Various curing conditions for controlling PTFE micro/nano-fiber texture of a bionic superhydrophobic coating surface

A simple and conventional coating-curing process to fabricate superhydrophobic coating surface with both the micro-nano-scale binary structure (MNBS) roughness, and the lowest surface energy hydrophobic groups (?CF₃) on engineering materials of stainless steel or other metals was developed by control of curing conditions. Results show that higher temperature and longer cooling time resulted in longer crystallizing process, and the forming PTFE aggregates could slowly produce the crystallization and create the willow-leaf-like or wheat-haulm-leaf-like polymer micro/nano-fiber on the atop surface. The curing temperature dramatically influences the micro/nano-fiber texture of the PTFE/PPS superhydrophobic coating surface, leading to the excellent superhydrophobicity at higher temperature. An increase of the curing temperature is beneficial to fluorine gradient-distribution, PPS thermal-oxidative cross-linking and oxidative reaction, resulting in the enhancement of adhesive strength and mechanical properties of the PTFE/PPS superhydrophobic coatings. A bionic superhydrophobic surface with porous gel-like network and PTFE micro/nano-fiber textures could be created by natural cooling in air, whereas PTFE nano-sphere/-papillates textures could be fabricated by hardening in H₂O.     

Antifouling on Gecko's Feet Inspired Fibrillar Surfaces: Evolving from Land to Marine and from Liquid Repellency to Algae Resistance

In nature, biological creatures (including plants and animals) have self‐cleaning capability despite the vagaries of the environment, i.e., from sky to land, and then to marine and vagaries of foulants (non‐living and living). Gecko's feet have the general self‐cleaning property both in air and underwater so as to keep their feet all clean for traveling through changing their adhesion. The present work reports Gecko's fibrillar structures to demonstrate general antifouling property in air through hydrophobicity and underwater after modification with hydrophilic polymer brushes. Fibrillar polypropylene (PP) nanoarrays are fabricated by hot embossing, exhibiting superhydrophobic antifouling in air. By grafting hydrophilic polyelectrolyte brushes (PSPMA) via surface‐initiated atom transfer radical polymerization, they show superoleophobic antifouling of oil droplet and algae adhesion underwater. The effect of the structure of PP nanofiber arrays on the wettability and adhesion behavior is evaluated in detail. The results provide an important scientific principle for fabricating self‐cleaning low‐fouling materials with micro/nanostructure, with the hydrophobic ones being more applicable in air and the hydrophilic ones well suited underwater.     

Robust Flower‐Like TiO2@Cotton Fabrics with Special Wettability for Effective Self‐Cleaning and Versatile Oil/Water Separation

Inspired by the hierarchical structure of the mastoid on the micrometer and nanometer scale and the waxy crystals of the mastoid on natural lotus surfaces, a facile one‐step hydrothermal strategy is developed to coat flower‐like hierarchical TiO₂ micro/nanoparticles onto cotton fabric substrates (TiO₂@Cotton). Furthermore, robust superhydrophobic TiO₂@Cotton surfaces are constructed by the combination of hierarchical structure creation and low surface energy material modification, which allows versatility for self‐cleaning, laundering durability, and oil/water separation. Compared with hydrophobic cotton fabric, the TiO₂@Cotton exhibits a superior antiwetting and self‐cleaning property with a contact angle (CA) lager than 160° and a sliding angle lower than 5°. The superhydrophobic TiO₂@Cotton shows excellent laundering durability against mechanical abrasion without an apparent reduction of the water contact angle. Moreover, the micro/nanoscale hierarchical structured cotton fabrics with special wettability are demonstrated to selectively collect oil from oil/water mixtures efficiently under various conditions (e.g., floating oil layer or underwater oil droplet or even oil/water mixtures). In addition, it is expected that this facile strategy can be widely used to construct multifunctional fabrics with excellent self‐cleaning, laundering durability, and oil/water separation. The work would also be helpful to design and develop new underwater superoleophobic/superoleophilic materials and microfluidic management devices.     

