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The study aimed to investigate the effects of two different plasma systems, including pinhole plasma jet and gliding arc (GA) plasma, for the degradation of herbicide, diuron, in plasma activated solutions (PAS).

Pd-based catalysts consisting of Pd nanoparticles on nitrogen-doped carbon quantum dots (N-CQDs) modified silica (SiO

A portable paper-based electrochemical sensor has been developed to determine 5-hydroxymethylfurfural (5-HMF). A screen-printed carbon electrode (SPCE) was facilely fabricated for the first time on poster paper which showed a very satisfactory electrochemical response. The analytical performance of the electrode was enhanced by electrochemical deposition of silver microdendrites (AgMDs). The cathodic peak of 5-HMF occurred at approximately -1.48 V, lower than that obtained from the bare poster-SPCE. Moreover, the modified electrode showed a higher current response than the bare electrode, revealing that the AgMDs not only exhibited highlighted electrocatalytic features but also improved the electrical conductivity and increased the electrode surface area. Afterward, some influencing conditions were optimized, including scan rate and the number of scan cycles for AgMD deposition, pH, temperature, and square wave voltammetric parameters. Under the optimal conditions, the analytical characteristics of the proposed sensor were evaluated. The cathodic peak current increased linearly according to 5-HMF concentration over the range of 3-100 ppm, and the detection limit was 1.0 ppm. This low-cost, disposable electrochemical sensor provided environmentally friendly, simple and rapid detection, acceptable precision, good stability, and high selectivity. Additionally, this method can be applied to quantify 5-HMF in honey samples with satisfying accuracy.

Fabrication of a new three-dimensional Cu(II) metal-organic framework, {[Cu

A cost-effective long-path absorption liquid core waveguide (LCW) device was fabricated from a typical Teflon tube, and using a high refractive index (RI) medium of acid. It was incorporated in a flow injection-gas diffusion system for the sensitive determination of sulfide via methylene blue (MB) chemistry. The gas diffusion unit could prevent some interferences in samples. The limit of detection of 0.13 μmol L

Electrocatalytic preparation of Pt-based nanocomposites has been investigated for improvement of direct ethanol fuel cells (DEFCs). In this study, new alternative catalysts of Pt-decorated cerium zirconium oxide-modified multiwalled carbon nanotubes (Pt/CeZrO4/MCNT) were successively prepared to improve the activity of the ethanol oxidation reaction (EOR). The prepared CeZrO4 with a face-centered cubic (fcc) structure compatibly dispersed onto MCNT provides abundant active Pt sites for highly active catalysts. The fcc-structured Pt was also satisfactorily decorated onto CeZrO4/MCNT, resulting in highly active Pt. The Ce4+/Ce3+ redox property can promote oxygen vacancies to improve the electrochemical activity for oxidation of carbonaceous species. An increase in roughness and a stabilized catalyst structure can also be produced by inserting Zr4+ into the ceria metal oxide. The prepared Pt/20%CeZrO4/MCNT catalysts present excellent electrochemical active surface area, mass activity, CO tolerance and high electron kinetic transfer with low resistance and high stability over commercial PtRu/C toward EOR. This promising catalyst material could be introduced to enhance the anodic oxidation reaction in DEFCs.

A smartphone camera-based colorimetric method is developed for the determination of iodine value of vegetable oils. The small amount of Wijs reagent is employed for halogenation of the unsaturated sites of the sample. The rest of unreacted reagent is transformed into iodine, which further reacts with the starch solution to form the blue color complex. The free download smartphone application is used for measuring the blue color intensity. More than one sample can be measured by taking only one photo shot. Under the controlled illuminance, the calibration graph for measuring the iodine values of various vegetable oils is constructed from the dissolved triiodide. The detection and quantitation limits are less than 0.02 and 0.032 mM I2, respectively. This method provides a better determination result of the iodine value compared with the standard titrimetric method. This method is convenient, simple, rapid, inexpensive, and easy operation with few chemical waste products.

