Bimetallic Gold Research Articles

Bimetallic Au-Ag Reduced Graphene Oxide Nanostructures for Enhanced Detection of Dengue Virus E Protein

The development of highly sensitive and specific diagnostic tools for early-stage detection of dengue virus (DENV) is critical for effective outbreak management, particularly in resource-limited settings. In this study, we report a novel electrochemical immunosensor based on bimetallic gold silver (Au-Ag) nanoparticles integrated with reduced graphene oxide (rGO) for the detection of dengue virus envelope (E) protein. The Au-Ag bimetallic nanostructures exhibit superior electron transfer kinetics and enhanced electrocatalytic activity, while rGO serves as an excellent platform due to its large surface area and high conductivity. This synergistic combination improves antigen-antibody interactions and significantly boosts sensor performance. The immunosensor demonstrated a broad linear detection range of 100 ag ml−1 to 10 ng ml−1, with a high correlation coefficient (R2 = 0.98519). It achieved an ultra-low limit of detection (LOD) of 4.959 ag ml−1 for DENV E protein, outperforming existing detection methods. These findings highlight the potential of the Au-Ag- rGO-based immunosensor as a promising tool for point-of-care diagnosis, enabling rapid and cost-effective disease management and control.

Novel 3S-shaped biophotonic sensor utilizing MoS2–NSs/ZnO–NWs/AuCu–NCs for rapid detection of Shigella flexneri bacteria

This paper describes a unique, extremely sensitive biophotonic sensor with a three-tier S-tapered (3S) structure. It is designed for the real-time detection of Shigella flexneri (S. flexneri), a common foodborne pathogen that causes severe gastrointestinal diseases. The sensor development includes three distinct diameters of S-tapered structures. The performance of tapered sections was improved by using molybdenum disulfide nanosheets (MoS2-NSs), zinc oxide nanowires (ZnO-NWs), and photoluminescent bimetallic gold–copper nanoclusters (AuCu–NCs). These nanoparticles greatly improve the sensor’s performance. The sensor is further functionalized using anti-S. flexneri antibodies, allowing for the precise detection and capture of the target bacterium. The results show that the sensor can detect S. flexneri rapidly and accurately, with a linear detection range of 1–108 colony-forming units per milliliter (CFU/ml) and a low detection limit of 4.412 CFU/ml. In addition, the sensor’s ability to identify S. flexneri biofilms is demonstrated. Biofilm detection allows us to better understand and control biofilm concerns in the environment, equipment, and biomedical devices. Aptamer examines confirm the sensor’s ability to detect S. flexneri from the lateral direction. This study makes a significant contribution to the field of biosensing because no biophotonic sensor has previously been developed specifically for the detection of S. flexneri, fulfilling a critical gap in the arena of food safety and pathogen detection. The 3S sensor’s performance, robustness, and potential for practical applications make it an important addition to the field of photonics.

Plasmonic-Enhanced Colorimetric Lateral Flow Immunoassays Using Bimetallic Silver-Coated Gold Nanostars.

The colorimetric lateral flow immunoassay (cLFIA) has gained widespread attention as a point-of-care testing (POCT) technique due to its low cost, short analysis time, portability, and capability of being performed by unskilled operators with minimal requirement of reagents. However, the low analytical sensitivity of conventional LFIA based on colloidal gold nanospheres limits their applications for sensitive detection of trace amounts of target analytes. In this study, we introduced a novel plasmonic-enhanced colorimetric LFIA (PE-cLFIA) platform featuring bimetallic silver-coated gold nanostars (BGNS) with exceptional optical properties, leading to ultrahigh visual color brightness. The BGNS-based PE-cLFIA was successfully applied to detect a model analyte, low-calcium response V (LcrV), a virulence protein factor found in Yersinia pestis, the causative agent of bubonic plague. The PE-cLFIA sensing using BGNS-3 composed of 45 nm silver thickness showed a high visual colorimetric sensitivity with a detection limit as low as 13.7 pg/mL, which was around 50 times more sensitive than that of a traditional gold nanoparticle-based LFIA. In addition, the antibody-conjugated BGNS-3 showed excellent stability over 6 months. To illustrate the potential for clinical applications, we demonstrated that our LFIA platform for detecting LcrV spiked in human serum without any sample preprocessing exhibited a detection limit of 22.8 pg/mL. These results open up new opportunities for developing hybrid nanoparticle systems for sensitive POCT PE-cLFIA screening for infectious disease detection.

