Absorbed Water Molecules Research Articles

Enhancement of fuel cell properties in polyethersulfone and sulfonated poly (ether ether ketone) membranes using metal oxide nanoparticles for proton exchange membrane fuel cell

The proton exchange membrane (PEM) was synthesized using polyethersulfone (PES), sulfonated poly (ether ether ketone) (SPEEK) and nanoparticles. The metal oxide nanoparticles such as Fe3O4, TiO2 and MoO3 were added individually to the polymer blend (PES and SPEEK). The polymer composite membranes exhibit excellent features regarding water uptake, ion exchange capacity and proton conductivity than the pristine PES membrane. Since the presence of sulfonic acid groups provides by added SPEEK and the unique properties of inorganic nanoparticles (Fe3O4, TiO2 and MoO3) helps to interconnect the ionic domain by the absorption of more water molecules thereby enhance the conductivity value. The proton conductivity of PES, SPEEK, PES/SPEEK/Fe3O4, PES/SPEEK/TiO2 and PES/SPEEK/MoO3 membranes were 0.22 × 10−4 S/cm, 5.18 × 10−4 S/cm, 3.57 × 10−4 S/cm, 4.57 × 10−4 S/cm and 2.67 × 10−4 S/cm respectively. Even though the blending of PES with SPEEK has reduced the conductivity value to a lesser extent, hydrophobic PES has vital role in reducing the solvent uptake, swelling ratio and improves hydrolytic stability. Glass transition temperature (Tg) of the membranes were determined from DSC thermogram and it satisfies the operating condition of fuel cell system which guarantees the thermal stability of the membrane for fuel cell application.

Swelling of fiber-reinforced soft tissues is affected by fiber orientation, fiber stiffness, and lamella structure.

Native and engineered fiber-reinforced tissues are composites comprised of stiff collagen fibers embedded within an extrafibrillar matrix that is capable of swelling by absorbing water molecules. Tissue swelling is important for understanding stress distributions between collagen fibers and extrafibrillar matrix, as well as for understanding mechanisms of tissue failure. The swelling behavior of fiber-reinforced tissues in the musculoskeletal system has been largely attributed to the glycosaminoglycan content. Recent work demonstrated anisotropy in the swelling response of the annulus fibrosus in the intervertebral disc. It is well known that collagen fiber orientation affects elastic behavior, but the effect of collagen fiber network on tissue swelling behavior is not well understood. In this study, we developed three series of models to evaluate the effect of collagen fiber orientation, fiber network architecture (i.e., single or multi-fiber families within a layer), and fiber stiffness on bulk tissue swelling, which was simulated by describing the extrafibrillar matrix as a triphasic material, as proposed by Lai et al. Model results were within one standard deviation of reported mean values for changes in tissue volume, width, and thickness under free swelling conditions. The predicted swelling response of single-fiber family structures was highly dependent on fiber orientation and the number of lamellae in the bulk tissue. Moreover, matrix swelling resulted in tissue to twist, which reduced fiber deformations, demonstrating a balance between fiber deformation and matrix swelling. Large changes in fiber stiffness (20 × increase) had a relatively small effect on tissue swelling (~ 2% decrease in swelling). In conclusion, fiber angle, fiber architecture (defined as single- versus multiple fiber families in a layer), and the number of layers in a single fiber family structure directly affected tissue swelling behavior, including fiber stretch, fiber reorientation, and tissue deformation. These findings support the need to develop computational models that closely mimic the native architecture in order to understand mechanisms of stress distributions and tissue failure.

H+ Intercalation into Molybdenum Oxide Nanosheets Under AFM Tip Bias

The local hydrogen ions intercalation behavior in α‐MoO3 nanoflakes is explored under the electric field of an atomic force microscopy (AFM) tip. Protons are excited by AFM tip bias‐induced electrolyzation of absorbed water molecules on the surface of α‐MoO3 nanosheets in ambient environment, and then intercalated into α‐MoO3 lattice. The formed HxMoO3 is shown to have a 0.2 eV reduction in the bandgap and also altered electric behaviors and surface morphologies. This research provides a unique approach for understanding the relationship between nanoscale hydrogen intercalation and the surface morphology and bandgap of two‐dimensional (2D) α‐MoO3 nanosheets. This investigation of ionic intercalation in 2D‐layered materials will help in future nanoscale engineering of batteries, electrochromism, photocatalysis, and supercapacitors.

