Inverse Opal Research Articles

Tunable slow photon effect and local surface plasmon in Ag-immobilized TiO2 inverse opal films for enhancing pollutant photodegradation

Plasmonic silver-decorated TiO2 inverse opal has shown an interesting potential for photocatalysis owing to its physically tunable optical absorbance, highly active area, and flexible fabrication.

Inverse opals with reactive surface chemistry as sensors for aqueous pollutants.

Inverse opal colorimetric sensors operating on wetting transitions usually rely on physical differences of the infiltrating liquid. Here, we exploit a reactive surface chemistry that changes wettability upon binding of an analyte. Upon binding of Fe3+ to a Schiff base immobilized on the porous structure, the surface becomes more hydrophilic, triggering the infiltration of the structure and causing the structural color to disappear.

Numerical modelling and analysis of porous surface-enhanced jet cooling using copper inverse opals in single-phase flow

Abstract In this study, we propose a novel cooling scheme that utilizes copper inverse opals (CIOs) for surface enhancement in a single-phase impingement jet cooling system. We perform computational fluid dynamics simulations to evaluate the cooling performance of the CIO jet coolers. Our modelling results indicate that the proposed CIO-coated cooler can significantly reduce the average temperature and improve the temperature uniformity across the entire chip surface. The average Nusselt number of the CIO-coated cooler can reach up to 2.8 times that of the flat surface jet cooler. However, the porous structure of the CIO-coated cooler increases the total pressure drop. To determine designs with high cooling performance and low energy consumption, we investigate two crucial design factors, namely the inlet velocity and the nozzle-to-CIO distance. Our analysis reveals that increasing the inlet velocity further enhances the heat transfer, but at the expense of high pressure drop. On the other hand, a larger nozzle-to-CIO distance results in a lower pressure drop but also reduces the heat transfer coefficient. The effects of nozzle-to-CIO distance are further understood by studying the flow resistance network. Furthermore, we present a reduced-order model that accurately captures the thermofluidic characteristics of the proposed design.

(Invited) Tuning and Transferring Slow Photons for Unprecedented Visible Light Photocatalysis

Periodic structures with alternating refractive indices such as inverse opal photonic crystals are capable of reducing the group velocity of light such that this slowed light can be more efficiently harvested for highly enhanced solar energy conversion. However, the generation, the manipulation and, in particular, the practical applications of these slow photons remain highly challenging. Here, we report the first proof of concept on the ability to control, in an inverse opal TiO2-BiVO4 hetero-composite, the transfer of slow photons generated from the inverse opal photonic structure to the photocatalytically active BiVO4 nanoparticles for highly enhanced visible light photoconversion. Tuning the slow photon frequencies, in order to accommodate the electronic band gap of BiVO4 for slow photon transfer and for significantly improved light harvesting, was successfully achieved by varying the structural periodicity (pore size) of inverse opal and the light incidence angle. The photocatalytic activity of BiVO4 in all inverse opal structures, promoted by slow photon effect, reached up to 7 times higher than those in the non-structured compact films. This work opens new avenues for the practical utilization of slow photon effect under visible light in photocatalytic energy-related applications like water splitting and carbon dioxide reduction and in photovoltaics.

Microstructures of Binary Oxides with an Inverse Opal Structure Used as Photoelectrodes for Water Splitting

Recently, the weather has experienced changes and these have affected our life style. Fossil fuels used by the human have contributed to climate change and today it is impossible to modify. Researchers have studied different kind of fuels that could use daily. Currently, hydrogen, from water splitting, is the best way to substitute the fossil fuels because water is present around the World. In photoelectrochemistry, the electrodes have a great importance. Behaviour of each semiconductor as , , , , , , , etc., give us individual efficiency respect to solar light. Also, the semiconductor chosen, type of crystallinity and superficial area are important points for achieve high in efficiency. This review shows that inverse opal has a greater contact compared to rod, cauliflower, nanotubes, etc. Different ways to deposit the polystyrene allows us gain more contact area and better photoelectrode efficiency. The main routes used to obtain binary oxides deposits, as electrophoretic, spin coating, vertical submersion, etc., help us to control polystyrene arrangement and obtain a uniform template. These techniques are discussed along this contribution. Resumen. Recientemente, el clima ha experimentado cambios que han afectado a nuestro estilo de vida. Los combustibles fósiles utilizados por el ser humano han contribuido al cambio climático y hoy es imposible modificarlo. Los investigadores estudian diferentes tipos de combustibles que podrían utilizarse diaria y actualmente, el hidrógeno, a partir de la ruptura de la molécula de agua, es la mejor manera de sustituir los combustibles fósiles porque el agua está presente en todo el mundo. En fotoelectroquímica, los electrodos tienen una gran importancia. El comportamiento de cada semiconductor como TiO2, Fe2O3, NiO, CuO, NiS, ZnO, Cu2O, etc., tiene cada uno una eficiencia individual respecto a la luz solar que reciben. Además, del semiconductor elegido, el tipo de cristalinidad y el área superficial de este son puntos determinantes para alcanzar un alto grado de eficiencia. La presente revisión muestra que el ópalo inverso tiene un mayor contacto y eficiencia en comparación con las varillas, la coliflor, los nanotubos, etc. Diferentes formas de depositar el poliestireno como molde nos permiten obtener mayor área de contacto y mejor eficiencia del fotoelectrodo semiconductor. Las principales vías utilizadas para obtener depósitos de óxidos binarios, como electroforesis vertical, etc., nos ayudan a controlar la disposición del poliestireno y obtener una capa uniforme. Estas técnicas se discuten a lo largo de esta contribución.

