Thin Silver Layer Research Articles

Enhancing Sensitivity of Piezoresistive Pressure Sensor at Low Pressures Using Photo‐Sensitive Resin Plate as Flexible Substrate

AbstractIn this paper, flexible highly sensitive piezoresistive pressure sensors for low compressive stress detection (9.8 Pa to 10.7 kPa) are proposed, by using Photo‐Sensitive Resin Plate (PSRP). The photolithography method is employed to create the micro‐dome structure pattern on PSRP. Finally, the active parts of the sensors are made by depositing a thin layer of silver (Ag), as the sensing element, on the micro‐dome patterns. Herein, the effect of three different surface pattern dimensions as well as two different thicknesses of the Ag layer on sensor sensitivity are evaluated. The sensor fabricated with a diameter of 300 µm for micro‐dome structure, and 70 nm for the thickness of Ag layer demonstrated ultrahigh sensitivity of 29343 and 5 × 106 kPa−1 in the pressure ranges of 0.2–5 and 5–10.7 kPa, respectively. The sensor with a diameter of 300 µm for micro‐domes and an Ag‐thickness layer of 100 nm has a low working voltage of 0.1 V, a high sensitivity of 223.69 kPa−1 in the pressure range <0.11 kPa, and lowest limit of detection 9.8 Pa. The response and recovery times of this sensor are 270 and 60 ms, respectively. Furthermore, the sensor maintained high and stable performance over a 17‐min period.

Scavenger-free solar photocatalytic degradation of Textile Dyes and Antibiotics using magnetically separable bi-junctional photocatalyst

The field of solar photocatalysis has been plagued by photocatalysts with low photon-to-electron conversion efficiency, resulting in poor photocatalytic degradation rates of water pollutants. With a keen idea to improve the existing photocatalysts, we developed a scavenger-free, magnetically separable, bi-junctional solar photocatalyst. The photocatalyst comprises Fe2+ doped zinc ferrite as core, ZnO as shell, and irregular CuO nanoparticles in conjunction with the surface of core-shell nanoparticles prepared using a combination of microwave-assisted solvothermal technique and microwave-assisted reflux method. The photocatalytic degradation properties of the solar photocatalyst were modelled and optimized with the help of Methyl Orange under direct sunlight. This novel composite degrades Methyl Orange roughly four times faster than core-shell nanoparticles. The photocatalyst meets most of the criteria for working of a promising solar photocatalyst, such as 1) excellent absorption of sunlight, 2) two physically distinct heterojunction and absorbing regions for efficient charge carrier generation and separation, 3) scavenger-free degradation of textile dyes and antibiotics, 4) High surface area (39 m2g −1), 5) good stability, 6) excellent reusability, 7) and easy separation of nanoparticles for reuse with the help of a magnet. The prepared photocatalyst efficiently degrades fluoroquinolone antibiotics such as Ciprofloxacin Hydrochloride, Norfloxacin, and Ofloxacin. The photocatalyst demonstrates the capability to efficiently degrade textile dyes such as Methyl Orange, Methylene Blue, Orange G, Fluorescein sodium salt, Rhodamine B, and Crystal Violet. Additionally, the bi-junctional photocatalyst can be coated with a thin layer of silver to achieve twice the degradation rate. This enhancement is attributed to the Localized Surface Plasmon Resonance (LSPR) effect. The current work presents an effective and economical option for removing dyes and antibiotics in wastewater, marking a significant stride towards sustainable industrial practices.

Strongly coupled plasmon-exciton polaritons for photobleaching suppression.

