Explosives sensing using Ag–Cu alloy nanoparticles synthesized by femtosecond laser ablation and irradiation

Herein we demonstrate the synthesis of Ag–Cu alloy NPs through a consecutive two-step process; laser ablation followed by laser irradiation. Initially, pure Ag and Cu NPs were produced individually using the laser ablation in liquid technique (with ∼50 femtosecond pulses at 800 nm) which was followed by laser irradiation of the mixed Ag and Cu NPs in equal volume. These Ag, Cu, and Ag–Cu NPs were characterised by UV-visible absorption, HRTEM and XRD techniques. The alloy formation was confirmed by the presence of a single surface plasmon resonance peak in absorption spectra and elemental mapping using FESEM techniques. Furthermore, the results from surface enhanced Raman scattering (SERS) studies performed for the methylene blue (MB) molecule suggested that Ag–Cu alloy NPs demonstrate a higher enhancement factor (EF) compared to pure Ag/Cu NPs. Additionally, SERS studies of Ag–Cu alloy NPs were implemented for the detection of explosive molecules such as picric acid (PA – 5 μM), ammonium nitrate (AN – 5 μM) and the dye molecule methylene blue (MB – 5 nM). These alloy NPs exhibited superiority in the detection of various analyte molecules with good reproducibility and high sensitivity with EFs in the range of 10⁴ to 10⁷.

Herein we demonstrate the synthesis of Ag–Cu alloy NPs through a consecutive two-step process; laser ablation followed by laser irradiation.     

Enhanced antibacterial properties of biocompatible titanium via electrochemically deposited Ag/TiO2 nanotubes and chitosan–gelatin–Ag–ZnO complex coating

A novel double-layered antibacterial coating was fabricated on pure titanium (Ti) via a simple three-step electrodeposition process. Scanning electronic microscopy (SEM) images show that the coating was constructed with the inner layer of TiO₂ nanotubes doped with silver nanoparticles (TNTs/Ag) and the outer layer of chitosan–gelatin mixture with zinc oxide and silver nanoparticles (CS–Gel–Ag–ZnO). In comparison, we also investigated the composition, structure and antibacterial properties of pure Ti coated with TNTs, TNTs/Ag or TNTs/Ag + CS–Gel–Ag–ZnO, respectively. The TNTs was about 100 nm wide and 240 nm to 370 nm tall, and most Ag nanoparticles (Ag NPs) with diameter smaller than 20 nm were successfully deposited inside the tubes. The CS–Gel–Ag–ZnO layer was continuous and uniform. Antibacterial activity against planktonic and adherent bacteria were both investigated. Agar diffusion test against Staphylococcus aureus (S. aureus) shows improved antibacterial capacity of the TNTs/Ag + CS–Gel–Ag–ZnO coating, with a clear zone of inhibition (ZOI) up to 14.5 mm wide. Dead adherent bacteria were found on the surface by SEM. The antibacterial rate against planktonic S. aureus was as high as 99.2% over the 24 h incubation period.

A novel complex antibacterial coating fabricated via a simple three-step electrodeposition process shows high antibacterial rate of 99.2%.     

Synthesis of Sn/Ag–Sn nanoparticles via room temperature galvanic reaction and diffusion

Tin (Sn) has a low melting temperature, i.e., 231.9 °C for the bulk, and the capability to form compounds with many metals. The galvanic reaction between Sn nanoparticles (NPs) as the core and silver nitrate at room temperature under argon gas in an organic solvent without any reducing power, was employed for the first time to coat an Ag–Sn intermetallic shell, i.e., Ag₃Sn and/or Ag₄Sn, on Sn NPs. For spherical Sn NPs, the NPs retained a spherical shape after coating. Uniform and Janus structures consisting of a β-Sn core with Ag–Sn shell were observed in the resulting NPs and their population related to the input molar ratios of the metal precursors. The observation of the intermetallic shell is general for both spherical and rod-shape Sn NPs. The formation of the intermetallic shell indicated that two reactions occurred sequentially, first reduction of Ag ions to Ag atoms by the Sn core, followed by interdiffusion of Ag and Sn to form the Ag–Sn intermetallic shell.