Characterization of Bimetallic (Zinc and Gold) Nanoparticles of Cryptostegia grandiflora Plant Extract and Their Biological Screening .

The goal of this learning was to explore the uses of Cryptostegia grandiflora plant extract in the green formulation of bimetallic zinc-gold nanoparticles along with pharmacological evaluation. Green synthesis and other techniques are more advantageous than chemical and physical procedures because they produce nanoparticles in an environmentally responsible and economically viable manner. An ethanolic extract of C. grandiflora was obtained through the use of Soxhlet extraction. Additionally, an ethanolic extract of C. grandiflora and components from the extract were identified using GC-MS research after mixing plant extract (C. grandiflora) with zinc acetate and chloroauric acid solutions and letting it sit for a while. UV-visible spectroscopy was employed to analyze the formation of nanoparticles, while FTIR was used for their characterization.

Exploring the influence of ionic liquids on bimetallic gold nanoclusters and cellobiose through DFT analysis

Exploring the influence of ionic liquids on bimetallic gold nanoclusters and cellobiose through DFT analysis

Influence of Ylide Functionalization on the Catalytic Performance of Ferrocenyldiphosphines in Au(I)‐Catalyzed Hydroaminations and Hydrohydrazinations

Ylide‐functionalized phosphines (YPhos) have been shown to yield highly active gold catalysts owing to their high donor capacity. To examine the impact of ylide functionalization on a given ligand structure, a series of ferrocenyl diphosphines functionalized with no, one or two ylide moieties and their corresponding bimetallic gold complexes were prepared. The complexes feature an anti‐conformation of the two phosphine moieties, guaranteeing the presence of two independent metal centers. Comparative studies of the complexes in the hydroamination and hydrohydrazination of alkynes revealed a significant increase in catalytic activity for each newly introduced ylide group. The di‐YPhos ligands were revealed to be the most active precatalysts, functioning effectively even at 0.1 or 0.2 mol% catalyst loading. This catalytic efficiency was demonstrated for a series of alkynes, amines and hydrazines.

Synthesis and characterization of Au@Ag/Ce-UIO-66 nanocomposite for highly sensitive detection of sulfadiazine residue

Antibiotic residue detection plays a key role in ensuring human health. However, rapid, reliable, and highly sensitive detection methods are still insufficient. To tackle this challenge, in this study, the Au@Ag/Ce-UIO-66, a nanocomposite material consisting of bimetallic gold core and silver shell (Au@Ag) introduced on the surface of Ce-UIO-66, was successfully synthesized. By meticulously regulating the exact concentration and volume of silver nitrate, we successfully generated an optimal matrix. This significantly enhanced the detection capability of the probe molecule CV to an impressive concentration of 10−9 M, with a remarkably low relative standard deviation of 7.54 %. The matrix exhibits excellent surface-enhanced Raman scattering (SERS) performance and stability, reaching adsorption equilibrium within 30 min. Moreover, employing this substrate enables the detection of sulfadiazine at concentrations as minimal as 2.5 μg/L, significantly surpassing the standards set by the European Union. Notably, the Raman spectral signal of sulfadiazine maintains stability across various pH conditions at a concentration of 10−5 M. Finally, the adsorption mechanism and enhancement mechanism between Au@Ag/Ce-UIO-66 and sulfadiazine were explored.

Ultrasensitive Aptasensing Platform for the Detection of β-Amyloid-42 Peptide Based on MOF Containing Bimetallic Porphyrin Graphene Oxide and Gold Nanoparticles.

