Surface Plasmon Resonance Absorption Band Research Articles

Ultra-broadband, high absorption, polarization-insensitive microwave absorbers designed based on multi-scale fractal metasurfaces

Microwave absorbers play an essential role in radar stealth applications. However, conventional microwave absorbers are hindered by limitations such as narrow bandwidth, large size, and inadequate absorption rates. Leveraging metasurfaces presents an ideal approach for creating microwave absorbers, but metasurface-based broadband absorbers typically entail intricate structures, natural absorbing materials, or electronic components, posing challenges in terms of fabrication and expansion. Here, we numerically demonstrate a simple multi-scale fractal metasurface microwave absorber, with the full width at half-maximum of band exceeding one optical octave. By integrating the localized surface plasmon resonance absorption band and the Salisbury-Screen-type absorption band, we achieve an average absorption of 90% ranging from 11.5 GHz to 27.1 GHz. Furthermore, this absorber exhibits excellent polarization insensitivity and maintains high absorption even at large incident angles. The device, offering both broadband absorption and a straightforward structure, holds significant promise for practical applications and widespread adoption.

Eco-Friendly Synthesis of Silver Nanoparticles Using Aqueous Extract of Ziziphus Spina-Christi Seeds: Characterization and Stability

In this study, silver nanoparticles (Ag-NPs) were prepared using an aqueous extract of Ziziphus Spina-Christi Seeds (ZSCS) powder as an eco-friendly material, reducing agent and capping ligand. The synthesized Ag-NP was characterized using UV-visible absorption spectroscopy (UV-Vis), Fourier transform infrared (FTIR), transmission electron microscopy (TEM) and dynamic light scattering (DLS). From The UV-Vis spectra, the surface plasmon resonance (SPR) absorption band at 443 nm confirmed the formation of Ag-NPs. The TEM results demonstrated that the synthesized Ag-NPs have mostly spherical shapes with a particle size of 21.54 nm. In addition, the particle size and the specific surface area (SSA) of Ag-NPs decreased with increasing ZSCS powder extract volume and AgNO3 concentration. The basic medium was found to be better than the acidic medium to prepare Ag-NPs. At a pH value equal to 9.5, within 30 minutes, the color of the solution was changed from colorless to brownish-orange. SPR absorption band of Ag-NPs demonstrated that the synthesized Ag-NPs have high stability over a period of 8 months. From FTIR results, the stretching of C-O group at 1223 and 1031 cm-1 disappeared after bioreduction of AgNO3, these results may be due to that Ag reduction was carried out by some hydroxyl groups that get oxidized at the expense of Ag+ because Ag+ is reduced to Ag-NPs.

Physicochemical robustness of pulse laser ablated silver-copper nanocomposoites against varied bacterial strains

Nanocomposites (NCs) of inorganic materials with controlled physicochemical characteristics became beneficial for diverse biomedicine and pharmacology applications. Thus, some new types of crystalline spherical silver (Ag)/copper (Cu) nanocomposites (Ag–CuNCs) were made at various laser fluences (ranged from 0 to 14.15 ± 3.9 J cm−2) using the pulsed laser ablation in liquid (PLAL) approach and characterized for the first time. The structures, morphologies, optical and bactericidal properties of these colloidal NCs were determined and the results for the best sample are presented. These NCs showed distinct surface plasmon resonance absorption bands at 402 and 580 nm accompanied by a blue shift. FTIR spectra verified the dispersion of pure Ag–CuNCs in deionized water and XRD pattern confirmed their crystalline nature. EDX analysis of samples confirmed their high purity with appropriate elemental distribution. HRTEM image of the optimum sample exhibited the presence of spherical Ag–CuNCs of mean diameter ≈ 6 ± 1.3 nm and lattice spacing of 0.073 nm and 0.155 nm. Model simulated optimized structure of Ag–CuNCs reaffirmed their stability and chemically reactive HOMO-LUMO isopotential surface. The antibacterial potential of the produced Ag–CuNCs was evaluated using the inhibition zone diameter (IZD) and optical density (at 600 nm) measurements. The optimum Ag–CuNCs prepared at 14.15 ± 3.9 J cm−2 when tested against E. coli, P. aeruginosa, B. subtilis and S. aureus bacteria showed the IZD of 23, 24, 21 and 22 mm, respectively. It was shown that by tuning the laser fluence, the physicochemical and bactericidal attributes of the proposed Ag–CuNCs can be customized, that may have significant implications for potential uses in nanomedicine.

