Absorbed Water Molecules Research Articles

Microscopic Characterization of Bioactivate Implant Surfaces: Increasing Wettability Using Salts and Dry Technology.

The surface topography of dental implants plays an important role in cell-surface interaction promoting cell adhesion, proliferation and differentiation influencing osseointegration. A hydrophilic implant leads to the absorption of water molecules and subsequently promotes the adhesion of cells to the implant binding protein. Dried salts on the implant surfaces allow one to store the implant surfaces in a dry environment while preserving their hydrophilic characteristics. This process has been identified as “dry technology”. The aim of the present study is to describe from a micrometric and nanometric point of view the characteristics of this new bioactivated surface obtained using salts dried on the surface. Topographic analysis, energy-dispersive X-ray spectroscopy, and contact angle characterization were performed on the samples of a sandblasted and dual acid-etched surface (ABT), a nanosurface (Nano) deriving from the former but with the adding of salts air dried and a nanosurface with salts dissolved with distilled water (Nano H2O). The analysis revealed promising results for nanostructured surfaces with increased wettability and a more articulated surface nanotopography than the traditional ABT surface. In conclusion, this study validates a new promising ultra-hydrophilic nano surface obtained by sandblasting, double acid etching and surface salt deposition using dry technology.

Humidity Sensors Realized via Negative Photoconductivity Effect in Nanodiamonds.

Herein, the negative photoconductivity (NPC) effect has been observed in nanodiamonds (NDs) for the first time, and with illumination under a 660 nm laser lamp, the conductivity of the NDs decreases significantly. The NPC effect has been attributed to the trapping of carriers by the absorbed water molecules on the ND surfaces. A humidity sensor has been constructed based on the NPC effect of the NDs, and the sensitivity of the sensor can reach 106%, which is the highest value ever reported for carbon-based humidity sensors.

Structural Insights into the Vapochromic Behavior of Pt- and Pd-Based Compounds

Anionic complexes having vapochromic behavior are investigated: [K(H2O)][M(ppy)(CN)2], [K(H2O)][M(bzq)(CN)2], and [Li(H2O)n][Pt(bzq)(CN)2], where ppy = 2-phenylpyridinate, bzq = 7,8-benzoquinolate, and M = Pt(II) or Pd(II). These hydrated potassium/lithium salts exhibit a change in color upon being heated to 380 K, and they transform back into the original color upon absorption of water molecules from the environment. The challenging characterization of their structure in the vapochromic transition has been carried out by combining several experimental techniques, despite the availability of partially ordered and/or impure crystalline material. Room-temperature single-crystal and powder X-ray diffraction investigation revealed that [K(H2O)][Pt(ppy)(CN)2] crystallizes in the Pbca space group and is isostructural to [K(H2O)][Pd(ppy)(CN)2]. Variable-temperature powder X-ray diffraction allowed the color transition to be related to changes in the diffraction pattern and the decrease in sample crystallinity. Water loss, monitored by thermogravimetric analysis, occurs in two stages, well separated for potassium Pt compounds and strongly overlapped for potassium Pd compounds. The local structure of potassium compounds was monitored by in situ pair distribution function (PDF) measurements, which highlighted changes in the intermolecular distances due to a rearrangement of the crystal packing upon vapochromic transition. A reaction coordinate describing the structural changes was extracted for each compound by multivariate analysis applied to PDF data. It contributed to the study of the kinetics of the structural changes related to the vapochromic transition, revealing its dependence on the transition metal ion. Instead, the ligand influences the critical temperature, higher for ppy than for bzq, and the inclination of the molecular planes with respect to the unit cell planes, higher for bzq than for ppy. The first stage of water loss triggers a unit cell contraction, determined by the increase in the b axis length and the decrease in the a (for ppy) or c (for bzq) axis lengths. Consequent interplane distance variations and in-plane roto-translations weaken the π-stacking of the room-temperature structure and modify the distances and angles of Pt(II)/Pd(II) chains. The curve describing the intermolecular Pt(II)/Pd(II) distances as a function of temperature, validated by X-ray absorption spectroscopy, was found to reproduce the coordinate reaction determined by the model-free analysis.

