Core-Shell Upconversion Nanophosphors for Deep Tissue Imaging
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Solution Overview
Problem
Current upconversion nanophosphors excited by infrared light emit green or blue visible light, which has poor tissue-infiltrating efficiency, and the use of 980 nm infrared light can cause temperature increases due to water absorption, limiting their effectiveness in in vivo imaging and magnetic resonance imaging.
Innovation Solution
A core/double shell structured red light-emitting upconversion nanophosphor is developed, doped with Yb3+, Ho3+, and Ce3+, capable of converting 800 nm infrared light into red light with low absorption in tissues, utilizing a fluoride-based nanoparticle core and shells to enhance luminescence and magnetic resonance imaging effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If 980 nm infrared light is used as excitation source, then deep tissue infiltration is achieved, but temperature increase occurs due to water absorption
Solution Approach 1:
The patent changes the excitation wavelength parameter from 980 nm to 800 nm to avoid water absorption peak, thereby reducing temperature increase while maintaining deep tissue infiltration capability. This parameter optimization resolves the contradiction between deep penetration and thermal damage.
2Temperature
If Nd is used as sensitizer for 800 nm excitation, then temperature increase is reduced, but activator luminescence intensity is greatly reduced
Solution Approach 1:
The patent introduces Yb3+ as an intermediary sensitizer that bridges the 800 nm excitation light and the Ho3+ activator. Yb3+ absorbs 800 nm light efficiently and transfers energy to Ho3+, enabling strong red luminescence while avoiding direct Nd-Ho3+ interaction that would quench luminescence. This intermediary approach resolves the contradiction between temperature control and luminescence intensity.
Solution Approach 2:
The patent creates a composite doped structure containing both Yb3+ and Ho3+ ions in the NaYF4 host matrix. This composite doping strategy combines the advantages of 800 nm excitation compatibility (via Yb3+) with efficient red luminescence (via Ho3+), resolving the performance trade-off.
3Illumination intensity
If green or blue visible light is emitted, then upconversion luminescence is achieved, but tissue-infiltrating efficiency of emitted light is poor
Solution Approach 1:
The patent changes the emission color from green/blue to red by selecting Ho3+ as the activator. Red light has longer wavelength and lower scattering/absorption in biological tissues, thereby achieving both strong luminescence intensity and deep tissue infiltration efficiency simultaneously.
4Illumination intensity
If core/shell structure is used, then luminescence efficiency is improved, but device complexity increases
Solution Approach 1:
The patent employs a core/shell structure where the shell is a thin protective layer that passivates the core surface. This thin film approach improves luminescence efficiency by reducing surface quenching while adding minimal structural complexity, making the design practical for biomedical applications.
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 nanophosphor achieves strong red luminescence and improved tissue-infiltrating efficiency, enhancing in vivo imaging accuracy and magnetic resonance imaging effects while minimizing tissue heating, making it suitable for both fluorescent and magnetic resonance imaging applications.
Implementation Method 1
upconversion nanophosphors which are excited by infrared light to emit visible light
Implementation Method 2
the absorption peak of the water molecule appears in this wavelength range
Data Source
AI summary
Provided is a nanophosphor having a core/double shell structure, the nanophosphor including a upconversion core including a Yb3+, Ho3+, and Ce3+− co-doped fluoride-based nanophosphor represented by Formula 1; a first shell surrounding at least a portion of the upconversion core, and comprising a Nd3+ and Yb3+ co-doped fluoride-based crystalline composition represented by Formula 2; and a second shell surrounding at least a portion of the first shell, and having paramagnetic properties represented by Formula 3.