Water Sensitive Materials Research Articles

Siloxane-Encapsulated Perovskite Nanocrystal for Highly Stable Color-Converting Material in Displays

Perovskite Nanocrystals (PNCs) have emerged as a high-performance color-converting materials in displays because of low material cost, facile color tunability depending on size or composition, high photoluminescence quantum yield (PLQY), and very narrow emission spectra, which allow them to achieve wide color gamut. Although they exhibit high optical performance, perovskite nanocrystals (PNCs) are vulnerable to decomposition or aggregation in humid or high-temperature environments, stemming from ion migration and the development of metastable states. Stability of PNCs have been increased by various methods such as formation of an inorganic shell, Janus structures, and NC/polymer nanocomposites. However, such strategies still showed limited stability of PNCs under ambient air or in water and entail complex processes to prevent aggregation of NCs in polymer matrixes. Moreover, PNCs that are stable under harsh conditions (acid or base solutions, polar solvents, high temperature with high humidity) have not been reported. Especially methylammonium (CH3NH3 +, MA) based PNCs decay faster in the presence of moisture than do others such as formamidinium or cesium or mixed cation-based PNCs even it can be fabricated by simple process. Therefore, highly stable, and uniformly dispersed PNC composites without complex processes such as ligand-exchange and formation of an inorganic shell are desirable.Herein, we report a simple but effective materials-design approach to achieve extraordinarily long stability of crosslinked MA lead bromide (MAPbBr3) NCs in various environments (air, water, chemicals, high temperature (85 °C) with high relative humidity (85%RH) (85 °C/85%RH)) by employing sol-gel derived methacrylate-functionalized siloxane hybrid matrix. The methacrylate in the siloxane matrix induces a chemical crosslinking with unsaturated hydrocarbon in acid (oleic acid) and base (oleylamine) ligands in PNCs at a molecular scale, to form a chemically crosslinked perovskite NCs with siloxane hybrid (CPN) that prevents decomposition of MA from the perovskites and achieves homogeneous distribution of NC in the siloxane matrix. Moreover, the low concentration of moisture that diffuses through the siloxane matrix during aging can chemically heal surface defects in the NCs, and thereby reduce nonradiative recombination in CPN. As a result, CPNs showed high PLQY of ≈70% which remained for >600 d in air, water and acid or base solutions, and various polar solvents, and for >100 d under 85 °C/85%RH. We demonstrate wide color gamut and stable color-converting white LEDs and OLEDs by integration with red-emissive Cd-based QDs. Moreover, water- and chemical-persistent CPNs were successfully applied to cell proliferation which has been impossible with water-sensitive materials with toxic elements (e.g., Cd and Pb).

Gel Cleaning in Heritage: Comparison of the Water Release among Gels and Traditional Pads.

Water release is a crucial aspect when considering cleaning effects on water-sensitive materials. In conservation practice, a water-based cleaning method which limits water release is very often needed. Unfortunately, this is not accompanied by an appropriate measure of the effectively released water. In this paper, water release has been measured by comparing traditional cleaning formulations, such as paper pulp and sepiolite, with several gar gel formulations, used by both Italian and European conservators. The assessment has been carried out by the gravimetric method, using three different stone material specimens as reference: Noto calcarenite, Manciano sandstone and Black Bergamo limestone, whose porosity values and distributions are known. Moreover, water distribution has been evaluated by portable NMR tests. Different commercial agar gel products (Bresciani, CTS, Sigma), having different concentrations (3, 4, and 5%), application modes (rigid at room T or fluid warm gels, with and without inserting Japanese tissue paper), and geometry (horizontal in gravity force direction or vertical), have been compared to obtain a full scenario among different water release mechanisms present in real conservation works. The paper faces the important issue of preparing reproducible chemical or water pads as well, useful for further research aimed at comparing cleaning effects in heritage conservation. The most interesting quantitative results can be summarized as follows. The water release measured from paper pulp and sepiolite was found to be 2 to 4 times higher than from any tested agar gel. Water release decreases by increasing agar concentration; an increase in the agar concentration by 1% induces a decrease in water release in the range 16.98-66.88 g depending on the stone; the increase from 4% to 5% is more obvious with respect to that from 3% to 4%. It is possible to assess the effect of the presence of Japanese paper, which is able to reduce the water release from 18 to 76%, depending on the stone and on the agar used. The gravimetric results were also used in the preliminary calibration tests of a contact probe named System Unit Salinity Index (SUSI), recently patented and useful in providing humidity and salinity indexes in a given porous material.

