Honeycomb-structured Films Research Articles

Realization of Honeycomb Tellurene with Topological Edge States.

The two-dimensional (2D) honeycomb lattice has attracted intensive research interest due to the appearance of Dirac-type band structures as the consequence of two sublattices in the honeycomb structure. Introducing strong spin-orbit coupling (SOC) leads to a gap opening at the Dirac point, transforming the honeycomb lattice into a 2D topological insulator as a platform for the quantum spin Hall effect (QSHE). In this work, we realize a 2D honeycomb-structured film with tellurium, the heaviest nonradioactive element in Group VI, namely, tellurene, via molecular beam epitaxy. We revealed the gap opening of 160 meV at the Dirac point due to the strong SOC in the honeycomb-structured tellurene by angle-resolved photoemission spectroscopy. The topological edge states of tellurene are detected via scanning tunneling microscopy/spectroscopy. These results demonstrate that tellurene is a novel 2D honeycomb lattice with strong SOC, and they unambiguously prove that tellurene is a promising candidate for a room-temperature QSHE system.

Fabrication of Adsorption-Type Hierarchical Functional Films by Using a Facile Swollen Based Breath Figure Method.

The morphology transition from primary to hierarchical adsorption-type microporous domains of amphiphilic block copolymer (BCP) honeycomb-structured films is demonstrated by a facile swollen based breath figure (BF) method. The characteristic parameters of poly(4-vinylpyridine)-block-polystyrene (P4VP-b-PS) hierarchical micro- and submicroporous films can be controlled by changing the length of segments or subsequent swelling conditions. A plausible mechanism is demonstrated in this research. A typical amphiphilic BCP with very low volume content of hydrophilic blocks (fP4VP ≤ 0.050) can efficiently stabilize water droplets and inherently assist in the formation of morphology transition. This BCP film can be used for Cr(VI) removal from wastewater, which additionally has enormous potential application in the field of novel optical devices, soft lithography, size-selective separation, etc.

Honeycomb Lattice in Metal-Rich Chalcogenide Fe2TeSupported by the National Natural Science Foundation of China (Grant Nos. 51788104, 11604366, 11774192, and 11634007), and the National Key R&D Program of China (Grant Nos. 2017YFA0304600 and 2018YFA0305603).

Two-dimensional honeycomb crystals have inspired intense research interest for their novel properties and great potential in electronics and optoelectronics. Here, through molecular beam epitaxy on SrTiO3(001), we report successful epitaxial growth of metal-rich chalcogenide Fe2Te, a honeycomb-structured film that has no direct bulk analogue, under Te-limited growth conditions. The structural morphology and electronic properties of Fe2Te are explored with scanning tunneling microscopy and angle resolved photoemission spectroscopy, which reveal electronic bands cross the Fermi level and nearly flat bands. Moreover, we find a weak interfacial interaction between Fe2Te and the underlying substrates, paving a newly developed alternative avenue for honeycomb-based electronic devices.

Single Polar Cell Trapping Based on the Breath Figure Method.

The ability to research individual cells is important for various biological studies. Currently reported biointerfaces for single-cell analysis can only trap individual cells in random morphologies. Cell polarity is a key factor in cellular functions, and the study of single-cell polarity can facilitate an understanding of cancer metastasis and stem-cell differentiation. For single polar cell trapping, anisotropic honeycomb-structured films were prepared. Elastic poly(1,2-butadiene) honeycomb films with ordered hexagonal pores were first prepared via the breath figure method. Subsequently, the films were subjected to mechanical stretching and fixed via photo-cross-linking under UV light irradiation. This stretched honeycomb structure was then transferred to a polystyrene surface. The resultant anisotropic porous films exhibited excellent capacity for single-cell trapping. Besides contributing to the physical spatial confinement of cells, the trapped single cells exhibited orientation in different polarities. The single polar cell array provided a novel platform for fundamental biological research.

Preparation of Hierarchic Porous Films of α-MnO2 Nanoparticles by Using the Breath Figure Technique and Application for Hybrid Capacitor Electrodes.

The honeycomb-structured film has advantages such as high wettability and high surface area. This structure and properties are suitable for the capacitor electrode. In this study, the electrode structure is controlled by the synthesis of MnO2 nanoparticles using the breath figure method. The electrode performance was calculated by electrochemical measurements. As a result, the capacitance value was 100.5 F/g at 1 mV s–1, which was improved 2.7 times as compared with that without structure control.

