TiO2 Inverse Opal Research Articles

Enhanced Photocatalysis via Inverse Opal Structures: Synthesis and Characterization of TiO2/ZnO and ZnO/TiO2 Composites Using Plasma-Enhanced ALD

Inverse opals (IO) based functional materials show potential in photocatalysis due to their unique light interaction properties. This study presents a low-temperature plasma-enhanced atomic layer deposition (PEALD) method for synthesizing TiO2, ZnO, and composite IOs using a polystyrene nanoparticle-based opal template. We comprehensively characterized the obtained materials using SEM-EDX, TSEM, TG, FTIR, XRD, Raman, ellipsometry, photoluminescence (PL), and UV-Visible spectroscopy. SEM analysis confirmed the successful formation of PEALD IOs with a periodically ordered structure, enabling conformal coating while preserving their original architecture. XRD and Raman analysis also confirmed that the IOs consisted of anatase for TiO2 and hexagonal wurtzite for ZnO. UV-Vis reflectance spectroscopy revealed strong UV absorption and modified photonic bandgaps (PBGs) for all materials. The bare and composite IOs exhibited PBGs in the visible region, suggesting that the arising "slow photon" effect might enhance photocatalysis. This study explored the photocatalytic degradation of 4-Nitrophenol (4-NP) and Rhodamine 6G (Rh6G) using pristine and composite IO photocatalysts under UV and visible light irradiation. Pristine TiO2 and ZnO IOs demonstrated superior performance for 4-NP degradation under UV light. This can be attributed to two key factors: their highly ordered macroporous structure (with a large surface area for efficient dye adsorption, and their band gaps (3.0 eV for TiO2 and 3.2 eV for ZnO) that enable strong absorption of UV light photons for effective pollutant degradation. Conversely, composite IOs (TiO2/ZnO and ZnO/TiO2) displayed higher activity for both test molecules under visible light due to a synergistic effect between bandgap harmonization and the PBG effect.

Preparation of Ag@Au core-shell nanoparticles embedded in TiO2 inverse opal for light harvesting and efficiency enhancement in quantum dot sensitized solar cells

In the fabrication of Quantum dot sensitized solar cells (QDSSCs), it is important to fabricate a photoanode with a high ability to trap photons as well as transfer photogenerated electrons. TiO2 inverse opal (TIO) photonic crystals with their organized porous structures, besides their chemical nature, have unique optical features such as the slow-photon effect, photon localization, and photonic bandgap (PBG). Herein, to improve the efficiency of QDSSCs, gold, silver, and silver/gold core-shell (Ag@Au) plasmonic nanoparticles (nps) are loaded on TIO. The plasmonic nanoparticle-decorated inverse opal improves the light scattering process and provides direct charge transfer tunnels, which can effectively prevent the recombination of electron-hole pairs. In this work, fabricated QDSSCs with TIO (double-layer)/ZnS/CdS/CdSe/ZnSe/ZnS photoanode, and a 6 μm total thickness of the TIO multilayer, has an open circuit voltage (Voc) of 0.745 V and short-circuit current density (JSC) of 16.22 mA/cm2. The obtained results are higher than the common anatase TiO2 (TiO2-A)/ rutile TiO2 (TiO2-R)/QD photoanode. Also, the TIO (double-layer)/Ag@Au/QDs photoanode exhibits JSC=20.3283 mA/cm2, Voc= 0.75 V, and a power conversion efficiency (PCE) of ƞ=10.79 %.

Enhanced Photocatalytic Properties and Photoinduced Crystallization of TiO2-Fe2O3 Inverse Opals Fabricated by Atomic Layer Deposition.