Facile phytosynthesis of gold nanoparticles using Nepeta bodeana Bunge: Evaluation of its therapeutics and potential catalytic activities

In the present study, the ethanol extract of leaves of Nepeta bodeana Bunge was utilized in environmentally friendly synthesis of gold nanoparticles (AuNPs) via an immediate, one-step, and cost-effective process. The biosynthesized AuNPs were characterized using a variety of techniques, including UV–visible spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), and laser Doppler electrophoresis (zeta potential), among others. Pink in hue, the manufactured AuNPs were practically spherical and had<20.5 nm in diameter. The peak of the localized surface plasmon resonance absorption band at 547 nm helped to explain the biogenic synthesis of AuNPs, which used the ethanolic extract of the Nepeta bodeana leaves. In addition to this, the biosynthesized AuNPs possessed the remarkable stability as a result of their zeta potential value of − 22.3 mV. The green synthesized AuNPs demonstrated the excellent catalytic activity because they were able to catalytically degrade methylene blue (MB) at a variety of concentrations. The results indicated that 94.2% of MB were degraded after 10 min. They also showed a remarkable antibacterial activity against both Gram-nrgative (Pseudomonas aeruginosa and Escherichia coli) and Gram-positive (Staphylococcus aureus and Bacillus cereus) bacteria. In addition, a proper antifungal activity with the minimum inhibitory concentration (MIC) values of 50 and 25 μg/mL against Candida albicans and Aspergillus niger, respectively, were determined. The phytosynthesized AuNPs indicated a considerable antioxidant activity of 83% and 74% in the applied DPPH and ABTS radical scavenging activity tests, respectively. The anti-inflammatory properties of the synthesized AuNPs were established to be dose-dependent and varied from 11% to 76%. The green synthesized AuNPs also exhibited a concentration-dependent cytotoxicity on human liver (HepG2) and breast (MCF-7) cancer cells, which were around 77.4 and 71.2% at 300 µg/mL, respectively. They showed as well a notable anti-diabetic activity with the 52% inhibition of α-amylase and the 62% glucose uptake activity by yeast cells at 300 µg/mL. All these findings suggested that the produced AuNPs could be explored for developing many therapeutic as well as catalytic useful products.

Surface grafted gold nanorods (GNRDs) using thermosensitive copolymers with various transition temperatures: Nanomaterials with potential application for photothermal therapy

A series of diblock copolymers containing a biocompatible polyethylene glycol (PEG) block and a thermoresponsive poly(N-vinyl caprolactam) (PNVCL) based block, were synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization. The cloud point temperature (Tcp) in water of the diblocks was adjusted from 35 to 42 °C by adding N-vinyl pyrrolidone (NVP) units in the thermoresponsive block. The terminal trithiocarbonate group evolving from the RAFT agent used in the synthesis, was modified to thiol to stabilize gold nanorods (GNRDs) via a “grafting-to” approach. Stability of the PEG-b-P(NVCL-co-NVP)@GNRDs nanomaterials was monitored during 8 days; where the localized surface plasmon resonance (LSPR) absorption band did not shifted or showed any broadening. Aqueous dispersed samples were irradiated with near-infrared laser light for 10 min, observing a temperature increase from 25 to 50 °C depending on the laser optical power (between 100 and 500 mW); while no precipitation was observed. For temperatures above the cloud point temperature of the copolymers (Tcp), the formation of aggregates in sizes around 200 nm was observed without precipitation. This study demonstrates that the stabilization of gold nanorods by grafting with the title thermoresponsive block copolymers, and the observed temperature-dependent block-copolymer@GNRD aggregation, has potential uses in drug-delivery applications for photothermal therapy.

Gold Nanoparticles: A Didactic Step-by-Step of the Synthesis Using the Turkevich Method, Mechanisms, and Characterizations