Effect of moisture exposure on scratch behavior of model polyurethane elastomers

Effect of moisture exposure on scratch behavior of four model cast polyurethane (CPU) elastomers with different soft segments is investigated. Two model CPU systems contain less polar ether groups and the other two contain more polar ester groups in the soft segment polyols. The ASTM D7027/ISO 19252 standard scratch test was chosen to determine the scratch behavior of the model CPU systems in dry and water-saturated conditions. It is found that the absorbed moisture alters the surface characteristics, mechanical properties and the corresponding scratch behaviors of PU elastomers in different fashions, depending on the PU chemical constituents. The homogeneously absorbed water molecules in the less polar polyether-based PU elastomers serve as plasticizer to degrade the mechanical properties and increase the coefficient of friction (COF), thus leading to deterioration in scratch resistance. However, for the more polar polyester-based PU elastomers, because of the interaction between water molecules and the polar bonding sites, clustering of water occurs on the surface and acts as lubricant to decrease the COF, which improves the scratch resistance. A 3-D finite element method (FEM) modeling was conducted to further understand the observed scratch-induced deformation in the model systems. The present study provides guidelines for preparing scratch-resistant PU elastomers that are exposed to humid environment during service.

The Mechanical Properties of Jute/E-glass Fiber Reinforced Polymer Composites influenced by Hygrothermal Effects

During service, almost all materials suffer degradation in their properties when subjected to different conditions such as high temperature and moisture. Composite materials are no exception to this general degradation. Here it is proposed to study jute/E-glass fiber reinforced polymer composite at different temperatures with varying humidity conditions. The composite materials are tested for tensile and flexural properties at ambient conditions and in wet-hot conditions. Influences of these variables on microstructure of these composite materials are studied using scanning electron microscopy (SEM). It is found that tensile strength of the composites that have undergone treatments mentioned above is reduced which assigns the absorption of water molecules on the surface which weakened the composites.

Self‐Assembly of Functionalized Oligothiophene into Hygroscopic Fibers: Fabrication of Highly Sensitive and Fast Humidity Sensors

AbstractA new symmetric oligothiophene exposing tetraethylene glycol (TEG)‐based side‐chains is designed and synthesized. This molecule is found to self‐assemble in solution forming supramolecular fibers, via π–π stacking between the conjugated oligothiophene backbones, which are phase segregated on the sub‐nanometer scale from the TEG side‐groups. The delocalization of the charges through the oligothiophene π–π stack ensures efficient charge transport while the hygroscopic shell, decorating the surface of the fibrillar structures, determines a certain affinity for polar molecules. Upon exposure to humidity, under environmental conditions, such supramolecular architectures are capable of reversibly absorbing and desorbing water molecules. Absorption of water molecules, due to increased environmental humidity, causes a fast and reproducible increase of the electrical current through the fibers by a factor 100 from 15% to 90% relative humidity, as measured in 2‐terminal devices. Such process is extremely fast, taking place in less than 45 ms. The humidity‐responsive characteristics of the presented oligothiophene‐based fibers can be exploited for the facile fabrication of high‐performances and solution‐processable electrical resistive humidity sensors.