A Combinatorial Library of Micro‐Topographies and Chemical Compositions for Tailored Surface Wettability

Surface modification of topography and chemistry in order to achieve a specific water contact angle (CA) has been explored by using a novel combinatorial screening platform. The screening arrays consisted of 507 distinct combinations of micro‐topographies and chemical compositions. By performing chemical modifications with 1H, 1H, 2H, 2H perfluoroethyltriethoxy‐silane (PFS) and n‐octadecyltriethoxysilane (ODS) on standard silicon wafers it was possible to include both superhydrophobic and very hydrophilic pad arrays in the same screening platform. Surfaces modified with PFS were more hydrophobic than surfaces modified with ODS, while the unmodified silicon surfaces were hydrophilic. For the PFS modified surfaces the largest CAs were achieved with a small pillar size of X = 1 µm and an intermediate inter‐pillar gap size of Y = 4 µm with superhydrophobic CAs over 170°. Surface analysis with X‐ray photoelectron spectroscopy (XPS) revealed that CF₃ groups were present at the surface, contributing to the superhydrophobic effect. The ODS modified surfaces had intermediate wettabilities with CAs between 100 and 150°, which were dependent on the pillar size, the inter‐pillar gap size, and the specific pillar pattern. The unmodified silicon topographical surfaces were very hydrophilic with CAs below 20° independent of specific topography. With this approach we have managed to fabricate 507 distinct surface areas covering a range of wettabilities, which is useful when screening these effects in several different applications. The measured CAs did not follow the simple Wenzel model. Furthermore, the adaptation of the Cassie model introduces Φ_s, the fraction of solid surface in contact with the liquid, which is difficult to estimate, thereby emphasizing the need for an experimental determination.     

Thermodynamic properties of seven gaseous halogenated hydrocarbons from acoustic measurements: CHClFCF3, CHF2 CF3, CF3 CH3, CHF2CH3, CF3CHFCHF2, CF3CH2CF3, and CHF2CF2CH2F

Measurements of the speed of sound in seven halogenated hydrocarbons are presented. The compounds in this study are 1-chloro-1,2,2,2-tetrafluoroethane (CHClFCF₃ or HCFC-124), pentafluoroethane (CHF₂ CF₃ or HFC-125), 1,1,1-trifluoroethane (CF₃CH₃ or HFC-143a), 1,1-difluoroethane (CHF₂CH₃ or HFC-152a), 1,1,1,2,3,3-hexafluoropropane (CF₃CHFCHF₂ or HFC-236ea), 1,1,1,3,3,3-hexafluoropropane (CF₃CH₂CF₃ or HFC-236fa), and 1,1,2,2,3-pentafluoropropane (CHF₂CF₂CH₂F or HFC-245ca). The measurements were performed with a cylindrical resonator at temperatures between 240 and 400 K and at pressures up to 1.0 MPa. Ideal-gas heat capacities and acoustic virial coefficients were directly deduced from the data. The ideal-gas heat capacity of HFC-125 from this work differs from spectroscopic calculations by less than 0.2% over the measurement range. The coefficients for virial equations of state were obtained from the acoustic data and hard-core square-well intermolecular potentials. Gas densities that were calculated from the virial equations of state for HCFC-124 and HFC-125 differ from independent density measurements by at most 0.15%, for the ranges of temperature and pressure over which both acoustic and Burnett data exist. The uncertainties in the derived properties for the other five compounds are comparable to those for HCFC-124 and HFC-125.     

Fabrication of Copper Nanowire Films and their Incorporation into Polymer Matrices for Antibacterial and Marine Antifouling Applications

With the ban of tributyltin, copper‐based biocides are now widely used in antifouling coatings as the major active ingredients. Given the past experience of heavy‐metal accumulation in harbors with limited water exchange, there is a significant interest in developing copper materials that greatly reduce the amount of copper ions released into marine surroundings. In this paper, copper nanowires (NWs) encapsulated in polymer matrices are investigated as the means to control the release of copper ions and to achieve a long‐lasting antifouling effect. Very long CuNWs with high aspect ratio in organic solution are drop‐coated onto substrates to fabricate uniform thin films. They are then incorporated into an elastomeric polydimethylsiloxane (PDMS) matrix. A small amount of CuNWs in PDMS can inhibit barnacle cyprid settlement, while it exhibits low mortality to cyprids and nauplii present in the surrounding seawater environment. The low levels of copper released after 50 days suggest that the intersecting and interconnected CuNWs embedded in PDMS could potentially release copper ions continuously over a few years in seawater. This approach provides a novel platform to use hybrid materials as effective marine antifouling coatings, and may be applied to fouling release materials to enhance their antifouling properties.     

