Alloyed Crystalline Au-Ag Hollow Nanostructures with High Chemical Stability and Catalytic Performance

Gum Arabic assisted the biomass synthesis of bimetallic silver copper oxide nanoparticles using gamma-rays for improving bacterial and viral wound healing: Promising antimicrobial activity against foot and mouth disease

In this work, gamma irradiation was used to create bimetallic silver‑copper oxide nanoparticles (Ag-CuO NPs) in an ecologically acceptable way using gum Arabic (GA) polymer as a capping and reducing agent. Bimetallic Ag-CuO NPs were investigated through UV-Vis. spectroscopy, HR-TEM, SEM, DLS, and XRD examinations. The potency of antimicrobial and antibiofilm activities against a few bacterial isolates and Candida sp. had been investigated. Clinical investigations of 30 cows and 20 buffaloes from different sites in Egypt's Sharkia governorate found ulcerative lesions on the mouth and interdigital region. The cytotoxic assay of the generated NPs on BHK-21 was examined. The bimetallic Ag-CuO NPs had an average diameter of 25.58 nm, and the HR-TEM results showed that they were spherical. According to our results, Ag-CuO NPs exhibited the highest antibacterial efficacy against S. aureus (26.5 mm ZOI), K. pneumoniae (26.0 mm ZOI), and C. albicans (28.5 mm ZOI). The growth of biofilms was also successfully inhibited through the application of Ag-CuO NPs by 88.12 % against S. aureus, 87.08 % against C. albicans, and 74.0 % against B. subtilis. The ulcers on the mouth and foot of diseased animals healed in 4-5 days and 1 week, respectively, following topical application of bimetallic Ag-CuO NPs. The results examined the potential protective effects of a dosage of 3.57 μg/mL on cells before viral infection (cell control). According to our research, bimetallic Ag-CuO NPs limit the development of the virus that causes foot-and-mouth disease (FMD). The reduction of a specific FMD virus's cytopathic impact (CPE) on cell development represented the inhibitory effect when compared to identical circumstances without pretreatment with bimetallic Ag-CuO NPs. Their remarkable antibacterial properties at low concentration and continued-phase stability suggest that they may find widespread use in a variety of pharmacological and biological applications, especially in the wound-healing process.

SiO2@AuAg/PDA hybrid nanospheres with photo-thermally enhanced synergistic antibacterial and catalytic activity

Wastewater discharged from industrial, agricultural and livestock production contains a large number of harmful bacteria and organic pollutants, which usually cause serious harm to human health. Therefore, it is urgent to find a "one-stone-two-birds" strategy with good antimicrobial and pollutant degradation activity for treating waste water. In this paper, SiO2@AuAg/Polydopamine (SiO2@AuAg/PDA) core/shell nanospheres, which possessed synergistic "Ag+-release-photothermal" antibacterial and catalytic behaviors, have been successfully prepared via a simple in situ redox polymerization method. The SiO2@AuAg/PDA nanospheres showed good catalytic activity in reducing 4-nitrophenol to 4-aminophenol (0.576 min-1 mg-1). Since the AuAg nanoclusters contain both gold and silver elements, they provided a high photothermal conversion efficiency (48.1%). Under NIR irradiation (808 nm, 2.5 W-2), the catalytic kinetics were improved by 2.2 times. Besides the intrinsic Ag+-release, the photothermal behavior originating from the AuAg bimetallic nanoclusters and the PDA component of SiO2@AuAg/PDA also critically improved the antibacterial performance. Both E. coli and S. aureus could be basically killed by SiO2@AuAg/PDA nanospheres at a concentration of 90 μg mL-1 under NIR irradiation. This "Ag+-release-photothermal" coupled sterilization offers a straightforward and effective approach to antimicrobial therapy, and further exhibits high potential in nanomedicine for combating bacterial contamination in environmental treatment and biological fields.

