Bimetallic Layers Research Articles

Sensitivity enhancement of surface plasmon resonance sensor using Al–Au–BaTiO3–Graphene layers

The performance of prism-based surface plasmon resonance sensor utilizing new sensing configuration composed of thin metallic (Al–Au) film coated with a thin layer of BaTiO3is investigated theoretically based on angular interrogation method. It is observed that optimizing the thickness of bimetallic (Al–Au) and BaTiO3 layers, the sensitivity of the sensor improved greatly and still can maintain its minimum reflectivity and linewidth of the SPR reflectivity curve. We also observed addition of dual layer of graphene on BaTiO3 further enhanced the sensitivity. The sensitivity of the proposed sensor is found to be 227 deg/RIU, and the FWHM of resonance curve is observed to be 4.47 deg for the thickness of 28 nm of Al, 8 nm of Au and 10 nm of BaTiO3added with double layer of graphene.

Solvent- and Temperature-Driven Photoluminescence Modulation in Porous Hofmann-Type SrII-ReV Metal-Organic Frameworks.

A unique family of three-dimensional (3D) luminescent SrII-ReV metal-organic frameworks (MOFs), {[SrII(MeOH)5][ReV(CN)4(N)(bpen)0.5]·MeOH}n [1·MeOH; N3- = nitrido ligand, bpen = 1,2-bis(4-pyridyl)ethane, and MeOH = methanol], {[SrII(MeOH)4][ReV(CN)4(N)(bpee)0.5]·2MeOH}n [2·MeOH; bpee = 1,2-bis(4-pyridyl)ethylene], and {[SrII(bpy)0.5(MeOH)2][ReV(CN)4(N)(bpy)0.5]}n (3·MeOH; bpy = 4,4'-bipyridine), is reported. They are obtained by the molecular self-assembly of Sr2+ ions with tetracyanidonitridorhenate(V) metalloligands, [ReV(CN)4(N)]2-, and pyridine-based organic spacers (L = bpen, bpee, bpy). Such a combination of molecular precursors results in bimetallic SrII-ReV cyanido-bridged layers further bonded by organic ligands into pillared Hofmann-type coordination skeletons. Because of the formation of {ReV-(L)-ReV} moieties providing emissive metal-to-ligand charge-transfer states, 1·MeOH-3·MeOH exhibit solid-state room-temperature photoluminescence tunable from green to orange by the applied organic ligand. The most stable MOF of 3·MeOH, based on the alternating {ReV-(bpy)-ReV} and {SrII-(bpy)-SrII} linkages, exhibits three interconvertible, variously solvated phases, methanol-solvated 3·MeOH, hydrated {[SrII(bpy)0.5(H2O)2][ReV(CN)4(N)(bpy)0.5]·0.6H2O}n (3·H2O), and desolvated {[SrII(bpy)0.5][ReV(CN)4(N)(bpy)0.5]}n (3). Their formation was correlated with water and methanol vapor sorption properties investigated for 3·H2O. The solvent content affects the luminescence mainly by tuning the emission energy within the series of 3·MeOH, 3·H2O, and 3. All of the obtained compounds exhibit temperature-driven modulation of luminescence, including the shift of the emission maximum and lifetime. The thermochromic luminescent response was found to be sensitive to the presence and type of solvent in the crystal lattice. This work shows that the construction of [ReV(CN)4(N)]2--based MOFs is an efficient route toward advanced solid luminophores tunable by external stimuli such as solvent or temperature.

