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International Year of Light - Sam Stanfield

Sam Stanfield

Tell us about your PhD project

Doctors who want to gain understanding about the pathophysiology of lung injury and infection currently have two main options, an x-ray or a biopsy; the former provides little detail in information whilst the latter is time consuming and difficult.

I am working as part of the Proteus research group (University of Edinburgh, Heriot-Watt University and the University of Bath) who are developing a novel fibre-optic healthcare technology for sensing and imaging the distal lungs of patients in the Intensive Care Unit.

The aim is to allow clinicians to make increasingly more accurate and timely bedside diagnoses and hence provide more appropriate and targeted treatments, improving patient outcomes, and reducing time and cost. Furthermore in the longer term, previously inaccessible physiological information gathered from the distal lung may provide new insights in to illness and disease.

My research focusses on the sensing aspect of the fibre by developing Surface-Enhanced Raman Spectroscopy (SERS) based nanosensors, which whilst attached to the tip of the fibre allow users to perform quantitative analyses of molecules and conditions present in blood and tissue, including but not limited to pH, redox potential and glucose and oxygen concentrations. A single optical fibre can be functionalised with a variety of different nanosensors to allow for simultaneous multiplexed sensing in-vivo and in real time.

Why is light important to your research?

Light is intrinsic to the method of detection and quantification I use, Raman spectroscopy, because the information sought is obtained by analysing the inelastic scattering of light upon interaction with the target analyte. Monochromatic laser light is used to momentarily excite the molecule from a vibrational state into a virtual state. When this light is inelastically scattered by optical phonons it undergoes a change in energy, this is known as Raman scattering. Raman scattered light is collected and its energy difference relative to the incident light is measured.

This energy difference represents the energy of the bond vibrations, which depend on a number of factors e.g. bond strength, mass of the atoms involved, overall molecular structure, conformation and chemical environment. By measuring the different bond vibrations and plotting their wavenumber against intensity, a unique ???fingerprint??? like spectrum is created for different compounds. Because structural changes within the molecule will give rise to changes in its Raman spectrum, sensor molecules can be designed to reliably and predictably change structure upon reaction with a particular analyte and can be used to quantify the amount of analyte present.

The sensitivity of this technique can be improved by (without going in to full detail) using localized electron oscillations on a nano-structured surface to increase the intensity of both the incident and the Raman scattered light, which in this case involves attaching the sensor molecule on to the surface of gold nanoshells.

Sam's customised rig for coupling light

Custom rig for coupling light into different cores of multi-mode optical fibre; comprising of an Ocean Optics laser and spectrometer with a Thorlabs breadboard and optical components.

Describe your average day of PhD work here in the School of Chemistry

The morning begins with a cup of tea whilst scanning the latest news articles and papers in my field. The rest of the day may be taken up in the wet-lab synthesising the nanosensors and functionalising the optical fibres, in the laser lab performing calibrations and measurements with the fibres, or in the office analysing data and preparing for meetings and presentations.

Sam in the lab

What do you enjoy doing when you are not at work?

Science ceilidh poster

When not in the lab I enjoy taking part in science communication and public engagement / outreach events, for example working as a member of teams who go to local schools to perform scientific demonstrations and workshops, such as Spectroscopy-In-A-Suitcase or Sci-Fun. Currently I am having a lot of fun being involved in designing ceilidh dances to help explain and bring to life scientific concepts. This year the theme is light and we aim to explore as much related to light as possible, including the fundamental theories behind the visible portion of the electromagnetic spectrum, to the effects of and uses for light from the smallest to the largest scales of our universe.

Outside of university I enjoy mountain biking, hiking and rock-climbing as well as riding my road bike and BMX. I also enjoy reading about politics, philosophy and the history of science, as well as topics outside of my research (such as cosmology and astrophysics).

What's your favourite chemical reaction?

It???s a very tough decision but I think it has to be ???The Barking Dog??? reaction, due to its demonstration of energy, light, colour and sound, plus its guaranteed crowd pleasing abilities. This involves an exothermic decomposition reaction between a mixture of carbon disulphide (the fuel) and nitrous oxide (the oxidant) in a long glass tube.

4NO + CS2 ??? 2N2 + CO2 + SO2 + ???S2

The combustion wave travels down the tube producing a bright blue light (via chemical luminescence of the gas phase) and the accompanying distinguishing woof/barking sound. Close contenders are ???The Pharaoh???s Serpent??? (mercury (II) thiocyanate plus a heat source in the presence of oxygen), and the oxidation of a gummi bear with potassium chlorate.