Coating of Ag–Sn intermetallic compound on Sn nanoparticles at room temperature.     

Discriminating sensing of explosive molecules using graphene–boron nitride–graphene heteronanosheets

Since the synthesis of graphene–boron nitride heterostructures, their interesting electronic properties have attracted huge attention for real-world nanodevice applications. In this work, we combined density functional theory (DFT) with a Green''s function approach to examine the potential of graphene–boron nitride–graphene heteronanosheets (h-NSHs) for discriminating single molecule sensing. Our result demonstrates that the graphene–boron nitride–graphene (h-NSHs) can be used for discriminate sensing of the 2,4-dinitrotoluene (DNT), octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), pentaerythritol tetranitrate (PENT), and 2,4,6-trinitrotoluene (TNT) molecules. We demonstrate that as the length of the BN region increases, the sensitivity of the heteronanosheets to the presence of these explosive substances increases.

Graphene–boron nitride–graphene (h-NSHs) heterostructures can be used for discriminate sensing of 2,4-dinitrotoluene (DNT), octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), pentaerythritol tetranitrate (PENT), and 2,4,6-trinitrotoluene (TNT) molecules.     

Synthesis of Ni–Ag–ZnO solid solution nanoparticles for photoreduction and antimicrobial applications

ZnO is one of the most promising and efficient semiconductor materials for various light-harvesting applications. Herein, we reported the tuning of optical properties of ZnO nanoparticles (NPs) by co-incorporation of Ni and Ag ions in the ZnO lattice. A sonochemical approach was used to synthesize pure ZnO NPs, Ni–ZnO, Ag–ZnO and Ag/Ni–ZnO with different concentrations of Ni and Ag (0.5%, 2%, 4%, 8%, and 15%) and Ni doped Ag–ZnO solid solutions with 0.25%, 0.5%, and 5% Ni ions. The as-synthesized Ni–Ag–ZnO solid solution NPs were characterized by powdered X-ray diffraction (pXRD), FT-IR spectroscopy, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), UV-vis (UV) spectroscopy, and photoluminescence (PL) spectroscopy. Ni–Ag co-incorporation into a ZnO lattice reduces charge recombination by inducing charge trap states between the valence and conduction bands of ZnO and interfacial transfer of electrons. The Ni doped Ag–ZnO solid solution NPs have shown superior 4-nitrophenol reduction compared to pure ZnO NPs which do not show this reaction. Furthermore, a methylene blue (MB) clock reaction was also performed. Antibacterial activity against E. coli and S. aureus has inhibited the growth pattern of both strains depending on the concentration of catalysts.

The synergic effect of Ni and Ag in Ni–Ag–ZnO solid solutions has tuned the optoelectronic properties of ZnO for photoreduction reactions.     

Luminescence and photoelectrochemical properties of size-selected aqueous copper-doped Ag–In–S quantum dots

Ternary luminescent copper and silver indium sulfide quantum dots (QDs) can be an attractive alternative to cadmium and lead chalcogenide QDs. The optical properties of Cu–In–S and Ag–In–S (AIS) QDs vary over a broad range depending on the QD composition and size. The implementation of ternary QDs as emitters in bio-sensing applications can be boosted by the development of mild and reproducible syntheses directly in aqueous solutions as well as the methods of shifting the photoluminescence (PL) bands of such QDs as far as possible into the near IR spectral range. In the present work, the copper-doping of aqueous non-stoichiometric AIS QDs was found to result in a red shift of the PL band maximum from around 630 nm to ∼780 nm and PL quenching. The deposition of a ZnS shell results in PL intensity recovery with the highest quantum yield of 15%, with almost not change in the PL band position, opposite to the undoped AIS QDs. Size-selective precipitation using 2-propanol as a non-solvent allows discrimination of up to 9 fractions of Cu-doped AIS/ZnS QDs with the average sizes in the fractions varying from around 3 to 2 nm and smaller and with reasonably the same composition irrespective of the QD size. The decrease of the average QD size results in a blue PL shift yielding a series of bright luminophors with the emission color varies from deep-red to bluish-green and the PL efficiency increases from 11% for the first fraction to up to 58% for the smallest Cu-doped AIS/ZnS QDs. The rate constant of the radiative recombination of the size-selected Cu-doped AIS/ZnS QDs revealed a steady growth with the QD size decrease as a result of the size-dependent enhancement of the spatial exciton confinement. The copper doping was found to result in an enhancement of the photoelectrochemical activity of CAIS/ZnS QDs introduced as spectral sensitizers of mesoporous titania photoanodes of liquid-junction solar cells.