Quantitative investigation and intelligent forecasting of thermal conductivity in lime-modified red clay.

This paper delves into the engineering applications of lime-stabilized red clay, a highly water-sensitive material, particularly in the context of the climatic conditions prevalent in the Dalian region. We systematically investigate the impact of water content, dry density, and freeze-thaw cycles (with a freezing temperature set at -10°C) on the thermal conductivity of stabilized soil, a crucial parameter for analyzing soil temperature fields that is influenced by numerous factors. By developing and validating both empirical and machine learning prediction models, we unravel the evolution of thermal conductivity in response to these factors: within the range of influencing variables, thermal conductivity exhibits an exponential or linear increase with rising water content and dry density, while it decreases exponentially with increasing freeze-thaw cycles. Furthermore, we quantitatively analyze the specific influence of water content and other factors on the thermal conductivity of stabilized soil and construct a comprehensive prediction model encompassing BP neural network, gradient boosting decision tree, and linear regression models. Comparative analysis highlights the significant enhancement in prediction accuracy achieved by the proposed ensemble model over single machine learning models, with root mean square error (RMSE) values below 0.05 and mean absolute percentage error (MAPE) values remaining under 2.5% in both frozen and unfrozen states. Additionally, a secondary validation using experimental data from other researchers confirms the model's good agreement with previous results, demonstrating its robust generalization ability. Our findings provide valuable insights for engineering studies in the Dalian region and red clay areas subjected to extreme climatic conditions.

Portable Electrochemical Sensor for Micromotor Speed Monitoring.

Autonomous movement promotes practical applications of micromotors. Understanding the moving speeds is a crucial step in micromotor studies. The current analysis method relies on an expensive optical microscope, which is limited to laboratory settings. Herein, we have developed a lightweight (0.15 g), portable (2.0 × 3.5 cm2), and low-cost (approximately $0.26) micromotor sensor (μ-Motor sensor), composed of water-sensitive materials for micromotor speed monitoring. Moving micromotors induce fluid flow, enhancing the evaporation rate of the liquid medium. Consequently, a high correlation between motor speed and water molecule concentration above the moving medium has been established. The μ-Motor sensor enables a real-time readout of the moving speed in various settings, with high accuracy (≥95% in the lab and ≥90% in field studies at a local beach). The μ-Motor sensor opens up a new way for detecting micro/nanomachine movements, illuminating future applications of micro/nanorobotics for diverse scenarios.

Flexible fluid-based encapsulation platform for water-sensitive materials

The next-generation semiconductors and devices, such as halide perovskites and flexible electronics, are extremely sensitive to water, thus demanding highly effective protection that not only seals out water in all forms (vapor, droplet, and ice), but simultaneously provides mechanical flexibility, durability, transparency, and self-cleaning. Although various solid-state encapsulation methods have been developed, no strategy is available that can fully meet all the above requirements. Here, we report a bioinspired liquid-based encapsulation strategy that offers protection from water without sacrificing the operational properties of the encapsulated materials. Using halide perovskite as a model system, we show that damage to the perovskite from exposure to water is drastically reduced when it is coated by a polymer matrix with infused hydrophobic oil. With a combination of experimental and simulation studies, we elucidated the fundamental transport mechanisms of ultralow water transmission rate that stem from the ability of the infused liquid to fill-in and reduce defects in the coating layer, thus eliminating the low-energy diffusion pathways, and to cause water molecules to diffuse as clusters, which act together as an excellent water permeation barrier. Importantly, the presence of the liquid, as the central component in this encapsulation method provides a unique possibility of reversing the water transport direction; therefore, the lifetime of enclosed water-sensitive materials could be significantly extended via replenishing the hydrophobic oils regularly. We show that the liquid encapsulation platform presented here has high potential in providing not only water protection of the functional device but also flexibility, optical transparency, and self-healing of the coating layer, which are critical for a variety of applications, such as in perovskite solar cells and bioelectronics.