Aquaporin: targets for dietary nutrients to regulate intestinal health.

Aquaporins (AQP) are a class of water channel membrane proteins that are widely expressed in the gut. The biological functions of aquaporins, which regulate the absorption and secretion of water molecules and small solutes, maintain the stable state of the intestine, regulate cell proliferation and migration, participate in the process of intestinal inflammation, and mediate tumorigenesis, demonstrate the physiological significance of these channels in intestinal health. The pathology of many intestinal diseases is associated with changes in the location and expression of aquaporins, such as intestinal infection, which can change the expression and distribution of AQPs in intestinal tissues/cells by affecting cytokines and chemokines. This can lead to various intestinal diseases such as diarrhoea, which also suggests the importance of aquaporins in the prevention and treatment of intestinal diseases. This review summarizes the relationship between aquaporins and intestinal physiology and diseases and focuses on drugs (such as plant extracts) or diets that can regulate intestinal health by regulating aquaporins. It provides a basis for establishing aquaporins as biomarkers and therapeutic targets for intestinal health.

Experimental Study of Parylene Based Capacitive Humidity Sensor for Integrated Thermal Comfort Sensing Application

In this letter, we report the temperature effect and noise characterization of the Parylene-based capacitive humidity sensor which can be used for integrated CMOS compatible thermal comfort sensing. The sensor is comprised of a pair of interdigitated Pt electrodes deposited on a silicon substrate and a parylene hygroscopic layer coated on the electrodes using room temperature chemical vapor deposition process. The sensor was characterized at different relative humidity (RH) values and working temperatures in a testing setup. The capacitance of the sensor increases with the RH due to the absorption of water molecules on the surface of the sensing film. The capacitance of the sensor also increases with temperature, which is due to the stronger thermal movement of the molecules that helps increase the polarization at increased temperature levels. Besides, a readout circuit was done on a printed circuit board using capacitance to voltage converter for the sensor. The sensor achieved a maximum sensitivity of 76.2 mV/%RH and response and recovery times of about 31.5 and 29.2 s, respectively. Besides, the sensor shows a noise level of 1.399 mV rms within 25 Hz bandwidth in the output voltage response. The experimental results also indicated a resolution of about 0.072-2% within the ASHRAE standard approved RH range (25-95%) for the fabricated sensor.

Improved Long‐Term Stability and Reduced Humidity Effect in Gas Sensing: SiO2 Ultra‐Thin Layered ZnO Columnar Films

AbstractThe undoped and metal‐doped zinc oxide columnar films (ZnO:Sn, ZnO:Fe, ZnO:Ag, and ZnO:Cu) are covered with an ultra‐thin layer of SiO2 (10–20 nm). The electrical, UV, and volatile organic compounds (VOCs) sensing properties are evaluated under different ambient conditions for ≈7 months to investigate the impact of the top SiO2‐layer on the long‐term stability of samples. The obtained results show a high immunity of sensing properties of SiO2‐coated samples to humidity. Furthermore, gas sensing measurements show that the loss in response after 203 days is significantly lower for coated samples indicating higher stability of sensing performance. For ZnO:Fe the gas response is reduced by about 90% after 203 days, but for SiO2‐coated ZnO:Fe columnar films the gas response is slightly reduced by only 38%. The density functional theory (DFT) calculations show that water species bind strongly with the surface SiO2 layer atoms with a −0.129 e− charge transfer, which is, much higher compared to the interaction with ethanol and acetone. Calculations show strong binding of water species on the SiO2 layer indicating preferential absorption of water molecules on SiO2. The obtained results demonstrate an important role of the top SiO2 ultra‐thin layer in order to produce humidity‐tolerant sensitive devices.

