Showing papers on "Surface plasmon resonance published in 2022"

Multi-mode surface plasmon resonance absorber based on dart-type single-layer graphene

Abstract: In this paper, a multi-mode surface plasmon resonance absorber based on dart-type single-layer graphene is proposed, which has the advantages of polarization independence, tunability, high sensitivity, high figure of merit, etc. The device consists of a top layer dart-like patterned single-layer graphene array, a thicker silicon dioxide spacer layer and a metal reflector layer, and has simple structural characteristics. The numerical results show that the device achieves the perfect polarization-independent absorption at the resonance wavelengths of λI = 3369.55 nm, λII = 3508.35 nm, λIII = 3689.09 nm and λIV = 4257.72 nm, with the absorption efficiencies of 99.78%, 99.40%, 99.04% and 99.91%, respectively. The absorption effect of the absorber can be effectively regulated and controlled by adjusting the numerical values such as the geometric parameters and the structural period p of the single-layer graphene array. In addition, by controlling the chemical potential and the relaxation time of the graphene layer, the resonant wavelength and the absorption efficiency of the mode can be dynamically tuned. And can keep high absorption in a wide incident angle range of 0° to 50°. At last, we exposed the structure to different environmental refractive indices, and obtained the corresponding maximum sensitivities in four resonance modes, which are SI = 635.75 nm RIU−1, SII = 695.13 nm RIU−1, SIII = 775.38 nm RIU−1 and SIV = 839.39 nm RIU−1. Maximum figure of merit are 54.03 RIU−1, 51.49 RIU−1, 43.56 RIU−1, and 52.14 RIU−1, respectively. Therefore, this study has provided a new inspiration for the design of the graphene-based tunable multi-band perfect metamaterial absorber, which can be applied to the fields such as photodetectors and chemical sensors.

Non-Noble Plasmonic Metal-Based Photocatalysts.

Abstract: Solar-to-chemical energy conversion via heterogeneous photocatalysis is one of the sustainable approaches to tackle the growing environmental and energy challenges. Among various promising photocatalytic materials, plasmonic-driven photocatalysts feature prominent solar-driven surface plasmon resonance (SPR). Non-noble plasmonic metals (NNPMs)-based photocatalysts have been identified as a unique alternative to noble metal-based ones due to their advantages like earth-abundance, cost-effectiveness, and large-scale application capability. This review comprehensively summarizes the most recent advances in the synthesis, characterization, and properties of NNPMs-based photocatalysts. After introducing the fundamental principles of SPR, the attributes and functionalities of NNPMs in governing surface/interfacial photocatalytic processes are presented. Next, the utilization of NNPMs-based photocatalytic materials for the removal of pollutants, water splitting, CO2 reduction, and organic transformations is discussed. The review concludes with current challenges and perspectives in advancing the NNPMs-based photocatalysts, which are timely and important to plasmon-based photocatalysis, a truly interdisciplinary field across materials science, chemistry, and physics.

Plasmonic Biosensor With Gold and Titanium Dioxide Immobilized on Photonic Crystal Fiber for Blood Composition Detection

Abstract: This paper proposes a photonic crystal fiber (PCF) based plasmonic biosensor for the detection of various blood compositions like red blood cells (RBCs), hemoglobin (HB), white blood cells (WBCs), plasma, and water. The finite element method (FEM) has been used to simulate and quantitatively evaluate this biosensor. The gold and titanium dioxide coated PCF operates on the surface plasmon resonance (SPR) theory, where the gold layer acts as a plasmonic material, and the titanium dioxide layer improves adhesion between the gold layer and the PCF surface. SPR occurs at the interface between gold and the sensing channel, when the core propagation mode is coupled with the surface plasmon polariton (SPP) mode in the vicinity of the phase-matching point. Due to the occurrence of SPR, the loss peak is noticed in the core propagation mode, and this loss peak is extremely sensitive to the various blood compositions that each have their unique refractive index (RI) poured into the sensing channel of the PCF. The proposed biosensor has maximum wavelength sensitivity of 12400 nm/RIU. However, the maximum amplitude sensitivity is −574.3 RIU−1. Furthermore, with the maximum detection limit of 0.02, the refractive index resolution varies from $8.06\times {10}^{-6} {\mathrm {RIU}}$ to $5.0\times {10}^{-5} {\mathrm {RIU}}$ . As a result, it is safe to say that this biosensor will work admirably in terms of detecting blood compositions. Thus, the proposed biosensor will explore the broad realms of medical diagnostics.

