Silver Layer Research Articles

Surface-Enhanced Raman Spectroscopy Chips Based on Silver Coated Gold Nanostars.

Surface-enhanced Raman scattering (SERS) is becoming widely used as an analytical tool, and the search for stable and highly responsive SERS substrates able to give ultralow detection of pollutants is a current challenge. In this paper we boosted the SERS response of Gold nanostars (GNS) demonstrating that their coating with a layer of silver having a proper thickness produces a 7-fold increase in SERS signals. Glass supported monolayers of these GNS@Ag were then prepared using simple alcoxyliane chemistry, yielding efficient and reproducible SERS chips, which were tested for the detection of molecules representative of different classes of pollutants. Among them, norfloxacin was detected down to 3 ppb, which is one of the lowest limits of detection obtained with this technique for the analyte.

Highly Directive Graphene Based Hybrid Plasmonic Nanoantenna for Terahertz Applications

To satisfy the necessity for elevated data transmission rates in 5G and beyond networks, terahertz band communication (0.1 - 10 THz) is envisaged as a crucial wireless technology. Two-dimensional graphene nanomaterial is being extensively integrated into the plasmonic antennas as it allows them to resonate in the terahertz wave spectrum. In this paper, a graphene-based hybrid terahertz plasmonic nano-scale antenna has been modelled to acquire a maximum gain and directivity of 8.1 dB and 8.23 dBi, respectively, by varying the conductivity of graphene via gate bias voltage. Moreover, a combination of several tailored radiating layers of silver, SiO2 and graphene sheets is arranged in the proposed nanoantenna in such a way that the return loss (S11) of -26.595 dB and a wider bandwidth of 1241.3 GHz are obtained. It is evident that the proposed graphene-based hybrid plasmonic nanoantenna could be considered as an ideal candidate for terahertz communication owing to its excellent radiation characteristics.

Surface hydroxyl modification for silicate-stabilized low-melting glassy tellurite adhesive enabling low resistance of silver conductive paste

With the booming development of new electronic devices, the demand of high-end silver conductive paste has been sharply increased. In this study, we achieve low sheet resistance silver paste by using silicate stabilized glassy tellurite adhesive with hydrophobic surface through effective surface modification. We developed a wet milling process and employed lauryl gallate to remove surface hydroxyl content of micro-scale silicate-containing tellurite low-melting glasses. This surface modification can effectively prevent agglomeration caused by hydroxyl condensation, meanwhile eliminate defects of sintered silver layer. The introduction of silicate to tellurite glassy adhesive is used to improve water and alkaline resistance and corrode wafer surface to enhance its contact with silver. A sintered silver layer with low sheet resistance of 35.6 mΩ/□ was obtained, despite only 1–3 μm size silver particles are used and sintered at relatively low temperature around 500 °C. This research provides a practical path-forward of improving overall performance of metal conductive pastes from a new angle of innovating glassy adhesive.

Highly sensitive sensing of a magnetic field and temperature based on two open ring channels SPR-PCF.

A surface plasmon resonance (SPR) sensor comprising photonic crystal fiber (PCF) is designed for magnetic field and temperature dual-parameter sensing. In order to make the SPR detection of magnetic field and temperature effectively, the two open ring channels of the proposed sensor are coated with gold and silver layers and filled with magnetic fluid (MF) and Polydimethylsiloxane (PDMS), respectively. The sensor is analyzed by the finite element method and its mode characteristics, structure parameters and sensing performance are investigated. The analysis reveals when the magnetic field is a range of 40-310 Oe and the temperature is a range of 0-60 °C, the maximum magnetic field sensitivity is 308.3 pm/Oe and temperature sensitivity is 6520 pm/°C. Furthermore, temperature and magnetic field do not crosstalk with each other's SPR peak. Its refractive index sensing performance is also investigated, the maximum sensitivity and FOM of the left channel sensing are 16820 nm/RIU and 1605 RIU-1, that of the right channel sensing are 13320 nm/RIU and 2277 RIU-1. Because of its high sensitivity and special sensing performance, the proposed sensor will have potential application in solving the problems of cross-sensitivity and demodulation due to nonlinear changes in sensitivity of dual-parameter sensing.