From Multi- to Single-Hollow Trimetallic Nanocrystals by Ultrafast Heating

Metal nanocrystals (NCs) display unique physicochemical features that are highly dependent on nanoparticle dimensions, anisotropy, structure, and composition. The development of synthesis methodologies that allow us to tune such parameters finely emerges as crucial for the application of metal NCs in catalysis, optical materials, or biomedicine. Here, we describe a synthetic methodology to fabricate hollow multimetallic heterostructures using a combination of seed-mediated growth routes and femtosecond-pulsed laser irradiation. The envisaged methodology relies on the coreduction of Ag and Pd ions on gold nanorods (Au NRs) to form Au@PdAg core-shell nanostructures containing small cavities at the Au-PdAg interface. The excitation of Au@PdAg NRs with low fluence femtosecond pulses was employed to induce the coalescence and growth of large cavities, forming multihollow anisotropic Au@PdAg nanostructures. Moreover, single-hollow alloy AuPdAg could be achieved in high yield by increasing the irradiation energy. Advanced electron microscopy techniques, energy-dispersive X-ray spectroscopy (EDX) tomography, X-ray absorption near-edge structure (XANES) spectroscopy, and finite differences in the time domain (FDTD) simulations allowed us to characterize the morphology, structure, and elemental distribution of the irradiated NCs in detail. The ability of the reported synthesis route to fabricate multimetallic NCs with unprecedented hollow nanostructures offers attractive prospects for the fabrication of tailored high-entropy alloy nanoparticles.

Gamma rays-assisted bacterial synthesis of bimetallic silver-selenium nanoparticles: powerful antimicrobial, antibiofilm, antioxidant, and photocatalytic activities

BACKGROUND

Bimetallic nanoparticles (BNPs) has drawn a lot of attention especially during the last couple of decades. A bimetallic nanoparticle stands for a combination of two different metals that exhibit several new and improved physicochemical properties. Therefore, the green synthesis and design of bimetallic nanoparticles is a field worth exploring.

METHODS

In this study, we present a green synthesis of silver nanoparticles (Ag NPs), selenium (Se) NPs, and bimetallic Ag-Se NPs using Gamma irradiation and utilizing a bacterial filtrate of Bacillus paramycoides. Different Techniques such as UV-Vis., XRD, DLS, SEM, EDX, and HR-TEM, were employed for identifying the synthesized NPs. The antimicrobial and antibiofilm activities of both the Ag/Se monometallic and bimetallic Ag-Se NPs were evaluated against some standard microbial strains including, Aspergillus brasiliensis ATCC16404, Candida albicans ATCC10231, Alternaria alternate EUM108, Fusarium oxysporum EUM37, Escherichia coli ATCC11229, Bacillus cereus ATCC15442, Klebsiella pneumoniae ATCC13883, Bacillus subtilis ATCC15442, and Pseudomonas aeruginosa ATCC6538 as a model tested pathogenic microbes. The individual free radical scavenging potentials of the synthesized Ag NPs, Se NPs, and bimetallic Ag-Se NPs were determined using the DPPH radical scavenging assay. The degradation of methylene blue (MB) dye in the presence of the synthesized Ag NPs, Se NPs, and bimetallic Ag-Se NPs was used to assess their photocatalytic behavior.

RESULTS

According to the UV-Vis. spectrophotometer, the dose of 20.0 kGy that results in Ag NPs with the highest O.D. = 3.19 at 390 nm is the most effective dose. In a similar vein, the optimal dose for the synthesis of Se NPs was 15.0 kGy dose with O.D. = 1.74 at 460 nm. With a high O.D. of 2.79 at 395 nm, the most potent dose for the formation of bimetallic Ag-Se NPs is 15.0 kGy. The recorded MIC-values for Ag-Se NPs were 62.5 µg mL- 1, and the data clearly demonstrated that C. albicans was the organism that was most susceptible to the three types of NPs. The MIC value was 125 µg mL- 1 for both Ag NPs and Se NPs. In antibiofilm assay, 5 µg mL- 1 Ag-Se NPs inhibited C. albicans with a percentage of 90.88%, E. coli with a percentage of 90.70%, and S. aureus with a percentage of 90.62%. The synthesized NPs can be arranged as follows in decreasing order of antioxidant capacity as an antioxidant result: Ag-Se NPs > Se NPs > Ag NPs. The MB dye degradation in the presence of the synthesized Ag NPs, Se NPs, and bimetallic Ag-Se NPs was confirmed by the decrease in the measured absorbance (at 664 nm) after 20 min of exposure to sunlight.