Mechanically robust reduced graphene oxide/bacterial cellulose film obtained via biosynthesis for flexible supercapacitor

We report the bio-assembly of holey graphene oxide/bacterial cellulose (HRGO/BC) with a three-dimensional (3D) honeycomb structure. The HRGO/BC composite films could be bended, twisted, knotted and even folded into an ingenious paper plane and yield a high tensile strength of 204 MPa with an elongation of 13.8%. Made of the mechanically robust free-standing HRGO/BC electrodes, the solid-symmetric supercapacitors exhibited a specific capacity of 65.9 F/g at a current density of 0.4 A/g and an energy density of 9.2 W h/kg at a power density of 112.9 W/kg. The excellent electrochemical properties of HRGO/BC electrodes without any other active materials are derived from the continuous 3D honeycomb structure, holey architecture of HRGO, good wettability and excellent mechanical flexibility. Besides, satisfactory mechanical performance and good biocompatibility confer the HRGO/BC promising candidates for multifunctional electronics, especially for wearable and implantable electronic devices. The unique bio-assembly method also provides novel pathway to fabricate integrated 3D honeycomb structure gels or films for medical or/and electrical fields.

Improved Electrochromic Characteristics of a Honeycomb-Structured Film Composed of NiO.

Color changes controlled by electronic energies have been studied for many years in order to fabricate energy-efficient smart windows. Reduction and oxidization of nickel oxide under the appropriate voltage can change the color of a window. For a superior nickel oxide (NiO) electrochromic device (ECD), it is important to control the chemical and physical characteristics of the surface. In this study, we applied polystyrene bead templates to nickel oxide films to fabricate a honeycomb-structured electrochromic (EC) layer. We synthesized uniform polystyrene beads using the chemical wet method and placed them on substrates to create honeycomb-structured NiO films. Then, the EC characteristics of the nickel oxide films with a honeycomb structure were evaluated with UV-Visible and cyclic voltammetry. FE-SEM and AFM were used to measure the morphologies of the nanostructures and the efficiencies of the redox reactions related to the specific surface area.

Interfacial self-assembly of monolayer Mg-doped NiO honeycomb structured thin film with enhanced performance for gas sensing

The relatively low sensitivity, slow response and complicated or energy consuming preparation processes of NiO-based sensors greatly restrict their further application. In this work, monolayer Mg-doped NiO thin film was fabricated via an interfacial self-assemble strategy and a subsequent annealing process. Polystyrene spheres with diameters of about 700 nm were used as templates. The as-prepared monolayer Mg-doped NiO thin film presents a honeycomb structure. The film formation process and possible sensing mechanism of the honeycomb structured Mg-doped NiO thin film are also discussed. Moreover, the film-based gas sensor presents a high selectivity to ethanol gas against other gases. The response ratio of the Mg-doped NiO film sensor to 100 ppm ethanol is 10.4 at 325 °C. This ratio is also much better than some of the previously reported values in literatures. Furthermore, the Mg-doped NiO sensor also shows a significantly enhanced sensing properties in terms of higher selectivity, faster response and recovery time than our honeycomb structured pure NiO thin film. The remarkable properties may be attributed to the honeycomb structure and the Mg doping, which produce more active sites for the gas reaction and adsorption on the surface of the sensing materials. This facile fabrication strategy can be further utilized to prepare other monolayer metal oxide film-based devices.

Molecular Design for Preparation of Hexagonal-Ordered Porous Films Based on Side-Chain-Type Liquid-Crystalline Star Polymer.

