Inverse Opal Photonic Crystals Research Articles

Effect of the Combination of Inverse Opal Photonic Crystal and Heterojunction on Active Free Radicals and its Effect on the Mechanism of Photocatalytic Removal of Organic Pollutants

Effect of the Combination of Inverse Opal Photonic Crystal and Heterojunction on Active Free Radicals and its Effect on the Mechanism of Photocatalytic Removal of Organic Pollutants

Personalized and Programmable Microneedle Dressing for Promoting Wound Healing.

Microneedle (MN) dressings, with the ability of transdermal drug delivery, have played an essential role in the field of wound healing. However, patients may still feel uncomfortable when sensitive unhealing wounds are pieced by strong needles. Here, inspired by the structure of mosquito mouthparts, which possess a fixation part and a liquid-transferring part, we present a novel MN wound dressing with superfine needle tips, personalized pattern design, programmable needle length, and multiple mechanical strengths for intelligent and painless drug delivery. By simply stretching the silicone rubber (Ecoflex) molds before engraving, superfine MNs can be formed in the restored molds. Meanwhile, by utilizing intelligent image recognition, precise treatment for irregular wounds is achieved. Notably, combined with temperature-responsive N-isopropylacrylamide (NIPAM) hydrogel and inverse opal (IO) photonic crystals (PCs), a controllable drug release system has been achieved on MN dressings. Moreover, the performance of the MN dressing in facilitating wound recovery has been demonstrated by full-thickness skin wounds of a mouse model. These results indicate that novel personalized and programmable MN wound dressings are of considerable value in the field of wound management.

Porphyrin-infiltrated SiO2 inverse opal photonic crystal as fluorescence sensor for selective detection of trace mercury ion

Sensing of heavy metal irons in aqueous medium is essential because the presence of heavy metals is very hazardous for environmental safety and human health. Here, a porphyrin-infiltrated inverse opal photonic crystal of silica (TPP-SiO2 IOPC) as the solid optical sensor has been prepared for the selective detection of mercury iron (Hg2+) in aqueous medium, while porphyrin is served as a fluorescence probe and the photonic crystal (PC) provides support as the backbone with special optical property. The intensity of fluorescence during the detection of Hg2+ on the TPP-SiO2 IOPC sensor is 38.9 times larger than that of control sample. The sensor has good linear response to the concentration of Hg2+ from 1.0 × 10−8 to 1.5 × 10−6 mol/L and the lower detection limit observed for Hg2+ concentration is 1.18 nM. Furthermore, the sensor exhibits excellent selection for Hg2+ rather than other metal ions. Therefore, the TPP-SiO2 IOPC sensor can be utilized for fast and simple monitoring of Hg2+.

Preparation and Application of Triplethiophene Derivative Functionalized SiO2 Inverse Opal Photonic Crystal Fluorescent Films

Preparation and Application of Triplethiophene Derivative Functionalized SiO2 Inverse Opal Photonic Crystal Fluorescent Films

Versatile titanium dioxide inverse opal composite photonic hydrogel films towards multi-solvents chip sensors

Photonic crystals with orderly periodic structure and manipulated structural colors have garnered widespread attention in sensors field. However, the unsatisfactory detection range, low sensitivity and inconvenient integration highly limit their further practical applications. In this paper, by combining TiO2 inverse opal photonic crystal with polyacrylamide hydrogel, a novel organic-inorganic composite solvents responsive photonic hydrogel (SRPH) was developed. By encapsulating TiO2 inverse opal photonic crystal with high refractive index in this hydrogel, the photonic hydrogels, therefore, possess bright structural colors. Due to the discrepancy in swelling rate of SRPH film in various solvents (ethanol, dimethyl formamide, dimethyl sulfoxide, etc.), it can identify these organic solvents through the rapid change of structural colors and detect the concentrations of the solvent in a wide range. Even for solvents with similar refractive index, it can be clearly distinguished, along with the excellent repeatability. Benefiting from the wide detection range and high sensitivity, the chip sensors were then developed by integrating multiple hydrogel films into the microfluidic system, which have high efficiency in solvent naked-eye multi-identification and concentration multi-detection. The new composite photonic hydrogels provide a reference for the design of functional photonic crystals and next-generation application of sensors.

