Colloidal Crystal Template Research Articles

Preparation and chromatographic properties of ordered macroporous polymer monoliths by colloidal crystal templating method

Preparation and chromatographic properties of ordered macroporous polymer monoliths by colloidal crystal templating method

Co3O4-modified 3DOM LaFe0.6Mg0.4O3 perovskite as robust catalysts for soot oxidation

In this study, 3DOM LaFe0.6Mg0.4O3 perovskite was prepared using a colloidal crystal template technique and subsequently decorated with Co3O4 for soot combustion. The results indicated that the LaFe0.6Mg0.4O3 perovskite with three-dimensional ordered macropores structure could facilitate the dispersion of Co3O4, boost the number of active sites for soot combustion, and significantly enhance the contact efficiency between the catalyst and soot. The interaction between Co3O4 and perovskite created additional oxygen vacancies and enhanced the redox ability of the catalysts. Meanwhile, the presence of Co3O4 facilitated the adsorption and activation of O2, which could accelerate the oxidation of soot particles. Notably, the 2.5 %Co/LaFe0.6Mg0.4O3 catalyst exhibited the highest performance, achieving a T50 of 407 °C for soot combustion in the presence of 500 ppm NO and 5 % O2. The catalyst also demonstrated excellent stability and water resistance, making it a promising candidate for practical applications.

A 3D ordered hierarchical crystalline porous organic salt for large-sized enzyme immobilization

Crystalline porous organic salts (CPOSs) are an emerging class of promising materials with intrinsic highly polar nanoconfined microporosity. However, their single microporous structure greatly hinders their development in the field of catalysis and adsorption. Constructing a hierarchical porous structure can effectively reduce the mass transport resistance, thus expanding the scope of their applications. Herein, we report the synthesis of a three-dimensional (3D) ordered macro-/microporous hierarchical CPOS (HCPOS-1) using a template-assisted approach for the first time. The as-synthesized HCPOS-1 prepared from a polystyrene colloidal crystal template showcases a 3D ordered macroporous structure while also preserving the microporous structure. The 3D ordered macroporous structure in such a hierarchical structure, together with its hydrophilic surface, endows HCPOS-1 with the ability to immobilize large-sized enzymes through physical adsorption under mild conditions. The resulting catalase/HCPOS-1 showcases a high enzyme immobilization capacity and avoids undesired conformational changes of enzymes during the immobilization process, thus exhibiting excellent catalytic activity for the decomposition of hydrogen peroxide.

Synthesis and Characterization of Boronate Affinity Three-Dimensionally Ordered Macroporous Materials.

Sample pretreatment is a key step for qualitative and quantitative analysis of trace substances in complex samples. Cis-dihydroxyl (cis-diol) group-containing substances exist widely in biological samples and can be selectively bound by boronate affinity adsorbents. Based on this, in this article, we proposed a simple method for the preparation of novel spherical three-dimensionally ordered macropore (3DOM) materials based on a combination of the boronate affinity technique and colloidal crystal template method. The prepared 3DOM materials were characterized using Fourier transform-infrared spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, and thermo-gravimetric analysis, and results showed that they possessed the characteristics of a high specific surface area, high porosity, and more boronic acid recognition sites. The adsorption performance evaluation results showed that the maximum adsorption capacity of the boron affinity 3DOMs on ovalbumin (OVA) could reach to 438.79 mg/g. Kinetic and isothermal adsorption experiments indicated that the boronate affinity 3DOM material exhibited a high affinity and selectivity towards OVA and adenosine. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of the proteins in egg whites was conducted and proved that the glycoprotein in the egg whites could be separated and enriched with a good performance. Therefore, a novel boronate affinity 3DOM material a with highly ordered and interconnected pore structure was prepared and could be applied in the separation and enrichment of molecules with cis-diol groups from complex samples with a good selectivity, efficiency, and high throughput.

