Sharp Surface Plasmon Resonance Research Articles

Ecofriendly ratiometric colorimetric determination of mercury(II) ion in environmental water samples using gallic acid-capped gold nanoparticles

Today, the monitoring and determination of heavy metal pollutants in the environment is an essential requirement for the environmental and research communities. Mercury ion is one of the most hazardous heavy metals, and scientists are trying to develop new methods for its detection. In this study, a new colorimetric sensor based on aggregation gallic acid-capped gold nanoparticles (GA-AuNPs) for the determination of mercury ions in environmental water samples was presented. The green synthesized GA-AuNPs exhibited a sharp surface plasmon resonance peak at 515 nm. The addition of mercury ions changed the surface properties of GA-AuNPs, resulting in the formation of a new peak near 670 nm due to the aggregation of GA-AuNPs, and an obvious color change from red to purple occurred. Thus, mercury ions were detected based on the change in the absorbance ratio (A670/A515). The developed sensor can determine the mercury ions in the concentration range of 78.0 nM to 8.3 µM with a detection limit of 5.5 nM. Based on the Environmental Protection Agency (EPA) and the World Health Organization (WHO) reports, the amount of Hg2+ ions in fresh water should be between 10.0 and 30.0 nM. The results indicate that the developed sensor can detect and determine trace amounts of Hg2+ ions in environmental water samples.

Biosynthesized silver nanoparticles based on bitter orange bloom extract and its application for the determination of cyanide ion in environmental samples

Developing new methods for detecting and determining toxic anions is an essential parameter from waste sources for industrial and environmental scientists. This study presented, a new process for the biosynthesis of silver nanoparticles (AgNPs) based on the bitter orange bloom extract and its potential as a highly selective and sensitive chemosensor for detecting and quantifying cyanide ions. These biosynthesized AgNPs have a sharp and intense surface plasmon resonance (SPR) peak around 405 nm. AgNPs with a yellow color can be changed to colorless in the presence of a certain concentration of cyanide ions due to forming a new adduct between AgNPs and cyanide ions. Hence, the SPR intensity of AgNPs decreases, and the color of the solution becomes colorless. The sensor response to cyanide ions was linear in the concentration range of 49.7 to 1208.8 nM, and the detection limit was equal to 7.9 nM. As an applicable alternative, this assay is highly capable of qualitative and quantitative measurements of cyanide ions in the waste and toxic samples.

NiO nanoparticles, an algorithm of their biosynthesis, toxicity, and biomedical activities

The green synthesis of metal oxide nanoparticles is interestingly becoming familiar as the reason of its non-toxicity, economical, eco-friendly, and commerciality. The secondary metabolites and bioactive molecules in biomaterial extract play an important role of reducing, capping, stabilizing and chelating activities to form the nanoparticles as a substitute of hazardous chemical surfactants. Hence this present work concentrated on the biogenic synthesis of NiO nanoparticles using grains extract of Oryza longistaminata (red rice), and their toxicity assessment as well as biomedical applications. The synthesized nanoparticles were widely characterized by using several analytical and biomedical techniques. The reduction mechanism of Ni2+ ions using major active phytocompound in red rice grains extract was stated. UV–visible spectroscopic analysis revealed the formation of NiO nanoparticles by emerging the sharp surface Plasmon resonance band at 326 nm. The absorption peaks of red rice grains extract at 206, 260, 330 and 410 nm stated the presence of phytocompounds in them. X-ray diffraction pattern explicated the high crystallinity of NiO nanoparticles and their average crystallite size was found to be at 36 nm. The diffraction pattern of red rice grains revealed the amorphous characteristic. Fourier transform infrared analysis displayed the different vibrational functional groups of nanoparticles and red rice grains. Dynamic light scattering analysis showed the particle size distribution was in between 30-65 nm. High-resolution transmission electron microscopic analysis showed the hexagonal, rectangular, oval and spherical shaped polymorphism of NiO nanoparticles and their size was in 25-50 nm. Energy dispersive X-ray spectrum and mapping analyses validated the formation of NiO nanoparticles by the major existence of Ni and O elements. The high toxicity of nanoparticles towards MG-63 osteosarcoma cancer cells was revealed at 94.69% in 100 μg/mL concentration. The nanoparticles showed no severe toxicity against HEK293 normal cells and red blood cells till higher concentration. The biomedical analyses such as antioxidant, anti-inflammatory and anti-diabetic activities exposed the potential bio-drug activity of NiO nanoparticles with maximum activity of 86.22, 84.23 and 85.18% in the high concentration of 80 μg/mL. The antibacterial activity divulged the good bactericidal drug nature of NiO nanoparticles against both Gram-positive (S. aureus and B. Subtilis) and Gram-negative (S. typhi and K. pneumonia) bacteria with low MBC/MIC ratio. As per the assessment of results, the biosynthesized NiO nanoparticles have non-carcinogenic, high biocompatible and potent nature and it suggests that they can be used as therapeutic candidates in biomedical, clinical and pharmaceutical fields for treating various diseases.

