This newsletter consists of a combination of articles, highlighting both recent grant successes and those of a personal nature. Items for future newsletters and/or the PSI website should be sent to Joan.Sharp@manchester.ac.uk.

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N e w s l e t t e r s U M M E R / a u t u m n 2 0 1 1

D a r r e n g r a h a m

Congratulations to Dr Darren Graham who was recently awarded the very prestigious EPSRC Career Acceleration Fellowship, which he will hold in the PSI for the next five years.

The fellowship entitled, ‘Terahertz electron para-magnetic resonance: a window on biological exploi-tation of quantum mechanics’, will focus on con-structing a novel electron paramagnetic resonance (EPR) spectrometer operating in the terahertz spec-tral range. By utilising the sub-picoseconds capabili-ties of ultrafast laser spectroscopy, this new instru-ment will enable Darren to address a fundamental question in enzyme catalysis, ‘Have biological cata-lysts (enzymes) evolved to exploit quantum mecha-

nics?’

Darren will be col-laborating with Nigel Scrutton and Steve Rigby (MIB), David Co l l i son and Er i c McInnes (EPSRC EPR faci l i ty), Hiroyuki Nojiri (Tohoku Uni-versity), as well as instrument manufac-t u r e r s , S p e c t r a -Physics Lasers and Bruker.

C O N T R O L L E D S Y N T H E S I S O F T U N E D B A N D G A P

N A N O D I M E N S I O N A L A L L O Y S

Research by members of the PSI aimed at optimizing the light-harvesting properties of chalcogenide quan-tum dots has been published in Journal of the American Chemical Society, widely regarded as the most prestig-ious journal in Chemistry.

The work by Prof Paul O’Brien, Dr Mohammad Afzaal, Dr Javeed Akhtar, Dr David Binks, Prof Wendy Flavell, Dr Darren Graham and Dr Samantha Hardman was carried out in col-laboration with partners in the Manchester Materials Science Centre and international collaborators in Italy, Poland and Saudi Arabia.

Small clusters of semiconducting material or ‘quantum dots’ offer great potential as the light-harvesting elements in next generation solar cells—in particular because under certain conditions it is possible to generate more than one set of current carriers for every photon absorbed—a phenomenon known as ‘multiple exciton generation’ or MEG. However, it can prove difficult to synthesise dots with uniform and reproducible composition. Prof O’Brien and his group have been able to find a way to produce truly alloyed PbSxSe1-x nanoparticles of uniform composition. As the band gap of the mate-rial varies with composition, this presents the tanta-lizing prospect of being able to tune the energy of the light absorbed by the dot by simply adjusting the

composition. An important task was to prove that the particles have a uniform composition. This was achieved using energy-filtered transmission electron microscopy in the Manchester Materials Science Centre and by PSI members using X-ray photoelec-tron spectroscopy at the SuperESCA beamline at the ELETTRA synchrotron in Trieste. PSI members also contributed to demonstrating the crucial direct cor-relation between composition and band gap.

Published in Journal of the American Chemical Soci-ety, 133, 5602 (2011) - see the following link:

PbSxSe1-x ’quantum dots’, imaged using energy-filtered transmission electron microscopy. The bright colours show regions with high selenium content. Each quantum dot is around 5 nanometres across—about 1/100,000th of a human hair. Credit: Manchester Materials Science Centre, School of Materials, The University of Manchester.

http://pubs.acs.org/doi/full/10.1021/ja200750s

Dr Darren Graham

P r o m o t i o n s

Congratulations to Matthew Halsall and Krikor Ozanyan of the School of Electrical and Electronic Engineering, who have been promoted to the position of chair as of 1st August 2011.

Congratulations are also due to Dr Thomas Waigh on his promotion to the position of Senior Lecturer in the School of Physics and Astronomy.

Matthew P Halsall Professor of Photonics

Krikor B Ozanyan Professor of Photonic Sensors and Systems

Thomas A Waigh Senior Lecturer in Biological Physics

P h i l i p d a w s o n

Professor Phil Dawson has been awarded an EPSRC grant for £497,000, for the study of semi-polar and non-polar nitride based structures for opto-electronic device applications.