CONCLUSION

Our study provides insight towards the synthesis of bimetallic NPs through green methodologies, to develop synergistic combinatorial antimicrobials with possible applications in the treatment of infectious diseases caused by clinically and industrial relevant drug-resistant strains.

Thermo-responsive palladium-ruthenium nanozyme synergistic photodynamic therapy for metastatic breast cancer management

Reactive oxygen species (ROS) have become an effective "weapon" for cancer therapy due to their strong oxidation and high anti-tumor activity. Photodynamic therapy (PDT) is one of the classical methods to induce reactive oxygen species. Therefore, an ultraminiature palladium ruthenium alloy (sPdRu) and Ru(II) were combined with thermally responsive phase change materials (PCMs). Polypyridyl-complex (RCE) co-encapsulation was performed to obtain thermally responsive nanoparticles (PdRu-RCE@PCMNPs) for multimodal synergistic anti-breast cancer therapy. On the one hand, the thermosensitive PCM protective layer can realize the slow release of sPdRu, and then catalyze the production of oxygen from tumor endogenous H₂O₂ to perform RCE-mediated PDT. At the same time, sPdRu further increased ROS levels through peroxidase (POD) activity. On the other hand, sPdRu has high photothermal conversion efficiency and can be effectively used for photothermal therapy and photodynamic therapy. Importantly, PdRu-RCE@PCM NPs not only can effectively inhibit primary tumor growth, but also can inhibit tumor metastasis. In addition, due to the effective accumulation of sPdRu and RCE, PdRu-RCE@PCM NPs also show excellent fluorescence and photothermal imaging capabilities of tumors, which can be used for tumor tracing and evaluation of treatment. Accordingly, PdRu-RCE@PCM NPs are useful in treating primary tumors and inhibiting tumor metastasis.

Correlation notice on the electrochemical dealloying and antibacterial properties of gold-silver alloy nanoparticles

Galvanic replacement reaction was used in the synthesis of bimetallic gold-silver alloy nanoparticles (Au-Ag NPs), where pre-synthesized Ag nanoparticles-polyvinylpyrrolidone (AgNPs-PVP) were used to reduce the aryldiazonium tetrachloroaurate(III) salt in water. TEM images and EDS elemental analysis showed the formation of spherical Au-Ag NPs with sizes of 12.8 ± 4.9 nm and 25.6 ± 14.4 nm for corresponding Au-Ag ratios and termed as Au_0.91Ag_0.09 and Au_0.79Ag_0.21, respectively, with different concentrations of the gold precursor. The hydrodynamic sizes measured using dynamic light scattering are 46.4 nm and 74.8 nm with corresponding zeta potentials of - 44.56 and - 25.09 mV in water, for Au_0.91Ag_0.09 and Au_0.79Ag_0.21 respectively. Oxidative leachability of Ag ion studies from the starting AgNPs-PVP in 1 M NaCl showed a significant decrease in the plasmon peak after 8 h, indicating the complete dissolution of Ag ions, however, there is enhanced oxidation resistivity of Ag from Au-Ag NPs even after 24 h. Electrochemical studies on glassy carbon electrodes displayed a low oxidation peak in aqueous solutions of 20 mM KCl at 0.16 V and KNO₃ at 0.33 V vs. saturated calomel electrode (SCE). We studied the antibacterial activity of Au-Ag alloy nanoparticles against gram-positive Staphylococcus aureus, Staphylococcus epidermidis, Enterococcus faecalis, and gram-negative Escherichia coli, Salmonella typhimurium, and Pseudomonas aeruginosa. Our findings demonstrated superior antibacterial activity of Au-Ag NPs compared with AgNPs-PVP. Moreover, the nanoparticles inhibited the S. epidermidis biofilm formation.

Cefotaxime incorporated bimetallic silver-selenium nanoparticles: promising antimicrobial synergism, antibiofilm activity, and bacterial membrane leakage reaction mechanism

