General Method to Increase Carboxylic Acid Content on Nanodiamonds

Area of Science:

• Materials Science
• Surface Chemistry
• Nanotechnology

Background:

• Carboxylic acid groups are crucial for conjugating carbon nanoparticles to surfaces.
• Traditional acid oxidation methods create a mix of oxygen-containing groups, not just carboxylic acids.
• Fluorescent nanodiamonds (FNDs) are promising nanomaterials for various applications.

Purpose of the Study:

• To develop a method for selectively enriching carboxylic acid content on FND surfaces.
• To improve the homogeneity and functionalization efficiency of FNDs.
• To create robust single-molecule probes using functionalized FNDs.

Main Methods:

• Surface oxygen-containing groups on FNDs were reduced to alcohols using lithium aluminum hydride.
• Alcohols were converted to carboxylic acids via rhodium-catalyzed carbene insertion with tert-butyl diazoacetate.
• Ester cleavage using trifluoroacetic acid yielded enriched carboxylic acid surfaces.

Main Results:

• The new method successfully enriched carboxylic acid content on FND surfaces.
• Nanodiamond homogeneity was significantly enhanced.
• Functionalization efficiency of FNDs improved, leading to stable biotin-conjugated probes.

Conclusions:

• The developed method provides a pathway for selective carboxylic acid enrichment on FNDs.
• Enhanced FNDs serve as stable and efficient probes for single-molecule fluorescence and optical trapping.
• This approach advances the utility of nanodiamonds in nanoscale research and diagnostics.