RH Conditions Research Articles

Reconstructing the Surface of K2SiF6:Mn4+ Phosphors toward Enhanced Moisture Resistance for White LED Applications.

The K2SiF6:Mn4+ (KSFM) phosphor featuring efficient ultranarrow red emissions is an outstanding candidate for white light-emitting diode (WLED) applications. However, poor moisture resistance seriously affects its application performance. In this study, a two-step surface reconstruction strategy is proposed to dramatically enhance the moisture resistance of commercially available KSFM phosphors, involving treatment with H2NbF7 and subsequent hydrothermal treatment. The modified KSFM phosphor exhibits a high internal quantum efficiency (IQE) of 98.9% after the two-step surface treatment. Meanwhile, nearly 100% of the initial emission intensity is retained for the modified KSFM phosphor even after aging in high temperature (85 °C) and high relative humidity (85% RH) environments for 6 days, in sharp contrast to only 18.6% retention for the original KSFM phosphor. The relative emission intensity of the modified KSFM remains at 98.9% even after being immersed in water for 6 h. Additionally, the phosphor-converted LED fabricated with the modified KSFM phosphor demonstrated excellent long-term stability, retaining up to 97.9% of initial luminous efficacy after aging under 85 °C and 85% RH conditions for 500 h. The moisture-resistance mechanism is elucidated on the basis of spectroscopic analysis as well as structural and compositional characterization of the phosphor surface layer, which can be attributed to the formation of a robust Mn4+-rare shell with high crystalline quality following this two-step surface treatment. The findings contribute to the performance improvements of KSFM phosphors for industrial applications.

Construction of hydrophobic HKUST-1 in wood with selective adsorption performance for toluene and moisture blends

The effect of moisture on the volatile organic compound (VOC) adsorption on biomass-derived metal–organic framework composites is significant in practical applications. In this study, wood-based metal organic frameworks (MOF199-W) and hydrophobic MOF199-W (HMOF199-W) were developed using HKUST-1 (MOF199) and long alkyl chains to investigate the adsorption performance of toluene and enhance the selectivity of adsorption under high humidity conditions. The results demonstrated that HKUST-1 could be anchored onto the surface of wood vessels and fibers through coordination with Cu2+, resulting in an improved surface area in comparison to natural wood. The toluene adsorption capacity of MOF199-W with a 20 % loading was comparable to that of an equivalent amount of MOF199, with adsorption capacities of 323.5 mg/g and 369.9 mg/g, respectively. Further, the Yoon-Nelson model was found to adequately describe the dynamic adsorption process. Following the introduction of long alkyl chains, MOF199 and MOF199-W were endowed with strong hydrophobic character (water contact angle of 107.0◦, 104.0◦, and water uptake of 30.5 mL/g, 55.3 mL/g). With the increase in humidity, the adsorption performance of MOF199 and MOF199-W for toluene sharply decreased, but HMOF199 and HMOF199-W still maintained the adsorption capacities at 304.7 mg/g and 226.7 mg/g, even under 80 % RH conditions. Therefore, HMOF199-W has shown great potential in wooden building materials with the ability for toluene capture under humid conditions.

Direct Measurement of the Diffusion Coefficient of Adhesives from Moisture Distribution in Adhesive Layers Using Near-Infrared Spectroscopy.

In this study, we used near-infrared spectroscopy to measure the moisture penetration in epoxy adhesives and investigated the difference in the diffusion coefficients between the bulk and the adhesive layer. Moisture diffusion was evaluated under 100% RH and water immersion conditions. First, the effects of the curing agents and additives on moisture diffusion in the bulk were gravimetrically evaluated using epoxy-coated quartz glass plates. Different diffusion behaviors were observed depending on the curing agent used. The presence of additives resulted in higher diffusion coefficients, whereas the overall moisture content was low. Next, the moisture distribution in the adhesive layer was visualized using a specimen sandwiched between the quartz glass plates, and the diffusion coefficient of the adhesive layer was calculated. The diffusion coefficient in the adhesive layer was larger than that in the bulk. For adhesives cured with hydrophobic diamine, the diffusion coefficient within the adhesive layer increased by approximately 1.5 times compared with that in the bulk, regardless of the exposure environment. The adhesive, composed of a resin, Dicyandiamide, and additives, showed a 2-fold increase in the diffusion coefficient under high-humidity exposure conditions but no significant change under the water immersion condition. Therefore, these results suggest that, for an accurate analysis of moisture distribution, it is important to measure the diffusion coefficient of the adhesive layer directly rather than using the diffusion coefficient of the material itself.