Detection of deposition rate of plasma-polymerized acrylate and methacrylate derivatives using quartz crystal microbalance

The deposition rates of plasma-polymerized (pp-)films of 12 acrylate derivatives (CH₂CHCOOR: substitution R is H, CH₃, CHCH₂, CH₂CH₃, CH₂CH₂CH₃, (CH₂)₃CH₃, C(CH₃)₃, CH₂CH(CH₃)₂, CH₂(CH₂)₄CH₃, CH₂CF₃, CH₂CF₂CF₃, CH₂(CF₂)₂CF₃), and 12 methacrylate derivatives (CH₂CCH₃COOR′: substitution R′ is H, CH₃, CHCH₂, CH₂CH₃, CH₂CH₂CH₃, (CH₂)₃CH₃, C(CH₃)₃, CH₂CH(CH₃)₂, CH₂(CH₂)₄CH₃, CH₂CF₃, CH₂CF₂CF₃, CH₂(CF₂)₂CF₃) are determined by the quartz crystal microbalance technique. Using the same polymerization conditions (100 W RF and 100 Pa vapor pressure) for the various monomers, it is found that the deposition rates were proportional to the polymerization time. The average deposition rate of pp-acrylate derivatives is larger than that of pp-methacrylate derivatives without pp-hexylacrylate. The average deposition rate of pp-fluoroalkylacrylates was higher than 7-25 times that of pp-alkylacrylate, and the average deposition rate of pp-fluoroalkylmethacrylates was higher than 10-31 times that of pp-alkylmethacrylates, respectively. The average deposition rate of pp-film depends on the chemical structure of the monomer suggesting different mechanisms under plasma-polymerization.     

Bio-inspired design of a transparent TiO<Subscript>2</Subscript>/SiO<Subscript>2</Subscript> composite gel coating with adjustable wettability

Although the superhydrophobicity and transparence are generally two contradictory characters as the roughness factor, it is literature abundant for achieving both of these two purposes. To our knowledge, the integration multipurpose (transparent, superhydrophobic, superhydrophilic, underwater superoleophobicity, anti-fogging, and photo-controllable ability) in one has not been reported so far and these are vital for their promising applications in various aspects which can attract broad attention from scholars to engineers. In this work, we are successful to bio-inspired design of a kind versatile transparent nanocoating with superhydrophobic or superhydrophilic/underwater superoleophobic properties. The TiO₂/SiO₂ nanocoatings can be transformed from superhydrophobicity into superhydrophilicity and underwater superoleophobicity after heat treatment (450 °C and 2 h). If it was coated on conductive glass, the electrical conductivity was impervious, while the wettability can be manipulated. Importantly, both these superhydrophobic and superhydrophilic TiO₂/SiO₂ composite nanocoatings were endowed with photo-induced self-cleaning nature and these antifouling coatings could prolong their service life.     

Superhydrophobic CuO@Cu2S nanoplate vertical arrays on copper surfaces

The present work reports a simple method to produce hierarchical CuO architectures on copper substrate through self-generation. Subsequently, CuO@Cu₂S composites have been successfully synthesized from the hierarchical CuO precursors via a facile solution-immersion process. These products were characterized by field-emission scanning electron microscopy, x-ray powder diffraction and x-ray photoelectron spectrum. The wettability of the products was also investigated. It was found that the wettability of the CuO@Cu₂S composite film could be easily changed from hydrophilic to superhydrophobic with simple fluorination modification. Compared with other methods, the method herein is mild, economical and easy to create large area superhydrophobic materials on copper substrate.     

