Pristine and Pt-doped CuO nano-flowers were synthesized by a simple water bath heating method in this paper. Highly sensitive hydrogen sulfide (H₂S) gas sensors based on Pt-doped CuO nano-flowers were fabricated. Scanning electron microscopy, X-ray diffraction, inductively coupled plasma atomic emission spectrometry, and energy dispersive X-ray spectroscopy were used to examine the characteristics and morphology of materials. The sensing performances of sensors with different concentrations of Pt dopants were evaluated at different operating temperatures. The results indicated that the CuO sensor doped with 1.25 wt % Pt exhibited the highest response (R_g/R_a, where R_g is the resistance in gas, and R_a is the resistance in air) of 135.1 to 10 ppm H₂S at 40 ${}^{\circ }$C, which was 13.1 times higher than the response of a pure CuO sensor. Pt doping also plays an important role for the enhancement of H₂S selectivity against C₂H₅OH, NH₃, H₂, CH₃COCH₃, and NO₂.

WO₃ nanostructure with nanocube morphology was synthesized through acidification of Na₂WO₄·2H₂O, which were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Moreover, the result of the present work implied that the sensor fabricated by nanocube WO₃ could detect the level of 330 ppb H₂S, which is much lower than the threshold limit value of 10 ppm. Compared with other results, the nanocube WO₃ sensor shows higher sensitivity, excellent selectivity and faster response/recovery to H₂S. Especially, the best operating temperature of this nanocube WO₃ for H₂S detection is 100 °C.