Preliminary Study of Stone Sawing Sludges-based Alkali Activated Materials (AAMs) for the Conservation of Archaeological Ceramics

This paper presents research into the feasibility of using stone sawing sludge-based Alkali Activated Materials (AAMs) for conservation of Cultural Heritage. Sawing sludges are a stone processing waste product resulting from the mixing of rock powder with the water used to cool down the cutting blades. The chemical composition of the sawing sludges, when aluminosilicatic, is suitable for acting as a precursor to produce AAMs. AAMs are known for their low environmental impact and versatility since their existence is drawn from recycling waste materials. One of their possible applications is in the conservation of Cultural Heritage objects. This work presents a preliminary investigation into three sawing sludge-based AAMs with different mineralogical compositions and contributes to formulating guidelines for applying them as fillers on modern and archaeological ceramic pottery based on the evaluation of their workability, appearance and physical properties over time from the moment of application and up to 30 days. Dynamic Vapor Sorption and X-Ray Diffraction results provided an overview of the structural and mineralogical changes under high RH conditions, where the tested AAMs showed a type II isotherm curve, as expected for concrete-like materials, as well as disappearance of thermonatrite after one isothermal cycle. Ultrasonic Pulse Velocity test demonstrated the general homogeneity of the AAMs despite the lower velocity exhibited by one of the formulations, probably due to its internal pore distribution and possible presence of microstratification. The Oddy tests, application tests and colourimetric measurements evidenced the advantages and weaknesses of the AAMs, with overall encouraging results ensuing investment in further in-depth studies of these innovative conservation materials in view of their future use in the field of conservation of Cultural Heritage as a result of a circular economy model.

Mesoporous Ag-K-Al2O3 catalysts prepared via a one-pot evaporation induced self-assembly approach and their application in catalytic oxidation of formaldehyde

Mesoporous Ag-Al2O3-m and Ag-K-Al2O3-m catalysts were fabricated by a one-pot technique based on an evaporation-induced self-assembly method. Among them, Ag-3 K-Al2O3-m exhibited the highest activity, achieving 100 % HCHO conversion at 40 °C. The catalyst’s performance was notably impacted by RH conditions, which showed improved activity at 30 % RH, due to the formation of active –OH groups. As the K loading increased, the aggregation of Ag particles gradually occurred. According to DFT computation, the presence of K promoted the adsorption and activation of HCHO, O2 and H2O on the catalyst surface. The superior low-temperature reducibility, adequate surface active oxygen and surface –OH groups were identified as key roles to the enhanced catalytic performance of Ag-K-Al2O3-m. Both Ag-Al2O3-m and Ag-K-Al2O3-m operated through the same oxidation mechanism for HCHO oxidation.

Seasonal simulation and source apportionment of SO42− with integration of major highlighted chemical pathways in WRF-Chem model in the NCP

Particulate sulfate (SO42−) is the major component of fine particles in the North China Plain (NCP). It plays an essential role in the entire atmosphere and climate system. Accurately reproducing the SO42− levels is challenging for chemical transport model. Here, the major highlighted multiple phase SO42− formation pathways are integrated into the WRF-Chem model and seasonal model performance of SO42− are assessed by observed SO42− at multiple sampling sites located in the NCP. The results show that the integration of these SO42− formation pathways obviously narrow the gap between simulation and observation in autumn, winter, and summer at three sampling sites in the NCP, for high RH conditions facilitate the hygroscopic growth of PM2.5 and promote the multiple phase reaction to form SO42−. The underestimation in autumn, winter, and summer may ascribe to the missed SO42− source from photo-induced chemical route and missed hygroscopicity of organic aerosols. The obviously discrepancy between simulation and observation in spring may ascribe to the large underestimation of SO2 levels and lack consideration of dust scheme. Source apportionment results show that the gas phase reaction played a vital role in the formation of SO42− in each season. The contribution of aqueous phase SO2 oxidation by H2O2 is higher in autumn and summer due to simultaneously high RH levels and stronger photochemical reaction activity. The Mn(II) catalytic SO2 oxidation pathway at the particle interface is important in autumn and make greater contribution to SO42− formation during winter severe haze events under extremely high RH levels.