Fabrication of regularly porous films by the breath-figure method has attracted much attention. The simple, low-cost technique uses the condensation of water droplets to produce these structures, but the phenomenon itself is complex, requiring control over many interacting parameters that change throughout the process. Developing a unified understanding for the molecular design of polymers to prepare ordered porous films is challenging, but required for further advancements. In this article, the effects of the chemical structure of polymers in the breath-figure technique were systematically explored using side-chain-type liquid-crystalline star polymers. The formation of porous films was affected by the structure of the polymers. Although the entire film surface of poly(11-[4-(4-cyanobiphenyl)oxy]undecyl methacrylate) (P11CB) had a hexagonal ordered porous structure over a certain Mn value, regularly arranged holes did not easily form in poly(methyl methacrylate) (PMMA), even though the main chain of PMMA is similar to that of P11CB. A comparison of P11CB and poly(11-[(1,1'-biphenyl)-4-yloxy]undecyl methacrylate) (P11B) (P11CB without cyano groups) showed that the local polar groups in hydrophobic polymers promoted the formation of ordered porous films. No holes were formed in poly(4-cyanobiphenyl methacrylate) (P0CB) (P11CB without alkyl spacers) films due to its hydrophilicity. The introduction of alkyl chains in P0CB allowed the preparation of honeycomb-structured films by increasing the internal tension. However, alkyl chains in the side chain alone did not result in a porous structure, as in the case of poly(undecyl methacrylate) (P11). Aromatic rings are also required to increase the Tg and improve film formability. In the present study, suitable molecular designs of polymers were found, specifically hydrophobic polymers with local polar groups, to form a regularly porous structure. Development of clear guidelines for the molecular design of polymers is the subject of our current research, which will enable the fabrication of porous films using various functional polymers.

Directed Self-Assembly in "Breath Figure" Templating of Melamine-Based Amphiphilic Copolymers: Effect of Hydrophilic End-Chain on Honeycomb Film Formation and Wetting.

Amphiphilic copolymers are widely used in the fabrication of hierarchically honeycomb-structured films through a "breath figure" (BF) process because the hydrophilic block plays a key role in stabilising water templating. However, the hydrophilic monomers reported are mainly confined to acrylic acid and its derivatives, which largely limits understanding of the formation of BF arrays and the introduction of additional functions on porous films. The relationship between polymer composition, film microstructure and surface properties are also less documented. Herein, a novel melamine-based hydrophilic moiety, N-[3-({3-[(4,6-bis{[3-(dimethylamino)propyl]amino}-1,3,5-triazin-2yl)amino]propyl}(methyl)amino)propyl]methacrylamide (ANME), was incorporated into polystyrene (PS) chains by combining atom-transfer radical polymerisation and post-modification to afford three well-defined end-functionalised PS-PANME derivatives. These polymers were used to fabricate honeycomb films through the BF technique. Both inner and outer microstructures of the films were characterised by optical microscopy, AFM and SEM. Polymer hydrophilicity is enhanced upon increasing the PANME content, which results in variation of the film microstructure and porosity, and provokes a transition from Cassie-Baxter to Wenzel behaviour. Furthermore, the surface wettability of as-prepared honeycomb films and corresponding pillared films is mainly governed by film morphology, rather than by the properties of the polymers. Knowledge of the relationships between polymer composition and film structure, as well as surface wettability, is beneficial to design and prepare hierarchically porous films with desirable structures and properties.

Rhodamine B-decorated poly(hydroxypropyl acrylate) and their effects on the self-assembly of breath figure arrays

Novel poly(hydroxypropyl acrylate)-co-poly(hydroxypropyl acrylate)-rhodamine B (PHPA-co-PHPA-RhB) hydrophilic copolymers were synthesized via radical polymerization in this paper. And then the honeycomb-structured porous films were fabricated by dropping the (PHPA-co-PHPA-RhB) copolymers and PS solution on glass substrates by breath figure method (BFM). The effects of solvent, hydrophilic copolymers’ molecular weight, the proportion of hydrophilic copolymers and hydrophobic polymers on the formation of porous films were investigated. The porous films were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), spectrofluorometer and confocal laser scanning microscope (CLSM). The results show that PHPA-co-PHPA-RhB and PS solutions can form regular honeycomb porous films; the average diameter of the films pore decreases with the proportion of hydrophobic polystyrene increased. Similar regular was also found when the molecular weight of PHPA-co-PHPA-RhB was enhanced. Furthermore, the fluorescence properties of the porous films were also investigated in this study.

Photoluminescent Honeycomb Structures from Polyoxometalates and an Imidazolium-Based Ionic Liquid Bearing a π-Conjugated Moiety and a Branched Aliphatic Chain.

