Stable Ag Research Articles

Monodisperse silver nanocubes composite Ag@C/SrTiO3 photocatalytic decomposition of water for hydrogen reduction

Metal-induced photocatalysis has been a relatively effective strategy for the efficient use of solar energy. In this paper, highly efficient and stable Ag@C/SrTiO3 photocatalysts were prepared by compounding silver nanocubes wrapped with few layers graphite with strontium titanate materials. We obtained silver nanocubes with a uniformly dispersed size of about 35 nm by varying the surface energy of silver and inducing the preferential binding of PVP on the (100) crystal plane with the help of selective adsorption of chloride ions on the different crystal planes of silver. As obtained under the characterisation of UV–visible absorption spectra, the material has a broad visible light absorption (450–900 nm). The Ag@C/SrTiO3 has a hydrogen reduction rate of up to 457.5 μmol g−1·h−1 under simulated sunlight, which is ∼200 % higher than the SrTiO3 and ∼900 % higher than the sliver. Moreover, the catalyst was stable, still producing 93.5 % hydrogen after three cycles of testing, and the photocatalyst structure did not change as known from the XRD data of the material before and after testing. The present work demonstrates the feasibility of rational design of efficient and stable silver-based photocatalysts.

Ag Intercalation in Layered Cs3Bi2Br9 Perovskite for Enhanced Light Emission with Bound Interlayer Excitons.

Cesium bismuth bromide (CBB) has garnered considerable attention as a vacancy-ordered layered perovskite with notable optoelectronic applications. However, its use as a light source has been limited due to its weak photoluminescence (PL). Here, we demonstrate metal intercalation as a novel approach to engineer the room-temperature PL of CBB using experimental and computational methods. Ag, when introduced into CBB, occupies vacant sites in the spacer region, forming octahedral coordination with surrounding Br anions. First-principles density functional theory calculations reveal that intercalated Ag represents the most energetically stable Ag species compared to other potential forms, such as Ag substituting Bi. The intercalated Ag forms a strong polaronic trap state close to the conduction band minimum and quickly captures photoexcited electrons with holes remaining in CBB layers, leading to the formation of a bound interlayer exciton, or BIE. The radiative recombination of this BIE exhibits bright room-temperature PL at 600 nm and a decay time of 38.6 ns, 35 times greater than that of free excitons, originating from the spatial separation of photocarriers by half a unit cell separation distance. The BIE as a new form of interlayer exciton is expected to inspire new research directions for vacancy-ordered perovskites.

Highly Stable Silver Nanowire Plasmonic Electrodes for Flexible Polymer Light-Emitting Devices.

Silver nanowire (AgNW) transparent electrodes are considered as a promising candidate for applications in flexible optoelectronic devices. However, it remains a great challenge to obtain flexible AgNW electrodes with excellent optoelectrical properties and mechanical flexibility. Here, highly stable Ag nanoparticle (AgNP)-enhanced plasmonic AgNW electrodes are demonstrated via the controllable in situ growth of AgNPs at the AgNW junctions and introduction of an l-histidine (l-His) wrapping layer. The flexible transparent electrodes of AgNW-AgNP/l-His possess a low sheet resistance (Rsh) of ∼17.5 Ω sq-1, a high transmittance of ∼92.5% (550 nm), and a robust mechanical stability (100,000 bending cycles). Benefiting from plasmon-coupling effects, flexible polymer light-emitting devices (FPLEDs) with AgNW-AgNP/l-His electrodes present a current efficiency (CE) of ∼14.8 cd A-1 and an external quantum efficiency (EQE) of ∼5.6%, constituting ∼80% and ∼75% increases compared to those of the reference devices with AgNW electrodes, respectively. Additionally, the laminated flexible transparent PLEDs (FT-PLEDs) are demonstrated by integrating polydimethylsiloxane/AgNW-AgNP anodes by a soft lamination process. The FT-PLEDs present a CE of ∼7.1 cd A-1 (cathode side: ∼3.9 cd A-1; anode side: ∼3.2 cd A-1) and an EQE of ∼2.7% (cathode side: ∼1.5%; anode side: ∼1.2%). Furthermore, the FPLEDs and FT-PLEDs exhibit robust mechanical durability, maintaining ∼89% and ∼86% of their initial luminance after 1000 bending cycles at a bending radius of 2 mm, respectively. This work opens up a new avenue for the development of high performance and stable flexible optoelectronic devices.

