Fabrication of rare earth (Tb+3) and alkaline earth metal (Mg+2) Co-doped CdAl2O4@MXene composite: A unique approach to tune bandgap energy through quantum confinement effect for photocatalytic applications.

The present work includes the use of effective strategy to improve the photocatalytic degradation activity of CdAl 2 O 4 via dopant assimilation to enhance the bandgap energy (E g) and to influence the light-sensitive activity of this spinel mixed oxide. In this study, CdAl 2 O 4 (CA), Mg–CdAl 2 O 4 (MCA), and Tb-doped Mg–CdAl 2 O 4 (TMCA) were fabricated by the facile co-precipitation route and an ultra-sonication approach was used to prepare a composite of Tb-doped Mg–CdAl 2 O 4 with MXene (TMCA@MXene). The obtained results from UV–Visible analysis deduce that there is an increase in E g of MCA (2.51 eV) and TMCA (2.67 eV) as compared to pure CA (2.45 eV) which follows the quantum confinement effect accompanying the decrease in crystallite sizes of doped samples as compared to CA. The significant increase in bandgap energy of TMCA is due to the confinement of electrons in a small area and also due to the conversion of continuous energy levels into discrete energy levels. Moreover, UV–Visible spectroscopic analysis was made to evaluate the catalytic performance of fabricated photocatalysts against harmful organic pollutants. The photocatalytic study showed that the co-doped CdAl 2 O 4 (TMCA) is a better photocatalyst than MCA and CA for the degradation of selected pollutants. Among all synthesized catalysts i.e. CA, MCA, TMCA, and TMCA@MXene, the highest photocatalytic activity was shown by MXene based nanocomposite. TMCA@MXene showed ∼86 % degradation of Rhodamine B (RhB) and 79.6 % degradation of Aspirin (acetylsalicylic acid). The outstanding photocatalytic efficacy of TMCA@MXene could be accredited to the quantum confinement effect produced by co-doping of alkaline earth metal (Mg+2) and rare earth metal (Tb+3) and large surface area, high conductivity, and excellent light harvesting capability provided by MXene sheets. Hence, TMCA@MXene could be an effective photocatalyst in future for the removal of toxic organic pollutants. [ABSTRACT FROM AUTHOR]