Showing papers by "Adisorn Tuantranont published in 2021"

A simple label-free electrochemical sensor for sensitive detection of alpha-fetoprotein based on specific aptamer immobilized platinum nanoparticles/carboxylated-graphene oxide.

Abstract: 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.

Effect of Er doping on flame-made SnO2 nanoparticles to ethylene oxide sensing

Abstract: In this research, 0.05–2 wt% Erbium (Er)-doped SnO2 nanoparticles were synthesized for the first time by flame spray pyrolysis and their gas-sensing properties were methodically characterized. The structural analyses based on scanning/transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, nitrogen sorption analysis, and photoluminescent spectroscopy suggested that nanocrystalline SnO2 nanoparticles were substitutionally doped with Er+3 species. The sensing films were prepared by powder pasting and spin-coating processes and their gas-sensing performances were evaluated in the temperature range of 200–400 °C under dry and humid air conditions. The test results reported that the optimum Er content of 0.1 wt% provided the optimally high and selective response of 347 to 30 ppm C2H4O with a short response time of ∼2 s and a low detection limit of 18 ppb, which were substantially better than those of undoped one at the best working temperature of 350 °C. The high selectivity was confirmed against CH2O, C3H6O, C2H5OH, NH3, C2H2, C2H4, H2, CH4, H2S, H2O and CO. Besides, the influence of humidity on C2H4O response of Er-doped SnO2 sensor was moderately low over a wide relatively humidity range of 0–80 %. The gas-sensing mechanisms were proposed with a new model describing the catalytic roles of p-type Er dopants to ethylene oxide adsorption.

Ultra-responsive and selective of formic acid sensors based on flame-made SnO2 nanoparticles loaded with core-shell Ir-IrO2 nanocatalysts

Abstract: 0.1–2 wt% Ir-loaded tin dioxide (SnO2) nanoparticles were prepared via flame spray pyrolysis and investigated for sensing of formic acid (CH2O2). The structural morphologies of the materials were investigated by various X-ray spectroscopic and electron microscopic analyses. The results revealed that very fine secondary core-shell nanoparticles containing Ir° and Ir4+ species were decorated on the surfaces of cassiterite SnO2 nanoparticles, resulting in an increase of specific surface area and a small reduction of SnO2 crystallize size. The gas-sensing performances of all fabricated sensors were evaluated towards several volatile organic acids particularly CH2O2, volatile organic compounds and hydrocarbon gases at working temperature in the range of 200–400 °C in dry and humid air. The data revealed that the 1 wt% Ir-loaded SnO2 provided the optimal sensor response of ∼1.43 × 105 to 1000 ppm CH2O2 at an optimum working temperature of 350 °C. In addition, the sensors presented moderately low humidity effect on CH2O2 response and high CH2O2 selectivity against C2H5OH, CH3OH, C3H6O, C7H8, C6H6, C8H10, HCHO, CH4, H2, C2H4O2, C3H6O2, C4H8O2, C5H10O2 and C3H6O3. The electronic and gas-sensing mechanisms could be primarily ascribed to metal-metal-semiconductor heterojunctions and catalytic effects of Ir-IrO2 via oxygen spill-over and oxygen evolution reaction mechanisms. Therefore, the loading of catalytic core-shell Ir nanoparticles on SnO2 nanostructures was a highly promising approach to achieve ultrasensitive and selective sensing of formic acid.

Selectivity towards acetylene gas of flame-spray-made Nb-substituted SnO2 particulate thick films