The use of solar energy for photocatalysis holds great potential for sustainable pollution reduction. Titanium dioxide (TiO2) is a benchmark material, effective under ultraviolet light but limited in visible light utilization, restricting its application in solar-driven photocatalysis. Previous studies have shown that semiconductor heterojunctions and nanostructuring can broaden the TiO2's photocatalytic spectral range. Semiconductor heterojunctions are interfaces formed between two different semiconductor materials that can be engineered. Especially, type II heterojunctions facilitate charge separation, and they can be obtained by combining TiO2 with, for example, iron(III) oxide (Fe2O3). Nanostructuring in the form of 3D inverse opals (IOs) demonstrated increased TiO2 light absorption efficiency of the material, by tailoring light-matter interactions through their photonic crystal structure and specifically their photonic stopband, which can give rise to a slow photon effect. Such effect is hypothesized to enhance the generation of free charges. This work focuses on the above-described effects simultaneously, through the synthesis of TiO2-Fe2O3 IOs via multilayer atomic layer deposition (ALD) and the characterization of their photocatalytic activities. Our results reveal that the complete functionalization of TiO2 IOs with Fe2O3 increases the photocatalytic activity through the slow photon effect and semiconductor heterojunction formation. We systematically explore the influence of Fe2O3 thickness on photocatalytic performance, and a maximum photocatalytic rate constant of 1.38 ± 0.09 h-1 is observed for a 252 nm template TiO2-Fe2O3 bilayer IO consisting of 16 nm TiO2 and 2 nm Fe2O3. Further tailoring the performance by overcoating with additional TiO2 layers enhances photoinduced crystallization and tunes photocatalytic properties. These findings highlight the potential of TiO2-Fe2O3 IOs for efficient water pollutant removal and the importance of precise nanostructuring and heterojunction engineering in advancing photocatalytic technologies.

Amine-Rich Hydrogels for Molecular Nanoarchitectonics of Photosystem II and Inverse Opal TiO2 toward Solar Water Oxidation.

Solar water oxidation is a crucial process in light-driven reductive synthesis, providing electrons and protons for various chemical reductions. Despite advances in light-harvesting materials and cocatalysts, achieving high efficiency and stability remains challenging. In this study, we present a simple yet effective strategy for immobilizing natural photosystems (PS) made of abundant and inexpensive elements, using amine-rich polyethylenimine (PEI) hydrogels, to fabricate organic/inorganic hybrid photoanodes. Natural PS II extracted from spinach was successfully immobilized on inverse opal TiO2 photoanodes in the presence of PEI hydrogels, leading to greatly enhanced solar water oxidation activity. Photoelectrochemical (PEC) analyses reveal that PS II can be immobilized in specific orientations through electrostatic interactions between the positively charged amine groups of PEI and the negatively charged stromal side of PS II. This specific orientation ensures efficient photogenerated charge separation and suppresses undesired side reactions such as the production of reactive oxygen species. Our study provides an effective immobilization platform and sheds light on the potential utilization of PS II in PEC water oxidation.

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.

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.

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.

Design and mechanism insight on SiC quantum dots sensitized inverse opal TiO2 with superior photocatalytic activities under sunlight

Design and mechanism insight on SiC quantum dots sensitized inverse opal TiO2 with superior photocatalytic activities under sunlight

Synthesis of TiO2/Al2O3 Double-Layer Inverse Opal by Thermal and Plasma-Assisted Atomic Layer Deposition for Photocatalytic Applications.

In comparison to conventional nano-infiltration approaches, the atomic layer deposition (ALD) technology exhibits greater potential in the fabrication of inverse opals (IOs) for photocatalysts. In this study, TiO2 IO and ultra-thin films of Al2O3 on IO were successfully deposited using thermal or plasma-assisted ALD and vertical layer deposition from a polystyrene (PS) opal template. SEM/EDX, XRD, Raman, TG/DTG/DTA-MS, PL spectroscopy, and UV Vis spectroscopy were used for the characterization of the nanocomposites. The results showed that the highly ordered opal crystal microstructure had a face-centered cubic (FCC) orientation. The proposed annealing temperature efficiently removed the template, leaving the anatase phase IO, which provided a small contraction in the spheres. In comparison to TiO2/Al2O3 plasma ALD, TiO2/Al2O3 thermal ALD has a better interfacial charge interaction of photoexcited electron-hole pairs in the valence band hole to restrain recombination, resulting in a broad spectrum with a peak in the green region. This was demonstrated by PL. Strong absorption bands were also found in the UV regions, including increased absorption due to slow photons and a narrow optical band gap in the visible region. The results from the photocatalytic activity of the samples show decolorization rates of 35.4%, 24.7%, and 14.8%, for TiO2, TiO2/Al2O3 thermal, and TiO2/Al2O3 plasma IO ALD samples, respectively. Our results showed that ultra-thin amorphous ALD-grown Al2O3 layers have considerable photocatalytic activity. The Al2O3 thin film grown by thermal ALD has a more ordered structure compared to the one prepared by plasma ALD, which explains its higher photocatalytic activity. The declined photocatalytic activity of the combined layers was observed due to the reduced electron tunneling effect resulting from the thinness of Al2O3.

