Noble metal nanoclusters allow for the atomically-precise control of their composition. However, to create nanoclusters with pre-defined optical properties, comprehensive description of their structure-property relation is required. Here, we report the gold atom doping impact on one-photon and two-photon absorption (TPA) and luminescence properties of ligated silver nanoclusters via combined experimental studies and time-dependent density functional theory simulations (TD-DFT). We synthesized a series of Ag 25À x Au x -(DMBT) 18 nanoclusters where x = 0, 1 and 5-10. For Ag 24 Au 1 (DMBT) 18 we demonstrate that the presence of the central Au dopant strongly influences linear and non-linear optical properties, increasing photoluminescence quantum yield and two-photon brightness, with respect to undoped silver nanoclusters. With improved TPA and luminescence, atomically-precise AuAg alloys presented in our work can serve as robust luminescent probes e.g. for bioimaging in the second biological window.
Plasmonic-enhanced luminescence of single molecules enables imaging and detection of low quantities of fluorophores, down to individual molecules. In this work, we present two-photon excited luminescence of single gold nanoclusters, Au18(SG)14, in close proximity to bare gold nanorods (AuNRs). We observed 25-times enhanced emission of gold nanoclusters (AuNCs) in near infrared region, which was mainly attributed to the resonant excitation of localized surface plasmon resonance (LSPR) of AuNRs and spectral overlap of LSPR band with photoluminescence of AuNCs. This work is an initial step in application of combined nanoparticles: gold nanorods and ultrasmall nanoclusters in a wide range of multiphoton imaging and biosensing applications.
By attaching pyridine groups to a diaza[6]helicene, a helical, bisditopic, bis-N N-coordinating ligand can be accessed. Dinuclear rhenium complexes featuring this bridging ligand, of the form [{Re(CO) 3 Cl} 2 (N NÀ N N)], have been prepared and resolved to give enantiopure complexes. These complexes are phosphorescent in solution at room temperature under one-and twophoton excitation. Their experimental chiroptical properties (optical rotation, electronic circular dichroism and circularly polarized emission) have been measured. They show, for instance, emission dissymmetry factors of c.a. � 3x10 À 3. Quantum-chemical calculations indicate the importance of stereochemistry on the optical activity, pointing towards further design improvements in such types of complexes.
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