The surface plasmon resonance-based fiber optic sensors: A theoretical comparative study with 2D TMDC materials

In this study, the surface plasmon resonance-based fiber optic sensor using two-dimensional (2D) TMDC materials covering the Au/Ag bimetallic layer has been reported. Since MoS2, MoSe2, WS2, and WSe2 are the most popular ones, they are constructed as the resonant layer of the sensor. The layer-dependencies and heterostructures of the TMDC materials are examined for the determination of their effect on the performance of the SPR sensor. The performance parameters of the SPR sensor, the sensitivity, accuracy, and figure of merit, are calculated with the help of the MATLAB simulations. It is found out that considering the very small change in the refractive index of the sensing medium (0.0025), the monolayer MoSe2 has the highest sensitivity value of 8096 nm/RIU. In contrast, the monolayer WS2 has the highest accuracy and figure of merit values of 0.34 and 136.89 RIU−1, respectively. This study will be benefited for a better understanding of the performance of the SPR based fiber optic sensor depending on the number of layers of TMDC materials and based on their heterostructures.

Palladium-rich plasmonic nanorattles with enhanced LSPRs via successive galvanic replacement mediated by co-reduction.

Catalytic transformations under light irradiation have been extensively demonstrated by the excitation of the localized surface plasmon resonances (LSPRs) in noble metal-based nanoparticles. To fully harness the potential of noble metal-based nanocatalysts, it is fundamentally imperative to explore hybrid nano-systems with the most desirable enhanced LSPRs and intrinsic catalytic activities. Pd-containing hollow multimetallic nanostructures transformed from the sacrificial template of Ag via galvanic replacement reaction (GRR) offer such ideal platforms to gain quantitative insights into nanoparticle-catalyzed reactions. In this work, we successfully fabricated Pd-rich plasmonic nanorattles by means of co-reduction mediated GRR using CTAC-stabilized Au@Ag nanocuboids as templates and H2PdCl4 as a Pd precursor in the presence of ascorbic acid (AA) acting as a mild reducing agent. Successive titration of Au@Ag nanocuboids with the Pd precursor in the presence of AA modulates the rate of the galvanic replacement reaction as well as effective diffusion of Pd into the Ag matrix, resulting in increased dimensions and enlarged cavity sizes. Reduction of oxidized Ag+ back to Ag0 by AA, along with the deposition of Pd to form homogeneously mixed bimetallic layers not only prevents LSPRs peak from damping with increasing Pd content but also ensures the enhanced catalytic activities. Through precise control of added H2PdCl4 titrant, an unconventional steep increase in extinction intensity accompanied by tunable plasmon resonances shifted towards the NIR spectral region was experimentally observed due to the increasing physical cross-sections and plasmon hybridization in hollow nanorattles. Four colloids of Pd-rich nanorattles obtained by addition of different amounts of the H2PdCl4 titrant were used as catalysts for reduction of 4-nitrothiophenol in the presence of NaBH4 monitored by SERS.

Improved Friction and Wear Properties of Al6061-Matrix Composites Reinforced by Cu-Ni Double-Layer-Coated Carbon Fibers

The friction and wear properties of an Al6061 alloy reinforced with carbon fibers (CF) modified with Cu-Ni bimetallic layers were researched. Cu-Ni double layers were applied to the CF by electroless plating and Al6061-matrix composites were prepared by powder metallurgy technology. The metal-CF/Al interfaces and post-dry-wear-testing wear loss weights, friction coefficients, worn surfaces, and wear debris were characterized. After T6 heat treatment, the interfacial bonding mechanism of Cu-Ni-CF changed from mechanical bonding to diffusion bonding and showed improved interfacial bonding strength because the Cu transition layer reduced the fiber damage caused by Ni diffusion. The metal–CF interfacial bonding strongly influenced the composite’s tribological properties. Compared to the Ni-CF/Al and Cu-CF/Al composites, the Cu-Ni-CF/Al composite showed the highest hardness, the lowest friction coefficient and wear rate, and the best load-carrying capacity. The wear mechanisms of Cu-Ni-CF/Al composite are mainly slight abrasive wear and adhesive wear.

