▎ 摘　　要

Recently, functionalized graphene has been used in a variety of biomedical applications such as drug delivery systems, nanocarriers, tissue scaffolds, biodetection, biosensors, and bioimaging. Most of the chemicals used to prepare functionalized graphene are generally costly and harmful, requiring the development of a one-step, ecofriendly production process that does not use toxic chemicals. In this study, a simple environmentally friendly exfoliation of graphite to functionalized few-layer graphene (FFG) using gallnut extract has been demonstrated for the first time. Gallnut was screened from 21 plant materials based on FFG yield, high polyphenol content, radical scavenging activity, and tannin presence. The polyphenols and flavonoids present in gallnut extract are solely responsible for the exfoliation, stabilization, and functionalization of graphene. Raman and atomic force microscopy analysis showed that FFG is within the range of 1-7 layers. The highest yield of FFG from graphite was 15.3%, which was higher than those produced using tannic and gallic acid solutions (0-9.5%). FFG was used in the preparation of Au-FFG, FFG/polyvinyl alcohol (FFG/PVA) aerogels, and FFG/PVA films. Au-FFG showed peroxidase mimicking activity and possessed higher substrate affinity than those of natural enzymes and some reported nanomaterials. FFG/PVA aerogel was able to remove up to 98% of both cationic and anionic dyes. FFG/ PVA nanocomposite films displayed increase in tensile strength by 33.8%, elongation at break by 79.6%, and higher UV-visible protection properties compared to those of control PVA film. This study provides a framework to develop a low-cost, eco-friendly, and highly efficient natural pyrogallol-catechol FFG for a variety of applications such as biosensor, dye adsorbents, and nanofillers to improve polymer composite properties.