Table 3.

Comparison of surface OH groups of different TiO₂ NPs.

Sample	SBET (m2/g)	Surface OH Conc. (mmol/g)	Surface OH Density (/nm2)	Analytical Method	Reference
Degussa P25	56	0.44	4.8	TGA	Mueller et al., 2003 [30]
Degussa P25	56	0.49	5.3	TGA	This work
Hombikat UV 100	337	1.15	2.5	NH3-TPD	Carneiro et al., 2010 [47]
Kanto	22	0.012	0.3	Ion-Exchange	Tamura et al., 1999 [48]
TiO2 by sol-gel	85	1.44	10.2	TGA	Zhao et al., 2008 [31]
Three-dimensional TiO2 by sol-gel	203	4.01	11.9	XPS	Guo et al., 2013 [15]
NaCl-TiO2 by sol-gel	— a	2.31	—	TGA	Wang et al., 2012 [9]
NaOH-Degussa P25	—	1.60	—	TGA	Eskandarloo et al., 2015 [17]
Ishihara ST-01	290	2.32	4.8	TGA	This work
AHP-ST-01	304	6.08	12.0	TGA	This work

^a No information available.