Crystallite phase-controlled preparation, characterisation and photocatalytic properties of titanium dioxide nanoparticles

Figures & data

Table 1. Crystallographic properties of rutile and anatase 4.

Crystal structure	Density (kg m^−3)	System	Space group	Cell parameters (nm)
	A		b		C
Rutile	4240	Tetragonal		0.4584		0.2953
Anatase	3830	Tetragonal		0.3758		0.9514

Table 2. Structure and characteristics of C. I. Acid Blue 9.

Other names	Brilliant Blue FCF, Erioglaucine, C.I. Food Blue 2, Brilliant Blue FCF, FD&C Blue no. 1
Colour index (C. I.) no.	42090
Molecular formula	C37H34N2Na2O9S3
Molecular mass	792.86 (g mol^−1)
Absorption maximum ()	625 (nm)
CAS No.	3844-45-9
Aqueous solubility	200 kg m^−3
Chemical class	Triphenylmethan dye
Chemical structure

Figure 1. Flow chart of the steps involved in the preparation of TiO₂ nanoparticles of anatase (left) and rutile (right).

Figure 2. Proposed mechanism for preparation of TiO₂ with rutile or anatase phases: (a) the orientation of the third octahedron determines whether a rutile or an anatase nucleus is formed; (b) interaction between and octahedral hydroxyls; (c) two octahedra share edge in the presence of ; (d) formation of anatase in the presence of .

Figure 3. X-ray diffraction (XRD) patterns of synthesised TiO₂ samples: (a) anatase, (b) rutile (c) rutile–anatase.

Figure 4. TEM images of the synthesised TiO₂ samples calcined at 400°C for 2 h.

Figure 5. SEM image (left) and XRD pattern (right) of the amorphous TiO₂ powder dried at room temperature under vacuum.

Figure 6. General mechanism of the photocatalysis on TiO₂ nanoparticle.

Figure 7. Comparison of the photocatalytic activity of different synthesised TiO₂ nanoparticles. [TiO₂]₀ = 150 mg L⁻¹, [AB9]₀ = 20 mg L⁻¹, pH = 6.2, V = 50 mL, I = 11.2 W m⁻²: (a) during different irradiation times, (b) at the irradiation time of 90 min.

Table 3. Physicochemical characteristics of the synthesised TiO₂ nanoparticles.

Crystalline phase of synthesised TiO2 sample	Anatase	Rutile	Anatase–Rutile
Anatase content (wt%) by XRD	100	0	70
Average crystallite size (nm)	8	11	6–10
BET surface area (m^2 g^−1)	119.96	28.31	75.29
Total pore volume (cm^3 g^−1)	0.3197	0.0747	0.2069
Pore size (nm)	9.59	10.11	12.92

Figure 8. Models of mixed-phase TiO₂: (a) rutile islands surround anatase particles, and rutile is an electron sink; (b) a small rutile core surrounded by anatase crystallites, where electrons are shuttled from rutile to anatase.

Figure 9. UV-Vis spectrum of AB9 (20 mg L⁻¹) during photocatalysis in the presence of the synthesised mixed-phase TiO₂ nanoparticles. [TiO₂]₀ = 150 mg L⁻¹, pH = 6.2, I = 11.2 W m⁻².

Table 4. Rate constants, half-lives, electrical energy per order and apparent quantum yield for photocatalytic decolorisation of AB9 in the presence of the synthesised TiO₂ nanoparticles. [AB9]₀ = 20 mg L⁻¹, [TiO₂]₀ = 150 mg L⁻¹, pH = 6.2.

Crystalline phase of synthesised TiO2 sample	k (min^−1)	R ^2	t 1/2 (min)	E EO (kWh m^−3 order^−1)	ϕapp × 10^−3
Rutile–Anatase	0.0374	0.98	18.53	616	6.75
Anatase	0.0159	0.96	43.59	1449	2.87
Rutile	0.0067	0.97	103.45	3439	1.21

Zheng , M , Gu , M , Jin , Y and Jin , G . 2000 . Preparation, structure and properties of TiO2–PVP hybrid films . Mat. Sci. Eng. B: Solid , 77 : 55 – 59 .

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