Layer Of Ag Nanoparticles Research Articles

Multi-metallic Layered Catalysts for Stable Electrochemical CO2 Reduction to Formate and Formic Acid.

Electrochemical CO2 reduction (ECR) to value-added products such as formate/formic acid is a promising approach for CO2 mitigation. Practical ECR requires long-term stability at industrially relevant reduction rates, which is challenging due to the rapid degradation of most catalysts at high current densities. Herein, we report the development of a bismuth (Bi) gas diffusion electrode on a polytetrafluoroethylene-based electrically conductive silver (Ag) substrate (Ag@Bi), which exhibits high Faradaic efficiency (FE) for formate of over 90 % in 1 M KOH and 1 M KHCO3 electrolytes. The catalyst also shows high selectivity of formic acid above 85 % in 1 M NaCl catholyte, which has a bulk pH of 2-3 during ECR, at current densities up to 300 mA cm-2. In 1 M KHCO3 condition, Ag@Bi maintains formate FE above 90 % for at least 500 hours at the current density of 100 mA cm-2. We found that the Ag@Bi catalyst degrades over time due to the leaching of Bi in the NaCl catholyte. To overcome this challenge, we deposited a layer of Ag nanoparticles on the surface of Ag@Bi to form a multi-layer Ag@Bi/Ag catalyst. This designed catalyst exhibits 300 hours of stability with FE for formic acid ≥70 % at 100 mA cm-2. Our work establishes a new strategy for achieving the operational longevity of ECR under wide pH conditions, which is critical for practical applications.

Preparation of a coating solution for antibacterial Ag nanoparticle layers

Preparation of a coating solution for antibacterial Ag nanoparticle layers

Study of dual Z-scheme photocatalytic response of TiO2/Ag/ZnO coating on plasma-modified cotton fabric for self-cleaning application

An innovative approach was adopted to improve the photocatalytic response of nanoparticle-coated cotton fabric for self-cleaning application. Fabrics with layers of TiO2, Ag, and ZnO nanoparticles were assessed for photodegradation of Rhodamine B, methyl orange, and methyl red. A dual-scheme charge transfer method was designed for the photocatalytic activity of TiO2/Ag/ZnO nanoparticles on cotton fabric. To produce the multilayer structure of nanoparticles, the fabric was first functionalized with atmospheric pressure nonthermal plasma and then sonochemically coated with TiO2/Ag/ZnO in a layered form. The plasma functionalization enhanced the stability of TiO2/Ag/ZnO nanoparticles on the fabric. It was revealed that a combination of Ag, TiO2, and ZnO nanoparticles produced a Schottky barrier among the silver metal and metal oxides (TiO2 and ZnO), resulting in enhanced photocatalytic properties. Methyl red underwent the highest photocatalytic degradation of 93% over the designed photocatalyst-coated fabric after 120 min of light exposure. This study provides a promising strategy for improving the photocatalytic self-cleaning efficacy of nanocoated fabrics.

Inkjet‐Printed Flexible Spin Seebeck Thermopile Device for Low‐Cost Spintronics Device Fabrication

Spin‐momentum‐mediated heat–charge conversion technologies for developing thin thermoelectric generators and heat flow sensors have been extensively studied. The thermoelectric generation (TEG) based on the spin Seebeck (SSE) effect is a promising technology. In this study, a flexible SSE thermopile device is fabricated using inkjet printing with Fe3O4 and Ag nanoparticle (NP) ink. A square Fe3O4 NP and a wire‐shaped Ag NP layer are used as the first and second layers, respectively. These layers are overlaid using inkjet printing twice. To obtain the SSE voltage (VSSE), a thin Pt film is deposited on a printed thermopile device. SSE generators consisting of a Pt thin film/Fe3O4 NP layer are connected through a Ag NP wire to form a thermopile structure. The saturated VSSE of the SSE thermopile device increases with the number of SSE generators. In addition, the SSE‐TEG of an SSE thermopile device is observed using a heat source with a curved surface. In these results, it is indicated that the inkjet‐printing fabrication method holds great potential in both the SSE thermopile devices and the flexible spintronic devices because it is a simple and fast process that does not require lithography.