Biosynthesis of Silver Nanoparticles at Various pH values and their Applications in Capturing Irradiation Solar Energy.

Metallic nanoparticles (NPs), in general, are able, due to the high surface area per unit volume, to absorb the maximum incoming light flux through the vicinity of plasmonic structures and then provide local heating. Thus, silver (Ag) NPs has been used to generate heat and increase the temperature of water from solar radiation energy. The optimal plasmonic heating generation can be obtained as soon as the wavelength of the light source is close to the plasmonic resonance wavelength of Ag NPs. Ag NPs have been fabricated through a straightforward, cheap, as well as environmentally friendly approach. In this study, Salix babylonica L., weeping willow leaf extract has been utilized as a reducing, capping, and stabilizing agent, without using any other toxic materials. The importance of this study lies in the generation of hot electrons, which can be obtained by collecting the solar spectrum near the infrared and infrared regions, which cannot be obtained by the conventional photocatalytic devices. Numerous characterization techniques such as; UV-Vis, FT-IR spectroscopy, X-ray diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) analysis were used to study the optical, chemical, structural, morphological, properties of the Ag NPs. The impact of pH on the properties of Ag NPs and their performance to generate heat during solar irradiation have been investigated intensively. This study showed that the synthesized Ag NPs with pH value 12 is the optimum condition and can increase the temperature of water dramatically. An evaluation of the current patents displays that the field of green synthesis Ag NPs utilizing plant extracts is a vital field and produces rather stable, safe and effective Ag NPs. The novelty of this patent is that Ag NPs can be synthesized from a one-pot reaction without using any exterior stabilizing and reducing agent, which is not conceivable by means of the existing processes. This study, also, is rare and distinctive, and it demonstrates that even a slight quantity of the Ag NPs is significantly raising the temperature of water effectively.

Constructing light-insensitive Ag(I) sites by in situ integration of nanoheaters for efficient adsorptive desulfurization

The π-complexation between Ag(I) and thiophene sulfides is considered as one of the key factors to selectively remove thiophenic compounds, but its application is very limited due to the instability of Ag(I) under light as well as the energy-intensive regeneration. In this study, stable and photothermal Ag(I)/Ag(0) composite sites are constructed in metal-organic frameworks (MOFs) and act as target-specific adsorption sites for the uptake of thiophenic compounds. Partial Ag(0) nanoparticles that were in situ introduced in MOF pores are oxidized to Ag(I). As a result, Ag(I) becomes light-insensitive because the light-induced electron of Ag(I) can be transferred to the integrated Ag(0) nanoparticles, protecting Ag(I) from reduction. Furthermore, Ag(0) nanoparticles are photothermal due to the localized surface plasmon resonance, thus can precisely heat Ag(I) for desorption by converting visible light to energy. This work provides a new avenue to stabilize Ag(I) and efficiently regenerate adsorbents.

Positively Charged Silver and Gold Nanoparticles with Controllable Size Distribution for SERS Detection of Negatively Charged Molecules.

Surface-enhanced Raman spectroscopy (SERS) has been demonstrated as an ultrasensitive tool for various molecules. However, for the negatively charged molecules, the widely used SERS substrate [negatively charged Ag and Au nanoparticles (Ag or Au NPs (-)] showed either low sensitivity or poor stability. The best solution is to synthesize positively charged silver or gold nanoparticles [Ag or Au NPs (+)] with high stability and excellent SERS performance, which are currently unavailable. To this end, we revitalized the strategy of "charge reversal and seed growth". By selection of ascorbic acid as the reductant and surfactant, the surface charge of Ag or Au NP (-) seeds is adjusted to a balanced state, where the surface charge is negative enough to satisfy the stabilization of the NPs (-) but does not hinder the subsequent charge reversal. By optimization of the chain length and electric charge of polyamine molecules, the highly stable and size-controllable uniform Ag NPs (+) and Au NPs (+) were seed-growth synthesized with high reproducibility. More importantly, the SERS performance of both Ag NPs (+) and Au NPs (+) achieved the trace detection of negatively charged molecules at the level of 1 μg/L, demonstrating an improved SERS sensitivity of up to 3 orders of magnitude compared to the previously reported sensitivity. Promisingly, the introduction of polyamine-capped Ag NPs (+) and Au NPs (+) as SERS substrates with high stability (1 year shelf life) will significantly broaden the application of SERS.