Control of Liquid Crystal Microarray Optical Signals Using a Microspectral Mode Based on Photonic Crystal Structures.

Herein, a novel liquid crystal microarray (LCM) film with optical regulation ability is first constructed by combining liquid crystals (LC) and the highly ordered microporous structure of inverse opal photonic crystals (IOPhCs). The LCM films are fabricated by infiltrating LC molecules into the LC polymer with the structure of IOPhCs, and their properties are very different from those without the LC. Interestingly, the optical property of LCM films can be controlled by changing the orientation of LC molecules, which varies with the interfacial force. In combination with polarization images, spectral reflection peak, circular dichroism spectra, potential difference, and fluorescence images of LCM films, the mechanism of this change is investigated. It is found that the exposed basic group of single-stranded DNA is the key to the change of the optical property of LC microarrays. Meanwhile, the optical signals of LC microarrays based on the PhCs provide a novel LC signal mode for an LC sensing system (microspectral signal mode), and it can be recorded by a fiber-optic spectrometer, which is a great improvement on LC sensing signals. Therefore, the LC microarray sensing signal can be used for accurate analysis of targets by the change of the reflection peak intensity of PhCs. When the LC molecules are induced by different aptamers, the LC microarray sensing interface can be further used for the determination of different targets, such as cocaine and Hg2+. The research on LCM films is of significant value for the development of LC sensing technology and also shows great application prospects in biochemical sensing fields.

Visual and ultrasensitive detection of mercury ions based on urease catalysis and responsive photonic crystals

In this study, a visual and ultrasensitive method for the determination of trace mercury ions in water was developed based on the high efficiency of urease catalysis and pH-sensitive inverse opal polymeric photonic crystals (IOPPCs). Mercury ions can inhibit urea hydrolysis and suppress the production of ammonium and bicarbonate ions in the solution, resulting in the redshift of IOPPCs. Therefore, the redshift of IOPPCs Bragg diffraction is directly related to the concentration of mercury ions. Meanwhile, the color of IOPPCs varied significantly with the shift of the Bragg diffraction wavelength, thus achieving the visual semi-quantitative detection of mercury ions by the naked eye. The minimum detection concentration of this method is 5 × 10−16 g/L, which is much lower than the maximum contaminant level for the safe drinking of water (2 × 10−6 g/L) recommended by the environmental protection agency (EPA), USA. In addition, this is a simple and quick method for effective on-site detection of mercury ions, which shows a great promise in emergency leakage monitoring and control.

H2O- and ethanol concentration-responsive polymer/gel inverse opal photonic crystal

Responsive photonic crystals have attracted much attention due to their strong capability to manipulate the propagation of light in the visible region, but it is still a big challenge to invisibility and mechanical stability. Here, the novel Poly(ether sulfone)/Poly(acrylic acid) inverse opal photonic crystals, which have high mechanical stability and can release visible patterns after wetting with water, are discussed. The Poly(ether sulfone)/Poly(acrylic acid) inverse opal photonic crystals are also responsive to the concentration of ethanol, and the structural color response times increase with increasing ethanol concentration. This design uses the selective infiltration, hydrogen bonding and capillary action of solvent to realize the spectral diversity of reflectance. Owing to the high polarity and hydrogen bonding ability of carboxyl groups, water molecules are adsorbed easily by the poly(acrylic acid) gel. Subsequently, the encrypted information is decrypted due to the redshift of the structural color. Because of its lower polarity and hydrogen bonding ability relative to water, ethanol can impede the absorption of solvent by gel. Therefore, the ethanol concentration can be identified based on the structural color response time. Furthermore, reliable information decryption methods make Poly(ether sulfone)/Poly(acrylic acid) inverse opal photonic crystals potentially uesful as trusted encryption devices.

