Distribution Of Metal Nanoparticles Research Articles

Electrical and Dielectric Properties of Polymer-Metal Hybrid Nanocomposites - A Short Review

Polymer-metal hybrid nanocomposites have garnered significant attention in recent years due to their exceptional electrical and dielectric properties, which find applications in a wide range of industries, including electronics, energy storage, and advanced materials. This review article provides a comprehensive overview of the current state-of-the-art in the field of polymer-metal hybrid nanocomposites, with a particular focus on their electrical and dielectric properties. The first section of the review delves into the synthesis and fabrication techniques employed to create these nanocomposites, highlighting the importance of controlling the dispersion and distribution of metal nanoparticles within the polymer matrix. Various approaches, such as in-situ polymerization, melt mixing, and electrospinning, are discussed in detail, along with their respective advantages and limitations.The subsequent sections explore the influence of metal nanoparticles on the electrical conductivity and dielectric constant of the nanocomposites. The role of factors such as nanoparticle size, shape, and concentration in determining these properties is thoroughly examined. Moreover, the impact of metal surface modifications and the choice of polymer matrix on enhancing electrical and dielectric performance are also addressed. In addition to discussing fundamental aspects, this review highlights practical applications of polymer-metal hybrid nanocomposites in the development of high-performance capacitors, sensors, electromagnetic shielding materials, and flexible electronics. The potential for these materials to revolutionize various technological sectors is discussed, emphasizing their role in advancing miniaturization, energy efficiency, and durability. Furthermore, the review outlines current challenges and future prospects in the field, including the need for a deeper understanding of the underlying mechanisms governing electrical and dielectric behavior in these nanocomposites. Emerging trends such as the incorporation of 2D materials and the development of multifunctional hybrid systems are also explored, hinting at exciting avenues for further research and innovation. In conclusion, polymer-metal hybrid nanocomposites offer a promising platform for tailoring electrical and dielectric properties to meet the demands of modern technology. This review serves as a valuable resource for researchers, engineers, and scientists seeking to explore the potential of these materials and drive advancements in the field of electrical and dielectric engineering.

Ti/Ta-based composite polysaccharide scaffolds for guided bone regeneration in total hip arthroplasty

Guided bone regeneration can play an important role in orthopedic applications. This work presents the synthesis and characterization of composite scaffolds based on polysaccharides loaded with microparticles of titanium or tantalum as novel materials proposed for composite systems with promising characteristics for guided bone regeneration. Ti/Ta composite scaffolds were synthesized using chitosan and gellan gum as organic substrates and crosslinked with oxidized dextran resulting in stable inorganic-organic composites. Physico-chemical characterization revealed a uniform distribution of metal nanoparticles within the scaffolds that showed a release of metals lower than 5 %. In vitro biological assays demonstrated that Ta composites exhibit a 2 times higher ALP activity than Ti and a higher capacity to support the full differentiation of human mesenchymal stem cells into osteoblasts. These results highlight their potential for bone regeneration applications.

Porous CN@MOF derived N, S-doped hierarchical framework carrying Co3Fe7/Fe0.8Co0.2S heterojunction: An efficient bifunctional cathode catalyst for Zn–air battery

The exploiting of bifunctional transition metal electrocatalysts for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) is of significance for the commercialization of rechargeable zinc-air batteries (ZABs). Herein, the N and S atoms-doped hierarchical carbon framework hosting the Co3Fe7/Fe0.8Co0.2S heterojunction is synthesized by employing porous g-C3N4 as framework and spacer, and FeCo-ZIF as metal source followed by sulfidation and pyrolysis. The detailed characterization confirms that the porous g-C3N4 plays a crucial role in improving the dispersion of metal nanoparticles. The obtained FeCo-Sx@NSC-900 catalysts exhibit layered accumulation configuration with uniformly distributed metal nanoparticles. Moreover, the typical carbon@metal nanoparticles and heterojunction structure can be observed from the HRTEM (High-Resolution Transmission Electron Microscopy) and HAADF-STEM (high-angle annular dark-field STEM) analysis results. The optimal FeCo-Sx@NSC-900 catalysts deliver exceptional ORR and OER performance with a potential difference between ORR and OER of merely 0.713 V, which is superior to the commercial Pt/C+RuO2 catalysts and other monometallic catalysts. Additionally, the ZAB assembled with the optimal FeCo-Sx@NSC-900 catalysts as cathode affords a good battery performance with high OCV (1.50 V), large power density (172 mW/cm2), good discharge stability, large specific capacity, and long-term charge/discharge stability (>300 cycles).

