Synthesis Of Au Nanoparticles Research Articles

Recent Advancements and Unexplored Biomedical Applications of Green Synthesized Ag and Au Nanoparticles: A Review.

Green synthesis of silver (Ag) and gold (Au) nanoparticles (NPs) has acquired huge popularity owing to their potential applications in various fields. A large number of research articles exist in the literature describing the green synthesis of Ag and Au NPs for biomedical applications. However, these findings are scattered, making it time-consuming for researchers to locate promising advancements in Ag and Au NPs synthesis and their unexplored biomedical applications. Unlike other review articles, this systematic study not only highlights recent advancements in the green synthesis of Ag and Au NPs but also explores their potential unexplored biomedical applications. The article discusses the various synthesis approaches for the green synthesis of Ag and Au NPs highlighting the emerging developments and novel strategies. Then, the article reviews the important biomedical applications of green synthesized Ag and Au NPs by critically evaluating the expected advantages. To expose future research direction in the field, the article describes the unexplored biomedical applications of the NPs. Finally, the articles discuss the challenges and limitations in the green synthesis of Ag and Au NPs and their biomedical applications. This article will serve as a valuable reference for researchers, working on green synthesis of Ag and Au NPs for biomedical applications.

Easy synthesis of Au nanoparticles at low temperature using Saponin quillaja sp. and its photocatalytic activity

With Saponin quillaja sp usage as a reducing and stabilizing agent, it was possible to obtain Gold Nanoparticles (AuNPs) at low temperature in short reaction times. The nanoparticles obtained have different sizes and are a function of the synthesis temperature, presenting by Uv–vis spectrocopy the characteristic band at 540 nm of the surface plasmon of the Au nanoparticles. By electron diffraction it was determined that the phase they show is cubic centered on the face, in addition, the AuNps, when impregnated with TiO2, show a strong photocatalytic activity for the reduction of CO2 to other products.

Synthesis of biogenic silver and gold nanoparticles from Anemopsis californica extract with antibacterial and cytotoxic activities

Silver (Ag) and gold (Au) nanoparticles, have gained attention for their unique properties and diverse applications, including medicine and antimicrobial agents. To meet the demand for eco-friendly synthesis methods, we explored plant-mediated nanoparticle synthesis using Anemopsis californica extracts. The Anemopsis californica leaves were used to extract bioactive compounds with water, methanol, and isopropanol. These extracts served as reducing and stabilizing agents for Ag and Au nanoparticle synthesis. The process involved mixing the extract, a metallic precursor solution, and deionized water in specific volume ratios, resulting in nanoparticles denoted as W-(Ag or Au), M-(Ag or Au), and I-(Ag or Au) for water, methanol, and isopropanol, respectively. The synthesized nanoparticles ranged from 5 to 30 nm in size and displayed various shapes. UV-Vis spectroscopy confirmed their presence with surface plasmon resonance bands. Antibacterial tests on Staphylococcus aureus and Escherichia coli showed significant antibacterial effects of Ag nanoparticles, especially those synthesized in methanol. In contrast, Au nanoparticles had limited antibacterial impact, regardless of the solvent. Cytotoxicity evaluations with macrophage cells indicated that Ag nanoparticles were more cytotoxic than Au nanoparticles, with the synthesis solvent influencing cytotoxicity. The observed antibacterial effects of Ag nanoparticles align with their reputation as potent antimicrobial agents, particularly against Gram-positive strains. The limited antibacterial impact of Au nanoparticles suggests differences in their antibacterial mechanisms. Varying cytotoxicity between Ag and Au nanoparticles underscores the significance of the chosen synthesis method in shaping nanoparticle properties.

Synthesis of Au-Nanoparticles on Carbon using Lysine as a Capping Agency in a Gas Diffusion Electrodes Cell for Electrocatalytic CO2 Reduction

Synthesis of Au-Nanoparticles on Carbon using Lysine as a Capping Agency in a Gas Diffusion Electrodes Cell for Electrocatalytic CO2 Reduction

Microwave Synthesis of Au Nanoparticles in the Presence of Tetrahydrothiophenocucurbituril.

