As-synthesized Nanocomposites Research Articles

Facile synthesis of ZnO-SnO2 anchored ZIF-8 nanocomposite: a potential photocatalyst

For the first time, ZnO-SnO2 nanocomposite has been anchored (ZS@Z) on ZIF-8 (zeolitic imidazolateframework) surface and encapsulated (ZS@Z1, ZS@Z2 and ZS@Z3) within ZIF-8 matrix during the in situ synthesis of ZIF-8. ZnO-SnO2 nanocomposites were synthesized in various molar ratio of Zn and Sn, i.e. 1:1, 2:8, 4:6, 6:4 and 8:2 (abbreviated as ZS-11, ZS-28, ZS-46, ZS-64 and ZS-82) using sol-gel and by grinding method (abbreviated as ZS-A, ZS-B, ZS-C, ZS-D and ZS-E). As-synthesized ZnO-SnO2 nanocomposites have been well characterized using various spectroscopic techniques. Further, ZS-E nanocomposite was succesfully anchored and encapsulated within ZIF-8 due to its good photocatalytic activity. Morphology of ZnO-SnO2 nanocomposites and their composites (ZS@Z, ZS@Z1, ZS@Z2 and ZS@Z3) was ensured by SEM (scanning electron microscopy) and TEM (transmission electron microscopy) images. The lowering of band gap of ZIF-8 from 5.2 to 3.25/3.79eV confirmed the proper anchored ZnO-SnO2@ZIF-8. Moreover, XPS analysis was also performed for the analysis of elemental composition of composites. In order to validiate thier photocatalytic application, adsorption capacity and photodegradation efficiency have been examined using methylene blue (MB) as model pollutant. It has been found that 10mg of ZnO-SnO2 nanocomposite (ZS-E) exhibits maximum photodegradation efficiency (58.68%) towards MB ([MB] = 1.6mgL-1) at pH = 7.89 while ZS@Z, ZS@Z1, ZS@Z2 and ZS@Z3 composites (10mg, 0.5mgmL-1) can degrade off 100%, 93%, 97% and 92% MB, respectively. Hence, ZS@Z, ZS@Z1, ZS@Z2 and ZS@Z3 composites exhibit enhanced photodegradation efficiency as compared to ZIF-8 and ZnO-SnO2 nanocomposites and can be used for water remediation.

Tunable and Ultraefficient Microwave Absorption Properties of Trace N-Doped Two-Dimensional Carbon-Based Nanocomposites Loaded with Multi-Rare Earth Oxides.

A high efficiency and great tunability of bandwidth and absorption-range electromagnetic wave absorber is proposed without precedent. A series of 2D carbon-based nanocomposites with the loading of cerium oxide (CN-Ce) and other types of rare earth oxides (CN-REOs) can be successfully synthesized by a simple solvothermal-sintering method. As-synthesized 2D nanocomposites with local graphite-like C3 N4 structure and trace N-doped are identified by transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray powder diffraction, Fourier transform infrared spectroscopy, and Raman spectroscopy. The CN-REOs and polyvinylidene fluoride composite absorbers with reflection loss values above -40 dB are obtained in C-band, X-band, and Ku-band, respectively. The empirical rules on effective bandwidth and frequency range are discovered and summarized, which can be successfully realized by simply tuning the doping amount or type of REO. The mechanism is explained by enhanced attenuation and tunable impedance matching. In addition co-filled samples by two types of CN-REOs nanocomposites are prepared to support these findings and inspire the preparation of absorber with desirable frequency band in the range of 2-18 GHz.

