Ag Core Research Articles

Optimization and performance assessment of Ag@SiO2 core–shell nanofluids for spectral splitting PV/T system: Theoretical and experiment analysis

Ag@SiO2 nanofluid is widely used in spectral splitting PV/T system. Its core–shell structure has great influence on the optical properties. In this work, we focus on the comprehensive analysis and structure optimization of Ag@SiO2 nanofluid to achieve its optimal spectral performance. DDA method is used to predict the optical properties of Ag@SiO2 nanofluid and an optimization model based on filter efficiency is proposed. The effect of the SiO2 shell thickness and Ag core mass concentration is analyzed. It indicates that the spectral performance of Ag@SiO2 nanofluid can be improved with SiO2 shell thickness of 15–40 nm and Ag core mass concentration of 81–135 mg/L. To achieve the same theoretical merit function of 1.46, the usage of Ag mass can be reduced by 25/33/44/62 % with SiO2 coating of 10/20/40/70 nm. The optimal structure to achieve the highest filter efficiency η of 37.8 % is with a shell thickness of 20 nm and a mass concentration of 113.9 mg/L. An indoor PV/T operation testing is conducted to verify the optimization results. The merit function of Ag-based nanofluids increases from 1.58 to 1.598 and a reduction in Ag usage of 17 % is achieved with a SiO2 coating shell of 17.8 nm. Operation stability is also enhanced with no aggregation observed during the working cycle and 7-day static experiment.

Synergy of photoluminescence emission and antibacterial activity of Ag-Cu2O nanocomposite

Conglomerate nanocomposites comprising metal and metal oxide hold significant potential for exhibiting properties that surpass the combined characteristics of their individual components, owing to the interactions occurring at the interfaces between the metal and metal oxide elements. In this study, we present the synthesis of Cu2O nanoparticles (NPs) (with diameters ranging from 40 to 53 nm) and Ag-Cu2O nanocomposites using an aqueous solution method at room temperature, employing varying concentrations of Ag NPs. Through optical absorption studies, we determined the optical band gap of Cu2O NPs in 0.5Ag-Cu2O, 1Ag-Cu2O, and 1.5Ag-Cu2O nanocomposites samples to be 2.13 eV, 2.25 eV, 2.34 eV, and 2.41 eV, respectively. The x-ray diffraction data are analysed using the Williamson–Hall technique and revealed noteworthy variations in microstructural characteristics such as strain and stress within the Cu2O nanocrystallites fabricated under different Ag concentrations. The nanocomposites amplified the intensities of violet-blue, blue, and green photoluminescence (PL) emissions, attributable to the interfaces between Ag and Cu2O, lattice mismatches, and the induced microstructural parameters lattice strain, and stress of Cu2O nanocrystallites. The enhanced PL intensities can be attributed to the influence of the local electric field on the Ag core composites. The Ag-Cu2O nanostructure exhibits potential applications in water purification technologies, while the PL emission properties and low band gap (∼2.13 eV) hold promising applications in optoelectronic devices. The antibacterial activities of Cu2O and Ag-Cu2O nanomaterials against Enterococcus faecalis and Escherichia fergusonii are examined using MH agar well plate diffusion methods. Here, Ag NPs enhance bactericidal effectiveness through enhanced interaction with bacteria and the release of Ag+ ions, while the Cu2O shell discontinuity on Ag NPs contributes to their unique antibacterial properties.

Simulated sunlight-driven photocatalytic activation of peroxydisulfate by core–shell Ag@SiO2/TiO2 nanocomposite for efficient methyl orange degradation

Herein, core–shell Ag@SiO2/TiO2 nanocomposites were synthesized and applied to activate peroxydisulfate (PDS) for wastewater purification. The Ag core and Ag-doped TiO2 shell were obtained by stober method and calcination method. The dispersion degree and size of Ag in TiO2 would influence the oxygen vacancy. Ag enhanced the visible absorption of TiO2 and activated PDS. Improved degradation performance was attributed to enhanced PDS activation by photogenerated e−, which separated h+and thus promoted methyl orange(MO) degradation. Reactive oxidative species were verified under dark and light conditions via quenching experiments and electron paramagnetic resonance tests, demonstrating SO4•–, h+, O2•–, and1O2were formed in light,whereasSO4•–, •OH, O2•–, and 1O2were responsible for MO degradation under dark conditions. The Ag@SiO2/TiO2/PDS/light system showed selectivity for removal of cationic dyes (e.g., methylene blue and malachite green) through adsorption and photocatalysis, whereas anionic dyes (e.g., MO) were degraded by photocatalysis alone. Besides, we found excess adsorption of micropollutant onto catalyst may be adverse to the activation of PDS. Therefore, the adsorption of oxidant (such as PDS) onto the catalyst surface would be beneficial for catalytic activation and micropollutant degradation, especially onto active sites. This work aims to provide a new avenue for core-shell structure catalyst synthesis in wastewater purification.

