School of Physics and Astronomy

Dr Andrei Sapelkin


Senior Lecturer | PhD Tutor

Telephone: 020 7882 3414
Room Number: G.O. Jones Building, Room 126


Current Teaching:

  • PHY5201 – Physics Laboratory, Year 2, Semester B
  • SPA6312 - Condensed Matter B, Year 3, Semester B

Past Teaching:

  • PHY108 – Condensed Matter Physics, Year 1, Semester A
  • PHY550 – Solid State Physics, Year 3, Semester B
  • PHY201 – Physics Laboratory, Year 2, Semester B


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

Zhang Yuanpeng, Structural methods for low dimensional systems

Osman Ersoy, Semiconductor quantum dots

Kemal Keseroglu, Semiconductor QDs for super-resolution

Nikolaos Papaioannou, Syntheis, structure and properties of carbon quantum dots

Past Members

Ali Karatutlu, Synthesis of semiconductor quantum dots, now Assistant Professor at Bursa Orhangazi University, Turkey

William Little, Structure and optical properties of semiconductor quantum dots

Mingying Song, Semiconductor quantum dots for super-resolution



Carbon nanodots: mechanisms of photoluminescence and principles of applicationReview
SUKHORUKOV G, Goryacheva I, Sapelkin A
Trends in Analytical Chemistry, 6th March 2017.
DOI: 10.1016/j.trac.2017.02.012

Spectroscopic super-resolution fluorescence cell imaging using ultra-small Ge quantum dots.
Song M, Karatutlu A, Ali I et al.
Opt Express, Volume 25, issue 4, page 4240, 20th February 2017.
DOI: 10.1364/OE.25.004240

Carbon Nanotube-Quantum Dot Nanohybrids: Coupling with Single Particle Control in Aqueous Solution
Attanzio A, Sapelkin A, Gesuele F et al.
Small, 10th February 2017.
DOI: 10.1002/smll.201603042


Local structure of amorphous and nanoscale systems by numerical XANES calculations
Zhang Y, Ersoy O, Karatutlu A et al.
Journal of Non-Crystalline Solids, Volume 451, page 10, 1st November 2016.
DOI: 10.1016/j.jnoncrysol.2016.07.001

In Situ Synthesis of Fluorescent Carbon Dots/Polyelectrolyte Nanocomposite Microcapsules with Reduced Permeability and Ultrasound Sensitivity.
Gao H, Sapelkin AV, Titirici MM et al.
ACS Nano, 4th October 2016.
DOI: 10.1021/acsnano.6b05088

Significance of bundling effects on carbon nanotubes' response to hydrostatic compression
Sun YW, Hernández I, González J et al.
Journal of Physical Chemistry C, Volume 120, issue 3, page 1863, 28th January 2016.
DOI: 10.1021/acs.jpcc.5b09082

Local structure of Ge quantum dots determined by combined numerical analysis of EXAFS and XANES data.
Zhang Y, Ersoy O, Karatutlu A et al.
J Synchrotron Radiat, Volume 23, issue 1, page 253, 1st January 2016.
DOI: 10.1107/S160057751501913X


Laser-induced particle size tuning and structural transformations in germanium nanoparticles prepared by stain etching and colloidal synthesis route
Karatutlu A, Little W, Ersoy O et al.
Journal of Applied Physics, Volume 118, issue 24, 29th December 2015.
DOI: 10.1063/1.4939066

Pressure-Induced Amorphization and a New High Density Amorphous Metallic Phase in Matrix-Free Ge Nanoparticles.
Corsini NRC, Zhang Y, Little WR et al.
Nano Lett, Volume 15, issue 11, page 7334, 11th November 2015.
DOI: 10.1021/acs.nanolett.5b02627

Aerosol assisted chemical vapour deposition of transparent conductive ZnO thin films with hexagonal microplate surfaces and ultrahigh haze values
Chen S, McLachlan M, Sapelkin A et al.
Journal of Materials Chemistry A, Volume 3, issue 44, page 22311, 25th September 2015.
DOI: 10.1039/c5ta06029j

Aerosol assisted chemical vapour deposition of Ga-doped ZnO films for energy efficient glazing: Effects of doping concentration on the film growth behaviour and opto-electronic properties
Chen S, Carraro G, Barreca D et al.
Journal of Materials Chemistry A, Volume 3, issue 24, page 13039, 28th June 2015.
DOI: 10.1039/c5ta02163d

Structure and effects of annealing in colloidal matrix-free Ge quantum dots.
Zhang Y, Karatutlu A, Ersoy O et al.
J Synchrotron Radiat, Volume 22, issue 1, page 105, 1st January 2015.
DOI: 10.1107/S1600577514022486