A novel Au-SnO2-rGO ternary nanoheterojunction catalyst for UV-LED induced photocatalytic degradation of clothianidin: Identification of reactive intermediates, degradation pathway and in-depth mechanistic insight

Herein, we have developed Au-SnO2-rGO ternary nanoheterojunction catalyst for photocatalytic degradation of clothianidin under UV-LED irradiation. Au nanoparticles (Au NPs) were decorated with quantum sized SnO2 nanoparticles (SnO2 NPs) and embedded in the reduced graphene oxide (rGO) matrix. The synthesized photocatalyst was characterized using common instrumentation techniques to evaluate the morphological, structural and surface chemical properties of the catalyst. The photocatalytic property of the as-synthesized nanocomposite was investigated by studying the degradation of clothianidin under UV-LED irradiation. Approximately 97% of the degradation was achieved in 120 min with pseudo first-order reaction rate of 0.0309 min-1. The effect of various parameters like contact time, catalyst dose, initial concentration, pH, irradiation source and interfering ions on the degradation performance has also been investigated. Identification of various intermediates in the degradation process was done with high performance liquid chromatography- mass spectral (LC/HRMS) technique. The reactive intermediates responsible for the degradation have also been identified with electron spin resonance (ESR) technique and complete mechanism of the degradation process has been proposed with the help of photo luminescence (PL) quenching studies.

Facile synthesis of nitrogen-doped cobalt/cobalt oxide/carbon/reduced graphene oxide nanocomposites for electromagnetic wave absorption

Electromagnetic wave absorption materials with strong absorption, thin thickness, broad bandwidth and low filler loading are highly desirable in the field of electromagnetic absorption. In this work, graphene oxide (GO) was firstly used as a template for growth of cobalt, zinc–zeolitic imidazolate frameworks (Co, Zn–ZIFs), and then nitrogen-doped cobalt/cobalt oxide/carbon/reduced graphene oxide (Co/CoO/C/RGO) nanocomposites were further constructed by the high-temperature pyrolysis strategy. Results of morphology observations demonstrated that numerous carbon frameworks with a slightly contracted polyhedron morphology were anchored on the crumpled surfaces of sheet-like RGO. Moreover, well-constructed structure of RGO loaded with carbon nanotubes wrapping carbon frameworks was observed, and considerable nitrogen atoms had been in situ doped into the porous carbon matrix of attained nanocomposites. Furthermore, the influences of filler loadings, calcination temperature, and addition of GO on the electromagnetic parameters and absorption performance of obtained nanocomposites were investigated. Results revealed that the addition of GO notably strengthened the electromagnetic absorption performance. Remarkably, the percolation transition was observed in the filler loading range of 20–25 wt%. The as-synthesized nanocomposite under 700 °C calcination treatment exhibited superior electromagnetic absorption performance with an optimal reflection loss of −63.0 dB and effective absorption bandwidth of 4.0 GHz (12.2–16.2 GHz) at a thin matching thickness of merely 1.6 mm and filler loading as low as 25 wt%. In addition, the underlying electromagnetic absorption mechanisms were proposed. This work provided a facile strategy for fabricating the carbon-based magnetic composites derived from metal–organic frameworks as light weight and high-performance electromagnetic absorption materials.

GO@Fe3O4@CuSilicate Composite with a Hierarchical Structure: Fabrication, Microstructure, and Highly Electromagnetic Shielding Performance.

Two nanocomposites with a hierarchical structure (GO@CuSilicate@Fe3O4 and GO@Fe3O4@CuSilicate) were fabricated in this paper. These as-synthesized nanocomposites were analyzed for their structural, compositional, and morphological features by X-ray diffraction, scanning electron microscopy (SEM), Raman spectroscopy, and Brunauer–Emmett–Teller methods. SEM images showed that both nanocomposites had a core–shell structure, and their shells were composed of CuSilicate nanoneedle arrays. Further, their total electromagnetic shielding efficiency was measured and compared in a wide frequency range of 8–12 GHz (X-band). Because of the “antenna” role of CuSilicate nanoneedle arrays and the polarization at the interface between graphene oxide (GO) and Fe3O4, GO@Fe3O4@CuSilicate showed higher electromagnetic shielding performance than that of GO@CuSilicate@Fe3O4. With 1 mm thickness, GO@Fe3O4@CuSilicate showed a high electromagnetic shielding efficiency (over 40 dB) in the whole X-band (8.2–12.4 GHz) and reached a maximum value (41.8 dB) at 8.2 GHz. Its total electromagnetic shielding efficiency was mainly contributed by absorption rather than reflection. This study provided an idea for the structural design of high-performance electromagnetic shielding materials in the GHz frequency range (X band).