Plasmonic Active “Hot Spots”‐Confined Photocatalytic CO2 Reduction with High Selectivity for CH4 Production

Abstract: Plasmonic nanostructures have tremendous potential to be applied in photocatalytic CO2 reduction, since their localized surface plasmon resonance can collect low‐energy‐photons to derive energetic “hot electrons” for reducing the CO2 activation‐barrier. However, the hot electron‐driven CO2 reduction is usually limited by poor efficiency and low selectivity for producing kinetically unfavorable hydrocarbons. Here, a new idea of plasmonic active “hot spot”‐confined photocatalysis is proposed to overcome this drawback. W18O49 nanowires on the outer surface of Au nanoparticles‐embedded TiO2 electrospun nanofibers are assembled to obtain lots of Au/TiO2/W18O49 sandwich‐like substructures in the formed plasmonic heterostructure. The short distance (< 10 nm) between Au and adjacent W18O49 can induce an intense plasmon‐coupling to form the active “hot spots” in the substructures. These active “hot spots” are capable of not only gathering the incident light to enhance “hot electrons” generation and migration, but also capturing protons and CO through the dual‐hetero‐active‐sites (Au‐O‐Ti and W‐O‐Ti) at the Au/TiO2/W18O49 interface, as evidenced by systematic experiments and simulation analyses. Thus, during photocatalytic CO2 reduction at 43± 2 °C, these active “hot spots” enriched in the well‐designed Au/TiO2/W18O49 plasmonic heterostructure can synergistically confine the hot‐electron, proton, and CO intermediates for resulting in the CH4 and CO production‐rates at ≈35.55 and ≈2.57 µmol g−1 h−1, respectively, and the CH4‐product selectivity at ≈93.3%.

Two-channel photonic crystal fiber based on surface plasmon resonance for magnetic field and temperature dual-parameter sensing.

Abstract: In this paper, a dual-parameter sensor based on surface plasmon resonance (SPR)-photonic crystal fiber (PCF) is proposed, which can be applied in detecting the magnetic field and temperature. In this sensor, two elliptical channels are designed on both sides of the fiber core. The left channel (Ch 1) is coated with gold film and filled with magnetic fluid (MF) to achieve a response to the magnetic field and temperature using SPR. The right channel (Ch 2) is coated with gold film as well as Ta2O5 film to improve the SPR sensing performance. Finally, Ch 2 is filled with polydimethylsiloxane (PDMS) to achieve a response to the temperature. The mode characteristics, structural parameters and sensing performance are investigated by the finite element method. The results show that when the magnetic field is in the range of 50-130 Oe, the magnetic field sensitivities of Ch 1 and Ch 2 are 65 pm Oe-1 and 0 pm Oe-1, respectively. When the temperature is in the range of 17.5-27.5 °C, the temperature sensitivities of Ch 1 and Ch 2 are 520 pm °C-1 and 2360 pm °C-1, respectively. By establishing and demodulating a sensing matrix, the sensor can not only measure the temperature and magnetic field simultaneously but also solve the temperature cross-sensitivity problem. In addition, when the temperature exceeds a certain value, the proposed sensor is expected to achieve dual-parameter sensing without a matrix. The proposed dual-parameter SPR-PCF sensor has a unique structure and excellent sensing performance, which are important for the simultaneous sensing of multiple basic physical parameters.