The preparation of gold nanoparticles (AuNPs) from tetrachloroauric acid in the presence of tetrahydrothiophenocucurbit[n]uril (THTmQ[n]) has been effectively achieved in a microwave reactor. The reaction was performed in the presence of an excess of the tetrahydrothiopheno function in a partial reductant role, while the remainder formed AuNP-THTmQ[n] conjugates after the reduction was completed with formic acid. An affinity for the AuNPs by the THTmQ[n] was observed in the purification of the NPs via centrifugation, removal of the supernatant and resuspension of the conjugate.

Synthesis of Single Nanometer-Sized Au Nanoparticles Coated with Silica Toward X-Ray Contrast Agent

In this study, we proposed a method for fabricating diagnostic imaging nanoparticles composed of Au nanoparticles and silica shells (Au/SiO2). The proposed method consisted of two steps. The first step was the synthesis of Au nanoparticles. In sodium hydroxide (NaOH) solution, hydrogen tetrachloroaurate (III) trihydrate was reduced with tetrakis(hydroxymethyl)phosphonium chloride to synthesize Au nanoparticles with a diameter of 1.7 ± 0.3 nm. The Au nanoparticles were then coated with silica in the following step. The silica coating was achieved via a sol–gel reaction of tetraethyl orthosilicate in the presence of Au nanoparticles in water/ethanol dissolved in NaOH. The Au/SiO2 nanoparticles degraded faster in saline or phosphate-buffered saline than in water, and the X-ray imaging capability was retained.

Decentralized core-shell Au/Ag bimetallic nanostructures prepared via green approach for catalytic and antimicrobial applications

Synthesis of noble metallic nanomaterials via green routes using various plant extracts has witnessed a remarkable rise in applications and research interest over the past decade. These biogenic routes are devoid of toxic chemicals, harsh preparation environments, and external capping agents, coupled with their cost-effectiveness, have attracted researchers to adopt green chemistry in nanotechnology. In this study, we synthesized Au, Ag, and Au/Ag nanoparticles (NPs) using a facile method employing an extract derived from a mixture of spices. Optical, morphological, and structural analysis is carried out using UV-visible spectroscopy, field emission scanning electron microscopy (FESEM), energy dispersive X-ray analysis (EDAX), Fourier- transform infrared spectroscopy (FTIR), and X-ray diffraction studies (XRD), respectively. The Zeta potential of the prepared NPs was determined using dynamic light scattering spectroscopy (DLS). Optimization of pH to 10 and 8 was performed for the synthesis of Ag and Au NPs, respectively, crucial for precise tuning of their optical absorption spectra. Finite difference time domain (FDTD) simulations validate the experimental findings. The Ag NPs exhibit primarily uniform and spherical size and shape, whereas the Au NPs display a variety of shapes including spheres, rods, and triangular plates. This variation is attributed to the influence of pH and concentration of precursors. TEM analysis confirmed the formation of Au/Ag bimetallic core-shell nanostructures (NSs), characterized by a decentralized gold core. XRD confirmed the formation of FCC crystallites. FTIR spectra identified the possible biological functional groups responsible for reduction and capping. Furthermore, a negative zeta potential exceeding 20 mV confirmed the stable formation of NPs. These NPs were capped by negatively charged functional groups, thereby avoiding agglomeration. Both mono and bimetallic NSs exhibited enhanced catalytic activity for reducing 4-nitrophenol in the presence of sodium borohydride (NaBH4). Furthermore, Ag and Au/Ag NPs have exhibited antibacterial properties against specific bacteria, which are discussed in detail.

Evaluating Antimicrobial Effectiveness of Gold Nanoparticles against Streptococcus oralis.

