J.
PS700
Case for support
Case for support
PS700
The Investigation of Illicit substances detection using silicon nanowires.
Overview of the project
This research project is primarily about new technology research in the area of explosives detection.
It involves using the Nano-wires in order to detect illicit substances at a very low level via changes in
electrical stability. Aspiring to develop more sensitive techniques for detecting explosives to meet
demand, as terrorist plots become more complex. Airport security is not the only application for
these techniques; clearing war-zones of mines and detecting explosives at a stand-off distance is also
becoming more and more desirable in this field. This project will entail the attempted detection of a
wide range of types of explosives, from nitroaromatics to peroxide based explosives, discovering
detection limits as we go. The focus project will then move on to the use of Nano-wires for detection
of other illicit substances, such as drugs of abuse, through the research of suitable compounds to
functionalise the surface of the nano-wires and methods to do that.
The need for research
The need for explosives detection has recently been prioritised by counter-terrorism units and
homeland securityi. In 2009 a total 10999 terrorist attacks were carried out, 4350 of these involved
the use of explosive materials, killing 10,000 and injuring 20,000 people.ii In the 4 years between
2005 and 2009 a 50% increase was seen in the number of suicide bombings and it doesn’t seem to
be slowing.iii A method for detecting explosives is needed for field use, this area of research is
incredibly important as it may save lives.
Current Methods for detecting explosives:
There are three methods of detection of explosives; through detection of vapours given off from the
explosive using methods such as electric nose sensors; detection of solid explosives, dissolved in
solutions or in suspensions via fluorescence quenching; as well as those that can be used on a solid
state samples.ivOther detection methods employ the use of animals; canines, or sniffer dogs. They
have sensitivity to detect vapours 3 to 5 orders of magnitude lower concentrations than humans.
Rats these have been investigated in research, they also have a heightened sense of detecting
vapours, however, the reliability of this area of detection is in question.v
Methods of detection can be made from different areas of chemistry such as: fluorescencevi and
colour change experimentsvii, however these methods do not meet necessary criteria. Nanosensors
have been researched in this area of detection yielding promising results with electronic nose
sensors. The more recent developments in nano-technologies have led to research in the area of
silicon nano-wires for explosives detection; they work on a similar principle to electronic nose
devices. Manufactured Si-NW are functionalised with an amine surface (APTES (3aminopropyltriethoxysilane)) The amine surface, reacts with the electron deficient nitro groups on
2,4,6-TNT through acid-base reactions which forms Meisenheimer complexes. These reactions
change the electrical stability of the nano-wires, reducing their conductance values. This can be
measured and has been used to detect 2,4,6-TNT at femtomolar levels.viii It is a sensitive technique,
but is yet to be proven as a selective one over a large range of explosives, this is what I plan to
achieve in this project.
Issues with current detection methods:
The importance of improving the current explosive detecting techniques is vital, as airport security
are yet to have a single method which is selective, sensitive and fast which can be used efficiently to
scan passengers for air travel. Current methods are time consuming, expensive and require experts
to use. Other disadvantages of current methods include those such as the branding of backscatter x1|Page
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PS700
Case for support
ray machines as “a virtual strip search”ix. The proposed introduction of backscatter x-ray technology
has raised questions as to the privacy issue as it allows you to see down to the skin of the subject.
However, issues of other methods being time consuming and inefficient would be solved.
Current methods of explosives detection are less than sufficient, methods including metal detectors
being used to detect concealed weapons and x-ray machines and CT-scanners being used to see
inside the baggage of passengers.x However, this problem can be easily avoided by criminals by not
using metal objects.
It is not unusual for explosives to be packaged with materials to prevent vapour leakagexi or to have
the explosive with less than 100% purity such as in the soil, making detection through vapour
methods very difficult, requiring sensitive techniques. What with vapour pressures of explosives
being incredibly low, this only enhances the need for more sensitive techniques.
Carbon nano-wires have been researched, however they have been shown to be extremely sensitive
in the presence of oxygen, in terms of their electronic properties.xii
Criteria for new research:
New research into explosives detection should fit the criteria that the resultant method produced
should be fast, in that the detection of explosives can be carried out within a few seconds, efficient
as in the method produced should be able to be economically mass produced for field use, sensitive
it must be able to detect explosives at the parts per trillion level due to low vapour pressures of
explosives, selective as in it must be able to detect a range of explosives and results produced must
indicate what the substance is, suitable for field use in that this method should be able to be
employed at airports across the globe seamlessly. The ease of use for airport personnel is also a
necessity as this will bring down costs.
