Silver Deposition Research Articles

Detection of methyltransferase activity and inhibitor screening based on rGO-mediated silver enhancement signal amplification strategy

DNA methylation refers to the chemical modification process of obtaining a methyl group by the covalent bonding of a specific base in DNA sequence with S-adenosyl methionine (SAM) as a methyl donor under the catalysis of methyltransferase (MTase), which is related to the occurrence of multiple diseases. Therefore, the detection of MTase activity is of great significance for disease diagnosis and drug screening. Because reduced graphene oxide (rGO) has a unique planar structure and remarkable catalytic performance, it is not clear whether rGO can rapidly catalyze silver deposition as an effective way of signal amplification. However, in this study, we were pleasantly surprised to find that using H2O2 as a reducing agent, rGO can rapidly catalyze silver deposition, and its catalytic efficiency of silver deposition is significantly better than that of GO. Therefore, based on further verifying the mechanism of catalytic properties of rGO, we constructed a novel electrochemical biosensor (rGO/silver biosensor) for the detection of dam MTase activity, which has high selectivity and sensitivity to MTase in the range of 0.1 U/mL to 10.0 U/mL, and the detection limit is as low as 0.07 U/mL. Besides, this study also used Gentamicin and 5-Fluorouracil as inhibitor models, confirming that the biosensor has a good application prospect in the high-throughput screening of dam MTase inhibitors.

Gene expression detection in developing mouse tissue using in situ hybridization and µCT imaging

High resolution and noninvasiveness have made soft-tissue X-ray microtomography (µCT) a widely applicable three-dimensional (3D) imaging method in studies of morphology and development. However, scarcity of molecular probes to visualize gene activity with µCT has remained a challenge. Here, we apply horseradish peroxidase-assisted reduction of silver and catalytic gold enhancement of the silver deposit to insitu hybridization in order to detect gene expression in developing tissues with µCT (here called GECT, gene expression CT). We show that GECT detects expression patterns of collagen type II alpha 1and sonic hedgehogin developing mouse tissues comparably with an alkaline phosphatase-based detection method. After detection, expression patterns are visualized with laboratory µCT, demonstrating that GECT is compatible with varying levels of gene expression and varying sizes of expression regions. Additionally, we show that the method is compatible with prior phosphotungstic acid staining, a conventional contrast staining approach in µCT imaging of soft tissues. Overall, GECT is a method that can be integrated with existing laboratory routines to obtain spatially accurate 3D detection of gene expression.

Antibacterial coatings for electroceutical devices based on PEDOT decorated with gold and silver particles

The continuous progression in the field of electrotherapies implies the development of multifunctional materials exhibiting excellent electrochemical performance and biocompatibility, promoting cell adhesion, and possessing antibacterial properties. Since the conditions favouring the adhesion of mammalian cells are similar to conditions favouring the adhesion of bacterial cells, it is necessary to engineer the surface to exhibit selective toxicity, i.e., to kill or inhibit the growth of bacteria without damaging mammalian tissues. The aim of this paper is to introduce a surface modification approach based on a subsequent deposition of silver and gold particles on the surface of a conducting polymer, poly(3,4-ethylenedioxythiophene) (PEDOT). The resulting PEDOT-Au/Ag surface is found to possess optimal wettability, roughness, and surface features making it an excellent platform for cell adhesion. By depositing Ag particles on PEDOT surface decorated with Au particles, it is possible to reduce toxic effects of Ag particles, while maintaining their antibacterial activity. Besides, electroactive and capacitive properties of PEDOT-Au/Ag account for its applicability in various electroceutical therapies.