Strong light-matter interactions have received a lot of attention, for example in the pursuit of plasmonic-excitonic structures as coherent light sources with low-power threshold. In this study, we investigate the influence of room temperature strong coupling between surface plasmon polaritons (SPP) and excitons on fluorescence lifetimes and photobleaching effects. Our plasmonic-photonic structure, comprising of thin silver (Ag) and gold (Au) layers with a Rhodamine 6G (R6G) dye layer, shows a clear shift in the plasmon resonance and R6G absorption lines with varying incident angles, indicative of strong coupling, with a measured Rabi splitting of approximately 90 meV. Fluorescence lifetime imaging microscopy (FLIM) was then employed to assess photobleaching, revealing a significant reduction in photobleaching effect for in strongly coupled plasmonic-excitonic structures compared to single Rhodamine R6G layers. Our findings indicate the pivotal role of strong light-matter interactions in reducing photobleaching effects and stabilizing fluorescence intensities, offering promising avenues for developing quantum multiparticle nanophotonic devices with enhanced stability and performance.

Honeycomb network structure constructed by silver nanoparticles achieving negative permittivity at low percolation threshold

Continuous conductive network is associated with the percolation effect, yet the method of fabricating network structure at low content is still a challenge. Herein, this work proposed a “honeycomb” structure via hot pressing to realize weak negative permittivity at low percolation threshold. By polydopamine (PDA) self-polymerization and silver mirror reaction plating, Ag nanoparticles coated polystyrene (PS) microsphere (PS@PDA@Ag) was prepared. Through hot pressing, the microspheres were compressed into “honeycomb”. The percolation threshold was reduced because the thin silver layer oscillated at low frequency plasma. Besides, by controlling the slivering time, weak negative permittivity in the range of −139 to −95 was observed and the percolation threshold was merely 2.23 vol%. The ac conductivity increased by four orders of magnitude and the thermal conductivity enhanced 79.08 %. The electric field and power loss density were simulated by finite element method. More than 100 V/m of electric field mode and 3 × 1011 W/m3 of power loss density were presented, explaining the generation of negative permittivity and the enhancement of dielectric loss. This work presented a method of achieving weak negative dielectric via honeycomb structure, and provided a novel perspective for the development of metal-based metacomposites.

High Energy Pulsed Laser Beam to Produce a Thin Layer of Crystalline Silver without Heating the Deposition Substrate and Its Catalytic Effects

Crystalline silver thin layers were obtained using high-energy pulsed laser ablation without the heating of the deposition substrate. The fluid Plateau–Rayleigh (PRI), Rayleigh–Taylor (RTI), and Richtmyer–Meshkov (RMI) instabilities, as well as the crown splash induced during the pulsed laser deposition (PLD) in the high energy regime, resulting in ring and pearl-shaped structures, offer the benefit of an increased sorption surface. These morphological structures obtained for the silver thin layers make them of interest for catalytic applications. This study addresses both fundamental and applied issues on the morphological structures obtained for the silver thin layers and their catalytic function in organic processes. In this sense, the catalytic action of the thin silver layer was highlighted by modifications of the Reactive Blue 21 dye (C.I.) in an aqueous solution with sodium bicarbonate. Specific investigations and analyses were carried out using electron microscopy and elemental analysis (SEM-EDX), atomic force microscopy (AFM) and profilometry, mass spectrometry, ablation plasma diagnosis, diffractograms (XRD), as well as IR spectroscopy (FTIR). In addition to the experimental investigation and analyses, the simulation of the ionization energy threshold was conducted in COMSOL for complementary evaluation on the involved processes and phenomena.

Tailored silver coated polymer pillar metasurfaces for near-infrared refractive index sensing applications

In this work, we report the design, numerical simulation, and fabrication of plasmonic metasurfaces consisting of two-dimensional array arranged polymer pillars on glass substrate coated by a thin silver layer. Silver coated polymer pillar metasurfaces with various silver thicknesses are designed and their optical characteristics analyzed with a finite-difference time-domain (FDTD) method. The designed structures for near-infrared refractive index (RI) sensing show the sensitivities and figure-of-merits (FOM) of ∼1438.3 nm/RIU and ∼71.5 RIU−1, for gaseous media, and ∼1444.0 nm/RIU and ∼59.2 RIU−1 for liquid media, respectively. By introducing and applying the fabrication processes of 3D laser direct writing combined with sputtering technique, we have demonstrated the facile implementation of the plasmonic metasurfaces working in the near-infrared region without using the precise fabrication techniques. This work will provide general guidelines and useful approaches for plasmonic metasurface device design.

