Bulk Solution Research Articles

Fuel Resistance of Firefighting Surfactant Foam Formulations

Aqueous film-forming foam (AFFF) is widely recognized for its excellent fire-extinguishing capabilities, yet the specific roles of its components remain insufficiently understood. AFFF typically consists of fluorocarbon and hydrocarbon surfactants, as well as organic solvents such as diethylene glycol butyl ether (DGBE), which can significantly influence foam performance. This study investigates the effects of surfactant mixtures and the DGBE additive on foam stability and fuel resistance at room temperature and ambient humidity. Static foam ignition experiments were conducted to assess fuel transport through foams using various hydrocarbon fuels, including n-octane, iso-octane, n-heptane, methylcyclohexane, methylcyclopentane, and a mixture of 25% trimethylbenzene with 75% n-heptane. Methylcyclopentane, with its higher vapor pressure and solubility, led to the shortest ignition times, indicating faster fuel transport. The addition of DGBE increased ignition times by a factor of 1.2 to 3.7 for individual surfactants, while the Capstone+Glucopon mixture improved ignition times by a factor of 2.4 to 5.5 compared to the individual surfactants. Further enhancement was observed with Capstone+Glucopon+DGBE, increasing ignition times by a factor of 3 to 7.3 compared to the individual surfactants. Additionally, combining DGBE with surfactant mixtures reduced fuel concentration in the bulk solution by over 60% compared to individual surfactants, significantly enhancing fuel resistance. Interface experiments showed that fuel presence, particularly methylcyclopentane and n-octane, altered the foam structure and accelerated drainage at the foam/fuel interface, impacting foam stability and fuel transport. These findings demonstrate that surfactant mixtures and DGBE-enhanced formulations substantially improve foam stability and fuel resistance.

Studies on the Electrochemical Behavior of Sulfite on Incoloy 800 in a Neutral Environment

Avoiding atmospheric pollution with sulfur dioxide is generally achieved by its absorption from combustion gases in alkaline solutions and conversion to sulfites. Afterwards, sulfites can be transformed into neutral and environmentally safe chemicals by oxidation to sulfates. The oxidation of sulfites to sulfates can also be carried out in a cell in which the fuel will be sulfite ions. In this way, in addition to the beneficial effect of neutralizing large quantities of sulfite waste, electrical energy is also obtained. This is one of the reasons why study of the anodic oxidation of sulfite to sulfate on various electrode materials was necessary. Given the sensitivity of electrode materials in the presence of sulfur compounds, in our research we approached the study of sulfite oxidation on the Incoloy 800 anode in neutral solution (1 mol L−1 Na2SO4). In this research, the results obtained in the study of the kinetic parameters of the anodic process as a function of the sulfite concentration (10−1, 0.5, and 1 mol L−1), using linear voltammetry, are presented. The appreciable values of the exchange current density (3.4, 3.0, and 2.6 A m−2) show that Incoloy 800 has a significant catalytic effect in the anodic oxidation of sulfite. Chronoamperometric studies have shown that the anodic oxidation of sulfite is controlled by the mass transfer of sulfite ions from the bulk solution to the electrode surface. According to the chronocoulometric diagrams, it can be appreciated that, up to anodic potentials of +1.50 V, sulfite oxidation occurs on the electrode, while at more positive potentials, the oxygen evolution reaction is the main process. Electrochemical impedance data provide evidence of a chemical reaction coupled with electron transfer, which was modeled using a Gerischer impedance. At high sulfite concentrations, the charge transfer resistance (Rct) decreases by a factor of 10, indicating that the sulfite oxidation reaction is fast at sufficiently positive potentials. On the other hand, the passivation tendency of stainless steels upon anodic polarization gives them a high corrosion resistance, so that Incoloy 800 can be a viable option as an anode material for sulfite/oxygen (air) fuel cells.

Nanoconfinement-Enabled Resistance to Water Matrix Components for Selective Degradation of Micropollutants.