Structural, morphological, and optical analysis of TiO2 inverse opals prepared under different synthesis conditions

Although TiO2 inverse opals have been used in different applications for the last decades, controlling their properties is still a matter of effort. In this paper, it is shown that the structure, morphology, and optical properties of TiO2 inverse opals can be precisely controlled by changing the synthesis conditions. Herein, TiO2 inverse opals were synthesized using the sol-gel method. First of all, opal photonic crystals were fabricated by monodisperse poly (methyl methacrylate) (PMMA) microspheres using the self-assembly-based vertical deposition technique. Then, the TiO2 precursor was synthesized by mixing ethanol, HCl, and selected ratios of titanium tetra isopropoxide (TTIP). Furthermore, four different amounts of the precursor were injected into the opal structures. The conditions for fabricating the most crack-free and uniform structures on a micro-scale were discussed. Also, the penetration rate, the thickness of the structure, its porosity, and photonic bandgap (PBG) qualities were investigated for different synthesized conditions. It has been believed that the results of this study can be beneficial for different TiO2 inverse opal applications to choose the best synthesizing conditions for the desired aim.

Design and synthesis of black phosphorus quantum dot sensitized inverse opal TiO2 photonic crystal with outstanding photocatalytic activities

Quantum dot sensitized photocatalyst is designed and applied in purification of dye wastewater, using black phosphorus nanoparticles (BPQDs) as the quantum dot and inverse opal (IO) TiO2 photonic crystal as the main photocatalyst. Due to electron density change within the composite, electrons can transfer from BPQDs to IO TiO2 directionally. Bandgap energies and relative energy band positions of BPQDs and IO TiO2 further provide efficient electronic transmission channels at the heterojunction interface. Therefore, interfacial resistance for charge transfer is reduced, the production of active oxidative species is promoted, and the photo induced charge transfer proceeds through a typical type-II route. Finally, excellent photocatalytic properties of BPQDs-IO TiO2 are achieved with the highest apparent kinetic constant (kapp) of 0.046 min−1, which is more than 3 times for bare IO TiO2 (0.014 min−1) and nearly 2 times for commercial P25 TiO2 (0.027 min−1). Furthermore, long-term stability and non-toxicity make the quantum dot sensitized photocatalyst have great applications in purifying environmental water pollution.

Composite TiO2/GeO2 for Higher Performance Inverse Opal Lithium-Ion Battery Electrodes