Single-step strategy for the fabrication of GaON/ZnO nanoarchitectured photoanode their experimental and computational photoelectrochemical water splitting

Electrode materials efficiency and stability are two indispensable bottlenecks in solar-driven water splitting which impedes its large-scale productions. Here, we report the novel fabrication of GaON/ZnO nanoarchitecture over FTO substrate, as a conceivable substitute for efficient solar-driven photoelectrochemical (PEC) water splitting. The synthesis of nitrogen enriched photoactive GaON/ZnO is accomplished by the single-step hydrothermal method. The formation of GaON /ZnO is observed in field emission scanning electronic micrographs (FE-SEM), which suggested that the ZnO hexagonal nanorods (NRs) bulging out from the nanosheets of GaON carving nanoarchitecture morphology. X-Ray Photoelectron Spectroscopy (XPS) reveals the formation of Ga-N and Ga-O bonds in GaON/ZnO. The Tauc’s plot shows red wavelength shift from 390 to 460nm corresponds to bandgap 3.26–2.58eV for ZnO/GaON. The observed photocurrent densities for GaON, ZnO and GaON/ZnO are ~ 0.2, ~ 0.4 and ~ 1.2mA/cm2, which reveals significant 6- and 3-folds increase for GaON/ZnO compared to pristine GaON and ZnO, respectively. The density functional theory (DFT) calculations for a model system consisting of Zn3O3 cluster on (111) surface of GaON shows strong water molecules absorption with probable water splitting reaction. Loading GaON surface with Zn3O3 nanoparticle further enhances the dissociative adsorption energy of water molecules. The experimental and theoretical findings provided a rational enhancement of water splitting process in GaON/ZnO nanoarchitecture.

Atomic/Molecular Layer Deposition of s‐Block Metal Carboxylate Coordination Network Thin Films

We present novel atomic/molecular layer deposition (ALD/MLD) processes for the fabrication of crystalline inorganic-organic coordination network thin films with different s-block elements. Terephthalic acid is employed as the organic precursor. Such thin films could enable for example, next-generation battery, sensor and gas-storage technologies. The deposition processes fulfill the basic principles of ALD/MLD-type growth including the sequential self-saturated gas-surface reactions and atomic/molecular-level control for the film thickness, and yield crystalline thin films in a wide deposition temperature range. Structural characterization of the films is performed by grazing incidence X-ray diffraction (GIXRD) and Fourier-transform infrared (FTIR) spectroscopy. The data do not unambiguously prove but also do not rule out the crystal structures previously reported for the corresponding bulk samples. We moreover demonstrate the growth of crystalline thin films of a new terephthalate material with La as the metal component. Upon humidity treatments the Li, Na, K, Ba, and La terephthalate films remain unaffected while the Mg, Ca, and Sr terephthalate films reversibly absorb water molecules forming well-defined crystalline water-derivative phases.

Analisis gugus fungsi pada polimer polyethylene glycol (PEG) coated-nanopartikel oksida besi hitam (Fe3O4) dan biomolekul

Telah dilakukan penelitian untuk analisis gugus fungsi pada sampel polimer polyethylene Glicol (PEG) coated- nanopartikel oksida besi hitam (Fe3O4) dan biomolekul menggunakan FTIR-Spectroscopy. Analisis gugus fungsi sampel dilakukan untuk mengetahui kemampuan nanopartikel oksida besi hitam (Fe3O4) yang dimodifikasi dengan penambahan polimer PEG, sangat berpotensi untuk mengikat senyawa biomolekul. Adanya serapan molekul air pada permukaan nanopartikel oksida besi hitam (Fe3O4) yang menyebabkan terjadi ikatan dengan polimer PEG ditunjukkan dengan puncak serapan pada vibrasi gugus –OH (hidroksil) pada bilangan gelombang 3441,01 cm-1. Hasil modifikasi nanopartikel oksida besi hitam (Fe3O4) dengan PEG, dapat mengikat biomolekul ditunjukkan pengulangan puncak serapan pada vibrasi gugus –OH (hidroksil) pada bilangan gelombang 3433,29 cm-1 bahkan munculnya puncak serapan yang baru pada vibrasi gugu C-O pada bilangan gelombang 1350,17 cm-1

Molecular Mechanics of the Moisture Effect on Epoxy/Carbon Nanotube Nanocomposites.

