TY  - JOUR
A1  - Liebig, Ferenc
A1  - Henning, Ricky
A1  - Sarhan, Radwan Mohamed
A1  - Prietzel, Claudia Christina
A1  - Bargheer, Matias
A1  - Koetz, Joachim
T1  - A new route to gold nanoflowers
JF  - Nanotechnology
N2  - Catanionic vesicles spontaneously formed by mixing the anionic surfactant bis(2-ethylhexyl)sulfosuccinate sodium salt with the cationic surfactant cetyltrimethylammonium bromide were used as a reducing medium to produce gold clusters, which are embedded and well-ordered into the template phase. The gold clusters can be used as seeds in the growth process that follows by adding ascorbic acid as a mild reducing component. When the ascorbic acid was added very slowly in an ice bath round-edged gold nanoflowers were produced. When the same experiments were performed at room temperature in the presence of Ag+ ions, sharp-edged nanoflowers could be synthesized. The mechanism of nanoparticle formation can be understood to be a non-diffusion-limited Ostwald ripening process of preordered gold nanoparticles embedded in catanionic vesicle fragments. Surface-enhanced Raman scattering experiments show an excellent enhancement factor of 1.7 . 10(5) for the nanoflowers deposited on a silicon wafer.
KW  - catanionic vesicles
KW  - gold cluster
KW  - gold nanoflowers
KW  - crystal growth
KW  - HRTEM
KW  - SEM
Y1  - 2018
U6  - https://doi.org/10.1088/1361-6528/aaaffd
SN  - 0957-4484
SN  - 1361-6528
VL  - 29
IS  - 18
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Liebig, Ferenc
A1  - Sarhan, Radwan Mohamed
A1  - Schmitt, Clemens Nikolaus Zeno
A1  - Thünemann, Andreas F.
A1  - Prietzel, Claudia Christina
A1  - Bargheer, Matias
A1  - Koetz, Joachim
T1  - Gold nanotriangles with crumble topping and their influence on catalysis and surface-enhanced raman spectroscopy
JF  - ChemPlusChem
N2  - By adding hyaluronic acid (HA) to dioctyl sodium sulfosuccinate (AOT)-stabilized gold nanotriangles (AuNTs) with an average thickness of 7.5 +/- 1 nm and an edge length of about 175 +/- 17 nm, the AOT bilayer is replaced by a polymeric HA-layer leading to biocompatible nanoplatelets. The subsequent reduction process of tetrachloroauric acid in the HA-shell surrounding the AuNTs leads to the formation of spherical gold nanoparticles on the platelet surface. With increasing tetrachloroauric acid concentration, the decoration with gold nanoparticles can be tuned. SAXS measurements reveal an increase of the platelet thickness up to around 14.5 nm, twice the initial value of bare AuNTs. HRTEM micrographs show welding phenomena between densely packed particles on the platelet surface, leading to a crumble formation while preserving the original crystal structure. Crumbles crystallized on top of the platelets enhance the Raman signal by a factor of around 20, and intensify the plasmon-driven dimerization of 4-nitrothiophenol (4-NTP) to 4,4 '-dimercaptoazobenzene in a yield of up to 50 %. The resulting crumbled nanotriangles, with a biopolymer shell and the absorption maximum in the second window for in vivo imaging, are promising candidates for biomedical sensing.
KW  - gold nanostructures
KW  - HRTEM
KW  - hyaluronic acid
KW  - monolayer formation
KW  - SERS
Y1  - 2020
U6  - https://doi.org/10.1002/cplu.201900745
SN  - 2192-6506
VL  - 85
IS  - 3
SP  - 519
EP  - 526
PB  - Wiley-VCH
CY  - Weinheim
ER  -