Second-order NLO response in chiral ferroelectric liquid crystals: Molecular and bulk consideration

First hyperpolarizability of cellulose nanocrystals: an experimental and theoretical investigation

Cellulose nanocrystals (CNCs) have attracted considerable interest due to their optical properties, though their nonlinear optical behavior remains largely unexplored. In this paper, we investigate the second-order nonlinear optical (SONLO) response of CNCs through both experimental and theoretical investigations. Hyper-Rayleigh scattering (HRS) experiments revealed values comparable to well-known nonlinear optical biomaterials, such as collagen, and on par with inorganic reference materials like KDP. The strong response in CNCs can be attributed to the well-ordered structure of the cellulose chains, which enhances the overall susceptibility of the nanoparticles. Quantum chemical modeling using density functional theory (DFT) was employed to simulate the molecular hyperpolarizability of CNCs. The study reduced the complex first hyperpolarizability tensor of the CNCs to two key components, βzzz and βzyy. An electrostatic model was applied to account for the CNCs' shape and dielectric properties, leading to strong agreement with the experimental data. Our findings highlight the potential of CNCs for optoelectronic applications and provide valuable insights for characterizing CNC-based mesomaterials through two-photon microscopy.

Organogels of FmocFF: Exploring the Solvent-Dependent Gelmorphic Behavior

FmocFF (9-fluorenyl methoxycarbonyl-phenylalanine) is an extensively studied low-molecular-weight hydrogel. Although there have been numerous studies on FmocFF hydrogel, its potential to form organogels has not been well explored. In this work, we systematically explore the organogels of FmocFF in a wide range of organic solvents. FmocFF is found to be a robust organogeltor, and the subsequent organogels exhibit diverse gelmorphic behavior exhibiting various degrees of crystallinity and morphology depending on the solvent used. The mechanical strength of the organogels is evaluated using rheology. A novel technique, in situ SHG microscopy, is introduced to study the gel structure in its native state. In addition to the solvent-solute interactions that are typically used to predict gelmorphic behavior, we observed indications that the degree of crystallinity also plays a significant role in determining the mechanical properties and structure of FmocFF organogels.

Imaging with a twist: Three-dimensional insights of the chiral nematic phase of cellulose nanocrystals via SHG microscopy

Cellulose nanocrystals (CNCs) are bio-based nanoparticles that, under the right conditions, self-align into chiral nematic liquid crystals with a helical pitch. In this work, we exploit the inherent confocal effect of second-harmonic generation (SHG) microscopy to acquire highly resolved three-dimensional (3D) images of the chiral nematic phase of CNCs in a label-free manner. An in-depth analysis revealed a direct link between the observed variations in SHG intensity and the pitch. The highly contrasted 3D images provided unprecedented detail into liquid crystal's native structure. Local alignment, morphology, as well as the presence of defects are readily revealed, and a provisional framework relating the SHG response to the orientational distribution of CNC nanorods within the liquid crystal structure is presented. This paper illustrates the numerous benefits of using SHG microscopy for visualizing CNC chiral nematic systems directly in the suspension-liquid phase and paves the road for using SHG microscopy to characterize other types of aligned CNC structures, in wet and dry states.