Despite recent substantial advances in water treatment, the ability to selectively degrade trace micropollutants in real waters with complex matrix components remains a grand challenge. Here we report rational crafting of graphene oxide (GO)-wrapped defective TiO2 composite catalysts that creates nanoscopic confinement over the TiO2 surface within GO, thereby enabling the selective degradation of micropollutants through effectively excluding natural organic matter (NOM) and anions from the nanoconfined catalytic sites. In contrast to unconfined counterparts, the nanoconfined composite catalysts retain high degradation efficiency when exposed to various concentrations of NOM and anions, even in real water samples. Oxygen vacancies in TiO2 promote electron separation and oxygen adsorption, leading to a 4.9-fold increase in hydroxyl radical concentration within the nanoconfined space compared to the bulk solution. In-situ X-ray photoemission spectroscopy and Raman spectroscopy unveil the nanoconfined catalytic sites on the TiO2 surface, where micropollutants smaller than the pores of GO are effectively degraded, while NOM with a larger size is excluded by GO. Furthermore, the formation of toxic disinfection byproducts is well controlled due to the exclusion of NOM. This work provides a simple yet viable strategy for designing 2D material-wrapped catalysts to selectively degrade target micropollutants in complex real waters.

Controlling the Spatiotemporal Self-Organization of Stimuli-Responsive Nanocrystals under Out-of-Equilibrium Conditions.

Self-organization under out-of-equilibrium conditions is ubiquitous in natural systems for the generation of hierarchical solid-state patterns of complex structures with intricate properties. Efforts in applying this strategy to synthetic materials that mimic biological function have resulted in remarkable demonstrations of programmable self-healing and adaptive materials. However, the extension of these efforts to multifunctional stimuli-responsive solid-state materials across defined spatial distributions remains an unrealized technological opportunity. This paper describes the use of a nonequilibrium reaction-diffusion process to achieve the synthesis of a multifunctional stimuli-responsive electrically conductive metal-organic framework (cMOF) in a gelled medium with control over particle size and spatial periodicity on a macroscopic scale. Upon integration into chemiresistive devices, the resulting cMOF particles exhibit a size-dependent response toward hydrogen sulfide gas, as determined by their distinct surface-to-volume ratio, porosity, unique synthesis methodology, and unusual microcrystallite morphology compared to their counterparts obtained through bulk solution phase synthesis. Taken altogether, these achievements pave the way toward gaining access to functional nanomaterials with well-defined chemical composition, dimensions, and precisely tailored functions using far-from-equilibrium approaches.

Molecular Photoelectrocatalysis for Radical Reactions.

ConspectusMolecular photoelectrocatalysis, which combines the merits of photocatalysis and organic electrosynthesis, including their green attributes and capacity to offer novel reactivity and selectivity, represents an emerging field in organic chemistry that addresses the growing demands for environmental sustainability and synthetic efficiency. This synergistic approach permits access to a wider range of redox potentials, facilitates redox transformations under gentler electrode potentials, and decreases the use of external harsh redox reagents. Despite these potential advantages, this area did not receive significant attention until 2019, when we and others reported the first examples of modern molecular photoelectrocatalysis. These studies showcased the immense synthetic potential of this hybrid strategy, which not only inherits the strengths of its parent fields but also unlocks unprecedented reactivity and selectivity, enabling challenging transformations under mild conditions while minimizing the reliance on external stoichiometric harsh oxidants or reductants.In this Account, we present our efforts to develop photoelectrocatalytic strategies that leverage homogeneous catalysts to facilitate diverse radical reactions. By integrating electrocatalysis with key photoinduced processes such as single electron transfer (SET), ligand-to-metal charge transfer (LMCT), and hydrogen atom transfer (HAT), we have established photoelectrocatalytic methods to transform substrates such as organotrifluoroborates, arenes, carboxylic acids, and alkanes into reactive radical intermediates. These intermediates subsequently engage in heteroarene C-H functionalization reactions. Importantly, under these photoelectrochemical conditions with homogeneous catalysts, reactive radical intermediates generated in the bulk solution readily participate in efficient radical reactions without undergoing further overoxidation into carbocations, a common challenge in conventional electrochemical systems.By further integration of photoelectrocatalysis with asymmetric catalysis, we have developed photoelectrochemical asymmetric catalysis (PEAC), which proves to be efficient in the enantioselective synthesis of chiral nitriles. This approach involves two relay catalytic cycles: the initial photoelectrocatalytic process engenders benzylic radicals from precursors such as alkyl arenes, benzylic carboxylic acids, and aryl alkenes, and these C-radicals are then subjected to enantioselective cyanation in a subsequent copper-electrocatalytic cycle.Within the realm of oxidative photoelectrochemical transformations, the anode serves as a crucial component for recycling or generating the photocatalyst, while the cathode promotes proton reduction. This dual functionality enables oxidative transformations via H2 evolution, eliminating the reliance on external chemical oxidants. Furthermore, the adaptability of electrochemical systems, achieved through precise manipulation of electric current or potential, ensures meticulous control over the generation and turnover of multiple catalytic species of diverse electrochemical properties. This unique tunability allows for exceptional control over the catalytic process. As a result, despite being a relatively nascent field, molecular photoelectrocatalysis has become instrumental in enabling numerous challenging transformations that were once difficult or required harsh conditions.