Grain Crystallinity, Anisotropy, and Boundaries Govern Microscale Hydrodynamic Transport in Semicrystalline Porous Media.

Polycrystallinity is often an unintended consequence of real manufacturing processes used to produce designer porous media with deterministic and periodic architectures. Porous media are widely employed as high-surface conduits for fluid transport; unfortunately, even small concentrations of defects in the long-range order become the dominant impediment to hydrodynamic transport. In this study, we isolate the effects of these defects using a microfluidic analogy to energy transport in atomic polycrystals by directly tracking capillary transport through polycrystalline inverse opals. We reveal─using high-fidelity florescent microscopy─the boundary-limited nature of flow motions, along with nonlinear impedance elements introduced by the presence of "grain boundaries" that are separating the well-ordered "crystalline grains". Coupled crystallinity, anisotropy, and linear defect density contribute to direction-dominated flow characteristics in a discretized manner rather than traditional diffusive-like flow patterns. Separating individual crystal grains' transport properties from polycrystals along with new probabilistic data sets enables demonstrating statistical predictive models. These results provide fundamental insight into transport phenomena in (poly)crystalline porous media beyond the deterministic properties of an idealized unit cell and bridge the gap between engineering models and the ubiquitous imperfections found in manufactured porous materials.

Comparing Cycling and Rate Response of SnO2 Macroporous Anodes in Lithium-Ion and Sodium-Ion Batteries

Tin oxide (SnO2) is a useful anode material due to its high capacity (1493 mAh g−1 and 1378 mAh g−1 vs Li/Li+ and vs Na/Na+, respectively) and natural abundance (tin is one of the thirty most abundant elements on Earth). Unfortunately, only moderate electrical conductivity and significant volume expansion of up to 300% for Li-ion, and as much as 520% for Na-ion can occur. Here, we use an ordered macroporous interconnected inverse opal (IO) architectures to enhance rate capability, structural integrity, and gravimetric capacity, without conductive additives and binders. Excellent capacity retention is shown during cycling vs Na/Na+ relative to Li/Li+. Cyclic voltammetry (CV) analysis, galvanostatic cycling, and differential capacity analysis extracted from rate performance testing evidence the irreversibility of the oxidation of metallic Sn to SnO2 during charge. This behavior allows for a very stable electrode during cycling at various rates. A stable voltage profile and rate performance is demonstrated for both systems. In a Na-ion half cell, the SnO2 retained >76% capacity after 100 cycles, and a similar retention after rate testing.

Boosting the photocathode performances of protected Cu2O inverse opals using photonic-crystal heterostructures

Cuprous oxide (Cu2O) is a highly efficient p-type semiconductor photocatalytic material with the capability for visible light absorption. In this work, three-dimensional Cu2O inverse opals with different diameters were prepared using the electrochemical deposition method. The photocathode performances were enhanced by adjusting the wavelength of photonic band gap, being co-modified by Au and Ag nanoparticles, applying the protective layers, and fabricating a photonic-crystal heterostructure with another p-type semiconductor. The slow-light effect leads a 23.9 % increase in photocurrent density. The co-modification of Au and Ag nanoparticles achieves a 77 % average increase in photocurrent density compared with pure Cu2O inverse opals. Conformal protective layers, consisting of ZnO and Al2O3 and deposited using atomic layer deposition, prevent the photocorrosion of the Cu2O photocathode while preserving its photocatalytic activity. After one hour of illumination, the photo-generated current density of protected Cu2O inverse opals is nearly three times higher than that of their uncoated counterparts. By fabricating Ag-doped ZnO with p-type characteristics and combining it with Cu2O into a heterostructure, the saturated photocurrent density of the Ag-doped ZnO/Cu2O heterostructure reaches −3.78 mA/cm2, which is almost 3.2 times higher than that of pristine Cu2O inverse opal at −0.12 V vs RHE.

