Absorbed Water Molecules Research Articles

Water Molecule Absorption Line Intensities in the IR Spectral Region

Water Molecule Absorption Line Intensities in the IR Spectral Region

Investigating the crystal structure of ZrB2 under varied conditions of temperature, pressure, and swift heavy ion irradiation

The influence of temperature, pressure, and swift heavy ions on the structural characteristics of a nano-sized zirconium diboride crystal (43 nm) was investigated using X-ray diffraction and Small-Angle X-ray Scattering/Wide-Angle X-ray Scattering (SAXS/WAXS) powder diffraction methods. Within the temperature range of 300–773 K, alterations in lattice parameters, lattice volume, coefficient of thermal expansion, and the kinetics of water molecule absorption on the active surface of the zirconium diboride crystal were comprehensively analyzed. Furthermore, the mechanism responsible for the structural degradation of absorbed water molecules was elucidated. The degree of amorphization in the ZrB2 nano crystal reached its maximum when subjected to irradiation by fast 132Xe26+ ions with an energy of 167 MeV, at fluences of up to 3.0 × 1014 ions/cm2. Additionally, the expansion mechanism of lattice parameters and the kinetics of the phase transformation process under the influence of swift heavy ions were studied. Notably, pressure variations did not induce a phase transition within the lattice structure. However, when exposed to an 8.0 GPa pressure, the lattice underwent substantial maximum contraction, reducing by up to 20.5 Å3.

Non‐destructive evaluations of water uptake in epoxy coating

AbstractA commercial epoxy coating was studied on steel panels and as free films to investigate water uptake using non‐destructive techniques (gravimetric analysis, Electrochemical Impedance Spectroscopy [EIS], Attenuated Total Reflection‐Fourier Transform Infrared Spectroscopy [ATR‐FTIR], and Scanning Acoustic Microscopy [SAM]) after immersion in 3.5 wt% NaCl solution. In epoxy free films, water uptake showed rapid absorption initially, slowing down due to the counteracting process between water uptake and leachable content. Later, a mass decrease indicated leaching dominance. On coated steel, EIS revealed rapid water absorption within 72 h, followed by slower uptake up to 336 h. The continuous increase in water content resulted from observed coating layer swelling, confirmed by SAM. ATR‐FTIR analysis indicated hydrogen bonding of most absorbed water molecules to the epoxy matrix. By combining non‐destructive techniques, water uptake mechanisms into the epoxy coating film were proposed.

Ultra-permeable polyamide nanofiltration membrane modified by hydrophilic-hydrophobic alternated lignocellulosic nanofibrils for efficient water reuse

Polyamide nanofiltration (NF) membranes are instrumental in water reuse due to their capability to efficiently remove trace organic contaminants (TrOCs), which pose potential health risks. However, while the current NF membranes offer acceptable TrOC rejection, their water permeance, which is highly related to the process energy consumption in water reuse, is relatively low. To address this limitation, we introduced a novel NF membrane by incorporating a lignocellulosic nanofibril interlayer—specifically, nanowires with alternating hydrophilic-hydrophobic regions (denoted as HONW). The resultant NF membrane achieved remarkable water permeance (52.4 L m−2 h−1 bar−1) while still ensuring high TrOC retention (including endocrine-disrupting compounds, pharmaceuticals, and antibiotics). A detailed mechanistic investigation revealed that the eliminated funnel effect or introduced gutter effect induced by the HONW interlayer, improved polyamide layer structure characterized by lower cross-linking degree and higher surface wettability, and reduced interlayer resistance (due to a unique water transport pattern: hydrophilic regions absorbed water molecules while hydrophobic regions strengthened water penetration) were significantly responsible for the enhanced membrane permeance. Moreover, the membrane also demonstrated low specific energy consumption as well as outstanding stability. This investigation unveils an appealing approach for constructing the ultra-permeable NF membrane for efficient water reuse.