Critical evaluation of silver nanoparticles synthesized at room temperature/microwave irradiation: A green approach

Biological routes of nanoparticle synthesis, especially the use of plant-based extracts, have shown great potential for the production of silver nanoparticles (Ag NPs). Ag NPs synthesized in this way is a simple one-step method that is economical and environmentally friendly. With the increasing need to develop new and effective antibacterial agents, a novel and stable Ag NPs is synthesized using aqueous seed extract of Strychnos potatorum (SP). Ag NPs obtained at room temperature (S1) and under optimal microwave irradiation (S2) were compared in the present work. The as-synthesized Ag NPs are characterized by Ultraviolet-Visible (UV-Vis) spectroscopy, X-Ray Diffraction (XRD), Fourier Transform Infrared (FT-IR) spectroscopy, Field Emission Scanning Electron Microscopy (FESEM) and Transmission Electron Microscopy (TEM). UV-Vis spectra showed Surface Plasmon Resonance (SPR) peaks at 430nm (S1) and 438nm (S2) associated with the formation of Ag NPs. XRD patterns indicate the crystallinity of Ag NPs, with an average crystallite size of approximately 23nm (S1) and 15nm (S2). FT-IR study revealed potential biomolecules to form Ag NPs. FESEM and TEM analysis revealed the spherical shape of Ag NPs. An average particle size of approximately 31nm (S1) and 19nm (S2) was revealed from TEM analysis. To the best of our understanding, this study is novel as Ag NPs synthesized from SP using a microwave oven are described in detail for the first time. The study also demonstrated the potential of Ag NPs for antibacterial effect against Gram-positive bacteria (Streptococcus pneumoniae, Staphylococcus aureus) and Gram-negative bacteria (Klebsiella pneumoniae, Vibrio vulnificus). Our findings show that at a specific concentration, small NPs are more efficient in inhibiting bacterial activity. This research indicates that Ag NPs synthesized from SP exhibit strong antibacterial activity for the treatment of bacterial infection.

Study on Ag-Ti Thin Film Structure with Compositional Gradient Fabricated by Sputtering Process

In this study, a composition-gradient thin film was applied for the formation of intermediate layer of Ti seed layer for an stable electrode stack Ag metal layer. Various composition of Ag-Ti hetero metal layer were simultaneously deposited by using the sputtering process with Ti and Ag target, respectively. An intermediate layer was deposited at a gradient composition ratio such as 5:5 and 7:3. In addition, the optimal deposition conditions were evaluated by confirming the plasma codition such as density of plasma ion, plasma potential with the Langmuir Probe (Hiden ESPion). Flow rate, power, and composition ratio were optimized as variables for thin film structures of compositional gradient thin films. In addition, thin film samples were heat treated at 200 ℃, 300 ℃, and 400 ℃ to relieve the residual stress between the interface of laminated thin films. Under these conditions, a composition-gradient thin film was evaluated by XRD (X-Ray Diffraction, SmartLab Rigaku 9kW), SEM (Scanning Electron Microscope, Nova NanoSEM 450), and EDS (energy dispersive X-ray spectroscopy). As a result of the measurement, it was confirmed that interfacial diffusion occurred due to the composition gradient thin film. When the composition gradient intermediate layer was applied to thin film stack, the residual stress increased more than that of single thin film stack. However, after stress relief annealing, residual stress was dramatically decreased compared to single stack.

Effects of Oxygen Adsorption on the Optical Properties of Ag Nanoparticles.

Plasmonic metal nanoparticles are efficient light harvesters with a myriad of sensing- and energy-related applications. For such applications, the optical properties of nanoparticles of metals such as Cu, Ag, and Au can be tuned by controlling the composition, particle size, and shape, but less is known about the effects of oxidation on the plasmon resonances. In this work, we elucidate the effects of O adsorption on the optical properties of Ag particles by evaluating the thermodynamic properties of O-decorated Ag particles with calculations based on the density functional theory and subsequently computing the photoabsorption spectra with a computationally efficient time-dependent density functional theory approach. We identify stable Ag nanoparticle structures with oxidized edges and a quenching of the plasmonic character of the metal particles upon oxidation and trace back this effect to the sp orbitals (or bands) of Ag particles being involved both in the plasmonic excitation and in the hybridization to form bonds with the adsorbed O atoms. Our work has important implications for the understanding and application of plasmonic metal nanoparticles and plasmon-mediated processes under oxidizing environments.

