A multi-layer nanoparticle platform for tunable, ultralong room-temperature phosphorescence in anti-counterfeiting applications

Background

The field of luminescent materials, particularly those exhibiting room-temperature phosphorescence (RTP), has garnered significant attention due to its potential applications in anti-counterfeiting, bioimaging, and advanced display technologies. RTP materials are valued for their ability to emit light long after excitation, providing a visible afterglow that can be leveraged for security features and authentication. However, most organic compounds naturally favor rapid nonradiative decay, resulting in short-lived fluorescence rather than persistent phosphorescence. The demand for robust, tunable, and long-lasting RTP materials is driven by the need for more secure anti-counterfeiting measures and the desire for new functional materials in optoelectronics and sensing.

Current approaches to achieving room-temperature phosphorescence in organic systems face several critical challenges. Traditional organic phosphors typically exhibit weak emission and extremely short afterglow durations—often limited to nanoseconds—due to efficient nonradiative quenching and oxygen sensitivity. Strategies such as embedding chromophores in rigid matrices, heavy atom doping, or crystallization can enhance phosphorescence, but these methods often suffer from poor processability, limited tunability, and incompatibility with aqueous environments or industrial printing processes. Additionally, many systems lose their luminescent properties upon drying or redispersion, making them unsuitable for practical applications like inkjet printing or repeated use. These limitations hinder the widespread adoption of organic RTP materials in commercial anti-counterfeiting and other advanced applications.

Technology

This technology is a sophisticated nanoparticle-based system designed to achieve ultralong room-temperature phosphorescence (URTP) with afterglow lifetimes extending up to several seconds. The core of each nanoparticle consists of weakly self-associating organic chromophores aggregated within a rigid polymer host, which is then encapsulated by a polymeric surfactant shell. This multi-layer structure, with particle sizes ranging from 20 to 250 nanometers, is engineered to suppress nonradiative quenching and maximize phosphorescent emission. The emission color and duration can be precisely tuned by selecting different chromophores and adjusting their concentration relative to the polymer host, as well as by controlling the overall solids concentration during synthesis. The nanoparticles are produced via flash nanoprecipitation in a confined impinging-jet mixer, resulting in stable aqueous dispersions that retain over 97% of their luminescent activity even after multiple drying and redispersion cycles. These dispersions can be readily formulated into inks compatible with industrial printing processes, making them ideal for applications such as anti-counterfeiting marks and advanced luminescent materials.

What differentiates this technology is its unique combination of tunability, stability, and scalability. Unlike traditional organic luminescent molecules, which typically exhibit only nanosecond-scale fluorescence, this system achieves second-scale afterglow at room temperature, a significant leap in performance. The rigid polymer host effectively isolates the chromophores, minimizing quenching and enabling long-lived emission, while the surfactant shell ensures colloidal stability in water and compatibility with existing manufacturing workflows. The synthesis process allows for rapid optimization of particle size, chromophore type, and loading ratios, supporting a wide range of emission wavelengths and lifetimes tailored to specific needs. Furthermore, the nanoparticles demonstrate exceptional resilience to processing stresses, maintaining their properties through repeated drying and redispersion, which is critical for commercial ink formulations. This combination of customizable optical properties, robust stability, and seamless integration with current industrial practices positions the technology as a highly differentiated solution for secure authentication and advanced photonic applications.

Benefits

• Ultralong room-temperature phosphorescence with afterglow lifetimes up to seconds, enabling advanced luminescent applications
• Highly tunable emission color and duration through selection and loading of organic chromophores
• Stable aqueous nanoparticle dispersions that retain over 97% activity after multiple dry–redispersion cycles
• Compatibility with existing inkjet printing and industrial processes for easy integration into anti-counterfeiting inks
• Scalable synthesis via flash nanoprecipitation allowing precise control over particle size and composition
• Robust core-shell nanoparticle design that suppresses nonradiative quenching and enhances phosphorescence stability
• Versatile platform applicable to various chromophores and emission frequencies for broad commercial use

Applications

• Currency anti-counterfeiting inks
• Luxury goods authentication labels
• Secure inkjet-printed documents
• Phosphorescent security packaging

Additional info

This multi-layer nanoparticle system embeds weakly self-associating organic chromophores as aggregates within a rigid polymer core, coated by a polymeric surfactant shell. This architecture suppresses nonradiative quenching, yielding ultralong room-temperature phosphorescence with afterglow lifetimes up to seconds. Emission color and duration are tunable. Synthesized via flash nanoprecipitation, these stable aqueous dispersions are compatible with industrial printing for anti-counterfeiting applications.