Conducting polymer-inorganic nanocomposite-based gas sensors: a review

Figures & data

Figure 1. Chemical structures of representative conducting polymers

Figure 2. (a) An optical image of PANI/TiO₂ nanocomposite-based sensor, (b) SEM images of TiO₂ microfibers and (c) PANI/TiO₂ nanocomposites. Reprinted with permission from [30]. Copyright 2020 American Chemical Society

Figure 3. Schematic diagram about synergic effect of CeO₂@PANI under NH₃ gas. The inset was schematic diagram of P − N junction in equilibrium state. Reprinted with permission from [28]. Copyright 2014 American Chemical Society

Figure 4. Schematic diagram of fabrication process of α-MoO₃/PANI nanocomposites. Reprinted with permission from [36]. Copyright 2017 Elsevier

Figure 5. SEM images of (a) MoO₃ nanorods, (b) PANI powder, (c) and (d) MoO₃/PANI films with different contents of MoO₃ (e.g. 0.1 mg, 0.3 mg, and 1 mg); (e, f) TEM images of the α-MoO₃/PANI nanocomposites.Reprinted with permission from [36]. Copyright 2017 Elsevier

Figure 6. Schematic diagram of fabrication process of the SnO₂@PPy tube-in-tube structure. Reprinted with permission from [37]. Copyright 2013 Royal Society of Chemistry

Table 1. Conducting polymer/metal oxides hybrid composites used in gas sensors

Polymer	Metal oxides	Target gas	Concentration (ppm)	Response	Response/recovery Time (s)	T (°C)	Ref.
PANI	TiO2	NH3	23	1.67	18 ~ 58	25	[25]
		CO	140	~1.9			[25]
		NH3	50 ppt	0.4%		RT	[30]
	SnO2	NH3	100		15 ~ 80		[44]
		NO2	50 ppb		5 ~ 15 (min)	25	[46]
		SO2	2				[46]
		NO2	37		17 ~ 25	140	[47]
		NH3	100	29		21	[45]
		NO2	10	~2			[45]
		NO2+ NH3	10	~5			[45]
		CO	25	15		30	[48]
	Fe2O3	LPG	50	0.5	< 60	28	[49]
		NH3	10.7	3070%		20	[32]
	GeO2	NH3	50	6.5		RT	[28]
		NH3	50	262.7%		25	[50]
		NO2	50	~40%			[50]
		HCHO	50	~20%			[50]
		H2S	50	~13%			[50]
		CO	50	~10%			[50]
		SO2	50	~5%			[50]
		O2	50	~5%			[50]
	ZnO	NH3	100	2.5		27	[34]
		NH3	20	14%	< 35	300 K	[51]
		NH3	10	2150%	431 ~ 387	RT	[52]
	Nb2O5	LPG	500	45.21%	30 ~ 50	RT	[53]
	WO3	NH3	5	24%	136 ~ 137	RT	[39]
		NH3	100	158%			[39]
		NO2	100	~40%			[39]
		H2S	100	~6%			[39]
		CH3OH	100	~3%			[39]
		C2H5OH	100	~1.5%			[39]
		NH3	10	7.1	13 ~ 49	RT	[38]
		NH3	100	25	136 ~ 130	20	[43]
		NH3	1	9%	< 32	RT	[41]
	MoO3	TEA	10	5.8		RT	[36]
PANI:PSS	Fe2O3	NO2	0.5	~8%		RT	[63]
PPy	SnO2	NH3	3		< 15	RT	[42]
		NH3	10.7	75%	259 ~ 468	RT	[31]
		DMMP	0.05 ppb	0.5%	1 ~ 30	RT	[37]
		NH3	0.1	57%	18 ~ 30	RT	[33]
	ZnO	LPG	1400	32.5%	4 ~ 40 min	RT	[26]
		NH3	0.5	21%	256 ~ 370	RT	[35]
		CH3NH2	280 μg	50%	< 50	100	[40]
	TiO2	LPG	1040	55%	112 ~ 131	RT	[57]
	FeOOH	DMMP	0.01	~7.5%	1.5 ~ 8.5	RT	[27]
	WO3	H2S	1	83%	6 ~ 210 min	RT	[64]
		NO2	100	61%		38	[54]
		TEA	100	680	7 ~ 49	RT	[29]
		C3H6O	0.37 μg		< 5	90	[55]
	Zn2SnO4	NH3	100	82.1%	35 ~ 26	RT	[56]
PPy:DBSA	WO3	NO2	100	72%	288 ~ 5990	38	[65]
PT	SnO2	NO2	100	3.69		90	[58]
	WO3	H2S	100	1.35	< 15	70	[59]
PEDOT:PSS	TiO2	NO2	0.005			RT	[61]
	WO3	NO2	0.05	~1.2	45.1 ~ 88.7	RT	[62]

