Synthesis of ZnO Hierarchical Structures and Their Gas Sensing Properties

Abstract

Firecracker-like ZnO hierarchical structures (ZnO HS1) were synthesized by combining electrospinning with hydrothermal methods. Flower-like ZnO hierarchical structures (ZnO HS2) were prepared by a hydrothermal method using ultrasound-treated ZnO nanofibers (ZnO NFs) as raw material which has rarely been reported in previous papers. Scanning electron microscope (SEM) and transmission electron microscope’s (TEM) images clearly indicated the existence of nanoparticles on the ZnO HS2 material. Both gas sensors exhibited high selectivity toward H2S gas over various other gases at 180 °C. The ZnO HS2 gas sensor exhibited higher H2S sensitivity response (50 ppm H2S, 42.298) at 180 °C than ZnO NFs (50 ppm H2S, 9.223) and ZnO HS1 (50 ppm H2S, 17.506) gas sensors. Besides, the ZnO HS2 sensor showed a shorter response time (14 s) compared with the ZnO NFs (25 s) and ZnO HS1 (19 s) gas sensors. The formation diagram of ZnO hierarchical structures and the gas sensing mechanism were evaluated. Apart from the synergistic effect of nanoparticles and nanoflowers, more point–point contacts between flower-like ZnO nanorods were advantageous for the excellent H2S sensing properties of ZnO HS2 material.

Effect of the Precursor on the Synthesis of ZnO and Its Photocatalytic Activity

“…The diffractograms (Figure 4) of the ZnO N and ZnO A powder show the wurtzite hexagonal phase of ZnO, corresponding to diffraction signals at 2θ = 31.52 , with a respective Miller index of (100), ( 002), ( 101), ( 102), ( 110), ( 103), ( 200), ( 112), ( 201), (004), and (202) planes (JCPDS No. 89-1397), in agreement with previous works [14,47,48]. On the other hand, the ZnO N showed reflection signals around 22.13 • , 29.04 • , and 44.6 • (2θ), which are representative of Zn(OH) 2 [49][50][51].…”

Fast and recoverable NO2 detection achieved by assembling ZnO on Ti3C2Tx MXene nanosheets under UV illumination at room temperature

“…The binding energies of 281.2 eV, 282.2 eV, 284.8 eV and 284.9 eV were attributed to C–Ti, C–C, C–O and CO, respectively. 35 Meanwhile, the intensity and spacing of peaks corresponding to F 1s decreased in the Ti 3 C 2 T x –ZnO NS compared with the pure Ti 3 C 2 T x sheet (Fig. 6a, d and Fig.…”

“…ZnO, a typical n-type metal–oxide–semiconductor material, with a wide bandgap of 3.37 eV, excellent chemical stability and rich oxygen vacancies has emerged as a promising gas-sensitive material. 35–38 In particular, ZnO or ZnO composite materials have been widely applied as NO 2 sensors at room temperature in recent years. 39 This is because of the abundant defects and the feasibility of shape control of ZnO.…”

An 8 MeV Electron Beam Modified In:ZnO Thin Films for CO Gas Sensing towards Low Concentration

“…Anions of oxygen such as O 2 − , O − and O 2− are formed during the process of extraction of electron from the conduction band by the adsorbed oxygen, leaving a layer depleted of electrons with high resistance. The formation of oxygen anions are as followed by the reactions [41]:…”