Adsorption Behavior Research Articles

Prof. George Whitesides’ Contributions to Self-Assembled Monolayers (SAMs): Advancing Biointerface Science and Beyond

Prof. George Whitesides’ pioneering contributions to the field of self-assembled monolayers (SAMs) have profoundly influenced biointerface science and beyond. This review explores the development of SAMs as highly organized molecular structures, focusing on their role in advancing surface science, biointerface research, and biomedical applications. Prof. Whitesides’ systematic investigations into the effects of SAMs’ terminal group chemistries on protein adsorption and cell behavior culminated in formulating “Whitesides’ Rules”, which provide essential guidelines for designing bioinert surfaces. These principles have driven innovations in anti-fouling coatings for medical devices, diagnostics, and other biotechnological applications. We also discuss the critical role of interfacial water in SAM bioinertness, with studies demonstrating its function as a physical barrier preventing protein and cell adhesion. Furthermore, this review highlights how data science and machine learning have expanded the scope of SAM research, enabling predictive models for bioinert surface design. Remarkably, Whitesides’ Rules have proven applicable not only to SAMs but also to polymer-brush films, illustrating their broad relevance. Prof. Whitesides’ work provides a framework for interdisciplinary advancements in material science, bioengineering, and beyond. The enduring legacy of his contributions continues to inspire innovative approaches to addressing challenges in biomedicine and biotechnology.

Toward Sustainable Non‐Emitting Asphalts: Understanding Diffusion–Adsorption Mechanisms of Hazardous Organic Compounds

AbstractAdvancing sustainable materials requires addressing their environmental impacts, particularly emissions. This study contributes to the development of sustainable, non‐emitting asphalt by providing a detailed understanding of the diffusion and adsorption behaviors of hazardous organic compounds (HOCs) emitted from asphalt. Using molecular simulations and quantum analysis, it is investigated how the diffusion and adsorption characteristics of sulfur‐ and oxygen‐containing HOCs change as aging progresses in asphalt. The results show that oxidation reduces the diffusion rate of HOCs and increases their adsorption energy. Dispersion forces and electrostatic attractions are key mechanisms stabilizing HOCs within the asphalt matrix. As oxidation progresses, hydrogen bonding and polar interactions between asphaltenes and highly polar HOCs become dominant. Among the asphalt components, asphaltenes, followed by resins, have the most significant impact on HOC binding. Additionally, non‐aromatic HOCs exhibit higher diffusion rates than aromatic HOCs. These findings provide crucial insights into the emission mechanisms of asphalt over its service life and offer guidance for designing future, sustainable, emission‐free asphalts. By reducing harmful emissions, this research contributes to pollution control, improved air quality, and the broader goal of sustainable pavement development.

Kinetic Separation of Butane Isomers Using a Formate Metal‐Organic Framework

n‐butane (n‐C4H10) and isobutane (i‐C4H10) are important raw materials in chemical industry. The separation of the two hydrocarbon isomers via distillation is challenging and energy‐consuming. Herein we report the adsorption behavior of a microporous cobalt formate framework [Co3(HCOO)6] for potential kinetic separation of butane isomers. Under ambient condition, [Co3(HCOO)6] shows near adsorption capacity for n‐C4H10 (1.77 mmol g−1) and i‐C4H10 (1.36 mmol g−1) with different adsorption kinetics. Study on the adsorption kinetic for butane indicates that the smaller isomer is adsorbed at a higher diffusion rate, resulting in a high kinetic selectivity of 193 for n‐C4H10/i‐C4H10 separation. Analyses of adsorption kinetics and breakthrough experiment have validated the separation potential of [Co3(HCOO)6] for butane purification.