Synthesis, Characterization and Anti-Biofilm Efficacy of Polypyrrole-Zinc Oxide Composites.

A nanocomposite of Polypyrrole (PPy) and zinc oxide (ZnO), termed as PPy-ZnO, was synthesized by two step route. In the first step, synthesis of PPy was carried out by chemical oxidative route. In the second step, the PPy-ZnO nanocomposite was synthesized under hydrothermal conditions. The as-synthesized PPy-ZnO nanocomposites were characterized using X-ray Diffraction (XRD), scanning electron microscopy (SEM), Fourier Transform Infra-red (FTIR) and Ultra violetvisible (UV-vis) spectroscopy to reveal the phase, morphology, chemical and optical properties. The physical and chemical characterizations confirmed presence of both PPy and ZnO phases in the nanocomposite. In the present work, antimicrobial activity of the PPy-ZnO nanocomposite against human pathogen Y. lipolytica has been investigated. Attempts have been made to reveal the influence of PPy percentage on the antimicrobial activity. Interestingly, all PPy-ZnO nanocomposites, irrespective of PPy percentage, showed 90 to 95% inhibited growth of Yarrowia lipolytica. The results obtained herein imply the potential of PPy-ZnO biofilm in inhibiting the growth of Y. lipolytica and thus preventing infections caused due to Y. lipolytica in humans.

Banana Peel-Derived Dendrite-Shaped Au Nanomaterials with Dual Inhibition Toward Tumor Growth and Migration.

PurposeIn order to prepare functional Au nanoparticles with low toxicity and high antitumor properties, we have used fruit waste (banana peel) to synthesize a new dendrite-shaped gold nanoparticle and used it for the treatment of tumors.MethodsDendrite-shaped gold nanoparticle (Au-dendrite) was synthesized through a facile hydrothermal process. The banana peel was used as both the reducing agent and the protective agent for reducing chloroauric acid to obtain Au-dendrite. The safety assessment of the Au-dendrite was conducted by H&E staining of the mouse’s eyelid skin and CCK-8 assay. The antitumor effects were evaluated through in vitro tumor cytotoxicity experiments and in vivo treatment of animal tumors.ResultsIn this work, a new type of gold nanomaterial (Au-dendrite) was synthesized by using a common agricultural waste (banana peel) through a facile hydrothermal process without any extra chemical reducing agent or protective agent. Subsequent experiments showed that, compared with some classical Au nanomaterials, the as-synthesized gold nanocomposites have superior biocompatibility and impressive characteristics of dual inhibition toward tumor growth and migration.ConclusionWe successfully synthesized a dendrite-shaped gold nanocomposite which was derived from a common agricultural waste (banana peel). A facile and environmentally friendly synthetic process was proposed accordingly without regular chemical additives. The as-prepared Au-dendrite nanocomposites not only had better biocompatibility than some classical gold nanoparticles but also exhibited unique advantages in tumor inhibition.

Electrical, Photocatalytic, and Humidity Sensing Applications of Mixed Metal Oxide Nanocomposites.

Mixed metal oxide nanocomposites (NCs) comprising Cu–Sr (CS), Sr–Cd (SC), and Cd–Cu (CC) were fabricated via a sol–gel method. Structural investigations of fabricated samples were carried out via X-ray diffraction (XRD), scanning electron microscopy (SEM), diffuse reflectance spectroscopy (DRS), and X-ray photoelectron spectroscopy (XPS). The Maxwell–Wagner model, attributing to poor conducting layers around the conducting grains, was indicated to be followed by all of the NCs while investigating the dielectric properties. The Space-charge polarization and hoping mechanism contributed to low AC conductivity at lower frequencies and high AC conductivity at higher frequencies. The as-synthesized NCs effectively degraded two toxic water contaminants, such as crystal violet (CV) and Congo red (CR). Furthermore, the NCs were also evaluated for humidity sensing measurements. All of the NCs indicated efficient response/recovery time with better stability. The extensive investigation suggested the synthesized NCs, well suited for various optical and microelectronic applications.