Honeycomb-structured films represent an intriguing class of two-dimensional porous materials. Specifically, polyoxometalate (POM) macroanions can be introduced into these films by complexing with oppositely charged, double-tailed surfactants. Here highly-ordered honeycomb structures are reported that can be constructed by the complexes between POMs and a room temperature ionic liquid (IL1) having an imidazolium moiety in the middle and a naphthyl unit and a branched aliphatic chain at the ends. The complexes can be produced through phase transfer between an aqueous solution of POMs (typically {Mo72 Fe30 }) and a CS2 (or chloroform) solution of IL1. Based on the intrinsic properties of {Mo72 Fe30 } and the functional groups of the IL1, the honeycomb structures show multiple functions with bright photoluminescence and rich electrochemical properties. This work shows that by simply engineering the organic ligands involved in the POM-based inorganic-organic complexes, supramolecular structures with improved properties and wide applications can be obtained.

Enhanced efficiency of the honeycomb-structured film WO3 composed of nanorods for electrochromic properties

To reduce solar heat and glare from visible light, the color of window panes need to be controlled by electronic energy. Metal oxides deposited on these “smart” windows such as WO3, Nb2O5, and NiO can change the color of the glass by absorbing visible rays. It is important to control the chemical and physical characteristics of the surface of films and to apply a uniformly thin film to obtain a superior product. In this study, we generated templates as nanostructured WO3 monolayers in nanorods with 400nm-sized polystyrene (PS) beads. Honeycomb structures were prepared from the well-ordered monolayer template with PS beads that were synthesized by wet chemistry. We investigated the enhanced electrochromic (EC) properties of a honeycomb structured WO3 thin films which were composed of WO3 nanostructures. Nanoarchitectural properties like morphology of films, crystalline phases and the structures of WO3 nanoparticles were examined by Field Emission Scanning Electron Microscopy, X-ray diffraction and Transmission Electron Microscopy. And EC standards such as the variation of transmittance, reaction time and efficiency of redox reactions called by “coloration efficiency” were measured by UV–Vis spectrophotometer, and cyclic voltammetry. The electrochromic reaction rate of honeycomb structured WO3 thin films was fast (coloration time: 5.86s and bleaching time: 6.65s) but, the variation of light transmission (Δ85.04% at 700nm wavelength) was comparable to that of flat WO3 film with the similar thickness of about 300nm. These results suggested that the surface area enlarged by the honeycomb structure induced by PS templating caused the simultaneous redox reaction in the entire WO3 film.

Hierarchical honeycomb-structured films by directed self-assembly in "breath figure" templating of ionizable "clicked" PH3T-b-PMMA diblock copolymers: an ionic group/counter-ion effect on porous polymer film morphology.

The self-assembly of 1,2,3-triazole and ionic 1,2,3-triazolium "clicked" poly(3-hexylthiophene)-b-poly(methylmethacrylate) (P3HT-b-PMMA) rod-coil diblock copolymers was used to fabricate honeycomb-patterned porous films via "breath figure" templating. The surface and inner morphologies of the honeycomb films can be both controlled by either ionizing the 1,2,3-triazole linker or changing the counter-ion nature.

Static and Dynamic Hydrophobic Properties of Honeycomb Structured Films via Breath Figure Method

This work reported the static and dynamic hydrophobic properties of the honeycomb porous and peeled films with pincushion structures by changing the concentrations of the copolymer solution. Honeycomb porous films were fabricated via breath figure technology employing a pentablock copolymer containing poly(ethylene glycol)/PEG, poly(methyl methacrylate)/PMMA, and poly(trifluoroethyl methacrylate)/PTFEMA. The relationship between the copolymer concentrations and the pore size (D) and rim width (W) was examined. Moreover, we studied the hydrophobic properties from different surfaces of flat, porous, and pincushion structures, and the contact angles, W/D ratios, and fraction of air on the porous and pincushion films were obtained. It was noteworthy that the W/D ratios and surface hydrophobic properties had a notable correlation. Finally, the dynamic behaviors of water droplets impacting on these porous and pincushion films were examined using a high speed camera. It examined the influence of the fraction of ...

Mussel-Inspired Modification of Honeycomb Structured Films for Superhydrophobic Surfaces with Tunable Water Adhesion

In this paper, we report novel superhydrophobic surfaces with tunable water adhesion by combining mussel-inspired surface chemistry and bioinspired multiscale surface structures. Highly ordered honeycomb porous films were prepared from a diblock copolymer polystyrene-block-poly(N,N-dimethylaminoethyl methacrylate) by the breath figure method. Removing the top surface layer of the honeycomb films leads to pincushion-like surfaces. The films were coated with polydopamine after completely prewetting by ethanol, followed by the reaction with 1H,1H,2H,2H-perfluorodecanethiol for fluorination. As a result of the surface modification, both the honeycomb and the pincushion-like surfaces are superhydrophobic with a water contact angle higher than 150°. Interestingly, the former is highly adhesive, on which water droplets are pinned at any tilted angles, whereas the latter is relatively low adhesive. Calculations indicate that the honeycomb films are in the Cassie state, whereas the pincushion-like surfaces are in ...