Exploring the biological application of Penicillium fimorum-derived silver nanoparticles: In vitro physicochemical, antifungal, biofilm inhibitory, antioxidant, anticoagulant, and thrombolytic performance

This study showed the anti-candida, biofilm inhibitory, antioxidant, anticoagulant, and thrombolytic properties of biogenic silver nanoparticles (AgNPs) fabricated by using the supernatant of Penicillium fimorum (GenBank accession number OQ568180) isolated from soil. The biogenic AgNPs were characterized by using different analytical techniques. A sharp surface plasmon resonance (SPR) peak of the colloidal AgNPs at 429.5 nm in the UV–vis spectrum confirmed the fabrication of nanosized silver particles. The broth microdilution assay confirmed the anti-candida properties of AgNPs with a minimum inhibitory concentration (MIC) of 4 μg mL−1. In the next step, the protein and DNA leakage assays as well as reactive oxygen species (ROS) assay were performed to evaluate the possible anti-candida mechanisms of AgNPs representing an increase in the total protein and DNA of supernatant along with a climb-up in ROS levels in AgNPs-treated samples. Flow cytometry also confirmed a dose-dependent cell death in the AgNPs-treated samples. Further studies also confirmed the biofilm inhibitory performance of AgNPs against Candia albicans. The AgNPs at the concentrations of MIC and 4*MIC inhibited 79.68 ± 14.38% and 83.57 ± 3.41% of biofilm formation in C. albicans, respectively. Moreover, this study showed that the intrinsic pathway may play a significant role in the anticoagulant properties of AgNPs. In addition, the AgNPs at the concentration of 500 μg mL−1, represented 49.27%, and 73.96 ± 2.59% thrombolytic and DPPH radical scavenging potential, respectively. Promising biological performance of AgNPs suggests these nanomaterials as a good candidate for biomedical and pharmaceutical applications.

Application of Forsskaolea tenacissima mediated gold nanoparticles in dyes discolouration, antibiotics removal, and metal ions detection

• Synthesis of F. tenacissima aqueous and ethanolic extracts mediated AuNPs. • Catalytic properties of the synthesized AuNPs in dyes degradation/reduction. • Antibiotics removal by synthesized AuNPs from tap and river water samples. • Metal ions sensing by synthesized AuNPs in tap and river water samples. Synthesis of nanoparticles using plant extract is environment-friendly, cost-effective, and sustainable. This study reports the synthesis of aqueous and ethanolic extracts mediated gold nanoparticles of aerial parts of F. tenacissima (FTAAuNPs) using chloroauric acid. The synthesized nanoparticles obtained from aqueous and ethanolic extracts under sunlight in 1:15 and 1:10 ratios with localized surface plasmon resonance (LSPR) peaks at 533 nm exhibited sizes of 15.7 nm and 27.6 nm, respectively, as revealed by scanning electron, transmission electron, and atomic force microscopic (SEM, TEM, AFM) techniques. Sharp intense surface plasmon resonance (SPR) peaks were obtained at basic pH (8 to 11), however, the same peaks broadened and reduced at elevated temperatures. FTAAuNPs demonstrated an efficient removal (>80%) of dyes such as methylene blue (70%), Congo red (80%), methyl orange (82%), Rhodamine B (50%), ortho -nitrophenol (85%) and para -nitrophenols (85%), and antibiotics (amoxicillin, levofloxacin, doxycycline) up to 90%. Furthermore, FTAAuNPs were successfully used for sensing of Pb ++ , Cu ++ , Ni ++ , and Zn ++ ions in tap and river water samples. Hence, this study offers simple, cost effective, and efficient removal of pollutants/hazards in the water samples, and could solve water and sanitation problems especially in Pakistan.