Adsorption and Bulk Assembly of Quaternized Hydroxyethylcellulose–Anionic Surfactant Complexes on Negatively Charged Substrates

This study examines the adsorption and bulk assembly behaviour of quaternized hydroxyethylcellulose ethoxylate (QHECE)–sodium dodecyl sulphate (SDS) complexes on negatively charged substrates. Due to its quaternized structure, QHECE, which is used in several industries, including cosmetics, exhibits enhanced electrostatic interactions. The phase behaviour and adsorption mechanisms of QHECE–SDS complexes are investigated using model substrates that mimic the wettability and surface charge of damaged hair fibres. Two preparation methodologies, high-concentration mixing and gradient-free mixing, were employed to examine their impact on the complex equilibrium, phase behaviour, and adsorption properties of the complexes. The measurements of turbidity, electrophoretic mobility, and conductivity demonstrate the existence of nonequilibrium dynamics during the mixing process, which exert a significant influence on the structural and functional characteristics of the complexes. The quartz crystal microbalance with dissipation monitoring (QCM-D) was employed to investigate the adsorption of the complexes onto the substrates. The results demonstrated the critical role of intermediate SDS concentrations in enhancing deposition. The findings emphasise the importance of formulation and preparation protocols in designing stable, high-performance cosmetic products. This research advances our understanding of polyelectrolyte–surfactant interactions and provides insights into optimising QHECE-based formulations.

Removal of Primamycin La from Milk Sample Using ZnCl2-Activated Biochar Prepared from Bean Plant as Adsorbent: Kinetic and Equilibrium Calculations

In this study, porous biochar (PvBC) was obtained by the pyrolysis of bean (phaseolus vulgaris) plant at 600 °C, and then activated biochar (PvBCZn) was synthesized by ZnCl2 activation at an equal biomass ratio (1.0:1.0). Some analytical techniques (SEM-EDX (scanning electron microscopy–energy dispersive X-ray spectroscopy), TGA/DTA (Thermogravimetric/Differential Thermal Analysis), BET (Brunauer–Emmett–Teller), FTIR (Fourier Transform Infrared Spectroscopy) and XRD (X-ray diffraction)) were used to characterize both PvBC and PvBCZn. In addition, their antibiotic sensitivity, water solubility, moisture content and swelling behavior were investigated in detail. Furthermore, both PvBC and PvBCZn were used for the adsorption of primamycin la, an anti-inflammatory drug used in veterinary medicine whose active ingredient is oxytetracycline, in a milk sample. The effect of both pH and adsorbent dosage on the adsorption capacity was investigated. Based on adsorption studies, while the maximum adsorption capacity (qmax) of PvBCZn was found to be 188.48 mg/g, that of PvBC was found to be 122.49 mg/g. According to these results, PvBCZn is an excellent adsorbent for the removal of primamycin la from milk samples. The Langmuir isotherm model and the pseudo-second-order kinetic model were more suitable to describe the adsorption behavior of primamycin la. The PvBCZn adsorbent exhibited rapid removal exceeding 75% in the first 20 min and reached equilibrium after about 50 min. In addition, studies on the desorption and reusability of PvBCZn were carried out under the same optimum experimental conditions. The qmax value of PvBCZn was found to be 171.40 mg/g even in the fifth cycle, confirming the idea that it is a potential adsorbent for the removal of primamycin la. At the same time, the antimicrobial activity of PvBCZn against Escherichia coli bacteria increases its potential to be used in both purification systems and hygiene products.

Cell Morphology, Material Property and Ni(II) Adsorption of Microcellular Injection-Molded Polystyrene Reinforced with Graphene Nanoparticles

Graphene’s incorporation into polymers has enabled the development of advanced polymer/graphene nanocomposites with superior properties. This study focuses on the use of a microcellular foamed polystyrene (PS)/graphene (GP) nanocomposite (3 wt%) for nickel (II) ion removal from aqueous solutions. Adsorption behavior was evaluated through FTIR, TEM, SEM, TGA, and XRD analyses. Key factors, including initial ion concentration, pH, temperature, and sorbent dosage, were examined. Results showed optimal nickel removal at specific pH levels with removal efficiency decreasing from 91 to 80% as Ni (II) concentrations increased from 10 to 100 mg/L. The adsorption capacity improved from 11 to 130 mg/g. Equilibrium data aligned with Langmuir and Freundlich isotherm models, while adsorption kinetics followed a second-order kinetic model. These findings highlight the potential of PS/GP nanocomposites for nickel ion removal, offering a promising solution for small-scale industrial applications.