Proton-controlled molecular ionic ferroelectrics

Molecular ferroelectric materials consist of organic and inorganic ions held together by hydrogen bonds, electrostatic forces, and van der Waals interactions. However, ionically tailored multifunctionality in molecular ferroelectrics has been a missing component despite of their peculiar stimuli-responsive structure and building blocks. Here we report molecular ionic ferroelectrics exhibiting the coexistence of room-temperature ionic conductivity (6.1 × 10−5 S/cm) and ferroelectricity, which triggers the ionic-coupled ferroelectric properties. Such ionic ferroelectrics with the absorbed water molecules further present the controlled tunability in polarization from 0.68 to 1.39 μC/cm2, thermal conductivity by 13% and electrical resistivity by 86% due to the proton transfer in an ionic lattice under external stimuli. These findings enlighten the development of molecular ionic ferroelectrics towards multifunctionality.

Performance optimization of nanometer-thin indium-tin oxide transistors by two-step air annealing

In this study, the influence of air annealing on nanometer-thin indium tin oxide (ITO) transistors was investigated. Compared with unannealed devices, the field-effect mobility and subthreshold swing of ultrathin ITO transistors with pre-annealing, post-annealing, and two-step annealing were greatly improved. Under a pre-annealing temperature at 200 °C and post-annealing temperature at 100 °C, the ultra-thin ITO transistors showed field-effect mobility of 34.2 cm2/Vs, steep subthreshold swing of 1.95 V/decade, and high Ion/Ioff ratio of 2.46 × 107. X-ray photoelectron spectroscopy revealed that the performance changes could be ascribed to the changes in the oxygen vacancies in the ITO channel under different annealing conditions. The dependence of subthreshold swing on the annealing process may be related to the absorption and release of water molecules from the ultrathin ITO surface. Overall, these results emphasize the importance of the annealing procedures for nanometer-thin ITO transistors.

Characterization and performance evaluation of fully biocompatible gelatin-based humidity sensor for health and environmental monitoring

Biomaterials will have far reaching effects on solving the ever-rising environmental problems caused by the presently used toxic materials. Disposal of hazardous materials based electronic devices is causing a huge environmental problem in the form of electronic wastes (E-wastes). This study is an effort to contribute in the reduction of E-wastes by presenting the design, fabrication, and performance evaluation of a fully biocompatible humidity sensor with gelatin as the active layer. Gelatin is an excellent choice for humidity sensing because it is a hygroscopic material with the natural ability to attract and absorb water molecules, allowing for an effective detection and measurement of humidity levels in its surrounding environment. We patterned highly conductive (2.05 μΩ-cm) gold (Au) interdigitated electrode (IDE) (50 nm thickness) structure on a glass substrate by using thermal vacuum evaporation followed by the deposition of gelatin thin film by using cost effective technique of spin coating (at 1,500 rpm for 15 s). The device size was 25 mm × 22 mm with a line spacing of 1.50 mm between IDEs. Electrical characterisation was carried out to determine necessary performance parameters of the fully biocompatible humidity sensor and the obtained results exhibited a fast response/recovery time (4/6.30 s), wide operating range (15 %RH to 86 %RH), highly repeatable behaviour of 3 different samples and long lifetime (1 month). Wide variation in the resistance of sensor was observed at extreme humidity sensors ranging from 2.45 MΩ (15 %RH) to 0.12 MΩ (86 %RH). The fabricated sensor was used for the practical applications of health monitoring, touch less sensing, and environment monitoring. Moisture content of multiple commercially available moisturizers was determined by using gelatin based fully biocompatible humidity sensor and the obtained results showed that moisturizing cream had highest moisture content of 87 %RH (0.1 MΩ), followed by 80 %RH (0.30 MΩ) of rose water, and 72 %RH (0.67 MΩ) of baby oil.

In-situ analysis of combustion aerosol using a supercontinuum lidar.

