A green and efficient conversion of redundant biomass into functional nanomaterials holds the key to sustainable future technologies. Recently, vertical graphene nanosheets (VGS) have emerged as promising nanomaterials for integration in high-performance biosensors and supercapacitors, owing to their excellent and unique structural, morphological and electrical properties. However, when considering the conventional techniques utilized in nanofabrication, such as thermal or chemical routes, these often involve complex, eco-destructive and resource-consuming processes. Here we report on a single-step, potentially scalable, environmentally-benign and plasma-enabled method to synthesize VGS from an underutilized and natural by-product precursor, honeycomb. The VGS multifunctionality is highlighted by its integration as supercapacitor electrodes for energy storage, and as an electrochemical biosensor for the detection of the neurotoxic Amyloid-beta (Aβ) biomarker of Alzheimer's disease. The VGS were employed as binder-free supercapacitor electrodes, and demonstrated high specific capacitance up to 240 F g−1 at a scan rate of 5 mV s−1 and 100% capacitance retention after 2000 charge/discharge cycles. Furthermore, the VGS were functionalized with curcumin bioreceptors, and exhibited good sensitivity and selectivity towards the detection of neurotoxic Aβ species, and demonstrated a detection limit of 0.1 μg mL−1.