One-pot Strategy Research Articles

Simultaneous extraction of hydroxylated polycyclic aromatic hydrocarbons and catecholamines with magnetic boronic acid hypercrosslinked polymers

Urinary hydroxylated polycyclic aromatic hydrocarbons (OH-PAHs) and catecholamines (CAs) are important biomarkers of PAHs exposure. In this study, a novel magnetic boronic acid hypercrosslinked composite (Fe3O4@HCP-BA) is synthesized using a facile one-pot strategy and applied as a sorbent for the simultaneous extraction of OH-PAHs and CAs in urine samples. The synthesized Fe3O4@HCP-BA composites are characterized by rich pore structure, highly specific surface area, good magnetic response, and excellent selectivity and adsorption efficiency (range: 65.26–496.71 and 1227.3–1581.8 µmol g−1 for CAs and OH-PAHs, respectively). The mechanisms governing the adsorption of the OH-PAHs and CAs to the Fe3O4@HCP-BA composites were systematically studied via adsorption kinetics, isotherm models, XPS characterization, and molecular simulation. The resultant Fe3O4@HCP-BA composite-based MSPE/HPLC-FLD method exhibited good linearity (R2 > 0.9916), low limits of detection (0.2–0.3 pg mL−1 and 0.2–0.3 ng mL−1 for OH-PAHs and CAs, respectively), and good precision (intra-day and inter-day RSDs < 11.1%). The analysis of CAs and OH-PAHs in the urine samples from 14 smokers and 14 non-smokers revealed a positive correlation between the concentrations of CAs and OH-PAHs. Our findings not only establish the proposed method as a green, environmentally friendly, and simple strategy for preparing magnetic adsorbents, but also confirm it as a promising alternative method for accurate determination of OH-PAHs and CAs in biological samples.

A MOFs-Based mixed-matrix membrane with improved chemical stability and robust mechanical properties

Metal-organic frameworks (MOFs) based mixed-matrix membranes (MMMs) have exhibited unique superiority in various fields from gas separation to chemical sensing. However, their mechanical property and stability has not been fully explored yet, which was essential for further practical application. Herein, MOFs-based MMMs (ZIF-8@PU MMMs) with robust mechanical property and improved chemical stability were prepared through one-pot synthesis strategy by adding ZIF-8 nanoparticles with the monomers of polyurea (PU) during polymerization. Compared with intrinsic fragile and rigid characteristics of pure MOFs crystals films, these MMMs were flexible and free-standing. Importantly, the ZIF-8@PU MMMs exhibited improved mechanical properties compared with pure PU, and the chemical stability especially in acid environments was enhanced owing to the protection from the hydrophobic chain of polymers. This work demonstrated this one-pot strategy was feasible to fabricate homogeneous dispersed MOFs-based MMMs with improved mechanical property and chemical stability. This study was anticipated to accelerate the implementation of MOFs materials for industrialized applications.

Ball-milled prepared Fe3O4-FeSAs-NPs@NC catalyst synergistically facilitate the generation of reactive oxygen species for oxidative trifluoromethylation of alkenes

Heterogeneous catalysts have recently regarded as a promising chose for the thermally-driven generation of the reactive oxygen species (ROS) through catalytic reactions with molecular oxygen, which can facilitate this process by specific geometric and electronic structure. However, the oxidative trifluoromethylation of alkenes to α-trifluoromethylated ketones by CF3SO2Na is rarely reported in this system. In this work, we report a one-pot polymerization ball milling strategy to construct precursor, and then pyrolyze it to obtain specific carbon nanotubes matrix with Fe/Fe3O4 nanoparticles and single atoms Fe. Remarkably, the optimized catalyst (Fe3O4-FeSAs-NPs@NC-1) displays excellent catalytic performance, broad substrates and recyclability for this fluorination reaction via radical pathway. Based on characterizations and mechanistic studies, we discover that the coexistence of Fe/Fe3O4 and Fe-Nx not only synergistically facilitates the catalytic efficiency in altering the electronic structure of Fe sites, but also benefits the absorption of O2 and the ability of the thermally-driven generating ROS which can activate CF3SO2Na to CF3 radical. This work offers a method of designing Fe-based catalysts and also opens up a new thermal-heterogeneous catalysis way for the oxidative trifluoromethylation of alkenes.