Influence of the configuration of metal sensing layers on the performance of a bimetallic (Ag–Cu) surface plasmon resonance biosensor

Bimetallic surface plasmon resonance (SPR) sensors have the potential to overcome the drawbacks of individual metals, but the effect of the configuration of the two metallic layers on the performance of the sensors has not been explored. This study examines the influence of different positions of a thin layer of silver in relation to a copper layer on the sensitivity of such a bimetallic SPR sensor. The design of this configuration aims to improve the SPR reflectance curve and strengthen the evanescent electric field to improve the sensor efficiency. Our findings indicate that, by optimizing the architectures of SPR sensors and using a silver–copper bimetallic structure, we can achieve superior performance compared to devices that utilize only silver or copper. The optimized Ag (5 nm)/Cu (55 nm) sensor design, with the best sensitivity of 299.09° RIU−1, can detect a change of 0.43°/(g dl−1) for hemoglobin in blood, 0.35°/(g dl−1) for glucose in urine, and 0.1°/(%) for methanol in ethanol. We also demonstrate the importance of signal quality by introducing two new parameters that offer a better quantitative indication of the efficiency of a sensor than is obtained by using only sensitivity.

A nano-imprinted graphene oxide-cellulose composite as a SERS active substrate.

Cellulose is a sustainable material capable of forming optically active nanoarrays on its surface. We created a composite of cellulose acetate (CA) and graphene oxide (GO), by mixing GO (0.1 mg mL-1) into CA. This was then imprinted with nanoscale surface features that form Bragg-like modes in resonance with the excitation laser when a thin layer of silver is vapor deposited onto the surface of the substrate. The addition of GO leads to improved surface-enhanced Raman scattering (SERS) signal strengths, obtaining an average SERS signal increase of 1.4-fold following the inclusion of GO. The combination of photonic and electromagnetic effects with charge transfer-based processes that support the SERS chemical mechanism and the possible presence of electromagnetic hot spots from the roughened surface results in an enhanced SERS signal strength when GO is added. This work shows the potential for nanoimprinted graphene oxide/cellulose acetate composites as flexible sensor platforms to detect target molecules.

Thermo‐Optical Switches Based on Spin‐Crossover Molecules with Wideband Transparency

AbstractIn this work, a thermally tunable optical resonator operating in the visible wavelength range is reported, which consists of a bilayer structure composed of a thin silver layer and a dielectric coating of [Fe(HB(1,2,4‐triazol‐1‐yl)3)2] switchable spin‐crossover (SCO) molecules. White light is coupled to the resonant structure using a prism and the resulting resonance spectra are investigated as a function of the incident angle and temperature. Switching the SCO molecules from the low‐spin to the high‐spin state gives rise to a substantial blueshift of the resonances reaching up to 30 nm (associated with a reflectance modulation of up to 70%), which can be linked, through transfer‐matrix simulations, to the variation of the optical thickness of the molecular layer. Interestingly, the study demonstrated that the large thermal tunability of the device also gives rise to a photothermal nonlinearity, which can be leveraged for achieving optical limiting applications. Overall, through the present study, it is shown that molecular SCO nanomaterials can be superior to commonly used thermo‐optical switches and well‐established optical phase‐change materials for applications requiring high broadband optical transparency in the visible spectral domain.

Thermochromic Nanocellulose Films for Temperature-Adaptive Passive Cooling.