Adsorption of CH3S and CF3S on Pt(111) surface: a density functional theory study

Density functional theory calculations have been performed to study binding modes of adsorbed CX₃S (X = H and F) on Pt(111) for a large range of adsorbate coverages and the consequent work function shifts. We find that these properties are all strongly correlated to the surface coverage. Depending on the molecular coverage on Pt surface, the work function shift may be as large as 0.7 eV for Pt–CH₃S and 1.5 eV for Pt–CF₃S with respect to the clean surface value. Two factors contribute to the work function shift: the charge transfer between the molecule and the surface, and the molecular dipole moment. While the charge transfer contribution always tend to decrease the work function, the molecular dipole moment contribution for the CH₃S and CF₃S cases are oppositely directed. Thus, appropriate choices of molecular components and control of surface coverage would be effective techniques to tune the work function of the metal surfaces.     

Mechanism of thermal decomposition of HFO-1234yf by DFT study

Twenty-two chemical reaction pathways of thermal decomposition of 2,3,3,3-tetrafluoro-1-propene (HFO-1234yf, CF₃CFCH₂) are proposed to investigate the formation mechanism of some possible products (CF₃H, CF₄, HF, H₂) by using density function theory (DFT) simulations with M06-2X/6–311++(d,p) level of theory. The results point out that the ground state CF₃CFCH₂ will excite into the lowest triplet state CF₃CF-CH₂ favorably in the first step with an energy barrier of 264.67 kJ mol⁻¹ and pathway 5 is the most preferred route of homolytic cleavage reactions with the lowest energy barrier of 205.70 kJ mol^-1. F radical is hard to generate during thermal decomposition processes because of its higher energy barrier. H radical and CF₃ radical play a dominant role in thermal decomposition of HFO-1234yf. H-abstraction and F-abstraction reactions are proposed in subsequent radical attacking chain reactions. CF₃H and H₂ are easier to be generated due to their lower energy barriers. Our work presents the mechanism of thermal decomposition of HFO-1234yf from the molecule level and provides a reference for studying the thermal stability of other working fluids.     

Langmuir–Blodgett Nanowire Devices for In Situ Probing of Zinc‐Ion Batteries

In situ monitoring the evolution of electrode materials in micro/nano scale is crucial to understand the intrinsic mechanism of rechargeable batteries. Here a novel on‐chip Langmuir–Blodgett nanowire (LBNW) microdevice is designed based on aligned and assembled MnO₂ nanowire quasimonolayer films for directly probing Zn‐ion batteries (ZIBs) in real‐time. With an interdigital device configuration, a splendid Ohmic contact between MnO₂ LBNWs and pyrolytic carbon current collector is demonstrated here, enabling a small polarization voltage. In addition, this work reveals, for the first time, that the conductance of MnO₂ LBNWs monotonically increases/decreases when the ZIBs are charged/discharged. Multistep phase transition is mainly responsible for the mechanism of the ZIBs, as evidenced by combined high‐resolution transmission electron microscopy and in situ Raman spectroscopy. This work provides a new and adaptable platform for microchip‐based in situ simultaneous electrochemical and physical detection of batteries, which would promote the fundamental and practical research of nanowire electrode materials in energy storage applications.     

Hierarchical Structured Multifunctional Self‐Cleaning Material with Durable Superhydrophobicity and Photocatalytic Functionalities

Self‐cleaning materials, which are inspired and derived from natural phenomena, have gained significant scientific and commercial interest in the past decades as they are energy‐ and labor‐saving and environmentally friendly. Several technologies are developed to obtain self‐cleaning materials. The combination of superhydrophobic and photocatalytic properties enables the efficient removal of solid particles and organic contaminations, which could reduce or damage the superhydrophobicity. However, the fragility of the nanoscale roughness of the superhydrophobic surface limits its practical application. Here, a hierarchical structure approach combining micro‐ and nanoscale architectures is created to protect the nanoscale surface roughness from mechanical damage. Glass beads of 75 µm are partially embedded into a low‐density polyethylene film. This composite surface is coated with silicone nanofilaments (SNFs) via the droplet‐assisted growth and shaping approach, providing the nanoscale surface roughness as well as the support for the photocatalyst with enlarged surface area. TiO₂ nanoparticles, which serve as the photocatalyst, are synthesized in situ on SNFs through a hydrothermal reaction. The self‐cleaning effect is proved using wettability measurements for various liquids, degradation of organic contamination under UV light, and antibacterial tests. The enhanced mechanical durability of the hierarchical structure of the composite material is verified with an abrasion test.     