Antimicrobial Antioxidant Polymer Films with Green Silver Nanoparticles from Symphyti radix.

Antimicrobial natural polymer film with silver nanoparticles (AgNPs) biosynthesized using aqueous plant root extracts as reducing capping agents and for film formatting show extensive applicability for pathogenic microorganism problems. The formation of AgNPs was confirmed by transmission electron microscopy (TEM) and scanning electron microscopy-energy-dispersive spectroscopy (SEM-EDS) techniques. The antimicrobial activity of biofilm with green AgNPs was analysed by inhibiting the growth of Gram-negative and Gram-positive bacteria culture using the Kirby-Bauer disk diffusion susceptibility test. Total phenolic content and antioxidant activity were slightly higher in aqueous extracts of Sym. Radix than in Sym. Radix/AgNPs. The antimicrobial effect of polymer film/AgNPs against selected test bacteria cultures was substantially more robust than with pure film. Pictures of AgNPs obtained by TEM revealed the presence of spherical-shaped nano-objects with an average size 27.45 nm. SEM-EDS studies confirmed the uniform distribution of metal nanoparticles throughout the biopolymeric matrix. Morphological studies of the surface showed that the obtained surface of the films was even, without holes or other relief irregularities. These apparent Symphyti radix polymer film/AgNPs' biological functions could provide a platform for fighting pathogenic bacteria in the era of multi-drug resistance.

Enhancing the Properties of Photo-Generated Metallized Nanocomposite Coatings through Thermal Annealing.

In this work, the effect of thermal annealing on silver nanoparticles@polymer (AgNPs@polymer) nanocomposite coatings was investigated. These photo-generated metallized coatings have a spatial distribution of metal nanoparticles, with a depth-wise decrease in their concentration. During annealing, both structural and morphological variations, as well as a spatial reorganization of AgNPs, were observed, both at the surface and in the core of the AgNPs@polymer coating. Owing to their increased mobility, the polymer chains reorganize spontaneously, and, at the same time, a hopping diffusion process, caused by the minimization of the surface energy, promotes the migration and coalescence of the silver nanoparticles towards the surface. The layer of discrete nanoparticles gradually transforms from a weakly percolative assembly to a denser and more networked structure. Consequently, the surface of the coatings becomes significantly more electrically conductive, hydrophobic, and reflective. The general trend is that the thinner the nanohybrid coating, the more pronounced the effect of thermal annealing on its spatial reorganization and properties. These results open up interesting prospects in the field of metallized coating technology and pave the way for integration into a wide variety of devices, e.g., efficient and inexpensive reflectors for energy-saving applications, electrically conductive microdevices, and printed electronic microcircuits.

Polydopamine-mediated in situ synthesis of gold nanoparticles uniformly distributed on silk fibers as reusable catalysts for efficient 4-nitrophenol reduction

Developing green fibrous materials with uniformly distributed metal nanoparticles for highly efficient and recyclable catalysis remains a major challenge. Herein, we developed a simple, effective, and green method to immobilize gold nanoparticles (AuNPs) on polydopamine (PDA)-functionalized silk fibers (SFs) for efficient catalytic reduction of 4-nitrophenol (4-NP). The density and size of AuNPs on the PDA-coated SFs can be tuned by adjusting precursor concentration and synthesis duration, respectively. The AuNPs-PDA-SFs catalysts prepared under optimized conditions could catalyze the reduction of 4-NP, 4-nitroaniline (4-NA), and 4-amino-3-nitrophenol (4-A-3-NP) at the apparent rate constants of 0.087, 0.091, and 0.063 min−1, respectively. After six rounds of flow-through reduction of 4-NP, the AuNPs-PDA-SFs could maintain a 4-NP conversion rate greater than 92%, indicating their superior reusability and consistent catalytic activity. Due to the protein properties of SFs, the AuNPs-PDA-SFs can be degraded by enzymes and alkali solutions. This work may provide new insights for designing advanced fiber-supported recyclable catalysts with high catalytic performance and reusability in wastewater treatment.

