Intense Surface Plasmon Resonance Research Articles

Construction of Au-modified CN-based donor-acceptor system coupled with dual photothermal effects for efficient photoreduction of carbon dioxide

Conversion of CO2 into high value-added fuels through the photothermal effect is an effective approach for utilizing solar energy. In this study, we prepared the CN-based photocatalyst Py-CTN-Au with both donor-acceptor (D-A) system and dual photothermal effects using a simple two-step method involving calcination and photo-deposition. Real-time monitoring with a thermal imaging camera revealed that Py-CTN-Au0.5 achieved a maximum stable temperature of 180 °C, which was approximately 1.2 times higher than that of Py-CTN (155 °C) and 1.9 times higher than that of g-CN (95 °C) under the same reaction conditions. Under the optimized reaction conditions, Py-CTN-Au0.5 exhibited a CO release rate of 30.59 umol g−1 after 4 h of reaction, which was 7.3 times higher than that of pure g-CN (4.18 umol g−1). The D-A system not only facilitated the separation and transformation of charge carriers but also induced a photothermal effect to accelerate the photoreduction of CO2. Additionally, the cocatalyst Au nanoparticles (Au NPs) further enhanced the charge carrier dynamics and photothermal effect by increasing the built-in electric field intensity and localized surface plasmon resonance (LSPR) effect, respectively. The dual photothermal effects resulting from the non-radiative photon conversion of the D-A structure and the Au NPs LSPR effect, along with the enhanced charge carrier dynamics, catalyzed the efficient photoreduction of CO2. DFT simulations were used to confirm the effect of D-A system and Au NPs. In-situ FTIR results demonstrated that the synergistic photothermal effect promoted the formation of the key intermediate species COOH*, which is beneficial for the photocatalytic reduction of CO2. This study provides valuable insights into the multiple photothermal synergistic effects in photocatalytic reactions.

Humic Polyelectrolytes Facilitate Rapid Microwave Synthesis of Silver Nanoparticles Suitable for Wound-Healing Applications.

This article describes the one-pot microwave synthesis of silver nanoparticles (AgNPs) assisted with natural polyelectrolytes-humic substances (HS). The humic polyelectrolytes served both as chemical reductants for silver ions and as end-capping agents for AgNPs. Three commercially available sodium humates extracted from lignites and leonardite and one sodium fulvate isolated from natural brown water seeped through peat deposits were used in this study. The dynamics of the growth rate of AgNPs was characterised by UV-VIS spectroscopy by measuring the intensity of surface plasmon resonance at 420 nm. Transmission electron microscopy was used to characterise the size and morphology of AgNPs. Dynamic light scattering was used to determine size distributions of the synthesised AgNPs in the solutions. It was established that both conventional and microwave syntheses assisted with the coal humates produced small-size AgNPs in the range from 4 to 14 nm, with the maximum share of particles with sizes of (6 ± 2) nm by TEM estimates. The peat fulvate yielded much larger NPs with sizes from 10 to 50 nm by TEM estimates. DLS measurements revealed multimodal distributions of AgNPs stabilised with HS, which included both single NPs with the sizes from 5 to 15 nm, as well as their dominating aggregates with sizes from 20 to 200 nm and a smaller portion of extra-large aggregates up to 1000 nm. The given aggregates were loosely bound by humic polyelectrolyte, which prevented the coalescence of AgNPs into larger particles, as can be seen in the TEM images. The significant acceleration in the reaction time-a factor of 60 to 70-was achieved with the use of MW irradiation: from 240 min down to 210-240 s. The coal humate stabilised AgNPs showed antimicrobial properties in relation to S. aureus. A conclusion was made regarding the substantial advantages of microwave synthesis in the context of time and scaling up for the large-scale production of AgNP-HS preparations with antimicrobial properties suitable for external wound-healing applications.

