Typical Synthesis and Environmental Application of Novel Ti Nanoparticles - Advanced Materials for Agriculture, Food and Environmental Safety - page 437

Very few reports are available in literature on the preparation of nano-
size transition metal-doped titanium dioxide photocatalyst [135-137],
however, this process is important for their preparation inspite of its
high cost.
a) Vapor phase technique: h is process involves dissociation-vaporiza-
tion of primary powders (reactants), followed by vigorous quenching of the
resulting vapors onto a cold metal substrate. It results in a rei ned deposite
of sample and/or substrate. h e sample required is recovered by scrub-
bing the deposit from substrate. Generally, the rate and the temperature of
decomposition determine the reaction kinetics and the rates at which the
decomposed products can crystallize on the reaction surface [138]. h ere
are three types of vapor phase preparation methods: (i) reactions between
gas and a solid, (ii) reactions between gas and a liquid, and (iii) reactions
between two or more gases.
b) Solution processing methods: h ese processes can also be termed
as chemical synthesis methods. h e solution processing method covers
a broad area of preparative methods of nanocrystalline materials, which
can be distinctly divided into two types: (i) precipitation from aqueous
or nonaqueous solutions includes aerosol, co-precipitation, controlled
hydrolysis of metal alkoxides, hydrothermal, colloid emulsion methods,
etc.; (ii) evaporation or evaporative decomposition of the liquid includes
spray drying, spray pyrolysis, freeze drying, sol-gel processing, the Pechini
methods, combustion, etc. In general, the solution processing method
of ers the advantage of easy preparation of nearly any composition, main-
taining compositional homogeneity and high purity. Various i ne titanium
dioxide-based nanophotocatalysts [139-142] have been successfully syn-
thesized using this method.
15.4.1 Fe(III)-DopedTiO 2 Nanophotocatalyst
h e most ef ective nanophotocatalyst, Fe(III)-doped TiO 2 , was synthesized
by novel chemical method. h e chemical synthesis of nanosized Fe(III)-
doped TiO 2 was studied on degradations of dif erent dyes like Methyl
orange (MO), Rhodamine B (RB), h ymol blue (TB) and Bromocresol
green (BG) under UV light irradiation it was found that Fe x Ti 1-x O 2 (x =
0.005) (FT) is more photoactive compared with all other compositions of
Fe x Ti 1-x O 2 and degussa P25 [41]. It was also found that among all the four
dye solutions, the rate of degradation of RB is best in the presence of FT
and UV light. h e present synthetic procedure is a low-temperture-based
method which produces nanosized, chemically homogeneous Fe(III)-
doped TiO 2 with narrow distribution of particle size. Zhang et al. [142]