Superstructures of copper nanoclusters as NIR TADF emitters: solvent-dependent optical and morphological modulation

Area of Science:

• Materials Science
• Nanotechnology
• Photophysics

Background:

• Copper nanoclusters (CuNCs) are emerging nanomaterials with unique optical properties.
• Controlling the emission characteristics of CuNCs is crucial for their application.
• Thermally activated delayed fluorescence (TADF) offers a pathway for efficient light emission.

Purpose of the Study:

• To synthesize and characterize 2-mercaptopyridine-templated CuNCs with tunable emission.
• To investigate the influence of solvent environment on CuNC morphology and photophysical properties.
• To elucidate the mechanism behind the observed emission tuning, particularly TADF.

Main Methods:

• Synthesis of CuNCs using 2-mercaptopyridine template in aqueous and mixed solvent systems.
• Photoluminescence spectroscopy (steady-state and time-resolved) to analyze emission properties.
• Temperature-dependent studies and excitation-transmittance dependent measurements to confirm TADF.
• Morphological characterization using electron microscopy.

Main Results:

• CuNCs synthesized in water exhibit strong near-infrared (NIR) emission.
• CuNCs prepared in a chloroform/methanol mixture show modulated orange emission.
• A solvent-dependent morphological tuning of CuNC superstructures was observed.
• Strong evidence for thermally activated delayed fluorescence (TADF) with a small singlet-triplet energy gap (58.2 meV) was established.

Conclusions:

• 2-mercaptopyridine-templated CuNCs display tunable emission properties based on solvent environment.
• Morphological changes driven by solvent significantly impact photophysical behavior.
• The observed emission tuning is attributed to solvent-modulated TADF, offering a new strategy for designing luminescent nanomaterials.