Showing papers by "Adisorn Tuantranont published in 2015"

Electrolytically exfoliated graphene-loaded flame-made Ni-doped SnO2 composite film for acetone sensing.

Abstract: In this work, flame-spray-made SnO2 nanoparticles are systematically studied by doping with 0.1–2 wt % nickel (Ni) and loading with 0.1–5 wt % electrolytically exfoliated graphene for acetone-sensing applications. The sensing films (∼12–18 μm in thickness) were prepared by a spin-coating technique on Au/Al2O3 substrates and evaluated for acetone-sensing performances at operating temperatures ranging from 150 to 350 °C in dry air. Characterizations by X-ray diffraction, transmission/scanning electron microscopy, Brunauer–Emmett–Teller analysis, X-ray photoelectron spectroscopy and Raman spectroscopy demonstrated that Ni-doped SnO2 nanostructures had a spheriodal morphology with a polycrystalline tetragonal SnO2 phase, and Ni was confirmed to form a solid solution with SnO2 lattice while graphene in the sensing film after annealing and testing still retained its high-quality nonoxidized form. Gas-sensing results showed that SnO2 sensing film with 0.1 wt % Ni-doping concentration exhibited an optimal respons...

Ultrasensitive NO2 Sensor Based on Ohmic Metal–Semiconductor Interfaces of Electrolytically Exfoliated Graphene/Flame-Spray-Made SnO2 Nanoparticles Composite Operating at Low Temperatures

Abstract: In this work, flame-spray-made undoped SnO2 nanoparticles were loaded with 0.1–5 wt % electrolytically exfoliated graphene and systematically studied for NO2 sensing at low working temperatures. Characterizations by X-ray diffraction, transmission/scanning electron microscopy, and Raman and X-ray photoelectron spectroscopy indicated that high-quality multilayer graphene sheets with low oxygen content were widely distributed within spheriodal nanoparticles having polycrystalline tetragonal SnO2 phase. The 10–20 μm thick sensing films fabricated by spin coating on Au/Al2O3 substrates were tested toward NO2 at operating temperatures ranging from 25 to 350 °C in dry air. Gas-sensing results showed that the optimal graphene loading level of 0.5 wt % provided an ultrahigh response of 26 342 toward 5 ppm of NO2 with a short response time of 13 s and good recovery stabilization at a low optimal operating temperature of 150 °C. In addition, the optimal sensor also displayed high sensor response and relatively shor...

Rapid ethanol sensor based on electrolytically-exfoliated graphene-loaded flame-made In-doped SnO2 composite film

Abstract: In this research, flame-made SnO2 nanoparticles doped with 0.2–1 wt% indium and loaded with 0.1–5 wt% electrolytically-exfoliated graphene are systematically investigated for ethanol sensing applications. The sensing films (∼10–50 μm in thickness) were prepared by spin coating technique on Au/Al2O3 substrates and evaluated for ethanol sensing performances at operating temperatures ranging from 150 to 350 °C in dry air. Characterizations by XRD, XPS, SEM, TEM and Raman spectroscopy demonstrated that In-doped SnO2 nanostructures had spheriodal morphology with polycrystalline tetragonal SnO2 phase and indium was confirmed to form solid solution with SnO2 lattice while graphene in the sensing film after annealing and testing still retained high-quality multilayer structure with low oxygen content. Gas-sensing measurement showed that SnO2 sensing film with 0.5 wt% In-doping concentration exhibited an optimal response of 110 and short response time of 2 s towards 1000 ppm C2H5OH at an optimal operating temperature of 300 °C. The additional loading of graphene at 5 wt% into 0.5 wt% In-doped SnO2 led to a drastic response enhancement to 965 with very short response time of 1.8 s and fast recovery stabilization at optimal operating temperature of 350 °C. The superior gas sensing performances of In-doped SnO2 nanoparticles loaded with graphene may be attributed to large specific surface area of the composite, high density of reactive sites of highly porous non-agglomerated graphene-SnO2 nanoparticle structure and high electronic conductivity of graphene, which allowed fast gas response and recovery. Therefore, the graphene loaded In-doped SnO2 sensor is a promising candidate for fast, sensitive and selective detection of ethanol.