Temperature Induced Unfolding and Compaction of Cytochrome c in the Same Aqueous Solutions.

Most conventional methods used to measure protein melting temperatures reflect changes in structure between different conformational states and are typically fit to a two-state model. Population abundances of distinct conformations were measured using variable-temperature electrospray ionization ion mobility mass spectrometry to investigate the thermally induced unfolding of the model protein cytochrome c. Nineteen conformers formed at high temperature have elongated structures, consistent with unfolded forms of this protein. However, one conformer that is more compact than the native state of the protein is also formed from this same solution upon heating. The abundance of this compact conformer increases with temperatures up to 90 °C. Rapid mixing and collision-induced gas-phase unfolding experiments demonstrate that formation of this compact conformer is not an artifact of rapid refolding during the ESI process or structural rearrangement in the gas-phase, and therefore the compact conformer must be formed in bulk solution at higher temperatures. The main folded conformer at 90 °C has a cross section that is ∼30 Å2 larger than that at 27 °C. Results from collision-induced unfolding experiments indicate that they have different gas-phase stabilities that are not directly related to differences in their initial internal energies upon transitioning into the gas phase and therefore have different structures. These results demonstrate the advantage of mass and ion mobility measurements for investigating protein conformational landscapes and provide the first evidence for formation of both unfolded and more compact conformations of a protein from the same solution upon heating.

Unravelling the cleavage-rate relationship from both the experimental and theoretical standpoint: The instance of fluorite dissolution.

The phenomenon of solid dissolution into a solution constitutes a fundamental aspect in both natural and industrial contexts. Nevertheless, its intricate nature at the microscale poses a significant challenge for precise quantitative characterization at a foundational level. In this work, the influence across three specific cleavage planes, namely (100), (111), and (110) on the dissolution kinetics of fluorite in aqueous environments was examined from both experimental and theoretical standpoints. For the very first time, the surface potential of fluorite planes during dissolution was measured by means of a fluorite single-crystal electrode. Experimental results indicate that the dissolution of fluorite leads to a marked increase in surface roughness as well as an augmentation in the surface area of all analyzed surfaces. The most significant alteration in roughness is observed on the (111) plane, whereas the most substantial increase in surface area occurs on the (110) plane. In comparison to the (100) crystallographic plane, which demonstrates the slowest dissolution kinetics, the (111) and (110) planes display dissolution at a comparatively expedited rate. Theoretical simulations corroborate this trend, concurrently facilitating an effective examination of the system's free-energy landscape to analyze the dynamics and rates associated with the attachment and detachment of ions to the fluorite surface. Notably, the presence of interfacial defects has the potential to influence the free energy landscape, thereby altering the transition of ions into the bulk solution. Ultimately, the interplay of correlations and discrepancies between experimental findings and theoretical predictions is critically examined.

Excitation wavelength-dependent quantum yield in water-soluble CdTe quantum dots.