In this study, gold nanoparticles (AuNPs) were synthesized using the Turkevich method. This article explains the didactic step-by-step synthesis, showing pictures of the entire process, including a well-explained mechanism and characterization study. Synthesis involves the reduction of NaAuCl4 using sodium citrate at high temperatures (approximately 90 °C). The two main mechanisms used to explain AuNPs synthesis via the Turkevich method are also discussed. The first mechanism considers that a nanowire intermediary and the other proposes that aggregate intermediates are not formed at any time during the synthesis. The materials (NaAuCl4 and AuNPs) were characterized using UV-Vis spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), and dynamic light scattering (DLS). The UV-Vis spectrum exhibits an absorption maximum at 521 nm because of the surface plasmon resonance (SPR) absorption band of the AuNPs. The SEM images of NaAuCl4 show crystals with cubic shapes, while the AuNPs have an average particle size of approximately 16–25 nm and particles that appear mainly spherical. To confirm the particle shapes, AFM was conducted, and it was possible to clearly observe individual spherical nanoparticles and their aggregates, and the average diameter of these AuNPs was approximately 12–19 nm. The XRD pattern of AuNPs showed four main characteristic peaks corresponding to the (111), (200), (220), and (311) planes, confirming the presence of cubic (FCC) gold. The DLS presented an average particle size of 3.3 ± 0.9 nm and a polydispersity index (PDI) of 0.574. AuNPs were synthesized using a simple and rapid method. The resulting spherical and ultra-small particles can be used in several applications.

Reflective Fiber Temperature Probe Based on Localized Surface Plasmon Resonance towards Low-Cost and Wireless Interrogation.

Reflection fiber temperature sensors functionalized with plasmonic nanocomposite material using intensity-based modulation are demonstrated for the first time. Characteristic temperature optical response of the reflective fiber sensor is experimentally tested using Au-incorporated nanocomposite thin films deposited on the fiber tip, and theoretically validated using a thin-film-optic-based optical waveguide model. By optimizing the Au concentration in a dielectric matrix, Au nanoparticles (NP) exhibit a localized surface plasmon resonance (LSPR) absorption band in a visible wavelength that shows a temperature sensitivity ~0.025%/°C as a result of electron-electron and electron-phonon scattering of Au NP and the surrounding matrix. Detailed optical material properties of the on-fiber sensor film are characterized using scanning electron microscopy (SEM) and focused-ion beam (FIB)-assisted transmission electron microscopy (TEM). Airy's expression of transmission and reflection using complex optical constants of layered media is used to model the reflective optical waveguide. A low-cost wireless interrogator based on a photodiode transimpedance-amplifier (TIA) circuit with a low-pass filter is designed to integrate with the sensor. The converted analog voltage is wirelessly transmitted via 2.4 GHz Serial Peripheral Interface (SPI) protocols. Feasibility is demonstrated for portable, remotely interrogated next-generation fiber optic temperature sensors with future capability for monitoring additional parameters of interest.

Effect of various concentrated copper and plant extract concentrations on the antibacterial activity.

Copper nanoparticles (Cu NPs) were created using two methods, one with reducing and stabilizing agents and the other with green tea extract. The formation of Cu NPs has been described by spectra of UV-Vis absorption, which showed the surface plasmon resonance (SPR) at 620 and 630 nanometers, respectively. The position and shape of the surface plasmon resonance and plasmon absorption bands strongly depend on the reaction conditions. The crystalline morphology and size of the nanoparticles were determined by XRD, FESEM, and TEM studies. In both ways, the average particle size of Cu nanoparticles was found to be in the range of 28 nm and 142 nm for the chemical and green methods, respectively. The effectiveness of the materials prepared by both methods was high, and the antibacterial activity of the products prepared by both ways was against E. coli and S. aureus pathogens represented by inhibition zones ranging from 14–20 mm, 30–38 mm, and 11–18 mm, 20–24 mm, respectively.

Propofol-induced in-situ formation of silver nanoparticles: A sensing colorimetric method

A simple and eco-friendly colorimetric sensing method has been developed for the extremely effective detection of propofol in exhaled breath condensate (EBC). In this study, we put forward a Tollens' procedure, in which silver nanoparticles (AgNPs) were produced using propofol as a reducing agent. To verify the in-situ synthesis of AgNPs, the TEM images, and UV-Vis absorbance were recorded in the absence and presence of propofol. The solution turned from a colorless to yellow and deep yellow color due to the surface plasmon resonance absorption band of formed AgNPs. The intensity of nanoparticle absorbance was quantitatively correlated with the propofol concentration. The proposed sensor revealed good linearity over the range of 0.01–0.8 µg mL−1 at 422 nm with the detection limit of 8.8 ng mL−1 under optimum conditions. Finally, the proposed colorimetric sensor was successfully used for the determination of propofol in the EBC sample of patients receiving propofol.

