Electrocatalytic nanoparticles: Nafion® nanostructures doped with redox active species

The transition metal complex, Ru(bpy)32+, is a widely used electrocatalyst due to its easily accessible redox potentials. It has also been deployed in electrochemiluminescence applications due to its robust nature and ability to form excited states, which emit light during relaxation.

Researchers at the University of Oxford have developed a synthesis route to Ru(bpy)32+ doped Nafion® nanostructures, which overcome several drawbacks of solution phase Ru(bpy)32+. The Nafion® support is chemically inert and allows for facile catalyst recovery without compromising reactivity. They are suitable for a wide range of applications from electrochemical sensors to biological imaging.

Redox cation doped Nafion® nanoparticles

Researchers at the University of Oxford have developed a simple synthesis route to Nafion® nanoparticles doped with redox active cationic species such as Ru(bpy)32+ or methylviologen. These nanostructures display the similar facile oxidation/reduction properties as the solution phase cations. The supported catalysts are easily removed from reaction mixtures through filtration or centrifugation, thus reducing wastage. These nanoparticles could be applied to sensors, fuel cells and imaging. We believe the benefits of the redox cation doped Nafion® nanoparticles are as follows:

  • Simple manufacture and recovery
  • Inert and stable Nafion® support
  • Incorporated cations retain their redox reactivity
  • Myriad applications due to the range of cations that can be selected for use

 

Ru(bpy)32+ – The current face of electrocatalysis

Electrocatalysts are a subset of catalysts that operate at the surface of an electrode. Ruthenium (II) tris(2,2’-bipyridyl) (Ru(bpy)­32+­) is a widely used electrocatalyst due to its accessible oxidation potential of 1.27 V vs SCE. The ability to electrochemically generate excited states of Ru(bpy)­32+ is also attractive as, upon relaxation to a ground state, such species will luminesce. The wavelength of the emitted photon is around 620nm, so will appear as red light.

In a separate application electrochemiluminescence (ECL) exploits the generation of excited species in an electrochemical reaction, which emits light upon relaxation to a lower-level state. ECL has been used in bioanalytical applications (DNA detection and Immunoassays), with Ru(bpy)32+ featuring as the ECL reagent of choice. Ru(bpy)32+ possesses excellent stability, a wide range of analyte tolerance and compatibility with many separation techniques. Numerous attempts have been made to immobilise Ru(bpy)­32+ on electrochemically inert substrates to aid with catalyst recovery and stability, however, success has been limited.

 

Transforming homogeneous redox chemistry into heterogeneous electrocatalysis

The developed methodology enables any homogeneous redox-based chemical reaction involving cations as reagents to be transformed into an electrochemically driven catalytic process. It will transform redox solution phase chemistry by making it heterogeneous and catalytic.

Patent Protection

A UK priority patent has been filed to protect this technology, and Oxford University Innovation Ltd. is looking to hear from anyone interested in helping in its commercialisation.

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