TY  - JOUR
A1  - Bald, Ilko
A1  - Schürmann, Robin Mathis
A1  - Ebel, Kenny
A1  - Nicolas, Christophe
A1  - Milosavljevic, Aleksandar R.
T1  - Role of valence band states and plasmonic enhancement in electron-transfer-induced transformation of nitrothiophenol
JF  - The Journal of Physical Chemistry Letters
N2  - Hot-electron-induced reactions are more and more recognized as a critical and ubiquitous reaction in heterogeneous catalysis. However, the kinetics of these reactions is still poorly understood, which is also due to the complexity of plasmonic nanostructures. We determined the reaction rates of the hot-electron-mediated reaction of 4-nitrothiophenol (NTP) on gold nanoparticles (AuNPs) using fractal kinetics as a function of the laser wavelength and compared them with the plasmonic enhancement of the system. The reaction rates can be only partially explained by the plasmonic response of the NPs. Hence, synchrotron X-ray photoelectron spectroscopy (XPS) measurements of isolated NTP-capped AuNP clusters have been performed for the first time. In this way, it was possible to determine the work function and the accessible valence band states of the NP systems. The results show that besides the plasmonic enhancement, the reaction rates are strongly influenced by the local density of the available electronic states of the system.
Y1  - 2019
UR  - https://pubs.acs.org/doi/10.1021/acs.jpclett.9b00848
U6  - https://doi.org/10.1021/acs.jpclett.9b00848
SN  - 1948-7185
VL  - 10
SP  - 3153
EP  - 3158
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Meiling, Till Thomas
A1  - Schürmann, Robin Mathis
A1  - Vogel, Stefanie
A1  - Ebel, Kenny
A1  - Nicolas, Christophe
A1  - Milosavljevic, Aleksandar R.
A1  - Bald, Ilko
T1  - Photophysics and Chemistry of Nitrogen-Doped Carbon Nanodots with High Photoluminescence Quantum Yield
JF  - The journal of physical chemistry : C, Nanomaterials and interfaces
N2  - Fluorescent carbon nanodots (CNDs) are very promising nanomaterials for a broad range of applications because of their high photostability, presumed selective luminescence, and low cost at which they can be produced. In this respect, CNDs are superior to well-established semiconductor quantum dots and organic dyes. However, reported synthesis protocols for CNDs typically lead to low photoluminescence quantum yield (PLQY) and low reproducibility, resulting in a poor understanding of the CND chemistry and photophysics. Here, we report a one-step synthesis of nitrogen-doped carbon nanodots (N-CNDs) from various carboxylic acids, Tris, and ethylenediaminetetraacetic acid resulting in high PLQY of up to 90%. The reaction conditions in terms of starting materials, temperature, and reaction time are carefully optimized and their influence on the photophysical properties is characterized. We find that citric acid-derived N-CNDs can result in a very high PLQY of 90%, but they do not show selective luminescence. By contrast, acetic acid-derived N-CNDs show selective luminescence but a PLQY of 50%. The chemical composition of the surface and core of these two selected N-CND types is characterized among others by high-resolution synchrotron X-ray photoelectron spectroscopy using single isolated N-CND clusters. The results indicate that photoexcitation occurs in the N-CND core, whereas the emission properties are determined by the N-CND surface groups.
Y1  - 2018
U6  - https://doi.org/10.1021/acs.jpcc.8b00748
SN  - 1932-7447
VL  - 122
IS  - 18
SP  - 10217
EP  - 10230
PB  - American Chemical Society
CY  - Washington
ER  -