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Tailoring ZnO Nanostructures through Precursor Concentration and Hydrothermal Duration: A Pathway to Efficient Solar Water Splitting
(2026-11-10)
Borklom, Phanlapa
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Khemasiri, Narathon
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Jessadaluk, Sukittaya
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Rattanawarinchai, Prapakorn
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Kayunkid, Navaphun
This work investigated the formation of ZnO nanostructures on ITO substrates prepared by self-seeding hydrothermal synthesis for photoelectrochemical ( PEC) water splitting applications. The hydrothermal parameters, precursor concentration and hydrothermal time, were varied to explore their influences on ZnO crystallinity, morphology, and PEC performance. The combinations of X-ray diffraction and field emission scanning electron microscopy revealed highly oriented ZnO nanostructures with diverse morphologies, including small granules, nanorods, dense films, and hexagonal platelets. Topographic profiling of the morphological parameters revealed complex relationships between synthesis conditions and nanostructure characteristics, highlighting the importance of considering aggregation phenomena in substrate-based growth. This aggregation led to deviations from conventional crystal growth theory predictions, particularly for grain density and diameter evolution. PEC performance evaluation identified ZnO nanorods as the optimal morphology, exhibiting a photocurrent density of 0.182 mA/cm² at 0 V vs. Ag/AgCl. Further enhancement was achieved by decorating ZnO nanorods with CdS nanoparticles, resulting in a six-fold increase in photocurrent density (1.2 mA/cm²). This improvement is attributed to expanded light absorption and improved charge separation at the CdS/ ZnO interface. Our findings demonstrate the potential of rationally designed ZnO-based nanostructures in the advancement of solar-driven water splitting technologies and provide valuable insights for optimizing PEC systems through precise control of hydrothermal synthesis parameters, consideration of substrate-induced aggregation, and strategies for photoelectrochemical (PEC) water splitting applications.
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Nondestructive Localization of Subvisual Defects in Laser-Induced Graphene via Machine-Learning-Assisted Electrical Resistance Tomography
(2026-06-16)
Minakawa, Keiya
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Takanashi, Kotaro
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Kimura, Yuki
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Klamchuen, Annop
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Wongwiriyapan, Winadda
Although conventional imaging techniques excel at capturing structural changes, they frequently overlook functional degradations that lack morphological signatures. Here, we demonstrate machine-learning-assisted electrical resistance tomography (ML-ERT) as a robust modality for the rapid, nondestructive localization of “subvisual” defects in porous laser-induced graphene (LIG). By employing masked O<inf>2</inf> plasma irradiation, we introduced localized defects that exhibit a dramatic resistance surge up to 4 orders of magnitude while remaining indistinguishable under visual and electron microscopy. Our ML-ERT framework, powered by a one-dimensional convolutional neural network inverse solver, successfully pinpointed these hidden failures once the resistance contrast reached a threshold of R/R<inf>0</inf> ≥ 6.71. Furthermore, 3D finite element analysis revealed that the tomographic contrast is driven by an effective conductive volume loss exceeding 30%, identifying the degradation of internal conductive pathways as the primary mechanism. These results establish ML-ERT as a high-sensitivity diagnostic tool capable of visualizing electrically critical but optically invisible failures, providing a definitive solution for the quality control of large-area carbon electronics.