In this research, we reported for the first time the simple incorporation of antibiotic cefotaxime (CFM) with the synthesized Ag NPs, Se NPs, and bimetallic Ag-Se NPs by gamma rays, as a promising cost-effective, and eco-friendly method. The synthesized nanocomposites were characterized by UV-Vis. spectroscopy, XRD, EDX, HR-TEM, SEM/mapping, and EDX studies. The antimicrobial synergistic potential was investigated after CFM drug incorporation. Antibiofilm activity, growth curve assay, and effect of UV illumination were examined against some pathogenic microbes. The antibacterial reaction mechanism was evaluated by protein leakage assay and SEM imaging. HRTEM imaging confirmed the spherical shape and an average diameter of 10.95, 20.54, and 12.69 nm for Ag NPs, Se NPs, and Ag-Se NPs, respectively. Ag NPs-CFM, Se NPs-CFM, and Ag-Se NPs-CFM possessed antimicrobial activity against Staphylococcus aureus (40, 42, and 43 mm ZOI, respectively), Escherichia coli (33, 35, and 34 mm ZOI, respectively) and Candida albicans (25, 22, and 23 mm ZOI, respectively). CFM-incorporated Ag-Se NPs were able to inhibit biofilm formation of S. aureus (96.09%), E. coli (98.32%), and C. albicans (95.93%). Based on the promising results, the synthesized nanocomposites showed superior antimicrobial potential at low concentrations and continued-phase durability; they may find use in pharmaceutical, and biomedical applications.

Assembly of bimetallic (Au-Ag)FON composite films at liquid/solid interfaces and their tunable optical properties

The regular structure provided by two-dimensional (2D) structural colloidal crystals is widely accepted to provide an ideal template that ensures that plasmonic bimetallic composite nanostructures are uniform. Herein, we report an effective method for fabricating bimetallic Au-Ag composite films loaded on the surfaces of 2D polystyrene@polyacrylic acid (PS@PAA) colloidal crystals. PS@PAA particles coated with uniform Ag particle layers (AgFON) were produced by a simple and effective sputtering-deposition technique, after which the galvanic replacement (GR) reaction was used to produce a bimetallic (Au-Ag)FON composite film at the liquid/solid interface in aqueous HAuCl₄. The morphology and relative contents of the bimetallic (Au-Ag)FON composite film can be regulated by changing the kinetic factors that control the GR reaction, including the concentration and pH of the HAuCl₄ solution, and the reaction time. We demonstrated that the fabricated bimetallic (Au-Ag)FON composite has localized surface plasmon resonance (LSPR) properties that can be regulated by varying the composite structure and Ag/Au composition. On the one hand, the regular 2D colloidal crystal structure provides an ideal template for preparing Au-Ag composite films, which ensures that the optical signals of plasmonic Au-Ag composite films are reproducible. On the other hand, the synergy between Ag and Au in the bimetallic alloy composite film ensures stable and tunable LSPR performance. Furthermore, the prepared 2D ordered (Au-Ag)FON Au-Ag bimetallic material is expected to be used in sensing and catalysis applications.

Non-Noble Plasmonic Metal-Based Photocatalysts

Solar-to-chemical energy conversion via heterogeneous photocatalysis is one of the sustainable approaches to tackle the growing environmental and energy challenges. Among various promising photocatalytic materials, plasmonic-driven photocatalysts feature prominent solar-driven surface plasmon resonance (SPR). Non-noble plasmonic metals (NNPMs)-based photocatalysts have been identified as a unique alternative to noble metal-based ones due to their advantages like earth-abundance, cost-effectiveness, and large-scale application capability. This review comprehensively summarizes the most recent advances in the synthesis, characterization, and properties of NNPMs-based photocatalysts. After introducing the fundamental principles of SPR, the attributes and functionalities of NNPMs in governing surface/interfacial photocatalytic processes are presented. Next, the utilization of NNPMs-based photocatalytic materials for the removal of pollutants, water splitting, CO₂ reduction, and organic transformations is discussed. The review concludes with current challenges and perspectives in advancing the NNPMs-based photocatalysts, which are timely and important to plasmon-based photocatalysis, a truly interdisciplinary field across materials science, chemistry, and physics.

