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.     

Green synthesis of silver nanoparticles using Macrotyloma uniflorum

Green synthesis of noble metal nanoparticles is a vast developing area of research. In this paper we report the green synthesis of silver nanoparticles using aqueous seed extract of Macrotyloma uniflorum. The effect of experimental parameters such as amount of extract, temperature and pH on the formation of silver nanoparticles was studied. The as prepared samples are characterized using XRD, TEM, UV-Visible and FTIR techniques. The formation of silver nanoparticles is evidenced by the appearance of signatory brown colour of the solution and UV-vis spectra. The XRD analysis shows that the silver nanoparticles are of face centered cubic structure. Well-dispersed silver nanoparticles with anisotropic morphology having size ～12 nm are seen in TEM images. FTIR spectrum indicates the presence of different functional groups in capping the nanoparticles. The possible mechanism leading to the formation of silver nanoparticles is suggested.     

Catalytic Reduction of p‐Nitrophenol and Hexacyanoferrate (III) by Borohydride Using Green Synthesized Gold Nanoparticles

A simple and green approach for the synthesis of well‐stabilized gold nanoparticles (AuNPs) using gum Acacia (GA) is presented here. The gum acacia acts as the reductant and stabilizer. The synthesized gold nanoparticles were characterized by using ultraviolet visible (UV‐Vis), fourier transform infrared spectroscopy (FTIR), x‐ray diffraction (XRD), dynamic light scattering (DLS) and transmission electron microscopy (TEM) techniques. The UV‐Vis study revealed a distinct surface plasmon resonance at 520 – 550 nm, due to the formation of AuNPs. FTIR analysis showed the evidence that –OH groups present in the gum matrix were responsible in reducing the tetra chloroauric acid into AuNPs. XRD studies confirmed the formation of well crystalline nanoparticles with fcc structure and the particle size ranges from 4 – 29 nm, as indicated by TEM analysis. The synthesized gold nanoparticles exhibited homogeneous catalytic activity. The two model reactions studied were the reduction of p‐nitro phenol and the reduction of hexacyanoferrate (III) by borohydride ions. Both the reactions were monitored by UV‐Vis spectroscopy. The kinetic investigations were carried out for the AuNPs‐catalyzed reactions at different temperatures and different amount of catalyst.     

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.     

The green synthesis of fine particles of gold using an aqueous extract of <Emphasis Type="Italic">Monotheca buxifolia</Emphasis> (Flac.)

This study deals with the synthesis and physicochemical investigation of gold nanoparticles using an aqueous extract of Monotheca buxifolia (Flac.). On the treatment of aqueous solution of tetrachloroauric acid with the plant extract, gold nanoparticles were rapidly fabricated. The synthesized particles were characterized by UV–Vis spectrophotometry (UV), Fourier transform infrared spectroscopy (FTIR), energy dispersive X-ray (EDX) and Scanning electron microscopy (SEM). The formation of AuNPs was confirmed by noting the change in color through visual observations as well as via UV–Vis spectroscopy. UV?Vis spectrum of the aqueous medium containing gold nanoparticles showed an absorption peak at around 540 nm. FTIR was used to identify the chemical composition of gold nanoparticles and Au-capped plant extract. The presence of elemental gold was also confirmed through EDX analysis. SEM analysis of the gold nanoparticles showed that they have a uniform spherical shape with an average size in the range of 70–78 nm. This green system showed to be better capping and stabilizing agent for the fine particles. Further, the antioxidant activity of Monotheca buxifolia (Flac.) extract and Au-capped with the plant extract was also evaluated using FeCl₃/K₃[Fe(CN)]₆ in vitro assay.     

Plant extract mediated synthesis of silver and gold nanoparticles and its antibacterial activity against clinically isolated pathogens

Biosynthesis of nanoparticles is under exploration is due to wide biomedical applications and research interest in nanotechnology. Bioreduction of silver nitrate (AgNO(3)) and chloroauric acid (HAuCl(4)) for the synthesis of silver and gold nanoparticles respectively with the plant extract, Mentha piperita (Lamiaceae). The plant extract is mixed with AgNO(3) and HAuCl(2), incubated and studied synthesis of nanoparticles using UV-Vis spectroscopy. The nanoparticles were characterized by FTIR, SEM equipped with EDS. The silver nanoparticles synthesized were generally found to be spherical in shape with 90 nm, whereas the synthesized gold nanoparticles were found to be 150 nm. The results showed that the leaf extract of menthol is very good bioreductant for the synthesis of silver and gold nanoparticles and synthesized nanoparticles active against clinically isolated human pathogens, Staphylococcus aureus and Escherichia coli.     

