Systems Pharmacology Strategy for the Investigation of Action Mechanisms of Qin Herb Libanotis Buchtormensis (Fisch.) DC. in Bone Diseases.

INTRODUCTION: Qin medicines are medicinal plants growing in habitat around the peak of Qinling Mountain. Their unique curative effects on bone metabolic diseases and pain diseases have been favoured by the local people in clinical trials for thousands of years. Libanotis buchtormensis (Fisch.) DC. (LBD), is one of the popular Qin herbs, which has been widely used for the treatment of various diseases, such as osteoporosis, rheumatic, and cardiovascular diseases. However, due to the multiple compounds in LBD, the underlying molecular mechanisms of LBD remain unclear. OBJECTIVE: This study aimed to systemically investigate the underlying mechanisms of LBD against bone diseases. METHODS: In this study, a systems pharmacology platform included the potential active compound screening, target fishing, and network pharmacological analysis was employed to decipher the action mechanisms of LBD. RESULTS: As a result, 12 potential active compounds and 108 targets were obtained. Furthermore, compound-target network and target-pathway network analysis showed that multi-components interacted with multi-targets and multi-pathways, i.e., MARK signalling pathway, mTORC1 signalling pathway, etc., involved in the regulation of the immune system and circulatory system. These results suggested the mechanisms of the therapeutic effects of LBD on various diseases through most compounds targeted by multiple targets. CONCLUSION: In conclusion, we successfully predicted the LBD bioactive compounds and potential targets, implying that LBD could be applied as a novel therapeutic herb in osteoporosis, rheumatic, and cardiovascular diseases. This work provides insight into the therapeutic mechanisms of LBD for treating various diseases.

Pseudomorphic Synthesis of Monodisperse Afterglow Carbon Dot-Doped SiO2 Microparticles for Photonic Crystals.

Synthesizing monodisperse afterglow microparticles (MPs) is crucial for creating photonic crystal (PC) platforms with multiple optical states for optoelectronics. However, achieving high uniformity in both size and morphology is challenging for inorganic afterglow MPs using conventional methods. In this contribution, a novel approach for the synthesis of carbon dot (CD)-doped SiO2 MPs with tunable afterglow properties and size distributions is reported. These mechanism studies suggest that the pseudomorphic transformation of SiO2 MPs enables CD doping, providing a hydrogen bond-enriched environment for triplet state stabilization, which generates green afterglow while retaining the uniformity in size and morphology of the parent SiO2 MPs. Furthermore, the utility of CD-doped SiO2 MPs in the fabrication of rationally designed PC patterns is shown using a combined consecutive dip-coating and laser-assisted etching strategy. The pattern displays multiple optical responses under different lighting conditions, including angle-dependent structural colors and blue luminescence under daylight and upon 365-nm irradiation, respectively, as well as time-dependent green afterglow after ceasing UV excitation. The findings pave the way for further controlling the dynamics of spontaneous emissions by PCs to enable complicated optical states for advanced photonics.

Multicolor Electrochromic Display and Patterned Device Based on Hollow-SiO2-Supported WO3 Photonic Crystals.

Electrochromic photonic crystals (PCs) have been intensively studied in the field of display, sensors, and intelligent materials due to their tunable brilliant structural colors. The mostly studied electrochromic PCs are based on the tunable lattice parameter after electrifying; namely, the electrochromic process is caused by the structural change of PCs. Besides the lattice parameter, the refractive index is another key factor to determine the structural color of PCs. Here, a kind of hollow-SiO2-supported WO3 (H-SiO2/WO3) PCs is designed, where the refractive index of the WO3 portion is changeable under charging. Benefiting from the support effect and tunable thickness of H-SiO2, large-area PC samples with good surface morphology and bright multicolor output are prepared. The reflection peaks of these composite PCs can shift by 30-90 nm, and their corresponding colors changed obviously after the voltage was applied. After being pixelated by laser-marking, the H-SiO2/WO3 PCs can dynamically display different numeric and alphabetic patterns in an electric-driven writing and erasing process. Not only does this composite PC structure broaden the color change range of WO3-based materials but also avoids the structural change in the electrochromic process. This work provides more possibilities for electrochromic PCs in the field of color-changing pattern displays.

Low-Angle-Dependent Anticounterfeiting Label Decoded by Alcohol Tissue Wiping Based on a Multilayer Photonic Crystal Structure.