Tailoring noble metal nanoparticle designs to enable sensitive lateral flow immunoassay

Lateral flow immunoassay (LFIA) with gold nanoparticles (AuNPs) as signal reporters is a popular point-of-care diagnostic technique. However, given the weak absorbance of traditional 20-40 nm spherical AuNPs, their sensitivity is low, which greatly limits the wide application of AuNP-based LFIA. With the rapid advances in materials science and nanotechnology, the synthesis of noble metal nanoparticles (NMNPs) has enhanced physicochemical properties such as optical, plasmonic, catalytic, and multifunctional activity by simply engineering their physical parameters, including the size, shape, composition, and external structure. Using these engineered NMNPs as an alternative to traditional AuNPs, the sensitivity of LFIA has been significantly improved, thereby greatly expanding the working range and application scenarios of LFIA, particularly in trace analysis. Therefore, in this review, we will focus on the design of engineered NMNPs and their demonstration in improving LFIA. We highlight the strategies available for tailoring NMNP designs, the effect of NMNP engineering on their performance, and the working principle of each engineering design for enhancing LFIA. Finally, current challenges and future improvements in this field are briefly discussed.

The wetting characteristics of molten Ag-Cu-Au on Cu substrates: a molecular dynamics study

Ag-Cu-Au ternary alloys are promising solder materials for wire bonding. Limited experimental studies on Ag-Cu-Au materials can be found due to the high cost of gold. In this study, face-centered-cubic Cu(100), Cu(111), and Cu(110) substrates wetted by molten Ag45Cu42Au13 were investigated via molecular dynamics (MD). As demonstrated by melting simulation results, the Ag45Cu42Au13 alloy has a lower melting temperature compared to the eutectic alloy, Ag60Cu40. MD methods were also used to investigate the dissolutive characteristics of Ag45Cu42Au13/Cu wetting. Density profiles and contact angles show an increase in wettability in the Ag45Cu42Au13/Cu(100) wetting system. For molten Ag60Cu40 and Ag45Cu42Au13 the spreading behavior on Cu(100) shows a promoted tendency, which contrasts with both Cu(111) and Cu(110). Solid-liquid adhesion is indicative of the comparative spreading degrees. The contact angles and PMF analysis of wetting behaviors on rough and smooth Cu substrates illustrate that solid-liquid adhesion in Wenzel states is stronger than in Cassie wetting states.

Gum Arabic polymer-stabilized and Gamma rays-assisted synthesis of bimetallic silver-gold nanoparticles: Powerful antimicrobial and antibiofilm activities against pathogenic microbes isolated from diabetic foot patients

In this research, irradiation by gamma rays was employed as an eco-friendly route for the construction of bimetallic silver-gold nanoparticles (Ag-Au NPs), while Gum Arabic polymer was used as a capping agent. Ag-Au NPs were characterized through UV-Vis., XRD, EDX, HR-TEM, FTIR, SEM/mapping and EDX analysis. Antibiofilm and antimicrobial activities were examined against some bacteria and Candida sp. isolates from diabetic foot patients. Our results revealed that the synthesis of Ag-Au NPs depended on the concentrations of tetra-chloroauric acid and silver nitrate. HR-TEM analysis confirmed the spherical nature and an average diameter of 18.58 nm. FTIR results assured many functional groups in Gum Arabic which assisted in increasing the susceptibility of incorporation with Ag-Au NPs. Our results showed that, Ag-Au NPs exhibited the highest antimicrobial performance against B. subtilis (14.30 mm ZOI) followed by E. coli (12.50 mm ZOI) and C. tropicalis (11.90 mm ZOI). In addition, Ag-Au NPs were able to inhibit the biofilm formation by 99.64%, 94.15%, and 90.79% against B. subtilis, E. coli, and C. tropicalis, respectively. Consequently, based on the promising properties, they showed superior antimicrobial potential at low concentration and continued-phase durability, they can be extensively-used in many pharmaceutical and biomedical applications.

Improved SERS Performance and Catalytic Activity of Dendritic Au/Ag Bimetallic Nanostructures Based on Ag Dendrites

Bimetallic nanomaterials, which exhibit a combination of the properties associated with two different metals, have enabled innovative applications in nanoscience and nanotechnology. Here, we introduce the fabrication of dendritic Au/Ag bimetallic nanostructures for surface-enhanced Raman scattering (SERS) and catalytic applications. The dendritic Au/Ag bimetallic nanostructures were prepared by combining the electrochemical deposition and replacement reaction. The formation of Au nanoparticle shell on the surface of Ag dendrites greatly improves the stability of dendritic nanostructures, followed by a significant SERS enhancement. In addition, these dendritic Au/Ag bimetallic nanostructures are extremely efficient in degrading 4-nitrophenol (4-NP) compared with the initial dendritic Ag nanostructures. These experimental results indicate the great potential of the dendritic Au/Ag bimetallic nanostructures for the development of excellent SERS substrate and highly efficient catalysts.

