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<p>In this study, ZnO nanoparticles were synthesized via coprecipitation at three different temperatures (20&#xa0;°C, 40&#xa0;°C, and 80&#xa0;°C), and their structural, morphological, optical, and photocatalytic properties were comprehensively examined. X-ray diffraction confirmed a hexagonal wurtzite structure for all samples, with crystallite sizes decreasing from 41.8&#xa0;nm (Zn20) to 34.8&#xa0;nm (Zn80) as synthesis temperature increased. These findings were further supported by FTIR analysis. Scanning electron microscopy revealed uniform pseudo-spherical morphologies, while UV–Visible and photoluminescence (PL) analyses showed a systematic increase in bandgap energy from 3.13&#xa0;eV to 3.20&#xa0;eV. Notably, PL measurements indicated significantly reduced emission intensity for Zn80, implying retarded electron–hole pair recombination and thus more efficient charge carrier separation. Photocatalytic experiments demonstrated that Zn80 exhibited the highest performance, achieving 96% degradation of methylene blue under simulated solar irradiation within 60&#xa0;min. This superior activity is attributed to its optimized defect structure, improved charge carrier dynamics, and increased surface area. Furthermore, scavenging tests confirmed hydroxyl radicals (⋅OH) as the dominant reactive species, and Zn80 maintained remarkable stability and reusability over four consecutive cycles with negligible efficiency loss. This work presents a novel approach focusing on the systematic investigation of coprecipitation synthesis temperature as a single, controllable parameter to tailor the properties of ZnO nanoparticles. Unlike conventional methods that rely on dopants, surfactants, or composite materials, this strategy demonstrates that significant enhancements in photocatalytic activity can be achieved through simple temperature modulation, paving the way for cost-effective and scalable production of high-performance ZnO photocatalysts.</p> Graphical abstract <p></p>

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Temperature-controlled synthesis of ZnO nanoparticles: optimizing structural and photocatalytic properties for enhanced degradation of methylene blue dye

  • 期刊论文

  • 发表日期：

    2025年8月20日

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  • Houari Hachemi,
  • Darlington C. Ashiegbu,
  • Nourredine Bettahar,
  • Rudolph Erasmus,
  • Herman J. Potgieter

摘要

In this study, ZnO nanoparticles were synthesized via coprecipitation at three different temperatures (20 °C, 40 °C, and 80 °C), and their structural, morphological, optical, and photocatalytic properties were comprehensively examined. X-ray diffraction confirmed a hexagonal wurtzite structure for all samples, with crystallite sizes decreasing from 41.8 nm (Zn20) to 34.8 nm (Zn80) as synthesis temperature increased. These findings were further supported by FTIR analysis. Scanning electron microscopy revealed uniform pseudo-spherical morphologies, while UV–Visible and photoluminescence (PL) analyses showed a systematic increase in bandgap energy from 3.13 eV to 3.20 eV. Notably, PL measurements indicated significantly reduced emission intensity for Zn80, implying retarded electron–hole pair recombination and thus more efficient charge carrier separation. Photocatalytic experiments demonstrated that Zn80 exhibited the highest performance, achieving 96% degradation of methylene blue under simulated solar irradiation within 60 min. This superior activity is attributed to its optimized defect structure, improved charge carrier dynamics, and increased surface area. Furthermore, scavenging tests confirmed hydroxyl radicals (⋅OH) as the dominant reactive species, and Zn80 maintained remarkable stability and reusability over four consecutive cycles with negligible efficiency loss. This work presents a novel approach focusing on the systematic investigation of coprecipitation synthesis temperature as a single, controllable parameter to tailor the properties of ZnO nanoparticles. Unlike conventional methods that rely on dopants, surfactants, or composite materials, this strategy demonstrates that significant enhancements in photocatalytic activity can be achieved through simple temperature modulation, paving the way for cost-effective and scalable production of high-performance ZnO photocatalysts.

Graphical abstract