Boosting Urea-Assisted Natural Seawater Electrolysis in 3D Leaf-Like Metal-Organic Framework Nanosheet Arrays Using Metal Node Engineering.

Metal node engineering, which can optimize the electronic structure and modulate the composition of poor electrically conductive metal-organic frameworks, is of great interest for electrochemical natural seawater splitting. However, the mechanism underlying the influence of mixed-metal nodes on electrocatalytic activities is still ambiguous. Herein, a strategic design is comprehensively demonstrated in which mixed Ni and Co metal redox-active centers are uniformly distributed within NH2-Fe-MIL-101 to obtain a synergistic effect for the overall enhancement of electrocatalytic activities. Three-dimensional mixed metallic MOF nanosheet arrays, consisting of three different metal nodes, were in situ grown on Ni foam as a highly active and stable bifunctional catalyst for urea-assisted natural seawater splitting. A well-defined NH2-NiCoFe-MIL-101 reaches 1.5 A cm-2 at 360 mV for the oxygen evolution reaction (OER) and 0.6 A cm-2 at 295 mV for the hydrogen evolution reaction (HER) in freshwater, substantially higher than its bimetallic and monometallic counterparts. Moreover, the bifunctional NH2-NiCoFe-MIL-101 electrode exhibits eminent catalytic activity and stability in natural seawater-based electrolytes. Impressively, the two-electrode urea-assisted alkaline natural seawater electrolysis cell based on NH2-NiCoFe-MIL-101 needs only 1.56 mV to yield 100 mA cm-2, much lower than 1.78 V for alkaline natural seawater electrolysis cells and exhibits superior long-term stability at a current density of 80 mA cm-2 for 80 h.

Dopant-Induced Charge Redistribution on the 3D Sponge-like Hierarchical Structure of Quaternary Metal Phosphides Nanosheet Arrays Derived from Metal-Organic Frameworks for Natural Seawater Splitting.

Dopant-induced electron redistribution on transition metal-based materials has long been considered an emerging new electrocatalyst that is expected to replace noble-metal-based electrocatalysts in natural seawater electrolysis; however, their practical applications remain extremely daunting due to their sluggish kinetics in natural seawater. In this work, we developed a facile strategy to synthesize the 3D sponge-like hierarchical structure of Ru-doped NiCoFeP nanosheet arrays derived from metal-organic frameworks with remarkable hydrogen evolution reaction (HER) performance in natural seawater. Based on experimental results and density functional theory calculations, Ru-doping-induced charge redistribution on the surface of metal active sites has been found, which can significantly enhance the HER activity. As a result, the 3D sponge-like hierarchical structure of Ru-NiCoFeP nanosheet arrays achieves low overpotentials of 52, 149, and 216 mV at 10, 100, and 500 mA cm-2 in freshwater alkaline, respectively. Notably, the electrocatalytic activity of the Ru-NiCoFeP electrocatalyst in simulated alkaline seawater and natural alkaline seawater is nearly the same as that in freshwater alkaline. This electrocatalyst exhibits superior catalytic properties with outstanding stability under a high current density of 85 mA cm-2 for more than 100 h in natural seawater, which outperforms state-of-the-art 20% Pt/C at high current density. Our work provides valuable guidelines for developing a low-cost and high-efficiency electrocatalyst for natural seawater splitting.

Ultrasensitive Monitoring of Cyanide Concentrations in Water Using a Aucore-Agshell Hybrid-Coating-Based Fiber Optical Sensor.

