Cl Ions Research Articles

Natural Disinfection-like Process Unveiled in Soil Microenvironments by Enzyme-Catalyzed Chlorination.

Substantial natural chlorination processes are a growing concern in diverse terrestrial ecosystems, occurring through abiotic redox reactions or biological enzymatic reactions. Among these, exoenzymatically mediated chlorination is suggested to be an important pathway for producing organochlorines and converting chloride ions (Cl-) to reactive chlorine species (RCS) in the presence of reactive oxygen species like hydrogen peroxide (H2O2). However, the role of natural enzymatic chlorination in antibacterial activity occurring in soil microenvironments remains unexplored. Here, we conceptualized that heme-containing chloroperoxidase (CPO)-catalyzed chlorination functions as a naturally occurring disinfection process in soils. Combining antimicrobial experiments and microfluidic chip-based fluorescence imaging, we showed that the enzymatic chlorination process exhibited significantly enhanced antibacterial activity against Escherichia coli and Bacillus subtilis compared to H2O2. This enhancement was primarily attributed to in situ-formed RCS. Based on semiquantitative imaging of RCS distribution using a fluorescence probe, the effective distance of this antibacterial effect was estimated to be approximately 2 mm. Ultrahigh-resolution mass spectrometry analysis showed over 97% similarity between chlorine-containing formulas from CPO-catalyzed chlorination and abiotic chlorination (by sodium hypochlorite) of model dissolved organic matter, indicating a natural source of disinfection byproduct analogues. Our findings unveil a novel natural disinfection process in soils mediated by indigenous enzymes, which effectively links chlorine-carbon interactions and reactive species dynamics.

Oxalate anions-intercalated NiFe layered double hydroxide as a highly active and stable electrocatalyst for alkaline seawater oxidation

Seawater electrolysis is gaining recognition as a promising method for hydrogen production. However, severe anode corrosion caused by the high concentration of chloride ions (Cl–) poses a challenge for the long-term oxygen evolution reaction. Herein, an anti-corrosion strategy of oxalate anions intercalation in NiFe layered double hydroxide on nickel foam (NiFe-C2O42– LDH/NF) is proposed. The intercalation of these highly negatively charged C2O42– serves to establish electrostatic repulsion and impede Cl– adsorption. In alkaline seawater, NiFe-C2O42– LDH/NF requires an overpotential of 337 mV to gain the large current density of 1000 mA cm−2 and operates continuously for 500 h. The intercalation of C2O42– is demonstrated to significantly boost the activity and stability of NiFe LDH-based materials during alkaline seawater oxidation.

Reduction effect of coercivity of electroplated Fe-Pt film magnets by chloride ion in plating baths

We recently reported the electroplating of Fe-Pt thick films using plating baths with varying concentrations of NaCl, suggesting the potential for coercivity enhancement by Na ions. In the present study, our focus shifted to not Na ions but Cl ones, and we investigated the effect of the Cl ions on the crystal structures and magnetic properties of electroplated Fe-Pt films. With the increasing concentration of Cl ions, the coercivity of the films decreased. Furthermore, XRD analysis suggested that the Cl ions in the plating baths prevent the L10 ordering of the Fe-Pt crystalline phase, leading us to conclude that a Cl-free bath is favorable for preparing Fe-Pt thick-film magnets with high coercivity.

Delineation of Soil Physical and Chemical Properties of Mahisagar District of Gujarat, India

The successful implementation of sustainable agriculture practices relies on maintaining a favorable physical and chemical environment in the soil. This study aimed to assess the soil properties of Mahisagar district in Gujarat, focusing on both physical and chemical aspects. A total of 180 surface soil samples (0-15 cm depth) were collected from cultivated fields in six talukas during April-May 2018. Key indicators, including bulk density, particle density, porosity, moisture-holding capacity (MWHC), electrical conductivity (EC2.5), pH2.5, free lime, organic carbon, and cation exchange capacity (CEC), were analyzed to provide a comprehensive understanding of the soil's characteristics. The results indicated that mean bulk density and particle density value of the soils of Mahisagar district was 1.32 and 2.53 Mg m-3 respectively, while porosity with a mean value of 47.97 per cent. The overall range of MWHC was with a mean value of 45.97 per cent. The soils of Mahisagar district were high in organic carbon content and non-calcareous in nature with alkaline in reaction. The mean EC2.5 value in the soils of Mahisagar district was (0.38 dS m-1). The mean CEC value was 24.47 cmol (p+) kg-1. among the exchangeable cations Ca++ and Mg++ was dominance in soil, while water soluble ions Cl- and Mg++ were found in higher proportion in Mahisagar district of Gujarat.