The quantum yield (QY) of semiconductor quantum dots (QDs) is severely hampered by the inherent fluorescence intermittency. The QY of QDs typically increases with an increase in the excitation wavelength. Here, we present a distinctive behavior, where the QY is found to decrease with an increase in the excitation wavelength in water-soluble CdTe QDs (CQDs). Single-particle level measurements highlight the increase in permanent single dark particles at longer wavelengths that comprehend the overall QY of the CQDs in bulk solution. Fluorescence correlation spectroscopy further revealed an increase in the number of dark particles at longer wavelengths. As confirmed by D2O/H2O exchange, the presence of H+ ions in water plays an important role in creating variable permanently dark states in the CQDs. This observation was further supported by the cell internalization study of the CQDs, where a much brighter image at a shorter wavelength than at a longer wavelength was observed. A study of the excitation wavelength-dependent QY in QDs may reveal new insights into the applicability of QDs in different device fabrication cases.

Why do some metal ions spontaneously form nanoparticles in water microdroplets? Disentangling the contributions of the air-water interface and bulk redox chemistry.

Water microdroplets containing 100 μM HAuCl4 have been shown to reduce gold ions into gold nanoparticles spontaneously. It has been suggested that this chemical transformation takes place exclusively at the air-water interface of microdroplets, albeit without mechanistic insights. We compared the fate of several metallic salts in water, methanol, ethanol, and acetonitrile in the bulk phase and microdroplet geometry (sprays). Experiments revealed that when HAuCl4 (or PtCl4) is added to bulk water (or methanol or ethanol), metal NPs appear spontaneously. Over time, the nanoparticles grow, evidenced by the bulk solutions' changing colors. If the bulk solution is sprayed pneumatically and microdroplets are collected, the NP size distribution is not significantly enhanced. We find that the reduction of metal ions is accompanied by the oxidation of water (or alcohols); however, these redox reactions are minimal in acetonitrile. This establishes that the spontaneous reduction of metal ions is (i) a bulk phase phenomenon in water and several non-aqueous solutions, (ii) minimally affected by the air-water interface or the microdroplet geometry, and (iii) is not limited to Au3+ ions and can be explained via the electrochemical series. These results advance our understanding of aquatic chemistry and liquids in general and should be relevant in soil chemistry, biogeochemistry, electrochemistry, and green chemistry.

Witnessing a discrete microdroplet freezing event via real-time electrochemical monitoring of solution temperature.

Temperature monitoring has immediate relevance to many areas of research, from atmospheric environmental studies to biological sample and food preservation to chemical reactions. Here, we use a triple-barrel electrode to provide temperature readouts in bulk solution and microdroplets, as well as electrochemically monitor freezing events in a microdroplet. Using this method, we are able to identify distinct characteristics of a freezing aqueous droplet (supercooling, ice formation beginning and end, temperature change, and thawing) with greater temporal resolution than a standard thermocouple and without the use of microscopy. By correlating the amperometric signal change caused by alterations in the diffusion coefficient of the electrochemical system in response to temperature changes, we can calculate the instantaneous temperature at our electrode, as well as the physical behavior of ice formation and expansion. Our results suggest that these electrochemical techniques can provide real-time monitoring of the physical processes involved in aqueous temperature change and ice nucleation events. Here, we employ a novel technique using triple-barrel electrodes to provide temperature readouts in bulk solution and microdroplets, as well as electrochemically monitor freezing events in a microdroplet. Because ice nucleation spans many research fields, it is important to have a variety of tools that can be used to better understand these frozen systems. Our data shows that electrochemistry can provide real-time information on the thermal properties of aqueous environments, and these types of measurements can be extended to microdroplets. The electrochemical signal details all the significant moments in a droplet freezing event, allowing us to use electrochemistry as a stand-alone tool for monitoring freezing events with excellent temporal and spatial resolution.