Synthesis and structure of free-standing germanium quantum dots and their application in live cell imaging
Karatutlu A, Song M, Wheeler AP et al.
RSC Advances, Volume 5, issue 26, page 20566, 1st January 2015.
DOI: 10.1039/c5ra01529d


Structural origin of light emission in germanium quantum dots.
Little W, Karatutlu A, Bolmatov D et al.
Sci Rep, Volume 4, page 7372, 9th December 2014.
DOI: 10.1038/srep07372

Origin of mechanical modifications in poly (ether ether ketone)/carbon nanotube composite
Pavlenko E, Boyer F, Puech P et al.
JOURNAL OF APPLIED PHYSICS, Volume 115, issue 23, 21st June 2014.
DOI: 10.1063/1.4883299

Organo-erbium systems for optical amplification at telecommunications wavelengths
Ye HQ, Li Z, Peng Y et al.
Nature Materials, Volume 13, issue April 2014, page 382, 1st January 2014.
DOI: 10.1038/NMAT3910

Resonance Raman spectroscopy of carbon nanotubes: pressure effects on G-mode
Sun YW, Hernández I, Ghandour AJ et al.
High Pressure Research, 1st January 2014.
DOI: 10.1080/08957959.2013.878714


Magnetically engineered microcapsules as intracellular anchors for remote control over cellular mobility.
Pavlov AM, De Geest BG, Louage B et al.
Adv Mater, Volume 25, issue 48, page 6945, 23rd December 2013.
DOI: 10.1002/adma.201303287

Investigating the source of deep-level photoluminescence in ZnO nanorods using optically detected x-ray absorption spectroscopy
Hatch SM, Sapelkin A, Cibin G et al.
Journal of Applied Physics, Volume 114, issue 15, 21st October 2013.
DOI: 10.1063/1.4824810

Structural Origin of Light Emission in Germanium Quantum Dots
SAPELKIN A, Bolmatov D, Karatutlu A et al.
16th September 2013.

Influence of anneal atmosphere on ZnO-nanorod photoluminescent and morphological properties with self-powered photodetector performance
Hatch SM, Briscoe J, Sapelkin A et al.
J. Appl. Phys., Volume 113, issue 20, page 204501, 28th May 2013.
DOI: 10.1063/1.4805349

Pressure coefficients of Raman modes of carbon nanotubes resolved by chirality: Environmental effect on graphene sheet
Ghandour AJ, Crowe IF, Proctor JE et al.
PHYSICAL REVIEW B, Volume 87, issue 8, 13th February 2013.
DOI: 10.1103/PhysRevB.87.085416

A time resolved microfocus XEOL facility at the Diamond Light Source
Mosselmans JFW, Taylor RP, Quinn PD et al.
DOI: 10.1088/1742-6596/425/18/182009

OD-XAS and EXAFS: Structure and Luminescence in Ge Quantum Dots
Karatutlu A, Little WR, Sapelkin AV et al.
DOI: 10.1088/1742-6596/430/1/012026


Above room temperature ferromagnetism in Si:Mn and TiO(2-delta)Co.
Granovsky A, Orlov A, Perov N et al.
J Nanosci Nanotechnol, Volume 12, issue 9, page 7540, 1st September 2012.
DOI: 10.1166/jnn.2012.6543

Charge transfer between carbon nanotubes and sulfuric acid as determined by Raman spectroscopy
Puech P, Hu T, Sapelkin A et al.
PHYSICAL REVIEW B, Volume 85, issue 20, 9th May 2012.
DOI: 10.1103/PhysRevB.85.205412

Raman excitation spectroscopy of carbon nanotubes: effects of pressure medium and pressure
Ghandour AJ, Sapelkin A, Hernandez I et al.
HIGH PRESSURE RESEARCH, Volume 32, issue 1, page 67, 1st January 2012.
DOI: 10.1080/08957959.2011.649280


Effect of water on resonant Raman spectroscopy of closed single-walled carbon nanotubes
Ghandour AJ, Dunstan DJ, Sapelkin A et al.
PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS, Volume 248, issue 11, page 2548, 1st November 2011.
DOI: 10.1002/pssb.201100074

Raman G-mode of single-wall carbon nanotube bundles under pressure
Ghandour AJ, Dunstan DJ, Sapelkin A
J RAMAN SPECTROSC, Volume 42, issue 8, page 1611, 1st August 2011.
DOI: 10.1002/jrs.2905

Neuron cells uptake of polymeric microcapsules and subsequent intracellular release.
Pavlov AM, Sapelkin AV, Huang X et al.
Macromol Biosci, Volume 11, issue 6, page 848, 14th June 2011.
DOI: 10.1002/mabi.201000494