With the ever-growing technology industry and the need for more sustainable energy, the race to develop better, more efficient, renewable materials for lithium ion batteries is at the forefront of research. Metal oxide materials for use as electrodes in lithium batteries have been promising in recent years, transition metal oxides are favourable due to their low cost and nanostructured metal oxides exhibit encouraging electrochemical properties.1-2 Photonic crystal structures, more specifically inverse opal (IO) structures, are porous, highly interconnected structures which have proven to have advantageous benefits such as increased surface area and lower ion diffusion distances.3 In this work we combine TiO2 and GeO2 in solution phase in two ratios, 2:1 and 5:1 in favour of TiO2. Titanium oxides have high working potentials, higher than graphite which is most commonly used today. TiO2 has previously shown excellent long life cyclability and has shown little structural strain during the lithiation/delithiation process.4 Germanium has a high theoretical capacity of 1384 mAh/g and high electrical conductivity however it is expensive for use as an anode.5 Previous reports have shown that by nano-structuring GeO2 into an inverse opal structure, it can behave like pure germanium during cycling beyond the initial reduction and lithitation cycles.6 By combining both materials, we were able to achieve high capacity values for both ratios, 3 times the capacity of titanium IOs on their own. Work is ongoing to investigate the optimal cost to benefit ratio of the TiO2/GeO2 composites. Initial capacity results showcase high capacity retention and voltage stability. Reddy, M. V.; Subba Rao, G. V.; Chowdari, B. V. R., Metal Oxides and Oxysalts as Anode Materials for Li Ion Batteries. Chemical Reviews 2013, 113 (7), 5364-5457.Wu, H. B.; Chen, J. S.; Hng, H. H.; Wen Lou, X., Nanostructured metal oxide-based materials as advanced anodes for lithium-ion batteries. Nanoscale 2012, 4 (8), 2526-2542.Armstrong, E.; O'Dwyer, C., Artificial opal photonic crystals and inverse opal structures – fundamentals and applications from optics to energy storage. Journal of Materials Chemistry C 2015, 3 (24), 6109-6143.McNulty, D.; Carroll, E.; O'Dwyer, C., Rutile TiO2 Inverse Opal Anodes for Li-Ion Batteries with Long Cycle Life, High-Rate Capability, and High Structural Stability. Advanced Energy Materials 2017, 7 (12), 1602291.Zhang, Q.; Chen, H.; Luo, L.; Zhao, B.; Luo, H.; Han, X.; Wang, J.; Wang, C.; Yang, Y.; Zhu, T.; Liu, M., Harnessing the concurrent reaction dynamics in active Si and Ge to achieve high performance lithium-ion batteries. Energy & Environmental Science 2018, 11 (3), 669-681.McNulty, D.; Geaney, H.; Buckley, D.; O'Dwyer, C., High capacity binder-free nanocrystalline GeO2 inverse opal anodes for Li-ion batteries with long cycle life and stable cell voltage. Nano Energy 2018, 43, 11-21. Figure 1. (a) SEM image of a TiO2/GeO2 inverse opal (b) SEM image of TiO2/GeO2 IOs with EDX mapping overlay indicating position of titanium (green) and germanium (red). (c) and (d) Charge discharge profiles at 150 mA/g for the first 100 cycles for the 2:1 ratio and 5:1 ratio respectively.(e) Rate capability test for both ratios with specific currents ranging from 75 mA/g-450 mA/g. Figure 1

Functionalization of TiO2 inverse opal structure with atomic layer deposition grown Cu for photocatalytic and antibacterial applications

TiO2 inverse opal (IO) structure surfaces were functionalized with a sub-monolayer amount of Cu by atomic layer deposition (ALD) and tested for photocatalytic and antimicrobial applications. Decomposition of acetylene (C2H2) into CO2 and reduction of CO2 into CH4 were tested in the gas phase and photodegradation of methylene blue (MB) was tested in the liquid phase. Antimicrobial activity was tested against Gram-positive Staphylococcus aureus (S. aureus) bacteria. ALD Cu without any post-deposition heat treatment (HT) decreased the photo degradation rate of both C2H2 and MB but improved the activity towards CO2 reduction. ALD Cu increased MB photodegradation rate and antimicrobial activity only after HT at 550 °C, which was linked to the improved chemical stability Cu after the HT. The same HT decreased the activity towards CO2 reduction and decomposition of C2H2. The HT induced desorption of loosely bound ALD Cu+/2+ from the TiO2 IO surface and the remaining Cu+/2+ was reduced to Cu+. The photocatalytic and antimicrobial activity of TiO2 IO can be tailored by the addition of a sub-monolayer amounts of Cu with performance depending on the targeted reaction.