Biofilm includes many microorganisms that causes the periodontal diseases. The increased drugs resistance against the infectious diseases is a major issue owing to excessive using of a broad spectrum of antibiotics. Recently, metallic nanoparticles (NPs) are being administered to control the growth of different types of microorganisms. For instance, gold nanoparticles (Au NPs) are found to be successful to control and limit the bacterial pathogenicity in the oral cavity without any cytotoxic effects on the human body. Aim. In this paper, it was aimed to detect the antibacterial effect of Au NPs and compare with chlorhexidine (CHX) against Streptococcus oralis (S. oralis) in dental plaque of patients with chronic periodontitis. Materials and Methods. First, supragingival and subgingival plaque samples were collected from the patients suffering from periodontal disease and incubated under aerobic or/and anaerobic conditions. Second, the morphological examination, and biochemical test by Vitec 2 machine are used to confirm the S. oralis species. Third, the synthesis of Au NPs was carried out by seed growth method and their properties were characterized. Finally, the antimicrobial effect of the Au NPs against S. oralis was evaluated by Agar well diffusion method for different Au NPs concentrations (100, 50, 25, 12.5, 6.25, 3.125, 1.562, 0.781, 0.391, 0.195, and 0.097 ppm). CHX was used as the positive control and distilled water as the negative control. The antibacterial activity data were statistically analyzed by least significant difference (LSD) using the Statistical Program for Social Science (SPSS) version 22. Results. The Au NPs with an average particles size of 43 nm, polycrystalline face-centered cubic structure were characterized. The Au NPs at 100 ppm concentration had similar antibacterial effect of CHX for inhibiting the growth of S. oralis, with no significant difference. Conclusions. The Au NPs as an antibacterial agent could be equally effective against S. oralis similar to the CHX when used at higher concentration.

Antifungal Effect of Polymethyl Methacrylate Resin Base with Embedded Au Nanoparticles.

Full and partial restorations in dentistry must replicate the characteristics of the patient's natural teeth. Materials must have good mechanical properties and be non-toxic and biocompatible. Microbes, which can form biofilms, are constantly in contact with restorations. In this study, we investigate how well Candida albicans adheres to a polymethyl methacrylate (PMMA) resin base with gold (Au) nanoparticles. We synthesized Au nanoparticles and characterized them. The average size of Au nanoparticles embedded in PMMA was 11 nm. The color difference ΔE between PMMA and PMMA/Au composites was 2.7 and was still esthetically acceptable to patients. PMMA/Au surfaces are smoother and more hydrophilic than pure PMMA surfaces, and the isoelectric point of both types of surfaces was 4.3. Above the isoelectric point, PMMA/Au surfaces are more negatively charged than PMMA surfaces. The added Au nanoparticles decreased the tensile strength, while the hardness did not change significantly. Adhesion measurements showed that PMMA surfaces modified with Au nanoparticles reduced the extent of microbial adhesion of Candida albicans.

Thymbra spicataleaf extract driven biogenic synthesis of Au/Fe3O4nanocomposite and its bio-application in the treatment of different types of leukemia

AbstractHerein, the bio-inspired synthesis of Au nanoparticles (NPs) adornedThymbra spicataextract functionalized Fe3O4NPs as a novel magnetic nanocomposite has been demonstrated. The plant phytochemicals act as a natural and non-toxic reductant as well as thein situstabilizing agent of the NPs. The Au–Thymbra@Fe3O4composite was characterized over a range of advance physicochemical techniques like fourier transformed infra red (FT-IR) spectroscopy, scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, elemental mapping, vibrating sample magnetometer and inductively coupled plasma-optical emission spectroscopy. Toward its bio-applications, the material was employed investigating the cytotoxicity and leukemic potential against several related cell lines, viz, 32D-FLT3-ITD, HL-60/vcr (acute myeloid leukemia) and MOLT-3, TALL-104 (acute lymphoblastic leukemia)in vitro, following MTT assay. The corresponding inhibition concentration by 50% level, i.e., IC50were evaluated as 125, 150, 133 and 170 µg/mL, respectively. In addition, the Au–Thymbra@Fe3O4nanocomposite proved to be a good antioxidant, which was validated from DPPH radical quenching assay and a significantly good IC50value.

