Monolayer Colloidal Crystal Template Research Articles

Fabrication and UV photoresponse of ordered ZnO nanonets using monolayer colloidal crystal template

Two-dimensionally Ordered macroporous films have attracted attention for their potential application such as sensors and optoelectronic devices. Here, highly ordered ZnO nanonets film were successfully prepared by a facile method, which uses monolayer colloidal crystal template composed of polystyrene spheres and sol-gel spin-coating method. Furthermore, ZnO nanonets-based ultraviolet photodetector are constructed, which showed high on/off current ratio of 2.7 × 10 5 under 370 nm UV light illumination with an intensity of 0.85 mW/cm 2 .

Nanoscale directional etching features and mechanism of HF/HNO3 etchant

Large-scale and periodic silicon nanostructure arrays are an essential component for various functional devices. However, the conventional selective etching mechanism of specific crystal faces for monocrystalline silicon generally achieves slope or vertical morphology, which greatly limits the preparation of other morphology of silicon nanostructures. In this work, the conventional isotropic etchant HF/HNO3 has successfully achieved nanoscale directional etching and cambered morphology on monocrystalline silicon surface for the first time by changing the synchronous process of oxidation and dissolution into an asynchronous process. Based on the self-assembled monolayer colloidal crystal templates, large-area and high-quality nanopore arrays are prepared on the monocrystalline silicon surface. Particularly, the directional etching ability of HF/HNO3 etchant is further confirmed by combining with electron beam lithography and scanning probe lithography technologies. Hence, this nanoscale directional etching mechanism and etchants provide a promising strategy to achieve cambered morphology nanopores on the monocrystalline silicon surface.

基于胶体晶体模板的表面图案化构建及其应用进展

基于胶体晶体模板的表面图案化构建及其应用进展

Drastically Enhanced Ammonia Sensing of Pt/ZnO Ordered Porous Ultra-Thin Films

Two-dimensional ordered thin films hold promise for high performance gas sensors owing to their controllable morphology. In this work, Pt/ZnO ordered porous sub-micrometer films were synthesized by polystyrene sphere monolayer colloidal crystal template method, and their gas-sensing properties were systematically studied. The ordered porous films presented a honeycomb-like morphology with a thickness of 500 nm. Pristine ZnO exhibited an unusual p-type like response to NH3 with resistance increase and low sensitivity, while Pt-loaded samples showed n-type sensing with remarkably enhanced sensor performance. Pt loading led to a 200-times larger response of 324 to 100 ppm NH3 and a high sensitivity of 10.5 ppm-1 at 330 °C. Significantly reduced response time and depressed the cross-sensitivity to common interfering gases were also achieved. These render the Pt/ZnO ordered porous films much superior NH3 sensing performance to state-of-the-art ZnO based sensors. The excellent performance may be attributed to the synergistic effects of the catalytic and electronic promotion of Pt and unique nano-morphology of the porous films.

Morphology-controllable gold hierarchically micro/nanostructured arrays prepared by electrodeposition on colloidal monolayer and their structurally related wettability

In this paper, we demonstrated a clean fabrication of the morphology-controllable gold hierarchically micro/nanostructured arrays (HMNAs) by electrochemical deposition on polystyrene monolayer colloidal crystal template. Through varying cathodic current density and deposition time to adjust electrocrystallization process, the HMNAs can be controlled from the one with microspheres and nanoparticles to the one with microbowls and nanorods. Further adjusting the nucleating sites via ion-sputtering deposition of gold film over the polystyrene spheres, we designed and prepared a new kind of HMNA with microspheres and nanowimbles. Interestingly, these Au HMNAs exhibited structurally related wettability. Correlated with their different hierarchical micro/nano-structures, they all showed superhydrophobicity after surface modification of low surface free energy material while with different surface adhesions. A water droplet can pine on the surface of the concave Au HMNA with microbowls and nanorods even turned upside down, showing ultrahigh liquid-solid adhesion. However, the convex Au HMNA with microspheres and nanowimbles shows very low surface adhesion with a sliding angle close to zero. These surface adhesion-controlled superhydrophobic surfaces can be found many potential applications, such as self-cleaning surfaces, liquid transportation, and multifunctional microfluidic devices.

Durable Broadband and Omnidirectional Ultra-antireflective Surfaces.