HEC/PVDF coated microbottle resonators for relative humidity detection

A micro-bottle resonator sensor is proposed here for relative humidity detection with an HEC/PVDF coating acting as a transducer. Microbottle resonators are a promising fiber optics sensing structure due to their high-quality factor and HEC/PVDF is used in detecting relative humidity due to its sensitivity to moisture and humidity. Soften-and-compress technique was used to form a 190 μm bulge micro-bottle sensing element. A 3 μm tapered microfiber was used to optically excite the micro-bottle resonator which showed a Q factor in an order of 105. The HEC/PVDF coated MBR resonator sensor showed good response to changes in relative humidity range of 40–80 %RH. The HEC/PVDF coated element had a sensitivity of 0.111 dB/RH% and linearity of 95 %. The HEC/PVDF absorption of water molecules with increasing relative humidity, the subsequent change in refractive index and change in the light propagation characteristics of the sensor improved the sensor’s response to relative humidity compared to the uncoated one. The proposed sensor’s simple fabrication, good sensitivity, linearity, and resolution make it a promising design for relative humidity detection.

Comparative study of free-volume changes in light-cured (dimeth)acrylate-type dental resin composites affected to artificial aging in dry-air and water-immersed mode

This research is intended to compare degradation processes in light-cured (dimeth)acrylate-type polymer/filler dental composites affected to aging in dry-air and water-immersed mode. The positron annihilation lifetime (PAL) spectroscopy has been employed to study changes in atomic-deficient structure in these composites under aging. Under light-curing polymerization initiating crosslinking of monomer chains, fragmentation of free-volume holes in resin matrix dominates over enhanced fraction of trapped positrons, since filler–particles assemblies get to be more tightly covered by surrounding polymer causing disappearing of interfacial voids at the filler–polymer surface. Therefore, the PAL spectra-transforming trend in light-cured composites obeys inverse positron-to-Ps trapping conversion. In contrast, the PAL spectra-transforming trend in these restoratives under aging obeys direct Ps-to-positron trapping conversion. After dry-air aging, the observed changes in the density of annihilation sites are ascribed to a strong agglomeration of Ps-decay holes in polymer sub-system accompanied by weaker agglomeration and appearance of positron traps in filler–polymer sub-system. Under the water aging, the agglomeration of Ps-decaying holes in the polymer sub-system is suppressed due to absorbed water molecules, this effect being slightly revealed at lower polymerization. New positron traps are observed at the filler–polymer interfaces in all light-cured composites. The agglomerated Ps-decay holes in a polymer matrix and positron traps inside filler–particles assemblies and filler–polymer interfaces of artificially aged composites cause their progressive microcracking.

Facile environment-friendly peptide-based humidity sensor for multifunctional applications

Humidity monitoring plays a key role in the human–machine interface (HMI) and health-related devices. Current inorganic sensing materials provide a stable and fast method to monitor relative humidity (RH). However, these materials require complicated preparation processes and even toxic reagents. Organic humidity-sensing materials were considered to be biocompatible, but they face slow response time and cannot be used in real-time systems. There is still a great challenge to seek biocompatible humidity-sensing materials with high performance. Micro-nano structures formed by self-assembled peptides have been proven to have good optical, mechanical, semiconductive properties and intrinsic biocompatibility, which can be used for monitoring human health and activities. Herein, we reported an environmentally friendly humidity sensor based on peptide self-assembled micro-nano fibers. This humidity sensor was fabricated by a drop-coating method, in which the peptide fiber served as the humidity-sensing material and the Au electrode was used as a substrate. Self-assembled fiber networks exhibit excellent absorption of water molecules, which result in an extraordinary humidity sensitivity of more than 30,000 as well as ultrafast response (66 ms). To demonstrate the multifunctional possibilities, peptide humidity sensors were applied to respiration monitoring, non-contact switch, and baby diaper wetting monitoring. Our results provide useful strategies for detecting humidity changes in physiological activities based on peptide self-assembled fibers. These results indicated that peptide could be a promising candidate for human–machine interaction and healthcare humidity monitoring.