A new strategy for prediction of water qualitative and quantitative parameters by deep learning-based models with determination of modelling uncertainties

ABSTRACT This study presents a new method based on three types of deep learning-based models (DLM) for estimation of water parameters. The DLM models were recurrent neural networks (RNN), long short-term memory (LSTM), and bidirectional long short-term memory (BiLSTM). The study areas were the Colorado River basin in the United States and the Mighan Wetland in Iran. The electrical conductivity (EC), dissolved oxygen (DO), total dissolved solids (TDS), chloride ions (Cl), and river flow rate (debi) were simulated by the DLM models. The Wilson score (WS) uncertainty analysis results for Colorado modelling showed that LSTMdebi, RNNDO, and RNNEC were the best models in simulating due to having the lowest errors (Mean ei equal to 0.36, −1.50, and −0.59), respectively. Finally, the highest value of the R2 index, 0.998, was achieved by the LSTM model in modelling the debi parameter, and 0.996 in EC modelling, in the Mighan Wetland.

Co-Self-Assembled Monolayers Modified NiOx for Stable Inverted Perovskite Solar Cells.

[4-(3,6-dimethyl-9H-carbazol-9yl)butyl]phosphonic acid (Me-4PACz) self-assembled molecules (SAM) are an effective method to solve the problem of the buried interface of NiOx in inverted perovskite solar cells (PSCs). However, the Me-4PACz end group (carbazole core) cannot forcefully passivate defects at the bottom of the perovskite film. Here, a Co-SAM strategy is employed to modify the buried interface of PSCs. Me-4PACz is doped with phosphorylcholine chloride (PC) to form a Co-SAM to improve the monolayer coverage and reduce leakage current. The phosphate group and chloride ions (Cl-) in PC can inhibit NiOx surface defects. Meantime, the quaternary ammonium ions and Cl- in PC can fill organic cations and halogen vacancies in the perovskite film to enable defects passivation. Moreover, Co-SAM can promote the growth of perovskite crystals, collaboratively solve the problem of buried defects, suppress nonradiative recombination, accelerate carrier transmission, and relieve the residual stress of the perovskite film. Consequently, the Co-SAM modified devices show power conversion efficiencies as high as 25.09% as well as excellent device stability with 93% initial efficiency after 1000 h of operation under one-sun illumination. This work demonstrates the novel approach for enhancing the performance and stability of PSCs by modifying Co-SAM on NiOx.

Hybrid radical coupling during MnO2-mediated transformation of a mixture of organic UV filters: Chemistry and toxicity assessment

Manganese oxide (MnO2) is one of the most abundant metal oxides, and it is renowned for its ability to degrade various phenolic micropollutants. However, under MnO2-mediated transformation, BP-3 transforms into 12 different radical-coupled transformation products (TPs) out of 15 identified TPs. These radical-coupled TPs are reported with adverse environmental impacts. This study explored the effects of MnO2 on organic UV filter mixtures and different water constituents (i.e., bicarbonate ion (HCO3−), humic acid (HA) and halide ions) in terms of degradation efficiency and transformation chemistry. When a mixture of benzophenone-3 (BP-3) and avobenzone (AVO) underwent transformation by MnO2, hybrid radical-coupled TPs derived from both organic UV filters were generated. These hybrid radical-coupled TPs were evaluated by an in silico prediction tool and Vibrio fischeri bioluminescence inhibition assay (VFBIA). Results showed that these TPs were potentially toxic to aquatic organisms, even more so than their parent compounds. The higher the concentration of HCO3−, HA, chloride ion (Cl−) and bromide ion (Br−), the greater the reduction in the efficiencies of degrading BP-3 and AVO. Contrastingly, in the presence of iodide ion (I−), degradation efficiencies of BP-3 and AVO were enhanced; however, iodinated TPs and iodinated radical-coupled TPs were formed, with questionable toxicity. This study has revealed the environmental risks of hybrid radical-coupled TPs, iodinated TPs and iodinated radical-coupled TPs when the organic UV filters BP-3 and AVO are transformed by MnO2.