Rapid synthesis of Au, Ag, and bimetallic Au core-Ag shell nanoparticles using Neem (Azadirachta indica) leaf broth

We report on the use of Neem (Azadirachta indica) leaf broth in the extracellular synthesis of pure metallic silver and gold nanoparticles and bimetallic Au/Ag nanoparticles. On treatment of aqueous solutions of silver nitrate and chloroauric acid with Neem leaf extract, the rapid formation of stable silver and gold nanoparticles at high concentrations is observed to occur. The silver and gold nanoparticles are polydisperse, with a large percentage of gold particles exhibiting an interesting flat, platelike morphology. Competitive reduction of Au3+ and Ag+ ions present simultaneously in solution during exposure to Neem leaf extract leads to the synthesis of bimetallic Au core-Ag shell nanoparticles in solution. Transmission electron microscopy revealed that the silver nanoparticles are adsorbed onto the gold nanoparticles, forming a core-shell structure. The rates of reduction of the metal ions by Neem leaf extract are much faster than those observed by us in our earlier studies using microorganisms such as fungi, highlighting the possibility that nanoparticle biological synthesis methodologies will achieve rates of synthesis comparable to those of chemical methods.     

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.     

Phytosynthesis of Au, Ag and Au-Ag bimetallic nanoparticles using aqueous extract and dried leaf of Anacardium occidentale

Present study reports a green chemistry approach for the biosynthesis of Au, Ag, Au-Ag alloy and Au core-Ag shell nanoparticles using the aqueous extract and dried powder of Anacardium occidentale leaf. The effects of quantity of extract/powder, temperature and pH on the formation of nanoparticles are studied. The nanoparticles are characterized using UV-vis and FTIR spectroscopies, XRD, HRTEM and SAED analyses. XRD studies show that the particles are crystalline in the cubic phase. The formation of Au core-Ag shell nanoparticles is evidenced by the dark core and light shell images in TEM and is supported by the appearance of two SPR bands in the UV-vis spectrum. FTIR spectra of the leaf powder before and after the bioreduction of nanoparticles are used to identify possible functional groups responsible for the reduction and capping of nanoparticles. Water soluble biomolecules like polyols and proteins are expected to bring about the bio-reduction.     

Biosynthesis of anisotropic gold nanoparticles using Maduca longifolia extract and their potential in infrared absorption

Metal nanoparticles, in general, and gold nanoparticles, in particular, are very attractive because of their size- and shape-dependent properties. Biosynthesis of anisotropic gold nanoparticles using aqueous extract of Madhuca longifolia and their potential as IR blockers has been demonstrated. The tyrosine residue was identified as the active functional group for gold ion reduction. These gold nanoparticles were characterized by of UV-Vis spectrophotometer, FTIR, TEM and HrTEM. The presence of proteins was identified by FTIR, SDS-PAGE, UV-Vis and fluorescence spectroscopy. The micrograph revealed the formation of anisotropic gold nanoaprticles. The biologically synthesized gold nanotriangles can be easily coated in the glass windows which are highly efficient in absorbing IR radiations.     

Immobilization of biogenic gold nanoparticles in thermally evaporated fatty acid and amine thin films

We have recently demonstrated the biological synthesis of gold nanoparticles by the reduction of aqueous chloroaurate ions by the fungus Fusarium oxysporum and with extract of geranium (Pelargonium graveolens) leaf. In this paper, we demonstrate the immobilization of biogenic gold nanoparticles in lipid thin films deposited by thermal evaporation. The charge on the gold nanoparticles synthesized by both the fungus and the geranium plant extract is used to facilitate their immobilization in both anionic and cationic lipid thin films. A rough estimate of the isoelectric point of the proteins capping the gold nanoparticles synthesized using the fungus could be made by pH-dependent microgravimetry studies of the immobilization process. An interesting size and shape selectivity in the immobilized gold nanoparticles is observed in the lipid thin films. The biogenic gold nanoparticle-lipid composite films were characterized using quartz crystal microgravimetry, UV-vis absorption spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and transmission electron microscopy.     