Synergetic surface enhancement of quantum dots-based electrochemiluminescence with photonic crystal light scattering and metal surface plasmon resonance for sensitive bioanalysis

Noble metal nanostructures and photonic crystals (PhCs) have been widely investigated as substrates for constructing surface enhanced electrochemiluminescence (SE-ECL) biosensors. However, their applications are hindered by the limited enhancement intensity of surface plasmon resonance (SPR) and an incomplete mechanism for the photonic enhancement effect. Hence, developing a novel SE-ECL strategy with better signal enhanced capability and enriching our understanding of the intrinsic mechanisms for efficient bioanalysis is extremely urgent.Here, a synergistic SE-ECL strategy was developed for the sensitive determination of prostate specific antigen (PSA) protein. The randomly arranged polystyrene (r-PS) spheres and PS PhC arrays were applied to enhance the ECL emission of cadmium sulfide quantum dots (CdS QDs) and the results suggested that the PhC arrays displayed superior intensity (0.22) than the r-PS interface (0.10). Au nanoparticles (NPs) were introduced onto the two kinds of surfaces and further boosted the ECL intensity. According to the ECL measurements, Au NPs modified at the r-PS surface exhibited only a slight increase (0.13), while the PhC arrays showed approximately 5-fold enhancement (0.92), benefiting from the synergistic enhancement. The finite-difference time-domain (FDTD) simulation indicated that the ECL enhancement was ascribed to the coupled electromagnetic (EM) field at the surfaces of PS PhCs and Au NPs. The SE-ECL could achieve a detection range from 1 pg/mL to 1 μg/mL with a detection limit of 0.41 pg/mL (S/N = 3).This study provides the first combination of PhC arrays and metal surface plasmon nanostructure for the synergetic enhancement of SE-ECL systems. It opens a new avenue for the rational design of advanced ECL biosensors and shows great perspective for clinical diagnosis.

Evaluation of Antibacterial Activity of Selenium and Copper Oxide Nanoparticles Synthesized by Hibiscus sabdariffa L. Extract

The aim of the present study is to synthesize selenium (SeNPs) and copper oxide (CuONPs) nanoparticles utilizing aqueous extract of Hibiscus sabdariffa L. as a reducing agent. The green synthesized Hibiscus sabdariffa L. selenium and copper oxide nanoparticles were identified by color change. The characterization of SeNPs and CuONPs was achieved by Ultraviolet-visible (UV-VIS) spectroscopy, Field Emission Scanning electron microscope (FESEM), Atomic force microscope (AFM), X-Ray diffraction analysis (XRD) and transform infrared spectroscopy (FTIR). These tests are utilized for detecting stability, morphology, size, crystalline nature and functional groups on nanoparticles surface prepared. The outcomes revealed appearance of the prick-red and green color, indicating a specific color of selenium and copper oxide nanoparticles respectively. It also disclosed that UV-VIS spectroscopy indicated band absorbance at 234 and 274 nanometer of intense surface Plasmon resonance, manifesting the formation and stability of prepared SeNPs and CuONPs. The FESEM image displayed mulit-shapes between spherical and vaulted for selenium and copper oxide nanosized. XRD at 2 theta revealed crystalline selenium and copper oxide nanoparticles, with (54.92-57.79) nm average size. FTIR revealed the presence of functional groups of the plant that act as stabilizing and reducing agents. The antibacterial activity of synthesized nanoparticles was studied against five different bacteria causing food spoilage.

Enhancing the prodigiosin pigment by adding Ag\\TiO2 synergism for antibacterial activity

To treat diseases brought on by drug-resistant microbes, researchers are presently using nanotechnology as one of the tools for studying the most obscure corners of medical sciences. The biological synthesis regarding Ag/TiO2 synergism in prodigiosin pigment was the primary focus of the presented work. Inhibitory and bactericidal properties of silver nanoparticles (AgNPs) have long been recognized. Titanium dioxide nanoparticles (TiO2 NPs) are employed as antibacterial agents in a variety of therapeutic sources. With using Nd:Yag laser (1064 nm), the composition has been synthesized by using environmentally friendly laser ablation in a liquid method. UV–visible spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM) have been utilized for the analysis of the synthesized NPs. Optimal biosynthesis results showed a rise in the intensity of Surface Plasmon Resonance (SPR) bands of the NPs with shifting at 300 nm. TiO2 absorption peak at 230 nm. The results showed that the UV visible absorbance regarding prodigiosin pigment was at OD529. AgNPs/TiO2 exerted maximum antibacterial activity towards (Streptococcus, Bacillus subtilis, E. coli, Proteus vulgaris) Gram-negative and Gram-positive bacteria. The various Gram-negative and Gram-positive bacteria were subjected to various treatments (prodigiosin with Ag, prodigiosin pigment, and prodigiosin synergism with Ag/TiO2). The synergism is the best for antimicrobials than each one alone.

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.