Identification of heavy metal ions from aqueous environment through gold, Silver and Copper Nanoparticles: An excellent colorimetric approach

Abstract: Heavy metal pollution has become a severe threat to human health and the environment for many years. Their extensive release can severely damage the environment and promote the generation of many harmful diseases of public health concerns. These toxic heavy metals can cause many health problems such as brain damage, kidney failure, immune system disorder, muscle weakness, paralysis of the limbs, cardio complaint, nervous system. For many years, researchers focus on developing specific reliable analytical methods for the determination of heavy metal ions and preventing their acute toxicity to a significant extent. The modern researchers intended to utilize efficient and discerning materials, e.g. nanomaterials, especially the metal nanoparticles to detect heavy metal ions from different real sources rapidly. The metal nanoparticles have been broadly utilized as a sensing material for the colorimetric detection of toxic metal ions. The metal nanoparticles such as Gold (Au), Silver (Ag), and Copper (Cu) exhibited localized plasmon surface resonance (LPSR) properties which adds an outstanding contribution to the colorimetric sensing field. Though, the stability of metal nanoparticles was major issue to be exploited colorimetric sensing of heavy emtal ions, but from last decade different capping and stabilizing agents such as amino acids, vitmains, acids and ploymers were used to functionalize the metal surface of metal nanoparticles. These capping agents prevent the agglomeration of nanoparticles and make them more active for prolong period of time. This review covers a comprehensive work carried out for colorimetric detection of heavy metals based on metal nanoparticles from the year 2014 to onwards.

Label-free plasmonic immunosensor for cortisol detection in a D-shaped optical fiber.

Abstract: Measuring cortisol levels as a stress biomarker is essential in many medical conditions associated with a high risk of metabolic syndromes such as anxiety and cardiovascular diseases, among others. One technology that has a growing interest in recent years is fiber optic biosensors that enable ultrasensitive cortisol detection. Such interest is allied with progress being achieved in basic interrogation, accuracy improvements, and novel applications. The development of improved cortisol monitoring, with a simplified manufacturing process, high reproducibility, and low cost, are challenges that these sensing mechanisms still face, and for which solutions are still needed. In this paper, a comprehensive characterization of a D-shaped fiber optic immunosensor for cortisol detection based on surface plasmon resonance (SPR) enabled by gold coating is reported. Specifically, the sensor instrumentation and fabrication processes are discussed in detail, and a simulation with its complete mathematical formalism is also presented. Moreover, experimental cortisol detection tests were performed for a detection range of 0.01 to 100 ng/mL, attaining a logarithmic sensitivity of 0.65 ± 0.02 nm/log(ng/mL) with a limit of detection (LOD) of 1.46 ng/mL. Additionally, an investigation of signal processing is also discussed, with the main issues addressed in order to highlight the best way to extract the sensing information from the spectra measured with a D-shaped sensor.

Plasmonic Nanozyme of Graphdiyne Nanowalls Wrapped Hollow Copper Sulfide Nanocubes for Rapid Bacteria‐Killing

Abstract: Plasmon stimulation represents an appealing way to modulate enzyme mimic functions, but utilization efficiency of plasmon excitation remains relatively low. To overcome this drawback, a heterojunction composite based on graphdiyne nanowalls wrapped hollow copper sulfide nanocubes (CuS@GDY) with strong localized surface plasmon resonance (LSPR) response in the near‐infrared (NIR) region is developed. This nanozyme can concurrently harvest LSPR induced hot carriers and produce photothermal effects, resulting in dramatically increased peroxidase‐like activity when exposed to 808 nm light. Both experimental results and theoretical calculations show that the remarkable catalytic performance of CuS@GDY is due to the unique hierarchical structure, narrow bandgap of GDY nanowalls, LSPR effect of CuS nanocages, fast interfacial electron transfer dynamics, and carbon vacancies on CuS@GDY. This plasmonic nanozyme exhibits rapid, efficient, broad‐spectrum antibacterial activity (>99.999%) against diverse pathogens (methicillin‐resistant Staphylococcus aureus, Staphylococcus aureus, and Escherichia coli). This study not only sheds light on the mechanism of the nanozyme‐/photocatalysis coupling process, but also opens up a new avenue for engineering plasmonic NIR light driven nanozymes for rapid synergistic photothermal and photo‐enhanced nanozyme therapy.