Tailored hydrogel entrapped catalyst with highly active, controlled catalytic activity for the removal of 4-nitrophenol (4-NP)

In catalytic reactions, achieving large specific surface area immobilisation of the catalyst is an important factor affecting the catalytic effect, however, the primary challenges in utilizing hydrogels as catalyst carriers are to enhance the mechanical properties of the hydrogel to improve the activity and controllability of the catalyst. In this study, a new structure of P(AM-co-AA)/SMA/NH2-SiO2 hydrogels was synthesized via free radical polymerization, and the effects of the content of AA and NH2-SiO2 on the mechanical properties of the hydrogels were investigated. Without the use of additional cross-linking agents, both a chemical cross-linking network and a hydrophobic linkage network were established, which effectively reconstructed the structure of the hydrogels and dissipated energy. As a result, P(AM-co-AA-1.5 %)/SMA/NH2-SiO2-0.5 % hydrogel exhibited high mechanical properties, with tensile strength, elongation, and toughness reaching 1456 KPa, 4605 %, and 23.59 MJ/m3, respectively. This hydrogel can be utilized as a template for in situ and stable Ag NPs. Additionally, P(AM-co-AA)/SMA/NH2-SiO2@Ag composite hydrogels were prepared using cation exchange and in situ reduction methods for the catalytic reduction of 4-nitrophenol (4-NP). The composite hydrogel exhibited fast catalysis, high efficiency, stable cycling, recyclability and adjustable catalytic activity at 35 °C with Kapp = 0.811 min−1. Furthermore, using this composite hydrogel alleviated the need for separating metal nanoparticle catalysts from the reaction system, thereby enabling the development of robust hydrogel materials with controlled catalytic activity for the wastewater treatment industry.

PH and NaCl Optimisation to Improve the Stability of Gold and Silver Nanoparticles' Anti-Zearalenone Antibody Conjugates for Immunochromatographic Assay.

The aim of this research is to define optimal conditions to improve the stability of gold and silver nanoparticles' anti-zearalenone antibody conjugates for their utilisation in lateral flow immunochromatographic assay (LFIA). The Turkevich-Frens method was used to synthesise gold nanoparticles (AuNPs), which were between 10 and 110 nm in diameter. Silver nanoparticles (AgNPs) with a size distribution of 2.5 to 100 nm were synthesised using sodium borohydride as a reducing agent. The onset of AuNP and AgNP aggregation occurred at 150 mM and 80 mM NaCl concentrations, respectively. Stable Au and Ag nanoparticle-antibody conjugates were achieved at 1.2 mM of K2CO3 concentration, which corresponds to the pH value of ≈7. Lastly, the highest degree of conjugation between Au and Ag nanoparticles and anti-zearalenone antibodies was at 4 and 6 µg/mL of antibody concentrations. The optimisation of the conjugation conditions can contribute to better stability of nanoparticles and their antibody conjugate and can improve the reproducibility of results of bioreporter molecules in biosensing lateral flow devices.

Tuning the Framework of Thioether-Functionalized Polyazamacrocycles: Searching for a Chelator for Theranostic Silver Radioisotopes.