Exploitation of SnO2/Polypyrrole Interface for Detection of Ammonia Vapors Using Conductometric and Optical Techniques: A Theoretical and Experimental Analysis.

This study describes the construction of a lab-built Surface Plasmon Resonance (SPR) system for gas sensing applications employing a highly sensitive and trustworthy optical approach. The nanocomposite thin film of tin oxide (SnO2) and Polypyrrole (PPy) were prepared for sensing highly toxic gas, i.e., ammonia (NH3) gas. The gas sensor was validated by both optical and conductometric techniques of gas sensing. The optical SPR gas sensor is based on the change in refractive index at the SnO2/Polypyrrole (PPy) interface with gas adsorption (NH3). The thickness of SnO2 and Polypyrrole thin films was optimised using theoretical calculations for a sharp SPR reflectance curve. The manuscript also offers theoretical SPR curves for different PPy and SnO2 layer thicknesses. To support the theoretical conclusions, the effects of NH3 gas on the prism/Au/SnO2/Polypyrrole system were also investigated experimentally. In comparison to other research described in the literature, it was observed that the constructed sensor’s sensitivity was higher. The obtained results demonstrate the utility of the SPR setup in the investigation of the interactions of adhered gas molecules with dielectrics and gas sensing. For conductometric gas sensing studies, the film having optimised thicknesses for sharp SPR reflectance curves was separately prepared on Interdigitated Electrodes. At a low working temperature of roughly 150 °C, the sensing response of the constructed film was observed and found to be maximal (60).

Antibacterial Activity of In Situ Generated Silver Nanoparticles in Hybrid Silica Films

Herein we present silver nanoparticles (AgNPs)-doped inorganic–organic hybrid silica films on glass and polypropylene substrates. A hybrid inorganic–organic silica sol in alcoholic medium was prepared at room temperature using TEOS, GLYMO, and APTES. Silver nanoparticles were generated in situ within the hybrid silica sol. AgNPs-SiO2 film was obtained by dip coating method following drying at 80 °C. FTIR spectra shows several vibrational bands of the hybrid silica network and amine functionalization. AgNPs formation was observed from the XRD spectra of the dried film. UV–Visible spectra show sharp surface plasmon resonance (SPR) band centered at 412 nm arising from the evenly distributed silver nanoparticle inside the silica film that was supported by morphological characterization. Both the coated films showed good antibacterial activity against E. coli bacterial strain by forming a zone of inhibition in the agar diffusion test. The antibacterial efficiency for coated glass and polypropylene was 72.5% and 83.75%. This coating approach provides a straight-forward solution to prepare antibacterial coatings on various substrates especially on plastics, where low temperature processing is necessary.

Fabrication of PVA-Silver nanoparticle composite film for elimination of microbial contaminant from effluent

The effluent contains many harmful microbes which should be eliminated before it is discharged into a water body. Silver nanoparticles (AgNPs) being high-quality significance and have a great impact on this research field as it inhibits microbial proliferation and infection. Therefore, it may use for Bioremediation purposes, our laboratory is fascinated by the production of polymer matrix entrapment silver nanoparticles for in situ bio-remediation purposes. The AgNPs was prepared from sawdust by decoction method. The yellowish solution turns into dark brown colour indicating the formation of AgNPs. A sharp SPR (Surface Plasmon Resonance) band formation in UV-vis spectroscopy scan establishes the formation and stability of silver nanoparticles in an aqueous solution. SEM microphotograph indicated roughly spheroidal structure with (63±3) nm average diameters of newly synthesized AgNp. Polyvinyl alcohol (PVA) is eco-friendly and non-toxic to the environment was chosen for the preparation of polymeric matrix. The non-toxic concentration (1 μg/mL) of AgNp was dispersed into PVA solution followed by cross-linked with maleic acid. PVA- maleic acid is cross-linked by the formation of an ester bond, whereas silver nanoparticles physically entrap into the cross-linked matrix. The silver nanoparticles were released from the matrix nearly after 10 min of swelling of the composite film. In a microbial assay using E. coli agar medium, PVA-AgNp composite film shows the significant killing of microorganisms. Microbial elimination is measured indirectly by pH measurement and dissolved oxygen concentration measurement of the effluent in situ against RO- water, taken as control. The dissolved oxygen concentration from RO water and effluent water was measured on Day “0” followed by treatment and incubation at the BOD chamber. The treatment with PVA-AgNp composite film reduced the BOD Level and increase dissolved oxygen level simultaneously increasing the quality of water.