CdS@CS/PVA inverse opal films as photocatalyst

We prepared CdS@CS/PVA inverse opal (IO) films by the colloidal photonic crystal (CPC) template method. The photonic structure of the CdS@CS/PVA IO films consists of three-dimensional periodic macropores interconnected by CS/PVA polymers. The as-prepared CdS@CS/PVA IO films were utilized as photocatalysts for the degradation of methylene blue dyes. The degradation rate of methylene blue by the CdS@CS/PVA IO film catalyst was 92%, while that of the CdS@CS/PVA film catalyst was 55% for 6 h. The photocatalytic degradation effect of the CdS@CS/PVA IO film catalyst on methylene blue is [Formula: see text]1.7 times higher than that of the CdS@CS/PVA film catalyst, which proves that the introduction of the inverse opal structure into the photocatalyst is beneficial to improve the efficiency of the photocatalyst for degrading dyes.

Comparative study on physicochemical properties of macroporous hydroxyapatite coatings on 316L stainless steel implants using sol-gel and inverse opal templating

This study focuses on enhancing metallic implant biocompatibility by fabricating a three-dimensional ordered macroporous hydroxyapatite (HAP) architecture through inverse opal technology. Utilizing colloidal crystal templates on 316L stainless steel, specifically with polystyrene and polymethyl methacrylate, successful fabrication was achieved through H2O2 plus H2SO4 etching. The calcination process at different temperatures (350, 500 and 700°C) resulted in distinct HAP structures, and the sample was calcined at 500°C (HAP500), exhibiting superior physicochemical properties, including enhanced crystallinity, surface roughness and wettability. Biological experiments demonstrated that HAP500 significantly promoted mesenchymal stem cell adhesion and proliferation compared to HAP350 and bare 316LSS, suggesting its potential as a highly effective medical device for bone implantation.

A photoactivated gas sensor of SnO2 ordered spherical pore array: Electrodeposition-based construction and application in room temperature detection of ethanol gas

The photoactivated semiconductor film gas sensor has received increasing attention in the room temperature detection of environmental gases, but the uncontrolled surface morphology and the associated light area still limit the application and the exploitation of the sensing response potential. Herein, a monolayer colloid crystal template strategy based on electrodeposition was introduced to in situ construct SnO2 ordered spherical macropore array (OSPA) sensors used for ethanol gas detection under a UV-LED. By adjusting the electrodeposition time, various OSPAs with regularly variable heights of pore-wall were obtained. The light area of the array could then be systematically regulated based on the spherical pore-walls’ curve characteristics. The OSPAs showed a nearly 5-fold change in response in detection of 100 ppm ethanol gas under a 265 nm UV-LED, corresponding to the light area from small to large. The highest sensing response is even higher than that of almost all SnO2-based room temperature sensors that have previously been reported. Moreover, the sensor has excellent selectivity and linearity, a 1 ppm lower detection limit, and exceptional long-term stability. These finds are corroborated by analyses of the electrodeposition mechanism, the sensing mechanism, optical simulations, and various characterizations. The strategy provides an efficient way to tune and enhance the sensing response of a photoactivated gas sensor, and is beneficial for exploiting the sensing potential of a semiconductor.

Hierarchically Periodic Macroporous Niobium Oxide Architecture for Enhanced Hydrogen Evolution.

The fabrication of periodic macroporous (PM) in Nb2O5 via morphological control is crucial for improving the photocatalytic hydrogen evolution efficiency. In this study, Nb2O5 with PM is synthesized using a straightforward colloidal crystal templating approach. This material features an open, interconnected macroporous architecture with nanoscale walls, high crystallinity, and substantial porosity. Extensive characterization reveals that this hierarchically structured Nb2O5 possesses abundant surface active sites and is capable of capturing light effectively, facilitating rapid mass transfer and diffusion of reactants and markedly suppressing the recombination of photoexcited charge carriers. Macroporous Nb2O5 exhibits superior water-splitting hydrogen evolution performance compared with its bulk and commercial counterparts, achieving a hydrogen production rate of 405µmol g-1 h-1, surpassing that of bulk Nb2O5 (B-Nb2O5) and commercial Nb2O5 (C-Nb2O5) by factors of 5 and 33, respectively. This study proposes an innovative strategy for the design of hierarchically structured PM, thereby significantly advancing the hydrogen evolution potential of Nb2O5.