Light reflection from surfaces is ubiquitous in nature. Diverse optoelectronic devices need durable, omnidirectional, and transparent ultra-antireflective surfaces. Here, we engineered antireflective transparent surfaces composed of silica nanocaps through a simple thermal treatment of a silica-coated monolayer colloidal crystal template. The relationship between the structure and the antireflective performance of the silica nanocaps was systematically studied both experimentally and numerically. On the basis of the understanding of the structure-antireflection relationships, ultra-antireflection coatings with a transmittance of ∼98.75 ± 0.15% in the visible wavelength range were prepared by fabricating two differently sized silica nanocaps. More importantly, the antireflection of the coatings formed by two differently sized nanocaps demonstrated poor dependence on the angle of the incident light (i.e., omnidirectionality). The reflection is <2.5% even at an incident angle of 60°. The prepared ultra-antireflective silica nanocap coatings outperform state-of-the-art transparent antireflective coatings regarding the antireflection performance, the wavelength range, and the omnidirectionality. The silica nanoshells were welded together with the underlying fused silica. Therefore, they can sustain common mechanical friction and scratching, demonstrating extraordinary mechanical durability as verified by sand abrasion tests. Further, the silanized silica nanocaps turned out to be hydrophobic with an outstanding self-cleaning performance without prominently influencing the transmittance. The durable and omnidirectional ultra-antireflective transparent silica nanocaps will have promising applications in solar energy conversion and storage, displays, optical lenses, and a wide range of optoelectronic devices.

Highly efficient production of ordered wafer-scale gold nanoparticle arrays film by simple heat treatment based on colloidal monolayer

Periodic hexagonal gold crystal spherical nanoparticle arrays with controllable size and periodicity are fabricated by physical vapor deposition and further heat treatment based on monolayer colloidal crystal template. The size and center-to-center spacing of nanoparticles (NPs) were manipulated conveniently by tuning the deposition thickness of Au film and the size of colloidal spheres of the template, respectively. The thickness range of deposited Au film dependent on the size of colloidal spheres was investigated comprehensively. Dewetting model was established and employed to analyze the whole process of the evolution from gold film to spherical nanoparticle with uniform size. Additionally, localized surface plasmon resonance (LSPR) responses of these Au nanoparticle arrays were systematically measured. It is found that the extinction properties are significantly influenced by the particle size and periodicity of arrays. With the increase of particle size, the LSPR peak shows a red shift due to the quantum size effect of the nanoscaled Au particle. Meanwhile, the diffraction peaks also show small red shift due to a slight increase of average refractive index of arrays. This is highly helpful to improve its practical applications for detecting biochemical molecules based on LSPR and diffraction peak sensing.

Synthesis of ordered bowl-like polyaniline film with enhanced electrochromic performances

A bowl-like polyaniline (PANI) film is synthesized by the combination of electrodeposition and monolayer colloidal crystal template (MCCT). The resulting film exhibits an ordered hexagonal close-packed bowl-like arrangement that is made up of macrobowls with a diameter of 450nm. The unique bowl-like structure endows PANI film with enhanced electrochromic performances due to its increased accessible intercalation sites originating from larger surface areas and shortened diffusion distances of ions resulting from macroporous structure. It is found that the bowl-like PANI film possesses faster switching responses (1.45s for coloration and 0.62s for bleaching), larger optical transmittance modulation (52.1% at 740nm) and higher coloration efficiency (118.2cm2C−1) than the dense PANI film prepared without the MCCT. Moreover, the bowl-like film also exhibits IR electrochromic performances in the wavelength range from 2.5–25μm, which depicts a reflectance modulation∼36.5% at 10μm. This work provides a promising strategy for constructing other bowl-like polymer electrochromic films.

High‐Performance Photodetectors Based on Organometal Halide Perovskite Nanonets

The booming development of organometal halide perovskites has prompted the exploration of morphology‐engineering strategies to improve their performance in optoelectronic applications. However, the preparation of optoelectronic devices of perovskites with complex architectures and desirable properties is still highly challenging. Herein, novel CH3NH3PbI3 nanonets and nanobowl arrays are fabricated facilely by using monolayer colloidal crystal (MCC) templates on different substrates. Specifically, highly ordered CH3NH3PbI3 nanonets with high crystallinity are fabricated on a variety of flat substrates, whereas regular CH3NH3PbI3 nanobowl arrays are produced on a coarse substrate. The photodetection performance of the CH3NH3PbI3 nanonet‐based photodetectors is significantly enhanced compared to the photodetectors based on conventional CH3NH3PbI3 compact films. Particularly, the nanonet photodetectors exhibit a high responsivity (10.33 A W−1 under 700 nm monochromatic light), which is six times higher than that for the compact CH3NH3PbI3 film devices, fast response speed, and good stability. Owing to the two‐dimensional arrayed structure, the CH3NH3PbI3 nanonets exhibit an enhanced light harvesting ability and offer direct carrier transport pathways. Meanwhile, the MCC template brings about larger grain sizes with enhanced crystallinity. Furthermore, the perovskite nanonets can be formed on a flexible polyethylene terephthalate substrate for the fabrication of promising flexible nanonet photodetectors.

