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Materials Research Institute

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Dr Kevin Donovan

Reader in Molecular Physics

Department School of Physics and Astronomy
 G O Jones 117, Mile End
Telephone +44 (0)20 7882 3410
Email k.j.donovan@qmul.ac.uk
Homepage http://ph.qmul.ac.uk/directory/k.j.donovan

Research Keywords

Molecular Electronics, Electron Transport, Polydiacetylenes, Langmuir-Blodgett Films, Carbon nanotubes

Research Interests

1. Single Walled Carbon Nanotubes. The induced polarisability of single walled carbon nanotubes, SWCNTs, has provided a powerful tool for their study. While there is no permanent dipole moment  the induced dipole can be substantial at even moderate fields allowing the manipulation of the SWCNTs under the action of various forces. This leads to several related but seperate studies;

(i) Dielectrophoresis.The differential polarisability of different species of SWCNT, specifically metallic and semiconducting, make the dielectrophoretic force an interesting candidate for use in the separation of SWCNTs. In a non-uniform electric field the induced dipole experiences a dielectrophoretic translational force and the motion of nanotubes under the action of such forces is the subject of study. Of particular interest is the relationship between Brownian and viscous forces and their action on nanoscale objects compared with the more familiar mesoscale objects described by classical hydrodynamics

 (ii) The Kerr Effect. In a uniform electric field, SWCNTs in suspension will experience a rotational torque and can be made to rotate in viscous media. The consequent alignment renders a previously  isotropic suspension anisotropic and thus birefringent (refractive index depending on polarisation state of light). The study of rotational dynamics of nanoscale objects becomes possible by imposing transient electric fields.

(iii) Induced Dichroism. Similarly, in a uniform field the isotropic sample will become increasingly dichroic (absorption depending on polarisation state of light) as alignment proceeds. Dynamic studies are undertaken of induced linear dichroism in order to more closely relate the dynamics of nanoscale objects to their well studied mesoscale counterparts.

(iv) Rheology of SWCNT suspensions. The application of a controllable torque and the measurement of the dynamic response of SWCNTs allows study of the efffect of the SWCNTs on the viscosity of their local environment and how the nanotube concentration affects this.

2. Charge Transport.  A second research interest is the study of the effects of reduced dimensionality on charge transport. This is a situation commonly encountered when the condensed matter is held together by a mixture of van der Waals and covalent bonding and has consequences for the rates of charge carrier scattering (mobility), trapping and bimolecular recombibnation which have been studied in the context of polydiacetylene single crystals.

The technique of photoconductivity including time resolved photoconductivity with temporal resolution covering times from 100 picoseconds to DC is used to study the effects of reduced dimensionality on charge transport. The high end of this temporal resolution is among the fastest achieved anywhere, worldwide. The Auston switch technique has been developed to this end with a novel application for samples suspended in solvents and contained in an integrated co-axial geometry cell based around the Auston technique.

The charge transport in a range of organic materials has been studied and these include;

(i) Columnar, Discotic Liquid Crystals.

(ii) Carbon nanotubes.

(iii) Polydiacetylene conjugated polymers. 

(iv) Langmuir Blodgett multilayers.

Key Publications

Donovan KJ and Scott K (2013). Anomalous intrinsic viscosity of octadecylamine-functionalised carbon nanotubes in suspension. J Chem Phys  vol. 138, (24) 10.1063/1.4811279

Robb-Smith TJ, Donovan KJ, Scott K and Somerton M (2011). Induced electro-optic effects in single-walled carbon nanotubes. II. Hydrodynamics of nanotubes in viscous media. Phys Rev B  vol. 83, (15) 10.1103/PhysRevB.83.155415

Robb-Smith TJ, Donovan KJ, Scott K and Somerton M (2011). Induced electro-optic effects in single-walled carbon nanotubes. I. Polarizability of metallic nanotubes. Phys Rev B  vol. 83, (15) 10.1103/PhysRevB.83.155414

Scott K, Somerton M, Bunning JC and DONOVAN KJ (2005). Bimolecular recombination on carbon nanotubes. Phys. Rev. B  vol. 71, (8) 085412-1-085412-6. 10.1103/PhysRevB.71.085412

Kreouzis T, Donovan KJ, Boden N, Bushby RJ, Lozman OR and Liu Q (2001). Temperature-independent hole mobility in discotic liquid crystals. J Chem Phys  vol. 114, (4) 1797-1802. 10.1063/1.1334958

2016

Sun YW, Hernández I, González J, Scott K, Donovan KJ, Sapelkin A, Rodríguez F and Dunstan DJ (2016). Significance of bundling effects on carbon nanotubes' response to hydrostatic compression. Journal of Physical Chemistry C  vol. 120, (3) 1863-1870. 10.1021/acs.jpcc.5b09082

2014

Velarde MG, Chetverikov AP, Ebeling W, Wilson EG and Donovan KJ (2014). On the electron transport in polydiacetylene crystals and derivatives. Epl  vol. 106, (2) 10.1209/0295-5075/106/27004

