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    Preparation of pH Sensor Based on Extended-Gate Field-Effect Transistor with Spinel ZnCo2O4 Thin Films by Electrostatic Spray Deposition
    (2023-12-01)
    Keawkusonwiwat, S.
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    Electrostatic spray deposition was applied to prepare pH sensing with spinel ZnCO<inf>2</inf>O<inf>4</inf> thin films based on the measurement of extended-gate field-effect transistors (EGFET). The influence of annealing temperatures on the characteristics of the prepared films was analyzed. The structural and morphological properties of the annealed ZnCo<inf>2</inf>O<inf>4</inf> films were assessed by x-ray diffraction, x-ray photoelectron spectroscopy, Raman spectroscopy, scanning electron microscopy, and contact angle measurement. The effect of the ZnCo<inf>2</inf>O<inf>4</inf> annealing temperature on the characteristics of pH sensing for the prepared ZnCo<inf>2</inf>O<inf>4</inf> films in EGFET measurement were examined with pH buffer solutions in a pH range of 2–12 at room temperature. The sensing films annealed at 550°C demonstrated a high voltage and current sensitivity at 67.6 mV/pH and 1.033 (µA)<sup>½</sup>/pH, with linearity values of 0.9968 and 0.9991, respectively. Moreover, the annealed 550°C ZnCo<inf>2</inf>O<inf>4</inf> film exhibited low hysteresis at 4.99 mV and high retention stability. The results revealed that the pH sensing of the ZnCo<inf>2</inf>O<inf>4</inf> EGFET device showed a super-Nernstian sensitivity, which indicated the influence of the surface properties of the annealed film. Therefore, the ZnCo<inf>2</inf>O<inf>4</inf> film should be considered a potential option for the pH sensing layer in EGFET applications.
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    Properties of CuPc/Se organics-inorganic hybrid thin films growth by electron beam evaporation technique
    Organic and Inorganic materials with copper (II) phthalocyanine (CuPc) and selenium (Se) were deposited to implement hybrid thin Alms by multi pocket electron beam evaporation technique. Crystallization of hybrid films was performed by x-ray diffraction (XRD) spectroscopy. XRD pattern exhibits monoclinic α-phase crystallizations structure of CuPc. Influences of the CuPc thickness on the crystalline structure of selenium films were obtained. As the thickness of CuPc layer was increased to 100 nm, the hexagonal Se was observed. Optical absorption spectra were measured by UV-Visible spectrophotometer. Results of hybrid absorption spectra were revealed to absorption spectra of CuPc and Se. Surface roughness of films can confirm with XRD spectra .The surface morphology was characterized by atomic force microscope (AFM) with non-contact mode, it illustrate the point that hybrid thin films is nanocrystal structure. © 2007 IEEE.
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    Multilevel conductance switching and carrier transport mechanisms of memory devices based on an ITO/PVK:Ag nanoparticles/Al structure
    Multilevel conductance switching was achieved using silver nanoparticles (Ag NPs) embedded in poly(9-vinylcarbazole) (PVK) with a structure of ITO/PVK:Ag NPs/Al. The current-voltage (I-V) curves of the memory devices at low reading voltages showed three distinguished states of current. The memory devices exhibited non-volatile rewritable memory characteristics. The carrier transport mechanisms of the devices in each state were analyzed by theoretical models based on the experimental I-V data. In addition, retention time measurements showed clearly three current states with good data retention properties. From the retention times test, the average values of ON/OFF, ON/intermediate (INTERM) and INTERM/OFF current ratios of the memory devices were 1.7 × 10<sup>6</sup>, 3.5 × 10<sup>2</sup> and 5.0 × 10<sup>3</sup>, respectively.
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    Supercapacitive properties of cobalt oxide thin films prepared by electrostatic spray deposition technique at different substrate temperature
    (2016-01-01)
    Chansaengsri, Kasidid
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    In this work, cobalt oxide thin films were prepared by electrostatic spray deposition (ESD) technique. The influence of the substrate temperatures on properties of film was investigated. Phase transformation of cobalt oxide thin films due to the effect of different substrate temperature was also observed. Cyclic voltammetry was used to measure the performance of cobalt oxide supercapacitor. At higher substrate temperature, the cobalt oxide thin films exhibit the high specific capacitance due to the effect of phase transformation in cobalt oxide films.
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    Preparation of Conductive Screen-Printing Ink for High-Performance Bendable and Wearable ECG Electrodes on Fabric Substrates
    (2022-12-15)
    Chansaengsri, Kasidid
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    Monitoring of vital signs is a necessary tool to diagnose the symptoms of illness. This work developed screen-printing inks for conductive nanomaterials to fabricate electrocardiogram (ECG)-compatible fabric electrodes. The contents of the polymer matrix, calcium carbonate additive filler, and conductive nanomaterials (silver nanoparticles and copper nanowires) on the resistivity of the composite inks were optimized. A facile process of screen printing was applied to fabricate the electrodes on fabric to create an efficient conductor with high stability in conduction. The fabricated electrodes exhibited flexible and bendable behavior over 0.7% bending strain for wearable components. The results showed that the fabricated electrode based on copper nanowires resistivity was 40.01 ± 1.94 k Ω/cm, and the proposed signal-to-noise ratio (SNR) was approximately 27.16 ± 9.37 dB. Therefore, these fabricated electrodes can be applied in wearable vital biosignal detection devices that perform with high sensitivity during movement, thereby providing health monitoring opportunities. Moreover, the fabricated electrodes can be used without excessive pressure or an electrolyte gel layer, thus overcoming the challenges of developing a portable device.