Operando Photonic Stopband Monitoring of Lithium-Ion Battery Electrodes

Research in lithium-ion batteries is often focused on optimising the electrode performance of either the anode1 or cathode2. One common research strategy is to explore alternative electrode material candidates for use as both the anode3 and cathode4. Another approach involves optimising the performance of existing electrode materials through structured electrode architectures with nano-sized features. Incorporating nanostructure into electrode design has reported advantages of shorter ion diffusion lengths and improved rate capability during cycling5. A common and simple technique for introducing nanostructure to electrodes is the use of a photonic crystal template, particularly inverse opal photonic crystals. The porous geometry, highly interconnected material and nano-sized features of the pore walls are all believed to contribute to improved electrochemical performance in inverse opal electrodes6 7.Photonic crystal materials are more than just a structural template and are renowned for their ability to tune the wavelengths of light propagating in the structure8 9. The repeating dielectric material comprising the structure reflects specific wavelengths, known as the photonic bandgap or stopband, depending on the size of the repeating lattice and the refractive index contrast between the composite materials. Tuning the photonic stopband of various inverse opal materials has been extensively studied10 11. Inverse opal battery electrodes have yet to exploit the optical potential of the photonic stopband.Here, we showcase a fundamentally new operando analysis technique for lithium-ion battery electrodes adopting a photonic crystal structure. Visible spectroscopy is used to monitor the presence and position of the photonic stopband of the electrode material during battery cycling, see Figure 1. Capitalizing on the sensitivity of the photonic stopband to lattice size and refractive index contrast, shifts or changes in the optical spectrum can be correlated to the electrode environment and material performance. Several optical effects are observed throughout the cycling process and linked back to the battery performance of the anode. A TiO2 inverse opal anode is reported on here, yet the technique is versatile and should be applicable to a wide range of electrode materials possessing a photonic crystal structure. References Kim, H.; Choi, W.; Yoon, J.; Um, J. H.; Lee, W.; Kim, J.; Cabana, J.; Yoon, W.-S., Exploring Anomalous Charge Storage in Anode Materials for Next-Generation Li Rechargeable Batteries. Chemical Reviews 2020, 120 (14), 6934-6976.Xu, J.; Dou, S.; Liu, H.; Dai, L., Cathode materials for next generation lithium ion batteries. Nano Energy 2013, 2 (4), 439-442.Liang, B.; Liu, Y.; Xu, Y., Silicon-based materials as high capacity anodes for next generation lithium ion batteries. Journal of Power Sources 2014, 267, 469-490.Manthiram, A.; Song, B.; Li, W., A perspective on nickel-rich layered oxide cathodes for lithium-ion batteries. Energy Storage Materials 2017, 6, 125-139.Mahmood, N.; Tang, T.; Hou, Y., Nanostructured Anode Materials for Lithium Ion Batteries: Progress, Challenge and Perspective. Advanced Energy Materials 2016, 6 (17), 1600374.McNulty, D.; Carroll, E.; O'Dwyer, C., Rutile TiO2 Inverse Opal Anodes for Li-Ion Batteries with Long Cycle Life, High-Rate Capability, and High Structural Stability. Advanced Energy Materials 2017, 7 (12), 1602291.McNulty, D.; Geaney, H.; Buckley, D.; O'Dwyer, C., High capacity binder-free nanocrystalline GeO2 inverse opal anodes for Li-ion batteries with long cycle life and stable cell voltage. Nano Energy 2018, 43, 11-21.John, S., Strong localization of photons in certain disordered dielectric superlattices. Phys. Rev. Lett. 1987, 58 (23), 2486-2489.Yablonovitch, E., Inhibited spontaneous emission in solid-state physics and electronics. Phys. Rev. Lett. 1987, 58 (20), 2059-2062.Schroden, R. C.; Al-Daous, M.; Blanford, C. F.; Stein, A., Optical Properties of Inverse Opal Photonic Crystals. Chemistry of Materials 2002, 14 (8), 3305-3315.Lonergan, A.; Hu, C.; O’Dwyer, C., Filling in the gaps: The nature of light transmission through solvent-filled inverse opal photonic crystals. Physical Review Materials 2020, 4 (6), 065201. Figure 1 (a) Schematic diagram of simultaneous electrochemical and optical characterisation techniques for photonic crystal electrodes. (b) Galvanostatic charge/discharge data for a TiO2 inverse opal electrode. (c) Optical spectrum for a TiO2 inverse opal submerged in LiPF6 electrolyte. (d) SEM image showing the ordered structure of a pristine TiO2 inverse opal. (e) Operando optical spectra obtained at 0.5 V intervals during discharge of the TiO2 inverse opal electrode. Figure 1

