TY - JOUR A1 - Gharabekyan, Hrant H. A1 - Koetz, Joachim A1 - Poghosyan, Armen H. T1 - A protonated L-cysteine adsorption on gold surface BT - a molecular dynamics study JF - Colloids and surfaces : an international journal devoted to the principles and applications of colloid and interface science ; A, Physicochemical and engineering aspects N2 - The adsorption of protonated L-cysteine onto Au(111) surface was studied via molecular dynamics method. The detailed examination of trajectories reveals that a couple of picoseconds need to be strongly adsorbed at the gold surface via L-cysteine's sulfur and oxygen atoms. The average distances of L-cysteine's adsorbed sulfur and oxygen from gold plane are-2.7 angstrom and-3.2 angstrom, correspondingly. We found that the adsorption of L-cysteine takes place preferentially at bridge site with possibility of-82%. Discussing the conformation features of protonated L-cysteine, we consider that the most stable conformation of protonated L-cysteine is "reverse boat" position, where sulfur and oxygen pointed down to the gold surface, while the amino group is far from the gold surface. KW - MD simulations KW - gold surface KW - GOIP KW - l-cysteine KW - adsorption KW - protonation Y1 - 2021 U6 - https://doi.org/10.1016/j.colsurfa.2021.127452 SN - 0927-7757 SN - 1873-4359 VL - 629 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Poghosyan, Armen H. A1 - Shahinyan, A. A. A1 - Koetz, Joachim T1 - Self-assembled monolayer formation of distorted cylindrical AOT micelles on gold surfaces JF - Colloids and surfaces : an international journal devoted to the principles and applications of colloid and interface science ; A, Physicochemical and engineering aspects N2 - Self-assembling features of sodium dioctyl sulfosuccinate (AOT) molecules and micelle adsorption on gold Au (111) surfaces have been examined using molecular dynamics simulation. We argue that AOT micelles display a strong adsorption on gold surfaces resulting in distorted cylindrical micelles attached to the (111) facets. The well protected Au(111) facets decorated by a dense packed elongated ellipsoidal AOT layer hinder the diffusion of the reactant to the (111) facets and could result in the preferential growth of ultra-thin gold nanoplatelets. KW - Surfactant micelles KW - Adsorption KW - Gold surface KW - Molecular dynamics Y1 - 2018 U6 - https://doi.org/10.1016/j.colsurfa.2018.02.067 SN - 0927-7757 SN - 1873-4359 VL - 546 SP - 20 EP - 27 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Poghosyan, Armen H. A1 - Shahinyan, A. A. A1 - Koetz, Joachim T1 - Catanionic AOT/BDAC micelles on gold {111} surfaces JF - Colloid and polymer science : official journal of the Kolloid-Gesellschaft N2 - A sodium dioctyl sulfosuccinate (AOT)/benzyl hexadecyl dimethyl ammonium chloride (BDAC) mixed micelle self-organization and adsorption on gold Au(111) surfaces have been investigated using a molecular dynamics approach. The spherical AOT/BDAC mixed micelle is strongly adsorbed on the gold surface and is disoriented to a cylinder-like shape. KW - AOT/BDAC micelles KW - Gold surfaces KW - Molecular dynamics Y1 - 2018 U6 - https://doi.org/10.1007/s00396-018-4348-1 SN - 0303-402X SN - 1435-1536 VL - 296 IS - 8 SP - 1301 EP - 1306 PB - Springer CY - New York ER - TY - JOUR A1 - Poghosyan, Armen H. A1 - Adamyan, Maksim P. A1 - Shahinyan, Aram A. A1 - Koetz, Joachim T1 - AOT Bilayer Adsorption on Gold Surfaces BT - A Molecular Dynamics Study JF - The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces & biophysical chemistry N2 - A molecular dynamics study was done to reveal the adsorption properties of sodium dioctyl sulfosuccinate (AOT) bilayers on gold Au(111) surfaces. Examining the rotational mobility of AOT molecules, we track that the correlation time of AOT molecules on the adsorbed layer is much higher. The data estimating the diffusive motion of AOT molecule show a substantially lower rate of diffusion (similar to 10(-10) cm(2)/s) in the adsorbed layers in comparison to other ones. The results show that an adsorbed layer is more rigid, whereas the outer layers undergo considerable lateral and vertical fluctuations. Y1 - 2019 U6 - https://doi.org/10.1021/acs.jpcb.8b11471 SN - 1520-6106 VL - 123 IS - 4 SP - 948 EP - 953 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Poghosyan, Armen H. A1 - Arsenyan, Levon H. A1 - Shahinyan, Aram A. A1 - Koetz, Joachim T1 - Polyethyleneimine