Fluorescence enhanced microfluidic sensor with CsPbI3 probe for lubricant copper ions on-site rapid detection based on SiO2 inverse opal photonic crystals

Cu2+ content in diesel engine lubricating oil refers to a vital parameter suggesting the quality of oil and judging mechanical wear. Accordingly, the on-site rapid copper ions content determination in lubricant is of great significance to safe operation of diesel engines. However, most of the current researches on detection are carried out in laboratory, requiring the use of large-scale equipment such as spectrometer, which are not suitable for rapid on-site detection. Quantum dot-based optical microfluidic chip provides the possibility for heavy metal ions on-site detection, but it is subject to the defect of weak fluorescence intensity, thereby the increase in sensitivity is limited. In the present study, a microfluidic sensor using SiO2 inverse opal photonic crystals (IOPCs) to heighten CsPbI3 perovskite quantum dots (PQDs) photoluminescence (PL) intensity is proposed, which can realize rapid Cu2+ content detection in lubricant. Firstly, the selective detection characteristic of CsPbI3 on Cu2+ was studied. Experimental results showed that the photoluminescence of CsPbI3 was significantly quenched by Cu2+ because electrons were effectively transferred from CsPbI3 to Cu2+. Subsequently, to enhance the fluorescence intensity of CsPbI3 probe, the SiO2 IOPCs structure was formed in chip detection well. The effective PL intensity of CsPbI3 PQDs was enhanced by the photonic stopband effect formed by the periodically arranged micro-nano structure of photonic crystals. This enhancement effect was attributed to the coupling effect between stopband with excitation and emission light. As the stopband of SiO2 IOPCs was coupled with the excitation light wavelength and emission light wavelength of CsPbI3, the enhancement factors could reach 17-fold and 22-fold, respectively. The mentioned strategy could effectively improve the detection sensitivity of the microfluidic sensor and reduce the detection limit to 0.34 nM. Moreover, the formed microfluidic sensor system can be used for determination of Cu2+ content in lubricating oil on site. Meanwhile, the sturdy porous structure of SiO2 IOPCs also facilitated target metal ions to be captured and enriched.

(Invited) Titania Inverse-Opal Photonic Crystals Incorporating Gold Nanoparticles in Void Spaces for Photoabsorption Enhancement

Designing of three-dimensional (3D) materials such as inverse-opal (IO) photonic crystals (PCs) has been identified as an effective pathway to enhance light harvesting to longer electromagnetic absorption regions such as visible and infrared [1]. IO PCs exhibit photonic band gap (PBG) and this band structure predicts the translation of photons with reduced velocity, namely as slow photons at certain crystallographic directions. The photonic effect from titania (TiO2)-IO structure was reported to enhance light-material interactions thus allowing better absorption of light at the wavelength at which the materials absorb poorly [2]. On the other hand, utilization of gold-nanoparticles (Au-NPs) on TiO2 could aid in charge separation and play its role as an amplifier for visible-light absorption due to its effects originating from localized surface plasmon resonance (LSPR) [3]. In this study, TiO2-IO PC with incorporated gold nanoparticles(Au-NPs) per void space was developed by implementing five important steps to achieve a good quality of TiO2-IO structure. Both photonic effects due to the slow photons in TiO2-IO structure and LSPR effects contributed by Au-NPs were expected to give visible-light absorption by the photocatalyst material.The experimental procedure consists of five steps as shown in Scheme 1 starting from (i) synthesis of Au-NPs, (ii) silica (SiO2) coating on Au-NP to form Au/SiO2 core-shells, (iii) self-assembly of Au/SiO2 to form high-quality opal structure, (iv) infiltration of TiO2 precursor via forced impregnation method and (v) selective etching of SiO2 to obtain the final TiO2-IO structure. Photodegradation of acetic acid was carried out in the presence of the photocatalyst material by using blue LED light (450 nm) with optical power of 0.3 W. SiO2 containing Au-NP (Au/SiO2) was used as the opal template for the 3D macroporous TiO2-IO containing Au-NP per void space (TiO2(Au)-IO). Figures 1a and 1b are images observed for Au/SiO2 opal structure exhibiting face-centered cubic (FCC) arrangement. As is observed, the closely packed opal structure could be obtained as the minimum variation among each particle was less than 5 %. However, extra precautions should be taken to avoid cracking on the opal structure to sustain the quality of the final desired material. Figures 1c and 1d are images of TiO2(Au)-IO which was successfully obtained after TiO2 infiltration via forced impregnation method followed by the removal of SiO2 to form the nanovoids. The strategy that has been implemented to enhance the light harvesting process was by designing the TiO2-IO structure with different diameter of nanovoids, which can be controlled by altering the SiO2 shell thickness in the second step of the synthesis process.Photocatalytic activities of those samples were evaluated by measuring the amount of carbon-dioxide(CO2) generated from acetic acid by TiO2(Au)-IO with different diameter of nanovoid diameters (Au-NP size: 44 nm) under LED light irradiation (4 h). Enhanced CO2 evolution was detected with TiO2(Au)-IO with nanovoid diameter of 215 nm suggesting the successful matching of photonic and LSPR effects in TiO2(Au)-IO.[1] X. Zheng, D. Li, X. Li, L. Yu, P. Wang, X. Zhang, J. Fang, Yu. Shao and Y. Zheng. Phys. Chem. Chem. Phys. 16 (2014) 15299–15306.[2] V. Jovic, H. Idriss and G.I.N. Waterhouse. Chem. Phys. 479 (2016) 109–121.[3] S.M. Yoo, S.B. Rawal, J.E. Lee, J. Kim, H. Ryu, D. Park and W.E. Lee. Appl. Catal. A Gen. 499 (2015) 47–54. Figure 1