Effects of anionic and cationic surfactants on the surface Plasmon resonance intensity of biogenic silver nanoparticles: Stability, and position of optical band

Fabrication of noble metal nanoparticles by using green plant extract as reducing agent have been the subject of various investigators due to their enhanced plasmonic properties for various applications. This paper describes the effects of cetyltrimethylammonium bromide (CTAB) and sodium dodecylsulfate (SDS) on the nucleation of silver sols formation by using coriander seeds extract and silver nitrate redox reaction. The wavelength maxima (λmax) were blue shifted from 433 nm to 425, 423, and 420 nm, respectively, with 0.0, 0.4, 1.0, and 1.6 mM CTAB. The blue and red shifts were also observed from 433 nm to 421, 421, 418, and 438 with 0.0, 0.4, 1.0, 1.6 and 2.0 mM SDS, respectively. The pre-micellar inhibition, and post-micellar catalytic effects were observed on the formation of silver sols with cationic CTAB surfactant. SDS exhibits inhibitory effect on the nucleation rate for an entire range of concentration. Additionally, antioxidant activity in vitro revealed that the percentage scavenging with 2,2-diphenyl-1-picrylhydrazyl (DPPH•) were depended on the dose of AgNPs.

Comparative study of four innovative earth-friendly platforms for rapid analysis of daclatasvir dihydrochloride: Application on different matrices

BackgroundDaclatasvir dihydrochloride has important roles not only in the management of COVID-19 pandemic symptoms but also in the treatment of chronic hepatitis C infection.ObjectiveThe current research presents four novel and simple platforms including silver-nanoparticles spectrophotometric technique and three electrochemical conductometric ones for daclatasvir analysis in its tablet, biological fluids, and dissolution media.MethodsThe spectrophotometric platform involved the synthesis of silvernanoparticles through a redox reaction between the reducing agent (daclatasvir) and the oxidizing agent (silver nitrate) in presence of polyvinylpyrrolidone as a stabilizing agent. The produced silver-nanoparticles have an intense surface plasmon resonance peak at 421 nm where the measured absorbance values were utilized for quantitative spectrophotometric determination of daclatasvir. While the electrochemical conductometric platforms involved the reaction of daclatasvir with three different precipitating reagents (silver nitrate, phosphomolybdic acid, and ammonium reineckate) to form ion associates between these reagents and daclatasvir in the aqueous system.ResultsAll proposed platforms were validated in line with recommendations of the international conference on harmonization producing satisfactory outcomes within the agreed boundaries.ConclusionThe proposed platforms are green alternatives for routine rapid assay of daclatasvir at the cheapest cost because their results were observed to be nearly similar to those of the reported platform. Moreover, the suggested spectrophotometric platform’s sensitivity can be employed for investigating daclatasvir bioequivalence.

Earth-friendly-assessed silver-nanoparticles spectrophotometric method for rapid and sensitive analysis of Molnupiravir, an FDA-approved candidate for COVID-19: application on pharmaceutical formulation and dissolution test

Molnupiravir is the first oral direct-acting antiviral prodrug recently approved for the COVID-19 pandemic. Here and for the first time, we present a novel, sensitive, robust, and simple silver-nanoparticles spectrophotometric technique for molnupiravir analysis in its capsules and dissolution media. This spectrophotometric technique involved silver-nanoparticles synthesis through a redox reaction between the reducing agent (molnupiravir) and the oxidizing agent (silver nitrate) in presence of polyvinylpyrrolidone as a stabilizing agent. The produced silver-nanoparticles have an intense surface plasmon resonance peak at 416 nm where the measured absorbance values were utilized for the quantitative analysis of molnupiravir. The produced silver-nanoparticles were recognized by using the transmission electron microscope. Under optimal conditions, a good linear rapport was accomplished between molnupiravir concentrations and the corresponding absorbance values in a range of (100–2000) ng/mL with a detection limit of 30 ng/mL. Greenness assessment was implemented using eco-scale scoring and GAPI disclosing the excellent greenness of the suggested technique. The suggested silver-nanoparticles technique was authenticated according to recommendations of the ICH and statistically assessed with the reported liquid chromatographic method without significant differences regarding accuracy or precision. Accordingly, the suggested technique is deemed a green and cheap alternative for assaying molnupiravir due to its reliance primarily on water. Furthermore, the suggested technique’s high sensitivity can be employed for investigating molnupiravir bioequivalence in future studies.Graphical

Green Fabrication of silver nanoparticles by leaf extract of Byttneria Herbacea Roxb and their promising therapeutic applications and its interesting insightful observations in oral cancer

