Ag Films Research Articles

Nanorod reassembling on a sprayed SERS substrate under confined evaporation inducing ultrasensitive TPhT detection

Triphenyltin is an estrogen like pollutant that poses significant environmental threats due to its highly accumulative toxicity. To improve regulation, a fast and sensitive detection method is urgently needed. SERS can capture fingerprint information and is capable of trace detection, making it an ideal solution. Here, we present a sprayed substrate comprised of lightconfining structures and gold nanorod assemblies that are easy to prepare, low-cost, and can form dense hotspots under confined evaporation. The substrates are three-layered: initially, a gold nanorod layer is sprayed as a support, then sputter Ag film on the surface to form a lightconfining structure, followed by another gold nanorod layer sprayed on the Ag film. The coupling of nanorod assembly with lightconfining Ag films leads to 10-fold sensitivity. In addition, sample droplet evaporation in a limited area called confined evaporation contributes to nanorod migration and reassembly on the corner of the substrate, enhancing analytes absorption, and substantially lowered the detection limits. By systematically evaluating the substrate performance, we were able to obtain an average enhancement factor of 3.31 × 106. After confined evaporation, the detection limit reached 10−18 M for R6G and for triphenyltin, it achieved 10−9 M. This novel method represents a significant advancement toward SERS application in detecting trace pollutants.

Enhanced Antibacterial Activity at Ag-Cu Nanojunctions: Unveiling the Mechanism with Simple Surfaces of CuNPs-on-Ag Films.

Deposition of CuNPs on silver film gives rise to the formation of active Ag-Cu interfaces leading to dramatic enhancements in antibacterial activity against Escherichia coli. Transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDAX) analyses reveal that CuNPs are covered in a thin Cu2O shell, while X-ray photoelectron spectroscopy measurements (XPS) reveal that the Ag film samples contain significant amounts of Ag2O. XPS analyses show that the deposition of CuNPs on Ag films leads to the formation of a photoactive Ag2O-Cu2O heterostructure. Following a Z-scheme mechanism, electrons from the conduction band of Ag2O recombine with photogenerated holes from the valence band of Cu2O. Consequently, electrons at Cu2O's conduction band render Cu reduced and cause reductive activation of surface oxygen species on Cu forming reactive oxygen species (ROS). Interaction between metallic Cu and ROS species leads to the formation of a Cu(OH)2 phase. Both ROS and Cu(OH)2 species have previously been reported to lead to enhanced antibacterial properties. Holes on Ag2O produce a highly oxidized AgO phase, a phase reported to exhibit excellent antibacterial properties. Quantitative analysis of Cu and Ag high-resolution X-ray photoelectron spectroscopy (HR-XPS) spectra directly reveals several-fold increases in these active phases in full agreement with the observed increase in antibacterial activities. This study provides insight and surface design parameters by elucidating the important roles of Ag and Cu's bifunctionality as active antibacterial materials.

Magnetron sputtering process for deposition of multilayered thin diamond-like carbon films with silver nanoparticles for anti-reflective coatings and refractometric sensing

Multilayered film stacks serving optical applications usually require multiple target sources for deposition. In this work, we present a convenient method for the deposition of single- and multilayered thin films with varying diamond-like carbon (DLC) and silver content employing a single magnetron in the deposition system. For this, a reactive magnetron sputtering system was utilized and the silver target was poisoned based on desired structure: clean target and argon gas resulted in a pure silver film, completely poisoned target and acetylene and argon gas resulted in a DLC film, and anything in between resulted in a nanocomposite DLC:Ag film. The films were deposited on fused quartz, crystalline silicon, and porous anodized aluminum oxide substrates. We investigated the optical properties of these films and showed their applications for anti-reflective, black-appearing coatings and refractometric sensors, both experimentally and by simulation methods.

