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In the field of mechanochromic materials that respond to external stimulation, although observation of mechanochromism is an essential effort, numerical data almost have not been obtained. The quantitative mechanical pressure sensing properties of mechanochromic fluorenylidene-acridane films were investigated using nanoimprinting, diffuse reflectance UV-vis spectroscopy, and Kelvin force microscopy. A linear mechanical pressure response and high spatial resolution as fine as 50 nm were observed, demonstrating the feasibility of applying fluorenylidene-acridane films in mechanical pressure measurements. Computational studies of the color change mechanisms indicate a change to a blue twisted conformer with disassembly and a return to a yellow folded conformer with assembly. An instant color change back to yellow upon contact with ethanol was demonstrated using a polyvinyl alcohol sheet and molded plastics containing fluorenylidene-acridane.

H5N1 is a highly pathogenic influenza virus that causes severe respiratory disease in birds and humans. The development of a highly sensitive detection method for H5H1 is vital to control spread and even terminate the outbreak of pandemic H5N1. Herein, we develop a highly sensitive local surface plasmon resonance (LSPR) sensor based on a gold-dot pattern chip for H5N1 detection. The LSPR sensor chip is fabricated by nano-imprint lithography, and it can detect and discriminate hemagglutinin H5 protein at femtogram-level sensitivity. Based on the results of the finite-difference time-domain simulation, the LSPR spectrum in the near-infrared region is suitable and appropriate to obtain the desired sensor sensitivity. The detection sensitivity of the sensor is 109 times higher than the immunochromatography method and is comparable to RT-PCR. Therefore, our sensor chip is very useful to provide valuable information for protection from pandemics.

Detection and monitoring of SO2 is important because it is a representative toxic gas in the atmospheric environment that is emitted from industrial and natural processes. Localized surface plasmon resonance (LSPR) sensing is a promising method to develop a robust and low-cost sensor for gaseous species. However, with conventional LSPR sensing, inorganic gases including SO2 are not detectable at the ppm level. In this study, we developed Au-nanopatterned chips coated with porous silica, which enabled detection of SO2 gas at ppm levels using the LSPR sensing system. The Au nanopattern was optimized using a finite-difference time-domain simulation and fabricated on quartz substrates using electron beam lithography. The Au-nanopatterned chips were coated with porous silica by the sol-gel method, which enables detection of 20 ppm of SO2. The sensitivity of the porous-silica-coated chip was four times higher than that of the uncoated chip. Modification of the porous silica layer with 3-aminopropyltrimethoxysilane (APTMS) using chemical vapor deposition further enhanced the sensitivity to SO2 gas, which was 13 times higher than that of the unmodified porous-silica-coated chip. Depth profiles by X-ray photoelectron spectroscopy indicated that APTMS was uniformly introduced into the porous silica layer. This study demonstrates that porous silica coatings on Au-nanopatterned chips and their additional modification with functional groups are potentially important to develop a low-cost and sensitive sensor for inorganic gases such as SO2.

Sulfur (S) assimilation, which is initiated by sulfate uptake, generates cysteine, the substrate for glutathione (GSH) and phytochelatin (PC) synthesis. GSH and PC contribute to cadmium (Cd) detoxification by capturing it for sequestration. Although Cd exposure is known to induce the expression of S-assimilating enzyme genes, including sulfate transporters (SULTRs), mechanisms of their transcriptional regulation are not well understood. Transcription factor SLIM1 controls transcriptional changes during S deficiency (&minus, S) in Arabidopsis thaliana. We examined the potential involvement of SLIM1 in inducing the S assimilation pathway and PC accumulation. Cd treatment reduced the shoot fresh weight in the sulfur limitation1 (slim1) mutant but not in the parental line (1, 2PGN). Cd-induced increases of sulfate uptake and SULTR1, 2 expressions were diminished in the slim1 mutant, suggesting that SLIM1 is involved in inducing sulfate uptake during Cd exposure. The GSH and PC levels were lower in slim1 than in the parental line, indicating that SLIM1 was required for increasing PC during Cd treatment. Hence, SLIM1 indirectly contributes to Cd tolerance of plants by inducing &minus, S responses in the cell caused by depleting the GSH pool, which is consumed by enhanced PC synthesis and sequestration to the vacuole.

