pH-driven chromophore amplification enables high-efficiency phosphorescent carbon dots

Area of Science:

• Materials Science
• Nanotechnology
• Photochemistry

Background:

• Solvothermal synthesis is a primary method for creating phosphorescent carbon dots (CDs).
• Controlling reaction conditions, especially pH, is crucial for tuning CD properties.
• The specific impact of pH on phosphorescent behavior requires systematic investigation.

Purpose of the Study:

• To investigate the influence of solvothermal pH on the phosphorescent properties of carbon dots.
• To establish the relationship between synthesis pH, surface carbonyl groups, and phosphorescent quantum yield (Φp).

Main Methods:

• Fabrication of carbon dots (CDs) under three distinct solvothermal pH conditions (9.5, 11, and 12).
• Quantification of phosphorescent quantum yields (Φp) for CDs synthesized at different pH values.
• Analysis of surface carbonyl group density on CDs.
• Combined experimental and computational analyses.

Main Results:

• Phosphorescent quantum yields (Φp) of CDs increased with increasing pH: 0.4% (pH 9.5), 0.58% (pH 11), and 1.69% (pH 12).
• A direct correlation was observed between synthesis pH, surface carbonyl group density, and Φp.
• Increased density of surface-bound carbonyl chromophores is identified as the primary factor for enhanced phosphorescence.

Conclusions:

• Solvothermal pH is a critical parameter for optimizing the phosphorescent properties of carbon dots.
• Surface carbonyl groups act as key chromophores, directly influencing phosphorescent quantum yield.
• This study provides a novel understanding of pH-modulated phosphorescence in carbon dots.