These new types of nitride quantum well structures could well lead to the develop-ment of LEDs capable of emitting linearly polarised light as well as the elimination of the effects of the internal electric fields that are so problematic in conventional polar quantum well structures.

C I N Z I A C A S I R A G H I

D r C i n z i a Casiraghi and her collaborators, Profs Novoselov a n d O ’ B r i e n , h a v e b e e n awarded a Royal S o c i e t y ‘ s e e d corn’ grant for

£15K to study "Synthesis and characterization of molybdenum and tungsten dichalcogenide

analogues of graphene".

Dr Cinzia Casiraghi

I n o r g a n i c p h o t o p h y s i c s a n d p h o t o c h e m i s t r y :

D D 1 3 — c a l l f o r a b s t r a c t s — D E A D L I N E 9 T H O C T O B E R 2 0 1 1 http://mxm.mxmfb.com/rsps/ct/c/1127/r/20807/l/465097

This is a call for abstracts for the conference on Inorganic Photophysics and Photochemis-try - Fundamentals and Applications : Dal-ton Discussion 13 will take place from 10-12 September 2012 at the University of Sheffield, UK

The call for abstracts deadline is 9th October 2011. Abstracts may be submitted via the above link.

The fields of photophysics and photochemis-try of metal complexes, and their associated spectroscopic methodology, have never been more topical.

Inorganic Photophysics and Chemistry - Fundamentals and Applications: DD13 aims to bring together researchers from a wide range of disciplines — from theory and ul-trafast spectroscopy to medicinal chemistry

and biology — but all with a shared interest in the use of light. Whilst the main focus of the meeting will be on inorganic com-pounds and materials the meeting will be broadly-based to reflect the interdiscipli-nary nature of the field, and contributions from all photophysics-based disciplines will be considered.

As the efficient use of light as a renewable energy source is becoming paramount this Discussion will focus on the following themes:

• Solar energy

• Energy and electron transfer

• Applications of strongly emissive com-plexes

• Bond breaking and isomerisation

Speakers include the following:

• Prof Majed Chergui, Ecole Polytechnique Fédérale de Lausanne, Switzerland

• Prof Luisa De Cola, Westfälische Wil-helms-Universität Münster, Germany

• Prof Richard Eisenberg, University of Rochester, USA

• Prof Peter Ford, University of California, USA

• Prof Chantal Daniel, Université Stras-bourg, France

• Prof Leif Hammarström, Uppsala Univer-sitet, Sweden

• Prof Craig Hill, Emory University, USA

• Prof David Parker, Durham University

Driven by the need for all weather flying, remote sensing environmental monitoring and security screening of personnel, milli-metre-wave imaging technology has been developed by QinetiQ. They are essentially video cameras working in the microwave and millimetre wave band and exploit the atmospheric properties that over path lengths of hundreds of meters, fog, cloud, haze and dust storms are largely transparent, but over much longer paths they provide in-formation about the weather and atmos-pheric constituents. Security screening of personnel is enabled by the semi-transparent nature of clothing and packaging materials.

The PSI has recently received a 35GHz quasi-optical security screening portal (photo below), which uses mechanical scan-ning, a focusing mirror, a 64-receiver ele-ment focal plane array and an illumination chamber to generate video rate imagery of persons. In maturity it constitutes a Tech-nology Readiness Level (TRL) 6 system and was used to demonstrate the capabilities of millimetre waves for security screening. Six years ago it represented the state-of-the-art in millimetre wave security screening tech-nology but was deemed by business leaders as being too large for deployment as an air- port security screening system; hence, it

has come to the University for use in educa-tion. It generates good quality images and could be used by students in image process-ing and sensor engineering projects.

The system represents several years of QinetiQ internally funded development; there were six precursors to this system which were trialled and sold to customers for evaluation. The system now in the Uni-versity represents the final and most sophis-ticated system of the series. The build cost of a single system was ~£400K and when the system is assembled it is 2m wide × 2m high × 4m long.

The 35GHz quasi-optical security screening portal showing the illumination chamber on the left hand side and the back of the imager on the right hand side. Photo credit: QuinetiQ Ltd.

