Understanding the Dynamics of Fluorescence Emission During Zeolite Detemplation Using Time Resolved Photoluminescence Spectroscopy

Time-resolved photoluminescence spectroscopy (TRPS) shows potential as a sensitive, non-destructive, high throughput, label-free laser-based spectroscopy technique capable of analysing low concentrations of organic species adsorbed on and within zeolite pores. Here we report the results from a study that uses TRPS to characterise photoluminescence (PL) arising from synthesised chabazite framework zeolites at three different stages of the detemplation process (from an uncalcined, partially calcined, and calcined zeolite). Temporal resolution was used to demonstrate the steric confinement effects of OSDA within a zeolite framework and therefore to establish a signature region for determining the presence of the template. Gated spectra comparisons between an uncalcined and a partially calcined zeolite demonstrated the presence of template alongside the proliferation of template-derived combustion products. An analysis of lifetime values demonstrated the ability for TRPS to track depletion of OSDA and establish a characteristic PL spectrum for a clean zeolite

Novel time-resolved camera based on compressed sensing

Time-resolved cameras with high temporal resolution (down to ps) enable a huge set of novel applications ranging from biomedicine and environmental science to material and device characterization. In this work, we propose, and experimentally validate, a novel detection scheme for time-resolved imaging based on a compressed sampling approach. The proposed scheme unifies into a single element all the required operations, i.e. space modulation, space integration and time-resolved detection, paving the way to dramatic cost reduction, performance improvement and ease of use

Multimodal Imaging of Autofluorescent Sites Reveals Varied Chemical Speciation in SSZ-13 Crystals

A multimodal imaging study of chabazite is used to show the distribution of and discriminate between different emissive deposits arising as a result of the detemplation process. Confocal imaging, 3D fluorescence lifetime imaging, 3D multispectral fluorescence imaging, and Raman mapping are used to show three different types of emissive behaviours each characterised by different spatial distributions, trends in lifetime, spectral signals, and Raman signatures. A notable difference is seen in the morphology of agglomerated surface deposits and larger subsurface deposits, which experience lifetime augmentation due to spatial confinement. The distribution of organic residue throughout the crystal volume is comparable to XRF mapping that shows Si enrichment on the outer edges and higher Al content through the centre, demonstrating that a fluorescence‐based technique can also be used to indirectly comment on the compositional chemistry of the inorganic framework

Integrated optical device for Structured Illumination Microscopy

Structured Illumination Microscopy (SIM) is a key technology for high resolution and super-resolution imaging of biological cells and molecules. The spread of portable and easy-to-align SIM systems requires the development of novel methods to generate a light pattern and to shift it across the field of view of the microscope. Here we show a miniaturized chip that incorporates optical waveguides, splitters, and phase shifters, to generate a 2D structured illumination pattern suitable for SIM microscopy. The chip creates three point-sources, coherent and controlled in phase, without the need for further alignment. Placed in the pupil of a microscope's objective, the three sources generate a hexagonal illumination pattern on the sample, which is spatially translated thanks to thermal phase shifters. We validate and use the chip, upgrading a commercial inverted fluorescence microscope to a SIM setup and we image biological sample slides, extending the resolution of the microscope. (C) 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreemen

On the robustness of machine learning algorithms toward microfluidic distortions for cell classification via on-chip fluorescence microscopy

Single-cell imaging and sorting are critical technologies in biology and clinical applications. The power of these technologies is increased when combined with microfluidics, fluorescence markers, and machine learning. However, this quest faces several challenges. One of these is the effect of the sample flow velocity on the classification performances. Indeed, cell flow speed affects the quality of image acquisition by increasing motion blur and decreasing the number of acquired frames per sample. We investigate how these visual distortions impact the final classification task in a real-world use-case of cancer cell screening, using a microfluidic platform in combination with light sheet fluorescence microscopy. We demonstrate, by analyzing both simulated and experimental data, that it is possible to achieve high flow speed and high accuracy in single-cell classification. We prove that it is possible to overcome the 3D slice variability of the acquired 3D volumes, by relying on their 2D sum z-projection transformation, to reach an efficient real time classification with an accuracy of 99.4% using a convolutional neural network with transfer learning from simulated data. Beyond this specific use-case, we provide a web platform to generate a synthetic dataset and to investigate the effect of flow speed on cell classification for any biological samples and a large variety of fluorescence microscopes (https://www.creatis.insa-lyon.fr/site7/en/MicroVIP)

