Scholarlink

<p>Starch-mediated ZnAl<sub>2</sub>O<sub>4</sub> spinel nanoparticles were synthesized using a simple auto-combustion sol-gel route and calcined at 800, 1000 and 1200 ℃. The influence of calcination temperature on the structural, vibrational, morphological, optical and photocatalytic characteristics of the materials was investigated using a combination of experimental techniques and density functional theory (DFT) calculations. Rietveld refinement confirms the presence of the cubic spinel phase ZnAl<sub>2</sub>O<sub>4</sub> and secondary hexagonal ZnO phase and reveals a gradual lattice contraction with increasing calcination temperature, in excellent agreement with DFT predictions. Analysis of the Photoluminescence (PL) spectra revealed the presence of five characteristic bands attributed to intrinsic defects (405–523&#xa0;nm): F<sup>+</sup> and F<sup>0</sup> oxygen vacancies and metal interstitials. The integrated emission intensity increased with greater crystallinity, indicating a lower concentration of non-radiative defect sites and, by extension, fewer defect traps available to assist in photocatalytic processes. Methylene blue photodegradation followed pseudo-first-order kinetics, with the apparent rate constant decreasing from 0.035&#xa0;min<sup>−1</sup> at 800 ℃ to 0.009&#xa0;min<sup>−1</sup> at 1200 ℃. Compared to higher calcination temperatures, the 800 ℃ sample shows greater photocatalytic efficiency, achieving nearly complete MB degradation within 75&#xa0;min, likely due to its defect-rich structure and enhanced surface availability. DFT calculations predicted a direct band gap widening from 3.858 to 4.090&#xa0;eV as temperature increased, consistent with the observed lattice contraction and PL transitions, which highlighted the critical role of defects in the material’s photo-oxidative reactivity. In summary, thermal treatment serves as a reliable approach to modulate the structural features, defect population and photocatalytic performance of ZnAl<sub>2</sub>O<sub>4</sub> nanoparticles.</p>

错误：搜索内容不能为空，请输入英文关键词
错误：关键词超出字数限制，请精简
高级检索

A Combined Experimental and Density Functional Theory Study of Calcination Temperature Effects on the Properties and Photocatalytic Activity of Starch-Mediated Spinel ZnAl2O4

  • 期刊论文

  • 发表日期：

    2025年8月27日

查看全文
  • Ines Dhifallah,
  • Sonia Ben Slama,
  • Afrah Bardaoui,
  • Radhouane Chtourou

摘要

Starch-mediated ZnAl2O4 spinel nanoparticles were synthesized using a simple auto-combustion sol-gel route and calcined at 800, 1000 and 1200 ℃. The influence of calcination temperature on the structural, vibrational, morphological, optical and photocatalytic characteristics of the materials was investigated using a combination of experimental techniques and density functional theory (DFT) calculations. Rietveld refinement confirms the presence of the cubic spinel phase ZnAl2O4 and secondary hexagonal ZnO phase and reveals a gradual lattice contraction with increasing calcination temperature, in excellent agreement with DFT predictions. Analysis of the Photoluminescence (PL) spectra revealed the presence of five characteristic bands attributed to intrinsic defects (405–523 nm): F+ and F0 oxygen vacancies and metal interstitials. The integrated emission intensity increased with greater crystallinity, indicating a lower concentration of non-radiative defect sites and, by extension, fewer defect traps available to assist in photocatalytic processes. Methylene blue photodegradation followed pseudo-first-order kinetics, with the apparent rate constant decreasing from 0.035 min−1 at 800 ℃ to 0.009 min−1 at 1200 ℃. Compared to higher calcination temperatures, the 800 ℃ sample shows greater photocatalytic efficiency, achieving nearly complete MB degradation within 75 min, likely due to its defect-rich structure and enhanced surface availability. DFT calculations predicted a direct band gap widening from 3.858 to 4.090 eV as temperature increased, consistent with the observed lattice contraction and PL transitions, which highlighted the critical role of defects in the material’s photo-oxidative reactivity. In summary, thermal treatment serves as a reliable approach to modulate the structural features, defect population and photocatalytic performance of ZnAl2O4 nanoparticles.