Dr Andrei Sapelkin

Senior Lecturer
Email: a.sapelkin@qmul.ac.ukTelephone: 020 7882 3414Room Number: G.O. Jones Building, Room 126
Teaching
Current Teaching:
- SEF006 - Fields and Waves, SEFP, Semester B
- SPA6312 - Condensed Matter B, Year 3, Semester B
Past Teaching:
- PHY5201 – Physics Laboratory, Year 2, Semester B
- PHY108 – Condensed Matter Physics, Year 1, Semester A
- PHY550 – Solid State Physics, Year 3, Semester B
- PHY201 – Physics Laboratory, Year 2, Semester B
Research
Research Interests:
My research interests are in quantum dots (QDs) preparation, their structural and optical characterisation and their use in bio-applications. Specifically, we have been looking into effects of various synthesis routes on light emission in nanostructures. Semiconductor nano-crystals have captivated the imagination of scientists and engineers since their technological potential became evident over two decades ago.
This is especially true for semiconductor quantum dots, where quantum size effects and carrier confinement allow unprecedented control over optical and electronic properties. Leading the way in this field, in both theoretical understanding and demonstrated applications, is indisputably the cadmium-based II-VI quantum dots discovered 1980s. However, concerns regarding their toxicity are yet to be resolved calling for the advancement of alternative nontoxic materials, including the group IV (C, Si, Ge) semiconductor and gold (Au) nanoparticles. Our interest is in bio-application of quantum dots and to this end we adopted synthesis routes that yield C, Ge and Au QDs in form of suspension. These nano-particles show low toxicity and photoluminescence in a visible range (500-700 nm) and hence could potentially be suitable for bio-application. Our synthesis methods provide a degree of control over surface termination and also over the light emission properties. We work together with our partners at QMUL, UCL and at University of Edinburgh to assess the possibility of using C, Ge and Au QDs for super-resolution imaging of live cells. This work requires a combination of in-house characterisation techniques (e.g. Raman, Photoluminescence, Fluorescence Imaging) and structural methods (e.g. XAS) available at the large scale facilities such as Diamond Light Source. Furthermore, understanding of relationship between atomic, electronic structure and optical properties requires firm theoretical support provided by members of CCMMP group at SP and by our partners at Imperial College and at KCL. Most recently we have been working on utilising quantum dots for optical super-resolution imaging (below the Abbe limit of around 250 nm) by means of spectroscopic signal separation.
Figure 1. A DNA ruler using QDs.
Another long standing interest is effects of high hydrostatic pressure on structural and optical properties of novel materials such as topologically disordered solids and nanostructures. This led to his interest in the development of experimental techniques for local structural characterisation of materials under pressure using synchrotron radiation. It’s well known that reduced dimensionality has profound effects on properties of matter. In our research we attempt to use reduced dimensionality to control a variety of physical properties. Crystalline Germanium is a narrow indirect band gap (0.661 eV, 1876 nm) semiconductor and appears as grey powder or metal-like crystal. However, reducing crystal size down to nanometers results in significant changes of electronic, optical and structural properties due to size effects. Furthermore, it’s well known that bulk crystalline germanium undergoes semiconductor-to-metal transition at around 10 GPa at room temperature. This is not the case for germanium quantum dots.Here pressure does clearly affect the bandgap as can be seen from the changing colour of the Ge QD sample compressed in a diamond anvil cell (DAC). However, the semiconductor phase can be observed at pressures as high 20 GPa and metallisation within an amorphous phase.
Figure. 2. Ge QDs evolution under pressure in a diamond anvil cell.
Research Group
Current members
Ying Liu, Atomic structure of low-dimensional materials
Past Members
Nikolaos Papaioannou, now with Unilever UK.
Kemal Keseroglu, now a Research Fellow at Cincinnati Children's, USA.
Zhang Yuanpeng, now at Oak Ridge National Laboratory, USA.