The present research was carried out to look into therapeutic insight of biosynthesized silver nanoparticles (AgNPs) by leaf extract of Byttneria herbacea Roxb (BH). The analysis of biosynthesized BH-AgNPs by UV-visible spectroscopy shows an intense surface plasmon resonance (SPR) peak at 422 nm initially and 437 nm after 30 min which certainly reveals the formation of BH-AgNPs. Fourier Infra-red Spectroscopy (FT-IR) reveals that BH-AgNPs are biosynthesized by using different bioactive compounds like O-H stretch of free hydroxyl alcohol and phenols, N-H bond of primary amines present in the leaf extract. Transmission Electron Microscope (TEM) analysis revealed that BH-AgNPs are almost spherical in nature with an average size range from of 2 nm to 12 nm. The particle size analysis by Dynamic Light Scattering (DLS) reveals that the BH-AgNPs are poly-dispersed in nature with an average size of 8 nm ± 2 nm, with a negative zeta potential value of −21 mV which reveals the biosynthesized BH-AgNPs are very stable. The BH-AgNPs ( Byttneria herbacea -AgNPs) revealed excellent free radical scavenging activity and exceptional antimicrobial activity. The anti-proliferative and cytotoxic studies in KB oral cancer cells revealed biosynthesized BH-AgNPs can employ as future novel therapeutic agents in cancer treatment and other biomedical applications.

Green Spectrophotometric Determination of Two Cephalosporin Drugs Used in COVID-19 Regimen Through Silver Nanoparticle Synthesis.

Cefixime trihydrate (CFX) and cefuroxime axetil (CFU) are antibacterial drugs. They are widely used in the treatment of bacterial infection and recently in COVID-19 treatment. In this article, the two antibacterial drugs, CFX and CFU, were determined by a new simple, sensitive, effective, and green spectrophotometric method via reaction with silver nitrate (AgNO3). The reaction was based on reduction of AgNO3 by the cited drugs to silver nanoparticles (Ag-NPs) in the presence of polyvinylpyrrolidine (PVP) as stabilizing agent. Very intense surface plasmon resonance peaks were obtained at 435 nm for CFX and CFU that allow quantitative determination of the drugs. The calibration curves were linear with concentration ranges of 0.2-1.4 μg/mL and 0.3-2.1 μg/mL for CFX and CFU, respectively. Validation of the proposed method has been done according to ICH (International Conference of Harmonization) guidelines; the method was verified on the Green Analytical Procedure Index and Analytical Greenness metric approach (AGREE) in regard to its greenness and was found to be an excellent green alternative method. A very sensitive and green spectrophotometric method was developed for determination of CFX and CFU in pure and dosage form. The developed method not previously reported for simultaneous determination of CFX and CFU.

Experimental analysis and simulation of the optical properties of gold nano-particles on sodium alginate

The reflectance and transmittance spectra of a set of thin gold films on sodium alginate are measured and simulated in the framework of the generalized transfer matrix method. In the simulation, the dielectric function for the nano-particles (NP) was modified from that of gold bulk by using a variable damping energy. A Lorentz oscillator was used to describe the localized surface plasmon resonance. The results elucidate the structural arrangement of the deposited material on the specific substrate. The collision frequency obtained from the simulation indicates that the aggregation of the NPs at the nanoscopic level correlates with the electrical properties. The intense surface plasmon resonance remains visible for film thicknesses up to 10 nm, in spite of the increasing loss of particle separation. In addition to the attained results, the developed methodology can be usefully applied on other case studies for a thorough characterization of the formation of the growing NP films on the specific substrate.

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.

Plasmon Induced Near‐Infrared Active Photocatalysts: A Review

AbstractIn the recent past, near‐infrared (NIR) active photocatalysts have received tremendous research attention to harvest solar NIR energy as the solar spectrum carries abundant NIR light. Again, plasmonic materials with their intense surface plasmon resonance (SPR) activity in the visible and NIR range can be a suitable candidate for NIR active photocatalysis. However, the ultrafast energy relaxation of the plasmon‐generated hot electrons restricts their application in photocatalysis. In this review, the recent progress in the plasmon‐induced NIR active photocatalysis has been summarized. Particular emphasis has been given to divulging the mechanism to NIR modulation of localized surface plasmon resonance (LSPR), LSPR intensification, LSPR induction mechanism in non‐noble metals, and suitable technologies to separate the photogenerated hot electrons efficiently and their exploration in photocatalytic reactions. The drawbacks, possible solutions, and potential of non‐noble metal plasmonic photocatalysis have been discussed in detail. Finally, the review ends with concluding remarks and possible prospects of plasmonic photocatalysts. It is believed that this review will inspire researchers to rationally design broad‐spectrum (UV–vis–NIR) active photocatalysts to harvest solar light efficiently.