High performance and robust durability proton conductive composite membranes containing CeO2-TiC incorporated sulfonated poly(arylene ether) for hydrogen fuel cells

Degradation of proton exchange membrane (PEM) due to free radicals often decreases the overall performance of proton exchange membrane fuel cells (PEMFC). The incorporation of antioxidative additives into the polymer matrix has been widely exploited to mitigate oxidative degradation but is still challenging. Herein, butylsulfonated poly(arylene ether)(SAFPAE) was synthesized by polycondensation followed by nucleophilic substitution and highly crystalline CeO2-TiC filler was prepared by simple hydrothermal process. SAFPAE alleviates the problematic characteristics of proton-exchange membranes (PEMs) whereas CeO2 scavenges free radicals and TiC improves tensile strength. Variable weight ratios of CeO2-TiC were blended into the SAFPAE matrix to study its physicochemical, and electrochemical properties. The random distribution of CeO2-TiC in the SAFPAE matrix enhanced thermal and mechanical strength and increased water absorption, ion exchange capacity, as well as proton conductivity. Specifically, SAFPAE/CeO2-TiC (1.0 wt%) exhibited a current output of 0.18 A cm−2 and a power output of 0.087 Wcm−2 at 20 % RH and 60°C. It also experienced a degradation of 0.145 mV h−1 over 1100 hours of operation. Under operating conditions of RH 20 % and 60°C, PEMFCs with SAFPAE/CeO2-TiC (1.0 wt%) membrane exhibited significantly improved performance and enhanced durability compared to PEMFCs with pure SAFPAE and without sacrificing their cell performance.

Raspberry ketone loaded self nanoemulsifying system of cardamom oil: Assessment of phase behavior, dissolution rate and anti-hyperlipidemic activity

Raspberry ketone (RK), a polyphenolic antioxidant, possesses free radical scavenging against oxidative species and has potential of anti-inflammatory, anti-proliferative and anti-aging activities. Major pharmaceutical restriction associated with RK is its poor dissolution characteristic owing to its hydrophobic nature. Present investigation is an attempt to improve dissolution behavior of RK using cardamom oil (CO) based self nanoemulsifying system (SNE) design and preclinical assessed for anti-hyperlipidemic activity. Demarcation of phase boundaries to exactly locate nanoemulsion areas were explored using ternary plots drawn between CO as oil phase, Tween 80/PEG 600 as Smix at 1:1; 1:2; 2:1 and 3:1 ratios. Previously ternary components were selected on the basis of solubility of RK and aqueous dispersibility of CO. Nanoemulsion areas developed under ternary phase region were quantified using trapezoidal method and found in the order 1:1 > 1:2 > 3:1 > 2:1 of Smix. Aqueous dilutibility of SNEs followed the pattern of dilutions lines drawn across the ternary phase and its interference. Optimized SNE produced 97.1 % transmittance with average droplet size 101 nm, zeta potential −2.27 mV and 0.186 mS/cm conductivity. In-vitro RK release was examined in HCl buffer at pH 1.2 and phosphate buffer at pH 6.8 showed a significant difference in the RK dissolved (p < 0.01) compared to RK suspension (control F6). Optimized formulation (F3) at two doses level (RK loading of 80 and 160 mg/kg) vs. RK suspension (160 mg/kg) was pre-clinically administered for four weeks to assess anti-hyperlipidemic activity. Lipid profile markers (levels of VLDL, HDL, LDL, total triglyceride and total cholesterol) were significantly reduced from nanoemulsion formulation as compared to its suspension. SNE formulations were stable with no appreciable loss in quality and performance for six month storage at 30 ± 2 °C; 65 ± 5 % RH conditions. CO based SNE design significantly extended the ternary area for nanoemulsion development as well as RK solubility; which in turn improved dissolution rate of RK and showed anti-hyperlipidemic activity.