Antioxidant, antibacterial, and catalytic performance of biosynthesized silver nanoparticles of Rhus javanica, Rumex hastatus, and Callistemon viminalis

Rhus javanica (Anacardiaceae) containing abundant glucopyranosidal constituents, is traditionally used to treat gastric and duodenal ulcer, dysentery, and diarrhea. Rumex hastatus (Polygonaceae) widely distributed in Pakistan, has traditional importance in treating wound healing, jaundice, rheumatism, and skin diseases. Callistemon viminalis (Myrtaceae), a rich source of essential oils, saponins, triterpenoids, phloroglucinols, and flavonoids is used in industries, perfumes, nutrition, and cosmetics. Taking the importance of the subject plants, this study is designed to synthesize silver nanoparticles via aqueous extracts of R. javanica (RJAgNPs), R. hastatus (RHAgNPs), and C. viminalis (CVAgNPs). Synthesis, surface, and sizes of silver nanoparticles (AgNPs) were confirmed using spectroscopic techniques including ultraviolet–visible (UV–Vis), Fourier transform-infrared (FT-IR), and scanning electron microscopy (SEM). AgNPs were produced in ratios 1:15, 1:16, and 1:9 and inferred via appearance of a sharp surface plasmon resonance (SPR) absorption peak (400–435 nm), which represented well-defined, stable, and spherical AgNPs. From SEM analysis, the sizes of RJAgNPs, RHAgNPs, and CVAgNPs were found to be 67 nm, 61 nm, and 55 nm, respectively. The synthesized AgNPs exhibited potential free radical scavenging, antibacterial, and catalytic properties in degradation of dyes including Congo red, methylene blue, methyl orange, rhodamine B, ortho and para-nitrophenols, and several food colours. Hence, the subject AgNPs in the current study might display promising role in drug development and remediation of environmental/industrial effluents.

Biomimetic Synthesis, Characterization, and Evaluation of Fluorescence Resonance Energy Transfer, Photoluminescence, and Photocatalytic Activity of Zinc Oxide Nanoparticles

Owing to the development of nanotechnology, biosynthesis of nanoparticles (NPs) is gaining considerable attention as a cost-effective and eco-friendly approach that minimizes the effects of toxic chemicals used in NP fabrication. The present work reports low-cost phytofabrication of zinc oxide (ZnO) NPs employing aqueous extracts of various parts (leaves, stems, and inflorescences) of Tephrosia purpurea (T. purpurea). The formation, structure, morphology, and other physicochemical properties of ZnO NPs were characterized by ultraviolet–visible (UV–Vis) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, and dynamic light scattering (DLS). UV–Vis spectral analysis revealed sharp surface plasmon resonance (SPR) at around 250–280 nm, while the XRD patterns confirmed distinctive peaks indices to the crystalline planes of hexagonal wurtzite ZnO NPs. TEM analysis confirmed the presence of spherical-shaped ZnO NPs with average particle sizes (PS) between 25–35 nm, which was in agreement with the XRD results. FTIR analysis revealed that phenolics, flavonoids, amides, alkaloids, and amines present in the plant extract are responsible for the stabilization of the ZnO NPs. Further, the hydrodynamic diameter in the range of 85–150 nm was measured using the DLS technique. The fluorescence resonance energy transfer (FRET) ability of biogenic ZnO NPs was evaluated, and the highest efficiency was found in ZnO NPs synthesized via T. purpurea inflorescences extract. Photoluminescence (PL) spectra of biogenic ZnO NPs showed three emission peaks consisting of a UV–Vis region with high-intensity compared to that of chemically synthesized ZnO NPs. The biosynthesized ZnO NPs showed photocatalytic activity under solar irradiation by enhancing the degradation rate of methylene blue (MB). Among the prepared biogenic ZnO NPs, T. purpurea leaves mediated with NPs acted as the most effective photocatalyst, with a maximum degradation efficiency of 98.86% and a half-life of 84.7 min. This is the first report related to the synthesis of multifunctional ZnO NPs using T. purpurea, with interesting characteristics for various potential applications in the future.