Highly efficient removal of phosphate by lanthanum modified nanochitosan-hierarchical ZSM-5 zeolite nanocomposite: characteristics and mechanism

In this study, nanochitosan-hierarchical ZSM-5 zeolite composite (NCS@ZSM-5-H) was synthesized via simple way at ambient temperature. The hierarchical ZSM-5 zeolite were prepared by hydrothermal processing without the use of zeolite seeding crystals or additional template. Lanthanum (La) was loaded onto the surface of samples to acquire a simply separable adsorbent for efficient separation of phosphate (P) from water. The synthesized materials are examined before and after adsorption of P by several characterization techniques. Results of adsorption experiments showed that NCS@ZSM-5-H/La is very effective in the adsorption of P species from aqueous solutions. Response surface methodology has been applied to optimize and model P uptake onto NCS@ZSM-5-H/La nanocomposite. A four-factor central composite design has been applied to find out the influence of different process parameters on P removal. Thermodynamic, isotherm, and kinetic studies were employed to understand the adsorption behavior. The P adsorption was not significantly by interfering anions of fluoride chloride, and sulfate but carbonate revealed further negative effects, indicating NCS@ZSM-5-H/La possessed highly selectivity to P. The NCS@ZSM-5-H/La was regenerated using 2.0 M NaOH, with up to ~ 80% recovery and the as-synthesized nanocomposite was reused in seven consecutive adsorption–desorption cycles without significant reduction in regeneration capacity.

Aqueous synthesis of glutathione-capped CuInS2/ZnS quantum dots-graphene oxide nanocomposite as fluorescence “switch OFF” for explosive detection

This work reports a simple and fast aqueous preparation of CuInS2/ZnS-graphene oxide (CIS/ZnS-GO) nanocomposite as a fluorescence “switch OFF” probe for the fluorescence detection of 2, 4, 6-trinitrophenol (TNP.) – a raw material for various explosive devices. The as-synthesized nanocomposites was characterised using Ultraviolet–visible (UV–Vis) spectroscopy, photoluminescence (PL) spectroscopy, high resolution transmission electron microscopy (HR-TEM), Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and Raman scattering. The PL studies revealed that the adsorption of TNP onto GO via π-π stacking enhanced the charges transfer from CuInS2/ZnS-GO to the analyte. The limit of detection (LOD) for the analyte is 57 μΜ.

Facile synthesis of Co0.5Zn0.5Fe2O4 nanoparticles decorated reduced graphene oxide hybrid nanocomposites with enhanced electromagnetic wave absorption properties

Herein, reduced graphene oxide/cobalt-zinc ferrite (RGO/Co0.5Zn0.5Fe2O4) hybrid nanocomposites were fabricated by a facile hydrothermal strategy. Results revealed that the contents of RGO could affect the micromorphology, electromagnetic parameters and electromagnetic wave absorption properties. As the contents of RGO increased in the as-synthesized hybrid nanocomposites, the dispersibility of the particles was improved. Meanwhile, numerously ferromagnetic Co0.5Zn0.5Fe2O4 particles were evenly anchored on the wrinkled surfaces of flaky RGO. Besides, the obtained hybrid nanocomposites exhibited superior electromagnetic absorption in both X and Ku bands, which was achieved by adjusting the RGO contents and matching thicknesses. Significantly, when the content of RGO was 7.4 wt%, the binary nanocomposites showed the optimal reflection loss of -73.9 dB at a thickness of 2.2 mm and broadest effective absorption bandwidth of 6.0 GHz (12.0–18.0 GHz) at a thin thickness of merely 2.0 mm. The enhanced electromagnetic absorption performance was primarily attributed to the multiple polarization effects, improved conduction loss caused by electron migration, and magnetic loss derived from ferromagnetic Co0.5Zn0.5Fe2O4 nanoparticles. Our results could provide inspiration for manufacturing graphene-based hybrid nanocomposites as high-efficient electromagnetic wave absorbers.