From Self-Affine Ag to Mounded Ag@Ag2O Core–Shell Nanoplasmonic Surfaces By Sonochemistry

A controllable ultrasound-assisted synthetic approach has been developed that allows deposition of elemental silver and core–shell Ag@Ag2O nanoparticles, close-packed in thin-film form on glass substrates, suitable for a wide range of applications. Ultrasonic irradiation modifies the reaction mechanism, allowing precise control over the composition of the nanoparticles and their packing in the form of thin films. The crystal radii of the synthesized materials fall within the nano range (∼9 nm in the case of bare Ag, 5 nm for the Ag core, and 9 nm for the Ag2O shell in the case of Ag@Ag2O films). Nanostructured Ag films exhibit self-affine, while the films built up by Ag@Ag2O core–shell nanocrystals exhibit a mounded morphology. The interface width and the mean roughness are significantly smaller for sonochemically synthesized surfaces. The observed trends in the localized surface plasmon resonance (LSPR) absorptions in the case of bare Ag plasmonic surfaces are dominated by the particle size, inhomogeneous broadening induced by the size dispersion of the nanoparticles, interparticle plasmon coupling, and nanocrystal–substrate interaction. The notable red shift of the LSPR absorption maximum in the case of films built up by Ag@Ag2O core–shell nanoparticles is governed by the influence of the dielectric shell.

Band edges positions prediction of the of Ag nanocluster-decorated titania surfaces and their relationship to NO and NO2 interaction from first-principles calculations

Metal nanoclusters deposited on oxides have been widely used in photocatalysis playing an important role in the design of model catalysts with applications in heterogeneous catalysis. In particular, we are interested in the potential activity of these cluster-supported systems for the removal of nitrogen oxides either by possible catalytic reduction and/or by their adsorption. In this work, using first-principles methods, we evaluate the main characteristics of Agn (n = 1–4) nanoclusters isolated and deposited on anatase TiO2(101) and rutile TiO2(110) surfaces. Our results indicate that they are preferably adsorbed on rutile surface. The different formation energy at each surface can be explained using a Bader charge analysis. Particularly for Ag4 the lowest formation energy is obtained for tetrahedral geometry while the isolated Ag4 geometry is planar. Small silver deposits placed superficially on titania surfaces modify its electronic structures and improve the conduction band edges positions for possible NO reduction. Band edges positions with respect to the vacuum potential have been studied. The comparison of the conduction band minimum with the reduction potentials of NO/N2O and N2O/N2 shows that they are higher, being Ag3 on rutile and Ag1, Ag2 and Ag4P on anatase better for NO reduction. To complete the analysis, the calculation of work function, energy gap, ionization energy and electron affinity are relevant since they allow the location of semiconductor band edges at point of zero charge. Finally, the adsorption of nitrogen oxides is studied where the NO2 adsorption is favored over NO.

The Spontaneous Escape Behavior of Silver from Graphite-like Carbon Coatings and Its Effect on Corrosion Resistance.

Silver-doped graphite-like carbon (Ag-GLC) coatings were prepared on the surface of aluminum alloy and single-crystal silicon by magnetron sputtering under different deposition parameters. The effects of silver target current and deposition temperature, as well as of the addition of CH4 gas flow, on the spontaneous escape behavior of silver from the GLC coatings were investigated. Furthermore, the corrosion resistance of the Ag-GLC coatings were evaluated. The results showed that the spontaneous escape phenomenon of silver could take place at the GLC coating, regardless of preparation condition. These three preparation factors all had an influence on the size, number and distribution of the escaped silver particles. However, in contrast with the silver target current and the addition of CH4 gas flow, only the change in deposition temperature had a significant positive effect on the corrosion resistance of the Ag-GLC coatings. The Ag-GLC coating showed the best corrosion resistance when the deposition temperature was 500 °C, which was due to the fact that increasing the deposition temperature effectively reduced the number of silver particles escaping from the Ag-GLC coating.

Silver Alloying in Highly Efficient CuGaSe2Solar Cells with Different Buffer Layers

This study evaluates the effect of silver alloying, stoichiometry, and deposition temperature of wide‐gap (Ag,Cu)GaSe2(ACGS) absorber films for solar cell applications. Devices using a standard CdS buffer exhibit a strong anticorrelation between the open‐circuit voltage (VOC) and short‐circuit current density (JSC), withVOCdecreasing andJSCincreasing toward stoichiometric absorber composition. Increasing the ACGS deposition temperature leads to larger grains and improvedJSC, whileVOCis not affected. By adding more silver to the absorber (maximum tested [Ag]/([Ag]+[Cu]) [AAC] = 0.4), the widening of the space charge region (SCR) significantly enhances carrier collection. Experimental quantum efficiency spectra can be accurately simulated when assuming a very low diffusion length and perfect collection in the SCR. The highest efficiency of 8.3% (without antireflection coating [ARC]) is reached for an absorber with AAC = 0.4 grown at 600 °C. Replacing CdS by a (Zn,Sn)O buffer with lower electron affinity strongly mitigates interface recombination. Moreover, theVOC–JSCanticorrelation is not evident anymore and the highest efficiency of 11.2% (11.6% w/ARC,VOC = 985 mV,JSC = 18.6 mA cm−2, fill factor = 61.0%) is reached for a close‐stoichiometric ACGS solar cell with AAC = 0.4 processed at 650 °C.

