Core-Multishell Upconversion Nanophosphor for Full-Color NIR Emission
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Solution Overview
Problem
Existing upconversion nanophosphors face limitations in achieving a variety of emission colors without reducing brightness, particularly when using a single laser beam for excitation, which restricts their application in transparent 3D displays and other fields requiring full-color tunability.
Innovation Solution
A core/multishell tetragonal upconversion nanophosphor is developed, comprising a blue-emitting core, green-emitting and red-emitting shells, with crystalline layers between and around these, allowing emission of blue, green, and red light by controlling the wavelength of an excitation laser beam, enhancing brightness and enabling full-color tunability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If upconversion nanophosphors of various compositions are mixed to achieve various emission colors, then color variety is improved, but device complexity and brightness control deteriorate because light corresponding to a combination of colors is ultimately observed
Solution Approach 1:
The patent divides a single nanophosphor particle into multiple functional shells, each responsible for specific color emission. The core contains Yb3+ and Tm3+ for blue emission, the first shell contains Yb3+ and Er3+ for green emission, and the second shell contains Yb3+ and Ho3+ for red emission. This segmentation allows independent control of each color component within a single particle, avoiding the complexity of mixing multiple different nanophosphor compositions while achieving full-color tunability.
2Adaptability or versatility
If the pulse of an applied laser beam is shortened to enable color tuning, then adaptability is improved, but upconversion luminescence intensity is greatly reduced
Solution Approach 1:
The patent incorporates Yb3+ ions in all shells as energy transfer mediators that pre-absorb the applied laser light and transfer energy to the respective lanthanide ions (Tm3+, Er3+, Ho3+). This preliminary energy absorption and transfer mechanism ensures efficient energy utilization, allowing the use of shorter laser pulses for color tuning while maintaining high upconversion luminescence intensity. The Yb3+ ions act as energy funnels that prepare the system for rapid color switching without significant intensity loss.
3Adaptability or versatility
If a single nanophosphor particle emits multiple colors, then adaptability is improved, but manufacturing precision requirements increase due to the need for precise shell composition and thickness control
Solution Approach 1:
The patent utilizes the different ionic radii and chemical properties of Yb3+, Tm3+, Er3+, and Ho3+ ions to achieve phase separation during the hydrothermal synthesis process. By controlling synthesis parameters such as temperature, pressure, and precursor ratios, the system automatically forms distinct shells with appropriate thicknesses and compositions. This parameter-based control method simplifies the manufacturing process compared to direct compositional control, as the shell structures self-organize based on thermodynamic principles during synthesis.
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 tunable emission of blue, green, and red light, maintaining high brightness, and can be applied in transparent displays, anti-counterfeiting codes, and bioimaging, leveraging near-infrared excitation for enhanced performance.
Implementation Method 1
an upconversion nanophosphor doped with trivalent lanthanide ions exhibits a unique emission color depending on the doped lanthanide element regardless of the type of a host material... Blue light is emitted when thulium (Tm) is doped on the host material of the nanophosphor, and green or red light is emitted when erbium (Er) or holmium (Ho) is doped
Implementation Method 2
luminescence is exhibited through an anti-Stokes shift process in which electrons are excited by infrared (IR) light and light having a shorter wavelength compared to the excitation light, i.e., visible light having higher energy, is emitted
Implementation Method 3
electrons are excited by infrared (IR) light and light having a shorter wavelength compared to the excitation light, i.e., visible light having higher energy, is emitted
Data Source
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AI summary
Provided is a core/multishell tetragonal upconversion nanophosphor capable of being excited by near-infrared (NIR) light having wavelengths of 800 ± 20 nm, 980 ± 20 nm, and 1532 ± 20 nm to emit light of blue, green, red, and combinations thereof.