Solvent-free Synthesis of Transition Metals Nanoparticles Decorated Foamy Flakes-like Nitrogen-doped Carbon as Bifunctional-catalyst for High-performance Rechargeable Zn-air Batteries

Transition metal-nitrogen-carbon (M/NC) demonstrates a promising effective electrocatalyst for enhancing oxygen evolution/reduction reactions (OER/ORR). However, synthesizing these catalysts is often complex, time-consuming, and involves hazardous solvents while producing a low yield. This work introduces a versatile, eco-friendly, and straightforward solvent-free method to produce M/NC (M = Co, Ni, and Fe) catalysts in ~3 h using a glucose, urea, and metal nitrate hydrate mixture. The high-yield M/NC catalysts exhibit a porous architecture and uniform distribution of metal nanoparticles within a foaming flakes-like nitrogen-doped carbon matrix. The metal nanoparticles are wrapped with protective nitrogen-doped carbon layers, producing stable active sites. Possessing these unique properties, the obtained M/NC catalysts show high-performance and stable bifunctional OER/ORR. As the best result, Co/NC presents an OER/ORR potential difference (ΔE) of 0.78 V and retains 96% and 89% of its OER and ORR performance after a 10 h stability test. In practical application, the Co/NC-based Zn-air battery depicts a high power density of 184 mW cm−2 and good rechargeability of up to 120 h, outperforming the battery with noble metal-based catalysts. This work sheds light on the versatile, eco-friendly, and scalable synthesis of M/NC catalysts while presenting a strategy to accelerate the generation of inexpensive and highly effective bifunctional OER/ORR catalysts.

Modified paper-based substrates fabricated via electrostatic attraction of gold nanospheres for non-destructive detection of pesticides based on surface-enhanced Raman spectroscopy.

Flexible surface-enhanced Raman spectroscopy (SERS) substrates such as paper-based substrates show great potential for rapid detection of residual chemicals on food surfaces. However, controlling the density and distribution of metallic nanoparticles adsorbed on the paper is still challenging. The amount of gold (Au) nanospheres (51 ± 4 nm) attached on the filter paper modified with 3-aminopropyltriethoxysilane (APTES) was tunable, increasing as the level of APTES (2.5-15.0 g kg-1 ) applied for paper modification increased. Moreover, the Au nanospheres were relative evenly distributed on the filter paper modified with 2.5-10.0 g kg-1 of APTES, which resulted in excellent intra- and inter-reproducibility of SERS signals for pesticides including thiram, diquat dibromide, and paraquat dichloride (relative standard deviation = 2.2-10.1%). The modified paper-based substrate could be used to detect as low as 0.05-0.2 mg L-1 of pesticides in standard solutions, and as low as 5-20 ng cm-2 of residual pesticides on apple skins with minimum sample pretreatment. This paper-based substrate with tunable feature for the density and distribution of nanoparticles is applicable for rapid SERS detection of residual pesticides in fruits and vegetables. © 2023 Society of Chemical Industry.

Size Analysis of Silver and Gold Nanoparticles Using Laser Ablation Single Particle ICP Mass Spectrometry: Evaluation of the Laser-Induced Disintegration of Nanoparticles.

Single particle inductively coupled plasma mass spectrometry combined with the laser ablation technique (LA-spICP-MS) has been used for the determination of particle size and the spatial distribution of metal nanoparticles (MNPs) in various solid samples such as biological samples and semiconductor materials. In this study, we investigated the effect of the fluence of the laser being used on the disintegration of MNPs. Commercially available MNPs of silver and gold (Ag NPs and Au NPs), the sizes of which were determined by transmission electron microscopy (TEM), were analyzed with LA-spICP-MS. We evaluated the degree of disintegration of the original-sized particles, based on a comparison of the size distributions obtained by LA-spICP-MS and other analytical techniques. The disintegration of both the Ag NPs and Au NPs was induced by a laser ablation process when the laser fluence was higher than 1.0 J cm-2, whereas no disintegration was observed when the fluence was lower than 1.0 J cm-2. Moreover, the mean diameter and standard deviation of the determined diameters obtained by LA-spICP-MS were in good agreement with solution-based spICP-MS and TEM analysis within analytical uncertainty. The data obtained here demonstrates that LA-spICP-MS represents a promising potential analytical technique for accurately determining the size of individual MNPs and their spatial distribution in solid samples.