Silver-111 is an attractive unconventional candidate for targeted cancer therapy as well as for single photon emission computed tomography and can be complemented by silver-103 for positron emission tomography noninvasive diagnostic procedures. However, the shortage of chelating agents capable of forming stable complexes tethered to tumor-seeking vectors has hindered their in vivo application so far. In this study, a comparative investigation of a series of sulfur-containing structural homologues, namely, 1,4,7-tris[2-(methylsulfanyl)ethyl)]-1,4,7-triazacyclononane (NO3S), 1,5,9-tris[2-(methylsulfanyl)ethyl]-1,5,9-triazacyclododecane (TACD3S), 1,4,7,10-tetrakis[2-(methylsulfanyl)ethyl]-1,4,7,10-tetraazacyclotridecane (TRI4S), and 1,4,8,11-tetrakis[2-(methylsulfanyl)ethyl]-1,4,8,11-tetraazacyclotetradecane (TE4S) was conducted to appraise the influence of different polyazamacrocyclic backbones on Ag+ complexation. The performances of these macrocycles were also compared with those of the previously reported Ag+/[111Ag]Ag+-chelator 1,4,7,10-tetrakis[2-(methylsulfanyl)ethyl]-1,4,7,10-tetraazacyclododecane (DO4S). Nuclear magnetic resonance data supported by density functional theory calculations and X-ray crystallographic results gave insights into the coordination environment of these complexes, suggesting that all of the donor atoms are generally involved in the metal coordination. However, the modifications of the macrocycle topology alter the dynamic binding of the pendant arms or the conformation of the ring around the metal center. Combined pH/pAg-potentiometric and spectroscopic experiments revealed that the 12-member N4 backbone of DO4S forms the most stable Ag+ complex while both the enlargement and the shrinkage of the macrocyclic frame dwindle the stability of the complexes. Radiolabeling experiments, conducted with reactor-produced [111Ag]Ag+, evidenced that the thermodynamic stability trend is reflected in the ligand's ability to incorporate the radioactive ion at high molar activity, even in the presence of a competing cation (Pd2+), as well as in the integrity of the corresponding complexes in human serum. As a consequence, DO4S proved to be the most favorable candidate for future in vivo applications.

Three-dimensional Ag NPs-cellulose fiber/polyacrylamide hydrogels as a novel SERS platform for the efficient determination of thiram in fruits and juice

The preparation of sensitive, homogeneous and reproducible surface-enhanced Raman spectroscopy (SERS) platforms is imperative for rapid in situ measurements, but remains a formidable task. We constructed a high-performance, stable and homogeneous Ag NPs-TOCNF/PAAM hydrogel SERS platform using a cellulose-based hydrogel with a porous network structure composed of TEMPO-oxidized cellulose nanofibers (TOCNF) and polyacrylamide (PAAM) to attach, coordinate and protect silver nanoparticles (Ag NPs). The -COO- group in the TOCNF is coordinated to the silver atoms, resulting in a more uniform distribution of Ag NPs. The encapsulation of hydrogel effectively protects the Ag NPs from oxidation and improves the stability of the substrate. The volume shrinkage treatment of the hydrogel can adjust the structural gap of the Ag NPs, thus exhibiting high sensitivity. The SERS performance of the hydrogel was evaluated using the molecule R6G. Its enhancement factor is up to 7.56 × 10−7. In addition, SERS activity remained above 85% even after 50 days. Finally, the Ag NPs-TOCNF/PAAM hydrogel platform was used to detect thiram in fruit peels with a detection limit of 10−6 M. In conclusion, the platform shows great promise for the determination of hazardous chemicals in the field environment.

Silver nanoparticles-based thioureidophosphonate composites: Synthesis approach and their exploitation in 4-nitrophenol reduction

Two novel mono- and bis-thioureidophosphonate cores (referred by MTP & BTP, respectively) were facilely synthesized in ionic liquid conditions and incorporated with silver nanoparticles (Ag NPs) via in-situ reduction method giving two heterogeneous nanocatalysts, denoted as Ag NP/MTP and Ag NP/BTP, respectively. X-ray diffraction (XRD), ultraviolet-visible (UV–Vis), and high-resolution transmission electron microscopy (HR-TEM) tools were conducted for the as-fabricated Ag NP/TP nanocomposites revealing the good dispersion of Ag NPs in spherical black dots with average size ranges of (∼9.5–12.7 nm) and (∼17.0–22.5 nm) for Ag NP/MTP and Ag NP/BTP, respectively. The Fourier transform infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS) techniques clarified that, MTP possessing (POPh, PO, C=S, HCO, and >NH) functionalities were participated in the reduction of Ag+ ions to Ag0 NPs. The catalytic properties of both Ag NP/TP nanocomposites were verified through the chemical conversion of 4-nitrophenol (4-NP) to less hazardous 4-aminophenol (4-AP) comparable to the slight catalytic reduction of Ag NPs-free TP derivatives. To assess the catalytic performance, some kinetic parameters such as rate constant (Kapp), normalized rate constant (Knor), and turnover frequency (TOF) were estimated at the highest concentration of 4-NP. Accordingly, Ag NP/MTP exhibited more remarkable catalytic activity and durability toward 4-NP reduction than that of Ag NP/BTP. The simple stereochemistry and accessibility of active sites for MTP tuned the surface function with Ag+ ions, affording more stable and regular Ag NPs over the same nanoparticle with BTP. Regarding Ag NP/MTP, catalytic improvement rates to 69%, 64%, and 69% were respectively recorded for Kapp, Knor, and TOF over Ag NP/BTP. Moreover, both nanocatalysts demonstrated good surficial stability through 10 consecutive cycles. Herein, this study has provided a new sustainable route for developing new TP-wrapped metal nanocomposites as robust and selective platforms in catalytic and environmental applications.