Enhanced catalytic nitrophenol reduction via highly porous hollow silica nanospheres stabilized Au nanoclusters

In this work, we report the synthesis of Au nanoparticles encaged in hollow porous silica nanospheres (Au@HPSNs), which features extremely small Au nanoclusters (∼1.3 nm) encapsulated in high specific surface area (∼800 m2/g) HPSNs. We used the electrostatic attraction between the anions of poly(acrylic acid) (PAA) and protonated poly(ethylenimine) (PEI) to build the micelles system in an ethanol–water system, which was employed as the templates for deposition of silica to give the core–shell structured PEI-PAA@SiO2. The final materials Au@HPSNs were obtained by soaking PEI-PAA@SiO2 in HAuCl4 solution and subsequent calcination. The Au@HPSNs show extremely high catalytic efficiency for 4-nitrophenol (4-NP) reduction with NaBH4, and exhibit the highest heterogeneous Au-based catalytic efficiency up to date for 4-NP reduction. The greatly enhanced performance of Au@HPSNs could be ascribed to ultra-fine Au nanoclusters and the small mass transfer hindrance with high specific surface area hollow porous silica.

Nanogold-decorated reduced graphene oxide for catalytic hydrogenation of 4-nitrophenol

The current work focuses on the efficacious synthesis of Au nanoparticles (NPs) decorated on reduced graphene oxide (RGO) sheets and evaluating and comparing the catalytic efficiency of the latter with graphene oxide (GO) and reduced graphene oxide (RGO) for the hydrogenation of 4-nitrophenol (4-NP). 4-NP is one of the most hazardous and widely investigated nitro compounds. Here, we report a single-step co-reduction approach for synthesizing AuRGO using hydrazine monohydrate as a reducing agent. X-ray diffraction (XRD) patterns of prepared samples confirmed the formation of GO, RGO, and AuRGO. Raman analysis gave insight into the structure and defects of prepared samples. The various oxygen-containing moieties are identified using Fourier transform infrared (FTIR) spectra and confirmed the loss of these functional groups during the reduction of GO into RGO. UV absorption analysis is carried out and is also reinforced by the finite difference time domain (FDTD) simulation studies. X-ray photoelectron spectroscopy (XPS) analysis yielded quantitative information regarding the reduction of GO into RGO and the decoration of zerovalent Au NPs on the RGO surface. Thermogram of the prepared samples manifests the thermal stability of the samples. Field emission scanning electron microscope (FESEM) and transmission electron microscopy (TEM) images depicted the morphology of GO, RGO, and AuRGO. The catalytic efficiency of AuRGO is tested by reducing 4-nitrophenol (4-NP) in the presence of sodium borohydride. AuRGO has shown enhanced catalytic efficiency compared to GO and RGO.

Engineering Shewanella-reduced graphene oxide aerogel biohybrid to efficiently synthesize Au nanoparticles

