ZIF-8 is a widely studied metal-organic framework, but questions remain about its crystallization mechanism, especially at the initial stages. In this study, we used in-situ nonlinear optical (NLO) light scattering techniques to probe nucleation and crystal growth of ZIF-8 nanocrystals. The NLO measurements provided unique insights into the crystallization mechanism of ZIF-8. The formation of crystalline ZIF-8 nanoparticles was probed through depolarization measurements. By comparing second and third harmonic scattering the formation of defects was revealed in the earliest stages. These measurements highlight the potential of NLO techniques to probe nucleation and crystal growth in situ, providing information missed by traditional X ray based techniques.
Optical interrogation of cellular electrical activity is a crucial tool for understanding how cells function and communicate in complex networks. Scientists often use voltage-sensitive dyes to measure the excitability of cells, but these dyes can interfere with cellular function. Label-free techniques offer a way to measure electrical activity without using external probes. In this study, researchers found that second-harmonic generation from live cells is highly sensitive to changes in transmembrane potential by electrode control, making it a promising label-free approach to measure electrical activity in more complex cellular networks. This research provides a promising framework for a non-invasive label-free tool to measure electrical activity in cells.
The integration of photonic materials in applications traditionally dominated by electronic components, such as light emitting diodes, photovoltaic cells and all-optical switches has emerged as a compelling area of study, unlocking new possibilities. Crystalline organic compounds are of particular interest for many applications where their performance is impacted by the crystalline properties. However, investigating crystallization processes in solution remains challenging because their rapid and complex dynamics are difficult to quantify. To this end, we developed an innovative multimodal optical setup capable of in-situ measurements of dynamic processes. Our approach combines a tunable femtosecond pulsed laser and a continuous wave laser, leveraging spectrally resolved scattering and fluorescence detection to measure up to nine different optical effects: second and third harmonic scattering and their depolarization ratios, linear light scattering, multi- and one photon excitation fluorescence, optical rotation and transmission. In this study, we aim to discover the crystallization dynamics of regioregular poly(3-hexylthiophene) through anti-solvent addition. Our findings demonstrate the capability of our setup to provide valuable insights for the optimization of photonic materials.
The chiral nematic phase of cellulose nanocrystals (CNC) in the suspension liquid state is commonly examined using polarized optical microscopy (POM) as it conveniently reveals the cholesteric pitch through fingerprint textures. However, POM has certain limitations, one of which is the requirement for a perpendicular alignment of the chiral axis with the optical axis to achieve accurate measurements. We propose employing SHG microscopy as an alternative technique, offering high-contrast imaging of the chiral nematic phase with inherent 2-photon confocal effect. An IR pulsed femtosecond laser is raster scanned through the microscope, and the cumulative SHG response of the aligned CNC recreates the fingerprint textures. As is shown in this present work, the tight focussing effect of SHG microscope allowed z-scanning to render high contrast 3D models of the structures. Morphological observations and the tracking of defects in 3-dimensional space was made possible.
Photonic crystals can serve as the basis for rewritable paper systems due to their structural color and its responsiveness to external stimuli. The present study reports on a hollow sphere colloidal photonic crystal system encapsulated by a poly(ethylene glycol) diacrylate polymer matrix. By exposing this system to an ionic liquid ink, the polymer will locally swell, red shifting its structural color away from its neutral blue state. The size of the shift is dependent on the type of ionic liquid and the exposure time. This system was shown to attain a maximum shift of 133 nm, which covers the entire RGB spectrum. Both the shift of the structural color as well as the rewritability of the system after water rinsing was confirmed through reflectance measurements. The use of a non-volatile ionic liquid ink ensures the stability of the system over time, allowing for its use as a durable written information storage system.
The development of silicon-organic hybrid (SOH) and plasmonic-organic hybrid (POH) electro-optic modulators in the 2010s has enabled the large electro-optic (EO) performance of organic chromophores to be leveraged for high-performance photonic components capable of integration with CMOS electronics. However, hybrid devices also present unique design considerations for maximizing material performance, including electrode-chromophore interactions, minimization of leak-through current, and maintaining material performance through all important processing and packaging steps. We report materials with an uncompromising combination of EO performance and thermal stability, as well as development of a new generation of materials and advances in processing techniques required to implement them for classical and quantum computing and networking applications.
Recent developments in hybrid electro-optic (EO) systems, in which an organic material with an ultra-large second-order susceptibility is combined with silicon (SOH) or gold (POH) waveguides at the nanoscale. Tight confinement of the optical and RF fields in such devices has enabled operating frequencies > 300 GHz and voltage-length parameters (UπL) < 40 V-μm with existing high-performance organic electro-optic (OEO) materials. However, achieving UπL values on the order of 1 V-μm will require a new generation of OEO materials. The short path lengths within hybrid devices greatly alleviate concerns about optical loss, enabling development of OEO chromophores with extraordinarily large hyperpolarizabilities and refractive indices at telecom wavelengths. However, as device dimensions shrink, chromophore-surface interactions, space-efficiency, and refractive index anisotropy become more critical. Practical device implementations also require materials with high thermal and chemical stability and uncompromising EO performance. We have used a theory-aided design process applying classical and quantum mechanical techniques to design a new generation of OEO materials intended to meet the needs of hybrid devices. We have synthesized these materials, characterized their hyperpolarizability by hyper-Rayleigh scattering, and evaluated their bulk electro-optic behavior and prospects for implementation in nanoscale devices.
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