Laser‐Induced Graphene in Controlled Atmospheres: From Superhydrophilic to Superhydrophobic Surfaces

The modification of graphene‐based materials is an important topic in the field of materials research. This study aims to expand the range of properties for laser‐induced graphene (LIG), specifically to tune the hydrophobicity and hydrophilicity of the LIG surfaces. While LIG is normally prepared in the air, here, using selected gas atmospheres, a large change in the water contact angle on the as‐prepared LIG surfaces has been observed, from 0° (superhydrophilic) when using O₂ or air, to >150° (superhydrophobic) when using Ar or H₂. Characterization of the newly derived surfaces shows that the different wetting properties are due to the surface morphology and chemical composition of the LIG. Applications of the superhydrophobic LIG are shown in oil/water separation as well as anti‐icing surfaces, while the versatility of the controlled atmosphere chamber fabrication method is demonstrated through the improved microsupercapacitor performance generated from LIG films prepared in an O₂ atmosphere.     

Photostriction of CH3NH3PbBr3 Perovskite Crystals

Organic–inorganic hybrid perovskite materials exhibit a variety of physical properties. Pronounced coupling between phonon, organic cations, and the inorganic framework suggest that these materials exhibit strong light–matter interactions. The photoinduced strain of CH₃NH₃PbBr₃ is investigated using high‐resolution and contactless in situ Raman spectroscopy. Under illumination, the material exhibits large blue shifts in its Raman spectra that indicate significant structural deformations (i.e., photostriction). From these shifts, the photostrictive coefficient of CH₃NH₃PbBr₃ is calculated as 2.08 × 10^?8 m² W^?1 at room temperature under visible light illumination. The significant photostriction of CH₃NH₃PbBr₃ is attributed to a combination of the photovoltaic effect and translational symmetry loss of the molecular configuration via strong translation–rotation coupling. Unlike CH₃NH₃PbI₃, it is noted that the photostriction of CH₃NH₃PbBr₃ is extremely stable, demonstrating no signs of optical decay for at least 30 d. These results suggest the potential of CH₃NH₃PbBr₃ for applications in next‐generation optical micro‐electromechanical devices.     

Engineering High‐Performance MoO2‐Based Nanomaterials with Supercapacity and Superhydrophobicity by Tuning the Raw Materials Source

Herein, a simple self‐assembly method is proposed for the fabrication of MoO₂‐based superhydrophobic material with record high contact angles (contact angle up to about 173°) for conductive metal oxides on hard/soft substrates. The spin‐coated surface demonstrates excellent oil–water separation efficiency (>98%) after 50 cycles and robust corrosion resistance after immersion into different pH solutions for 20 d. These water‐resistant coatings retain excellent superhydrophobicity after oil immersion, knife‐scratch, and long‐cycle sandpaper abrasion, which is not observed on most artificial surfaces. Meanwhile, the functionality switching from superhydrophobicity to supercapacity, which have an inverse relationship in aqueous solutions because of poor electrode wettability, is achieved simply by editing the raw materials source. Tuning of the raw materials leads to the same product MoO₂/graphitic carbon with different morphologies and functionalities. Different from superhydrophobic MoO₂/carbon ball flowers, MoO₂ nanotubes with carbon exhibit excellent supercapacity with a large gravimetric capacitance and great cycling stability.     

