In this work, we have synthesized MoS$_2$ nanosheets (NSs) through hydrothermal as well as liquid-phase sonication methods and studied their ability to degrade organic dyes, methyl red (MR) and methylene blue (MB) undervisible light irradiation. The as-synthesized photocatalysts have been characterized by powder X-ray diffraction, Raman Spectroscopy and transmission electron microscopy to confirm their structure and surface morphology. XRD patterns show that crystalline nature of MoS$_2$ NSs prepared by hydrothermal method appears at 160°C for 15 h. In contrast, sharp and intense diffraction peaks appear for liquid exfoliation method even at room temperature, exhibiting better crystallinity of the as-prepared NSs. The difference (${\Delta}$) of ${\sim}$25 cm$^{-1}$ between E$^1$$_{2g}$ and A$_{1g}$ modes of Raman spectra indicates formation of 5–6 layers of MoS$_2$ from both the synthesis routes. UV–V is spectroscopy has been utilized to study the degradation of dyes by MoS$_2$ NSs as catalyst. Hydrothermally assisted synthesis of MoS$_2$ NSs exhibit lesser degradation efficiency with 58.92% for MR and 49.28% for MB, while exfoliation-assisted MoS$_2$ NSs act as better photocatalyst with 63.40 and 62.40% degradation of MR and MB, respectively. Faster degradation rate for MR compared to MB has been attributed to the presence of lesser chromophoric sites in MR.

In this study, we have synthesized MoS$_2$ nanostructures (NSs) through a simple and facile hydrothermal method and studied various factors affecting the degradation of organic azo dye methyl red (MR) under the illumination of visible light. The as-synthesized photo-catalyst has been characterized by powder X-ray diffraction, Raman spectroscopy and transmission electron microscopy to confirm its structure and surface morphology. The results reveal that the prepared MoS$_2$ NSs have 2H crystal phase. The peak frequency difference of ${\sim}$25 cm$^{-1}$ exhibits preparation of 5–6 layers of MoS$_2$ NSs. Ultraviolet–visible spectroscopy has been utilized to study the change in percentage degradation of the dye with variation in dosages of photocatalyst, dye concentration and variation in pH of the dye. MoS$_2$ NSs show the best adsorption of 80.35% at low pH of 4.24 with 14 mg of catalyst dosage and 50 ppm of dye concentration in 6 h of irradiation time.