Colloidal Crystal Template Research Articles

Three-Dimensional Ordered Macro/Mesoporous Cu/Zn as a Lithiophilic Current Collector for Dendrite-Free Lithium Metal Anode.

Li dendrites are considered as the primary cause for degradation and inevitable short circuit in lithium-metal batteries (LMBs). Although contemporary strategies have shown potential for addressing dendrite growth, none have achieved complete elimination. In this paper, a dendrite-free, three-dimensional, ordered, macro/mesoporous Cu/Zn current collector was prepared using a combination of simple colloidal crystal template and electrochemical method (electrodeposition and pulse plating). When paired with a hierarchically structured mesoporous (20-50 nm) and macroporous (450 nm) anode, this novel current collector achieved stable charge/discharge cycles of over 2000 h and a small plating/stripping potential (≈8 mV) at a current density of 0.2 mA cm-2. Coulombic efficiencies (CE) also reached 94.7% after 400 cycles. This three-dimensional, ordered, macro/mesoporous structure provides a greater specific surface area, reduces local current density, and contains a lithiophilic Zn coating that serves as preferred Li nucleation sites. By combining these factors, dendrite-free Li deposition and superior electrochemical performance improvements in LMBs have been realized.

Temperature-dependent mechanical behavior of three-dimensionally ordered macroporous tungsten

Abstract

Fabrication and photoelectrochemical activity of hierarchically Porous TiO2–ZnO heterojunction film

For the first time, we report the fabrication of hierarchically (macro with nested meso) porous nanocrystalline TiO2–ZnO heterojunction film onto fluorine-doped tin oxide-coated glass substrate by colloidal crystal templating technique using poly(methyl methacrylate) (PMMA) spheres as template. Accordingly, the precursor solutions of titanium isopropoxide and zinc acetate dihydrate in the presence of Pluronic P123 were used to impregnate the individual solution into the template. Initially, nanocrystalline TiO2 inverse opal mesoporous film was deposited using the titanium precursor. The film was cured at 450 °C in an air atmosphere. A similar process was adopted to deposit nanocrystalline ZnO inverse opal mesoporous film onto the TiO2 to obtain hierarchically porous TiO2–ZnO heterojunction nanocrystalline film. Morphology of the fabricated films showed a periodic arrangement of macropores, whereas the microstructural analysis confirmed the presence of nested mesopores in the film network. Chemical interaction existed between TiO2 with ZnO forming the heterojunction film was ascertained by X-ray photoelectron spectroscopy. Light harvesting efficiency of the samples was studied, and the photoelectrochemical (PEC) performance of the hierarchically porous heterojunction films as photoanode showed about 5 times enhancement in photocurrent density compared to the pristine metal–oxide–semiconductor film under visible light exposure. The porous nanocrystalline hierarchically porous inverse opal heterojunction film could be used as an efficient photoanode in PEC cell.

High-efficient non-noble metal catalysts of 3D ordered macroporous perovskite-type La2NiB’O6 for soot combustion: Insight into the synergistic effect of binary Ni and B’ sites

Double perovskite-type La2NiB’O6 (B’=Mn, Fe, Co, Cu) catalysts with three-dimensional ordered macroporous (3DOM) structure were synthesized by colloidal crystal template method. 3DOM structure promotes the contact efficiency between soot and catalyst. The periodic arrangement of [NiO6] and [B’O6] octahedrons in La2NiB’O6 induces the formation of coordination unsaturated B-site ions. 3DOM La2NiB’O6 catalysts exhibited super catalytic performance for soot combustion under the simulated exhaust, and their catalytic performances are dependent on the synergistic effect of binary Ni and B'-site ions. 3DOM La2NiCoO6 catalyst had the highest catalytic activity for soot combustion, i.e., its T50, SCO2m, TONs and TOFOv values are 362 °C, 98.2 %, 7.80 and 0.151 h−1, respectively. The mechanism was proposed that the synergistic effect of Ni and B’ ions boosts the key step of NO oxidation to NO2. It is meaningful for the development of the non-precious metal catalysts during soot combustion.

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.