One-pot sonochemical synthesis of CuS nanoplates decorated partially reduced graphene oxide for biosensing of dopamine neurotransmitter.

The sonochemical methods have been used as a straight forward method for the synthesis of various composite materials, including the transition metal dichalcogenide composites. In the present work, we report a simple sonochemical synthesis of CuS nanoplates decorated partially reduced graphene oxide (PrGO) nanocomposite for the first time. The PrGO-CuS nanocomposite was synthesized using bath-sonication (frequency: 37kHz; power: 150W) of graphene oxide (GO), and CuS precursors at 80°C for 60min. The physicochemical characterization (FESEM, XRD, FTIR, and Raman spectroscopy) results confirmed the successful formation of CuS nanoplates on PrGO nanosheets. The as-synthesized PrGO-CuS nanocomposite was further utilized for electroanalysis of dopamine neurotransmitter. The obtained electroanalytical results revealed that PrGO-CuS nanocomposite has superior electrochemical activity towards dopamine than those obtained for GO, CuS, and GO-CuS composite. The fabricated biosensor shows a lower limit of detection (0.022µM) with a more comprehensive linear response range (0.1-155.1µM) for the detection of dopamine. Moreover, the PrGO-CuS nanocomposite electrode was successfully used for the detection of dopamine in bovine serum albumin.

CeO2 nano-hexagons decorated rGO/CNT heterostructure for high-performance LPG sensing

This paper reports, the improved sensitivity and selectivity of liquefied petroleum gas (LPG) sensing at room temperature based on ternary heterostructure nanocomposite (CeO2–rGO/CNT). Detection of LPG is required for proper environment monitoring to avoid any health hazards in the household and industrial areas. Towards this, a low-cost, high performance, and high stable room temperature gas sensor was fabricated. CeO2 nanopuzzles was synthesized by Eggshell membrane template assisted hydrothermal method and nanocomposites by sono-chemical route. As-synthesized materials and nanocomposites were analyzed by employing characterizations like XRD, Raman, FT-IR, FESEM, and TEM, which confirmed the formation of shape, size, structure, and functional groups involved. The current study focuses on the fabrication of room temperature LPG sensor based on hybrid nanocomposites coated on flexible polyethylene terephthalate substrate working electrodes for In-house chemiresistive LPG detection unit to study response, stability, and selectivity parameters. The ternary heterostructure nanocomposite gas sensor exhibited good selectivity to LPG at room temperature. This sensor showed the response of 42% at 400 ppm of LPG, which is 2.21 times than pure CeO2 sensor with a short response time 26 s and recovery time of 98 s, and gained 99% response after bending with 95.2% stability and 85.7% periodic stability of the sensor.

GQDs/Sb2S3/TiO2 as a co-sensitized in DSSs: Improve the power conversion efficiency of DSSs through increasing light harvesting by using as-synthesized nanocomposite and mirror

In present work, GQDs/Sb2S3/TiO2 composite was prepared by sonochemistry method with ultrasonic probe with 60 W/cm2 intensity and 18 kHz frequency. Based on this composite, two different cells in the configuration of FTO/TiO2/GQDs/Sb2S3/TiO2/N719/Pt and M/FTO/TiO2/GQDs/Sb2S3/TiO2/N719/Pt/GQDs/M (M:Mirror) have been fabricated to improve the efficiency of our reference devices. Optical and electrical properties of these configurations were studied by both theoretical and experimental techniques. Our experimental results indicate that the first configuration shows 43% improvement and the second configuration shows 72% improvement in PCE compare to the reference device. PDOS analysis for the charge carrier migration between GQD and TiO2. According to our theoretical results, O 2p orbitals shows the must contribution to create the valence band of TiO2 while conduction band consist of Ti 3d. DFT results show that G-S-T is more stable than S-G-T and Eb of G-S-T is more negative than S-G-T (Eb G-S-T = −3.96 and Eb S-G-T = −3.23 eV). The band gap of the G-S-T is about 0.78 eV that is less than of TiO2 and GQDs/TiO2, result in the electronic transition from the valence band to the conduction band in G-S-T is easier than that of TiO2 and GQDs/TiO2. So, excitation needs less energy. As a result, the photocatalytic performance of G-S-T is stronger than that of TiO2 and GQDs/TiO2.