Numerical investigation of optical bistability in a nonlinear plasmonic structure containing a phase change material

In this paper, a controllable nonlinear plasmonic structure is proposed based on a phase change material (PCM) layer to achieve tunable bistability characteristics. To this end, the Ge2Sb2Te5 (GST) layer (as a PCM) is sandwiched between a thin film of Ag and a Kerr material substrate. Then, this multilayered structure is used as a substrate for the ZnSiAs2 grating whose grooves are filled with the Kerr nonlinear material. Next, the grating is covered with a layer of CaF2. In this structure, we first calculate the reflection spectrum for different crystallization fractions using the finite element method (FEM) in the linear regime. The reflectance spectrum shows a dip in the near-infrared region, which is redshifted with increasing the crystallization fraction of the GST layer. This effect results from the movement of surface plasmon resonance to longer wavelengths with increasing the crystallization fraction. Then, we find that the dip in the reflectance spectrum is redshifted with enhancing the input intensity of the incident wave for different crystallization fractions in the nonlinear regime. This behavior confirms the existence of optical bistability through the proposed structure. So, we calculate the bistability curves at a fixed operating wavelength of 1550 nm for different crystallization fractions. Our results demonstrate that as the phase transition from the amorphous to the crystalline state occurs at a fixed operating wavelength, the bistability thresholds reduce while the hysteresis width also decreases and the bistability effect eventually disappears. Therefore, for each crystallization fraction of the GST layer we find a special wavelength at which a reasonable bistability curve with a reasonable hysteresis width is obtained. This operating wavelength is shifted by 33 nm as the crystallization fraction varies from 0.2 to 0.8. Finally, the effects of increasing the thickness of the GST layer on the bistability characteristics are examined. Our results show that stronger tunability of the operating wavelength by 50 nm with variation of crystallization degree from 0.2 to 0.8 is achieved when a thicker GST layer is used instead of a thinner one.

Improved quality and inhibited aggregation of Ag–In alloy films

Ag atoms agglomeration at environmental conditions limits its applications. Here, the influences of indium addition on the microstructure and performance of Ag films were investigated. The results show that the particle size, pore size, and roughness of Ag–In alloy films are greatly reduced compared with those of the Ag film. A small amount of indium can efficiently inhibit the agglomeration/migration of Ag atoms and thus significantly improve the reflective performance at damp heat environment. These results show that alloying is an effective method to inhibit Ag atoms migration/agglomeration at environmental conditions.

Low Albumin Determination as a Biomarker Cancer with Cyclic Voltammetry in Agfilm/ITO and AgNOfilm/ITO Electrodes

Ag and AgNO film were fabricated through sputter deposition on indium tin oxide (ITO) conductive glass. Electrochemical detection using cyclic voltammetry (CV) was carried out for low albumin levels in blood as a parameter of cancer patients. This study aims to determinate low albumin level as a biomarker cancer. Albumin adsorption on the Agfilm/ITO and AgNOfilm/ITO was also investigated to determine the level of sensitivity of both electrodes. Analysis of the CV measurements indicated that the Agfilm/ITO electrode was more sensitive compared to the AgNOfilm/ITO electrode, with a sensitivity value of 4.564 µA M-1cm-2 for the Agfilm/ITO electrode and 2.123 µA M-1cm-2 for the AgNOfilm/ITO electrode. The testing of albumin levels in blood within a range of low concentration levels between 10-1 and 10-8 g/dL indicated a detection limit of 10-9 g/mL. The selectivity of Ag electrodes was found to be very good for other interfering molecules such as urine, glucose, and lysozyme. The results of the modeling of electric field and magnetic field distribution showed that the Agfilm/ITO electrode possessed larger values than the AgNOfilm/ITO electrode. From this analysis, it can be concluded that the electrode modified with micro-sized Ag achieved more effective results than the electrode modified with AgNO. This sensor can determine low albumin level as a blood cancer biomarker. This sensor holds great promise for use in real samples in the future. HIGHLIGHTS Early detection with albumin biomarkers before metastasis cancer The testing of albumin levels with Cyclic Voltammetry and Electric Impedance Spectroscopy in the cancer within a wide range of low concentration levels (10-1 - 10-8) indicated a detection limit of 10-9 g/mL. The total mass of adsorbed BSA in electrode surface is more higher (281 mgm-2) than previous study. The Agfilm/ITO electrode exhibited high sensitivity and long-term stability for future applications. GRAPHICAL ABSTRACT

Preparation and Characterization of Low- emissivity AlN/Ag/AlN Films by Magnetron Cosputtering Method