Preparation of GaN Nanocrystals with Single Ag Cores

Preparation of GaN Nanocrystals with Single Ag Cores

Nanoscale dosimetry for a radioisotope-labeled metal nanoparticle using MCNP6.2 and Geant4.

Metal nanoparticles (MNPs) labeled with radioisotopes (RIs) are utilized as radio-enhancers due to their ability to amplify the radiation dose in their immediate vicinity. A thorough understanding of nanoscale dosimetry around MNPs enables their effective application in radiotherapy. However, nanoscale dosimetry around MNPs still requires further investigation. This study aims to provide insight into the radio-enhancement effects of MNPs by elucidating nanoscale dosimetry surrounding MNPs labeled with Auger-emitting RIs. We particularly focus on distinguishing the respective dose contributions of photons and electrons emitted by Auger-emitting RIs in the context of dose enhancement. A 50nm diameter NP of silver (Ag) core and gold (Au) shell (Ag@Au NP) was assumed to emit mono-energetic electrons and photons (3, 5, 10, 20, and 30keV), or the energy spectrum corresponding to one of three Auger-emitting RIs (103Pd, 125I, and 131Cs) from the Ag core. Nanoscale radial dose distributions around a single radioactive Ag@Au NP were evaluated in spherical shells of water. Monte Carlo simulations were conducted using single-event and track structure transport methods implemented in MCNP6.2 and Geant4-DNA-Au physics, respectively. To evaluate the extent of radio-enhancement by the Ag@Au NP, two scenarios were considered: Ag@Au NPs (Au shell included) and Ag@water NPs (Au shell replaced by water). The radial doses of 10, 20, and 30keV electrons estimated by both codes were comparable. However, the radial doses of 3 and 5keV electrons by MCNP6.2 were much larger near the NP surface than those by Geant4. There was a dose enhancement of a few % to tens % by the Au shell in the region of the NP surface to 10µm, depending on the electron energy. The radial doses of photons with the Au shell were higher up to their secondary electron ranges than those without the Au shell. The maximum dose enhancement factor of photons occurred at 20keV and was 63.4 by MCNP6.2 and 50.5 by Geant4. The overall radial doses of electrons were 1-2 orders of magnitude larger than those of photons. As a result, in cases of RIs emitting both electrons and photons, the radial doses up to electron ranges were dominantly governed by electrons. The dose enhancement estimated by both codes for the RIs ranged from a few % except in the immediate vicinity of the NP surface. Given the dominant contribution of electrons to radial doses of MNP labeled with Auger-emitting RIs, physical dose enhancement expected by interactions with photons was hindered. Since there are no available RIs emitting exclusively photons, achieving enhanced physical doses within a cell through a combination of MNPs and RIs appears currently unattainable. The radial doses of photons near the NP surface exhibited considerable discrepancies between the codes, primarily attributed to low-energy electrons. The difference may arise from higher cross-sections of Au inelastic scattering in Geant4-DNA-Au compared to MCNP6.2.

