Structural defect-induced white light emission from synthetic Zn-rich trioctahedral smectite: Fid-Bau Portal

Structural defect-induced white light emission from synthetic Zn-rich trioctahedral smectite

Soren, Dhani / Mehena, Gayatree / Das, Jiban K. / Behera, J.N. / Pattojoshi, Puspalata / Deheri, Pratap Kumar

Abstract In this research work, Al^III substituted by Mg^II and Zn^II atoms in smectites (Sm) of the formula [Na0.7Mg2.5-xZnxLi0.3Si4O10(OH)2] were synthesized. Its structural and intrinsically highly photoluminescent (PL) properties were reported. The complex distributions of Mg^II and Zn^II atoms were observed in both octahedral and tetrahedral sites in the synthesized Sm (as evident with XRD, XPS, and ESR studies). The visible white light emission was observed when excited with UV light (250 nm). The observed strong photoluminescence (PL) was attributed to the electronic transition from oxygen vacancy to acceptor atoms induced by isomorphous substitution in both tetrahedral and octahedral sites ( ${Mg}_{Al}^{'}, {Mg}_{Si}^{''}, {Zn}_{Al}^{'}, {Zn}_{Si}^{''})$ . With introduction of Zn^II atom, there was an increase in ${Mg}_{Al}^{'} and {Mg}_{Si}^{''}$ defects energy levels that resulted in bathochromic shifts in $V_{O}^{∙ ∙} \to {Mg}_{Al}^{''}$ , $V_{O}^{∙ ∙} \to {Mg}_{Si}^{''}$ and $V_{O}^{∙ ∙} \to V_{O}$ emission lines. Moreover, two additional emission lines in blue and red-light regions were observed due to two new ${Zn}_{Al}^{'}, {Zn}_{Si}^{''}$ defect centers that led to $V_{O}^{∙ ∙} \to {Zn}_{Al}^{'}$ and $V_{O}^{∙ ∙} \to {Zn}_{Si}^{''}$ electronic transitions.

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Highlights • Intrinsically luminescent, Zn^II substituted trioctahedral smectite (Sm) synthesis by simple hydrothermal method. • White colour emission in synthesized Sm with UV (λ = 250 nm) light irradiation. • Defect-induced electronic transition leads to broad emission in the visible region. • Bathochromic shift and red light emission with Zn^II substitutions.