Ablation characteristics of pre-heated region in laser line scanning process

The conditions for obtaining a completely connected ablated line on a Ag nanoparticle (NP) layer were investigated. In the scanning ablation process, the area pre-heated by a previous laser pulse is sintered, and its physical properties are changed. We examined the line patterning of AgNP layers at different sintering temperatures. The ablation thresholds of AgNP layers that were dried, sintered at 150 °C, and sintered at 200 °C were 0.211, 0.536, and 1.84 J/cm2, respectively. Some of the line patterns in the AgNP layers were not completely ablated when the applied laser fluence was higher than the ablation threshold fluence for each AgNP layer. A higher fluence was needed to form an ablated line properly. The line ablation threshold was approximately two to four times the ablation threshold. The ablated linewidth at the line ablation threshold was similar for all sintering temperatures.

Highly Conductive and Sensitive Wearable Strain Sensors with Metal/Nanoparticle Double Layer for Noninterference Voice Detection.

Human voice recognition via skin-attachable devices has significant potential for gathering important physiological information from acoustic data without background noise interference. In this study, a highly sensitive and conductive wearable crack-based strain sensor was developed for voice-recognition systems. The sensor was fabricated using a double-layer structure of Ag nanoparticles (NPs) and Ag metal on a biocompatible polydimethylsiloxane substrate. The top metal layer acts as a conducting active layer, whereas the bottom Ag NP layer induces channel cracks in the upper layer, effectively hindering current flow. Subsequently, the double-layer film exhibits a low electrical resistance value (<5 × 10-5 Ω cm), ultrahigh sensitivity (gauge factor = 1870), and a fast response/recovery time (252/168 μs). A sound wave was detected at a high frequency of 15 kHz with a signal-to-noise ratio (SNR) over 40 dB. The sensor exhibited excellent anti-interference characteristics and effectively differentiated between different voice qualities (modal, pressed, and breathy), with a systematic analysis revealing successful detection of the laryngeal state and glottal source. This ultrasensitive wearable sensor has potential applications in various physiological signal measurement methods, personalized healthcare systems, and ubiquitous computing.

To improve device performance of self-driven heterojunction photodetectors by inserting a thin layer of silver nanoparticles into the electron-transporting layer

Lead selenide colloidal quantum dots (CQDs) are widely used in infrared photodetectors due to their size-dependent bandgap tunability, facile solution-processing techniques and low cost. Heterojunctions (HJs) are usually used to construct device to facilitate the separation of excitons and the transportation of photogenerated carriers. Based on the solution-processed HJ photodetector ITO/ZnO/PbSe/Ag, in which PbSe CQDs layer acts as the active layer and ZnO nanoparticles (NPs) layer as the electron-transporting layer, a greatly enhanced-performance was obtained after inserting 10 nm Ag NPs layer within the ZnO NPs layer close to the HJ ZnO/PbSe interface. By optimizing the concentration of Ag NPs solutions and the location of Ag NPs thin layer in ZnO film, the maximum responsivity of the self-driven HJ photodetector ITO/ZnO(50 nm):Ag-NPs(10 nm):ZnO(50 nm)/PbSe(300 nm)/Ag reaches to 6.25 mA/W with a specific detectivity D* of 5.17 ×1011 Jones under 8.5 μW/cm² 1550 nm illumination at zero bias. Further, the underlain physical mechanisms for the enhanced-performance were discussed in details. In this way, it provides a very efficient method for enhanced-performance self-driven HJ photodetectors by inserting a thin layer of metal NPs into the electron-transporting layer close to the heterojunction interface.

