TY - JOUR A1 - Polley, Nabarun A1 - Werner, Peter A1 - Balderas-Valadez, Ruth Fabiola A1 - Pacholski, Claudia T1 - Bottom, top, or in between BT - combining plasmonic nanohole arrays and hydrogel microgels for optical fiber snsor applications JF - Advanced materials interfaces N2 - Attractive label-free plasmonic optical fiber sensors can be developed by cleverly choosing the arrangement of plasmonic nanostructures and other building blocks. Here, the final response depends very much on the alignment and position (stacking) of the individual elements. In this work, three different types of fiber optic sensing geometries fabricated by simple layer-by-layer stacking are presented, consisting of stimulus-sensitive poly-N-isopropylacrylamide (polyNIPAM) microgel arrays and plasmonic nanohole arrays (NHAs), namely NHA/polyNIPAM, polyNIPAM/NHA, polyNIPAM/NHA/polyNIPAM. Their optical response to a representative stimulus, namely temperature, is investigated. NHA/polyNIPAM monitors the volume phase transition of polyNIPAM microgels through changes in the spectral position and the amplitude of the reflection minimum of plasmonic NHA. In contrast, polyNIPAM/NHA shows a more complex response to the swelling and collapse of polyNIPAM microgels in their reflectance spectra. The most pronounced changes in optical response are observed by monitoring the amplitude of the reflectance minimum of this sensor during heating/cooling cycles. Finally, the triple stack of polyNIPAM/NHA/polyNIPAM at the end of a optical fiber tip combines the advantages of the NHA/polyNIPAM, polyNIPAM/NHA double stacks for optical sensing. The unique layer-by-layer stacking of microgel and nanostructure is customizable and can be easily adopted for other applications. KW - bottom-up fabrication KW - layer-by-layer stacking KW - microgel arrays KW - optical KW - fiber sensors KW - plasmonic nanohole arrays Y1 - 2022 U6 - https://doi.org/10.1002/admi.202102312 SN - 2196-7350 VL - 9 IS - 15 PB - Wiley CY - Hoboken ER - TY - GEN A1 - Pacholski, Claudia A1 - Agarwal, Vivechana A1 - Balderas-Valadez, Ruth Fabiola T1 - Fabrication of porous silicon-based optical sensors using metal-assisted chemical etching N2 - Optical biosensors based on porous silicon were fabricated by metal assisted chemical etching. Thereby double layered porous silicon structures were obtained consisting of porous pillars with large pores on top of a porous silicon layer with smaller pores. These structures showed a similar sensing performance in comparison to electrochemically produced porous silicon interferometric sensors. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 316 KW - fourier-transform spectroscopy KW - nanostructures KW - nanowires Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-394426 SP - 21430 EP - 21434 ER - TY - JOUR A1 - Balderas-Valadez, Ruth Fabiola A1 - Antunez, E. E. A1 - Olive-Mendez, Sion Federico A1 - Pacholski, Claudia A1 - Campos-Alvarez, Jose A1 - Bokhimi, Xim A1 - Agarwal, V. T1 - Porous silicon pillar and bilayer structure as a nucleation center for the formation of aligned vanadium pentoxide nanorods JF - Ceramics International N2 - Porous silicon single layer (PSM), bilayer (PSB) and pillar (PSP) structures have been evaluated as nucleation centers for vanadium pentoxide (V2O5) crystals. Deposition of vanadium precursor over different substrates (drop casting technique), followed by annealing treatment under Ar-H-2 (5% H-2) atmosphere, induced crystallization of vanadium oxide. With respect to c-Si/SiO2 substrate, V2O5 nanorods with relatively large aspect ratio were formed over and within PSP structures. On the other hand, pores in PSM and PSB were found to be filled with relatively smaller crystals. Additionally, PSB provided a nucleation substrate capable to align the nanocrystals in a preferential orientation, while V2O5 crystals grown on PSP were found to be randomly aligned around the nanoporous pillar microstructure. Nanorods and nanocrystals were identified as V2O5 by temperature-controlled XRD measurements and evidence of their crystalline nature was observed via transmission electron microscopy. A careful analysis of electronic microscopy images allows the identification of the facets composing the ends of the crystals and its corresponding surface free energy has