Figure 7. (a–c) TEM images of the hybrid PPy/Au system and (d) size distribution of Au NPs. Reprinted with permission from [75]. Copyright 2013 Elsevier

Figure 8. Possible gas detection mechanism of PPy/Au hybrids. Reprinted with permission from [75]. Copyright 2013 Elsevier

Table 2. Conducting polymer/metal nanostructures hybrid composites used in gas sensors

Metal	Polymer	Target gas	Concentration (ppm)	Response	Response/recovery Time (s)	T (°C)	Ref.
Pd	PANI	CH3OH	10		2 ~ 720		[66]
		NH3	500	21.9		RT	[83]
		NH3	100	~10			[83]
		H2	100	~6.5			[83]
		CO2	100	~1.7			[83]
		C2H5OH	100	~3.5			[83]
		LPG	100	~2.2			[83]
	PPy	NH3	50	13.9%	14 ~ 148	RT	[19]
	P(ANI-co-ASA):PSS	H2	5		90 ~ 40	RT	[71]
Pt	PPy	H2	1000		~330	RT	[69]
		LPG				170	[76]
Cu	PANI	NH3	50	86%	7 ~ 160	RT	[70]
Au	PANI	NH3	100	~3	5 ~ 7		[67]
		H2S	1				[79]
		CH3SH	1.5				[79]
	PPy	NH3	100	~1.35	20 ~ 40	RT	[75]
	PT	CH3NH2	1				[77]
Ag	PANI	C2H6O	500	~7.25	102 ~ 52	RT	[68]
		TEA	39	0.73	< 120		[81]
		NH3	10	~9.1		RT	[73]
		H2S	10	100%	~360		[82]
	PPy	NH3	10	0.54		RT	[72]
		NO2	100	68%	148 ~ 500	RT	[74]
	PEDOT	NH3	50	~25%	2 ~ 7	RT	[80]

Figure 9. (a) Cyclic voltammograms of pristine SWNTs, PANI, and SWNT/PANI nanocomposites; (b) Three oxidation states of PANI. Reprinted with permission from [85]. Copyright 2010 John Wiley and Sons

Figure 10. Schematic diagram of fabrication process of the hierarchically PANI/FMWCNT nanocomposites. Reprinted with permission from [88]. Copyright 2015 John Wiley and Sons

Figure 11. (a), (b) Gas-sensing sensitivity of sensors based on PANI/FMWCNT nanocomposite network; (c) selectivity and (d) flexibility of the sensors based on PANI/FMWCNT nanocomposite network. Reprinted with permission from [88]. Copyright 2015 John Wiley and Sons

Table 3. Conducting polymer/CNT and polymer/graphene nanostructures hybrid composites used in gas sensors