A Comparison of Transition Metal Oxide Ordered Macroporous Materials Used in Battery Electrodes

This talk will summarize recent results of ordered macroporous (inverse opal) materials made from a range of transition metal oxides when used as Li-ion battery electrodes. The basic methodology for macroporous material formation will be presented for electrodes fabricated with macroporous ordered materials included TiO2, SnO2, GeO2, V2O5, their mixtures and other compounds.The talk will compare the basic lithiation response in these porous materials in Li-in battery half cells and detail the electrochemical response of each oxide and porous structure as a function of specific current (rate) and cycle life. Several of these materials offer surprisingly good electrochemical stability during long (>5000 cycles in the case of TiO2) cycle life, in a binder and conductive additive-free electrode formulation. We also summarize limits of some macroporous oxide materials at very high charge and discharge rates when used in Li-ion batteries and compare the influence of phase and structure on reversible lithiation.Related work and References O'Hanon, D. McNulty, R. Tian, J. Coleman, and C. O'Dwyer, High Charge and Discharge Rate Limitations in Ordered Macroporous Li-ion Battery Materials, J. Electrochem. Soc. 167, 140532 (2020).McNulty, H. Geaney, Q. Ramasse, and C. O'Dwyer, Long Cycle Life, Highly Ordered SnO2/GeO2 Nanocomposite Inverse Opal Anode Materials for Li‐Ion Batteries, Adv. Funct. Mater., 2005073 (2020).McNulty, H. Geaney, D. Buckley, and C. O'Dwyer, High Capacity Binder-free Nanocrystalline GeO2 Inverse Opal Anodes for Li-ion Batteries with Long Cycle Life and Stable Cell Voltage, Nano Energy 43, 11 (2018).McNulty, E. Carroll, and C. O'Dwyer, Rutile TiO2 Inverse Opal Anodes for Li-ion Batteries with Long Cycle Life, High-rate Capability and High Structural Stability, Adv. Energy Mater. 7, 1602291 (2017).McNulty, A. Lonergan, S. O'Hanlon, and C. O'Dwyer, 3D open-worked inverse opal TiO2 and GeO2 materials for long life, high capacity Li-ion battery anodes, Solid State Ionics 314, 195 (2018).Lonergan, D. McNulty, and C. O'Dwyer, Tetrahedral framework of inverse opal photonic crystals defines the optical response and photonic band gap, J. Appl. Phys. 124, 095106 (2018).O'Hanlon, D. McNulty, and C. O'Dwyer, The influence of colloidal opal template and substrate type on 3D macroporous single and binary vanadium oxide inverse opal electrodeposition, J. Electrochem. Soc. 164, D111 (2017).O'Dwyer, Colour-Coded Batteries – Inverse Opal Materials Circuitry for Enhanced Electrochemical Energy Storage and Optically Encoded Diagnostics, Adv. Mater. 28, 5681 (2016).