Boosting Catalytic Selectivity through a Precise Spatial Control of Catalysts at Pickering Droplet Interfaces.

Exploration of new methodologies to tune catalytic selectivity is a long-sought goal in catalytic community. In this work, oil-water interfaces of Pickering emulsions are developed to effectively regulate catalytic selectivity of hydrogenation reactions, which was achieved via a precise control of the spatial distribution of metal nanoparticles at the droplet interfaces. It was found that Pd nanoparticles located in the inner interfacial layer of Pickering droplets exhibited a significantly enhanced selectivity for p-chloroaniline (up to 99.6%) in the hydrogenation of p-chloronitrobenzene in comparison to those in the outer interfacial layer (63.6%) in pure water (68.5%) or in pure organic solvents (46.8%). Experimental and theoretical investigations indicated that such a remarkable interfacial microregion-dependent catalytic selectivity was attributed to the microenvironments of the coexistence of water and organic solvent at the droplet interfaces, which could provide unique interfacial hydrogen-bonding interactions and solvation effects so as to alter the adsorption patterns of p-chloronitrobenzene and p-chloroaniline on the Pd nanoparticles, thereby avoiding the unwanted contact of C-Cl bonds with the metal surfaces. Our strategy of precise spatial control of catalysts at liquid-liquid interfaces and the unprecedented interfacial effect reported here not only provide new insights into the liquid-liquid interfacial reactions but also open an avenue to boost catalytic selectivity.

Design and synthesis of Pd decorated rGO-MoSe2 2D hybrid network as high performance electrocatalyst toward methanol electrooxidation

Direct methanol fuel cells (DMFCs) have attracted profound interest for development of future green energy sources, which are being powered by methanol as a fuel. The critical problem identified with DMFCs is the deactivation of electrocatalysts resulting from the adsorption of CO during methanol oxidation. In this work, we have employed a new synthetic approach by a green microwave method for the synthesis of hybrid Pd-MoSe2-rGO and Pd-rGO nanocomposites. The synthesized electrocatalysts were successfully characterized by XRD, which is used to identify the crystalline phases, FESEM and TEM analyses for morphological features, XPS for analyzing the elements constituting the composites surface and Raman spectroscopy for the analysis of molecular structural bonding. Electrocatalytic activity was explored by cyclic voltammetry (CV), chronoamperometry (CA) and CO stripping techniques. Electroactive surface area (EASA) of the developed hybrid electrocatalyst Pd-MoSe2-rGO (51.81 m2 g−1Pd) was more than 3.4 times superior activity than that of Pd-rGO catalyst (15.30 m2 g−1Pd). It was observed that the synthesized catalyst with 3D cross-linked hybrid network facilitated even distribution of metal nanoparticles and exhibited nearly four times enhanced electrocatalytic activity (1935 mA mg−1Pd) towards methanol oxidation reaction (MOR) in alkaline medium, compared to Pd-rGO (546 mA mg−1Pd). Under constant applied potential investigations, catalytic activity of Pd-MoSe2-rGO was nearly 50 times higher than that of Pd-rGO at the end of about 1 h. The ease of the availability of more active sites and high tolerance against CO poisoning resulted by the insertion of MoSe2 led to enhanced catalytic activity of Pd-MoSe2-rGO towards MOR. It is conceived that this synthetic strategy by employing a combination of 2D materials like MoSe2, graphene and Pd nanoparticles together as building blocks for 3D hybrid network led to efficient electrocatalysts with high surface area and long-term stability towards methanol oxidation. This synthetic strategy exhibits a promising prospect to develop durable and stable electrocatalyst for DMFC applications.