A Transparent Hydrogel-Ionic Conductor with High Water Retention and Self-Healing Ability.

This study presents a transparent and ion-conductive hydrogel with suppressed water loss. The hydrogel comprises agarose polymer doped with sucrose and sodium chloride salt (NaCl-Suc/A hydrogel). Sucrose increases the water retention of the agarose gel, and the Na and Cl ions dissolved in the gel provide ionic conductivity. The NaCl-Suc/A gel shows high retention capability and maintains a 45% water uptake after 4 h of drying at 60 °C without encapsulation at the optimum gel composition. The doped NaCl-Suc/A hydrogel demonstrates improved mechanical properties and ionic conductivity of 1.6 × 10-2 (S/cm) compared to the pristine agarose hydrogel. The self-healing property of the gel restores the electrical continuity when reassembled after cutting. Finally, to demonstrate a potential application of the ion-conductive hydrogel, a transparent and flexible pressure sensor is fabricated using the NaCl-Suc/A hydrogel, and its performance is demonstrated. The results of this study could contribute to solving problems with hydrogel-based devices such as rapid dehydration and poor mechanical properties.

Numerical simulation of copper electrodeposition for Through Silicon Via (TSV) with SPS-PEG-Cl additive system

Through silicon via (TSV) technology is crucial for modern semiconductor device package, enabling high-performance integrated microsystems. This paper investigates the mechanism of the bottom-up copper deposition process in TSV, leveraging a co-adsorbed polyether-Cl-suppression layer and accelerators for optimized filling profiles. We present numerical simulations of the effects of additives (accelerator, suppressor) and chloride ions (Cl−) on the TSV filling. By varying the substance concentration, we obtain three distinct filling models, including filling with voids, conformal filling and bottom-up filling. We analyzed the distribution of various substances and current densities to elucidate the filling mechanism. Furthermore, TSV filling experiments were conducted, and the simulated profiles were in good match with the filling experiments. It is verified that the feasibility of the proposed numerical model by generalizing to 90μm × 180 μm, 50μm × 100 μm, and 10μm × 100 μm via holes of different sizes and aspect ratios.

Mechanism of anodic activation of chloride to generate singlet oxygen for fast organic removal using an innovative anode

Electrochemical persulfate activation (E-PS) has recently emerged as a highly effective advanced oxidation process in water decontamination. However, the presence of chloride ions (Cl−) in waters can accelerate anodic corrosion as well as lead to the formation of toxic chlorinated byproducts (i.e., ClO4−), limiting its practical application. In this study, we introduce a novel Nd/Bi@SnO2 anode to construct E-PS, which exhibits high stability in chloride-containing water with a long-expected service lifetime of 13.7 years. The Nd/Bi@SnO2 electrode can effectively convert Cl− to reactive chlorine with the assistance of PMS, triggering singlet oxygen (1O2) generation for superior organic removal while avoiding toxic chlorinated byproducts (i.e., ClO4−) generation as well as greatly reducing the energy consumption. Comprehensive structural and electrochemical characterization results demonstrate Nd/Bi co-doping introduces oxygen vacancy on Nd/Bi@SnO2, enabling the anode with high oxygen evolution potential, excellent conductivity and superior stability. Scavenging experiments and electron paramagnetic resonance illustrate the generation of various reactive species in the system, among which 1O2 predominantly contributes to organic removal and results in harmless intermediates. This innovative approach transforms Cl− into ROSs for eco-friendly, energy-efficient water decontamination.

Deciphering the influence of PdII and PdIV oxidation states on non-standard chemical bonds within bis(jN-heterocyclic carbene) complexes: insights from DFT.

