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Your search keyword '"Sapelkin, Andrei V."' showing total 122 results
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122 results on '"Sapelkin, Andrei V."'

1. Tunable colloidal spinners: Active chirality and hydrodynamic interactions governed by rotating external electric fields.

Author

Libet, Pavel A., Yakovlev, Egor V., Kryuchkov, Nikita P., Simkin, Ivan V., Sapelkin, Andrei V., and Yurchenko, Stanislav O.

Abstract

The rotational dynamics of microparticles in liquids have a wide range of applications, including chemical microreactors, biotechnologies, microfluidic devices, tunable heat and mass transfer, and fundamental understanding of chiral active soft matter which refers to systems composed of particles that exhibit a handedness in their rotation, breaking mirror symmetry at the microscopic level. Here, we report on the study of two effects in colloids in rotating electric fields: (i) the rotation of individual colloidal particles in rotating electric field and related to that (ii) precession of pairs of particles. We show that the mechanism responsible for the rotation of individual particles is related to the time lag between the external field applied to the particle and the particle polarization. Using numerical simulations and experiments with silica particles in a water-based solvent, we prove that the observed rotation of particle pairs and triplets is governed by the tunable rotation of individual particles and can be explained and described by the action of hydrodynamic forces. Our findings demonstrate that colloidal suspensions in rotating electric fields, under some conditions, represent a novel class of chiral soft active matter—tunable colloidal spinners. The experiments and the corresponding theoretical framework we developed open novel prospects for future studies of these systems and for their potential applications. [ABSTRACT FROM AUTHOR]

Published
2024
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2. Atomic structure of CdS magic-size clusters by X-ray absorption spectroscopy

Author

Liu, Ying, Tan, Lei, Cibin, Giannantonio, Gianolio, Diego, Han, Shuo, Yu, Kui, Dove, Martin T., and Sapelkin, Andrei V.

Subjects
Condensed Matter - Materials Science, Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

Magic-size clusters are ultra-small colloidal semiconductor systems that are intensively studied due to their monodisperse nature and sharp UV-vis absorption peak compared with regular quantum dots. However, the small size of such clusters (<2 nm), and the large surface-to-bulk ratio significantly limit characterisation techniques that can be utilised. Here we demonstrate how a combination of EXAFS and XANES can be used to obtain information about sample stoichiometry and cluster symmetry. Investigating two types of clusters that show sharp UV-vis absorption peaks at 311 nm and 322 nm, we found that both samples possess approximately 2:1 Cd:S ratio and have similar nearest-neighbour structural arrangements. However, both samples demonstrate a significant departure from the tetrahedral structural arrangement, with an average bond angle determined to be around 106.1 degree showing a bi-fold bond angle distribution. Our results suggest that both samples are quazi-isomers. Their core structure has identical chemical composition but a different atomic arrangement with distinct bond angle distributions., Comment: 7 pages, 5 figures

Published
2020

5. Spectroscopic super-resolution fluorescence cell imaging using ultra-small Ge quantum dots

Author

Song, Mingying, Karatutlu, Ali, Ersoy, Osman, Zhou, Yun, Yang, Yongxin, Zhang, Yuanpeng, Little, William R., Wheeler, Ann P., and Sapelkin, Andrei V.

Subjects
Physics - Optics
Abstract

In single molecule localisation super-resolution microscopy the need for repeated image capture limits the imaging speed, while the size of fluorescence probes limits the possible theoretical localisation resolution. Here, we demonstrated a spectral imaging based super-resolution approach by separating the overlapping diffraction spots into several detectors during a single scanning period and taking advantage of the size-dependent emission wavelength in nanoparticles. This approach has been tested using off-the-shelf quantum dots (Qdot) and in-house novel ultra-small (~3 nm) Ge QDs. Furthermore, we developed a method-specific Gaussian fitting and maximum likelihood estimation based on a Matlab algorithm for fast QDs localisation. We demonstrate that this methodology results in ~ 40 nm localisation resolution using commercial QDs and ~12 nm localisation resolution using Ge QDs. Using a standard scanning confocal microscope we achieved data acquisition rate of 1.6 seconds/frame. However, we show that this approach has a potential to deliver data acquisition rates on ms scale thus providing super-resolution in live systems., Comment: This paper has been withdrawn by the authors due to an author dispute. This paper will not be replaced or revised

Published
2015

14. Experimental validation of interpolation method for pair correlations in model crystals.

Author

Yakovlev, Egor V., Chaudhuri, Manis, Kryuchkov, Nikita P., Ovcharov, Pavel V., Sapelkin, Andrei V., and Yurchenko, Stanislav O.

Subjects
CRYSTAL models, PHYSICAL & theoretical chemistry, MATERIALS science, CONDENSED matter, COLLOIDAL crystals, INTERPOLATION, COLLOIDAL suspensions
Abstract

Accurate analysis of pair correlations in condensed matter allows us to establish relations between structures and thermodynamic properties and, thus, is of high importance for a wide range of systems, from solids to colloidal suspensions. Recently, the interpolation method (IM) that describes satisfactorily the shape of pair correlation peaks at short and at long distances has been elaborated theoretically and using molecular dynamics simulations, but it has not been verified experimentally as yet. Here, we test the IM by particle-resolved studies with colloidal suspensions and with complex (dusty) plasmas and demonstrate that, owing to its high accuracy, the IM can be used to experimentally measure parameters that describe interaction between particles in these systems. We used three- and two-dimensional colloidal crystals and monolayer complex (dusty) plasma crystals to explore suitability of the IM in systems with soft to hard-sphere-like repulsion between particles. In addition to the systems with pairwise interactions, if many-body interactions can be mapped to the pairwise ones with some effective (e.g., density-dependent) parameters, the IM could be used to obtain these parameters. The results reliably show that the IM can be effectively used for analysis of pair correlations and interactions in a wide variety of systems and therefore is of broad interest in condensed matter, complex plasma, chemical physics, physical chemistry, materials science, and soft matter. [ABSTRACT FROM AUTHOR]

Published
2019
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18. High-pressure neutron diffraction study of magnetite, Fe3O4, nanoparticles.