Energy efficiency in habitation spaces is a pivotal topic for maintaining energy sufficiency, cutting climate impact, and facilitating economic savings; thus, there is a critical need for solutions aimed at tackling this problem. One viable approach involves complementing active cooling methods with powerless or passive cooling ones. Moreover, considerable scope remains for the development of passive radiative cooling solutions based on sustainable materials. Cellulose, characterized by its abundance, renewability, and biodegradability, emerges as a promising material for this purpose due to its notable radiative cooling potential exploiting the mid-infrared (MIR) atmospheric transmission window (8-13 μm). In this work, we propose the utilization of thermochromic (TC) materials in conjunction with cellulose nanofibrils (CNF) to confer temperature-dependent adaptivity to hybrid CNF films. We employ a concept where high reflection, coupled with MIR emission in the heated state, facilitates cooling, while high visible light absorption in the cold state allows heating, thus enabling adaptive thermal regulation. CNF films were doped with black-to-leuco TC particles, and a thin silver layer was optionally applied to the films. The films exhibited a rapid transition (within 1 s) in their optical properties at ∼22 °C, becoming transparent above the transition temperature. Visible range transmittance of all samples ranged from 60 to 90%, with pronounced absorption in the 8-13 μm range. The cooling potential of the films was measured at 1-4 °C without any Ag layer and ∼10 °C with a Ag layer. In outdoor field testing, a peak cooling value of 12 °C was achieved during bright sunshine, which is comparable to a commercial solar film. A simulation model was also built based on the experimental results. The concept presented in this study extends beyond applications as standalone films but has applicability also in glass coatings. Overall, this work opens the door for a novel application opportunity for green cellulose-based materials.

Self-assembled Ag-modified multigranular chromium oxide nanocomposite particles in half-metallic CrO2 configuration for efficient room temperature magnetoresistance

We report on the embedding of half-metallic ferromagnetic CrO2 phase in self-assembled Ag-modified chromium oxide nanocomposite granular particles for room temperature magnetoresistive applications. The multigranular nanostructure consists of small ferromagnetic domains of rutile-type-tetragonal CrO2 (t-CrO2) & orthorhombic CrO2 (o-CrO2) phases in the matrix of various chromium oxide phases. The matrix consisted of antiferromagnetic and insulating Cr3O8 and Cr2O3 phases as well as paramagnetic Cr2O and CrO3 phases in addition to CrO2. The nanocomposite particles consist of a correlated thin diamagnetic shell layer of silver of discontinuous formation over the core of multigranular chromium oxide nanostructure proficiently engineering the room temperature magnetoresistance (RTMR) properties. The nanocomposite structure possesses ferromagnetic properties predominantly due to the presence of ferromagnetic t-CrO2 &o-CrO2 phases, canted surface spins from antiferromagnetic Cr2O3 behaving as ferromagnetic domains and contribution from paramagnetic phase spins under the effect of magnetic field. Structural information derived from X-ray diffraction (XRD) based Rietveld analysis matched well with those obtained from the selected area electron diffraction (SAED) pattern of the as-synthesized multigranular chromium oxides nanocomposite particles. Fourier transform infrared spectroscopy (FTIR) provided structural bonding characteristics, while Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) gave surface bonding features in deconvoluted spectrum for comprehensive analysis of the as-synthesized multigranular chromium oxides nanocomposite particles. Electrical properties in a typical plot of lnρ vs.T−1/2 showed the half-metallic behaviour characteristic of t-CrO2 in a predominantly spin-dependent tunneling (SDT) mechanism in the heat-treated nanocomposite particles. Cold-pressed compacts of the as-synthesized nanocomposite particles revealed a significantly enhanced RTMR of − 80% under an applied in-plane magnetic field (H) of 3 kOe. The RTMR curves were acquired in two different geometries with H parallel (H || I) and perpendicular to the direction (H ┴ I) of applied current, respectively.