Track record and experience
My track record in terms of projects consist of my final year university project involving new
materials for explosives detection which used electron rich solid state labelled polymers which,
when exposed to vapours of various nitroaromatics, the fluorescence of these samples would
quench. As a result I have conducted a lot of research in the area of explosives detection and
therefore my knowledge of the subject is vast. It also gives me experience which I can take forward
and apply to this project as it involved handling similar chemicals as well as understanding the
integral mechanics behind explosive chemicals and their detection.
My supervisor for this project will be Dr. S.J. Holder, he was my supervisor for my project on New
Materials for the detection of explosives and so he has experience on guidance throughout projects
as well as interpretation of results. He has to his name, over 60 published papers and projects since
1984, mostly on materials chemistry and polymer properties. His past work includes:
[1]. Synthesis and characterisation of pyrene-labelled polydimethylsiloxane networks: towards the in situ detection of
strain in silicone elastomers, Nicholas A. A. Rossi, Elizabeth J. Duplock, Jon Meegan, David R. T. Roberts, Julian J. Murphy,
Mogon Patel and Simon J. Holder, J. Mater. Chem., 2009, 19, 7674–7686
[2]. Optical response to stress in pyrene labelled polydimethylsiloxane elastomers: Monitoring strain in 1D and 2D, David
R.T, Roberts, Mogon Patel, Julian J. Murphy, Simon J. Holder, Sensors and Actuators B: Chemical, Elsevier, Volume 162,
Issue 1, 20 February 2012, Pages 43–56
[3]. Mechanochromic systems for the detection of stress, strain and deformation in polymeric materials Roberts,
DRT ; Holder, SJ , Journal of materials chemistry, volume 21, 23, 8256-8268, 2011
[4].High, LRH; Holder, SJ; Penfold, HV"Synthesis of star polymers of styrene and alkyl (meth)acrylates from a porphyrin
initiator core via ATRP"MACROMOLECULES, 40: 7157-7165, 2007
[5].Holder SJ, Achilleos M, Jones RG,Increasing molecular weight parameters of a helical polymer through polymerization in
a chiral solvent ,JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 128 (38): 12418-12419 SEP 27 2006
[6].Popescu DC, van Leeuwen ENM, Rossi NAA, Holder SJ, Jansen JA, Sommerdijk NAJM , Shaping amorphous calcium
carbonate films into 2D model substrates for bone cell culture ANGEWANDTE CHEMIE-International Edition 45 (11): 17621767 2006
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[7].Popescu DC, Lems R, Rossi NAA, Yeoh CT, Loos J, Holder SJ, Bouten CVC, Sommerdijk NAJM , The patterning and
alignment of muscle cells using the selective adhesion of poly(oligoethylene glycol methyl ether methacrylate)-based ABA
block copolymers , Advanced Materials 17 (19): 2324+ OCT 4 2005
[8].Street G, Illsley D, Holder SJ, Optimization of the synthesis of poly(octadecyl acrylate) by atom transfer radical
polymerization and the preparation of all comblike amphiphilic diblock copolymers
Journal of science, Part A-Polymer Chemistry,43 (5): 1129-1143 MAR 1 2005
[9].Kurjata J, Chojnowski J, Yeoh CT, Rossi NAA, Holder SJ, Synthesis of poly[dimethylsiloxane-block-oligo (ethylene glycol)
methyl ether methacrylate]: an amphiphilic copolymer with a comb-like block , Polymer 45 (18): 6111-6121 AUG 19 2004
Other papers include the modification of polymers and copolymers for uses in biochemical and
biomedical research as well as self-assembly of molecular receptors into nanostructures of
controlled shape and size.
A full list of published papers can be found at:
http://apps.webofknowledge.com.chain.kent.ac.uk/summary.do?SID=X21dA7OOL474C1NoF1B&pro
duct=WOS&qid=1&search_mode=
An increase in citations over recent yearsxiii shows the ever
increasing value of his research, something which he aims to
bring to this project. With a total of 518 citing articles
without self-citation and an average of over 12 citations per
paper, it shows that the experience in the novelty research
shows to promote further research in the subjects which he
chooses.