Fabrication of Fe3O4@Polypyrrole@Sulfamic Acid Composite for Efficient Adsorption of Four Cationic Dyes in Aqueous Solution

ABSTRACTWith the continuous development of industry, the issue of industrial wastewater emissions is increasing. Adsorption, as an effective means possessing the features of no pollution, high efficiency, and easy operation, has become one of the effective methods to treat industrial wastewater. Fe3O4@polypyrrole@sulfamic acid (Fe3O4@PPy@SA) composite is successfully prepare by hydrothermal method, in situ polymerization, and modification. Its adsorption behaviors of the composite on MG, MB, CV, and RhB are investigated by UV–Vis, and the impacts of temperature, dye concentration, and the contact time between the composite and the dyes on the adsorption efficiency are researched. The adsorption kinetics and adsorption isotherms exhibit that the adsorption of these four dyes is more in accordance with pseudo‐second‐order kinetic model and Langmuir adsorption isotherm model, the diffusion behaviors are affected through the combined effect of intraparticle diffusion and Boyd membrane diffusion, and the thermodynamic studies display that all these adsorption behaviors are spontaneous heat absorption behaviors. The prepared Fe3O4@PPy@SA is an efficient adsorbent in the field of applications.

Regulating Intermediate Adsorption and Promoting Charge Transfer of CoCr-LDHs by Ce Doping for Enhancing Electrooxidation of 5-Hydroxymethylfurfural.

Electrochemical oxidation of 5-hydroxymethylfurfural (HMFOR) to generate high-value chemicals under mild conditions acts as an energy-saving and sustainable strategy. However, it is still challenging to develop electrocatalysts with high efficiency and good durability. Here, nickel foam (NF) supported CoCrCe(7.5%)-LDH (layered double hydroxides) by doping Ce into CoCr-LDH show high 5-hydroxymethylfurfural (HMF)conversion (99%), 2,5-furandicarboxylic acid (FDCA) yield (99%), and Faraday efficiency (100%) at 1.4 VRHE. The CoCrCe(7.5%)-LDH also exhibits remarkable stability with 97% conversion of HMF after 10 cycles. The X-ray absorption near-edge spectroscopy (XANES) and theoretical calculation show that Ce doping into CoCr-LDH is beneficial to the formation of high-valance Co and significantly facilitates the electron transfer, regulates the adsorption behavior of intermediates, reduces the Gibbs free energy barrier and accelerates the reaction rate. This work promotes the use of rare earth elements as electrocatalysts to promote the oxidation of HMF.

Modeling ethanol/water adsorption in all-silica zeolites using the real adsorbed solution theory.

A comprehensive set of single-component and binary isotherms were collected for ethanol/water adsorption into the siliceous forms of 185 known zeolites using grand-canonical Monte Carlo simulations. Using these data, a systematic analysis of ideal/real adsorbed-solution theory (IAST/RAST) was conducted and activity coefficients were derived for ethanol/water mixtures adsorbed in different zeolites based on RAST. It was found that activity coefficients of ethanol are close to unity while activity coefficients of water are larger in most zeolites, indicating a positive excess free energy of the mixture. This observation can be attributed to water/ethanol interactions being less favorable than water/water interactions in the single-component adsorption of water at comparable loadings. The deviation from ideal behavior can be highly structure-dependent but no clear correlation with pore diameters was identified. Our analysis also demonstrates the following: (1) accurate unary isotherms in the low-loading regime are critical for obtaining physically sensible activity coefficients; (2) the global regression scheme to solve for activity model parameters performs better than fitting activity models to activity coefficients calculated locally at each binary state point; and (3) including the dependence on adsorption potential offers only a minor benefit for describing binary adsorption at the lowest fugacities. Finally, the Margules activity model was found incapable of capturing the non-ideal adsorption behavior over the entire range of fugacities and compositions in all zeolites, but for conditions typical of solution-phase adsorption, RAST predictions using zeolite-specific or even bulk Margules parameters provide an improved description compared to IAST.

Comparative investigation on the adsorption behavior of bromate in aqueous solutions using Zn/Ni/Al-LDH and Ni/Al-LDH: optimization, equilibrium analysis, and mechanistic insights

Comparative investigation on the adsorption behavior of bromate in aqueous solutions using Zn/Ni/Al-LDH and Ni/Al-LDH: optimization, equilibrium analysis, and mechanistic insights

Exploring the Fluorination and Hydroxylation of Pore-Space-Partitioned Metal-Organic Frameworks for C2H2/CH4 Separation.