The strong structural integrity of polymer nanocomposite is influenced in the moist environment; but the fundamental mechanism is unclear, including the basis for the interactions between the absorbed water molecules and the structure, which prevents us from predicting the durability of its applications across multiple scales. In this research, a molecular dynamics model of the epoxy/single-walled carbon nanotube (SWCNT) nanocomposite is constructed to explore the mechanism of the moisture effect, and an analysis of the molecular interactions is provided by focusing on the hydrogen bond (H-bond) network inside the nanocomposite structure. The simulations show that at low moisture concentration, the water molecules affect the molecular interactions by favorably forming the water-nanocomposite H-bonds and the small cluster, while at high concentration the water molecules predominantly form the water-water H-bonds and the large cluster. The water molecules in the epoxy matrix and the epoxy-SWCNT interface disrupt the molecular interactions and deteriorate the mechanical properties. Through identifying the link between the water molecules and the nanocomposite structure and properties, it is shown that the free volume in the nanocomposite is crucial for its structural integrity, which facilitates the moisture accumulation and the distinct material deteriorations. This study provides insights into the moisture-affected structure and properties of the nanocomposite from the nanoscale perspective, which contributes to the understanding of the nanocomposite long-term performance under the moisture effect.

Black P/graphene hybrid: A fast response humidity sensor with good reversibility and stability

Black phosphorus (BP) materials have attracted considerable attention owing to their ultra-sensitive humidity sensing characteristics because of the natural absorption of water (H2O) molecules on the BP surface caused by the specific 2D layer-crystalline structure. On the other hand, the BP-based humidity sensor is less repeatable due to the instability of BP with water molecules and the stability of the sensor is reduced. In this study, this limitation of the BP-based humidity sensor was overcome by preparing a BP/graphene hybrid as a novel humidity sensing nanostructure. The BP/graphene interface improved the stability of the humidity sensor after a few weeks with a linear response within the relative humidity (RH) range of 15–70%. The sensor’s response/recovery speed of the humidity sensor was extremely fast within few seconds. The response (S) of the humidity sensor based on the BP/graphene hybrid is 43.4% at RH = 70%. The estimated response and recovery time of the sensor is only 9 and 30 seconds at RH = 70% at room temperature. The experimental investigation reveals that the BP/graphene hybrid not only improves the reversibility and hysteresis factors but also enhances the stability of the humidity sensor.

Thermally modified amorphous polyethylene oxide thin films as highly sensitive linear humidity sensors

Polyethylene oxide (PEO) is a polymer hydrogel possessing ionic conductivity that varies with different percentage of absorbed water molecules and ions. This property makes it a good candidate to be used in humidity sensors’ active layers. The degree of crystallinity of PEO thin films decrease with increasing humidity that facilitates the ion conduction in the thin films, thus reducing the film impedance. In this research work, the humidity sensing properties of the thin films of semi-crystalline PEO have been investigated and the material is then modified to its amorphous dominant phase by heating the thin films beyond the melting point of the polymer. The slowly cooled resulting thin films had a waxy solid like appearance and showed an excellent response towards quantitative detection of relative humidity in the surrounding environment. The results show a roughly linear impedance versus relative humidity curve in the range of 0% RH to 90% RH with a very high maximum achieved sensitivity of ∼35kΩ/%RH. The response and recovery times measured for the modified sensors were 2.8s and 5.7s respectively. The 30day trial of stability readings showed a standard deviation of only 1%. The results prove thermally modified amorphous PEO thin films to be strong candidates for high end electronic relative humidity sensors.

Effect of water molecules on nanoscale wetting behaviour of molecular ethanol on hydroxylated SiO2 substrate

The wettability property of silica (SiO2) substrate by the ethanol molecules may play important roles in nanomedicine and nanomaterials fabrication. In this paper, by molecular dynamics (MD) simulations, we show that ethanol molecules can form an ordered monolayer on hydroxylated β-cristobalite SiO2 (1 1 1) substrate, therefore an ethanol droplet can form on this ordered monolayer. We found that water molecules could affect the formation of ethanol monolayer on SiO2 surface when the amount of water molecules is large, thus regulates the wetting transformation of ethanol molecules. The absorbed water molecules would disrupt the ordered ethanol monolayer and the ethanol molecules could not form the droplet.