WO3 Inversce Opal Photonic Crystals: Unique Property, Synthetic Methods and Extensive Application

AbstractTungsten trioxide inverse opal photonic crystals (WO3 IOPCs) not only possess the intrinsic properties of WO3, but also own the unique characteristics of IOPCs structure. The evolution of preparation method of WO3 IOPCs has been briefly presented as electrodeposition method, sol‐gel methodology and ‘dynamic hard‐template’ strategy in this review. Then the crystalline structure, optical property and electrical performance of WO3 IOPCs are later described. Afterwards, this review focuses on the wide application of WO3 IOPCs in chemical sensor, photo(electro)catalysis, electrochromic material and photochromic field in the last decade. Finally, a brief outlook over future investigation in preparation and modification, as well as promising application is proposed. This paper aims to encourage the attention and effort of researchers on WO3 IOPCs and other semiconductor materials with IOPCs structure.

Influence of Alumina Addition on the Optical Properties and the Thermal Stability of Titania Thin Films and Inverse Opals Produced by Atomic Layer Deposition

TiO2 thin films deposited by atomic layer deposition (ALD) at low temperatures (<100 °C) are, in general, amorphous and exhibit a smaller refractive index in comparison to their crystalline counterparts. Nonetheless, low-temperature ALD is needed when the substrates or templates are based on polymeric materials, as the deposition has to be performed below their glass transition or melting temperatures. This is the case for photonic crystals generated via ALD infiltration of self-assembled polystyrene templates. When heated up, crystal phase transformations take place in the thin films or photonic structures, and the accompanying volume reduction as well as the burn-out of residual impurities can lead to mechanical instability. The introduction of cation doping (e.g., Al or Nb) in bulk TiO2 parts is known to alter phase transitions and to stabilize crystalline phases. In this work, we have developed low-temperature ALD super-cycles to introduce Al2O3 into TiO2 thin films and photonic crystals. The aluminum oxide content was adjusted by varying the TiO2:Al2O3 internal loop ratio within the ALD super-cycle. Both thin films and inverse opal photonic crystal structures were subjected to thermal treatments ranging from 200 to 1200 °C and were characterized by in- and ex-situ X-ray diffraction, spectroscopic ellipsometry, and spectroscopic reflectance measurements. The results show that the introduction of alumina affects the crystallization and phase transition temperatures of titania as well as the optical properties of the inverse opal photonic crystals (iPhC). The thermal stability of the titania iPhCs was increased by the alumina introduction, maintaining their photonic bandgap even after heat treatment at 900 °C and outperforming the pure titania, with the best results being achieved with the super-cycles corresponding to an estimated alumina content of 26 wt.%.

Microstructure design and energy transfer in Gd2(WO4)3: Yb3+/Er3+ phosphors

Rare-earth-doped upconverison luminescent (UCL) materials have wide application prospects in the field of nanoptoelectronics technology. However, achieving highly efficient UCL materials is still a big challenge due to the serious nonradiative energy loss in the host materials. In this research, Gd2(WO4)3: Yb3+, Er3+ inverse opal photonic crystals (IOPCs) were prepared using a polymethylmethacrylate (PMMA) template-assisted method, and the effects of modulations of the IOPC structure on UC emission properties of Er3+ were investigated systemically. As a result, the emission intensity of 2H11/2-4I15/2 in IOPC was found to be suppressed 37.4%, and the radiative lifetimes of 4S3/2-4I15/2 were prolonged 1.55 times. The effects of the doping concentration on the reciprocal of fluorescence lifetimes of 4S3/2-4I15/2 between the IOPC and the reference (REF) samples showed that the cross-energy transfer (CET) rate and the electronic transition rate were greatly inhibited, which could be due to the effect of the modulation of the effective index on the radiative transition rate and on the decrease of nonradiative transition rate caused by periodic thin-walled structure of IOPC. The power-dependent UC emission properties validated the supposition that the IOPC structure could be effectively suppressed the local thermal effect and thermal quenching. This research presents a further step in the exploration of the new kind of UCL materials with high luminous efficiency.

