Designed synthesis of Au/Ag/Pd trimetallic nanoparticle-based catalysts for Sonogashira coupling reactions

B and N Codoped Cellulose-Supported Ag-/Bi-Doped Mo(S,O)3 Trimetallic Sulfo-Oxide Catalyst for Photocatalytic H2 Evolution Reaction and 4-Nitrophenol Reduction

Cellulose plays a significant role in designing efficient and stable cellulose-based metallic catalysts, owing to its surface functionalities. Its hydroxyl groups are used as anchor sites for the nucleation and growth of metallic nanoparticles and, as a result, improve the stability and catalytic activity. Meanwhile, cellulose is also amenable to surface modifications to be more suitable for incorporating and stabilizing metallic nanoparticles. Herein, the Ag-/Bi-doped Mo(S,O)3 trimetallic sulfo-oxide anchored on B and N codoped cellulose (B-N-C) synthesized by a facile approach showed excellent stability and catalytic activity for PHER at 573.28 μmol/h H2 with 25 mg of catalyst under visible light, and 92.3% of the 4-nitrophenol (4-NP) reduction was achieved within 135 min by in situ-generated protons. In addition to B and N codoping, our use of the calcination method for B-N-C preparation further increases the structural disorders and defects, which act as anchoring sites for Ag-/Bi-doped Mo(S,O)3 nanoparticles. The Ag-/Bi-doped Mo(S,O)3@B-N-C surface active site also stimulates H2O molecule adsorption and activation kinetics and reduces the photogenerated charge carrier's recombination rate. The Mo4+ → Mo6+ electron hopping transport and the O 2p and Bi 6s orbital overlap facilitate the fast electron transfer by enhancing the electron's lifetime and photoinduced charge carrier mobility, respectively. In addition to acting as a support, B-N-C provides a highly conductive network that enhances charge transport, and the relocated electron in B-N-C activates the H2O molecule, which enables Ag-/Bi-doped Mo(S,O)3@B-N-C to have appreciable PHER performance.

Advanced Functionalized Nanoclusters (Cu, Ag, and Au) as Effective Catalyst for Organic Transformation Reactions

A considerable amount of research has been carried out in recent years on synthesizing metal nanoclusters (NCs), which have wide applications in the field of optical materials with non-linear properties, bio-sensing, and catalysis. Aside from being structurally accurate, the atomically precise NCs possess well-defined compositions due to significant tailoring, both at the surface and the core, for certain functionalities. To illustrate the importance of atomically precise metal NCs for catalytic processes, this review emphasizes 1) the recent work on Cu, Ag, and Au NCs with their synthesis, 2) the parameters affecting the activity and selectivity of NCs catalysis, and 3) the discussion on the catalytic potential of these metal NCs. Additionally, metal NCs will facilitate the design of extremely active and selective catalysts for significant reactions by elucidating catalytic mechanisms at the atomic and molecular levels. Future advancements in the science of catalysis are expected to come from the potential to design NCs catalysts at the atomic level.

Visible Light Induced Nano-Photocatalysis Trimetallic Cu0.5Zn0.5-Fe: Synthesis, Characterization and Application as Alcohols Oxidation Catalyst

Here, we report a visible light-induced-trimetallic catalyst (Cu0.5Zn0.5Fe2O4) prepared through green synthesis using Tilia plant extract. These nanomaterials were characterized for structural and morphological studies using powder x-ray diffraction (P-XRD), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The spinel crystalline material was ~34 nm. In benign reaction conditions, the prepared photocatalyst oxidized various benzylic alcohols with excellent yield and selectivity toward aldehyde with 99% and 98%; respectively. Aromatic and aliphatic alcohols (such as furfuryl alcohol and 1-octanol) were photo-catalytically oxidized using Cu0.5Zn0.5Fe2O4, LED light, H2O2 as oxidant, 2 h reaction time and ambient temperature. The advantages of the catalyst were found in terms of reduced catalyst loading, activating catalyst using visible light in mild conditions, high conversion of the starting material and the recyclability up to 5 times without loss of the selectivity. Thus, our study offers a potential pathway for the photocatalytic nanomaterial, which will contribute to the advancement of photocatalysis studies.