Nitrogen-Doped Pitch-Based Activated Carbon Fibers with Multi-Dimensional Metal Nanoparticle Distribution for the Effective Removal of NO

The design of catalytic materials for NOX removal by the selective catalytic reduction with NH3 (NH3-SCR) has been a focus of research in the field of waste gas treatment. In this work, pitch-based activated carbon fibers (ACFs) were impregnated with copper nitrate and cerium nitrate, and then the ACFs that were loaded with bimetallic nanoparticles (ACF@Cu/Ce) were obtained after the pyrolyzation and reduction were performed. Moreover, the ACF@Cu/Ce were furtherly treated through the chemical vapor deposition and NH3 activation, through which the N-doped carbon nanofibers (N-CNFs) were grown on the surface of the ACFs. Thus, the catalytic material with a multi-dimensional metal nanoparticle distribution and nitrogen-rich network structure, namely the N-CNF/ACF@Cu/Ce, was constructed. In the NH3-SCR reaction, the NO conversion of the N-CNF/ACF@Cu/Ce could be maintained at about 72~81% in a wide temperature window of 295~495 °C, which enabled the N-CNF/ACF@Cu/Ce to meet the requirements of the practical applications.

Monometallic and bimetallic SiC(O) ceramic with Ni, Co and/or Fe nanoparticles for catalytic applications

Monometallic (Ni, Co or Fe-SiC(O)) and bimetallic (Ni, Co or FeM-SiC(O) with M = Ni or Co) ceramic nanocomposites have been successfully prepared using polymeric precursors obtained by chemical modification of polycarbosilane with metal acetylacetonate. The nanocomposites consist of homogeneously distributed metal nanoparticles within an amorphous SiC(O). The specific surface area (SSA) of Ni, Co or Fe-SiC(O)600 nanocomposites were found to be 155, 50 or 14 m2/g. However, the addition of Fe to the Ni-or Co-containing precursors tends to increase the SSA to 290 or 170 m2/g. Maximum CO2 conversion for monometallic samples was found to be 40% at 500 °C for Ni-SiC(O)600 and maximum CH4 selectivity was 61% at 300 °C for Co-SiC(O)600. The additional presence of Co and Ni in the respective nanocomposites helps to increase the CO2 conversion and selectivity at 500 °C whereas Fe modification shows high methane selectivity at lower temperature < 350 °C.

Tunable and enhanced microwave absorption properties by adjusting the distribution of Co/CoFe embedded into the carbon nanohorns and graphene microspheres

Designing unique structures of magnetic particle/carbon composites with multiple heterogeneous interfaces is an effective strategy for improving the properties of microwave absorption. Herein, hierarchical spacing arrangements for Co@carbon nanohorns and Co@graphene microspheres (Co@CNHs/G) with N enrichment were synthesized by a simple self-assembly method. As a result, Co@CNHs/G exhibited excellent electromagnetic wave absorption performance, and its reflection loss (RL) values of − 44.72 dB and − 41.39 dB at the C band had thicknesses of 2.9 mm and 2.5 mm, respectively. Additionally, the maximum effective absorption bandwidth (RL ≤ −10 dB) was 5.7 GHz at 1.4 mm. More importantly, the distribution of metal nanoparticles into CNHs and graphene microspheres were adjusted by forming the CoFe alloy embedded into CNHs and graphene microspheres during arc discharge process. Consequently, the frequency of RL ≤ −40.00 dB was from the C band to the X band by changing the multiple scattering paths, and the corresponding thickness for the minimum RL (−40.00 dB) was 1.8 mm. The outstanding electromagnetic absorbing performance was mainly attributed to the enhanced dielectric loss involving interfacial polarization derived from multiple heterogeneous interfaces, dipolar polarization induced by N-doping, and defects in the CNHs and graphene. In addition, multiple complex scattering paths can further improve the attenuation of electromagnetic waves.

Formation of Iron Oxide Nanoparticles in the Internal Cavity of Ferritin-Like Dps Protein: Studies by Anomalous X-Ray Scattering