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.

Enhancing the Photocatalytic Performance of Antibiotics Using a Z-Scheme Heterojunction of 0D ZnIn2S4 Quantum Dots and 3D Hierarchical Inverse Opal TiO2.

Limited light absorption and rapid photo-generated carriers' recombination pose significant challenges to the practical applications of photocatalysts. In this study, we employed an efficient approach by combining the slow-photon effect with Z-scheme charge transfer to enhance the photo-degradation performance of antibiotics. Specifically, we incorporated 0D ZnIn2S4 quantum dots (QDs) into a 3D hierarchical inverse opal (IO) TiO2 structure through a facile one-step process. This combination enhanced the visible light absorption and provided abundant active surfaces for efficient photo-degradation. Moreover, the ZnIn2S4 QDs formed an artificial Z-scheme system with IO-TiO2, facilitating the separation and migration of charge carriers. To achieve a better band alignment with IO-TiO2, we doped Ag into the ZnIn2S4 QDs (Ag: ZIS QDs) to adjust their energy levels. Through an investigation of the different Ag contents in the ZnIn2S4 QDs, we found that the optimal photo-degradation performance was achieved with Ag (2.0): ZIS QDs/IO-TiO2, exhibiting degradation rates 19.5 and 14.8 times higher than those of ZnIn2S4 QDs and IO-TiO2, respectively. This study provides significant insights for elevating the photocatalytic capabilities of IO-TiO2 and broadening its prospective applications.

Ultrasensitive electrochemiluminescence sensor for the detection of synthetic cannabinoids based on perovskite as coreaction accelerator and light-scattering effects of photonic crystals

As is common knowledge, a strong electrochemiluminescence (ECL) signal is required to ensure the high sensitivity of trace target detection. Here, a dual signal amplification strategy by integrating of perovskite and photonic crystal was fabricated for quantitative synthetic cannabinoids (AB-PINACA) detection based on Zr-connected PTCA and TCPP (PTCA-TCPP) with excellent ECL performance as luminophores. On the one hand, the co-reaction accelerator perovskite (LaCoO3) improved the effective electroactive area of the electrode and promoted the decomposition of K2S2O8, resulting in a stronger ECL signal value. On the other hand, polystyrene inverse opal (PIOPCs) formed after the swelling of PS microspheres not only taken advantage of the light scattering effect and excellent catalytic property of photonic crystals to amplify the ECL signal, but also could be used as a binder to fix LaCoO3 and PTCA-TCPP on the electrode surface to generate unprecedented ECL response and stable ECL signals. Subsequently, the detection substance AB-PINACA was loaded on the electrode surface via the amide bond with the luminophores PTCA-TCPP, thus quenching the ECL signal, so as to realize the sensitive detection of synthetic cannabinoids. Under the optimal conditions, the proposed sensor achieved highly sensitive AB-PINACA detection with a dynamic range from 1.0 × 10−12 to 1.0 × 10−3 g/L and the detection limit was 1.1 × 10−13 g/L, which had great application potential in the detection of synthetic cannabinoids.

Steaming‐Assisted Conversion: A New Strategy for the Synthesis of Anatase TiO2, Nb, and W‐doped Anatase TiO2 2D Inverse Opal Films

AbstractSteaming‐assisted conversion route, a new strategy, is first adapted for the synthesis of highly crystallized anatase TiO2 2D inverse opal (IO) monolayer films, and then to Nb‐doped TiO2 and W‐doped TiO2 2D IO monolayer films. Pure water, ammonia, or HCl solutions are used as a source of steaming vapor to convert dry films of amorphous TiO2 IO, NbCl5/TiO2, and WCl6/TiO2 composite IOs into anatase TiO2, Nb‐doped TiO2, and W‐doped TiO2 IO films. This new strategy renders possible the doping of metal ions within the framework of the anatase TiO2 IO films under low temperature and liquid‐free conditions. Further, the ordered array structure of the IO films is also effectively retained. The low steaming conversion temperature allows high dopant rates of homogeneously distributed heteroatoms, resulting in Nb doping as high as ≈34%. The thus prepared TiO2, Nb‐doped TiO2, and W‐doped TiO2 anatase IO films are successfully used as active electrodes in the fabrication of electrochromic devices.

