es5b04958_si_001.pdf (431.93 kB)
Quantitative Aspects of the Interfacial Catalytic Oxidation of Dithiothreitol by Dissolved Oxygen in the Presence of Carbon Nanoparticles
journal contribution
posted on 2016-01-19, 00:00 authored by Jean-Jacques Sauvain, Michel
J. RossiThe
catalytic nature of particulate matter is often advocated to
explain its ability to generate reactive oxygen species, but quantitative
data are lacking. We have performed molecular characterization of
three different carbonaceous nanoparticles (NP) by 1. identifying
and quantifying their surface functional groups based on probe gas-particle
titration; 2. studying the kinetics of dissolved oxygen consumption
in the presence of suspended NP’s and dithiothreitol (DTT).
We show that these NP’s can reversibly change their oxidation
state between oxidized and reduced functional groups present on the
NP surface. By comparing the amount of O2 consumed and
the number of strongly reducing sites on the NP, its average turnover
ranged from 35 to 600 depending on the type of NP. The observed quadratic
rate law for O2 disappearance points to a Langmuir–Hinshelwood
surface-based reaction mechanism possibly involving semiquinone radical.
In the proposed model, the strongly reducing surface site is assumed
to be a polycyclic aromatic hydroquinone whose oxidation to the corresponding
conjugated quinone is rate-limiting in the catalytic chain reaction.
The presence and strength of the reducing surface functional groups
are important for explaining the catalytic activity of NP in the presence
of oxygen and a reducing agent like DTT.