Ascorbic Acid Carbon Dots: A Fluorescent Nanomaterial for Anti-Counterfeiting and Bioimaging Applications

Abstract

Semiconductor quantum dots (SQDs) are extensively used nanomaterial for sensing, electronics, drug delivery, and bioimaging. However, their poor aqueous solubility, lack of uniformity in synthesis, toxicity, and challenges in scalable fabrication frequently limit their applications. Carbon quantum dots (CDs) emerged as new safer alternatives to SQDs with comparable optical properties and diverse applications. Herein, fluorescent, biocompatible, and water-soluble, carbon dots were synthesized via cost-effective hydrothermal method using ascorbic acid (AA) as the sole precursor. The as-synthesized spherical 3–4 nm ascorbic acid-derived carbon dots (AA-CDs) exhibited maximum excitation at 340 nm, emission at 400 nm and displayed fluorescence quantum yield of ∼29.89% with average fluorescence lifetime decay of ∼1.12 ns. For technological domain, this study successfully formulated AA-CDs into anti-counterfeiting fluorescent ink that resembled conventional ink under visible light but exhibited bright blue fluorescence under UV excitation. Furthermore, AA-CDs displayed negligible toxicity toward both mycobacterial (e.g., Mycobacterium marinum) and mammalian (phorbol myristate acetate-treated human THP-1 macrophages) cells, supporting their safe applications in biomedicine. Rapid and efficient internalization of AA-CDs into M. marinum and THP-1 macrophage cells was evidenced by presence of bright blue fluorescence inside the cells, which highlighted their potential as nano-probe for real-time bioimaging and tracking cellular processes. Collectively, this study demonstrated AA-CDs as a proof-of-concept dual-function nanomaterial for applications across fluorescent ink-based security technology and nanomedicine.