ZnO and Bi-metallic (Ag–Au) Layers Based Surface Plasmon Resonance (SPR) Biosensor with BaTiO3 and Graphene for Biosensing Applications

In this work, a novel design of Zinc Oxide (ZnO) and bi-metallic (Ag–Au) layers based surface plasmon resonance (SPR) biosensor with barium titanate (BaTiO3) and graphene is proposed. The proposed structure consists of SF10 glass prism, ZnO, Ag, Au, BaTiO3, and graphene as a top layer for biomolecules adsorption. Here, the performance of this structure is studied and analysed for sensitivity along with the accuracy of detection and quality parameter for the shift in refractive index (RI) from 1.33 (sensing medium) to 1.45 and our reported results show that addition of bimetallic (Ag–Au) layers along with BaTiO3, improve the sensitivity of the proposed structure to 14.85% for the same RI range compared to last reported MoS2-graphene-based SPR sensor. Here at maximum sensitivity is reported as 116.67 degree/RIU while the accuracy of detection and the quality parameter are obtained as 4.54 and 37.87 RIU−1 respectively. These high-performance parameters of the design make this structure suitable for biosensing applications.

Sensitivity Enhancement of Surface Plasmon Resonance Sensor with Two Dimensional Materials Covered on Silver-Nickel Bimetallic Thin Solid Films

In this paper a new sensing configuration with enhanced sensitivity utilizing 2D materials on the bimetallic layers of Magnetic Material Ni over Ag for Kretschmann configuration is proposed and analyzed numerically using Fresnel equation and transfer matrix method. Results show that such a hybrid configuration with well optimized thickness of metallic layer and utilization of specific no. of 2D materials can increases the sensitivity as high as 298°/RIU is absorbed for the configuration consist 10 nm of Ni over 40 nm thickness of Ag added with a 2 layers of WSe2.

Effect of sulfosalt and polymers on performance parameter of SPR biosensor

The aim of the paper is to see the influence of Franckeite on the sensing application of SPR based biosensor. Franckeite is an emerging (2D) material from sulfosalt family having naturally presented spontaneously vander Waals (vdW) Heterostructure. We have investigated and carried out detailed analysis to design the high-performance biosensor by exploiting the unique properties of Franckeite. The performance of the biosensor is quantified in terms of Sensitivity and other performance parameters. Proposed work is theoretical where we have proposed a surface plasmon resonance (SPR) biosensor in combination of the nanosheets of (Bimetallic layer + Franckeite + TMDC + BP) in order to enhance the sensitivity. It’s also shown in the paper that by sandwiching a buffer (polymer) with low refractive index (close to water) between metal layer (Au in this case) and dielectric medium prism, the value of FWHM reduced dramatically and significant enhancement observed in FOM (100RIU−1) and detection accuracy (2.38 deg−1). We have also illustrated the concept of long range –SPR (LRSPR) in this paper by giving the comparative analysis of different polymers. As an air-stable 2D material, we expect that 2D Franckeite Nano sheets could have potential applications in the field of chemical as well as biosensing application in the future.

Ultrathin Quasibinary Heterojunctioned ReS2/MoS2 Film with Controlled Adhesion from a Bimetallic Co-Feeding Atomic Layer Deposition.

Heterojunctioned transition-metal dichalcogenide (TMD) films with regulatable interface adhesion have shown broad application prospects in the design of advanced materials and the manufacturing of novel functional devices. To date, the controlled fabrication of TMD heterojunctions or heterojunction-rich films with tailorable thickness and composition has proved challenging. Herein, a bimetallic co-feeding atomic layer deposition (ALD) system was developed capable of fulfilling these requirements. In the co-feeding ALD fabrication, by adjusting the Re/Mo ratio, 3-layered quasibinary heterojunctioned ReS2/MoS2 films with adjustable composition and grain size were prepared. Moreover, the measurements between atomic force microscopy Si tip coated with the ReS2/MoS2 films and films on the substrate indicate that the adhesion force can be regulated from 13.5 to 136.3 nN. Further experimental data and theoretical analysis show that the adhesion force between the coated tip and films possesses a positive correlation with the "tip-film unanimity" in composition.

MoS2-ReS2 Heterojunctions from a Bimetallic Co-chamber Feeding Atomic Layer Deposition for Ultrasensitive MiRNA-21 Detection.