Facile Electrochemical Routes for the Composite Coating on Au Inverse Opals As Highly-Sensitive Enzyme-Free Biosensors

The highly sensitive detection of hydrogen peroxide (H2O2) is of practical importance due to its involvement in the biofunction and signal transduction of cells. Various electrochemical techniques have been explored and studied for its detection, which can be realized through either enzymatic or non-enzymatic sensors. Particularly, non-enzymatic biosensors have been in great demand because of their high stability, high reproducibility, and less susceptible to environmental factors compared to the enzyme-based approach. However, many of them display inferior sensitivity or poor selectivity. Hence, this work aims to develop a highly sensitive non-enzymatic biosensor through structural and compositional approaches. From a structural point of view, Au inverse opals are utilized as the sensor scaffold due to their intriguing porous structure. The spatial arrangement of these materials resembles a honeycomb structure, which provides a high specific surface area, efficient mass transport, and strong mechanical stability. In addition to the benefits brought by inverse opals, we further incorporate a composite coating based on Cu2O to decorate the scaffold surface. Through the combination of a well-ordered pore structure with additional functionalization by composite formation, a synergistic improvement could be realized. To fabricate such structural biosensors, an expedited self-assembly process exploiting electrophoresis technique is first adopted to produce a colloidal crystal template. Subsequent electrodeposition processes are performed to construct the Au inverse opals and relevant functional coatings. The sensing performance of these 3D sensors is then evaluated by the detection of H2O2 using cyclic voltammetric analysis. Their structural and compositional characterizations are conducted by SEM, EDX, XPS, and Raman spectroscopy.

Simple synthesis of hierarchically porous Sn/TiO2/graphitic carbon microspheres for CO2 reduction with H2O under simulated solar irradiation.

A simple colloidal crystal template method was used to prepare Sn/TiO2/graphite carbon microsphere composites (xSn/TiO2/GCM, x = 2.0, 1.0, 0.2, 0.5) with porous layers. Then, the composites were represented using X-ray diffraction, energy dispersive spectrometry, scanning electron microscopy, transmission electron microscopy, and nitrogen physical adsorption/desorption. Meanwhile, the photocatalytic activities in CO2 reduction were studied under simulation of visible light exposure. It was confirmed that the Sn/TiO2/GCM composites had layered porosity, graphitized carbon matrix, and high metal compound content, and their morphology was greatly affected by the acetone amount. The outputs of CO and CH4 coming into the photocatalytic CO2 reduction reaction of Sn/TiO2/GCM were 619.46 and 14.46μmolg-1, respectively. Among the two products, the highest production rate observed in 0.5Sn/TiO2/GCM. Because of these factors, the layered porous Sn/TiO2/GCM composites have good photocatalytic performance under simulated visible light irradiation and have unique composition and structure characteristics, which give broad application prospects in electrode materials, catalysts, and adsorbents. Graphical abstract.

Preparation of Inverse Opal Hydroxyapatite and Drug Delivery Properties

AbstractHydroxyapatite(HA) are widely used in the field of drug delivery, especially nano‐HA and porous HA. However, there are few reports on the use of inverse opal HA as drug carrier. In this paper, based on the colloidal crystal template prepared by polystyrene microsphere with the diameter of 380 ± 10 nm, inverse opal HA was prepared by template method as the drug sustained‐release carrier using different dispersants and ratio of template to precursor. The results indicated that when the ratio of template to precursor was 1 : 15 and the dispersant was a mixture of water and alcohol, the prepared inverse opal HA showed a complete ordered porous morphology with uniform pore spacing. In the drug delivery test of amoxicillin, the drug loading and release properties of the inverse opal HA were significantly better than that of nano‐HA. The drug loading of the inverse opal HA was about 2.17 times of nano‐HA, and the drug‐loading performance was also obviously improved. At the same time, sustained release ability of the inverse opal HA was better than that of nano‐HA when releasing amoxicillin. In the first 3 h, the cumulative release rate of amoxicillin on the inverse opal HA was less than 40%, much lower than about 60% of nano‐HA, significantly slowing down the drug release rate and showing good persistence. Therefore, the inverse opal HA as a drug carrier could also improve the sudden release effect of the drug and make the release rate gentler.