Enhanced cell adhesion to the dimpled surfaces of golf-ball-shaped microparticles.

Engineering surface morphology as in honeycomb-structured planar films is of great importance for providing new potential application and improved performance in biomedical fields. We demonstrate potential new applications for the uniform biocompatible golf-ball-shaped microparticles that resembles 3D feature of honeycomb-structured film. Dimple size controllable golf-ball-shaped microparticles were fabricated by microfluidic device. Surface dimples not only can act as picoliter beaker but also enhance cell adhesion without any chemical modification of the surface.

Fabrication of Structured Porous Films by Breath Figures and Phase Separation Processes: Tuning the Chemistry and Morphology Inside the Pores Using Click Chemistry

Herein, a facile water-assisted templating technique, the so-called breath figures method, in combination with phase separation process, was employed to prepare multifunctional micropatterned films. Tetrahydrofuran solutions of incompatible ternary blends consisting of high-molecular-weight polystyrene, an amphiphilic block copolymer, polystyrene-b-poly[poly(ethylene glycol) methyl ether methacrylate] (PS40-b-P(PEGMA300)48), and a fluorinated homopolymer, poly(2,3,4,5,6-pentafluorostyrene) (P5FS21) were casted under humid atmosphere varying the proportion of the components. Two simultaneously occurring processes, i.e., the breath figures mechanism and the phase separation process, lead to unprecedented morphologies that could be tuned by simply varying the relative humidity or the composition of the blend. Confocal micro-Raman spectroscopy served to provide information about the location and distribution of the different functionalities in the films. As a result, both the amphiphilic block copolymer and the fluorinated polymer were mainly located in the cavities. Above a certain percentage of relative humidity, honeycomb structured films were obtained in which the block copolymer is distributed on the edge of the pore as a result of the affinity by the condensing water droplet and the coffee stain effect. The homopolymer is also preferentially situated at the pore edge, but forming spherical domains with narrow polydisperse sizes. Moreover, thiolated glucose molecules were specifically attached to the P5FS21 domains via thiol-para fluorine "click" reaction. Subsequently, the specific lectin (Concanavalin A, Canavalia ensiformis) was attached to the surface by conjugation with the glucose moieties. The successful binding of the Con A was demonstrated by the fluorescence, observed exclusively at the areas where P5FS21 domains are located. This nonlithographic method opens a new route to fabricate a huge variety of microstructured polymer films in terms of morphology not only for protein patterning, as illustrated in this manuscript, but also to produce a diversity of functional group arrangements.

Advances in Fabrication Materials of Honeycomb Structure Films by the Breath-Figure Method.

Creatures in nature possess almost perfect structures and properties, and exhibit harmonization and unification between structure and function. Biomimetics, mimicking nature for engineering solutions, provides a model for the development of functional surfaces with special properties. Recently, honeycomb structure materials have attracted wide attention for both fundamental research and practical applications and have become an increasingly hot research topic. Though progress in the field of breath-figure formation has been reviewed, the advance in the fabrication materials of bio-inspired honeycomb structure films has not been discussed. Here we review the recent progress of honeycomb structure fabrication materials which were prepared by the breath-figure method. The application of breath figures for the generation of all kinds of honeycomb is discussed.

Patterned Honeycomb Structural Films with Fluorescent and Hydrophobic Properties

We have fabricated the patterned porous honeycomb‐like film with the aggregation‐induced emission (AIE) property successfully by breath figure method. Characterization of contact angles (CA) indicated that the patterned porous honeycomb structure can improve the hydrophobicity of the film, while smooth films do not have this function. Characterization of the fluorescence property indicates that the patterned honeycomb structure films are highly emissive. This work could not only be promising for controlling molecular group reorientation and suitable for the application of manipulating surface composition of the film but also make the tetraphenylethene derivatives with AIE properties have a promising application future in special wettability surface. The present findings should open a way for the new application of honeycomb structure materials, which will be useful in many areas, such as sensors, tissue engineering, clinical medicine, and biomaterials.