A new electrochemical immunosensor is developed for the label-free simultaneous detection of mucin1 (MUC1), cancer antigen 15-3 (CA15-3), and human epidermal growth factor receptor 2 (HER2) early breast cancer biomarkers. The biosensor is simply designed using the deposition of three different systems of redox species-antibody-conjugated polyethylenimine coated-gold nanoparticles (PEI-AuNPs), for the first time. The screen-printed carbon electrode (SPCE) comprising a three-working electrode array is modified with the conjugated PEI-AuNPs. Multiplex sensing is performed by utilizing the distinguishable electrochemical responses of the redox-active species; anthraquinone-2-carboxylic acid (AQ), thionine chloride (TH), and AgNO3 (Ag+) on the PEI-AuNPs conjugates for the detection of MUC1, CA15-3, and HER2, respectively. The single-run determination of the biomarkers by the proposed immunosensor is carried out by measuring the decrease (%) in the oxidation peak currents due to the formation of three kinds of antibody-antigen complexes. The decreased currents are logarithmically proportional to the antigen concentrations in the ranges of 0.10-100 U mL-1 CA15-3 and 0.10-100 ng mL-1 MUC1 and HER2 with detection limits of 0.21 U mL-1, 0.53 ng mL-1 and 0.50 ng mL-1, respectively, which are significantly lower than the clinically relevant cut-off levels. The sensor reveals high selectivity and satisfactory reproducibility. After storing for two weeks, the sensor retains the responses with ca. 90% of the initial currents. The immunosensor is successfully applied to detect three tumor markers in human serum and can provide a new technological platform for the development of low-cost, highly stable, sensitive, selective, and point-of-care (POC) diagnosis.

Electrocatalytic oxidation of methanol, ethanol, and formic acid has currently attracted research attention for low-temperature fuel cells. However, the efficiencies of these fuel cells mainly depend on the electrocatalytic activities of Pt-based anodic catalysts due to the problems of low kinetics for small organic molecule electro-oxidation. An anode catalyst can be developed by the addition of some metal oxides into a Pt-based catalyst, which can effectively promote the electro-oxidation of fuels based on small organic molecules. In this work, a nanocomposite catalyst consisting of multi-wall carbon nanotubes (CNTs), copper oxide (CuO) and Pt nanoparticles was synthesized and used to improve fuel cell oxidation. Due to its low cost and oxophilic character, the metal oxide can play a major role in the oxidation of CO. The synthesis of xPt−yCuO/CNT electrocatalysts was executed through two steps: supporting of CuO nanoparticles on CNTs by the alcothermal method followed by Pt loading onto the prepared CuO/CNT by chemical reduction. The as-prepared catalysts were physically characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Raman spectroscopy, and electrochemical measurements. The results demonstrate that CuO is well dispersed onto the CNTs and that this oxide can further interact with the active Pt present on the as-prepared catalyst composites. The activity of various xPt−yCuO/CNT electrocatalysts was determined by cyclic voltammetry (CV), where x and y are the mass ratios of Pt and CuO, respectively. The presence of CuO was found to significantly contribute to enhanced electroactivity towards oxidation reactions. The 1Pt–3CuO/CNT electrocatalyst is a capable catalyst for improving low-temperature fuel cell applications.

In this research, the pH differential method was explored for the first time using a mobile phone as a detector, replacing UV-Vis spectrophotometry. A smartphone digital image colorimetric (SDIC) system was developed for the determination of the total monomeric anthocyanin content in black rice grains using colour values. The change in colour of anthocyanin cyanidin-3-glucoside (C3G) at pH 1.0 and pH 4.5 was investigated and described through colour model systems (RGB and CIELAB). Under optimum conditions, the quantitative method based on the chroma difference, was able to quantify the total amount of monomeric anthocyanins with a linear correlation (R2 = 0.989) to that of UV-Vis spectrophotometry and high performance liquid chromatography (HPLC) (reference method). The SDIC system displayed good precision (≤1.88% RSD) and a low detection limit (2.2 ± 0.1 μg g-1). The validated results demonstrated that the developed method was a cost-effective alternative for the quantitation of anthocyanins. In addition, the effect of six mineral elements on black rice cultivation was investigated. The results showed that the addition of the Ca fertiliser resulted in black rice grains with an anthocyanin content 2-fold higher than that of the control with a significant difference (p < 0.05).

