TY - GEN A1 - Sengül, Akant A1 - Reiter, Sebastian A1 - Lotfi, Zahra A1 - Efremenko, Julia A1 - Laroussi, Arwa A1 - Corley-Wiciak, Agnieszka Anna A1 - Ratzke, Markus A1 - Mirsky, Vladimir M. A1 - Wenger, Christian A1 - Fischer, Inga Anita T1 - Titanium nitride plasmonic nanohole arrays with polymer coating : optical properties and their humidity-induced modifications T2 - Optical materials express N2 - The use of titanium nitride (TiN) for the fabrication of plasmonic structures such as nanohole arrays (NHAs) can enable their integration into optoelectronic devices on the silicon (Si) platform, for example, for the realization of on-chip chemical sensors and biosensors based on refractometric transduction. With a corresponding functionalization of the TiN nanohole arrays, these ultra-compact devices can be utilized in the development of various affinity sensors and sensor systems, such as cost-effective electronic noses for the early detection of gases in the food industry or agriculture. In this work, we focus on two types of coating for functionalization of TiN nanohole arrays: electrochemically synthesized poly-N-methylaniline and layer-by-layer deposited polyacrylic-acid/poly-allylamine (PAA/PAH). Our investigation comprises the experimental characterization of the optical properties of TiN nanhole arrays coated with polymer layers of different thicknesses as well as a comparison with simulation results. We demonstrate the potential of our setup sensing applications by measuring changes in optical properties of TiN nanohole arrays coated with PAA/PAH upon exposure to air of different humidity. Y1 - 2026 U6 - https://doi.org/10.1364/ome.578871 SN - 2159-3930 VL - 16 IS - 2 SP - 184 EP - 196 PB - Optica Publishing Group CY - Washington, DC ER - TY - GEN A1 - Laurinavichyute, Veronika K. A1 - Nizamov, Shavkat A1 - Mirsky, Vladimir M. T1 - Cyclic voltarefractometry of single TiO₂ nanoparticles in large ensembles in nonaqueous electrolyte T2 - Analytical chemistry N2 - Single nanoparticle (NP) cyclic voltarefractometry (CVR), realized as wide-field surface plasmon resonance microscopy (SPRM) in combination with potential cycling, has been proposed and applied to the in situ study of TiO₂ NPs. Electrochemical activity of TiO₂ is mainly observed outside the electrochemical stability window of water. Therefore, the response of individual anatase (a-TiO₂) and rutile (r-TiO₂) NPs adsorbed on a gold layer was studied in 0.25 M LiClO4 acetonitrile solutions. The use of acetonitrile allows us to exploit a much wider potential window compared to water, while due to the almost identical refractive index (nD = 1.344 and 1.333 for acetonitrile and water, respectively), the conditions of the SPR are not changed. This greatly expands the variety of electrochemical reactions that can be studied by SPR techniques. Cyclic polarization of a-TiO₂ and r-TiO₂ NPs results in pronounced electrochemical and optical responses around −1.55 V and around −1.8 V vs Fc+/Fc, respectively. This specific optoelectrochemical response allows them to be distinguished from other NPs. Based on this difference in characteristic potentials, a mixture of a-TiO₂ and r-TiO₂ NPs can be analyzed by CVR as well. The proposed correction algorithm compensates for the drift in the SPRM background caused by the accompanying formation of insoluble compounds and separates the optical response of the NPs out of the background. The results obtained in the study of this complex system demonstrate the capabilities of the developed analytical method. The CVR can be applied to the quantitative analysis of many other types of NPs in nonaqueous solutions, providing information on the electrochemical properties of each individual particle on the electrode surface. Y1 - 2025 U6 - https://doi.org/10.1021/acs.analchem.4c04181 SN - 0003-2700 SN - 1520-6882 VL - 97 IS - 2 SP - 1160 EP - 1169 PB - American Chemical Society CY - Washington, D.C. ER - TY - GEN A1 - Efremenko, Yulia A1 - Laroussi, Arwa A1 - Sengül, Akant A1 - Corley-Wiciak, Agnieszka Anna A1 - Fischer, Inga Anita A1 - Mirsky, Vladimir M. T1 - Deposition of Polymers on Titanium Nitride Electrodes T2 - Coatings N2 - The application of titanium nitride (TiN) as an electrode for electrochemical deposition or characterization requires the removal of an insulating layer from its surface. This process was studied and optimized, and the conditions for the complete removal of this layer through treatment with oxalic acid were formulated. The obtained TiN surfaces were used for the deposition of various conducting and non-conducting polymers. Two different approaches were applied: (i) in situ electrochemical synthesis of the main classes of conducting polymers, including polyaniline, polypyrrole, polythiophene, and