Ali Karatutlu, now an Assistant Professor at Bursa Orhangazi University, Turkey.
Mingying Song, now a Research Fellow at The State Key Laboratory of Laser Interaction with Matter, China.
Osman Ersoy, Semiconductor quantum dots
William Little, Structure and optical properties of semiconductor quantum dots.
Publications
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Yakovlev EV, Kryuchkov NP, Ovcharov PV et al. (2020). Direct Experimental Evidence of Longitudinal and Transverse Mode Hybridization and Anticrossing in Simple Model Fluids.. nameOfConference
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Papaioannou N, Titirici MM, Sapelkin A (2019). Investigating the Effect of Reaction Time on Carbon Dot Formation, Structure, and Optical Properties. nameOfConference
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Tan L, Pickard CJ, Yu K et al. (2019). Structures of CdSe and CdS Nanoclusters from Ab Initio Random Structure Searching. nameOfConference
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Tan L, Misquitta AJ, Sapelkin A et al. (2019). X-ray total scattering study of magic-size clusters and quantum dots of cadmium sulphide.. nameOfConference
DOI: 10.1039/c9nr06355b
QMRO: qmroHref -
Kokorina AA, Bakal AA, Shpuntova DV et al. (2019). Gel electrophoresis separation and origins of light emission in fluorophores prepared from citric acid and ethylenediamine. nameOfConference
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Yakovlev EV, Chaudhuri M, Kryuchkov NP et al. (2019). Experimental validation of interpolation method for pair correlations in model crystals.. nameOfConference
DOI: 10.1063/1.5116176
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Luo H, Papaioannou N, Salvadori E et al. (2019). Manipulating the optical properties of carbon dots via fine tuning their structural features.. nameOfConference
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Yakovlev EV, Kryuchkov NP, Ovcharov PV et al. (2019). Defect-governed double-step activation and directed flame fronts. nameOfConference
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Papaioannou N, Marinovic A, Yoshizawa N et al. (2018). Structure and solvents effects on the optical properties of sugar-derived carbon nanodots. nameOfConference
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Vostrikova AV, Prikhozhdenko ES, Mayorova OA et al. (2018). Thermal carbonization in nanoscale reactors: Controlled formation of carbon nanodots inside porous CaCO
3 microparticles. nameOfConference
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Brazhkin VV, Prescher C, Fomin YD et al. (2018). Comment on "Behavior of Supercritical Fluids Across the Frenkel Line".. nameOfConference
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ZHANG D, PAPAIOANNOU N, David NM et al. (2018). Photoelectrochemical response of carbon dots (CDs) derived from chitosan and their use in electrochemical imaging. nameOfConference
DOI: 10.1039/c7mh00784a
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Kokorina AA, Prikhozhdenko ES, Tarakina NV et al. (2017). Dispersion of optical and structural properties in gel column separated carbon nanoparticles. nameOfConference
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Smith D, Hakeem MA, Parisiades P et al. (2017). Crossover between liquidlike and gaslike behavior in CH4 at 400 K. nameOfConference
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SUKHORUKOV G, Goryacheva I, Sapelkin A (2017). Carbon nanodots: mechanisms of photoluminescence and principles of applicationReview. nameOfConference
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Song M, Karatutlu A, Ali I et al. (2017). Spectroscopic super-resolution fluorescence cell imaging using ultra-small Ge quantum dots.. nameOfConference
DOI: 10.1364/OE.25.004240
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Attanzio A, Sapelkin A, Gesuele F et al. (2017). Carbon Nanotube-Quantum Dot Nanohybrids: Coupling with Single Particle Control in Aqueous Solution. nameOfConference