Aims of the project
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To further the fundamental research and apply it to detection of a wide range of explosives
Gain increased knowledge into the flexibility of new Nano technologies
To research possible alternative materials for functionalizing nano-wires to detect illicit
substances.
To determine the limiting parameters of Si-NW technologies and determine the lengths to
which analysis can be made using them.
Objectives
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To manufacture Silicon nanowires and distinguish the best method for such manufacture.
To functionalise these Nano-wires with an amine surface
To use the functionalised Nano-wires to attempt to detect a range of nitroaromatics in liquid
and vapour state.
To research possible alternatives to APTES to functionalise the Nano-wires in order to detect
peroxide based explosives both in liquid and vapour state.
To research possible alternatives to APTES that could be used to detect drugs of abuse.
To obtain the new functional material and functionalise the Nano-wires with it.
To functionalise these Nano-wires them to detect other substances such as drugs of abuse
and their limits of detection.
To expand the range of substances that new Nano-technologies can be used to detect, whether
through expanding the library of explosive compounds, or to branch out into a different set of
compounds which are illicit thereby increasing knowledge of the selectivity of the technology. The
flexibility of this technology should be discovered as well as the sensitivity.
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PS700
Case for support
Beneficiaries
My choice institution is the University of Kent.My reasons for selecting this institution is it's record
for excellence in research in the physical sciences and materials chemistry, largely the area of this
proposed research. The beneficiaries of this research are primarily the everyday airline travellers,
who could travel in safety, should this project produce a detection method fulfilling all the criteria.
The airlines would also benefit from the production of a detection method from this research, saving
them time and money and hence through safer air travel, increasing their turnovers through
increased popularity of air travel. Other researchers will also benefit from further research into
nano-technologies, it is a relatively recent area of research and so there is very little information at
the moment, this project would expand on this data. The University of Kent will benefit as it will
become recognised as a centre for ground-breaking research. I shall benefit from the project
through the production of bi-annual progress reports and presentations of progress, skills for report
writing and public speaking shall be improved as well as confidence in the matters. Analytical
chemistry skills will be improved using a wider range of techniques than in previous projects.The
possible improvements to detection of substances of abuse and a wider range of explosives could
give rise to benefits to the military and the police force in harnessing the technology for the field.
Research programme
The first step in this project, after the purchase of all necessary materials, is creating the nano-wires,
the next step is creating a set-up allowing exposure of molecules to the nano-wires. The next step is
the preparation of samples both in liquid and vapour phase for analysis and run the samples. A limit
of detection shall be established using less and less concentrated samples in an experiment.
Research will then be needed to be conducted on a new material to be used to functionalize the
Nano-wires to enable the detection of peroxide based explosives. A method must be formed for the
physical functionalization process. Then, samples must be prepared for analysis and samples of
peroxide explosives analysed in both vapour and liquid phase. Experiments will be conducted to
achieve detection limits of the method
A final research phase will be employed to extend the technique and explore its flexibility to detect
other illicit substances, for example, drugs of abuse. Research will need to be done on a new
functionalization molecule. A new method must be discovered for the functionalization process. This
method will then be used and a range of drugs of abuse shall be analysed. A detailed schedule of
work can be found attached.
Milestones
Year 1
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Manufacturing and characterization of the Si-nano-wires
Functionalizing the wires successfully
Detection of nitro-aromatics using the nano-wires
Determination of a detection limit using the wires.
Determination of a degree of selectivity that the wires possess for detection
Comparing all results with experiments performed on the purchased nano-wires to
determine the reproducibility of the technology.
Data interpretation of the year’s collection.
Production of progress reports every 6 months.
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Year 2
 Discovering a replacement for APTES for the functionalization of the nano-wires for peroxide
detection
 Obtaining a method for the functionalization of the nano-wires using the molecule.
 Using Peroxide based explosives determine a qualitative experiment for detection.
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PS700
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Year 3
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Case for support
Determine a detection limit of the technology to detect peroxide based explosives
Data interpretation of the experiments.
Production of progress reports, every 6 months.
Discovering a replacement for APTES for the functionalization of the nano-wires for drug
detection
Obtaining a method for the functionalization of the nano-wires using the molecule.