Carbon Nanotubes on Polymeric Microcapsules: Free-Standing Structures and Point-Wise Laser Openings
Yashchenok AM, Bratashov DN, Gorin DA et al.
ADV FUNCT MATER, Volume 20, issue 18, page 3136, 23rd September 2010.
DOI: 10.1002/adfm.201000846

Study of albumin and fibrinogen membranes formed by interfacial crosslinking using microfluidic flow.
Chang H, Khan R, Rong Z et al.
Biofabrication, Volume 2, issue 3, page 035002, 1st September 2010.
DOI: 10.1088/1758-5082/2/3/035002


Structure, electrical and magnetic properties, and the origin of the room temperature ferromagnetism in Mn-implanted Si
Orlov AF, Granovsky AB, Balagurov LA et al.
J EXP THEOR PHYS+, Volume 109, issue 4, page 602, 1st October 2009.
DOI: 10.1134/S1063776109100069

G-mode behaviour of closed ended single wall carbon nanotubes under pressure
Ghandour AJ, Dunstan DJ, Sapelkin A
PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS, Volume 246, issue 3, page 491, 1st March 2009.
DOI: 10.1002/pssb.200880503


High-pressure Raman response of single-walled carbon nanotubes: Effect of the excitation laser energy
Ghandour AJ, Dunstan DJ, Sapelkin A et al.
PHYS REV B, Volume 78, issue 12, 1st September 2008.
DOI: 10.1103/PhysRevB.78.125420

Raman G band in double-wall carbon nanotubes combining p doping and high pressure
Puech P, Ghandour A, Sapelkin A et al.
PHYS REV B, Volume 78, issue 4, 1st July 2008.
DOI: 10.1103/PhysRevB.78.045413

Structural and optical properties of porous nanocrystalline Ge
Kartopu G, Sapelkin AV, Karavanskii VA et al.
J APPL PHYS, Volume 103, issue 11, 1st June 2008.
DOI: 10.1063/1.2924417

Large-scale, reliable and robust SERS-active nanowire substrates prepared using porous alumina templates
Kartopu G, Es-Souni M, Sapelkin AV et al.
JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY, Volume 8, issue 2, page 931, 1st February 2008.
DOI: 10.1166/jnn.2008.D204

Chemical doping by sulfuric acid in double wall carbon nanotubes
Puech P, Ghandour A, Sapelkin A et al.
NSTI NANOTECH 2008, VOL 1, TECHNICAL PROCEEDINGS, page 23, 1st January 2008.


Surface texturing of Si, porous Si and TiO2 by laser ablation
Mills D, Kreouzis T, Sapelkin A et al.
APPLIED SURFACE SCIENCE, Volume 253, issue 15, page 6575, 30th May 2007.
DOI: 10.1016/j.apsusc.2007.01.078

Raman study of nano-crystalline Ge under high pressure
Sapelkin AV, Karavanskii VA, KartopU G et al.
PHYS STATUS SOLIDI B, Volume 244, issue 4, page 1376, 1st April 2007.
DOI: 10.1002/pssb.200642432

Ferromagnetism of 3-D transition metals solid solutions in titanium oxides
Balagurov LA, Klimonsky SO, Kobeleva SP et al.
J MAGN MAGN MATER, Volume 310, issue 2, page E714, 1st March 2007.
DOI: 10.1016/j.jmmm.2006.10.779


Impact of vacuum thermal treatments on the structure and magnetic properties of titanium oxide films doped with Co
Balagurov LA, Klimonsky SO, Kobeleva SP et al.
J PHYS-CONDENS MAT, Volume 18, issue 48, page 10999, 6th December 2006.
DOI: 10.1088/0953-8984/18/48/027

A novel SERS-active substrate system: Template-grown nanodot-film structures
Kartopu G, Es-Souni M, Sapelkin AV et al.
PHYS STATUS SOLIDI A, Volume 203, issue 10, page R82, 1st August 2006.
DOI: 10.1002/pssa.200622238

Nanoscale pressure effects in individual double-wall carbon nanotubes
Puech P, Flahaut E, Sapelkin A et al.
PHYS REV B, Volume 73, issue 23, 1st June 2006.
DOI: 10.1103/PhysRevB.73.233408

Formation of porous silicon at elevated temperatures
Balagurov LA, Loginov BA, Petrova EA et al.
ELECTROCHIM ACTA, Volume 51, issue 14, page 2938, 15th March 2006.
DOI: 10.1016/j.electacta.2005.09.022

Interaction of B50 rat hippocampal cells with stain-etched porous silicon
Sapelkin AV, Bayliss SC, Unal B et al.
BIOMATERIALS, Volume 27, issue 6, page 842, 1st February 2006.
DOI: 10.1016/j.biomaterials.2005.06.023