A Silver(I)‐Estrogen Nanocluster: GSH Sensitivity and Targeting Suppression on HepG2 Cell

A structure‐determined silver nanocluster of [Ag₁₀(Eth)₄(CF₃COO)₆(CH₃OH)₃]·3C­H₃OH (Eth = ethisterone) ( 1 ), is firstly demonstrated by self‐assembly of silver salt and ethisterone. Due to the thiophilicity of silver(I) ions, complex 1 shows reactivity with glutathione (GSH) molecules in solution and induces the fluorescence quenching behavior. Thus, complex 1 can be used as a fluorescent sensor for GSH. In consideration of the higher level of GSH in cancerous cells, complex 1 presents significant tumor suppression reactivity toward the human hepatocellular carcinoma (HepG2) cells with IC₅₀ value of 165 × 10^?9 m . Especially, complex 1 displays 3.4‐fold higher in vitro cytotoxicity to HepG2 cells than that of the normal CCC‐HEL‐1 cells, which makes complex 1 a potential targeting suppression agent for cancerous cells. The molecular design of complex 1 not only generates a new medicine‐silver(I) cluster family, but also opens a new avenue to the targeting anticancer organosilver(I) materials.     

Highly Efficient p‐i‐n Perovskite Solar Cells Utilizing Novel Low‐Temperature Solution‐Processed Hole Transport Materials with Linear π‐Conjugated Structure

Alternative low‐temperature solution‐processed hole‐transporting materials (HTMs) without dopant are critical for highly efficient perovskite solar cells (PSCs). Here, two novel small molecule HTMs with linear π‐conjugated structure, 4,4′‐bis(4‐(di‐p‐toyl)aminostyryl)biphenyl (TPASBP) and 1,4′‐bis(4‐(di‐p‐toyl)aminostyryl)benzene (TPASB), are applied as hole‐transporting layer (HTL) by low‐temperature (sub‐100 °C) solution‐processed method in p‐i‐n PSCs. Compared with standard poly(3,4‐ethylenedioxythiophene): poly(styrenesulfonic acid) (PEDOT:PSS) HTL, both TPASBP and TPASB HTLs can promote the growth of perovskite (CH₃NH₃PbI₃) film consisting of large grains and less grain boundaries. Furthermore, the hole extraction at HTL/CH₃NH₃PbI₃ interface and the hole transport in HTL are also more efficient under the conditions of using TPASBP or TPASB as HTL. Hence, the photovoltaic performance of the PSCs is dramatically enhanced, leading to the high efficiencies of 17.4% and 17.6% for the PSCs using TPASBP and TPASB as HTL, respectively, which are ≈40% higher than that of the standard PSC using PEDOT:PSS HTL.     

Superhydrophobic surfaces with hierarchical structure

The physics related to superhydrophobic surfaces has been investigated with attention of its potential applications in a variety of industrial and research fields. In the present study, we report a facile method for preparing superhydrophobic surfaces based on micro and nano scaled structures. Composite thin films are formed by using SiO₂ nanoparticles and poly(dimethylsiloxane) (PDMS). The static contact angle, advancing contact angle, and receding contact angle are measured to investigate the surfaces' water repelling property. The formed SiO₂-PDMS composite films, with different nanoparticle concentrations and sizes, can render the surfaces with superhydrophobicicty, exhibiting large contact angles and small contact angle hysteresis. The composite films are observed by using the Scanning Electron Microscope (SEM). It is demonstrated that the hierarchical structure in micro and nano scale on the surface, plays an important role in prompting the superhydrophobic (water-repelling) properties. Wetting phenomena and related theories are also discussed within the paper.     

Saturated liquid viscosities and densities of environmentally acceptable hydrochlorofluorocarbons (HCFCs)

Measurements of saturated liquid viscosities and densities were performed on environmentally acceptable hydrochlorofluorocarbons (HCFCs), CH₃CCl₂F (HCFC-141b), CH₃CClF₂ (HCFC-142b; only for viscosity), CF₃CF₂CHCl₂ (HCFC-225ca), and CClF₂CF₂CHClF (HCFC-225cb), using a capillary viscometer and a glass pycnometer in the temperature range from 273 to 353 K. The uncertainty in the measurement of viscosity is estimated to be 5% based on the comparison of the present data with those in the literature for HCFC-141b. An equation is given to represent our saturated liquid viscosity data as a function of temperature.