Laser shock introduces strained wrinkling of CVD monolayer MoS2 and atomic gapping of plasmonic phototransistors

Monolayer MoS2, an atomic direct bandgap 2D material with excellent mechanical properties, is considered one of the top candidates for next-generation electronics. However, the phototransistor based on MoS2 synthesized through chemical vapor deposition (CVD) has relatively weak optical emissivity and absorption, low field-effect mobility, and a narrow response spectral range These limitations hinder the widespread application of MoS2 in optoelectronic devices. Here, to improve the performance of CVD 2D electronic devices in large-scale applications, we designed a hybrid nano-system with laser shock-enhanced plasmon and strain coupling. Wrinkles of CVD monolayers of MoS2 sandwiched between two layers of Ag nanoparticles (NPs) are tensile strained to form gap-mode localized surface plasmon resonance (LSPR). The strain of the laser shock (LS) leads to the co-deformation of MoS2 and Ag NPs, achieving an extremely narrow gap LSPR (<1 nm). The residual inhomogeneous elastic strain, remaining after the shock, not only enhances the LSPR but also modulates the band structure of MoS2 favorably. In comparison to a phototransistor employing CVD-monolayer MoS2 on a flat substrate (1L-MoS2), the laser-shock phototransistor (LS_Ag-MoS2) is improved by nearly 50 times, the response range is extended to near-infrared, and the field effect mobility is increased by 30 times. In addition, the response time is reduced from 1.28 s to 20 ms, which is comparable to the current high-K dielectric multilayer MoS2 phototransistor. Our work presents an advanced and scalable fabrication method for future applications of ultra-thin and high-performance phototransistors utilizing CVD two-dimensional materials.

Incorporation of ZnO/Ag-ZnO nanoparticles into a cotton fiber by the LbL method for Self-Cleaning applications

This paper reports the ZnO particles synthesis and characterization stabilized in poly-(diallyldimethylammonium chloride) polymer (ZnO-PDDA). By means of the TEM images, ZnO nanoparticles showed ellipsoid-shaped particles, with diameters ranging from 100–500 nm. The LbL method was utilized for the cotton fibers functionalization, using Ag and ZnO nanoparticles. The nano-hybrids incorporation through this method was carried out after a chemical modification in the cotton fabric surface. The functionalized cotton fibers characterization was performed and showed an excellent photocatalytic activity, degrading about 75 % of methylene blue (MB) in 8 h of sun exposure. The presence of one layer of Ag nanoparticles improved photocatalytic efficiency reasonably, completely degrading the MB dye in 4 h. Fabric washing tests showed that even after 15 consecutive-cycle washes, the particle detachment is minimal (about 0.1 ppm), so the LbL technique is a good alternative for the functionalization of new materials, including textile materials.

High response plasma-enhanced graphene/GaAs near-infrared photodetector

In this paper, a graphene/GaAs near-infrared photodetector with Ag nanoparticles (NPs) is fabricated and the photoelectric characteristics of the device under near-infrared light is investigated. By spin-coating a 30 nm Ag NPs layer on the surface of the device, the local surface plasmon resonance (LSPR) of the Ag NPs can enhance the absorption of near-infrared light, thereby improving the sensitivity of the device. Compared with the device without Ag NPs, the responsivity of the device is significantly increased to 96 mA/W (increased by 1.6 times) under zero bias voltage at 808 nm near infrared light, the maximum detectivity of the device can be up to 4.72 × 1011cmHz1/2W−1. In addition, the response time (τr) and recovery time (τf) of the device are 28.21 μs/68.11 μs. The quantum efficiency of the detector is increased from 37% to 84% compared with the device without Ag NPs. This result shows the graphene/GaAs photodetectors have a broad application prospect in the field of near-infrared detection.

Investigation of Dielectric Functions of a Layer of Ag Nanoparticles on Silicon Using Spectro-Ellipsometry and Spectrophotometry

Investigation of Dielectric Functions of a Layer of Ag Nanoparticles on Silicon Using Spectro-Ellipsometry and Spectrophotometry

A Bioinspired Ag Nanoparticle/PPy Nanobowl/TiO2 Micropyramid SERS Substrate.