AlN and Ag thin films were deposited independently on the Si(100) wafers and glass slides by sputtering techniqueat various times to find the optimum deposition times for coating AlN and Ag films layers. The results obtained fromglazing-incident X-ray diffraction (GIXRD), field-emission scanning electron microscopy (FE-SEM), and transmittancemeasurements showed that the optimum deposition time for coating AlN and Ag film layers were 40 min and 15 scorresponding to the film thickness of 46.7 and 19.6 nm, respectively. The optimum deposition times were used forcoating AlN and Ag films in the multilayer AlN/Ag/AlN film stack. Then, the multilayer AlN/Ag/AlN film stack wasdeposited on the glass slide for transmittance measurement and a test glass plate with a size of 10 cm x 10 cm for infraredprotection testing. The average solar transmittances in the visible range ( = 380-780 nm) and in the near infrared range( = 780-2,000 nm) were found to be 48.05 and 15.17%, respectively which are comparable with those of a commercialglass.

Pore evolution and size effect of nanoporous silver on SERS for malachite green detection

The nanoporous silver (NPS) films with the average pore size ranging from 51 to 246 nm were synthesized by dealloying co-sputtered AgxAl100-x (x = 30–56 at%) precursor films in 1 M HCl for 30–120 min. The structure of the NPS films, the dissociation of Al, and the aggregation of Ag were evaluated by field emission scanning electron microscopy as a function of dealloying time. The results showed that the pore size first decreased as the dealloying time increased, followed by pore coarsening, regardless of the relative density of NPS films. The finite-difference time-domain (FDTD) simulation further indicated that the smaller the nanopores, the higher the hot-spot area and surface electric field. As the average pore size of NPS film decreased to 51 nm, the enhanced Raman intensity of rhodamine 6G (R6G) using the NPS film as substrate was at least two orders higher than that using pure Ag film. Meanwhile, the detection limit of malachite green, a wildly used chemical in aquaculture, was 10-5 M with the enhancing factor 1.58 × 105.

Influence of poly(butyl acrylate-co-methacrylic acid) stabilized silver nanoparticles on mechanical and antibacterial properties of peroxide prevulcanized natural rubber

Colloidal poly(butyl acrylate-co-methacrylic acid) (P(BA-co-MAA)) particles were synthesized by surfactant-free emulsion polymerization. The polymeric particles were then mixed with natural rubber latex which was further prepared as peroxide prevulcanized natural rubber-poly(butyl acrylate-co-methacrylic acid)/silver (PPNR-P(BA-co-MAA)/Ag) nanocomposites. UV–visible (UV–vis) spectra and transmission electron microscope (TEM) images indicated the octahedral shape of AgNPs in the nanocomposite films. The presence of P(BA-co-MAA) in the nanocomposite films increased tensile strength compared to films without P(BA-co-MAA). The highest enhancement of mechanical properties of the nanocomposites was obtained with 10,000 and 5000 ppm of P(BA-co-MAA) and AgNO3, respectively. The PPNR-P(BA-co-MAA)/Ag films exhibited a bactericidal effect against E. coli and S. aureus. The successful bacterial reduction results corresponded to Ag+ released from the nanocomposite films and the presence of Ca2+ from a coagulant in the dipping process.

Sunlight harvesting in thin-film silicon solar cells using latticed Al2O3 anti-reflection coating, Ag disk NPs, and Ag back-reflector

Solar energy is one of the renewable energy sources that has been made available to humans at no cost. Therefore, solar cells are a suitable alternative candidate for fossil fuels. Thin-film solar cells, despite being a cost-effective technology, have low efficiency. Therefore, in this research work, we provided a new architecture for a 200 nm Si solar cell, in which a latticed Al2O3 ARC is used as an antireflection, and Ag disk shape nanoparticles are placed on the front surface of the active layer in the center of the lattices. Furthermore, an Ag film is used as a back-reflector in the rear surface of the cell. By this design, because of the forward light scattering and near-field enhancement plasmonic effect of the Ag disk, reducing the Fresnel reflection from the cell surface by latticed ARC, and recycling the unabsorbed transmitted photons by BRS, the short-circuit current density and the efficiency can be reached to 14.67 mA cm−2, and 7.11%, respectively. These parameters equal 3.94 mA cm−2, and 1.78% for the bare cell, respectively.