selected derivatives thereof, and (ii) electrostatically driven layer-by-layer (LbL) deposition of multilayers of oppositely charged polyelectrolytes. The deposited polymers were characterized by electrochemical methods. The electrochemical properties of the deposited conducting polymers and their deposition on the TiN surface were comparable to those of the metallic electrodes. The films produced via LbL deposition exhibited a pronounced influence of the charge of the last deposited polymer on the redox reaction of ferri/ferrocyanide, validating the charge alteration with each successive polymer layer deposition. The studied deposition technologies can be used for the modification of TiN surfaces required in applications of this material in chemical sensors and other devices. Y1 - 2024 U6 - https://doi.org/10.3390/coatings14020215 SN - 2079-6412 VL - 14 IS - 2 ER - TY - GEN A1 - Efremenko, Yulia A1 - Mirsky, Vladimir M. T1 - Chemosensitive properties of electrochemically synthesized poly-3-thienylboronic acid: conductometric detection of glucose and other diol-containing compounds under electrical affinity control T2 - Polymers N2 - Due to the presence of the boronic acid moieties, poly-3-thienylboronic acid has an affinity for saccharides and other diol-containing compounds. Thin films of this novel chemosensitive polymer were synthesized electrochemically on the gold surface. The adhesion of the polymer was enhanced by the deposition of a monomolecular layer of thiophenol. The technology was used to fabricate conductometric sensors for glucose and other diol-containing compounds. Simultaneous two- and four-electrode conductivity measurements were performed. The chemical sensitivity to sorbitol, fructose, glucose, and ethylene glycol was studied at different pH and electrode potentials, and the corresponding binding constants were obtained. Depending on the electrode potential, the reciprocal values of the binding constants of glucose to poly-3-thienylboronic acid at neutral pH are in the range of 0.2 mM–1.0 mM. The affinity for glucose has been studied in buffer solutions and in solutions containing the major components of human blood. It was shown that the presence of human serum albumin increases the affinity of poly-3-thienylboronic acid for diol-containing compounds. KW - glucose sensor KW - saccharide sensor KW - chemosensitive polymer KW - poly-3-thienylboronic acid KW - conductometric sensor KW - glucose biosensor Y1 - 2024 U6 - https://doi.org/10.3390/polym16131938 SN - 2073-4360 VL - 16 IS - 13 PB - MDPI AG ER - TY - GEN A1 - Snopok, Borys A. A1 - Nizamov, Shavkat A1 - Snopok, Tetiana V. A1 - Mirsky, Vladimir M. T1 - Agglomeration compaction promotes corrosion of gold nanoparticles T2 - Nanoscale Advances N2 - Engineered nanoparticles are increasingly being used in various areas of human activity. However, the degradation mechanism of nanobodies in harsh environments is still a puzzle for theory and experiment. We report here the results of optical spectroscopy and nanoparticle tracking analysis, quantifying agglomeration and sizing of 50 nm citrate stabilized gold nanoparticles (GNPs) in HCl solutions containing H2O2. The mechanism of a consecutive corrosion reaction of GNPs is discussed within the framework of the near-field approach. We found that the disappearance of single nanoparticles from a suspension does not occur due to their dissolution per se, but is a consequence of the formation of aggregates. The neutralization of electrostatic shielding at high ionic strength allows gold nanoparticles to approach the subnanometer distance within the region of capping defects, at which the Casimir and van der Waals attractive forces dominate. It is suggested that electric field fluctuations in the confined space between highly conductive gold nanoparticles cause complexant-stimulated loss of metal from the core in the contact area. Going beyond the charge screening limitations by constraining the reaction space and reducing the double electrical layer thickness allows for chemical processes flow along otherwise not accessible reaction pathways. Y1 - 2024 U6 - https://doi.org/10.1039/D4NA00109E SN - 2516-0230 VL - 6 IS - 15 SP - 3865 EP - 3877 PB - Royal Society of Chemistry (RSC) ER - TY - GEN A1 - Beisembek, Alisher A1 - Dimchevska Sazdovska, Simona A1 - Mirsky, Vladimir M. T1 - Separation of shifts in surface plasmon resonance into refractive index and thickness of deposited layers T2 - Sensors and actuators. B, Chemical N2 - Routine Surface Plasmon Resonance (SPR) measurements, which are widely applied in affinity (bio)sensors and surface science, do not allow one to separate the obtained SPR signals into the change of the refractive index and thickness of