Dr Neil Salmon, a QinetiQ Fellow, holds a Royal Soci-ety Industry Fel-lowship to work in the PSI, and has been responsible for d e v e l o p i n g a 22GHz millimetre wave imaging sys-

tem from a technique initially pioneered for radio astronomy into one with commercial and research applications in other areas.

The small 22GHz TRL 4 proof-of-principle

Dr Neil Salmon

aperture synthesis imager uses a 32-receiver element aperture array, a 300MHz bandwidth digital cross-correlator and algo-rithms running in a standard PC, to gener-ate video imagery in the near and far-field. It represents the current state-of-the-art in next generation millimetre-wave imagers and a possible future for imaging in this band, as it has the potential to deliver bet-te r qua l i ty images (namely th ree -dimensional in the near-field) and be made much more compact. As the technology could ultimately be integrated into a 2cm thick printed circuit substrate, it could be

integrated into existing building infrastruc-tures for security screening, into aircraft skins for all-weather flying.

This system generated its first images in April of this year, to the delight of Technol-ogy Strategy Board and European Space Agency sponsors. The system is unique and is generating exciting new data, which is currently being evaluated so that a next generation TRL 5 system can be designed and built for existing and new customers in the security and aerospace industries.

Continued on page 4

Q i n e t i q d e v e l o p m e n t s

N e w D e v i c e D e v e l o p e d t o M e a s u r e O p a q u e M a t e r i a l

V e l o c i t y P r o f i l e s

Dr Matthew Harvey and Dr Tom Waigh of the Biological Physics group, School of Physics and Astronomy, have built a new device that allows the velocity profiles of opaque materials to be measured as they are sheared. They have used it to study a range of soft matter systems under flow including colloids (polystyrene spheres in water), polyelectrolytes, margarine and plant cell suspensions (tomato ketchup). Unusual fluid mechanics/viscoelastic

phenomena have been measured such as wall slip and shear banding. The apparatus uses optical fibres. It is built around a Michelson interferometer and functions at infra red wavelengths.

Reference: M Harvey, T A Waigh, ‘Optical coherence tomography velocimetry in con-trolled shear flow’, Physical Review E, 2011, 83, 031502.

Two dimensional velocity profile of colloidal spheres measured across the gap of a plate-plate rheometer sheared at a constant rate.

Other developments achieved by the Royal Society Fellowship funded QinetiQ Fellow, Dr Neil Salmon, include 94GHz and 183GHz aperture synthesis imagers (photos overleaf). These have been developed as TRL 4 laboratory demonstrators for the European Space Agency (ESA) Terahertz Camera initiative. They are dual use test beds for security screening imagers and the ESA Geostationary Atmospheric Sounder (GAS) programme. Used for security screening, the system generates small im-ages with a spatial resolution of 2cm at a range of 2m.

The GAS programme has the 10-year time-scale goal of launching an Earth observation satellite into orbit to monitor the environ-ment. The imager of this sensor needs to have an aperture size of 7m to achieve the required 30km diffraction limited spatial resolution on the Earth’s surface for short

term weather forecasting (now-casting). Only an aperture synthesis imager can meet the launch weight and volume payload re-quirements; a quasi-optical imager would exceed the payload limits.

The Michelson interferometer Fourier trans-form spectrometer, located in the PSI, is ca-pable of making very precise measurements of the refractive index and extinction coeffi-cients of materials with sub-GHz frequency resolution over the 80-1200GHz spectral range. The system has been used extensively by QinetiQ in the characterisation of materi-als used in its millimetre wave imagers and for understanding the signatures of threats and the properties of clothing and packaging materials for security screening. The system is on long-term loan to the University of Manchester to support research and technol-ogy development projects in the millimetre and sub-millimetre wave bands.

The 94GHz, 10-channel aperture synthesis imager (above) and the 183GHz, 4 channel aper-ture synthesis imager (below), as demonstrators for next generation earth observation and secu-rity screening technology.

Q I N E T I Q d e v e l o p m e n t s c o n t i n u e d

C o v e r a r t i c l e

Dr David Binks has written a 'perspective' article by invitation of the editors of 'the Jour-nal of Physical Chemistry Chemical Physics, enti-tled ‘Multiple exciton generation in nanocrys-tal quantum dots – controversy, current status and future prospects’.