Highly Polarized SERS Based on Random Working Domains Composed of Nanorod Arrays for Self-Referenced Detection

When Ag film is sputtered onto polystyrene (PS) spheres, the curved Ag nanocaps form with scattered Ag nanoparticles along the brim of the Ag nanocap. Ion etching results in parallel PS nanorods due to the masking effects of the scattered Ag nanoparticles when the Ag cap array is transferred to another substrate with the top down. The highly polarized SERS substrate of random working domains composed of parallel nanorods is prepared when another 5 nm film is deposited. The nanorod diameters range from 10 nm to 20 nm, depending on the sizes of the masking Ag nanoparticles prepared by the magnetron control system and the ion etching process. Compared with other techniques, our nanorods have the advantages of highly ordered patterns in each domain, which show the excellent behavior of the polarized SERS for all PS spheres. This polarized SERS substrate is used to detect thiram with a concentration as low as 10−9 M when the background noise is successfully removed by a self-reference technique.

Fabrication and Characterization of Hybrid and Tunable ZnO@Ag Flexible Thin Films Used as SERS Substrates

Flexible substrates have known increased popularity over rigid ones due to their use in surface-enhanced Raman scattering (SERS). They provide irregular surfaces, ideal for in situ sensing. In this context, we report the SERS performance of hybrid ZnO@Ag thin films deposited by magnetron sputtering (MS) on flexible, thermoplastic substrates. This physical deposition method is acknowledged for obtaining high-quality and reproducible ZnO films that can be embedded in (bio)sensing devices with various applications. Three types of thermoplastic-based, commercially available substrates with different glass transition temperatures (Tg) were chosen for the variation in flexibility, transparency, and thickness. Zeonor® (Tg = 136 °C, thickness of 188 μm) and two types of Topas (Topas®: Tg = 142 °C, thickness of 176 μm; Topas2: Tg = 78 °C, thickness of 140 μm) thermoplastic sheets are nonpolar and amorphous cyclo-olefin polymer (COP) and cyclo-olefin copolymers (COC), respectively. Their thicknesses and different values of Tg can greatly affect the topographical and roughness properties of films with small thicknesses and, thus, can greatly influence the enhancement of the Raman signal. The ZnO films deposited on top of Zeonor® or Topas® have identical morphological properties, as shown by the scanning electron microscopy (SEM) characterization. Subsequently, by using the MS technique, we tuned the thickness of the deposited silver (Ag) films in the range of 7–30 nm to assess the growth influence on the morphology and the SERS signal amplification of the substrates with and without the ZnO intermediate layer. The SEM analysis showed that the Ag atoms migrated both into the interstitial areas, filling the voids between the ZnO granular structures, and over the latter, forming, in this case, isolated Ag clusters. SERS analysis performed on the ZnO-Ag hybrid films using crystal violet (CV) molecule revealed a limit of detection (LOD) of 10−7 M in the case of 15 nm thick Ag/Zeonor® interlayer films ZnO and relative standard deviation (RSD) below 10%.

Interfacial characteristics of single layer semiconductor WS2 (SnS2) film and Ag film

Based on density functional theory (DFT), the interface contact and electronic properties of Ag/WS2 (SnS2) interfaces are studied under vertical strain and electric field, respectively. For Ag/WS2 interface, 12% compression strain or −0.40 VÅ−1 electric field can induce the transition of interface charge from n-type Schottky contact to ohmic contact, which is due to the transfer of interface charge from Ag to WS2. Under the action of strain and electric field, the interface of Ag/SnS2 shows ohmic contact. Our research shows that, as the interface system of field effect transistor (FET), Ag/WS2 can show excellent performance, while Ag/SnS2 cannot because it does not have the characteristics of FET.