Qualitatively detecting drugs of abuse using the functionalized Si-NW.
Discover a detection limit for the detection of various drugs of abuse.
Compare the results of all experiments with those using nano-wires purchased and
produced by Angewandte Chemie.
Production of a progress report for the first half of the year
Completion of full report and data analysis.
Methodologies
Creating the nano-wires
The research in this project very much follows the methodology employed in the research conducted
by Yoni Engel ET. alxiv. They manufactured nanowires field-effect transistors through CVD- Chemical
Vapour deposition; they were then fabricated using photolithography. Source and drain electrodes
which had been passivated were briefly deposited using a multilayer photoresist structure. The
contacts were then metallized by electron beams and thermal evaporation; the wires were then
insulated using a layer of Si3N4 using PECVD (plasma-enhanced chemical vapour deposition).Finally,
the chip was coated with a 100μm SU-8 3050 photoresist. My aim is to purchase these nano-wires
from Angewandte Chemie, but also to try and create the nano-wires myself, following the same
method. Determination of the thickness and orientation of the nano-wires will be employed
through the characterisation of the nanowires including techniques such as EDS (Energy dispersive xray spectroscopy), xps ( x-ray photoelectron spectroscopy)xv. The employment of a new
SEM(scanning electron microscope) at Kent will also aid in the characterization process.
Creation of a fluid delivery system
The next step involves the creation of a fluid delivery system. This will be done through the use of
the elastomer: PDMS (the elastomer which I previously used in my final year project and the subject
of many research projects conducted by Holder.SJ)mixed in a 10:1 ratio of base to curing agent. The
PDMS is then cured in an oven at 60oC, overnight and then cut into rectangular pieces. A fluid
delivery system is created by the lithographically-defined SU-8 channel sealed by the PDMS.xi
Functionalization of the Nano-wires
To functionalise the surface of the Si-NW, the chip is treated, primarily with 1%(v/v) 3aminopropylethoxysilanesilane in ethanol, it is left to stand and then filtered through a cut-off
syringe filter. It is then immersed in a solution of silane/ethanol, then rinsed and dried in a stream of
nitrogen gas, then baked. Ellipsometry will then be employed in order to determine correct
molecular layer thickness.xi
Project Management
Every task shall be performed by me, my supervisor will provide three hours of supervision a week,
including one meeting of 1 hour per week to discuss progress, the other two hours are allocated for
overrunning of the meetings and also for occasional help in the lab. Management of the project shall
also be achieved by target setting and goal achievement which is time-based. Through the following
of a strict schedule of tasks and the displaying of time-management skills. Co-ordination between
the supervisor and myself will result in all deadlines being met and the smooth running of the
project.
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Case for support
Dissemination of Results
The supervisor of this project has demonstrated publishing in a number of journals, with papers
written and referenced by a huge number of other research projects and fellows. Exploitable results
shall be made available and broadcast to the scientific community via talks at conferences and
publishing of papers. The beneficiaries of the project shall be contacted as interpreted results are
analysed and verified. The creation of a website by myself shall contain the on-going updating
process of results and progress of the project in real time format. Any arising opportunities to
patent technologies, methods, new chemicals and functional materials shall be achieved through
contact with university offices and the relevant authorities.
Where does this research fit in with ESRPC?
This research will not only provide postgraduate training but also extend and promote basic, and
applied research into the area of nano technologies. The successful production of an explosives
detection technique will add to the advancements in technology to spring from the United Kingdom
as well as improve both the quality and length of life of worldwide travellers. The research will
generate public understanding of the technology as well as generating awareness of the very real
threat of explosives in airports and the current issues. Advice will be given to the beneficiaries of the
project on what steps to employ on the road to their goals through innovation and ground-breaking
research.
Referees
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Case for support
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PS700
Case for support
Funding Justification
My Directly Incurred costs will result from the purchase of the required chemicals from sigmaaldrich, the exact cost of these chemicals cannot be established due to research being needed
into specific compounds needed for the creation of functionalising molecules.
The purchase of books and relevant research material regarding Nano-wires and the
production of new functionalising molecules.
Exceptions
This cost of £15,000 is allocated to the purchase of the technology to produce the sensing chip
from which the nano-wires put on to
University fees
University fees remain payable at the rate at which I started university as the institution I am
choosing- The University of Kent was where I did my undergraduate Masters in forensic
science.
