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The sol–gel process is an effective method for the preparation of homogeneous structured nanomaterials whose physico-chemical properties strongly depend on the experimental conditions applied. The control of a three-component reaction with silanes showing multiple reaction sites revealed the need for an analytical tool that allows a rapid response to ongoing transformations in the reaction mixture. Herein, we describe the implementation of near-infrared (NIR) spectroscopy based on compact, mechanically robust, and cost-efficient micro-optomechanical system technology in the sol–gel process of three silanes with a total of nine reaction sites. The NIR-spectroscopically controlled reaction yields a long-time stable product with reproducible quality, fulfilling the demanding requirements for further use in coating processes. 1H nuclear magnetic resonance measurements are used as reference values for the calibration of a partial least squares (PLS) regression model. The precise prediction of the desired parameters from collected NIR spectroscopy data acquired during the sol–gel reaction proves the applicability of the calibrated PLS regression model. The determined shelf-life and further processing tests verify the high quality of the sol–gel and the produced highly cross-linked polysilane. Osterreichische Forschungsforderungsgesellschaft 864703 Version of record

In this article, we demonstrate a promising inline near-infrared measurement scheme for 24/7 biofilm monitoring based on cost-effective microelectromechanical system-based spectrometer technology. The shown near-infrared spectral data, acquired at a beer-canning line during a representative time span of 10 days, are analyzed by means of principal component analysis and the performance of the monitoring system and its capability to identify biofilms on its sensor surface are investigated by comparing spectral response with results of offline polymerase chain reaction measurements of smear samples. Correlations between presence of a biofilm and its thickness with scores on PC1 and PC2, respectively, were observed.

In this contribution we present results on non-destructive chemical imaging in the mid-infrared (MIR) region of well-defined biofilms formed by Pseudomonas simiae. Biofilms were grown on stainless steel slides using a static biofilm model (incubation lasted for seven days at 10 °C, with repetitive medium changes). The MIR spectra correlate with fundamental molecular vibrations and are therefore characteristic for chemical composition and structure [1, 2]. Besides a brief insight into the systematic of how the investigated biofilms were grown the main focus will be on MIR spectroscopic measurements including dynamic observation of drying processes of bacteria, as well as spatially resolved scans of the steel plates with an MIR microscope. The obtained hyperspectral chemical images of biofilms were analyzed by various spectroscopic data analysis techniques. Furthermore, the dynamic spectroscopic observation of the drying process of planktonic Pseudomonas simiae cultures in nutrient solution gave insight in dynamic variances in certain functional chemical groups of the bacteria. These variances have also been observed in biofilm samples and may correlate with vitality. The MIR chemical images, where each pixel is composed of an entire MIR spectrum (4000-400 cm-1) provide detailed information of the investigated biofilms such as their composition and spatial structure. The overlay with conventional microscope images relates spectroscopic to visual data, both laterally resolved in the µm-range, over a scan area of up to 10 x 40 mm². The variation of the vibrational bands was screened, revealing high and low variance bands, to identify certain spectral regions suitable for classification of the investigated biofilm samples. Characteristic spectral bands were found and related to data from literature. Furthermore, differences in the spatial distribution of proteins and carbohydrates as part of the bacteria and extracellular polymeric substances were clearly identified. Acknowledgment: This work was created within a research project of the des Austrian Competence Centre for Feed and Food Quality, Safety and Innovation (FFoQSI). The COMET-K1 competence centre FFoQSI is funded by the Austrian ministries BMVIT, BMDW and the Austrian provinces Niederoesterreich, Upper Austria and Vienna within the scope of COMET -Competence Centers for Excellent Technologies. The programme COMET is handled by the Austrian Research Promotion Agency FFG. References:[1] Andreas Schwaighofer, Markus Brandstetter and Bernhard Lendl , “Quantum cascade lasers (QCLs) in biomedical spectroscopy”, Chem. Soc. Rev. 46, 5903-5924 (2017)[2] Jakob Kilgus, Gregor Langer, Kristina Duswald, Robert Zimmerleiter, Ivan Zorin, Thomas Berer, and Markus Brandstetter, "Diffraction limited mid-infrared reflectance microspectroscopy with a supercontinuum laser," Opt. Express 26, 30644-30654 (2018)