The application of photonic crystals (PCs) as anticounterfeiting materials has been widely investigated because of their tunable photonic stop band and corresponding changeable structural colors. In this work, we designed a composite PC structure including an information CdS PC layer at the bottom and a polymer-based layer composed of an inverse opal PC (IOPC) layer and a disordered porous layer on the top, which can be decoded by an alcohol tissue. The high refractive index of the bottom patterned CdS PC layer provides the structure with a vivid low-angle-dependent structural color in the decoded mode, which ensures the stability of the information conveyed by this label. When the incident angle changed from 5 to 45°, the structural color of the patterned CdS layer changed slightly. In the hidden mode, the low transmittance shields the structural color of the CdS layer. When the structure was wiped with the alcohol tissue, the transmittance of the upper IOPC layer could be increased quickly due to the similar refractive indexes of the used polymer and alcohol, and the pattern of the CdS layer was decoded. Thus, the designed composite PC can act as an anticounterfeiting label, in which the encrypted pattern can be decoded by alcohol tissue wiping and shows a vivid low-angle-dependent structural color. To enhance the anticounterfeiting ability of the designed structure, a double-sided label with different encryption patterns on both sides was designed. Based on the simple reversible encryption and decryption process as well as the color stability, the label shows great application potential in the daily anticounterfeiting field.

Upconversion Nanoparticle-Integrated Bilayer Inverse Opal Photonic Crystal Film for the Triple Anticounterfeiting.

Optical anticounterfeiting plays a vital role in information security because it can be recognized by the naked eye and is difficult to imitate. Herein, a hydrophilic modified upconversion nanoparticle (M-UCNP)-integrated bilayer inverse opal photonic crystal (IOPC) film was designed in which the luminescent M-UCNPs were deposited on the surface of the optimized bilayer structure with double photonic stop bands. The structure which can modulate light to produce structural colors can also enhance the upconversion luminescence (UCL) to improve the anticounterfeiting effect synergistically. On the one hand, the reflection colors from green to blue were observed in the specular angles on the front (540-layer) of the film. Meanwhile, the scattering colors under nonspecular angles from red to blue on the back (808-layer) appeared in the natural light. On the other hand, the bilayer structure in which the 808-layer functions as a "secondary excitation source" to improve the intensity of the excitation light on M-UCNPs and the 540-layer reflects the emission light of the M-UCNPs to enhance the UCL intensity endows the film with good night vision ability. Finally, the dual-mode structural colors and enhanced UCL of the patterned film work together to realize triple anticounterfeiting in banknotes.

Biomimetic Janus photonic soft actuator with structural color self-reporting.

Soft actuators with variable signal/color play an important role in the fields of targeted locomotion, artificial phototropism, drug screening, cargo transportation, and interactive sensing. The ability to achieve rapid response, large curvature, wide bending angle, and full-color display continues to be an unresolved challenge for artificial actuating materials. Inspired by the angle-dependent structural color of broad-tailed hummingbird and the Janus wettability of the lotus leaf, a Janus photonic soft actuator (JPSA) was fabricated by integrating an underwater super-oleophilic copper micro-nano array and oil-phobic inverse opal through a Laplace channel. The JPSA exhibits unidirectional permeability to underwater oil droplets. Attractively, with the combination of a swellable super-oleophilic surface and photonic crystals, JPSAs were endowed with oil-controlled reversible bending behavior with self-reporting angle-dependent color indication. We described for the first time the directional actuating mechanism induced by underwater oil unidirectional penetration and revealed the corresponding actuating kinetics and the inner-stress distribution/transfer by using structural color. As an extension of such theory, a rapid responsive JPSA with a wide bending angle and full-color self-reporting is further fabricated. This work provides an efficient strategy for oil directional transportation and separation in aqueous media and inspires the fabrication of a soft actuator/sensor with structural color self-reporting.

Structural Colored Fabrics with Brilliant Colors, Low Angle Dependence, and High Color Fastness Based on the Mie Scattering of Cu2O Spheres.

Compared with conventional textile coloring with dyes and pigments, structural colored fabrics have attracted broad attention due to the advantages of eco-friendliness, brilliant colors, and anti-fading properties. The most investigated structural color on fabrics is originated from a band gap of multilayered photonic crystals or amorphous photonic structures. However, limited by the nature of the color generation mechanism and a multilayered structure, it is challenging to achieve structural colored fabrics with brilliant noniridescent colors and high fastness. Here, we propose an alternative strategy for coloring a fabric based on the scattering of Cu2O single-crystal spheres. The disordered Cu2O thin layers (<0.6 µm) on the surface of fabrics were prepared by a spraying method, which can generate vivid noniridescent structural color due to the strong Mie scattering of Cu2O single-crystal spheres. Importantly, the great mechanical stability of the structural color was realized by firmly binding Cu2O spheres to the fabric using a commercial binder. The structural color can be tuned by changing the diameter of Cu2O spheres. Furthermore, complex patterns can be easily obtained by spray coating Cu2O spheres with different particle sizes using a mask. According to color fastness test standards, the dry rubbing, wet rubbing, and light fastness of the structural color on fabric can reach level 5, level 4, and level 6, respectively, which is sufficient to resist rubbing, photobleaching, washing, rinsing, kneading, stretching, and other external mechanical forces. This coloring method may carve a practical avenue in textile coloring and has potentials in other practical applications of structural color.