A non-toxic synergistic antibacterial platform based on green silver nanoparticles deposited on hydroxyapatite/graphene oxide composites

A composite containing hydroxyapatite, graphene oxide and silver nanoparticles was obtained by performing a microwave-assisted hydrothermal method, a modified Hummer’s synthesis, and advantageously, by using dietary quercetin for silver nanoparticles formation and deposition. The pure constituents and composites were characterized by complementary physicochemical techniques, and evaluated in human keratinocytes and bacteria. In eukaryotic cells, it was found a dose-dependent toxic response that mainly depends on the presence of graphene oxide, and a superior cytocompatibility was observed for the samples containing hydroxyapatite. The ternary system showed a half maximal inhibitory concentration of about 116.8 μg/mL, ranged in a safety threshold. In comparison with silver nanoparticles alone, this ternary composite increased in 43% and 38% the inhibition zone for S. aureus and E. coli, respectively. Its minimum inhibitory concentration was found, respectively, close to 6.5 and 52.1 μg/mL, resulting in a fractional inhibitory concentration index < 0.5. Thus, this synergistic system can potentially be applied as a bactericidal for tissue replacement and surface coating.

Plasmon mediated extra-ordinary optical transmission through an apertureless plasmonic metagrating

Extra-ordinary optical transmission (EOT) through subwavelength plasmonic nanoapertures is possible due to the funneling of light via surface plasmons (SPs) at the resonant wavelengths through the apertures. In this Letter, we experimentally demonstrate EOT through a plasmonic metagrating which does not have any open apertures. The plasmonic metagrating was fabricated by deposition of silver (Ag) on a one-dimensionally patterned flexible and transparent polydimethylsiloxane grating obtained via pattern imprinting and subsequent peeling off a commercially available blue ray disk. For normal incidence of transverse magnetic-polarized light on the top surface of plasmonic metagrating, transmission of light through it was obtained in the visible wavelength range of electromagnetic spectrum. Control experiments on variation of Ag film thickness were performed to attain optimal parameters for maximum transmission, followed by polarization and refractive index (RI) dependent performance of the plasmonic metagrating. Electric fields and Poynting vector profiles were simulated using a finite element method to explain the interaction of light with the plasmonic metagrating and the mechanism of plasmon mediated optical transmission. Such a large optical transmission is possible because the SP modes generated at metal–air interface penetrate through metagrating and couple with those supported by the metal–substrate interface. As a model application, RI sensing using the plasmonic metagrating was demonstrated. The present study shows that optical transmission is possible from apertureless structures and enriches literature with better understanding of EOT. Moreover, it opens avenues for development of flexible, cost-effective plasmonic metagratings for sensors, spectral filters, polarizers, etc.

Anodization Time Effect on Silver Particles Deposition on Anodic Oxide Coating over Al Produced by Plasma Electrolytic Oxidation

In this study, 6061 Al alloy was galvanostatically anodized under the Plasma Electrolytic Oxidation (PEO) condition. A factorial design of 22 was carried out using two variables (anodization time and presence of silver in the electrolyte) on two levels, i.e., 20 and 60 min of anodization and the absence/presence of silver ions in the electrolyte. The Al anodization was performed in sodium silicate electrolyte, applying a constant current density of 20 mA cm−2. The oxide characterization was performed by Scanning Electron Microscopy (SEM), surface roughness analysis (RMS), Energy Dispersive Spectroscopy (EDS), Rutherford Backscattered Spectroscopy (RBS), and Grazing Incidence X-ray Diffraction (GIXRD). The SEM micrographs revealed an irregular porous structure with cracks on the oxide surface composed of a thin crystalline layer of γ-Al2O3 over the Al substrate. From EDS and RBS analysis, it was possible to identify the elements Al, O, Si, Ag, and Na, demonstrating that a shorter anodization time (20 min) led to a significant amount of silver deposits on the outer layer of the oxide coating, mainly deposited in the surroundings of the pores. Conversely, the silver content on the PEO film anodized for 60 min was meager. These results demonstrated that the anodization time was the critical control variable for the amount of silver deposited over the oxide film. The shorter the anodizing time, the higher the silver content on the PEO coating.