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Zhang Y, Ersoy O, Karatutlu A et al. (2016). Local structure of amorphous and nanoscale systems by numerical XANES calculations. nameOfConference
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Gao H, Sapelkin AV, Titirici MM et al. (2016). In Situ Synthesis of Fluorescent Carbon Dots/Polyelectrolyte Nanocomposite Microcapsules with Reduced Permeability and Ultrasound Sensitivity.. nameOfConference
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Sun YW, Hernández I, González J et al. (2016). Significance of bundling effects on carbon nanotubes' response to hydrostatic compression. nameOfConference
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Zhang Y, Ersoy O, Karatutlu A et al. (2016). Local structure of Ge quantum dots determined by combined numerical analysis of EXAFS and XANES data. nameOfConference
QMRO: qmroHref -
Karatutlu A, Little W, Ersoy O et al. (2015). Laser-induced particle size tuning and structural transformations in germanium nanoparticles prepared by stain etching and colloidal synthesis route. nameOfConference
DOI: 10.1063/1.4939066
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Corsini NRC, Zhang Y, Little WR et al. (2015). Pressure-Induced Amorphization and a New High Density Amorphous Metallic Phase in Matrix-Free Ge Nanoparticles. nameOfConference
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Karatutlu A, Song M, Wheeler AP et al. (2015). Synthesis and structure of free-standing germanium quantum dots and their application in live cell imaging. nameOfConference
DOI: 10.1039/c5ra01529d
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Ye HQ, Li Z, Peng Y et al. (2014). Organo-erbium systems for optical amplification at telecommunications wavelengths. nameOfConference
DOI: 10.1038/NMAT3910
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Sun YW, Hernández I, Ghandour AJ et al. (2014). Resonance Raman spectroscopy of carbon nanotubes: pressure effects on G-mode. nameOfConference
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Little W, Karatutlu A, Bolmatov D et al. (2014). Structural origin of light emission in germanium quantum dots. nameOfConference
DOI: 10.1038/srep07372
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Hatch SM, Sapelkin A, Cibin G et al. (2013). Investigating the source of deep-level photoluminescence in ZnO nanorods using optically detected x-ray absorption spectroscopy. nameOfConference
DOI: 10.1063/1.4824810
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Puech P, Hu T, Sapelkin A et al. (2012). Charge transfer between carbon nanotubes and sulfuric acid as determined by Raman spectroscopy. nameOfConference
QMRO: qmroHref -
Yashchenok AM, Bratashov DN, Gorin DA et al. (2010). Carbon Nanotubes on Polymeric Microcapsules: Free-Standing Structures and Point-Wise Laser Openings. nameOfConference
QMRO: qmroHref -
Puech P, Flahaut E, Sapelkin A et al. (2006). Nanoscale pressure effects in individual double-wall carbon nanotubes. nameOfConference
QMRO: qmroHref -
Sapelkin AV, Bayliss SC, Unal B et al. (2006). Interaction of B50 rat hippocampal cells with stain-etched porous silicon. nameOfConference
QMRO: qmroHref -
SAPELKIN A, Bayliss SC (2002). Distance dependence of mean-square relative displacements in EXAFS. nameOfConference
QMRO: qmroHref -
Sapelkin AV, Bayliss SC (2002). X-ray absorption spectroscopy under high pressures in diamond anvil cells. nameOfConference
QMRO: qmroHref
Performance
My Talks
Quantum Dots for imaging Talk [PDF 3,298KB] at a British Council Sponsored Workshop, Saratov, Russia, September 2012
Quantum Dots Raman and PL Talk [PDF 2,757KB] at Renishaw Inside Raman workshop, Rutherford Appleton Laboratory, 11th-12th September 2012
Interaction of nanostructures with living cells Talk [PDF 2,091KB] at Royal Holloway, University of London, December 2011
Nanostructures under pressure Talk [PDF 1,028KB] at a CSEC, Edinburgh, 25 Feb 2010 and at CEMES-CNRS Toulouse, France 4th Oct 2010
In the Media
Reference to our work on Wikipedia (see Ref 16, or search Sapelkin) and in online publications