Carbon quantum dots (CDs) have gained significant importance as optical sensors/ probes owing to their selective, excitation wavelength (λex) dependent fluorescence (FL) properties. Hence, shedding light on origin of FL has become a great deal of interest.    It is generally conceived that the fluorescence of CDs originate from the n-π* transitions of the surface defect states, involving the surface functional groups like -OH, −COOH, and −NH<sub>2</sub> which makes them highly water soluble. Recent studies on citric acid based carbon dots, have attributed the origin of fluorescence to molecular fluorophores having the chemical structure of citrazinic acid. However, there is a further need for investigation into the existence and probable chemical structure of molecular fluorophores in CDs which are derived from organic precursors. apart from citric acid  Herein, we have reported a facile one-step microwave-assisted pyrolysis method for the synthesis of fluorescent water-soluble nitrogen-doped blue emissive  carbon dots (N-mCDs) using simple, inexpensive organic precursors (malic acid and urea in an optimum mole ratio of 1:3), with a reasonably high quantum yield (QY) of 37%. We have investigated the origin of intense blue emission of our as synthesized N-mCDs. On co-relating the inferences drawn from various experimental techniques including High resolution mass spectrometry (HRMS), 1H NMR, 13C NMR, XPS along with theoretical calculations, corroborated the origin of blue fluorescence due to the formation of putative pyridinic type molecular fluorophore and supramolecular network, which enhanced charge transfer within entangled polyamide chains. We have also proposed a probable mechanism leading to the structure of pyridine based moiety. We believe that our findings will lead to further investigation into the fundamental mechanism responsible for various optical properties of carbon dots like fluorescence quenching and broaden their application in the sensing of environmentally hazardous materials.

Origin of blue emission in N-doped carbon dots

Fall 2022 abstracts, posters, and presentations will launch in mid-September.

ACS Fall 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.