A grey case.

We present an unusual case of a 67-year-old woman who gradually noted blue–grey pigmentation developing in a photodistributed pattern. She felt well in herself and there were no systemic features. She had a history of hypertension, hypercholesterolaemia and absence seizures for which she took ramipril, atorvastatin, levetiracetam as well as alternative therapies for recurrent urinary tract infections.

Delimitation of massive sulphide bodies – Mise‐à‐la‐masse method associated with induced polarization (IP) – A case history from Brazil

AbstractThis paper presents a successful application of the mise‐à‐la‐masse (MALM) or applied potential method in association with induced polarization (IP). MALM is known, since 1920, to be able to delimit electrically conductive massive mineralization. The method is used at the point where a drill hole intercepts a massive, mineralized body, to estimate its extent and shape. It is thus used as a complementary mineral exploration tool. IP is normally used in conjunction with resistivity. However, the acquisition of IP data together with the MALM method is rarely found in the literature. This survey shows that it is possible to successfully detect and delimit areas of disseminated sulphides using MALM with IP. In this paper, the MALM method is presented and discussed in detail. A short description of the IP method is also provided. Data are from the Camaquã Project (Caçapava do Sul, RS, Brazil) and the Santa Maria (lead, zinc and associated silver) deposit, 5 km south of Caçapava do Sul. In a well that intercepted a massive mineralization (borehole 8011) with electrical continuity, ∆V measurements delineated the extent, shape and orientation (NS) of a conductive sulphide body. Mineralization intercepted by other two wells (8011 and 8103) did not present enough electrical continuity to exhibit potential contours that could be associated to massive sulphides; it was, however, successfully detected by IP.

Insight into the action mechanism of ammonia in one-pot synthesis of hermetic Al@Ag core–shell particles via deposition model

In this study, Al@Ag particles with hermetic silver shell were successfully prepared by a facile one-pot electroless plating method and the effect of NH3·H2O in reaction process was investigated. The result shows that the concentration ratio of NH3·H2O to Ag+ from 18:1–55:1 triggers a continuous transition of the silver coating from raspberry-like granule to hermetic and then loose. This transition is mainly dependent on the suppression of Ag deposition as increasing NH3·H2O concentration. It was confirmed using silver deposition kinetic and electrochemistry tests. Based on these experimental results, a deposition model was proposed to quantify the specific behavior of NH3·H2O in inhibiting Ag deposition from the perspective of interfacial reaction between active center and [Ag(NH3)2]+. The deposition model was fitted well with experimental results and the effective chemical reaction rate (keff) at solid-liquid interface were calculated, which is the critical factor affecting nucleation and coating quality. As CNH3·H2O:CAg+= 48:1, keff is 0.0117 mol L−1 min−1, a compact core-shell Al@Ag particle is realized and the resistivity as low as 1.21 × 10−4 Ω·cm even with Ag content is 15.61 wt%. This work revealed the dual role of NH3·H2O in complexing Ag+ and regulating keff to control silver grain size and distribution.

A Colorimetric Aptasensor for Ochratoxin A Detection Based on Tetramethylrhodamine Charge Effect-Assisted Silver Enhancement.

A novel colorimetric aptasensor based on charge effect-assisted silver enhancement was developed to detect ochratoxin A (OTA). To achieve this objective, gold nanoparticles (AuNPs), which can catalyze silver reduction and deposition, were used as the carrier of the aptamers tagged with a positively charged tetramethylrhodamine (TAMRA). Due to the mutual attraction of positive and negative charges, the TAMRA attracted and retained the silver lactate around the AuNPs. Thus, the chance of AuNP-catalyzed silver reduction was increased. The charge effect-assisted silver enhancement was verified by tagging different base pair length aptamers with TAMRA. Under optimized conditions, the as-prepared OTA aptasensor had a working range of 1 × 102-1 × 106 pg mL-1. The detection limit was as low as 28.18 pg mL-1. Moreover, the proposed aptasensor has been successfully applied to determine OTA in actual samples with satisfactory results.

