TY  - JOUR
A1  - Bekir, Marek
A1  - Jelken, Joachim
A1  - Jung, Se-Hyeong
A1  - Pich, Andrij
A1  - Pacholski, Claudia
A1  - Kopyshev, Alexey
A1  - Santer, Svetlana
T1  - Dual responsiveness of microgels induced by single light stimulus
JF  - Applied physics letters
N2  - We report on the multiple response of microgels triggered by a single optical stimulus. Under irradiation, the volume of the microgels is reversibly switched by more than 20 times. The irradiation initiates two different processes: photo-isomerization of the photo-sensitive surfactant, which forms a complex with the anionic microgel, rendering it photo-responsive; and local heating due to a thermo-plasmonic effect within the structured gold layer on which the microgel is deposited. The photo-responsivity is related to the reversible accommodation/release of the photo-sensitive surfactant depending on its photo-isomerization state, while the thermo-sensitivity is intrinsically built in. We show that under exposure to green light, the thermo-plasmonic effect generates a local hot spot in the gold layer, resulting in the shrinkage of the microgel. This process competes with the simultaneous photo-induced swelling. Depending on the position of the laser spot, the spatiotemporal control of reversible particle shrinking/swelling with a predefined extent on a per-second base can be implemented.
Y1  - 2021
U6  - https://doi.org/10.1063/5.0036376
SN  - 0003-6951
SN  - 1077-3118
VL  - 118
IS  - 9
PB  - American Institute of Physics
CY  - Melville
ER  - 
TY  - JOUR
A1  - Zakrevskyy, Yuriy
A1  - Kopyshev, Alexey
A1  - Lomadze, Nino
A1  - Morozova, Elena
A1  - Lysyakova, Liudmila
A1  - Kasyanenko, Nina
A1  - Santer, Svetlana
T1  - DNA compaction by azobenzene-containing surfactant
JF  - Physical review : E, Statistical, nonlinear and soft matter physics
N2  - We report on the interaction of cationic azobenzene-containing surfactant with DNA investigated by absorption and fluorescence spectroscopy, dynamic light scattering, and atomic force microscopy. The properties of the surfactant can be controlled with light by reversible switching of the azobenzene unit, incorporated into the surfactant tail, between a hydrophobic trans (visible irradiation) and a hydrophilic cis (UV irradiation) configuration. The influence of the trans-cis isomerization of the azobenzene on the compaction process of DNA molecules and the role of both isomers in the formation and colloidal stability of DNA-surfactant complexes is discussed. It is shown that the trans isomer plays a major role in the DNA compaction process. The influence of the cis isomer on the DNA coil configuration is rather small. The construction of a phase diagram of the DNA concentration versus surfactant/DNA charge ratio allows distancing between three major phases: colloidally stable and unstable compacted globules, and extended coil conformation. There is a critical concentration of DNA above which the compacted globules can be hindered from aggregation and precipitation by adding an appropriate amount of the surfactant in the trans configuration. This is because of the compensation of hydrophobicity of the globules with an increasing amount of the surfactant. Below the critical DNA concentration, the compacted globules are colloidally stable and can be reversibly transferred with light to an extended coil state.
Y1  - 2011
U6  - https://doi.org/10.1103/PhysRevE.84.021909
SN  - 1539-3755
VL  - 84
IS  - 2
PB  - American Physical Society
CY  - College Park
ER  - 
TY  - JOUR
A1  - König, Tobias
A1  - Papke, Thomas
A1  - Kopyshev, Alexey
A1  - Santer, Svetlana
T1  - Atomic force microscopy nanolithography fabrication of metallic nano-slits using silicon nitride tips
JF  - Journal of materials science
N2  - In this paper, we report on the properties of nano-slits created in metal thin films using atomic force microscope (AFM) nanolithography (AFM-NL). We demonstrate that instead of expensive diamond AFM tips, it is also possible to use low cost silicon nitride tips. It is shown that depending on the direction of scratching, nano-slits of different widths and depths can be fabricated at constant load force. We elucidate the reasons for this behavior and identify an optimal direction and load force for scratching a gold layer.
Y1  - 2013
U6  - https://doi.org/10.1007/s10853-013-7188-x
SN  - 0022-2461
VL  - 48
IS  - 10
SP  - 3863
EP  - 3869
PB  - Springer
CY  - New York
ER  -