Author

Tan, Lei, Sapelkin, Andrei V., Misquitta, Alston J., Bull, Craig L., Lin, He, Tian, Haolai, Huang, Haijun, and Dove, Martin T.

Subjects
*NANOPARTICLE size, *MAGNETITE, *NEUTRON diffraction, *NANOPARTICLES, *MAGNETIC structure, *X-ray scattering, *ELASTICITY
Abstract

We use in situ high-pressure neutron powder diffraction to study elastic properties of Fe3O4 magnetite nanoparticles of different sizes. It is found that nanoparticles are elastically softer than the bulk. Apart from the smallest nanoparticle of diameter 8 nm, the atomic and magnetic structures do not change significantly with nanoparticle size or pressure. The 8 nm sample appears to take a disordered spinel structure instead of the inverse spinel structure of the bulk and larger nanoparticles, as seen in bond lengths and magnetic structures. Synchrotron x-ray total scattering was used to support this interpretation. Furthermore, this study suggests that the influence of magnetic disorder at the nanoparticle surface is significant for the size of 8 nm. [ABSTRACT FROM AUTHOR]

Published
2022
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31. Carbon dot aggregates as an alternative to gold nanoparticles for the laser-induced opening of microchamber arrays

Author

Sindeeva, Olga A., primary, Prikhozhdenko, Ekaterina S., additional, Bratashov, Daniil N., additional, Vostrikova, Anna M., additional, Atkin, Vsevolod S., additional, Ermakov, Aleksey V., additional, Khlebtsov, Boris N., additional, Sapelkin, Andrei V., additional, Goryacheva, Irina Yu., additional, and Sukhorukov, Gleb B., additional

Published
2018
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42. Luminescent carbon nanoparticles: synthesis, methods of investigation, applications

Author

Kokorina, Alina A., Prikhozhdenko, Ekaterina S., Sukhorukov, Gleb B., Sapelkin, Andrei V., and Yu, Irina

Abstract

Luminescent carbon nanoparticles represent a new class of photoluminescent nanomaterials. Growing interest in these nanoparticles stems from straightforward methods of their synthesis, a wide variety of available precursors, the lack of toxicity, photo stability and simple surface modification for further application. Due to low cytotoxicity and tunable optical properties of carbon nanoparticles, they are used in various fields of biology and medicine. At the same time, current application of carbon nanoparticles is limited by the lack of understanding of the fundamental relationship between their structure and properties. The review focuses on the latest trends in the synthesis, study of the structure, composition and properties of carbon nanoparticles and on their biomedical applications.The bibliography includes 112 references.

Published
2017

43. In SituSynthesis of Fluorescent Carbon Dots/Polyelectrolyte Nanocomposite Microcapsules with Reduced Permeability and Ultrasound Sensitivity

Author

Gao, Hui, Sapelkin, Andrei V., Titirici, Magdalena M., and Sukhorukov, Gleb B.

Abstract

Designing and fabricating multifunctional nanocomposite microcapsules are considerable interests in both academic and industrial research aspects. This work first reports an innovative approach to in situsynthesize and assemble fluorescent carbon dots (CDs) into polyelectrolyte microcapsules, obtaining highly biocompatible nanocomposite microcapsules with excellent luminescence that facilitate imaging and identification in vitro, yet with the feasibility to load small molecules and ultrasound responsiveness to trigger their release. CDs are produced in situin (PAH/PSS)4microcapsule shells by carbonization of dextran molecules under relatively mild hydrothermal treatment. Compared with the collapsed and film-like (PAH/PSS)4microcapsules, the novel composite microcapsules show a free-standing structure, smaller size, and thicker shell. CDs are proven to be fabricated and embedded in PAH/PSS multilayers, and the formed PAH/PSS/CD microcapsules are endowed with strong luminescence, as verified by the transmission electron microscopy, fluorescence spectra, and confocal laser scanning microscopy results. The in situformation of CDs in capsule shells also empowers these capsules with ultrasound responsiveness and reduced permeability. The feasibility of encapsulation of small molecules (rhodamine B) and ultrasound-triggered release is also shown. Most importantly, due to the intrinsic biocompatible property and photostability of CDs, these fluorescent PAH/PSS/CD microcapsules show negligible cell toxicity and low photobleaching, which are impossible for capsules composited with conventional organic dyes and semiconductor quantum dots.

Published
2016
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45. Carbon Nanotubes on Polymeric Microcapsules: Free-Standing Structures and Point-Wise Laser Openings

Author

Yashchenok, Alexey M., primary, Bratashov, Daniil N., additional, Gorin, Dmitry A., additional, Lomova, Maria V., additional, Pavlov, Anton M., additional, Sapelkin, Andrei V., additional, Shim, Bong Sup, additional, Khomutov, Gennady B., additional, Kotov, Nicholas A., additional, Sukhorukov, Gleb B., additional, Möhwald, Helmuth, additional, and Skirtach, Andre G., additional

Published
2010
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