Alkynyl transmetalation triggered by a nucleophilic attack

We report an interesting alkynyl transmetalation process in the cyclization of π-Au,σ-M acetylides (M = Pd, Ni, Pt) bearing a N-propiolic formamidine moiety. The cyclization was triggered by nucleophilic attack,...

Synthesis and potential applications of trimetallic nanostructures

The present review highlights the synthetic strategies and potential applications of TMNs for organic reactions, environmental remediation, and health-related activities.

Silver nanomaterials: synthesis and (electro/photo) catalytic applications

In view of their unique characteristics and properties, silver nanomaterials (Ag NMs) have been used not only in the field of nanomedicine but also for diverse advanced catalytic technologies. In this comprehensive review, light is shed on general synthetic approaches encompassing chemical reduction, sonochemical, microwave, and thermal treatment among the preparative methods for the syntheses of Ag-based NMs and their catalytic applications. Additionally, some of the latest innovative approaches such as continuous flow integrated with MW and other benign approaches have been emphasized that ultimately pave the way for sustainability. Moreover, the potential applications of emerging Ag NMs, including sub nanomaterials and single atoms, in the field of liquid-phase catalysis, photocatalysis, and electrocatalysis as well as a positive role of Ag NMs in catalytic reactions are meticulously summarized. The scientific interest in the synthesis and applications of Ag NMs lies in the integrated benefits of their catalytic activity, selectivity, stability, and recovery. Therefore, the rise and journey of Ag NM-based catalysts will inspire a new generation of chemists to tailor and design robust catalysts that can effectively tackle major environmental challenges and help to replace noble metals in advanced catalytic applications. This overview concludes by providing future perspectives on the research into Ag NMs in the arena of electrocatalysis and photocatalysis.

Study of Ultrasonic Attenuation and Thermal Conduction in Bimetallic Gold/Platinum Nanofluids : Effect of thermal conductivity on ultrasonic attenuation of gold and gold/platinum nanofluids

Here, we report the frequency dependent ultrasonic attenuation of monometallic gold and bimetallic gold/platinum based aqueous nanofluids (NFs). The as-synthesised bimetallic NFs (BMNFs) revealed less resistance to ultrasonic waves compared to the monometallic NFs. Thermal conductivity of both NFs taken at different concentrations revealed substantial conductivity improvement when compared to the base fluid, although gold/platinum showed lesser improvement compared to gold. Characterisation of the as-synthesised nanoparticles (NPs) and fluids was carried out with X-ray diffraction (XRD), ultraviolet-visible (UV-vis) spectroscopy, transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDS). The distinct two-phase bimetallic nature of gold/platinum, its two plasmonic band optical absorption features and the spherical morphology of the particles were shown. The findings were correlated with the observed thermal and ultrasonic behaviour and proper rationalisation is provided. It was revealed that the comparatively lesser thermal conductivity of gold/platinum had direct implication on its attenuation property. The findings could have important repercussions in both industrial applications and in the mechanistic approach towards the field of ultrasonic attenuation in NFs.

Development of Multi-concentration Cu:Ag Bimetallic Nanoparticles as a Promising Bactericidal for Antibiotic-Resistant Bacteria as Evaluated with Molecular Docking Study