Research advances on surface plasmon resonance biosensors

Abstract: The surface plasmon resonance (SPR) phenomenon is of wide interest due to its sensitivity to changes in surface refractive index for the label-free, highly sensitive and rapid detection of biomarkers. This paper reviews research progress on SPR biosensors modified with different substrate structures and surface materials, surface plasmon resonance imaging (SPRI), and SPR-enhanced electrochemiluminescent (ECL) biosensors for applications in biosensing in the last five years. This paper focuses on the research on the application of the SPR phenomenon in the field of bio-detection, reviews the sensing characteristics of SPR biosensors with substrate structures of prisms, gratings, and optical fibers, and summarizes and analyzes the sensitivity and interference resistance of SPR sensors with surface modification of different materials (high-refractive index dielectric films, metallic micro- and nanostructures, and surface antifouling materials). Considering that imaging is an important tool for biomedical detection, this paper reviews the research progress on SPRI technology in the field of biomedical detection. In addition, this paper also reviews the research progress on SPR-enhanced ECL biosensors in the field of biosensing. Finally, this paper provides an outlook on the development trends of biosensing technology in terms of portable high-precision SPR sensors, reduction of self-loss of thin film materials, optimization of image processing techniques and simplification of electrode modification for ECL sensors.

Principles of surface-enhanced Raman spectroscopy

Abstract: Surface-enhanced Raman spectroscopy (SERS) has manifested its power in clinical applications, benefitted from the ability to provide fingerprint information even down to single-molecule level. In this chapter, we will guide you through the principles of SERS, including the electromagnetic field enhancement and chemical enhancement, with emphasis on the surface plasmon resonance effect. Some practical issues, such as spectral analysis and selection of SERS substrates, will also be briefed from the mechanistic understanding. The main purpose of this chapter is to provide you the necessary background to understand the literatures and start your own journey of applying SERS for clinical diagnosis.

Surface plasmon resonance biosensor based on graphene layer for the detection of waterborne bacteria

Abstract: As a result of the risks that waterborne bacteria bring to the human body, identifying them in drinking water has become a global concern. In this article, a highly sensitive surface plasmon resonance (SPR) biosensor consisting of prism, Ag, graphene, affinity layer and sensing medium is proposed for rapid detection of the waterborne bacteria. Four SPR‐based sensors are first studied with the structures prism/Ag/sensing medium, prism/Ag/affinity layer/sensing medium, prism/Ag/graphene/sensing medium, and prism/Ag/graphene/affinity layer/sensing medium. The latter structure is found to have the highest sensitivity so it is considered for further investigations. Four different commonly used prisms are then demonstrated which are N‐FK51A, 2S2G, SF10 and BK7. The structure with the prism N‐FK51A is found to correspond to the highest sensitivity so it is considered for further investigations. The structure parameters are then optimized. The proposed SPR sensor can achieve high sensitivity of about 221.63 °/RIU for Escherichia coli and 178.12 °/RIU for Vibrio cholera bacteria with an average value of 199.87 °/RIU. We believe that the proposed structure will open a new window in the field of microorganism detections.

Ultrasensitive detection of SARS-CoV-2 nucleocapsid protein using large gold nanoparticle-enhanced surface plasmon resonance

Abstract: The COVID-19 pandemic has created urgent demand for rapid detection of the SARS-CoV-2 coronavirus. Herein, we report highly sensitive detection of SARS-CoV-2 nucleocapsid protein (N protein) using nanoparticle-enhanced surface plasmon resonance (SPR) techniques. A crucial plasmonic role in significantly enhancing the limit of detection (LOD) is revealed for exceptionally large gold nanoparticles (AuNPs) with diameters of hundreds of nm. SPR enhanced by these large nanoparticles lowered the LOD of SARS-CoV-2 N protein to 85 fM, resulting in the highest SPR detection sensitivity ever obtained for SARS-CoV-2 N protein.