loaded inverse SDS micelle in pentanol/toluene media JF - Colloids and surfaces : an international journal devoted to the principles and applications of colloid and interface science ; A, Physicochemical and engineering aspects N2 - An atomic scale molecular dynamics simulation (100 ns) was carried out to reveal the conformational features of a cationic polyelectrolyte, i.e., hyperbranched polyethyleneimine (PEI), inside of water-in-oil microemulsion droplets stabilized by the anionic sodium dodecyl sulfate surfactant (SDS) layer. Simulations show that the polymer reorients very quickly and is localized at the headgroup region, i.e., the polymer nitrogens are close to SDS sulfur atoms. In spite of the availability of surface roughness caused by the polymer, we track a stable inverse micelle during the production run. In overall, the obtained parameters are well compared with experimental findings. (C) 2016 Elsevier B.V. All rights reserved. KW - SDS inverse micelle KW - Polyethyleneimine KW - Molecular dynamics simulations KW - Microemulsions Y1 - 2016 U6 - https://doi.org/10.1016/j.colsurfa.2016.07.018 SN - 0927-7757 SN - 1873-4359 VL - 506 SP - 402 EP - 408 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Liebig, Ferenc A1 - Sarhan, Radwan Mohamed A1 - Bargheer, Matias A1 - Schmitt, Clemens Nikolaus Zeno A1 - Poghosyan, Armen H. A1 - Shahinyanf, Aram A. A1 - Koetz, Joachim T1 - Spiked gold nanotriangles BT - Formation, characterization and applications in surface-enhanced Raman spectroscopy and plasmon-enhanced catalysis JF - RSC Advances N2 - We show the formation of metallic spikes on the surface of gold nanotriangles (AuNTs) by using the same reduction process which has been used for the synthesis of gold nanostars. We confirm that silver nitrate operates as a shape-directing agent in combination with ascorbic acid as the reducing agent and investigate the mechanism by dissecting the contribution of each component, i.e., anionic surfactant dioctyl sodium sulfosuccinate (AOT), ascorbic acid (AA), and AgNO3. Molecular dynamics (MD) simulations show that AA attaches to the AOT bilayer of nanotriangles, and covers the surface of gold clusters, which is of special relevance for the spike formation process at the AuNT surface. The surface modification goes hand in hand with a change of the optical properties. The increased thickness of the triangles and a sizeable fraction of silver atoms covering the spikes lead to a blue-shift of the intense near infrared absorption of the AuNTs. The sponge-like spiky surface increases both the surface enhanced Raman scattering (SERS) cross section of the particles and the photo-catalytic activity in comparison with the unmodified triangles, which is exemplified by the plasmon-driven dimerization of 4-nitrothiophenol (4-NTP) to 4,4'-dimercaptoazobenzene (DMAB). Y1 - 2020 U6 - https://doi.org/10.1039/d0ra00729c SN - 2046-2069 VL - 10 IS - 14 SP - 8152 EP - 8160 PB - RSC Publishing CY - London ER - TY - GEN A1 - Liebig, Ferenc A1 - Sarhan, Radwan Mohamed A1 - Bargheer, Matias A1 - Schmitt, Clemens Nikolaus Zeno A1 - Poghosyan, Armen H. A1 - Shahinyanf, Aram A. A1 - Koetz, Joachim T1 - Spiked gold nanotriangles BT - Formation, characterization and applications in surface-enhanced Raman spectroscopy and plasmon-enhanced catalysis T2 - Postprints der Universität Potsdam : Mathematisch Naturwissenschaftliche Reihe N2 - We show the formation of metallic spikes on the surface of gold nanotriangles (AuNTs) by using the same reduction process which has been used for the synthesis of gold nanostars. We confirm that silver nitrate operates as a shape-directing agent in combination with ascorbic acid as the reducing agent and investigate the mechanism by dissecting the contribution of each component, i.e., anionic surfactant dioctyl sodium sulfosuccinate (AOT), ascorbic acid (AA), and AgNO3. Molecular dynamics (MD) simulations show that AA attaches to the AOT bilayer of nanotriangles, and covers the surface of gold clusters, which is of special relevance for the spike formation process at the AuNT surface. The surface modification goes hand in hand with a change of the optical properties. The increased thickness of the triangles and a sizeable fraction of silver atoms covering the spikes lead to a blue-shift of the intense near infrared absorption of the AuNTs. The sponge-like spiky surface increases both the surface enhanced Raman scattering (SERS) cross section of the particles and the photo-catalytic activity in comparison with the unmodified triangles, which is exemplified by the plasmon-driven dimerization of 4-nitrothiophenol (4-NTP) to 4,4'-dimercaptoazobenzene (DMAB). T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 829 Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-445568 SN - 1866-8372 IS - 829 ER - TY - JOUR A1 - Poghosyan, Armen H. A1 - Arsenyan, Levon H. A1 - Antonyan, Lilit A. A1 - Shahinyan, Aram A. A1 - Koetz, Joachim T1 - Molecular dynamics simulations of branched polyethyleneimine in water-in-heptanol micelles stabilized by zwitterionic surfactants JF - Colloids and surfaces : an international journal devoted to the principles and applications of colloid and interface science ; A, Physicochemical and engineering aspects N2 - We have performed a 50 ns molecular dynamics simulation of a hyperbranched polymer, i.e. polyethyleneimine (PEI), inside inverse micelles formed with zwitterionic surfactants 3-(N, N-dimethyldodecylammoniio)-propansulfonate (SB) in heptanol. The runs were performed using the GROMACS simulation package. During simulation time the PEI molecule undergoes a conformational deformation and compaction. The radius of gyration of the PEI molecule finally located in the center of the water droplet is decreased from 3 nm to 1.7 nm. The unusual shrinking of the PEI molecule inside the micelle explains the extraordinary template effect of these microemulsions by making cadmium sulfide or gold clusters. (C) 2015 Elsevier B.V. All rights reserved. KW - Surfactant micelles KW - Molecular dynamics simulations KW - Polyethyleneimine Y1 - 2015 U6 - https://doi.org/10.1016/j.colsurfa.2015.03.053 SN - 0927-7757 SN - 1873-4359 VL - 479 SP - 18 EP - 24 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Poghosyan, Armen H. A1 - Arsenyan, Levon H. A1 - Gharabekyan, Hrant H. A1 - Falkenhagen, Sandra A1 - Koetz, Joachim A1 - Shahinyan, Aram A. T1 - Molecular dynamics simulations of inverse sodium dodecyl sulfate (SDS) micelles in a mixed toluene/pentanol solvent in the absence and presence of poly(diallyldimethylammonium chloride) (PDADMAC) JF - Journal of colloid and interface science N2 - We have performed a 15 ns molecular dynamics simulation of inverse sodium dodecyl sulfate (SDS) micelles in a mixed toluene/pentanol solvent in the absence and presence of a cationic polyelectrolyte, i.e. poly(diallyldimethylammonium chloride) (PDADMAC). The NAMD code and CHARMM force field were used. During the simulation time, the radii of SOS inverse micelles changed and the radii of the water droplets have been calculated. The behavior of SDS hydrocarbon chains has been characterized by calculating the orientation order parameter and the chain average length. The water droplet properties (water flow, water molecules displacement) have been examined. In summary the MD simulations indicate a more rigid and ordered surfactant film due to the formation of a polyelectrolyte palisade layer in full agreement with the experimental findings, e.g. the viscosity increase and shift of the percolation boundary. KW - Surfactant micelles KW - Molecular dynamics simulations KW - SDS Y1 - 2011 U6 - https://doi.org/10.1016/j.jcis.2011.01.091 SN - 0021-9797 VL - 358 IS - 1 SP - 175 EP - 181 PB - Elsevier CY - San Diego ER - TY - JOUR A1 - Poghosyan, Armen H. A1 - Arsenyan, Levon H. A1 - Gharabekyan, Hrant H. A1 - Koetz, Joachim A1 - Shahinyan, Aram A. T1 - Molecular dynamics study of poly(diallyldimethylammonium chloride) (PDADMAC)/sodium dodecyl sulfate (SDS)/ decanol/water systems N2 - We have performed a 50 ns of molecular dynamics study of poly(diallyldimethylammonium chloride) (PDADMAC)/ sodium dodecyl sulfate (SDS)/decanol/water systems. The influence of the cationic polyelectrolyte on the anionic SDS- based lamellar liquid crystalline system was investigated. The main structural parameters have been calculated and compared with experimental data. We obtain two types of PDADMAC conformation, a more folded structure A and a structure B where the PDADMAC molecule is adsorbed at the anionic head groups of the surfactant molecules. The polyelectrolyte- induced coexistence of two lamellar phases at a concentration of 2-3% of PDADMAC is observed, which is in agreement with experimental findings. Y1 - 2009 UR - http://pubs.acs.org/journal/jpcbfk U6 - https://doi.org/10.1021/Jp806289c SN - 1520-6106 ER -