The present study is concerned with evaluating the influence of various concentrations of Ag within Cu:Ag bimetallic nanoparticles developed for use as a promising anti-bacterial agent against antibiotic-resistant bacteria. Here, Cu:Ag bimetallic nanoparticles with various concentration ratios (2.5, 5.0, 7.5, and 10 wt%) of Ag in fixed amount of Cu labeled as 1:0.025, 1:0.050, 1:0.075, and 1:0.1 were synthesized using co-precipitation method with ammonium hydroxide and deionized water as solvent, polyvinyl pyrrolidone as a capping agent, and sodium borohydride and ascorbic acid as reducing agents. These formulated products were characterized through a variety of techniques. XRD confirmed phase purity and detected the presence of distinct fcc structures belonging to Cu and Ag phases. FTIR spectroscopy confirmed the presence of vibrational modes corresponding to various functional groups and recorded characteristic peak emanating from the bimetallic. UV-visible spectroscopy revealed reduction in band gap with increasing Ag content. SEM and HR-TEM micrographs revealed spherical morphology of Ag-doped Cu bimetallic with small and large scale agglomerations. The samples exhibited varying dimensions and interlayer spacing. Bactericidal action of synthesized Cu:Ag bimetallic NPs depicted statistically significant (P < 0.05) inhibition zones recorded for various concentrations of Ag dopant against Staphylococcus aureus (S. aureus), Escherichia coli (E. coli), and Acinetobacter baumannii (A. baumannii) ranging from (0.85-2.8 mm), (0.55-1.95 mm) and (0.65-1.85 mm), respectively. Broadly, Cu:Ag bimetallic NPs were found to be more potent against gram-positive compared with gram-negative. Molecular docking study of Ag-Cu bimetallic NPs was performed against β-lactamase which is a key enzyme of cell wall biosynthetic pathway from both S. aureus (Binding score: - 4.981 kcal/mol) and A. bauminnii (Binding score: - 4.013 kcal/mol). Similarly, binding interaction analysis against FabI belonging to fatty acid biosynthetic pathway from A. bauminnii (Binding score: - 3.385 kcal/mol) and S. aureus (Binding score: - 3.012 kcal/mol) along with FabH from E. coli (Binding score: - 4.372 kcal/mol) was undertaken. These theoretical computations indicate Cu-Ag bimetallic NPs as possible inhibitor of selected enzymes. It is suggested that exploring in vitro inhibition potential of these materials may open new avenues for antibiotic discovery.

Chitosan capped noble metal doped CeO2 nanomaterial: Synthesis, and their enhanced catalytic activities

Chitosan (Ch) capped Ch-CeO₂, Ch-CeO₂/Ag, Ch-CeO₂/Pd and Ch-CeO₂/Ag/Pd nanomaterials were fabricated using seedless and metal displacement plating method. The Ce⁴⁺ ions first formed complex with Ch through amino and hydroxyl groups and then reduced in presence of NaOH and molecular oxygen at higher temperature. Ch-Ag⁺ and Ch-Pd²⁺ complexes adsorbed on the surface of Ch-CeO₂ and reduced under potential deposition. Ninhydrin reaction test was conducted to confirm the presence of chitosan on the surface of NMs. The catalytic efficiency was increases markedly with incorporating noble metal into Ch-CeO₂ NMs. Ch-CeO₂/Ag/Pd exhibits higher catalytic performance towards hydrogen generation due to the narrow band gap (2.65 eV) and smaller work function of CeO₂ (ϕ = 2.8 eV) than that of Ag⁰(ϕ =4.6 eV) and Pd⁰ (ϕ = 5.2 eV). Hydrogen generation rates increases with temperature and activation energies were found to be 63.2, 60.3, 56.2 and 53.0 kJ/mol for Ch-CeO₂, Ch-CeO₂/Ag, Ch-CeO₂/Pd, and Ch-CeO₂/Ag/Pd, respectively. CeO₂/Ag/Pd shows better catalytic efficiency due to the strong interaction between Ag/Pd metal and active support CeO₂. The photocatalytic rates drastically inhibited with scavengers, demonstrate that the reactive radical oxygen species (HO and O₂^-), holes (h⁺) and electrons (e^-) played major role in the NaBH₄ hydrolysis.