Pt nanoparticles stabilized within MOF derivative on inverse opal ZnO for acetone prediction

We report a surface anchoring strategy for encapsulating Pt nanoparticles into MOF derivative cavities on inverse opal (IO) ZnO to enhance the sensing properties of metal oxide semiconducting gas sensors. This approach offers significant advantages over existing methods which are limited in synthetic modes and stability. Through in-situ growing ZIF-8 derivative (ZD) onto IO-ZnO, we achieve effective confinement and stabilization of Pt nanoparticles in small size and remarkable catalytic activity as confirmed by CO-TPR. Meanwhile, in-situ growth of ZD supply abundant adsorption sites for gas sensing as verified by acetone-TPR. The sensing material, IO-Pt@ZD/ZnO, comprising Pt nanoparticles encapsulated in IO-ZnO and confined in ZD is prepared for acetone sensor, which exhibits highly sensitivity (S = 36.4 vs. 100 ppm) and robust repeatability (130 cycles at 275 °C for 50 days). Meanwhile, Deep Neural Networks are applied to predict acetone concentration in moisture ambience from an individual sensor (Mean Square Error = 0.05 %). This work establishes a promising prospect for rational construction of metal oxide semiconducting combined with noble metal nanoparticles for highly catalytic activity, robust stability, and outstanding sensitivity in gas sensor application.

Enhanced heat transfer using wafer-scale crack-free well-ordered porous structure surface

Boiling heat transfer through porous medium is one of the prevalent cooling strategies in electronic thermal management due to its superior heat transfer capability. However, multiple optimization goals generally have conflicting requirements for the physical design of surface structure during boiling heat transfer. In order to reveal the potential mechanism, the boiling characteristics of a heated surface composed of three-dimensional ordered porous inverse opal (IO) structure were studied. From a numerical perspective, the change in critical heat flux does not always have a linear relationship with the thickness of the structure. When the thickness approaches 4.1 μm, the maximum critical heat flux (CHF) of 122 W/cm2 was obtained at a lower superheat (<15 K). Compared with smooth surfaces, the heat transfer performance of IO structure was largely enhanced with a maximum heat transfer coefficient (HTC) improvement of 945%. For IO structures with the thickness of 3.3 μm, the simulated CHF value is 102 W/cm2 which is in close agreement with the experimental value of 103 W/cm2. Due to its uniform porous structure and high capillary capacity, it can persistently maintain small bubbles before approaching CHF, thereby improving heat transfer performance. This high-performance IO structure provides an alternative thermal dissipation method for electronics.

Study on nonreciprocal radiation and photothermal conversion of VO2-based tunable inverse opal thermal emitter

In this work, a novel tunable nonreciprocal thermal emitter, consisting of an InAs magneto-optic inverse opal film and a VO2 film, is designed to achieve strong and tunable nonreciprocal radiation in the mid-infrared band of 6.8–7.8 μm. A more appropriate Lorentz-Drude model is used to describe the material properties of InAs, and the nonreciprocal band in the mid-infrared range for doped InAs is obtained through the Lorentz-Drude model. The effect of different middle layers on the structure of films and inverse opals is investigated under a magnetic field at an incident angle of 26° The inverse opal structure is found to have better nonreciprocal properties, while VO2 has the role of replacing noble metals in the tuning of nonreciprocal radiation. In addition, the strengthening mechanism of the inverse opal structure and the physical mechanism of the nonreciprocal radiation are further analysed and revealed through electric field energy distribution plots and impedance matching theory. A comparison of the nonreciprocal radiation and the photothermal effect of three inverse opal structures with different pore distributions and porosities for different parameters shows that the simple cubic structure has the strongest nonreciprocal radiation performance and a relatively high photothermal conversion effect, which can further increase the radiation capacity of the thermal emitter over a range. Therefore, the designed inverse opal composite structure can be used for the fabrication of tunable thermal emitters with nonreciprocal effects, where the amount of light absorbed in one channel of the thermal emitter can be controlled to tune the radiation capacity of the other channel. Providing a degree of assistance in the development and application of nonreciprocal thermal radiation devices in the mid-infrared wavelength band.