been evaluated employing the Wulff theorem. Such high surface area composite structures have potential applications as cathode material in Lithium-ion batteries. KW - Porous silicon KW - Vanadium pentoxide KW - Nanorods KW - Crystallization KW - Nanostructures Y1 - 2017 U6 - https://doi.org/10.1016/j.ceramint.2017.03.114 SN - 0272-8842 SN - 1873-3956 VL - 43 SP - 8023 EP - 8030 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Balderas-Valadez, Ruth Fabiola A1 - Schürmann, Robin Mathis A1 - Pacholski, Claudia T1 - One Spot-Two Sensors: Porous Silicon Interferometers in Combination With Gold Nanostructures Showing Localized Surface Plasmon Resonance JF - Frontiers in chemistry N2 - Sensors composed of a porous silicon monolayer covered with a film of nanostructured gold layer, which provide two optical signal transduction methods, are fabricated and thoroughly characterized concerning their sensing performance. For this purpose, silicon substrates were electrochemically etched in order to obtain porous silicon monolayers, which were subsequently immersed in gold salt solution facilitating the formation of a porous gold nanoparticle layer on top of the porous silicon. The deposition process was monitored by reflectance spectroscopy, and the appearance of a dip in the interference pattern of the porous silicon layer was observed. This dip can be assigned to the absorption of light by the deposited gold nanostructures leading to localized surface plasmon resonance. The bulk sensitivity of these sensors was determined by recording reflectance spectra in media having different refractive indices and compared to sensors exclusively based on porous silicon or gold nanostructures. A thorough analysis of resulting shifts of the different optical signals in the reflectance spectra on the wavelength scale indicated that the optical response of the porous silicon sensor is not influenced by the presence of a gold nanostructure on top. Moreover, the adsorption of thiol-terminated polystyrene to the sensor surface was solely detected by changes in the position of the dip in the reflectance spectrum, which is assigned to localized surface plasmon resonance in the gold nanostructures. The interference pattern resulting from the porous silicon layer is not shifted to longer wavelengths by the adsorption indicating the independence of the optical response of the two nanostructures, namely porous silicon and nanostructured gold layer, to refractive index changes and pointing to the successful realization of two sensors in one spot. KW - porous silicon KW - interferometry KW - gold nanostructures KW - surface plasmon resonance KW - optical sensor Y1 - 2019 U6 - https://doi.org/10.3389/fchem.2019.00593 SN - 2296-2646 VL - 7 PB - Frontiers Research Foundation CY - Lausanne ER - TY - JOUR A1 - Balderas-Valadez, Ruth Fabiola A1 - Pacholski, Claudia T1 - Plasmonic Nanohole Arrays on Top of Porous Silicon Sensors BT - A Win-Win Situation JF - ACS applied materials & interfaces N2 - Label-free optical sensors are attractive candidates, for example, for detecting toxic substances and monitoring biomolecular interactions. Their performance can be pushed by the design of the sensor through clever material choices and integration of components. In this work, two porous materials, namely, porous silicon and plasmonic nanohole arrays, are combined in order to obtain increased sensitivity and dual-mode sensing capabilities. For this purpose, porous silicon monolayers are prepared by electrochemical etching and plasmonic nanohole arrays are obtained using a bottom-up strategy. Hybrid sensors of these two materials are realized by transferring the plasmonic nanohole array on top of the porous silicon. Reflectance spectra of the hybrid sensors are characterized by a fringe pattern resulting from the Fabry–Pérot interference at the porous silicon borders, which is overlaid with a broad dip based on surface plasmon resonance in the plasmonic nanohole array. In addition, the hybrid sensor shows a significant higher reflectance in comparison to the porous silicon monolayer. The sensitivities of the hybrid sensor to refractive index changes are separately determined for both components. A significant increase in sensitivity from 213 ± 12 to 386 ± 5 nm/RIU is determined for the