Biosynthesizing Au nanoparticles (AuNPs) from gold-bearing scraps provides a sustainable method to meet the urgent demand for AuNPs. However, it remains challenging to efficiently biosynthesize AuNPs of which the diameter is less than 10 nm from a trace amount of Au3+ concentration at the level of tens ppm. Here, we constructed an exoelectrogenic cell (eCell)-conductive reduced-graphene-oxide aerogel (rGA) biohybrid by assembling Shewanella sp. S1 (SS1) as living biocatalyst and rGA as conductive adsorbent, in which Au3+ at trace concentrations would be enriched by the adsorption of rGA and reduced to AuNPs through the extracellular electron transfer (EET) of SS1. To regulate the size of the synthesized AuNPs to 10 nm, the strain SS1 was engineered to enhance its EET, resulting in strain RS2 (pYYD-Ptac-ribADEHC & pHG13-Pbad-omcC in SS1). Strain RS2 was further assembled with rGA to construct the RS2-rGA biohybrid, which could synthesize AuNPs with the size of 7.62 ± 2.82 nm from 60 ppm Au3+ solution. The eCell-rGA biohybrid integrated Au3+ adsorption and reduction, which enabled AuNPs biosynthesis from a trace amount of Au3+. Thus, the required Au3+ ions concentration was reduced by one or two orders of magnitude compared with conventional methods of AuNPs biosynthesis. Our work developed an AuNPs size regulation technology via engineering eCell's EET with synthetic biology methods, providing a feasible approach to synthesize AuNPs with controllable size from trace level of gold ions.

Data-Driven Optimization of Au Nanoparticle Synthesis with Automated Flow Microreaction System

We developed a flow microreaction system automated by a LabVIEW-based program enabling a control of flow rates of four pumps, an in-line UV–visible spectroscopic monitoring, and a process data logging including the pump pressures. The system was applied to the synthesis of gold nanoparticles (NPs) by a reduction of hydrogen tetrachloroaurate (III) (HAuCl4) with sodium tetrahydroborate (NaBH4) in the presence of trisodium citrate (Na3C6H5O7). Concentrations of the three reagents were controlled by changing the flow rates and were optimized so that the spectrum of the NPs gave higher peak at shorter wavelength. A gradual change in the concentrations from the dilute condition according to decision-tree algorithm as well as a careful monitoring of the pump pressures were shown to be effective for the optimization without clogging of the particles in the reactor.

Mechanism and kinetics of gold recovery and Au nanoparticle synthesis by Gas-Diffusion Electrocrystallization (GDEx)

Standing at the forefront of cutting-edge research, the electrochemical reduction of gases is not only driving the industrial shift towards electrification and decarbonization but also unlocking the immense potential to pioneer uncharted realms of electrochemical conversions, including metal transformations. Carbon monoxide issued from the electrochemical reduction of CO2 on gas-diffusion electrodes (GDEs), was used for the in-situ reduction of AuCl4− ions into elemental gold nanoparticles (NPs). A minimal extent of CO2 reduction on the uncatalyzed activated carbon of the GDEs was sufficient to fully remove the AuCl4− ions from the electrolyte bulk present in the aqueous electrolyte, while steering their complete precipitation as Au0. A maximum current efficiency of 19% towards CO formation was achieved, under a flow-through gas regime. The efficiency for Au0 precipitation was improved by manipulating the gas-flow regime and cathode polarization. The mechanism and kinetic description for gold recovery and nanoparticle synthesis are portrayed for the reactions underpinning the gas-diffusion electrocrystallization process (GDEx).

Synthesis of Au nanoparticles coated with silica containing polyethylene glycol for extracorporeally dischargeable X-ray contrast agents

Synthesis of Au nanoparticles coated with silica containing polyethylene glycol for extracorporeally dischargeable X-ray contrast agents

Conductometric sensor for gaseous sulfur-mustard simulant by gold nanoparticles anchored on ZnO nanosheets prepared via microwave irradiation