Effect of CTABr (surfactant) on the kinetics of formation of silver nanoparticles by Amla extract

The work reported for the first time in this article describes the kinetic study of silver nanoparticles formation using Phyllanthus emblica amla extract. The synthesized silver particles exhibit an intense surface plasmon resonance band in the visible region at 455 nm. The variation in concentrations of amla extract, Ag+ ions, cetyltrimethyl ammonium bromide (CTABr), and reaction time play crucial roles for nucleus formation and the growth processes. The Ag+ ions reduction into metallic Ag0 is due to the presence of polyphenolic groups in the amla extract and thereafter, their agglomeration into nanoparticles. Due to the formation of spherical Ag-nanoparticles there is a appearance of a sharp surface plasmon resonance band in the UV–visible region. Silver nanoparticles (AgNPs) were characterized by TEM, XRD and FTIR techniques.

Performance analysis of graphene-based surface plasmon resonance biosensor for blood glucose and gas detection

The present study exhibits excellent sensing characteristics of graphene-based prism-coupled surface plasmon resonance (SPR) biosensor for effectual sensing of both glucose concentrations in human blood samples in the range 25–175 mg/dl and gas with refractive index variations from 1.0000 to 1.0007 at a wavelength of 589 nm. The foremost attractiveness of the proposed SPR biosensor lies with excellent optical properties of N-FK51A-based glass prism along with the inclusion of a gold layer and a thin graphene layer. Transfer matrix method and angular interrogation technique are employed to envisage sharp SPR reflectance curves by optimizing the thickness of the gold layer and number of graphene layers. Aside this, an excellent electric field enhancement factor is accomplished near the graphene and sensing layer interface, which dramatically escalates the absorption of glucose and gas analytes. Subsequently, several performance measuring factors such as sensitivity, detection accuracy, resonance angle shift, and quality factor are thoroughly scrutinized and compared with other conventional SPR sensors. Moreover, simulation results reveal some noteworthy upshots like sensitivity of 275.15°/RIU, detection accuracy of 1.41/°, and quality factor of 76.2 that are obtained for glucose analytes, whereas sensitivity of 92.1°/RIU, detection accuracy of 2.55/° and quality factor of 230.2 are attained for gaseous analytes. Interestingly, it is found that the aforementioned parameters fitted excellently with a linear trend line, which leads to accurate investigation of glucose concentration as well as gaseous analytes. Hence the suggested structure opens up an avenue for suitable biomedical application.

Gold nanopillar array with sharp surface plasmon resonances and the application in immunoassay

Nanoimprinting followed by metal deposition is a low-cost, high-throughput, and highly reproducible process for the fabrication of large-size plasmonic substrates required for commercial products. However, the plasmonic substrates prepared by the process usually have very broad surface plasmon resonances, which cannot be well reproduced by numerical simulations. The poor agreement between experiments and calculations has prevented the detailed analysis of the field enhancement behavior and the improvement of the performance as plasmonic substrates. In this work, we demonstrate that large-area plasmonic substrates with sharp surface plasmon resonances, which can be well reproduced by numerical simulations, are produced by sputter-deposition of gold (Au) on a commercially available nanoimprinted substrate. The good agreement between experiments and simulations allow us to identify the locations and field distributions of the hot spots. The angle dependence of specular reflectance and diffuse reflectance measurements in combination with numerical simulations reveal that a dipolelike bright mode and a higher-order dark mode exist at gaps between Au nanorods. Finally, we demonstrate the application of the developed plasmonic substrates for surface-enhanced fluorescence in sandwich immunoassays for the detection of influenza virus nucleoprotein. We show that the sharp resonance and the capability of precise tuning of the resonance wavelength significantly enhance the luminescence signal.