Dual-active-component assembly catalyst based continuous flow system for organic reactions with high processing rate

Designing and fabricating suitable packing catalyst with high activity and low flow resistance for continuous flow system is highly desirable but remains a grand challenge. Here we report a facile one-pot strategy to synthesize a dual-active-component assembly catalyst (DACAC) with N-doped holey graphene (NHG) anchored single-atom Pd (Pd1) self-assembled on fibrous aluminum silicate cluster (FASC) skeleton. The resultant Pd1/NHG–FASC DACAC possesses dual-active-components (i.e., Pd atoms and NHG) and hierarchical architecture and can be easily integrated into a fixed-bed platform to construct a catalytic continuous flow system. This fixed-bed system based on the assembly catalyst architecture effectively drives continuous flow reactions with excellent catalytic efficiency for nitroarene reduction and phenylboronic acid oxidative hydroxylation reactions. The processing rate for catalytic reduction of 4-nitrophenol is 1.5 × 10–3 mmol·mg−1·min−1, which is much higher than that of other previously reported packing catalysts based fixed-bed systems. The activity enhancement strategy of dual-active-component provides a new approach to design highly efficient catalytic materials.

One-pot strategy to enhance nanofibrillation and esterification of cellulose using ternary deep eutectic solvent

Establishing green and efficient method for the nanofibrillation and modification of cellulose is the foundation to prepare the cellulose functional material. Herein, we provided a "one-pot " strategy to achieve the high-efficiency nanofibrillation and esterification of nanocellulose using the ternary deep eutectic solvents (DESs). The widths of cellulose nanofiber (CNF) with 18.9 ± 2 nm were successfully prepared by swelling with maleic acid/choline chloride (MA/ChCl) DES at 100 °C for 3 h, followed by mechanical colloid milling. The corresponding acid anhydrides maleic anhydrides (MAH) was added to form MAH/MA/ChCl DES for enhanced esterification of nanocellulose. As a result, the nanocellulose achieved a high degree of substitution (DS) of up to 0.84. The feasibility of "one-pot " strategy based on other ternary DESs (acetic anhydride/acetic acid/choline chloride (AAH/AA/ChCl), succinic anhydride/succinic acid/choline chloride (SAH/SA/ChCl) as representative) was further studied to fibrillate and esterify nanofibers, demonstrating it is an efficient method for the nanofibrillation and modification of cellulose.

Novel multienzyme cascade for efficient synthesis of d-allulose from inexpensive sucrose

d-Allulose is one of the most common rare sugars with low calorie and is extensively applied in the food, cosmetic, and pharmaceutical fields. Here, a novel in vitro multienzyme cascade route (MCAS) was designed to produce d-allulose from sucrose. The MCAS route comprised three modules (sucrose phosphorolysis, phosphorylation–dephosphorylation, and ATP regeneration), including five enzymes (sucrose phosphorylase, fructokinase, d-allulose 6-phosphate 3-epimerase, d-allulose 6-phosphatephosphatase, and polyphosphate kinase). As a rate-limiting enzyme, d-allulose 6-phosphate 3-epimerase from Pantoea sp. was semi-rationally engineered, and variant Y143F led to 88.8% yield of d-allulose from 10 mM sucrose using one-pot strategy. ATP consumption was reduced to 5% of the sucrose concentration after introducing ATP-regeneration system. At elevated sucrose concentration of 100 mM by two-step strategy, a d-allulose yield of 70.4% was achieved with a space-time yield of 1.06 g L−1·h−1. This study provides an efficient and cost-effective approach for producing d-allulose from sucrose.

Pushing Up the Size Limit of Boron-doped peri-Acenes: Modular Synthesis and Characterizations.

Heteroatom-doped peri-acenes (PAs) have recently attracted considerable attention considering their fascinating physical properties and chemical stability. However, the precise sole addition of boron atoms along the zigzag edges of PAs remains challenging, primarily due to the limited synthetic approach. Herein, we present a novel one-pot modular synthetic strategy toward unprecedented boron-doped PAs (B-PAs), including B-[4,2]PA (1 a-2), B-[4,3]PA (1 b-2) and B-[7,2]PA (1 c-3) derivatives, through efficient intramolecular electrophilic borylation. Their chemical structures are unequivocally confirmed with a combination of mass spectrometry, NMR, and single-crystal X-ray diffraction analysis. Notably, 1 b-2 exhibits an almost planar geometry, whereas 1 a-2 displays a distinctive bowl-like distortion. Furthermore, the optoelectronic properties of this series of B-PAs are thoroughly investigated by UV/Vis absorption and fluorescence spectroscopy combined with DFT calculation. Compared with their parent all-carbon analogs, the obtained B-PAs exhibit high stability, wide energy gaps, and high photoluminescence quantum yields of up to 84 %. This study reveals the exceptional ability of boron doping to finely tune the physicochemical properties of PAs, showcasing their potential applications in optoelectronics.