We report real-time monitoring of coarse aerosol particle distribution in a 9 m wide full-scale industrial boiler using a broadband supercontinuum lidar. The technique utilizes the light backscattered from the aerosol to map the extinction profile using the Klett inversion method, with measured extinction values of 0.04 - 0.2 m-1 across the furnace. The technique further exploits differential absorption of water molecules in the 1.25 - 1.5 µm region to map the water vapor concentration profile in the furnace up to a distance of 3.9 m with a spatial resolution of 30 cm. We also take advantage of the strong reflection from the boiler back-wall to simultaneously measure the average water vapor temperature and concentration in the boiler in good agreement with reference readings from the boiler. Our results open novel perspectives for versatile 3D profiling of flue gas parameters and other industrial process analysis.

EFFECT OF WATER ABSORPTION ON THE MECHANICAL PROPERTIES OF SILANE-TREATED WOOD FLOUR POLYPROPYLENE COMPOSITES

The behavior of the wood flour-polypropylene composites prepared with various contents of untreated and silane-treated wood flour by immersion in water was studied, as well as the effect of the water absorbed by the samples on their mechanical properties. The highest degree of water absorption was observed for the composites containing 30 – 50 mass% alkali pre-treated wood flour. For the materials with 50 mass% untreated, silane-treated and alkali pre-treated wood flour, the water absorption measured was 8.76%, 7.84% and 13.91%, respectively, after 15 days immersion in water. The value of the thickness swelling calculated for the samples prepared with 50 mass% silane-treated wood flour – polypropylene was the lowest – 1.29%. It was proved that the absorption of water molecules results in change of the tensile profile of the thermoplastic polypropylene composites filled with hygroscopic filler.

Multifunctional and High‐Performance FAPBI3 Quantum Dots/Graphene UV Photodetectors by the Modulation of Photoconductivity

AbstractLow‐dimensional devices with different photoconductive effects attract much attention in optoelectronics. In this work, negative photoconductivity (NPC) monolayer graphene photodetectors are fabricated by chemical vapor deposition (CVD), and a positive photoconductivity (PPC) photodetector is realized by decorating perovskite FAPbI3 quantum dots prepared by a simple and cost‐effective non‐polar solvent synthesis method on a graphene surface. The graphene‐based photodetector exhibits an NPC characteristic, which is attributed to the absorption and desorption of water molecules on the graphene surface. The responsivity of the photodetector with an NPC characteristic is −0.86 A W−1 under intense ultraviolet light irradiation, and the detectivity is −2.45 × 109 Jones. The FAPbI3 quantum dots/graphene photodetector with a PPC feature has a responsivity of 8.03 A W−1 and a detectivity of 1.89 × 1010 Jones under the irradiation of ultraviolet light of 365 nm and 55.3 mW cm−2 intensity. Due to the intense light absorption of perovskite combined with the extremely high mobility of graphene, photodetectors have high exciton separation and photocurrents when the devices are irradiated by ultraviolet light. Individual photodetectors are successfully created with NPC and PPC effects; the critical analysis for the different photoconductive mechanisms is provided, which will benefit the development of future multifunctional systems.

Graphene oxide decorated multi-frequency surface acoustic wave humidity sensor for hygienic applications

This work presents the single-chip integration of a multi-frequency surface acoustic wave resonator (SAWR) based humidity sensor. Graphene oxide (GO), a humidity-sensing material, is integrated onto a confined sensing area of SAWR via electrospray deposition (ESD). The ESD method allows ng-resolution deposition of GO, optimizing the amount of sensing material. The proposed sensor consists of SWARs at three different resonant frequencies (180, 200 and 250 MHz) with a shared common sensing region, thus allowing direct analysis of sensor performances at different operating frequencies. Our findings reveal that the resonant frequency of the sensor impacts both measurement sensitivity and stability. A higher operating frequency ensures better sensitivity but suffers from a larger damping effect from absorbed water molecules. The maximum measurement sensitivity of 17.4 ppm/RH% is achieved with low drift. In addition, the developed sensor exhibits improved stability and sensitivity by as much as 150% and 75% in frequency shift and Quality factor (Q), respectively, by carefully selecting the operating frequencies at a given RH% range. Finally, the sensors are used for various hygienic applications, such as non-contact proximity detection and face mask inspection.

