Ag Core Shell Research Articles

Chiral plasmonic Au–Ag core shell nanobipyramid for SERS enantiomeric discrimination of biologically relevant small molecules

The identification of enantiomers is of great importance in chiral separations and medicinal chemistry. While Surface-enhanced Raman spectroscopy (SERS) is a technique that provides vibrational fingerprints of analytes. The enantiomers identification relies on the SERS difference between left and right-handed circularly polarized light or additional selectors for indirect distinction. In this work, Au–Ag core shell nanobipyramid (L/D-Au@Ag BPs) were synthesized guiding by chiral encoder of L/D-cysteine. L/D-Au@Ag BPs produced plasmon-induced circular dichroism signals in the plasmon resonance absorption band, which can be tuned by modulation the amount of cysteine. Moreover, the chiral anisotropy factor of L/D-Au@Ag BPs at 532 nm can reach 5.11 × 10−3. Due to the selective resonance coupling between L/D-Au@Ag BPs and different enantiomers, L/D-Au@Ag BPs were further used as SERS substrates for efficient discrimination of biologically relevant small molecules. Chiral Au@Ag BPs display the potential for chiral drug identification.

Study the influence of shell thickness in bimetallic Ag core&Au shell configurations integrated in bare Si PN junction solar cells

The effect of the gold layer thickness of Ag core&Au shell configurations on the performance of the bare Si n-type layer of a PN junction solar cell was explored. The different forms of Ag core&Au shell configurations were formed via pulsed laser ablation method of Ag and Au plate using second harmonic generation (SHG) of Nd:YAG laser wavelength at 530 nm with 0.61 J/cm2 energy flounce and various pluses repetition rate 350-500. The integrating of Ag core&Au shell configurations in n-type of bare PN Si junction was accomplished via pluses laser illumination of bare PN junction substrate. The photovoltaic results of formed solar cells showed strong dependence on Au shell thickness. Tangible enhancement was observed in the performance of bare Si solar cells after inserting core–shell configuration with specific shell thickness owning to the broadband absorption of plasmonics nanoparticles and the high values of specific surface area.

Screen-Printable Cu–Ag Core–Shell Nanoparticle Paste for Reduced Silver Usage in Solar Cells: Particle Design, Paste Formulation, and Process Optimization

Copper–silver (Cu–Ag) core–shell nanoparticles are promising for replacing the silver particles and flakes used in printed conductors in current solar cells since they deliver good conductivity, chemical stability, and optical performance, while also reducing the silver content, thus significantly impacting the cost. The bare nanoparticles offer excellent air stability thanks to the silver-covered copper structure. We demonstrate a screen-printable paste for use in solar cell conductor applications. We report a printed morphology and light reflection properties similar to those achieved with commercial silver pastes. The reported Cu–Ag core–shell paste is uniquely formulated with an epoxy binder and an aliphatic hardener, delivering significantly improved electrical conductivity, while simultaneously reducing the overall silver content by ∼36 wt %. This is attributable to the cross-linked polymeric structure, low-temperature conversion, and improved loading of conductive core–shell nanoparticles. As needed for contact formation in conventional top-contact silicon solar cells, the paste is additionally loaded with lead bisilicate and delivers conductivity on par with that of commercial silver paste. Thus, by combining the reduction of the silver content with excellent electronic and optical properties, this Cu–Ag nanoparticle-based paste becomes attractive for low-cost printed-conductor applications, including photovoltaics and electronics.

Influence of dissolution on the uptake of bimetallic nanoparticles Au@Ag-NPs in soil organism Eisenia fetida.

