Table 11.

Summary of the gas sensing properties of various 1-D nanostructures for non-conventional sensing oxides.

Materials and Morphology	Gas Tested	Crystal Structure	Size		DetectionRange	Detection Temperature (°C)	Optimum Working Temperature (°C)	Response			Response Time	Recovery Time	Reference
			Diameter	Length				Sensitivity	Concentration	Temperature (°C)
WO2.72 Nanowire	H2	Monoclinic	5–30 nm	100–500 nm	100–1,000 ppm	25	–	22 A	1,000 ppm	25	38 s	26 s	[59]
WO2.72 Nanowire	LPG	Monoclinic	5–30 nm	100–500 nm	100–1,000 ppm	25	–	15 A	1,000 ppm	25	38 s	26 s	[59]
WO3 Nnowire	NH3	Monoclinic	70 nm	Few micrometer	300–1,500 ppm	200–300	250	9.67 A	1,500 ppm	250	7 s	8 s	[97]
β-AgVO3 Nanowire	H2S	Monoclinic	50–100 nm (thickness)	100–700 nm (width)	50–400 ppm	250	–	>1.12 A	400 ppm	250	<10 s	<20 s	[35]
CdO Nanowire (porous)	NOx	Cubic	120 nm	100 μm	1–300 ppm	100	–	>150 C	150 ppm	100	–	–	[99]
MoO3 Needle	O2	–	–	–	1,000 ppm	370	–	39 C	1,000 ppm	370	1 s	5 s	[39]
MoO3 Lameller	NO2	Orthorhombic	500 nm (thickness)	5 μm (width)	0.6–10 ppm	180–300	225	1.18 C	10 ppm	250	–	–	[100]
CuO Nanoribbon	HCHO	–	2–8 nm	30–100 nm	5–500 ppm	200	–	∼4 B	500 ppm	200	2–4 s	3–7 s	[101]
CuO Nanoribbon (Au loaded)	HCHO	–	2–8 nm	30–100 nm	5–500 ppm	200	–	∼5.5 B	500 ppm	200	–	–	[101]
CuO Nanoribbon (Pt loaded)	HCHO	–	2–8 nm	30–100 nm	5–500 ppm	200	–	∼8 B	500 ppm	200	–	–	[101]
CuO Nanoribbon	Ethanol	–	2–8 nm	30–100 nm	5–1,000 ppm	200	–	∼3.5 B	1,000 ppm	200	3–6 s	4–9 s	[101]
CuO Nanoribbon (Au loaded)	Ethanol	–	2–8 nm	30–100 nm	5–1,000 ppm	200	–	∼3.5 B	1,000 ppm	200	–	–	[101]
CuO Nanoribbon (Pt loaded)	Ethanol	–	2–8 nm	30–100 nm	5–1,000 ppm	200	–	∼6 B	1,000 ppm	200	–	–	[101]
TeO2 Nanowire	NO2	Tetragonal	30–200 nm	Tens of micrometer	10–100 ppm	26	–	–	–	–	2 min	–	[32]
α-Fe2O3 Porous urchin	H2S	Hexagonal	30–40 nm	500 nm	1–100 ppm	150–450	250 (n-type response)	∼2.5 C	100 ppm	250	5 s	10 s	[31]

Note: ^A S = R_a/R_g, ^B S = R_g /R_a and ^C S = ΔR/R_a.