Recent developments in mid-infrared (MIR) spectroscopic ellipsometry enabled by quantum cascade lasers (QCLs) have resulted in a drastic improvement in signal-to-noise ratio compared to conventional thermal emitter based instrumentation. Thus, it was possible to reduce the acquisition time for high-resolution broadband ellipsometric spectra from multiple hours to less than 1 s. This opens up new possibilities for real-time in-situ ellipsometry in polymer processing. To highlight these evolving capabilities, we demonstrate the benefits of a QCL based MIR ellipsometer by investigating single and multilayered polymer films. The molecular structure and reorientation of a 2.5 µm thin biaxially oriented polyethylene terephthalate film is monitored during a stretching process lasting 24.5 s to illustrate the perspective of ellipsometric measurements in dynamic processes. In addition, a polyethylene/ethylene vinyl alcohol/polyethylene multilayer film is investigated at a continuously varying angle of incidence (0∘– 50∘) in 17.2 s, highlighting an unprecedented sample throughput for the technique of varying angle spectroscopic ellipsometry in the MIR spectral range. The obtained results underline the superior spectral and temporal resolution of QCL ellipsometry and qualify this technique as a suitable method for advanced in-situ monitoring in polymer processing.

We have monitored the evolution of the optical properties of ultrathin N,N′-dipentylperylene-3,4,9,10-tetracarboxylic diimide (PTCDI-C5) molecular thin films during their growth on muscovite mica surfaces using differential reflectance spectroscopy (DRS) and fluorescence spectroscopy (FL). In the monolayer regime, the DRS shows a monomer-like absorption, whereas the FL reveals a transition from monomeric to excimer-like emission accompanied by a quenching of the intensity with the increase of coverage. The observed evolution of the FL signals can be explained by a two dimensional (2D) gas to condensed phase transition. The characteristic fluorescence of the condensed phase implies an enhancement of the intermolecular coupling and the opening of new channels for the relaxation of the excited state. The π–π stacking, which is manifested by both DR and FL spectroscopies, emergences only after the completion of the first monolayer. Finally, by analyzing the variation of the fluorescence spectrum, we have revealed the dewetting of the uncompleted PTCDI-C5 monolayer upon air exposure. This observation has been verified by atomic force microscopy (AFM).

Miniature spectrometers based on microelectromechanical systems (MEMS) are a compact, cost-efficient and rugged alternative to conventional infrared spectrometers. Different practical applications of this emerging technology are presented to demonstrate its applicability in industrial process monitoring.

In this work, the findings of an in situ fluorescence spectroscopy and microscopy investigation of the growth of $\ensuremath{\alpha}$-sexithiophene ($\ensuremath{\alpha}\text{\ensuremath{-}}6\mathrm{T}$) thin films on muscovite mica are presented. The sensitive dependence of the fluorescence emission on the molecular arrangement is exploited to reveal the details of the $\ensuremath{\alpha}\text{\ensuremath{-}}6\mathrm{T}$ thin film growth from the initial stage. A Stranski-Krastanov growth mode with a two-monolayer-thick wetting layer is observed. The molecules within the wetting layer lie flat on the mica surface and their molecular arrangement evolves as a function of the surface coverage. After the completion of the wetting layer, needlelike three-dimensional islands consisting of flat-lying molecules and flat islands containing nearly-upright-standing molecules grow competitively. Exposing the $\ensuremath{\alpha}\text{\ensuremath{-}}6\mathrm{T}$ thin films to air leads to dewetting and this process is found to be partially reversible, i.e., a large fraction of the wetting layer recovers gradually after the sample is transferred back into vacuum. This dewetting (rewetting) process is attributed to the surface modification due to the adsorption (desorption) of water molecules.