Bis-N-heterocyclic carbene ligands (bis(NHC)) have introduced a new approach to designing homogeneous and heterogeneous catalysts, demonstrating the versatility of ligand concepts in catalysis. This study presents a computational analysis of palladium (+ii and +iv) complexes containing either a normally (bis(nNHC)) or an abnormally (bis(aNHC)) bound CH2-bridged bis-N-heterocyclic carbene ligand; in addition, ancillary ligands are permuted from chlorides (X = Cl) to bromides (X = Br). Density functional theory at the B3PW91/6-31G(d)/Lanl2DZ level in the gas phase was used to investigate the electronic structure and bonding properties of bis(NHC)PdIIX2 and bis(NHC)PdIVX4 for bis(NHC) palladium(ii) dihalide and palladium(iv) tetrachloride complexes, respectively. Results indicate that all of the palladium complex structures prefer a flexible boat-type conformation with an average C 2v symmetry, according to bond property (Ccarbene-Pd and Pd-Cl[Br]) analysis. The strength of these bonds depends on coordinating halide ions (Cl- and Br-), the type of ligand (bis(nNHC) and bis(aNHC)), and the palladium oxidation state (+ii and +iv). Analysis of thermodynamic parameters (ΔH 0, ΔG 0, and ΔE bind) shows an increase in values from an abnormal to normal chelating mode in tetrahalides, whereas the opposite is observed for dihalide complexes. The lower π-backbonding ability of the metal, which is influenced by the quantity and size of halide ions involved, could be one possible explanation for this deficiency.

Dual light-responsive shape transformations of a nanocomposite hydrogel sheet enabled by in situ etching shaped plasmonic nanoparticles.

We report here on dual shape transformations of the same thermo-responsive hybrid hydrogel sheet under irradiation of a laser with two different wavelengths (808 nm and 450 nm). By in situ etching the silver nanoprisms in the sheet to silver nanodiscs by using chloride ions (Cl-), two areas with distinct light extinction properties are integrated in a single sheet. The conversion of photon energy to thermal energy in local areas by the silver nanoprisms or nanodiscs under laser irradiation with an appropriate wavelength heats up the sheet locally and causes a local volumetric shrinkage, and hence a volumetric mismatch in different areas in the sheet. The sheet then transforms in a specific way to accommodate this volumetric mismatch. Different patterns of silver nanoprisms and nanodiscs in the sheet are achieved by controlling the delivery patterns of the etchant Cl-. We demonstrate that by designing the distribution pattern of silver nanoprisms and nanodiscs in the sheet, the same hybrid sheet transforms either to a saddle or to a helical twisted shape, while with another type of distribution pattern, it transforms either to a hoof-like or to a boat-like shape under the irradiation of a laser with a wavelength of either 808 nm or 450 nm. We point out that to program arbitrary curvature of the transformed shape of our sheet, the pattern size of silver nanoprisms and nanodiscs (i.e. actuation area) in the sheet needs to be largely reduced, which however limits the heat generated and hence the shape transformations. Factors that affect the sheet's shape transformations are discussed and solutions are suggested to enhance its performance. The hybrid sheet may find applications in soft robotics, for example, as a robotic finger.

Multi-stimuli-responsive polymer degradation by polyoxometalate photocatalysis and chloride ions.

Photocatalytic polymer degradation based on harnessing the abundant light energy present in the environment is one of the promising approaches to address the issue of plastic waste. In this study, we developed a multi-stimuli-responsive photocatalytic polymer degradation system facilitated by the photocatalysis of a polyoxometalate [γ-PV2W10O40]5- in conjunction with chloride ions (Cl-) as harmless and abundant stimuli. The degradation of various polymers was significantly accelerated in the presence of Cl-, which was attributed to the oxidation of Cl- by the polyoxometalate photocatalysis into a highly reactive chlorine radical that can efficiently generate a carbon-centered radical for subsequent polymer degradation. Although organic and organometallic photocatalysts decomposed under the conditions for photocatalytic polymer degradation in the presence of Cl-, [γ-PV2W10O40]5- retained its structure even under these highly oxidative conditions.

High resistance of superconducting TiN thin films against environmental attacks.

Superconductors, an essential class of functional materials, hold a vital position in both fundamental science and practical applications. However, most superconductors, including MgB2, Bi2Sr2CaCu2O8+δ, and FeSe, are highly sensitive to environmental attacks (such as from water and moist air), hindering their wide applications. More importantly, the surface physical and chemical processes of most superconductors in various environments remain poorly understood. Here, we comprehensively investigate the high resistance of superconducting titanium nitride (TiN) epitaxial films against acid and alkali attacks. Unexpectedly, despite immersion in acid and alkaline solutions for over 7 days, the crystal structure and superconducting properties of TiN films remain stable, as demonstrated by high-resolution X-ray diffraction, electrical transport, atomic force microscopy, and scanning electron microscopy. Furthermore, combining scanning transmission electron microscopy analysis with density functional theory calculations revealed the corrosion mechanisms: acid corrosions lead to the creation of numerous defects due to the substitution of Cl ions for N anions, whereas alkaline environments significantly reduce the film thickness through the stabilization of OH* adsorbates. Our results uncover the unexpected stability and durability of superconducting materials against environmental attacks, highlighting their potential for enhanced reliability and longevity in diverse applications.