SERS aptasensor for simultaneous detection of ochratoxin A and zearalenone utilizing a rigid enhanced substrate (ITO/AuNPs/GO) combined with Au@AgNPs

The contamination of mycotoxins poses a serious threat to global food security, hence the urgent need for simultaneous detection of multiple mycotoxins. Herein, two SERS nanoprobes were synthesized by embedded SERS tags (4-mercaptopyridine, 4MPy; 4-mercaptobenzonitrile, TBN) into the Au and Ag core–shell structure, and each was coupled with the aptamers specific to ochratoxin A (OTA) and zearalenone (ZEN). Meanwhile, a rigid enhanced substrate Indium tin oxide glass/AuNPs/Graphene oxide (ITO/AuNPs/GO) was combined with aptamer functionalized Au@AgNPs via π-π stacking interactions between the aptamer and GO to construct a surface-enhanced Raman spectroscopy (SERS) aptasensor, thereby inducing a SERS enhancement effect for the effective and swift simultaneous detection of both OTA and ZEN. The presence of OTA and ZEN caused signal probes dissociation, resulting in an inverse correlation between Raman signal intensity (1005 cm−1 and 2227 cm−1) and the concentrations of OTA and ZEN, respectively. The SERS aptasensor exhibited wide linear detection ranges of 0.001–20 ng/mL for OTA and 0.1–100 ng/mL for ZEN, with low detection limits (LOD) of 0.94 pg/mL for OTA and 59 pg/mL for ZEN. Furthermore, the developed SERS aptasensor demonstrated feasible applicability in the detection of OTA and ZEN in maize, showcasing its substantial potential for practical implementation.

Hyaluronic acid-coated silver nanoparticles releasing Doxorubicin for combinatorial antitumor therapy

Although various nanocarriers have been developed to deliver anticancer drugs to the target tumors, it is still remaining great challenges, including burst release, non-specific targetability and insufficient therapeutic efficacy. Herein, we prepared a multifunctional nanoparticle composed of Ag core and hyaluronic acid shell (Ag NPs@HA) for stimultaneously intracellular delivery of Doxorubicin (DOX) and Ag NPs to improve the anticancer therapeutic efficacy. For our approach, Ag NPs was simply synthesized via the redox reaction between Ag+ ions and catechol group of functional HA, and DOX was subsequently loaded into the HA-coated Ag NPs through the interaction between the remaining catechol groups and DOX (Ag NPs@HA/DOX). The particles exhibited uniform morphology, good biocompatibility to normal cells, and pH-sensitive drug release. Notably, thanks to the specific interaction of HA and CD44 receptor-overexpressing cancer cells, Ag NPs@HA/DOX could dramatically improve the anti-tumor efficacy in vitro as well as in vivo mimicking 3D spheroid model, compared to the free DOX. Moreover, Ag NPs@HA/DOX exhibited superior tumor supression in vivo on a HELA-xenografted mouse model, while minimizing the systemic toxicity of free DOX. From the obtained results, we suggest Ag NPs@HA as potential nanocarrier for targeting delivery of various therapeutic drugs in anticancer therapy.

Controllable Silver Release for Efficient Treatment of Drug-Resistant Bacterial-Infected Wounds.

The use of traditional Ag-based antibacterial agents is usually accompanied by uncontrollable silver release, which makes it difficult to find a balance between antibacterial performance and biosafety. Herein, we prepared a core-shell system of ZIF-8-derived amorphous carbon-coated Ag nanoparticles (Ag@C) as an ideal research model to reveal the synergistic effect and structure-activity relationship of the structural transformation of carbon shell and Ag core on the regulation of silver release behavior. It is found that Ag@C prepared at 600 °C (AC6) exhibits the best ion release kinetics due to the combination of relatively simple shell structure and lower crystallinity of the Ag core, thereby exerting stronger antibacterial properties (>99.999 %) at trace doses (20 μg mL-1) compared with most other Ag-based materials. Meanwhile, the carbon shell prevents the metal Ag from being directly exposed to the organism and thus endows AC6 with excellent biocompatibility. In animal experiments, AC6 can effectively promote wound healing by inactivating drug-resistant bacteria while regulating the expression of TNF-α and CD31. This work provides theoretical support for the scientific design and clinical application of controllable ion-releasing antibacterial agents.