Angle-independent responsive organogel retroreflective structural color film for colorimetric sensing of humidity and organic vapors

The angle dependence of photonic crystals (PCs) dramatically limits their practical applications in the colorimetrical sensing of humidity and volatile organic compound (VOC) vapors. In addition, it is challenging for inverse opal PCs to colorimetrically distinguish between vapors with similar refractive indices. Different from the mechanism of PC-based sensors, here, we report an angle-independent polyacrylamide (PAAm) organogel structural color film based on the mechanisms of retroreflection, total internal reflection (TIR) and interference with a shape similar to a single-sided “egg waffle”. During the process of responding to humidity and VOC vapors, the color of the film remains angle-independent in the normal angle range of 0° to 45° under coaxial illumination and observation conditions. At the same time, the film can colorimetrically distinguish between vapors with similar refractive indices, such as methanol and ethanol, which is mainly due to the differences in their polarity and solubility parameters. The film shows good stability, reversibility and selectivity when exposed to vapors. A colorimetric sensor with a new response mechanism is proposed and has the potential to effectively distinguish between vapors with similar refractive indices. Furthermore, this responsive retroreflective structural color film (RRSCF) provides a universal strategy to develop targeted angle-independent structural color sensors by selecting optimized materials.

Fluorescence Sensing of Formaldehyde and Acetaldehyde Based on Responsive Inverse Opal Photonic Crystals: A Multiple-Application Detection Platform.

Formaldehyde (FA) and acetaldehyde (AcH) used as common chemicals in many fields are carcinogenic. The presently reported detection methods usually need expensive instruments, professional technicians, and time-consuming processes, and the detection sensitivity still needs further improvement. Herein, we report a highly effective fluorescence (FL) sensing film for FA and AcH based on naphthalimide derivative-infiltrated responsive SiO2 inverse opal photonic crystals (PCs), establishing a practically multiple-application detection platform for FA and AcH in air, aquatic products, and living cells. Nucleophilic addition products between the amine group of the naphthalimide derivative and aldehydes emit strong FL at ∼550 nm, realizing selective FL detection for FA and AcH. The emitted FL can be enhanced remarkably because of the slow photon effect of PCs, in which the FL wavelength is located at the stopband edge of PCs. A highly sensitive detection for FA and AcH with limits of detection of 10.6 and 7.3 nM, respectively, is achieved, increasing 3 orders of magnitude compared with that in the solution system. Additionally, the interconnected three-dimensional microporous inverse opal structure endows the sensor with a rapid response within 1 min. Furthermore, the as-prepared PC sensor can be reused by simple washing in an acidic aqueous solution. The sensing system can be used as a FL multi-detection platform for FA and AcH in air, aqueous solution, and living cells. This FL sensing approach based on small organic molecule-functionalized PCs is universally available to develop various sensors for target analytes by designing new functional organic compounds.

Nonintrusively Adjusting Structural Colors of Sealed Two-Dimensional Photonic Crystals: Immediate Transformation between Transparency and Intense Iridescence and Their Applications.