Cyanides, which are extremely toxic chemicals that are rapidly absorbed into the human body and interact with cytochrome oxidase, strongly inhibit cellular respiration to body death with convulsions. Cyanide ions that exist in many forms in nature such as those found in apricot kernels, cassava roots, and bamboo shoots as cyanogenic glycosides are inevitably used in various industries, including gold and silver mining as well as in dyes and plastic industries. In this study, for the sake of developing ultrahigh-sensitive sensors for cyanide monitoring in a simple manner, we chemically synthesize Aucore-Agshell hybrid nanomaterials of different core/shell thicknesses for colorimetric sensors and fiber optical sensors. Their sensing principle relies on the formation of the Ag/Au cyanocomplex upon cyanide injection. The generated metal cyanocomplex induced changes in refractive indices, causing changes in properties of localized surface plasmon resonance (LSPR), i.e., optical absorbance change for the colorimetric sensors. For fiber optical sensors, the hybrid metal nanoparticles were immobilized on the fiber core surface and the metal cyanocomplex formation induced changes in the fiber cladding refractive index, enabling quantitative cyanide detection with ultrahigh sensitivity. The LSPR-based colorimetric sensor provided the lowest detectable cyanide concentration of 5 × 10-6 M, whereas the value for the fiber-based sensor was 8 × 10-11 M.

Facile Hydrothermal Synthesis of Ag/Fe3O4/Cellulose Nanocomposite as Highly Active Catalyst for 4-Nitrophenol and Organic Dye Reduction.

Novel effluent treatment solutions for dangerous organic pollutants are crucial worldwide. In recent years, chemical reduction using noble metal-based nanocatalysts and NaBH4, a reducing agent, has become common practice for eliminating organic contaminants from aquatic environments. We suggest a straightforward approach to synthesizing magnetic cellulose nanocrystals (CNCs) modified with magnetite (Fe3O4) and silver nanoparticles (Ag NPs) as a catalyst for organic contamination removal. Significantly, the CNC surface was decorated with Ag NPs without using any reducing agents or stabilizers. PXRD, FE-SEM, TEM, EDX, VSM, BET, and zeta potential tests characterized the Ag/Fe3O4/CNC nanocomposite. The nanocomposite's catalytic activity was tested by eliminating 4-nitrophenol (4-NP) and the organic dyes methylene blue (MB) and methyl orange (MO) in an aqueous solution at 25 °C. The Ag/Fe3O4/CNC nanocomposite reduced 4-NP and decolored these hazardous organic dyes in a short time (2 to 5 min) using a tiny amount of catalyst (2.5 mg for 4-NP and 15 mg for MO and MB). The magnetic catalyst was removed and reused three times without losing catalytic activity. This work shows that the Ag/Fe3O4/CNC nanocomposite can chemically reduce harmful pollutants in effluent for environmental applications.

Highly Efficient and Stable Hydrogen Evolution from Natural Seawater by Boron-Doped Three-Dimensional Ni2P-MoO2 Heterostructure Microrod Arrays.

The rational design of highly active and stable electrocatalysts toward the hydrogen evolution reaction (HER) is highly desirable but challenging in seawater electrolysis. Herein we propose a strategy of boron-doped three-dimensional Ni2P-MoO2 heterostructure microrod arrays that exhibit excellent catalytic activity for hydrogen evolution in both alkaline freshwater and seawater electrolytes. The incorporation of boron into Ni2P-MoO2 heterostructure microrod arrays could modulate the electronic properties, thereby accelerating the HER. Consequently, the B-Ni2P-MoO2 heterostructure microrod array electrocatalyst exhibits a superior catalyst activity for HER with low overpotentials of 155, 155, and 157 mV at a current density of 500 mA cm-2 in 1 M KOH, 1 M KOH + NaCl, and 1 M KOH + seawater, respectively. It also exhibits exceptional performance for HER in natural seawater with a low overpotential of 248 mV at 10 mA cm-2 and a long-lasting lifetime of over 100 h.

Promoting High-Oxidation-State Metal Active Sites in a Hollow Ternary Metal Fluoride Nanoflake Array for Urea Electrolysis.