Role of Cu-doping concentration in the synthesis, microstructure and properties of Ag thin films via magnetron co-sputtering method

The outstanding optical property and shielding effectiveness of the ultra-thin Ag films make them ideal for use as windows in various applications, such as TV-guided missiles, laser-guided missiles, and shielded cabin. The magnetron co-sputtering method was utilized for depositing ultra-thin Ag films (10 nm) on SiO2 substrates, and their properties were improved by introducing Cu dopants. The influence of Cu concentrations on the structure, optical and shielding performance was analyzed extensively. The study revealed that the addition of a few Cu could inhibit the growth of Ag particles in 3D-island mode, thereby facilitating their nucleation and continuous growth in the plane. The 10 nm Cu-doped Ag thin films by preparing with a Cu doping concentration of 2 mol%, displayed a uniform, continuous and smooth surface morphology whose root-mean-square (RMS) roughness is only 0.88 nm. Furthermore, the films demonstrated excellent optical property with a maximum transmittance of about 79.7% in the visible region. The highest shielding effectiveness (SE) at an optimal concentration of 2 mol% can reach peak value of 36.8 dB. These exceptional properties make Cu-doped Ag films highly valuable and applicable for electromagnetic shielding in transparent windows.

On the O2 "Surfactant" Effect during Ag/SiO2 Magnetron Sputtering Deposition: The Point of View of In Situ and Real-Time Measurements.

The use of gaseous species has been proposed in the literature to counteract the three-dimensional growth tendency of noble metals on dielectric substrates and favor an earlier percolation without compromising electrical properties. This "surfactant" effect is rationalized herein in the case of O2 presence during magnetron sputtering deposition of Ag films on SiO2. In situ and real-time techniques (X-ray photoemission, film resistivity, UV-visible optical spectroscopy) and ex situ characterizations (X-ray diffraction and transmission electron microscopy) were combined to scrutinize the impact of O2 addition in the gas flow (%O2), revealing three regimes of evolution of film resistivity, morphology, structure, and chemical composition. At low oxygen flow conditions (%O2 < 4), the observed drastic decrease of the percolation threshold is assigned to a combination of (i) a change in nanoparticle density, wetting, and crystallographic texture and (ii) a delayed coalescence effect. The driving force is ascribed to the presence of specific adsorbed oxygen moieties, the nature of which starts evolving at intermediate oxygen flow conditions (10 ≤ %O2 < 20). At high oxygen flow (20 ≤ %O2 < 40), the found detrimental impact on film resistivity is assigned to an actual oxidation in the form of a Ag2O-like poorly crystallized compound. For all %O2, a composition gradient is observed across the film thickness, with a more metallic Ag at the substrate interface. A correlation between percolation and the nature of the detected O moieties is observed. In parallel to an oxygen spillover mechanism, this gradient can be explained by the competition between different surface processes occurring before percolation, namely, aggregation, metal oxidation, and substrate reactivity. Such findings pave the way to a rational use of O2 as a modifier for Ag growth.

Nanocrystalline Ag–Cu–Al Alloy thin films with densely dispersed alumina particles prepared using reactive sputtering method with Ar–O2 mixed gas

As a first step to challenge the fabrication of highly O2-permeable Ag membranes, thin films of nanocrystalline Ag–Cu–Al alloys with densely dispersed Al2O3 particles were successfully prepared via reactive sputtering using Ar–O2 mixed gas. The effect of O2 partial pressure on the thin film structure during sputtering was investigated. A critical O2 partial pressure was required to obtain a nanocrystalline structure via simultaneous internal oxidation during sputtering. The critical condition was correlated with the flux ratio of O2 to Al impinging on the Ag film surface and the stoichiometric ratio of O to Al in Al2O3.

Hollow-waveguide-based light-induced thermoelastic spectroscopy sensing.

In this Letter, a hollow waveguide (HWG)-based light-induced thermoelastic spectroscopy (LITES) gas sensing is proposed. An HWG with a length of 65 cm and inner diameter of 4 mm was used as the light transmission medium and gas chamber. The inner wall of the HWG was coated with a silver (Ag) film to improve reflectivity. Compared with the usually used multi-pass cell (MPC), the HWG has many advantages, such as small size, simple structure and fast filling. Compared with a hollow-core anti-resonant fiber (HC-ARF), the HWG has the merits of easy optical coupling, high system stability, and wide transmission range. A diode laser with output wavelength of 1.53 µm and a quantum cascade laser (QCL) with output wavelength of 4.58 µm were selected as the sources of excitation to target acetylene (C2H2) and carbon monoxide (CO), respectively, to verify the performance of the HWG-based LITES sensor in the near-infrared and mid-infrared regions. The experimental results showed that the HWG-based LITES sensor had a great linear responsiveness to the target gas concentration. The minimum detection limit (MDL) for C2H2 and CO was 6.07 ppm and 98.66 ppb, respectively.