Trimetallic Nanoparticles: Greener Synthesis and Their Applications

Nanoparticles (NPs) and multifunctional nano-sized materials have significant applications in diverse fields, namely catalysis, sensors, optics, solar energy conversion, cancer therapy/diagnosis, and bioimaging. Trimetallic NPs have found unique catalytic, active food packaging, biomedical, antimicrobial, and sensing applications; they preserve an ever-superior level of catalytic activities and selectivity compared to monometallic and bimetallic nanomaterials. Due to these important applications, a variety of preparation routes, including hydrothermal, microemulsion, selective catalytic reduction, co-precipitation, and microwave-assisted methodologies have been reported for the syntheses of these nanomaterials. As the fabrication of nanomaterials using physicochemical methods often have hazardous and toxic impacts on the environment, there is a vital need to design innovative and well-organized eco-friendly, sustainable, and greener synthetic protocols for their assembly, by applying safer, renewable, and inexpensive materials. In this review, noteworthy recent advancements relating to the applications of trimetallic NPs and nanocomposites comprising these NPs are underscored as well as their eco-friendly and sustainable synthetic preparative options.

Pd-Promoted cross coupling of iodobenzene with vinylgold via an unprecedented phenyl transmetalation from Pd to Au

Oxidative addition of Pd/Au vinylene species with iodobenzene reveals the effect of a strong metallophilic Pd⋯Au interaction on phenyl transmetalation from Pd^IV to Au^I, which allows subsequent reductive elimination of LAuI at Pd and Au.

Ag-Based nanocomposites: synthesis and applications in catalysis

Ag-Based nanocomposites, including supported Ag nanocomposites and bimetallic Ag nanocomposites, have been intensively investigated as highly efficient catalysts because of their high activity and stability, easy preparation, low cost, and low toxicity. Herein, we systematically summarize and comprehensively evaluate versatile synthetic strategies for the preparation of Ag-based nanocomposites, and outline their recent advances in catalytic oxidation, catalytic reduction, photocatalysis and electrocatalysis. In addition, the challenges and prospects related to Ag-based nanocomposites for various catalytic applications are also discussed. In light of the most recent advances in Ag-based nanocomposites for catalysis applications, this review provides a comprehensive assessment on the material selection, synthesis and catalytic characteristics of these catalysts, which offers a strategic guide to build a close connection between Ag nanocomposites and catalysis applications.

Three to tango requires a site-specific substitution: heterotrimetallic molecular precursors for high-voltage rechargeable batteries

Design of heterotrimetallic molecules, especially those containing at least two different metals with close atomic numbers, radii, and the same coordination number/environment is a challenging task. This quest is greatly facilitated by having a heterobimetallic parent molecule that features multiple metal sites with only some of those displaying substitutional flexibility. Recently, a unique heterobimetallic complex LiMn2(thd)5 (thd = 2,2,6,6-tetramethyl-3,5-heptanedionate) has been introduced as a single-source precursor for the preparation of a popular spinel cathode material, LiMn2O4. Theoretical calculations convincingly predict that in the above trinuclear molecule only one of the Mn sites is sufficiently flexible to be substituted with another 3d transition metal. Following those predictions, two heterotrimetallic complexes, LiMn2-x Co x (thd)5 (x = 1 (1a) and 0.5 (1b)), that represent full and partial substitution, respectively, of Co for Mn in the parent molecule, have been synthesized. X-ray structural elucidation clearly showed that only one transition metal position in the trinuclear molecule contains Co, while the other site remains fully occupied by Mn. A number of techniques have been employed for deciphering the structure and composition of heterotrimetallic compounds. Synchrotron resonant diffraction experiments unambiguously assigned 3d transition metal positions as well as provided a precise "site-specific Mn/Co elemental analysis" in a single crystal, even in an extremely difficult case of severely disordered structure formed by the superposition of two enantiomers. DART mass spectrometry and magnetic measurements clearly confirmed the presence of heterotrimetallic species LiMnCo(thd)5 rather than a statistical mixture of two heterobimetallic LiMn2(thd)5 and LiCo2(thd)5 molecules. Heterometallic precursors 1a and 1b were found to exhibit a clean decomposition yielding phase-pure LiMnCoO4 and LiMn1.5Co0.5O4 spinels, respectively, at the relatively low temperature of 400 °C. The latter oxide represents an important "5V spinel" cathode material for the lithium ion batteries. Transmission electron microscopy confirmed a homogeneous distribution of transition metals in quaternary oxides obtained by pyrolysis of single-source precursors.