Nanoscale chemical heterogeneity enables the co-existence of opposing superhydrophobic and hygroscopic properties

Superhydrophobicity and hygroscopicity are two properties that are theoretically exclusive to each other. The fabrication of functional fabrics with these two properties remains very challenging. In this work, it is demonstrated that a non-sticky superhydrophobic and hygroscopic fabric coating can be prepared via the photo polymerization of hexadecyl acrylate and methacrylic acid. On coating surface, the phase-separation-induced chemical heterogeneity has a unique feature of possessing elevated continuous hydrophobic domain and depressed hydrophilic domain, as evidenced by atomic force microscopy measurement. The elevation of hydrophobic domain (i.e., depression of hydrophilic domain) allows the hydrophilic domain to make negligible contribution to the surface wettability to water drop, but can absorb water molecules, thus inducing the unique superhydrophobic but hygroscopic property. The coating has a very low total surface energy of 22.61 mN m−1, with its polar part (0.01 mN m−1) being negligible, thereby showing a high static water contact angle of ~112° on flat glass slide. The coated polyester fabric shows a non-sticky superhydrophobicity with a static water contact angle of ~151° and a water shedding angle of ~10°, as well as good hygroscopic and anti-static properties. We anticipate that this novel coating and the reported strategy of generating the particular chemical heterogeneity may lead to the development of advanced special wettability coatings for various applications.

Bioinspired heterogeneous and hierarchical porous structure of oxo-graphene assembly for spontaneous energy harvesting from air

Environmentally adaptive energy harvesting without additional stimuli is glamorous for next-generation energy technology. The ubiquitous air offers an alternative, but existing carbon-based moisture-electric generators can only generate desultory or insufficient power under air, owing to the absence of sustaining and effective energy harvesting and conversion architecture and mechanism. Here an eco-friendly and direct solid molding strategy was applied to rapidly fabricate heterogeneous oxo-graphene (H-mrGO) assembly. Inspired by root and trunk in natural vascular plants, rational fabrication of hierarchical porous structure immensely enhances spontaneous absorption of water molecules from air, which further induces rapid proton diffusion because of self-maintained and huge concentration difference. A single H-mrGO device can spontaneously produce an ultrahigh voltage of ∼1.39 V under air (RH ≈ 99%) and a high voltage of ∼1.2 V at low humidity (∼30%) is obtained, accompanied by a power density of ∼1.1 W/m2. Meanwhile, it realizes a sustaining power output for external resistance over 40,000 s with good stability. Connecting several H-mrGO devices linearly magnifies voltage up to 10 V and obtains a wearable device, which can directly power different electronics without additional transverters. This work demonstrates the feasibility of a sustaining moisture-electric energy-harvesting strategy that loosens rigorous requirements of location or environmental conditions.

NaGaSe2: A Water-Loving Multifunctional Non-van der Waals Layered Selenogallate.

A missing member of well-known ternary chalcometallates, a sodium selenogallate, NaGaSe2, has been synthesized by employing a polyselenide flux and stoichiometric reaction. Crystal structure analysis using X-ray diffraction techniques reveals that it contains supertetrahedral adamantane-type Ga4Se10 secondary building units. These Ga4Se10 secondary building units are further connected via corners to form two-dimensional (2D) [GaSe2]∞- layers stacked along the c-axis of the unit cell, and the Na ions reside in the interlayer space. The compound has an unusual ability to absorb water molecules from the atmosphere or a nonanhydrous solvent to form distinct hydrated phases, NaGaSe2·xH2O (where x can be 1 and 2), with an expanded interlayer space, as verified by X-ray diffraction (XRD), thermogravimetric-differential scanning calorimetry (TG-DSC), desorption, and Fourier transform infrared spectroscopy (FT-IR) studies. The in situ thermodiffractogram indicates the emergence of an anhydrous phase before 300 °C with the decrease of interlayer spacings and reverting to the hydrated phase within a minute of re-exposure to the environment, supporting the reversibility of such a process. Structural transformation induced through water absorption results in an increase of Na ionic conductivity by 2 orders of magnitude compared to that of the pristine anhydrous phase, as verified by impedance spectroscopy. Na ions from NaGaSe2 can be exchanged in the solid-state route with other alkali and alkaline earth metals in a topotactic or nontopotactic way, leading to 2D isostructural and three-dimensional networks, respectively. Optical band gap measurements show a band gap of ∼3 eV for the hydrated phase, NaGaSe2·xH2O, which is in good agreement with the calculated band gap using a density functional theory (DFT)-based method. Sorption studies further confirm the selective absorption of water over MeOH, EtOH, and CH3CN with a maximum water uptake of 6 molecules/formula unit at a relative pressure, P/P0, of 0.9.