deposited layers. For thin layers the signal is proportional to the product of the layer thickness and the difference in the refractive indices of this layer and of the aqueous media. In this study, we suggest an approach to separate these parameters. It is performed by subsequent measurements in the presence and in the absence of polyethylene glycol (PEG), an inert additive which modifies the refractive index of the liquid phase but do not penetrate into the adsorbed layer. Both parameters were successively determined for human serum albumin (HSA) as well as for anti-HSA IgG in three different settings: i) HSA adsorbed directly onto a gold surface, ii) HSA chemically immobilized on a gold surface coated with a self-assembled monolayer of 1,16 mercaptohexadecanoic acid and iii) chemically immobilized HSA with additional monomolecular layer of anti- HSA IgG antibodies bond to this protein layer. The suggested approach can be applied in most SPR devices with a flow cell for analysis of various adsorbed layers. KW - Surface plasmon resonance KW - Thin layer thickness KW - Refractive index measurement Y1 - 2023 U6 - https://doi.org/10.1016/j.snb.2023.134606 SN - 1873-3077 SN - 0925-4005 VL - 396 ER - TY - GEN A1 - Nizamov, Shavkat A1 - Dimchevska Sazdovska, Simona A1 - Mirsky, Vladimir M. T1 - A review of optical methods for ultrasensitive detection and characterization of nanoparticles in liquid media with a focus on the wide field surface plasmon microscopy T2 - Analytica Chimica Acta N2 - Development of nanotechnology and corresponding industries during the last decade resulted in a new challenge for analytical science. This includes an ultrasensitive detection and characterization of nanoparticles of different origin and other nanomaterials in various media, including so complex ones as food, biological or environmental samples. The goal of this review is a systematic analysis of possible approaches and description of physical principles behind these methods. The main attention is paid to optical methods which are considered by authors to be mostly effective for the formulated task. Different approaches for detection and analysis of nanoparticles in a volume as well as of those adsorbed on a surface are discussed. While the technologies based on direct analysis of nanoparticle suspensions belong to the established approaches whose development potential has been in large extent exhausted, the novel technologies based on the surface sensing of adsorbed nanoparticles demonstrate intensive development. Therefore, the final part of the review is focused on the wide-field surface plasmon resonance microscopy. It allows one an ultrasensitive detection and characterization of individual nanoparticles of different origin in complex media and provides numerous possibilities for subsequent chemical identification of the detected particles using a hyphenation with other analytical technologies. KW - Nanoparticles KW - Detection of nanoparticles KW - Characterization of nanoparticles KW - Optical techniques KW - Surface plasmon resonance microscopy KW - Nanoparticle tracking analysis Y1 - 2022 U6 - https://doi.org/10.1016/j.aca.2022.339633 SN - 1873-4324 VL - 1204 ER - TY - GEN A1 - Karačić, Dalibor A1 - Gutić, Sanjin J. A1 - Vasić, Borislav A1 - Mirsky, Vladimir M. A1 - Skorodumova, Natalia V. A1 - Mentus, Slavko V. A1 - Pašti, Igor A. T1 - Electrochemical reduction of thin graphene-oxide films in aqueous solutions – Restoration of conductivity T2 - Electrochimica Acta N2 - Graphene oxide finds applications in different fields of science, including energy conversion. Electrochemical reduction of graphene oxide (GO) significantly improves its conductivity. However, the kinetics of this process depends on the solvent, supporting electrolyte, pH, and numerous other factors. Most studies report the macroscopic views and ex-situ properties of reduced GO. To expand the knowledge about GO reduction, in this study, we used cyclic voltammetry (CV), simultaneous 2 points and 4 points resistance measurement (s24), conductive atomic force microscopy (AFM), and theoretical calculations. Using CV, we demonstrated that the choice of supporting electrolyte (KCl or LiCl) influences the potential range in which electrochemical GO reduction occurs. The activation energy of this process was estimated to be below 30 kJ mol‒1 in both electrolytes, being significantly lower than that required for thermal reduction of GO. Simultaneous in situ s24 resistance measurements suggest that GO films reach a highly conductive state at deep negative potentials, with an abrupt, irreversible switch from non-conductive to the conductive state. However, conductive AFM presents a more exact picture of this process: the reduction of GO films