Biosynthesis of silver nanoparticles using citrus sinensis peel extract and its antibacterial activity

Biosynthesis of silver nanoparticles (AgNPs) was achieved by a novel, simple green chemistry procedure using citrus sinensis peel extract as a reducing and a capping agent. The effect of temperature on the synthesis of silver nanoparticles was carried out at room temperature (25°C) and 60°C. The successful formation of silver nanoparticles has been confirmed by UV-vis, FTIR, XRD, EDAX, FESEM and TEM analysis and their antibacterial activity against Escherichia coli, Pseudomonas aeruginosa (gram-negative), and Staphylococcus aureus (gram-positive) has been studied. The results suggest that the synthesized AgNPs act as an effective antibacterial agent.     

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.     

Spacer-mediated synthesis of size-controlled gold nanoparticles using geminis as ligands

We report a new methodology for the size-controlled aqueous synthesis of gold nanoparticles using geminis with different spacers as ligands. Geminis possess a unique structure in which two hydrophobic chains and two polar headgroups are combined via a spacer. We herein demonstrate that the spacer can be used as a tool to control particle size when geminis are used as ligands for gold nanoparticles. Varying the spacer length of geminis yields facile control over the size and size distribution of nanoparticles. For the 18-s-18-capped gold nanoparticles, FTIR and TGA experiments indicate that the geminis form bilayers on the surface of gold nanoparticles, which serve as templates that control the formation of nanoparticles. The smallest particles are obtained with a moderate spacer length (s = 8) because in that case the gemini bilayers interdigitate to the fullest degree to reach the maximum chain-chain interaction, thus yielding the most compact coating on the surface of gold nanoparticles. This work provides a new approach to the size control of nanoparticles.     

Synthesis and Catalytic Evaluation of Silver Nanoparticles Synthesized with <Emphasis Type="Italic">Aloysia triphylla</Emphasis> Leaf Extract

In this investigation, we report the biosynthesis of the silver nanoparticles using Aloysia triphylla leaves extract. The as-prepared silver nanoparticles were characterized by ultraviolet–visible (Uv–vis) spectroscopy, X-ray diffractometry, scanning electron microscopy and transmission electron microscopy The infrared spectroscopy (FTIR) and Raman spectroscopy techniques were also used to evaluate the chemical groups of the plant extract involved in the silver ions bioreduction. The results indicate that as the plant extract/precursor salt ratio increases, the size of the nanoparticles decreases. Also, as the reaction temperature increases, the reduction rate increased too, resulting in the formation of smaller nanoparticles-size ranges. Uv–vis spectroscopy illustrates absorption peaks in the range of wavelengths of 430–445 nm corresponding to surface plasmon resonance band of silver nanoparticles. The X-ray diffraction (XRD) confirmed the presence of silver solids with fcc structure type. The FTIR analysis showed that the bands corresponding to phenolic compounds and the amide group were involved in the synthesis and stabilization of silver nanoparticles, respectively. The Raman studies showed bands at 1380 and 1610 cm^?1, which correspond to the aromatic and amide compounds, confirming the FTIR results. The Uv–vis results indicate the capacity of silver nanoparticles to reduce the methylene blue.     

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.     

Biosynthesis and characterization of silver nanoparticles using strawberry seed extract and evaluation of their antibacterial and antioxidant activities

Synthesis of nanomaterials is an emerging field due to their fascinating properties for applications in different field and green synthesis offers various advantages versus physical and chemical methods. Herein, green protocol has been adopted for the synthesis of silver nanoparticles (Ag NPs) using seeds extract of strawberry. The Ag NPs were characterized using advanced techniques comprising UV/Vis, XRD, FTIR, SEM, DLS and EDX. The λ_max for the Ag NPs was recorded at 405 nm. The functional groups present in the extract and involved in Ag ions reduction were determined using FTIR analysis. The SEM-EDX analysis confirmed the mono-dispersive nature of Ag NPs along with confirmation of elemental composition. The nanoparticles size distribution was recorded in 50-70 nm range. Bio-fabricated Ag NPs were appraised for antioxidant activity (DPPH with % inhibition 56.61 and ABTS with % inhibition 77.81) and antimicrobial activity, i.e., Escherichia coli, Salmonella typhimurium, Shigella sonnei, Halomonas halophile, Staphylococcus aureus and Bacillus subtilis. It is concluded that these synthesized NPs could probably be applied as potent antibacterial and antioxidant materials.     