Silane modification of semi-curing epoxy surface: High interfacial adhesion for conductive coatings

Weak interfacial bonding between epoxy resin and plated metallic layer limits the development of epoxy resin in electronic devices and multilayer circuits. In this work, we propose a surface silane graft strategy by utilizing the active epoxy groups of semi-curing epoxy resin, which can replace the alkali washing and coarsening steps before metallization and achieve higher interfacial adhesion strength to the metallic layer. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) were used to characterize the chemical composition of the surface after the modification process. The effects of modification time and concentration of 3-mercaptopropyltriethoxysilane (MPTES) solution on the adhesion strength were studied by 180° peeling test. When the modification time reached 20 min or the concentration of MPTES solution was above 8 %, the adhesive strength was stable at 16 N/cm, showing a strong adhesive effect on the silver layer. This research may have positive implications for improving interfacial bonding between metal and polymer surfaces.

Visible light metasurface for adaptive photodetection

Semiconductor-based sub-wavelength metasurfaces are promising device platforms for the realization of optically thick and electrically thin photodetectors. Strong light–matter interactions in ultrathin film regions provide an opportunity to achieve near-unity absorption in dimensions comparable with carrier diffusion length and this, in turn, leads to an efficient collection of photogenerated carriers. Moreover, the use of phase change materials can provide real-time active tuning of optical responses of metasurface-based devices. In the first part of this paper, a tunable color filtering device is demonstrated using a metasurface design made of sub-wavelength antimony trisulphide (Sb2S3) grating placed on top of a continuous silver layer. Four distinct optical states can be acquired upon (a) the changes in the incident light polarization and (b) the phase transitions of Sb2S3. Numerical simulations and theoretical modeling data show that Fabry–Perot resonances are the driving phenomena when the proposed design is normally illuminated by an electromagnetic field with transverse electric polarization. In contrast, surface plasmon resonances are excited in transverse magnetic polarization. Furthermore, it is shown that the resonance wavelengths of the proposed design can be dynamically tuned using the geometrical parameters. Later, in the second part of the paper, adaptive photodetection is designed by integrating a nm Sb2S3 layer as a collection layer into the structure. The proposed metasurface design provides light–matter interaction in the Sb2S3 layer and maximizes the photogenerated carriers’ collection efficiency. The optically thick and electrically thin adaptive photodetection offers an opportunity to design efficient active optoelectronic and photonic devices.

Tailoring linear and nonlinear surface plasmon responses in borophene nanostructures

The newly reported 2D material ‘borophene’ provides a novel building block for nanoscale materials and devices. In this work, the linear and nonlinear plasmonic response of the electric dipole (ED) moment in metallic borophene is theoretically investigated. In our proposed model, a borophene nanostructure is deposited on the top of a dielectric layer sandwich with a silver layer acting as a mirror. It was found that the scattering at the scattering peak originates mainly from the exciting total ED. Our calculations demonstrate that scattering in the proposed model can be tuned well with carrier relaxation time, effective electron mass and free carrier density. The strongly localized fundamental field induces the desired increase in the second harmonic wave, which is discussed in detail by introducing the second-order nonlinear source. In addition, the evolution of the lifetime of linear and nonlinear plasmonic modes is also investigated, which helps us to study the underlying mechanism of microprocessing in the borophene plasmonic–photonic interaction. The manipulation of plasmonic behaviour and lifetime evolution makes borophene an excellent platform for tunable plasmonic–photonic devices.

Faraday Angle and Accuracy Measurement of Magneto-Optic Current Transmission Based on New Telluride Glass

Two robust temperature-insensitive magneto-optical current sensor prototypes, based on double polarimetric processing schemes and single light way methods, were constructed using light reflection and light transition, respectively. A diamagnetism TeO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -PbO-ZnO-BaF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> bulk glass was fabricated as a sensing head which, with/without a silver layer, acts as a mirror sputtered by RF sputtering. The Verdet constant of the TPZBF glass was measured using the self-made optical bench. The current sensors were evaluated under various currents and different temperatures. Results indicated that the constructed low-cost current sensor prototypes are accurate and stable for current sensing applications.