An ultra-stable microporous supramolecular framework with highly selective adsorption and separation of water over ethanol

A microporous supramolecular framework with high water and thermal stability can selectively absorb water molecules over methanol or ethanol due to the suitable channels. The model separation test on columns shows that an ultra-pure ethanol (99.9%) can be obtained from the mixture of ethanol/water (95:5). Additionally, after refluxing the desolvated sample in 95% ethanol at 60 °C for 5 h, the purity of ethanol rises up to 97.43%, which is obviously higher than 96.56% for 4 A molecular sieves.

Synthesis of the superabsobents enriched in chitosan derivatives with excellent water absorption properties

The superabsorbent polymers (SAPs) containing up to 30% w of N-succinylchitosan and N-maleoylchitosan were successfully synthesized by free radical polymerization in an aqueous solution. The structures and surfaces of the synthesized SAPs were characterized by FTIR and SEM, respectively. The influence of the parameters such as type and content of polysaccharide, cross-linker, and comonomer mixture content on the swelling rate was researched. The chitosan-derivative-based SAPs have a higher swelling rate compared to chitosan-based SAPs. Equilibrium swelling rate, Qe, of the synthesized SAPs lying in the range 102–1144 g/g decreases with the rise of polysaccharide content. It was found that N-succinylchitosan-based SAPs are characterized by higher Qe values compared to N-maleoylchitosan ones. The highest swelling rate (Qe = 1144 g/g) was achieved for N-succinylchitosan-based polymer containing 2% w of N-succinylchitosan, 0.5% w of cross-linker, and acrylamide-acrylic acid weight ratio was 1:3. Researching the swelling kinetics shows equilibrium swelling is reached during 0–30 min for all synthesized polymers, and equilibrium reaching time rises with the increase in polysaccharide content. Also, swelling is correctly described by the pseudo-second-order model and controlled by chemical absorption of water molecules. The synthesized eco friendly SAPs enriched in polysaccharide content are characterized by excellent water-absorbing properties.

Insight into the behavior at the hygroscopicity and interface of the hydrophobic imidazolium-based ionic liquids

Abstract How to completely remove the water from ionic liquids (ILs) is difficult for researchers because of the hygroscopicity of ILs. In order to study the hygroscopicity of ILs, two kinds of ILs, 1-Butyl-3-methylimidazolium hexafluorophosphate ([Bmim][PF6]) and 1-Butyl-3-methylimidazolium Bis(trifluoromethanesulfonyl) ([Bmim][NTf2]) were investigated by molecular dynamics simulations. Although [Bmim][PF6] and [Bmim][NTf2] are hydrophobic, both of the ILs could absorb water molecules from the vapor. In this work, the process of absorbing water from the vapor phase was studied, and the water molecules could disperse into the IL. Aggregation was observed with increasing the water concentration. Although the absorbed water increases obviously, the amount of free water and small cluster in the ILs does not change significantly and always stays at a certain level. The amount of free water and small cluster in [Bmim][PF6] is more than that in [Bmim][NTf2], which is consistent with their hydrophobicity. In addition, the liquid-vacuum and liquid–liquid interfaces of the ILs were simulated and analyzed in detail. The number density distribution and angle distribution indicated that [Bmim]+ cations arrangement regularly at the IL-vacuum interface. The butyl chain point to the vacuum, while the imidazlium ring is close to the IL phase region and perpendicular to the interface. While at the IL-water interface, the cations and anions are disordered.

Moisture Absorption and Desorption in an Ionomer-Based Encapsulant: A Type of Self-Breathing Encapsulant for CIGS Thin-Film PV Modules

As an alternative to conventional encapsulation concepts for a double glass photovoltaic (PV) module, we introduce an innovative ionomer-based multi-layer encapsulant, by which the application of additional edge sealing to prevent moisture penetration is not required. The spontaneous moisture absorption and desorption of this encapsulant and its raw materials, poly (ethylene- co -acrylic acid) and an ionomer, are analyzed under different climatic conditions in this work. The relative air humidity is thermodynamically the driving force for these inverse processes and determines the corresponding equilibrium moisture content (EMC). Higher air humidity results in a larger EMC. The homogenization of the absorbed water molecules is a diffusion-controlled process, in which temperature plays a dominant role. Nevertheless, the diffusion coefficient at a higher temperature is still relatively low. Hence, under normal climatic conditions for the application of PV modules, we believe that the investigated ionomer-based encapsulant can “breathe” the humidity: During the day, when there is higher relative humidity, it “inhales” (absorbs) moisture and restrains it within the outer edge of the module; then at night, when there is a lower relative humidity, it “exhales” (desorbs) the moisture. In this way, the encapsulant protects the cell from moisture ingress.

