Exploration of photocatalytic dye degradation and non-linear optical absorption of BiVO4-TiO2 nanocomposites

Abstract

In this study, a simple hydrothermal approach was utilized to synthesize BiVO4 nanoparticles (NPs), TiO2 NPs, and BiVO4–TiO2 nanocomposites for the applications in degrading Rhodamine—B dye molecules and exploring optical limiting properties through the nonlinear optical studies. X-ray diffraction studies reveal that the synthesized samples displayed a monoclinic crystal structure of BiVO4 NPs and a combination of tetragonal rutile and anatase structures of TiO2 NPs. The successful formation of BiVO4–TiO2 nanocomposites was confirmed by a modification in the band gap which is tuned from 3.15 to 2.87 eV. The efficiency of the samples in degrading Rhodamine–B dye molecules under direct sunlight was examined, revealing that the 1:3 BiVO4–TiO2 (1:3–BT) nanocomposites showed a remarkable photodegradation efficiency of 97.1% at 60 min for a 2 g catalyst dosage and maintained good photostability throughout five cycles. Analysis of scavenger species evidenced the significant contribution of the hydroxyl radicals in the degradation process. Under Nd: YAG laser excitation, the open aperture Z-scan technique demonstrated that BiVO4–TiO2 nanocomposites exhibit reverse saturable absorption as a result of the two-photon absorption process. Here, 1:3–BT nanocomposite possesses a high two-photon absorption coefficient (β) of 1.22 × 10–10 m/W and a low optical limiting threshold of 2.49 × 1012 W/m2 suggesting the potential application as optical limiters towards the prevention of laser damages.