Smart microgel-metal hybrid particles of PNIPAM-co-PAA@AgAu: synthesis, characterizations and modulated catalytic activity

Smart pH and thermoresponsive, poly(N-isopropyl acrylamide co acrylic acid) (PNIPAM-co-PAA) microgel particles are used as microreactors to prepare hybrids of gold (Au) and silver (Ag) nanoparticles (PNIPAM-co-PAA@AgAu) using a facile two steps in situ approach. These hybrid particles are characterized using the transmission electron microscope (TEM), UV-VIS spectrometer, and dynamic light scattering (DLS). TEM directly confirms the successful loading of metal nanoparticles onto microgels and the hybrid particles have a narrow size distribution. UV-VIS spectroscopy at different concentration ratios of silver/gold chloride strongly reveals the presence of plasmon peaks of both silver and gold between 10% to 25% of gold chloride concentration. DLS studies demonstrate that these hybrid microgels exhibit both pH and thermoresponsive properties comparatively with a lesser swelling than the pure microgels without loaded nanoparticles. Further, the catalytic activities of PNIPAM-co-PAA@AgAu hybrids are studied through a reduction of 4-nitrophenol (4-NP)-to-4-aminophenol (4-AP) in the presence of sodium borohydride at different pH. Interestingly, these hybrid particles exhibit modulating catalytic activity with variation in pH. The reduction kinetics decreases with increasing pH and the corresponding apparent rate constant exhibits two linear regimes with one at pH below pK_a and another at pH above pK_a of acrylic acid. This pH-modulated catalytic behavior of PNIPAM-co-PAA@AgAu hybrids is discussed based on pH-induced swelling/deswelling transition, the core-shell nature of microgel particles, and its intrinsic interplay with the diffusion of nitrophenols within the microgel network. Finally, our results are compared and discussed in the context of previously studied catalytic activities in different polymer-metal hybrids.

In Situ Decoration of Gold Nanoparticles on Graphene Oxide via Nanosecond Laser Ablation for Remarkable Chemical Sensing and Catalysis

Gold decorated graphene-based nano-hybrids find extensive research interest due to their enhanced chemical catalytic performance and biochemical sensing. The unique physicochemical properties and the very large surface area makes them propitious platform for the rapid buildouts of science and technology. Graphene serves as an outstanding matrix for anchoring numerous nanomaterials because of its atomically thin 2D morphological features. Herein, we have designed a metal-graphene nano-hybrid through pulsed laser ablation. Commercially available graphite powder was employed for the preparation of graphene oxide (GO) using modified Hummers' method. A solid, thin gold (Au) foil was ablated in an aqueous suspension of GO using second harmonic wavelength (532 nm) of the Nd:YAG laser for immediate generation of the Au-GO nano-hybrid. The synthesis strategy employed here does not entail any detrimental chemical reagents and hence avoids the inclusion of reagent byproducts to the reaction mixture, toxicity, and environmental or chemical contamination. Optical and morphological characterizations were performed to substantiate the successful anchoring of Au nanoparticles (Au NPs) on the GO sheets. Remarkably, these photon-generated nano-hybrids can act as an excellent surface enhanced Raman spectroscopy (SERS) platform for the sensing/detection of the 4-mercaptobenzoic acid (4-MBA) with a very low detection limit of 1 × 10-12 M and preserves better reproducibility also. In addition, these hybrid materials were found to act as an effective catalyst for the reduction of 4-nitrophenol (4-NP). Thus, this is a rapid, mild, efficient and green synthesis approach for the fabrication of active organometallic sensors and catalysts.