Efficiently catalytic ozonation of 2,4-dichlorophenoxyacetic acid by natural ferrihydrite: A pH dependent and surface -OH group involved reaction mechanism

The heterogeneous catalytic ozonation with natural iron oxides has been proven to be a powerful technology for the removal of recalcitrant organics in water due to the involvement of reactive oxygen species. However, little information can be obtained about the performance of Ferrihydrite in catalytic ozonation especially the relavant reaction mechanism. In this study, Ferrihydrite was synthesized via a simple precipitation method and 2,4-Dichlorophenoxyacetic acid (2,4-D) degradation was used to evaluate its catalytic ozonation performance. Compared with sole ozonation, Ferrihydrite had an excellent activity in catalytic ozonation and 2,4-D was always efficiently degraded (> 90%) at a wide pH range (3.0-8.0). Electron spin resonance (ESR) and radical scavenging tests proved that •OH and O2•- were the dominant reactive oxygen species (ROS) in 2,4-D degradation (92.33% vs. 77.4% in ozone alone) and mineralization (63% vs. 16.2% in ozone alone). Based on a series of characterizations, Ferrihydrite processed a higher BET area and surface -OH groups than other iron oxides such as FeOOH, Fe2O3 and Fe3O4. The efficiently exposed surface -OH group with a high density was the reactive centers for the generation of ROS. Importantly, pHPZC of Ferrihydrite (6.3) and pKa of 2,4-D (2.73) induced a pH-dependent 2,4-D removal patterns (surface reaction at pH < 6.3 and reaction in bulk solution at pH > 6.3) were proposed via the electrostatic attraction or repulsion between the hydrogenated/hydroxylated surface of Ferrihydrite and negative charged 2,4-D.

Electrochemical kinetic fingerprinting of single-molecule coordinations in confined nanopores.

Metal centers are essential for enzyme catalysis, stabilizing the active site, facilitating electron transfer, and maintaining the structure through coordination with amino acids. In this study, K238H-AeL nanopores with histidine sites were designed as single-molecule reactors for the measurement of single-molecule coordination reactions. The coordination mechanism of Au(III) with histidine and glutamate in biological nanopore confined space was explored. Specifically, Au(III) interacts with the nitrogen (N) atom in the histidine imidazole ring of the K238H-AeL nanopore and the oxygen (O) atom in glutamate to form a stable K238H-Au-Cl2 complex. The formation mechanism of this complex was further validated through single-molecule nanopore analysis, mass spectrometry, and molecular dynamics simulations. Introducing histidine and negative charge amino acids with carboxyl group into different positions within the nanopore revealed that the formation of the histidine-Au coordination bond in the confined space requires a suitable distance between the ligand and the central metal atom. By analyzing the association and dissociation rates of the single Au(III) ion under the applied voltages, it was found that a confined nanopore increased the bonding rate constant of Au(III)-histidine coordination reactions by around 10-100 times compared to that in the bulk solution and the optimal voltage for single-molecule. Therefore, nanopore techniques for tracking single-molecule reactions could offer valuable insights into designing metalloenzymes in metal-catalyzed organic reactions.

Unveiling hidden reaction kinetics of carbon dioxide in supercritical aqueous solutions

Dissolution of CO2 in water followed by the subsequent hydrolysis reactions is of great importance to the global carbon cycle, and carbon capture and storage. Despite numerous previous studies, the reactions are still not fully understood at the atomistic scale. Here, we combined ab initio molecular dynamics (AIMD) simulations with Markov state models to elucidate the reaction mechanisms and kinetics of CO2 in supercritical water both in the bulk and nanoconfined states. The integration of unsupervised learning with first-principles data allows us to identify complex reaction coordinates and pathways automatically instead of a priori human speculation. Interestingly, our unbiased modeling found an unknown pathway of dissolving CO2(aq) under graphene nanoconfinement, involving the pyrocarbonate anion [C2O[Formula: see text](aq)] as an intermediate state. The pyrocarbonate anion was previously hypothesized to have a fleeting existence in water; however, our study reveals that it is a crucial reaction intermediate and stable carbon species in the nanoconfined solutions. We even observed the formation of pyrocarbonic acid [H2C2O5(aq)], which was unknown in water, in our AIMD simulations. The unexpected appearance of pyrocarbonates is related to the superionic behavior of the confined solutions. We also found that carbonation reactions involve collective proton transfer along transient water wires, which exhibits concerted behavior in the bulk solution but proceeds stepwise under nanoconfinement. The first-principles Markov state models show substantial promise for elucidating complex reaction kinetics in aqueous solutions. Our study highlights the importance of large oxocarbons in aqueous carbon reactions, with great implications for the deep carbon cycle and the sequestration of CO2.

