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<p><i>α</i>-NiMoO<sub>4</sub> sample was prepared using the hydrothermal method. The measured high-precision synchrotron X-ray diffraction pattern manifested a single phase <i>α</i>-NiMoO<sub>4</sub> with a monoclinic structure, space group C2/m. The sample was further characterized by applying FTIR and Raman spectroscopy techniques. Detailed structure and microstructure analysis, utilizing Rietveld refinement method, indicated that the Mo octahedra exhibit greater distortion compared to Ni octahedra. Meanwhile, Ni<sub>1</sub> and Mo<sub>1</sub> octahedra display more distortion than their counterparts Ni<sub>2</sub> and Mo<sub>2</sub>, with Ni<sub>2</sub>-octahedra exhibit the least distortion. Diffuse reflectance measurements manifested three prominent absorption bands and a shoulder one within the ultraviolet, visible, and near-infrared regions, assigned to a ligand-to-metal charge transfer (LMCT) and the spin-allowed <i>d</i>-<i>d</i> transitions occurring within the Ni-octahedra ions. Racah parameter (the parameter representing electron–electron repulsion) has been determined, <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10854_2025_14428_Article_IEq1.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="200" /> </InlineMediaObject> <EquationSource Format="TEX">\(B=969 {\text{ cm}}^{-1}=0.12014 \text{ eV}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>B</mi> <mo>=</mo> <mn>969</mn> <msup> <mrow> <mspace width="0.333333em" /> <mtext>cm</mtext> </mrow> <mrow> <mo>-</mo> <mn>1</mn> </mrow> </msup> <mo>=</mo> <mn>0.12014</mn> <mspace width="0.333333em" /> <mtext>eV</mtext> </mrow> </math></EquationSource> </InlineEquation>, through two distinct procedures: applying a numeric equation and utilizing Tanabe-Sugano diagram. Also, the crystal-field splitting parameter (E(e<sub>g</sub>)–E(t<sub>2g</sub>)) is determined: <InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10854_2025_14428_Article_IEq2.gif" Format="GIF" Height="21" Rendition="HTML" Resolution="72" Type="Linedraw" Width="235" /> </InlineMediaObject> <EquationSource Format="TEX">\(10{D}_{q}=7945.8 {\text{ cm}}^{-1}=0.9851\text{ eV}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mn>10</mn> <msub> <mi>D</mi> <mi>q</mi> </msub> <mo>=</mo> <mn>7945.8</mn> <msup> <mrow> <mspace width="0.333333em" /> <mtext>cm</mtext> </mrow> <mrow> <mo>-</mo> <mn>1</mn> </mrow> </msup> <mo>=</mo> <mn>0.9851</mn> <mspace width="0.333333em" /> <mtext>eV</mtext> </mrow> </math></EquationSource> </InlineEquation>. The calculated value of the direct band-gap energy for <i>α</i>-NiMoO<sub>4</sub> is 2.555 eV. The conduction band (E<sub>CB</sub>) and valence band (E<sub>VB</sub>) potentials of the present <i>α</i>-NiMoO<sub>4</sub> are quantified at 0.375 eV and 2.928 eV in relation to the normal hydrogen electrode (NHE). A schematic representation of the primary electronic levels within the <i>α</i>-NiMoO<sub>4</sub> material is presented. The CIE chromaticity diagram for <i>α</i>-NiMoO<sub>4</sub> sample possesses (<i>x</i> = 0.1159, <i>y</i> = 0.3572) coordinates which represent a cyan-green color.</p>

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Investigating the electronic structure and UV–Vis–NIR optical properties of α-NiMoO4 nanoparticles

  • 期刊论文

  • 发表日期：

    2025年2月15日

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  • Zein K. Heiba,
  • M. Abdellatief,
  • Mohamed Bakr Mohamed,
  • Ali Badawi

摘要

α-NiMoO4 sample was prepared using the hydrothermal method. The measured high-precision synchrotron X-ray diffraction pattern manifested a single phase α-NiMoO4 with a monoclinic structure, space group C2/m. The sample was further characterized by applying FTIR and Raman spectroscopy techniques. Detailed structure and microstructure analysis, utilizing Rietveld refinement method, indicated that the Mo octahedra exhibit greater distortion compared to Ni octahedra. Meanwhile, Ni1 and Mo1 octahedra display more distortion than their counterparts Ni2 and Mo2, with Ni2-octahedra exhibit the least distortion. Diffuse reflectance measurements manifested three prominent absorption bands and a shoulder one within the ultraviolet, visible, and near-infrared regions, assigned to a ligand-to-metal charge transfer (LMCT) and the spin-allowed d-d transitions occurring within the Ni-octahedra ions. Racah parameter (the parameter representing electron–electron repulsion) has been determined, \(B=969 {\text{ cm}}^{-1}=0.12014 \text{ eV}\) B = 969 cm - 1 = 0.12014 eV , through two distinct procedures: applying a numeric equation and utilizing Tanabe-Sugano diagram. Also, the crystal-field splitting parameter (E(eg)–E(t2g)) is determined: \(10{D}_{q}=7945.8 {\text{ cm}}^{-1}=0.9851\text{ eV}\) 10 D q = 7945.8 cm - 1 = 0.9851 eV . The calculated value of the direct band-gap energy for α-NiMoO4 is 2.555 eV. The conduction band (ECB) and valence band (EVB) potentials of the present α-NiMoO4 are quantified at 0.375 eV and 2.928 eV in relation to the normal hydrogen electrode (NHE). A schematic representation of the primary electronic levels within the α-NiMoO4 material is presented. The CIE chromaticity diagram for α-NiMoO4 sample possesses (x = 0.1159, y = 0.3572) coordinates which represent a cyan-green color.