A Combinatorial Approach towards Antibacterial and Antioxidant Activity Using Tartaric Acid Capped Silver Nanoparticles

Abstract: The convenient synthetic strategy for the one-pot synthesis of silver nanoparticles capped by tartaric acid with a controlled size is reported here. Their characterization is revealed through spectroscopic protocols, such as UV/Vis and FTIR, while SEM, DLS and a Zetasizer revealed the surface morphology, size distribution and surface charge on the nanoparticles. The surface plasmon resonance (SPR) band was observed at 406 nm with 1.07 a.u absorbance, the image for SEM shows that the particles were monodispersed and spherical in shape, while the z-average size distribution of AgNPs/TA in a colloidal solution was found to be 79.20 nm and the surface charge was monitored as −28.2 mV. The antibacterial activities of these capped nanoparticles alone and in synergism with selected fluoroquinolones (ofloxacin, sparfloxacin, ciprofloxacin and gemifloxacin) and macrolides (erythromycin and azithromycin) were assessed on selected Gram-negative as well as Gram-positive organisms by employing the disc diffusion method. Antioxidant activity against the DPPH (1,1-diphenyl-2-picrylhydrazyl) was also evaluated using the standard assay method. The antibacterial activity of the antibiotics has been increased against studied microorganisms, showing the positive synergistic effect of the capped nanoparticles. A potential therapeutic application of AgNPs/TA in combination with antibiotics is determined from the results of the present research. These capped nanoparticles also possess good antioxidant activity and, therefore, can be used in various fields of biomedical sciences.

Ultrasensitive detection of SARS-CoV-2 nucleocapsid protein using large gold nanoparticle-enhanced surface plasmon resonance

Abstract: The COVID-19 pandemic has created urgent demand for rapid detection of the SARS-CoV-2 coronavirus. Herein, we report highly sensitive detection of SARS-CoV-2 nucleocapsid protein (N protein) using nanoparticle-enhanced surface plasmon resonance (SPR) techniques. A crucial plasmonic role in significantly enhancing the limit of detection (LOD) is revealed for exceptionally large gold nanoparticles (AuNPs) with diameters of hundreds of nm. SPR enhanced by these large nanoparticles lowered the LOD of SARS-CoV-2 N protein to 85 fM, resulting in the highest SPR detection sensitivity ever obtained for SARS-CoV-2 N protein.

Au surface plasmon resonance promoted charge transfer in Z-scheme system enables exceptional photocatalytic hydrogen evolution

Abstract: Highly efficient photocatalytic water reduction to evolve hydrogen can be achieved by the construction of Z-scheme systems that mimics natural photosynthesis. However, coupling appropriate semiconductors with suitable water reduction potential still remains challenging. Herein, we report a novel Z-scheme system, based on the Au decorated 5,10,15,20-tetrakis(4-trimethylammoniophenyl) porphyrin tetra(p-toluene sulfonate) functionalized iron-doped carbon nitride. We prepared carbon nitride by varying the amount of iron dopant and then functionalized with porphyrin to obtain heterostructure photocatalyst. Owing to the strong interfacial contact and proper band alignment, a Z-scheme system is fabricated. Finally, we deposited Au nanoparticles over the surface of the as-fabricated Z-scheme system to promote the surface redox properties via efficient charge carrier’s separation and transfer. The 3Au-3 P/30Fe-CN photocatalyst achieved excellent H2 evolution activity by producing 3172.20 µmol h−1 g−1 under UV–visible irradiation. The calculated quantum efficiencies for 3Au-3 P/30Fe-CN photocatalyst at 365 and 420 nm irradiation wavelengths are 7.2% and 3.26%, respectively. The experimentally observed efficiency of our photocatalyst is supported by the density functional theory simulations in terms of the lowest work function and strong electrostatic interaction among the constituents of Z-scheme system.