ZnS/Fe2O3/Ag Ternary Nanocomposite Photocatalyst for the Degradation of Dyes Under Visible Light

Recently the researchers have shown great interest on photocatalysis, especially in dyes degradation by nanocomposites under visible light. In this work, the photocatalytic degradation of dye pollutants such as Malachite green (MG) and Eosin blue (EB) by zinc sulfide based ternary nanocomposite (ZnS–Fe2O3–Ag) under visible light irradiation, was reported for the first time. As-synthesized nanocomposite was studied for its structural, morphological and optical properties by using different instrumental techniques such as XRD, FTIR, FESEM, EDS, TGA, and UV-DRS. The obtained results apparently stated that the formation of pure phase of ZnS/Fe/Ag confirmed by XRD and the spherical shape obtained from FESEM. The presence of Zn, S, Fe, and Ag in prepared composite according to EDS without impurities, confirmed that pure ternary nanocomposite was formed. The bandgap of prepared composite is found to be 2.33 eV, which is striven for visible light, resulting in the better photocatalytic activity towards the degradation of dye pollutants. The optimized conditions for degradation of both dyes are alkaline pH, and 30 mg catalyst load. The photocatalytic degradation of both MG and EB dyes by prepared nanocomposite was completed in one hour without adding of any oxidizing agent.

Novel ZnO/CuBi2O4 heterostructures for persulfate-assisted photocatalytic degradation of dye contaminants under visible light

New visible-light-induced photocatalysts were synthesized through a hydrothermal method, which possess excellent activation efficiency for potassium persulfate (PS) to remove water contaminants. The features of as-synthesized nanocomposites were studied by different instruments. The results showed that the binary ZnO/CuBi2O4 (5.0 %) sample has best photocatalytic capability in the elimination of methyl orange (MO), rhodamine B (RhB), and Congo red (CR). The photodegradation rate constant of RhB over the ZnO/CuBi2O4 (5.0 %) photocatalyst in the existence of 1.48 mM of PS ions, was 178 × 10−4 min−1, which is about 26.4, 5.11, 4.31, and 2.44-times as large as the pristine ZnO, PS ions, ZnO/PS, and ZnO/CuBi2O4 (5.0 %) nanocomposite, respectively. The improving photodegradation efficiency was attributed to larger surface area, high absorption of visible light, and the formation of heterojunction at the interface of ZnO and CuBi2O4 nanoparticles. In our view, this study supplies a new method for the production of effective heterojunction photocatalysts using ZnO, which could solve environmental problems according to the practical requirements.

ZrO2/ZnO nanocomposite materials for chemiresistive butanol sensors

Zirconia/zinc oxide (ZrO2/ZnO) nanocomposites have been prepared by electrospinning method followed by in-situ high temperature calcination approach. Compared with pure ZnO materials, ZrO2/ZnO nanocomposites have improved sensing properties for butanol. The doping content of zirconia has significant impact on the sensing behavior of ZrO2/ZnO nanocomposites. Especially, at the optimum operating temperature of 245 °C, the nanocomposite of 10.7 % ZrO2/ZnO shows high response (107) to 100 ppm butanol, which is twice as high as that of pure ZnO (about 52), and the response time and recovery time of the nanocomposite to 100 ppm butanol are about 20 s and 40 s, respectively. Moreover, the ZrO2/ZnO gas sensor exhibits high selectivity and good repeatability to butanol. The as-synthesized nanocomposites were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), inductively coupled plasma (ICP) and X-ray photoelectron spectrometer (XPS). By the investigation of the structures and butanol gas sensing behavior of the nanocomposites, it is believed that their high sensitivity and fast response/recovery time are based on the synergistic effect of zirconia and zinc oxide.