A nanostructured Fc(COCH3)2 film prepared using silica monolayer colloidal crystal templates and its electrochromic properties.

Since oxidation and reduction reactions mainly take place on surfaces, enlarging the specific surface of redox materials is the key to achieving excellent electrochemical performance. In this work, by using silica monolayer colloidal crystal templates (MCCTs), a nanostructured Fc(COCH3)2 film is prepared successfully, and such a nanostructure could exhibit the following unique electrochemical properties: the MCCTs could impede the aggregation tendency of Fc(COCH3)2 and possess high electrochemical activity; Fc(COCH3)2 enlarges the contact area and offers more active sites and faster electronic transmission channels. The structure, optical and electrochemical properties of the nanostructured Fc(COCH3)2 were tested and then compared with those of compact Fc(COCH3)2 films to evaluate the role of the nanoarchitecture. The unique structure design of the Fc(COCH3)2 film enables outstanding performance, showing a large transmittance change (ΔT) of 37% at 550 nm when switched between 0.5 V and -2.5 V, which is approximately ninefold higher than that of the compact Fc(COCH3)2 film (approximately 4%). Response times of coloration and bleaching are found to be only 16.15 s and 5.56 s. Furthermore, the nanostructured Fc(COCH3)2 film shows much better cycling stability than the compact one. The results indicate that the nanostructure could significantly improve the electrochemical performance of the Fc(COCH3)2 film due to the increase in electrochemical active sites and the enhancement of the "D-to-A" redox switch of ferrocene.

Recent progress in the fabrication of SERS substrates based on the arrays of polystyrene nanospheres

Micro/nanostructures have broad applications in diverse application fields, such as surface enhanced Raman spectroscopy (SERS), photocatalysis, field emission, photonic crystals, microfluidic devices, electrochemical devices, etc. Using polystyrene (PS) spheres formed monolayer colloidal crystal templates as masks, scaffolds, or molds with different materials growth techniques, many different periodic nanostructured arrays can be obtained with the building units varied from nanoparticles, nanopores, nanorings, nanorods, to nanoshells. Significant progresses have been made on the synthesis of micro/nanostructures with efficient SERS response. In this review, we mainly focus on the various PS template-based fabrication techniques in realizing micro/nanostructured arrays and the SERS applications.

Oxygen vacancy-related room temperature ferromagnetism in TiO2 nanohole arrays

Room temperature ferromagnetism was observed in hole-like TiO2 nanostructure arrays prepared by a monolayer colloidal crystal template.

Combining the Masking and Scaffolding Modalities of Colloidal Crystal Templates: Plasmonic Nanoparticle Arrays with Multiple Periodicities.

Surface patterns with prescribed structures and properties are highly desirable for a variety of applications. Increasing the heterogeneity of surface patterns is frequently required. This work opens a new avenue toward creating nanoparticle arrays with multiple periodicities by combining two generally separately applied modalities (i.e., scaffolding and masking) of a monolayer colloidal crystal (MCC) template. Highly ordered, loosely packed binary and ternary surface patterns are realized by a single-step thermal treatment of a gold thin-film-coated MCC and a nonclose-packed MCC template. Our approach enables control of the parameters defining these nanoscale binary and ternary surface patterns, such as particle size, shape, and composition, as well as the interparticle spacing. This technique enables preparation of well-defined binary and ternary surface patterns to achieve customized plasmonic properties. Moreover, with their easy programmability and excellent scalability, the binary and ternary surface patterns presented here could have valuable applications in nanophotonics and biomedicine. Specific examples include biosensing via surface-enhanced Raman scattering, fabrication of plasmonic-enhanced solar cells, and water splitting.

Progress in Preparation and Properties of the Bowl-like Particles and Arrays

Nonspherical particles include various morphologies, such as snow-shaped, mushroom-shaped, dumbbell-shaped, H2O molecules-shaped, bowl-like. Their unique structures not only provide novel assembly units, but also bring many special physical and chemical properties. During the last ten years, micro/nanometer bowl-like particles and arrays have been given widely attention. Due to their large specific surface area, low structure symmetry, the bowl-like particles and bowl-like arrays have unique optical, magnetic properties and provide broad potential applications in nano-reactors, drug delivery, high-sensitivity sensor, data storage, assembly units, solar cell and other fields. This review gives a systematic overview on the recent advances in the fabrication and properties of the bowl-like particles and bowl-like arrays. First, various synthesis routes are introduced in detail, including the monolayer colloidal crystal template approach, the bowl-like array template approach, induced growth, heterodimeric particle approach, hollow microspheres invagination, seed polymerization, sol- vent-treatment approach. Next, the relationship between the structure and the property of the bowl-like particles and arrays are investigated according to the types of material. The diverse applications of the obtained materials are also summarized, for example photo catalysis, solar cells, micro/nanometer devices, sensors, and so on. Finally, the advantages and disadvan- tages of various synthesized methods are discussed and an outlook on future developments in this area is also provided.