transfer of the plasmonic nanohole array sensors from solid glass substrates to porous silicon monolayers. In contrast, the spectral position of the interference pattern of porous silicon monolayers in different media is not affected by the presence of the plasmonic nanohole array. However, the changes in fringe pattern reflectance of the hybrid sensor are increased 3.7-fold after being covered with plasmonic nanohole arrays and could be used for high-sensitivity sensing. Finally, the capability of the hybrid sensor for simultaneous and independent dual-mode sensing is demonstrated. KW - optical sensors KW - porous silicon KW - surface plasmon resonance KW - plasmonic KW - nanohole arrays KW - bottom-up fabrication Y1 - 2021 U6 - https://doi.org/10.1021/acsami.1c07034 SN - 1944-8244 SN - 1944-8252 VL - 13 IS - 30 SP - 36436 EP - 36444 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Stanglmair, Christoph A1 - Neubrech, Frank A1 - Pacholski, Claudia T1 - Chemical routes to surface enhanced infrared absorption (SEIRA) substrates JF - Zeitschrift für physikalische Chemie : international journal of research in physical chemistry and chemical physics N2 - Bottom-up strategies for fabricating SEIRA substrates are presented. For this purpose, wet-chemically prepared gold nanoparticles are coated with a polystyrene shell and subsequently self-assembled into different nanostructures such as quasi-hexagonally ordered gold nanoparticle monolayers, double layers, and honeycomb structures. Furthermore elongated gold nanostructures are obtained by sintering of gold nanoparticle double layers. The optical properties of these different gold nanostructures are directly connected to their morphology and geometrical arrangement - leading to surface plasmon resonances from the visible to the infrared wavelength range. Finally, SEIRA enhancement factors are determined. Gold nanoparticle double layers show the best performance as SEIRA substrates. KW - bottom-up KW - gold nanoparticles KW - self-assembly KW - surface enhanced spectroscopy Y1 - 2018 U6 - https://doi.org/10.1515/zpch-2018-1132 SN - 0942-9352 VL - 232 IS - 9-11 SP - 1527 EP - 1539 PB - De Gruyter CY - Berlin ER - TY - JOUR A1 - Holland-Moritz, Henry A1 - Graupner, Julia A1 - Möller, Wolfhard A1 - Pacholski, Claudia A1 - Ronning, Carsten T1 - Dynamics of nanoparticle morphology under low energy ion irradiation JF - Nanotechnology N2 - If nanostructures are irradiated with energetic ions, the mechanism of sputtering becomes important when the ion range matches about the size of the nanoparticle. Gold nanoparticles with diameters of similar to 50 nm on top of silicon substrates with a native oxide layer were irradiated by gallium ions with energies ranging from 1 to 30 keV in a focused ion beam system. High resolution in situ scanning electron microscopy imaging permits detailed insights in the dynamics of the morphology change and sputter yield. Compared to bulk-like structures or thin films, a pronounced shaping and enhanced sputtering in the nanostructures occurs, which enables a specific shaping of these structures using ion beams. This effect depends on the ratio of nanoparticle size and ion energy. In the investigated energy regime, the sputter yield increases at increasing ion energy and shows a distinct dependence on the nanoparticle size. The experimental findings are directly compared to Monte Carlo simulations obtained from iradina and TRI3DYN, where the latter takes into account dynamic morphological and compositional changes of the target. KW - ion beam KW - nanoparticles KW - sputtering KW - Monte Carlo KW - in situ Y1 - 2018 U6 - https://doi.org/10.1088/1361-6528/aac36c SN - 0957-4484 SN - 1361-6528 VL - 29 IS - 31 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Polley, Nabarun A1 - Basak, Supratim A1 - Hass, Roland A1 - Pacholski, Claudia T1 - Fiber optic plasmonic sensors BT - Providing sensitive biosensor platforms with minimal lab equipment JF - Biosensors and bioelectronics : the principal international journal devoted to research, design development and application of biosensors and bioelectronics N2 - A simple, convenient, and inexpensive method to fabricate optical fiber based biosensors which utilize periodic hole arrays in gold films for signal transduction is reported. The