Details of Grant 

EPSRC Reference:	GR/R43440/01
Title:	Photonic Materials: Dipole Reversal Without Molecular Reorientation
Principal Investigator:	Ashwell, Professor G
Other Investigators:
Researcher Co-Investigators:
Project Partners:
Department:	Sch of Engineering
Organisation:	Cranfield University
Scheme:	Standard Research (Pre-FEC)
Starts:	01 April 2002	Ends:	30 September 2005	Value (£):	179,939
EPSRC Research Topic Classifications:	Materials Characterisation Materials Synthesis & Growth
EPSRC Industrial Sector Classifications:	Electronics
Related Grants:
Panel History:	Panel Date Panel Name Outcome 09 Apr 2001 Photonics/Photonic Materials Deferred
Summary on Grant Application Form
Our recent discovery has shown that the dipole orientation of cationic dyes, either up or down, is influenced by the location of the counterion and, thus, when carefuly controlled the dipole may be independent of the orientation of the donor-(electron-bridge)-acceptor chromophore. Thus, for the first time, we have been able to effectively cancel the dipoles in films that are non-centrosymmetric and, conversely, dipole alignment is now possible even when the chromophore arrangement is nominaly centric with an antiparallel alignment of polar molecules. This discovery has important implications where non-centrasymmetry (of the dipoles not the molecules) is essential for such effects as second-harmonic generation (SHG) and molecular rectification. It may be used to provide a new approach to achieving this goal in a variety of different media: e.g. self-assembled and Langmuir-Blodgett films as well as crystals in the longer term.Dipole reversal without molecular reorientation has been confirmed at Cranffeld by both molecular rectification and SHG studies. Rectification occurs in different quadrants of the current-voltage plot and oppositey aligned dipoles of the two forms cause the second-harmonic intensity to be cancelled even though the molecular orientation is unaffected. Based on this discovery, the aim is to perform a variety of experimental studies to manipulate the phenomenon and to assess its general applicability to a broad range of dyes.
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Organisation Website:	http://www.cranfield.ac.uk