The utilization of metallic nanostructures is a very promising means of improving the efficiency of photochemical and photophysical processes of organic fluorophores. Indeed, the spectral properties of fluorescent species can be dramatically altered by near-field interactions with the electron clouds present in metals. These interactions modify the emission in ways not seen in classical fluorescence experiments, and can be exploited to facilitate the photophysical processes responsible for the emission of nearby excited-state chromophores, ultimately increasing quantum yield and photostability. In particular, the presence of silver nanoparticles (AgNP) can result in an increased rate of excitation as well as in the radiative decay rate of fluorochromes in their proximity, thereby improving their brightness, in accordance with the principles of radiative decay engineering. In addition to increasing signal to noise, AgNP permit shorter photoreaction times and low irradiance–all of which have important implications for applications of fluorescence activation and switching in portable fluorescence patterning, bioimaging and super-resolution microscopy. This synergistic combination of emissive molecules and metal nanoparticles can be exploited for developing innovative photoresponsive materials that would not otherwise be accessible through their separate organic and inorganic (metallic) components alone. Metal-enhanced fluorescence (MEF) effects can thus be exploited to increase fluorescence intensities, resulting in new experimental protocols and novel probes for applications in fluorescence microscopy or lithographic techniques.  Importantly, single molecule fluorescence microscopy (SMFM) can provide unique insights into the MEF mechanism which are hidden by ensemble-averaged measurements, demonstrating that fusion between classic spectroscopic techniques and single molecule methods can bring remarkable advantages for quantitatively characterizing particle-molecule interactions, such as those responsible for the relative contributions of increased excitation and plasmophoric emission toward overall MEF.

Synergistic integration of switchable fluorophores and metal nanoparticles: Photoactivated and metal-enhanced fluorescence

ACS Fall 2020 Virtual Meeting

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