Electrodeposited superhydrophobic hierarchical structures as sensitive surface enhanced Raman scattering substrates

Ag ternary architectures composed of micro-, submicro-, and nano-structures formed large area (>1 cm2), ordered arrays were realized by a simple, rapid, low-cost, and high throughput site-specific electrochemical growth on a double-layer colloidal crystal template with a gold seed layer. The ternary architecture array with a hierarchical structure was highly roughened with the surface passivated by sodium dodecyl ions, giving rise to a superhydrophobic surface with a contact angle of 158° without any intentional chemical functionalization processes. The highly roughened surface of the ternary architecture array makes it an excellent candidate as a surface-enhanced Raman scattering (SERS) substrate. Most importantly, the superhydrophobic property can be further employed to significantly enhance the SERS sensitivity of the ternary architecture array relying on a concept of a superhydrophobic surface induced enrichment effect. The ternary architecture array, as a powerful SERS substrate, will find potential applications in low concentration chemical and biological sensing fields.

A Smart Magnetic Responsive Microfiltration Membrane Based on Three-Dimensionally Inverse Colloidal Crystal

In this article, a magnetic-responsive microfiltration membrane based on three-dimensional (3 D) inverse colloidal crystal (ICC) was prepared with relatively simple approach. We designed the ICC membrane using self-assembly of Fe3O4@SiO2 colloidal crystal into a colloidal crystal template. The resulting close-packed colloidal crystal was infiltrated with a reactive monomer solution. After polymerization, the silica spheres were etched away, resulting in an ICC membrane with Fe3O4 nanoparticles inside. The typical ICC membrane was characterized by SEM and XRD. Meanwhile, We used the KCl diffusion to test the permeability of the membrane. The results illustrated that the highly ordered permeable polymer membrane was successfully prepared by using Fe3O4@SiO2 colloidal crystals as the templates. Furthermore, the functional ICC membrane exhibited excellent magnetic-responsive gating property to separation. The smart environment-responsive gating membranes have potential applications in filtration, sensors and other applications.

Polystyrene-Based Hierarchically Macro–Mesoporous Solid Acid: A Robust and Highly Efficient Catalyst for Indirect Hydration of Cyclohexene to Cyclohexanol by a One-Pot Method under Mild Conditions

As a promising synthesis route, indirect hydration of cyclohexene into cyclohexanol by heterogeneous catalysts shows high conversion than that in direct hydration; however, increasing the yield of cyclohexanol from cyclohexene is still a significant challenge. Notably, fabricating a high-performance catalyst is an effective method to improve the yield of the target product. Consequently, a kind of polystyrene-based hierarchically macro–mesoporous solid acid (HP CLPS-SO₃H) was successfully prepared by the combination of a colloidal crystal template method with Friedel–Crafts (F–C) cross-linking. Compared with that of other catalysts (3DOM CLPS-SO₃H, Amberlyst-15, and HZSM-5) with single-sized pore distributions, HP CLPS-SO₃H shows remarkable catalytic performance under mild conditions, in which 90.2% cyclohexanol yield from cyclohexene was obtained. Even after 10 times reuse of the HP solid acid, 80.3% cyclohexanol yield was retained. Moreover, the original morphology was well preserved and the acid sites almost hardly reduced. The as-prepared HP CLPS-SO₃H shows promising prospects in the field of cyclohexanol production.

Fabrication of Bioactive Inverted Colloidal Crystal Scaffolds Using Expanded Polystyrene Beads.

Inverted colloidal crystal (ICC) hydrogel scaffolds have emerged as a new class of three-dimensional cell culture matrix that represents a unique opportunity to reproduce lymphoid tissue microenvironments. ICC geometry promotes the formation of stromal cell networks and their interaction with hematopoietic cells, a core cellular process in lymphoid tissues. When subdermally implanted, ICC hydrogel scaffolds direct unique foreign body responses to form a vascularized stromal tissue with prolonged attraction of hematopoietic cells, which together resemble lymphoid tissue microenvironments. While conceptually simple, fabrication of ICC hydrogel scaffold requires multiple steps and laborious handling of delicate materials. Here, we introduce a facile route for ICC hydrogel scaffold fabrication using expanded polystyrene (EPS) beads. EPS beads shrink and fuse in a tunable manner under pressurized thermal conditions, which serves as colloidal crystal templates for ICC scaffold fabrication. Inclusion of collagen in the precursor solution greatly simplified preparation of bioactive hydrogel scaffolds. The resultant EPS-templated bioactive ICC hydrogel scaffolds demonstrate characteristic features required for lymphoid tissue modeling in both in vitro and in vivo settings. We envision that the presented method will facilitate widespread implementation of ICC hydrogel scaffolds for lymphoid tissue engineering and other emerging applications. Impact statement Inverted colloidal crystal (ICC) hydrogel scaffolds have emerged as a new class of three-dimensional cell culture matrix that represents a unique opportunity for lymphoid tissue modeling and other emerging novel bioengineering applications. While conceptually simple, fabrication of the ICC hydrogel scaffold requires multiple steps and laborious handling of delicate materials with highly toxic chemicals. The presented method for ICC hydrogel scaffold fabrication using expanded polystyrene (EPS) beads is simple, cost-effective, and involves less toxic chemicals than conventional methods, while retaining comparable biological significance. We envision that EPS bead-based hydrogel scaffold fabrication will greatly facilitate the widespread implementation of ICC hydrogel scaffolds and their practical applications.

