Structural Flexibility-Driven Dual Emission Switching in Ultrathin Gold Nanorod Clusters

Area of Science:

• * Computational chemistry and materials science.
• * Focus on atomically precise gold nanoclusters (AuNCs).

Background:

• * Dual emission phenomena in gold nanoclusters (AuNCs) are known but poorly understood.
• * The relationship between AuNC emission properties, structure, and size requires elucidation.

Purpose of the Study:

• * Investigate the structure-size dependency of dual emission mechanisms in one-dimensional (1D) rod-shaped AuNCs (Au24, Au42, Au60).
• * Establish a quantitative framework linking size, flexibility, and emission behavior in anisotropic AuNCs.

Main Methods:

• * Utilized density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations.
• * Analyzed electronic structure, transition dipole moments, and energy gaps (ΔEST).

Main Results:

• * Increasing aspect ratio (AR) from 3.1 to 9.4 stiffened cluster cores and enhanced x-axis transition dipole moments.
• * Narrowed singlet-triplet energy gaps (ΔEST) and increased radiative rate constants (kr F) and intersystem crossing (kISC).
• * Shorter clusters showed dual fluorescence (F1+F2), while elongated ones exhibited fluorescence-phosphorescence (F+P) dual emission.

Conclusions:

• * Size-dependent structural changes in AuNCs directly influence their dual emission mechanisms.
• * Developed a quantitative model for predicting emission behavior based on AuNC size and flexibility.
• * Provides design principles for creating tunable dual emission probes for optical imaging and sensing.