A key aspect in the safety testing of metal nanoparticles (NPs) is the measurement of their dissolution and of the true particle uptake in organisms. Here, based on the tendency of Ag-NP to dissolve and Au-NP to be inert in the environment, we exposed the earthworm Eisenia fetida to Au core-Ag shell NPs (Au@Ag-NPs, Ag-NPs with a Au core) and to both single and combined exposures of non-coated Au-NPs, Ag-NPs, Ag+ and Au+ ions in natural soil. Our hypothesis was that the Ag shell would partially or completely dissolve from the Au@Ag-NPs and that the Au core would thereby behave as a tracer of particulate uptake. Au and Ag concentrations were quantified in all the soils, in soil extract and in organisms by inductively coupled plasma mass spectrometry (ICP-MS). The earthworm exposed to Au@Ag-NPs, and to all the combinations of Ag and Au, were analyzed by single particle inductively coupled plasma time-of-flight mass spectrometry (spICP-TOFMS) to allow the quantification of the metals that were truly part of a bimetallic particle. Results showed that only 5% of the total metal amounts in the earthworm were in the bimetallic particulate form and that the Ag shell increased in thickness, suggesting that biotransformation processes took place at the surface of the NPs. Additionally, the co-exposure to both metal ions led to a different uptake pattern compared to the single metal exposures. The study unequivocally confirmed that dissolution is the primary mechanism driving the uptake of (dissolving) metal NPs in earthworms. Therefore, the assessment of the uptake of metal nanoparticles is conservatively covered by the assessment of the uptake of their ionic counterpart.

Apocynin loaded silver nanoparticles displays potent in vitro biological activities and mitigates pyrogallol-induced hepatotoxicity

Drug-loaded nanoparticles are currently gaining attention due to their improved drug delivery properties. Apocynin, a natural polyphenolic compound, is a component of many plants. It has many medicinal and pharmacological properties. Pyrogallol is an anti-psoriatic agent. However, its clinical usage is limited due to its cumulative and dose-dependent hepatotoxicity. The objective of this study was to synthesize silver nanoparticles coated with Apocynin (Apo-AgNPs), and investigate the antioxidant and liver protective effects of Apo-AgNPs on pyrogallol-induced toxicity in rats. The nanoparticles were characterized and it was determined that the synthesis technique results in homogeneously dispersed core–shell Ag structures with spherical forms and an average diameter of 13 nm (6.3 nm). Our results showed that Apo-AgNPs exhibited potent antioxidant and excellent membrane stability activities in vitro. In rats, Apo-AgNPs (10 and 30 mg/kg) significantly prevented pyrogallol-induced elevations of alkaline phosphatase, gamma-glutamyl transferase, creatinine, urea, aspartate aminotransferase, alkaline aminotransferase, total bilirubin, and decreased blood levels of uric acid. Moreover, Apo-AgNPs restored the decreased activities of the liver antioxidant enzymes, including superoxide dismutase and glutathione peroxidase, glutathione transferase, as well as non-enzyme antioxidant glutathione, as well as significantly decreased catalase activities which were induced by pyrogallol treatment. Histological studies indicated that pyrogallol -induced liver damage was alleviated following Apo-AgNPs treatment in rats. Apo-AgNPs significantly suppressed the up-regulation of Cyclooxygenase-2 (COX-2), Interleukin 6 (IL-6) and Nuclear factor-κB (NF-κB) protein expression. These results indicated that Apo-AgNPs protected the rats from damage via preserving the antioxidant defense systems, lowering pro-inflammatory cytokines, and expression of COX-2 and NF-κB in rats.

Colorful Conductive Threads for Wearable Electronics: Transparent Cu-Ag Nanonets.

Electronic textiles have been regarded as the basic building blocks for constructing a new generation of wearable electronics. However, the electronization of textiles often changes their original properties such as color, softness, glossiness, or flexibility. Here a rapid room‐temperature fabrication method toward conductive colorful threads and fabrics with Ag‐coated Cu (Cu‐Ag) nanonets is demonstrated. Cu–Ag core–shell nanowires are produced through a one‐pot synthesis followed by electroless deposition. According to the balance of draining and entraining forces, a fast dip‐withdraw process in a volatile solution is developed to tightly wrap Cu–Ag nanonets onto the fibers of thread. The modified threads are not only conductive, but they also retain their original features with enhanced mechanical stability and dry‐wash durability. Furthermore, various e‐textile devices are fabricated such as a fabric heater, touch screen gloves, a wearable real‐time temperature sensor, and warm fabrics against infrared thermal dissipation. These high quality and colorful conductive textiles will provide powerful materials for promoting next‐generation applications in wearable electronics.