Ca and Sr co-doping induced oxygen vacancies in 3DOM La2−xSrxCe2−yCayO7−δ catalysts for boosting low-temperature oxidative coupling of methane

It is urgent to develop catalysts with application potential for oxidative coupling of methane (OCM) at relatively lower temperature. Herein, three-dimensional ordered macroporous (3DOM) La2−xSrxCe2−yCayO7−δ (A2B2O7-type) catalysts with disordered defective cubic fluorite phased structure were successfully prepared by a colloidal crystal template method. 3DOM structure promotes the accessibility of the gaseous reactants (O2 and CH4) to the active sites. The co-doping of Ca and Sr ions in La2−xSrxCe2−yCayO7−δ catalysts improved the formation of oxygen vacancies, thereby leading to increased density of surface-active oxygen species (O2−) for the activation of CH4 and the formation of C2 products (C2H6 and C2H4). 3DOM La2−xSrxCe2−yCayO7−δ catalysts exhibit high catalytic activity for OCM at low temperature. 3DOM La1.7Sr0.3Ce1.7Ca0.3O7−δ catalyst with the highest density of O2− species exhibited the highest catalytic activity for low-temperature OCM, i.e., its CH4 conversion, selectivity and yield of C2 products at 650 °C are 32.2%, 66.1% and 21.3%, respectively. The mechanism was proposed that the increase in surface oxygen vacancies induced by the co-doping of Ca and Sr ions boosts the key step of CH bond breaking and CC bond coupling in catalyzing low-temperature OCM. It is meaningful for the development of the low-temperature and high-efficient catalysts for OCM reaction in practical application.

Cerium Doping Effect in 3DOM Perovskite-Type La2−xCexCoNiO6 Catalysts for Boosting Soot Oxidation

Herein, we present an in-depth investigation into the enhancement of catalytic soot oxidation through cerium-doped three-dimensional ordered macroporous (3DOM) La-Co-Ni-based perovskites synthesized with the colloidal crystal template (CCT) method. The 3DOM structure significantly contributes to the accessibility and interaction efficiency between soot and catalyst. Based on the results of powder X-ray diffraction (XRD), N2 adsorption-desorption measurements, scanning electron microscopy (SEM), temperature-programmed oxidation of NO (NO-TPO), temperature-programmed reduction of H2 (H2-TPR), in situ infrared Fourier transform spectroscopy (In-situ DRIFTS), and temperature-programmed oxidation (TPO) reactions, the role of cerium doping in modifying the structural and catalytic properties of 3DOM perovskite-type La2−xCexCoNiO6 catalysts was investigated systematically. The optimized cerium doping ratio in La2−xCexCoNiO6 catalysts can improve the microenvironment for efficient soot-catalyst contact, enhancing the catalytic activity of soot oxidation. Among the catalysts, the 3DOM La0.8Ce1.2CoNiO6 catalyst shows the highest catalytic activity for soot oxidation, whose T10, T50, and T90 values are 306 °C, 356 °C, and 402 °C, respectively. The mechanism of the cerium doping effect for boosting soot oxidation is proposed: The doping of Ce ions can increase the surface oxygen species, which is the main active species for promoting the key step of NO oxidation to NO2 in catalyzing soot oxidation. This research provides a new strategy to develop high-efficient non-noble metal catalysts for soot oxidation in pollution control and sustainable environmental practices.

Three-dimensionally ordered macroporous ZSM-5 zeolite supported high-dispersed Ni2P: Highly active catalyst for quinoline hydrodenitrogenation

Zeolite catalysts have shown significant advantages in hydrogenation reactions due to their ordered pore structure and abundant acid sites. Common zeolites exhibit pore accessibility limited to microporous states, which restricts their application in diffusion-limited processes. In this study, a steam-seeding-assisted colloidal crystal template (SSAC) method was used to prepare ZSM-5 zeolite with a three-dimensionally ordered macroporous (3DOM) structure, which was then loaded with nickel phosphide for hydrodenitrogenation reactions. SEM and TEM characterization demonstrated that the prepared zeolite material possessed a highly ordered 3DOM structure with interconnected macropores. XRD, FT-IR, and BET analysis indicated that the macroporous zeolite material exhibited a typical MFI structure, mesoporous channels, and a higher specific surface area. The high external surface area facilitated the formation of uniformly sized Ni2P nanoparticles on the zeolite surface. The introduction of macroporous structures also leads to suitable Brönsted acid and Lewis acid sites in zeolite materials. The resultant Ni2P/3DOMZSM-5 catalyst exhibited higher reaction rate constants and TOF (10.87×10−2 μmolg−1s−1 and 1.5×10−3s−1, respectively) compared to other zeolite catalysts and commercial catalysts.