process of hole array formation mainly relies on self-assembly of hydrogel microgels in combination with chemical gold film deposition and subsequent transfer of the perforated film onto an optical fiber tip. In the fabrication process solely chemical wet lab techniques are used, avoiding cost-intensive instrumentation or clean room facilities. The presented method for preparing fiber optic plasmonic sensors provides high throughput and is perfectly suited for commercialization using batch processing. The transfer of the perforated gold film onto an optical fiber tip does not affect the sensitivity of the biosensor ((420 +/- 83) nm/refractive index unit (RIU)), which is comparable to sensitivities of sensor platforms based on periodic hole arrays in gold films prepared by significantly more complex methods. Furthermore, real-time and in-line immunoassay studies with a specially designed 3D printed flow cell are presented exploiting the presented optical fiber based biosensors. KW - Surface plasmon resonance KW - Optical fiber KW - Bottom-up fabrication KW - Biosensor KW - 3D printed flow-cell Y1 - 2019 U6 - https://doi.org/10.1016/j.bios.2019.03.020 SN - 0956-5663 SN - 1873-4235 VL - 132 SP - 368 EP - 374 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Semenyshyn, Rostyslav A1 - Hentschel, Mario A1 - Stanglmair, Christoph A1 - Teutsch, Tanja A1 - Tarin, Cristina A1 - Pacholski, Claudia A1 - Giessen, Harald A1 - Neubrech, Frank T1 - In vitro monitoring conformational changes of polypeptide monolayers using infrared plasmonic nanoantennas JF - Nano letters : a journal dedicated to nanoscience and nanotechnology N2 - Proteins and peptides play a predominant role in biochemical reactions of living cells. In these complex environments, not only the constitution of the molecules but also their three-dimensional configuration defines their functionality. This so-called secondary structure of proteins is crucial for understanding their function in living matter. Misfolding, for example, is suspected as the cause of neurodegenerative diseases such as Alzheimer’s and Parkinson’s disease. Ultimately, it is necessary to study a single protein and its folding dynamics. Here, we report a first step in this direction, namely ultrasensitive detection and discrimination of in vitro polypeptide folding and unfolding processes using resonant plasmonic nanoantennas for surface-enhanced vibrational spectroscopy. We utilize poly-l-lysine as a model system which has been functionalized on the gold surface. By in vitro infrared spectroscopy of a single molecular monolayer at the amide I vibrations we directly monitor the reversible conformational changes between α-helix and β-sheet states induced by controlled external chemical stimuli. Our scheme in combination with advanced positioning of the peptides and proteins and more brilliant light sources is highly promising for ultrasensitive in vitro studies down to the single protein level. KW - Plasmonics KW - surface-enhanced infrared absorption spectroscopy KW - proteins KW - conformational changes KW - biosensing Y1 - 2019 U6 - https://doi.org/10.1021/acs.nanolett.8b02372 SN - 1530-6984 SN - 1530-6992 VL - 19 IS - 1 SP - 1 EP - 7 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Balderas-Valadez, Ruth Fabiola A1 - Estevez-Espinoza, J. O. A1 - Salazar-Kuri, U. A1 - Pacholski, Claudia A1 - Mochan, Wolf Luis A1 - Agarwal, Vivechana T1 - Fabrication of ordered tubular porous silicon structures by colloidal lithography and metal assisted chemical etching BT - SERS performance of 2D porous silicon structures JF - Applied surface science : a journal devoted to applied physics and chemistry of surfaces and interfaces N2 - Fabrication of well-ordered porous silicon tubular structures using colloidal lithography and metal assisted chemical etching is reported. A continuous hexagonal hole/particle gold pattern was designed over monocrystalline silicon through deposition of polyNIPAM microspheres, followed by the surface decoration with gold nanoparticles and thermal treatment. An etching reaction with HF, ethanol and H2O2 dissolved the silicon in contact with the metal nanoparticles (NP), creating a porous tubular array in the "off-metal area". The morphological characterization revealed the formation of a cylindrical hollow porous tubular shape with external and internal diameter of approx. 