The Effect of Pyranine and MoS₂ Content on the Optical Properties of Polyacrylamide-MoS₂ Composite Gels

Abstract

The most favorable members of the class of two-dimensional (2D) materials, molybdenum sulfide (MoS2), graphene, and tungsten disulfide (WS2) have become a thriving research frontier for many applications, ranging from catalysis to optoelectronic devices, due to their superior electronic behavior and mechanical properties. Making a new, smart, hydrogel when incorporating MoS2 into basic hydrogels can change their optical, electronic, and mechanical properties. In this work, MoS2-doped polyacrylamide (PAAm) gels were prepared via the free radical crosslinking copolymerization technique at room temperature without pyranine which is often used for crosslinking PAAm. The optical properties of PAAm-MoS2 composite gels were investigated, and they were analyzed using ultraviolet (UV) and fluorescence spectroscopy. The absorbance was measured before and after diffusion of MoS2-doped PAAm, and after the release of pyranine in and out of the composite gel, respectively. The shift of the absorption edge toward shorter wavelengths was seen when the quantity of MoS2 in the PAAm composite gels was decreased. The constituents included in the polymer composites exhibited notable photon energy absorption within the visible and ultraviolet spectra. This absorption phenomenon induced electron transitions to states of elevated energy. Parameters, such as refractive index and extinction coefficient, were analyzed with respect to the content of MoS2. When the MoS2 amount was increased in the gels, the percentage of reflectance increased. The extinction coefficient increased at longer wavelength and it decreased in the UV range, the shorter wavelength region. The results suggested that MoS2-doped PAAm composite gels show promising optoelectronic properties for developing optoelectronic devices.