Luminescent Layered Composition for Upconversion Nanoparticles
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Solution Overview
Problem
Lanthanide-doped upconversion nanoparticles (UCNPs) exhibit poor upconversion efficiencies, particularly under low-intensity laser excitations, due to low absorption cross-sections and parity forbidden transitions, leading to heating issues in biological applications, and existing methods to enhance efficiency are unsuitable for biosensors.
Innovation Solution
A three-layered 'sandwich' composition with spatially separated sensitizer and emitter layers, where the second layer is between two sensitizer layers, mitigates energy back-transfer, allowing for brighter visible and UV emissions at lower excitation powers, and absorbs 808 nm light to minimize heating in aqueous systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high-power density laser excitation is used to overcome low absorption cross-section and improve luminescent intensity, then upconversion efficiency is improved, but thermal toxicity increases due to significant heating in aqueous systems
Solution Approach 1:
The UCNP is divided into multiple functional layers: a core containing emitters, an intermediate shell with sensitizer dopants, and an outer shell with additional sensitizer dopants. This segmentation allows each layer to perform its specific function optimally while working together to improve overall upconversion efficiency at lower excitation powers.
Solution Approach 2:
The patent creates a composite nanoparticle structure combining different dopant materials (emitters and sensitizers) within a UCNP framework. The intermediate and outer shells contain sensitizer dopants that enhance light absorption, while the core contains emitter dopants that produce upconverted luminescence, creating a composite material with superior performance.
2Use of energy by moving object
If Yb3+ concentration is increased to improve absorption of 980 nm NIR light, then absorption cross-section is improved, but Yb3+-Yb3+ cross-relaxation occurs which reduces efficiency
Solution Approach 1:
The sensitizer dopants are segmented into two separate locations: the intermediate shell and the outer shell. This spatial distribution allows the UCNP to utilize sensitizer dopants more efficiently, improving absorption without requiring excessively high concentrations in a single region, thereby reducing cross-relaxation losses.
Solution Approach 2:
The intermediate shell acts as an intermediary layer between the core and the outer shell. It contains sensitizer dopants that absorb excitation light and transfer energy to the core, while also preventing direct interaction between sensitizer dopants in the core and outer shell, thereby reducing cross-relaxation.
3Device complexity
If lanthanide-Yb3+ energy back-transfer is allowed to occur, then energy transfer pathway is simplified, but spectral profile is degraded with red emissions at the expense of green emissions and decreased luminescent intensity
Solution Approach 1:
The patent extracts or removes the harmful energy back-transfer pathway by carefully designing the dopant concentrations and spatial distributions. The sensitizer dopant concentrations in the intermediate and outer shells are optimized to ensure unidirectional energy transfer from sensitizer to emitter, effectively taking out the back-transfer pathway that would otherwise degrade the spectral profile.
Solution Approach 2:
Different regions of the UCNP are given different local qualities: the core contains emitter dopants optimized for luminescence, while the intermediate and outer shells contain sensitizer dopants optimized for light absorption. This local quality differentiation ensures that each region performs its specific function optimally, preventing energy back-transfer and maintaining high luminescent intensity.
4Length of moving object
If 980 nm NIR excitation is used to achieve deep tissue penetration, then penetration depth is improved, but heating effect increases significantly in aqueous systems
Solution Approach 1:
The patent changes the operational parameters of the UCNP by optimizing dopant concentrations and spatial distributions to improve absorption efficiency. This allows the UCNP to achieve the same or better luminescent output at lower excitation power densities, thereby reducing heating effects while maintaining the ability to penetrate biological tissues.
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 composition enables bio-imaging, sub-cellular labeling, and sensing without thermal toxicity, with enhanced luminescent intensity and deeper tissue penetration, and can detect dopamine at low concentrations, demonstrating improved performance over traditional UCNPs.
Implementation Method 1
Lanthanide-doped upconversion nanoparticles (UCNPs) are a unique class of inorganic phosphors capable of absorbing near-infrared (NIR) excitations and converting it, through the sequential absorption of NIR photons, to ultraviolet (UV) and/or visible emissions
Implementation Method 2
The sensitizing core and sensitizing shell are each doped with a sensitizer dopant, such as Yb3+ and/or Nd3+, and the luminescent shell is doped with an emitter dopant
Implementation Method 3
This architecture serves to minimize the probability of energy back-transfer from excited state emitter ions to adjacent sensitizer ions by spatially separating them in different layers
Data Source
AI summary
Disclosed herein are embodiments of a composition comprising at least three layers. Layers one and two each either comprises a sensitizer or an emitter, typically a metal ion or a dye, and the third layer may or may not comprise a sensitizer or emitter. Upon exposure to light, such as infrared light, the composition produces visible and/or UV light. The composition may further comprise a capping moiety, a therapeutic agent, an uptake enhancer, a detection moiety that binds to a desired target, a quenching moiety, or a combination thereof. The composition may be a particle, such as a nanoparticle, or it may be a planar composition. Also disclosed are embodiments of a method for using the composition, including, but not limited to, a method for delivering a therapeutic agent, or a method for detecting a target, such as a biological target.