The prompt detection of diseases hinges on the accessibility and the capability to identify relevant biomarkers. The integration of aptamers and the incorporation of nanomaterials into signal transducers have not only expedited but also enhanced the development of nanoaptasensors, enabling heightened sensitivity and selectivity. Here, the bimetallic nickel-cobalt-porphyrin metal-organic framework ((Ni + Cu)TPyP MOF) is regarded as an electron mediator, immobilization platform for an Alzheimer aptamer and to increase the electrochemical signal for the detection of the main biomarker of Alzheimer's disease (AD), amyloid β (Aβ-42). Furthermore, the ((Ni + Cu)TPyP MOF) was combined with reduced graphene oxide (rGO) and gold nanoparticles (AuNPs), on a gold electrode (GE) to provide an efficient interface for immobilizing aptamer strands. Concurrently, the incorporation of rGO and AuNPs imparts enhanced electrical conductivity and efficacious catalytic activity, establishing them as adept electrochemical indicators. Owing to the superior excellent electrical conductivity of rGO and AuNPs, coupled with the presence of ample mesoporous channels and numerous Ni and Cu metal sites within (Ni + Cu)TPyP MOF, this nanostructure with abundant functional groups is proficient in immobilizing a substantial quantity of aptamer. These interactions are achieved through robust π-π stacking and electrostatic interactions, alongside the high affinity between the thiol group of the aptamer and AuNPs concurrently. The as-prepared ternary (Au@(Ni + Cu)TPyP MOF/rGO) nanostructure electrode exhibited an enhancement in its electrochemically active surface area of about 7 times, compared with the bare electrode and the Aβ-42 redox process is highly accelerated, so the peak currents are significantly higher than those obtained with bare GE substrate. Under the optimized conditions, the designed aptasensor had the quantitative detection of Aβ-42 with a low detection limit of 48.6 fg mL-1 within the linear range of 0.05 pg mL-1 to 5 ng mL-1 by differential pulse voltammetry (DPV), accompanied by precise reproducibility, satisfactory stability (95.6% of the initial activity after 10 days), and minimal impact of interfering agents. Recorded results in human blood plasma demonstrated the high efficacy of porphyrin MOF system sensing even in the clinical matrix. The great performance of this aptasensor indicates that our new design of Au@(Ni + Cu)TPyP MOF/rGO nanostructure provides more opportunities for the detection of chemical signals in early diagnosis of Alzheimer's disease.

Label-Free Surface-Enhanced Raman Scattering Detection of Fire Blight Pathogen Using a Pathogen-Specific Bacteriophage.

Fire blight is one of the most devastating plant diseases, causing severe social and economic problems. Herein, we report a novel method based on label-free surface-enhanced Raman scattering (SERS) combined with an Erwinia amylovora-specific bacteriophage that allows detecting efficiently fire blight bacteria E. amylovora for the first time. To achieve the highest SERS signals for E. amylovora, we synthesized and compared plasmonic nanoparticles (PNPs) with different sizes, i.e., bimetallic gold core-silver shell nanoparticles (Au@AgNPs) and monometallic gold nanoparticles (AuNPs) and utilized the coffee-ring effect for the self-assembly of PNPs and enrichment of fire blight bacteria. Furthermore, we investigated the changes in the SERS spectra of E. amylovora after incubation with an E. amylovora-specific bacteriophage, and we found considerable differences in the SERS signals as a function of the bacteriophage incubation time. The results indicate that our bacteriophage-based label-free SERS analysis can specifically detect E. amylovora without the need for peak assignment on the SERS spectra but simply by monitoring the changes in the SERS signals over time. Therefore, our facile method holds great potential for the label-free detection of pathogenic bacteria and the investigation of viral-bacterial interactions.

Synthesis of Bimetallic Gold-Silver Nanoclusters and Its Application as Pb (II) Sensing Based on Fluorescence Technique

Much research has been done on gold nanoclusters stabilized by biomolecules because of their remarkable fluorescence properties and potential biological applications. Here, we synthesize bimetallic gold-silver nanoclusters in a protein template using Galvanic Exchange (GE) Method. The samples were analyzed using UV-visible spectroscopy, a fluorolog (fluorescence spectrometer), and a lifetime kit using Time-Correlated Single-Photon Counting method. It is found that the bimetallic gold-silver nanoclusters emit bright red fluorescence with a long fluorescence lifetime in the range of microseconds. The bimetallic gold nanoclusters were used for Pb (II) detection using fluorescence technique. The fluorescence intensity of nanoclusters increased as the concentration of added Pb (II) increased. This work suggests that bimetallic gold-silver nanoclusters can be used for Pb detection with a detection limit of 15 nmol/L and this sensing will contribute to providing clean water without Pb contamination.