The design and development of facile, rapid, selective, and sensitive electroanalytical methods for the simultaneous determination of serotonin (ST) along with other interfering species are in huge...

A powerful anodic stripping voltammetry (ASV) was proposed using a bismuth film coated on screen-printed carbon electrode (Bi-SPCE) in conjunction with the Tessier’s sequential extraction procedure...

A simple and low cost colorimetric procedure using an Android smartphone was developed for determination of copper(II) in copper supported silica catalysts. The developed software was installed in a smartphone for measuring the intensity of the blue color produced by the reaction between copper(II) and 2-carboxy-2'-hydroxy-5'-sulfoformazyl-benzene in an acidic solution. More than one sample can be measured by taking only one photo shot. Under the selected conditions, the linear range from 0 to 5 mg/L was obtained with the detection and quantitation limits of 0.04 and 0.13 mg/L, respectively. The method provided a good precision with the percent relative standard deviation values less than 5%. The percent recoveries were in the range of 97–104%. The results corresponded well with those obtained by atomic absorption spectrophotometry. This developed method is convenient, rapid and simple with an uncomplicated device.

A miniaturized microfluidic hydrodynamic sequential injection system for multi-parameter analysis with a sensitive colorimetric detection was developed to improve the analytical performance for the measurement of phosphate, nitrite, and nitrate based on molybdenum blue and Griess methods. A homemade colorimetric detection with a light emitting diode as a light source and phototransistor light sensor was integrated into the microfluidic platform to achieve a low cost compact system with low reagent consumption and high sensitivity. Under the optimized working conditions, a linear calibration graph of phosphate (two working range), nitrite and nitrate (as nitrogen, N) in the range of 0.01–0.1 and 0.3–1.0 mg of PO43− P L−1, 0.005–0.05 mg of NO2− N L−1 and 0.01–0.12 mg of NO3− N L−1, respectively were achieved with a sample-throughput of 10 h−1. The limit of detections were 0.005 mg of PO43− P L−1, 0.0026 mg of NO2− N L−1 and 0.005 mg of NO3− N L−1. The percentage of recovery for phosphate, nitrite, and nitrate were 90.3–115.0, 90.0–117.0 and 91.3–117.0, respectively, with relative standard deviations in the range of 1.07–4.90%. Capabilities of the developed device for consecutive analysis of multiple analytes were demonstrated to be an excellent choice for water quality monitoring.

A dual-mode electrochemical biosensor is successfully developed for simultaneous detection of two different kinds of breast cancer biomarkers, namely cancer antigen 15-3 (CA 15-3) and microRNA-21 (miRNA-21), for the first time. The sensor composes of a poly(3-aminobenzylamine)/two-dimensional (2D) molybdenum selenide/graphene oxide nanocomposite modified two-screen-printed carbon electrode array (dual electrode), functionalized individually with 2,3-diaminophenazine-gold nanoparticles and toluidine blue-gold nanoparticles. Both kinds of the redox probe-gold nanoparticles are employed as signaling molecules and supports for immobilization of anti-CA 15-3 antibodies and capture DNA-21 probes, respectively. Due to the good conductivity and high surface-to-volume ratio of the nanocomposite, high amount of the antibodies and capture probes can be immobilized on the modified dual-electrode, giving the efficient duplex detection. Consequently, the biosensor provides good selectivity, and high sensitivity for the dual target analyte detection. The experimental results show that this label-free biosensor exhibits good linear responses to the concentrations of both target analytes with the limits of detection (LODs) of 0.14 U mL