Growth of Au-Pd2Sn Nanorods via Galvanic Replacement and Their Catalytic Performance on Hydrogenation and Sonogashira Coupling Reactions

Colloidal Pd₂Sn and Au-Pd₂Sn nanorods (NRs) with tuned size were produced by the reduction of Pd and Sn salts in the presence of size- and shape-controlling agents and the posterior growth of Au tips through a galvanic replacement reaction. Pd₂Sn and Au-Pd₂Sn NRs exhibited high catalytic activity toward quasi-homogeneous hydrogenation of alkenes (styrene and 1-octene) and alkynes (phenylacetylene and 1-octyne) in dichloromethane. Au-Pd₂Sn NRs showed higher activity than Pd₂Sn for 1-octene, 1-octyne, and phenylacetylene. In Au-Pd₂Sn heterostructures, X-ray photoelectron spectroscopy evidenced an electron donation from the Pd₂Sn NR to the Au tips. Such heterostructures showed distinct catalytic behavior in the hydrogenation of compounds containing a triple bond such as tolan. This can be explained by the aurophilicity of triple bonds. To further study this effect, Pd₂Sn and Au-Pd₂Sn NRs were also tested in the Sonogashira coupling reaction between iodobenzene and phenylacetylene in N, N-dimethylformamide. At low concentration, this reaction provided the expected product, tolan. However, at high concentration, more reduced products such as stilbene and 1,2-diphenylethane were also obtained, even without the addition of H₂. A mechanism for this unexpected reduction is proposed.

Eco-friendly green synthesis of Ag@Fe bimetallic nanoparticles: Antioxidant, antimicrobial and photocatalytic degradation of bromothymol blue

Silver-iron bimetallic nanoparticles (BMNPs) were synthesized by using AgNO₃ and Fe(NO₃)₃ as an Ag/Fe source in presence of Palm dates fruit. Upon addition of extract to a solution of Ag⁺ and Fe³⁺, a prefect transparent stable dark brown color appears with in a few minuets at room temperature. In order to conform the nature of resulting color, UV-visible spectroscopy, transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDX) techniques were used. The absence of surface plasmon resonance (SPR) peaks in the entire UV-visible region suggests the formation of silver_core-iron_shell BMNPs. The obtained nanoparticles were used as a catalyst for the degradation of bromothymol blue (BTB) in absence and presence of sunlight. The degradation kinetics was studied in presence of electron acceptors and scavengers, such as hydrogen peroxide, ammonium oxalate, ammonium per sulphate, benzoquinone, isopropyl alcohol, n-butanol, potassium bromate and potassium iodide. Radical trapping experiments demonstrates that active holes (h⁺) and generated hydroxy radical are primary species involved in H₂O₂ assisted catalytic degradation process. The free-radical scavenging, antioxidant and antimicrobial activities were determined for extract and BMNPs. The 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging activities were found to increase with increasing the amounts of extract. The silver-iron showed good invitro antibacterial activities against human pathogens.

Galvanic replacement reaction: recent developments for engineering metal nanostructures towards catalytic applications

Recent developments to achieve further physicochemical control in metallic nanomaterials by galvanic replacement are discussed towards applications in catalysis.

Asymmetric transfer hydrogenation–Sonogashira coupling one-pot enantioselective tandem reaction catalysed by Pd(0)–Ru(iii)/diamine-bifunctionalized periodic mesoporous organosilica

Pd(0)–Ru(iii)/diamine-functionalized periodic mesoporous organosilica for asymmetric transfer hydrogenation–Sonogashira coupling of iodoacetophenone and arynes is investigated.

