Electrochemical Synthesis of Carbon dots from Industrial Orange Peel Waste for Catalytic and Photochemical Applications

In this work, an efficient and easily repeatable electrochemical approach for the preparation of high quality carbon dots is presented. The electrochemical synthesis of carbon dots (CDs) from industrial orange peels waste (OPW) was performed using a simple electrolysis at room temperature on an aqueous liquid (L-HC) obtained from hydrothermal carbonization process. [1] The popularity of electricity as a reagent is enhanced by the efficient conversion of wet agro-industrial biomass through a circular chemistry application. [2] The integration of hydrothermal carbonization (HTC) and electrochemical (EC) synthesis allowing a winning approach to obtain high-quality CDs with high yields (∼%) from organic precursors. The so-called “bottom-up” procedure, used in this work, allow preparation of nano carbon structures with less defects and more homogeneous chemical compositions. Although different techniques are used to prepare the C-points, their photoluminescence (PL) emission profiles, their quantum yields (QY) and difficulties to be reproduced remain important topics. EC methods offer advantages of mild reaction conditions, high yields, and purity, simple instrumentation, and cost containment for mass production. [3]The choice to synthesize the CDs by the bottom-up EC methods is linked to the choice to use green precursors which originate from biological materials, the OPW, to make sure the as-prepared CDs are non-toxic and biocompatible. The carbon nanoparticles have been characterized by SEM, the functional groups on the surface has been determined by FT-IR analysis and optical properties and quantum yield have been evaluated by UV-Visible and PL measurements. They exhibit a blue emission (λem = 420-440 nm, λexc = 340 nm) and a very good QY that are promising for photochemical applications. The obtained carbon dots were used as an effective and recyclable carbo catalyst for the generation of carbon−carbon bond leading to Knoevenagel adducts under very mild reaction conditions. The results establish this nanoscale form of carbon as an alternative carbo catalyst for important catalyzed organic transformations.