Direct detection of polystyrene microspheres by using easily fabricated Ag core embedded Au film SERS substrates with high sensitivity

Plastics as very important materials have been extensively utilized, and they make people’s lives comparative and economic. However, recent studies find that the micro/nano-plastic particles degenerating from plastic materials especially for food containers may lead to some unknown diseases when they enter into the human lung or stomach. The methods of detecting micro/nano-plastic particles are urgently required, and conventional methods necessitate intricate pre-processing steps and specialized equipment. Hence, this paper introduces a highly sensitive and direct detection method based on Surface-Enhanced Raman Spectroscopy (SERS) in quantitatively and qualitatively analyzing polystyrene (PS) nanoplastics that are drop cast on substrate. The mechanism of SERS performance of the proposed Ag core embedded Au film (Ag@AuFilm) SERS substrate is studied by using the finite-different time-domain (FDTD) method. By optimizing the gap distance between the Ag core and the Au film, PS nanoplastics with three diameters were used to validate the effectiveness of the SERS substrate. The limits of detection (LOD) for PS nanoparticles with diameters of 50 nm, 70 nm, and 310 nm in DI water and real-river water were the same and the corresponding LODs were 50, 50, and 25 μg/mL, respectively. Thus, this study proposes an easily fabricated SERS substrate and provides a rapid, quantitative, and qualitative method for detecting PS nanoplastics. This new way of addressing the pervasive issue of nanoplastics pollution provided an accurate, efficient, and rapid detection of the nanoplastics.

Atomistic simulation of temperature dependence of tensile properties and estimation of DBTT of Cu–Ag core–shell nanowires

An atomistic model of Cu-Ag core–shell nanowire using molecular dynamics is proposed. The simulation model was utilized for the evolution of temperature dependent (in the range of 10–500 K) tensile behavior and the identification of ductile-to-brittle transition temperature (DBTT) of single-crystal Cu-Ag core–shell nanowire. The evolution of defects such as point defects, dislocations, and stacking faults, arising from tensile deformation in the mentioned temperature rage were analyzed. The Wigner-Seitz Defect analysis, Dislocation analysis, and Common Neighbor analysis methods were implemented in this study to estimate the various defects concentration in the nanowire. The study identified that Cu-Ag core–shell (core diameter = 4 nm and shell thickness = 1 nm nanowire) exhibits DBTT somewhere in the temperature between 25 K to 30 K. The modulus of elasticity found to be increasing from 19.7 TPa at 10 K to 23.7 TPa at 30 K (within brittle regime), followed by a steep fall to 14.9 TPa at 500 K where fracture seems to be in ductile mode. The observed mechanical properties of the nanowire are discussed in the article in view of the dislocation and stacking faults generation in the core–shell nanostructures.

Adsorption properties and catalytic activity of Fe3O4-Ag nanostructures

The morphology and magnetic properties as well as adsorption capacity and catalytic activity of Fe3O4-Ag nanoparticles synthesized by the solvothermal method were studied in dependence on the duration of the thermolysis process (3, 6, and 8 h). X-ray diffraction, transmission electron microscopy, and energy-dispersive spectroscopy measurements showed that the morphology of nanoparticles changed strongly as the duration of thermolysis increased. At 6 and 8 h duration, Fe3O4 nanocrystals grow and assemble into porous spherical globules with an Ag core (samples 2 and 3). These samples demonstrate high magnetization value and very low coercivity. The adsorption capacity of nanoparticles was studied with respect to two organic dyes: cationic methylene blue (MB) and anionic Congo red (CR). The particles showed preferential adsorption of the cationic dye. High catalytic activity towards four dyes: MB, methyl orange (MO), CR, and Rhodamine C (RhC) at the presence of NaBH4 is the remarkable property of these samples. The rate constant of the catalytic reaction was 1.4 min−1. Simultaneous exposure of CR and MO dyes to nanoparticles and NaBH4 caused their irreversible 100 % degradation while in the case of MB and RhC, a transition to their leuco form occurred.

Synergistic effect of Silver-Nanodiamond composite as an efficient antibacterial agent against E. coli and S. aureus

