. 2019 Jan 9;19(2):233. doi: 10.3390/s19020233

Table 2.

Summary of the gas-sensing performances of semiconductor metal oxides for ethanol gas.

Order	Dimensions	Materials	Synthesis Method	Conc. (ppm)	LOD (ppm)	Temp. (°C)	τ_res (s)	τ_rec (s)	Resp.	Ref.
1	0D	CuBi₂O₄ powders	polymerized complex method	1000	5	400	57	294	10.4 ^b	[85]
2	0D	SnO₂ nanoparticles	microwave treatment	250	NA	100	16	25	30 ^c	[86]
3	1D	Co₃O₄ microrods	interfacial-reaction	100	NA	220	0.8	10.8	9.8 ^b	[87]
4		CuO/In₂O₃ nanorods	thermal evaporation and sputtering	50	NA	300	53	149	3.82 ^a	[88]
5		In₂O₃ microrods	hydrothermal	100	1	300	15	20	18.33 ^a	[89]
6		LaFeO₃ nanotubes	electrospinning	100	NA	160	2	4	9.4 ^b	[90]
7		Pd/Fe₂O₃ nanotubes	electrospinning	50	0.1	240	8	30	65.4 ^a	[91]
8		ZnO nanotubes	electrodeposition and electrochemical etching	700	1	RT	4.56 min	1.53 min	64.17% ^c	[83]
9		LaMnO₃/SnO₂ nanofibers	electrospinning	100	NA	260	6	34	20 ^a	[92]
10		WO₃/SnO₂ nanofibers	coaxial electrospinning	10	NA	280	18.5	282	5.09 ^a	[93]
11		ZnO nanowires	solvothermal	500	NA	340	6	26	10.68 ^a	[94]
12		SnO₂/Fe₂O₃ nanowires	VLS, hydrothermal and spin coating	5	NA	300	100	300	3.07 ^a	[95]
13		SnO₂/ZnO nanowires	carbon-assisted thermal evaporation	400	NA	400	NA	NA	128 ^c	[96]
14		SnO₂/ZnO nanowires	thermal evaporation and spray-coating	100	NA	400	NA	NA	14.1^a	[97]
15	2D	CuO films	RF sputtering	12.5	NA	180	31	52	2.2 ^b	[98]
16		Pd/Ce/SnO₂ films	co-precipitation	100	NA	250	6	20	88 ^c	[99]
17		NiO nanosheets	hydrothermal	50	1	240	4	7	11.15 ^b	[100]
18		ZnO nanosheets	hydrothermal	50	1	330	15	12	83.6 ^a	[101]
19	3D	SnO₂ nanoflowers	hydrothermal	200	4.52	240	10	16	62.2 ^a	[102]
20		SnO₂ nanoflowers	hydrothermal	100	NA	300	10	16	47.29 ^a	[103]
21		Au/SnO₂ hierarchical structures	hydrothermal	100	NA	340	5	10	18 ^a	[104]
22		NiO hierarchical structures	hydrothermal	400	NA	300	4	8	32 ^b	[105]
23		SnO₂ macropores structures	sol-gel method	500	NA	240	NA	NA	70.94 ^a	[106]
24		MoO₃ microboxes	hydrothermal	100	1	260	15	5	78 ^a	[107]
25		SnO₂ nanocubes	hydrothermal	100	1	200	23	21	1670.5 ^a	[108]
26		ZnSnO₃ nanocubes	co-precipitation	100	NA	260	4	276	34.1 ^a	[109]
27		PdO/Zn₂SnO₄ octahedrons	hydrothermal and wet impregnation treatment	100	0.5	250	1	206	82.3 ^a	[110]
28		WO₃ urchin-like structures	hydrothermal	100	NA	350	28	12	68.56 ^a	[111]
29		Co₃O₄ microspheres	interfacial-reaction	100	1	220	0.1	0.7	38.2 ^b	[112]
30		CuO microspheres	precipitation	400	NA	250	17	11.9	5.6 ^b	[113]
31		CuO microspheres	hydrothermal	100	NA	200	2	8	390% c	[114]
32		Fe₂O₃/Co₃O₄ microspheres	solution route	100	NA	170	3.3	5.4	16.1 ^b	[115]
33		SnO₂ microspheres	ion exchange method	200	NA	260	NA	NA	103.1 ^a	[116]
34		SnO₂/Fe₂O₃ microspheres	hydrothermal	100	0.1	260	3	4	41.7 ^a	[117]
35		ZnFe₂O₄ microspheres	solvothermal	10	0.5	180	5.1	6.5	6.85 ^a	[118]
36		Pt/SnO₂ nanospheres	spray drying and Kirkendall diffusion	5	0.25	325	1	1577	1399.9 ^a	[119]
37		SnO₂ nanospheres	precipitation	200	NA	260	10	8	274.5 ^a	[120]
38		SnO₂ nanospheres	hydrothermal	100	0.5	350	5	NA	10.5 ^a	[121]
39		SnO₂/ZnO nanospheres	self-sacrificial template	50	NA	270	0.4	235	7.5 ^a	[122]
40		ZnSnO₃ nanospheres	hydrothermal	100	NA	200	4	30	32 ^a	[123]
41		Zn₂SnO₄ nanospheres	hydrothermal	50	5	180	NA	NA	23.4 ^a	[124]

Note: Conc. = concentration; LOD = limit of detection; Temp. = temperature; τ_res = response time; τ_cov = recovery time; Resp. = Response; Ref. = References; RT = room temperature; ^a S = R_a/R_g; ^b S = R_g/R_a; ^c S = (ΔR/R_a)*100%; ^d S = I_g/I_a; NA = not available.