Fabrication and characterization of doxorubicin conjugated bimetallic gold and platinum nanoparticles for human cancer cells and its cell death mechanism

An environmentally friendly preparation technique was used to explore the mechanism of action of hybrid hydrophilic bimetallic gold-platinum (Au@Pt-NPs) against human cancer cell lines, followed by conjugation with doxorubicin (DOX). The synthesized DOX-loaded Au@Pt-NPs (DOX/Au@Pt-NPs) were examined using transmission electron microscopy, X-ray diffraction, and UV–vis spectroscopy to determine their physicochemical characteristics. Using a straightforward incubation method, phytochemicals-mediated capping efficiency and loading of DOX onto the Au@Pt-NPs surface (84%) was demonstrated by FT-IR spectroscopy. Studies on the release kinetics of DOX under acidic tumor conditions revealed a pH-regulated dependence response. According to the in vitro anticancer assessment, human cancer cells treated with DOX-loaded Au@Pt-NPs demonstrated a 3-fold increase in apoptosis compared to DOX treatment alone. Additionally, the DOX/Au@Pt-NPs nanocarrier demonstrated a time-dependent increase in phosphatidylserine flipping, an apoptosis induction marker, and a cell-specific reaction in HeLa and HepG2 cells, according to luminescent results from a real-time, bioluminescent recombinant annexin V test. According to the results, the manufacturing process is simple, and the hydrophilic Au@Pt-NPs were successful in DOX delivery and loading against human cancer cell lines, indicating their prospective as a supplementary for cervical and hepatocellular cancer therapy.

Bimetallic Gold–Iron Oxide Nanoparticles as Carriers of Methotrexate: Perspective Tools for Biomedical Applications

Bimetallic nanoparticles (BMNPs) combine unique and synergistic properties of two metals, allowing new specific applications. In this study, bimetallic AuFe nanoparticles and their conjugates with methotrexate (MTX) were obtained with an environmentally safe method of metal-vapor synthesis. The composition and electronic structure of the particles were investigated with X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray (EDX) spectrum and X-ray absorption spectroscopy (XANES and EXAFS). The effects of BMNP-MTX conjugates on human primary cells and tumor cell lines were evaluated with neutral red uptake and MTT in vitro cytotoxicity assays. Bright-field microscopy analyses of tumor spheroid size and evaluations of tumor spheroid vitality based on SFDA AM staining were carried out. In vitro assays for an antibacterial activity evaluation of the generated samples were performed. The influence of BMNP-MTX on cytokine production with normal leukocytes was assessed using ELISA. X-ray analyses of the samples demonstrated that gold was in the ground state Au0 as well as Au+ and Au3+ states are present in small quantities, whereas iron existed as a mixture of non-histometric oxides with states close to Fe2+ and Fe3+. The modification of the AuFe system with MTX is accompanied by a threefold increase in the relative proportion of the Au+ state. BMNP-MTX conjugates demonstrated significant antitumor activity compared to the drug alone, which proves the ability of the generated nanoconjugates to improve the effectiveness of MTX therapy. This was confirmed by a marked reduction in the size and vitality of AuFe-MTX-treated 3D tumor spheroids. In addition to their selective antitumor activity, AuFe-MTX exhibited moderate antibacterial activity and induced sample-specific cytokine production with normal human leukocytes—which points to an immunostimulatory potential. The present findings indicate important and diverse biological properties of BMNP-MTX conjugates and thus highlight perspectives for their biomedical applications and new immune-specific abilities.

Role of Plasmonic Antenna in Hot Carrier-Driven Reactions on Bimetallic Nanostructures.