A colorimetric aptasensor for chlorpyrifos detection utilizing the localized surface plasmon resonance (LSPR) of gold nanoparticle (AuNP) aggregates coupling with a specific aptamer and cationic polyethyleneimine (PEI) has been developed. The measurement principle is based on a remarkable characteristic of AuNPs that can change their colors under the aggregation and dispersion conditions, which enables a sensitive colorimetric detection. In the absence of chlorpyrifos, negatively charged phosphate backbones of the aptamer potentially interact with the cationic PEI, resulting in the red color appearance of the dispersed AuNPs, whereas, in the presence of chlorpyrifos, the aptamer binds explicitly to chlorpyrifos, consequently releasing cationic PEI. Uninteracted PEI induces AuNP aggregation, causing a color change from red to blue that can be observed through the naked eye. Under the optimized conditions, 6 nM PEI, 10 nM aptamer, and a pH buffer of 7.5, the colorimetric aptasensor gives a linear response in the range of 20-300 ng mL-1 with a low detection limit of 7.4 ng mL-1. The developed method has been successfully applied to complex sample analysis. The accuracy and precision of chlorpyrifos quantification in spiked samples, including tap water, pomelo, and longan samples, are in the acceptable criteria of method validation, indicating that the developed aptasensor can be utilized as an alternative analytical tool for chlorpyrifos determination in complex samples. This aptasensor provides advantages such as a simple procedure, low cost, short analysis time, and involving uncomplicated instruments. Moreover, it offers high sensitivity, selectivity, and stability.

A label-free electrochemical aptamer-based sensor has been fabricated for alpha-fetoprotein (AFP) detection. Platinum nanoparticles on carboxylated-graphene oxide (PtNPs/GO-COOH) modified screen-printed graphene-carbon paste electrode (SPGE) was utilized as an immobilization platform, and the AFP aptamer was employed as a bio-recognition element. The synthesized GO-COOH helps to increase the surface area and amounts of the immobilized aptamer. Subsequently, PtNPs are decorated on GO-COOH to enhance electrical conductivity and an oxidation current of the hydroquinone electrochemical probe. The aptamer selectively interacts with AFP, causing a decrease in the peak current of the hydroquinone because the binding biomolecules on the electrode surface hinder the electron transfer of the redox probe. Effects of aptamer concentration and AFP incubation time were studied, and the current changes of the redox probe before and after AFP binding were investigated by square wave voltammetry. The developed aptasensor provides a linear range from 3.0–30 ng mL−1 with a detection limit of 1.22 ng mL−1. Moreover, the aptamer immobilized electrode offers high selectivity to AFP molecules, good stability, and sensitive determination of AFP in human serum samples with high recoveries.

A series of platinum nanoparticle-loaded carbon composites composed of reduced graphene oxide and multi-walled carbon nanotubes (rGO-CNT/Pt) was chemically synthesized at room temperature. The prepared catalysts were characterized using X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The results confirm that rGO mixed CNT composites were successfully prepared with small and highly dispersed Pt nanoparticles on the composite supports. The cyclic voltammetry (CV) and chronoamperometry (CA) electrochemical measurements indicated that the composite carbon catalyst increased the intensity and stability for the methanol oxidation reaction (MOR). In addition, fewer carbon intermediate species were observed in the CO stripping experiment. The incorporation of CNTs into rGO decreases the agglomeration between rGO sheets and increases the active surface of dispersed Pt nanoparticles, resulting in the enhanced oxidation activity of the as-prepared electrocatalysts. The combined characteristics of the highly active Pt nanoparticles and potent electron transfer of the rGO-CNTs enable excellent methanol oxidation with high stability. Consequently, this hybrid carbon material is a good candidate for MOR catalysis, which can be applied to direct methanol fuel cells.

