectroscopy and thermogravimetric analysis. The TEM images showed that a mixture of shapes (triangular, hexagonal and spherical) structures was formed at lower leaf broth concentration and high pH, while smaller spherical shapes were obtained at higher leaf broth concentration and low pH.     

DNA-embedded Au/Ag core-shell nanoparticles

Here, we synthesized highly stable DNA-embedded Au/Ag core-shell nanoparticles (NPs) by a straightforward silver-staining of DNA-modified Au nanoparticles (AuNPs); unlike conventional DNA-surface modified NPs that present particle stability issues, DNA-embedded core-shell NPs offer an extraordinary stability with nanoscale controllability of silver shell thickness; these DNA-embedded core-shell NPs show excellent biorecognition properties and Ag shell-thickness-based optical properties, distinctively different from those of a mixture of AuNPs and AgNPs or Ag/Au alloy nanoparticles.     

Size‐Controlled Synthesis of Highly Monodisperse Gold Nanoparticles without a Size‐Selection and Long Range Ordered 2‐D Arrangement

A simple method is used to control the size of cetyltrimethylammoniumbromide‐protected Au nanoparticles by a reversal micelle in safe organic solvent. These Au nanoparticles can be evolved to highly monodisperse Au nanoparticles capped 1‐dodecanthiol in the 2, 3, and 5 nm diameter by refluxing at～160°C for 7 hours. Their ultraviolet visible spectroscopy (UV‐vis), x‐ray diffraction (XRD, transmission electron microscopy (TEM) showed that all the three different size gold nanoparticles(NPs) displayed high size homogenous properties and easy formed large areas of long ordered two‐dimensional arrangement at the air/solid interface.     

Gelatin-coated gold nanoparticles as an effective pH-sensitive methotrexate drug delivery system for breast cancer treatment

The present study investigates the synthesis and effectiveness of gold/gelatin nanoparticles (NPs) biopolymer as a carrier for methotrexate (MTX) drug. Two different shapes of gold particles, including spherical AuNPs (50 & 100 nm) and gold nanorods (AuNRs) with three different sizes (20, 50 and 100 nm length) were synthesized using the chemical reduction method. The effect of AuNPs size and shape on the entrapment efficiency (E.E), the release rate of the drug, and cellular uptake were investigated. The surfaces of both AuNPs and AuNRs were coated with a gelatin biopolymer, and the stability and property of the generated compounds were studied. Moreover, MTX as a chemotherapeutic agent was loaded on the gelatin-coated AuNPs/AuNRs complexes. The physicochemical properties of the gelatin-coated AuNPs/AuNRs complexes were studied using ultraviolet-visible (UV–Vis) spectroscopy, dynamic light scattering (DLS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Fourier transform infrared (FT-IR) spectroscopy. The E.E and MTX release behavior from the complexes at pH values of 7.4 and 5.4 and temperatures of 37 and 40 °C were investigated in vitro. The cytotoxic effects of AuNPs, AuNPs-Gelatin, AuNPs-Gelatin-MTX, AuNRs, AuNRs-Gelatin, AuNRs-Gelatin-MTX and free MTX were studied. The results indicated that the E.E of AuNPs was higher than that of AuNRs. The highest release rate of the drug was related to the AuNR1-gelatin complex (pH 5.4 and temperature of 40 °C). In addition, MTX loaded AuNR2-gelatin showed the highest cytotoxic effect on the MCF-7 breast cancer cell line so that even its cell cytotoxicity was more than that of the free drug.     