Cellulose eutecticgel electrolytes based on ethylene glycol/zinc chloride deep eutectic solvent for flexible solid-state capacitors

In the present work, we successfully prepared a conductive eutecticgel with good mechanical properties, adhesion properties and excellent antifreeze properties by mixing ethylene glycol (EG) as the hydrogen bonding donor and zinc chloride (ZnCl2) as the hydrogen bonding acceptor in different molar ratios to form an anhydrous deep eutectic solvent (DES). Water-soluble cellulose acetate (WSCA), monomer acrylamide (AM), initiator ammonium persulfate (APS) and cross-linking agent MBA (N, N′-methylene bis(acrylamide)) were added into the prepared DES to form a eutecticgel by a simple one-pot cooking strategy. The mechanical properties of the eutecticgel were strengthened by cross-linking of WSCA and PAM chains through hydrogen bonding, and the addition of the DES and ZnCl2 increased the freezing-resistant property of the eutecticgel. The stresses of DES-WSCA/PAM eutecticgel increased with the content of WSCA. The stress of DES-WSCA/PAM eutecticgel gradually becomes larger with the increase of WSCA content, and it can reach 184.07 kPa at 2 % WSCA content. In addition, the capacitor prepared by DES-WSCA/PAM eutecticgel shows excellent performance, with a voltage window of 2 V and a capacitance of 371.5 F/g, which can be operated stably for a long period, and the capacitance can still reach 145.4 F/g even under the condition of −40 °C. Moreover, DES-WSCA/PAM eutecticgel capacitor has a long service life, its capacitance retention rate and coulombic efficiency can reach more than 91 % and 95 %, respectively, after 10,000 times of charging and discharging tests. In summary, DES-WSCA/PAM eutecticgel electrolyte is an ideal material for capacitors, which opens up a new way of thinking for the development of multifunctional cellulose-based eutecticgels with low-temperature resistance, good mechanical properties, and non-irritating for wearable energy storage devices.

One pot synthesis of hydrophobic nanochitin aerogel via tert-butyl alcohol/water binary solvents as antibacterial and renewable oil superabsorbent

In this study, hydrophobic nanochitin aerogels are synthesized via one-pot synthesis strategy and subsequent freeze-drying technique, employing nanochitin, hexanal and formaldehyde as primary components. The tert-butyl alcohol (TBA)/water binary solvents are found efficient for well mixing of hydrophilic nanochitin and hydrophobic hexanal, which is fundamental for fabricating hydrophobic aerogels with water contact angle as high as 105°. Schiff base reaction between amino groups in nanochitin and aldehyde groups in hexanal is believed to be the main reason for the successful hydrophobization of nanochitin aerogels. Additionally, formaldehyde is employed to enhance the mechanical properties of aerogels via ice templated crosslinking technique. Nanochitin aerogels prepared in this work possess surface area as high as 237 m2 g−1, which are believed benefiting from the TBA/water binary solvents with lower density, smaller ice crystal and convenience in freeze-drying. The ultralow density, ultrahigh porosity, and hydrophobicity nature also lead to the advanced oil adsorption (as high as 210 g g−1) of nanochitin aerogels. The simple preparation process, nature sustainability and excellent adsorption performance is believed rendering nanochitin aerogels as a viable alternative for the remediation of oil spills.

Design and One-Pot Ultrasound Synthesis of Inorganic Base-Promoted Fluorescent Ligand-Gated Ion Channel Fused Arylpyrazole Sulfonamide Skeletons to Enhance Phloem Mobility and Insecticidal Activity as GABA and nACh Receptors Inhibitors.

