Switchable photon and phonon emission properties of an atomically precise Ag14 core-based two-dimensional silver cluster-assembled material

Abstract

A strategy for determining the structure–property correlation of a newly synthesized two-dimensional [Ag₁₄(S^tBu)₁₀(CF₃COO)₄(4,4′-azopyridine)₂] (Ag₁₄ CAM), cluster-assembled material (CAM) with a unique distorted ortho-bielongated square pyramidal core geometry, composed of two face-fused Johnson solids (J8), stitched by a 4,4′-azopyridine linker, is demonstrated here. Our approach represents a new way of controlling the photophysical properties of atom-precise CAMs via interchangeable cluster–solvent interactions. From structural understanding and theoretical modeling studies, it was shown that additional inter-layer non-covalent interactions confine the linker molecule with an unexpected stimuli-responsive frontier molecular orbital arrangement that promotes the charge transfer (linker to metal) phenomenon. This structural transformation is reflected in the photoluminescence (PL) properties, with ∼650 times enhancement of the room temperature PL quantum yield. To manifest this restricted molecular vibration in the non-radiative phonon emission process, the photoacoustic (PA) signal strength was measured which suggests a concomitant photon and phonon emission pathway. Further, an innovative technique, pre-illumination was introduced to amplify the PA signal strength (>85%) at the desired frequency region to provide a path to biomedical imaging applicability. This technique has also been applied to confirm the blood vessel mimicking capability of the portrayed material while it is embedded inside chicken breast tissue at a depth of ∼2 mm to find a new route of wideband plausible applicability.