Rhenium disulfide (ReS2), which possessed a unique direct band gap from the bulk to monolayer, played a very important role in establishing optoelectronic devices, while the rapid recombination of electron-hole pairs might hinder its further applications. Therefore, to improve its photocurrent performance, a bimetallic co-chamber feeding atomic layer deposition (ALD) with a precise dose regulation strategy was used to fabricate MoS2-ReS2 heterojunctions with a controllable Mo-to-Re ratio in this work. Furthermore, because of the controlled addition of Mo atoms, the electron-transfer capacity, carrier mobility, and photocurrent response of these heterojunctions were significantly improved among which the sample obtained under 100 supercycles (one supercycle for this sample consists of the following in turn: one ReCl5 pulse, one H2S pulse, one ReCl5 pulse, one MoCl5 pulse, and one H2S pulse; the real Mo-to-Re ratio Rr = 57.9%) exhibited the best photocurrent response. Due to the significant improvement in optoelectronic performance, a photoelectrochemical (PEC) biosensor with the basis of the above optimized sample could achieve the ultrasensitive detection of cancer-related miRNA-21 ranging from 10 aM to 1 nM with a low detection limit of 2.8 aM.

Facile Direct Seed-Mediated Growth of AuPt Bimetallic Shell on the Surface of Pd Nanocubes and Application for Direct H2O2 Synthesis

The selective enhancement of catalytic activity is a challenging task, as catalyst modification is generally accompanied by both desirable and undesirable properties. For example, in the case of the direct synthesis of hydrogen peroxide, Pt on Pd improves hydrogen conversion, but lowers hydrogen peroxide selectivity, whereas Au on Pd enhances hydrogen peroxide selectivity but decreases hydrogen conversion. Toward an ideal catalytic property, the development of a catalyst that is capable of improving H-H dissociation for increasing H2 conversion, whilst suppressing O-O dissociation for high H2O2 selectivity would be highly beneficial. Pd-core AuPt-bimetallic shell nanoparticles with a nano-sized bimetallic layer composed of Au-rich or Pt-rich content with Pd cubes were readily prepared via the direct seed-mediated growth method. In the Pd-core AuPt-bimetallic shell nanoparticles, Au was predominantly located on the {100} facets of the Pd nanocubes, whereas Pt was deposited on the corners of the Pd nanocubes. The evaluation of Pd-core AuPt-bimetallic shell nanoparticles with varying Au and Pt contents revealed that Pd-core AuPt-bimetallic shell that was composed of 2.5 mol% Au and 5 mol% Pt, in relation to Pd, exhibited the highest H2O2 production rate (914 mmol H2O2 gmetal−1 h−1), due to the improvement of both H2O2 selectivity and H2 conversion.

Revealing the role of oxygen vacancies in bimetallic PbBiO2Br atomic layers for boosting photocatalytic CO2 conversion

The effect of surface defects on photogenerated carriers separation and CO2 activation is not always clear. Herein, the well-defined bimetallic oxyhalide PbBiO2Br atomic layers with tunable oxygen vacancies (OVs) concentrations have been synthesized and investigated to reveal the role of OVs for photocatalytic CO2 conversion. Ultrafast transient absorption spectroscopy and theoretical calculations revealed that the rich oxygen vacancies (ROV) in PbBiO2Br atomic layers facilitated the transfer of photogenerated electrons from the internal structure to surface and prolonged their lifetime on the surface OVs. PbBiO2Br atomic layers with ROV demonstrated superior CO2 reduction performance with enhanced CO evolution rate of 4.58 μmol g−1 h−1 in water under visible light irradiation, which was 2.05 and 10.90 times higher than that of deficient oxygen vacancies (DOV) PbBiO2Br atomic layers and bulk PbBiO2Br, respectively. Intermediate products of CO2 conversion were investigated by in-situ Fourier-transform infrared spectroscopy and the corresponding reaction mechanism was proposed.

