@article{seed_acharya_perelygin_smirnov_krim_2021, title={Tribotronic control and cyclic voltammetry of platinum interfaces with metal oxide nanofluids}, volume={11}, DOI={10.1016/j.apsusc.2021.150675}, abstractNote={Nanotribological and electrochemical behavior of platinum-nanofluid interfaces are reported for aqueous suspensions of positively charged Al2O3 and negatively charged TiO2 nanoparticles, employing Quartz Crystal Microbalance (QCM) and cyclic voltammetry (CV) techniques. Tribotronic methods were employed to adjust the nanoparticles’ positions relative to Pt surface electrodes, and both voltammetry and tribological performance measures were observed to be highly sensitive to the adjustments. Interfacial friction levels were observed to be higher for both types of nanoparticles when electrostatically driven towards the surface. For electric fields of sufficient amplitude and duration, the TiO2 nanosuspension exhibited properties consistent with reversible electrophoretic deposition of the nanoparticles, accompanied by changes in the electrochemical attributes of the electrode itself. Overall, the study suggests a method for active tribological control and optimization of device performance in applications where suspensions of charged nanoparticles are present and can be exposed to external fields.}, journal={Applied Surface Science}, author={Seed, C.M and Acharya, B. and Perelygin, V. and Smirnov, A.I. and Krim, J.}, year={2021}, month={Jul} }
 @article{perelygin_voinov_marek_ou_krim_brenner_smirnova_smirnov_2019, title={Dielectric and Electrostatic Properties of the Silica Nanoparticle–Water Interface by EPR of pH-Sensitive Spin Probes}, volume={123}, url={https://doi.org/10.1021/acs.jpcc.9b08007}, DOI={10.1021/acs.jpcc.9b08007}, abstractNote={Interfacial electrostatic properties of monodisperse silica nanoparticles (SiNPs) in aqueous suspensions as a function of bulk pH were characterized by spin labeling EPR of two ionizable nitroxides: (1) IMTSL (S-(1-oxyl-2,2,3,5,5-pentamethylimidazolidin-4-yl)methylmethanesulfo-nothioate) and IKMTSL (S-4-(4-(dimethylamino)-2-ethyl-5,5-dimethyl-1-oxyl-2,5-dihydro-1H-imidazol-2-yl). SiNPs of ca. 116 nm in diameter (by particle number) were synthesized using the Stöber method, and their surface was modified by silanization under harsh conditions to ensure robust attachment of the thiol-terminated ligands to the silica surface. These ligands were consequently modified with either IMTSL or IKMTSL to characterize the surface electrostatic potential of the nanoparticles from their EPR spectra. EPR titration data for these two pH-sensitive nitroxides allowed for differentiating the dielectric and electrostatic contributions to the interfacial properties of SiNPs. From such a titration at room temperature an effective local dielectric constant experienced by IMTSL at the silica nanoparticle–water interface was found to be εeff = 70.8 ± 5.0 whereas εeff ≈ 57 ± 4 was found for IKMTSL. Surface electrostatic potential calculated from EPR titration of IKMTSL demonstrated an approximately linear increase in the magnitude starting at about zero at pH ∼4.0 and reaching ∼−150 mV at pH ∼8.5. This is in agreement with the existing literature on the surface potential associated with the silanol deprotonation developing over a wide pH range. While the attachment linker employed for the two nitroxides has some flexibility, it still ensures the location of the pH-sensitive tags close to the surface. For these reasons the values of the electrostatic surface potential reported by these nitroxides are significantly higher than those reported by the zeta potential measurements. Overall, spin labeling methods developed here expand the applicability of spin-labeling EPR to measurements of interfacial electrostatic properties of metal oxide nanoparticles.}, number={49}, journal={The Journal of Physical Chemistry C}, publisher={American Chemical Society (ACS)}, author={Perelygin, Vladislav and Voinov, Maxim A. and Marek, Antonin and Ou, Erkang and Krim, Jacqueline and Brenner, Donald and Smirnova, Tatyana I. and Smirnov, Alex I.}, year={2019}, month={Nov}, pages={29972–29985} }