Exploring bimetallic Au–Ag core shell nanoparticles reduced using leaf extract of Ocimum tenuiflorum as a potential antibacterial and nanocatalytic agent

Biosynthesis of bimetallic Au–Ag core shell nanoparticle under ambient condition using Ocimum tenuiflorum (Krishna Tulsi) leaf extract is being reported for the first time. For the biosynthesized bimetallic core shell nanoparticles (OTAuAgNPs) visual and spectrophotometric analysis was performed. Development of a deep purple color suggested the creation of OTAuAgNPs. It was then validated by UV–Vis spectrophotometry within 4 h of incubation showing a surface plasmon resonance peak at 560 nm. FESEM-EDAX, FT-IR, particle analyzer and XRD were the analytical techniques employed to characterize the biosynthesized OTAuAgNPs. Using a known antibiotic as a control, OTAuAgNPs (10 mg/ml) had a substantial bacteriostatic effect against Gram + ve (Bacillus subtilis) and Gram −ve (E.coli, Pseudomonas aeruginosa) bacteria. The OTAuAgNPs (6.5 mg) showed good catalytic action for the adsorption of Coomassie brilliant blue R250 dye (CBB) (50 mg/L, 25 mL), confirmed by the reduction in absorbance maxima that is time dependent. A remarkable adsorption of CBB (94.79%) was attained within 120 min, and the results were best-suited PSO and Elovich models with adsorption kinetic constant of 5.96E−04 g/mg.min and 37.81 mg/g.min, respectively. Further the toxicity studies of brilliant blue R250 dye and metabolite of CBB (post nano-remediated dye solution) was carried out on Vigna radiata (green gram) germination and growth. OTAuAgNPs as nanocatalyst remediated water revealed that it was nontoxic. Thus an ecofriendly and cost-effective approach for bimetallic nanoparticle synthesis could be further explored for removal of CBB from wastewater effluents.

Hybrid SERS platform by adapting both chemical mechanism and electromagnetic mechanism enhancements: SERS of 4-ATP and CV by the mixture with GQDs on hybrid PdAg NPs

Surface-enhanced Raman spectroscopy (SERS) is a versatile analytical technique widely adapted for the identification of target analytes even at an extremely low concentration. Herein, a unique hybrid SERS platform is demonstrated by utilizing the graphene quantum dots (GQDs) and hybrid PdAg NPs for the detection of 4-amino-thiophenol (4-ATP) and crystal violet (CV). GQDs offer the rich charge transfer to the LUMO and HOMO of 4-ATP and CV by the CM enhancement. A significant EM enhancement is achieved by the strong localized surface plasmon resonance (LSPR) of uniquely designed hybrid core-shell PdAg NP, possessing the narrow nano-gaps with the highly dense small Ag NPs and Pd core Ag shell configuration. As a result, orders of enhancement of originally weak 4-ATP and CV Raman signal is witnessed by the combination of electromagnetic mechanism (EM) and chemical mechanism (CM) enhancements on a single SERS substrate. The hybrid GQD/HNP SERS substrate demonstrates significantly improved hot spots and strongly localized electromagnetic fields as confirmed by the finite-difference time-domain (FDTD) simulations. A proper mixture ratio of GQDs and probe molecules presents largely enhanced SERS signals by a strong adsorption of probe molecules through π - π interaction and the enhancement factors vary by the mixture ratio depending on the adsorption kinetics and Raman cross-section of molecules.