Silver-platinum bimetallic nanoparticles as heterogeneous persulfate activator for the oxidation of malachite green

Fabrication of noble metal nanoparticles by using green chemical method with plant extract as reducing agent to the in situ oxidation toxic water contaminants have been the subject of various investigators due to their enhanced catalytic efficiencies. This paper describes the extraction of caffeic acid from Artemisia herba-alba aqueous extract, and preparation of silver (Ag), platinum (Pt), and silver-platinum (Ag-Pt) nanoparticles with caffeic acid as a reducing and capping agent. The as-prepared Ag-Pt NPs was used as a heterogeneous activator of persulphate (K2S2O8) for the in situ chemical oxidation of malachite green (MG). The Ag-Pt NPs shows no surface Plasmon resonance absorption band. The malachite green dye was completely decolorized in presence of Ag-Pt/K2S2O8 system. SO4-• and HO• radicals generated by the cleavage of S2O82- peroxide activation with Ag-Pt were responsible for the MG decolorization as well as mineralization. The Ag-Pt NPs acted as a sacrificial electron donor. The Ag-Pt NPs were characterized by using conventional techniques such as, UV–visible, FTIR, SEM, TEM, EDX, XPS, and XRD spectroscopic methods.

Quercetin- and caffeic acid-functionalized chitosan-capped colloidal silver nanoparticles: one-pot synthesis, characterization, and anticancer and antibacterial activities.

The presented study comprises the one-pot synthesis and the characterization of quercetin- and caffeic acid-functionalized chitosan-capped colloidal silver nanoparticles (Ch/Q- and Ch/CA-Ag NPs), and their antibacterial and anticancer activities. The formation of Ch/Q- and Ch/CA-Ag NPs has been confirmed by ultraviolet-visible (UV-vis) spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, and transmission electron microscopy (TEM). The characteristic surface plasmon resonance (SPR) absorption band has been found at 417 and 424 nm for Ch/Q- and Ch/CA-Ag NPs, respectively. The formation of a chitosan shell comprising quercetin and caffeic acid, which surround the colloidal core Ag NPs, was confirmed by UV-vis, and FTIR analyses, and monitored by TEM microscopy. The size of nanoparticles has been determined as 11.2 and 10.3 nm for Ch/Q- and Ch/CA-Ag, respectively. The anticancer activity of Ch/Q- and Ch/CA-Ag NPs has been evaluated against U-118 MG (human glioblastoma) and ARPE-19 (human retinal pigment epithelium) cells. Both NPs showed anticancer activity, but Ch/Q-Ag NPs seemed to be more effective on cancer cell lines (U-118 MG) in comparison to healthy ones (ARPE-19). Furthermore, the antibacterial activity of Ch/Q- and Ch/CA-Ag NPs against Gram-negative (P. aeruginosa and E. coli) and Gram-positive (S. aureus and S. epidermidis) bacteria was determined, and dose-dependent antibacterial effects were found.

Gold-silver alloy hollow nanoshells-based lateral flow immunoassay for colorimetric, photothermal, and SERS tri-mode detection of SARS-CoV-2 neutralizing antibody

Although many approaches have been developed for the quick assessment of SARS-CoV-2 infection, few of them are devoted to the detection of the neutralizing antibody, which is essential for assessing the effectiveness of vaccines. Herein, we developed a tri-mode lateral flow immunoassay (LFIA) platform based on gold–silver alloy hollow nanoshells (Au–Ag HNSs) for the sensitive and accurate quantification of neutralizing antibodies. By tuning the shell-to-core ratio, the surface plasmon resonance (SPR) absorption band of the Au–Ag HNSs is located within the near infrared (NIR) region, endowing them with an excellent photothermal effect under the irradiation of optical maser at 808 nm. Further, the Raman reporter molecule 4-mercaptobenzoic acid (MBA) was immobilized on the gold–silver alloy nanoshell to obtain an enhanced SERS signal. Thus, these Au–Ag HNSs could provide colorimetric, photothermal and SERS signals, with which, tri-mode strips for SARS-CoV-2 neutralizing antibody detection were constructed by competitive immunoassay. Since these three kinds of signals could complement one another, a more accurate detection was achieved. The tri-mode LFIA achieved a quantitative detection with detection limit of 20 ng/mL. Moreover, it also successfully detected the serum samples from 98 vaccinated volunteers with 79 positive results, exhibiting great application value in neutralizing antibody detection.

