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Crystallization from solution is a materials synthesis process common both in nature and in the laboratory. Unlike conventional high-temperature solid-state synthesis, solution-based syntheses often yield metastable phases, contrary to expectations from equilibrium thermodynamics. Using a recently developed ab initio scheme to calculate the surface energy of a critical nucleus in equilibrium with the aqueous environment, we present a framework to compare relative nucleation rates between competing polymorphs as a function of solution chemistry. We apply this approach to demonstrate how seawater chemistry can preferentially bias nucleation toward the metastable aragonite phase of calcium carbonate, rather than the stable phase calcite––which is of great relevance to biomineralization, carbon sequestration, paleogeochemistry, and the vulnerability of marine life to ocean acidification. Predicting the conditions in which a compound adopts a metastable structure when it crystallizes out of solution is an unsolved and fundamental problem in materials synthesis, and one which, if understood and harnessed, could enable the rational design of synthesis pathways toward or away from metastable structures. Crystallization of metastable phases is particularly accessible via low-temperature solution-based routes, such as chimie douce and hydrothermal synthesis, but although the chemistry of the solution plays a crucial role in governing which polymorph forms, how it does so is poorly understood. Here, we demonstrate an ab initio technique to quantify thermodynamic parameters of surfaces and bulks in equilibrium with an aqueous environment, enabling the calculation of nucleation barriers of competing polymorphs as a function of solution chemistry, thereby predicting the solution conditions governing polymorph selection. We apply this approach to resolve the long-standing “calcite–aragonite problem”––the observation that calcium carbonate precipitates as the metastable aragonite polymorph in marine environments, rather than the stable phase calcite––which is of tremendous relevance to biomineralization, carbon sequestration, paleogeochemistry, and the vulnerability of marine life to ocean acidification. We identify a direct relationship between the calcite surface energy and solution Mg–Ca ion concentrations, showing that the calcite nucleation barrier surpasses that of metastable aragonite in solutions with Mg:Ca ratios consistent with modern seawater, allowing aragonite to dominate the kinetics of nucleation. Our ability to quantify how solution parameters distinguish between polymorphs marks an important step toward the ab initio prediction of materials synthesis pathways in solution.

Activated carbon prepared from lemon (Citrus limon) wood (ACL) and ACL/Fe3O4 magnetic nanocomposite were effectively used to remove the cationic dye of crystal violet (CV) from aqueous solutions. The results showed that Fe3O4 nanoparticles were successfully placed in the structure of ACL and the produced nanocomposites showed superior magnetic properties. It was found that pH was the most effective parameter in the CV dye adsorption and pH of 9 gave the maximum adsorption efficiency of 93.5% and 98.3% for ACL and ACL/Fe3O4, respectively. The Dubinin–Radushkevich (D-R) and Langmuir models were selected to investigate the CV dye adsorption equilibrium behavior for ACL and ACL/Fe3O4, respectively. A maximum adsorption capacity of 23.6 and 35.3 mg/g was obtained for ACL and ACL/Fe3O4, respectively indicating superior adsorption capacity of Fe3O4 nanoparticles. The kinetic data of the adsorption process followed the pseudo-second order (PSO) kinetic model, indicating that chemical mechanisms may have an effect on the CV dye adsorption. The negative values obtained for Gibb’s free energy parameter (−20 < ΔG < 0 kJ/mol) showed that the adsorption process using both types of the adsorbents was physical. Moreover, the CV dye adsorption enthalpy (ΔH) values of −45.4 for ACL and −56.9 kJ/mol for ACL/Fe3O4 were obtained indicating that the adsorption process was exothermic. Overall, ACL and ACL/Fe3O4 magnetic nanocomposites provide a novel and effective type of adsorbents to remove CV dye from the aqueous solutions.

