Physical characteristics of nanostructured silica synthesized from synthetic chemical precursors.

Sl No.	Precursor	BET surface area (m2 g−1)	Particle size (nm)	Pore size (nm) and volume (cm3 g−1)	Method	Ref.
1	Sodium silicate solution	160.29	—	0.57	Sol–gel method	38
					Precipitation by HCl
2	Sodium silicate solution	—	—	—	Precipitation by H2SO4 at pH 4, 7, and 9	39
3	Tetraethylorthosilicate	—	—	—	Sol–gel method	40
					Non-capping and PVA capping of particles
4	Tetraethylorthosilicate	—	60 to 100	—	Sol–gel method	41
					Ablation
					Crushing
5	Tetraethylorthosilicate	—	—	—	Sol–gel method assisted by freeze drying	42
					Capping agent: polyethylene glycol
6	Tetraethylorthosilicate	—	∼150 to 190	—	Modified Stober method	43
					Particles modified by silane coupling agents with different alkyl chain lengths
					- Dimethyldichlorosilane (CH3)2SiCl2)
					- 3-Methacryloxypropyl-trimethoxy silane (KH570)
					- 3-Aminopropyl-triethoxy silane (KH550)
7	Tetraethylorthosilicate	0 CTAB: 45 H2O: 7.8	0 CTAB: 45 H2O: spheres 700–800	0 CTAB: 45 H2O: size: n.a.; volume: 0.01	Sol gel method	44
		0.1 CTAB: 45 H2O: 308	0.1 CTAB: 45 H2O: spheres 600–700	0.1 CTAB: 45 H2O: size: 2.9; volume: 0.21	Surfactant: CTAB
8	Tetraethylorthosilicate	—	Average: 79.68 to 87.35	—	Sol–gel method	45
					Precipitation by acetic acid
9	Water glass	—	Less than 100: avg ∼ 25–43	—	Precipitation by HCl	46
10	Tetraethylorthosilicate	Reaction parameters dependent: 515.4 to 1164.9	—	Reaction parameters dependent	Precipitation method	47
				- Pore size: 2.7 to 4.9
				- Pore vol: 0.6 to 1.5
			—		Porogen; n-octadecyl-trimethoxysilane (C18TMS)
11	Sodium silicate	—	CTAB: 90 to 250 with an average of 148	—	Precipitation from wet–gel	48
			DTAB: 100 to 350 with an average of 212		Cationic surfactants
					- CTAB
					- DTAB
12	Tetraethylorthosilicate	—	DTAB: ∼140	—	Sol–gel method	49
			TTAB: ∼95		Cationic surfactants
					- DTAB
					- TTAB
					- CTAB
			CTAB: ∼55
13	Tetraethylorthosilicate	n-SiO2: 5.5	Span 60: ∼80	—	Sol gel method	50
		n-SiO2 (Span 20): 6.2	Span 20, Span 40 and Span 60: range 150-80		Nonionic surfactants
					- Span 20
		n-SiO2 (Span 40): 9.1			- Span 40
		n-SiO2 (Span 60): 11.5			- Span 60
		n-SiO2 (pH 10): 6.5
		n-SiO2 (pH 11): 5.3
		n-SiO2 (pH 12): 4.9
14	Sodium silicate	Up to 130	Majority of primary particles: ∼15 to 30	—	Precipitation by coagulation with H2SO4	51
			Tendency to form bigger particles (aggregate)