Flexible free-standing antibacterial nanoporous Ag ribbon

The biomedical field has the potential to significantly benefit from the use of flexible free-standing Ag nanostructures due to their outstanding mechanical and antibacterial properties. However, the intricate process of synthesizing these nanostructures, as well as the potential toxicity of nanostructured Ag, pose significant challenges. This study used a facile etching method to synthesize the free-standing nanoporous Ag (NP-Ag) ribbons with a homogeneous and bicontinuous three-dimensional ligament structure. The free-standing NP-Ag ribbons demonstrated stable mechanical performance and excellent flexibility when subjected to various deformation states on artificial fingers. Additionally, the NP-Ag ribbons exhibited remarkable antibacterial capacity with rates of 99.81 ± 0.14% against Escherichia coli, 96.11 ± 1.49% against Staphylococcus aureus, and 95.37 ± 1.24% against methicillin-resistant Staphylococcus aureus. The antibacterial mechanism of NP-Ag is attributed to the rapid release of Ag ions (Ag+) in 24 h, causing damage to the bacterial membrane. Moreover, the in vivo results demonstrate that the NP-Ag ribbons provide rapid antibacterial efficacy and are biosafe due to the long-term stable Ag+ release of NP-Ag. The development of these free-standing flexible NP-Ag ribbons offers a new avenue for wearable antibacterial applications.

CHFR promotes metastasis of human gastric carcinoma by activating AKT and ERK via NRF2- ROS axis

Tumor suppressor gene CHFR (The Checkpoint with Forkhead-associated and Ring finger domains) is a mitotic checkpoint and frequently hypermethylated in gastric cancer. Our previous study found CHFR played a certain extent pro-tumor function in gastric cancer. However, little is known about the underlying mechanism. In this study, we tried to further elucidate the role and mechanism for CHFR in gastric cancer (GC) by constructing CHFR stably expressed cell lines. As expected, the ectopic expression of CHFR slowed the cell proliferation in both two SGC-7901 and AGS cells, while significantly promoted the potential of cell migration and invasion. For the first time, our data indicated that stable expression of CHFR in SGC-7901 and AGS restrained cellular reactive oxygen species (ROS) generation and promoted the activation of AKT and ERK, two regulators of redox hemostasis. Furthermore, H2O2 treatment effectively elevated ROS level and reversed CHFR-induced cell invasion in stable SGC-7901 and AGS cells with the decreased phosphorylation of AKT and ERK. We also confirmed that CHFR exerted its function by promoting NRF2 expression. The most important is, the ectopic expression of CHFR significantly inhibited SGC-7901 cell-derived xenografts and obviously promoted lung metastasis of GC cell with NRF2, p-AKT and p-ERK increased. Taken together, our findings suggested that CHFR might take part in gastric cancer progression especially cancer metastasis by activating AKT and ERK via NRF2- ROS axis.

Synthesis of highly stable silver nanoparticles as computed tomography contrast agents

In this work, highly stable Ag nanoparticles solution was synthesized using TBAB to reduce Ag+ in the presence of OLA in organic solvents at room temperature, and poly(acrylic acid) (PAA) as a phase transfer ligand in organic solvents. The effects of different solvents on the morphology and properties of the Ag nanomaterials were investigated in detail. The products were characterized by using transmission electron microscopy (TEM), X-ray diffraction (XRD), and absorption spectroscopy. Structural analysis demonstrated that the Ag nanomaterials showed good crystallinity. We have successfully synthesized Ag nanoparticles (Ag NPs) with small particle size (6.1 - 7.3 nm), high uniformity in organic solvents at room temperature. The Ag NPs obtained after phase transformation with PAA are well dispersed, endurance and stability in aqueous solvents. The obtained in-vitro CT imaging results have good X-ray absorption value. These findings suggest the potential application of PAA-coated Ag nanoparticles in the biomedical field, especially in imaging diagnostics using CT computed tomography.