An Electrochemical Sensor Based on Three-Dimensional Porous Reduced Graphene and Ion Imprinted Polymer for Trace Cadmium Determination in Water

Three-dimensional (3D) porous graphene-based materials have displayed attractive electrochemical catalysis and sensing performances, benefiting from their high porosity, large surface area, and excellent electrical conductivity. In this work, a novel electrochemical sensor based on 3D porous reduced graphene (3DPrGO) and ion-imprinted polymer (IIP) was developed for trace cadmium ion (Cd(II)) detection in water. The 3DPrGO was synthesized in situ at a glassy carbon electrode (GCE) surface using a polystyrene (PS) colloidal crystal template and the electrodeposition method. Then, IIP film was further modified on the 3DPrGO by electropolymerization to make it suitable for detecting Cd(II). Attributable to the abundant nanopores and good electron transport of the 3DPrGO, as well as the specific recognition for Cd(II) of IIP, a sensitive determination of trace Cd(II) at PoPD-IIP/3DPrGO/GCE was achieved. The proposed sensor exhibited comprehensive linear Cd(II) responses ranging from 1 to 100 μg/L (R2 = 99.7%). The limit of detection (LOD) was 0.11 μg/L, about 30 times lower than the drinking water standard set by the World Health Organization (WHO). Moreover, PoPD-IIP/3DPrGO/GCE was applied for the detection of Cd(II) in actual water samples. The satisfying recoveries (97–99.6%) and relative standard deviations (RSD, 3.5–5.7%) make the proposed sensor a promising candidate for rapid and on-site water monitoring.

Slow photon photocatalytic enhancement of H2 production in TaON inverse opal photonic crystals

In this study, tantalum oxynitride inverse opal (TaON IO) photonic crystals with different macropore diameters (D) were synthesized in a two-step process involving colloidal crystal templating and thermal nitridation, then applied as visible light-driven photocatalysts for hydrogen production. The TaON inverse opals showed photonic band gaps (PBGs) at visible wavelengths, with the PBG position redshifting as the diameter of the macropores increased in accordance with a modified Bragg's law expression. By aligning the electronic absorption edge of TaON (Eg ∼ 2.4 eV) with the blue edge (short-wavelength side) or red edge (long-wavelength side) of the PBGs, slow photon enhancement of photocatalytic H2 generation was realized. H2 production tests conducted in 10 vol% methanol containing H₂PtCl6 under Xe lamp irradiation (150 W) showed that the hydrogen production rate was enhanced by ∼1.3–1.4 times when the TaON absorption edge (∼510 nm) aligned with blue edge of the PBG (0.3421 mmol g−1 h−1) or the red edge of the PBG (0.3254 mmol g−1 h−1) in the inverse opals. The red edge enhancement was due to increased light absorption and charge carrier generation in TaON, whereas the blue edge effect was likely due to suppression of electron-hole pair recombination. Results demonstrate that photonic crystal engineering to exploit slow photon effects is a viable approach for boosting photocatalytic hydrogen production rates.

A flexible humidity sensor constructed by ordered-pore-array of slightly reduced graphene oxide with much enhanced sensing response

Reduced graphene oxide (rGO) flexible film humidity sensor has received increasing attention, but the low sensing response caused by lack of available hydrophilic functional groups is still a limitation. Herein, a slightly reduced graphene oxide (SrGO) ordered-pore-array, fabricated via a monolayer colloid crystal template method, was introduced as a resistive humidity sensor. It was obtained based on adsorption between the GO sheets and the template microspheres, in-situ slight reduction of the GO shells and the removal of template. The reduction way allows the functional groups of GO to be retained as much as possible, and the unique structures (e.g., spherical double surfaces and small through-holes on pore-walls) facilitate the substantial exposure of functional groups, the penetration of water molecules and the utilization of buried functional groups. The available functional groups are thereby efficiently increased, giving the sensor an unprecedented high sensing response, more than 2600 times the maximum response of existing rGO sensors. The sensor also demonstrated excellent practical characteristics, and by detecting a single exhale, it could be employed in quick and quantitative evaluation of human activities and health. This strategy paves a facile and promising route to improve the sensing response and application of graphene-based humidity sensors or gas sensors.