Highly sensitive bimetallic plasmonic sensing probe for aqueous samples

In spite of having very large real part of permittivity, Rhodium (Rh) is rarely used as a plasmonic metal in surface plasmon resonance (SPR) based sensing applications. Here, we theoretically present a simple SPR based prism-coupled refractive index sensor in Kretschmann geometry utilizing a bimetallic layer of Rhodium (Rh) and Silver (Ag) as plasmonic metal layer on the base of the SF10 glass prism. In addition Silicon is used as an upper most layer, which not only protects the oxidation-prone Ag film but also enhances the field and thereby the sensor’s performance. Each of the layers is optimized for maximum sensitivity in the visible region at 632 nm wavelength of excitation. The sensor exhibits an extremely high sensitivity of 229 degree/refractive index unit (RIU) for analyte refractive indices (RIs) varying from 1.33 to 1.37 RIU.

Oxygen Vacancy Modulation of Bimetallic Oxynitride Anodes toward Advanced Li‐Ion Capacitors

AbstractBinary metal oxides (such as NiCo2O4) are regarded as attractive electrode materials for advanced energy storage devices since they offer more electrochemical activity and higher capacity than monometal oxide. However, the volume expansion and low electronic conductivity are the main bottleneck seriously hindering their application. To overcome these barriers, a novel strategy that introduces a bimetallic oxynitride layer (NiCoON) with oxygen vacancy to the surface of NiCo2O4 nanowires as an anode for Li‐ion capacitors (LICs) is proposed. The oxygen vacancy on the surface and the modulation of multiple valence states are investigated by the electron paramagnetic resonance, X‐ray photoelectron spectroscopy characterization, and first‐principles calculation. Benefiting from the merits of substantially improved electrical conductivity and increased concentration of active sites, the optimized NiCoON electrode delivers remarkable capacity (1855 mAh g−1 at 0.2 A g−1) and rate performance. The LIC device assembled by NiCoON anodes and N‐doped carbon nanowire cathodes delivers excellent rate capability, high energy density (148.5 Wh kg−1), and outstanding power density (30 kW kg−1). This study provides a new pathway for developing bimetallic oxides with an improved performance in electrochemical energy storage, conversion fields, and beyond.

Reusable Plasmon-Decorated Chestnut-like Copper Oxide Nanostructures for SERS Sensing