3D ordered honeycomb-shaped CuO⋅Mn2O3: Highly active catalysts for CO oxidation

Highly 3D ordered honeycomb-shaped xCuO⋅Mn2O3 (CuO content (x) = 10, 20, and 30 wt%) catalysts with various CuO contents were synthesized by adopting a colloidal crystal template method with poly(methyl methacrylate) (PMMA) as template, and the as-prepared catalysts were used in oxidation of CO. The catalysts possessed a macro-mesoporous structure. The catalytic performance at low temperatures improved significantly with a rise in CuO content. The light-off temperature (10 % conversion) and the temperature for CO complete conversion were 71 and 98 oC over 30 wt% CuO⋅Mn2O3, respectively. Good stability of the 30 wt% CuO⋅Mn2O3 catalyst was also observed under the dry and wet (in the presence of water vapor) conditions. It is concluded that high catalytic activity of 30 wt.% CuO.Mn2O3 was related to its unique pore structure, high oxygen adspecies concentration, and oxygen vacancy.

Conductive ITO Interfaces for Optoelectronic Applications Based on Highly Ordered Inverse Opal Thin Films

AbstractA three‐step fabrication process for optically transparent, conducting ITO thin films with an intrinsic inverse opal structure is described. The preparation is based on colloidal crystal templating using polystyrene microspheres (100 nm–600 nm). For the realization of varying periodicities in this structure, different sphere sizes were assembled to monolayers on a substrate by spin coating and infiltrated afterwards similarly. The influence of rotation parameters as well as dispersion concentration was studied. Using this approach different geometries of the surface are accessible by systematically varying the rotation parameters and infiltration volume. The thin films show excellent anti‐reflection behavior, good transmission (>80% in the visible range) as well as a low resistance of 200 Ω/sq compared to other porous ITO interfaces. The properties are very promising for several optoelectronic applications such as in‐ or out‐coupling structures in solar cells and organic light emitting diodes.

A novel adsorbent of three-dimensional ordered macro/mesoporous carbon for removal of malachite green dye

Three-dimensional ordered macro/mesoporous carbon (3DOM/m-C) with high specific surface area was synthesized by colloid crystal template method with chemical activation by KOH and used as the adsorbent for removing malachite green (MG) in aqueous solution. The microstructures of the adsorbents were characterized by FESEM, TEM and BET, and the effects of initial dye concentration, contact time, solution pH, and temperature on adsorption performance were investigated. The results show that the 3DOM/m-C exhibits extremely high adsorption capacity of 3541.1 mg/g within 2 h, which could be attributed to the novel ordered hierarchical structure with mesopores on three-dimensional ordered macroporous carbon walls. And the adsorption behavior conforms to the pseudo-second-order kinetic and Langmuir adsorption isotherm. 3DOM/m-C can be recycled after being desorbed by absolute ethanol, and still maintains a high capacity of 2762.06 mg/g after 5 cycles.