Beads‐on‐string hierarchical structured electrocatalysts for efficient oxygen reduction reaction

AbstractRational design of hierarchically structured electrocatalysts is particularly important for electrocatalytic oxygen reduction reaction (ORR). Here, ZIF‐67 crystals are stringed on core–shell Ag@C nanocables using a coordination‐modulated process. Upon pyrolysis, Ag@C strings of Co nanoparticles embedded with three‐dimensional porous carbon with beads‐on‐string hierarchical structures are developed. Due to the advantages of the rich electrochemical active sites of Co‐based “beads” and the efficient electron transfer pathways via Ag@C “strings,” the resultant NH3–Ag@C@Co–N–C‐700 catalyst shows an improved electrocatalytic activity toward ORR. NH3–Ag@C@Co–N–C‐700 shows a high onset potential of 0.99 V versus RHE, a high half‐wave potential of 0.88 V versus RHE, and a large limiting current of 5.8 mA cm−2, which are better than those of commercial Pt/C electrocatalysts. Additionally, the NH3–Ag@C@Co–N–C‐700 catalyst shows high stability and preeminent methanol tolerance, which makes NH3–Ag@C@Co–N–C‐700 a promising catalyst for oxygen electrocatalysis in fuel cell applications.

Core-shell Ag@C spheres derived from Ag-MOFs with tunable ligand exchanging phase inversion for electromagnetic wave absorption

It has become greatly significant to achieve structurally tunable electromagnetic wave absorption materials (EMAs) derived from metal-organic frameworks (MOFs) via controllably continuous phase inversion. Herein, a series of core–shell Ag@C EMAs were successfully fabricated from Ag-MOFs via adjustable phase inversion. Replacing terephthalic acid (H2BDC) with 2-methylimidazole (Hmim) continuously led to the gradual transformation of Ag-MOF-5 structure into ZIF-L, which determined the crystal and morphological structure of Ag@C EMAs. In addition, due to the optimization of relaxation loss, the minimum reflection loss (RLmin) of S2 reached −50.14 dB with a thickness of 3.0 mm. The EMA derived from the original Ag-MOF had the widest absorption bandwidth (fE) of 5.44 GHz and RLmin of −47.36 dB at only 2.2 mm, respectively. This work can shed new light on the core–shell EMAs derived from phase inversion MOFs, and provide guidance to design novel high-performance EMAs.

Core/Shell Ag/SnO2 Nanowires for Visible Light Photocatalysis

This study presents core/shell Ag/SnO2 nanowires (Ag/SnO2NWs) as a new photocatalyst for the rapid degradation of organic compounds by the light from the visible range. AgNWs after coating with a SnO2 shell change optical properties and, due to red shift of the absorbance maxima of the longitudinal and transverse surface plasmon resonance (SPR), modes can be excited by the light from the visible light region. Rhodamine B and malachite green were respectively selected as a model organic dye and toxic one that are present in the environment to study the photodegradation process with a novel one-dimensional metal/semiconductor Ag/SnO2NWs photocatalyst. The degradation was investigated by studying time-dependent UV/Vis absorption of the dye solution, which showed a fast degradation process due to the presence of Ag/SnO2NWs photocatalyst. The rhodamine B and malachite green degraded after 90 and 40 min, respectively, under irradiation at the wavelength of 450 nm. The efficient photocatalytic process is attributed to two phenomenon surface plasmon resonance effects of AgNWs, which allowed light absorption from the visible range, and charge separations on the Ag core and SnO2 shell interface of the nanowires which prevents recombination of photogenerated electron-hole pairs. The presented properties of Ag/SnO2NWs can be used for designing efficient and fast photodegradation systems to remove organic pollutants under solar light without applying any external sources of irradiation.

Tuning the surface enhanced Raman spectroscopy performance of Au core-Ag shell nanostructure for label-free highly sensitive detection of colorectal cancer Marker

Early detection is vital for the prevention and treatment of patients with colorectal cancer (CRC). However, existent methods (such as enzyme immunoassay, chemiluminescent immunoassay and radioimmunoassay) for early detection of CRC are time consuming, costly and complicated multistage processes, limiting their further applications. Here, a novel label-free and ultrasensitive detection method is developed for CRC protein marker NDKA by Cr3+ ions aggregating Au@Ag NPs (ICNPs) via surface-enhanced Raman spectroscopy (SERS) spectra for the first time. The Au@Ag NPs with size-controlled Ag shell thickness (1 nm, 3 nm, 5 nm, 7 nm and 9 nm Ag shells) are prepared as the SERS substrates and its Raman signals are Ag shells thickness-dependent sensitivity to proteins. By using Cr3+ ions as aggregating agents, the aggregating effect between the SERS substrates of Au@Ag ICNPs and protein analyte results in significantly enhanced and reproducible Raman signals owing to formation of lots of hotspots. Using this novel method, several label-free proteins, myoglobin (3 fg/mL), human serum albumin (30 fg/mL), lysozyme (30 ng/mL) and cytochrome C (30 ng/mL) were also detected at ultralow concentrations with good reproducibility and high sensitivity, demonstrating the potential applications in the fields of medical therapy and clinical diagnosis.

