| EPSRC Reference: |
EP/J010006/1 |
| Title: |
Searching for 'Cryptoelectrons': Redox Chemistry of Insulating Materials |
| Principal Investigator: |
Holt, Professor KB |
| Other Investigators: |
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| Researcher Co-Investigators: |
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| Project Partners: |
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| Department: |
Chemistry |
| Organisation: |
UCL |
| Scheme: |
Standard Research |
| Starts: |
18 July 2012 |
Ends: |
17 July 2014 |
Value (£): |
237,744
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| EPSRC Research Topic Classifications: |
| Electrochemical Science & Eng. |
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| EPSRC Industrial Sector Classifications: |
| No relevance to Underpinning Sectors |
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| Related Grants: |
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| Panel History: |
| Panel Date | Panel Name | Outcome |
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01 Dec 2011
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EPSRC Physical Sciences Chemistry - December 2011
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Announced
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Summary on Grant Application Form |
A redox process involves reduction - gain of electrons, and oxidation - loss of electrons. To be redox active a material must have electrons it can lose or energy levels that can be occupied by electrons. An insulating material does not conduct electricity as all of its electrons are occupied in bonding and so has been considered to be not redox active. However, in this project we are aiming to study the redox activity of such materials by exploiting what happens when make the material very small - i.e. as it becomes a nanoparticle.
To predict how a material will behave chemically we consider the reactivity of its constituent atoms. When a material has large dimensions, most of its atoms are within the bulk of the material with only a small proportion found at its surface. Thus the properties are dictated by the majority bulk atoms and the behaviour of the surface atoms can be ignored. In contrast, when the dimension of the material is small - at the nanoscale - there may be as many atoms at the surface as in the bulk, and surface chemistry can no longer be overlooked.
A good example is diamond. We have shown that diamond nanoparticles ('nanodiamond') undergo redox processes. However, diamond is well-known as an insulating material, as most of its electrons are occupied in bonding; so how can nanodiamond be redox active? The reason is the large surface area that allows surface properties to dominate. Surface atoms have fewer neighbours so don't use all their electrons in bonding - these are available for redox processes, as we observe. We cannot therefore assume a material at the nanoscale will retain its bulk chemical and electronic properties and this may impact on how we use the material.
Some of the inspiration for this project came from recent studies of causes of electrostatic charging, which as well as being of fundamental interest has wide application. It is a well-known phenomenon that when two different materials are rubbed together they become charged with static electricity. Although common, there is little agreement on how this charging occurs. Recently it has been shown that the charging may have a redox origin. This is initially quite surprising as the material involved (e.g. plastics) are usually insulators and hence do not readily lose or accumulate electrons. It was suggested that in some way these materials were able to store electrons in their structure, perhaps associated with the surface or maybe with structural defects. These extra electrons were termed 'cryptoelectrons' and hence the aim of this project is learn more about crytoelectrons and how and where they exist.
The nanomaterials under investigation will be attached onto the surface of an electrode and studied using electrochemical methods. The potential of the electrode will be varied and the resulting current flow recorded. The potential of the electrode represents the energy of electrons within it; if the energy is higher than empty energy levels on the nanomaterial surface, electrons will flow from the electrode to the nanomaterial and a reduction current will be observed. Conversely, if the electrons on the surface of the nanomaterial are of a higher energy than those in the electrode, electrons will flow from the nanomaterial to the electrode and an oxidation current will be obtained. In this way we can map out the redox characteristics of the different nanomaterials.
Combined with electrochemistry we will use spectroscopic techniques to determine the chemical identity of the surface groups responsible for the observed activity. The nanomaterials will be immobilised on top of a prism through which infrared radiation is reflected. The infrared is absorbed by the chemical groups on the surface of the nanomaterials. The energy of the absorbed radiation enables us to identify which groups are present.
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Key Findings |
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This information can now be found on Gateway to Research (GtR) http://gtr.rcuk.ac.uk
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Potential use in non-academic contexts |
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This information can now be found on Gateway to Research (GtR) http://gtr.rcuk.ac.uk
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Impacts |
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| Description |
This information can now be found on Gateway to Research (GtR) http://gtr.rcuk.ac.uk |
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| Date Materialised |
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Sectors submitted by the Researcher |
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This information can now be found on Gateway to Research (GtR) http://gtr.rcuk.ac.uk
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