Real-time measurements and adjustments of critical process parameters are essential for the precise control of fermentation processes and thus for increasing both quality and yield of the desired product. However, the measurement of some crucial process parameters such as biomass, product, and product precursor concentrations usually requires time-consuming offline laboratory analysis. In this work, we demonstrate the in-line monitoring of biomass, penicillin (PEN), and phenoxyacetic acid (POX) in a Penicillium chrysogenum fed-batch fermentation process using low-cost microspectrometer technology operating in the near-infrared (NIR). In particular, NIR reflection spectra were taken directly through the glass wall of the bioreactor, which eliminates the need for an expensive NIR immersion probe. Furthermore, the risk of contaminations in the reactor is significantly reduced, as no direct contact with the investigated medium is required. NIR spectra were acquired using two sensor modules covering the spectral ranges 1350–1650 nm and 1550–1950 nm. Based on offline reference analytics, partial least squares (PLS) regression models were established for biomass, PEN, and POX either using data from both sensors separately or jointly. The established PLS models were tested on an independent validation fed-batch experiment. Root mean squared errors of prediction (RMSEP) were 1.61 g/L, 1.66 g/L, and 0.67 g/L for biomass, PEN, and POX, respectively, which can be considered an acceptable accuracy comparable with previously published results using standard process spectrometers with immersion probes. Altogether, the presented results underpin the potential of low-cost microspectrometer technology in real-time bioprocess monitoring applications © 2019 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

Mid-infrared hyperspectral imaging is advanced by the application of novel supercontinuum laser technology enabling short acquisition times and high SNR. Diffraction limited microscopic as well as macroscopic measurements at standoff distances are presented.

Producers of pharmaceuticals have to guarantee the quality of their products. Therefore, substantial efforts are invested in process monitoring and control. However, crucial parameters, such as the nutrient and product precursor concentrations often require time-consuming analysis of a sample. Infrared (IR) spectroscopy is a promising measurement technique for the online quantification of multianalyte solutions, such as fermentation broths. Besides the high investment cost of devices, chemometric models often are not fully transferable and provide noisy estimates which need to be treated before further usage. To increase robustness and accuracy of these measurements they can be combined with kinetics models under the usage of a state observation algorithms, such as Kalman- or Particle filters. In this work, we present a unique combination of a transferable mechanistic process description with the real-time information derived from near and mid IR spectroscopy leading to stable, smooth and accurate state estimates. IR spectra were collected in Penicillium chrysogenum fed-batch processes. PLS models were trained for the prediction of nitrogen, product and product precursor concentrations, which were used as inputs for the state observer. The resulting probabilistic estimates provide a good basis for automatic control.

Chemical mapping was demonstrated with a mid-infrared (MIR) microspectroscopy setup based on a supercontinuum source (SC) emitting in the spectral range from 1.55 to 4.5 µm and a MEMS-based Fabry-Perot filter spectrometer. Diffraction limited spatial resolution in reflection geometry was achieved. A multilayer film consisting of different polymers and mixtures thereof was measured and results were compared to those gained with a conventional FTIR microscope equipped with a thermal MIR source. Results show that compared to thermal sources, the application of the SC source results in higher signal-to-noise ratios together with better spatial resolution and faster scanning. Furthermore, diffraction limited imaging of red blood cells was demonstrated for the first time in the MIR spectral region in reflection mode. The distinctive characteristics of the MIR spectral region in conjunction with the high brightness, spatial coherence and broadband nature of supercontinuum radiation show the potential for improving infrared microscopy significantly.

Laser-based infrared spectroscopic ellipsometry (SE) is demonstrated for the first time, to the best of our knowledge, by applying a tunable quantum cascade laser (QCL) as a mid-infrared light source. The fast tunability of the employed QCL, combined with phase-modulated polarization, enabled the acquisition of broadband (900–1204 cm−1), high-resolution (1 cm−1) ellipsometry spectra in less than 1 second. A comparison to a conventional Fourier-transform spectrometer-based IR ellipsometer resulted in an improved signal-to-noise ratio (SNR) by a factor of at least 290. The ellipsometry setup was finally applied for the real-time monitoring of molecular reorientation during the stretching process of an anisotropic polypropylene film, thereby illustrating the advantage of sub-second time resolution. The developed method exceeds existing instrumentation by its fast acquisition and high SNR, which could open up a set of new applications of SE such as ellipsometric inline process monitoring and quality control.