Size specific emission in peptide capped gold quantum clusters with tunable photoswitching behavior

Area of Science:

• Nanomaterials Science
• Quantum Chemistry
• Bioconjugate Chemistry

Background:

• Gold clusters are emerging as novel nanomaterials with unique optical and electronic properties.
• Controlling the size and surface chemistry of gold clusters is crucial for tuning their functionalities.
• Peptide-based ligands offer biocompatibility and precise control over cluster formation and solubility.

Purpose of the Study:

• To synthesize and characterize fluorescent gold clusters with tunable emission colors (blue, green, red).
• To investigate the semiconducting and photoswitching properties of these peptide-capped gold clusters.
• To explore the potential of these nanomaterials in optoelectronic applications.

Main Methods:

• Synthesis of fluorescent gold clusters using chloroauric acid and a cysteine-containing dipeptide.
• Characterization using UV-visible, fluorescence, XPS, MALDI-TOF MS, and UHR-FEG-TEM.
• Computational studies including TD-DFT and TCSPC for excited state behavior analysis.

Main Results:

• Successfully prepared blue, green, and red emitting fluorescent gold clusters.
• Demonstrated semiconducting and photoswitching (I_on/I_off) properties controllable by cluster size.
• Identified intersystem crossing (S₁ → T₁) in red-emitting Au₂₃ clusters via computational and experimental methods.

Conclusions:

• Peptide-capped gold clusters offer an eco-friendly approach to nanomaterial synthesis.
• Tunable photoswitching behavior in these gold clusters shows promise for optoelectronics.
• The size-dependent properties highlight the potential for advanced nanomaterial design.