Doping material	Polymer	Target gas	Concentration (ppm)	Response	Response/recovery Time (s)	T (°C)	Ref.
SWCNT	PT	DMMP	25	~0.18		70	[84]
	PANI	N2H4	0.05				[85]
		NH3	0.1		120		[86]
CNT	PANI	NH3	300	2.07 MHz	375	45	[89]
MWCNT	PEDOT:PSS	NH3	5	~16%	900	RT	[93]
	PANI	NH3	100	30			[88]
		C6H8OS	100	~0.04			[88]
		CH4O	100	~0.03			[88]
		C3Cl6O	100	~0.02			[88]
		C3H8O	100	~0.04			[88]
		NH3	2	15.5%	6 ~ 35	RT	[94]
		CH4O	250	~3			[95]
		NH3	100	140.99%	5 ~ 12	RT	[87]
		NH3	25	46.9%		RT	[96]
Nitrogen-doped MWCNT	PPy	NO2	5	24.82%	~60	RT	[97]
Graphene	PANI	H2	1%	16.57%			[90]
		NH3	20	3.65	50 ~ 23	25	[91]
		NH3	20	~0.6		RT	[98]
	PANI:PSS	H2S	20	~60	90 ~ 150		[99]
GO	PPy	C7H8	200	~20			[100]
rGO	PANI	NH3	50	59.2%	3.4 ~ 10.4		[101]
		NH3	100	344.2	52 ~ 80	RT	[102]
		NH3	10	~6	36 ~ 18	RT	[92]
Nitrogen-doped graphene quantum dots (GQDs)	PANI	NH3	1500	110.92	540 ~ 588	RT	[103]
	PEDOT:PSS	NH3	1500	212.32%	462 ~ 600		[104]
		CO2	1500	~3%			[104]
		C2H6O	1500	~10%			[104]
		C3H6O	1500	~5%			[104]
		C7H8	1500	~9%			[104]
S and N co-doped GQDs	PANI	NH3	10	42%	115 ~ 44	RT	[105]

Figure 12. Schematic diagram of fabrication process of the PANI-TiO₂-Au ternary nanocomposites. Reprinted with permission from [107]. Copyright 2017 Elsevier

Figure 13. Fabrication process of the (CPPy)/CNTs/Pd nanocomposites. Reprinted with permission from [110]. Copyright 2015 Royal Society of Chemistry

Table 4. Conducting polymer/multicomponent nanostructures hybrid composites used in gas sensors

Polymer	Multicomponent		Target gas	Concentration (ppm)	Response	Response/recovery Time (s)	T (°C)	Ref.
PPy	Ag	SnO2	NH3	0.02	3.15%		RT	[106]
	Au	TiO2	NH3	0.02	3.2%		RT	[106]
	Pd	CNT	H2	10	~4.5%	< 1	RT	[110]
	TiO2	Gr	NH3	50	102.2%	36 ~ 16	25	[113]
			CH3OH	50	~11			[113]
			CO	50	~5			[113]
			H2S	50	~4			[113]
	Au	nitrogen doped Gr	C6H6O2	0.0016 μM	3			[111]
	Cu2+	SnO2	H2S	50	~89		RT	[108]
	Cu3(BTC)2(H2O)3	rGO	NH3	50	14.3%	13 ~ 22	RT	[112]
PANI	ZnO	SnO2	TEA	100	69		21	[118]
	ZnO	GO	NH3	50	38.31%	< 30		[114]
	Au	TiO2	NH3	10	48.6%	52 ~ 122	RT	[107]
			NH3	50	123%			[107]
			NO2	50	~28%			[107]
			CO	50	~19%			[107]
			H2S	50	~16%			[107]
			H2	50	~7%			[107]
			HCHO	50	~5%			[107]
			SO2	50	~3%			[107]
			O3	50	~2.5%			[107]
	SnO2	rGO	NH3	10	0.83	~80	RT	[115]
			LPG	10	~0.23			[115]
			CO2	10	~0.46			[115]
			C2H6O	10	~0.17			[115]
	Au	In2O3	NH3	100	~46	118 ~ 144	RT	[109]
			NH3	10	~9.5			[109]
			NO	10	~1			[109]
			CH2O	10	~1			[109]
			C6H6	10	~1			[109]
			C7H8	10	~1			[109]
			CH3COCH3	10	~0.9			[109]
			C2H4	100	~0.9			[109]
			CH4	100	~0.9			[109]
	MoS2	MWCNT	NH3	0.25	11%	32 ~ 36	RT	[120]
			NH3	6	40%			[120]
			C2H5OH	6	~13%			[120]
			C6H6	6	~5%			[120]
			CH4	6	~2.5%			[120]
			CH3COCH3	6	~7%			[120]
			C3H8	6	~2.5%			[120]
	SnO2	rGO	H2S	0.2	23.9%	82 ~ 78	25	[116]
	ZnO	S and N co-doped GQDs	CH3COCH3	0.5	2%	15 ~ 27	25	[117]
PANI	CuO+TiO2+ SiO2		NH3	100	45.67		RT	[119]

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