We have developed a novel method for simple, rapid and selective synthesis of one dimensional nano materials as well as their selective surface functionalization, all in low-temperature and liquid-phase conditions, for highly integrated chemical sensor applications. In specific, localized heating by micro heater allows selective synthesis and in-situ integration of ZnO nanowires on sensing electrodes. High surface area and chemical reactivity of nanowires enable high sensitivity and fast response to hydrogen (H-2) molecules. Furthermore, subsequent localized heating process in metal precursor solution allows facile surface functionalization of ZnO nanowires with catalytic metal nanoparticles (Pt or Pd), which dramatically enhanced the gas sensing performances. This approach has demonstrated a practical method of developing integrated chemical sensors with heterogeneous nanostructures, potentially for multiplexed chemical detection purposes.