Leucine as a Moisture-Protective Excipient in Spray-Dried Protein/Trehalose Formulation

The incorporation of leucine (Leu), a hydrophobic amino acid, into pharmaceutically relevant particles via spray-drying can improve the physicochemical and particulate properties, stability, and ultimately bioavailability of the final product. More specifically, Leu has been proposed to form a shell on the surface of spray-dried (SD) particles. The aim of this study was to explore the potential of Leu in the SD protein/trehalose (Tre) formulation to control the water uptake and moisture-induced recrystallization of amorphous Tre, using lysozyme (LZM) as a model protein. LZM/Tre (1:1, w/w) was dissolved in water with varied amounts of Leu (0 - 40%, w/w) and processed by spray-drying. The solid form, residual moisture content (RMC), hygroscopicity, and morphology of SD LZM/Tre/Leu powders were evaluated, before and after storage under 22°C/55% RH conditions for 90 and 180 days. The X-ray powder diffraction results showed that Leu was in crystalline form when the amount of Leu in the formulation was at least 20% (w/w). Thermo-gravimetric analysis and scanning electron microscopy results showed that 0%, 5%, and 10% (w/w) Leu formulations led to comparable RMC and raisin-like round particles. In contrast, higher Leu contents resulted in a lower RMC and increased surface corrugation of the SD particles. Dynamic vapor sorption analysis showed that partial recrystallization of amorphous Tre to crystalline Tre·dihydrate occurred in the 0% Leu formulation. However, adding as little as 5% (w/w) Leu inhibited this recrystallization during the water sorption/desorption cycle. In addition, after storage, the formulations with higher Leu contents showed reduced water uptake. Instead of observing recrystallization of amorphous Tre in 0%, 5%, and 10% (w/w) Leu formulations, recrystallization of amorphous Leu was noted in the 5% and 10% (w/w) Leu formulations after storage. In summary, our study demonstrated that the addition of Leu has the potential to reduce water uptake and inhibit moisture-induced recrystallization of amorphous Tre in the SD protein/Tre powder system.

The key role of water on the transformation of the precursors to nano-crystalline C–S–H

The mechanism of multi-step nucleation, which means that a precursor phase exists before the formation of the final crystal, has undergone significant development as an advanced strategy for the production of high-performance structural materials and the mitigation of carbon emissions. This study investigated the potential transformation of C–S–H precursors in water, 98 % RH, and high-temperature environments. The findings suggest that C–S–H precursors, produced by disrupting the two-step nucleation process, can transform in both aqueous and 98%RH conditions, while high temperature alone is insufficient to induce the transformation. The progress of the transformation under 98%RH was impeded by the limited mass transport resulting from the constrained formation of nano-crystalline C–S–H in adsorbed water on the external surface and the pores. This study emphasizes the crucial role of water in facilitating the transformation process, presenting potential opportunities for the nanoengineering of C–S–H-based composites and cementitious materials.

Pyridine substitution strategy for one-dimensional perovskite: Toward efficient and stable mixed-dimensional photovoltaics

Surface passivation via one-dimensional (1D) perovskite has emerged as a promising method to suppress trap states and enhance charge extraction and transportation, leading to improved efficiency and long-term stability. Ionic liquid engineering, characterized as environmental-green additive, has shown particular promise in this regard. Herein, we explore the influence of the electronegativity and dipole moment of two different ionic liquids, benzamidine hydrochloride (BZ) and 2-amidinopyridine hydrochloride (2AP), on the formation of 1D perovskite and the performance of resulting devices. An effective passivation 1D layer has been formed through post-treatment, resulting in nano-rod crystal modified morphology with effectively passivated defects at grain boundaries, enhanced hydrophobicity, prolonged charge carrier lifetime, tailored energy level, and decreased trap density. Notably, the perovskite film treated with 2AP exhibited superior performance due to its stronger interaction with 3D perovskite and better passivation ability on defects originating from the presence of a pyridine ring. As a result, the PSCs incorporating 2AP achieved a champion power conversion efficiency of 24.55 % and retain 90 % of their initial efficiency after storage for over 1000 h at room temperature under ∼ 50 % RH conditions without encapsulation. This study provides valuable insights for expanding the selection of ionic liquids applied in 1D perovskite-assisted surface passivation towards efficient and stable photovoltaics.