Ultra-sensitive H2S sensors based on hydrothermal/impregnation-made Ru-functionalized WO3 nanorods ☆

Abstract: Ultra-sensitive H2S gas sensors based on the hydrothermal/impregnation-synthesized WO3 one-dimensional (1D) nanostructures functionalized with Ru are presented. The particle properties were characterized by XRD, BET, SEM, TEM and EDS analyses. The H2S-sensing performances in terms of sensor response, response/recovery times and selectivity were optimized by varying Ru concentration. The optimal sensing film (0.50 wt% Ru-WO3) showed an ultra-high sensor response of ∼192 and short response time of ∼0.8 s to 10 ppm of H2S at 350 °C. In addition, 0.50 wt% Ru-WO3 nanorods (NRs) exhibited much higher H2S selectivity against NO2, SO2, C2H5OH and NH3 compared with unloaded WO3 NRs. Furthermore, the catalyst selectivity of Ru toward H2S was found to be significantly higher than those of three other metals including Ni, Nb and Au, respectively. Therefore, 0.50 wt% Ru-WO3 sensor is one of the most promising candidates for highly sensitive and selective detection of H2S.

Effects of cobalt doping on nitric oxide, acetone and ethanol sensing performances of FSP-made SnO2 nanoparticles

Abstract: In the present work, gas-sensing properties of flame-spray-made Co-doped SnO2 nanoparticles are systematically studied for detection of nitric oxide (NO), acetone (C3H6O) and ethanol (C2H5OH) gases occurred in human breathe. Structural characterizations by electron microscopy and X-ray analysis confirmed the formation of loosely agglomerated SnO2 nanoparticles (5–20 nm) with highly crystalline tetragonal-cassiterite SnO2 structure and Co substitutional doping with Co2+ and Co3+ oxidation states. The gas-sensing properties of unload SnO2 and Co-doped SnO2 sensors were systematically tested towards NO, acetone and ethanol. Tested results indicated that small Co-doping levels in the range of 0.2–0.5 wt% led to enhanced sensing properties toward NO, acetone and ethanol compared with undoped one. In particular, 0.2 wt% Co-doped SnO2 sensor showed very high response of ∼1637–1000 ppm NO at 350 °C while 0.5 wt% Co-doped SnO2 one exhibited high responses of ∼660–2000 ppm acetone and ∼806–1000 ppm ethanol. Thus, Co-doped SnO2 sensors are potential for responsive detections of NO, acetone and ethanol at ppm-level but with limited selectivity and may be useful for general environmental, industrial and biomedical applications.

Novel surfactant-stabilized graphene-polyaniline composite nanofiber for supercapacitor applications

Abstract: In this work, we present a new synthesis method for surfactant stabilized graphene (SSG) combined with polyaniline nanofiber (PANI-Nf) and apply the composite material as supercapacitor (SC) electrodes by screen-printing technique. Surfactant stabilized graphene polyaniline nanofiber composite (PANI-SSG) was synthesized by electrolytic exfoliation of graphite and subsequent interfacial polymerization. Firstly, graphite was electrolytically exfoliated in an electrolyte containing anionic surfactant. Next, ammonium peroxydisulfate initiator and hydrochloric acid were added to the graphene dispersion to form the aqueous phase for interfacial polymerization of polyaniline nanofiber. This dispersion was then added to the water-insoluble solvent phase containing aniline monomer. The polymerization only occurred at the interface of the two immiscible phases leading to polyaniline nanofiber decorated graphene structures. Characterizations by scanning electron microscopy, transmission electron microscopy, atomic force microscopy and Raman spectroscopy suggested nanocomposite formation with intermolecular π-π bonding of graphene with polyaniline nanofibers. Pastes of the materials were screen printed on stainless steel current collectors and tested for SC performance by cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD) measurements with 2 M H 2 SO 4 electrolyte using a home-built two-electrode test-cell. CV results showed redox peaks of polyaniline with wide cyclic loop, indicating large pseudocapacitance of the nanocomposite. From GCD measurement, a high specific capacitance of 690 Fg −1 at 1 Ag −1 was achieved. Therefore, PANI-SSG nano-composite prepared by electrolytic exfoliation and interfacial polymerization is a promising candidate for SC applications.

The IoT wearable stretch sensor using 3D-Graphene foam

Abstract: In this work, we have developed flexible and wearable Stretch Sensor based on the Internet of thing technology. These sensors were realized using a 3D-Graphene foam amalgam with Polydimethylsiloxane (PDMS). To demonstrate the 3D-graphene foam sensors, we constructed an armband muscle measurement using such sensors and developed software based on IoT for real-time muscle expansion and stretch tracking. Wi-Fi was used to transfer data from the sensor to a cloud via web-socket based on Node.js. The data are display expansion of muscle on a website. This muscle stretch tracking is very useful in many contexts such as workout performance measuring, rehabilitation and tele-robotics application. The wearable stretch sensor is consisting of two pieces of 5 centimeters 3D-graphene foam strip and packed with clasped by conductive epoxy. For accuracy, at the end of sensor edge are coated with silver paste for better conductivity. Main CPU uses Intel Edison, which made the sensor connect to the Internet easier. In order to deploy this sensor with another application the ADXL335 was chosen as a 3-axis accelerometer for tracking of gestures or fitness tracking application. An accelerometer was attached to the down side of the Intel Edison main CPU board and including battery and analog to digital converter circuit.