900 nm and 400 nm respectively, though it can be tuned to other desired sizes by choosing an appropriate dimension for the microspheres. The porous morphology and optical properties were studied as a function of resistivity of silicon substrates. Compared to two different gold templates on cSi and nontubular porous pillar structures, porous silicon tubular framework revealed a maximum surface enhanced Raman scattering enhancement factor of 10(6) for the detection of 6-mercaptopurine (6-MP). Due to the large surface area available for any surface modification, open nanostructured platforms such as those studied here have potential applications in the field of reflection/photoluminescene and SERS based optical bio-/chemical sensors. KW - SERS KW - Porous silicon KW - MACE KW - Colloidal lithography KW - PolyNIPAM KW - 6-Mercaptopurine Y1 - 2018 U6 - https://doi.org/10.1016/j.apsusc.2018.08.120 SN - 0169-4332 SN - 1873-5584 VL - 462 SP - 783 EP - 790 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Balderas-Valadez, Ruth Fabiola A1 - Agarwal, Vivechana A1 - Pacholski, Claudia T1 - Fabrication of porous silicon-based optical sensors using metal-assisted chemical etching JF - RSC Advances N2 - Optical biosensors based on porous silicon were fabricated by metal assisted chemical etching. Thereby double layered porous silicon structures were obtained consisting of porous pillars with large pores on top of a porous silicon layer with smaller pores. These structures showed a similar sensing performance in comparison to electrochemically produced porous silicon interferometric sensors. Y1 - 2016 U6 - https://doi.org/10.1039/c5ra26816h SN - 2046-2069 VL - 6 SP - 21430 EP - 21434 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Schürmann, Robin A1 - Nagel, Alessandro A1 - Juergensen, Sabrina A1 - Pathak, Anisha A1 - Reich, Stephanie A1 - Pacholski, Claudia A1 - Bald, Ilko T1 - Microscopic understanding of reaction rates observed in plasmon chemistry of nanoparticle-ligand systems JF - The journal of physical chemistry : C, Nanomaterials and interfaces N2 - Surface-enhanced Raman scattering (SERS) is an effective and widely used technique to study chemical reactions induced or catalyzed by plasmonic substrates, since the experimental setup allows us to trigger and track the reaction simultaneously and identify the products. However, on substrates with plasmonic hotspots, the total signal mainly originates from these nanoscopic volumes with high reactivity and the information about the overall consumption remains obscure in SERS measurements. This has important implications; for example, the apparent reaction order in SERS measurements does not correlate with the real reaction order, whereas the apparent reaction rates are proportional to the real reaction rates as demonstrated by finite-difference time-domain (FDTD) simulations. We determined the electric field enhancement distribution of a gold nanoparticle (AuNP) monolayer and calculated the SERS intensities in light-driven reactions in an adsorbed self-assembled molecular monolayer on the AuNP surface. Accordingly, even if a high conversion is observed in SERS due to the high reactivity in the hotspots, most of the adsorbed molecules on the AuNP surface remain unreacted. The theoretical findings are compared with the hot-electron-induced dehalogenation of 4-bromothiophenol, indicating a time dependency of the hot-carrier concentration in plasmon-mediated reactions. To fit the kinetics of plasmon-mediated reactions in plasmonic hotspots, fractal-like kinetics are well suited to account for the inhomogeneity of reactive sites on the substrates, whereas also modified standard kinetics model allows equally well fits. The outcomes of this study are on the one hand essential to derive a mechanistic understanding of reactions on plasmonic substrates by SERS measurements and on the other hand to drive plasmonic reactions with high local precision and facilitate the engineering of chemistry on a nanoscale. Y1 - 2022 U6 - https://doi.org/10.1021/acs.jpcc.2c00278 SN - 1932-7447 SN - 1932-7455 VL - 126 IS - 11 SP - 5333 EP - 5342 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Weiler, Markus A1 - Menzel, Christoph A1 - Pertsch, Thomas