▎ 摘　　要

NOVELTY - Graphene quantum dot/zinc oxide/chlorella composite film comprises 15-21% zinc oxide nano crystal grains, 60-69% carbonized chlorella, 4-10% graphene quantum dots and 2-10% platinum nanoparticles. USE - The composite film is used as a sensitive layer on a gas sensor, preferably methanol gas sensor (all claimed). ADVANTAGE - The film has high sensitivity and low detection limit with a sensitivity of 3.3 for methanol with a concentration of 50 ppb, and excellent selectivity for methanol. DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for preparing the composite film, comprising (a) roasting the chlorella under the protection of inert gas to obtain the carbonized chlorella, (b) using chloroplatinic acid to prepare platinum nanoparticles, and preparing platinum nanoparticles low-carbon alcohol solution, (c) adding the zinc precursor and graphene quantum dot into low-carbon alcohol, stirring uniformly, carrying out ultrasonic dispersion, adding platinum nano particles, and ultrasonically dispersing to obtain mixed solution, (d) rotating and evaporating the mixed solution, concentrating to 1 divide by 4 to 1 divide by 2 of the original volume, adding the carbonized chlorella and stirring uniformly to obtain the mixed solution, (e) spin coating the mixed solution on the device substrate with inter digital electrode, heating and drying, orderly performing post-heat treatment and oxygen plasma treatment to obtain dry sample, and (f) adding the dry sample under the inert gas heat treatment.