Preparation of fluorescent Au–SiO2 core–shell nanoparticles and nanorods with tunable silica shell thickness and surface modification for immunotargeting

Scalable methods for preparing and modifying Au–SiO₂ core–shell nanoparticles provide a platform for engineering size-dependent multifunctional properties for in vivo biomedical applications.

Mixed Phytochemicals Mediated Synthesis of Multifunctional Ag-Au-Pd Nanoparticles for Glucose Oxidation and Antimicrobial Applications

The growing awareness toward the environment is increasing commercial demand for nanoparticles by green route syntheses. In this study, alloy-like Ag-Au-Pd trimetallic nanoparticles have been prepared by two plants extracts Aegle marmelos leaf (LE) and Syzygium aromaticum bud extracts (CE). Compositionally different Ag-Au-Pd nanoparticles with an atomic ratio of 5.26:2.16:1.0 (by LE) and 11.36:13.14:1.0 (by LE + CE) of Ag:Au:Pd were easily synthesized within 10 min at ambient conditions by changing the composition of phytochemicals. The average diameters of the nanoparticles by LE and LE + CE are ∼8 and ∼11 nm. The catalytic activity of the trimetallic nanoparticles was studied, and they were found to be efficient catalysts for the glucose oxidation process. The prepared nanoparticles also exhibited efficient antibacterial activity against a model Gram-negative bacteria Escherichia coli. The catalytic and antimicrobial properties of these readymade trimetallic nanoparticles have high possibility to be utilized in diverse fields of applications such as health care to environmental.

Bacteriagenic silver nanoparticles: synthesis, mechanism, and applications

Silver nanoparticles (AgNPs) have received tremendous attention due to their significant antimicrobial properties. Large numbers of reports are available on the physical, chemical, and biological syntheses of colloidal AgNPs. Since there is a great need to develop ecofriendly and sustainable methods, biological systems like bacteria, fungi, and plants are being employed to synthesize these nanoparticles. The present review focuses specifically on bacteria-mediated synthesis of AgNPs, its mechanism, and applications. Bacterial synthesis of extra- and intracellular AgNPs has been reported using biomass, supernatant, cell-free extract, and derived components. The extracellular mode of synthesis is preferred over the intracellular mode owing to easy recovery of nanoparticles. Silver-resistant genes, c-type cytochromes, peptides, cellular enzymes like nitrate reductase, and reducing cofactors play significant roles in AgNP synthesis in bacteria. Organic materials released by bacteria act as natural capping and stabilizing agents for AgNPs, thereby preventing their aggregation and providing stability for a longer time. Regulation over reaction conditions has been suggested to control the morphology, dispersion, and yield of nanoparticles. Bacterial AgNPs have anticancer and antioxidant properties. Moreover, the antimicrobial activity of AgNPs in combination with antibiotics signifies their importance in combating the multidrug-resistant pathogenic microorganisms. Multiple microbicidal mechanisms exhibited by AgNPs, depending upon their size and shape, make them very promising as novel nanoantibiotics.

Improved catalytic activity and surface electro-kinetics of bimetallic Au–Ag core–shell nanocomposites

The Au_core–Ag_shell and hollow Ag–Au alloy nanostructures significantly improved (∼2 times) the reduction of 1,3-dinitrobenzene relative to the monometallic ones demonstrating the role of the synergistic effect of the Au–Ag interface in catalytic activity.