Methods to Tune the Optical Response of Porous Photonic Crystal Structures

Photonic crystals are periodic dielectric structures which selectively tune the wavelengths of light propagating through the material1 2. The highly ordered, repeating structural lattice induces a photonic bandgap or stopband which inhibits or partially attenuates certain frequencies of light, similar to the electronic bandgap with forbidden energies present in semiconductor materials3. These forbidden frequencies are blocked in transmission and reflected from the material surface. The inherent sensitivity of this photonic response to repeating lattice size dimensions and the magnitude of the refractive index contrast between the constituent materials allows for tailored optical behaviour by adjusting the photonic crystal structural parameters or environment4 5.A range of interesting applications using both the photonic bandgap and material porosity have emerged, predicated on the ability to accurately forecast the wavelength position of the photonic response. Colorimetric sensors6 7, photocatalysts8 9 and solar cells10 are prime examples of these types of applications; the porosity of the photonic crystal facilitates greater material infiltration and reactions, while the photonic bandgap acts to enhance the optical component of the process. Critically, the use of these structures is tied to our ability to predict and interpret the signature optical response.Here, we examine several techniques which can be used modify the photonic bandgap/stopband for photonic crystal structures. For TiO2 and SnO2 inverse opal photonic crystals, we explore how solvent infiltration into the highly porous network red-shifts the observed photonic response. Using solvents with different refractive indices, we apply the shifted photonic stopband data to determine the fill fraction of solid material comprising the photonic crystal network. We also examine functionalization of artificial opal and inverse opal photonic crystals with metal films. We detail the emergence of a consistent photonic stopband blue-shift with increasing metal content and propose a reduction in the effective refractive index of the entire photonic crystal introduced by the specific properties of the metal film. Importantly, the effects investigated here are broadly applicable to a range of realistic operating conditions across many disciplines where an understanding of the photonic stopband is paramount to the application. References Yablonovitch, E., Inhibited Spontaneous Emission in Solid-State Physics and Electronics. Physical Review Letters 1987, 58 (20), 2059-2062.John, S., Strong localization of photons in certain disordered dielectric superlattices. Physical Review Letters 1987, 58 (23), 2486-2489.Joannopoulos, J. D.; Villeneuve, P. R.; Fan, S., Photonic crystals: putting a new twist on light. Nature 1997, 386 (6621), 143-149.Blanford, C. F.; Schroden, R. C.; Al-Daous, M.; Stein, A., Tuning Solvent-Dependent Color Changes of Three-Dimensionally Ordered Macroporous (3DOM) Materials Through Compositional and Geometric Modifications. Advanced Materials 2001, 13 (1), 26-29.Aguirre, C. I.; Reguera, E.; Stein, A., Tunable Colors in Opals and Inverse Opal Photonic Crystals. Advanced Functional Materials 2010, 20 (16), 2565-2578.Zhang, Y.; Qiu, J.; Hu, R.; Li, P.; Gao, L.; Heng, L.; Tang, B. Z.; Jiang, L., A visual and organic vapor sensitive photonic crystal sensor consisting of polymer-infiltrated SiO2 inverse opal. Physical Chemistry Chemical Physics 2015, 17 (15), 9651-9658.Li, H.; Chang, L.; Wang, J.; Yang, L.; Song, Y., A colorful oil-sensitive carbon inverse opal. Journal of Materials Chemistry 2008, 18 (42), 5098-5103.Chen, J. I. L.; von Freymann, G.; Choi, S. Y.; Kitaev, V.; Ozin, G. A., Amplified Photochemistry with Slow Photons. Advanced Materials 2006, 18 (14), 1915-1919.Collins, G.; Lonergan, A.; McNulty, D.; Glynn, C.; Buckley, D.; Hu, C.; O'Dwyer, C., Semiconducting Metal Oxide Photonic Crystal Plasmonic Photocatalysts. Advanced Materials Interfaces 2020, 7 (8), 1901805.Liu, L.; Karuturi, S. K.; Su, L. T.; Tok, A. I. Y., TiO2 inverse-opal electrode fabricated by atomic layer deposition for dye-sensitized solar cell applications. Energy & Environmental Science 2011, 4 (1), 209-215. Figure 1 SEM images and optical transmission spectra for (a) TiO2 and (b) SnO2 inverse opals. In each case the wavelength position of the photonic stopband is red-shifted significantly when a solvent infiltrates the porous photonic crystal network. SEM images and optical transmission spectra for (c) artificial polystyrene opals coated with a gold film and (d) TiO2 inverse opals coated with a copper film. Metal film incorporation into the photonic crystal network acts to consistent blue-shift the observed photonic stopband. Figure 1