The polyglycerol esters (PGEs) of fatty acids have a wide range of HLB values and applications in diverse industries, such as pharmaceuticals and cosmetics. While the physicochemical properties of oil-soluble PGEs dissolved in oil phases are well studied in the literature, there is no information on their structuring in aqueous phases and emulsifying abilities. We combined rheological and differential scanning calorimetry (DSC) measurements and microscopy observations to characterize the dependence of oil-soluble PGE structuring in aqueous phases on the PGE concentration, the temperature of solution homogenization, and the PGE molecular structure. Excellent correlations between the considerable changes in solution viscosity and the temperatures of the two endo- and exothermic peaks in the DSC thermograms are observed. Single-tail PGE molecules, which have a higher number of polyglycerol units, are better organized in networks, and the viscosity of their aqueous solutions is higher compared to that of the respective double-tail PGE molecules. PGEs exhibit good emulsifying ability and the viscosity of the produced emulsions at room temperature can differ by orders of magnitudes depending on the temperature of emulsification. The reported properties of oil-soluble PGEs could be of interest for increasing the range of their applicability in practice.

Tin selenide (SnSe) is one of the most promising candidates to realize environmentally friendly, cost‐effective, and high‐performance thermoelectrics, derived from its outstanding electrical transport properties by appropriate bandgaps and intrinsic low lattice thermal conductivity from its anharmonic layered structure. Advanced aqueous synthesis possesses various unique advantages including convenient morphology control, exceptional high doping solubility, and distinctive vacancy engineering. Considering that there is an urgent demand for a comprehensive survey on the aqueous synthesis technique applied to thermoelectric SnSe, herein, a thorough overview of aqueous synthesis, characterization, and thermoelectric performance in SnSe is provided. New insights into the aqueous synthesis‐based strategies for improving the performance are provided, including vacancy synergy, crystallization design, solubility breakthrough, and local lattice imperfection engineering, and an attempt to build the inherent links between the aqueous synthesis‐induced structural characteristics and the excellent thermoelectric performance is presented. Furthermore, the significant advantages and potentials of an aqueous synthesis route for fabricating SnSe‐based 2D thermoelectric generators, including nanorods, nanobelts, and nanosheets, are also discussed. Finally, the controversy, strategy, and outlook toward future enhancement of SnSe‐based thermoelectric materials are also provided. This Review guides the design of thermoelectric SnSe with high performance and provides new perspectives as a reference for other thermoelectric systems. Herein, aqueous‐solution‐based synthesis, characterizations, and thermoelectric performance in SnSe thermoelectrics are thoroughly reviewed by providing new insights including vacancy synergy, crystallization design, doping limit breakthrough, local lattice imperfection engineering, and a promising flexible thermoelectric generator based on appropriate synthesis design.

Photodynamic therapy (PDT) has shown a promising capability for cancer treatment with minimal side effects. Indocyanine green (ICG), the only clinically approved near-infrared (NIR) fluorophore, has been used as a photosensitizer for PDT in clinical application. However, the main obstacle of directly utilizing ICG in the clinic lies in its low singlet oxygen ( 1 O 2 ) quantum yield (QY) and instability in aqueous solution. To improve the PDT efficacy of ICG, free ICG molecules were assembled with free oxygen nanobubbles (NBs-O 2 ) to fabricate ICG-NBs-O 2 by hydrophilic-hydrophobe interactions on the gas—liquid interface. Interestingly, 1 O 2 QY of ICG-NBs-O 2 solution was significantly increased to 1.6%, which was estimated to be 8 times as high as that of free ICG solution. Meanwhile, ICG-NBs-O 2 exhibited better aqueous solution stability compared with free ICG. Furthermore, through establishing tumor models in nude mice, the therapeutic efficacy of ICG-NBs-O 2 was also assessed in the PDT treatment of oral cancer. The tumor volume in ICG-NBs-O 2 treated group on day 14 decreased to 0.56 of the initial tumor size on day 1, while the tumor volume in free ICG treated group increased to 2.4 times. The results demonstrated that ICG-NBs-O 2 showed excellent tumor ablation in vivo . Therefore, this facile method provided an effective strategy for enhanced PDT treatment of ICG and showed great potential in clinical application.