Near-perfect multi-band graphene absorber with a compound grating-based resonant structure

We proposed a multi-band graphene absorber composed of a resonant compound grating (RCG), monolayer graphene, a thin silver layer, and a distributed Bragg reflector (DBR). A multi-band near-perfect absorption spectrum can be determined by three different physical mechanisms, including guided mode resonance (GMR), quasi-bound states in the continuum (quasi-BIC), and Tamm plasmon polaritons states (TPPs). Interestingly, the quasi-BIC mode can be achieved by changing grating layer spacing. In addition, the BIC mode can also be realized by varying grating periods. The variation of the absorption peak can be observed by changing the spacing layer thickness of the DBR structure, and the waveguide layer and grating layer thickness of the compound grating. Simulation results show that the absorption peaks of the three modes excited by our proposed absorbers are high as 80% at an incident light angle of 25°.

Formation of Silver Layer with a Multiporous Structure from Silver Nanoparticles for Highly Efficient Electromagnetic Interference Shielding Materials

In this work, we describe a simple and effective strategy for the fabrication of a thin silver (Ag) layer with a multiporous structure, showing a high electromagnetic interference shielding effectiveness (EMI SE). The Ag layer with a multiporous structure was produced by a simple spray coating of conductive ink containing porous Ag nanoparticles synthesized using a simple chemical reduction method in a wet medium, followed by a low-energy sintering process to develop the Ag layer with an interconnected multiporous structure and average thickness of ∼5.5 μm. The produced Ag layer possessed a remarkable multiporous structure, which was composed of pores in Ag NPs and additional pores generated by coalescence of Ag NPs during the sintering process. Even the thin Ag layer exhibited a high EMI SE (62.3 dB, 99.9% shielding) owing to the multiporous structure, which was comparable to that of Ag foil with much lower Ag loading. This multiporous structure helped to increase the internal multiple reflections of electromagnetic waves. The substantial shielding effectiveness of the obtained multiporous Ag layer was demonstrated by measuring the EMI SE of the Ag layer coated PCB antenna. Our approach is a suitable and alternative EMI shielding method to replace present package-level EMI shielding materials such as Ag foil for a wide range of applications.

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.

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

Designing Optical Coatings with Incorporated Thin Metal Films

In the world of nanomaterials and meta-materials, thin films are used which are an order of magnitude thinner than historically used in optical thin film coatings. A problem stems from the island structure that is seen as the film nucleates and grows until there is coalescence or percolation of the islands into a nearly continuous film. The application problem is that the indices of refraction, n and k, vary with thickness from zero thickness up to some thickness such as 30 or 40 nanometers for silver. This behavior will be different from material to material and deposition process to deposition process; it is hardly modeled by simple mathematical functions. It has been necessary to design with only fixed thicknesses and associated indices instead. This paper deals with a tool for the practical task of designing optical thin films in this realm of non-bulk behavior of indices of refraction; no new research is reported here. Historically, two applications are known to have encountered this problem because of their thin metal layers which are on the order of 10 nm thick: (1) architectural low emittance (Low-E) coatings on window glazing with thin silver layers, and (2) black mirrors which transmit nothing and reflect as little as possible over the visible spectrum with thin layers of chromium or related metals. The contribution reported here is a tool to remove this software limitation and model thin layers whose indices vary in thickness.

Analysis of riboflavin/ultraviolet a corneal cross-linking by molecular spectroscopy

Corneal cross-linking (CXL) with riboflavin and ultraviolet A light is a therapeutic procedure to restore the mechanical stability of corneal tissue. The treatment method is applied to pathological tissue, such as keratoconus and induces the formation of new cross-links. At present, the molecular mechanisms of induced cross-linking are still not known exactly. In this study, we investigated molecular alterations within porcine cornea tissue after treatment with riboflavin and ultraviolet A light by surface enhanced Raman spectroscopy (SERS). For that purpose, after CXL treatment a thin silver layer was vapor-deposited onto cornea flaps. To explore molecular alterations induced by the photochemical process hierarchical cluster analysis (HCA) was used. The detailed analysis of SERS spectra reveals that there is no general change in collagen secondary structure while modifications on amino acid side chains are the most dominant outcome. The formation of secondary and aromatic amine groups as well as methylene and carbonyl groups were observed. Even though successful cross-linking could not be registered in all treated samples, Raman signals of newly formed chemical groups are already present in riboflavin only treated corneas.