starts locally while the formed conductive islands grow during the reduction. This mechanism was confirmed by theoretical calculations indicating that the reduction starts on isolated oxygen-functional groups over the GO basal plane, while clustered OH groups are more difficult to reduce. The presented results can help in tailoring reduced GO for a particular electrochemical application by precisely controlling the reduction degree and percentage of the conductive area of the reduced GO films. KW - Electrochemical reduction of graphene oxide KW - Supporting electrolyte effect KW - Simultaneous 2-point 4-point resistance measurements KW - Conductive atomic force microscopy KW - Theoretical calculations Y1 - 2022 UR - https://www.sciencedirect.com/science/article/pii/S0013468622002183 U6 - https://doi.org/10.1016/j.electacta.2022.140046 SN - 1873-3859 SN - 0013-4686 VL - 410 ER - TY - GEN A1 - Efremenko, Yulia A1 - Mirsky, Vladimir M. T1 - 3-Thienylboronic Acid as a Receptor for Diol-Containing Compounds: A Study by Isothermal Titration Calorimetry T2 - Chemosensors N2 - The electrochemical activity of 3-thienylboronic acid and its feature to form polymer films makes it a perspective receptor material for sensor applications. The affinity properties of this compound were studied here by isothermal titration calorimetry. A number of different analytes were tested, and the highest binding enthalpy was observed for sorbitol and fructose. An increase of pH in the range of 5.5–10.6 results in the rise of the binding enthalpy with an increase of the binding constant to ~8400 L/mol for sorbitol or ~3400 L/mol for fructose. The dependence of the binding constant on pH has an inflection point at pH 7.6 with a slope that is a ten-fold binding constant per one pH unit. The binding properties of 3-thienylboronic acid were evaluated to be very close to that of the phenylboronic acid, but the electrochemical activity of 3-thienylboronic acid provides a possibility of external electrical control: dependence of the affinity of 3-thienylboronic acid on its redox state defined by the presence of ferro/ferricyanide in different ratios was demonstrated. The results show that 3-thienylboronic acid can be applied in smart chemical sensors with electrochemically controllable receptor affinity. KW - chemical sensors KW - affinity KW - isothermal titration calorimetry KW - 3-thienylboronic acid KW - diol-containing compounds Y1 - 2022 UR - https://www.mdpi.com/2227-9040/10/7/251 U6 - https://doi.org/10.3390/chemosensors10070251 SN - 2227-9040 VL - 10 IS - 7 ER - TY - GEN A1 - Snopok, Borys A. A1 - Laroussi, Arwa A1 - Cafolla, Clodomiro A1 - Voitchovsky, Kislon A1 - Snopok, Tetiana V. A1 - Mirsky, Vladimir M. T1 - Gold surface cleaning by etching polishing: Optimization of polycrystalline film topography and surface functionality for biosensing T2 - Surfaces and Interfaces N2 - Modern bio-chemical sensors rely on functional interfacial architectures with well-defined structural nano-motifs over a physical transducer. Gold-coated interfaces are of particular interest for their desirable chemical (functionalization) and optical (plasmonic) properties. Here we investigate the cleaning and polishing of polycrystalline gold films in preparation of advanced surface functionalization. We focus on soft wet chemical etching to decrease the small-scale roughness commonly observed after evaporation or sputtering of gold. We show that optimized surfaces are obtained by etching in solutions of hydrochloric acid and hydrogen peroxide. We systematically quantify the films wettability, surface nano-topography, UV-VIS spectrum and the electrochemical and Surface Plasmon Resonance (SPR) changes throughout the etching process. Optimal results are obtained by etching with a HCl(37%):H2O2(30%):H2O mixture, with a volume ratio of reagents 3:3:94 during 15-20 minutes at room temperature for the main step. This reduces by a factor two the root-mean-square roughness, removes contaminants, increases hydrophilicity and modifies the gold surface by Au(Cl)x complexes. Significantly, the resulting the surface is hydrophilic enough to prevent globular proteins such as HSA to unfold upon deposition at concentrations more than ~1 mg/mL. Our protocol offers a simple, reliable and rapid method for the preparation of gold surface in view of further functionalization including the binding of receptor layers and various micro- and nanostructures required in chemical and biochemical sensing. KW - polycrystalline gold films KW - soft wet chemical polishing KW - gold cleaning KW - hydrochloric acid and hydrogen peroxide KW - protein adsorption KW - surface plasmon resonance Y1 - 2021 U6 - https://doi.org/10.1016/j.surfin.2020.100818 SN - 2468-0230 VL - 22 ER -