Silver Layer Research Articles

Bottom‐Up Tunable Broadband Semi‐Reflective Chiral Mirrors

AbstractConventional mirrors flip the handedness of circularly polarized light upon reflection. However, there is an increasing demand for the design and fabrication of handedness‐preserving mirrors as well as chiral reflective metasurfaces with tunable spin states of reflected photons that work in a broad wavelength range in the UV and visible domain. Most chiral mirrors fabricated up to now are prepared by top‐down techniques, such as e‐beam lithography, which are very costly and difficult to scale up to macroscopic devices. Here, an efficient bottom‐up strategy is introduced for fabricating chiral mirrors by using Layer‐by‐Layer assembly of oriented silver nanowire layers prepared by grazing incidence spraying on a semi‐reflective silver layer. The resulting chiral metasurfaces display structure‐dependent differential reflectance for circularly polarized light in a broad wavelength range in the UV, visible, and near infrared domains, reaching an extremely high figure of merit. Their differential reflectance reaches up to 95% of the maximum polarization efficiency, with the handedness of the reflected light being partially preserved. These large‐area chiral mirrors with tunable chiral reflectance open perspectives in various fields, such as in optics, sensing, and chiral light‐matter interactions.

Tamm Plasmon Resonance as Optical Fingerprint of Silver/Bacteria Interaction.

The incorporation of responsive elements into photonic crystals is an effective strategy for fabricating active optical components to be used as sensors, actuators, and modulators. In particular, the combination of simple multilayered dielectric mirrors with optically responsive plasmonic materials has proven to be successful. Recently, Tamm plasmon (TP) modes have emerged as powerful tools for these purposes. These modes arise at the interface between a distributed Bragg reflector (DBR) and a plasmonic layer and can be excited at a normal incidence angle. Although the TP field is located usually at the DBR/metal interface, recent studies have demonstrated that nanoscale corrugation of the metal layer permits access to the TP mode from outside, thus opening exciting perspectives for many real-life applications. In this study, we show that the TP resonance obtained by capping a DBR with a nanostructured layer of silver is responsive to Escherichia coli. Our data indicate that the modification of the TP mode originates from the well-known capability of silver to interact with bacteria, within a process in which the release of Ag+ ions leaves an excess of negative charge in the metal lattice. Finally, we exploited this effect to devise a case study in which we optically differentiated between the presence of proliferative and nonproliferative bacteria using the TP resonance as a read-out. These findings make these devices promising all-optical probes for bacterial metabolic activity, including their response to external stressors.

Effect of Large Amplitude Thermal Cycles on Power Assemblies Based on Ceramic Heat Sink and Multilayer Pressureless Silver Sintering

The effect of large amplitude thermal cycles between -500C and 1800C on power assemblies based on pressureless sintering of successive silver layers on an Aluminium Nitride (AlN) heat sink is investigated. In order to evaluate the impact of various adhesion layers on AlN as well as the relative density of the current track layers, various configurations with silver cermet, TiNiAg and WNiAg adhesion layers and track layer relative density of 81 cermet as adhesion layer and a track layer with a high relative density of about 81 behaviour with a low delaminated area ratio (16 shear stress value (7 MPa) after 1000 thermal cycles. For this configuration, the surface analysis performed after the shear tests on 1000 cycles aged samples show that the fracture takes place at the interface between the die attach layer and the device as well as the interface between the die attach and the track layer. However, for all other tested configurations, the fracture surface analysis performed at the end of the cycling tests highlights that the interfaces between the adhesion layer and the sintered track layers or the AlN ceramic are the weakest points of the assembly. The relationship between cracks observed after the aging and the adhesion layer nature, the track layer density, the die attach thickness as well as the void presence in the die attach is discussed. Finally, main guidelines allowing achieving device to heat sink assemblies able to withstand large amplitude thermal cycles are proposed.

