Table 1. Ti 2p_3/2, O 1s, and N 1s BEs Taken from the Literature for Different Methods of Preparing N-Doped TiO₂ NTs in Comparison with NTs Modified by Plasma Nitriding^a.

TiO2 NTs obtained using anodic oxidation procedures
	parameters of TiO2 NTs		results of XPS analysis.
methods of nitrogen doping and source of nitrogen	average pore diameter/nm	average wall thickness/nm	Ti 2p3/2 (eV)	O 1s (eV)	N 1s (eV)	chemical bonds	the possible applications of N-doped TiO2 NTs	refs
Chemical Methods
wet immersion in NH3 solution + heat treatment (300–700 °C)	140	10	459.29	530.51		Ti–O in TiO2	photodegradation of methyl orange (MO)	(22)
					397.0	O–Ti–N (NS)
					400.37	Ti–O–N (NI)
wet immersion in NH3 solution + heat treatment (450–700 °C)	80	15					photodegradation of methyl orange (MO)	(18)
					395.9	O–Ti–N (NS)
					402.0	molecularly adsorbed N2 (NMA)
hydrothermal method at 120 °C (trimethylamine)	80	15	458.1	529.3		Ti–O in TiO2	photoelectrocatalytic degradation of RhB (rhodamine B)	(23)
					396.9	O–Ti–N (NS)
					399.8	Ti–O–N (NI)
					401.9	molecularly adsorbed N2 (NMA)
Electrochemical Methods
electrochemical doping (various kinds of amines: DETA, TEA, EDA, urea)	70	20	458.5	529.8		Ti–O in TiO2	photodegradation of MB (methylene blue)	(24)
					397.5–397.8	O–Ti–N (NS)
					399.7–399.9	molecularly adsorbed N2 (NMA)
					401.8–402.0	Ti–O–N (NI)
electrochemical doping (various concentrations of urea) + heat treatment at 450 °C	61–114	4.5–13.5	459.5	530.7		Ti–O in TiO2	photodegradation of phenol (model pollutant)	(15)
			458.0			Ti–O in Ti2O3
					400.7	O–Ti–N (NS)
electrochemical doping (urea) + heat treatment at 400 °C	45–125	4–10	459.4	530.5		Ti–O in TiO2	photocurrent investigations	(25)
			458.0	530.9		Ti–O in Ti2O3

			456.9			Ti–O–N in TiOxNy
			455.6			Ti–O in TiO
					396.8	O–Ti–N (NS)
					400.2	Ti–O–N (NI)
					403.1	molecularly adsorbed N2 (NMA)
electrochemical doping (trimethylamine TEA) + heat treatment at 450 °C	65	30	458.9	530.3		Ti–O in TiO2	photoelectrocatalytic degradation of MB (methylene blue)	(26)
					400.6	O–Ti–N (NS)
electrochemical doping (NH4Cl) + heat treatment at 450 °C	140		458.6	530.0		Ti–O in TiO2	photodegradation of RhB (rhodamine B)	(27)
					400.0	O–Ti–N (NS)
electrochemical doping (NH4F and CH3NO) + heat treatment at 400 °C	65.3–67.6	∼11	458.1–458.6	529.5–529.7		Ti–O in TiO2	photodegradation of rhodamine B (RhB)	(28)
					399.5–399.9	O–Ti–N (NS)
Physical Methods
heat treatment in N2 atmosphere	40	12	458.6		398.2	Ti–O in TiO2	photodegradation of acephate	(29)
						O–Ti–N (NS)
decomposition of pure ammonia (NH3) gas at 550 °C	100	15			396.0		photocurrent investigations	(17)
	50	12			400.0	O–Ti–N (NS)
						molecularly adsorbed N2 (NMA)
ion implantation, heat treatment at 450 °C	100	10			396.0		photocurrent investigations	(30)
					400.0	O–Ti–N (NS)
						molecularly adsorbed N2 (NMA)
ion implantation, heat treatment at 450 °C	100			529.8	399.4		photocurrent investigations	(31)
					400.1	Ti–O–N (NI)
						O–Ti–N (NS)
plasma nitriding at 540 °C in NH3 atmosphere (micro-arc oxidation film)					398.9		photodegradation of MB (methylene blue)	(32)
					401.2	O–Ti–N (NS)
						Ti–O–N (NI)
plasma nitriding in N2 atmosphere at 800 °C	80–100	∼20	455.5			Ti–N w TiN		(33)
			456.8			Ti–O–N in TiOxNy
			458.9	529.8		Ti–O in TiO2
					396.86	O–Ti–N (NS)
					398.5	Ti–O–N in TiOxNy (NS)

^a(N_s)—substitutional nitrogen; (N_I)—interstitial nitrogen; (N_MA)—molecularly adsorbed nitrogen (chemisorbed nitrogen).