The adsorption ability of hydrogen, hydroxide, and oxygenic intermediates plays a crucial role in electrochemical water splitting. Electron-deficient metal-active sites can prompt electrocatalytic activity by improving the adsorption ability of intermediates. However, it remains a significant challenge to synthesize highly abundant and stable electron-deficient metal-active site electrocatalysts. Herein, we present a general approach to synthesizing a hollow ternary metal fluoride (FeCoNiF2) nanoflake array as an efficient and robust bifunctional electrocatalyst for the hydrogen evolution reaction (HER) and urea oxidation reaction (UOR). We find that the F anion withdraws electrons from the metal centers, inducing an electron-deficient metal center catalyst. The rationally designed hollow nanoflake array exhibits the overpotential of 30 mV for HER and 130 mV for UOR at a current density of 10 mA cm-2 and superior stability without decay events over 150 h at a large current density of up to 100 mA cm-2. Remarkably, the assembled urea electrolyzer using a bifunctional hollow FeCoNiF2 nanoflake array catalyst requires cell voltages of only 1.352 and 1.703 V to afford current densities of 10 and 100 mA cm-2, respectively, which are 116 mV less compared with that required for overall water splitting.

Insight into the direct conversion of methane to methanol on modified ZIF-204 from the perspective of DFT-based calculations.

Direct oxidation of methane over oxo-doped ZIF-204, a bio-mimetic metal-organic framework, is investigated under first-principles calculations based on density functional theory. In the pristine ZIF-204, the tetrahedral methane molecule anchors to an open monocopper site via the so-called η2 configuration with a physisorption energy of 0.24 eV. This weak binding arises from an electrostatic interaction between the negative charge of carbon in the methane molecule and the positive Cu2+ cation in the framework. In the modified ZIF-204, the doped oxo species is stabilized at the axial position of a CuN4-base square pyramid at a distance of 2.06 Å. The dative covalent bond between Cu and oxo is responsible for the formation energy of 1.06 eV. With the presence of the oxo group, the presenting of electrons in the O_pz orbital accounts for the adsorption of methane via hydrogen bonding with an adsorption energy of 0.30 eV. The methane oxidation can occur via either a concerted direct oxo insertion mechanism or a hydrogen-atom abstraction radical rebound mechanism. Calculations on transition-state barriers show that reactions via the concerted direct oxo insertion mechanism can happen without energy barriers. Concerning the hydrogen-atom abstraction radical rebound mechanism, the C-H bond dissociation of the CH4 molecule is barrierless, but the C-O bond recombination to form the CH3OH molecule occurs through a low barrier of 0.16 eV. These predictions suggest the modified ZIF-204 is a promising catalyst for methane oxidization.

Optimization of Oligomer Chitosan/Polyvinylpyrrolidone Coating for Enhancing Antibacterial, Hemostatic Effects and Biocompatibility of Nanofibrous Wound Dressing.

A synergistic multilayer membrane design is necessary to satisfy a multitude of requirements of an ideal wound dressing. In this study, trilayer dressings with asymmetric wettability, composed of electrospun polycaprolactone (PCL) base membranes coated with oligomer chitosan (COS) in various concentrations of polyvinylpyrrolidone (PVP), are fabricated for wound dressing application. The membranes are expected to synergize the hygroscopic, antibacterial, hemostatic, and biocompatible properties of PCL and COS. The wound dressing was coated by spraying the solution of 3% COS and 6% PVP on the PCL base membrane (PVP6-3) three times, which shows good interaction with biological subjects, including bacterial strains and blood components. PVP6-3 samples confirm the diameter of inhibition zones of 20.0 ± 2.5 and 17.9 ± 2.5 mm against Pseudomonas aeruginosa and Staphylococcus aureus, respectively. The membrane induces hemostasis with a blood clotting index of 74% after 5 min of contact. In the mice model, wounds treated with PVP6-3 closed 95% of the area after 10 days. Histological study determines the progression of skin regeneration with the construction of granulation tissue, new vascular systems, and hair follicles. Furthermore, the newly-growth skin shares structural resemblances to that of native tissue. This study suggests a simple approach to a multi-purpose wound dressing for clinical treatment.