Total reflectivity for infrared radiation based on one-dimensional gyroidal metallic photonic crystals

In this research, a one-dimensional photonic crystal with such a novel and simple design is introduced to serve as an efficient reflector for infrared (IR) wavelengths. The construction of the proposed photonic crystal design based on the gyroidal geometry is the mainstay of this research to investigate the total reflectivity through a wide band of IR wavelengths. In this regard, [Air/(A/B)10/substrate] is indeed the configuration of the suggested photonic crystal structure. The layer symbols, A and B represent two layers of silver with a gyroidal configuration in host materials of titanium dioxide and silicon, respectively. Meanwhile, our numerical findings demonstrate the existence of a cutoff feature at a wavelength of 1[Formula: see text][Formula: see text]m of the propagating electromagnetic waves. Moreover, the filling fraction of sliver through layers (A) and (B) provides a substantial role in the tunability of the cutoff frequency and the reflectivity of the structure as well. Then, we have taken into account how the host material’s thicknesses and refractive indices will affect the proposed structure’s reflectance. In particular, the refractive index of the host material could lead to a significant variation of the permittivities of the considered materials. Finally, we think that the proposed structure may be of a great interest in a variety of physical and engineering applications including the optical reflectors, smart windows and solar cells applications as well.

Assessment of antimicrobial and anthelmintic activity of silver nanoparticles bio-synthesized from Viscum orientale leaf extract

BackgroundViscum orientale is a largely used parasitic plant with traditional medicinal properties. They are considered to possess the medicinal properties of host tree which they grow on. It’s a least explored plant with ethanopharmacological importance. As a result, the current work aimed to investigate the biological effects of Viscum orientale extract and silver nanoparticles (AgNPs) generated from it.MethodsAgNPs synthesized using Viscum orientale plant extract and analysed on time dependent series and was characterized using Ultra Violet UV–visible spectra, Fourier Transform Infrared Spectroscopy FTIR, X-ray diffraction (XRD), Energy Dispersive X-ray Spectroscopy (EDX), Scanning Electron Microscopy (SEM). Further using disc method anti-microbial assay was performed following antioxidation screening using 1,1-diphenyl-2-picryl-hydrazyl (DPPH), reducing power and nitric oxide content and heamgglutination with human blood.ResultsOn green synthesis using silver, the phyto contituents of plant Viscum orientale effectively reduced silver ions at 3-4 h of continuous stirring to form AgNPs. UV–vis spectra showed a typical peak of AgNPs at 480 nm. The FTIR analysis confirmed the covering of silver layers to bio-compounds of the extract. SEM analysis represented AgNPs as spherical morphologies ranging from 119–222 nm. AgNPs exhibited impressive zone of inhibition against Escherichia coli (8.1 ± 0.3 mm), Staphylococcus aureus (10.3 ± 0.3 mm), Bacillus subtilis (7.3 ± 0.3 mm), Bacillus cereus (8.2 ± 0.3 mm), Salmonella typhi (7.1 ± 0.2 mm). AgNps exhibited efficiency against DPPH at EC50 value of 57.60 µg/ml. and reducing power at EC50 of 53.42 µg/ml and nitric oxide scavenging of EC50 of 56.01 µg/ml concentration. Further, anthelmintic activity results showed synthesized nanoparticles significant reduction in the paralysis time to 5.4 ± 0.3 min and death time to 6.5 ± 0.6 min in contrast to the individual factors. On hemagglutination using AgNPs, above 80 µg/ml of concentration showed very significant effect on comparison with water extract.ConclusionSynthesized AgNPs using Viscum orientale water extract displayed versatile biological activity than individual extract. This study has forecasted a new path to explore more on this AgNPs for further research.

Scalable fabrication of silver covered polyurethane nanofibers as flexible SERS nanosensors for aflatoxin detection

Flexible surface enhanced Raman spectroscopy (SERS) nanosensors, constructed by integration of plasmonic nanostructures with polymeric substrates, have received increasing research interests for recent decades. When compared to abundant works on optimization of the plasmonic nanostructures, the research involving the influence of polymeric substrates on analytical performance of resultant flexible SESR nanosensors is unexpectedly limited. Herein, the ultra-thin silver layer has been deposited on the electrospun polyurethane (ePU) nanofibrous membranes via vacuum evaporation to prepare the flexible SRES nanosensors. Interestingly, we find that the molecular weight and polydispersion index of synthesized PU play important roles in regulating the fine morphology of electrospun nanofibers, which in turns determine the Raman enhancement of resultant flexible SERS nanosensors. Specifically, the optimized SERS nanosensor, obtained by evaporating 10 nm silver layer on top of nanofibers derived from electrospinning of PU with a weight-average molecular weight of 140,354 and polydispersion index of 1.26, enables label-free detection of the carcinogen of aflatoxin down to 0.1 nM. Thanks to its scalable fabrication and good sensitivity, the current work opens new way for design of cost-effective flexible SERS nanosensors for environmental monitoring and food security applications.