Green Synthesis of Silver Nanoparticles from Leaf Extract of Nyctanthes arbor-tristis L. and Assessment of Its Antioxidant, Antimicrobial Response

The UPLC-Q-TOF–MS/MS analysis of ethanol extract of leaf confirmed the presence of important flavonoids like rutin (RT 5.95), hesperidin (RT 5.99), quercitrin (RT 6.33) and kaempferol-3-O-glucoside (RT 6.82). Photo-induced green synthesis of silver nanoparticles was reported in Nycanthes arbor-tristis. Nanoparticles were efficiently synthesized after mixing of 1% ethanol leaf extract and 1 mM silver nitrate solution under 10 min light exposure at room temperature. The UV–Vis spectrum of the brown colored reaction mixture showed sharp surface plasmon resonance at 460 nm. It confirmed the biosynthesis of silver nanoparticles. Nanoparticles were characterized by using SEM, TEM, and EDX. The results suggest that synthesized nanoparticles lie in the range of 10–50 nm. XRD, SAED and AFM data confirmed the polycrystalline nature of biosynthesized nanoparticles. Silver nanoparticles exhibited strong antibacterial activity than extract. All bacterial clinical isolates were sensitive to nanoparticles. Methicilin resistant Staphylococcus aureus was most susceptible than other isolates. The silver nanoparticles also exhibited good free radical scavenging activity (EC50 670.67 ± 15.70 µg/ml).

Graphene-MoS2-Au-TiO2-SiO2 Hybrid SPR Biosensor: A New Window for Formalin Detection

In this article, numerically a surface plasmon resonance (SPR) biosensor is developed based on Graphene-M­­­­OS2-Au-TiO2-SiO2 hybrid structure for formalin detection. This developed sensor sensed the presence of formalin by applying attenuated total reflection (ATR). In ATR method, we developed and observed two characteristics curve, one is “SPR angle versus minimum reflectance (Rmin)” and another is “SPR frequency (SPRF) versus maximum transmittance (Tmax). In the proposed sensor, Chitosan is used as probe legend to perform specific reaction with the formalin (40% formaldehyde) as target legend. Here, graphene and MoS2 both are used as biomolecular acknowledgment element (BAE). And TiO2 as well as SiO2 bilayers are used to improve sensor sensitivity and Gold (Au) is to sharp SPR curve. In numerical results, the variation of SPRF and SPR angle for inappropriate sensing of formalin is quiet insignificant which confirms the absence of formalin. On the other hand, these variations for appropriate sensing is considerably significant that confirms the presence of formalin. At the end of this article, a study of variation of sensitivity of the proposed biosensor in corresponding to the increment of refractive index with a refractive index step 0.01 RIU is measured. In inclusion of TiO2-SiO2 bilayers with Graphene-M­­­­OS2, maximum sensitivity of 85.375% more is numerically reported.

Biosynthesis, Characterization and Biological Activities of Silver Nanoparticles from Pogostemon cablin Benth. Methanolic Leaf Extract.

This study reports the biosynthesis of silver nanoparticles (AgNPs) using methanolic leaf extract of Pogostemon cablin Benth. (Patchouli) as a reducing agent, and their potent biological (antibacterial, antioxidant and anticancer) activities. The P. cablin extract when exposed to silver nitrate reduced silver ions to form crystalline AgNPs within 1 h of incubation at room-temperature. UV-visible spectra showed a sharp surface plasmon resonance (SPR) at around 430 nm for the biosynthesized AgNPs and the XRD pattern indicated the crystalline planes of the face centered cubic silver. The FE-SEM analysis revealed the occurrence of predominant spherical shaped AgNPs with a huge disparity in their particle size distribution with an average size of 25 nm, while, the FTIR data confirmed the bio-reduction and capping of AgNPs by several phytocompounds present in the methanolic leaf extract. AgNPs effectively inhibited the growth of all the tested human pathogenic bacterial strains (Bacillus subtilis, Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli), while, the methanolic leaf extract failed to inhibit the growth of S. aureus and P. aeruginosa. AgNPs showed the highest free radical scavenging activity (79.0 ± 0.76%) compared to methanolic leaf extract (68.3 ± 0.68%) at 100 μg/ml. Further, the cytotoxicity study using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) confirmed that AgNPs successfully inhibited the human colon adenocarcinoma cell line (HT-29) in a dose dependent manner. At higher concentrations (500 μg/ml), only 4% of cells survived after 72 hrs of exposure with IC50 value of 120 μg/ml. Thus, these findings offer a new source of biomolecules with diverse biological activities.

