InP/ZnS quantum dots as efficient visible-light photocatalysts for redox and carbon–carbon coupling reactions

Abstract

Energy research is enormously inspired by one of the most fascinating and elegant phenomena known to mankind, called photosynthesis. (1,2) The efficient harvesting of visible light and movement of electrons through a number of molecules and redox active metal centers (leading to new chemical bonds) is the heart of photosynthesis. (3,4) Understanding and mimicking of such processes in artificial systems is the central idea of solar to chemical energy conversion research, especially photocatalysis. (5−13) A diverse pool of catalytic supplies ranging from organic to inorganic to polymeric materials has been explored for harvesting photons and driving various chemical reactions. (5−13) Among them, semiconductor nanoparticles or quantum dots (QDs) have emerged strongly due to their high absorption extinction coefficient (∼106 M–1 cm–1) and electron–hole mobility, size- and shape-tunable band gap, photostability, and flexible surface chemistry. (14−25) A thorough review of the literature reveals that the common practice in the area of QD photocatalysis is to use them in combination with other catalytic materials (like metal ions/complexes, semiconductors, 2D materials, etc.). (26−29) Strikingly, recent reports have shown the sole use of QDs as photocatalyst for various reactions, including C–C bond formation, without the aid of any cocatalysts or sacrificial reagents. (30−35) To hold this promise on a longer perspective, these exciting results with toxic metal-ion-based QDs should be tested and demonstrated with more environmentally friendly QDs. Even though extensive studies were performed on the fundamental properties of environmentally friendly QDs (synthesis, surface engineering, imaging and biotargeting, energy/charge transfer processes, etc.), (36−43) the photocatalytic aspects of them are still at its infancy. (27,35,44,45) For instance, recent reports have used CuAlS2/ZnS QD for carbon dioxide reduction (35) and InP/ZnS QD (as a sensitizer of nickel complex) for photocatalytic production of hydrogen. (27) To this end, a successful demonstration of environmentally friendly QDs photocatalyzing different classes of chemical reactions will strengthen their claim of potential “greener” alternatives for toxic metal-ion-based QDs. In this regard, we explored the potency of InP/ZnS QD as a visible-light photocatalyst for mimicking the two key classes of reactions in photosynthesis, namely metal-centered redox and carbon–carbon bond forming reactions