We report three novel pore-space-partitioned metal-organic frameworks (MOFs) functionalized with fluorine and hydroxyl groups using 2,3,5,6-tetrafluorobenzene-1,4-dicarboxylic acid (F4-BDC) and a new ligand 3,6-difluoro-2,5-dihydroxybenzene-1,4-dicarboxylic acid (F2(OH)2-BDC) as organic building blocks, with 1,3,5-tris(4-pyridyl)-2,4,6-triazine (TPT) as pore partition agent. With the polar fluorine and hydroxyl groups and the open metal sites being blocked by TPT, moderate molecule-framework interactions can be engineered. These three isoreticular microporous frameworks Mn-TPT-BDC-F4 (NCKU-21), Mn-TPT-BDC-F2(OH)2 (NCKU-22), and Mg-TPT-BDC-F2(OH)2 (NCKU-23) (NCKU=National Cheng Kung University) exhibit distinct single-component gas adsorption behaviors. Although NCKU-22 uptakes a much lower amount of C2H2 compared to NCKU-21 and -23, dynamic breakthrough experiments show that these three materials are all capable of efficient C2H2/CH4 separations. These MOFs possess moderate isosteric heat of adsorption for C2H2 (25.7-32.1 kJ mol-1), allowing easy regeneration and energy-efficient C2H2/CH4 separations.

Effective removal of heavy metal ions (Pb, Cu, and Cd) from contaminated water by limestone mine wastes

Limestone mining waste and its derived CaO were checked as an adsorbents of pb2+, Cu2+, and Cd2+ ions from water solution. The characterization of Limestone and calcined limestone was studied by using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), Scanning Electron Microscope (SEM), and Surface area measurements (BET). The optimum conditions of sorbent dosage, pH, initial concentration, and contact time factors were investigated for pristine limestone and calcined limestone absorbents. The results indicate that the optimum initial concentrations of (Ci) were 1200, 500, and 300 ppm for Pb, Cu, and Cd, respectively, using calcined limestone adsorbent, while using the pristine limestone adsorbent, the corresponding optimum initial concentrations were 700, 110, and 50 ppm. In the ternary system sorption, the results indicated that the selectivity sequence of the studied metals by limestone can be expressed as Pb2+ > Cd2+ > Cu2+, while calcined limestone exhibits a higher selectivity for Pb2+ compared to Cu2+ and Cd2+. Hence, various adsorption isotherm and kinetic models were examined to explore different patterns and behaviors of adsorption. So, the results indicate that calcined limestone has great potential for eliminating cationic heavy metal species from industrial water solutions.

Effect of Polymer Network Architecture on Adsorption Kinetics at Liquid–Liquid Interfaces: A Comparison Between Poly(NIPAM-co-AA) Copolymer Microgels and Interpenetrating Network Microgels

Understanding the adsorption features of polymer microgels with different chemical compositions and structures is crucial in studying the mechanisms of respective emulsion stabilization. Specifically, the use of stimuli-responsive particles can introduce new properties and broaden the application range of such complex systems. Recently, we demonstrated that emulsions stabilized by microgels composed of interpenetrating networks (IPNs) of poly-N-isopropylacrylamide (PNIPAM) and polyacrylic acid (PAA) exhibit higher colloidal stability upon heating compared to PNIPAM homopolymer and other relevant PNIPAM-based copolymer counterparts. In the present work, using pendant drop tensiometry, we studied the evolution of water–tetradecane interfacial tension during the adsorption of PNIPAM-PAA IPN particles, comparing them with single-network P-(NIPAM-co-AA) and PNIPAM microgels. The results showed that, despite having the same chemical composition, copolymer particles exhibit completely different adsorption behavior in comparison to other microgel architectures. The observed disparity can be attributed to the nonuniform distribution of charged acrylic acid groups within the P-(NIPAM-co-AA) network obtained through precipitation polymerization. Oppositely, the presence of IPN architecture provides a uniform distribution of different monomers inside respective microgels. Additionally, hydrogen bonding between PNIPAM and PAA subchains appears to reduce the electrostatic energy barrier, enhancing the ability of IPN particles to successfully cover the liquid interface. Overall, our findings confirm the efficiency of using PNIPAM-PAA IPN microgels for the preparation of oil-in-water emulsions and their stability, even when the temperature rises above the lower critical solution temperature of PNIPAM.

Acetamiprid retention in agricultural acid soils: Experimental data and prediction.