One-pot fabrication of Ag @Ag2O core\u2013shell nanostructures for biosafe antimicrobial and antibiofilm applications

Microbial contamination is one of the major dreadful problems that raises hospitalization, morbidity and mortality rates globally, which subsequently obstructs socio-economic progress. The continuous misuse and overutilization of antibiotics participate mainly in the emergence of microbial resistance. To circumvent such a multidrug-resistance phenomenon, well-defined nanocomposite structures have recently been employed. In the current study, a facile, novel and cost-effective approach was applied to synthesize Ag@Ag2O core–shell nanocomposites (NCs) via chemical method. Several techniques were used to determine the structural, morphological, and optical characteristics of the as-prepared NCs. XRD, Raman, FTIR, XPS and SAED analysis revealed a crystalline hybrid structure of Ag core and Ag2O shell. Besides, SEM and HRTEM micrographs depicted spherical nanoparticles with size range of 19–60 nm. Additionally, zeta potential and fluorescence spectra illustrated aggregated nature of Ag@Ag2O NCs by − 5.34 mV with fluorescence emission peak at 498 nm. Ag@Ag2O NCs exhibited higher antimicrobial, antibiofilm, and algicidal activity in dose-dependent behavior. Interestingly, a remarkable mycocidal potency by 50 μg of Ag@Ag2O NCs against Candida albican; implying promising activity against COVID-19 white fungal post-infections. Through assessing cytotoxicity, Ag@Ag2O NCs exhibited higher safety against Vero cells than bulk silver nitrate by more than 100-fold.

Synthesis of porous silicon based nanoparticles for applications in surface enhanced Raman spectroscopy

In this work porous Si (PSi) nanoparticles (NPs) were prepared by magnesiothermic reduction of the synthesized SiO2 spheres, and Ag NPs were deposited on the PSi with formaldehyde or HF. In addition, silver NPs were deposited on the porous Si obtained by milling and etching the Si wafer. Silver NPs on SiO2 spheres and particles with Ag core and mesoporous SiO2 shell were also synthesized. SEM analysis showed the Ag NPs size distributions between 30.1 and 64.3 nm. The synthesized samples were quite stable in aqueous media and had zeta potential between −11.5 and −44.3 mV. The samples exhibited reversible physisorption isotherms of type II except for the sample with Ag core and SiO2 (Ag–S) coating, which exhibited a type IVa isotherm accompanied by the hysteresis characteristic of mesoporous adsorbents. The BET surface areas of the samples ranged from 9 to 56 m2g-1, with the mesoporous Ag–S sample having the largest surface area of 378 m2g-1. The surface enhanced Raman spectroscopy (SERS) performance of the synthesized samples was studied by analysing the detection limit of 4-mercaptophenylboronic acid (4-MPBA) as a probe molecule at 532 nm laser excitation. The lowest limit of detection of 1 × 10−5 mol dm−3 was obtained with the sample in which silver NPs were deposited on silica spheres (S–Ag).

Core-shell Ag–Pt nanoparticles: A versatile platform for the synthesis of heterogeneous nanostructures towards catalyzing electrochemical reactions

Heterogeneous nanostructures that are defined as a hybrid structure consisting of two or more nanoscale domains with distinct chemical compositions or physical characteristics have attracted intense efforts in recent years. In this review, we focus on the introduction of a number of heterogeneous nanostructures derived using core-shell Ag–Pt nanoparticles as starting materials, including hollow, dimeric and composite structures and also highlight their application in catalyzing electrochemical reactions, e.g., methanol oxidation reaction and oxygen reduction reaction. This review not only shows the capability of core-shell Ag–Pt nanoparticles in producing various heterogeneous nanostructures as starting templates, but also highlights the structural design or electronic interaction that endows the heterogeneous nanostructures with enhanced catalytic properties either in methanol oxidation or in oxygen reduction. Further, we also make some perspectives for more heterogeneous nanostructures that may be prepared by using core-shell Ag–Pt particles or their derivatives so as to offer the readers the opportunities and challenges in this field.