Performance-enhanced fiber optic humidity sensors based on SiO2/porous PMMA coatings.

Employing functional and structured thin films on fiber optic sensors has tremendously improved capabilities in humidity sensing applications. In this paper, we demonstrate fabrication of a fiber optic evanescent wave humidity sensor based on S i O 2/porous polymethyl methacrylate (PMMA) thin films. With the exposure to moisture, S i O 2/porous PMMA thin films absorb water molecules. The refractive index and absorption coefficient of thin films change with ambient humidity, resulting in modulation of the light intensity transmitted in fiber. A good linearity is determined between the logarithm of output light intensity and relative humidity (RH). An optimal average sensitivity of 188.3 lux/%RH is achieved with an increase of 11.7 fold in the RH range of 5% to 95%. The response and recovery times are 8s and 23s, respectively. Furthermore, the sensor exhibits low hysteresis, and excellent stability and repeatability.

Quantifying Microalgae Growth by the Optical Detection of Glucose in the NIR Waveband.

Microalgae have become a popular area of research over the past few decades due to their enormous benefits to various sectors, such as pharmaceuticals, biofuels, and food and feed. Nevertheless, the benefits of microalgae cannot be fully exploited without the optimization of their upstream production. The growth of microalgae is commonly measured based on the optical density of the sample. However, the presence of debris in the culture and the optical absorption of the intercellular components affect the accuracy of this measurement. As a solution, this paper introduces the direct optical detection of glucose molecules at 940-960 nm to accurately measure the growth of microalgae. In addition, this paper also discusses the effects of the presence of glucose on the absorption of free water molecules in the culture. The potential of the optical detection of glucose as a complement to the commonly used optical density measurement at 680 nm is discussed in this paper. Lastly, a few recommendations for future works are presented to further verify the credibility of glucose detection for the accurate determination of microalgae's growth.

Incoherent Neutron Scattering and Terahertz Time-Domain Spectroscopy on Protein and Hydration Water

Incoherent inelastic and quasi-elastic neutron scattering (INS) and terahertz time-domain spectroscopy (THz-TDS) are spectroscopy methods that directly detect molecular dynamics, with an overlap in the measured energy regions of each method. Due to the different characteristics of their probes (i.e., neutron and light), the information obtained and the sample conditions suitable for each method differ. In this review, we introduce the differences in the quantum beam properties of the two methods and their associated advantages and disadvantages in molecular spectroscopy. Neutrons are scattered via interaction with nuclei; one characteristic of neutron scattering is a large incoherent scattering cross-section of a hydrogen atom. INS records the auto-correlation functions of atomic positions. By using the difference in neutron scattering cross-sections of isotopes in multi-component systems, some molecules can be selectively observed. In contrast, THz-TDS observes the cross-correlation function of dipole moments. In water-containing biomolecular samples, the absorption of water molecules is particularly large. While INS requires large-scale experimental facilities, such as accelerators and nuclear reactors, THz-TDS can be performed at the laboratory level. In the analysis of water molecule dynamics, INS is primarily sensitive to translational diffusion motion, while THz-TDS observes rotational motion in the spectrum. The two techniques are complementary in many respects, and a combination of the two is very useful in analyzing the dynamics of biomolecules and hydration water.