The overuse of pesticides in agriculture has led to widespread pollution of soils and water resources, becoming a problem of great concern. Nowadays, special attention is given to neonicotinoids, particularly acetamiprid, the only neonicotinoid insecticide allowed for outdoor use in the European Union. Once acetamiprid reaches the soil, adsorption/desorption is the main process determining its bioavailability and environmental fate. Therefore, in this work, the adsorption/desorption behaviour of acetamiprid in 60 agricultural soils was studied. The results indicate that acetamiprid has a low affinity for soil constituents, with values ranging from 0.2 to 4.28 L kg-1 for Kd(ads). At the same time, acetamiprid shows high desorption levels (up to 96.3%), indicating that it is poorly retained in soils, thus presenting high bioavailability and a potential risk for transport to other environmental compartments. Regarding the influence of soil properties on the adsorption/desorption process, soils with a high content of organic matter, clay, and exchangeable basic cations showed higher retention of acetamiprid, with greater adsorption and lower desorption. Finally, robust and universal models were successfully developed to predict the adsorption and desorption behaviour of acetamiprid in soil.

Recovery of Li Through Selective Adsorption on Two Types of Calix[4]arene Derived Adsorbents

ABSTRACT Recovery of Li is one of urgent issues owing to exponential increase of Li demand of Li-ion battery. More efficient and selective reagents for Li recovery have been required. Calixarene as a host oligomer was focused on this purpose, and it was applied to adsorptive reagents. Two types of adsorbents incorporating trialkyl monoacetic acid derivatives of calix[4]arene through either impregnation or crosslinking were synthesized. The impregnated adsorbents were synthesized by impregnation of four trialkyl monoacetic acid derivatives of calix[4]arene into macroporous Ambelite XAD-7. The crosslinked adsorbents were synthesized by crosslinking of three trialkyl monoacetic acid derivatives of debutylated calix[4]arene each other using sym-trioxane under an acidic condition. Their adsorption behaviors and Li+ selectivities over other alkali metal ions were investigated. Incorporation of the ligand into the adsorbents had a negligible effect on the time required to reach equilibrium. The impregnated adsorbents exhibited extremely high Li+ selectivity over other alkali metal ions that reflected those of the incorporated ligand, whereas the crosslinked adsorbents exhibited Cs+ selectivity and mixed effects arising from incomplete dehydration and ion discrimination. The adsorption of alkali metal ions was driven by ion-exchange mechanism. The apparent adsorption equilibrium constants for alkali metal ions on both adsorbents and the separation factors between the metal ions were estimated. It was found that three alkyl branches affected the adsorption efficiency, together with separation efficiency.

Synergistic SERS effects in organic/MoS2 heterojunctions with cavity structure enabling nanoplastics screening and antibiotic adsorption behavior detection

Synergistic SERS effects in organic/MoS₂ heterojunctions with cavity structure enabling nanoplastics screening and antibiotic adsorption behavior detection

Boundary Lubrication with Adsorbed Anionic Surfactant Bilayers in Hard Water.

The adsorption behavior of an anionic surfactant, hydroxy alkane sulfonate with an alkyl chain length of 18 (C18HAS), from its hard water solution onto a mica surface and resulting lubrication properties were investigated. Because of the double chain-like chemical structure and aggregation behavior, C18HAS formed vesicles in hard water, which adsorbed onto a negatively charged mica surface via cation (Ca2+) bridging and then transformed into a bilayer film. The number of bilayers formed on the surface was evaluated by force curve measurements using an atomic force microscope (AFM), and the results showed a time-dependent increase of the number of adsorbed bilayers. Friction and lubrication properties were evaluated for the confined film of the C18HAS hard water solution between mica surfaces using the surface forces apparatus (SFA). When the two surfaces were brought into contact under load and sheared against each other, the lubricating film consisted of two adsorbed C18HAS bilayers whose friction coefficient μ was of the order of 10-3 or below. The detailed analysis of the friction features revealed that the slipping in the boundary film does not occur at the interface between the opposed headgroup region of the two adsorbed bilayers, which is the typical mechanism for the low friction of adsorbed phospholipid bilayers extensively studied in the literature. Instead, slipping occurs at the interface between opposed liquid-like alkyl chain tails within the adsorbed bilayers; the low friction coefficient comes from the existence of two slip planes in the boundary film.