Extraordinary upconversion enhancement in mono-dispersed plasmonic resonant nanocavity coupling with lanthanide doped upconversion nanoparticles

In this work, we reported a monodispersed MDM (metal–dielectric-metal) type upconversion composite material with ultrahigh emission enhancement for the first time. Different from the planar configuration of traditional MDM systems, the proposed materials here consisting of silver nanoparticles as the metallic core, upconversion nanoparticles(UCNPs) as the intermediate dielectric layer, and silver layer as the metallic shell. The structural characteristics were investigated to explore the spectral band match between the plasmonics and UCNPs. The sandwich structure can create high density hot carriers at the nearfield region around the UCNPs, leading to the remarkable excitation enhancement. According to the proper structure design, the upconversion intensity can be enhanced by over five orders of magnitude. The outer metallic layer thickness, the diameter of attached UCNPs and the ambient refractive index were found responsible for the intensity enhancement. Such upconversion materials combined the merit of monodispersity and the high emission efficiency, which can improve their performance in bioimaging and photovoltaic device.

Direct-Writing Flexible Metal Circuit with Polymer/Metal Precursor Ink and Interfacial Reaction

In this study, flexible metal circuits are fabricated with polymer/metal precursor ink and an interfacial reaction by direct-writing technology. Poly(vinyl alcohol) (PVA) is selected as one component of ink, which could be a flexible composite in a metal circuit and an adhesive layer to connect the flexible metal circuit with the flexible substrate. Silver nitrate (AgNO3) is added to the ink as a source of metal. After the direct-writing structure was placed in contact with an ascorbic acid (VC) aqueous solution with an adjustable process, silver nanoparticles (AgNPs) with 100-400 nm uniform size could be generated on the direct-writing PVA skeleton. The resistivity of the composite silver layer could reach 10-6 Ω·m without any postprocessing. Meanwhile, the resistance change could keep within 20% with 180° bending after 10 000 repeat times. Patterned flexible metal circuits could be facilely fabricated by direct-writing technology, which presented excellent electrical conductivity and flexibility.

Improving Temperature-Sensing Performance of Photonic Crystal Fiber via External Metal-Coated Trapezoidal-Shaped Surface

This article describes a photonic crystal fiber (PCF) temperature sensor that utilizes a flat, metal-coated trapezoidal surface. The PCF is made up of two layers of elliptical air holes and a polished trapezoidal surface that allows temperature sensing. An external sensing approach is used to deposit a thin silver layer on the reflective surface, while a thin SiO2 film acts as an oxidation-resistant coating. The top elliptical air hole serves as the interface for energy transformation from the core-guided mode to the surface plasmon-polariton (SPP) mode. Simulations carried out using the finite element method indicate that the proposed SPR-PCF temperature sensor can achieve a maximum temperature sensitivity and resolution of up to 5200 pm/°C and 0.01923 °C, respectively, across a temperature range of 10 to 60 °C. This research has significant potential for sensor design and real-time temperature remote sensing applications.