Ligand-gated ion channels are essential in living organisms, and sulfonamides have antibacterial effects and can be readily coordinated with metal ions with good biological activity. A series of fluorescent ligand-gated ion channel fused arylpyrazole sulfonamide skeletons (APSnM) were synthesized based on a one-pot ultrasound strategy promoted by an inorganic base. APSnM had a high fluorescence quantum yield and a large Stokes shift in ethanol solvent. The ligand bonded ions took on a different color from the ligand and can be used as a probe to detect their own residue on plant surfaces. Their hydrophobic parameters and the fluorescence distribution in Chinese cabbage leaves indicated that APSnM significantly increased the phloem mobility of the plant. The insecticidal activity of APS3Na was higher (LC50 = 7.2423 μg/mL) than that of fipronil (15.2312 μg/mL) against Plutella xylostella, and the mechanism of high insecticidal activity of APS3Na was simulated by molecular docking, which confirmed its strong interactions with the GABA and nACh receptors of Plutella xylostella. Analysis of the crystal structure of these ligand-gated ion channels further confirmed the consistency of their structure and biological activity.

Highly Stable Fluorescent-Traffic-Light Sensor for Point-of-Care Detection of Tetracycline.

Fluorescent point-of-care (POC) sensors have found great utility in fields like clinical diagnosis, food testing, and environmental monitoring. Herein, we developed a highly stable POC sensor that enabled the visual detection of tetracycline (TC) in a distinct fluorescent-traffic-light manner. In the sensor, a composite material of copper nanoclusters and metal-organic framework (CuNCs@MOF-5) prepared with a facile one-pot synthetic strategy was employed as the core element for target recognition and signal transduction. As evidenced by experiments, the as-prepared CuNCs@MOF-5 exhibited significantly improved fluorescence properties in terms of emission enhancement (about 28-fold) and stability improvement (over 110 days) compared to the CuNCs without confining and protection by MOF-5. More importantly, it was found that TC could uniquely interact with Zn(II) to trigger the disassembly of CuNCs@MOF-5, resulting in green fluorescence emission from the TC-Zn(II) complex and red fluorescence weakening of CuNCs. On the basis of this finding, a simple and stable sensor was proposed for POC detection of TC, which demonstrated high sensitivity, selectivity, and reproducibility. In addition to homogeneous visual detection in a 96-well plate, a CuNCs@MOF-5-contained agarose gel array was easily fabricated to achieve direct detection of TC in milk without any pretreatment, thanks to the size-sieving effect of the gel. Moreover, a test paper array was also put forward for low-cost TC detection, which indicates the extensibility and practicability of this sensing strategy.

Tailoring stimuli-responsive PVDF-based copolymer membrane with engineered pore structure for efficient antibody purification

Membrane chromatography is considered as a sustainable alternative for downstream purification to overcome the production bottleneck of biopharmaceuticals. However, two of the major factors impeding its industrial adoption are the lack of controllable functionalization and competitive binding capacity. This work aimed to develop a one-pot synthesis strategy for fabricating a new class of pH-responsive poly(vinylidene fluoride)-graft-poly(dimethylaminoethyl methacrylate) (PVDF-g-PDMAEMA) membranes with anion exchangers, to achieve fast and accurate removal of albumin impurities from antibody streams. By utilizing a pre-functionalized copolymer with controlled ligand density, PVDF-g-PDMAEMA membranes with advantageous bicontinuous pore network structure were obtained via an unconventional nonsolvent thermally induced phase separation method. The membrane showed a competitive water permeance of > 6000 L m-2h−1 bar−1. Combining with dedicated static binding and isotherm studies, the membranes demonstrated distinct pH-responsive binding behaviour to model impurity bovine serum albumin (BSA) with maximal binding of 318.0 mg/g at pH 5.5. The dynamic flow-through binding experiments indicated that the membrane could effectively capture BSA from immunoglobulin G (IgG) (model antibody)/BSA mixed solution with a competitive binding capacity of 210.5 mg/g, producing IgG with purity > 90 % and nearly full recovery. Also, comprehensive analysis demonstrated the robustness of the membrane performance through five consecutive operation cycles, with or without harsh alkaline regeneration. The biocompatibility analysis further proved the membranes’ suitability in biopharmaceutical applications. This study provided a new route for designing future chromatographic membranes to promote its industrial uptake, pushing for energy-saving and effective downstream bioprocessing.