Design and analysis of graphene–MoS2 hybrid layer based SPR biosensor with TiO2–SiO2 nano film for formalin detection: numerical approach

In this paper, a Surface Plasmon Resonance (SPR) biosensor has been numerically developed that used Graphene–MoS2–Au–TiO2–SiO2 hybrid structure for the detection of formalin. This developed sensor has been sensed the presence the formalin based on attenuated total reflection (ATR) method by observing the change of “surface plasmon resonance angle-the change of minimum reflectance attributor” and “the resonance frequency characteristics (RFC)-maximum transmittance attributor”. Chitosan has been used as probe sensing medium to accelerate particular reaction with the formalin. Here, graphene is used as biomolecular recognition element because of its high adsorption ability and optical characteristics which helps to improve sensor sensitivity, MoS2 used for it has larger band gap, high fluroscence quenching ability, higher optical absorption efficiency, TiO2–SiO2 bilayer as the improvement of sensitivity and Gold (Au) as the sharp SPR curve. Numerical results give the impression that the variation of RFC and SPR angle for improper sensing of formalin is quiet negligible that confirms no formalin is detected whereas for proper sensing these change are considerably countable that confirms the detection of formalin. From the sensor sensitivity analysis, owing to add TiO2–SiO2 bilayer with Graphene–MoS2 Hybrid layer, maximum sensitivity of 85.375% has been numerically resulted. This high sensor performance is for taking advantages of Graphene surface high selectively which detect bio molecular compounds through pi-stacking force, larger work function (5.1 eV) of MoS2 which allows the high sensitive detection of bio targets and Rich plasmon happens at the TiO2–SiO2 interface.

Copper nanoparticles prepared by pulsed exploding wire

In this work copper nanopowder was created at different liquidmedias like DDDW, ethylene glycol and Polyvinylpyrrolidone(PVP). Copper nanopowder prepared using explosion wire processand investigated the effects of the exploding energy, wire diameter,the type of liquid on the particle size, and the particles sizedistribution. The nanoparticles are characterized by x-ray diffraction,UV-visible absorption spectroscopy and transmission electronmicroscopy (TEM). The x-ray diffraction results reveal that thenanoparticles continue to routine lattice periodicity at reducedparticle size. The UV-Visible absorption spectrum of liquid solutionfor copper nanoparticles shows sharp and single surface Plasmonresonance (SPR) peak centered at a wavelength of 590 nm inethylene glycol media, but don’t have peak in PVP fluid. This peakindicated the production of pure and spherical copper nanoparticle.

Theoretical study on negative permittivity of the material producing sharp surface plasmon resonance dips

Using theoretical simulations for optical fiber surface plasmon resonance (SPR) sensors and prism-based SPR sensors coated with negative permittivity material (NPM), we investigated the effect of the permittivity of NPM on the transmitted spectrum of optical fiber SPR sensors and the reflected spectrum of prism-based SPR sensors and then obtained optimum permittivity of the NPM, which can excite the sharpest SPR spectrum in the white light region (400–900 nm).

Sensing and Manipulation of Bianisotropic Biomolecules Using a Surface Plasmon Resonance Based Optical Fiber Sensor

We report a mechanism to sense and manipulate bianisotropic chiral biomolecules by a surface plasmon resonance based side-polished optical fiber sensor. To simulate such planar layered structure containing anisotropic and magnetoelectric coupling biomolecules, the propagation matrix method is expanded. This method allows us to access the radiation pressure exerted on the bianisotropic molecular layer via the derivation of the Maxwell stress tensor. The complicated behavior of incident plane waves on the sensing and trapping of biomolecules with different medium parameters is clarified. We find that the optical fiber sensor is capable of simultaneous detection of chirality parameter, anisotropy, and refractive index of biomolecules. The structure can also be used to separate chiral molecules from achiral ones by using an emerging sharp surface plasmon resonance. The paper may provide new insights for SPR based sensors and imaging systems, optical tweezers, and nanomechnical devices.