Skills Training
As I have never used Chemical Vapour deposition before, I require skills training for the its
use. The funding in this section also includes training on handling explosive chemicals, which
are to be used in this project and also on the safety certificates required to be able to possess
these chemicals.
High Spec Computer
The funding for a high specification computer is essential as data interpretation is a huge part
of this research. It includes the purchase of necessary software and the purchase of a
computer with high processing power capable of interpreting the results. It also includes the
requirement for highly technical electronics in the set-up of the experiment.
Directly allocated costs
The cost of £25,000 is the cost to the institution- The University of Kent should the proposed
research not go ahead. It includes the use of already available equipment at the university,
access to research materials in the form of subscriptions to publishers, it also includes estates
costs such as utilities and the cost of repairs and maintenance to analytical instrumentation
that would be used in the project for research purposes and characterization of substances.
Financial area
Directly Incurred costs
Direct allocated costs
Indirect costs
Exceptions
University fees
Living/maintenance
Skills training
Conference fees
High Specification
computer
Total
Year 1
2,000
15,000
3,675
14,000
3,500
1,500
5,000
Year 2
1,500
Year 3/ One off
1,500
25,000
8,500
3,675
14,000
3,675
14,000
2,000
1,000
Total(£)
5,000
25,000
8,500
15,000
11,025
42,000
3,500
4,500
5,000
£119,525
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PS700
Case for support
References for case for support
i
Current Trends in Explosive Detection Techniques, . Sarah Caygill, Frank Davis and Seamus P. J.Higson,
Talanta, Volume 88, 15 Jan 2012 Pages 14-29
ii
Nanosensors for explosives detection security briefing, Observatory Nano, February 2011.
http://www.observatorynano.eu/project/filesystem/files/ObservatoryNANO%20Briefing%20No.11%20Nanose
nsors%20for%20Explosives%20Detection.pdf
iii
Nano sensors for trace explosive detection, L. Senesac, T.G.Thundat, Materials Today, 11(2008), n.3 , p.28;
Current Trends in Explosive Detection Techniques, J. Sarah Caygill, Frank Davis and Seamus P. J. Higson,
Talanta, Vol 88, Jan 2012, pages 14-29
iv
v
A Technical Assessment of Portable Explosives Vapor Detection Devices, M. R. Nyden, NIJ Rep. 300-89 (NIST,
Gaithersburg, MD, 1990).
vi
C. A. Heller, S. R. Greni, and E. D. Erickson, Anal. Chem. 54, 286(1982)
vii
Polymer sensors for nitro-aromatic explosives detection, Sarah J. Toal and William C. Trogler, J. Mater.
Chem., 2006, 16, 2871–2883
viii
Supersensitive Detection of Explosives by Silicon Nanowire Arrays, Yoni Engel, Roey Elnathan, Alexander
Pevzner, Guy Davidi, Eli Flaxer, and Fernando Patolsky, Angew. Chem. Int. Ed. 2010, 49, 6830 –6835
ix
"ACLU Backgrounder on Body Scanners and "Virtual Strip Searches"". aclu.org. January 8, 2010. visited
21/3/2012
x
http://www.analogic.com/solutions-security-checked-baggage.htm
xi
Detection and disposal of improvised explosives By Hiltmar Schubert, Andrey Kuznetsov
xii
www.sciencemag.org Science 287, 1801 (2000);
xiii
http://apps.webofknowledge.com.chain.kent.ac.uk/CitationReport.do?product=WOS&search_mode=Citatio
nReport&SID=X21dA7OOL474C1NoF1B&page=1&cr_pqid=1&viewType=summary
xiv
Supersensitive Detection of Explosives by Silicon Nanowire Arrays, Yoni Engel, Roey Elnathan, Alexander
Pevzner, Guy Davidi, Eli Flaxer, and Fernando Patolsky, Angew. Chem. Int. Ed. 2010, 49, 6830 –6835
xv
Control of Thickness and Orientation of Solution-Grown Silicon Nanowires., Holmes, Justin D.,Johnston,
Keith P.Doty, R. Christopher, Korgel, Brian A. Science; 02/25/2000, Vol. 287 Issue 5457, p147
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