CuInS2/In2S3/ZnS Double-Layer Core-Shell Quantum Dots
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Solution Overview
Problem
CuInS2 quantum dots have low fluorescence quantum yields and photochemical stability, and existing core-shell structures like CuInS2/ZnS suffer from a blue shift in fluorescence emission, reducing their effectiveness in the red region.
Innovation Solution
A CuInS2/In2S3/ZnS quantum dot with a double-layer core-shell structure is developed, where a CuInS2 core is surrounded by an In2S3 shell and further coated with a ZnS shell, using dialkyldithiophosphate as a monomolecular precursor for the In2S3 shell and zinc diethyldithiocarbamate for the ZnS shell, with specific molar ratios and reaction conditions to enhance stability and quantum yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a CuInS2 quantum dot is used, then it is non-toxic and free of heavy metals, but the fluorescence quantum yield is low (below 10%) and photochemical stability is poor
Solution Approach 1:
The patent applies composite materials by constructing a CuInS2/In2S3/ZnS core-shell quantum dot structure. The CuInS2 core provides non-toxic properties, while the In2S3 intermediate shell and ZnS outer shell work together to passivate surface defects and improve fluorescence quantum yield to over 80%, resolving the contradiction between non-toxicity and high quantum yield.
Solution Approach 2:
The patent uses the nested doll principle by creating a multi-layer core-shell structure where the CuInS2 core is nested within the In2S3 shell, which is in turn nested within the ZnS shell. This hierarchical nesting allows each layer to contribute specific functions: the core provides non-toxicity, the intermediate shell improves lattice matching, and the outer shell enhances quantum yield and stability.
2Reliability
If a CuInS2/ZnS core-shell structure is constructed, then the fluorescence quantum yield is improved, but a blue shift in fluorescence emission occurs which reduces quantum yields in the red region
Solution Approach 1:
The patent introduces an In2S3 intermediate shell as a mediator between the CuInS2 core and ZnS outer shell. This intermediate layer has a bandgap that bridges the core and shell, allowing for better lattice matching and reducing strain-induced blue shifts. It enables the maintenance of red-region emission while achieving high quantum yield through effective surface passivation.
Solution Approach 2:
The patent applies parameter changes by carefully controlling the thickness and composition ratios of each shell layer. By optimizing the In2S3 and ZnS shell thicknesses, the patent achieves the desired balance between quantum yield enhancement and emission wavelength stability, preventing blue shifts while maintaining red-region fluorescence.
3Reliability
If a core-shell structure is constructed to improve photochemical stability, then surface defect states increase causing blue shift, but the desired red region emission is compromised
Solution Approach 1:
The patent uses composite materials with the CuInS2/In2S3/ZnS structure where the intermediate In2S3 shell specifically addresses the contradiction between surface passivation and wavelength control. This composite structure provides photochemical stability through surface passivation while the intermediate shell's optical properties prevent blue shifts, maintaining red-region emission.
Solution Approach 2:
The patent applies local quality by assigning different functional properties to different parts of the core-shell structure. The In2S3 intermediate shell specifically targets the interface region between core and shell to passivate defects without inducing blue shifts, while the ZnS outer shell provides overall protection. This localized functional differentiation resolves the contradiction between stability and wavelength control.
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 CuInS2/In2S3/ZnS quantum dots achieve a quantum yield of over 80% in the red region, improving surface defect states and preventing blue shifts, making them non-toxic and suitable for various applications.
Implementation Method 1
motion of conduction band electrons and valence band holes are confined in a three-dimensional potential well, which leads to unique physical properties
Implementation Method 2
With the quantum size effects, optical and electrical properties of a quantum dot can be flexibly tuned by adjusting its size
Implementation Method 3
CuInS2 quantum dots are free of heavy metals and non-toxic, they become research hotspots in the field of fluorescent quantum dots
Data Source
AI summary
The present invention provides a CuInS2/In2S3/ZnS fluorescent quantum dot with a double-layer core-shell structure, aiming to overcome the defects of the existing CuInS2 quantum dots. CuInS2 serves as a core, In2S3 serves as a first shell for cladding the core, and ZnS serves as a second shell for cladding the first shell. The present invention further provides a preparation method for the CuInS2/In2S3/ZnS fluorescent quantum dot with a double-layer core-shell structure. The CuInS2 quantum dot is synthesized using two stabilizers, and indium thiophosphate serves as a monomolecular precursor of the In2S3 shell.