Fabrication of flexible self-powered humidity sensor based on super-hydrophilic titanium oxide nanotube arrays

Stable and flexible super-hydrophilic nanotubular-based titanium oxide electrode has been utilized as the active electrode of self-powered humidity sensor. TiO2 nanotubular electrodes fabricated through anodization method and utilized in combination with Kapton electrode as the triboelectric nanogenerator (TENG). Vertical contact-separation mode TENG performance has been examined in various range of frequencies and the maximum output voltage and current more than 300 V and 40 μA respectively with maximum power of 1.25 ± 0.67 mW has been achieved at 4 Hz. The fabricated TENG has been employed as the active self-powered humidity sensor. Super-hydrophilic feature of TiO2 nanotubes resulted in full absorption of water molecules, and noticeable decrease in charge transfer across two triboelectric materials upon increasing humidity. The TiO2-based TENG sensor was exposed to various relative humidity (RH) and the results showed that by increasing the humidity the output voltage and output current decreased from 162.24 ± 35.99 V and 20.4 ± 4.93 μA at RH = 20% to 37.92 ± 1.54 V at RH = 79% and 40.87 88 6.88 ± 1.7 μA at RH = 84%, respectively, Which shows the responsivity more than 300%. This method of measuring humidity has a simple and cost-effective fabrication that has various applications in many fields such as industry and medicine.

Water Molecule-Triggered Anisotropic Deformation of Carbon Nitride Nanoribbons Enabling Contactless Respiratory Inspection

The exploitation of the interaction between nanostructured matter and small molecules, such as H2O at interfaces via dynamic hydrogen bonding, is essentially the key for smart, responsive nanodevic...

Study on the hygrothermal aging behavior and diffusion mechanism of Ti/CF/PMR polyimide composite laminates

A series of hygrothermal aging experiments were performed on Ti/CF/PMR polyimide (TCPP) composite laminates in this work in order to verify the moisture diffusion characteristics and diffusion mechanism of the laminate. The specimens were subjected to various hygrothermal aging parameters, specifically 70 °C/95RH%, 85 °C/75RH%, 85 °C/85RH% and 90 °C/95RH%. The results illustrate that the temperature affected the diffusion rate of water molecules in the composite laminates, and the relative humidity determined the saturated moisture absorption rate. For the orthogonally laminated TCPP composite laminates, two equations have been obtained to predict the saturated moisture absorption and diffusion rate of water molecules of the prepreg layer. Additionally, the moisture absorption as a function of time has been expressed for the prepreg layer.

Water Transport Mechanisms of Poly(acrylic acid), Poly(vinyl alcohol), and Poly(ethylene glycol) in C-S-H Nanochannels: A Molecular Dynamics Study.

The transport properties of water molecules in nanochannels are critical to the durability of porous materials. In this article, molecular dynamics simulations are used to study the effects of poly(acrylic acid) (PAA), poly(vinyl alcohol) (PAA), and poly(ethylene glycol) (PEG) on the durability of modified cement-based materials. By establishing ideal composite nanopores, the absorption of water molecules in the channel is simulated. The results show that PEG has the best water-blocking effect under the same simulated conditions, followed by PVA, and PAA is the most unfavorable. This difference in the water-blocking effect can be explained by two factors. On the one hand, hydrophobic alkane groups in these polymers can inhibit water molecule transport. A large number of -COOH and -OH functional groups in PAA and PVA will form a complex H-bond network with the water molecules in the nanopore, dragging the water molecules forward, thereby speeding up the water molecule transmission to a certain extent. However, PEG, which mainly contains low-polar oxygen (C-O-C), has weak hydrogen bonding with water molecules, so the water-blocking effect is more obvious. On the other hand, the van der Waals interaction and the electrostatic interaction mainly derived from Op-Caw-Os can ensure the absorption of the polymer on the C-S-H surface during the transport process. The -COOH in PAA ensures its strongest absorption. But PVA and PEG will morphologically agglomerate during the water absorption, occupying pores and hindering the transport of water molecules.