Electrolytically exfoliated graphene–polylactide-based bioplastic with high elastic performance

Abstract: This work reports an innovative way to prepare biopolymer composite by incorporating graphene (GP) synthesized from electrolytic exfoliation into biodegradable polymer blend (polylactide/epoxidized palm oil: PLA/EPO) based on melt-blending method and studies their physical properties for food packaging and related applications. Multilayer GP structure synthesized by electrolytic exfoliation is confirmed by transmission electron microscopy and Raman spectroscopy, whereas homogeneous GP incorporation in PLA/EPO is verified by scanning electron microscopy and X-ray diffraction. From thermogravimetric analysis and heat deformation temperature (HDT) studies, the decomposition and HDTs of PLA/EPO/GP composites are higher than those of PLA/EPO but are lower than those of pristine PLA and tend to decrease with increasing GP content because of thermal conductivity effect. From standard tensile test, loading of GP in PLA/EPO at an optimal concentration of 0.6 wt % results in higher elongation at break by as much as 52%. The observed additional elongation under a given tension and the corresponding lower tensile strength/Young's modulus may be attributed to lower binding force of materials in the composite because of the presence of relatively weak GP–PLA/EPO interfaces. Moreover, oxygen permeability is found to decrease with increasing GP contents and oxygen permeability is reduced by 40.33% at the GP loading concentration of 0.6 wt %. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41439.

Fabrication of stretchable 3D graphene foam/poly-dimethylsiloxane composites for strain sensing

Abstract: In this work, we present the fabrication of a 3D graphene and polydimethylsiloxane (PDMS) composite for strain sensing applications. A three-dimensional (3D) graphene foam (GF) was synthesized by chemical vapor deposition (CVD) with nickel foam as a template. GF/PDMS composite was then formed by dip coating the graphene foam into PDMS solution and the nickel template was removed by etching in a hot hydrochloric acid. The ratio of PDMS and curing agent was varied to obtain the optimum condition for high conductivity and flexibility. The results from SEM showed that the composite of graphene foam with high PDMS:curing agent ratio provided more pores in the composite structure. The mechanical test demonstrates that the flexibility of optimal GF/PDMS composite with higher PDMS:curing agent ratio was higher than those prepared with other curing agent contents. The electrical resistance change of the GF/PDMS composite as a function of applied strain was studied. In addition, the resistance of the composite increased with increasing applied strain until the break at the strain of 15%, 21%, 23% and 83% for the composite with PDMS/curing agent ratios of 5∶1, 10∶1 and 15∶1, and 20:1 respectively, respectively. The studied of electrical properties of the GF/PDMS composite under bending stress showed that the resistance of the GF/PDMS composite decreased considerably with increasing bending curvature and can be fully recovered after straightening. Therefore, GF/PDMS composites can be potentially to be used as a flexible strain sensor.

RT-LAMP detection of shrimp Taura syndrome virus (TSV) by combination with a nanogold-oligo probe

Abstract: This study describes the application and optimization of a newly developed specific gold nanoparticle (AuNP) visual detection method to detect a reverse transcription loop-mediated isothermal amplification (RT-LAMP) product of Taura syndrome virus (TSV) in shrimp with simple and cheaper in comparison to conventional gel electrophoresis. Briefly, the visual detection method is based on prevention of a salt induced DNA-labelled AuNP colour change from red to blue–purple due to hybridization with complementary DNA amplicons that arise from a positive TSV RT-LAMP reaction. RT-LAMP combined with visual amplicon detection using the DNA-labelled AuNP-probe had high sensitivity and the probe did not cross react with amplicons obtained using specific LAMP methods with other shrimp viruses. The advantages of this assay include simplicity, short analysis time and low-cost, suitable for field laboratory applications.