Multiple Exciton Generation (MEG) is an effect in nanocrystals by which a single ab-sorbed photon can produce multiple charges, and has the potential to significantly improve the efficiency of solar cells. The article

discusses the controversy that has surrounded MEG in recent years and the improved un-derstanding of experimental data that has emerged recently, which has allowed seem-ingly contradictory results to be reconciled. The article also examines the current state-of-the-art, the potential impact on solar cell efficiency and proposes a quantum dot struc-ture designed to optimise MEG efficiency.

http://pubs.rsc.org/en/journals/journalissues/cp

t a l k p r i z e

At the Centre for Doctoral Training Nano-conference Conference 2011, held on 5-8 June, Mr Thanasis Georgiou was awarded third prize for his talk entitled, “Graphene bubble as adaptive focus lens”. Supervised by Dr Cinzia Casiraghi and Prof Kostya Novoselov, Thanasis is in his first year of PhD study and has shown that gra-phene bubbles are good candidates for mak-ing adaptive-focus lenses.

Robust, cheap and optically transparent, graphene is a useful material for use in op-tics. However, small bubbles are found when large area graphene flakes are depos-ited on a substrate. These bubbles are highly

E P S S C H O L A R S H I P

Published by Research Councils UK, “Big Ideas for the Future,” June 2011, includes an article on the microsphere optical nano-scope developed by Prof Lin Li, Dr Zengbo Wang et al. on page 34, entitled, “More Powerful Microscopes.”

http://www.rcuk.ac.uk/documents/publications/

Professor David W a t t s o f t h e School of Dentistry was awarded the 2011 President’s Prize for leadership in B iomater i a l s research at the UK Society for Bioma-terials annual con-ference held at the

University of Greenwich, 30 June to 1 July 2011. David gave a keynote lecture entitled, “Are you enjoying biomaterials research”.

The UK Society of Biomaterials (UKSB) was set up to serve a diverse, interdisciplinary biomaterials research community. This was in response to the findings of a joint working

party of the Institute of Materials and the Institute of Engineering in Medicine. The UKSB is the demographic Society for the whole biomaterials community.

In Berlin earlier that week, on 27 June, David attended a lecture on science policy by Federal Chancellor, Dr Angela Merkel. Attendance by invitation only was organized by the Alexander von Humboldt Founda-tion.

Every year the Foundation enable more than 2,000 researchers from all over the world to spend time researching in Germany. The Foundation maintains a network of well over 25,000 Humboldtians from all disci-plines in more than 130 countries world-wide, including 44 Nobel Prize winners.

Prof David Watts

I n c om pe t i t i o n with other appli-c a n t s , M i s s Huafeng Yang has been awarded a Faculty Scholar-ship, which will pay her fees and maintenance for three years.

Miss Yang will commence PhD study in September under the supervision of Dr Cin-zia Casiraghi to study a project entitled, “New composite materials based on gra-phene for solar cells and photovoltaics”.

stable under am-bient conditions. T h a n a s i s h a s shown it is possi-ble to control the curvature of a b u b b l e a n d change its shape by applying a gate v o l t a g e . T h i s behaviour enables graphene to be used in optical elements, for example, as the basis for an adaptive focus lens.

Thanasis Georgiou

Huafeng Yang

N E W X - R A Y I M A G I N G B E A M l i n e

A new Coherent X-ray imaging beam line (l13) has been commissioned at the Diamond Synchrotron Centre, opening up a range of new opportunities for imaging condensed matter with 10-50nm resolution for the UK Science Community.

The imaging techniques do not need invasive sample preparation methods, as are required

for transmission electron microscopy — microtoming of specimens is not required. Furthermore, fluorescent staining is not required, as with super-resolution microscopies at visible optical wavelengths. In addition, thick opaque samples can be investigated. A new review of

Dr Tom Waigh

the emerging techniques has been published.1

Condenser lens

Sample Phase ring

Detector

Objective lens

X-ray and neutron imaging of nanoparticles

Reference1: X-ray and neutron imaging with colloids, T A Waigh, C Rau, Current Opinion in Colloids and Interface Science, 2011, see above link.