Photoluminescence relaxation kinetics in vapor etched porous silicon - art. no. 63441A
Karavanskii V, Gillin W, Sapelkin A et al.
Advanced Laser Technologies 2005, Pts 1 and 2, Volume 6344, page A3441, 1st January 2006.
DOI: 10.1117/12.694292


Formation of porous silicon on a non-conductive substrate and its use as a sacrificial layer
Andrushin SY, Balagurov LA, Liberova GV et al.
SEMICOND SCI TECH, Volume 20, issue 12, page 1217, 1st December 2005.
DOI: 10.1098/0268-1242/20/12/013

Susan Caroline Bayliss - Obituary
Sapelkin AV
PHYS TODAY, Volume 58, issue 7, page 78, 1st July 2005.
DOI: 10.1063/1.2012477


Anisotropic nanoclustered carbon phases prepared from fullerite C-60 under non-hydrostatic high pressure
Lyapin AG, Mukhamadiarov VV, Brazhkin VV et al.
FULLERENES NANOTUBES AND CARBON NANOSTRUCTURES, Volume 12, issue 1-2, page 235, 1st January 2004.
DOI: 10.1081/FST-120027163

Concerning signaling in in vitro neural arrays using porous silicon
Bayliss SC, Ashraf I, Sapelkin AV


Structural and elastic anisotropy of carbon phases prepared from fullerite C-60
Lyapin AG, Mukhamadiarov VV, Brazhkin VV et al.
APPL PHYS LETT, Volume 83, issue 19, page 3903, 10th November 2003.
DOI: 10.1063/1.1625432

The rheology of collapsing zeolites amorphized by temperature and pressure
Greaves GN, Meneau F, Sapelkin A et al.
NAT MATER, Volume 2, issue 9, page 622, 1st September 2003.
DOI: 10.1038/nmat963

Pressure-induced crossover between diffusive and displacive mechanisms of phase transitions in single-crystalline alpha-GeO2.
Brazhkin VV, Lyapin AG, Voloshin RN et al.
Phys Rev Lett, Volume 90, issue 14, page 145503, 11th April 2003.
DOI: 10.1103/PhysRevLett.90.145503

On the origin of the 2.2-2.3 eV photoluminescence from chemically etched germanium
Kartopu G, Bayliss SC, Karavanskii VA et al.
J LUMIN, Volume 101, issue 4, page 275, 1st April 2003.
DOI: 10.1016/S0022-2313(02)00570-7


Distance dependence of mean-square relative displacements in EXAFS
Physical Review B, Volume 65, issue 17, page 172, 1st May 2002.
DOI: 10.1103/PhysRevB.65.172104

Distance dependence of mean-square relative displacements in EXAFS
Physical Review B, Volume 65, issue 17, page 172104-1, 1st April 2002.
DOI: 10.1103/PhysRevB.65.172104

X-ray absorption spectroscopy under high pressures in diamond anvil cells
Sapelkin AV, Bayliss SC
HIGH PRESSURE RES, Volume 21, issue 6, page 315, 1st January 2002.
DOI: 10.1080/08957950108202590


The preparation and characterisation of gallium nitride using the Hi-Prexx facility
Russell D, Bayliss SC, Sapelkin AV et al.
DOI: 10.1016/S0921-5107(00)00673-5

High-pressure high-temperature studies of structural ordering in GaSb
Vanpeteghem CB, Nelmes RJ, Allan DR et al.
PHYS STATUS SOLIDI B, Volume 223, issue 2, page 405, 1st January 2001.


Structural studies of semiconductor-to-metal transition in the bulk amorphous solid solutions (GaSb)(1-x)(Ge-2)(x) under high pressure
Sapelkin AV, Bayliss SC, Lyapin AG et al.
Materials Science Forum, Volume 228-231, page 543, 1st July 1996.
DOI: 10.4028/


Semiconductor-metal transition in amorphous gallium antimonide at high-pressure
JETP LETTERS, Volume 59, page 130, 27th January 1994.


Carbon Nanotubes-Quantum Dot Nanohybrids: Coupling with Single Particle Control in Aqueous Solution
Small, DOI: 10.1002/smll.201603042

Influence of anneal atmosphere on ZnO-nanorod photoluminescent and morphological properties with self-powered photodetector performance
Hatch SM, Briscoe J, Sapelkin A et al.
Journal of Applied Physics, DOI: 10.1063/1.4805349

PHYSICAL REVIEW LETTERS, Volume 73, page {3262-3265}, DOI: 10.1103/PhysRevLett.73.3262

Phase transformations and the nature of the semiconductor-to-metal transition in bulk a-GaSb and a-(Ge-2)(1-x)(GaSb)(x) semiconductors under high pressure
Brazhkin VV, Lyapin AG, Khvostantsev LG et al.
PHYSICAL REVIEW B, Volume 54, page {1808-1818}, DOI: 10.1103/PhysRevB.54.1808


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