Construction of dense plasmonic hotspots on coarse Ag layer coated nylon fibers for ultrasensitive SERS sensing

Surface-enhanced Raman scattering is a powerful sensing tool effectively and rapidly to detect chemicals in environmental monitoring and food safety. Textile fiber-based surface-enhanced Raman scattering substrates have been fabricated to contribute to the practical applications of surface-enhanced Raman scattering sensing. Inspired by the metallic nanostructures with dense plasmonic hotspots which have excellent surface-enhanced Raman scattering activity, coarse silver layer coated nylon fibers are used in this study to combine with gold nanoparticles by a simple immersion method forming enriched plasmonic hotspots on textile fibers for ultrasensitive surface-enhanced Raman scattering detection. The fiber-based surface-enhanced Raman scattering substrate denoted as gold nanoparticle@silver layer coated nylon fiber shows a high sensitivity to rhodamine 6G with an excellent enhancement factor of 2.41 × 1010 and a detection limit of 10−14 M. The finite-difference time-domain simulations indicate that ultra-high sensitivity arises from the enhanced electric fields densely formed in the inter-particle and particle-film gap in the twisted gold nanoparticle@silver layer coated nylon fiber structure. In addition, the gold nanoparticle@silver layer coated nylon fiber substrate demonstrates outstanding surface-enhanced Raman scattering signal reproducibility (relative standard deviation 6.14%) as well as application flexibility. Through a simple swab procedure, gold nanoparticle@silver layer coated nylon fibers absorb rhodamine 6G molecules on apple and the detection limit can reach 10−13 M. Our results allowed us to foresee the use of synthetic fibers enriched with plasmonic hotspots in ultrasensitive wearable sensors.

Achieving high response of poly (3-hexylthiophene-2,5-diyl) molecules to gaseous ammonia using anodic aluminum oxide nanoporous substrate operated under 1 V

ppb level sensing of gaseous ammonia is of utmost importance in several sectors including health and industrial zones. Among various ammonia gas sensors based on different transducing principles (optical, electrical, electrochemical), conductometric sensors are highly promising due to simplicity in device fabrication and measurements but suffer from relatively low sensitivity and limit of detection. In this work, we have fabricated highly efficient conductometric ammonia gas sensors with custom-made interdigitated electrodes by laser-patterning 200 nm thick silver layer on anodic aluminum oxide (AAO) and on glass substrates for comparison. Poly (3-hexylthiophene-2,5-diyl) molecules (P3HT molecules) is used as the indicator molecules in the proposed ammonia gas sensor. The proposed sensor fabricated on AAO substrate exhibits an extraordinarily high response (ratio of difference in currents in presence and absence of gas molecules to the current in absence of gas molecules) of 0.56 at 100 ppb ammonia environment under 0.5 V, which is the highest response hitherto achieved in ammonia gas sensor based on P3HT molecules. The results suggest that a simple custom-made laser patterned silver electrode could replace the electrode designed by photolithographic or rigorous nano-engineering methods to achieve highly efficient devices. Interestingly, the unique application of AAO through-hole membrane as a substrate allows gas molecules to enter through the bottom of the substrate to interact with the indicator molecules on top, suggesting complete accessibility of the top substrate for the fabrication of devices without hindering the gas sensing phenomenon.

Model of the SARS-CoV-2 Virus for Development of a DNA-Modified, Surface-Enhanced Raman Spectroscopy Sensor with a Novel Hybrid Plasmonic Platform in Sandwich Mode.