Colloidal size-selected copper-doped Ag–In–S quantum dots were produced directly in aqueous solutions by fractionation/redispersion with a plethora of emission colors and a top luminescence quantum yield of around 60%.     

Natural assembly of a ternary Ag–SnS–TiO2 photocatalyst and its photocatalytic performance under simulated sunlight

Natural assembly method was utilized to prepare a novel ternary Ag–SnS–TiO₂ nanocomposite, in which TiO₂ nanobelts were used as templates. The co-loading of Ag and SnS nanoparticles endows TiO₂ nanobelts with enhanced photocatalytic capability, resulting from the broadened light absorption spectra and decreased band gaps. Comparing with raw TiO₂ nanobelts and commercial Degussa P25, an improvement in photodegradation of simulated organic pollutants was successfully demonstrated due to the decreasing recombination of photogenerated electron–hole pairs. Our work presents a new strategy for the preparation of ternary TiO₂-based photocatalysts in the practical application of wastewater treatment.

Natural assembly method was utilized to prepare a novel ternary Ag–SnS–TiO₂ nanocomposite, in which TiO₂ nanobelts were used as templates.     

Spontaneous alloying of ultrasmall non-stoichiometric Ag–In–S and Cu–In–S quantum dots in aqueous colloidal solutions

The effect of spontaneous alloying of non-stoichiometric aqueous Ag–In–S (AIS) and Cu–In–S (CIS) quantum dots (QDs) stabilized by surface glutathione (GSH) complexes was observed spectroscopically due to the phenomenon of band bowing typical for the solid–solution Cu(Ag)–In–S (CAIS) QDs. The alloying was found to occur even at room temperature and can be accelerated by a thermal treatment of colloidal mixtures at around 90 °C with no appreciable differences in the average size observed between alloyed and original individual QDs. An equilibrium between QDs and molecular and clustered metal–GSH complexes, which can serve as “building material” for the new mixed CAIS QDs, during the spontaneous alloying is assumed to be responsible for this behavior of GSH-capped ternary QDs. The alloying effect is expected to be of a general character for different In-based ternary chalcogenides.

The effect of spontaneous alloying of aqueous glutathione-capped Ag–In–S and Cu–In–S quantum dots (QDs) into quaternary Cu(Ag)–In–S QDs is reported.     

A selective detection approach for copper(ii) ions using a hydrazone-based colorimetric sensor: spectroscopic and DFT study

The development of an efficient and miniaturized analytical approach to determine trace levels of toxic ions in aqueous fluids presents a current research challenge. Hydrazone-based chemosensors are considered potential candidates due to their high sensitivity and selectivity towards heavy metal ions. Computational techniques can be properly implemented to elucidate possible modes of ligand–metal interaction and provide an in-depth understanding of the chemistry involved. The present study reports the use of 3-hydroxy-5-nitrobenzaldehyde-4-hydroxybenzoylhydrazone (3-HNHBH) ligand for highly sensitive, quick and re-usable colorimetric sensing of copper(ii) ions in aqueous media. DFT calculations suggest that the complexation of 3-HNHBH with copper(ii) ions adopts a seesaw coordination geometry and results in the largest HOMO–LUMO gap and most effective coulombic interaction compared to Zn and Ni counterparts. It demonstrated a high selectivity towards copper ions with a detection limit of 0.34 μg L⁻¹. The ligand was readily regenerated using a 0.5 M HCl solution, indicating its feasibility to be used as a re-usable sensor for the convenient detection of copper ions in aqueous media. The influence of metal interference, pH and solvents on the selectivity and regeneration of the ligand was also investigated.