We report the microwave-assisted synthesis of Au nanoparticles (NPs) anchored porous ZnO nanosheets (Au-ZnO NSs) and their application in the sensitive detection of 2-chloroethyl ethyl sulfide (2-CEES) vapors, which are a simulant of sulfur mustard chemical weapon. Upon microwave irradiation for < 1 min with an annealing, highly crystalline Au NPs with a narrow particle-size distribution (2.32 ± 0.40 nm) are densely formed on the surface of porous ZnO NSs, which increases the density of oxygen vacancies in the ZnO. Under the optimal working temperature (450 °C), the response of the Au-ZnO NS sensor was measured to be 787 for 10 ppm 2-CEES, which is ∼14 times higher than that observed for the bare porous ZnO NSs-based sensor. Moreover, Au-ZnO NSs can detect 2-CEES gas even under high humidity (∼80 %) benefiting from its high sensitivity. The highly reproducible sensing performance was verified by repeated sensing test (20 times for 12 h). According to gas screening data, the Au-ZnO NSs exhibited outstanding selectivity toward sulfide compounds due to the high Au-S affinity. In summary, we have successfully demonstrated a simple and facile approach to form the Au-ZnO heterostructure by microwave irradiation and enhanced the gas-sensing performance by inducing catalytic activity.

In situ studies on free-standing synthesis of nanocatalysts via acoustic levitation coupled with pulsed laser irradiation

Acoustic levitation is a distinctive and versatile tool for levitating and processing free-standing single droplets and particles. Liquid droplets suspended in an acoustic standing wave provide container-free environments for understanding chemical reactions by avoiding boundary effects and solid surfaces. We attempted to use this strategy for the production of well-dispersed uniform catalytic nanomaterials in an ultraclean confined area without the addition of external reducing agents or surfactants. In this study, we report on the synthesis of gold and silver nanoparticles (NPs) via acoustic levitation coupled with pulsed laser irradiation (PLI). In situ UV–Visible and Raman spectroscopic techniques were performed to monitor the formation and growth of gold and silver NPs. The PLI was used for the photoreduction of targeted metal ions present in the levitated droplets to generate metal NPs. Additionally, the cavitation effect and bubble movement accelerate the nucleation and decrease the size of NPs. The synthesized Au NPs with ∼ 5 nm size showed excellent catalytic behavior towards the conversion of 4-nitrophenol to 4-aminophenol. This study may open a new door for synthesizing various functional nanocatalysts and for achieving new chemical reactions in suspended droplets.

Microelectromechanical Microsystems-Supported Photothermal Immunoassay for Point-of-Care Testing of Aflatoxin B1 in Foodstuff.

Accurate identification of acutely toxic and low-fatality mycotoxins on a large scale in a quick and cheap manner is critical for reducing population mortality. Herein, a portable photothermal immunosensing platform supported by a microelectromechanical microsystem (MEMS) without enzyme involvement was reported for point-of-care testing of mycotoxins (in the case of aflatoxin B1, AFB1) in food based on the precise satellite structure of Au nanoparticles. The synthesized Au nanoparticles with a well-defined, graded satellite structure exhibited a significantly enhanced photothermal response and were coupled by AFB1 antibodies to form signal conversion probes by physisorption for further target-promoted competitive responses in microplates. In addition, a coin-sized miniature NIR camera device was constructed for temperature acquisition during target testing based on advanced MEMS fabrication technology to address the limitation of expensive signal acquisition components of current photothermal sensors. The proposed MEMS readout-based microphotothermal test method provides excellent AFB1 response in the range of 0.5-500 ng g-1 with detection limits as low as 0.27 ng g-1. In addition, the main reasons for the efficient photothermal transduction efficiency of Au with different graded structures were analyzed by finite element simulations, providing theoretical guidance for the development of new Au-based photothermal agents. In conclusion, the proposed portable micro-photothermal test system offers great potential for point-of-care diagnostics for residents, which will continue to facilitate immediate food safety identification in resource-limited regions.

Efficient preparation of polyoxometalate-junctional cross-linking hybrid nanocomposites by polymerization-induced self-assembly.

We reported a facile method for the preparation of POM-polymer hybrids in one-pot via polymerization-induced self-assembly. Polyoxometalate macroanions were complexed with cations to prepare cross-linking agents. RAFT dispersion polymerization was conducted in the presence of the cross-linking agent. The hybrid nanoparticles can be used as nanoreactors for the photocatalytic synthesis of Au nanoparticles.