Hydration Characteristics of High Chloride Cement

High-chloride cement, enriched with calcium chloro aluminate (CCA), a compound of CaO-Al<sub>2</sub>O<sub>3</sub>-CaCl<sub>2</sub>, displays a higher Cl content than ordinatry portland cement. This specialized cement, incorporating limestone, clay, siliceous materials, and Cl-abundant cement kiln dust, is known for its superior early strength, making it an attractive option for resource recycling. However, the excessive Cl content can lead to reinforcement corrosion and a decrease in the durability of the hardened cement paste. Current research has primarily focused on its manufacturing characteristics, with studies on hydration reactions for practical application remaining limited. This study aims to explore the hydration reactions of high-chloride cement to determine its practicality. The experimental results reveal that high-chloride cement with abundant CCA significantly promotes the formation of ettringite, an Al-based hydrate, in the initial hydration stages. This process results in the binding of leached Cl ions with monosulfate, forming Friedel’s salt. Although the early formation of expansive hydrates might negatively affect long-term durability, mixing this cement with ordinary Portland cement in appropriate amounts can improve workability and enhance early strength and setting. Furthermore, the transformation of Cl ions into a crystallographically stable form like Friedel’s salt indicates a potential for safer usage, especially in reducing risks such as reinforcement corrosion.

The Use of Carboxyfluorescein Reveals the Transport Function of MCT6/SLC16A5 Associated with CD147 as a Chloride-Sensitive Organic Anion Transporter in Mammalian Cells

Oral drug absorption involves drug permeation across the apical and basolateral membranes of enterocytes. Although transporters mediating the influx of anionic drugs in the apical membranes have been identified, transporters responsible for efflux in the basolateral membranes remain unclear. Monocarboxylate transporter 6 (MCT6/SLC16A5) has been reported to localize to the apical and basolateral membranes of human enterocytes and to transport organic anions such as bumetanide and nateglinide in the Xenopus oocyte expression system; however, its transport functions have not been elucidated in detail. In this study, we characterized the function of MCT6 expressed in HEK293T cells and explored fluorescent probes to more easily evaluate MCT6 function. The results illustrated that MCT6 interacts with CD147 to localize at the plasma membrane. When the uptake of various fluorescein derivatives was examined in NaCl-free uptake buffer (pH 5.5), the uptake of 5-carboxyfluorescein (5-CF) was significantly greater in MCT6 and CD147-expressing cells. MCT6-mediated 5-CF uptake was saturable with a Km of 1.07 mM and inhibited by several substrates/inhibitors of organic anion transporters and extracellular Cl ion with an IC50 of 53.7 mM. These results suggest that MCT6 is a chloride-sensitive organic anion transporter that can be characterized using 5-CF as a fluorescent probe.

Effect of Sulfide and Chloride Ions on Pitting Corrosion of Type 316 Austenitic Stainless Steel in Groundwater Conditions Using Response Surface Methodology.

This study investigates the corrosion resistance of Type 316 stainless steel as a candidate material for radioactive waste disposal canisters. The viability of stainless steel is examined under groundwater conditions with variations in pH, bisulfide ions (HS-), and chloride ions (Cl-) concentrations. Utilizing response surface methodology, correlations between corrosion factors and two crucial response variables, passive film breakdown potential and protection potential, are established. Cyclic potentiodynamic polarization tests and advanced analytical techniques provide detailed insights into the material's behavior. This research goes beyond, deriving an equation through response surface methodology that elucidates the relationship between the factors and breakdown potential. HS- weakens the passive film and reduces the pitting corrosion resistance of the stainless steel. However, this study highlights the inhibitory effect of HS- on pitting corrosion when Cl- concentrations are below 0.001 M and at equivalent concentrations of HS-. Under these conditions, immediate re-passivation occurs from the destroyed passive film to metal sulfides such as FeS2, MoS2, and MoS3. As a result, no hysteresis loop occurs in the cyclic polarization curve in these conditions. This research contributes to the understanding of Type 316 stainless-steel corrosion behavior, offering implications for the disposal of radioactive waste in geological repositories.