In this paper, the micropyramid structure was transferred to the TiO2 substrate by soft imprinting. Then, the PPy nanobowls were assembled onto the surface of the TiO2 micropyramids through the induction of the PS template. Finally, a layer of Ag nanoparticles was deposited on the surface of PPy nanobowls to form a novel Ag nanoparticle/PPy nanobowl/TiO2 micropyramid SERS substrate. Its structure is similar to the bioinspired compound eyes. This substrate exhibited excellent antireflection, ultra-sensitivity, excellent uniformity, and recyclability. The concentration of R6G molecules can be detected as low as 10-9 mol/L, and the Raman enhancement factor can reach 3.4 × 105. In addition, the excellent catalytic degradation performance of the substrate ensures recyclability. This work proves that the micropyramid structure can be applied to other SERS materials besides silicon by the above methods, which broadens the selection range of composite SERS materials.

Ag nanoparticle-modified porous nickel foam nanotemplate: An efficient surface-enhanced Raman scattering platform for the rapid detection of artemisinin

Because of the advantages of rapid sampling and real-time detection, the surface-enhanced Raman scattering (SERS) technique provides greater potential for ultrasensitive detection of active components in traditional Chinese medicine. In this paper, an ultrasensitive SERS detection system was successfully designed using controllable magnetron sputtering technology for the rapid and quantitative detection of artemisinin, a traditional Chinese medicine. Using nickel foam (NF) with a three-dimensional porous mesh structure as a template, Ag nanoparticle layers were sputtered on the NF surface by the magnetron sputtering technique to prepare Ag-NF-20 (the magnetron sputtering time was 20 min) SERS substrates with high SERS performance. According to the SERS signal response of the R6G molecule on the Ag-NF-20 substrate, this efficient SERS platform showed excellent Raman signals and enhanced performance and time-stability. The results suggested that owing to the abundant electromagnetic enhancement “hot spots” distributed on Ag-NF-20 nanostructures, an experimental enhancement factor value of 6.57 × 105 was obtained. The time-stability for 30 days in an atmospheric environment was also determined, which revealed that a minimum decrease of 2.6% in Raman signal intensity was recorded, indicating the excellent time-stability of the Ag-NF-20 substrate. Furthermore, when applying this in the detection of artemisinin, the limit of detection value for artemisinin was 1 × 10−4 ng/ml. Therefore, the Ag-NF-20 SERS substrate has great potential for trace detection of other active ingredients in traditional Chinese medicine and is expected to expand the detection of pharmacodynamic substances in clinical drugs.

Synergistic effect of modest pores and lithiophilic surface on 3D current collectors for stable Li metal anodes

The increasing demand for high energy density battery systems has accelerated the development of lithium metal batteries, and it is imperative to seek strategies for alleviating the large volume change and inhibiting dendrite growth of the Li metal anode. 3D porous anode current collectors cooperated with surface modification have been considered as effective methods. Herein, we develop 3D porous Cu with modest pores by powder metallurgy method, combined with surface modification by lithiophilic Ag nanoparticles. The obtained ingenious porous structure ensures the reduction of local current density when served as the Li anode current collector, while the Ag nanoparticle layer provides numerous lithiophilic nucleation sites. Smooth and uniform Li plating morphologies are confirmed on the PM Cu@AgNP electrode surface, and the PM Cu@AgNP-Li symmetric cell presents a stable cycle of 1600 h, which effectively inhibits the Li dendrite growth. When coupled with the LiFePO 4 cathode, the assembled full cell exhibits superb capacity retention and stability for 600 cycles at 0.5 C. This facile and rational strategy with synergistic effect of modest pores and surface lithiophilicity provides a way to achieve highly stable Li metal anodes for next-generation Li batteries. • Powder metallurgy method is introduced to prepare the Li metal anode current collector. • Synergistic effect of the structure and lithiophilicity makes stable Li anode. • An average pore size of 21.2 µm is modest for the porous current collector. • Surface Ag nanoparticles significantly reduce Li nucleation overpotential.

