Molecular photonic switches employing ions and nanoparticles of coinage and platinum metals

Organic molecules containing a fluorophore-spacer-receptor (F-S-R) combination are a hot topic of contemporary research due to their wide applicability in information processing devices. This work is the first report of the use of metal ions and nanoparticles of coinage metals (Cu, Ag, Au) and platinum metals (Ni, Pt, Pd) in developing molecular photonic switches. In the presence of these metals, the photoinduced electron transfer (PET) normally responsible for fluorescence quenching of F-S-R molecules is hindered. These metal ions and their corresponding nanoparticles interact with the receptor (R) site; preventing its participation in PET, thus increasing the fluorescence of the F-S-R molecule. This is comparable to the "switching-on" operation of a light switch. However, beyond a certain critical concentration that varies from metal to metal, the quenching effect of the ions overrules their fluorescence enhancement (FE) effect and thus the fluorescence of the probe decreases. This is equivalent to the "switching-off" operation of a switch. Thus, digital instruments operating with the 1 (on) or 0 (off) principle can employ such metal ion/nanoparticle-probe combinations as efficient molecular photonic switches. Maintaining the critical concentration as a borderline, such systems can efficiently function as OR logic gates.