Standing Ag nanoplate-built hollow microsphere arrays: Controllable structural parameters and strong SERS performances

A simple and flexible strategy is presented to fabricate the Ag nanoplate-built hollow microsphere arrays with centimetre-squared scale, based on electrodeposition onto the Au-coated monolayer colloidal crystal template. The array consists of periodically arranged micro-sized hollow spheres, which are built by vertically standing and cross-linking Ag nanoplates. The nanoplates are of single crystal in structure, several hundred nanometres in the planar dimension and about 30 nm in thickness. The number density and size of silver nanoplates can be controlled by the deposition conditions. The formation of nanoplates is mainly attributed to the electrodeposition-induced nanoplates' growth in the initial stage and subsequent electrophoretic deposition-induced oriented connection of Ag nanoparticles, formed in solution, under a low current density. Importantly, such hollow sphere micro-/nano-structured arrays have shown significant surface-enhanced Raman scattering (SERS) effect associated with their geometry, exhibiting strong SERS performances with high stability and good homogeneity. The enhanced factor is higher than 108. The minimum detectable concentration of 4-aminothiophenol molecules can be lower than 10−15 M. Further, such arrays could be re-usable based on an argon plasma cleaning method. This study is of significance, not only in the deep understanding Ag nanoplates' formation and growth, but also in device application of micro-/nano-structured arrays based on SERS effect.

Recent progress on surface pattern fabrications based on monolayer colloidal crystal templates and related applications

This review summarizes the recent progress toward the fabrication of surface patterns depending on the monolayer colloidal crystal templates. Based on the structural differences of the acquired surface patterns, various synthesis routes are introduced in detail. The diverse device applications of the synthesized surface patterns are also summarized, including sensors, energy-related devices, field emissions, wettability control, and so on. Future research should focus on surface patterns composed of multiple-layered structures and hybrid materials, and the widening of their application explorations.

Janus particle arrays with multiple structural controlling abilities synthesized by seed-directed deposition

Janus particle arrays have attracted much investigation interest in recent years due to their wide application potentialities. Here, we introduce a new protocol to synthesize Janus particle arrays depending on seed-directed eletrophoretic deposition on monolayer colloidal crystal (MCC) templates. The size and feature of the Janus particles can be conveniently tailored by selecting different sized polystyrene spheres and deposition current densities and/or times, respectively. Non-close-packed Janus particle arrays can be prepared by adopting plasma treated monolayer colloidal crystal templates. The spacing between neighbouring Janus particles in the ordered array is determined by the plasma etching time of the MCC template. Due to the symmetry breaking and the plasmon hybridization, the Janus particle arrays show interesting plasmonic properties. They have multiple plasmonic peaks and have infrared absorption, making them have applications in sensing and bio-related areas.

Micro/Nanostructured Ordered Porous Films and Their Structurally Induced Control of the Gas Sensing Performances

AbstractA simple and flexiable route is presented to fabricate ordered micro/nanostructured porous films, based on a monolayer colloidal crystal template and solution dipping. In2O3 is chosen as a main model material to demonstrate the validity of the given fabrication strategy. It has been shown that the porous films with different microstructures, can be constructed directly on any desired substrate (with flat, curved, or even rough surface). The separately tunable sensitivity and response time in a large range and the gas sensing performances with both high sensitivity and fast response have been obtained only by controlling microstructures of the porous films. High stability, good reproducibility, and selectivity of the sensing performance have been achieved. Further, micro/nanostructured porous film sensors with desired sensing performances are designed and fabricated. This work could be important towards practical applications of micro/nanostructured porous‐film‐based sensors in the near future.

Ordered Micro/Nanostructured Arrays Based on the Monolayer Colloidal Crystals

Besides the traditional lithographical techniques to fabricate the ordered mciro/nanostructured arrays, the route of the monolayer colloidal crystal template is a recently promising, alternative process for the synthesis of the micro/nanostructures with different designed morphologies. By this strategy, two-dimensional ordered arrays, e.g., nanoparticle arrays, pore arrays, nanoring arrays, nanobowl arrays, hollow sphere arrays, etc., even one-dimensional nanostructures of ordered nanorod/nanopillar/nanowire arrays, etc., could be prepared. Recent progress in this area is reviewed, including synthesis strategies and morphology-dependent properties of the micro/nanostructured arrays such as optical properties, wettability, surface-enhanced Raman scattering, and photonic bandgap.