Morphology and Optical Properties of Gas-Phase-Synthesized Plasmonic Nanoparticles: Cu and Cu/MgO.

In this paper, an investigation of the properties of Cu and Cu/MgO nanoparticles (NPs) is presented. The NPs were obtained with gas-phase synthesis, and the MgO shells or matrices were formed via the co-deposition method on inert substrates. SEM and AFM were used to investigate the NP morphology on Si/SiOx, quartz, and HOPG. The Cu NPs revealed flattening of their shape, and when they were deposited on HOPG, diffusion and formation of small chains were observed. The embedding of Cu NPs in MgO was confirmed by TEM and EDX maps. XPS showed that Cu was in its metallic state, regardless of the presence of the surrounding MgO. UV–Vis revealed the presence of an intense localized surface plasmon resonance (LSPR) for Cu/MgO and for “bare” NPs. These results confirmed the role of MgO as a protective transparent medium for Cu, and the wavelength position of the LSPR in the Cu/MgO system was consistent with calculations. The wavelength position of the LSPR observed for “bare” and post-oxidized Cu NPs was probably affected by the formation of copper oxide shells after exposure to air. This study paves the way for the use of Cu/MgO NPs as plasmonic nanomaterials in applications such as photovoltaics and sensor technology.

Directed self-assembly of Ag+-deposited MoS2 quantum dots for colorimetric, fluorescent and fluorescence-lifetime sensing of alkaline phosphatase.

We developed a triple-readout probe for colorimetric, fluorescent, and fluorescence-lifetime sensing of alkaline phosphatase (ALP) through the hydrolyzed ascorbic acid phosphate (AAP)-mediated formation of silver nanoparticles (AgNPs) on Ag+-deposited MoS2 quantum dots (QDs). Ag+ ions were self-assembled on a monolayer MoS2 QD surface through the formation of Ag-S bonds. When ALP hydrolyzed AAP in an alkaline buffer, the resultant ascorbic acid (AA) triggered the reduction of the bound Ag+ ions into AgNPs on the MoS2 QD surface. The resultant AgNPs induced an efficient fluorescence quenching of the MoS2 QDs through simultaneous static and dynamic quenching processes, generated an intense surface plasmon resonance peak, and triggered a reduction in the fluorescence lifetime of the MoS2 QDs. Electron microscopy and spectroscopic techniques revealed the successful fabrication of Ag+-deposited MoS2 QDs and the ALP-mediated formation of AgNPs on the MoS2 QD surface. The linear quantification ranges for ALP were 0.05-2.5, 0.1-4, and 1-4 units L-1 in the fluorescent, colorimetric, and fluorescence-lifetime detection modes, respectively. In addition, the proposed probe integrated with an ALP-linked sandwich immunoassay exhibited high sensitivity and selectivity for the fluorescence sensing of rabbit immunoglobulin G with a detection limit of 8pgmL-1 and linear range of 25-1000pgmL-1. The sensitivity of the probe is comparable to those of previously reported immunoassays involving ultrasensitive electrochemical detection, hydrogen evolution reactions, or electron spin resonance. The probe integrated with the sandwich assay serves as a promising platform for the detection of target proteins in clinical samples.

Combination of Capped Gold Nanoslit Array and Electrochemistry for Sensitive Aqueous Mercuric Ions Detection.

