Robust
materials capable of heterogeneous reactivity are valuable
for addressing toxic chemical clean up. Synthetic manipulations for
generating titanium oxide nanomaterials have been utilized to alter
both photochemical (1000 nm > λ > 400 nm) and chemical
heterogeneous
reactivity with 2-chloroethyl ethyl sulfide (2-CEES). Synthesizing
TiO2 nanomaterials in the presence of long-chain alkylphosphonic
acids enhanced the visible light-driven oxidation of the thioether
sulfur of 2-CEES. Photooxidation reaction rates of 99 and 168 μmol/g/h
(quantum yields of 5.07 × 10–4 and 8.58 ×
10–4 molecules/photon, respectively) were observed
for samples made with two different alkylphosphonic acids (C14H29PO3H2 and C9H19PO3H2, respectively). These observations
are correlated with (i) generation of new surface defects/states (i.e.,
oxygen vacancies) as a result of TiO2 grafting by alkylphosphonic
acid that may serve as reaction active sites, (ii) better light absorption
by assemblies of nanorods and nanowires in comparison to individual
nanorods, (iii) surface area differences, and (iv) the exclusion of
OH groups due to the surface functionalization with alkylphosphonic
acids via Ti–O–P bonds on the TiO2. Alternatively,
nanowire-form H2Ti2O5·H2O was produced and found to be capable of highly efficient
hydrolysis of the carbon–chlorine (C–Cl) bond of 2-CEES
in the dark with a reaction rate of 279.2 μmol/g/h due to the
high surface area and chemical nature of the titanate structure.
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