A facile and green strategy to achieve metallized woven carbon fiber through the triple roles of dopamine in in-situ thermal reduction of Ag

Metallized carbon fiber (CF) has received lots of attention due to its improved electrical conductivity and electromagnetic interference (EMI) shielding performance. Herein, we propose a facile and environmental strategy to achieve uniform and dense silver (Ag) deposition on polydopamine (PDA) modified woven CF by a simple in-situ thermal reduction approach. PDA plays three important roles for anchoring and formatting Ag layer by accommodating the CF surface with improved interfacial actions, capturing the silver ions (Ag+) and then reducing the Ag+ during the hot-pressing process. The CF as intrinsic conductive substrate simultaneously promoted the reduction capability of PDA through electrons transfer during the reduction process. As a result, the single-layered Ag coated CF fabric can be easily formed and exhibits excellent EMI shielding effectiveness (73.08 dB) and reliable shielding performance. This strategy saves tedious fabrication process and avoids the use of toxic and harmful substances, which is highly promising in fabricating large scale metallized fiber cloths.

Dual signal amplification detection of m6A in serum of hepatocellular carcinoma patient by hybridization chain reaction and biocatalytic silver deposition

N6-methyladenosine (m6A) modification has an impact on RNA metabolism, and it has been demonstrated that m6A regulatory mechanisms play an important role in tumorigenesis and may serve as a potential hepatocellular carcinoma (HCC) marker. We constructed a dual-signal amplification strategy electrochemical biosensor based on biocatalytic silver deposition and hybridization chain reaction (HCR). Enzymatic silver deposition was performed on the electrode and detected by linear sweep voltammetry (LSV), which was used for the quantitative detection of m6A. There was a nice linear relationship between the current response values and the logarithm of the m6A RNA concentration in the range of 0.5 pM-5 μM, with a detection limit as low as 25 fM. The concentration of m6A detected by the sensor constructed in this work is consistent with the results obtained using commercial colorimetric immunoassays. What's more, the analysis of m6A RNA in the serum of HCC patients using the developed sensor showed the high analytical efficiency of the designed strategy, which was superior to three other markers (AFP, CEA, CA199). The constructed electrochemical biosensor has good sensitivity, specificity and reproducibility for the detection of m6A RNA, and the sensing platform has promising clinical applications in the diagnosis and prognosis of HCC.

Developing highly reliable SERS substrates based on Ag grown on alumina nanomeshes anodized under 1 V for efficiently sensing Raman-active molecules

We have developed silver-nanostructures grown on anodic alumina nanomesh (AAN) films to create new-type substrates for surface-enhanced Raman scattering (SERS). AAN with uniform thin sidewall of ∼ 5 nm was fabricated by anodizing Al sheets at 1 V in 6% H3PO4 solution. Subsequent AC electrochemical deposition of silver created an array of nanoparticles or nano-islands depending on growth time. The particle-island transition is non-monotonic evolution, since metal growth and dissolution compete in AC electrodeposition process. Systematic SERS study on various Ag-AAN films with trial probes of adenine solutions reveals collective contribution of electron-plasma oscillation and surface area of silver nanostructures in Raman enhancements. SERS signals are primarily contributed by surface area under excitation wavelength of 532 nm (away from plasmonic resonance). The average correlation coefficient between the SERS intensity and surface area was 0.85, indicating robust correlation. This value was reduced to 0.61 under excitation wavelength of 633 nm (closer to plasmonic resonance). Furthermore, increased Ag-deposition reduced the relative standard deviation of SERS intensities and thus improved both the uniformity and quality consistency of SERS substrates. Therefore, fabrication of SERS substrate with larger Ag surface area under similar SERS enhancement factors is suggested for high throughput in commercial sectors.