MoS2 modified NiFe LDH hierarchical structure as efficient photoanode towards photoelectrochemical water splitting

Designing effective photo electrode for photo-electrochemical (PEC) water splitting is highly demanded yet challengeable because of the limited sunlight utilization and retarded redox reaction kinetics. This work introduces a feasible one-pot hydrothermal strategy of fabricating MoS2/NiFe LDH p-n heterojunctions on conductive porous nickel foam as an efficient photoanode for PEC water splitting. A great enhancement for PEC water oxidation is achieved because of the improved sunlight absorption and the increased photo-excited charge separation. The optimal 10% MoS2/Ni0.9Fe0.1 LDH/nickel foam photoanode demonstrates 3.8 times enhanced PEC activity than the Ni0.9Fe0.1 LDH/NF counterpart and a low Tafel plot of 54 mV dec−1. The bandgap modulation and the Z-scheme charge transfer dynamics due to the formation of MoS2/NiFe LDH p-n heterostructure, along with the high conductivity of porous nickel foam account for the increased photo-current conversion efficiency and the boosted charge transfer.

Defect Driven Opto-Critical Phases Tuned for All-Solar Utilization.

Materials imbued with uniformly dispersed, photo-responsive nanoparticles are instrumental in sustainable energy and photonic applications. Conventional methods, however, constrain their all-solar response. An innovative alternative is proposed: submerged photo-synthesis of crystallites (SPsC). It is shown that strategic doping with copper and oxygen vacancies can induce opto-critical phases from the non-stoichiometric tungstic acids (WO3 ·H2 O). These opto-critical phases enable a dynamic equilibrium shift in lattice defect stabilization, facilitating an unprecedented a whole solar wavelength response. This response manifests as photothermal, photo-assisted water evaporation, and photo-electrochemical characteristics. Harnessing all-solar energy, this one-pot SPsC strategy may steer the design and development of advanced oxide materials, enhancing functionality across diverse application domains. This article is protected by copyright. All rights reserved.

Design of magnetic multivariate metal–organic framework for high-efficient adsorption and rapid magnetic separation of bisphenol pollutants

Herein, a magnetic multivariate metal–organic framework (MTV-MOF) named as 95.7 %BTB/MOF-525@Fe3O4 was synthesized by one-pot mixing ligand strategy. The magnetic MTV-MOF exhibited large specific surface area (320 m2·g−1) and high porosity. The 95.7 %BTB/MOF-525@Fe3O4 was used as sorbent for extraction and enrichment of bisphenol pollutants (BPs). The experimental results demonstrated that adsorption kinetics and isotherms conform to pseudo-second-order model and Langmuir model. The maximum adsorption capacities for bisphenol F, bisphenol A, bisphenol B, bisphenol AF were 275.1, 233.6, 302.1 and 277.2 mg·g−1, respectively. With 95.7 %BTB/MOF-525@Fe3O4 as sorbent, the magnetic solid phase extraction coupling HPLC was used to detect trace BPs in environmental water. The limits of detection were determined as between 0.067 and 0.167 ng·mL−1. The enrichment factors were in the range of 242–295. The recoveries were ranged from 79.4 to 103 % with relative standard deviations not higher than 8.85 %. In addition, the recovery rate of sorbent remained above 80 % after 21 times of reuse. The work provides an effective material for extraction and removal of BPs in the environment.

Synthesis of carbon aerogels with controlled morphology and pore structure to modulate their bulk density and thermal conductivity via a quick one-pot preparation strategy

How to improve the preparation efficiency and reduced production costs in synthesizing high-performance polymer-derived carbon aerogel materials with ultra-low density and excellent thermal protection properties is currently a crucial research topic that has been plaguing scientists for decades. In this study, we innovatively propose a “one-pot” preparation strategy to synthetize carbon aerogel, which can simplify the complex processes of conventional fabrication methods, greatly shorten the preparation time of phenolic resin-based organic aerogel, and obtain the corresponding carbon aerogels after carbonization. Here, a series of carbon aerogel samples are obtained by regulating the solvent species, and their physicochemical properties such as morphology, pore structure shrinkage, density, and thermal conductivity of these samples are discussed in detail. CA@isoamylol is screened out exhibiting the lowest bulk density (0.15 g/cm3) and thermal conductivity (0.0499 ± 0.0029 W/m·K at 25 °C and 0.1069 ± 0.0090 W/m·K at 1200 °C), which is comparable to the reported values of best-in-class carbon aerogel values, and much lower than the conventional carbon foams. The synthesized CA@isoamylol is promising as a condidate for thermal insulation material. It is expected that the “one-pot” method could alleviate the above-mentioned bottlenecks of the carbon aerogel discipline to produce high-performance carbon aerogel materials with a low-cost and efficient routes.