Interfacial adsorption behavior of amine-functionalized MCM-41 for Mo(VI) capture from aqueous solution.

Given the environmental and ecological risks posed by wastewater bearing Mo, the characteristics and microscopic interactions of existing silica-based adsorbents have not been thoroughly investigated, highlighting the need to enhance the porosity and chemical interactions of these materials. Considering the effectiveness of amino groups in binding metal oxyanions, this study investigates the adsorption performance and mechanism of amino-functionalized MCM-41 for Mo(VI), with the goal of efficiently remediating Mo-contaminated wastewater. MCM-41 modified by amino group retains its original structure and mesoporous characteristics while featuring a positively charged surface and chemically bonded amino groups. When employed to treat Mo(VI)-containing solutions, adsorption equilibrium is attained within 20 minutes, adhering to pseudo-second-order kinetics, characterized by a high R2 value of 0.9999, indicating a predominantly chemisorptive method. Thermodynamic evaluation offers uniform single-layer adsorption of specific ions onto the adsorbent interface. It demonstrates the nature of the adsorption method being spontaneous and fits the Langmuir model. A maximum of 242.33 mg/g of adsorption capacity was achieved. Spectroscopic characterization confirms that charge attraction, hydrogen bonding, and coordination are the primary driving forces behind the method of adsorption. Density Functional Theory (DFT) results further support the advantageous role of two-tooth chelation between amino group and silanol groups in the Mo(VI) adsorption mechanism. This study provides information on adsorbent design and the control of Mo(VI)-containing aqueous solutions by confirming the substantial promise of amino modified mesoporous silica with suitable pore configurations for treating Mo(VI)-containing solutions.

Enhanced remediation of naphthalene from aqueous solutions using synthesized organoclay: characterization, mechanisms, and isotherms.

Water contamination by polycyclic aromatic hydrocarbons (PAHs), particularly naphthalene, is a serious environmental concern due to its persistence, bioaccumulation, and toxicity. This study explores the adsorption behavior of naphthalene using organobentonite (OBt), synthesized by intercalating cetyltrimethylammonium bromide (CTAB) into sodium bentonite (SBt) with varying cation exchange capacities (CECs). The effectiveness of OBt in naphthalene adsorption was evaluated by analyzing key parameters, including CEC, contaminant concentration, and contact time. The morphological and structural properties of all adsorbents were characterized before and after the adsorption process. The results demonstrated a significant improvement in the adsorption capacity of OBt compared to SBt, with a maximum naphthalene adsorption capacity of 14.08mg/g at 2.0 CEC, versus 5.22mg/g for SBt. The Freundlich isotherm model provided the best fit for adsorption data (R2 > 0.97), indicating that the partitioning mechanism primarily governed the process. CTAB-modified OBt showed enhanced hydrophobicity, larger basal spacing, and faster adsorption kinetics, with most naphthalene removal occurring within the first 15min. These findings indicated that OBt, due to its improved adsorption efficiency, rapid kinetics, and cost-effectiveness, is a promising adsorbent that can enhance the remediation of hydrophobic organic pollutants from contaminated water.

Surface Hydration and Antifouling Activity of Coatings of Polymers and Their Zwitterionic Derivatives Prepared Using Initiated Chemical Vapor Deposition (iCVD).

Sum frequency generation vibrational spectroscopy was applied to study the surface hydration and protein adsorption behavior on several polymer coatings based on pyridine, imidazole, and amine side groups along with vinyl or methacrylate backbones and their corresponding zwitterionic forms with carboxybetaine or sulfobetaine side chains, prepared by initiated chemical vapor deposition (iCVD). iCVD also enables facile tuning of the cross-linking density of the polymer coatings by blending in a cross-linker during the deposition, namely, 1,3,5,7-tetramethyl-1,3,5,7-tetravinyl cyclotetrasiloxane. Our results show that both the low- and high-cross-linking density zwitterionic polymers exhibit significantly better antifouling activities compared to those of the polymers without the zwitterionic side chains. The weak hydration signals from the low-density zwitterionic polymer/water interfaces were caused by the permeation of the polymer layer by water. The iCVD method is a widely applicable methodology to prepare zwitterionic polymer coatings with an excellent antifouling property.