A1 - Alaee, Rasoul A1 - Rockstuhl, Carsten A1 - Pacholski, Claudia T1 - Bottom-Up Fabrication of Hybrid Plasmonic Sensors: Gold-Capped Hydrogel Microspheres Embedded in Periodic Metal Hole Arrays JF - Polymer : the international journal for the science and technology of polymers N2 - The high potential of bottom-up fabrication strategies for realizing sophisticated optical sensors combining the high sensitivity of a surface plasmon resonance with the exceptional properties of stimuli-responsive hydrogel is demonstrated. The sensor is composed of a periodic hole array in a gold film whose holes are filled with gold-capped poly(N-isoproyl-acrylamide) (polyNIPAM) microspheres. The production of this sensor relies on a pure chemical approach enabling simple, time-efficient, and cost-efficient preparation of sensor platforms covering areas of cm(2). The transmission spectrum of this plasmonic sensor shows a strong interaction between propagating surface plasmon polaritons at the metal film surface and localized surface plasmon resonance of the gold cap on top of the polyNIPAM microspheres. Computer simulations support this experimental observation. These interactions lead to distinct changes in the transmission spectrum, which allow for the simultaneous, sensitive optical detection of refractive index changes in the surrounding medium and the swelling state of the embedded polyNIPAM microsphere under the gold cap. The volume of the polyNIPAM microsphere located underneath the gold cap can be changed by certain stimuli such as temperature, pH, ionic strength, and distinct molecules bound to the hydrogel matrix facilitating the detection of analytes which do not change the refractive index of the surrounding medium significantly. KW - bottom-up KW - hydrogel KW - hole array KW - sensor KW - surface plasmon resonance Y1 - 2016 U6 - https://doi.org/10.1021/acsami.6b08636 SN - 1944-8244 VL - 8 SP - 26392 EP - 26399 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Fallah, Mohammad A. A1 - Stanglmair, Christoph A1 - Pacholski, Claudia A1 - Hauser, Karin T1 - Devising Self-Assembled-Monolayers for Surface-Enhanced Infrared Spectroscopy of pH-Driven Poly-L-lysine Conformational Changes JF - Langmuir N2 - Surface-enhanced infrared absorption spectroscopy (SEIRA) is applied to study protein conformational changes. In general, the appropriate functionalization of metal surfaces with biomolecules remains a challenge if the conformation and activity of the biomolecule shall be preserved. Here we present a SEIRA study to monitor pH-induced conformational changes of poly-L lysine (PLL) covalently bound to a thin gold layer via self assembled monolayers (SAMs). We demonstrate that the composition of the SAM is crucial. A SAM of 11-mercaptoundecanonic acid (MUA) can link PLL to the gold layer, but pH-driven conformational transitions were hindered compared to poly-L lysine in solution. To address this problem, we devised a variety of SAMs, i.e., mixed SAMs of MUA with either octanethiol (OT) or 11-mercapto-1-undecanol (MUoL) and furthermore SAMs of MT(PEG)(4) and NHS-PEG(10k)-SH. These mixed SAMs modify the surface properties by changing the polarity and the morphology of the surface present to nearby PLL molecules. Our experiments reveal that mixed SAMs of MUA-MUoL and SAMs of NHS-PEG(10k)-SH-MT(PEG)(4) are suitable to monitor pH-driven conformational changes of immobilized PLL. These SAMs might be applicable for chemoselective protein immobilization in general. Y1 - 2016 U6 - https://doi.org/10.1021/acs.langmuir.6b01742 SN - 0743-7463 VL - 32 SP - 7356 EP - 7364 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Pacholski, Claudia A1 - Rosencrantz, Sophia A1 - Rosencrantz, Ruben R. A1 - Balderas-Valadez, Ruth Fabiola T1 - Plasmonic biosensors fabricated by galvanic displacement reactions for monitoring biomolecular interactions in real time JF - Analytical and bioanalytical chemistry : a merger of Fresenius' journal of analytical chemistry, Analusis and Quimica analitica N2 - Optical sensors are prepared by reduction of gold ions using freshly etched hydride-terminated porous silicon, and their ability to specifically detect binding between protein A/rabbit IgG and asialofetuin/Erythrina cristagalli lectin is studied. The fabrication process is