To improve the electrocatalytic activity of alcohol oxidation, functionalized carbon nanotubes (CNTs) decorated with various compositions of metal alloy catalyst nanoparticles (PtxMy, where M = Au and Pd; x and y = 1–3) have been prepared via reduction. The CNTs were treated with an nitric acid solution to promote the oxygen-containing functional groups and further load the metal nanoparticles. X-ray diffraction (XRD) scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to probe the formation of catalyst microstructure morphologies. A uniform dispersion of the spherical metal particles with diameters of 2–6 nm was acquired. The catalytic properties of the catalyst for oxidation were thoroughly studied by electrochemical methods that involved in the cyclic voltammetry (CV), linear sweep voltammetry (LSV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS). To maximize the electrocatalytic performance and minimize the metal integration of the loaded CNTs, various compositions of active catalysts with large active surface areas are expected to increase the activity of the enhanced catalysts for alcohol oxidation. Most of the prepared bimetallic catalysts have better alcohol oxidation kinetics than commercial PtRu/C. Among the prepared catalysts, the PtAu/CNTs and PtPd/CNTs catalysts with high electrochemically active surface area (ECSA) show excellent activities for alcohol oxidation resulting in their low onset potentials, small charge transfer resistances and high peak current densities and If/Ib ratios, stability, and better tolerance to CO for alcohol oxidation. The integration of Pt and different metal species with different stoichiometric ratios in the CNTs support affects the electrochemical active surface area achieved in the catalytic oxidation reactions.

The noble metals (Pt and Pd) loaded on polydopamine (PDA) modified graphene oxide (GO) as catalysts were prepared by a reduction. The catalysts were characterized by Fourier transform infrared spec...

A simple and compact microfluidic hydrodynamic sequential injection system with a colorimetric detection has been developed for the consecutive determination of phosphate and ammonium in water samples based on molybdenum blue and Berthelot methods. A light-emitting diode as a light source and light dependent resistor light sensor were mounted onto the acrylic microfluidic unit for on-line sample and reagents mixing. This portable and miniaturized analytical system was operated automatically by computerized control switching of solenoid valves. Under the optimum operational condition, a linear calibration graph of phosphate and ammonium (as phosphorus, P, and nitrogen, N) in the range of 0.2–3.0 mg P L−1 and 0.3–4.0 mg N L−1, were achieved with a sample-throughput of 12 h−1. Limit of detection values for phosphate and ammonium were 0.18 and 0.27 mg L−1, respectively. The developed system provides a good precision with relative standard deviations of 2.9 and 4.1% for 11 replicated injections of 1 mg P L−1 and 2 mg N L−1, respectively. Percent recoveries of the analysis of phosphate and ammonium were obtained in the range of 93.5–109.4 and 92.4–107.0, respectively. The developed system offers a compact, durable, cost-effective instrument, with low reagents consumption, that is suitable for monitoring water quality.

Novel FeVO4/Bi7O9I3 nanocomposites with different weight percentages (3, 6.25, 12.5, and 25%wt) of FeVO4 were successfully synthesized by cyclic microwave irradiation, followed by wet impregnation. The applications for photocatalytic dye degradation and photoelectrochemical (PEC) were investigated. The 6.25%wt-FeVO4/Bi7O9I3 nanocomposite exhibited excellent photocatalytic degradation of methylene blue, rhodamine B, and methyl orange with decolorization efficiencies of 81.3%, 98.9%, and 94.9% within 360 min, respectively. Moreover, this nanocomposite possessed excellent reusability and stability during the photocatalytic degradation process. PEC performance in water oxidation of the 6.25%wt-FeVO4/Bi7O9I3 photoanode was evaluated by linear sweep voltammetry (LSV) measurement. Enhanced PEC performance with photocurrent density of 0.029 mA cm−2 at 1.23 V (vs. RHE) was observed under visible-light irradiation, which was ca. 3.7 times higher than that of the pure Bi7O9I3. Based on the optical characterization, energy band positions, and active species trapping experiments, a possible photocatalytic mechanism of the FeVO4/Bi7O9I3 heterojunction was discussed. The enhancement in the photocatalytic and the PEC performance ascribed to synergistic effects of visible-light absorption and a favorable “type II heterojunction” structure of the FeVO4/Bi7O9I3 nanocomposite. These were the main effects that promoted the photogenerated electrons and holes transfer across the contact interface between FeVO4 and Bi7O9I3, as well as suppressed the recombination of photogenerated electron-hole pairs and facilitated charge separation and transportation.

Methylene blue (MB) adsorption onto a two-dimensional molybdenum disulfide (2D MoS