Design, Preparation and Evaluation of HPMC-Based PAA or SA Freeze-Dried Scaffolds for Vaginal Delivery of Fluconazole.

Aim of this work was preparation of bioadhesive gel formulations based on Hydroxypropyl methylcellulose (HPMC), Poly(acrylic acid) (PAA) or Sodium alginate (SA) loaded with anise/fluconazole β-cyclodextrin inclusion complexes in 1:2 and 1:3 ratios intended for vaginal applications. Freeze-drying method was effectively utilized and superporous morphology was obtained. The superporous morphology of the lyophilized gels, dynamic water vapor sorption measurements, drug release kinetics studies and their antimicrobial activities are presented. HPMC content influences especially the sorption/desorption behaviour of HPMC-based PAA gels and the morphology of the gel formulations with fluconazole/β-cyclodextrin inclusion complexes, due to the interactions among the gel networks absorbing water molecules. It was found that fluconazole release kinetics correspond to quasi-Fickian, Fickian diffusion and non-Fickian mechanisms for the studied hydrogels. The tested vaginal formulations with β-cyclodextrin inclusion complexes exhibited selectivity toward S. aureus ATCC 25923 and all tested Candida strains in comparison with the gel formulation without β-cyclodextrin. The fluconazole/β cyclodextrin inclusion complexes ensure a controlled release of fluconazole over a few days, the highest amount of drug release (92%) being observed after 43h. These bioadhesive gel formulations could be very promising topical alternative for treatment of vaginal fungal infections.

Amphiphilic Antifogging/Anti-Icing Coatings Containing POSS-PDMAEMA-b-PSBMA.

Highly transparent antifogging/anti-icing coatings were developed from amphiphilic block copolymers of polyhedral oligomeric silsesquioxane-poly[2-(dimethylamino)ethyl methacrylate]-block-poly(sulfobetaine methacrylate) (POSS-PDMAEMA-b-PSBMA) with a small amount of ethylene glycol dimethacrylate (EGDMA) via UV-curing. The excellent antifogging properties of the prepared coatings were originated from the hygroscopicity of both PDMAEMA and PSBMA blocks in the semi-interpenetrating polymer network (SIPN) with polymerization of EGDMA and hydrophobic POSS clusters aggregated on the surface. PDMAEMA with a lower critical solution temperature and PSBMA with an upper critical solution temperature in the block copolymers facilitated dispersion and absorption of water molecules into the SIPN coatings, fulfilling the enhanced antifogging function. Analysis of differential scanning calorimetry further confirmed that there was bond water and nonfreezable bond water in the SIPN coatings. The amphiphilic SIPN coatings exhibited the anti-icing ability with a freezing delay time of more than 2 min at -15 °C, owing to the aggregation of hydrophobic POSS groups and the self-lubricating aqueous layer generated by nonfreezable bond water on the surface. The prepared transparent antifogging/anti-icing coatings could have novel potential applications in practice.

Engineering water-tolerant core/shell upconversion nanoparticles for optical temperature sensing.

Luminescence thermometry is a promising approach using upconversion nanoparticles (UCNPs) with a nanoscale regime in biological tissues. UCNPs are superior to conventional fluorescent markers, benefiting from their autofluorescence suppression and deep imaging in tissues. However, they are still limited by poor water solubility and weak upconversion luminescence intensity, especially at a small particle size. Recently, YVO4:Er+3,Yb+3 nanoparticles have shown high efficiency upconversion (UC) luminescence in water at single-particle level and high contrast imaging in biological models. Typically, a 980-nm laser triggers the UC process in the UCNPs, which overlaps with maximum absorption of water molecules that are dominant in biological samples, resulting in biological tissues overheating and possible damaging. Interestingly, neodymium (Nd+3) possesses a large absorption cross section at the water low absorption band (808nm), which can overcome overheating issues. In this Letter, we introduce Nd+3 as a new near-infrared absorber and UC sensitizer into YVO4:Er+3,Yb+3 nanoparticles in a core/shell structure to ensure successive energy transfer between the new UC sensitizer (Nd+3) to the upconverting activator (Er+3). Finally, we synthesized water-tolerant YVO4:Er+3,Yb+3@Nd+3 core/shell nanoparticles (average size 20nm) with strong UC luminescence at a biocompatible excitation wavelength for optical temperature sensing where overheating in water is minimized.