DNA-binding protein from starved cells (Dps) takes a special place among dodecamer mini-ferritins. Its most important function is protection of bacterial genome from various types of destructive external factors via in cellulo Dps–DNA co-crystallization. This protective response results in the emergence of bacterial resistance to antibiotics and other drugs. The protective properties of Dps have attracted a significant attention of researchers. However, Dps has another equally important functional role. Being a ferritin-like protein, Dps acts as an iron depot and protects bacterial cells from the oxidative damage initiated by the excess of iron. Here we investigated formation of iron oxide nanoparticles in the internal cavity of the Dps dodecamer. We used anomalous small-angle X-ray scattering as the main research technique, which allows to examine the structure of metal-containing biological macromolecules and to analyze the size distribution of metal nanoparticles formed in them. The contributions of protein and metal components to total scattering were distinguished by varying the energy of the incident X-ray radiation near the edge of the metal atom absorption band (the K-band for iron). We examined Dps specimens containing 50, 500, and 2000 iron atoms per protein dodecamer. Analysis of the particle size distribution showed that, depending on the iron content in the solution, the size of the nanoparticles formed inside the protein molecule was 2 to 4 nm and the growth of metal nanoparticles was limited by the size of the protein inner cavity. We also found some amount of iron ions in the Dps surface layer. This layer is very important for the protein to perform its protective functions, since the surface-located N-terminal domains determine the nature of interactions between Dps and DNA. In general, the results obtained in this work can be useful for the next step in studying the Dps phenomenon, as well as in creating biocompatible and solution-stabilized metal nanoparticles.

Reduced graphene oxide supported cobalt catalysts for ethylene hydroformylation: Modified cobalt-support interaction by rhodium

The metal-support interaction (MSI) alters the geometric morphologies, electronic properties, or distribution of metal nanoparticles, which is indeed to influence the heterogenous catalytic system. Two heterogenous ethylene hydroformylation catalysts, cobalt supported on reduced graphene oxide (RGO) with or without Rhodium (5%Rh-20%Co/RGO and 20%Co/RGO), were successfully synthesized. The effect of the MSI between Co and RGO and a MSI tuning strategy by Rh on the ethylene hydroformylation (EH) were investigated. CoO nanorods was present in fresh Rh-Co/RGO, while only CoO nano-particles were formed in fresh Co/RGO. Rh enhanced the reducibility of the cobalt species. After reduction and the ethylene hydroformylation reaction, Co2C was formed in spent Rh-Co/RGO, while a mixture of Co and CoO were present in the spent Co/RGO. Co2C grew to a large flat plane structure in spent Rh-Co/RGO, while Co and CoO formed smaller nano-particles in spent Co/RGO. The changes of the geometric morphologies and the phases of the active species made by the Rh-Co-RGO interaction significantly enhance the activity of the CO and the selectivity for the production of the C3 oxygenates. A Model on how the nanoparticles distributed on the RGO were hypothesized.

Tailoring the size of silver nanoparticles by controlling mixing in microreactors

Microreactors are commonly regarded by their high mass transfer rates associated to their small diameters. Although this is true, especially when compared to batch systems, mixing is frequently exclusively dominated by diffusion in single phase flow microreactors, being the fast mixing of reactants an aspect often overlooked during their design. This paper presents the first quantitative analysis of the effect of mixing of precursors on the size and distribution of metal nanoparticles synthesized in flow microreactors. Silver nanoparticles with a range of sizes are continuously synthesized by controlling mixing efficiency in rationally-designed microreactors. The particle size decreases as the mixing index increases due to an increase in nucleation rate and thus the resulting nuclei concentration. Herein, the mixing efficiencies of different 3D curved microreactors are quantitatively evaluated using accurate simulations of their concentration profiles, avoiding the so-called numerical diffusion errors using a novel method based on backward particle tracking. A method based on forward particle tracking is improved to simulate the residence time distributions (RTD) in microreactors at a reduced computational cost. Curving the reactors channels is known to lead to the formation of Dean vortices however, these well-defined rotations lead to stagnant zones. The mixing efficiency can be enhanced and the RTD narrowed by periodically changing the direction of the Dean vortices along the length of the channel. In addition, we demonstrate the effect of the configuration of the inlet streams relative to the curvature of the reactor and thus, the Dean vortices, on the resulting mixing. These results provide rational design guidelines for the design of microreactors to manipulate advection as a way of manipulating the reaction rates as demonstrated here to control nanoparticle sizes.

Influence of Random Plasmonic Metasurfaces on Fluorescence Enhancement.

