Revealing the polar nature of a ferroelectric nematic by means of circular alignment

The recent discovery of spontaneously polar nematic liquid crystals—so-called ferroelectric nematics—more than a century after the first discussions about their possible existence—has attracted large interest, both from fundamental scientific and applicational points of view. However, the experimental demonstration of such a phase has, so-far, been non-trivial. Here I present a direct method for the experimental verification of a ferroelectric nematic liquid crystal phase. The method utilizes a single sample cell where the two substrates are linearly and circularly rubbed, respectively, and the ferroelectric nematic phase (NF) is revealed by the orientation of the resulting disclination lines in the cell.

Revealing the Polar Nature of a Ferroelectric Nematic

The recent discovery of spontaneously polar nematic liquid crystals - so-called ferroelectric nematics - more than a century after the first discussions about their possible existence - has attracted large interest, both from fundamental scientific and applicational points of view. However, the experimental demonstration of such a phase has, so-far, been non-trivial. Here I present a direct method for the experimental verification of a ferroelectric nematic liquid crystal phase. The method utilizes a single sample cell where the two substrates are linearly and circularly rubbed, respectively, and the ferroelectric nematic phase (NF) is revealed by the orientation of the resulting disclination lines in the cell.

Electrochemical Anodic Synthesis and Analysis of TiO2 Nanotubes for Biomedical Applications

Nowadays, titanium and alloy materials are encouraged for biomedical applications. Fabrication of the passive layer over the titanium materials is limited. Typically, a plain titanium sample is not suitable for bioimplant applications because the adhesion of biological elements like blood cells, tissues, and bones is poor. The use of surface-modified titanium resolves this issue. Surface modifications on titanium by electrochemical methods are simple and cost-effective. The addition of water to the ethylene-based electrolyte-enhanced the oxidation process to increase the length of the nanotubes. Surface morphological analysis shows that the length of the nanotubes has been increased, nanoindentation analysis delivers that increasing the length has been increased the hardness level, and corrosion analysis indicates that the length of nanotubes encouraged the corrosion resistance. Potentiodynamic polarization, Bode and Nyquist plots were models fit analyzed with equivalent electrical circuits. Sample cell viability was characterized with NIH-3T3 cells using an inverted microscopy analyzer.

A sample cell for the study of enzyme-induced carbonate precipitation at the grain-scale and its implications for biocementation

Biocementation is commonly based on microbial-induced carbonate precipitation (MICP) or enzyme-induced carbonate precipitation (EICP), where biomineralization of $$\text {CaCO}_{3}$$ CaCO 3 in a granular medium is used to produce a sustainable, consolidated porous material. The successful implementation of biocementation in large-scale applications requires detailed knowledge about the micro-scale processes of $$\text {CaCO}_{3}$$ CaCO 3 precipitation and grain consolidation. For this purpose, we present a microscopy sample cell that enables real time and in situ observations of the precipitation of $$\text {CaCO}_{3}$$ CaCO 3 in the presence of sand grains and calcite seeds. In this study, the sample cell is used in combination with confocal laser scanning microscopy (CLSM) which allows the monitoring in situ of local pH during the reaction. The sample cell can be disassembled at the end of the experiment, so that the precipitated crystals can be characterized with Raman microspectroscopy and scanning electron microscopy (SEM) without disturbing the sample. The combination of the real time and in situ monitoring of the precipitation process with the possibility to characterize the precipitated crystals without further sample processing, offers a powerful tool for knowledge-based improvements of biocementation.

Cavity Enhanced Multi-Channels Gases Raman Spectrometer

Raman spectroscopy has the advantages of multi-component detection, with a simple device and wide concentration ranges, and it has been applied in environmental monitoring and gas logging. However, its low sensitivity has limited its further applications. In fact, the Raman signal is not weak, but the utilization efficiency of the Raman signal is low, and most of the signal is wasted. Given this, in this paper we report a cavity-enhanced multi-channel gas Raman spectrometer with an eight-sided cuvette. First, we simulated the Raman scattering intensity at angles from 30 degrees to 150 degrees. The simulation results showed that the signal intensity at an angle of 45° is 1.4 times that observed at 90°. Based on the simulation results, we designed a three-channel sample cell for higher sensitivity. The results of these experiments showed that the sensitivity could be increased by adding all signal together, and the limit of detection (LOD) for CO2 was 75 ppm, which is better than that of each channel. This paper thus presents a new method to enhance the Raman signal, which can be used in field applications.

Grazing Incidence Small-Angle Neutron Scattering: Background Determination and Optimization for Soft Matter Samples

Grazing incidence small-angle neutron scattering (GISANS) provides access to interfacial properties, e.g., in soft matter on polymers adsorbed at a solid substrate. Simulations in the frame of the distorted wave Born approximation using the BornAgain software allow to understand and quantify the scattering pattern above and below the sample horizon, in reflection and transmission, respectively. The small-angle scattering from the interfacial layer, visible around the transmitted beam, which might contribute also on the side of the reflected beam, can be understood in this way and be included into the analysis. Background reduction by optimized sample cell design is supported by simulations, paving the way for an optimized GISANS cell.

A high-flux automated laboratory small-angle X-ray scattering instrument optimized for solution scattering

A commercially available small-angle X-ray scattering (SAXS) NanoSTAR instrument (Bruker AXS) with a liquid-metal-jet source (Excillum) has been optimized for solution scattering and installed at iNANO at Aarhus University. The instrument (named HyperSAXS) employs long high-quality parabolic Montel multilayer optics (Incoatec) and a novel compact scatterless pinhole slit with Ge edges, which was designed and built at Aarhus University. The combination of the powerful source and optimized geometry gives an integrated X-ray intensity close to 109 photons s−1 for a standard range of scattering vector moduli q = 0.0098–0.425 Å−1, where q = (4πsinθ)/λ and λ is the Ga Kα wavelength of 1.34 Å. The high intensity of the instrument makes it possible to measure dilute samples of, for example, protein or surfactant with concentrations of 1 mg ml−1 in a few minutes. A flow-through cell, built at Aarhus University, in combination with an automated sample handler has been installed on the instrument. The sample handler is based on the commercial Gilson GX-271 injection system (Biolab), which also allows samples to be stored under thermostatted conditions. The sample handler inserts and removes samples, and also cleans and dries the sample cell between measurements. The minimum volume of the flow-through capillary is about 20 µl. The high intensity additionally allows time-resolved measurements to be performed with a temporal resolution of seconds. For this purpose a stopped-flow apparatus, (SFM-3000, Bio-Logic) was connected to the flow-through cell by high-performance liquid chromatography tubing. This configuration was chosen as it allows vacuum around the sample cell and thus maintains a low background. The instrument can readily be converted into a low-q setup with a q range of 0.0049–0.34 Å−1 and an X-ray intensity of about 5 × 107 photons s−1.

Design of a multipurpose sample cell holder for the Diamond Light Source high-throughput SAXS beamline B21

The design of a multipurpose sample cell holder for the high-throughput (HT) beamline B21 is presented. The device is compatible with the robot bioSAXS sample changer currently installed on BM29, ESRF, and P12 Petra IV synchrotrons. This work presents an approach that uses 3D-printing to make hardware alterations which can expand the versatility of HT beamlines at low cost.