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Growth window and metal-insulator transition behavior of VO2 thin films deposited by pulsed laser deposition for thermal switch applications
(2026-05-01)
Jessadaluk, Sukittaya
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Rahong, Sakon
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Kayunkid, Navaphun
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Khemasiri, Narathon
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Rangkasikorn, Adirek
Vanadium dioxide (VO<inf>2</inf>) is a strongly correlated transition metal oxide that exhibits a sharp and reversible metal-insulator transition (MIT) near room temperature, making it a promising material for thermal switching and adaptive electronic applications. In this study, VO<inf>2</inf> thin films were deposited on single-crystalline Si, thermally grown SiO<inf>2</inf>, and fused quartz substrates by pulsed laser deposition, and the influence of substrate temperature and oxygen partial pressure on phase formation, structural properties, and MIT behavior was systematically investigated. By optimizing deposition conditions within a narrow oxygen pressure window, phase-pure monoclinic VO<inf>2</inf>(M) thin films with high crystalline quality were achieved while suppressing the formation of over-oxidized vanadium oxide phases. Structural and chemical analyses using X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy confirmed the stabilization of the V4+ oxidation state and uniform film stoichiometry. Temperature-dependent electrical measurements revealed a pronounced and reproducible MIT characterized by an abrupt change in resistance and a clear thermal hysteresis. In-situ temperature-dependent X-ray diffraction further demonstrated a direct correlation between the monoclinic-rutile structural transformation and the electronic transition. Importantly, the MIT behavior was consistently observed across all investigated substrates, indicating robust film growth and substrate tolerance. These results provide insight into the structure-property relationships governing VO<inf>2</inf> thin films and highlight their potential for integration into thermal switch and thermally adaptive device architectures.
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Shape memory laser-induced graphene electrode based on polybenzoxazine-co-epoxy coated fabric and its electrochemical sensor application
(2025-12-01)
Luengrojanakul, Panuwat
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Klamchuen, Annop
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Leepheng, Piyawan
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Tunhoo, Benchapol
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Charoensuk, Krittapas
In this investigation, CO<inf>2</inf> direct laser writing is performed on BA-a/NGDE shape memory polymer matrix coated fabric. Findings show that the quality and surface coverage of formed laser-induced graphene (LIG) are dependent on BA-a content. The LIGs acquired at higher BA-a content possess low sheet resistance (∼10–15 Ω/sq), facilitating its use as joule heater for shape memory actuation (T<inf>avg</inf> ∼130 °C at 20 V for BOZ70-LIG). Furthermore, the fabricated LIG electrode shows potential use as electrochemical sensor with ΔE<inf>p</inf> of 88–200 mV and k0 of 0.005 cm s-1 (20 mm length) for 1 mM K<inf>4</inf>[Fe(CN)<inf>6</inf>]/0.1 M KCl. The 40 mm electrode length also maintains respectable electrochemical performance even after subjecting LIG to shape deformation and recovery. Moreover, the molecular imprinted polymer (MIP) modified LIG electrode also exhibits promising results in selective dopamine detection through leucodopaminechrome in PBS with linear detection range of 1.0–15.0 μM and LOD of 0.61 μM.
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Rational concept for fully designing metal-oxynitride films through reactive gas-timing magnetron sputtering: A case study on zinc oxynitride film
(2025-08-10)
Khemasiri, Narathon
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Chananonnawathorn, Chanunthorn
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Horprathum, Mati
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Pornthreeraphat, Supanit
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Saekow, Bunpot
Amorphous metal-oxynitride films—particularly zinc oxynitride (ZnON)—are emerging as promising materials for next-generation high-speed switching electronics, due to the absence of a potential barrier above the conduction band, unlike metal-doped ZnO. However, conventional reactive magnetron sputtering often face challenges in precisely controlling in an anion ratio, N/(N + O), because of the different reactivities of nitrogen and oxygen gases. In this work, we present a strategy to precisely control both the crystal structure and N/(N + O) ratio in ZnON films using a reactive gas-timing technique. By adjusting the oxygen gas-timing sequence (t<inf>O₂</inf>), we selectively induce different crystalline phases, which are closely related to the nitridation and oxidation of the sputtered Zn atom/cluster. This technique facilitates effective N incorporation into ZnO, enabling a broad range of N/(N + O) ratios from 0.048 to 0.964 and optical band gap variations from 1.49 eV to 3.22 eV. At an optimal t<inf>O₂</inf>, an amorphous phase is formed, attributed to a balanced nitridation and oxidation rate of the sputtered Zn atom/cluster that suppresses crystallization. The resultant amorphous ZnON film exhibits a high carrier mobility of 84.81 cm²/Vs, which is 1.16-fold and 35.89-fold greater than those of the cubic and hexagonal ZnON films, respectively. Our findings highlight the effectiveness of the reactive gas-timing technique as a powerful tool for the rational design of metal-oxynitride films, paving the way for their application in advanced electronic devices.
