Bottom-up microwave transformation of molecules to carbon dots for detection and encryption applications

The development of low-cost, stable, and effective fluorescent materials for detecting carcinogenic water contaminants and antibiotic drugs is a significant step toward protecting the environment and public health. In this work, we have prepared CDs using simple precursors, tartaric acid and di-aminopropane, via a facile, fast, one-step microwave-assisted method in 4 minutes. The as-prepared CDs were thoroughly investigated using sophisticated analytical techniques, including UV-Vis, PL lifetime, HR-TEM, and XRD. The exciting fluorescent excitation-dependent and independent character was revealed by photoluminescence, XPS, and FT-IR measurements, and it was found that CDs were made with a uniform core and an electron-rich surface functional group. Also, the prepared CDs exhibit greater stability in various environmental conditions. Furthermore, the core fluorescent character of CDs was effectively employed to detect Cr⁶⁺ and doxycycline, with lower detection limits of 0.14 and 0.09 µM, among the various metal cation and antibiotic groups. Additionally, it retains its sensitivity in the presence of multiple co-existing metal cations and antibiotics individually. In addition to environmental protection, we have utilized CDs for the secure transport of information via fluorescent ink and anti-counterfeiting security features. This present work displays the multifunctional ability of CDs, that can serve as a potential sensor for toxic metal ions and antibiotics in water based environments and also an excellent information encryptor for secure information transportation.