Monitoring transient nanoparticle interactions with liposome-confined plasmonic transducers

The encapsulation of individual pairs of plasmonic nanoparticles(NPs)in liposomes is introduced as a new strategy for utilizing plasmon coupling to monitor interactions between co-confined NPs in a nanoconfinement that ensures high local NP concentrations.We apply the approach to monitor transient binding contacts between noncovalently tethered 55 nm diameter gold NPs,which were functionalized with cytosine(C)-rich DNAs,in acidic and mildly basic buffer conditions.At pH=8,a rich spectral dynamics indicates DNA-mediated transient binding and unbinding of co-confined NPs due to weak attractive interparticle interactions.A decrease in pH from 8 to 4 is observed to favor the associated state for some co-confined NPs,presumably due to a stabilization of the bound dimer configuration through noncanonical C-C^(+)bonds between the DNA-functionalized NPs.Plasmonic nanoemitters whose spectral response switches in response to chemical cues(in this work pH)represent optical transducers with a rich application space in chemical sensing,cell analysis and nanophotonics.