Time-staggered delivery of erlotinib and doxorubicin by gold nanocages with two smart polymers for reprogrammable release and synergistic with photothermal therapy

Photochemotherapy is currently an effective anticancer therapy. Recently, it has been reported that cancer cells pretreated with epidermal growth factor receptor (EGFR) inhibitor erlotinib (Erl) can significantly synergize its apoptosis against the DNA damaging agent doxorubicin (Dox). As a result, we designed two gold nanocages (Au NCs) microcontainers covered with different smart polymer shell-PAA (pH responsive) and p (NIPAM-co-AM) (temperature responsive) containing Erl and Dox respectively. The acidic tumor microenvironment and NIR light irradiation can selectively activate the release of Erl and Dox. Time staggered release of Erl and Dox and photothermal therapy enhance the apoptotic signaling pathways, resulting in improved tumor cell killing in both MCF-7 (low EGFR expression) and A431 (very high EGFR expression) tumor cells, but more efficient in the latter. The photochemotherapy strategy controls the order and duration of drug exposure precisely in spatial and temporal, and significantly improves the therapeutic efficacy against high EGFR expressed tumors.

Engineering Lignin Stabilized Bimetallic Nanocomplexes: Structure, Mechanistic Elucidation, Antioxidant, and Antimicrobial Potential

Lignin, being a natural antioxidant and antimicrobial underutilized biopolymer derived mainly from agro-waste, is a material of great interest. In this study, lignin was chosen as a matrix to synthesize silver-gold bimetallic and monometallic nanocomplexes to explore the synergistic antioxidant and antimicrobial properties of the lignin stabilized nanoagents. The synthesis of the nanocomplexes was carried out using a one pot method, utilizing lignin as the sole source for reducing, capping, and stabilizing the nanoagents. Further, characterization studies were performed to determine the exact structure of the nanocomplexes. The developed nanocomplexes were found to possess substantial phenolic and flavonoid contents, which contributed to their high antioxidant activity. Further, the antioxidant and antimicrobial activity of the lignin-bimetallic and monometallic nanocomplexes was evaluated and compared with pristine lignin. Moreover, the mechanism behind the antimicrobial activity of the nanocomplexes was elucidated through various methods, namely, reactive oxygen generation, nucleic acid leakage, and DNA cleavage studies. The obtained results were greatly supported by scanning electron microscopy, transmission electron microscopy, and live-dead cell imaging techniques. This study is a contribution in converting waste to value added functional nanomaterials for potential antioxidant and antimicrobial applications.

Chemically Engineered Au-Ag Plasmonic Nanostructures to Realize Large Area and Flexible Metamaterials

We developed a simple and systematic method to fabricate optically tunable and thermally and chemically stable Au-Ag nanocrystal-based plasmonic metamaterials. An Ag nanocrystal-based metamaterial with desirable optical properties was fabricated via nanoimprinting and ligand-exchange process. Its optical properties were controlled by selectively substituting Ag atoms with Au atoms through a spontaneous galvanic replacement reaction. The developed Au-Ag-based metamaterials provide excellent tunable plasmonic properties required for various applications in the visible and near-infrared regions by controlling the Au-Ag composition according to the conditions of the galvanic displacement. Furthermore, their thermal and chemical stabilities significantly improved because of the protective Au thin layer on the surface. Using this developed process, chemically and thermally stable and flexible plasmonic metamaterials were successfully fabricated on a flexible polyester terephthalate substrate.

Dilute Au-Containing Ag Nanosponges as a Highly Active and Durable Electrocatalyst for Oxygen Reduction and Alcohol Oxidation Reactions

Zero-dimensional nanoparticles (NPs) have been demonstrated as the promising class of catalysts for various chemical and electrochemical reactions. However, the emerging Au-Ag NP catalysts suffer from single functionality, limited activity enhancement, and unsatisfactory stability problems. Here, we report a facile kinetically controlled solution method to prepare a new class of Au-Ag nanoporous sponges (NSs) composed of three-dimensional networks without using additional stabilizing agents at room temperature. The unexpected shift of the d-band center in our Au-Ag NSs was observed for the first time in Au-Ag bimetallic systems, which effectively activates the Au-Ag NSs for electrochemical reactions. The robust electronic effect coupled with abundant accessible active sites from the hierarchically porous architecture make the bare Au-Ag NSs a superior multifunctional catalyst for oxygen reduction, ethylene glycol (EG) oxidation, and glucose oxidation reactions compared to the commercial Pt/C electrocatalyst in alkaline medium. The optimized AuAg_3.2 NSs deliver a mass activity of 1.26 A mg_Au^-1 toward oxygen reduction reaction, which is ∼8.2 times as high as that of the Pt/C electrocatalyst, simultaneously showing outstanding stability with negligible activity decay after 10 000 cycles. For the anodic reactions, these AuAg_3.2 NSs show extremely high activity and stability toward both EG and glucose catalytic oxidation reactions with a higher mass activity of 7.58 and 1.48 A mg_Au^-1, about 3- and 18.5-fold enhancement than Pt/C, respectively. This work provides important insights into the structural design, performance optimization, and cost reduction to promote the practical applications of liquid fuel cells.