Reusable plasmonic substrates are crucial for the development of biosensing applications using surface-enhanced Raman scattering (SERS), as they can provide unique advantages for ultrafast and accurate single-molecule recognition of different species. In this research, we employed thermally annealed cupric CuO and cuprous oxide Cu2O heterostructures to serve as highly stable nanotextured surfaces for designing robust 3D plasmonic biochips.Figure 1: Schematic representation of a research outline. Step 1 – controllable surface texturing by thermal annealing at oxygen-enriched atmosphere. Step 2 – plasmonic activation by ion spattering of Au/Pd alloy film. Step 3 – SERS performance monitoring by means of R6G dye fingerprint detection. Step 4 – Recovery test under ultra-fast mild cleaning in reactive oxygen/argon plasma. Step 5 – Simplified scheme of Rhodamine degradation inside plasma followed by the vanishing of the characteristic peaks in the Raman spectrum.Figure 2: (A-E) – SEM images showing the cuprous oxide Cu2O surface morphology altering with Au/Pd alloy thickening. (F) – Broadband Raman spectra representing vibrational features of chestnut Cu2O structures decorated by different plasmonic thicknesses together with ethanol diluted Rhodamine 10-5 M absorbed on the surface. (G) – Normalized intensity of the in-plane C-H bending vibrations of R6G 10-5 M as a function of bimetallic film thickness.The influence of bimetallic layer thickness on SERS performance has been studied for the chestnut patterned substrate. Figure 2 F depicts Raman spectra of Rhodamine used as a model biomarker (600-1800 cm-1) complemented by a signal originated from the Cu2O layers (100-800 cm-1). During Au/Pd film thickness reduction from 80 nm down to 20 nm, the R6G peak intensities undergo a gradual decrease, simultaneously, acoustic bands originated from Cu2O nanoparticles located in a range of 100-800 cm-1 become dominant. In accordance with Figure 2 G, that displays a signal intensity dropping for in-plane C-H bending vibrations as a function of bimetallic layer thicknesses, the analytical enhancement factor AEF acquires the following values: for 60 nm ~ 9.8×104, for 40 nm ~ 8.4×104 and for 20 nm ~ 1.1×104, respectively. The analogous finding was observed for Au decorated CuO nanoflakes, where EF increases with a noble metal film thickening [1]. Due to prominent anti-reflection properties, CuO/Cu2O heterostructures [2] appear to be an extremely suitable material for designing SERS-active substrates. Moreover, the high chemical inertness of Au/Pd alloy plasmonic layer allows a non-destructive substrate recovery with the assistance of reactive plasma species. Furthermore, the generation of reactive oxygen species-rich plasma by introducing oxygen gas into argon plasma drastically reduces cleaning session to less than 1 minute. For our best knowledge, this is the shortest recovery time for any 3D plasmonic SERS substrate reported in the literature. Additionally, results indicate that the nano-roughness is more important for achieving optimal plasmonic activity than micro-roughness. Overall, the designed chestnut-like Au/Pd@/Cu2O substrate is a ready-to-use chip that possesses a decent signal enhancement ~ 105 and reveals remarkable robustness under multiple plasma treatment showing nearly 100% of self-recovery with no degradation of a plasmonic layer. These findings are of great significance for the development of novel reliable SERS substrates with low-cost manufacture which can be utilised with great success in a wide area of plasmonic biosensing. REFERENCES [1] A. Balčytis, M. Ryu, G. Seniutinas, J. Juodkazyte, B. C. C. Cowie, P. R. Stoddart, M. Zamengo, J. Morikawa, S. Juodkazis, “Black-CuO: Surface-enhanced Raman scattering and infrared properties”, Nanoscale, 7, 43, October 2015, 18299-18304.[2] J. Yu, M. Yang, C. Zhang, S. Yang, Q. Sun, M. Liu, Q. Peng, X. Xu, B. Man, F. Lei, “Capillarity-Assistant Assembly: A Fast Preparation of 3D Pomegranate-Like Ag Nanoparticle Clusters on CuO Nanowires and Its Applications in SERS”, Advanced Materials Interfaces, 5, 19, July 2018, 1-8. Figure 1

Design of Magnetic-Plasmonic Nanoparticle Assemblies via Interface Engineering of Plasmonic Shells for Targeted Cancer Cell Imaging and Separation.

Magnetic-plasmonic nanoparticles have received considerable attention for widespread applications. These nanoparticles (NPs) exhibiting surface-enhanced Raman scattering (SERS) activities are developed due to their potential in bio-sensing applicable in non-destructive and sensitive analysis with target-specific separation. However, it is challenging to synthesize these NPs that simultaneously exhibit low remanence, maximized magnetic content, plasmonic coverage with abundant hotspots, and structural uniformity. Here, a method that involves the conjugation of a magnetic template with gold seeds via chemical binding and seed-mediated growth is proposed, with the objective of obtaining plasmonic nanostructures with abundant hotspots on a magnetic template. To obtain a clean surface for directly functionalizing ligands and enhancing the Raman intensity, an additional growth step of gold (Au) and/or silver (Ag) atoms is proposed after modifying the Raman molecules on the as-prepared magnetic-plasmonic nanoparticles. Importantly, one-sided silver growth occurred in an environment where gold facets are blocked by Raman molecules; otherwise, the gold growth is layer-by-layer. Moreover, simultaneous reduction by gold and silver ions allowed for the formation of a uniform bimetallic layer. The enhancement factor of the nanoparticles with a bimetallic layer is approximately 107 . The SERS probes functionalized cyclic peptides are employed for targeted cancer-cell imaging and separation.

