Surface plasmon resonance refers to collective oscillations within the conduction electron cloud on the surfaces of metal nanoparticles. Chiral plasmonic nanostructures can be made using spherical gold nanoparticles and a helical template of choice. When the nanoparticles are sufficiently closely positioned, the oscillations become coupled to allow collective excitations. If the nanoparticles are additionally assembled in a helical manner, the optical response acquires a circular dichroic (CD) signal.1 Cellulose nanocrystals (CNCs) are crystalline rod-like particles with nanodimensions (average diameter 7 nm, length 150 nm). They are made by sulfuric acid hydrolysis of cellulose that destroys the amorphous parts of the fibers leaving the crystalline parts intact. Hydrolysis also creates anionic sulfate groups on the surface of the CNCs. Individual CNC is helically twisted along the longitudinal direction previously visualized by electron tomography (ET).2 Here we show a route based on CNCs forming supracolloidal adducts with electrostatically bound cationic gold nanoparticles (Au NPs). We pursue towards using individually dispersed CNC nanorods as templates to bind Au NPs on their surfaces, where their expected chiral assembly emerges due to twisting along the native CNC nanorod. CNC/Au NP adducts are characterized using cryo transmission electron microscopy and ET. Chiral plasmonic responce of the adducts is verified using UV-Vis and CD spectroscopy. Even if there are no particular mechanisms involved to control the separation of the nanoparticles, the used procedure allows sufficient control of the average separation of the nanoparticles to render CD-signal characteristic for chiral nanoparticle plasmonics. 1A. Kuzyk et al., Nature, 2012, 483, 311-314 2J. Majoinen et al., JACS, 2014, 136, 866-869

Facile route for chiral plasmonic gold nanoparticle assemblies via templating with cellulose nanocrystals

251st National Meeting (2016)

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