Study on the Freeze-Thaw Resistance of Concrete Pavements in Seasonally Frozen Regions.

In seasonally frozen regions, concrete pavement is exposed to cycles of freeze-thaw and erosion from de-icing salt, which can lead to unfavorable service conditions and vulnerability to damage. This paper examines the compressive strength, flexural-tensile strength, abrasion resistance, permeability, and spacing factor of concrete, taking into account the impact of various curing conditions, de-icing salt solutions, and mass fractions on the concrete's freeze-thaw resistance. Two test methods, the single-face method and the fast-freezing method, were used to comparatively analyze the freeze-thaw resistance of concrete. The analysis was based on the surface scaling, water absorption rate, mass loss rate, relative dynamic elastic modulus, and relative durability index. The results indicate that the presence of salt solution significantly worsened the degree of concrete damage caused by freeze-thaw cycles. The use of freeze-thaw media, specifically sodium chloride (NaCl), calcium chloride (CaCl2), and potassium acetate (KAc) at mass fractions of 5%, 4.74%, and 5%, respectively, had the greatest impact on the surface scaling of concrete. However, their effect on the water absorption rate was inconsistent. When the freeze-thaw medium was water, the concrete's relative dynamic elastic modulus and relative durability index were 9.6% and 75.3% higher, respectively, for concrete cured in 20 °C-95% RH conditions compared to those cured in 0 °C-50% RH conditions. We propose a comprehensive relative durability index (DFw) by combining the results of two methods of freeze-thaw tests. The DFw of concrete cured in 0 °C-50% RH conditions was 83.8% lower than that of concrete cured in 20 °C-95% RH conditions when exposed to a freeze-thaw medium of 5% mass fraction NaCl solution. To evaluate the salt freeze-thaw resistance of concrete pavement, it is recommended to use surface scaling and DFw together.

A robust metal–organic framework for simultaneous C2H4/C3H6 capture and C2H2/CO2 separation

Simultaneously capturing and separating high-purity C2H4 and C3H6 from cracked gas mixtures presents a significant challenge. Herein, a robust metal–organic framework (Cu(BF4)2(4-DPDS)2) was designed featuring a gourd-shaped one-dimensional channel. Its specific alkenes match structure can only adsorb alkenes while completely excluding alkanes. With a remarkable adsorption selectivity of 76,203 for equimolar C2H4/C2H6 and high selectivity of 159 for equimolar C3H6/C3H8, Cu(BF4)2(4-DPDS)2 not only achieves >99 % purity separation of C2H4 and C3H6 from binary mixtures but also simultaneously captures and separates these compounds from seven-component cracking gases at ambient conditions. Its performance stability remains intact even under 75 % RH conditions, thanks to its robust framework. Based on the particular gourd-shaped channel, it can also achieve efficient C2H2/CO2 separation. Ab initio Molecular Dynamics simulations demonstrate the dynamic diffusion process of gas molecules in the structure, and in situ infrared analyses reveal the framework's rich C-H•••F and S•••π binding sites with C2H4 and C3H6. This material's robust structure, exceptional alkene sieving capabilities, and repeatable separation performance comprehensively showcase Cu(BF4)2(4-DPDS)2 as a unique metal–organic framework for simultaneous recognition and capture of C2H4 and C3H6.

Effect of Heat Treatment on Hygroscopicity of Chinese Fir (Cunninghamia lanceolata [Lamb.] Hook.) Wood