Artificial Chameleon Skin with Super-Sensitive Thermal and Mechanochromic Response.

Both the nonclose-packed structure and the large refractive index contrast of guanine nanocrystals and cytosols in iridophores play a vital role in the dynamic camouflage of chameleons, including the bright skin color and color tuning sensitivity to external stimulus. Here, the nonclose-packed photonic crystals consisting of ZnS nanospheres and polymers, which have similar refractive indices with guanine nanocrystals and cytosols, respectively, are constructed by a two-step filling strategy. ZnS@SiO2 nanospheres are self-assembled to build intermediate close-packed photonic crystals followed by filling polymers in their interstices. The nonclose-packed photonic crystal is successfully achieved when the silica portion is etched by HF solution and refilled by polymers. Excitingly, the stimulus response of the designed photonic crystal is as sensitive as the skin of chameleons due to the similar contrast of refractive indices and nonclose-packed structure. The reflection peak of the structure can blue-shift more than 200 nm as the temperature increases from 30 to 55 °C or under 20% compressional strain. This work not only builds the nonclose-packed photonic crystals by introducing a two-step filling strategy but also proves that high refractive contrast in photonic crystals is an effective strategy to achieve ultrasensitivity, which is highly desirable for various applications.

Lotus Seedpod Inspiration: Particle-Nested Double-Inverse Opal Films with Fast and Reversible Structural Color Switching for Information Security.

The integration of novel structures into colloidal crystals provides the possibility of constructing stimuli-responsive photonic materials. However, in most opal and inverse opal structures, replacing the interior air with an infiltrated liquid will cause partial refractive index matching, resulting in the reduction or even disappearance of the photonic band gap. Herein, inspired by the lotus seedpod, an innovative particle-nested double-inverse opal film with fast and reversible structural color switching (≈1 s) is first fabricated by introducing polystyrene (PS) spheres into an inverted opal backbone. Importantly, refractive index matching can be effectively avoided due to the existence of internal PS spheres, and optical switching from diffusive to photonic behavior is achieved by a liquid with low surface tension for the response. Furthermore, a reversible ethanol stimuli-response bilayer double-inverse opal film with multistate switching for information encryption is proposed by combining optical scattering and diffraction. The scattered light from the top layer caused by the randomly distributed and weakly scattering PS spheres within the pores makes the pattern at the bottom invisible. Simultaneously, the display and discoloration of the pattern can be realized instantaneously by ethanol response. Thus, this new preparation strategy exhibits great potential in the security fields.

Synthetic infrared nano-photosensitizers with hierarchical zoom-in target-delivery functionalities for precision photodynamic therapy.

Surgical assailment at the vulnerable subcellular organelles (e.g. mitochondria) by photodynamic therapy (PDT) is perceived as the most devastating approach to eradicate the tumors. Herein, we programmed a novel near-infrared (NIR) PDT construct illustrating appreciable hierarchical zoom-in targeting scenario, namely, primary cell-level targeting to carcinoma post systemic dosage and subcellular level targeting to mitochondria. Pertaining to tumor-targeting function, charge reversal chemistry selectively responsive to acidic tumoral microenvironments (pH 6.8) was implemented as the external corona of PDT constructs. This charge transformative exterior entitled minimal biointerfacial reactions in systemic retention but intimate affinities to cytomembranes selectively in tumoral microenvironments, thereby resulting in preferential uptake by tumors. Furthermore, the proposed PDT constructs were equipped with mitochondria targeting triphenylphosphonium (TPP) motif, which appeared to propel intriguing 88% colocalization with mitochondria. Therefore, overwhelming cytotoxic potencies were accomplished by our carefully engineered photodynamic constructs. Another noteworthy is the photodynamic constructs characterized to be excited at tissue-penetrating NIR (980 nm) based on energy transfer between their internal components of anti-Stoke upconversion nanoparticles (UCN, donor) and photodynamic chlorin e6 (Ce6, acceptor). Therefore, practical applications for photodynamic treatment of intractable solid carcinoma were greatly facilitated and complete tumor eradication was achieved by systemic administration of the ultimate multifunctional NIR photodynamic constructs.