Noble metal nanostructures can efficiently harvest electromagnetic radiation, which, in turn, is used to generate localized surface plasmon resonances. Surface plasmons decay, producing hot carriers, that is, short-lived species that can trigger chemical reactions on metallic surfaces. However, noble metal nanostructures catalyze only a very small number of chemical reactions. This limitation can be overcome by coupling such nanostructures with catalytic-active metals. Although the role of such catalytically active metals in plasmon-driven catalysis is well-understood, the mechanistics of a noble metal antenna in such chemistry remains unclear. In this study, we utilize tip-enhanced Raman spectroscopy, an innovative nanoscale imaging technique, to investigate the rates and yields of plasmon-driven reactions on mono- and bimetallic gold- and silver-based nanostructures. We found that silver nanoplates (AgNPs) demonstrate a significantly higher yield of 4-nitrobenzenehtiol to p,p'-dimercaptoazobisbenzene (DMAB) reduction than gold nanoplates (AuNPs). We also observed substantially greater yields of DMAB on silver-platinum and silver-palladium nanoplates (Ag@PtNPs and Ag@PdNPs) compared to their gold analogues, Au@PtNPs and Au@PdNPs. Furthermore, Ag@PtNPs exhibited enhanced reactivity in 4-mercatophenylmethanol to 4-mercaptobenzoic acid oxidation compared to Au@PtNPs. These results showed that silver-based bimetallic nanostructures feature much greater reactivity compared to their gold-based analogues.

Recent Advances in Bimetallic Nanoporous Gold Electrodes for Electrochemical Sensing.

Bimetallic nanocomposites and nanoparticles have received tremendous interest recently because they often exhibit better properties than single-component materials. Improved electron transfer rates and the synergistic interactions between individual metals are two of the most beneficial attributes of these materials. In this review, we focus on bimetallic nanoporous gold (NPG) because of its importance in the field of electrochemical sensing coupled with the ease with which it can be made. NPG is a particularly important scaffold because of its unique properties, including biofouling resistance and ease of modification. In this review, several different methods to synthesize NPG, along with varying modification approaches are described. These include the use of ternary alloys, immersion-reduction (chemical, electrochemical, hybrid), co-electrodeposition-annealing, and under-potential deposition coupled with surface-limited redox replacement of NPG with different metal nanoparticles (e.g., Pt, Cu, Pd, Ni, Co, Fe, etc.). The review also describes the importance of fully characterizing these bimetallic nanocomposites and critically analyzing their structure, surface morphology, surface composition, and application in electrochemical sensing of chemical and biochemical species. The authors attempt to highlight the most recent and advanced techniques for designing non-enzymatic bimetallic electrochemical nanosensors. The review opens up a window for readers to obtain detailed knowledge about the formation and structure of bimetallic electrodes and their applications in electrochemical sensing.

Activity of bimetallic gold–copper catalysts in the photodegradation of malachite green and the photosynthesis of 1,2,3-triazole derivatives

Activity of bimetallic gold–copper catalysts in the photodegradation of malachite green and the photosynthesis of 1,2,3-triazole derivatives

Silver ions-regulated two-stage photoluminescence transformations of glutathione-capped gold nanoclusters from near-infrared (NIR) to visible region: Anti-galvanic reaction and Ag deposition

In the present study, glutathione-capped gold nanoclusters (AuNCs@GSH) were prepared by an improved hydrothermal method, which showed near-infrared (NIR) emission centered at 805 nm. Besides, Ag+ can induce the NIR emission transformations in a two-stage mode under different concentration ranges of Ag+. At the first stage (0.50–15 μM), a new emission at 615 nm was generated while the original NIR emission was quenched upon Ag+ addition; at the second stage (15–120 μM), it shifted to 720 nm gradually along with more Ag+ addition, which realized precise regulation of the emission range of metal nanoclusters from red to NIR region. The in-depth mechanism investigation revealed the transformations in both stages originated from the anti-galvanic reaction (AGR) of AuNCs toward Ag+ and Ag deposition. In detail, the first stage was attributed to the formation of bimetallic gold and silver nanoclusters (Au-AgNCs); while the second stage ascribed to the Ag deposition-induced size growth and composition changes of Au-AgNCs. Therefore, the present study supplies a simple and rapid method for preparing NIR-emitted AuNCs and provides a facile approach to regulate the photoluminescence ranges based on the AGR and Ag deposition.

Radiolysis-Assisted Direct Growth of Gold-Based Electrocatalysts for Glycerol Oxidation.

