▎ 摘　　要

NOVELTY - A medical device comprises graphene varactor (100) comprising graphene layer (108a, 108b) and self-assembled monolayer formed on outer surface of graphene layer through pi - pi stacking interactions. The self-assembled monolayer provides Langmuir theta value of greater than or equal to 0.9. USE - The medical device is used for detecting analytes in gaseous sample, such as breath of patient, to identify disease states including cancer, cardiac diseases, infections, multiple sclerosis, Alzheimer's disease, and Parkinson's disease. ADVANTAGE - The graphene varactor exhibits high sensitivity for volatile organic compounds (VOCs) found in gaseous samples at or near ppm or parts-per-billion levels. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for: (1) modification of graphene surface to create graphene varactor, by forming self-assembled monolayer on outer surface of graphene layer through pi - pi stacking interactions; quantifying the extent of surface coverage of self-assembled monolayer using contact angle goniometry, Raman spectroscopy, or X-ray photoelectron spectroscopy; and selecting derivatized graphene layers that exhibit Langmuir theta value of greater than or equal to 0.9; and (2) detection of analyte by collecting gaseous sample from patient, and contacting the gaseous sample with graphene varactor(s). DESCRIPTION OF DRAWING(S) - The drawing shows schematic perspective view of graphene varactor. Graphene varactor (100) Insulator layer (102) Gate electrode (104) Gate electrode fingers (106a-106h) Graphene layers (108a, 108b) Contact electrode (110)