Preventing the Transmission of Murine Norovirus to Mice (Mus musculus) by Using Dry-heat Sterilization.

A critical component of an animal care biosecurity plan includes the sterilization of materials that come into direct contact with the animals. Dry-heat sterilization is gaining popularity in animal research facilities due to lower cost, less space utilization, no water usage, and the ability to sterilize water-sensitive materials. Currently, dry-heat sterilization ovens are validated against Bacillus atropheus spore strips with the assumption that a lack of sporulation is equivalent to successful sterilization. However, no published studies describe sterilization of rodent cages that contain relevant rodent pathogens by using this method. To determine if a dry-heat sterilizer can sterilize rodent cages and bedding against relevant rodent pathogens, we created murine norovirus (MNV)-contaminated cages by using mice with known MNV infection and shedding. The contaminated cages were either sterilized with the dry-heat sterilizer or not sterilized. Naïve, 4-wk-old, CD-1 mice were placed in the dry-heat-sterilized cages, contaminated unsterilized cages, or standard autoclaved cages for 2 wk. The mice were subsequently placed into clean, autoclaved cages for the remainder of the study. Fresh fecal pellets were collected at weeks 0, 12, and 16 and submitted for MNV PCR. Whole blood was collected for MNV serology at weeks 0, 8, 12, and 16. At week 16, all mice that had been in the unsterilized contaminated cages were positive for MNV by both fecal PCR and serology, whereas the mice in the dry-heat-sterilized and autoclaved cages were negative for MNV by both methods at all time points. Our study supports the use of dry heat sterilization as a viable sterilization method for rodent cages and bedding.

Ionothermal synthesis of calcium-based metal–organic frameworks in a deep eutectic solvent

The ionothermal synthesis of Ca-MOFs has been performed using the 1 : 2 choline chloride : e-urea deep eutectic solvent, allowing the preparation of water sensitive materials.

FORMULATION AND DEVELOPMENT OF LIPID BASED NON-AQUEOUS NANO EMULSION FOR SELECTED NSAID

Oral administration of non-steroidal anti-inflammatory drugs is avoided in patients with disease like peptic ulcer, gastro esophageal reflux (GERD), irritable bowel syndrome. Administration of drug through topical route through the skin could reduce the above side effects associated with oral administered drug formulation. Hence, the aim of present study was to develop Nonaqueous Nanoemulsion (NANEs) of Naproxen for topical administration. NANEs is a multiphase colloidal dispersion heterogeneous system consist of fine nonaqueous polar solvent in oil dispersion with surfactant. NANEs of naproxen were prepared using high energy emulsification method, which break large micro droplets into nano size droplets. Drug-excipients Compatibility was studied by FT-IR. Rheology, Flow behavior, Viscosity, pH, Globule size, Drug content, in-vitro drug release of NANE were performed. For optimization of nonaqueous nanoemulsion Box- Behnken experimental design was implemented. The variables selected are phase volume ratio, surfactant concentration and stirring time. Data analysis showed that surfactant concentration and phase volume ratio significantly affect the viscosity of the formulation. From the present study, it can be concluded that a stable non-aqueous nanoemulsion can be obtained by using glycerin as dispersed phase, mineral oil as continuous phase and glycerol monostearate as surfactant, which can be used as vehicle for the water sensitive materials. This nonaqueous nanoemulsion has improved the stability of Naproxen and overcome the oral drawback associated with it.

Processing and characterization of thermoplastic corn starch-based film/paper composites containing microcrystalline cellulose.