Numerical analysis of hafnium oxide and phase change material-based multi-layered infrared and visible frequency sensor for biomolecules sensing application

We report on the results of a numerical investigation into a phase transition material and hafnium (IV) oxide-based refractive index sensor with a wide spectral range, including both the visible and infrared regions of the electromagnetic spectrum. The sensor relies on hafnium (IV) oxide and a phase transition material (HfO2). Three layered versions of the proposed structure are studied; each configuration is built from alternating layers of HfO2, silica, Ge2Sb2Te5(GST), and silver. The three different arrangements have all been studied. The reflectance response of such multilayer structures is discussed in this manuscript for refractive indices ranging from 1 to 2.4. In addition, we have investigated how the varying heights of the materials affect the overall performance of the structure. Finally, we have supplied several formulae for resonating traces that may be used to calculate the sensing behaviour across a specific wavelength range and refractive index values. The corresponding equations are shown below. We have computed numerous equation traces throughout this inquiry to calculate the wavelength and refractive index values. Computational methods may be used to analyze the proposed structure, which might aid in creating biosensors for detecting a wide variety of biomolecules and biomarkers, such as saliva-cortisol, urine, glucose, cancerous and cancerous, and hemoglobin.

Balance between the diffraction efficiency and process robustness for plasmonic lithographic alignment technology considering the Fabry-Perot resonator effect.

Different from traditional lithography, metal material with high absorptivity and high reflectivity is introduced into plasmonic lithography technology. In particular, a silver/photo resist/silver film stack can form a Fabry-Perot (F-P) resonator structure, which can greatly change the behavior of the light reflection and transmission. Since the silver layer has a strong absorption ability to the alignment probe light with a wavelength of 532 or 633nm, the quality of the alignment signal is seriously affected. In this paper, a thin film Fourier transfer model is established to quantitatively calculate the amplitude and phase information of the diffraction light with different orders. The results show that the diffraction optical power can be enhanced by the thickness optimization of all film stacks, and the maximum wafer quality (normalized diffraction efficiency) can be increased to 25.7%. The mechanism analysis of alignment signal enhancement is based on the F-P resonator phase oscillation amplification effect. However, it can also bring the reverse of both the power and phase for the alignment probe signal when the thickness fluctuation of the F-P resonator exists, which will be a great challenge for through-the-mask moiré fringe alignment technology. To obtain the optical power distribution of the structure surface and image of moiré fringes, a transfer matrix method is given to point-by-point calculate the incidence and reflection of the probe light in the vertical direction. The finite-difference time-domain method is also used to demonstrate alignment performance. It is proved that the subtle fluctuation of the photoresist thickness can make a huge difference to moiré fringes. A balance between the diffraction efficiency and process robustness can be achieved for plasmonic lithographic alignment technology by controlling the thickness range of the F-P resonator structure. In addition, the metal-insulator-metal structure has excellent thickness sensitivity and is applicable to optical signal detection and material property monitoring.

Morphology dependent excitation of hybrid Tamm-bandedge state in metal coated opal three-dimensional photonic crystal

The optical Tamm state is a type of electromagnetic mode that exists at the interface between a periodic dielectric structure and a metal layer. While optical Tamm states have recently gained attention as a potential replacement for surface plasmon polaritons in various applications, most of these demonstrations have been limited to one-dimensional periodic dielectric structures, such as Bragg mirrors. In this article, we present a detailed study on the existence of optical Tamm states at the interface between a metal layer and opal-like three-dimensional photonic crystal (3D-PhC) structures, with a focus on two types of devices with different cross-sectional morphologies. One device consisted of a corrugated silver layer on self-assembled PS opals, while the second one was realized by self-assembling PS opals on a thin flat gold film. Our experimental and numerical observations revealed a dip in the reflection spectra for both configurations, but a hybrid Tamm-PhC bandedge state was found to exist only between the corrugated metal layer and 3D-PhC. Importantly, the nature of the hybrid Tamm-PhC bandedge states was found to strongly depend on the thickness of the metal layer. In contrast, no mode hybridization was observed at the interface between the flat metal and 3D-PhC, and the reflection dip in this case corresponded to a PhC edge mode. Our demonstration highlights the potential for realizing cost-effective and integrated hybrid plasmonic-photonic crystal structures for sensitive nanophotonic sensors.