Polymer-induced synthesis of stable gold and silver nanoparticles and subsequent ligand exchange in water

A simple, inexpensive, single-step synthesis of gold and silver nanoparticles using poly(allylamine) (PAAm) as a reducing and stabilizing agent is reported. The synthetic process was carried out in aqueous solution, making the method versatile and environmentally friendly. The synthesized polymer-stabilized nanoparticles are stable in water without particle aggregation at room temperature for at least a month. We demonstrate successful ligand exchange on the polymer-stabilized gold nanoparticles (AuNPs) with a variety of omega-functionalized acid-, alcohol-, amine-, and biotin-terminated alkylthiols. The methodologies, including ligand exchange, also are applicable for the generation of finely dispersed silver nanoparticles. The synthesized gold and silver nanoparticles are characterized by UV-visible absorption spectroscopy and transmission electron microscopy (TEM). The different ligand-stabilized AuNPs are also analyzed by Fourier transform infrared (FTIR) spectroscopy.     

Magnetically separable tea leaf mediated nickel oxide nanoparticles for excellent photocatalytic activity

Synthesis of nanoparticles having low chemical toxicity has been interest of researchers for decades. Utilization of plant phytochemicals as reducing agent is now a globally recognized alternative technique for environmental friendly and low-cost production of nanoparticles. This work reports a facile green synthesis protocol of Nickel Oxide nanoparticles (NiO NPs) using fresh tea leaf extract. The synthesized nanoparticles have been characterized through various analytical techniques like Powder XRD (P-XRD), Fourier Transform Infrared Spectroscopy (FT-IR), Transmission electron microscopy (TEM), Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The XRD results reveal the formation of crystalline nickel oxide nanoparticles. FTIR spectrum displays the existence of different polyphenolic groups over NiO NPs surface. TEM and SEM images indicate the formation of slightly agglomerated spherical nanoparticles with particle size 3–5 ​nm. The nanoparticles were used towards the photocatalytic degradation of both cationic, anionic dyes and their mixtures under optimum conditions in the presence of UV light irradiation. More than 95% degradation was observed for all the dye solutions with 30 ​mg ​L^-1 catalytic dose. Moreover, the degradation efficiency of the nanoparticle was studied by altering various parameters like pH, initial dye concentration and amount of catalytic dose. Pseudo first order kinetic model was employed in all the reactions. A detailed mechanism and kinetics of the all the reactions were studied. Interestingly, the catalyst showed excellent recyclability up-to 4th cycles with very low catalytic activity loss.     

Synthesis of gold nanoparticles by microemulsion assisted photoreduction method

A new, clean, cost-effective and rapid method for the synthesis of stable spherical gold nanoparticles (AuNPs) is developed. This novel technique combines microemulsion as one of soft-nanotechnology techniques of wet chemistry, with photo-physics of UV-radiation in a unique versatile method to design and obtain controlled nanostructures for multifunctional materials. Based on a phase diagram in ternary water/Brij 30/n-heptane system pristine, and thiol functionalized, gold nanoparticles were obtained by a microemulsion assisted photoreduction technique, allowing increased flexibility during the synthesis and selection of materials. The spherical nanoparticles obtained by this route show a homogeneous size distribution, with an average diameter of 11 nm, for pristine gold nanoparticles and of 12 nm, for functionalized species. The evolution of the system at the nanoscale has been studied using, in tandem, UV-VIS and DLS measurements. The structure, size and shape of the final nanoparticles obtained have been evaluated by adequate instrumental techniques: FTIR, XRD and TEM image analysis. Kinetic studies have also been performed in order to follow the evolution of nanospecies during irradiation procedure.