Nanodiamond Synthesis Using Polycyclic Aromatic Precursors
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Solution Overview
Problem
Existing methods for preparing nanodiamonds, such as detonation and high-pressure high-temperature (HPHT) methods, result in particles with large sizes, metal contaminants, and non-uniform shapes, making them unsuitable for certain biomedical and quantum sensing applications.
Innovation Solution
A process involving a polycyclic aromatic compound as a diamond precursor, subjected to a pressure of at least 8 GPa and a temperature of at least 900°C, without the use of metal catalysts, to produce nanodiamond particles with a narrow size distribution and average particle size of less than 20 nm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If detonation method is used to prepare nanodiamonds, then nanodiamonds are formed in clusters with sizes down to 5 nm, but graphitic shells and soot-like structures surround the nanodiamond particles and the structure is less crystalline
Solution Approach 1:
The patent changes the pressure parameter from conventional HPHT (≥7 GPa) to a specific range of 2-5 GPa, and temperature from conventional HPHT (up to 2200°C) to a specific range of 1000-1800°C. These parameter changes enable direct synthesis of nanodiamonds with crystalline structure without requiring ball-milling post-treatment, thus resolving the contradiction between small size and crystalline quality.
2Productivity
If HPHT method with metal catalysts is used, then diamonds are formed, but high levels of metal contaminants are present requiring laborious post-treatment
Solution Approach 1:
The patent extracts/removes the metal catalyst component from the HPHT synthesis process entirely. By using a metal-free synthesis approach with pressures of 2-5 GPa and temperatures of 1000-1800°C, the invention produces nanodiamonds without metal contaminants, eliminating the need for laborious post-treatment while maintaining productivity.
3Length of moving object
If high energy ball milling is used to reduce microdiamonds to nanodiamonds, then particle size is reduced, but metal impurities increase and non-diamond layers form on particle surfaces
Solution Approach 1:
The patent performs preliminary action by directly synthesizing nanodiamonds at the desired size (2-50 nm) through controlled HPHT conditions of 2-5 GPa and 1000-1800°C, avoiding the need for subsequent ball-milling size reduction. This preliminary formation at correct size prevents the introduction of metal impurities and non-diamond layers that would occur during mechanical size reduction.
4Length of moving object
If ball-milling treatment is applied to micron-sized fluorescence nanodiamonds, then nanodiamonds are produced, but non-uniform shapes with sharp edges and non-uniform photoluminescence properties result
Solution Approach 1:
The patent changes the synthesis parameters to pressures of 2-5 GPa and temperatures of 1000-1800°C, which directly produce nanodiamonds with uniform spherical shapes and consistent photoluminescence properties. This eliminates the need for ball-milling that would create sharp edges and non-uniform characteristics, achieving both size reduction and shape uniformity simultaneously.
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 process achieves high-yield production of nanodiamonds with low metal contaminants and minimal non-diamond carbon, resulting in particles that are suitable for biomedical and quantum sensing applications due to their small size, uniform shape, and narrow size distribution.
Implementation Method 1
subjecting a diamond precursor material to a pressure of at least 8 GPa and a temperature of at least 900°C
Implementation Method 2
high pressure high temperature (HPHT) method
Data Source
AI summary
The present invention relates to a process for preparing diamond particles, comprising subjecting a nanodiamond precursor material to a pressure of at least 8 GPa and a temperature of at least 900°C, wherein the diamond precursor material comprises a polycyclic aromatic compound which contains from 10 to 200 fused six-membered aromatic rings.