Coupling Amorphous Ni Hydroxide Nanoparticles with Single-Atom Rh on Cu Nanowire Arrays for Highly Efficient Alkaline Seawater Electrolysis.

Exploring efficient catalysts for alkaline seawater electrolysis is highly desired yet challenging. Herein, coupling single-atom rhodium with amorphous nickel hydroxide nanoparticles on copper nanowire arrays is designed as a new active catalyst for the highly efficient alkaline seawater electrolysis. We found that an amorphous Ni(OH)2 nanoparticle is an effective catalyst to accelerate the water dissociation step. In contrast, the single-atom rhodium is an active site for adsorbed hydrogen recombination to generate H2. The NiRh-Cu NA/CF catalyst shows superior electrocatalytic activity toward HER, surpassing a benchmark Pt@C. In detail, the NiRh-Cu NA/CF catalyst exhibits HER overpotentials as low as 12 and 21 mV with a current density of 10 mA cm-2 in fresh water and seawater, respectively. At high current density, the NiRh-Cu NA/CF catalyst also exhibits an outstanding performance, where 300 mA cm-2 can be obtained at an overpotential of 155 mV and shows a slight fluctuation in the current density over 30 h.

The Efficacy of Silver-Based Electrospun Antimicrobial Dressing in Accelerating the Regeneration of Partial Thickness Burn Wounds Using a Porcine Model.

(1) Background: Wounds with damages to the subcutaneous are difficult to regenerate because of the tissue damages and complications such as bacterial infection. (2) Methods: In this study, we created burn wounds on pigs and investigated the efficacy of three biomaterials: polycaprolactone-gelatin-silver membrane (PCLGelAg) and two commercial burn dressings, Aquacel® Ag and UrgoTulTM silver sulfadiazine. In vitro long-term antibacterial property and in vivo wound healing performance were investigated. Agar diffusion assays were employed to evaluate bacterial inhibition at different time intervals. Minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and time-kill assays were used to compare antibacterial strength among samples. Second-degree burn wounds in the pig model were designed to evaluate the efficiency of all dressings in supporting the wound healing process. (3) Results: The results showed that PCLGelAg membrane was the most effective in killing both Gram-positive and Gram-negative bacteria bacteria with the lowest MBC value. All three dressings (PCLGelAg, Aquacel, and UrgoTul) exhibited bactericidal effect during the first 24 h, supported wound healing as well as prevented infection and inflammation. (4) Conclusions: The results suggest that the PCLGelAg membrane is a practical solution for the treatment of severe burn injury and other infection-related skin complications.

Tailoring chemical compositions of biodegradable mesoporous organosilica nanoparticles for controlled slow release of chemotherapeutic drug.

Biodegradable periodic mesoporous organosilica nanoparticles (B-PMO) are an outstanding nanocarrier due to their biodegradability and high drug load capacities. The present study describes a synthesis of a phenylene-containing tetrasulfide based B-PMO, named P4S. The incorporation of aromatic phenylene groups into the framework creates a strong interaction between nanoparticles (NPs) with aromatic rings in the cordycepin molecules. This results in the low release profile under various conditions. In addition, the replacement of this linker slowed the degradation of nanoparticles. The physicochemical properties of the nanoparticles are evaluated and compared with a biodegradable ethane-containing tetrasulfide based PMO and a non-degradable MCM-41. The biodegradability of P4S is also demonstrated in a reducing environment and the 100 nm spherical nanoparticles completely decomposed within 14 days. The porous structure of P4S has a high loading of hydrophilic cordycepin (approximately 731.52 mg g-1) with a slow releasing speed. The release rates of P4S NPs are significantly lower than other materials, such as liposomes, gelatin nanoparticles, and photo-crosslinked hyaluronic acid methacrylate hydrogels, in the same solution. This specific release behavior could guarantee drug therapeutic effects with minimum side-effects and optimized drug dosages. Most importantly, according to the in vitro cytotoxicity study, cordycepin-loaded P4S NPs could retain the toxicity against liver cancer cell (HepG2) while suppressed the cytotoxicity against normal cells (BAEC).