Different thermoplastic starch (TPS) films were prepared with or without the addition of microcrystalline cellulose (MCC) obtained via the melt-extrusion method, and then the hot-press method was used to produce environmentally friendly TPS-based film/paper composites to replace petroleum-based materials. The paper-plastic composites exhibited good interfacial adhesion from the scannign elctron microscopy images. It was seen that 5wt.% MCC was added to reinforce the mechanical properties of TPS films, such that it also improved the barrier properties of MCC@TPS/paper composites and extended the path of water vapor through TPS films, which decreased the water vapor transmission rate of MCC@TPS/paper composites. TPS/paper composites and MCC@TPS/paper composites have better physical properties (i.e. smoothness, flexibility and folding resistance) than only paper. In particular, it was found that the water contact angle of MCC@TPS/paper composites and TPS/paper composites were higher than single-layer paper. Furthermore, MCC reinforced paper-plastic composites demonstrated good barrier properties which can meet the requirement of the need for lower water sensitive materials in the food packaging industry. Thermoplastic corn starch-based film/paper composites have good application properties as a potential source of bioplastic materials. © 2021 Society of Chemical Industry.

Humidity Effect on Resistive Switching Characteristics of the CH3NH3PbI3 Memristor.

Organic-inorganic hybrid halide perovskites (OIHPs) with inherent mixed ionic-electronic conduction ability have been proposed as promising candidates for memristors with unique optoelectronic characteristics. Despite the great achievements toward understanding the working mechanism and exploring their functionality as water-sensitive materials, the humidity effect on the resistive switching (RS) characteristics still remains to be studied. This study investigates the humidity effect on the RS characteristics of Au/CH3NH3PbI3/FTO memristor. The memristor works well at moderate relative humidity (RH, <75%) and degrades rapidly at higher RH of 90%. An obvious decrease in low resistance states on increasing the RH level is observed, which could be attributed to water-induced reduction of the iodide migration barrier. Raman and X-ray diffraction analyses indicate that the migration barrier reduction possibly originated from the weakening of the Pb-I bond caused by the intercalation of water molecules into the crystal lattice. The humidity-sensitive RS characteristics of the memristor could extend the scope of OIHP application for sensing and security applications and also prompt researchers to pay attention to the humidity effect on memristor devices with OIHPs.

X-ray tomographies of a water-sensitive granular material (couscous) exposed to high relative humidity: an experimental study

Several granular materials are hydro-sensitive, i.e., contact with water severely affects their morphology and mechanical behaviour. To this broad class belong a series of materials of great relevance for the pharmaceutical and food industry. Former studies have been conducted on the effect that moisture or humidity have on granular flow or on the individual grain mechanical response, but the processes occurring at the microlevel and their influence on the overall granular packing behaviour is yet to be fully understood. This study presents an experimental investigation of the response of a water-sensitive material (couscous) exposed to high relative humidity (97%). 4D (3D plus time) x-ray tomographies were acquired in operando. A data treatment approach based on Dicrete Digital Image Correlation (dDIC) is developed and detailed here. This allows for following each individual grain throughout the 4+ days of the humidification test. This, in turn, allows the study of the interand intra-granular strain, which is particularly pronounced in water sensitive materials. The expansion of the individual grains also severely affects the contact network, whose evolving properties are here analysed and correlated to the macroscopic (sample-scale) deformation.

Implications of Aqueous Processing for High Energy Density Cathode Materials: Part I. Ni-Rich Layered Oxides

Combining the use of nickel-rich layered oxide cathode materials with the implementation of aqueous electrode processing can pave the way to cost-reduced and environmentally friendly electrodes and simultaneously increase the energy density of cells. Herein, LiNi0.33Co0.33Mn0.33O2 (NCM111), LiNi0.6Co0.2Mn0.2O2 (NCM622), LiNi0.8Co0.1Mn0.1O2 (NCM811) and LiNi0.8Co0.15Al0.05O2 (NCA) were evaluated in terms of their response to aqueous processing under the same conditions to facilitate a direct comparison. The results illustrate that mainly nickel driven processes lead to lithium leaching which is combined with the increase of the pH value in the alkaline region. For NCA an additional aluminum-involving lithium leaching mechanism is assumed, which could explain the highest amount of leached lithium and the additional detection of aluminum. Electrochemical tests show a reduced capacity for cells containing water-based electrodes compared to reference cells for the NCM-type materials which increases during the first cycles indicating a reversible Li+/H+-exchange mechanism. In contrast, the NCA cells were completely electrochemically inactive making NCA the most water sensitive material tested in this report. By comparing the cycling performance of cells containing aqueous processed electrodes, a more pronounced capacity fade for nickel-rich cathode materials as compared to their reference cells can be observed.