A Green Approach for Recycling Compact Discs.

Compact discs (CDs) and digital versatile discs (DVDs) are mainly made by polycarbonate disc, a thin layer of aluminum or silver, a thin layer of a coating and a thin layer of a label of paper or PET. The recycling of these discs is difficult due to the removal of these non-polymeric layers and to our best knowledge, no industrial plants have been resent for their recycling. In this work, we propose a facile way to remove the non-polymeric layers and investigate the effect of the repetitive extrusion process on the processability and on the mechanical properties of the recycled polycarbonate. A few works have been published dealing with both the removal of the non-polymeric layers and the mechanical recycling of the disk of polycarbonate. In our approach, the removal of the non-polymeric layers is easily obtained through a thermo-mechanical treatment in a basic solution by ammonia. This process can be considered green because is made at a low temperature with a small amount of water and a very small amount of ammonia, saving energy and water. The properties of the polycarbonate remain good if the mechanical recycling is made after drying the post-consumer polycarbonate.

Probing the stability of perovskite solar cell under working condition through an ultra-thin silver electrode: Beyond the halide ion diffusion and metal diffusion

Perovskite solar cells (PSCs) with an excellent optoelectronic performance have intrigued mushrooming research interests, and the undesirable intrinsic stability of halide perovskite materials still remains a severe constraint for their practical application. Fortunately, the ambiguous and complicated incentives for the degradation process of PSCs under working condition can be directly reflected on the corrosion of silver electrode by halogens. Here, a new perspective for evaluating the long-term stability of PSCs is presented by the time-dependent transverse resistance of the ultrathin silver electrode under different working conditions. Being anode or cathode, the stability of ultra-thin silver layer has been systematically investigated through adjusting the external operating conditions of devices, i.e. light illumination and bias voltage. Experimental results indicate that the gradual resistance increases of silver film can be attributed to the oxidation of I− existing on the top surface of perovskite layer by non-equilibrium holes generated from light illumination or electrical injection for producing corrosive I2 gas, which will diffuse through the carrier transporting layer and attack the thin silver layer. The interaction probability of I− and non-equilibrium holes at the interface plays a critical role on the generation of I2 gas and resistance variation of the top thin silver electrode. The stability study of electrode indicator will shed light on the ambiguous degradation mechanisms of PSC under working condition, paving a path for conquering the fatal problems of the practical application.

Investigations into the Photocatalytic and Antibacterial Activity of the Nitrogen-Annealed Titanium Oxide/Silver Structure

In this study, a thin silver (Ag) layer was evaporated onto the anatase-titanium oxide (TiOx) film. This structure was then annealed at various temperatures under nitrogen ambient to realize the Ag nanoparticles formed on the TiOx surface. The photocatalytic activities of these TiOx/Ag structures to decompose pollutants were determined from the rate constant while they were applied to decolorize the methylene blue (MB) solution in the presence of the UV light irradiation. According to the investigations on their surface bond configurations, the Ag nanoparticles were favorable for the transformation of the Ti4+ into the Ti3+ state in the TiOx film, which functioned to prohibit the recombination of the photogenerated electron-hole-pairs on the TiOx surface. The exposed TiOx surface distributed over the 500 °C-annealed TiOx/Ag structure performed an increase of about 40% in the rate constant compared to the individual TiOx film. Moreover, this surface morphology composed of the anatase-TiOx structures and Ag nanoparticles which was abundant in the oxide-related radical and Ag+ chemical state also showed a perfect antibacterial efficiency against Escherichia coli.