Investigating the effect of multi-coated hydrogel layer on characteristics of electrospun PCL membrane coated with gelatin/silver nanoparticles for wound dressing application.

In this study, the effect of coated hydrogel layer on characteristics of the whole gelatin/silver nanoparticles multi-coated polycaprolactone membrane (PCLGelAg) was investigated through systematic and typical wound dressing characterizations to select the optimal number of layers for practical applications. Scanning electron microscopy, free swell absorptive capacity and tensile test in both wet and dry conditions were conducted to characterize all fabricated membranes of six coating times. In vitro cytotoxicity and agar diffusion evaluation were also carried out to assess the biocompatibility and antibacterial activity of the membranes. The findings illustrated that as the coated layers increase, the absorptive capacity, and degradation rate were higher, the membranes were stiffer in dry state while the tensile strength in wet state, elongation, and cell viability were significantly decreased. PCLGelAg3 was chosen to be the best fit for wound healing since it maintained quite sufficient maximum buffer uptake, elasticity, cell viability along with inducing abnormalities in bacterial morphology and preventing biofilm formation.

Metal-enhanced sensing platform for the highly sensitive detection of C-reactive protein antibody and rhodamine B with applications in cardiovascular diseases and food safety.

The potential applications of metal-enhanced fluorescence (MEF) devices include biosensors for the detection of trace amounts in biosciences, biotechnology, and pathogens that are relevant to medical diagnostics and food control. In the present study, the silver (Ag) film thickness (56 nm) of an MEF system was calibrated to maximize the depth-to-width ratio (Γ) of the surface plasmon resonance (SPR) active metal from reflectance dip curves. Upon plasmon coupling with thermally evaporated Ag, we demonstrated a 2.21-fold enhancement compared to the pristine flat substrate with the coefficient of variation (CV) ≈0.22% and the limit of detection (LOD) 0.001 mg L-1 of the concentration of an Alexa Fluor 488-labeled anti-C-reactive protein antibody (CRP@Alexa fluor 488). The structure was developed to simplify the in situ generation of biosensors for the surface-enhanced Raman spectroscopy (SERS) to determine Rhodamine B (RhB) with a highly robust performance. The procedure presented a simple and rapid sample pretreatment for the determination of RhB with a limit of quantification of 10-10 M and a satisfactory linear response (0.98). The results showed the excellent performance of the surface plasmon coupled emission (SPCE), which opens up possibilities for the accurate detection of small-volume and low-concentration target analytes due to the improved sensitivity and signal-to-noise ratio (SNR).

Coupling of silver nanoparticle-conjugated fluorescent dyes into optical fiber modes for enhanced signal-to-noise ratio.

We present the optical coupling of the silver nanoparticles (AgNPs)-conjugated dye molecule into fiber optical modes for detecting fluorescence with the enhanced signal-to-noise (S/N) ratio. This near field coupling of the excited state of organic dye (FAM) molecules into the fiber multimodes occurs by immobilizing them on the exposed surface of fiber core, permitting the coupled light to be guided along the fiber for detection. This fiber based scheme is the first attempt to single out the fluorescence using fiber modes not for carrying excitation light but only for collecting emission light via the dye-fiber coupling. The emission-selective coupling into fiber modes turns out to be effective in reducing the unwanted background noise arising from both the false detection of excitation light and bulk autofluorescence. This scheme differs from the previously reported fluorescence sensors based on waveguides where guided modes at λex excite dye molecules via their evanescent fields. In addition, the local fields enhanced by AgNPs in close proximity to FAM molecules on the fiber core surface increase the rates of dye excitation and radiative decay/AgNP supported surface plasmon coupled emission. While focusing on demonstrating the proof-of-concept of the scheme presented, we obtain the maximum of 4.2-fold enhancement of the signal-to-noise (S/N) ratio in detecting fluorescence as compared to a conventional fluorescence detection scheme. The results presented in the fiber-based scheme may find an application where high S/N ratio fluorescence based biochemical assay is required in a small-sized device with remote sensing capability.