High-throughput multimodal wide-field Fourier-transform Raman microscope

Raman microscopy is a powerful analytical technique for materials and life sciences that enables mapping the spatial distribution of the chemical composition of a sample. State-of-the-art Raman microscopes, based on point-scanning frequency-domain detection, have long (∼1 s) pixel dwell times, making it challenging to acquire images of a significant area (e.g., 100×100 μm). Here we present a compact wide-field Raman microscope based on a time-domain Fourier-transform approach, which enables parallel acquisition of the Raman spectra on all pixels of a 2D detector. A common-path birefringent interferometer with exceptional delay stability and reproducibility can rapidly acquire Raman maps (∼30 min for a 250 000 pixel image) with high spatial (<1 μm) and spectral (∼23 cm-1) resolutions. Time-domain detection allows us to disentangle fluorescence and Raman signals, which can both be measured separately. We validate the system by Raman imaging plastic microbeads and demonstrate its multimodal operation by capturing fluorescence and Raman maps of a multilayer-WSe2 sample, providing complementary information on the strain and number of layers of the material

Performances of a portable Fourier transform hyperspectral imaging camera for rapid investigation of paintings

Abstract: Scientific investigation in the cultural heritage field is generally aimed at the characterization of the constituent materials and the conservation status of artworks. Since the 1990s, reflectance spectral imaging proved able to map pigments, reveal hidden details and evaluate the presence of restorations in paintings. Over the past two decades, hyperspectral imaging has further improved our understanding of paints and of its changes in time. In this work, we present an innovative hyperspectral camera, based on the Fourier transform approach, utilising an ultra-stable interferometer and we describe its advantages and drawbacks with respect to the commonly used line- and spectral-scanning methods. To mitigate the weaknesses of the Fourier transform hyperspectral imaging, we propose a strategy based on the virtual extension of the dynamic range of the camera and on the design of an illumination system with a balanced emission throughout the spectral range of interest. The hyperspectral camera was employed for the analysis of a painting from the “Album of Nasir al-din Shah”. By applying analysis routines based on supervised spectral unmixing, we demonstrate the effectiveness of our camera for pigment mapping. This work shows how the proposed hyperspectral imaging camera based on the Fourier transform is a promising technique for robust and compact in situ investigation of artistic objects in conditions compatible with museum and archaeological sites. Graphic abstract: [Figure not available: see fulltext.

A Multimodal Label-Free Imaging Study of Zeolite Crystals

Zeolites are complex materials that are widely employed in industry as heterogenous catalysts. Their unique open framework structures allow them to not only act as size-selective sieves, but to play host to an adsorbed phase of organic guest molecules. Imaging both the framework and the concomitant adsorbed organic material in a single micrograph is very challenging because each material has different requirements for generating image contrast. In particular, chemically interesting organic material is hard to see using electron imaging techniques that otherwise resolve the framework relatively successfully

The structural bases for agonist diversity in an Arabidopsis thaliana glutamate receptor-like channel

Arabidopsis thaliana glutamate receptor-like (GLR) channels are amino acid-gated ion channels involved in physiological processes including wound signaling, stomatal regulation, and pollen tube growth. Here, fluorescence microscopy and genetics were used to confirm the central role of GLR3.3 in the amino acid-elicited cytosolic Ca2+ increase in Arabidopsis seedling roots. To elucidate the binding properties of the receptor, we biochemically reconstituted the GLR3.3 ligand-binding domain (LBD) and analyzed its selectivity profile; our binding experiments revealed the LBD preference for L-Glu but also for sulfur-containing amino acids. Furthermore, we solved the crystal structures of the GLR3.3 LBD in complex with 4 different amino acid ligands, providing a rationale for how the LBD binding site evolved to accommodate diverse amino acids, thus laying the grounds for rational mutagenesis. Last, we inspected the structures of LBDs from nonplant species and generated homology models for other GLR isoforms. Our results establish that GLR3.3 is a receptor endowed with a unique amino acid ligand profile and provide a structural framework for engineering this and other GLR isoforms to investigate their physiology