The effect of the anionic surfactant SDS (sodium dodecyl sulfate) on the adsorption behaviors of cationic hydroxyethyl celluloses (Polymer JR-125, JR-400, and JR-30M) and hydrophobically modified cationic cellulose (Quatrisoft LM-200) at silica surfaces in the presence of a 10 mM NaCl solution has been investigated by null ellipsometry. The adsorbed amount of LM-200 is found to be considerably larger than adsorbed amounts of other polymers. The rate of adsorption for the LM-200 is also lower than that for the Polymer JR series under comparable conditions. Electrostatic interaction is found to be the major driving force for the adsorption. The effect of SDS on adsorption was studied under two different conditions:  adsorption of polymer/SDS complexes from premixed solutions and additions of SDS to the preadsorbed polymer layers. In all cases, associative binding of the surfactant to the polymer seems to control interfacial behavior, which depends on the surfactant concentration. Maximum adsorption was obtained at the surfactant concentration below the phase separation region, and the complex desorbed from the surface at a high SDS concentration above the critical micelle concentration. The reversibility of the polymer/SDS complexes adsorption upon rinsing with NaCl solutions was also investigated. When the premixed polymer/SDS solutions at high SDS concentrations (>5 mM) were diluted by salt solutions, the adsorbed amount increased sharply with precipitation of the complex. A larger amount of the JR-400/SDS complex precipitated during the rinsing process seemed to adsorb to a larger extent to silica than the corresponding LM-200/SDS complex.

The effect of the anionic surfactant SDS (sodium dodecyl sulfate) on the adsorption behavior of cationic hydroxyethyl cellulose (Polymer JR-400) and hydrophobically modified cationic cellulose (Quatrisoft LM-200) at hydrophobized silica has been investigated by null ellipsometry and compared with the previous data for adsorption onto hydrophilic silica surfaces. The adsorbed amount of LM-200 is found to be considerably larger than the adsorbed amount of JR-400 at both surfaces. Both polymers had higher affinity toward hydrophobized silica than to silica. The effect of SDS on polymer adsorption was studied under two different conditions: adsorption of polymer/SDS complexes from premixed solutions and addition of SDS to preadsorbed polymer layers. Association of the surfactant to the polymer seems to control the interfacial behavior, which depends on the surfactant concentration. For the JR-400/SDS complex, the adsorbed amount on hydrophobized silica started to increase progressively from much lower SDS concentrations, while the adsorbed amount on silica increased sharply only slightly below the phase separation region. For the LM-200/SDS complex, the adsorbed amounts increased progressively from very low SDS concentrations at both surfaces, and no large difference in the adsorption behavior was observed between two surfaces below the phase separation region. The complex desorbed from the surface at high SDS concentrations above the critical micelle concentration. The reversibility of the adsorption of polymer/SDS complexes upon rinsing was also investigated. When the premixed polymer/SDS solutions at high SDS concentrations (>5 mM) were diluted by adding water, the adsorbed amount increased due to the precipitation of the complex. The effect of the rinsing process on the adsorbed layer was determined by the hydrophobicity of the polymer and the surface.

The hetero Diels−Alder reaction of nonactivated conjugated dienes 1 with arylglyoxals 2 and glyoxylate esters 7 proceeded enantioselectively in the presence of a catalytic amount of cationic chiral BINAP−palladium or −platinum complexes and 3 Å molecular sieves (MS3A). The addition of MS3A effectively improved the enantioselectivity of the reaction. Excellent ee's were obtained from the reactions of 2,3-dimethyl-1,3-butadiene (1a) and 1,3-cyclohexadiene (1d) with dienophiles 2 and 7. The square-planar structure of [Pd(S-BINAP)(PhCN)2](PF6)2 was determined by X-ray diffraction, and a chiral induction model involving the square-planar palladium complex coordinated with BINAP and a dienophile is proposed.

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Evaluating the presence of a slight amount of water plays a crucial role in practical applications such as the advanced detection of dew condensation and the microdetermination of perspiration and transpiration. For this purpose, we have developed a configuration for the moisture sensor that consists of a microgalvanic cell composed of narrow metal arrays. It is inferred that the output response current arising from this sensor should depend on the geometric parameters (e.g., number, area, volume, etc.) of water droplets attaching on the sensor surface. In this study, the output current was recorded, while the microscopic images of the sensor surface were captured. The droplets on the sensor surface were analyzed manually and by computational image processing with deep learning and ImageJ. The deep learning technique shortened the processing time to 1/1000 of the manual one and was able to match 90–100% of the manual count. The results revealed that the response current increased with the total projected area of droplets bridging the galvanic-coupled arrays on the sensor surface. In addition, a straight line with relatively strong positive correlation was obtained between the response current and the total volume of the bridging droplets. These findings suggested that our sensor can be practically used to estimate the presence of a slight amount of water.

Behavior of water droplets at around 100%RH (relative humidity) was examined using developed galvanic arrays with micro/nano gap. Experimental results showed that the response current detected while observing arrays and gap surfaces depended on the variation of RH according to the adsorption behavior of water droplets. At 100%RH, response current showed a steady value determined by the equilibrium between the condensation of liquid phase and the evaporation of vapor phase. These results indicated that, once the liquid water was formed on the sensor surface above 100%RH, the response current that depended on the water droplet’s size could be estimated kinetically.

Dissimilar metal arrays with micron/nano gap detect water droplet and agglomerated molecules between them by galvanic action. At 100% in relative humidity (RH), dew condensation occurs on solid surface. The purpose of this study was to clarify the detection behaviour of the above-mentioned galvanic arrays around 100%RH and simultaneous measurement of galvanic current and observation of arrays and gap surface were carried out. Research results showed that the response current depended on RH owing to equilibrium of water molecules between vapor and adsorbed state on the sensor surface when RH increases up to 100%. At 100%RH, current showed steady value determined by balance between condensation of liquid water and evaporation of vapor. Once liquid water was formed on the sensor surface over 100%RH, the response current depended on the size of water determined kinetically. This dependence was observed during the decreasing process of the relative humidity over 100% and even under 100%.

Sensor surfaces with micron- and nano-gap scales possess high surface-to-volume ratio which greatly affects their contribution towards water adsorption and condensation. However, the quantitative relationship between adsorbed water molecules and condensed water droplets remains unclear. In this study, we used the humidity-based detected galvanic current within the micron gaps of our newly developed moisture sensor chip (MSC) to emphasize the quantitative relationship between adsorbed water molecules and condensed water droplets. The mass of adsorbed water molecules was detected using a quartz-crystal-microbalance electrode (QCM) whereas the mass of condensed water droplets was estimated microscopically based on their occupying volumes at MSC surface. Experimental results demonstrated that the minimum detection limit of MSC under these experimental conditions was ~150 ng/cm2 for adsorbed water molecules and ~700 ng/ cm2 for condensed water droplets. The detected-response galvanic current arises when a water bridges between two adjacent arrays is found to be linearly correlated to the adsorbed and/or the condensed water’s mass. Such correlation is believed to provide a feasible long-range sensor that can distinguish the status of its surface-existing water either in adsorbed molecular or condensed droplet-wise regimes.