Spectroscopic ellipsometry study of dielectric functions of Ag films and chemically deposited layers of Ag nanoparticles on silicon

The optical properties of thin films and layers of Ag nanoparticles on a c-Si substrate are modeled by calculating the complex pseudo-dielectric function <ε>. The evolution of the imaginary part <ε2> with an increase in the thickness of continuous layers from the dielectric function ε of the substrate to ε of bulk silver is studied, which demonstrates the appearance of optical characteristics of Ag and the suppression of c-Si features in the form of critical points. The data measured on the spectroscopic ellipsometer for Ag films produced by magnetron sputtering for several nominal thicknesses from 10 to 300 nm, and layers of Ag nanoparticles chemically deposited on a c-Si substrate, were interpreted using a pseudo-dielect ric function and by calculating the complex dielectric functions ε using the Drude-Lorentz model. Morphological parameters obtained by atomic force microscopy and scanning electron microscopy were also used in the calculations. Since the Ag layers and films were deposited on the c-Si substrate without any additional layers (except for the native layer), the determined pseudo-dielectric functions for thicknesses in the range of 7−50 nm turned out to be close to the calculations of the dielectric functions using the Drude-Lorentz model. It was found that in the calculated and experimental spectra in the imaginary part of ε2 and <ε2> a peak appears at E ∼ 3.9 eV, which is interpreted as a plasmon resonance in the longitudinal mode at oblique incidence of light. In the ε2 spectrum of a layer of disordered Ag nanoparticles produced by chemical deposition, there is a broader localized surface plasmon resonance peak at E ∼ 2.5 eV, in contrast to thin films. Whereas, in a layer of larger nanoparticles, the peak is absent, and its ε dependence is close to ε for bulk Ag.

Facile Lithiophilic 3D Copper Current Collector for Stable Li Metal Anode

Lithiophilic hosts are confirmed to effectively enhance the electrochemical stability of lithium (Li) anodes, thereby guaranteeing the safe, practical application of Li metal as the anode in rechargeable Li-ion batteries. This study reveals a lithiophilic three-dimensional copper current collector (Ag@CF). Silver (Ag) nanoparticles were anchored on the surface of a skeleton of copper foam (CF) via a facile displacement reaction under ultrasonic conditions. The introduced Ag nanoparticle layer reduces the nucleation barrier of Li, leading to a homogeneous Li nucleation and plating. Simultaneously, porous Ag@CF provides the structural support and storage volume of the Li anode, eliminating its volume change in the process of plating/stripping. Benefiting from the above, the Ag@CF electrode shows a superior electrochemical performance in half-type cells (near 100% coulomb efficiency for 350 cycles at 1 mA cm−2). Composite electrodes (Li-Ag@CF) preloaded in the Ag@CF network deliver an ultra-long lifespan of over 1600 h with a low over-potential at 1 mA cm−2 in Li-Ag@CF symmetric cells. Furthermore, LiFePO4∣Li-Ag@CF full cells display enhanced capacity retention (over 80% for 800 cycles at 1 or 3 C). More importantly, this method is facile, large-scalable, and low-cost, which offers an alternation strategy for the practical application of stable Li anodes. Graphical Abstract

Localized surface plasmon enhanced electroluminescence of n-ZnCdO/MgO/p-GaN via Ag nanoparticle decoration