Abstract: 0.1–2 wt% Nb-doped SnO2 nanoparticles were produced via flame spray pyrolysis (FSP) in a single step for the first time. The structural characterizations including X-ray diffraction, nitrogen sorption analysis, electron microscopy, energy dispersive and photoelectron X-ray spectroscopy revealed that Nb5+ species were substitutionally doped into the lattice of nanocrystalline tetragonal SnO2 nanoparticles (5–15 nm). The sensing layers produced by spin coating were tested towards 0.05–1 vol% C2H2 at 200–400 °C in air. Gas-sensing results indicated that the optimal Nb content of 0.5 wt% provided the best sensor response of ~776 with an excellent response time of 1.1 s to 1 vol% C2H2 at the optimal sensing temperature of 350 °C. Additionally, the optimal Nb-doped SnO2 sensor exhibited low humidity dependence, good long-term stability and high C2H2 selectivity relative to HCHO, CH3OH, C2H5OH, C3H6O, CH4, C2H4, C6H6, C7H8, C8H10, H2, NO2, NO and NH3. Moreover, low direct cross interferences were demonstrated against CH3OH and C8H10. The results were explained by the catalytic and electronic roles of n-type Nb dopants on C2H2 interaction. Thus, the Nb-doped SnO2 sensor is an attractive candidate for selective C2H2-sensing applications.

Ready-to-use paraquat sensor using a graphene-screen printed electrode modified with a molecularly imprinted polymer coating on a platinum core.

Abstract: We propose the fabrication of a novel ready-to-use electrochemical sensor based on a screen-printed graphene paste electrode (SPGrE) modified with platinum nanoparticles and coated with a molecularly imprinted polymer (PtNPs@MIP) for sensitive and cost-effective detection of paraquat (PQ) herbicide. Successive coating of the PtNPs surface with SiO2 and vinyl end-groups formed the PtNPs@MIP. Next, we terminated the vinyl groups with a molecularly imprinted polymer (MIP) shell. MIP was attached to the PtNPs cores using PQ as the template, methacrylic acid (MAA) as the monomer, ethylene glycol dimethacrylate (EGDMA) as the cross-linker, and 2,2′-azobisisobutyronitrile (AIBN) as the initiator. Coating the SPGrE surface with PtNPs@MIP furnished the PQ sensor. We studied the electrochemical mechanism of PQ on the MIP sensor using cyclic voltammetry (CV) experiments. The PQ oxidation current signal appears at −1.08 V and −0.71 V vs. Ag/AgCl using 0.1 M potassium sulfate solution. Quantitative analysis was performed by anodic stripping voltammetry (ASV) using a deposition potential of −1.4 V for 60 s and linear sweep voltammetric stripping. The MIP sensor provides linearity from 0.05 to 1000 μM (r2 = 0.999), with a lower detection limit of 0.02 μM (at −0.71 V). The compact imprinted sensor gave a highly sensitive and selective signal toward PQ. The ready-to-use MIP sensor can provide an alternative approach to the determination of paraquat residue on vegetables and fruits for food safety applications.

Sensitivity Validation of EWOD Devices for Diagnosis of Early Mortality Syndrome (EMS) in Shrimp Using Colorimetric LAMP-XO Technique.

Abstract: Electrowetting-on-dielectric (EWOD) is a microfluidic technology used for manipulating liquid droplets at microliter to nanoliter scale. EWOD has the ability to facilitate the accurate manipulation of liquid droplets, i.e., transporting, dispensing, splitting, and mixing. In this work, EWOD fabrication with suitable and affordable materials is proposed for creating EWOD lab-on-a-chip platforms. The EWOD platforms are applied for the diagnosis of early mortality syndrome (EMS) in shrimp by utilizing the colorimetric loop-mediated isothermal amplification method with pH-sensitive xylenol orange (LAMP–XO) diagnosis technique. The qualitative sensitivity is observed by comparing the limit of detection (LOD) while performing the LAMP–XO diagnosis test on the proposed lab-on-a-chip EWOD platform, alongside standard LAMP laboratory tests. The comparison results confirm the reliability of EMS diagnosis on the EWOD platform with qualitative sensitivity for detecting the EMS DNA plasmid concentration at 102 copies in a similar manner to the common LAMP diagnosis tests.

