Low‐Quality Indian Coal Derived Fluorescent Carbon Nano‐Onions for Tissue Imaging

Abstract The synthesis of novel contrast agents based on carbon nanomaterials is garnering significant attention because of their unique properties, such as biocompatibility, ease of fabrication, colloidal stability, and low cost. This article describes a possible and sustainable approach for developing blue‐emitting fluorescent carbon nano‐onions from low‐quality Indian coal using simple mild acid oxidation. The high‐resolution transmission electron micrograph of prepared carbon nanomaterials reveals the crystalline graphitic and multilayer nano‐onion morphology, further supported by Raman and X‐ray diffraction study. Optical coherence tomography was used to capture the tissue image by employing carbon nano‐onions as a contrast agent. The surface defect caused by the carboxylic and hydroxyl functional groups of fluorescent carbon nano‐onions enhances the contrast by increasing the backscattering signal received from the deeper regions in the tissue sample. The transmission electron microscopic study and tunable emission property of carbon nano‐onions confirmed the different sizes of carbon nano‐onions, which also play a crucial role in backscattering. This inventive approach for producing large‐scale fluorescent carbon nano‐onions from low‐quality Indian coal opens up new possibilities for the economical and sustainable development of contrast agents for biomedical imaging.