Herein, a n-ZnCdO/MgO dual-layer structure was prepared on p-GaN/c-Al2O3 substrate by pulsed laser deposition method. Then, a layer of Ag nanoparticles, obtained by annealing Ag films with different thicknesses in vacuum, were introduced onto the MgO film to form localized surface plasmon. n-ZnCdO/p-GaN heterojunction diodes were constructed by evaporating Ni/Au electrodes on the p-GaN surface and sintering In pellets on the n-ZnCdO surface. By using 6 nm and 20 nm Ag films, whose extinction spectra match to emission peak of p-GaN and n-ZnCdO respectively, electroluminescence of p-GaN and n-ZnCdO have been observably enhanced. The enhanced emissions are mainly depended on resonant coupling between electron-hole pairs in emission layers and surface plasmon of Ag nanoparticles. These results show that the heterojunction diodes can achieve the enhanced dual-mode emission by adjusting the thickness of the Ag film when the MgO blocking layer is located between n-ZnCdO and p-GaN. This work of realizing multi-color luminescence can provide an experimental method for the design of white light devices.

Glucose-to-Resistor Transduction Integrated into a Radio-Frequency Antenna for Chip-less and Battery-less Wireless Sensing.

To maximize the potential of 5G infrastructure in healthcare, simple integration of biosensors with wireless tag antennas would be beneficial. This work introduces novel glucose-to-resistor transduction, which enables simple, wireless biosensor design. The biosensor was realized on a near-field communication tag antenna, where a sensing bioanode generated electrical current and electroreduced a nonconducting antenna material into an excellent conductor. For this, a part of the antenna was replaced by a Ag nanoparticle layer oxidized to high-resistance AgCl. The bioanode was based on Au nanoparticle-wired glucose dehydrogenase (GDH). The exposure of the cathode-bioanode to glucose solution resulted in GDH-catalyzed oxidation of glucose at the bioanode with a concomitant reduction of AgCl to highly conducting Ag on the cathode. The AgCl-to-Ag conversion strongly affected the impedance of the antenna circuit, allowing wireless detection of glucose. Mimicking the final application, the proposed wireless biosensor was ultimately evaluated through the measurement of glucose in whole blood, showing good agreement with the values obtained with a commercially available glucometer. This work, for the first time, demonstrates that making a part of the antenna from the AgCl layer allows achieving simple, chip-less, and battery-less wireless sensing of enzyme-catalyzed reduction reaction.

Исследование диэлектрических функций слоя наночастиц Ag на кремнии с помощью спектроэллипсометрии и спектрофотометрии

An investigation of the optical characteristics of a layer of Ag nanoparticles deposited from an AgNO3 solution on the surface of single-crystal Si is presented. The measurements were carried out using spectroscopic ellipsometry and spectrophotometry at the same tilt angle and sample probe location in a wide spectral range from 200 to 1700 nm. From the obtained experimental data, the parameters of the Drude-Lorentz model and the complex dielectric function were determined, which was compared with the pseudo-dielectric function. Both dependences revealed resonances of a bulk plasmon near the energy E = 3.8 eV, while a localized plasmon was detected in the pseudo-dielectric function at E = 1.65 eV, and in the dielectric function at E = 1.84 eV.

Investigation of dielectric functions of a layer of Ag nanoparticles on silicon using spectro-ellipsometry and spectrophotometry

An investigation of the optical characteristics of a layer of Ag nanoparticles deposited from an AgNO3 solution on the surface of single-crystal Si is presented. The measurements were carried out using spectroscopic ellipsometry and spectrophotometry at the same tilt angle and sample probe location in a wide spectral range from 200 to 1700 nm. From the obtained experimental data, the parameters of the Drude-Lorentz model and the complex dielectric function were determined, which was compared with the pseudo-dielectric function. Both dependences revealed resonances of a bulk plasmon near the energy E = 3.8 eV, while a localized plasmon was detected in the pseudo-dielectric function at E = 1.65 eV, and in the dielectric function at E = 1.84 eV. Keywords: dielectric function, Drude-Lorentz model, silver nanoparticles, plasmon, pseudo-dielectric function, spectrophotometry, ellipsometry