Rapid microwave heating and fast quenching for the highly efficient production of long-term stable supported Ag nanoclusters

Given the exciting potential of metallic clusters in a variety of fields, the development of novel preparation methods to accurately controlling the cluster size has become a research priority. Specifically, for catalytic applications, the synthesis and deployment of metallic nanoclusters on a proper substrate is perhaps the main bottleneck. Here, we have adopted an alternative reactor that uses simultaneous ice cooling and microwave heating (unlike water ice is a low microwave absorber) for the synthesis of Ag nanoclusters directly over a support with ordered mesopores (SBA-15). The reactor design exploits the selectivity of microwave heating, assuring a rapid localized nucleation followed by a nearly instantaneous quenching that largely avoids the aggregation of nascent clusters as well as Ostwald ripening mechanisms. We have compared this new synthesis approach with some previously reported methods for the production of supported silver nanoclusters: conventional batch reactor and also a continuous flow microreactor. The resulting Ag clusters were initially analyzed in terms of size distribution, textural properties and catalytic activity in the reduction of 4-nitrophenol. Finally, encouraged by the good results obtained, these nanoclusters were also employed in the production of different cyclic organic compounds, building blocks for pharmaceutical and photochemical applications. The nanoclusters displayed a high catalytic activity, lowering the metal loading required to achieve high yield and selectivity. Furthermore, the stabilization of the clusters over the mesoporous substrate allowed their reuse in several reaction cycles. In fact, the method produced exceptionally stable Ag clusters, whose catalytic properties were preserved even after one year of storage.

Zn(II) to Ag(I) Swap in Rad50 Zinc Hook Domain Leads to Interprotein Complex Disruption through the Formation of Highly Stable Agx(Cys)y Cores.

The widespread application of silver nanoparticles in medicinal and daily life products increases the exposure to Ag(I) of thiol-rich biological environments, which help control the cellular metallome. A displacement of native metal cofactors from their cognate protein sites is a known phenomenon for carcinogenic and otherwise toxic metal ions. Here, we examined the interaction of Ag(I) with the peptide model of the interprotein zinc hook (Hk) domain of Rad50 protein from Pyrococcus furiosus, a key player in DNA double-strand break (DSB) repair. The binding of Ag(I) to 14 and 45 amino acid long peptide models of apo- and Zn(Hk)2 was experimentally investigated by UV-vis spectroscopy, circular dichroism, isothermal titration calorimetry, and mass spectrometry. The Ag(I) binding to the Hk domain was found to disrupt its structure via the replacement of the structural Zn(II) ion by multinuclear Agx(Cys)y complexes. The ITC analysis indicated that the formed Ag(I)-Hk species are at least 5 orders of magnitude stronger than the otherwise extremely stable native Zn(Hk)2 domain. These results show that Ag(I) ions may easily disrupt the interprotein zinc binding sites as an element of silver toxicity at the cellular level.

Size-controllable colloidal Ag nano-aggregates with long-time SERS detection window for on-line high-throughput detection

Making metal nanoparticle aggregates is a common way to improve surface-enhanced Raman scattering (SERS) enhancement via the formation of hot spots between nanoparticles. Here, we propose a “freeze-thaw-ultrasonication” method to obtain stable colloidal Ag nano-aggregates (AgNAs) with controllable sizes, which can remain stable for a few days. Compared with other method using aggregation reagents (e.g., organic molecules and salt), this method can maintain metal surface charges and adsorption affinity, which ensures the excellent SERS stability and sensitivity. The SERS detection window during the experiment can reach more than 25 min, which makes it a prerequisite for accurate SERS detection during a long-time range. Combining the obtained stable AgNAs with microfluidic devices, we established a sequential SERS on-line continuous detection method for the high-throughput detection of multiplex samples. The UV-Fenton degradation process of methylene blue (MB) is continuously on-line monitored through this platform, which is more sensitive than the UV–Vis Spectrum. Moreover, we have realized the sensitive and accurate detection of 5-nitro-8-hydroxyquinoline (5-NQ) with antibacterial and anticancer activities based on chloride-functionalized silver, which paved a way for SERS high-throughput analysis in bioanalysis and other fields.