Functionalization of zirconium-based metal-organic frameworks for gas sensing applications.

The functionalization and incorporation of noble metals in metal-organic frameworks have been widely used as efficient methods to enhance their applicability. Herein, a sulfone-functionalized Zr-MOF framework labeled Zr-BPDC-SO2 (BPDC-SO2 =dibenzo[b,d]-thiophene-3,7-dicarboxylate 5,5-dioxide) and its Pd-embedded composite were efficiently synthesized by adjusting their functional groups. The obtained compounds were characterized to assess their potential for gas sensing applications. X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, specific surface area measurements, and thermogravimetric analysis were employed to characterize the new sensor materials. The gas sensing properties of the novel functionalized sensor materials were systematically investigated under various temperature, concentration, and gas type conditions. Owing to the strong hydrogen bonds of the sulfonyl groups and Zr6 clusters in the framework with the hydroxyl groups of ethanol, Zr-BPDC-SO2 emerged as an effective sensor for ethanol detection. In addition, Pd@Zr-BPDC-SO2 exhibited efficient hydrogen sensing performance, in terms of sensor dynamics and response. More importantly, the material showed a higher sensing response to hydrogen than to other gases, highlighting the important role of Pd in the Zr-MOF-based hydrogen sensor. The results of the sensing tests carried out in this study highlight the promising potential of the present materials for practical gas monitoring applications.

Bimetallic Thin-Film Combination of Surface Plasmon Resonance-Based Optical Fiber Cladding with the Polarizing Homodyne Balanced Detection Method and Biomedical Assay Application.

In this work, we present the optical birefringence properties of the optical fiber cladding that exists as an evanescent field where the refractive index (RI) of the analysis solution is applied for optical sensor aspiration. To enhance the performance of the sensor, we have investigated the sensor with different thicknesses of TiO2 coating and bimetallic (Ag-Al) film alloy combinations by thermal evaporation coating. We described a special balanced homodyne detection method for the intensity difference change between the p- and s-polarization lights in the surface plasmon resonance sensing systems, which is strongly determined by the RI of the test medium. The plasmonic optical fiber can measure a very small change of the RI of a glycerol solution, which is a resolution of 4.37 × 10-8 RI unit (RIU). This method has great advantages of a small-sized optical setup, high stability, high selectivity, easy chemical modification, and low cost. Furthermore, because of the experiment results, we observe that our approach can also eliminate the surrounding noise in the Mach-Zehnder interferometer, which shows the feasibility of this proposed technique. We demonstrate the fluorescence enhancement in detecting the C-reactive protein antibody conjugated with fluorescein isothiocyanate by means of near-field coupling between surface plasmons and fluorophores at spectral channels of emission. This technique can also be extended for application in a biomedical assay and in biochemical science, including molecular diagnostics relying on multichannels that require a small volume of the analyte at each channel which would suffer from the weakness of fluorescence if it were not for the enhancement technology.

In Situ Charge Transfer at the Ag@ZnO Photoelectrochemical Interface toward the High Photocatalytic Performance of H2 Evolution and RhB Degradation.

