Microwave enhanced carbon dots synthesis from eggshell membrane: Versatile applications in heavy metal ion sensing, strain free detection of fingerprints, UV shielding, food packing and anti-counterfeiting

In this study, a one-step microwave irradiation process combined with a sodium hydroxide (NaOH) solution allowed for the quick and easy synthesis of carbon dots (CDs) from eggshell membrane (ESM) ashes. The resultant CDs demonstrated exceptional selectivity for Fe³⁺ and excellent fluorescence (FL) with a quantum yield (QY) of 15.3 %. Utilizing synthetic CDs, a sensitive nanoprobe is utilized to identify free Fe³⁺ within the 0–350 μM (R² = 0.9976) range, with a 0.281 μM limit of detection (LoD). Additionally, the CDs were shown to be useful for intracellular Fe³⁺ detection applications because of their low cytotoxicity and biocompatibility. Investigations using real samples at 475 nm excitation wavelength showed promising results in terms of real-world application. In order to transform molecular data into FL signal outputs, a multi-input logic gate is also constructed. In the UV-A (93 %), UV-B (88 %), UV-C (98 %) and high energy blue light (HEBL) (79 %) regions, blue colour-emitting CDs had the maximum UV blockage, but pure polyvinyl alcohol (PVA) absorbed less than 22–30 % of the light in all UV regions. The integration of CDs into the polymer improved the thermal characteristics of the PVA film. Additionally, testing of in vitro cell viability demonstrated that the CDs, when embedded in the PVA, did not cause cytotoxicity to the Neuroblastoma cell line (SH-SY-5Y). As a paradigm for perishable commodities, the effects of CDs and PVA were assessed on the shelf life of tomatoes. When fresh tomatoes were coated with CDs@PVA and PVA, weight and moisture loss were effectively decreased, according to the results of the long-term monitoring study. Throughout almost 36 days at room temperature, it also dramatically reduced the growth of fungi and prevented spoiling, all the while maintaining the fruits original colour and appearance. The CDs FL under 365 nm UV light excitation makes them well-suited for creating fluorescent inks to deter counterfeiting. Additionally, the study explored the CDs exceptional FL properties for use as a luminescent fingerprint powder, aiding in the detection of latent fingerprints (LFPs) on various surfaces. The findings from this study highlight the potential of cost-effective and safe CDs for a range of applications, including non-cytotoxic UV blocking, active packaging, Fe³⁺ sensing, fingerprint detection, anti-counterfeiting (AC) measures and flexible nanocomposite (NC) films.