TY  - JOUR
A1  - Gu, Sasa
A1  - Risse, Sebastian
A1  - Lu, Yan
A1  - Ballauff, Matthias
T1  - Mechanism of the oxidation of 3,3′,5,5′-tetramethylbenzidine catalyzed by peroxidase-like Pt nanoparticles immobilized in spherical polyelectrolyte brushes
BT  - a kinetic study
JF  - ChemPhysChem
N2  - Experimental and kinetic modelling studies are presented to investigate the mechanism of 3,3 ',5,5 '-tetramethylbenzidine (TMB) oxidation by hydrogen peroxide (H2O2) catalyzed by peroxidase-like Pt nanoparticles immobilized in spherical polyelectrolyte brushes (SPB-Pt). Due to the high stability of SPB-Pt colloidal, this reaction can be monitored precisely in situ by UV/VIS spectroscopy. The time-dependent concentration of the blue-colored oxidation product of TMB expressed by different kinetic models was used to simulate the experimental data by a genetic fitting algorithm. After falsifying the models with abundant experimental data, it is found that both H2O2 and TMB adsorb on the surface of Pt nanoparticles to react, indicating that the reaction follows the Langmuir-Hinshelwood mechanism. A true rate constant k, characterizing the rate-determining step of the reaction and which is independent on the amount of catalysts used, is obtained for the first time. Furthermore, it is found that the product adsorbes strongly on the surface of nanoparticles, thus inhibiting the reaction. The entire analysis provides a new perspective to study the catalytic mechanism and evaluate the catalytic activity of the peroxidase-like nanoparticles.
KW  - kinetics
KW  - nanoparticles
KW  - reaction mechanisms
KW  - spherical polyelectrolyte
KW  - brushes
KW  - UV
KW  - vis spectroscopy
Y1  - 2019
U6  - https://doi.org/10.1002/cphc.201901087
SN  - 1439-4235
SN  - 1439-7641
VL  - 21
IS  - 5
SP  - 450
EP  - 458
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Feldmann, David
A1  - Maduar, Salim R.
A1  - Santer, Mark
A1  - Lomadze, Nino
A1  - Vinogradova, Olga I.
A1  - Santer, Svetlana
T1  - Manipulation of small particles at solid liquid interface
BT  - light driven diffusioosmosis
JF  - Scientific reports
N2  - The strong adhesion of sub-micron sized particles to surfaces is a nuisance, both for removing contaminating colloids from surfaces and for conscious manipulation of particles to create and test novel micro/nano-scale assemblies. The obvious idea of using detergents to ease these processes suffers from a lack of control: the action of any conventional surface-modifying agent is immediate and global. With photosensitive azobenzene containing surfactants we overcome these limitations. Such photo-soaps contain optical switches (azobenzene molecules), which upon illumination with light of appropriate wavelength undergo reversible trans-cis photo-isomerization resulting in a subsequent change of the physico-chemical molecular properties. In this work we show that when a spatial gradient in the composition of trans- and cis- isomers is created near a solid-liquid interface, a substantial hydrodynamic flow can be initiated, the spatial extent of which can be set, e.g., by the shape of a laser spot. We propose the concept of light induced diffusioosmosis driving the flow, which can remove, gather or pattern a particle assembly at a solid-liquid interface. In other words, in addition to providing a soap we implement selectivity: particles are mobilized and moved at the time of illumination, and only across the illuminated area.
KW  - genomic DNA conformation
KW  - photosensitive surfactants
KW  - optical manipulation
KW  - photocontrol
KW  - azobenzene
KW  - films
KW  - gradients
KW  - transport
KW  - tracking
KW  - brushes
Y1  - 2016
U6  - https://doi.org/10.1038/srep36443
SN  - 2045-2322
VL  - 6
PB  - Nature Publishing Group
CY  - London
ER  -