The molecular dynamics (MD) method is a promising technique to dissect the atomistic details of water dynamics around a solute. However, the quantitative predictions of experimentally measured kinetic properties, e.g. translational diffusion coefficient (D) and rotational relaxation time (τ), are not straightforward. Current water models have failed to reproduce these properties quantitatively; therefore, the fine-tuning of water models is required. In this study, we examined the effects of ion–water Lennard-Jones (LJ) potentials on the water dynamics around a monovalent atomic ion. For the TIP5P water model, we introduced new LJ potentials for the ion–hydrogen and ion–pseudoatom interactions, which were zero in the original TIP5P model. The hydration properties, i.e. D, τ, and the radius of the first hydration shell (rMO), were examined for various parameter settings. As a result, the new parameters certainly improved the reproducibility of the hydration properties in correspondence with experimental values. However, it is still difficult to reproduce faster rotational relaxation of hydration water than that of bulk water. In addition, we found that the three hydration properties (D, τ, and rMO) were artificially correlated in the MD simulations.

X-ray fluorescence (XRF) analysis is a well-established analytical technique with a long research history. Many applications have been reported in various fields, such as in the environmental, archeological, biological, and forensic sciences as well as in industry. This is because XRF has a unique advantage of being a nondestructive analytical tool with good precision for quantitative analysis. Recent advances in XRF analysis have been realized by the development of new x-ray optics and x-ray detectors. Advanced x-ray focusing optics enables the making of a micro x-ray beam, leading to micro-XRF analysis and XRF imaging. A confocal micro-XRF technique has been applied for the visualization of elemental distributions inside the samples. This technique was applied for liquid samples and for monitoring chemical reactions such as the metal corrosion of steel samples in the NaCl solutions. In addition, a principal component analysis was applied for reducing the background intensity in XRF spectra obtained during XRF mapping, leading to improved spatial resolution of confocal micro-XRF images. In parallel, the authors have proposed a wavelength dispersive XRF (WD-XRF) imaging spectrometer for a fast elemental imaging. A new two dimensional x-ray detector, the Pilatus detector was applied for WD-XRF imaging. Fast XRF imaging in 1 s or even less was demonstrated for Euro coins and industrial samples. In this review paper, these recent advances in laboratory-based XRF imaging, especially in a laboratory setting, will be introduced.

An enzymatic cycling system for detecting formaldehyde in water and indoor environments has been developed. The system is based on both the dehydrogenation of formaldehyde and the reduction of nicotinamide adenine dinucleotide (NAD + ) in the presence of formaldehyde dehydrogenase. NADH generated in the reaction then reduces 4-[3-(2-methoxy-4-nitrophenyl)-2-(4-nitrophenyl)-2H-5-tetrazolio]-l,3-benzene disulfonate sodium salt (WST-8) to yellow WST-8 formazan in the presence of enzyme diaphorase. The quantity of formaldehyde can be detected by the color change resulting from the formation of WST-8 formazan. The assay solution was optimized with respect to the pH, type of buffer, and enzyme and WST-8 concentrations. The limit of detection for formaldehyde in water was found to be 10 ppb after 3 min. The assay solution also displayed a highly selective response to formaldehyde over other pollutant gases present in indoor air. In addition, formaldehyde gas was detected after bubbling prepared formaldehyde/air mixtures with known formaldehyde concentrations in assay solutions. The limit of detection for formaldehyde gas was 1.5 ppb after 5 min. This system can quickly and accurately detect low concentration of formaldehyde in water and gas.

Cadmium (Cd) is a highly toxic and non-essential element for plants, whereas phytochelatins and glutathione are low-molecular-weight sulfur compounds that function as chelators and play important roles in detoxification. Cadmium exposure is known to induce the expression of sulfur-assimilating enzymes and sulfate uptake by roots. However, the molecular mechanism underlying Cd-induced changes remains largely unknown. Accordingly, we analyzed the effects of Cd treatment on the uptake and translocation of sulfate and accumulation of thiols in Arabidopsis thaliana Both wild type (WT) and null mutant (sel1-10 and sel1-18) plants of the sulfate transporter SULTR1;2 exhibited growth inhibition when treated with CdCl2 However, the mutant plants exhibited a lower growth rate and lower Cd accumulation. Cadmium treatment also upregulated the transcription of SULTR1;2 and sulfate uptake activity in WT plants, but not in mutant plants. In addition, the sulfate, phytochelatin and total sulfur contents were preferentially accumulated in the shoots of both WT and mutant plants treated with CdCl2, and sulfur K-edge XANES spectra suggested that sulfate was the main compound responsible for the increased sulfur content in the shoots of CdCl2-treated plants. Our results demonstrate that Cd-induced sulfate uptake depends on SULTR1;2 activity, and that CdCl2 treatment greatly shifts the distribution of sulfate to shoots, increases the sulfate concentration of xylem sap and upregulates the expression of SULTRs involved in root-to-shoot sulfate transport. Therefore, we conclude that root-to-shoot sulfate transport is stimulated by Cd and suggest that the uptake and translocation of sulfate in CdCl2-treated plants are enhanced by demand-driven regulatory networks.