Chinese fir (Cunninghamia lanceolata [Lamb.] Hook.) is a widely planted species of plantation forest in China, and heat treatment can improve its dimensional stability defects and improve its performance. The wood samples were heat-treated at various temperatures (160, 180, 200, and 220 °C) for 2 h. To clarify the effect of heat treatment on wood hygroscopicity, the equilibrium moisture content (EMC) was measured, the moisture adsorption and desorption rates were determined, the hygroscopic hysteresis was examined, and the Guggenheim, Anderson, and de Boer (GAB) model was fitted to the experimental data. The moisture absorption isotherms of all samples belonged to the Type II adsorption isotherm, but the shape of the desorption isotherm was more linear for heat-treated wood samples, especially when the heat treatment temperature was higher. According to the results analyzed with ANOVA, there were significant differences in equilibrium moisture content between the control samples and the heat-treated samples under the conditions of 30%, 60%, and 95% relative humidity (RH, p &lt; 0.05), and the results of multiple comparisons were similar. The decrease in hygroscopicity was more pronounced in wood treated at higher temperatures. The EMC of the 160–220 °C heat-treated samples of the control samples was 14.00%, 22.37%, 28.95%, and 39.63% lower than that of the control sample at 95% RH. Under low RH conditions (30%), water is taken up mainly via monolayer sorption, and multilayer sorption gradually predominates over monolayer sorption with the increase in RH. The dynamic vapor sorption (DVS) analysis indicated that the heat-treated wood revealed an increase in isotherm hysteresis, which was due to the change in cell wall chemical components and microstructure caused by heat treatment. In addition, the effective specific surface area of wood samples decreased significantly after heat treatment, and the change trend was similar to that of equilibrium moisture content.

Characterization of size-resolved aerosol hygroscopicity and liquid water content in Nanjing of the Yangtze River Delta

Aerosol hygroscopicity and liquid water content (ALWC) have important influences on the environmental and climate effect of aerosols. In this study, we measured the hygroscopic growth factors (GF) of particles with dry diameters of 40, 80, 150, and 200 nm during the wintertime in Nanjing. Both the GF-derived hygroscopicity parameter (κgf) and ALWC increased with particle size, but displayed differing diurnal variations, with κgf peaking around the midday, while ALWC peaking in the early morning. Nitrate, ammonium and oxygenated organic aerosols (OOA) were found as the chemical components mostly strongly correlated with ALWC. A closure study suggests that during midday photo-oxidation and nighttime high ALWC periods, the κ of organic aerosols (κorg) was underestimated when using previous parameterizations. Accordingly, we re-constructed parameterizations for κorg and the oxidation level of organics for these periods, which indicates a higher hygroscopicity of photochemically formed OOA than the aqueous OOA, yet both being much higher than the generally assumed OOA hygroscopicity. Additionally, in a typical high ALWC episode, concurrently increased ALWC, nitrate, OOA as well as aerosol surface area and mass concentrations were observed under elevated ambient RH. This strongly indicates a coupled effect that the hygroscopic secondary aerosols, in particular nitrate with strong hygroscopicity, led to large increase in ALWC, which in turn synergistically boosted nitrate and OOA formation by heterogeneous/aqueous reactions. Such interaction may represent an important mechanism contributing to enhanced formation of secondary aerosols and rapid growth of fine particulate matter under relatively high RH conditions.

Effects of postharvest piling up in bulk on qualities of Camellia oleifera seeds

The study investigated the effects of postharvest piling up in bulk on Camellia oleifera seed qualities, including moisture content, oil content, fatty acid composition, soluble sugar, soluble protein content, acid value, peroxide value, lipase activity, lipoxygenase activity, and mold colony, under varying relative humidity (60%, 80%, 98%) and time durations (1–8 days). Additionally, it examined the impact of piling temperature and diverse postharvest treatments. The results revealed that piling up in bulk promoted the post-ripening of Camellia oleifera seeds, leading to a gradual decrease in seed moisture content while initially increasing oil content before stabilizing. After 2 days of piling, seed oil content increased by 5.65%, 4.40%, and 1.06% under RH conditions of 60%, 80%, and 98%, respectively. However, after 4 days, the oil content declined by 8.36%, 6.06%, and 4.14%, respectively. The proportions of saturated and polyunsaturated fatty acids declined gradually, while monounsaturated fatty acids increased significantly. The acid value decreased, correlating positively with lipase activity. Mold colonies on seeds increased minimally with piling duration, while those on fruit shells increased sharply by 1–4 logarithmic units after the 4th day. When examining the effect of temperature, higher piling temperatures were found to gradually increase the seed oil content. Based on the order of oil content, the different treatment methods were ranked as follows: piling up in bulk-sun drying > piling up in bulk-drying > shelling-sun drying > direct sun drying > shelling-drying. Therefore, these findings advance our understanding of postharvest piling up in bulk of Camellia oleifera seeds and provide valuable insights for selecting treatment methods and parameters.

Proton Conductivity in a Metal-Organic Cube-Based Framework and Derived Hydrogel with Tubular Morphology.

