Synergistic Effect of Yb<sup>3+</sup>, Tm<sup>3+</sup>, Nd<sup>3+</sup> Doped NaYF<sub>4</sub> Nanoparticles and MoS<sub>2</sub> Nanosheets for Enhanced Photocatalytic Dye Degradation under Visible Light
Simranjit Singh, Vishakha Takhar, Shivanand H. Nannuri, Sajan D. George, Rupak Banerjee, Superb K. Misra
Abstract
The synergistic influence of synthesized MoS 2 ( syn -MoS 2 ) nanosheets and NaYF 4:Yb,Tm,Nd upconversion nanoparticles (UCNP) on effective dye degradation is demonstrated. A detailed characterization of bulk MoS 2 ( b -MoS 2 ), syn -MoS 2 (with enhanced photocatalytic activity compared to the commercially available b -MoS 2 ), and UCNP was done. Optical properties revealed that emission spectra of UCNP corresponding to 450, 475, and 650 nm overlap with absorption spectra of MoS 2 (∼455 and 635 nm). A comparative methylene blue degradation of 96% could be achieved with the combination of UCNP and syn -MoS 2 in comparison to 56.4% for syn -MoS 2 and 42% for b -MoS 2 . Concentration-dependent dye degradation study of UCNP and syn -MoS 2 revealed a maximum dye removal efficiency of 99.6% for 150 mg L –1 of syn -MoS 2 and 200 mg L –1 of UCNP within 2 hrs. Comparative degradation investigations were performed on various dyes (methylene blue, methylene orange, rhodamine B, and their mixture) and water systems (artificial river-water and artificial seawater) to assess the potential applicability of the system in environmental remediation. After five cycles of reusability studies, an efficacy of 88% dye removal was obtained. The mechanism behind this was investigated using the ESR and scavengers test, which confirmed that the primary radicals responsible for dye degradation were superoxide ( • O 2 – ) and hydroxyl ( • OH). A comparative photocurrent experiment also verified that the presence of UCNP enhances the efficiency of the syn -MoS 2 by 98% in the presence of visible light.