A compact integrated dual-spectroscopy gas detection structure based on QEPAS and QEPTS using a QTF

If the acetylene (C2H2) content in the oxygen production device exceeds the standard, it is highly susceptible to explosion. It is necessary to detect C2H2 gas and reach the detection limit of ppm. A novel single quartz tuning fork (QTF) compact integrated dual-spectroscopy gas detection structure based on quartz-enhanced photoacoustic spectroscopy (QEPAS) and quartz-enhanced photothermal spectroscopy (QEPTS) was designed for improving detection intensity and reducing sensor size. The detection structure (40 mm × 90 mm × 50 mm) includes gas buffer, gas detection structure, and preamplifier circuit. In the structure, an off-beam acoustic micro-resonator (AMR) was used to enhance the photoacoustic signal. After passing the AMR, the laser beam was turned back by the right-angle prism and incident on the side of the QTF fork again to generate the photothermal signal. The silver layer on the QTF surface was chemically etched to further enhance the photothermal signal. For the traditional off-beam photoacoustic excitation, the photothermal signal is excited by the way of laser retracting. The superposition of the dual-spectroscopy detection technology on a single QTF is realized. And the structure is finely integrated which is convenient to carry and measure. Under the same conditions, photoacoustic signal, photothermal signal and dual-spectroscopy signal were measured respectively. The measured dual-spectroscopy signal was approximately the superposition value of photoacoustic signal and photothermal signal, which showed the effective signal lifting effect. With C2H2 as the target gas, the experimental results showed that the signal value of the dual-spectroscopy structure was 1.94 times that of QEPAS structure, 2.18 times that of QEPTS structure. And the minimum detection limit at atmospheric pressure was 6.64 ppm. The integrated dual-spectroscopy structure was compact, and was suitable for small space measurement, mobile measurement, and other fields.

Improved heating method for shape-memory alloy using carbon nanotube and silver paste

Shape memory alloys (SMAs) have a special ability to remember their initial shape and return from operating temperature. For this special ability, there are many studies in the field of smart wearables to replace rigid, heavy, and large electric actuators with SMAs that can be a fabrication. The usual operating method of the SMA is heating the SMA by direct Joule heating with electricity. Although direct Joule heating is fast and easy, there is overshooting, unstable, and high-power consumption. For these issues to use the SMA as textile actuators, this research suggested a heating method with silver paste required lower power consumption and coating the basic fabric with carbon nanotubes (CNTs) to support heating stability and heat uniformity. The heating method evaluated the efficiency of heat by comparing direct heating and silver layer heating and the uniformity of heat with the infrared images of whether CNTs coated or not. In this research, we reached higher temperatures with lower power than direct Joule heating using wearable heaters manufactured using silver paste. In addition, we confirmed that coating the basic fabric with carbon nanotubes reduce the temperature imbalance, and improved the heating stability. This research is expected that SMA will be used as a wearable actuator to help develop wearable devices that can move.

Degradation of Fourteenth-century Mordant Gilding Layers: Synchrotron-based Microfocus XRF, XRD, and XANES Analyses of Two Paintings by Pietro Lorenzetti

ABSTRACT Analyses of the degraded mordant gilding on two early fourteenth-century paintings by Pietro Lorenzetti were undertaken at the UK synchrotron facility Diamond Light Source. Previous studies revealed a complex orpiment-tinted mordant and its application for adhering two separate layers of silver and gold leaf and demonstrated degradation of the original materials. A new study involving synchrotron radiation (SR) microfocus X-ray fluorescence (µ-XRF) maps on cross-sections of the discolored mordant allowed imaging of the extent of migration of mobile As-Ag-S bearing species and provided ideal positions from which to collect microfocus X-ray absorption near edge structure (µ-XANES) maps of As, Ag, and S for oxidation state analysis. SR µ-XANES indicates that arsenolite (As2O3) is present throughout the mordant suggesting light-induced photooxidation of orpiment. Both As3+ (as oxide) and As5+ have been detected and these are known signs for orpiment degradation. SR microfocus X-ray diffraction (µ-XRD) was used to reveal the nature of altered phases in the mordant layer and identified the presence of acanthite Ag2S, xanthoconite Ag3AsS3, and arsenolite As2O3. The analysis confirmed that the darkening of the mordant is most probably caused by finely dispersed grey-colored Ag + -bearing acanthite particles (Ag2S). The results are discussed in the context of analysis of contemporary paintings and recent studies on the alteration of orpiment.