The recent severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection has posed a great challenge for the development of ultra-fast methods for virus identification based on sensor principles. We created a structure modeling surface and size of the SARS-CoV-2 virus and used it in comparison with the standard antigen SARS-CoV-2—the receptor-binding domain (RBD) of the S-protein of the envelope of the SARS-CoV-2 virus from the Wuhan strain—for the development of detection of coronaviruses using a DNA-modified, surface-enhanced Raman scattering (SERS)-based aptasensor in sandwich mode: a primary aptamer attached to the plasmonic surface—RBD-covered Ag nanoparticle—the Cy3-labeled secondary aptamer. Fabricated novel hybrid plasmonic structures based on “Ag mirror-SiO2-nanostructured Ag” demonstrate sensitivity for the detection of investigated analytes due to the combination of localized surface plasmons in nanostructured silver surface and the gap surface plasmons in a thin dielectric layer of SiO2 between silver layers. A specific SERS signal has been obtained from SERS-active compounds with RBD-specific DNA aptamers that selectively bind to the S protein of synthetic virion (dissociation constants of DNA-aptamer complexes with protein in the range of 10 nM). The purpose of the study is to systematically analyze the combination of components in an aptamer-based sandwich system. A developed virus size simulating silver particles adsorbed on an aptamer-coated sensor provided a signal different from free RBD. The data obtained are consistent with the theory of signal amplification depending on the distance of the active compound from the amplifying surface and the nature of such a compound. The ability to detect the target virus due to specific interaction with such DNA is quantitatively controlled by the degree of the quenching SERS signal from the labeled compound. Developed indicator sandwich-type systems demonstrate high stability. Such a platform does not require special permissions to work with viruses. Therefore, our approach creates the promising basis for fostering the practical application of ultra-fast, amplification-free methods for detecting coronaviruses based on SARS-CoV-2.

The Roman monetary system from Augustus till Diocletianus 27 B.C- 305 A.D

The Roman monetary system is considered one of the most ancient financial system that distinguished with success and stability during events of history, inspite of the changes which came about through it, for remaining one standard for trustworthy coins during two centuries of time. By virtue of this stability the trade and the investment of money were become a widespread without any counterpart in any era of the previous eras.&#x0D; The Roman emperors tried to operate some substantial adjustments on the Roman monetary system from the first century till the end of the third century (A.D) to go with the political and economical crises. They had done some essential steps during sequential periods to decrease or increase the weight of Aureus, or increase the ratio of silver in Denarius. In addition to, minting a new bronzy coins, but according to the keeping up of the economical crisis, the decreasing of silver was continued and at last it reached to the beginning of the third century (A.D) about 50%.&#x0D; Inspite of the essential and monetary rectifications which were made by the emperor Diocletianus in the end of the third century as a trial to put down the problem of the economical inflation, and also for the decreasing of the ratio of silver in Denarius and also the rising of prices of craftsmen and the basic goods. All the trials did not succeed due to the issuance of very large groups of bronzy Follis which coated with a flimsy layer of silver, and as a result, spending a great amount of silver to dim the bronzy Follis, but on the other hand, a few groups of golden and silver coins were issued.&#x0D; All these events were happened beside the most problem which facing that era, which represented in the greed of the merchants and their urgent desires to get hold of a great deal of money as far as possible.&#x0D;

Hemoglobin detection in blood samples using a graphene-based surface plasmon resonance biosensor

In the proposed work, the detection of hemoglobin has been carried out using an SPR biosensor. The detection of hemoglobin is necessary because excessive concentration can cause severe disorders like anemia or polycythemia. The proposed device can detect hemoglobin concentration in blood samples. The performance of the proposed biosensor is numerically analyzed using the angle interrogation method. A hemoglobin increment of 6.1025 g/L caused by a refractive index increment of 0.001 in the blood samples in the sensing medium has been detected using an SPR biosensor. The proposed configuration consists of layers of bimetallic silver layers (45 nm and 7 nm), MXene (2D transition metal carbides, carbonitrides, and nitrides), graphene, and zinc oxide (ZnO), along with a sensing medium to analyze biomolecule. The MXene, graphene, and ZnO thickness has been taken as 0.998, 0.34, and 2 nm, respectively. The analysis of the proposed sensor has been carried out using the transfer matrix method. The sensitivity attained is 161 deg/RIU with other performance parameters computed: full-width half maximum of 2.37 deg, detection accuracy of 0.4219 deg−1, and figure of merit of 67.93 RIU−1 for two MXene and three graphene layers.