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Laser-induced graphene electrochemical immunosensors for rapid and sensitive serological detection: A case study on dengue detection platform
(2025-06-01)
Inlumphan, Supawee
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Wongwiriyapan, Winadda
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Khemasiri, Narathon
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Rattanawarinchai, Prapakorn
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Leepheng, Piyawan
Here, we present a diagnostic on a chip platform based on laser-induced graphene (LIG) electrochemical immunosensors for serological detection. The electrochemical immunosensors are fabricated through CO<inf>2</inf> laser induction on polyimide (PI) sheets. Optimal electrochemical activity of LIG electrodes is obtained under optimized conditions of laser fluence. To verify the application, the serological detection platform was demonstrated. After functionalization with dengue virus (DENV) antigen, the LIG electrochemical immunosensors are able to sense the presence of mouse anti-flavivirus monoclonal (4G2) antibody in a wide linear working range of 25–20,000 ng/ml with the limit of detection (LOD) of 17.41 ng/ml. A specific recognition with 4G2 antibodies against with media protein and isotype is confirmed. Furthermore, the reliability of LIG electrochemical immunosensors compared to conventional enzyme-linked immunosorbent assay (ELISA) is verified through the NS1 antibodies identification in human blood serum clinical samples at room temperature. Our results highlight that the LIG-based electrode is a promising platform for electrochemical immunosensors, aimed at developing reliable and practical diagnostic tools for serological detection. These tools enable early diagnosis of infectious diseases, as well as non-invasive and rapid screening.
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Selective formations of antimony-dopant for highly sensitive nitrogen dioxide responsive behavior of tin oxide-based chemiresistive sensor
(2025-02-15)
Rattanawarinchai, Prapakorn
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Khemasiri, Narathon
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Rahong, Sakon
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Rangkasikorn, Adirek
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Kayunkid, Navaphun
Here, selective formation of antimony (Sb) dopant species responsible for highly sensitive gas sensors based on tin oxide (SnO<inf>2</inf>) film grown via pulsed laser deposition is presented. By elevating a forming energy through controlling substrate temperature, not only crystallinity of Sb-SnO<inf>2</inf> (ATO) is notably enhanced but the Sb5 + also predominantly replace at Sn4+ site rather than Sb3+ counterpart. Such Sb-species selection plays a crucial role on the density of oxygen vacancy and free electron enabling to rationally design conductive behaviour of ATO film from insulative to degenerated semiconductor. As a practical example, detection of nitrogen dioxide (NO<inf>2</inf>) gas is selected as an application model. We found a narrow window for high NO<inf>2</inf> sensing performance of ATO film which strongly corresponds with the amount of carrier density. At certain window, ATO film exhibits high NO<inf>2</inf> response of 24.65 (10 ppm) and low limit of detection of 0.5 ppm, which is 5-fold higher and 10-fold lower than that of undoped-SnO<inf>2</inf>, respectively. Our finding demonstrates a facile approach to design over the chemical state, defect, and conductivity of the active sensing layer, allowing us to achieve an excellent sensing performance of functional materials conjugated to a nano-electronic platform.