One of the strategies employed to increase the sensitivity of the fluorescence-based biosensors is to deposit chromophores on plasmonic metasurfaces which are periodic arrays of resonating nano-antennas that allow the control of the electromagnetic field leading to fluorescence enhancement. While artificially engineered metasurfaces realized by micro/nano-fabrication techniques lead to a precise tailoring of the excitation field and resonant cavity properties, the technological overhead, small areas, and high manufacturing cost renders them unsuitable for mass production. A method to circumvent these challenges is to use random distribution of metallic nanoparticles sustaining plasmonic resonances, which present the properties required to significantly enhance the fluorescence. We investigate metasurfaces composed of random aggregates of metal nanoparticles deposited on a silicon and glass substrates. The finite difference time domain simulations of the interaction of the incident electromagnetic wave with the structures reveals a significant enhancement of the excitation field, which is due to the resonant plasmonic modes sustained by the nanoparticles aggregates. We experimentally investigated the role of these structures in the fluorescent behaviour of Rhodamine 6G dispersed in polymethylmethacrylate finding an enhancement that is 423-fold. This suggests that nanoparticle aggregates have the potential to constitute a suitable platform for low-cost, mass-produced fluorescent biosensors.

Sustainable iron-olive stone-based catalysts for Fenton-like olive mill wastewater treatment: Development and performance assessment in continuous fixed-bed reactor operation

Iron oxide catalysts supported on activated carbon prepared from olive stones (OSAC–Fe) were used for the catalytic wet peroxide oxidation of refractory polyphenolic solutions and real olive mill wastewater (OMW) in a fixed-bed reactor (FBR). Catalysts were prepared with different precursors and Fe-loadings. The resulting catalysts were essentially microporous materials with well-developed surface areas (SBET = 588–689 m2/g), whereas the nature and distribution of metallic nanoparticles were found to be strongly dependent on the precursor used.The stability and catalytic performance were screened in a batch reactor using a synthetic solution and the most promising catalyst – prepared at 5 wt.% Fe using Fe(NO3)3 as the precursor – was selected for the operation of a continuous FBR. Different operational conditions were evaluated through a parametric study. At 60 °C, [H2O2]feed = 1.5 g/L and Q = 0.75 mL/min, 87% total phenolic content removal (TPh), 28% mineralization and 88% H2O2 conversion were achieved at steady-state. Real OMW samples were then treated at a fixed [H2O2]/[COD] in the feed, and TPh removals of 57–71% and COD (chemical oxygen demand) reductions of 26–34% were attained. The resulting effluents showed an overall reduction of eco-toxicity and improvement of biodegradability indices.

Bio-Based Graphene Sheet/Copolymer Composite as Supporting Material for Nanocatalysts towards Electrochemical Studies and Direct Alkaline Alcohol Fuel Cells

In this work, graphene carbon sheets (BGS) were prepared from writing paper and lemon peel, and its polymer composite has a higher surface area compared with the existing Vulcan carbon. Further, the use of lead as a promoter for the oxidation of alcohol and CO on platinum-supported poly(amine-terminated cyclophosphazene-co-cyclophosphazene)-biobased graphene sheet (Poly(AFCP-co-CP)-BGS) composite was demonstrated. The size, phase morphology, and distribution of metal nanoparticles on Poly(AFCP-co-CP)-BGS composite as well as the formation of composite based catalysts were confirmed from TEM, XRD, and FTIR studies. The catalytic activity and stability of the prepared catalysts were tested and compared to methanol, ethylene glycol, glycerol, and CO in 0.5 M KOH solution. The results conclude that the lead-doped Pt/Poly(AFCP-co-CP)-BGS catalyst shows higher oxidation current with respect to onset potential and lower I f / I r ratio for alcohol as well as CO oxidation. In addition, Pt-Pb/Poly(AFCP-co-CP)-BGS catalyst was checked for direct alkaline fuel cells and proved as a potent anode catalyst in alkaline medium for real-time fuel battery applications. In addition, Poly(AFCP-co-CP)-BGS composite also promotes the catalytic reaction compared to Poly(AFCP-co-CP) and BGS supports as noticed from methanol oxidation in alkaline medium. The surface area of the prepared supporting material is 750.72 m2g-1, which is higher than the activated carbon (250.12m2g-1). So, the prepared Poly(AFCP-co-CP)-BGS composite is a potent support for metal deposition, electrooxidation, and single stack fuel cell constructions.