Water absorption measurements on WPCs: Assessment of size and direction dependencies in order to design fast and accurate quality control tests

Abstract Wood-plastic composites (WPCs) are water-sensitive materials. Standards describe water absorption protocols on composites to obtain results after a long period of aging. From an industrial point of view, it is necessary to obtain the same information (i.e. equilibrium water content and absorption kinetics) over a short time. In this paper, we propose a new immersion aging protocol based on cubes taken from a reference WPC. This new methodology was validated by varying several test parameters (temperature, sample size, etc.) and applying it to other WPCs. Cubic samples were found to diverge from a Fickian behavior after a certain time of aging because of swelling and cracking that creates another characteristic pore scale and an increase of diffusion coefficient. Compared to the same formulation of cubic samples, the plate samples usually used for water absorption didn't crack. Fick's law approximation was used to determine the diffusion coefficient on plate materials. The coefficients measured in the three directions of WPC decks and a 3D model enabled us to recalculate the apparent coefficient of cubic samples for short-term absorption. Comparison of diffusion coefficients for short and long-term absorption showed the water concentration dependence of composites. Long-term diffusion coefficients and swelling stress coefficients were used in the pseudo-Fickian model to predict the water absorption behavior for composites undergoing water concentration dependence.

Stretchable PEG-DA Hydrogel-Based Whispering-Gallery-Mode Microlaser with Humidity Responsiveness

Optical microcavities have been widely employed for sensing and detection, because of their ultrasensitive responsiveness to surrounding environment. Here we report an active disk-shaped whispering gallery mode (WGM) microcavity fabricated from a water-sensitive material of dye-doped PEG-DA hydrogel through two-photon polymerization. We demonstrate that as the environment humidity changes the microcavity can homogenously expand or shrink to keep the disk-shaped structure, producing stable WGM lasing emissions. We further show that the WGM wavelength of the microlaser shifts linearly as the humidity increases from 25% to 65%, resulting in a wavelength variation of about 1.72 nm, which indicates that the stretchable microlaser can be acted as a humidity sensor. Due to the “smart” response of humidity and biocompatibility of PEG-DA hydrogel material, our results provide a way to the design and fabrication of flexible PEG-DA hydrogel biochips for biomedical applications.

Surface cleaning? Yes, freshly grated Agar gel, please

Polysaccharide-based rigid hydrogels are by now well-established means for delivering water or, more generally an aqueous solution, to a surface in a controllable way so as to minimize diffusion and possible side-effects on water-sensitive materials during cleaning treatments. These gels can be applied as pre-formed solid bricks on planar surfaces or brushed onto objects in a semi-solid state. In this note, a different application procedure is presented, suitable for surface cleaning treatments of sensitive painted surfaces: pre-formed rigid gels grated to tiny particles that can be brushed onto the surface. A general discussion on the strategies that can be adopted when water is required to clean a water-sensitive soiled surface is presented, then the new procedure is discussed and a representative case study is shown, supporting the procedure described.

Non-structural injection grouts with reduced water content: Changes induced by the partial substitution of water with alcohol

Conventional grouting – used to stabilise delaminated plaster – typically involves the use of water as suspension medium. Water can be dangerous when water-sensitive original materials are present and can cause the solubilisation of salts, leading to their re-crystallisation on drying. Ethyl alcohol is a less effective solvent for soluble salts and generally does not affect the original materials. This is the reason why it was used as a partial substitute for water in grout preparations in the present research. Three water–ethyl alcohol-based grouts were compared with the correspondent water-based grout. The working properties and performance characteristics of the injection grouts with reduced water content were measured to assess their suitability for use on historic plasters.