Responsive photonic crystals (PCs), which can adjust structural colors in response to external stimuli, show great potential applications in displays, sensors, wearable electronics, encryption, and anticounterfeiting. In contrast, conventional structure-intrusive adjustment manners that external stimuli directly interact with the ordered arrays may lead to structural damage or longer response time. Here, a noninvasive adjustment of the structural colors of two-dimensional (2D) PCs (2D-PCs) is explored based upon diffraction theory. Sealed 2D-PCs and 2D inverse opal photonic crystal (IOPC) flexible devices are prepared. They are highly transparent in air but immediately exhibit intense viewing angle-dependent structural colors after being dipped in water. The mechanism of transparent-iridescent immediate transformation is explained by Bragg's law. The design mechanism is examined by numerical simulation and spectral shifts in different external media. We demonstrate its applications in the fields of information encryption and anticounterfeiting by using the transparent-iridescent immediate transformation of sealed 2D-PC patterns and 2D IOPC free-standing films sealed on the product surface. Because of the strong contrast between transparency and intense iridescence, reversible and immediate transformation, and durability, sealed 2D-PCs and 2D IOPC flexible devices designed by the noninvasive adjustment strategy will lead to a variety of new applications in displays, sensors, wearable electronics, encryption, and anticounterfeiting.

Comparison of Sm3+ and Tb3+ dopant effects on the silica-based three-dimensional inverse opal photonic crystal coatings

Three-dimensional inverse opal photonic crystal (PC) materials have attracted a lot of attention nowadays due to their numerous innovative features. The structural color stands out with low toxic and environmentally friendly properties. In this study, it has been shown that eco-friendly and fadeless bright colors can be obtained at SiO2 inverse opal PC coatings and controlled by Sm3+ or Tb3+ rare-earth dopants. The obtained Sm3+ and Tb3+ peaks proved that dopants entered the amorphous silica structure according to the XPS analysis. All synthesized inverse opal coatings surround the entire 3D structure with the honeycomb morphology. In addition, it was observed that Tb3+ doping made regularly arranged honeycomb morphology more perfect. The pseudo-photonic bandgap (pPBG) was blue-shifted by increasing the Tb3+ dopant ratio, while red-shifted by increasing the Sm3+ dopant ratio. Therefore, Sm3+ doping made PC coating surfaces’ blue color dominate, while Tb3+ doping made purple color dominate. Furthermore, Sm3+ doping led to the obtained color more vivid and clear with narrowed pPBG.

Fabrication of SiO2/PEGDA Inverse Opal Photonic Crystal with Fluorescence Enhancement Effects.

The present paper reports the fabrication of inverse opal photonic crystals (IOPCs) by using SiO2 spherical particles with a diameter of 300 nm as an opal photonic crystal template and poly(ethylene glycol) diacrylate (PEGDA) as an inverse opal material. Characteristics and fluorescence properties of the fabricated IOPCs were investigated by using the Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD), reflection spectroscopy, and fluorescence microscopy. The results clearly showed that the IOPCs were formed comprising of air spheres with a diameter of ∼270 nm. The decrease in size led to a decrease in the average refractive indexes from 1.40 to 1.12, and a remarkable stopband blue shift for the IOPCs was thus achieved. In addition, the obtained results also showed a fluorescence enhancement over 7.7-fold for the Fluor® 488 dye infiltrated onto the IOPCs sample in comparison with onto the control sample.

Improved thermal stability of zirconia macroporous structures via homogeneous aluminum oxide doping and nanostructuring using atomic layer deposition

Dopants are regularly used in sol-gel and powder metallurgy routes, however, the controlled insertion of such is quite challenging, especially in the case of nanostructures. Here we investigate the use of atomic layer deposition (ALD) as a potential technique to precisely introduce aluminum oxide as dopant or second phase into zirconia 3D macroporous nanostructures. The results show that the introduction of high Al2O3 contents into the zirconia nanostructures successfully inhibited sintering when in comparison to undoped zirconia. Moreover, for the multi-nanolaminated and full-mix structures, the tetragonal phase was stabilized up to 1200 °C. Furthermore, the structures presented a photonic band gap even after heat treatment at 1200 °C for 2 h, enabling its application as inverse opal photonic crystals in high-temperature environments. The enhancement of thermal stability and high-temperature tetragonal phase stabilization is enabled jointly by the nanostructuring and homogeneous distribution of aluminum oxide provided by ALD super-cycles.