The development of an efficient and miniaturized analytical approach to determine trace levels of toxic ions in aqueous fluids presents a current research challenge.     

Charge transfer-induced enhancement of a Raman signal in a hybrid Ag–GaN nanostructure

A hybrid system consisting of Ag nanoparticles dispersed onto a GaN nanowall network (GaN NWN) exhibited characteristic optical properties and electronic band structure. Surface-sensitive XPS studies of this high-surface-area system revealed the presence of a high surface charge carrier concentration due to dangling bonds, which resulted in a high metal-like surface conductivity. The low coverage of absorbed Ag led to the nanocluster formation, facilitating charge transfer from GaN to Ag, and thereby further increasing the surface charge carriers. Photoluminescence studies revealed the presence of a high density of band tail states at the conduction band, which is significantly (14-fold) larger than in the GaN epilayer. Raman studies show an increase (2.46-fold) in the interfacial strain at the Ag/GaN interface after the deposition of the Ag nanoparticles. We show that these surface modifications increase the density of hot spots, resulting in an intense Raman signal with an enhancement factor of 10⁷. The role of the charge transfer between Ag nanoparticles and GaN NWN in the enhancement of Raman signal has been demonstrated.

The optical properties and electronic band structure of Ag nanoparticles dispersed on a GaN nanowall network were studied. High metal like surface conductivity was revealed, and charge transfer between Ag and GaN was involved in the enhancement of Raman signals.     

One-pot facile simultaneous in situ synthesis of conductive Ag–polyaniline composites using Keggin and Preyssler-type phosphotungstates

Two heteropolytungstate structures, Keggin (H₃PW₁₂O₄₀) and Preyssler (H₁₄[NaP₅W₃₀O₁₁₀]), were used to synthesize conductive silver nanoparticle–polyaniline–heteropolytungstate (AgNPs–PAni–HPW) nanocomposites. During the oxidative polymerization of aniline, heteropolyblue was generated and served as the reducing agent to stabilize and distribute AgNPs within “PAni–Keggin” and “PAni–Preyssler” matrixes as well as on their surfaces. The prepared nanocomposites and AgNPs were characterized using UV-visible (UV-Vis) and Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), pore size distribution BET, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). UV-Vis results showed different stages of the formation of metal NPs embedded in the polymer–HPW composites, and FT-IR spectra presented characteristic bands of PAni, Keggin and Preyssler anions in the composites confirming no changes in their structures. The presence of AgNPs and an intensely crystalline matrix were confirmed by the XRD pattern. The BET surface areas were found to be 38.426 m² g⁻¹ for “AgNPs–PAni–Keggin” and 29.977 m² g⁻¹ for “AgNPs–PAni–Preyssler” nanocomposites with broad distributions of meso-porous structure for both nanocomposites. TEM and SEM images confirmed that the type of heteropolyacids affected the size of AgNPs. This is the first report that uses Keggin and Preyssler-type heteropolytungstate to synthesize “AgNPs–PAni–HPW” nanocomposites in an ambient condition through a low-cost, facile, one-pot, environmentally friendly and simultaneous in situ oxidative polymerization protocol.

Two heteropolytungstate structures, (a) Keggin (H₃PW₁₂O₄₀) and (b) Preyssler (H₁₄(NaP₅W₃₀O₁₁₀]), have been used to synthesize conductive silver nanoparticle–polyaniline–heteropolytungstate, (AgNPs–PAni–HPW) nanocomposites.     