Bacterial antimicrobial resistance (BAMR) seems to pose the greatest threat to public health, food safety, and agriculture in this century. The development of novel efficient antimicrobial agents to combat bacterial infections has become a global issue. Silver nanoparticles (Ag NPs) appeared as a feasible alternative to antibiotics. However, Ag NPs face cost, toxicity, and aggregation issues which limit their antibacterial activity. This work aims to stabilize Ag NPs with enhanced antimicrobial activity at comparatively lower Ag concentrations to prevent bacterial infections. For this purpose, the Ag core was covered with nanodiamonds (NDs). Ag-NDs composite have been synthesized by microplasma technique. TEM analysis confirmed the presence of both Ag and NDs in the Ag-NDs composite. A particle size (∼19 nm) was reported for Ag-NDs at the highest concentration as compared to Ag NPs (∼3 nm). The conduction band of the diamond acted as an extremely strong reducing agent for Ag NPs. The large surface area of NDs stabilized the Ag NPs. A redshift (∼400 nm–406 nm) in UV–visible spectra of the Ag-NDs composite indicated the formation of bigger-sized Ag NPs after incorporating NDs. XRD and LIBS analysis verified the increase in intensity of Ag-NPs by increasing ND concentration. The presence of functional groups including OH, CH, and Ag/Ag2O was confirmed by FTIR. Bacterial inhibition growth appeared to be a dose-dependent process. The minimum inhibition concentration value of Ag-NDs composite at the highest NDs concentration against E. coli (∼ 0.69 μg/ml) and S. aureus (∼44 μg/ml). This is the first study to report the smallest MIC for E. coli (<1 μg/ml). Ag-ND composites emerged to be more efficient than Ag NPs and preferred to be used against BAMR. The enhanced antibacterial activity of the Ag-NDs composite makes it a potential candidate for antibiotics, food products, and pesticides.

Plasmon near-field coupling and universal scaling behavior in shifted-core coaxial nano-cavity pair

We computationally and analytically investigate the plasmon near-field coupling phenomenon and the associated universal scaling behavior in a pair of coupled shifted-core coaxial nano-cavities. Each nano-cavity is composed of an InGaAsP gain medium sandwiched between a silver (Ag) core and an Ag shell. The evanescent coupling between the cavities lifts the degeneracy of the cut-off free transverse electromagnetic (TEM) like mode. The mode splitting of the supermodes is intensified by shifting the metal core position, which induces symmetry breaking. This coupling phenomenon is explained with spring-capacitor analogy and circuit analysis. The numerical simulation results reveal an exponential decay in the fractional plasmon wavelength relative to the ratio of gap distance and core shifting distance, which aligns with the plasmon ruler equation. In addition, by shifting the Ag cores in both cavities toward the center of the coupled structure, the electromagnetic field becomes strongly localized in nanoscale regions (hotspots) in the gain medium between the cavities, thus achieving extreme plasmonic nanofocusing. Utilizing this nanofocusing effect, we propose a refractive index sensor by placing a fluidic channel between the two cavities in close vicinity to the hotspots and reaching the highest sensitivity of ∼700nm/RIU.

Near-Infrared Responsive Ag@Au Nanoplates with Exceptional Stability for Highly Sensitive Colorimetric and Photothermal Dual-Mode Lateral Flow Immunoassay.

Lateral flow immunoassay (LFIA) has played a vital role in point-of-care (POC) testing on account of its simplicity, rapidity, and low cost. However, the low sensitivity and difficulty of quantitation limit its further development. Sensitive markers with new detection modes are being developed to dramatically improve LFIA's performance. Herein, a ligand-complex approach was proposed to uniformly coat a thin layer of Au onto Ag triangular nanoplates (Ag TNPs) without etching the Ag cores, which not only retain the unique optical properties from Ag TNPs but also acquire the surface stability and biocompatibility of gold. The localized surface plasmon resonance absorption of these Ag@Au TNPs could be finely adjusted from visible (550 nm) to the second near-infrared region (NIR-II) (1100 nm), and even longer, by simply adjusting the ratio between edge length and thickness. Utilizing the Ag@Au TNPs as new markers for LFIA, a highly sensitive colorimetric and photothermal dual-mode detection of the SARS-CoV-2 nucleocapsid protein was achieved with a very low background. The Ag@Au TNPs showed an exceedingly high photothermal conversion efficiency of 61.4% (ca. 2 times higher than that of Au nanorods), endowing the LFIA method with a low photothermal detection limit (40 pg/mL), which was 25-fold lower than that of the colorimetric results. The generality of the method was further verified by the sensitive and accurate analysis of cardiac troponin I (cTnI). This method is robust, reproducible, and highly specific and has been successfully applied to SARS-COV-2 detection in 35 clinical samples with satisfactory results, demonstrating its potential for POC applications.