Optical hydrogen sensing by MoO3 films deposited by a facile flame synthesis method

Nanostructured MoO3 films were deposited on glass by an atmospheric solid-fed flame vapor deposition (SF-FVD) technique at different substrate temperatures (25 (SRT), 300 (S300) and 400 °C (S400)). FESEM showed web-like morphology for SRT and S300 and plate-like for S400. TEM revealed existing spherical at lower and 2D structures at higher temperatures. Monoclinic and orthorhombic phases were observed for SRT and S300/S400, respectively. With a sputter-deposited Pd film, MoO3 films turn dark blue after hydrogen exposure, for which localized surface plasmon resonance (LSPR) absorption bands have appeared in the NIR region. The LSPR showed a linear blue shift up to 35 nm with < 4% hydrogen concentration. Using a 640 nm LED light source, the capability at very low concentrations of hydrogen and different working temperatures (up to 200 °C) was investigated. Significant sensitivity was observed with a sigmoidal behavior toward hydrogen concentration (0.05–10%). Also, the repeatability and selectivity among interfering gases were desirable. Sample S300 at a working temperature of 150 °C showed the best sensing performance in coloration, reversibility and response time. Raman, XRD and FESEM were used that reveal structural and morphological degradation, where the partial formation of molybdenum oxide bronze (H0.93MoO3) was observed.

Fabrication of SERS Substrates Based on Porous- Si Nanostructures and Silver Nanoparticles for Application in Identification of Carbendazim

In this work, we present a quick and simple approach for fabrication of active-surface-enhanced Raman scattering (SERS) substrates based on silver nanoparticles (AgNPs) and porous silicon nanostructures (denoted by Si/Ag substrate). SERS substrates were fabricated by a 3-stage-process including the deposition of Au nanoparticles on Si wafer, etching for porous Si wafer, and coating Ag NPs on porous Si to produce SERS-active layer. To control the uniformity and cleanliness of the SERS substrate, sputtering technique was used to coat Au and AgNPs. The absorption spectra of the Si/Ag substrates exhibited a strong surface plasmon resonance absorption band of AgNPs at 425 nm. Using Si/Ag substrates to detect carbenzadim (CBZ) residue dispersed in acetone has shown that Si/Ag substrates morphology greatly affected the Raman intensity of carbendazim which opens up a promising and potential approach using SERS spectroscopy for food, environment and especially pharmaceutical applications.&#x0D; Keywords: Raman, SERS, plasmon, nanoparticles, carbendazim.&#x0D; &#x0D;

Optimizing the shape anisotropy of gold nanoparticles for enhanced light harvesting and photocatalytic applications

Hybrid nanoparticles (NP) of bismutite nanodisks (BSC ND) with gold nanoparticles (Au NP) of different aspect ratios (AR), such as spheres, rods and etched rods were synthesized via a facile sonochemical method. To better control the shapes of Au NP deposited on the substrate, these were pre-synthesized prior to the deposition using a modified seed mediated growth method by altering the pH and supersaturation of the growth solution. The shift in the peak position and shape of the localized surface plasmon resonance (LSPR) absorption band associated with fine-tuning of the shape of Au NP, led to enhanced light harvesting capabilities of the hybrid. Introducing shape anisotropy in the NP brought about narrowing of bandgap and lowering of PL intensity in the hybrids, suggesting better electronic contact of the NP with BSC, and effective suppression of recombination effects. Hybrids of BSC with Au nanorods showed 14% improved degradation of methylene blue (MB) dye compared to the hybrids with nanospheres. With this study, we provide a novel promising strategy to maximize the light harvesting capacity of semiconductors by tailoring the AR of Au NP, for improved solar to chemical energy conversion.Graphical abstract

MICROWAVE-ASSISTED GREEN SYNTHESIS OF SILVER NANOPARTICLES USING EXTRACT OF SPONDIAS PINNATA BARK

Formation of silver nanoparticles with irradiation of microwaves using biological agents such as plant extracts is one of the eco-friendly green synthesis approaches which is economical in comparison with the physical and chemical methods. This study is focused at preparation of silver nanoparticles silver using Spondias pinnata bark extract by microwave irradiation and its comparison with aging method. Formation of silver nanoparticles was identified by observing the surface plasmon resonance absorption band peak at ~432 nm by UV-visible spectrophotometer. Optimization of the synthesis procedure was carried out using different amount of extract, concentration of substrate and microwave irradiation time and morphological features were characterised. A solution containing 8ml plant extract and 8 mM silver nitrate exposed to 90 sec microwave irradiation time was identified as optimised condition for the production of spherical shaped silver nanoparticles with a size of 34.52 nm which indicates that faster formation of silver nanoparticles compared to the aging method. Present research shows the importance of optimization of bio reduction conditions and the amount of reactants required for regulation of the morphology of silver nanoparticles as well as to obtain homogenous solution which is the main problem encountered in plant- mediated production of silver nanoparticles.