Structural Control over Bimetallic Core-Shell Nanorods for Surface-Enhanced Raman Spectroscopy.

Bimetallic nanorods are important colloidal nanoparticles for optical applications, sensing, and light-enhanced catalysis due to their versatile plasmonic properties. However, tuning the plasmonic resonances is challenging as it requires a simultaneous control over the particle shape, shell thickness, and morphology. Here, we show that we have full control over these parameters by performing metal overgrowth on gold nanorods within a mesoporous silica shell, resulting in Au–Ag, Au–Pd, and Au–Pt core–shell nanorods with precisely tunable plasmonic properties. The metal shell thickness was regulated via the precursor concentration and reaction time in the metal overgrowth. Control over the shell morphology was achieved via a thermal annealing, enabling a transition from rough nonepitaxial to smooth epitaxial Pd shells while retaining the anisotropic rod shape. The core–shell synthesis was successfully scaled up from micro- to milligrams, by controlling the kinetics of the metal overgrowth via the pH. By carefully tuning the structure, we optimized the plasmonic properties of the bimetallic core–shell nanorods for surface-enhanced Raman spectroscopy. The Raman signal was the most strongly enhanced by the Au core–Ag shell nanorods, which we explain using finite-difference time-domain calculations.

Synthesis and design of Ag\u2013Fe bimetallic nanoparticles as antimicrobial synergistic combination therapies against clinically relevant pathogens

The inappropriate use of antibiotics and the inadequate control of infections have led to the emergence of drug-resistant strains. In recent years, metallo-pharmaceutics and metallic nanoparticles have been proposed as potential alternative antimicrobials due to their broad-spectrum antimicrobial properties. Moreover, recent findings have shown that combinations of transition metal compounds can exhibit synergistic antimicrobial properties. Therefore, the synthesis and design of bimetallic nanoparticles is a field worth exploring to harness the interactions between groups of metals and organic complex structures found in different microbial targets, towards the development of more efficient combinatorial antimicrobials composed of synergistic metals. In this study, we present a green synthesis of Ag–Fe bimetallic nanoparticles using an aqueous extract from the leaves of Gardenia jasminoides. The characterization of the nanoparticles demonstrated that the synthesis methodology produces homogenously distributed core–shell Ag–Fe structures with spherical shapes and average diameter sizes of 13 nm (± 6.3 nm). The Ag–Fe bimetallic nanoparticles showed magnetic and antimicrobial properties; the latter were evaluated against six different, clinically relevant multi-drug-resistant microbial strains. The Ag–Fe bimetallic nanoparticles exhibited an antimicrobial (bactericidal) synergistic effect between the two metals composing the bimetallic nanoparticles compared to the effects of the mono-metallic nanoparticles against yeast and both Gram-positive and Gram-negative multidrug-resistant bacteria. Our results provide insight towards the design of bimetallic nanoparticles, synthesized through green chemistry methodologies, to develop synergistic combinatorial antimicrobials with possible applications in both industrial processes and the treatment of infections caused by clinically relevant drug-resistant strains.

Au-Ag core-shell composite nanoparticles as a selective and sensitive plasmonic chemical probe for l-cysteine detection in Lens culinaris (lentils).

