Luminescent Nanocompounds for Security Document Authentication
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Solution Overview
Problem
Current security documents rely on rare earth-based luminescent systems that are expensive, difficult to incorporate, and have fixed excitation and emission characteristics, limiting their adaptability and sustainability for authentication purposes.
Innovation Solution
Development of charge-transfer complexes of metal atomic quantum clusters (AQCs) with tunable excitation and emission wavelengths, allowing for customizable Stokes shifts and stability without photobleaching, using transition metals like Au or Ag, which are non-toxic and abundant, and can be synthesized with organic ligands for enhanced properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If rare earth-based luminescent systems are used, then huge Stokes' displacement and slow decaying times are achieved, but they are expensive, difficult to incorporate, and have fixed excitation and emission characteristics
Solution Approach 1:
The patent changes the fundamental parameters of the luminescent system by transitioning from rare earth ions to metal atomic quantum clusters. This enables continuous tuning of excitation and emission wavelengths by controlling AQC size (2-50 atoms), while maintaining huge Stokes shifts (>200 nm) and microsecond decay times. The size-dependent optical properties allow customization for different authentication applications.
Solution Approach 2:
The invention creates composite structures by coordinating organic ligands (carboxylic acids, phosphonic acids, amines) with metal atomic quantum clusters to form stable luminescent complexes. This composite approach enables incorporation into various security document matrices while preserving luminescent properties, overcoming the difficulty of integrating rare earth systems.
2Reliability
If rare earth luminescent systems are used, then authentication features are provided, but they are expensive and scarce materials
Solution Approach 1:
The patent replaces expensive, scarce rare earth materials with abundant, inexpensive transition metals (Au, Ag, Cu, Pt, Pd, Ni, Co, Fe, Cr, Rh). These metal atomic quantum clusters can be synthesized cost-effectively and are readily available, making large-scale implementation in security documents economically viable while maintaining authentication reliability.
3Reliability
If luminescence pigments are incorporated into security documents, then authentication is enabled, but they require excitation light in particular wavelength regions and may be susceptible to environmental changes
Solution Approach 1:
The patent applies local quality protection by surrounding metal atomic quantum clusters with specifically designed organic ligand shells (carboxylic acids, phosphonic acids, amines). This local protective environment stabilizes the AQCs against aggregation, oxidation, and environmental factors while preserving their size-dependent luminescent properties and huge Stokes shifts.
Solution Approach 2:
The invention creates composite luminescent systems where organic ligands form protective matrices around metal atomic quantum clusters. This composite structure provides environmental stability (pH range 3-10, temperature resistance) while maintaining tunable optical properties for reliable authentication across different conditions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The AQC-based charge-transfer complexes provide a sustainable, cost-effective, and adaptable solution for security documents, offering high Stokes shifts and long decay times, ensuring enhanced authentication capabilities and resistance to environmental changes.
Implementation Method 1
fluorescent nanocompounds in the form of charge-transfer complexes of AQCs with huge Stokes' shifts and decaying times much greater than those described in the state of the art
Implementation Method 2
luminescence pigments or substances have been incorporated into various security documents for certifying the authenticity thereof, the detection or observation of which requires the use of an excitation light in a particular region of wavelengths
Data Source
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AI summary
The present invention relates to the use of nanocompounds as non deactivable security markers comprising a charge-transfer complex of at least two different size metal atomic quantum clusters (AQCs). These nanocompounds are luminescent, particularly fluorescent after external excitation. The invention also relates to security documents, articles or elements incorporating these markers as well as to a method and a system for detecting the same.