The hydrogels, formed by self-assembly of predesigned, discrete metal-organic cubes (MOCs), have emerged as a new type of functional soft material whose diverse properties are yet to be explored. Here, we explore the proton conductivity of a MOC-based supramolecular porous framework {(Me2NH2)12[Ga8(ImDC)12]·DMF·29H2O} (1) (ImDC = 4,5-imidazole dicarboxylate) and derived hydrogel (MOC-G1). The intrinsic charge-assisted H-bonded (between anionic MOC {[Ga8(ImDC)12]12-} and dimethylammonium cations) framework 1 exhibits an ambient condition proton conductivity value of 2.3 × 10-5 S cm-1 (@40% RH) which increases with increasing temperature (8.2 × 10-4 S cm-1 at 120 °C and 40% RH) and follows the Grotthuss type of mechanism of proton conduction. Self-assembly of the MOCs in the presence of ammonium cations, as molecular binders, resulted in a hydrogel (MOC-G1) that shows directional H-bonded 1D nanotubular morphology. While guest water molecules are immensely important in deciding the proton conductivity of both 1 and MOC-G1, the presence of additional proton carriers, such as DMA and ammonium cations, resulted in at least 1 order increment in the proton conductivity of the latter (1.8 × 10-2 S cm-1) than the former (1.4 × 10-3 S cm-1) under 25 °C and 98% RH condition. The values of proton conductivity of 1 and MOC-G1 are comparable with those of the best proton conduction reports in the literature. This work may pave the way for the development of proton conductors with unique architecture and conductivity requisite for the state-of-the-art technologies by selecting appropriate MOC and molecular binders.

Implementation of the ISORROPIA-lite aerosol thermodynamics model into the EMAC chemistry climate model (based on MESSy v2.55): implications for aerosol composition and acidity

Abstract. This study explores the differences in performance and results by various versions of the ISORROPIA thermodynamic module implemented within the ECHAM/MESSy Atmospheric Chemistry (EMAC) model. Three different versions of the module were used, ISORROPIA II v1, ISORROPIA II v2.3, and ISORROPIA-lite. First, ISORROPIA II v2.3 replaced ISORROPIA II v1 in EMAC to improve pH predictions close to neutral conditions. The newly developed ISORROPIA-lite has been added to EMAC alongside ISORROPIA II v2.3. ISORROPIA-lite is more computationally efficient and assumes that atmospheric aerosols exist always as supersaturated aqueous (metastable) solutions, while ISORROPIA II includes the option to allow for the formation of solid salts at low RH conditions (stable state). The predictions of EMAC by employing all three aerosol thermodynamic models were compared to each other and evaluated against surface measurements from three regional observational networks in the polluted Northern Hemisphere (Interagency Monitoring of Protected Visual Environments (IMPROVE), European Monitoring and Evaluation Programme (EMEP), and Acid Deposition Monitoring Network of East Asia (EANET)). The differences between ISORROPIA II v2.3 and ISORROPIA-lite were minimal in all comparisons with the normalized mean absolute difference for the concentrations of all major aerosol components being less than 11 % even when different phase state assumptions were used. The most notable differences were lower aerosol concentrations predicted by ISORROPIA-lite in regions with relative humidity in the range of 20 % to 60 % compared to the predictions of ISORROPIA II v2.3 in stable mode. The comparison against observations yielded satisfactory agreement especially over the USA and Europe but higher deviations over East Asia, where the overprediction of EMAC for nitrate was as high as 4 µg m−3 (∼20 %). The mean annual aerosol pH predicted by ISORROPIA-lite was on average less than a unit lower than ISORROPIA II v2.3 in stable mode, mainly for coarse-mode aerosols over the Middle East. The use of ISORROPIA-lite accelerated EMAC by nearly 5 % compared to the use of ISORROPIA II v2.3 even if the aerosol thermodynamic calculations consume a relatively small fraction of the EMAC computational time. ISORROPIA-lite can therefore be a reliable and computationally efficient alternative to the previous thermodynamic module in EMAC.