Monosex-Male Sex Reversal of Nile Tilapia Eggs Using Pulse-Electric Field Inductions

Abstract: This work proposes an alternative technique of monosex-male reversal for Nile tilapia (O.niloticus) using transient pulse-electric fields to minimize time consumption of the sex reversal treatment and androgen hormone dose instead of 28-days conventional feed-fry treated and immersion techniques which uses very large amounts of 17-methyltestosterone (MT) hormone. Electrical model of nonspherical fish’s egg was developed to evaluate the induced transmembrane potential using an RCmodel to correct the ambiguities about the shell thickness and the estimated dielectric properties of the egg membrane for inductions. The parallel-plate electrode equipped with a sequential signal pulse-generator (SPG) (to be patented) has been developed. The eggs of O.niloticus (2‐3 days postfertilization) were carefully induced in square-wave electric fields of 0.25‐87.50 kV ·m −1 .W e experimentally optimized induction of O.niloticus’s egg by adjusting the number of 1‐5 square wave pulses and 5‐10 s pulse durations. The suspending medium of electroporation (EPM) was prepared by mixing HEPES buffer with the minimized concentration of MT. Verifications of sex reversal of the induced eggs have been carried out with autopsies of 2 months old of sex-reversed fry by using the aceto-carmine stain technique. The optimized conditions were 3 square wave pulses of 87.50 kV ·m −1 electric fields but a 89.25% sex reversal of eggs was achieved with less than 25% egg death. The prototype of the electrode equipped with the controlled SPG for on-site inductions could operate with 50 eggs of O.niloticus for each induction with the rapid time consumption.

Real-time and label-free biosensing with microfluidic-based split-ring-resonator sensor

Abstract: In this work, a split ring resonator (SRR), the most important building block of metamaterial, is fabricated and integrated with a microfluidic chamber for biosensing. The SRR is patterned on a microwave printed circuit board while the microfluidic chamber is fabricated by casting of polydimethylsiloxane (PDMS). SRR was immobilized with Anti-Immunoglobulin G (IgG) for IgG detection by a standard covalent immobilization using Cystamine. The PDMS chamber was aligned and clamped on the circuit board and the electromagnetic response of the SRR sensor was continuously monitored when IgG analytes was flowed through the chamber. The reaction of Immunoglobulin G (IgG) and Anti-IgG results in a shift of resonance frequency. It was found that the response of the resonance frequency is sensitive to the IgG concentrations. Therefore, the SRR microfluidic scheme can be effectively used as an advanced bio-sensing device.

Novel 3D graphene foam-polyaniline-carbon nanotubes supercapacitor prepared by electropolymerization

Abstract: In this work, we present a novel supercapacitor (SC) material based on 3D graphene foam-polyaniline (Pani)-Carbon nanotubes (CNTs) composite for supercapacitor applications. Graphenefoam was fabricated by chemical vapor deposition (CVD) on Ni foam using acetylene carbon source and hydrogen gas carrier at 700°C for 3 minutes. Next, the foam was etched in 3M HCl for an hour to remove most of Ni support. Multi-wall CNTs powder were then dispersed in 1M HCl and 0.2 M aniline monomer was then added, stirred and filtered to remove non-dispersed CNTs. Electro-polymerization in the CNTs-aniline monomer solution was then conducted at working electrode potential of 0.55 V vs. Ag/AgCl. SEM and Raman characteirzation confirmed the incorporation of CNTs in Pani/graphene foam network with a number of nanowire features appeared on graphene foam surface and dominant D and G carbon's peaks. SC performances were then tested by cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) measurements in 2M H2SO4 electrolyte. CV results showed that PANI's redox peaks were broadened due to the presence of CNTs, indicating enhanced pseudocapacitance. From GCD measurements, it is found that CNTs-Pani-graphene foam exhibits a high specific capacitance of 920 Fg−1 at a specific current of 0.8 Ag−1, which is more than twice higher than that of Pani-graphene foam (430 Fg−1).

Synthesis and characterization of nitrogen-doped 3D graphene foam prepared by inductively-coupled plasma-assisted chemical vapor deposition

Abstract: In this work, we developed a new CVD process for the direct synthesis of N-doped graphene based on thermal CVD with inductively-coupled plasma (ICP) assistance using pure nitrogen (N2) gas source. 3D N-doped graphene foam (GP foam) was fabricated by CVD with ICP on Ni foam using acetylene (C2H2) carbon source and hydrogen (H2) gas carrier at 700–1000°C. The effects of various synthesis parameters including N2/C2H2/H2 gas flow ratio, ICP power, pressure, temperature and time on N-doped graphene structure have been systematically studied. Ni foam template was then etched in 3M HCl for an hour before subsequent characterizations by Raman spectroscopy, X-ray photoemission spectroscopy (XPS) and scanning/transmission electron microscopy (SEM/TEM). An optimal condition for high-quality N-doped graphene foam structure was found to be N2/C2H2/H2 of 7/4/84, ICP power of 200 W, pressure of 0.7 Tor, temperature of 900°C and time of 1 minute. Rama spectra exhibited dominant 2D and G peaks with low D peak and notable D' peak at 1624 cm−1, indicating successful N-doping of few-layer graphene structure. The presence of N atoms and N-doping concentration in graphene was confirmed by XPS. SEM/TEM data confirm that the structures are nanometer-thick N-doped 3D graphene structure with good crystallinity. Therefore, the CVD with ICP process is a new promising method for direct synthesis of N-doped graphene due to advantages including the use of non-toxic nitrogen source, high crystallinity of produced N-doped graphene structure and well controlled N-doping process.