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Low resistance bisphenol-A based polybenzoxazine derived laser-induced graphene (LIG) and its microsupercapacitor application
(2024-11-01)
Luengrojanakul, Panuwat
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Klamchuen, Annop
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Khemasiri, Narathon
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Chotsuwan, Chuleekorn
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Charoensuk, Krittapas
Herein, we demonstrate the use of conventional BA-a based polybenzoxazine as a laser-induced graphene (LIG) forming precursor. The effects of laser power and the engraving speed on formation and properties of LIG are explored. By optimizing the laser fluency related to laser power along with engraving speed, poly(BA-a) derived LIG with high graphitization degree and low sheet resistance (R<inf>s</inf>) of ∼ 2–10 Ω/sq can be acquired. The morphologies and surface area of LIGs in such low R<inf>s</inf> region are then validated through SEM and BET, respectively. The resulting poly(BA-a) derived LIG exhibits a high amount of macropores in the structure with marginal differences in the specific surface area being 27–88 m2/g. In addition, electrochemical performances of the two-electrode based microsupercapacitor (LIG-MSC) of the selected samples in low R<inf>s</inf> region with different specific surface area are evaluated. The LIG-MSC shows a specific capacitance of 1.39 mF/cm2 (0.04 mA/cm2), and good cycling stability of 10,000 cycles with capacitance retention of 92% (0.2 mA/cm2). Our results highlight that poly(BA-a) derived LIG is promising for high performance LIG applications.
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Enhancement in Sensitivity and Selectivity of Electrochemical Technique with CuO/g-C3N4 Nanocomposite Combined with Molecularly Imprinted Polymer for Melamine Detection
(2024-07-01)
Limthin, Dalawan
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Leepheng, Piyawan
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Tunhoo, Benchapol
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Klamchuen, Annop
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Suramitr, Songwut
This study focused on enhancing the sensitivity and selectivity to detect melamine by utilizing a photoelectrochemical method. This was achieved by combining a melamine-imprinted polymer with a CuO/g-C<inf>3</inf>N<inf>4</inf> nanocomposite, which was synthesized through chemical precipitation and calcination. The resulting nanocomposite exhibits improved carrier mobility and photoelectrochemical properties. A molecularly imprinted receptor for selective detection was created through bulk polymerization with methacrylic acid and a melamine template. The characterization of the nanocomposite was performed using X-ray photoelectron spectroscopy for the chemical oxidation state, X-ray diffraction patterns for the crystalline structure, and ultraviolet/visible/near-infrared spectroscopy for optical properties. The CuO/g-C<inf>3</inf>N<inf>4</inf> nanocomposite exhibits photoactivity under visible light. The modified electrode, incorporating the CuO/g-C<inf>3</inf>N<inf>4</inf> nanocomposite and melamine-imprinted polymer, demonstrates a linear detection range of 2.5 to 50 nM, a sensitivity of 4.172 nA/nM for melamine, and a low detection limit of 0.42 nM. It shows good reproducibility and high selectivity to melamine, proving effective against interferences and real samples, showcasing the benefits of the molecularly imprinted polymer.
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Urinary dengue NS1 detection on Au-decorated ZnO nanowire platform
(2024-06-15)
Sitthisuwannakul, Kannika
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Sukthai, Ratchanon
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Zhu, Zetao
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Nagashima, Kazuki
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Chattrairat, Kunanon
Biodetection for non-invasive diagnostics of fluids, especially urine, remains a challenge to scientists due to low target concentrations. And biological complexes of the detection target may contain contaminants that also interfere with any assay. Dengue non-structural 1 protein (Dengue NS1) is an important biomarker for dengue hemorrhagic fever and dengue shock syndrome. Here, we developed an Au-decorated nanowire platform and applied it with a sandwich fluorophore-linked immunosorbent well plate assay (FLISA) to detect Dengue NS1 in urine. For the platform, we fabricated zinc oxide (ZnO) nanowires to provide a high surface area and then coated them with gold nanoparticles (ZnO/Au nanowires) to simply modify the Dengue NS1 antibody and enhance the fluorescence intensity. Our platform employs a sandwich FLISA that exhibits high sensitivity, specifically detecting Dengue NS1 with a limit of detection (LOD) of 1.35 pg/mL. This LOD was 4500-fold lower than the LOD of a commercially available kit for Dengue NS1 enzyme-linked immunosorbent assay. We believe that our ZnO/Au nanowire platform has the potential to revolutionize the field of non-invasive diagnostics for dengue.

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