A colorimetric sensing platform for the determination of H2O2 using 2D–1D MoS2-CNT nanozymes

A novel colorimetric platform based on nano-composites of two-dimensional (2D) molybdenum disulfide nanosheets (MoS₂ NSs) and one-dimensional (1D) carbon nanotubes (CNTs), called 2D–1D MoS₂-CNT nanozyme, was fabricated for the selective and sensitive determination of hydrogen peroxide (H₂O₂) in soda water. The MoS₂-CNT nanozyme was synthesized through a one-step solvothermal reduction method. The introduced CNTs could effectively prevent the stacking of MoS₂ nanosheets (NSs) and not only expanded the interlayer distance of MoS₂ NSs from 0.620 nm to 0.710 nm but also improved their specific surface. Under acidic conditions, the as-prepared 2D–1D MoS₂-CNT nanozymes could oxidize the colorless 3,3′,5,5′-tetramethylbenzidine (TMB) to blue-oxidized TMB (oxTMB) in the presence of H₂O₂, resulting in enhanced peroxidase-like (POD-like) activity. The kinetic study showed that MoS₂-CNT nanozyme had stronger catalytic activity than natural horseradish peroxidase (HRP). The linear range for H₂O₂ colorimetric determination was 5.00–500 μmol L⁻¹ with a limit of detection (LOD) of 1.40 μmol L⁻¹. Furthermore, the established determination method was applied to actual samples and the recoveries of H₂O₂ spiked in soda water were in the range of 92.3–107%, showing feasibility for the analysis of food.

A novel colorimetric platform based on 2D–1D MoS₂-CNT nanozymes, was fabricated for the selective and sensitive determination of hydrogen peroxide (H₂O₂) in soda water.     

An approach to new chiral bicyclic imines and amines via Horner–Wadsworth–Emmons reaction

New chiral bicyclic imines, enamines and amines were prepared via Horner–Wadsworth–Emmons reaction of hexahydroquinoxalin-2(1H)-one-derived phosphonate, as the source of a phosphonate carbanion, and a wide range of structurally diverse carbonyl substrates. The simplicity of the synthetic protocol, high selectivity, and broad substrate scope are the main advantages of the presented methodology.

New chiral cyclic imines and enamines were prepared via HWE reaction, with selectivity dependent on the carbonyl substrate.     

CuInS2–In2Se3 quantum dots – a novel material via a green synthesis approach

Novel CuInS₂–In₂Se₃ QDs were prepared by a two stage organometallic colloidal synthesis procedure. A layer of indium selenide was grown over the CuInS₂ QD core, under high temperature in the presence of oleylamine. The optical properties of the nanostructures grown were studied using UV-Vis absorption spectroscopy and the band gap obtained was in line with the cyclic voltammetry (CV) results. The elemental composition was analysed using energy dispersive X-ray spectroscopy (EDAX), inductive coupled plasma-atomic emission spectroscopy (ICP-AES) and X-ray photoelectron spectroscopy (XPS). The structural properties were investigated using X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). The TEM images showed spherical nanostructures of size about 4.8 nm with well-defined lattice planes which were also evident from selected area electron diffraction (SAED) patterns. The XRD pattern indicated a tetragonal chalcopyrite crystal structure for the nanostructures.

Novel CuInS₂–In₂Se₃ QDs prepared by a two stage organometallic colloidal synthesis.     

Molecularly resolved,label-free nucleic acid sensing at solid–liquid interface using non-ionic DNA analogues

Nucleic acid-based biosensors, where the capture probe is a nucleic acid, e.g., DNA or its synthetic analogue xeno nucleic acid (XNA), offer interesting ways of eliciting clinically relevant information from hybridization/dehybridization signals. In this respect, the application of XNA probes is attractive since the drawbacks of DNA probes might be overcome. Within the XNA probe repertoire, peptide nucleic acid (PNA) and morpholino (MO) are promising since their backbones are non-ionic. Therefore, in the absence of electrostatic charge repulsion between the capture probe and the target nucleic acid, a stable duplex can be formed. In addition, these are nuclease-resistant probes. Herein, we have tested the molecularly resolved nucleic acid sensing capacity of PNA and MO capture probes using a fluorescent label-free single molecule force spectroscopy approach. As far as single nucleobase mismatch discrimination is concerned, both PNA and MO performed better than DNA, while the performance of the MO probe was the best. We propose that the conformationally more rigid backbone of MO, compared to the conformationally flexible PNA, is an advantage for MO, since the probe orientation can be made more upright on the surface and therefore MO can be more effectively accessed by the target sequences. The performance of the XNA probes has been compared to that of the DNA probe, using fixed nucleobase sequences, so that the effect of backbone variation could be investigated. To our knowledge, this is the first report on molecularly resolved nucleic acid sensing by non-ionic capture probes, here, MO and PNA.