Improved photoenergy properties of low-emissivity coatings deposited by sputtering with an ion gun treatment

This work studies the effect of ion treatment on low-emissivity (low-e) coatings deposited by magnetron sputtering. Specifically, we have investigated the application of an ion treatment in the dielectric layer before deposition of a layer of silver. This reduces layer roughness which means the silver layer can be deposited with enhanced characteristics. We have also evaluated the etching rate on the SnOx layer due to the ion treatment on already deposit coatings of equal thicknesses. Subsequently, we studied the effects on the coating's photoenergy properties. For equivalent coatings, we found that those treated with ions were more transparent in the visible region, more reflective, and had a lower emissivity, which are essential requirements for low-e coatings applied in architectural glass.

Facile fabrication of tailorable Ag/AgCl reference electrodes for planar devices

• Ag/AgCl planar reference electrodes were fabricated using a facile process. • Planar reference electrodes show an open circuit potential of ∼15 mV vs a commercial. • The reference electrodes showed 70 h of stability in a chloride solution. • Planar reference electrodes were used for electrodeposition and glucose sensing. We report the fabrication of tailorable and planar silver-silver chloride (Ag/AgCl) solid-state reference electrodes (SSREs) deposited onto a flexible acetate. A silver layer was thermally evaporated and then was chlorinated in an iron (III) chloride solution. The solid salt reservoir composite consisted of salt crystals embedded in a pre-cured poly(dimethylsiloxane) matrix solution. We performed cyclic voltammetry to study the suitability of the fabricated SSREs in a three-electrode system and showed a negligible difference in the voltammograms obtained by the redox reaction of Fe 3+ /Fe 2+ compared to a commercial Ag/AgCl reference electrode, showing the reduction and oxidation peaks very slight potential shifts. Also, we used the planar SSRE in a glucose reactive strip sensor and for electroplating deposition of four different metals. These planar SSREs have a lifetime of at least 70 h of continuous monitoring at open-circuit potential, a result that makes possible the use of these electrodes in disposable devices. The principal advantage of this system is that the SSREs can be tailored to any desired form to fabricate planar devices that require reference electrodes, like most of chemical and biological sensors, and could be used where access to a laboratory is difficult.

High Sensitivity SERS Substrate of a Few Nanometers Single-Layer Silver Thickness Fabricated by DC Magnetron Sputtering Technology.

Surface-enhanced Raman spectroscopy (SERS) is commonly used for super-selective analysis through nanostructured silver layers in the environment, food quality, biomedicine, and materials science. To fabricate a high-sensitivity but a more accessible device of SERS, DC magnetron sputtering technology was used to realize high sensitivity, low cost, a stable deposition rate, and rapid mass production. This study investigated various thicknesses of a silver film ranging from 3.0 to 12.1 nm by field emission scanning electron microscope, X-ray diffraction, and X-ray photoelectron spectroscopy. In the rhodamine 6G (R6G) testing irradiated by a He-Ne laser beam, the analytical enhancement factor (AEF) of 9.35 × 108, the limit of detection (LOD) of 10−8 M, and the relative standard deviation (RSD) of 1.61% were better than the other SERS substrates fabricated by the same DC sputtering process because the results showed that the 6 nm thickness silver layer had the highest sensitivity, stability, and lifetime. The paraquat and acetylcholine analytes were further investigated and high sensitivity was also achievable. The proposed SERS samples were evaluated and stored in a low humidity environment for up to forty weeks, and no spectrum attenuation could be detected. Soon, the proposed technology to fabricate high sensitivity, repeatability, and robust SERS substrate will be an optimized process technology in multiple applications.