Constitutive unsaturated hydro-mechanical model based on modified mixture theory with consideration of hydration swelling

This paper has extended modified mixture theory with consideration of hydration swelling in unsaturated rock. By using non-equilibrium thermodynamics and Biot elasticity, a fully coupled formulation including hydration swelling term is derived. Standard arguments of non-equilibrium thermodynamics are used to derive the Darcy’s law for unsaturated flow. Helmholtz free energy has been used to give the relationship between the stress and pore pressure. The chemical potential of water in pore space and clay platelets has been included in the analysis of water sensitive materials such as shale. Finally, a simple numerical example has been presented for illustrative purpose, the results show that the swelling parameter has a strong influence on stress and strain.

Covalent Layer-by-Layer Assembly of Water-Permeable and Water-Impermeable Polymer Multilayers on Highly Water-Soluble and Water-Sensitive Substrates

Aqueous methods for the layer-by-layer (LbL) assembly of polyelectrolyte multilayers (PEMs) are not, by their nature, well suited for the fabrication of thin films on substrates that are highly water-soluble or composed of water-sensitive materials. Here, we demonstrate that organic solvent-based processes for covalent (or “reactive”) LbL assembly can be used to fabricate multilayers directly on the surfaces of model water-soluble, water-reactive, and water-sensitive substrates that are either difficult or impossible to coat effectively using aqueous-based LbL methods. Our approach is based on methods for the reactive assembly of multilayers using poly(ethyleneimine) (PEI) and an amine-reactive polymer containing azlactone functionality (PVMDA) in polar-aprotic solvents. The amine-reactive nature of the resulting PEI/PVDMA films facilitated subsequent modification of film-coated surfaces by reaction with primary amine-based nucleophiles. Functionalization of films with the hydrophobic small-molecule amine n-decylamine resulted in the prolonged dissolution and release of underlying water-soluble substrates, and could be used to tune interfacial properties (e.g., to render these water-permeable films more hydrophobic). Fabrication of thicker PEI/PVDMA films resulted in coatings with superhydrophobic properties (e.g., water contact angles of ∼160°) that resisted the penetration of water and enhanced considerably the stabilities of water-sensitive substrates. This approach can, therefore, also be used, in various ways, and to varying extents, to design barriers that protect, enhance the stabilities of, or control/pattern the responses of water-soluble/reactive substrates when they are exposed to aqueous environments. Finally, our results demonstrate that the solubility of PEI and PVDMA in a range of different polar-aprotic solvents can provide flexibility with respect to coating water-soluble/sensitive materials that may also be soluble in some other polar organic solvents. The versatility of this approach could prove useful for modifying the interfacial properties of water-soluble and water-sensitive materials of interest in biotechnology, catalysis, and many other fundamental and applied contexts.

Hypoplastic constitutive modeling of wetting deformation of weathered rockfill materials

The wetting deformation of weathered rockfill materials has been attracting growing attention from both engineers and scientists. The importance of realistic predictions of wetting deformations for high earth and rockfill dams is a strong motivation to establish a suitable constitutive model. Recently, the hypoplastic constitutive model by Gudehus and Bauer was extended by introducing solid hardness depending on the state of weathering. The extended model takes into account the influence of the current density, the effective stress state, the rate of deformation, and the time dependent process of degradation of the solid hardness. In the present paper, the performance of this model is evaluated by comparing numerical simulations with experiments obtained from a water sensitive rockfill material. In particular, triaxial compression paths and creep deformation under deviatoric stress states are considered. Finally, the constitutive model proposed is used to study the influence of a degradation of the solid hardness on the long term behavior of a hypothetical fill dam.

Influence of water chemical potential on the swelling of water sensitive materials

A coupled formulation based on non-equilibrium thermodynamics is derived to model the behaviour of expansive shales. Darcy's law is derived from the dissipation process by using standard arguments of non-equilibrium thermodynamics. The chemical potential of water has been included in classical Biot theory. Thus, the swelling effects due to hydration can be analysed. Finally, finite elements are used to solve the governing equations. The numerical results are consistent with swelling stress and strain responses observed experimentally. The deformations due to swelling are shown to be strongly affected by the choice of swelling parameter.