Optical nonreciprocity in multilayer nanoisland systems of [Ag–Al2O3] N

We study the effect of optical nonreciprocity in [Ag–Al2O3] N multilayer structures. The percolation threshold for Ag films was found to be . An anomalously large optical nonreciprocity effect was found in the structures with Ag island layers. This effect appeared as a change in the reflected light polarization () when the sample was rotated around its axis from the initial position by 180∘. The effect magnitude reached . We suggest that a possible mechanism for the optical nonreciprocity effect in these structures can be related to the excitation of localized plasmons in Ag islands. We show that essentially depends on the interlayer and intralayer interaction between Ag layers in multilayer structures and is suppressed in the case of strong intralayer and interlayer interaction of plasma oscillations.

Effect of Ultraviolet Illumination on the Fixation of Silver Ions on Zinc Oxide Films and Their Photocatalytic Efficiency

This study focuses on the fabrication and characterization of nanostructured zinc oxide films deposited on glass substrates using sol–gel dip-coating methods. The thin films are functionalized with silver ions at various Ag+ concentrations (10−2, 10−3, 10−4 M) through room temperature ion fixation process with and without ultraviolet (UV) illumination. Physicochemical characterization techniques, such as employing Scanning Electron Microscopy with Energy-dispersive X-ray spectroscopy (SEM-EDX), X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), Ultraviolet–Visible Spectroscopy and Electron Paramagnetic Resonance (EPR) techniques. The SEM-EDX and XRD confirmed a characteristic ganglia-like structure with a hexagonal crystalline structure. The photocatalytic performance and available surface area of the pure and Ag films are investigated in the removal of methylene blue dye under UV and visible light illumination and in darkness. It is observed that the photocatalytic activity increases proportionally to the Ag+ ion concentration: ZnO &lt; Ag(10−4 M)/ZnO, &lt; Ag(10−3 M)/ZnO &lt; Ag(10−2 M)/ZnO. Moreover, the catalysts modified under UV illumination during the fixation treatment (Ag-UV/ZnO) exhibited a higher photocatalytic efficiency and degraded the dye in comparison with those without a light source (Ag/ZnO). The experimental results are confirmed using total organic carbon (TOC) analysis. The optimal silver concentration (10−2 M) is established, which shows the highest photocatalytic efficiency (in both cases of ion fixation treatment). The results can be used as a guideline for the development of co-catalyst-functionalized semiconductor photocatalysts.

High-Adhesion Ag Film with Enhanced Electromagnetic Shielding Performance via Post-Treatment of a Polydopamine Adhesive Layer.

Low adhesion limits the application of the conformal metal coating based on metal-organic complexing deposition (MOD) ink in electromagnetic interference shielding with an ultrathin thickness and excellent electromagnetic shielding performance. Here, the mussel-inspired polydopamine (PDA) coating with double-sided adhesive characteristic was used to modify the substrate surface, and a high-adhesion silver film was prepared by spin-coating MOD ink on the PDA-modified substrate. The surface chemical bond of the deposited PDA coating was found to change with the exposure time under air in this work, and three post-treatment methods were carried out on the PDA coatings, including exposure to air for 1 min, exposure to air for a day, and oven heat treatment. The influences of such three post-treatment methods of PDA coating on the structure of the substrate surface, the silver film adhesion property, the electrical property, and the electromagnetic shielding property were studied. The adhesion of the silver film was effectively enhanced up to 20.45 MPa by controlling the post-treatment method of the PDA coating. The PDA coating was found to increase the sheet resistance of the silver film and to absorb electromagnetic waves. By optimizing the deposition time and the post-treatment condition of the PDA coating, superior electromagnetic shielding effectiveness up to 51.18 dB was obtained with a thin silver film of 0.42 μm. The introduction of the PDA coating improves the applicability of the MOD silver ink in the field of conformal electromagnetic shielding.