The effects of hydrogen bonds on the molecular structure of water-tetrahydrofuran (H2O–THF), water-dimethyl sulfoxide (H2O–DMSO), and water-tetrahydrofuran-dimethyl sulfoxide (H2O–THF–DMSO) in binary aqueous solutions and ternary aqueous solutions were studied using Raman spectroscopy. The results indicate that in the binary aqueous solution, the addition of THF and DMSO will generate hydrogen bonds with water molecules, resulting in changes in the peak positions of S=O bonds and C–O bonds. Compared with the binary aqueous solutions, the hydrogen bonds between DMSO and THF, and the hydrogen bonds between DMSO and H2O in the ternary aqueous solutions are competitive, and the hydrogen bond competition is susceptible to water content. In addition, the formation of hydrogen bonds will destroy the fully hydrogen-bonded water and make it change to the partially hydrogen-bonded water. By fitting the spectra into the three Gaussian components assigned to water molecules with different hydrogen bonding (HB) environments, these spectral features are interpreted by a mechanism that H2O in different solution systems has equal types of water molecules with similar HB degrees-fully hydrogen-bonded H2O (FHW) and partially hydrogen-bonded H2O (PHW). The ratio of the intensity transition from FHW to PHW is determined based on Gaussian fitting. Therefore, the variation of hydrogen bond competition can be supplemented by the intensity ratio of PHW/FHW ((IC2 + IC3)/IC1). This study provides an experimental basis for enriching the hydrogen bonding theory of multivariate aqueous solution systems.

Magnetic aluminum-based adsorbents (MLDHs) were prepared with a coprecipitation method and used to separate lithium ions from the aqueous solutions. In static adsorption experiment, the adsorption capacity of MLDHs for lithium ions reached 8.22 mg/g. In a mixed solution of various metal ions, the adsorbents exhibited higher selectivity for lithium ions. Kinetic studies indicated that the adsorption process conformed to a pseudo-second-order model. The experimental data were fitted with nonlinear regression using commonly used adsorption isotherms. It was found that the adsorption isotherm process could be described by the Langmuir model. In addition, the thermodynamic parameters revealed that the adsorption of lithium was a spontaneous endothermic process.

A series of macrocycles, including crown ethers, cyclodextrins, calixarenes, pillararenes and cucurbiturils, are well known to be able to associate various organic/inorganic/biological guest molecules and ions in their well-defined cyclic cavities to form stable host-guest complexes and supramolecular systems through the cooperative contributions of various non-covalent interactions. When one or more functional groups are attached to the cavity of macrocycles or guest molecules, enhanced and/or controlled host-guest associations may take place, leading to not only improved host-guest binding abilities but also fascinating properties. In this review, some representative contributions in the construction of controllable macrocyclic supramolecular assemblies in aqueous solution are presented with an emphasis on the stimuli-responsive control manner and wide applications of this property.

Cellulose is a biopolymer with numerous advantages that make it an ecological, economical, and high-performing choice for various applications. To fully exploit the potential of cellulose, it is often necessary to dissolve it, which poses a current challenge. The aqueous zinc oxide/sodium hydroxide (ZnO/NaOH/Water) system is a preferred solvent for its rapid dissolution, non-toxicity, low cost, and environmentally friendly nature. In this context, the behavior of cellulose chains in the aqueous solution of ZnO/NaOH and the impact of temperature on the solubility of this polymer were examined through a molecular dynamics simulation. The analysis of the root means square deviation (RMSD), interaction energy, hydrogen bond curves, and radial distribution function revealed that cellulose is insoluble in the ZnO/NaOH solvent at room temperature (T = 298 K). Decreasing the temperature in the range of 273 K to 268 K led to a geometric deformation of cellulose chains, accompanied by a decrease in the number of interchain hydrogen bonds over the simulation time, thus confirming the solubility of cellulose in this system between T = 273 K and T = 268 K.

The peculiarities of the crystal formation from supersaturated aqueous solutions of CuSO4 on polymer substrates were studied using X-ray diffractometry. During the crystal formation, the test solutions were irradiated with one or two counter-propagating ultrasonic beams. Test solutions were prepared using natural deionized water with a deuterium content of 157 ± 1 ppm. The other liquid used was deuterium-depleted water with a deuterium content of 3 ppm. It was shown that irradiation with one/two ultrasonic beams resulted in drastic changes in the structure of the crystal deposit formed on the polymer substrate in the case when natural deionized water was chosen for preparing the supersaturated solution of CuSO4.