Preparation and characterization of nanostructured thin films of Au and Ag nanoparticles synthesized by ascorbic acid on modified glass surface

Immobilization of Ag and Au nanoparticles (NPs) synthesized by ascorbic acid on chemically modified glass surface has been studied. 3‐[2‐(2‐Aminoethylamino)ethylamino]propyl‐trimethoxysilane (AMPTS), N‐(2‐aminoethyl)‐3‐aminopropyltrimethoxysilan, and 3‐trimethoxysilyl‐1‐propanethiol (MSPT) were used as surface modifying agents. To improve immobilization efficiency, the ammonia solution has been used along with the silane reagents, which assisted to adsorb the metal NPs on glass surface. It was found that AMPTS and MSPT have considerable effect on deposition of Ag and AuNPs on glass substrate. The fabricated thin films were characterized by using UV‐Vis spectroscopy, atomic force microscopy, energy‐dispersive X‐ray spectroscopy and subjected to antimicrobial resistance test. The UV–Vis spectra show a distinctive plasmon resonance absorbance peak for thin films of Au and AgNPs prepared with MSPT and AMPTS, respectively. Atomic force microscopy images indicate that formation of Au and AgNPs with spherical morphology after immobilization on the glass substrate and also the dimensions of NPs on the surface appear larger than those observed in the parent colloidal solution. Energy‐dispersive X‐ray spectroscopy measurements confirmed the presence of silver and gold on the modified glass surface, and elemental composition was measured. The Au and AgNPs thin films show antibacterial activity against gram negative (Escherichia coli) and gram positive (Staphylococcus aureus) bacteria in comparison with a blank sample. Copyright © 2015 John Wiley & Sons, Ltd.     

Colloids based on gold nanoparticles dispersed in castor oil: Synthesis parameters and the effect of the free fatty acid content

Herein, we present our results related to the synthesis of colloidal solutions of gold nanoparticles (AuNPs) dispersed in castor oil. These colloids were prepared via a wet chemistry process by mixing specific amounts of castor oil, ethanol, and aqueous solutions of tetrachloroauric(III) acid and sodium hydroxide. The size and shape of the AuNPs obtained could be modulated by the amount of gold source added and the Au/OH^– molar ratio used. In this study, we observed that the free fatty acid content in the reaction medium was an important parameter to be considered in the syntheses of the colloidal solutions and the respective form and shape of the AuNPs produced. Thus, we evaluated the effect of oil acidity by adding different amounts of myristic acid (MA) in the reaction medium. The colloids were characterized by UV–vis spectroscopy, and the size and shape of the AuNPs produced were characterized by transmission electron microscopy (TEM).     

Synthesis and characterization of palladium–tin bicolloids prepared by chemical liquid deposition

Palladium–tin bicolloids have been prepared by chemical liquid deposition. The metals were cocondensed at 77 K with ethanol, 2-propanol, 2-methoxyethanol, 2-butanone and acetone. The distribution of particle sizes was determined by transmission electron microscopy of the stables dispersions. The sizes ranged from 3.8 nm for 2-methoxyethanol to 8.3 nm for acetone colloids. Electrophoretic measurements such as colloid charge and zeta potential were achieved. lt was found that the colloids possess electrical charge; therefore, it is postulated that their stability is by simple solvatation. The colloids showed stability over 1 week at room temperature. The zeta-potential values are in agreement with the stability and electrophoretic mobility. The highest zeta potential was obtained for PdSn–2-methoxyethanol colloids with 379 mV and the lowest for 2-butanone with 114 mV. The colloids exhibit absorption bands in the UV region. In the visible region no plasma absorption was found. Active solids obtained by evaporation of the solvent contain a certain amount of the solvent incorporated, and owing to their reactivity they produce a mixture of tin oxide with palladium and tin. The presence of solvents can be observed by Fourier transform IR incorporation in the finely divided solids. Characteristic bands for each solvent were measured. By means of thermogravimetric analysis and differential scanning calorimetry the thermal stability of the solids and the transition heat give us the carbonaceous residues in the films. The elemental analysis of the powders was carried out.     