Application of defective TiO2 inverse opal in photocatalytic non-oxidative CH4 coupling

Application of defective TiO2 inverse opal in photocatalytic non-oxidative CH4 coupling

Photonic density of states and photonic bandgap of deformed titanium dioxide inverse opal structure

Titanium dioxide (TiO2) inverse opal, a well-ordered nanoporous media, has a good potential in light-matter enhancement application. In this work, the fabricated TiO2 inverse opal structures were prepared by well-ordered template from convective deposition. This measured photonic bandgap was shorter in wavelength from the theoretical prediction of the perfect well-ordered pore structure due to structural shrinkage and incomplete matrix fill. Shorter lattice distance from shrinkage and lower refractive index of matrix from incomplete-filled structure resulted in higher eigen energies of photonic crystal. The scanning electron microscope images indicated that the pore size of TiO2 inverse opal was reduced around 39% from the initial template size. Additionally, to explore the detail on photonic bandgap shift of deformed inverse opal, the photonic band-structures and density of states (DOS) spectra under variation of refractive index and fill fraction were evaluated by plane-wave expansion method. It was found that the zero DOS range has a narrow bandwidth at low fill fraction and refractive index of the matrix which agreed with the perturbation theory on the Hermitian Maxwell eigenvalue problem.

Novel Photoelectrochemical Sensor for Cholesterol Based on Ch3nh3pbbr3 Perovskite /Tio2 Inverse Opal Heterojunction Coated with Molecularly Imprinted Polymers

Novel Photoelectrochemical Sensor for Cholesterol Based on Ch3nh3pbbr3 Perovskite /Tio2 Inverse Opal Heterojunction Coated with Molecularly Imprinted Polymers

Controlled photocatalytic activity of TiO2 inverse opal structures with atomic layer deposited (ALD) metal oxide thin films

Atomic layer deposited (ALD) thin films of Al2O3, SiO2, and TiO2 with thicknesses ranging from 0.25 nm to 10 nm were studied on TiO2 inverse opal (IO) structures for their effect on photocatalytic activity under ultraviolet A (UVA) excitation. 1 nm coating of Al2O3 suppressed the photocatalytic activity significantly by more than 90% removing all water molecules from the surface. On the contrary, 0.25 nm SiO2 layer enhanced the photocatalytic activity by 112% by increasing the number of water molecules on the surface whereas 3 nm SiO2 layer reduced the activity by 87% as the thicker layer prevented electron and hole diffusion onto the surface. The highest photocatalytic activity enhancement up to 226% was observed with 10 nm ALD TiO2 layer.

Visible Light Trapping against Charge Recombination in FeOx-TiO2 Photonic Crystal Photocatalysts.

Tailoring metal oxide photocatalysts in the form of heterostructured photonic crystals has spurred particular interest as an advanced route to simultaneously improve harnessing of solar light and charge separation relying on the combined effect of light trapping by macroporous periodic structures and compositional materials’ modifications. In this work, surface deposition of FeOx nanoclusters on TiO2 photonic crystals is investigated to explore the interplay of slow-photon amplification, visible light absorption, and charge separation in FeOx–TiO2 photocatalytic films. Photonic bandgap engineered TiO2 inverse opals deposited by the convective evaporation-induced co-assembly method were surface modified by successive chemisorption-calcination cycles using Fe(III) acetylacetonate, which allowed the controlled variation of FeOx loading on the photonic films. Low amounts of FeOx nanoclusters on the TiO2 inverse opals resulted in diameter-selective improvements of photocatalytic performance on salicylic acid degradation and photocurrent density under visible light, surpassing similarly modified P25 films. The observed enhancement was related to the combination of optimal light trapping and charge separation induced by the FeOx–TiO2 interfacial coupling. However, an increase of the FeOx loading resulted in severe performance deterioration, particularly prominent under UV-Vis light, attributed to persistent surface recombination via diverse defect d-states.