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    Solvent-Dependent Green Synthesis of ZnO Nanopowders Using Mitragyna speciosa Leaf Extract: Impact on Piezo-Photocatalytic and Antibacterial
    (2026-07-01)
    Sanyen, Thanyapa
    ;
    Songpanit, Maneerat
    ;
    Kansaard, Thanaphon
    ;
    Wirunchit, Supamas
    ;
    Chutipaijit, Sutee
    ZnO nanopowders were synthesized via a solvent-mediated green route using Mitragyna speciosa Korth. leaf extract as reducing and stabilizing agents. Deionized water and methanol were employed to tailor the phytochemical composition of the extracts. The influence of extract concentration (5–20 mL) and solvent polarity on structural, morphological, and functional properties was systematically investigated. Structural analyses confirmed the formation of Zn-O bonds and a phase-pure hexagonal wurtzite ZnO without secondary phases. Surface morphology revealed solvent-dependent morphological evolution toward spherical shapes and reduced aggregation in the methanol-derived system. For antibacterial activity, green ZnO nanopowders demonstrated enhanced biocidal effects against Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus, comparable to that of commercial ZnO nanoparticles. Enhanced piezo-photocatalytic degradation of rhodamine B was achieved under combined light and ultrasonic irradiation, with superior performance observed for methanol-derived ZnO. This enhancement is attributed to the synergistic interplay of solvent-induced defect states, reduced particle size, and piezoelectric field-driven charge separation. Scavenger analysis confirmed that superoxide radicals ((Formula presented.)) dominate the degradation pathway by green-synthesized ZnO nanopowders prepared from different solvent extracts. Thus, a correlation between solvent-mediated phytochemical environments and piezo-photocatalytic activity provides new insights for the design of sustainable, high-performance ZnO-based catalysts.
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    Effective detection of ZnO in nicotine using butterfly wing scales
    (2022-01-01)
    Changcharoen, Thanachai
    ;
    Apiphatnaphakul, Thidsanu
    ;
    Watjanavarreerat, Wasupon
    ;
    Locharoenrat, Kitsakorn
    This study aimed to elucidate the optical functions of naturally butterfly wing scales via precise control of morphology as an effective photonic sensor and confirm the content of metal oxide nanoparticles in surrounding nicotine. Metal oxide nanoparticles mixed with nicotine were deposited on the wing scales through the spin-coating method and hence investigated using optical microscopy and spectroscopy. Experimental results demonstrated that absorption intensities of ZnO and TiO<inf>2</inf> mixed with nicotine on Danaus genutia were remarkably enhanced. Due to the relatively high concentration of zinc found in e-cigarette aerosol, the intensity of ZnO/nicotine modelled as aerosol adsorption on Danaus genutia, further held a certain linear relationship with the concentration of ZnO. The limit of detection of ZnO was as low as 1 nM. The working mechanism of our sensor was explained through the molecular adsorption after H-bond formation of ZnO/nicotine molecules as high-index materials on the wing scales of Danaus genutia without aggregation. This photonic sensor is an alternative to the present-day methods for the rapid test of ZnO content, which is very simple without complicated instrumentation. Furthermore, our method might become a starting point for the advancement of portable instruments for onsite ZnO detection.
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    Use of zinc oxide nanoparticles for detection of fluoride in toothpaste gel
    (2022-01-01)
    Watjanavarreerat, Wasupon
    ;
    Steier, Liviu
    ;
    Locharoenrat, Kitsakorn
    This study aimed to investigate the metal-binding effect of fluoride, contained in different commercial toothpaste gels; the study aimed to determine if the toothpastes contained excessive concentrations of fluoride, which result in white spot lesions. A spectrophotometric method that used spectrophotometric reagents, including zinc oxide nanoparticles and iron chloride, was used to determine fluoride distribution; the analysis was based on the selective attack of fluoride ions on metals. Fluoride concentrations between 0 and 1450 ppm were analyzed. Although the iron–fluoride complex was a more sensitive reagent, the zinc–fluoride complex could serve as a suitable alternative to it for fluoride analysis, partly because the method was less time consuming and more stable. The detection and quantification limits obtained from the linear calibration curves of the zinc–fluoride complexes, in deionized water, were 0.191:1 and 0.579:1 w/w ZnO, respectively. A model calibration curve was suggested to detect the unknown products of fluoride degradation. Dentists could use a fluoride treatment similar to the protocol used in this study, to prevent potential enamel demineralization, and exclude physical cavity preparation and restoration.
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    Antitumor activities of carboplatin–doxorubicin–ZnO complexes in different human cancer cell lines (breast, cervix uteri, colon, liver and oral) under UV exposition
    (2021-01-01)
    Pairoj, Suttirak
    ;
    Damrongsak, Pattareeya
    ;
    Damrongsak, Badin
    ;
    Jinawath, Natini
    ;
    Kaewkhaw, Rossukon
    This study aimed to examine the pharmacological profiles of multiple chemo drug candidates in systematic circulation to enhance their specific interactions with five human cancer cell lines. ZnO nanoparticles were successfully bound with chemo drugs via physical adsorption. The drug loading capacity was confirmed by FTIR, whereas the loading efficiency was determined via UV–vis spectrometry. The mean hydrodynamic size increased to 69–82 nm after chemo-drug immobilization via non-covalent interaction with ZnO. Among the nine formulated chemo drugs, the carboplatin (CP)–doxorubicin (DOX)–ZnO complex under UV light irradiation exhibited high sensitivity towards human breast adenocarcinoma cells without affecting human keratinocyte immortal cells with an IC<inf>50</inf> of 0.137 µg/mL, whereas the loading capacity and efficiency of CP–DOX–ZnO were 77.81% and 99.05%, respectively. Fluorescence images confirmed that CP–DOX–ZnO using DOX served as a fluorescence enhancer specifically bound onto the cell membranes, which became almost saturated after 24 h incubation. Carboplatin–DOX–ZnO was possibly endocytosed by cancer cells and was selectively internalized into the target cells; thus, free chemo drug was released in the cytoplasm, which induced acute apoptosis. This resulted in complete inhabitation of growth signal of target cancer cells.
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    Size-Independent Unipolar and Bipolar Resistive Switching Behaviors in ZnO Nanowires
    (2019-06-15)
    Srikimkaew, Oradee
    ;
    Suebka, Sartanee
    ;
    Sriborriboon, Panithan
    ;
    Khemasiri, Narathon
    ;
    Kasamechonchung, Panita
    In this work, we report on the mixed bipolar and unipolar resistive switching behavior in ZnO nanowires observed through conductive atomic force microscopy measurements on an individual nanowire. Both bipolar and unipolar resistive switching in ZnO nanowires are size-independent, suggesting that the switching is due to conductive filaments with dimensions much smaller than the cross-section of the nanowire. During bipolar resistive switching, both the low resistance and the high resistance states exhibit ohmic conduction at low voltage, consistent with the filament-based model. During unipolar switching, the low-resistance state is a mix of defect-free ohmic conduction and defect-dominated space-charge-limited conduction, which may not be observed in larger devices. Defects also influence transport in the high resistance state, which exhibits trap-controlled space-charge-limited conduction. Our results clearly demonstrate the key role of defects on the resistive switching behavior of ZnO-nanowires, an important consideration for optimizing the material for nonvolatile memory applications.