The dielectrophoresis microfluidic chip for cell separation: Case study of separation of floating cell and moving cells

Abstract: Dielectrophoresis technique is one of the useful techniques in cell manipulation, especially for separating cells which has similar morphology but cannot separated by simple centrifugation technique. In this work, dielectrophoresis microfluidic device exploit the cells separation technique in two different cases; floating cells (leukocytes) and moving cells (spermatozoa). In this study leukocytes were chosen for floating cells due to they are nearly immotile and have five subpopulations which have similar electrical properties and external morphology, therefore it is very challenge to see the effect of electrophoresis in the separation. On the other hands, the spermatozoa have been chosen as the moving cell because the spermatozoa are activity motile and have two subpopulation, X and Y spermatozoa. Therefore it is very interested to see the effect of electrophoresis in the separation of subpopulation of both leukocyte and spermatozoa. The device is composed of patterning Indium Tin Oxide (ITO) electrode integrated with microchannel. The separation performance was combined with dielectrophroresis force and on-line flow in microfluidic channel. The crossover frequency was used for optimal of separated conditions. Leukocyte were response significantly at 4 Vp-p potential in frequency range from 200–600 kHz in 56 mS/m conductive medium, while bovine spermatozoa highly response at 4 Vp−1 potential in frequency 1–24 MHz in 10 mS/m conductive medium.

Graphene-based flexible circuit on cotton fabric using wax patterning method

Abstract: With recent development in the field of wearable devices for biomedical applications, various studies have been conducted on the fabrication of electrically conductive circuit on flexible substrate materials such as paper or textile. In this project, we propose the fabrication of electrically conductive circuit on cotton fabric using simple wax patterning method. Using this method, hydrophilic and hydrophobic regions were patterned on the fabric and graphene-poly (3,4-ethylenedioxythiophene): poly (styrenesulfonic acid) (graphene-PEDOT:PSS) ink was deposited on the hydrophilic region using pipetting method. Conductive lines with higher conductance were fabricated by multiple deposition of the conductive ink and electronic components were successfully attached on the fabric to develop a simple fully functional flexible circuit.

Increased Probability of Cell Membrane Breakdown by Use of Microfluidic System

Abstract: This research shows the experiment results of cell membrane breakdown. We did the experiments by using plant protoplasts in a microfluidic system to increase the efficiency of membrane charging process. In the experiment, we apply 5 MHz of sine wave to attract the cell to target position and then apply 10–200 kHz to make breakdown occur. Under the experiment conditions (R = 10–25 μm, U = 10 VP, tL = 10 ms, σ = 45–55 mS/m), the use of microfluidic system with insulating wall and orifice increased breakdown probability. Breakdown probability is 86.8%, and the probabilities of fL at 10–100 kHz are higher than the probability of fL at 200 kHz.

Three-dimensional graphene-polydimethylsiloxane composite as a conductive substrate for cell-based electrochemical detection

Abstract: Recently, three-dimensional (3D) graphene interconnected network has attracted a great interest in biological applications due to its biocompatibility, high electrical conductivity, large surface area and porous structure that is appropriate for cell growth. In this work, we cultured L929 fibroblast cells on 3D graphene composited with polydimethylsiloxane (PDMS) which is also used as working electrode for assessment of the electrochemical cell signal. Graphene was grown on Ni foams by chemical vapor deposition method using acetylene/hydrogen. The characterizations by scanning electron microscope (SEM) showed that open-pores of graphene foam were partially covered with thin layers of PDMS. In addition, PDMS-3D graphene composite exhibited a good electrical conductivity of 0.03 Scm−1. Cells were immobilized on PDMS-3D graphene composite surface and the electrochemical behavior of cell was determined by cyclic voltammetry (CV). The result showed oxidation peak current at +0.8 V whose amplitude was linearly proportional to cell number. Alamar blue assay was performed to confirm the results of cell viability data obtained from CV analysis. The result from immunofluorescence staining of vinculin affirmed that cell adhered on surface of PDMS-3D graphene composite. Therefore, 3D-graphene is highly biocompatible and can potentially be used as conductive substrate for cell culture in cell-based electrochemical applications such as drug or toxin screening.