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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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The optoelectronic properties of semiconductor nanoparticles make them valuable candidates for the long-term monitoring of transmembrane electric fields in excitable cells. In this work, we show that the electric field sensitivity of the fluorescence intensity of type-I and quasi-type-II quantum dots and quantum rods is enhanced under two-photon excitation compared to single-photon excitation. Based on the superior electric field sensitivity of the two-photon excited fluorescence, we demonstrate the ability of quantum dots and rods to track fast switching E-fields. These findings indicate the potential of semiconductor nanoparticles as cellular voltage probes in multiphoton imaging.

Most optical phenomena result from the interaction of electromagnetic waves with matter. However, the light structure can be eminently more complex than plane waves, with many degrees of freedom and dimensions involved, yielding intricate configurations. Light transcends the conventional landscape of electromagnetism, offering the possibility to tailor light in three dimensions (intermixing all three electric field components), in four-dimensional spacetime (for fields manifesting both temporal and spatial patterns), and, beyond that, to make structured quantum light, tuning its characteristics at an unprecedented new level of control. This article addresses the physical foundations of structured light, its interactions with matter, including the nonlinear regime and probing chirality, its classical benefits with holography as a specific highlight, and quantum mechanical applications. It describes the various applications connecting structured light with material physics, quantum information, and technology. Notably, we discuss weak measurements with structured light acting as the meter with connections to probing structured-light beam shifts at interfaces. Ultimately, revealing the interplay between structured light and matter opens attractive avenues for different new technologies and applications, covering both the classical and the quantum realms. [ABSTRACT FROM AUTHOR]

An original series of bipyrimidine‐based chromophores featuring alkoxystyryl donor groups bearing short chiral (S)‐2‐methylbutyl chains in positions 4, 3,4 and 3,5, connected to electron‐accepting 2,2‐bipyrimidine rings, has been developed. Their linear and non‐linear optical properties were studied using a variety of techniques, including one‐ and two‐photon absorption spectroscopy, fluorescence measurements, as well as Hyper‐Rayleigh scattering to determine the first hyperpolarizabilities. Their electronic and geometrical properties were rationalized by TD‐DFT calculations. The thermal properties of the compounds were also investigated by a combination of polarized light optical microscopy, differential scanning calorimetry measurements and small‐angle X‐ray scattering experiments. The derivatives were found not to have mesomorphic properties, but to exhibit melting temperatures or cold crystallization behavior that enabled the isolation of well‐organized thin films. The nonlinear optical properties of amorphous or crystalline thin films were studied by wide‐field second harmonic generation and multiphoton fluorescence imaging, confirming that non‐centrosymmetric crystal organization enables strong second and third harmonic generation. This new series confirms that our strategy of functionalizing 3D organic octupoles with short chiral chains to generate non‐centrosymmetric organized thin films enables the development of highly second order nonlinear optical active materials without the use of corona‐poling or tedious deposition techniques. [ABSTRACT FROM AUTHOR]

New synthesized bipyrimidine‐based chromophores presenting alkoxystyryl donor groups carrying aliphatic achiral and chiral chains in the 4 position, connected to electron‐accepting 2,2‐bipyrimidine cores have been synthesized. Their linear and nonlinear optical (NLO) properties were investigated as well as their mesomorphic properties by various techniques (light‐transmission measurements, polarized‐light optical microscopy, differential scanning calorimetry measurements and two‐photon excited fluorescence). The derivatives with achiral linear carbon chains were found to exhibit liquid‐crystal properties with the formation smectic phases over large temperature ranges, which were confirmed by small‐angle X‐ray scattering analysis via stacking models. The nonlinear optical properties in the solid state for derivatives with C14 and the citronellol chains have been studied by wide‐field second‐harmonic generation and multi‐photon fluorescence imaging, confirming centrosymmetry for these achiral mesogens and their excellent third‐order nonlinearity whereas the chiral compound exhibits non‐centrosymmetric organization resulting in a strong Second Harmonic Generation at the crystal state. [ABSTRACT FROM AUTHOR]

Electrochemically switched 2nd order non‐linear optical responses have been demonstrated for the first time in polyoxometalates (POMs), with an arylimido‐derivative showing a leading combination of high on/off contrast (94 %), high visible transparency, and cyclability. Spectro‐electrochemical and TD‐DFT studies indicate that the switch‐off results from weakened charge transfer (CT) character of the electronic transitions in the reduced state. This represents the first study of an imido‐POM reduced state, and demonstrates the potential of POM hybrids as electrochemically activated molecular switches. [ABSTRACT FROM AUTHOR]

This paper reports a multifunctional platform based on a nanocomposite hydrogel combining poly(ethylene glycol), with rhodamine B‐containing silica nanoparticles (RhB@SiO2), as temperature sensors, and gold nanorods (AuNRs) as plasmonic heaters. This composite material acts as a light‐addressable cellular matrix able to induce 3D temperature gradients locally and dynamically using the localized surface plasmon resonance (LSPR) of AuNRs under near‐infrared (NIR) laser illumination. At the same time, the temperature changes are probed locally by monitoring changes of the RhB@SiO2 NPs fluorescence. As a result of plasmonic heating, and, depending on the preparation protocol, the light‐addressable hydrogel also deforms controllably and reversibly, allowing mechanical and thermal cellular stimulation in a 3D matrix. The hydrogel deformation is quantified by means of inline holographic microscopy. This approach makes it possible to accurately and locally control and simultaneously measure temperature gradients and deformation in soft, 3D deformable materials and will enable novel platforms for studying cellular thermo‐ and mechanobiology. [ABSTRACT FROM AUTHOR]