Surface Functionalised Nanoparticles via In-Situ Ligand Coordination
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Solution Overview
Problem
Current methods for producing surface-functionalized semiconductor quantum dot nanoparticles often result in lower quantum yield and increased particle size due to damage to the inorganic surface and the need for post-synthesis surface modification procedures, limiting their stability and compatibility with applications.
Innovation Solution
A method involving the reaction of nanoparticle precursor species in the presence of a nanoparticle surface binding ligand, such as 11-mercapto-undecene, which allows for in-situ coordination of functionalized ligands during core growth or shelling, eliminating the need for post-synthesis modification and maintaining high quantum yield and small diameter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If post-synthesis surface modification procedures are used to functionalize quantum dots, then surface functionality is improved, but quantum yield decreases and particle size increases
Solution Approach 1:
The patent applies preliminary action by incorporating surface-functionalizing ligands during the core growth phase rather than performing post-synthesis modification. The ligands are present from the beginning and coordinate to surface atoms as they form, preventing defects before they occur. This is evident in the method where precursor species react in the presence of nanoparticle surface binding ligands that already contain the desired functional groups, eliminating the need for subsequent modification steps that would damage the surface and reduce quantum yield.
2Adaptability or versatility
If post-synthesis surface modification procedures are used to functionalize quantum dots, then surface functionality is improved, but particle diameter increases
Solution Approach 1:
The patent performs the surface functionalization action in advance during core growth rather than after synthesis. The ligands are already bound to the nanoparticle surface when the core forms, so no additional size-increasing modification steps are needed. The functional groups are incorporated as the nanoparticle grows, maintaining the original small diameter while achieving the desired surface functionality.
3Stability of the object's composition
If core semiconductor nanoparticles have an outer organic passivating layer, then surface stability is improved, but quantum efficiency decreases due to electron-hole recombination at surface defects
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the shell material has different properties than the core. The shell is composed of materials with higher bandgap energies (ZnS, CdS, HgS) that form a potential barrier, confining electron-hole pairs within the core region where radiative recombination occurs. This local differentiation of material properties at the core-shell interface prevents surface recombination while maintaining core functionality.
Solution Approach 2:
The patent uses composite materials by combining core semiconductor nanoparticles with shell materials of different bandgap energies. The core contains materials like CdSe, InP, or GaAs, while the shell uses wider bandgap materials such as ZnS, CdS, or HgS. This composite structure creates a type-II or type-III band alignment that confines carriers in the core while the shell provides surface passivation, achieving both stability and high quantum efficiency.
4Reliability
If a graded alloy layer is grown on the core to improve structural stability, then photoluminescence emission is enhanced, but manufacturing complexity increases
Solution Approach 1:
The patent applies parameter changes by systematically varying the composition of the shell material to create a graded alloy structure. The shell transitions from core-matched composition at the interface to a terminal composition at the outer surface, with intermediate compositions in between. This compositional gradient is achieved by controlling the ratio of precursor species during sequential addition, allowing gradual lattice parameter adjustment that reduces strain and defects while enhancing photoluminescence.
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
This approach generates physically and chemically robust nanoparticles with high quantum yield, suitable for various applications, including incorporation into solvents, devices, and biological systems, while maintaining small diameter and enhanced stability.
Implementation Method 1
reacting first and second nanoparticle precursor species in the presence of a nanoparticle surface binding ligand incorporating a nanoparticle binding group and a functional group, said reaction being effected under conditions permitting binding of said surface binding ligand to the growing nanoparticles
Implementation Method 2
the band gap energy being inversely proportional to the size of the semiconductor nanoparticle as a consequence of quantum confinement effects
Implementation Method 3
the Coulombic interaction cannot be neglected. This leads to a narrow bandwidth emission, which is dependent upon the particle size and composition of the nanoparticle material
Implementation Method 4
to grow a second inorganic material, having a wider band-gap and small lattice mismatch to that of the core material epitaxially on the surface of the core particle, to produce a 'core-shell' particle
Data Source
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AI summary
The present invention relates to a process for the production of surface functionalised nanoparticles, such as the production of semiconductor quantum dot nanoparticles incorporating surface-bound functional groups which increase the ease with which the dots can be employed in applications, such as incorporation into solvents, inks, polymers, glasses, metals, electronic materials and devices, bio-molecules and cells. The method comprises reacting first and second nanoparticle precursor species in the presence of a nanoparticle surface binding ligand, wherein the nanoparticle surface binding ligand is 10-Undecylenic acid, 11-mercapto-undecene or has a formula said reaction being effected under conditions permitting binding of said surface binding ligand to the growing nanoparticles to produce said surface functionalised nanoparticles.