▎ 摘　　要

Atmospheric pressure microwave plasma has the lead in synthesizing freestanding and scalable graphene within seconds without the need for high vacuum and temperature. However, the process is limited in utilizing chemical sources for synthesis, such as methane and ethanol. Herein, the usage of an extract of a sustainable precursor, that is, Melaleuca alternifolia, commonly known as tea tree, is for the first time reported to synthesize graphene nanosheets in atmospheric pressure microwave plasma. The synthesis is carried out in a single step at a remarkably low microwave power of 200 W. The morphology, structure, and electrochemical properties of graphene are studied using state-of-the-art characterization techniques such as Raman spectroscopy, X-ray diffraction, transmission electron microscopy (TEM) and electrochemical impedance spectroscopy. The TEM images reveal the presence of a combination of nanostructures such as nano-horns, nano-rods, or nano-onions consisting of multi-layer graphitic architectures. An excellent sensing capability of as-synthesized graphene is demonstrated through the detection of diuron herbicide. A commendable linear range of 20 mu m to 1 mm and a limit of detection of 5 mu m of diuron is recorded.