Treffer: 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. ; sponsorship: TL, SVC, and WT acknowledge the support of the KU Leuven Research Grant IDN/19/014. SVC further acknowledges support from KU Leuven (C14/19/079), and FWO (G086522N). WT acknowledges KU Leuven (grants C14/18/061 and C14/23/093) for financial support. YdC acknowledges support from the research foundation Flanders (FWO) for a senior postdoctoral fellowship (1268825N). The calculations were performed on the computers of the "Consortium des equipements de Calcul Intensif (CECI)" (https://www.ceci-hpc.be), including those of the "UNamur Technological Platform of High-Performance Computing (PTCI)" (https://www.ptci.unamur.be) and those of the Tier-1 supercomputer of the Federation Wallonie-Bruxelles, for which we gratefully acknowledge the financial support from the FNRS-FRFC, the ...