Author Affiliations
1School of Material Science and Engineering, Tiangong University, Tianjin 300387, China2Physical Department, Tianjin University Renai College, Tianjin 301636, China3Department of Obstetrics Tianjin Hospital of ITCWM, Nankai Hospital, Tianjin 00100, Chinashow less
Fig. 1. SEM/TEM images of the materials in Table 1. (a) Co3O4 porous microspheres in Ref. [39]; Reproduced with permission from Ref. [39]. (b) SnO2 nanospheres in Ref. [46]; Reproduced with permission from Ref. [46]. (c) SnO2 elephantidens-like nanospheres in Ref. [47]; Reproduced with permission from Ref. [47]. (d) In2O3 microspheres in Ref. [48]; Reproduced with permission from Ref. [48]. (e) ZnO hollow microspheres in Ref. [30]; Reproduced with permission from Ref. [30]. (f) ZnO double-shelled microspheres in Ref. [43]. Reproduced with permission from Ref. [43].
Fig. 2. SEM images of (a) pristine In2O3 NWs, (b) Au–In2O3 NWs, (c) Ag–In2O3 NWs, and (d) Pt–In2O3 NWs. Dynamic response curves of (e) Au–In2O3 and pristine In2O3 NWs, (f) Ag–In2O3 and pristine In2O3 NWs, (g) Pt–In2O3 and pristine In2O3 NWs, (h) schematic diagram of the electrospinning process for In2O3 NWs and the preparation of the sensor array, (i) selective tests of three gas sensors, (j) pattern recognition based on PCA using three sensor arrays. Reproduced with permission from Ref. [51].
Fig. 3. (a) FESEM image of PdAu/SnO2; (b) six periods of response curve of three sensors to 20-ppm acetone at working time of 250 °C; (c) the response of the PdAu/SnO2 sensor to different concentrations of acetone in 94% RH environment at working temperature of 250 °C. Reproduced with permission from Ref. [54].
Fig. 4. Gas responses of the (a) pure SnO2 and (b) 5Tb–SnO2 sensors to acetone at 450 °C under both humid and dry conditions; (c) 30 repetitive sensing transients to 20-ppm acetone and (d) long-term stability of 5Tb–SnO2 sensor at 450 °C in RH 80%. Reproduced with permission from Ref. [59]. (e) Gas responses of the 12Pr–In2O3 macroporous spheres to 20 ppm of acetone. (f) Dynamic sensing transients, (g) responses and (h) 15 repetitive sensing transients of the 12Pr–In2O3 macroporous spheres to 20-ppm acetone at 450 °C. Reproduced with permission from Ref. [60].
Fig. 5. (a) TEM images of 3D OP SnO2–ZnO HM; (b) the sensor-based SnO2–ZnO HM to acetone in the range 0.25 ppm–100 ppm at 275 °C; (c) the identification of human exhaled breath (healthy subjects and simulated diabetics) based on SnO2–ZnO sensor; (d) dynamic resistance change transients of the SnO2–ZnO sensor to human exhaled breath. Reproduced with permission from Ref. [30].
Fig. 6. (a) The SEM and (b) TEM images of the GQD-modified 3DOM ZnO sample; (c) XRD patterns of 3DOM ZnO and GQD-modified 3DOM ZnO samples; (d) the dynamic response curves in the acetone concentration range of 0.3 ppm–2 ppm; (e) the linear relationship response of various acetone concentrations; (f) the response/recovery time to acetone; (g) the selectivity tests for the 3DOM ZnO sensor and GQD-modified 3DOM ZnO sensor; (h) the responses of the GQD-modified 3DOM ZnO sensor toward healthy and simulated diabetes exhaled breaths and a schematic diagram of the breath collecting process; (i) the band diagram structure. Reproduced with permission from Ref. [8].
Materials | Morphology | SSA/m2⋅g−1 | Pore/nm | Concentration/ppm | Temperature/°C | Responce | (tres/trec)/s | LOD/ppm | Reference |
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Co3O4 | porous microspheres | 21.2 | – | 100 | 180 | Rg/Ra = 7.6 | 2/5 | 10 | [39] | SnO2 | nanospheres | 38.86 | 22.61 | 50 | 220 | Ra/Rg = 5.1 | 8/27 | 0.246 | [46] | SnO2 | elephantidens-like nanospheres | 161.16 | 3 | 50 | 180 | Ra/Rg = 37 | – | – | [47] | In2O3 | microspheres | 30.3 | ∼4 and 80 | 100 | 275 | Ra/Rg = 13.2 | 1/51 | – | [48] | ZnO | hollow microspheres | 42.6 | ∼9 and ∼60 | 100 | 350 | Ra/Rg = 17.2 | 1/20 | 5 | [30] | ZnO | double-shelled microspheres | 76.11 | ∼70 | 100 | 300 | Ra/Rg = 101.1 | 1/7 | 0.5 | [43] |
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Table 1. The performance of sensors based on MOSs of different sphere structures.
Materials | Morphology | Concentration/ppm | Humidity/% | Temperature/°C | Response | LOD/ppb | Reference |
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Ru/WO3 | nanoparticles | 1.5 | – | 300 | Ra/Rg = 7.3 | 500 | [49] | Pt/SnO2 | 3D spheres | 5 | 90 | 400 | Ra/Rg = 44.8 | 200 | [50] | Pt/In2O3 | nanowires | 1 | – | 300 | Ra/Rg = 17.9 | 20 | [51] | Au/ZnO | nanorods | 5 | – | 150 | Ra/Rg = 44.5 | 5 | [52] | Pt/SnO2 | pill-like network | 0.2 | 80 | 300 | Ra/Rg = 1.4 | 3.6 | [7] | Ag/CuO/Cu2O | nanopattern | 0.125 | – | 300 | ΔR/Ra = 8.04 | – | [53] | PdAu/SnO2 | 3D nanosheets | 2 | 94 | 250 | Ra/Rg = 6.5 | 45 | [54] |
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Table 2. The performance of sensors based on MOSs functioned by noble metals for acetone detecting.