Density-dependent flow generation in active cytoskeletal fluids

The actomyosin cytoskeleton, a protein assembly comprising actin fibers and the myosin molecular motor, drives various cellular dynamics through contractile force generation at high densities. However, the relationship between the density dependence of the actomyosin cytoskeleton and force-controlled ordered structure remains poorly understood. In this study, we measured contraction-driven flow generation by varying the concentration of cell extracts containing the actomyosin cytoskeleton and associated nucleation factors. We observed continuous actin flow toward the center at a critical actomyosin density in cell-sized droplets. The actin flow exhibited an emergent oscillation in which the tracer advection in the bulk solution periodically changed in a stop-and-go fashion. In the vicinity of the actomyosin density where oscillatory dynamics occur, the velocity of tracer particle motion decreases with actomyosin density but exhibits superdiffusive motion. Furthermore, the increase or decrease in myosin activity causes the oscillatory flow generation to become irregular, indicating that the density-dependent flow generation of actomyosin is driven by an interplay between actin density and myosin force generation.

Biomass-burning organic aerosols as a pool of atmospheric reactive triplets to drive multiphase sulfate formation

Biomass-burning organic aerosol(s) (BBOA) are rich in brown carbon, which significantly absorbs solar irradiation and potentially accelerates global warming. Despite its importance, the multiphase photochemistry of BBOA after light absorption remains poorly understood due to challenges in determining the oxidant concentrations and the reaction kinetics within aerosol particles. In this study, we explored the photochemical reactivity of BBOA particles in multiphase S(IV) oxidation to sulfate. We found that sulfate formation in BBOA particles under light is predominantly driven by photosensitization involving the triplet excited states (3BBOA*) instead of iron, nitrate, and S(IV) photochemistry. Rates in BBOA particles are three orders of magnitude higher than those observed in the bulk solution, primarily due to the fast interfacial reactions. Our results highlight that the chemistry of 3BBOA* in particles can greatly contribute to the formation of sulfate, as an example of the secondary pollutants. Photosensitization of BBOA will likely become increasingly crucial due to the intensified global wildfires.

Conjugation Chemistry Markedly Impacts Toxicity and Biodistribution of Targeted Nanoparticles, Mediated by Complement Activation.

Conjugation chemistries are a major enabling technology for the development of drug delivery systems, from antibody-drug conjugates to antibody-targeted lipid nanoparticles inspired by the success of the COVID-19 vaccine. However, here it is shown that for antibody-targeted nanoparticles, the most popular conjugation chemistries directly participate in the activation of the complement cascade of plasma proteins. Their activation of complement leads to large changes in the biodistribution of nanoparticles (up to 140-fold increased uptake into phagocytes of the lungs) and multiple toxicities, including a 50% drop in platelet count. It is founded that the mechanism of complement activation varies dramatically between different conjugation chemistries. Dibenzocyclooctyne, a commonly used click-chemistry, caused aggregation of conjugated antibodies, but only on the surface of nanoparticles (not in bulk solution). By contrast, thiol-maleimide chemistry do not activate complement via its effects on antibodies, but rather because free maleimide bonded to albumin in plasma, and clustered albumin is then attacked by complement. Using these mechanistic insights, solutions are engineered that reduced the activation of complement for each class of conjugation chemistry. These results highlight that while conjugation chemistry is essential for the future of nanomedicine, it is not innocuous and must be designed with opsonins like complement in mind.

Ion Effects on Terahertz Spectra of Microsolvated Clusters.

Water clusters containing Na+ and Cl- ions play a key role in the atmospheric chemistry of sea salt aerosols. While Na+ is clearly buried deep inside, Cl- appears to be a chameleon since evidence for both surface-localized and interior solvation states are reported. Thus, disclosing the preferred location of Cl- within clusters remains challenging. Here, we investigate whether THz spectroscopy, a powerful tool for directly probing hydrogen bonds in water, provides insights into the location of Cl- ions in water clusters. We performed ab initio molecular dynamics simulations on water clusters containing a single Cl- ion and up to 64 water molecules to compute the THz spectra with reference to Na+ and bulk. The THz spectrum of the 64-water Cl- cluster closely agrees with that of the bulk solution. Surprisingly, this match is not caused by bulk-like solvation of Cl- as suggested by phenomenological line shape analyses. Instead, the similarity stems from Cl- being mostly located at the cluster surface, thus leaving the water-water interactions largely unperturbed.