Preparation of a new PVDF membrane with inverse opal structure for high-precision separation

Inspired by natural isoporous materials and the highly arranged structure of photonic crystals (PCs), an inverse opal (IO)-structured membrane with a highly interconnected through-hole structure, a high porosity, and a nearly uniform pore size was prepared by multiosmosis method. Silica (SiO2) microspheres were assembled as building blocks into opal crystals, and poly (vinylidene fluoride) (PVDF) acted as the frame material of the membrane. The influencing factors in the fabrication of high-quality opal PCs were studied. Binary PVDF/SiO2 composite PCs were obtained by multiosmosis of a PVDF solution, and the infiltration mechanism was investigated, which indicated that the PVDF polymers were uniformly cured throughout the crystal area to form SiO2/air/PVDF composite PCs until completely infiltrated. Then, the IO-structured membrane was achieved after etching SiO2 microspheres. Different particle sizes of SiO2 microspheres were used to prepare PVDF membranes with various pore sizes. The pure water flux and porosity could reach as high as 5208.71 L m−2h−1 and 83.59%, respectively. The membranes displayed excellent rejection of SiO2 microspheres, almost 100%, and great antifouling performance. This work provided a simple and efficient method for constructing a filtration membrane with IO structure, which hopefully would solve the problems encountered in realizing efficient, high-precision separation.

Research and Application Progress of Inverse Opal Photonic Crystals in Photocatalysis

In order to solve the problem of low photocatalytic efficiency in photocatalytic products, researchers proposed a method to use inverse opal photonic crystal structure in photocatalytic materials. This is due to a large specific surface area and a variety of optical properties of the inverse opal photonic crystal, which are great advantages in photocatalytic performance. In this paper, the photocatalytic principle and preparation methods of three-dimensional inverse opal photonic crystals are introduced, including the preparation of basic inverse opal photonic crystals and the photocatalytic modification of inverse opal photonic crystals, and then the application progresses of inverse opal photonic crystal photocatalyst in sewage purification, production of clean energy and waste gas treatment are introduced.

Photochromic Azobenzene Inverse Opal Film toward Dynamic Anti-Fake Pattern.

Azobenzene mesogens have garnered considerable research attention in the realm of photo-responsive materials due to their reversible trans-cis isomerization. In this paper, we demonstrate an azobenzene inverse opal film synthesized via photo-polymerization from a SiO2 opal template. The proposed design exhibits intriguing optical properties, including dynamic fluorescent features, distinct fluorescent enhancement, and an anti-fake micropattern with a switchable structure color. This work holds significant importance for advancing the development of novel optical devices.

Application of Carbon Nanosphere Templates for Preparation of Inverse Opal Photonic Crystals in Dye‐Sensitized Solar Cells

Carbon nanospheres are successfully synthesized with a particle size of about 140 nm using a two‐step hydrothermal method and used the carbon nanospheres as the deposition template material on the surface of P25(TiO2) by means of vertical deposition method. The antiopaline TiO2 photonic crystal (PC) structure is further prepared via immersed carbon nanospheres in TiO2 precursor solution, and the antiopal PC is used as the scattering layer of the photoanode of dye‐sensitized solar cell (DSSCs). As a comparison, the antiopal PC reflective layer is also prepared on the photoanode of DSSCs using polystyrene nanospheres as the template material. The photoanodes with those PC scattering layers prepared with different template materials are fabricated into complete DSSCs. The final photoelectric conversion efficiency of the DSSCs prepared with carbon nanospheres as the template material reaches 7.02%, which is comparable to the cells prepared with polystyrene nanospheres as the template material. The efficiency of the cell with the scattering layer is increased by about 16% compared with that of the normal DSSC based on P25.

In Situ Ultra-Small- and Small-Angle X-ray Scattering Study of ZnO Nanoparticle Formation and Growth through Chemical Bath Deposition in the Presence of Polyvinylpyrrolidone.

ZnO inverse opals combine the outstanding properties of the semiconductor ZnO with the high surface area of the open-porous framework, making them valuable photonic and catalysis support materials. One route to produce inverse opals is to mineralize the voids of close-packed polymer nanoparticle templates by chemical bath deposition (CBD) using a ZnO precursor solution, followed by template removal. To ensure synthesis control, the formation and growth of ZnO nanoparticles in a precursor solution containing the organic additive polyvinylpyrrolidone (PVP) was investigated by in situ ultra-small- and small-angle X-ray scattering (USAXS/SAXS). Before that, we studied the precursor solution by in-house SAXS at T = 25 °C, revealing the presence of a PVP network with semiflexible chain behavior. Heating the precursor solution to 58 °C or 63 °C initiates the formation of small ZnO nanoparticles that cluster together, as shown by complementary transmission electron microscopy images (TEM) taken after synthesis. The underlying kinetics of this process could be deciphered by quantitatively analyzing the USAXS/SAXS data considering the scattering contributions of particles, clusters, and the PVP network. A nearly quantitative description of both the nucleation and growth period could be achieved using the two-step Finke-Watzky model with slow, continuous nucleation followed by autocatalytic growth.