Converting Waste Papers to Fluorescent Carbon Dots in the Recycling Process without Loss of Ionic Liquids and Bioimaging Applications

Recycling is a fascinating topic in academia due to the environmental and economic benefits in industries. In this paper, we report on the method to recycle cellulose waste papers using a green (eco-friendly) approach based on ionic liquids (ILs) where the regenerated cellulose was converted to carbon dots (CDs). The addition of waste papers to the IL, 1-allyl-3-methylimidazolium chloride ([Amim][Cl]), disrupted the chemical arrangement of cellulose and completely dissolved the waste paper under microwave irradiation. Subsequent cellulose regeneration by an additional antisolvent, absolute ethanol, was carried out to recover IL and obtain cellulosic materials' units from waste papers. Furthermore, we report a practical strategy to fabricate CDs under microwave-assisted irradiation. The CDs made by the regenerated cellulose (RC-CDs) were characterized by using analytical and spectroscopic techniques, such as transmission electron microscopy (TEM) and X-ray diffraction (XRD). Finally, we confirmed that RC-CDs exhibited low cytotoxicity, which suggests RC-CDs acts as a promising fluorescent probe for bioimaging.