2013

Donovan KJ and Scott K (2013). Anomalous intrinsic viscosity of octadecylamine-functionalised carbon nanotubes in suspension. J Chem Phys  vol. 138, (24) 10.1063/1.4811279

2012

Donovan KJ and Scott K (2012). Anomalous effective hydrodynamic radius of octadecylamine functionalised single walled carbon nanotubes. Carbon  vol. 50, (10) 3807-3815. 10.1016/j.carbon.2012.04.007

2011

Robb-Smith TJ, Donovan KJ, Scott K and Somerton M (2011). Induced electro-optic effects in single-walled carbon nanotubes. II. Hydrodynamics of nanotubes in viscous media. Phys Rev B  vol. 83, (15) 10.1103/PhysRevB.83.155415

Robb-Smith TJ, Donovan KJ, Scott K and Somerton M (2011). Induced electro-optic effects in single-walled carbon nanotubes. I. Polarizability of metallic nanotubes. Phys Rev B  vol. 83, (15) 10.1103/PhysRevB.83.155414

2010

Preece MMPINSPRASKKJDAJA (2010). Design and Synthesis of Novel Calamitic and Discotic Materials Based on the Photorefractive Carbazole Unit. Inforaworld  Mol. Crys. Liq. Crys  vol. 84, (518) 84-100. 10.1080/15421400903568054

2006

Donovan KJ, Scott K, Somerton M, Preece J and Manickam M (2006). Transient photocurrents in a charge transfer complex of trinitrofluorenone with a carbazole substituted discotic liquid crystal. Chem Phys  vol. 322, (3) 471-476. 10.1016/j.chemphys.2005.09.036

2005

Donovan KJ and Scott K (2005). Transient electric birefringence in suspensions of single-walled carbon nanotubes. Phys Rev B  vol. 72, (19) 10.1103/PhysRevB.72.195432

Lutz T and Donovan KJ (2005). Macroscopic scale separation of metallic and semiconducting nanotubes by dielectrophoresis. Carbon  vol. 43, (12) 2508-2513. 10.1016/j.carbon.2005.05.002

Bunning JC, Donovan KJ, Bushby RJ, Lozman OR and Lu Z (2005). Electron photogeneration in a triblock co-polymer discotic liquid crystal. Chem Phys  vol. 312, (1-3) 145-150. 10.1016/j.chemphys.2004.11.032

Scott K, Somerton M, Bunning JC and DONOVAN KJ (2005). Bimolecular recombination on carbon nanotubes. Phys. Rev. B  vol. 71, (8) 085412-1-085412-6. 10.1103/PhysRevB.71.085412

Bushby RJ, Donovan KJ, Kreouzis T and Lozman OR (2005). Molecular engineering of triphenylene-based discotic liquid crystal conductors. Opto-Electron Rev  vol. 13, (4) 269-279.

2004

Bunning JC, Donovan KJ and Scott K (2004). Observation of transient photocurrents on suspended nanotubes. J Appl Phys  vol. 96, (7) 3939-3944. 10.1063/1.1789268

2003

Scott K, Donovan KJ, Kreouzis T, Bunning JC, Bushby RJ, Boden N and Lozman OR (2003). Quantum efficiency of photogeneration in discotic liquid crystals: Part 1: Temperature and wavelength dependence. Molecular Crystals and Liquid Crystals  vol. 397, 553-561. 10.1080/15421400390214185

Donovan KJ, Kreouzis T, Scott K, Bunning JC, Bushby RJ, Boden N, Lozman OR and Movaghar B (2003). Molecular engineering the phototransport properties of discotic liquid crystals. Molecular Crystals and Liquid Crystals  vol. 396, 91-112. 10.1080/15421400390213221

Bunning JC, Donovan KJ, Kreouzis T, Scott K, Bushby RJ, Boden N and Lozman OR (2003). Quantum efficiencies of photogeneration in discotic liquid crystals. Part 2: Electric field and temperature dependence. Molecular Crystals and Liquid Crystals  vol. 397, 563-571. 10.1080/15421406390214194

2002

Pecchia A, Lozman OR, Movaghar B, Boden N, Bushby RJ, Donovan KJ and Kreouzis T (2002). Photoconductive transients and one-dimensional charge carrier dynamics in discotic liquid crystals. Phys Rev B  vol. 65, (10) 10.1103/PhysRevB.65.104204

2001

Boden N, Bushby RJ, Donovan K, Liu QY, Lu ZB, Kreouzis T and Wood A (2001). 2,3,7, 8,12,13-Hexakis[2-(2-methoxyethoxy)ethoxy]-tricycloquinazoline: a discogen which allows enhanced levels of n-doping. Liq Cryst  vol. 28, (12) 1739-1748. 10.1080/02678290110082383

Kreouzis T, Donovan KJ, Boden N, Bushby RJ, Lozman OR and Liu Q (2001). Temperature-independent hole mobility in discotic liquid crystals. J Chem Phys  vol. 114, (4) 1797-1802. 10.1063/1.1334958

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