One-Pot Assembly of the Highly Branched Tetradecasaccharide from Ganoderma lucidum Glycan GLSWA-1 with Immune-Enhancing Activities.

The highly branched tetradecasaccharide repeating unit and shorter sequences of GLSWA-1 with immune-enhancing activities from Ganoderma lucidum have been prepared via a one-pot glycan assembly strategy. The synthetic route features (1) orthogonal one-pot glycosylation on the basis of PVB glycosylation to streamline glycan synthesis avoiding such issues as aglycone transfer, (2) one-pot assembly of oligosaccharides with up to four different glycosyl linkages, and (3) modular and convergent [4+5+5] one-pot assembly of the highly branched tetradecasaccharide.

One-Pot Synthesis of 3,4-Dihydrocoumarins via C-H Oxidation/Conjugate Addition/Cyclization Cascade Reaction.

The 3,4-dihydrocoumarin derivatives were obtained from 2-alkyl phenols and oxazolones via C-H oxidation and cyclization cascade in the presence of silver oxide (Ag2O) and p-toluenesulfonic acid as a Brønsted acid catalyst. This approach provides a one-pot strategy to synthesize the multisubstituted 3,4-dihydrocoumarins with moderate to high yields (64-81%) and excellent diastereoselectivity (>20:1).

One-pot synthesis of CdS nanoparticles with surface-phase junctions to catalyze the photo-reduction of CO2 into CO and CH4 selectively

Without any external template & surfactant, CdS nanoparticles (NPs) with surface-phase junctions were synthesized directly from CdCl2 and the CS2-storage material (CS2SM) with a simple one-pot strategy, in which only stirring was needed. Under visible light irradiation, the as-synthesized CdS NPs could selectively catalyze the reduction of CO2 to produce CO and CH4 sustainably with a perfect catalyst stability even after 33 h. At 4 °C and the optical power density of 370 mW/cm2, the as-synthesized CdS NPs from 0.5 g CS2SM exhibited 195.41 μmol/gcat CH4 generation capacity and the 9.01 μmol·gcat−1·h−1 maximum average yield, in which the generation ratio of CH4/CO was at 8:2; and the as-synthesized CdS NPs from 2.0 g CS2SM exhibited 119.95 μmol/gcat CO generation capacity and the 3.75 μmol·gcat−1·h−1 maximum average yield, in which the generation ratio of CH4/CO was at 1:3. The research results indicated that CdS NPs with higher hexagonal content and smaller particle size is more active in CO2 photoreduction, which may be due to the low potential CdS NPs surface phase junction reducing the recombination rate of electron hole pairs and improving photocatalytic activity. The simple preparation of CdS NPs and their further photocatalytic CO2 reduction provide a green and sustainable foundation for the application of sulfide photocatalysts.

Experimental and theoretical insights on the photophysical properties of ester-substituted indolizines

In this report, we present our latest results on the photophysical properties of substituted indolizines, which were previously obtained through the utilization of ultrasound (US) irradiation, in a one-pot and multicomponent strategy, allowing for a streamlined and straightforward preparation process. The photophysical properties of these derivatives were evaluated in solution using UV–Vis absorption and steady-state fluorescence emission spectroscopy. Our results reveal that these compounds exhibit absorption maxima in the UV-A-violet region. The electronic transitions could be related to spin and symmetry allowed ¹π→π* electronic transitions. The indolizines present fluorescence in the violet-to-green region. Both ground and excited states were shown to be tailored by the substituents in the indolizine core. In addition, the role of the solvent in the deactivation of the excited state proved to be critical in the successful exploration of these compounds as optical sensors for benzene. When benzene was added to the ethanolic solution, the indolizines usually exhibited fluorescence quenching, with a linear relationship between the amount of benzene and the emission intensity. Theoretical calculations were also employed to gain a deeper understanding of the solute-solvent interactions.