Morphology details and size distribution characteristics of single-pot-synthesized silica nanoparticles

A series of silica nanoparticles (SNP-1, SNP-2, SNP-3, SNP-4, SNP-5 and SNP-6) were synthesized in ethanol by the hydrolysis and polycondensation reaction of tetraethoxysilane with the aids of water initiator and ammonia catalyst and then investigated in a comprehensive manner in terms of morphological structure by using synchrotron transmission small-angle X-ray scattering and grazing incidence wide-angle X-ray scattering and combined together with dynamic light scattering, scanning electron microscopy, infrared spectroscopy and thermogravimetry. They were confirmed to be successfully synthesized as oblate amorphous ellipsoids (Re=9.70∼56.30nm, equatorial radius; ε=0.78∼0.80, ellipsoidicity) with sharp surfaces in single unimodal and narrow size distributions. The radial density profile details, including two-phases (i.e., less dense core and denser shell), were determined for the first time, in addition to a set of structural parameter details (radius of gyration, radius, core radius, shell thickness, and radius distribution). Larger particle was synthesized conveniently by higher loading of ammonia solution with respect to the silane monomer. The as-synthesized silica particles were found to undergo two-step mass loss behaviors in heat treatment up to 500°C; the first-step loss took place below 120°C due to removals of physically absorbed water molecules and possible solvent residues and the second-step loss above 180°C occurred by removals of water and ethanol byproducts due to the post condensation reactions of hydroxy and ethoxy residues.

On dusty plasma formation in Martian ionosphere

A self-consistent model for the formation and evolution of dusty plasmas in the Martian ionosphere is developed. The effects of the initial distributions of dust particles, as well as condensation and absorption of carbon dioxide and water molecules by dust particles, are studied. Theory values of characteristic sizes of dust grains and their charges are obtained. The theoretical values of the sizes are in agreement with the data of observations. The possibility of the formation of dusty plasma structures in the Martian ionosphere which are analogous to noctilucent clouds in the atmosphere of the Earth is discussed.

Reactive molecular dynamics research on influences of water on aging characteristics of PMIA insulation paper

The diffusion of moisture in the meta-aramid fiber (PMIA) oil-paper insulation system and the thermal decomposition of PMIA insulation paper in different moisture contents were studied via molecular dynamics simulations. The results showed that the PMIA insulation paper had a stronger ability to absorb water molecules than the insulating oil; therefore, water molecules in the insulating oil diffuse to the insulation paper, which further affects the thermal decomposition of the PMIA insulation paper. The activation energy of the water-bearing composite model was 129.96 kJ/mol, which was 5.5% lower than that of the pure PMIA (137.61 kJ/mol). It indicated that moisture could promote PMIA decomposition. The micromechanism of the enhanced thermal decomposition of PMIA with moisture contents could be described as follows: The O–H bond of the water can easily break to generate H atoms and hydroxyl radicals (•OH). The strong activity of H atoms allows it to easily combine with the ammonia base at the end of PMIA to generate NH3. Additionally, the free •OH radical can easily combine with the amido and carbonyl bonds at two ends of PMIA, undergo an oxidation reaction, and generate an oxhydryl. Therefore, it can reduce the chemical stability of the PMIA chain and further drive thermal decomposition. Statistical data on fragments generated by the thermal decomposition of the water-bearing PMIA composite system show that the main products include H2, C/H/O-containing molecules, hydrocarbon molecules, N-bearing molecules, and free radicals.