Chemical and Morphological Modifications Induced by Argon Plasma Treatments on Fluorinated Polybenzoxazole Films.

Fluorinated photodefinable polymers are widely employed as re-distribution layers in wafer-level packaging to produce microelectronic devices because of their suitable low dielectric constant and moisture absorption, high mechanical toughness, thermal conductivity and stability, and chemical inertness. Typically, fluorinated photodefinable polybenzoxazoles (F-PBOs) are the most used in this field. In the present work, we investigated by atomic force microscopy, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy the morphological and chemical modifications induced by Ar plasma treatments on F-PBO films. This process, used to remove surface contaminant species, as well as increase the polymeric surface roughness, to improve the adhesion to the other components during electronic packaging, is a crucial step during the manufacturing of some microelectronic devices. We found that argon plasma treatments determine the wanted drastic increase of the polymer surface roughness but, in the presence of a patterned silver layer on F-PBO, needed for the fabrication of electric contacts in microelectronic devices, also induce some unwanted formation of silver fluoride species.

Sensitive detection of malachite green in aquaculture water by surface enhanced Raman scattering using silver coated urchin-like gold nanoparticles

Urchin-like gold nanoparticles (ULGNs) exhibit rich surface plasmon optical properties especially in Surface-enhanced Raman Scattering (SERS) due to their tunable branch number and length. In this work, ULGNs with hollow structure and tunable branches were successfully prepared by the one-pot method. By controlling its morphology, we found the number and length of branches increased with the increase of ascorbic acid. The size of nanoparticles and number of branches decreased with the increase of silver nitrate. To get better SERS activity, we prepared silver coated ULGNs (ULGNs@Ag). When the ULGNs@Ag branches were partially exposed beyond the silver layer, it shows the best SERS properties and we used it as a SERS substrate to complete the detection of malachite green. The linear detection range is from 10−8-10−3 mol·L−1, and the detection limit is 2.5 nmol·L−1, suggesting this research developed a new approach to food safety testing.

Effect of the Thin Silver Layer in SnO2/Ag/SnO2 Nano-Coatings with Low Emission for Energy Storage

Effect of the Thin Silver Layer in SnO2/Ag/SnO2 Nano-Coatings with Low Emission for Energy Storage

Silver Prism Interface Plasmon Resonance for Biosensor in Ir-Visible Spectrum Region

The performance of a surface Plasmon resonance (SPR) sensor with silver film was demonstrated. The Kretschmann setup's evanescent field, which can activate the sensor. The sensitivity and FWHM of the SPR sensor drop as the thickness of the silver layer in the metallic film increases. Using water as a sensing medium, it can create a simulation model at various thicknesses of the silver layers placed on the semicircular glass prism D-ZLAF50 with a thickness of dAg = 10–80 nm. The proposed sensor can function at wavelengths of up to 600,700nm in the visible area and the infrared region at wavelengths of 900 & 1000 nm. Optimum sensitivity (S = 100–140) may be observed in the visible and infrared spectrum with thicknesses ranging from dAg = (10–80) nm , ∆n = 0.1. At silver layer thicknesses, the values of SPR dip length and FWHM are excellent (40–60 nm).

Fabrication of superhydrophobic surfaces for applications in total internal reflection effects

Superhydrophobic surfaces have attracted significant attention in the applied science community. This paper presents three different methods for fabricating superhydrophobic surfaces, which can be applied in liquid light guides with the total internal reflection effect playing a central role. The selective bi-polymer etching only produces a hydrophobic porous poly(methyl methacrylate) surface but is simple and versatile for use on an arbitrary surface. In metal-assisted chemical etching, wet etching of a silver layer on a silicon sample creates porous silicon with superhydrophobicity, characterized by a water contact angle of 160°. The metal-assisted chemical etching method modified with the presence of polystyrene nanoparticles further improved the water contact angle to 164° by creating a nanopillar silicon structure. The metal-assisted chemical etching methods are more complicated but can produce superhydrophobic surfaces with very high water contact angles. These results show that superhydrophobic surfaces fabricated by methods in this study can be used for total internal reflection effect at the interface between water with huge potential applications in liquid light guides.