Dewdrop-templated clean growth of graphene micromeshes on SiO₂/Si substrates for highly sensitive NO₂ gas sensors

Graphene meshes (GMs) have attracted considerable attention as advanced materials for high-performance gas sensing due to their high-density active edge sites and excellent electronic properties. However, the contamination-free preparation of GMs remains a challenge. Herein, we present a dewdrop-templated chemical vapor deposition approach to directly grow clean and intact graphene micromeshes (GMM) on SiO₂/Si substrates. The self-assembled micrometer-sized dewdrops from controlled water vapor condensation serve as a residue-free template for directing the growth of GMM with tunable hole sizes from submicrons to tens of microns. Density functional theory (DFT) calculations reveal that carbon species preferentially adsorb on pristine SiO₂ regions to form a mesh structure. Contamination-free GMM gas sensors were fabricated using a simple transfer-free process, demonstrating a record-high sensitivity of 7.25 %·ppm⁻¹ and an ultra-low detection limit of 1.18 ppb for NO₂ at room temperature. Complementary DFT studies elucidate that NO₂ molecules adsorb more strongly on the edges of GMM, leading to a high response of the sensor. This work offers profound insights into dewdrop-templated graphene growth mechanisms and establishes a simple yet effective approach for fabricating high-performance transfer-free GMM sensors, thus paving the way for their practical applications in environmental monitoring and industrial safety fields.