Large-area crack-free Au–SiO2 2D inverse opal composite films: Fabrication and SERS applications

Plasmonic-photonic metallo-dielectric structures have attracted recent research interests due to their novel optical properties. Au–SiO2 based photonic structures have been built and have shown promising applications for example, as SERS substrates. However, due to the lack of control over the constraints in the various stages of conventional colloidal crystal templating approach, monolayer metallo-dielectric inverse opal structures have not been widely reported. In this work, a 2D hexagonal inverse opal (IO) photonic structure of Au nanoparticles (NP) embedded in a SiO2 matrix is constructed using a new strategy. Here in, a binary Au–SiO2 sol was infiltrated into the accommodative interstices of 2D self-assembled polystyrene (PS) spheres in an air-water interface. Effective removal of the PS spheres by chemical method resulted in Au–SiO2 IO structures. Optical properties of these structures show interesting plasmonic-photonic coupling. When they are used as substrates for Raman signal enhancement of crystal violet, they show better enhancement than either Au nanoparticles aggregates or Au–SiO2 non-photonic structures. The Au–SiO2 IO structures were also used to perform Raman spectroscopy analysis of astaxanthin rich shrimp oil, a novel value-added product extracted from the water used in shrimp processing. The surface enhanced Raman spectra showed the presence of favourable esterified form of astaxanthin in shrimp oil.

Bioinspired polydopamine coating as a versatile platform for synthesizing asymmetric Janus particles at an air-water interface

Janus particles with controlled asymmetries and functionalities represent promising building blocks and functional materials due to their unique anisotropic features. Herein, we show a facile and general approach towards preparing colloidal Janus particles with adjustable surface asymmetries and functionalities based on monolayer colloidal crystal (MCC) templates combined with mussel-inspired polydopamine (PDA) chemistry at an air-water interface. First, monodisperse colloidal polystyrene/polydopamine (PS/PDA) Janus particles with tunable asymmetrical geometries are synthesized by polymerizing dopamine onto two-dimensional (2D) polystyrene (PS) monolayer colloidal crystals formed at the air-water interface. Moreover, the good chemical reactivity of the PDA coating makes it a versatile platform to introduce a variety of functional materials, e.g., metal nanoparticles and organic molecules, producing colloidal Janus particles with adjustable functionalities. Finally, we demonstrate this synthetic strategy not only provides a controllable method for the fabrication of monodisperse colloidal Janus particles but also opens up a new Janus platform for artificially designed Janus particles with tunable asymmetries and functionalities.

Stable white photoluminescence from Mn-contained organic lead bromide perovskite ring arrays formed from 2D colloidal crystal templates

C4N2H14PbxMn1−xBr4 perovskite ring arrays with stable white light emission and controllable size for high color quality white light-emitting diodes.

Preparation and modification of inverse opal zirconia pigment

Inverse opal zirconia pigment prepared by traditional process has the disadvantages of low color saturation and variegated color which restrict its further application. In this work, the inverse opal zirconia pigment was prepared by colloidal crystal template fabricated using polystyrene microspheres with particle size of 340 ? 10 nm as raw material and further modified by sintering at 600 ?C for 2 h with heating rate of 2 ?C/min in an atmosphere tube of 0.8 L min-1 nitrogen flow. The morphology, phase crystallinity and color performance of the inverse opal zirconia pigment before and after modification were characterized in detail and the modified mechanism was investigated. The results showed that morphology of the inverse opal zirconia pigment before modification was basically a highly ordered porous structure, the phase was relatively pure, and the overall appearance was variegated color. Some parts of the samples exhibited low color saturation and different areas showed various colors, indicating that the samples had certain angle dependence. After modification, the samples showed bigger-area single blue-green color, suggesting that the color saturation was significantly improved and the angle dependence was reduced evidently. The mechanism for modification was that the zirconia precursor and polystyrene templates were carbonized when sintered in nitrogen atmosphere. The generated in-situ carbon remained in the samples and absorbed the tray background light, which significantly suppressed the multiple scattering of structural defects.

Porous Polyvinylidene Fluoride Thin-Film Sensors from Colloidal Crystal Templates.

With the development of the materials science, biosensors tend to be thin, flexible, versatile, and are extensively employed in biotechnology, clinical diagnosis, biochips, etc. However, most existing biosensors are single-functionalized and destitute in contrivable microstructure, which result in some inherent limitations. In this work, a novel thin-film sensor that had dual response generated from one stimulus was designed based on the colloidal crystal templates and devisable circuit system. Benefiting from designed platinum coating, the thin-film appeared as a flexible strain sensor which presented corresponding resistance changes with the slight deformation of the thin-film. In addition, with the sacrificial template method, the porous thin-film derived from the colloidal crystal template was endowed with manageable porous structure and splendid structural color, and the resultant color could be various when the environment changed. These features laid the foundation for the construction of multifunctional thin-film biosensor and presented potential applicability for a variety of biological research and flexible sensing devices.