B i g i d e a s f o r t h e

f u t u r e D A V I D W A T T S

http://www.sciencedirect.com/science/article/pii/S1359029411000938

P U T T I N G S U N S H I N E I N T H E T A N K — U S I N G N A N O T E C H N O L O G Y T O M A K E S O L A R F U E L

http://royalsociety.org/summer-science/2011/solar-nanotech/

Scientists from the PSI are working on how to use the energy of the Sun to make fuels, which could help to solve the world’s esca-lating energy crisis and presented their re-search at the Royal Society’s annual Summer Science Exhibition held 5-10 July 2011.

Working with the Universities of East An-glia, York and Nottingham and using nanotechnology 100,000 times smaller than the thickness of a human hair, the research-ers are working to harness the vast energy of the Sun to produce clean fuel.

Members of the consortium at UEA have al-ready found a way to produce hydrogen from water. A revolutionary future use of this technology could be to make the fuel for hydrogen-powered cars, rather than making it from fossil fuel. Now the scientists are aiming to use the same technology to create alternatives for other fuels and feedstock chemicals, including turning methane into liquid methanol and carbon dioxide into car-bon monoxide.

The sun’s potential is vast – just one hour of sunlight is equivalent to the amount of en-ergy used over the world in an entire year – yet no one has yet tapped into its immense power to make fuels directly.

Professor Wendy Flavell, from the School of Physics and Astronomy, and her colleagues are working to create a solar-nano-device using ‘quantum dots’ – tiny clusters of semiconducting material which

absorb sunlight.

When sunlight is absorbed, carriers of elec-tric current are created. Together with cata-lyst molecules grafted to the surfaces of the dots, these create the new fuel – for exam-ple hydrogen can be produced from water.

Professor Flavell said: “Our sun provides far more energy than we will ever need, but we use it really inefficiently. To make better use of the fantastic resource we have in our Sun, we need to find out how to create solar fuel that can be stored, shipped to where it is needed and used on demand. Most hydro-gen has so far been obtained from fossil fuels, which will not last forever, so it is important to get energy from renewable sources.

One of the key questions is: ‘what do we do when the sun goes down, what happens at

night?’ If we can store the energy harnessed from the sun during the day then we will have supplies ready to use when the sun is not shining. This is a first step in taking the vast power of the sun and using it to pro-vide the world’s fuel needs.”

The Royal Society Summer Science Exhibi-tion showcased cutting edge research in science and engineering from across the UK and is held annually at the Royal Society, the UK’s national academy of science. This year, 21 exhibits were selected from 97 applications.

At the exhibition, Professor Flavell and her team displayed an interactive world map which showed children and other visitors just how much energy the Sun provides.

There was also a chance to see the quantum dots at work, and show simply by changing the size of the dots, how the colour of light they absorb or give out can be changed. A solar cell that produces hydrogen directly from the electricity generated was on dis-play and a chance to race solar-powered and hydrogen-powered model racing cars.

The team working on the exhibit was 25-strong, from four participating universities. The PSI team included Wendy Flavell, David Binks, Andrew Thomas, Dar-ren Graham, Samantha Hardman, Karen Syres, Patrick Lunt, David Cant, Jon Treacy and Icell Mah-moud.

Making solar fuel: light-driven generation of hy-drogen at an electrode using a molybdenum catalyst. Photo credit: Energy Materials Laboratory, Univer-sity of East Anglia

H e l e n g l e e s o n

At the recent International Conference on Frontiers of Polymers and Advanced Mate-rials, held in Pretoria (May 2011), Profes-sor Helen Gleeson was presented with an award in Recognition of her Achieve-ments in Scientific Endeavors. Helen was one of two women who received the award, which was presented at the confer-ence dinner, having had her face painted in traditional Zulu style!

The conference covered a wide variety of topics in materials science and Helen gave a Plenary Lecture on Laser Tweezing in Liq-uid Crystals. Attending the conference also gave the opportunity to follow up on a Royal Society funded visit to the Laser Insti-tute in Pretoria, made with Mark Dickinson and David Binks in September 2010.

Prof Heleln Gleeson

Please send any items you have either for The Photon Science Institute website or the next newsletter to joan.sharp@manchester.ac.uk