Morphology dependent EMI shielding performance of Ag-Ni core-shell nanowires

The proposed work reports a facile chemical reduction method for synthesizing the hierarchical silver-nickel core-shell nanowire structures with controllable morphologies by varying the Ag concentration. The growth of Ni shells around the Ag core to make thorny and smooth Ag-Ni core-shell nanowires is studied for addressing electromagnetic interference (EMI). The synthesized Ag-Ni nanowires show better EMI shielding effectiveness (SE) than Ni nanowires with much-improved absorption loss (SEA). Due to high electrical conductivity (8630 S cm−1), magnetic permeability (44.1 emu/g), and heterojunction core-shell interfaces, the bimetallic nanowires flakes exhibit exceptional average EMI SE of 90.5 dB in the X-band frequency range (8–12 GHz) with a thickness of 0.11 mm, taking specific EMI SE to 822.72 dB/mm. In addition, the EMI shielding performance of the smooth Ag-Ni nanowires showed a 45% enhancement in SEA with marginal change in reflection loss (SER) compared to the thorny ones, indicating high absorption of EM waves. The unique core-shell nanowires with high aspect ratio with tunable physical properties can be ideal candidates for futuristic applications in microwave absorption and electromagnetic interference shielding.

Low-temperature iodinated plasmonically tuned Ag@AgI core-shell nanostructured thin films for highly specific ascorbic acid SERS detection at ultra-low concentrations

A simple low temperature iodination route was developed to controllably iodinate silver nanoislands film (Ag) into silver@silver iodide core-shell nanoparticles film (Ag@AgI) as a chemically stable, near infrared active surface enhanced Raman scattering (SERS) substrate. The localised surface plasmon resonance (LSPR) of the core-shell film exhibits a huge red-shift of 100 nm. The formation of Ag core and a complete ultra-thin AgI shell layer on top of the core is confirmed by transmission electron microscope. Selected area electron diffraction reveals the amorphous nature of AgI shell layer. These results are further substantiated by Raman and x-ray diffraction measurements. The enhancement factor of Ag@AgI film estimated with methylene blue is 5 × 106, an order of magnitude higher compared to that of Ag film. It demonstrated excellent chemical stability and unwavering SERS performance for two months since fabrication. The Ag@AgI film fielded as a label-free SERS substrate exhibited a lowest limit-of-detection of 1 × 10−12 M for ascorbic acid and a linear detection range of 1 × 10−6 to 1 × 10−12 M. The ascorbic acid selective signal enhancement of Ag@AgI film at low concentration region offers a practical sample dilution strategy to suppress interference from non-target molecules in biofluids.

Nanoconfined tandem three-phase photocatalysis for highly selective CO2 reduction to ethanol.

The conversion of CO2 and H2O into ethanol with high selectivity via photocatalysis is greatly desired for effective CO2 resource utilization. However, the sluggish and challenging C-C coupling hinders this goal, with the behavior of *CO holding the key. Here, a nanoconfined and tandem three-phase reaction system is established to simultaneously enhance the *CO concentration and interaction time, achieving an outstanding ethanol selectively of 94.15%. This system utilizes a tandem catalyst comprising an Ag core and a hydrophobic Cu2O shell. The hydrophobic Cu2O shell acts as a CO2 reservoir, effectively overcoming the CO2 mass-transfer limitation, while the Ag core facilitates the conversion of CO2 to CO. Subsequently, CO undergoes continuous reduction within the nanoconfined mesoporous channels of Cu2O. The synergy of enhanced mass transfer, nanoconfinement, and tandem reaction leads to elevated *CO concentrations and prolonged interaction time within the Cu2O shell, significantly reducing the energy barrier for *CO-*CO coupling compared to the formation of *CHO from *CO, as determined by density functional theory calculations. Consequently, C-C coupling preferentially occurs over *CHO formation, producing excellent ethanol selectivity. These findings provide valuable insights into the efficient production of C2+ compounds.

