A cooperative effect of copper-induction and AIE leading to bright luminescence of gold nanoclusters

Abstract

Emission enhancement of gold nanoclusters protected with 6-propyl-2-thiouracil (PRT-AuNCs) is achieved through incorporating a suitable amount of Cu²⁺. Sophisticated mechanisms are involved in the modulation of emission properties of the PRT-AuNCs/Cu²⁺ system, instead of merely a metal ion induced aggregation. X-ray photoelectron spectroscopy, IR spectroscopy and mass spectroscopy reveal that the Cu²⁺ is reduced by 6-propyl-2-thiouracil to form a Cu(I)–thiolate complex, which then co-assembles with the AuNCs to form a PRT-Au/Cu composite at an appropriate Cu²⁺ concentration. Systematic microscopic characterization studies including scanning electron microscopy, X-ray diffraction etc. demonstrate the crucial effect of compact aggregation driven by metallophilic interactions on the emission enhancement of PRT-Au/Cu. Detailed analysis of the photophysical parameters validates that the presence of Cu(I) changes the radiative transition mechanisms of PRT-Au/Cu with respect to primitive PRT-AuNCs. As a result, a cooperative effect of copper-induction and aggregation induced emission (AIE) leads to a strongly emissive composite with bathochromic-shifted emission energy. Moreover, the high molar ratio between Cu and Au in PRT-Au/Cu can effectively reduce the cost of the material in production, and we have developed a WLED to exemplify the potential application of this composite material.