Dr Daren Caruana

Research Overview

Gas Phase Electrochemistry

The presence of ions in plasmas presents a realistic prospect for performing electrochemical reactions at an electrode within a gaseous environment. The thrust of this work is to apply the well-established underlying principles of liquid and solid phase electrochemistry, to the gas phase. The ionisation that occurs in plasma is sufficient to carry a current between two electrodes and support redox reactions at an electrode surface. We have shown that it is possible to apply conventional electrochemical techniques such as, potentiometry and voltammetry using a specially designed burner shown in the figure below. [57] This project is supported by the EPSRC and has been previously supported by the Leverhulme trust, the Royal Society, Sherwood Scientific and UCL graduate school.

Photo of flame cell

Figure 1 Photograph showing a two-compartment flame cell developed to carry out electrochemical measurements. The cell is made up of two flames placed close together. Each flame is fed by two separate streams of premixed gases containing specific gaseous ionic species. The two flames do not mix due to the fast flowing streams of gases and create two defined electrolyte compartments.

To view a public lecture about this work visit:http://www.ucl.ac.uk/lhl/lhlpub2/13_251108

Plasma Electrochemical Sensor for Airborne Particulates

Allergic reaction to airborne pollen affect about 15% of the population of industrialised countries. Real-time detection and identification of airborne particles combined with antigen specific medication, can help improve the quality of life for many hay fever sufferers. Current methods for measuring airborne particles are based on the archaic capture and count technique which is expensive and laborious, and normally give an average over 24 hours.

In this work a new approach to detect and identify particles such as pollen, or any bioaerosol in the atmosphere. The method relies on the breakdown of the particles in a flame to produce a large number of smaller fragments in a flame. These smaller particles are often charged and can then be measured by electrochemical means. [8] The advantage of this method is the amplification through the fragmentation process as shown in figure 2. Funding is provided by EPSRC EP/F028423/1.

Video frames showing combustion of a particle

Figure 2 Showing the combustion of a particle tracked through a flame using high speed video (500 s-1) taken by Dr Dimitris Sarantaridis.

Electrochemically Driven Protein/Peptide Assembly

Molecular assembly at surfaces is an approach that is becoming very popular for the fabrication of nano-scale architectures. We are interested in the real-time visualisation of such architectures during their creation. We have developed an electrochemical AFM cell and an electrochemical optical microscope cell which will control the switching between the globular and fibrous states of HbS using electrochemical modulation of oxygen (in collaboration with Mike Horton and Rachel McKendry, London Centre for Nanotechnology). This method will be used to investigate the kinetics, dynamics and orientation of fibre growth. [6]

We are also interested in synthesis (in collaboration with Alethea Tabor, UCL Chemistry) of small peptides (>50 residues) which can be designed to assemble in specific ways to form organised and regular structures such as fibres, tubes, or spheres, through the manipulation of non covalent interactions. The focus for this project is to investigate the reversible and controlled switching between a soluble protein or peptide into insoluble state by direct electrochemical oxidation or reduction.

This project is supported by the IRC in Nanotechnology and UCL Chemistry

Free Standing Surfactant films

We are interested in electrochemical investigations into the transport properties of free standing ultra-thin surfactant films and the associated meniscus. We have developed a new electrochemical cell composed of a 25 μm diameter gold wire placed through a stable surfactant film which served as the electrolyte. [1] Solutions containing anionic sodium dodecyl sulphate (SDS) or non-ionic Triton-X100 surfactants, with background electrolyte NaCl and with electroactive probe ferrocyanide or ferrocene methanol, were used to create the surfactant films. The electrolyte was an ultra-thin surfactant film creating a two dimensional solution with a thickness between 300 and 1000 nm, and its meniscus at the gold wire, within which the electroactive probe was free to diffuse. This work is in collaboration withProf. David E. Williams, Chemistry Auckland NZ, and Dr. Katherine Holt, UCL Chemistry.

Final reports for recent grants are available here.

Selected publications

  1. D. C. Braide-Azikiwe, K.B. Holt, D.E. Williams, D.J. Caruana, “Soap Film Electrochemistry” Electrochem. Commu., (2009) On line.
  2. R.Schlapak, D. Armitage, N. Saucedo-Zeni, W. Chrzanowski, M. Hohage, D. Caruana, S. Howorka, (2009) Selective Protein and DNA Adsorption on PLL-PEG Films Modulated by Ionic Strength, Soft Matter, 3, 613-621.
  3. J. Sanchez Galiani, E. Hadzifejzovic, R.A. Harvey, D.J. Caruana, (2008) Plasma Electrochemistry: Absorption of flame borne species in platinum electrodes. Electrochimica Acta, 53, 3271-3278.
  4. K.B. Holt, C. Ziegler, D.J. Caruana, J. Zang, E. Millán-Barrios, J. Hu, J.S. Foord, “Redox properties of undoped 5 nm diamond nanoparticles.” Phys. Chem. Chem. Phys., (2008)10, 303-310.
  5. Emina Hadzifejzovic, Jovan Stankovic, Steven Firth, Paul F McMillan, Daren J Caruana, "Plasma Electrochemistry: Electroreduction in a Flame", Phys. Chem. Chem. Phys., (2007), 9, 5335-5339.
  6. Zeshan Iqbal, Rachel McKendry, Michael Horton, Daren J. Caruana, "Electrochemical modulation of sickle cell haemoglobin polymerization." Analyst (2007), 132(1), 27-33.
  7. E. Hadzifejzovic,; J. A. Sanchez Galiani,; D. J. Caruana,. "Plasma electrochemistry: potential measured at boron doped diamond and platinum in gaseous electrolyte." Physical Chemistry Chemical Physics (2006), 8(24), 2797-2809.
  8. D.J. Caruana and J. Yao, " Gas phase electrochemical detection of single latex particles." Analyst , (2003) 128, 1286-1290.