Preparation and optimization of conductive PDMS composite foams with absorption-dominated electromagnetic interference shielding performance via silvered aramid microfibers

Electromagnetic interference (EMI) shielding materials with absorption-dominated EMI shielding mechanism can effectively annihilate electromagnetic waves (EMW) and avoid their repeated EMW pollution. However, it is difficult to achieve this goal for conductive polymer-based composites (CPC), because the interface impedance mismatch between air and CPC leads to massive reflection of EMW at the interface. Pores are beneficial to EMW penetrating into the interior of CPC and causing their multiple reflection, scattering and absorption in pores, thus endowing CPC with absorption-dominated EMI shielding characteristic. Herein, highly conductive silvered aramid microfibers (CAMF) were first synthesized via dopamine-assisted electroless deposition of silver coating on aramid microfibers (AMF), and then the conductive porous PDMS composite foams (PDMSF) with absorption-dominated EMI shielding characteristic were prepared and optimized via salt template method. As a result, PDMSF with 1.7 vol% silver content, the conductivity of PDMSF can reach 10-1 S/m, the EMI shielding efficiency (EMI SE) can reach 36.7 dB in X-band, and the average absorption ratio in EMI SE is 87%, while the density of PDMSF is only 0.28 g/cm3. The combination of lightweight, high EMI SE and absorption-dominated EMI shielding characteristic makes the porous PDMSF the latent EMI shielding materials in special constructions (e.g. military, confidential and nuclear facilities, etc.), aerospace, military equipments and transportation, etc.

Antimicrobial activity of porous metal injection molded (MIM) 316L stainless steel by Zn, Cu and Ag electrodeposition

Porous 316L stainless steel samples were functionalized with electrodeposited zinc, copper, and silver coatings for antimicrobial activity against gram-positive bacteria Staphylococcus aureus (S. aureus). Porous stainless steel samples were created by combining metal injection molding (MIM) with a powder space holder (PSH) technique using sodium chloride (20 wt%) as a space holder material. Galvanostatic (0.10 A) electrodeposition was used for zinc, copper, and silver deposition, and antimicrobial activity of functionalized samples was evaluated using a touch test protocol with S. aureus. All electrodeposited samples completely prevented the growth of S. aureus. These results confirm that metal depositions only in the pores of the porous 316L were sufficient to inhibit the growth of S. aureus completely.

H-rGO-Pd NPs Nanozyme Enhanced Silver Deposition Strategy for Electrochemical Detection of Glypican-3

Glypican-3 (GPC3), as an emerging biomarker, has been shown to be beneficial for the early diagnosis and treatment of hepatocellular carcinoma (HCC). In this study, an ultrasensitive electrochemical biosensor for GPC3 detection has been constructed based on the hemin-reduced graphene oxide-palladium nanoparticles (H-rGO-Pd NPs) nanozyme-enhanced silver deposition signal amplification strategy. When GPC3 specifically interacted with GPC3 antibody (GPC3Ab) and GPC3 aptamer (GPC3Apt), an "H-rGO-Pd NPs-GPC3Apt/GPC3/GPC3Ab" sandwich complex was formed with peroxidase-like properties which enhanced H2O2 to reduce the silver (Ag) ions in solution to metallic Ag, resulting in the deposition of silver nanoparticles (Ag NPs) on the surface of the biosensor. The amount of deposited Ag, which was derived from the amount of GPC3, was quantified by the differential pulse voltammetry (DPV) method. Under ideal circumstances, the response value was linearly correlated with GPC3 concentration at 10.0-100.0 μg/mL with R2 of 0.9715. When the GPC3 concentration was in the range from 0.01 to 10.0 μg/mL, the response value was logarithmically linear with the GPC3 concentration with R2 of 0.9941. The limit of detection was 3.30 ng/mL at a signal-to-noise ratio of three and the sensitivity was 1.535 μAμM-1cm-2. Furthermore, the electrochemical biosensor detected the GPC3 level in actual serum samples with good recoveries (103.78-106.52%) and satisfactory relative standard deviations (RSDs) (1.89-8.81%), which confirmed the applicability of the sensor in practical applications. This study provides a new analytical method for measuring the level of GPC3 in the early diagnosis of HCC.