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    Interdigitated Extended Gate Field Effect Transistor for pH Sensor Based on Porous Silicon Layer
    (2025-01-01)
    Atiwongsangthong, Narin
    Study introduces a pH sensor utilizing an interdigitated extended gate field-effect transistor (IEGFET) structure, incorporating a porous silicon (PS) layer. The PS layer was created via electrochemical etching on p-Type <100> silicon wafers, apply current density of 10 mA/cm2 in a 48% HF solution for a duration of 10 minutes. Surface characteristics of the resulting PS layer were examined through scanning electron microscopy (SEM). The sensor integrates this PS layer with a standard N-MOSFET, forming the IEGFET configuration. Due to increasing surface area inherent in porous structure, device demonstrated improved pH sensitivity and response linearity. The sensing capability was tested across pH levels 4, 7, and 10. Results revealed a current mode sensitivity of 0.7636 μA2/pH and a linearity of 99.89%. Voltage mode sensitivity of 53.5 mV/pH and a linearity of 99.86%. These findings validate porous silicon as an excellent for efficient and reliable pH sensing.
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    Colorimetric Screen-Printed Label Using Low Molecular Weight Chitosan Grafted with Rosolic Acid for pH and Ammonia Gas Sensing
    (2024-10-15)
    Ronte, Arnat
    ;
    Chalitangkoon, Jongjit
    ;
    Monvisade, Pathavuth
    Colorimetric sensing technologies are valued for their simplicity and adaptability, yet their large-scale production remains economically challenging. This study presents a cost-effective colorimetric pH sensor developed from low molecular weight chitosan (LC) grafted with rosolic acid (LCRA), engineered as a pH-sensitive colorant for screen-printing inks. LCRA was synthesized via a Mannich reaction and characterized using<sup>1</sup> H NMR, FT-IR, and UV-Vis spectroscopy. LCRA showed reduced crystallinity and thermal stability alongside notable improvements in water solubility compared to its LC precursor. The LCRA ink displayed compatibility with various substrates, including polypropylene spun bond, filter paper, and cotton, applying easily via screen printing without any dye leaching. Notably, it exhibited a responsive color change from orange-yellow to pink-red in response to pH adjustments between 4.0 and 12.0 and upon exposure to ammonia gas. These findings position the LCRA label as a versatile and efficient solution for visual pH detection across various applications.
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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.
    ;
    Tunhoo, B.
    ;
    Onlaor, K.
    ;
    Thiwawong, T.
    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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    Design and improvement of wireless crayfish breeding system by controlling water temperature and monitoring pH via cloud system services
    (2018-06-08)
    Photsathian, Thongchai
    ;
    Suttikul, Thitiporn
    ;
    Tangsrirat, Worapong
    This work proposes the design and improvement of the wireless cloud system services for controlling water temperature and monitoring the pH-value for the crayfish breeding system. The cooling system employs a set of peltier, microcontroller board, and temperature and pH sensors. The circulate water system is used in order to maintain well-distributed water temperature in the water tank. The record data is displayed via the cloud computing processing system, which can be access the measured data at any time and everywhere by various PDA devices via internet network.