Effect of Chlorine on Copper Electrodissolution

A computational study on the role of adsorbed Cl ions on copper dissolution is presented. Extensive grand canonical Monte Carlo (GCMC) calculations using reactive force-field (ReaxFF) are used to check the formation chlorine (Cl) adlayer structures on Cu (100) surface as a function of the chemical potential (µ). From experimental studies conducted by other researchers it has been observed that Cl adlattice on Cu in c(2X2) at maximum coverage. We observe that at low µ, Cl adlayer is disordered and moves to ordered c(2X2) structure at high µ. The binding energy of Cl, oxygen (O), hydroxide (OH-) and H2O on Cu at different sites is calculated and compared with Density-functional theory (DFT) values. Metal surface is often highly uneven and rough during electrodissolution process. Therefore, we also discuss the adsorption isotherm, disorder-order transformation, and preferential adsorption sites for rough surfaces. Specific anion adsorption (SAA) of Cl involves partial charge transfer to Cu substrate and these effect the type of bond and bond strength which is also briefly discussed. The electrodissolution of Cu in the presence of Cl is modelled using kinetic Monte Carlo simulation to obtain the polarization curve.Keywords: Adsorbed chlorine, electrodissolution, grand canonical monte carlo, molecular dynamics, ReaxFF, kinetic monte carlo.

Evaluation of corrosion inhibition efficiency of chitosan oligosaccharide-derived quaternary ammonium vanillyl aldehyde oligosaccharide derivative for CO2 corrosion control

This study presents the synthesis of a non-toxic, water-soluble chitosan oligosaccharide derivative, quaternary ammonium vanillyl aldehyde oligosaccharide (GCOS), using chitosan oligosaccharide, vanillin, and 2,3-epoxypropyltrimethylammonium chloride as precursors, aimed at serving as a novel eco-friendly corrosion inhibitor. The successful synthesis of the derivative was confirmed through Fourier Transform Infrared Spectroscopy (FTIR) and Proton Nuclear Magnetic Resonance (1H NMR) analysis. The corrosion inhibition properties of GCOS on 20# carbon steel were investigated in a 60 °C CO2-saturated 3.0 wt% NaCl solution employing an array of methods including weight loss measurements, Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), electrochemical characterization, and molecular dynamics simulation. Additionally, the synergistic effect of protonated GCOS with halide ion Cl- on corrosion inhibition was analyzed at the molecular level. The results indicated an enhancement in inhibition efficiency with increasing concentrations of the inhibitor. Weight loss measurements showed a maximum inhibition efficiency of 90.9% at 200 ppm of GCOS after 3 days. The adsorption of GCOS on the carbon steel surface was found to follow the Langmuir adsorption isotherm, predominantly through chemisorption. Potentiodynamic polarization measurements classified GCOS as a mixed-type inhibitor, affecting both anodic and cathodic reactions by blocking the active corrosion sites. SEM and AFM analyses confirmed the formation of a protective inhibitor film on the metal surface. Furthermore, molecular dynamics simulations elucidated the synergistic corrosion inhibition effect between the protonated GCOS molecules and Cl- ions in the acidic solution.

Universal insertion of molecules in ionic compounds under pressure.

Using first-principles calculations and crystal structure search methods, we found that many covalently bonded molecules such as H2, N2, CO2, NH3, H2O and CH4 may react with NaCl, a prototype ionic solid, and form stable compounds under pressure while retaining their molecular structure. These molecules, despite whether they are homonuclear or heteronuclear, polar or non-polar, small or large, do not show strong chemical interactions with surrounding Na and Cl ions. In contrast, the most stable molecule among all examples, N2, is found to transform into cyclo-N5- anions while reacting with NaCl under high pressures. It provides a new route to synthesize pentazolates, which are promising green energy materials with high energy density. Our work demonstrates a unique and universal hybridization propensity of covalently bonded molecules and solid compounds under pressure. This surprising miscibility suggests possible mixing regions between the molecular and rock layers in the interiors of large planets.