Localized surface plasmon resonance effect of 3-mercaptopropionic acid capped on silver nanoparticles for sensing probe application

Metal nanoparticles such as gold and silver are often used in various nanotechnology applications due to the localized plasmon resonance effect that occurs when incident photons interact with metal nanoparticles. 3-mercaptopropionic acid (3-MPA) is one of the capping molecules that can be provided for surface functionalization on gold or silver core because it has thiol and carboxylic group as a linking biomolecule, and this allows the use of nanoparticles for biosensor applications. In this study, we successfully synthesized silver nanoparticles capped by 3-mercaptopropionic acid (AgMPA) by use of two kinds of methods i.e ligand exchange and direct reduction, which reveal the unique characteristic plasmonic peaks of AgNP around 430 nm and 436 nm, respectively with spherical shape of AgNP and diameter size about 6-20 nm. The transmittance spectra from Fourier Transform Infrared (FTIR) measurement shows that S-H coordination from 3-MPA is invisible after 3-MPA attach on Ag core due to the strong coordination between Ag and the sulfur (S) ion, while the broaden peaks at 1589 and 1385 cm-1 for AgMPA are assigned to asymmetric and symmetric vibrations of carboxylate groups which overlap between carboxylate from citrate and 3-MPA. Finally, the colorimetric detection using AgCA and AgMPA as sensing probe was carried out by use of Biocytin-Avidin system molecule as analyte, which resulted in the colour changed rapidly from yellow to transparent-yellow and the red-shifted of absorbance spectra indicating the attachment of analyte to functionalized molecule of our synthesized AgCA and AgMPA.

Nanosized Pd@Ag heterojunction with tunable shapes: Morphological modulation for improving plasma-mediated catalytic hydrogen evolution

Catalytic ability of bi-metal hybrid nanoagents largely depends on their phase constitution and morphology, also bearing a close correlation to the fabrication process. We herein design and develop a modified polyol protocol with inorganic ion induction for rationally constructing Ag nanoagents with tunable shapes (nanowire, nanocube, and nanoparticle), followed by evenly anchoring of stepwise reduced Pd nanograins on the surface of Ag nanoagents to foster Ag core - Pd shell (i.e. Pd@Ag) nanosized heterostructure. A home-made photochemical reaction device is used to scientifically evaluate the catalytic ability of the Pd@Ag nanoagents on hydrolyzing ammonia borane to evolve hydrogen gas. The ample characterization reveals that the fabricated Ag nanoagents hold the expected regular and uniform shapes, with 10–15 nm thick Pd layer cladded on their surfaces. The particular shapes of the Ag nanoagents can be duly manipulated via the induction of inorganic ions, and the thickness and compactness of the Pd shell can also be suitably regulated by controlling reduction duration. The verified formation of electron synergistic effect among the both metals is favorable to elevate the catalytic ability. The bimetal Pd@Ag nanoagents perform the superior catalytic activity under visible light irradiation, far exceeding that of the respective monometal counterparts, with the order of catalytic activity: Pd@Ag-NWs > Pd@Ag-NCs > Pd@Ag-NPs. The hydrolysis reaction at the given conditions is confirmed to be quasi first-order reaction, with the apparent activation energy of 53.44 kJ·mol−1 and TOF value of 47.04 min−1. The Pd@Ag-NWs catalyst behaves satisfactory stability, with 87.8 % initial catalytic activity retained after five cyclic use.

Core-satellite nanocomposites via PEI-induced self-assembly for enhanced SERS sensing of thiram and ciprofloxacin

Developing sensitive, reliable, and robust surface-enhanced Raman spectroscopy (SERS) substrates relies heavily on fabricating a substantial number of hot spots. In this study, we present a straightforward method for creating Ag@PEI/Ag core-satellite nanocomposites. Large Ag nanospheres serve as the cores, and smaller Ag nanoparticles are electrostatically assembled around them through the introduction of polyethyleneimine (PEI). This assembly process generates numerous hot spots not only between two Ag satellites but also between the inner Ag core and Ag satellites, thanks to the sub-nm PEI interlayer. The nanocomposites exhibit great potential for SERS analysis, enabling effective sensing of various organic pollutants, such as thiram and ciprofloxacin, using a portable Raman spectrometer. Notably, these nanocomposites obtain an exceptional detection limit of as low as 10−8 M for them, which falls below the safety level set by the United States Environmental Protection Agency. Additionally, the substrates demonstrate excellent uniformity, reproducibility and storing stability. Consequently, the Ag@PEI/Ag core-satellite nanocomposites hold great promise as efficient SERS platforms for reliable and highly sensitive monitoring of food safety and environmental analysis.