Highly Sensitive and Selective Sensing of H 2 S Gas Using Precipitation and Impregnation-Made CuO/SnO 2 Thick Films

Abstract: In this work, CuO-loaded tetragonal SnO2 nanoparticles (CuO/SnO2 NPs) were synthesized using precipitation/impregnation methods with varying Cu contents of 0–25 wt% and characterized for H2S detection. The material phase, morphology, chemical composition, and specific surface area of NPs were evaluated using X-ray diffraction, transmission electron microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and Brunauer–Emmett–Teller analysis. From gas-sensing data, the H2S responses of SnO2 NPs were greatly enhanced by CuO loading particularly at the optimal Cu content of 20 wt%. The 20 wt% CuO/SnO2 sensor showed an excellent response of 1.36 × 105 toward 10 ppm H2S and high H2S selectivity against H2, SO2, CH4, and C2H2 at a low optimum working temperature of 200 °C. In addition, the sensor provided fast response and a low detection limit of less than 0.15 ppm. The CuO–SnO2 sensor could therefore be a potential candidate for H2S detection in environmental applications.

Nanomaterials in agricultural and food applications

Abstract: Nanotechnology has played increasing roles in the development of modern agriculture for sustainable improvement of people life quality. This chapter covers the synthesis, properties, and applications of nanomaterials in agriculture and food. The related nanomaterials are classified into six groups including metal nanomaterials, metal oxide nanomaterials, carbon nanomaterials, nanoclays/surface-modified nanoclays, nanoencapsulates, and nano(bio)composites. Their use for food safety, diagnostic of diseases and contaminations in agricultural entities, enhancements of agrochemicals (i.e., fertilizers, soil nutrients, and pest control chemicals), and monitoring and controlling of agricultural environmental factors are described and exemplified. In particular, carbon nanomaterials including graphene and carbon nanotubes in agriculture and food-related sensing applications are substantially elaborated.

High performance aqueous Li-ion capacitors with palladium nanoparticle/graphene composite anode and activated carbon cathode employing safe and environmentally friendly electrolytes

Abstract: Lithium-ion capacitors (LICs) are a potential bridge between conventional Li-ion batteries (LIBs) with high energy density and capacitors with high power density. In this work, we demonstrate high energy, power, and cycle life LICs with anodes based on palladium nanoparticle-decorated reduced graphene oxide (rGO@Pd) and activated carbon (AC)-based cathodes. Aqueous LiNO3 solution has been employed as electrolyte due to its superior safety characteristics and environmental friendliness. GO was prepared by modified Hummers’ method, and rGO@Pd was subsequently synthesized by facile hydrothermal reduction with PdCl2. Electrodes were fabricated by drop casting additive-free rGO@Pd and AC slurry on carbon paper current collectors. Scanning electron microscopy with energy dispersive X-ray spectroscopy, transmission electron microscopy, and X-ray diffraction as well as Raman spectroscopy have been used to characterize the developed materials. We were able to show successful Pd nanoparticle formation and uniform distribution in the composite. The prepared electrodes have been used to construct CR2032 coin cell LICs the performance of which was evaluated by 2-electrode cyclic voltammetry and galvanostatic charge–discharge with 1 M LiNO3 electrolyte. The LICs exhibited excellent electrochemical performance with specific capacitance of 188.6 F g−1 and energy and power densities of 51.3Wh kg−1 and 46.5 kW kg−1 at a current of 1 A g−1. The capacitors retained 95.3% of initial capacitance after 10,000 charge–discharge cycles.

Mini-Potentiostat for Low Power Chemical Sensing of Graphene-Carbon Paste Lab on a Chip

Abstract: This research studied the development of mini-potentiostat for portable electrochemical measurement. The mini-potentiostat was fabricated for analysis of electrochemical values with substances in low concentrations to use with lab on a chip. The mini-potentiostat was designed by using electronic circuits and fabricated from integrated circuits and controlled by microcontrollers. The lab on a chip was designed to be T-shaped and uses digital microfluidics for acting on microfluid to move the liquid droplets to electrochemical sensor of lab on a chip. The sensor consists of screen-printing electrodes: a graphene-carbon paste working and counter electrodes and a silver/silver chloride paste reference electrode. The electrochemical electrodes were fabricated by screen printing methods. The mini-potentiostat was calibrated to test for electrochemical sensor. For analysis, the lab on a chip was tested using low concentration, using potassium hexacyanoferrate and varying concentration of minimal reagent consumption from 200 mM to 1000 mM with increment of 200 mM. This mini-potentiostat can distinguish the concentration of substances with low concentrations effectively