Influence of the relative humidity and H2S - SO2 polluted air on the fretting wear behavior of silver-plated electrical contacts

The use of connectors in electrical devices for automotive industry has significantly increased during the last decades. These connectors need to keep low and stable electrical contact resistance (ECR) otherwise disconnects may occur inducing critical failures. Close to the engine, these connectors are subjected to vibrations inducing fretting wear damage. The aim of this study is to investigate the influence of relative humidity and the presence of pollutant sulfurous gases (H2S, SO2) on the silver-plated electrical contact resistance (ECR) behavior. The ECR fretting endurance Nc (i.e. when ΔR> ΔRth = 4 mΩ) displays a fast increase above RHth(Air)=50%. The debris layer becomes more conductive so a larger wear volume is required to reach the ECR failure. At the same time, the debris layer becomes more cohesive and the wear rate decreases. Alternatively, synergic interaction between H2S, SO2 gases and relative humidity above RHth(Air&S) = 60% leads to the formation of lubricating Ag2S sulphide and Ag2SO4 sulphate tribofilm which, by decreasing the friction coefficient and the silver layer wear rate, sharply increases the ECR endurance. Finally, using simple explicit formulations, both ECR endurances under polluted and non-polluted air are formalized.

Modeling and analysis of D–shaped plasmonic refractive index and temperature sensor using photonic crystal fiber

In this study, a D–type photonic crystal fiber (PCF) based surface plasmon resonance (SPR) sensor is proposed for measurement of both refractive index (RI) and temperature. The RI sensing part is constructed by deposition of a silver layer on the plane of the D–type structure, and the temperature sensing part is formed by filling the silver nanowire and the liquid analyte into an elliptical hole in the PCF. The proposed design then can be used for temperature and analyte RI sensing through the coupling between the core guided modes and the surface plasmon modes around the nano silver rod and layer. We study the coupling characteristic and sensing performance of the sensor. The numerical results show that the maximal sensitivity in terms of RI units (RIU) is 6.9 μm/RIU in the range of 1.33–1.38, and the maximal temperature sensitivity is 3 nm /°C in the range of 27–67 °C.

Design of a high-performance graphene/SiO2-Ag periodic grating/MoS2 surface plasmon resonance sensor.

This study optimizes a surface plasmon resonance (SPR) sensor based on SiO2-Ag periodic grating using graphene and a MoS2 hybrid structure to enhance sensitivity. The sensing performance was analyzed by wavelength modulation. By optimizing the structural parameters, we can obtain the quality factor and sensitivity of 90.192RIU-1 and 960nm⋅RIU-1. The periodic grating surface covered with MoS2 prevents the oxidation of the silver layer and increases the adsorption of biomolecules. Compared with the conventional silver grating SPR sensor, the sensor's sensitivity and quality factor can be significantly enhanced. Experiments were carried out using sucrose solutions with different refractive indices, and the results indicate there was a good linear relationship between the resonance wavelength and the sucrose solution. The sensor has vast potential for practical applications.

Graphene and Nickel Nanomaterials Based Surface Plasmon Resonance (SPR) Biosensor: A Theoretical Study

An extremely sensitive surface plasmon resonance (SPR) based biosensor has been simulated in the present study using an angular interrogation technique. The large surface area of the graphene layer facilitates biomolecule absorption. The SPR biosensor is proposed in a five-layer Kretschmann configuration with a ferromagnetic material and a silver layer. The proposed SPR biosensor’s sensitivity has been significantly raised in comparison to traditional film-based SPR biosensors. By refining the proposed structure to include a ferromagnetic materials nickel and monolayer of graphene with thicknesses of 15 nm and 0.34 nm and a silver layer of 45 nm, respectively, it is possible to increase sensitivity to 266°/RIU. Furthermore, the proposed SPR sensor design has a very small FWHM, a high detection accuracy (DA), and a high-quality factor (QF). Monolayer of graphene with a fixed mono-layer Nickle configuration were found to have the highest sensitivity of 266°/RIU. Additionally, it should be noted that the proposed SPR biosensor exhibits superior performance compared to SPR sensor parameters previously recorded.