Typical Synthesis and Environmental Application of Novel Ti Nanoparticles - Advanced Materials for Agriculture, Food and Environmental Safety - page 432

1.0

0.8

0.6

0.4 CNT1

CNT2
CNT3
CNT4
NT
CT
TiO 2

0.2

0.0

0 20406080
Irradiation Time (min)

100 120 140 160 180 200

Figure 15.9 h e changes in concentrations of RB solution at 554 nm in the presence of
CNT1, CNT2, CNT3, CNT4, NT, CT, TiO 2 and Hg lamp.

due to the decrease of specii c surface area for the dif erent doped catalysts.
h e photocatalytic activity was also observed in the presence of visible
light, but the catalytic activity was not so signii cant like UV light.
Highly crystalline anatase TiO 2 nanoparticles with dif erent sizes and
shapes could be obtained with the polycondensation of titanium alkoxide
in the presence of tetramethylammonium hydroxide [120, 121]. In a typi-
cal procedure, spherical nanoclusters of Fe x Nb x Ti 1-2x O 2-x/2 (x = 0.01) were
prepared by sol-gel method at pH 9 with triethanolamine (TEA) [122]. h e
pH of the solution can be adjusted by adding NaOH solution. Figure 15.10
shows representative TEM images of the novel TiO 2 nanoparticles at under
pH 9 with the control shape of FNT1 [122]. Secondary amines, such as
diethylamine, and tertiary amines, such as trimethylamine and triethyl-
amine, act as complexing agents of Ti(IV) ions to promote the growth
of ellipsoidal particles with lower aspect ratios. h e shape of the TiO 2
nanoparticle can also be tuned from rounded-corner cubes to sharp-edged
cubes with sodium oleate and sodium stearate [123]. h e shape control is
attributed to the tuning of the growth rate of the dif erent crystal planes
of TiO 2 nanoparticles by the specii c adsorption of shape controllers to
these planes under dif erent pH conditions [123]. A prolonged heating
time below 100

C for the as-prepared gel can be used to avoid the agglom-
eration of the TiO 2 nanoparticles during the crystallization process [124].
By heating amorphous TiO 2 in air, large quantities of single-phase anatase
TiO 2 nanoparticles with average particle sizes between 7 and 50 nm can be
obtained, as reported by Zhang and Bani eld [125-128]. Much ef ort has

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