Near-infrared light triggered superior photocatalytic activity from MoS2-NaYF4:Yb3+/Er3+ nanocomposites

A near infrared (NIR) responsive photocatalyst, composed of a narrow band gap semiconductor (i.e. MoS2) and an optical material possessing upconverting ability (i.e. NaYF4:Yb3+/Er3+) has been successfully prepared via a simple hydrothermal method. The latter has the ability to convert NIR light into visible light while the MoS2 uses the light to degrade organic pollutants. Upon near infrared (NIR) excitation of the MoS2-NaYF4:Yb3+/Er3+ nanocomposites, the energy of the strong green and the red emissions along with the weak violet emissions from the NaYF4: Yb3+/Er3+ nanocrystals (NCs) is transferred to MoS2. This results in enhanced NIR light triggered photocatalytic performance, as verified by studying the degradation of Rhodamine B (RhB) dye under 980 nm laser excitation. The strong photocatalytic activity of MoS2-NaYF4: Yb3+/Er3+ composites is attributed to the layered nature of the photocatalyst which leads to the efficient separation of photogenerated carriers (electron-hole pairs) and excellent upconversion properties of NaYF4: Yb3+/Er3+ NCs. The study also shows the importance of the composite formation, as the physical mixture leads to only very low photocatalytic activity. Our results can be helpful in the structural design and development of high-performance photocatalysts.