Ultra-high sensitive ammonia chemical sensor based on ZnO nanopencils

► Well-crystalline ZnO nanopencils were synthesized by very simple and facile hydrothermal process using simply available laboratory chemicals. ► Using ZnO nanopencils, a liquid ammonia chemical sensor is fabricated based on convenient and simple current-voltage (I-V) principle. ► The fabricated liquid ammonia chemical sensor exhibits the highest sensitivity ever reported in the literature. ► The obtained detection limit of the fabricated sensor is lower than the previously reported literature values.