Preparation and nonlinear optical properties of Au nanoparticles doped TiO2 thin films

Nano-sized noble metal nanoparticles doped dielectric composite films with large third-order nonlinear susceptibility due to the confinement and the enhancement of local field were considered to be applied for optical information processing devices, such as optical switch or all optical logical gates. In this paper, sol–gel titania thin films doped with gold nanoparticles (AuNPs, ~10 nm in average size) were prepared. AuNPs were firstly synthesized from HAuCl₄ in aqueous solution at ~60 °C, using trisodium citrate as the reducing agent, polyvinylpyrrolidone as the stable agent; then the particle size and optical absorption spectra of the AuNPs in aqueous solutions were characterized by transmitting electron microscopy and UV–Vis–NIR spectrometry. Sol–gel 2AuNPs–100TiO₂ (in %mol) thin films (5 layers, ~1 μm in thickness) were deposited on silica glass slides by multilayer dip-coating. After heat-treated at 300–1,000 °C in air, the AuNPs–TiO₂ thin films were investigated by X-ray diffraction, scanning electron microscopy and atomic force microscopy. The nonlinear optical properties of the AuNPs–TiO₂ thin films were measured with the Z-scan technique, using a femtosecond laser (200 fs) at the wavelength of 800 nm. The third-order nonlinear refractive index and nonlinear absorption coefficient of 2AuNPs–100TiO₂ films were at the order of 10^?12 cm²/W, and the order of 10^?6 cm/W, respectively, and the third-order optical nonlinear susceptibility χ⁽³⁾ was ~6.88 × 10^?10 esu.     

A Novel Green Synthesis of Silver Nanoparticles Using Gum Karaya: Characterization,Antimicrobial and Catalytic Activity Studies

Stable silver nanoparticles have been synthesized using gum karaya acting as both reducing and stabilizing agent without using any synthetic reagent. The reaction is performed using water, which is an environmentally safe solvent. This reaction was carried out in an autoclave at a pressure of 15 psi and 120 °C temperature by varying the time. The influence of different parameters such as time, change of concentration of silver nitrate and concentration of gum karaya on the formation of silver nanoparticles has been studied. The synthesized silver nanoparticles are characterized by UV–Vis spectroscopy, FTIR, XRD and TEM. UV–Vis analysis of the sample confirmed the formation of silver nanoparticles exhibiting a sharp peak at a wavelength of 420 nm. TEM micrographs showed the formation of well-dispersed silver nanoparticles of size 2–4 nm. The antimicrobial activity of silver nanoparticles stabilized in gum karaya is tested against Escherichia coli, Micrococcus luteus and is found to be possessing inhibiting property. The silver nanoparticles stabilized in gum karaya exhibited very good catalytic activity and the kinetics of the reaction was found to be pseudo first order with respect to the 4-nitrophenol.     

Formulation of gold nanoparticles with hibiscus and curcumin extracts induced anti-cancer activity

Gold nanoparticles (AuNPs) have shown a potential for biological applications due to their biocompatibility and high efficiency in drug delivery. Most of the times, the chemical routs are being used to synthesize the AuNPs products. In this paper, eco-friendly non-chemical rout was used to prepare AuNPs by utilizing hibiscus and curcumin extracts as reducing and stabilizing agents, and subsequently their anticancer activities were investigated. The synthesized AuNPs were characterized by using ultraviolet–visible spectroscopy (UV–Vis spectroscopy), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). UV–Vis spectroscopy analysis confirmed the characteristics absorption peak of gold, and FTIR findings were highlighted the characteristics boding. SEM and TEM analyses showed that the particles were predominantly spherical in shape. The particles were well dispersed when they were prepared under Hibiscus extracts with average size ～ 13 nm. An interesting morphology was observed when AuNPs were prepared with curcumin, where particles displayed an interconnected morphology (average size ～ 18 nm). The anticancer cell activity of AuNPs was studied against human colorectal carcinoma cells (HCT-116) and breast cancer cells (Michigan Cancer Foundation-7 (MCF-7)). The results of anticancer study showed that the treatment of cancer cells with AuNPs decreased the number of cells significantly as compared to control cells. The AuNPs -Hibiscus specimen showed a better inhibiting property than AuNPs -Curcumin, which is attributed to their uniform dispersion and small size.