Tungsten Carbide as Supports for Trimetallic AuPdPt Electrocatalysts for Methanol Oxidation

Direct methanol fuel cell (DMFCs) is one of the best positioned toward widespread commercialization and the most viable alternative to lithium-ion batteries for portable applications. A major drawback of this technology is in large part related to the dependence on Pt-based electrocatalysts for methanol oxidation reaction (MOR) at the anode. To address this issue, low-Pt electrocatalysts are desired for keeping high performance of MOR. In this article, tungsten carbide (WC) enhanced trimetallic AuPdPt nanocomposite was prepared through the two-step method, i) intermittent microwave heating method (IMH) and ii) direct chemical reduction method. Trimetallic AuPdPt nanoparticles are dispersed well on the nanostructured WC, confirmed by scanning electron microscopy (SEM), energy X-ray diffraction spectroscopy (EDX), and transmission electron microscopy (TEM). The electrocatalytic performance of the as-synthesized nanocomposite for MOR was tested using cyclic voltammetry and chronopotentiometry in alkaline media. The results revealed that the WC enhanced trimetallic AuPdPt nanocomposites has better performance of MOR and stability than that of commercial Pt/C catalyst.

The fabrication of an MoS2 QD-AuNP modified screen-printed electrode for the improved electrochemical detection of cefixime.

Herein, we report a voltammetric method for the nanomolar detection of cefixime, a third-generation antibiotic. The determination of cefixime is validated on a glassy carbon electrode (GCE) as well as on a screen-printed carbon electrode (SPCE). In the present study, we have reported a facile "one step simple hydrothermal synthesis" of MoS2 quantum dots and with the oxidation of aurochloric acid for the further formation of an MoS2 QD-AuNP composite. The as-synthesized nanocomposite was characterized via UV-Vis spectroscopy, FTIR spectroscopy, XRD, TEM and EDX techniques, and further applied in the modification of working electrodes, showing excellent electroactivity. The sensing of cefixime was done via cyclic and differential pulse voltammetry techniques. The presence of the only anodic peak in the voltammogram reveals the irreversible oxidation of cefixime in the potential range of about 1.3 ± 0.1 V vs. Ag/AgCl. The study was also performed at different scan rates, which indicate a diffusion-controlled mechanism. The proposed cefixime sensor showed a linear response in the concentration range of 0.33-90.82 μM (at S/N = 3) with a limit of detection (LOD) of 3.9-4.5 nm. The electrochemical sensitivity is calculated as 8.63 μA μM-1 cm-2 and 7.07 μA μM-1 cm-2 in buffer and pharmaceutical formulation (commercially available cefixime tablet), respectively. The effects of several interferents were also investigated. The proposed sensor is effectively used for estimating cefixime in phosphate buffer and the commercially available cefixime tablets with no cross-reactivity or matrix effects and shows a promising prospect for real applications.

Application of novel Fe3O4-g-GO-g-RAFT agent nanoabsorbents for D-SPME of biogenic amines in smoked fish

Herein, a dispersive solid phase microextraction (D-SPME) approach based on magnetic nanoabsorbents was developed for the simultaneous extraction of histamine, cadaverine, putrescine, and tyramine in smoked fish. The desired magnetic nanocomposite was prepared with surface modification of Fe3O4 nanoparticles with graphene oxide via surface reversible addition fragmentation chain transfer (RAFT) copolymerization. Preparation, size, morphology, surface functional groups and magnetic properties of as-synthesized nanocomposite was characterized. The obtained results showed acceptable r2 values (≥0.9949) for all analyte as well as good recovery (>98.36), repeatability (RSD%<3.57), and reproducibility (RSD%<5.16) of the developed method. The developed method was successfully employed to estimate four biogenic amines in 40 samples from different species of smoked fishes available in northern Iran. Thirty-six out of 40 samples exceeded an acceptable level of histamine (50 mg Kg−1). Cadaverine and putrescine were founded at a higher level, while tyramine was detected at the lowest level in comparison with other BAs (<11 %).