simple, fast, and reproducible, and does not require complicated lab equipment. The resulting nanostructured gold layer on silicon shows an optical response in the visible range based on the excitation of localized surface plasmon resonance. Variations in the refractive index of the surrounding medium result in a color change of the sensor which can be observed by the naked eye. By monitoring the spectral position of the localized surface plasmon resonance using reflectance spectroscopy, a bulk sensitivity of 296 nm +/- 3 nm/RIU is determined. Furthermore, selectivity to target analytes is conferred to the sensor through functionalization of its surface with appropriate capture probes. For this purpose, biomolecules are deposited either by physical adsorption or by covalent coupling. Both strategies are successfully tested, i.e., the optical response of the sensor is dependent on the concentration of respective target analyte in the solution facilitating the determination of equilibrium dissociation constants for protein A/rabbit IgG as well as asialofetuin/Erythrina cristagalli lectin which are in accordance with reported values in literature. These results demonstrate the potential of the developed optical sensor for cost-efficient biosensor applications. KW - Optical sensor KW - Gold nanostructure KW - Localized surface plasmon resonance KW - Surface functionalization KW - Biomolecular interactions KW - Lectin Y1 - 2020 U6 - https://doi.org/10.1007/s00216-020-02414-0 SN - 1618-2642 SN - 1618-2650 VL - 412 IS - 14 SP - 3433 EP - 3445 PB - Springer CY - Heidelberg ER - TY - GEN A1 - Behrens, Karsten A1 - Balischewski, Christian A1 - Sperlich, Eric A1 - Menski, Antonia Isabell A1 - Balderas-Valadez, Ruth Fabiola A1 - Pacholski, Claudia A1 - Günter, Christina A1 - Lubahn, Susanne A1 - Kelling, Alexandra A1 - Taubert, Andreas T1 - Mixed chloridometallate(ii) ionic liquids with tunable color and optical response for potential ammonia sensors T2 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - Eight d-metal-containing N-butylpyridinium ionic liquids (ILs) with the nominal composition (C4Py)2[Ni0.5M0.5Cl4] or (C4Py)2[Zn0.5M0.5Cl4] (M = Cu, Co, Mn, Ni, Zn; C4Py = N-butylpyridinium) were synthesized, characterized, and investigated for their optical properties. Single crystal and powder X-ray analysis shows that the compounds are isostructural to existing examples based on other d-metal ions. Inductively coupled plasma optical emission spectroscopy measurements confirm that the metal/metal ratio is around 50 : 50. UV-Vis spectroscopy shows that the optical absorption can be tuned by selection of the constituent metals. Moreover, the compounds can act as an optical sensor for the detection of gases such as ammonia as demonstrated via a simple prototype setup. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1316 Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-587512 SN - 1866-8372 IS - 1316 SP - 35072 EP - 35082 ER - TY - JOUR A1 - Behrens, Karsten A1 - Balischewski, Christian A1 - Sperlich, Eric A1 - Menski, Antonia Isabell A1 - Balderas-Valadez, Ruth Fabiola A1 - Pacholski, Claudia A1 - Günter, Christina A1 - Lubahn, Susanne A1 - Kelling, Alexandra A1 - Taubert, Andreas T1 - Mixed chloridometallate(ii) ionic liquids with tunable color and optical response for potential ammonia sensors JF - RSC Advances N2 - Eight d-metal-containing N-butylpyridinium ionic liquids (ILs) with the nominal composition (C4Py)2[Ni0.5M0.5Cl4] or (C4Py)2[Zn0.5M0.5Cl4] (M = Cu, Co, Mn, Ni, Zn; C4Py = N-butylpyridinium) were synthesized, characterized, and investigated for their optical properties. Single crystal and powder X-ray analysis shows that the compounds are isostructural to existing examples based on other d-metal ions. Inductively coupled plasma optical emission spectroscopy measurements confirm that the metal/metal ratio is around 50 : 50. UV-Vis spectroscopy shows that the optical absorption can be tuned by selection of the constituent metals. Moreover, the compounds can act as an optical sensor for the detection of gases such as ammonia as demonstrated via a simple prototype setup. Y1 - 2022 U6 - https://doi.org/10.1039/d2ra05581c SN - 2046-2069 VL - 12 SP - 35072 EP - 35082 PB - RSC CY - London ER - 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 -