A Revolutionary Approach to Study the Hydrogen Electrode Formation on Different Noble Metals Exposed to Monolayer to Sub-Monolayers Range of Water Using Scanning Kelvin Probe

The inadequacy of modern surface analytical tools to probe the electrochemical double layer (EDL) which governs the catalytic reactions at the interface hampers its in-depth investigation. The reason for this is that the EDL is usually buried under the bulk electrolyte. Though great progress was made in computational modeling the EDL [1,2], at the experimental level similar progress is necessary. One approach is to study the EDL of electrodes covered by electrolyte of nano-scale thickness. Till date, such studies of electrodes covered by electrolyte in the monolayer to sub-monolayer range are scarce, although they were at the center of the birth of electrochemical surface science [3]. Recently the “hydrogen electrode in the dry” concept which was established on palladium surface under dry nitrogen conditions could be a novel approach to understand that facet of the electrode interface activities [4]. The amount of water in this case is confined to just 1-2 monolayers to adsorbed water or even below. Similarly, this approach was successful applied for studying the current-potential relationships for oxygen reduction reaction exposed to different amounts of water ranging from micro meter to monolayers of thickness [5]. In this study, this concept was explored to other noble metal systems such as Pd, Au, Pt, and Ir to understand the hydrogen electrode formation.The present study focuses on hydrogen electrode formation on palladium, iridium, gold, and platinum exposed to inert conditions carried out by scanning Kelvin probe method (see fig) at different hydrogen activities. The activities of hydrogen on the surface was defined by electrochemically (entry side from a=0 to a=0.2) cathodic hydrogen charging method. Firstly, the hydrogen activity of 0.2 was defined on the palladium side by increasing the cathodic potential stepwise by potentiostatic hydrogen charging and measuring the corresponding potential on the exit side by Kelvin probe. This potential on palladium in both wet (>95% rh) and dry (<0.1% rh) conditions follows a 1:1 correlation with the applied entry potential, in accordance with the Nernst equation. Iridium samples show 1:1 in humid conditions, but not in dry conditions, i.e. in presence of a much thinner layer of adsorbed water molecules. At intermediate partial pressures of water, a linear response with slope lower than 1 was observed, that increased with increasing humidity. Whereas, gold samples show no correlation in both wet and dry conditions. Additionally, hydrogen electrode formation on emersed surface was checked to understand the effect of an already existing EDL on the formation of the hydrogen electrode. Also, ellipsometry spectroscopy measurements were carried out to determine the water layer thickness at different partial pressures of water. Overall, the current experimental approach of measuring the potential of these different “dry” electrodes gives more insights about hydrogen electrode formation on noble metals at different hydrogen activities, effect of adsorbed anions, and the effect of different amounts of adsorbed water.

Severe photochemical pollution formation associated with strong HONO emissions from dew and guttation evaporation

The unknown daytime source of HONO has been extensively investigated due to unexplained atmospheric oxidation capacity and current modelling bias, especially during cold seasons. In this study, abrupt morning increases in atmospheric HONO at a rural site in the North China Plain (NCP) were observed almost on daily basis, which were closely linked to simultaneous rises in atmospheric water vapor content and NH3 concentrations. Dew and guttation water formation was frequently observed on wheat leaves, from which water samples were taken and chemically analyzed for the first time. Results confirmed that such natural processes likely governed the daily nighttime deposition and daytime release of HONO and NH3, which have not been considered in the numerous HONO budget studies investigating its large missing daytime source in the NCP. The dissolved HONO and NH3 in leaf surface water droplets reached 1.4 and 23 mg L−1 during the morning on average, resulting in averaged atmospheric HONO and NH3 increases of 0.89 ± 0.61 and 43.7 ± 29.3 ppb during morning hours, with relative increases of 186 ± 212 % and 233 ± 252 %, respectively. The high atmospheric oxidation capacity contained within HONO was stored in near surface liquid water (such as dew, guttation and soil surface water) during nighttime, which prevented its atmospheric dispersion after sunset and protected it from photodissociation during early morning hours. HONO was released in a blast during later hours with stronger solar radiation, which triggered and then accelerated daytime photochemistry through the rapid photolysis of HONO and subsequent OH production, especially under high RH conditions, forming severe secondary gaseous and particulate pollution. Results of this study demonstrate that global ecosystems might play significant roles in atmospheric photochemistry through nighttime dew formation and guttation processes.