Designing an efficient hybrid structure photocatalyst for photocatalytic decomposition and hydrogen (H2) evolution has been considered a great choice to develop renewable technologies for clean energy production and environmental remediation. Enhanced charge transfer (CT) based on the interaction between a noble metal and a semiconductor is a crucial factor influencing the movement of photogenerated electron-hole pairs. Herein, we focus on the recent advances related to plasmon-enhanced noble metals and the semiconductor nature to drive the photocatalytic H2 production and photodegradation of the organic dye rhodamine B (RhB) under UV and visible light irradiation. Specifically, the combination of concerted catalysis and green nanoengineering strategies to design ZnO-based composite photocatalysts and their decoration with metallic Ag have been realized by the radio frequency (RF) sputtering technique at room temperature. This simultaneity enhances the interface coupling between Ag and ZnO and reduces the energy threshold. The creation of charge transfer in the heterojunction and Schottky barrier changes the photoelectronic properties of the as-synthesized Al-doped ZnO (AZO); afterward, these effects promote the migration, transportation, and separation of photoinduced charge carriers and enhance the light-harvesting efficiency. As a result, the as-synthesized AZO-20 hybrid nanostructure exhibits a photocurrent density of 2.5 mA/cm2 vs Ag/AgCl, which is improved by almost 12 times compared with that of bare ZnO (0.2 mA/cm2). The hydrogen evolution rates of AZO-20 were ∼38 and ∼24 µmol/h under UV and visible light exposure, which are almost five- and tenfold higher than those of pristine ZnO, respectively. Additionally, the RhB degradation efficacies of the obtained AZO-20 were greater than almost 97 and 82% under UV and visible light illumination, respectively. The achieved apparent rate constant for the photocatalytic RhB decomposition was 0.014 min-1, indicating that it is 14-fold than that in pristine ZnO (0.001 min-1). Heterostructure AZO photocatalysts possess excellent practical stability in the water-splitting reaction and photocatalytic RhB decomposition, posing as promising candidates in practical works for pollution and energy challenges.

Resistive switching effect and magnetic properties of iron oxide nanoparticles embedded-polyvinyl alcohol film.

In this study, the memory device of iron oxide (IO) nanoparticles (NPs) embedded in polyvinyl alcohol (PVA) demonstrates the bipolar resistive switching characteristics under an external electric field. The phase and magnetic properties of iron oxide nanoparticles change corresponding to its resistive states. At the high resistance state (HRS) of device, iron oxide nanoparticles are primarily in Fe2O3 phase and the ferromagnetism behavior is observed. In contrast, the iron oxide nanoparticles clustered by the bridging oxygen vacancies lead to mainly Fe3O4 phase and no hysteresis magnetic curve is observed at the low resistance state (LRS) of device. The results reveal that oxygen vacancies/ions in nanoparticles notably influence the resistance and magnetic behavior of nanocomposite thin films. Our study indicated that the magnetic NPs is high potential of multi-dimensional storage fields.

Correction: Resistive switching effect and magnetic properties of iron oxide nanoparticles embedded-polyvinyl alcohol film.

[This corrects the article DOI: 10.1039/C9RA10101B.].

The highly sensitive determination of serotonin by using gold nanoparticles (Au NPs) with a localized surface plasmon resonance (LSPR) absorption wavelength in the visible region.

The development of improved methods for the synthesis of monodisperse gold nanoparticles (Au NPs) is of high priority because they can be used as substrates for surface-enhanced Raman scattering (SERS) applications relating to biological lipids. Herein, Au NPs have been successfully synthesized via a seed-mediated growth method. The LSPR peak is controlled via adjusting the gold nanoseed component, and different fabrication methods were studied to establish the effect of sonication time on NP size. The simple, facile, and room-temperature method is based on a conventional ultrasonic bath, which leads to ultrasonic energy effects on the size and morphology of the Au NPs. This research offers new opportunities for the production of highly monodispersed spherical Au NPs without the use of a magnetic stirrer method, as evidenced by ultraviolet-visible reflectance spectra and scanning electron microscopy (SEM) analysis. SEM images indicate that the spherical Au NP colloidal particles are stable and reliable, which paves the way for their use as a nanostructured biosensor platform that can be exploited for multiple applications, for example, in materials science, sensing, catalysis, medicine, food safety, biomedicine, etc. The highest enhancement factor that could be achieved in terms of the SERS enhancement activity of these Au NP arrays was determined using 10-9 M serotonin (5-hydroxytryptamine, 5-HT) as the Raman probe molecules.