Two dimensional structures represent a large spectrum of organization of matter on flat surfaces. The behavior of particular nano-objects in confined 2D space is interesting especially when adding functionality to the 2D materials in the form of, for example, sensors, transistors, or optoelectronic templates among others.  Our present efforts are focused on understanding how 2D structures are formed from plant-based components. In this study, the assembly of rod-like cellulose nanocrystals upon spin coating on flat substrates was investigated. To understand the mechanisms behind the formation of the 2D structures, different parameters were probed: pH of the nanocellulose suspension, nature of the counter-ion, concentration of nanocrystals in the spin coating suspension and the nature of the substrates. The morphologies were examined with Atomic Force Microscopy.  The results showed that the decisive factor for the assembly of the nanocrystals during spin coating was the pH of the solution, which was largely attributed to the role of sulfate groups on the nanocrystal surface. Under specific conditions, the formation of micron-sized cellular networks from the nanosized cellulose nanocrystals was detected. Such networks have been previously reported with, for example, spherical gold nanoparticles and their formation has been assigned to relatively complex hydrophobic forces during evaporation. The results in this work show that a robust spin coating method with straightforward control over electrostatic forces can be used to prepare cellular networks from biologically derived nanorods. These structures can be interesting, for example, as templates for various micro- and nanostructures in 2D space.

Tuning the assembly of cellulose nanocrystals in 2D networks by adjusting the chemical conditions in spin coating

247th National Meeting (2014)

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