D-Shaped Photonic Crystal Fiber–Based Surface Plasmon Resonance Biosensors with Spatially Distributed Bimetallic Layers

This paper deals with the development and analysis of D-Shaped photonic crystal fiber (PCF) biosensors using surface plasmon resonance (SPR). A thin metal layer is deposited on the outer flat surface of the PCF that behaves as the plasmonic material. Analyte is filled in the outermost peripheral region of metal layer. Finite element method (FEM) with perfectly matched layer (PML) is applied to analyze the proposed sensors. Mode analysis is performed on the proposed structures to evaluate various parameters of SPR-based PCF sensors. Three D-shaped PCF structures have been proposed with silver (Ag), gold (Au) and two-half layers of both (Ag-Au) on its flat surface. The first two structures are analyzed to the range of wavelength where the SPR will occur to facilitate understanding of the third structure. It is observed that the structures with one metal have only one sensitive plasmonic peak whereas the structure with two metal layers has two sensitive plasmonic peaks, making it suitable candidate for two-molecule sensing present in a sample analyte. Good sensitivities and resolutions are achieved for both plasmonic peaks.

Sensitivity enhancement of surface plasmon resonance sensor using hybrid configuration of 2D materials over bimetallic layer of Cu–Ni

This Theoretical study aims at improving the sensitivity of surface plasmon resonance biosensor under angular interrogation. We observed that the sensor configuration composed of bimetallic layer of Cu–Ni attached with 2D materials MoS2/WS2/MoSe2/WSe2/graphene enhanced the sensitivity of the sensor to a great extends. The thickness of the bimetallic layers and the number of layers of 2D materials are optimized to achieve maximum sensitivity. Numerical results shows that sensitivity as high as 480∘/RIU is achieved for the well optimized bimetallic configuration consist of 35 nm of Cu and 20 nm of Ni thickness for the analyte refractive indices ranging from 1.33–1.335. Up on functionalizing the metal layers with bimolecular recognizing 2D materials, we noted that configuration with 35 nm of Cu, 15 nm of Ni with monolayer of 2D material WS2 enhanced the sensitivity as high as 426∘/RIU. We expect that such a simple structure and promising results will lead the proposed sensor as a suitable and potential candidate for detecting biomolecules organic elements and other analytes.

Enhanced sensitivity of bimetallic optical fiber SPR sensor based on MoS2 nanosheets

In this paper, we have fabricated and characterized a bimetallic optical fiber surface plasmon resonance (SPR) sensor, followed by molybdenum disulfide (MoS2) nanosheets have been coated on the surface of metal film. The performance of the sensor is discussed in terms of the sensitivity and the figure of merit (FOM) theoretically and experimentally. The effect of different thickness of Au/Ag film on the performance of the sensor was studied. The results indicate that the FOM of sensor with silver film is much higher than that with gold film, although gold film is conducive to the sensitivity improvement. Two types of sensors are fabricated, which are the sensor with silver layer and the sensor with bimetallic layers of silver and gold. The sensitivity of the sensor with silver film and the sensor with bimetallic layers are 2141 nm/RIU and 2487 nm/RIU, respectively; and the FOM values are 19.44 RIU−1 and 18.47 RIU−1, respectively. Then, it is theoretically confirmed that MoS2 has the potential to promote the sensitivity of SPR sensor, and the sensitivity is tuned by the number of layers of MoS2 nanosheets. MoS2 nanosheets successfully bridged the gold film with the help of chemical bonds. The sensitivity of the sensor with MoS2 nanosheets is 3061 nm/RIU, and its FOM value is 23.29 RIU−1.

Surface Plasmon Resonance sensor based on a D-shaped photonic crystal fiber with a bimetallic layer

The investigation of a D-shaped photonic crystal fiber sensor with a bimetallic layer for operation at the visible and infrared spectra is presented. The bimetallic layer is composed by silver and gold slabs deposited adjacently on the flat face of the fiber. It is shown that this architecture allows the excitation of two sharply distinguished plasmon resonance, which suggest potential applications for multiparameter sensing.