Improved nucleic acid sensing in terms of single nucleobase mismatch discrimination, as achieved by the surface-confined non-ionic PNA and MO capture probes, is exemplified by single molecule force spectroscopy.     

Na–Ga–Si type-I clathrate single crystals grown via Na evaporation using Na–Ga and Na–Ga–Sn fluxes

Single crystals of a Na–Ga–Si clathrate, Na₈Ga_5.70Si_40.30, of size 2.9 mm were grown via the evaporation of Na from a Na–Ga–Si melt with the molar ratio of Na : Ga : Si = 4 : 1 : 2 at 773 K for 21 h under an Ar atmosphere. The crystal structure was analyzed using X-ray diffraction with the model of the type-I clathrate (cubic, a = 10.3266(2) Å, space group Pm$\bar{3}$n, no. 223). By adding Sn to a Na–Ga–Si melt (Na : Ga : Si : Sn = 6 : 1 : 2 : 1), single crystals of Na₈Ga_xSi_46−x (x = 4.94–5.52, a = 10.3020(2)–10.3210(3) Å), with the maximum size of 3.7 mm, were obtained via Na evaporation at 723–873 K. The electrical resistivities of Na₈Ga_5.70Si_40.30 and Na₈Ga_4.94Si_41.06 were 1.40 and 0.72 mΩ cm, respectively, at 300 K, and metallic temperature dependences of the resistivities were observed. In the Si L_2,3 soft X-ray emission spectrum of Na₈Ga_5.70Si_40.30, a weak peak originating from the lowest conduction band in the undoped Si₄₆ was observed at an emission energy of 98 eV.

Single crystals of a Na–Ga–Si clathrate, Na₈Ga_4.94Si_41.06, of size 3.7 mm were grown via the evaporation of Na from a Na–Ga–Si–Sn melt with the molar ratio of Na : Ga : Si : Sn = 6 : 1 : 2 : 1 at 873 K for 3 h under an Ar atmosphere.     

Enhanced visible-light photodegradation of fluoroquinolone-based antibiotics and E. coli growth inhibition using Ag–TiO2 nanoparticles

Antibiotics in wastewater represent a growing and worrying menace for environmental and human health fostering the spread of antimicrobial resistance. Titanium dioxide (TiO₂) is a well-studied and well-performing photocatalyst for wastewater treatment. However, it presents drawbacks linked with the high energy needed for its activation and the fast electron–hole pair recombination. In this work, TiO₂ nanoparticles were decorated with Ag nanoparticles by a facile photochemical reduction method to obtain an increased photocatalytic response under visible light. Although similar materials have been reported, we advanced this field by performing a study of the photocatalytic mechanism for Ag–TiO₂ nanoparticles (Ag–TiO₂ NPs) under visible light taking in consideration also the rutile phase of the TiO₂ nanoparticles. Moreover, we examined the Ag–TiO₂ NPs photocatalytic performance against two antibiotics from the same family. The obtained Ag–TiO₂ NPs were fully characterised. The results showed that Ag NPs (average size: 23.9 ± 18.3 nm) were homogeneously dispersed on the TiO₂ surface and the photo-response of the Ag–TiO₂ NPs was greatly enhanced in the visible light region when compared to TiO₂ P25. Hence, the obtained Ag–TiO₂ NPs showed excellent photocatalytic degradation efficiency towards the two fluoroquinolone-based antibiotics ciprofloxacin (92%) and norfloxacin (94%) after 240 min of visible light irradiation, demonstrating a possible application of these particles in wastewater treatment. In addition, it was also proved that, after five Ag–TiO₂ NPs re-utilisations in consecutive ciprofloxacin photodegradation reactions, only a photocatalytic efficiency drop of 8% was observed. Scavengers experiments demonstrated that the photocatalytic mechanism of ciprofloxacin degradation in the presence of Ag–TiO₂ NPs is mainly driven by holes and ˙OH radicals, and that the rutile phase in the system plays a crucial role. Finally, Ag–TiO₂ NPs showed also antibacterial activity towards Escherichia coli (E. coli) opening the avenue for a possible use of this material in hospital wastewater treatment.