Uniform hydrophobic electrospun nanofibrous layer composed of polysulfone and sodium dodecyl sulfate for improved desalination performance

Abstract Recently, water reclamation and water reuse have received considerable attention because of high water demand. Membrane processes constitute the most convenient technology for water treatment and desalination. In this study, a novel class of enhanced performance membranes consisting of a highly hydrophobic nanofibrous layer and hydrophilic cellulose filter paper (CFP) for membrane distillation (MD) was thoroughly examined. The nanofibrous layer was produced through electrospinning of polysulfone (PSF) doped with a sodium dodecyl sulfate (SDS) surfactant for uniformity and homogeneity in fiber diameter. The SDS surfactant was found to be the ideal additive for increasing the conductivity of the PSF polymeric solution, which helps in lowering the critical voltage required to initiate the electrospinning process, resulting in greater elongation of the nanofibers because of the increase in charge density. In the fabricated membranes, the PSF–SDS nanofibrous layer acts as a top active layer, whereas the CFP acts as the bottom supportive layer. Cellulose paper can absorb water molecules, which enhances vapor flux across the membrane in MD. The surface area, pore size distribution, fiber diameter, mechanical strength, water flux, and rejection percentage of the modified dual-layer PSF–SDS/CFP membranes were studied. The salt rejection of the PSF–SDS/CFP membrane was more than 99%, and a high permeate flux of approximately 9 LMH was maintained for long-term operation of 16 h.

Cantilever with High Aspect Ratio Nanopillars on Its Top Surface for Moisture Detection in Electronic Products

This work reports the patterning silicon pillars by metal‐assisted chemical etching (MACE) process as a post process on a silicon cantilever for a moisture detection. Although the cantilever is very fragile, the patterning of the pillar structures on the cantilever has been successfully demonstrated. The cantilever coated with a material absorbing water (such as polyimide and mesoporous silica) can use as a humidity sensor. Its bending is due to the surface stress change from water molecule absorption. However, the bending of the cantilever is usually at a small value. Here, the silicon cantilever with high aspect ratio pillars on its surface is proposed, which is expected for a larger bending of the cantilever during the water molecule absorption. The moisture detection utilizes the principle that the pillars stack together based upon the condensation behavior of a water vapor on their surfaces.

Measurement of the concentration of water vapor in a glow discharge plasma

The absorption of water molecules in glow discharge plasma in moist inert gases with reduced pressure is studied by diode laser spectroscopy. A non-axial scheme with an external resonator is used, which allows the determination of kinetic temperature from Doppler broadening in order to obtain the partition function of water molecules, required for estimating the concentration of particles under non-equilibrium conditions.

H+ emission under room temperature and non-vacuum atmosphere from a sol–gel-derived nanoporous emitter

A high proton-conducting P2O5-SiO2 nanoporous glass rod was prepared via sol–gel technique, and its tip was sharpened by a meniscus-etching method. The glass rod shows proton conductivity of 1 × 10−3 at room temperature after absorption of water molecules. A palm-sized proton gun was prepared by utilizing the glass rod as a H+ emitter. A high voltage (~2.5 kV) was applied between the tip of glass rod and an extraction electrode, and a high ionic current was successfully observed even under non-vacuum atmosphere at room temperature. Protonation reaction for polyaniline was confirmed from the structural changes of C=N in quinone to protonated C–N+. New applications of proton implantation will be expected especially in bioscience and medical technology.