In-situ gas foaming synthesis of N, S-rich co-doped hierarchically ordered porous carbon as an efficient oxygen reduction reaction catalyst

The design and manufacture of cost-effective and efficient oxygen reduction reaction (ORR) catalysts is critical to the widespread application of multiple energy conversion devices. Herein, a combination of in-situ gas foaming and the hard template method is proposed to construct the N, S-rich co-doped hierarchically ordered porous carbon (NSHOPC) as an effective metal-free electrocatalyst for ORR via carbonizing a mixture of polyallyl thiourea (PATU) and thiourea in silica colloidal crystal template (SiO2-CCT) voids. Benefiting from the hierarchically ordered porous (HOP) architectures and the mass doping of N and S, NSHOPC displays excellent ORR activities (the half-wave potential of 0.889 V in 0.1 M KOH and 0.786 V in 0.5 M H2SO4) and long-term stability, which are all better than those of Pt/C. As the air cathode in a Zn-air battery (ZAB), NSHOPC exhibits a high peak power density of 174.6 mW·cm−2 and long-term discharge stability. The remarkable performance of the as-synthesized NSHOPC signifies broad prospects for actual applications in energy conversion devices.

Surface tuning of 3DOM LaFe0.6Mg0.4O3 perovskite by acid etching to enhance catalytic performance for soot combustion

Acid etching is one of the most widely used methods for surface tuning of perovskite. In this paper, 3DOM LaFe0.6Mg0.4O3 was synthesized by a colloidal crystal template method, and was further etched by acetic acid at different times, which made the Mg element at the B-site of perovskite selectively dissolved. Through analysis of multiple characterization results, the introduction of B-site deficiency by acid etching could not only enhance oxygen vacancies, form the Fe4+/Fe3+ redox cycles on the surface of the catalyst, but also generate mesopores structure and increase the specific surface area. After acid treatment, the soot and NO oxidation performances were improved. Among all the as-prepared catalysts, 3DOM LaFe0.6Mg0.4O3 treated by acetic acid for 1 h (LFM-1) exhibited superior reducibility and better activity for soot combustion. The T50 of LFM-1 was 417 °C under 5 % O2/N2 and 500 ppm NO, and the activation energy and TOF were 66 kJ·mol−1 and 2.17 × 10-3 s−1, respectively. Herein, the strategy of introducing B-site deficient by acid treatment is an effective method to improve soot combustion activity, which might be applicable to other catalytic fields.

Effect of B-Site Element on the Structure and Catalytic Performance for Toluene of the 3DOM CeBO3 Catalyst.

A series of 3DOM cerium-based perovskite catalysts with different B-site elements were prepared by the colloidal crystal template method and excess impregnation method with Cr, Ni, and Mn as the B-site elements. The physical and chemical properties of the catalysts were investigated by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), hydrogen temperature-programmed reduction (H2-TPR), and oxygen temperature-programmed desorption (O2-TPD) characterization techniques. The results showed that the catalyst with Mn as the B-site element had a high-quality macropore structure (pore size 200-250 nm), large specific surface area (45.26 m2/g), and abundant surface adsorbed oxygen content (Oads/Olatt = 0.46). The addition of manganese enhanced the low-temperature reducibility, and the main reduction peak was below 400 °C. The O2-TPD results showed that 3DOM CeMnO3 expressed the highest adsorption oxygen content. The 3DOM CeMnO3 possessed the best catalytic performance with T50% = 102 °C and T90% = 203 °C during the catalytic oxidation of toluene. Intermediate product study hinted that toluene was first converted into benzoic acid and benzaldehyde and then further degraded into small molecules. The catalyst with the best activity also exhibited good stability, and toluene degradation rate remained above 85% at 200°C for more than 20 h of continuous experiments.