Label-free surface plasmon resonance (SPR) detection of mercuric ions in various aqueous solutions, using capped gold nanoslit arrays combined with electrochemical (EC) sensing technique, is demonstrated. The nanoslit arrays are fabricated on flexible cyclo-olefin polymer substrates by a nanoimprinting lithography method. The EC and SPR signals for the investigation of current responses and transmission SPR spectra are simultaneously measured during metal ions electrodeposition. Glycerol–water solution is studied to evaluate the resonant peak wavelength sensitivity (480.3 nm RIU−1) with a FOM of 40.0 RIU−1 and the obtained intensity sensitivity is 1819.9%. The ferrocyanide/ferricyanide redox couple performs the diffusion controlled electrochemical processes (R2 = 0.99). By investigating the SPR intensity changes and wavelength shifts of various mercuric ion concentrations, the optical properties are evaluated under chronoamperometric conditions. The sensors are evaluated in the detection range between 100 μM and 10 nM with a detection limit of 1 μM. The time dependence of SPR signals and the selectivity of 10 μM Hg2+ in the presence of 10 μM interfering metal ion species from Ca2+, Co2+, Ni2+, Na+, Cu2+, Pb2 + and Mn2+ are determined. The capped gold nanoslit arrays show the selectivity of Hg2+ and the EC sensing method is effectively utilized to aqueous Hg2+ detection. This study provides a label-free detection technique of mercuric ions and this developed system is potentially applicable to detecting chemicals and biomolecules.

Synthesis of bimetallic AuAg nanoparticles by sequential ion implantation for modifying surface-plasmon-resonance properties

Bimetallic AuAg (Au (80%) and Ag (20%)) nanoparticles (NPs) have been synthesized in fused quartz matrix using sequential ion implantation and post-annealing in air at 600 °C, 700 °C, 800 °C and 900 °C. X-ray diffraction (XRD) results confirm the formation of crystalline Au80Ag20 bimetallic NPs after annealing. Transmission electron microscopy (TEM) investigations have confirmed presence of spherical AuAg alloyed and few AuAg alloy core- Ag shell/satellite NPs. Rutherford backscattering spectra, along with fittings, revealed the mixing of Au and Ag atoms after annealing and movement of elements towards the surface. The peak position of the surface plasmon resonance (SPR) feature of Au has been shifted towards higher energy after sequential Ag implantation. The SPR peak position and intensity is further modified after annealing of Au80Ag20 NPs. The mechanism of modified SPR properties is mechanistically discussed by considering the diffusion, alloying, segregation and redistribution of Au/Ag in the host matrix.

Manipulating Hot-Electron Injection in Metal Oxide Heterojunction Array for Ultrasensitive Surface-Enhanced Raman Scattering.

Efficient photoinduced charge transfer (PICT) resonance is crucial to the surface-enhanced Raman scattering (SERS) performance of metal oxide substrates. Herein, we venture into the hot-electron injection strategy to achieve unprecedented enhanced PICT efficiency between substrates and molecules. A heterojunction array composed of plasmonic MoO2 and semiconducting WO3-x is designed to prove the concept. The plasmonic MoO2 generates intense localized surface plasmon resonance under illumination, which can generate near-field Raman enhancement as well as accompanied plasmon-induced hot-electrons. The hot-electron injection in direct interfacial charge transfer and plasmon-induced charge transfer process can effectively promote the PICT efficiency between substrates and molecules, achieving a record Raman enhancement factor among metal oxide substrates (2.12 × 108) and the ultrasensitive detection of target molecule down to 10-11 M. This work demonstrates the possibility of hot-electron manipulation to realize unprecedented Raman enhancement in metal oxides, offering a cutting-edge strategy to design high-performance SERS substrates.

Nanoparticles encapsulation of Phoenix dactylifera (date palm) mucilage for colonic drug delivery

Compressed tablet formation from granular drug require binder with Cohesiveness property. Plants mucilage as pharmaceutical excipients are available. In this study, biocompatible date palm mucilage was encapsulated with silver nano particles for sustained drug release to provoke an immune response. Nano formulated mucilage was characterized by UV/VIS, FTIR, XRD, SEM/EDX spectrophotometry. UV/VIS spectra revealed an intense surface plasmon resonance peak at 406 nm for spherical mono dispersed silver nano formulated mucilage resulted from efficient reduction of silver ions to AgNPs. Zeta sizer disclosed the emergence of single peak at 139.7 nm with 100% intensity. Crude mucilage exhibited number of peaks in the region of 4000-500 cm−1 by FT-IR spectroscopy whereas purified as well as nano formulated samples showed somewhat different pattern of peaks in addition to peaks of crude sample. XRD spectra of crude mucilage revealed somewhat regular pattern while purified and modified mucilage displayed irregular structure. In SEM analysis, crude mucilage was appeared as granular that turned into porous network with entangled tiny silver nano spheres. A controlled release of drug levofloxacin hemihydrate was evaluated using crude/ nano formulated mucilage as excipient. Nano formulated mucilage delayed the onset exposure of drug in gastric medium giving recommendations as value added bio binder for drug to the target organ.