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    Structural and optical properties of CuPc/ZnSe multilayer hybrid thin films prepared by electron beam evaporator
    Multilayer hybrid thin films consisting of alternating layers of organic and inorganic materials were fabricated with powder of copper-phthalocyanine (CuPc) and zinc selenide (ZnSe) by electron beam evaporator. The structural and optical characterization of multilayer hybrid thin film were carried out by using X-ray diffraction (XRD), atomic force microscope (AFM) and UV-Vis absorption spectroscopy. XRD patterns show two peaks of the orientation of (200) plane monoclinic structure in CuPc material and (111) plane cubic structure in ZnSe material where pair numbers of multilayer hybrid thin film higher than two pairs. With the variation in the number of pairs of CuPc/ZnSe, AFM images present almost similar morphology but the optical absorption spectra are significantly changed. Such spectral changes can be interpreted by the effect of the aggregate size and the characteristic of the multilayer hybrid structure. © 2007 IEEE.
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    Preparation of copper doped zinc oxide nanoparticles by precipitation process for humidity sensing device
    (2018-09-05) ; ;
    Chaithanatkun, Natpasit
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    In this work, nanoparticles of copper-doped zinc oxide were synthesized using the precipitation process at different copper doping molars. The structure of the synthesized nanoparticles was examined by X-ray diffraction and X-ray photoelectron spectroscopy. From the results, it was indicated that the nanoparticles were composed of mixed copper oxide-zinc oxide. To fabricate the humidity sensor, the nanoparticles were dispersed in ethanol and deposited on an electrode using the electrostatic spray deposition technique. The humidity sensing behavior was assessed at various humidity levels in a closed vessel of saturated salt solution. Moreover, the response times for the device were recorded. The Cole-Cole plot of the real and imaginary parts of impedance could be useful for description of the equivalent circuit that indicates the mechanism for humidity sensing behavior.
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    Transparent write-once-read-many-times memory devices based on an ITO/EVA:rGO/ITO structure
    (2018-10-01)
    Songkeaw, P.
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    Fully transparent electronic devices play an important role in electronic applications. Well-known examples are the wearable devices and transparent displays; their applications are transparent memory devices of interest. The transparent write-once-read-many-times (WORM) memory devices based on synthesized graphene oxide (GO) blended in poly (ethylene-co-vinyl acetate) (EVA) had been fabricated by a thermal roll lamination technique in which the synthesized GO inside the EVA matrix was reduced into reduced graphene oxide (rGO) during the lamination process. The memory devices exhibited an optical transmittance of more than 60% in the visible light region. The conduction mechanisms of the memory devices were identified using theoretical models based on the current–voltage (I–V) curves. The fitted I–V results were described by the conductive filaments in which electrons were transported through the rGO direct contacts. In addition, the maximum ON/OFF current ratio of the transparent WORM memory device was approximately 5 × 10<sup>5</sup>, and the retention time tests showed two current states with good data retention properties under different temperatures.
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    A humidity sensor based on silver nanoparticles thin film prepared by electrostatic spray deposition process
    In this work, thin film of silver nanoparticles for humidity sensor application was deposited by electrostatic spray deposition technique. The influence of the deposition times on properties of films was studied. The crystal structures of sample films, their surface morphology, and optical properties have been investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and UV-VIS spectrophotometer, respectively. The crystalline structure of silver nanoparticles thin film was found in the orientation of (100) and (200) planes of cubic structure at diffraction angles 2θ = 38.2° and 44.3°, respectively. Moreover, the silver nanoparticles thin films humidity sensor was fabricated onto the interdigitated electrodes. The sensor exhibited the humidity adsorption and desorption properties. The sensing mechanisms of the device were also elucidated by complex impedance analysis. © 2013 Thutiyaporn Thiwawong et al.
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    Selective electrochemical determination based on magnetic molecularly imprinted polymers for albumin detection
    (2022-06-01)
    Leepheng, Piyawan
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    Limthin, Dalawan
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    Egg allergy is one of the most common allergies in humans. Allergenic egg protein as ovalbumin is the most abundant protein found in egg white. A selective electrode in electrochemical analysis for albumin from egg white was developed based on magnetic molecularly imprinted polymers (albumin-MMIPs) modified on a screen-printed electrode. Surface modification was applied using methyl methacrylate polymer to create surface specificity for albumin protein. The modified surface was characterized by a field-emission scanning electron microscope (FE-SEM). The average pore size was obtained by Brunauer-Emmett-Teller (BET) analysis, and the potentiostat obtained all electrochemical analysis. The albumin-MMIP electrode was selectivity with albumin, comparison with gluten, glycine, casein, and glucose. The modified electrodes present selectivity of 1.13 × 104 μAg-1ml and a limit of detection of 0.18 mg ml-1. The electrode can be applied to albumin protein detection in solution form in food industries.