Carbon quantum dots from carbonized walnut shells: Structural evolution, fluorescence characteristics, and...

Area of Science:

• Materials Science
• Nanotechnology
• Biochemistry

Background:

• Carbon quantum dots (CQDs) are recognized for their fluorescence, stability, and biocompatibility.
• Developing sustainable and cost-effective methods for CQD synthesis is crucial for their widespread application.
• Walnut shells, rich in cellulose, present a promising biomass source for CQD production.

Purpose of the Study:

• To develop a facile method for synthesizing carbon quantum dots (CQDs) from readily available walnut shells.
• To characterize the structural and photoluminescent properties of the synthesized CQDs.
• To evaluate the potential of these CQDs as fluorescent probes for live-cell imaging.

Main Methods:

• Carbonization of walnut shells followed by acid treatments to yield CQDs.
• High-resolution transmission electron microscopy (HRTEM) for size and morphology analysis.
• Photoluminescence spectroscopy to investigate optical properties.
• Live-cell imaging using confocal microscopy and Raman mapping.

Main Results:

• Successfully synthesized CQDs with an average size of 3.4nm, displaying zigzag and armchair edges.
• Observed green fluorescence (excitation 360-460nm) with properties including hydrophilicity, pH-sensitivity, and up-conversion.
• Demonstrated reversible photoluminescence changes in response to pH and solvent variations.
• Validated CQDs' utility in live-cell imaging, visualizing intracellular distribution and uptake mechanisms.

Conclusions:

• A straightforward and sustainable method for producing CQDs from walnut shells was established.
• The synthesized CQDs possess tunable photoluminescence and favorable characteristics for biological applications.
• These CQDs show significant potential as biocompatible fluorescent probes for intracellular studies.