Influence of Air Humidity Level on the Structure and Mechanical Properties of Thermoplastic Starch-Montmorillonite Nanocomposite during Storage.

Thermoplastic starch (TPS) consisting of corn starch and glycerol as a plasticizer, and TPS-montmorillonite (MMT) nanocomposite were stored at room temperature in the air with relative humidities (RH) of 11, 55 and 85% for seven weeks. Mechanical testing and dynamic mechanical thermal analysis (DMTA) were performed to detect changes in their mechanical properties. Solid-state NMR spectroscopy monitoring the changes in molecular mobility in the samples provided an insight into relations between mechanical properties and local structure. The results of mechanical testing indicated that the addition of MMT results in the increase in the tensile strength and Young's modulus while elongation at break decreased, indicating the reinforcing effect of MMT. DMTA experiments revealed a decrease in glass transition temperature of starch-rich phase below room temperature for samples stored at higher RH (55 and 85%). This indicates that absorbed water molecules had additional plasticizing effect on starch resulting in higher mobility of starch chain segments. Recrystallization in these samples was deduced from the shape of cross-polarization magic-angle spinning 13C NMR spectra. The shape of broad-line 1H NMR spectra reflected changes in molecular mobility in the studied samples during seven weeks of storage and revealed that a high amount of water molecules impacts the starch intermolecular hydrogen bond density.

Self-hygroscopic and smart color-changing hydrogels as coolers for improving energy conversion efficiency of electronics

Phase change materials as a potential passive cooling solution is widely used to cool electronic devices, since the high temperature accompanied by the continuous operation of these electronic devices significantly affects their efficiencies and causes irreversible damage. However, there is a lack of the feedback on cooling potential and recessive failures such as ineffective cooling due to overuse. Here, we report a self-hygroscopic and smart color-changing Co@Li-PAM hydrogel, composed of polyacrylamide (PAM)-based polymer chains, H2O molecules, and functional ions including Li+, Co2+, [Co(H2O)]2+, Cl-, and Br-. It has been found that the hydrophilic porous PAM network acts as the main framework with excellent biocompatibility and reliable chemical stability, LiBr acts as the adsorbent in the PAM network to absorb water molecules in the air during electronic device downtime, and Co ions are introduced into hydrogels through coordination bonds formed with amide groups of polymer chains. The reversible transformation between [Co(H2O)6]2+ and Co2+ driven by the water content in Co@Li-PAM triggers color changes, which indicates the current heat dissipation potential of hydrogels. Applying the as-designed Co@Li-PAM hydrogel to cooling commercial polycrystalline silicon solar cells can increase its energy conversion efficiency by 1.26 % under the illumination of 1 kW m-2. This strategy is expected to provide exotic solutions for the development of electronic devices, carbon neutrality, and global sustainable development goals.

Humidity sensors based on molecular rectifiers.

Ambient humidity plays a key role in the health and well-being of us and our surroundings, making it necessary to carefully monitor and control it. To achieve this goal, several types of instruments based on various materials and operating principles have been developed. Reducing the production costs for such systems without affecting their sensitivity and reliability would allow for broader use and greater efficiency. Organic materials are prime candidates for incorporation in humidity sensors given their extraordinary chemical diversity, low cost, and ease of processing. Here, we designed, assembled and tested humidity sensors based on molecular rectifiers that can electrically transduce the changes in the ambient humidity to offer accurate quantitative information in the range of 0 to 70% relative humidity. Their operation relies on the changes occurring in the electric field experienced by the molecular layer upon absorption of the polar water molecules, resulting in modifications in the height and shape of the tunneling barrier. The response is reversible and reproducible upon multiple cycles and, coupled with the simplicity of the device architecture and manufacturing, makes these nanoscale sensors attractive for incorporation in various applications.