Core-size-dependent catalytic properties of bimetallic Au/Ag core-shell nanoparticles

Bimetallic core-shell nanoparticles have recently emerged as a new class of functional materials because of their potential applications in catalysis, surface enhanced Raman scattering (SERS) substrate and photonics etc. Here, we have synthesized Au/Ag bimetallic core-shell nanoparticles with varying the core diameter. The red-shifting of the both plasmonic peaks of Ag and Au confirms the core-shell structure of the nanoparticles. Transmission electron microscopy (TEM) analysis, line scan EDS measurement and UV-vis study confirm the formation of core-shell nanoparticles. We have examined the catalytic activity of these core-shell nanostructures in the reaction between 4-nitrophenol (4-NP) and NaBH4 to form 4-aminophenol (4-AP) and the efficiency of the catalytic reaction is found to be increased with increasing the core size of Au/Ag core-shell nanocrystals. The catalytic efficiency varies from 41.8 to 96.5% with varying core size from 10 to 100 nm of Au/Ag core-shell nanoparticles, and the Au100/Ag bimetallic core-shell nanoparticle is found to be 12-fold more active than that of the pure Au nanoparticles with 100 nm diameter. Thus, the catalytic properties of the metal nanoparticles are significantly enhanced because of the Au/Ag core-shell structure, and the rate is dependent on the size of the core of the nanoparticles.

Trimetallic nanostructures: the case of AgPd-Pt multiply twinned nanoparticles

We report the synthesis, structural characterization, and atomistic simulations of AgPd-Pt trimetallic (TM) nanoparticles. Two types of structure were synthesized using a relatively facile chemical method: multiply twinned core-shell, and hollow particles. The nanoparticles were small in size, with an average diameter of 11 nm and a narrow distribution, and their characterization by aberration corrected scanning transmission electron microscopy allowed us to probe the structure of the particles at an atomistic level. In some nanoparticles, the formation of a hollow structure was also observed, that facilitates the alloying of Ag and Pt in the shell region and the segregation of Ag atoms on the surface, affecting the catalytic activity and stability. We also investigated the growth mechanism of the nanoparticles using grand canonical Monte Carlo simulations, and we have found that Pt regions grow at overpotentials on the AgPd nanoalloys, forming 3D islands at the early stages of the deposition process. We found very good agreement between the simulated structures and those observed experimentally.

Generation of nanoparticles with adjustable size and controlled stoichiometry: recent advances

We present a bottom-up fabrication route based on the sputtering gas aggregation source that allows the generation of nanoparticles with controllable and tunable chemical composition while keeping the control of the cluster size. We demonstrate that the chemical composition of the particles can be monitored by the individual adjustment of the working parameters of the magnetrons inserted in a gas aggregation zone. Such control of the parameters leads to a fine control of the ion density of each target material and hence to the control of the chemical composition of the nanoparticles. In particular, we show through X-ray photoemission, atomic force microscopy, and high-resolution transmission electron microscopy that it is possible to generate bimetallic (AgAu) and trimetallic (AgAuPd) alloy nanoparticles with well-defined and tunable stoichiometries from three targets of pure Ag, Au, and Pd. The proposed route for the generation of nanoparticles opens new possibilities for the fabrication of nanoparticles using a physical method that, for some applications, could be complementary to the chemical methods.

Lateral etching of core-shell Au@Metal nanorods to metal-tipped au nanorods with improved catalytic activity

Selective growth/etching of hybrid materials is very important for the rational synthesis of hierarchical structures and precise modulation of their physical properties. Here, the lateral etching of the core-shell Au@Ag nanorods is achieved by FeCl(3) at room temperature, producing a number of dumbbell-like Ag-tipped Au nanorods. This selective etching at the side of the core-shell nanorods is attributed to the increased reactivity of the side facets, due to less surface passivation of cetyltrimethylammonium bromide. The similar synthetic strategy has also been demonstrated to be successful for the Pd-tipped Au nanorods that have not been reported before, indicating the great potential of this selective etching. The Ag-tipped Au nanorods are examined as a catalyst for the reduction of p-nitrophenol at room temperature. The Ag-tipped Au nanorods exhibit a higher catalytic activity than Au nanorods and core-shell Au@Ag nanorods, which could be attributed to the electronic effect and the unique structure in the Ag-tipped Au nanorods.