Ag nanoparticles decorated-TiO₂ P25 are a viable alternative for the degradation, through a rutile-mediated mechanism, of fluoroquinolone-based antibiotics under visible light irradiation and, at the same time, for bacteria inactivation in water.     

Deposition of Ag and Ag–Au nanocrystalline films with tunable conductivity at the water–toluene interface

Thin films of Au, Ag and Ag–Au alloy nanocrystals extending to areas of several square centimetres are obtained by deposition at the interface of water and toluene. Toluene containing chlorotris(triphenylphosphine)silver(i) and/or chlorotriphenylphosphine gold(i) is reacted with aqueous tetrakishydroxymethylphosphonium chloride to obtain nanocrystalline films adhered to the interfacial region. Alloying was induced by varying the composition of the toluene layer. The composition change results in regular and reproducible variation in the transport characteristics of the films, with the initially metallic deposits turning non-metallic with increased Au content. The films at the interface were transferred to different substrates and characterised using atomic force microscopy, UV-visible spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, scanning and transmission electron microscopy.

Thin films of Au, Ag and Ag–Au alloy nanocrystals extending to areas of several square centimetres are obtained by deposition at the interface of water and toluene.     

One-pot synthesis of Ag–Cu–Cu2O/C nanocomposites derived from a metal–organic framework as a photocatalyst for borylation of aryl halide

Mixed metal–metal oxide/C (Ag–Cu–Cu₂O/C) nanocomposites were synthesized by the heat treatment of a metal–organic framework under a N₂ flow using the one-pot synthesis method. The as-prepared nanocomposites were characterized using a range of techniques, such as TEM, elemental mapping, XRD, N₂ sorption, UV-Vis DRS, and XPS. The nanoparticles were successfully formed with high dispersion in porous carbon materials and high crystallinity based on the analysis results. The Ag–Cu–Cu₂O/C nanocomposites (35 nm) showed high photocatalytic activity and good recyclability toward the borylation of aryl halides under a xenon arc lamp. This result can enhance the interest in photocatalysis for various applications, particularly in organic reactions, using a simple and efficient synthesis method.

Ag–Cu–Cu₂O/C nanocomposites derived from metal–organic framework through one-pot thermal reduction method were synthesized. The material exhibits high catalytic activity in the borylation of aryl halide under xenon lamp condition across 7 cycles, with no yield decrease.     

Preparation and characterization of Ag–Pd bimetallic nano-catalysts in thermosensitive microgel nano-reactor

Thermosensitive microgels consisting of a solid core of polystyrene and a shell of cross-linked poly(N-isopropylacrylamide) (PNIPA) were synthesized as nano-reactors, in which Ag–Pd bimetallic nanoparticles were prepared through simultaneous in situ reduction reaction. The spatial distribution of metallic nanoparticles in the microgels was analyzed by small angle X-ray scattering (SAXS) and the results indicated that metal nanoparticles were mainly located in the inner layer of microgels. The catalytic activity of Ag–Pd bimetallic nanoparticles was investigated using the reduction of p-nitrophenol to p-aminophenol by NaBH₄ as model reaction. The data demonstrated that Ag–Pd bimetallic nanoparticles showed enhanced catalytic activity compared to each monometallic nanoparticle alone and their catalytic activity was controllable by temperature due to the volume transition of PNIPA microgels.

Thermosensitive microgels with PS core and cross-linked PNIPA shell were synthesized as nano-reactor to prepare Ag–Pd bimetallic nanoparticles.