The electrocatalytic oxidation of glycerol by metal electrocatalysts is an effective method of low-energy-input hydrogen production in membrane reactors in alkaline conditions. The aim of the present study is to examine the proof of concept for the gamma-radiolysis-assisted direct growth of monometallic gold and bimetallic gold-silver nanostructured particles. We revised the gamma radiolysis procedure to generate free-standing Au and Au-Ag nano- and micro-structured particles onto a gas diffusion electrode by the immersion of the substrate in the reaction mixture. The metal particles were synthesized by radiolysis on a flat carbon paper in the presence of capping agents. We have integrated different methods (SEM, EDX, XPS, XRD, ICP-OES, CV, and EIS) to examine in detail the as-synthesized materials and interrogate their electrocatalytic efficiency for glycerol oxidation under baseline conditions to establish a structure-performance relationship. The developed strategy can be easily extended to the synthesis by radiolysis of other types of ready-to-use metal electrocatalysts as advanced electrode materials for heterogeneous catalysis.

Selective aerobic oxidation of benzyl alcohol under ambient conditions using polyionic nanoclay-supported gold/palladium nanoparticles

Oxidation of alcohols to their respective aldehydes, esters, and acids is a common value-added industrial process, though techniques often rely on harsh reaction conditions (e.g., high temperature, strong base, organic solvents, hydrothermal processes) to achieve rapid reaction turnovers. The incorporation of gold and palladium nanoparticles facilitates the dehydrogenation and O2 reduction processes, respectively, and these advantages can be dually incorporated and enhanced using supported nanoparticle alloys. Herein, we utilize polyionic nanoclays (PINCs) as two-dimensional inorganic-organic architectures for supporting monometallic and bimetallic gold and palladium nanocatalysts for the model oxidation of benzyl alcohol to the corresponding aldehyde, ester, and acid. In addition, we present two new PINC surface chemistries (N-methylpyrrolidinium- and pyridinium-functionalized PINCs) and compare their performances as catalyst supports to show that catalyst enhancement is altered by the PINC surface chemistry. Reaction conditions are mild (aqueous, room temperature, open to atmosphere, weak or no base) yet reaction turnovers are comparable to those of more demanding literature accounts.

Electrochemically nanotuned surface comprising 3D bimetallic dendrites fabricated on MWCNT for detection of 1,4-dioxane in water

Water quality has become one of the most serious environmental problems throughout the globe. The recalcitrant molecule, 1,4-Dioxane (1,4-D) has been recognized as a pollutant of rising concern in water, according to the World Health Organization (WHO), and can cause harm to aquatic organisms, animals, and even humans. Thus, it is important to detect 1,4-D in water bodies accurately and sensitively. In light of this, by fine-tuning the electrodeposition conditions, a novel bimetallic copper and gold nanodendritic structure was fabricated on the multiwalled carbon nanotube (MWCNT) functionalized glassy carbon electrode (GCE). The nanosensor was characterized by several physical and electrochemical techniques. The sensor probe exhibits good analytical performance and possess linear dynamic ranges (LDR) between 5 to 103 nM and 0.5 × 105 to 2 × 105 nM. The sensor showed limit of detection (LOD) and limit of quantification (LOQ) of 3.27 ± 0.04 pM and 10.92 ± 0.07 pM, respectively, with a mean response time of 1.65 ± 0.05 s. The sensor's performance was analyzed using tap water and Ganga water, with 90.24–99.57 % and 90.05–98.88 % of 1,4-D recovered without interference, respectively. The entire process of fabricating the surface and testing the 1,4-D takes hardly around 30 min, showing the sensor's applicability in monitoring 1,4-D in the environment.

First principal study of interaction of copper doped gold nanoclusters with glycine

Gold nanoclusters and bimetallic gold nanoclusters are interesting areas of research. These nanoclusters are used for the detection of organic molecules, cancer treatment, bio-imaging, drug delivery etc. In this paper, we studied the interaction of copper doped Au nanoclusters of five, eight, thirteen, fifteen, and eighteen atoms with glycine amino acid. Their HOMO-LUMO gap, adsorption energy, non-covalent interaction, hardness, electrophilicity index, electrochemical potential, and UV-Visible spectra were analyzed. The maximum adsorption energy is found in the nanoclusters Au4Cug(A,B) and Au12Cug(C). Additionally, strong non-covalent interaction is observed in the Au4Cug(A,B) and Au12Cug(B) nanoclusters, which makes them suitable for applications like drug delivery, biosensing etc. These nanoclusters are also more stable compared to other nanoclusters in this work (only exception Au7Cu(A,B,C)) owing to their large HOMO-LUMO gap and symmetric structure.