LSPR Tuning from 470 to 800 nm and Improved Stability of Au-Ag Nanoparticles Formed by Gold Deposition and Rebuilding in the Presence of Poly(styrenesulfonate)

Stability and precise control over functional properties of metal nanoparticles remain a challenge for the realization of prospective applications. Our described process of shell formation and rebuilding can address both these challenges. Template silver nanoparticles (AgNPs) stabilized by poly(styrenesulfonate) are first transformed with gold deposition, after which the resulting shell rebuilds with the replaced silver. The shell formation and rebuilding are accompanied by large shifts in localized surface plasmon resonance (LSPR) peak position, which enables LSPR tuning in a range from 470 to 800 nm. Furthermore, chemical stability of Au-AgNPs is significantly improved compared to AgNPs due to gold stability. Silver templates of different shapes and sizes were demonstrated to transform to AuAg composite NPs to further extend the accessible LSPR range tuning. Stabilization of template AgNPs with poly(styrenesulfonate), in contrast to commonly used poly(vinylpyrrolidone), was found to be a key factor for shell rebuilding. The developed Au-AgNPs were shown to be advantageous for surface plasmon resonance (SPR) detection and surface-enhanced Raman spectroscopy (SERS) owing to their tunable LSPR and enhanced stability.

A novel environmentally sustainable synthesis of Au–Ag@AgCl nanocomposites and their application as an efficient and recyclable catalyst for quinoline synthesis

An eco-friendly synthesis of Au–Ag@AgCl NCs was described using the tuber extract of Nephrolepis cordifolia. The synthetic utility of the NCs was demonstrated by the synthesis of pharmaceutically important quinoline derivatives.

Catalytic CO2 reduction to valuable chemicals using NiFe-based nanoclusters: a first-principles theoretical evaluation

The catalytic performance and possible mechanisms of CO₂ hydrogenation on noble-metal-free NiFe bimetal nanoparticles are theoretically evaluated.

Morphology evolution of Ag/Au nanocomposites via temperature-controlled galvanic exchange to enhance catalytic activity

Morphology-controlled Ag/Au nanocomposites have been fabricated facilely via a modified galvanic replacement reaction using Ag nanocubes as sacrificial templates.

Plasmonic and photo-electrochemical enhancements of the AuAg@Au/RGO–C3N4 nanocomposite for the detection of DA

Plasmonic photocatalyst has attracted significant attention due to its valuable theoretical study and promising practical applications in solar cells, functional composites, and sensors.

Branched Ag nanoplates: synthesis dictated by suppressing surface diffusion and catalytic activity for nitrophenol reduction

Highly branched Ag nanoplates were achieved at extremely low Ag atoms surface diffusion rate, fulfilledviathe Cu under potential deposition.

One-Pot Fabrication of Hollow and Porous Pd-Cu Alloy Nanospheres and Their Remarkably Improved Catalytic Performance for Hexavalent Chromium Reduction

Noble metal nanostructures (NMNSs) play a crucial role in many heterogeneous catalytic reactions. Hollow and porous NMNSs possess generally prominent advantages over their solid counterparts due to their unordinary structural features. In this work, we describe a facial one-pot synthesis of hollow and porous Pd-Cu alloy nanospheres (Pd-Cu HPANSs) through a polyethylenimine (PEI)-assisted oxidation-dissolution mechanism. The strong coordination interaction between Cu^II and PEI facilitates the oxidation-dissolution of the Cu₂O nanospheres template under air conditions, which is responsible for the generation of the Pd-Cu alloy and the convenient removal of the Cu₂O nanospheres template at room temperature. Compared to the commercial Pd black, the Pd-Cu HPANSs show remarkably improved catalytic activity for the reduction of K₂Cr₂O₇ by HCOOH at room temperature, attributing to the enhanced catalytic activity of the Pd-Cu HPANSs for the dehydrogenation decomposition of HCOOH.