Binding of Sulfates and Water to Monovalent Cations.

The binding of the sulfate ligand group to monovalent cations in the presence of water is important for many systems. To understand the structure and energetics of sulfate complexes, we use density functional theory to study ethyl sulfate binding to the monovalent cations Li+, Na+, and K+, and to water. The free energies of binding and optimal structures are calculated for a range of the number of ethyl sulfates and waters. Without water, the most optimal structure for all the cations is bidentate binding by two ethyl sulfates, yielding a 4-fold coordination. With water, the lowest free energy structures also have two ethyl sulfates, but the coordination varies with cations. For complexes with water, the four oxygen atoms in the sulfate group enable multiple binding geometries for the cations and for hydrogen bonding with water. Many of these geometries differ in free energy by only a small amount (1-2 kcal/mol), meaning there will be multiple binding configurations in bulk solution. In comparison to the optimal structures for binding to the carboxylate group, there is more variation for binding to the sulfate group as a function of cation type and the number of waters. The polarization of the atoms is significant and varies among the sulfate oxygen atoms. The water oxygen charge is often larger than that of sulfate oxygen, which plays a role in the preference for monodentate ligand binding to cations in the presence of water.

Productivity and aseptic process evaluation during batch production simulation of intravenous medications using a semi-automated compounding device.

Intravenous (IV) medications can be prepared using compounding devices to increase productivity, and reduce risks associated with aseptic compounding. This study evaluated the productivity and quality outcomes of the aseptic process for simulated batches of IV medications used in clinical practice produced using a semi-automated compounding device (Gri-fill; Grifols). Simulated batches from 50 to 600 preparations were completed representing hazardous and non-hazardous drugs, including one-step single component (atropine sulfate, cisplatin) and multistep, multiple component (mitomycin C, piperacillin/tazobactam, trastuzumab, 5-fluorouracil and gemcitabine). Productivity, device autonomy, quality of the aseptic process (media-fill test) and sterility of the preparations were evaluated. A total of 2024 final preparations and 460 intermediate products were compounded during 78 working hours. For low and high complexity level preparations, median (minimum-maximum) production speed was 1.3 (0.6-1.7) and 3.7 (2.6-4.3) min per preparation, respectively. The longest process (36.2 min/bag) was the preparation of a simulated gemcitabine 3 L bulk solution bag, which included reconstitution of vials and filling the bulk bag. All operational errors (0.6%) were resolved autonomously by the user. None of the 883 media fill preparations showed microbiological growth and all 114 analyzed preparations passed the sterility test. Using a semi-automated compounding device, preparation efficiency of IV medications ranged from 14 preparations/h for multicomponent preparations from vials requiring reconstitution, to 100 preparations/h for low complexity preparations using a bulk solution bag. The aseptic processes demonstrated the absence of microbial growth in all tested preparations.

Modulation of Ion Transport in Nanopores Using Polyethylene Glycol.

Ion transport in nanopores is crucial for various biological and technological processes, exhibiting unique behaviors compared to bulk solutions. In this study, we systematically explore how polyethylene glycol (PEG) modulates ion transport within a conical nanopore. Our experiments reveal that introducing PEG into the ionic solution induces a reversal in ion current rectification (ICR). We further investigate the impact of PEG concentration, molecular weight, nanopore size, and cation type on ion transport. Additionally, we assess three different configurations of PEG introduction, identifying diffusive flow driven by an asymmetric cation distribution within the nanopore as a dominant transport mechanism. Our results confirm that the interactions between PEG and cations significantly affect ion transport properties. These findings advance our understanding of macromolecular crowding effects on ion transport and suggest potential applications in iontronic devices and biomolecule sensing.