Coassembly of gold nanoparticles and cellulose nanocrystals in composite films.

Coassembly of nanoparticles with different size-, shape-, and composition-dependent properties is a promising approach to the design and fabrication of functional materials and devices. This paper reports the results of a detailed investigation of the formation and properties of free-stranding composite films formed by the coassembly of cellulose nanocrystals and shape-isotropic plasmonic gold nanoparticles. The effect of gold nanoparticle size, surface charge, and concentration on the structural and optical properties of the composite films has been studied.

Structure and properties of composite films formed by cellulose nanocrystals and charged latex nanoparticles.

We report the structural and optical properties of composite films formed from mixed suspensions of cellulose nanocrystals (CNCs) and fluorescent latex nanoparticles (NPs). We explored the effect of NP concentration, size, surface charge, glass transition temperature and film processing conditions on film structure and properties. The chiral nematic order, typical of CNC films, was preserved in films with up to 50 wt% of negatively-charged latex NPs.

Coassembly of nanorods and nanospheres in suspensions and in stratified films.

The entropically driven coassembly of nanorods (cellulose nanocrystals, CNCs) and nanospheres (dye-labeled spherical latex nanoparticles, NPs) was studied in aqueous suspensions and in solid films. In mixed CNC-latex suspensions, phase separation into an isotropic latex-NP-rich and a chiral nematic CNC-rich phase took place; the latter contained a significant amount of latex NPs. Drying the mixed suspension resulted in CNC-latex films with planar disordered layers of latex NPs, which alternated with chiral nematic CNC-rich regions.

Trace cancer biomarker quantification using polystyrene-functionalized gold nanorods.

We demonstrate the application of polystyrene-functionalized gold nanorods (AuNRs) as a platform for surface enhanced Raman scattering (SERS) quantification of the exogenous cancer biomarker Acetyl Amantadine (AcAm). We utilize the hydrophobicity of the polystyrene attached to the AuNR surface to capture the hydrophobic AcAm from solution, followed by drying and detection using SERS. We achieve a detection limit of 16 ng/mL using this platform.

Copolymerization of metal nanoparticles: a route to colloidal plasmonic copolymers.

The resemblance between colloidal and molecular polymerization reactions is very useful in fundamental studies of polymerization reactions, as well as in the development of new nanoscale systems with desired properties. Future applications of colloidal polymers will require nanoparticle ensembles with a high degree of complexity that can be realized by hetero-assembly of NPs with different dimensions, shapes, and compositions. A method has been developed to apply strategies from molecular copolymerization to the co-assembly of gold nanorods with different dimensions into random and block copolymer structures (plasmonic copolymers).

Controlling the degree of polymerization, bond lengths, and bond angles of plasmonic polymers.

Plasmonic polymers present an interesting concept that builds on the analogy between molecular polymers and linear chains of strongly interacting metal nanoparticles. Ensemble-averaged optical properties of plasmonic polymers are strongly influenced by their structure. In the present work, we formed plasmonic polymers by using solution-based assembly of gold nanorods (NRs) end-tethered with photoactive macromolecular tethers.