The present work reported is a simple and selective method for the colorimetrical detection of l-cysteine in Lens culinaris (or lentils) using Au–Ag core–shell (Au core Ag shell) composite nanoparticles as a chemical probe. The phenomenon is based on the color change of composite nanoparticles from yellowish brown to light blue, followed by a shift of the localized surface plasmon resonance (LSPR) absorption band in the UV-visible region (i.e., 200–800 nm) with the addition of l-cysteine into the solution of bimetallic nanoparticles. The mechanism for the detection of l-cysteine is based on the electrostatic interaction of the metal ion with the thiol group of the amino acid, which causes the red shift of the LSPR band at 685 nm. The size distribution, morphology, composition and optical properties of the Au–Ag core–shell composite nanoparticles were characterized by transmission electron microscopy (TEM), dynamic light scattering (DLS), energy dispersive X-ray diffraction (EDX), UV-visible spectrophotometer and Fourier transform infrared spectroscopy (FTIR) techniques. An excellent linearity range for the present method was observed in the range of 20–140 μg mL−1 with a limit of detection at 1.95 μg mL−1 and correlation coefficient (R2) of 0.986. A good% recovery of 4.0% showed the selectivity of the method for l-cysteine determination from sample matrices. The advantageous features of the present method are being simple, rapid, low cost and selectivity towards the determination of l-cysteine in lentils.

Development of an electrochemical sensor for the determination of antibiotic sulfamethazine in cow milk using graphene oxide decorated with Cu-Ag core-shell nanoparticles.

Determination and sensing of antibiotics in dairy products are the biggest challenges in the world. In continuation of our earlier study, a facile and novel determination method for the detection of sulfamethazine (SMZ) in cow milk has been developed using a glassy carbon electrode modified with graphene oxide decorated with Cu-Ag core-shell nanoparticles. The Cu-Ag core-shell nanoparticles and graphene oxide were synthesized and characterized via different techniques such as TEM, SEM, XRD and FTIR. The as-synthesized Cu-Ag core-shell nanoparticles were used for the decoration of the glassy carbon electrode modified with graphene oxide. The electroanalytical measurements including cyclic voltammetry and square wave voltammetry were performed and compared with HPLC, which was utilized for the determination of SMZ in cow milk. The experimental conditions were optimized to obtain a well-defined response signal. The concentration linear range was 10-1000 μM and the limit of detection was 0.46 μM for S/N = 3. The obtained results show good agreement with HPLC reported data.

The [Ag25Cu4H8Br6(CCPh)12(PPh3)12]3+ : Ag13H8 silver hydride core protected by [CuAg3(CCPh)3(PPh3)3]+ motifs.

Copper alkynyl complexes [CuAg3(C[triple bond, length as m-dash]CAr)3(PPh3)3]+ (Ar = Ph, p-C6H4Me), in which three Ag(PPh3) units are bound among three C[triple bond, length as m-dash]CAr arms of trigonal-planar [Cu(C[triple bond, length as m-dash]CAr)3]2-, were selected as a protecting unit to cover the metal core of an atomically precise core-shell-type cluster. First, the formation of the protecting unit through the reaction of Cu(NCMe)4(PF6) with Ag(C[triple bond, length as m-dash]CAr) and PPh3 in a 1 : 3 : 3 ratio was confirmed. The reaction gave dimeric [CuAg3(C[triple bond, length as m-dash]CAr)3(PPh3)3]22+, in which the two planar [CuAg3(C[triple bond, length as m-dash]CAr)3(PPh3)3]+ units were stacked. Next, core-shell-type clusters were synthesized by adding NaBH4 and Et4NX (X = Cl, Br) to a solution similar to that used to prepare the protecting unit. The trigonal-planar protecting units nicely formed core-shell-type Ag nanoclusters formulated as [Ag13H8X6{CuAg3(C[triple bond, length as m-dash]CAr)3(PPh3)3}4]3+ (X = Cl, Ar = p-C6H4Me; X = Br, Ar = p-C6H4Me; X = Br, Ar = Ph). Their crystal structures revealed that the four [CuAg3(C[triple bond, length as m-dash]CAr)3(PPh3)3]+ units are linked by six halogen ions to form a tetrahedral cage that accommodates a polyhydride-Ag cluster formulated as Ag13H85+. As a concrete proof of the existence of the polyhydride, deuterated analogs Ag13D85+ were synthesized and subsequently characterized by high-resolution electrospray-ionization mass spectrometry measurements.