Managing photoinduced electronic interactions on a molybdenum disulfide/diblock copolymer/anionic porphyrin nanoensemble

Abstract

Exploring the modular nature of MoS2 and its ability to be easily functionalized, both in covalent and non-covalent ways and with a variety of chemical species, a MoS2/diblock copolymer system was conceptualized. As the constituents of this diblock copolymer, the poly(benzyl methacrylate), abbreviated as pBzMA, block was designed to serve as the immobilization point of the polymeric chains onto the MoS2 lattice, taking advantage of the S-π non-covalent interactions between phenyl rings and ample S atoms, while the quaternized poly(dimethylamino-ethyl methacrylate), abbreviated as QpDMAEMA, was incorporated as the second block to capture the tetrasulfo-tetraphenyl anionic porphyrin, abbreviated as TPPS4 via electrostatic interactions with the ammonium groups of the quaternized polymeric chain. The so-formed MoS2/QpDMAEMA-b-pBzMA/TPPS4 ensemble was characterized and assessed via spectroscopic (UV-Vis), electron microscopy imaging (TEM) and dynamic light scattering (DLS) techniques. Markedly, efficient quenching of the characteristic fluorescence of the porphyrin species by the MoS2 nanosheets was observed, suggesting the development of photoinduced charge-transfer phenomena within the MoS2/QpDMAEMA-b-pBzMA/TPPS4 ensemble. This was further corroborated by time-correlated single photon counting (TCSPC) and blank experiments, signifying the role of Coulombic interactions for bringing into electronic communication the porphyrin moieties with MoS2. Overall, this rationally designed nanoensemble based on non-covalently modified MoS2 with polymers and photoactive species sets the foundations for inexpensive yet potent systems to be used in energy-related applications.