Surface modification of small particle TiO{sub 2} collloids with cysteine for enhanced photochemical reduction: An EPR study

Journal Article · Thu Mar 14 04:00:00 EST 1996 · Journal of Physical Chemistry

DOI:https://doi.org/10.1021/jp952002p· OSTI ID:226768

Rajh, T; Ostafin, A E; Micic, O I; Tiede, D M; Thurnauer, M C ^[1]

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1. Argonne National Lab., IL (United States)

Surface complexation of colloidal titanium dioxide nanoparticles (40-60 A) with cysteine was investigated by electron paramagnetic resonance (EPR) and infrared (diffuse reflectance infrared Fourier transform - DRIFT) spectroscopies. Cysteine was found to bind strongly to the TiO{sub 2} surface, resulting in formation of new trapping sites where photogenerated electrons and holes are localized. Illumination of cysteine-modified TiO{sub 2} at 77 K resulted in formation of cysteine radicals with the unpaired electron localized on the carboxyl group. Upon warming to 150 K, these radicals are transformed into sulfur-centered radicals as observed by EPR spectroscopy. We have demonstrated the existence of two surface Ti(III) centers on cysteine-modified TiO{sub 2} particles having different extents of tetragonal distortion of the octahedral crystal field. Upon addition of lead ions, a new complex of cysteine that bridges surface titanium atoms and lead ions was detected by IR spectroscopy. Illumination of lead/cysteine-modified TiO{sub 2} did not result in the formation of sulfur-centered radicals. Instead, a symmetrical, lattice defect type EPR signal for trapped holes was observed. Addition of methanol to this system resulted in the formation of a .CH{sub 2}OH radical at 8.2 K. After the temperature was raised to 120 K, doubling of the signal associated with electrons trapped at the particle surface (Ti(III){sub surf}) was observed. 46 refs., 6 figs.

• Research Organization: Argonne National Laboratory (ANL), Argonne, IL
• DOE Contract Number: W-31109-ENG-38
• OSTI ID: 226768
• Journal Information: Journal of Physical Chemistry, Journal Name: Journal of Physical Chemistry Journal Issue: 11 Vol. 100; ISSN JPCHAX; ISSN 0022-3654
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
40 CHEMISTRY
54 ENVIRONMENTAL SCIENCES
66 PHYSICS
COLLOIDS
CYSTEINE
ELECTRON SPECTRA
ELECTRON SPIN RESONANCE
ELECTRON TRANSFER
LEAD
PHOTOCHEMICAL REACTIONS
PRECIPITATION
QUANTUM EFFICIENCY
REDUCTION
SURFACE TREATMENTS
TEMPERATURE DEPENDENCE
TITANIUM OXIDES
WATER POLLUTION CONTROL
WATER TREATMENT