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Details of Grant 

EPSRC Reference: EP/X040259/1
Title: Circularly Polarised Luminescent Photography and Lanthanide Complexes for Advanced Intelligent Security Applications
Principal Investigator: Pal, Professor R
Other Investigators:
Researcher Co-Investigators:
Project Partners:
Department: Chemistry
Organisation: Durham, University of
Scheme: Standard Research
Starts: 01 January 2024 Ends: 31 March 2026 Value (£): 295,444
EPSRC Research Topic Classifications:
Analytical Science Co-ordination Chemistry
Materials Characterisation
EPSRC Industrial Sector Classifications:
No relevance to Underpinning Sectors
Related Grants:
Panel History:
Panel DatePanel NameOutcome
03 May 2023 EPSRC Physical Sciences Prioritisation Panel - May 2023 Announced
Summary on Grant Application Form
Counterfeiting is extremely detrimental to society. Authenticating products and documents is vital to global commerce, health and personal identity. A plethora of noticeable and concealed anti-counterfeiting measures and technologies have been developed to combat counterfeiting. Perhaps the most well-known class of anti-counterfeiting labels are luminescent security inks, which are commonly applied to bank notes and passports.

Lanthanide complexes are widely used in luminescent security inks due to their unique and robust photophysical properties such as fingerprintlike emission profiles and long luminescent lifetimes. The proposed project will harness the phenomenon of Circularly Polarised Luminescence (CPL), where different enantiomers of the same chemical entity produce different handedness (left or right) of light. Lanthanide complexes can be engineered to emit CPL, which encodes chiral molecular fingerprints in luminescence spectra that cannot be decoded by conventional optical measurements. However, chiral CPL signals have not yet been exploited as an extra security layer in advanced security inks due to the lack of suitable handheld rapid 'ad-hoc' CPL detection technology.

Over the past decade, we have led the way in the development of CPL active bright optical probes and dyes based on lanthanide luminescence (Dalton Trans., 2015 ,44, 4791-4803). Several Ln(III) complexes possess high thermal stability and resistance, with complete CPL fingerprint preservation, making them suitable candidates (Chem. Sci., 2018, 9, 1042-1049) to be used as extra layers in hidden Chameleon Security Inks (CSI).

CSI's combine organic short-lived (ns) green/blue emitters and chiral (CPL active) red/green (terbium/europium) long-lived (ms) emitters embedded into transparent polymer matrices. They pave the way towards multi-layered: multi-coloured, -spectral, -helicity, high spatial and temporal resolution unclonable QR code generation with an unprecedented 5 layers of 'invisible to the naked eye' security. The wide-spread use of 'plastic' banknotes facilitates the introduction of 'hidden in plain sight' CSI features, when combined with the right instrument can facilitate ad-hoc verification further advancing security and authenticity.

In 2020 our pioneering solid-state CPL spectrometer (Nat. Commun., 2020, 11, 1676) triggered a paradigm shift in CPL spectroscopy that has been hindered over the last 50 years due to its stagnant design that prevented its use and widespread application. For the first time, our novel CPL spectrometer allowed rapid time-resolved CPL spectroscopy to be exploited.

Earlier this year (Nat. Commun., 2022, 13, 553) we constructed and validated the world's first CPL Laser Scanning Confocal Microscope (CPL-LSCM), which is uniquely capable of simultaneously recording left- and right-handed CPL allowing enantioselective differential chiral contrast (EDCC) imaging of emissive chiral molecules, yet again igniting and broadening the horizon of CPL research.

In this project we set out to adapt and embed our patented CPL chiroptical separator unit into a hand-held, solid-state CPL photographic (CPLP) camera system. Once it is fully developed and validated it can be used for 'ad-hoc' time-resolved EDCC measurements. This could truly amplify the underlying potential of CPL and pave the way towards novel unclonable luminescent security inks. Harnessing the so far unexploited benefits of CPL detection would allow the broad communities of life and material sciences to adopt this facile technology. We forecast a potentially game-changing impact on a global scale that reaches further than the scientific benefits associated with this project and could generate immense commercial interest.

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