Finding the Needle in a Haystack: Capturing Veiled Plexcitonic Coupling through Differential Spectroscopy

Meera Mohankumar, Mahima Unnikrishnan, Gopal Narmada Naidu, Sanoop Mambully Somasundaran, Mavilakizhakke Puthiyaveetil Ajaykumar, Rotti Srinivasamurthy Swathi, K. George Thomas

Research output: Contribution to journalArticlepeer-review

8 Scopus citations


Light-matter interactions in chromophore-bound nanoparticles result in various plasmon-mediated processes such as energy transfer, electron transfer, and enhanced emission. Although significant, plexcitonic states formed as a result of noncovalent interactions between plasmonic nanoparticles and chromophores are seldom sighted. Since the binding of chromophores via noncovalent interactions is predominantly an equilibrium process, the finer features of the newly formed plexcitonic states are often masked by the excessive absorption of the unbound chromophoric systems. Herein, we adopt differential extinction spectroscopy to bring out the otherwise hidden plexcitonic states in chromophore-bound plasmonic systems: Cyanine and squaraine dyes bound on plasmonic nanoparticles through various noncovalent interactions. These chromophore-bound plasmonic nanoparticles in water showed a single peak that is broadened when water is used as the reference; however, they displayed a conspicuous Rabi splitting with the chromophoric dye solution as the reference. The formation of plexcitonic states is evident from the well-defined splitting of the extinction band in the differential extinction spectrum of cyanine dyes bound on Ag nanoparticles/Au nanorods. The nature of the plexcitonic states is further established by finite-difference time-domain simulations and a two-state model. The results presented herein ascertain that the plasmon-exciton coupling in chromophore-functionalized metal nanoparticles should be well considered while investigating various plasmon-assisted photophysical processes.

Original languageEnglish
Pages (from-to)26387-26395
Number of pages9
JournalJournal of Physical Chemistry C
Issue number48
StatePublished - 3 Dec 2020
Externally publishedYes

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© 2020 American Chemical Society.


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