A novel spectrophotometric method based on plasmonic nanoparticles for nicotine detection

In this paper, a spectrophotometric method for nicotine detection based on plasmonic nanoparticles (AuNPs and AgNPs) is proposed. Due to their specific properties, plasmonic nanoparticles have become interesting to use in the development of sensitive analytical methods. The localized surface plasmon resonance (LSPR) absorption bands for AgNPs and AuNPs with a wavelength at 395.5 nm (A395.5) and 543.5 (A543.5) nm, respectively, are used for the detection. Experimental variables such as solvent type and pH were optimized so as to determine the optimum working conditions. The analytical calibration curve for both AgNPs and AuNPs based on spectrophotometric methods was prepared with nicotine concentrations range from 0.10 to 5.00 μM (R2 = 0.9903) and 0.001–0.300 μM (R2 = 0.9960), respectively. The detection limits were found to be 0.001 µM for AuNPs based method and 0.09 µM for AgNPs based method. The proposed nanoparticle-based spectrophotometric methods showed a good stability, selectivity and low detection limit

Bulky Thiolate-Protected Silver Nanocluster Ag 213 (Adm-S) 44 Cl 33 with Excellent Electrocatalytic Performance toward Oxygen Reduction

Bulky Thiolate-Protected Silver Nanocluster Ag ₂₁₃ (Adm-S) ₄₄ Cl ₃₃ with Excellent Electrocatalytic Performance toward Oxygen Reduction

A novel photo-thermo-refractive glass with chlorine instead of bromine for holographic application

The well-known standard photo-thermo-refractive (PTR) glass has some limitations in holographic applications in the visible region due to light scattering on the large NaF nanocrystals formed during the photo-thermo-induced (PTI) crystallization process. The large size of the NaF nanocrystals can be reduced by forming more nucleation centers (silver nanoparticles). We suppose this can be achieved by introducing more silver into the batch composition of the glass. However, bromine does not permit high silver concentrations due to the spontaneous crystallization and high Mie-scattering. Therefore, we introduce a novel PTR glass by replacing bromine with chlorine. The novel glass enables us to increase the silver concentration and consequently increase the concentration of the formed nanoparticles. The optical properties, differential scanning calorimetry, and X-ray diffraction analyses were performed on the novel glasses. An experimental and theoretical investigation of the PTI crystallization process was carried out by monitoring the evolution of the surface plasmon resonance (SPR) absorption band. It was found that the UV exposure and heat treatment lead to precipitation of the NaF crystalline phase on a chlorine-containing dielectric shell that surrounds the silver nanoparticle. It was also found that using chlorine instead of bromine leads to a blue shift in the SPR absorption peak location.Volume Bragg gratings were successfully recorded in the novel PTR glasses. The maximum value of the refractive index modulation amplitude obtained for the novel glass is comparable with that for the standard PTR glass.

Efficient and recyclable AuNPs/aminoclay nanocomposite catalyst for the reduction of organic dyes

Industrial dye effluents and organic pollutants pose serious environmental threats for which efficient catalytic adsorbents have been indispensable in treating them. In the present work, the synthesis of gold nanoparticles (AuNPs) dispersed over aminopropyl-functionalized magnesium phyllosilicate (AMP) composites (AuNPs/AMP NC) is reported, involving the organic-inorganic hybrid structure with the strategy of AuNP formation over AMP clay. The AuNPs decorated AMP hybrid nanocomposite was characterised by XRD, FTIR, TGA, UV-Visible, SEM-EDAX, and TEM techniques. The presence of a surface plasmon resonance (SPR) absorption band at 520 nm in UV-Visible spectra revealed the formation of AuNPs over AMP support, which was supported by XRD results. The average particle size of AuNPs with spherical morphology was in the range of 3 nm, respectively. The catalytic performance of the AuNPs/AMP NC was studied through the reduction of malachite green (MG), phenol red (PR), rhodamine B (RhB), rhodamine 6 G (Rh6G), and Congo red (CR) in the presence of NaBH4, respectively. The progress of reductive dye degradation was monitored via UV–Vis spectrophotometry. The kinetic data was analysed and apparent rate constants were determined for the respective dyes. The reduction efficiency of the nanocatalyst over MG, PR, RhB, Rh6G, and CR, in the presence of NaBH4 was determined as > 98%, respectively. Such prolific nanocomposite catalysts could be employed as an alternative to toxic dye and organic component degradation in environmental treatment.