Integration of carbon microcapsules with beef omasum like shells by interconnected Macropores for removal of phenol from aqueous solution

A bulk carbon adsorbent with a bionic structure was synthesized based on wrinkled silica microspheres colloidal crystal templates (WSMs-CCTs). As a result, the carbon microcapsules with the internal structure of beef omasum are closely integrated by interconnected macropores to form the bulk carbon adsorbent (ICM-BO). ICM-BO was further applied as a phenol adsorbent to achieve efficient phenol removal. Compared with the reported adsorbents, ICM-BO with excellent adsorption capacity and reusability are attributed to the hierarchical nanoscale needle-like structure of the inner walls, interconnected macropores, and the robust monolith nature. The isothermal adsorption process can be well described through the Liu model with a maximum proposed absorption value of 504. 8 mg g−1 at 318 K. In addition, the morphology of ICM-BO is maintained and the regeneration efficiency (RE) is relatively stable after 10 cycles, indicating that ICM-BO has excellent reusability. Notably, in the simulated industrial effluent experiment, the removal rate of phenolic compounds by ICM-BO reach 93.5%, indicating that the ICM-BO is hardly affected by other components and has excellent adsorption capacity, which is expected to be an ideal choice for the adsorption of phenols.

Flexible and Speedy Preparation of Large-Scale Polystyrene Monolayer through Hemispherical-Depression-Assisted Self-Assembling and Vertical Lifting

Liquid interfacial self-assembled two-dimensional nanomonolayers are promising as colloidal crystal templates or lithographic masks for the mass production of periodic nanoarrays. However, the interfacial self-assembled monolayers usually suffer various defects such as grain boundaries, line defects, vacancy defects, and multilayers due to imperfect process technology. Here, we demonstrated a series of optimized strategies including the hemispherical-depression-assisted self-assembly, dot coating approach, and vertical lifting transfer protocol to eliminate surface defects especially multilayers jointly. After stabilizing the hemispherical depression height to 1.5 mm with a 40° tilted silicon slide, the self-assembly time was significantly shortened to 10 min for a 1 × 2 cm2 area of PS monolayer. The series of strategies were successfully implemented not only on glass and silicon flat substrates but also on the side and end face of optical fiber, even on flexible substrates, while maintaining great morphologies. Besides, in association with nanospherical lens photolithography and nanosphere lithography technologies, various two-dimensional nanoarrays such as nanotriangles and nanoholes could be successfully obtained for subsequent optical properties research, which present broad application prospects in biochemical sensing, medicine, environmental protection, and other fields.

Facile Synthesis of ZnO/WO3 Nanocomposite Porous Films for High-Performance Gas Sensing of Multiple VOCs.

Volatile organic compounds (VOCs) in indoor environments have typical features of multiple components, high concentration, and long duration. The development of gas sensors with high sensitivity to multiple VOCs is of great significance to protect human health. Herein, we proposed a sensitive ZnO/WO3 composite chemi-resistive sensor facilely fabricated via a sacrificial template approach. Based on the transferable properties of self-assembled monolayer colloidal crystal (MCC) templates, two-dimensional honeycomb-like ordered porous ZnO/WO3 sensing matrixes were constructed in situ on commercial ceramic tube substrates with curved and rough surfaces. The nanocomposite thin films are about 250 nm in thickness with large-scale structural consistency and integrity, which facilitates characteristic responses with highly sensitivity and reliability. Furthermore, the nanocomposite sensor shows simultaneous responses to multiple VOCs that commonly exist in daily life with an obvious suppression sensing for traditional flammable gases. Particularly, a detection limit of 0.1 ppm with a second-level response/recovery time can be achieved, which is beneficial for real-time air quality assessments. We proposed a heterojunction-induced sensing enhancement mechanism for the ZnO/WO3 nanocomposite film in which the formation of abundant heterojunctions between ZnO and WO3 NPs significantly increases the thickness of the electron depletion layer in the bulk film and improves the formation of active oxygen species on the surface, which is conducive to enhanced responses for reducing VOC gases. This work not only provides a simple approach for the fabrication of high-performance gas sensors but also opens an achievable avenue for air quality assessment based on VOC concentration detection.