Cephalopod-Inspired Chromotropic Ionic Skin with Rapid Visual Sensing Capabilities to Multiple Stimuli.

Biological skin systems can perceive various external stimuli through ion transduction. Especially, the skin of some advanced organisms such as cephalopods can further promptly change body color by manipulating photonic nanostructures. However, the current skin-inspired soft iontronics lack the rapid full-color switching ability to respond to multiple stimuli including tension, pressure, and temperature. Here, an intelligent chromotropic iontronics with these fascinating functions is developed by constructing a biomimetic ultrastructure with anisotropic electrostatic repulsion. This skin-like chromotropic iontronics can synchronously realize electrical response and optical visualization to mechanical strain and tactile sensation by adjusting the ultrastructure in cooperation with ionic mechanotransduction. Notably, it can perform instantaneous geometric changes to thermal stimuli via an anisotropic electrostatic repulsion interior. Such a capability allows bionic skin to transduce temperature or infrared light into ionic signals and color changes in real time. The design of anisotropic photonic nanostructures expands the intelligent application for soft iontronics at higher levels, providing a concise, multifunctional, interactive sensing platform that dynamically displays stimuli information on its body.

Pinoresinol diglucoside attenuates neuroinflammation, apoptosis and oxidative stress in a mice model with Alzheimer's disease.

For Alzheimer's disease (AD), there is still no effective treatment strategy. Pinoresinol diglucoside (PDG) is one of the major lignans isolated from Eucommia ulmoides. It is endowed with multiple pharmacological activities, including anti-inflammatory, antioxidant and anticancer activities. In this study, we investigated the potential neuroprotective functions of PDG in AD. Mice model with AD was established adopting stereotactic hippocampal injection of Aß1-42 (410 pmol/mouse), and 3 days later, mice were administrated with 5 and 10 mg/kg PDG by intragastric administration every day for 3 weeks. Morris water maze and Y-maze tests demonstrated that PDG treatment could markedly reverse Aß1-42-induced memory impairment in mice. It is found that PDG restrained the release of proinflammatory cytokines (tumor necrosis factor α and interleukin 1ß), reactive oxygen species and malondialdehyde, and promoted the activity of the antioxidant enzyme (superoxide dismutase and catalase) by quantitative real-time-PCR, colorimetric method and ELISA assay. Western blot assay results have shown that PDG could also upregulate the ratio of Bcl-2/Bax and downregulate cytochrome c and cleaved caspase-3 expressions, thereby inhibiting neuronal apoptosis. Furthermore, PDG also significantly reduced the expression of Toll-like receptor 4 (TLR4) and the activation of nuclear factor-κB (NF-κB) p65, and promoted nuclear factor E2-related factor 2 (Nrf2) and heme oxygenase 1 (HO-1) expressions. In conclusion, PDG can attenuate neuroinflammation, neuronal apoptosis and oxidative stress through the TLR4/NF-κB and Nrf2/HO-1 pathways, and ameliorate memory dysfunction induced by Aß1-42 in mice.

Afterglow Carbon Dots: From Fundamentals to Applications.

The ability of carbon dots (CDs) to emit afterglow emission in addition to fluorescence in response to UV-to-visible excitation allows them to be a new class of luminescent materials. When compared with traditional organic or inorganic afterglow materials, CDs have a set of advantages, including small size, ease of synthesis, and absence of highly toxic metal ions. In addition, high dependence of their afterglow color output on temperature, excitation wavelength, and aggregation degrees adds remarkable flexibility in the creation of multimode luminescence of CDs without the need for changing their intrinsic attributes. These characteristics make CDs particularly attractive in the fields of sensing, anticounterfeiting, and data encryption. In this review, we first describe the general attributes of afterglow CDs and their fundamental afterglow mechanism. We then highlight recent strategic advances in the generation or activation of the afterglow luminescence of CDs. Considerable emphasis is placed on the summarization of their emergent afterglow properties in response to external stimulation. We further highlight the emerging applications of afterglow CDs on the basis of their unique optical features and present the key challenges needed to be addressed before the realization of their full practical utility.

Robust, Portable, and Specific Water-Response Silk Film with Noniridescent Pattern Encryption for Information Security.

In modern days, information is a key resource for accelerating the development of society, economy, and culture. Thus, information security has always been a high priority for any country, business, and department. Herein, a simple and effective strategy for preparing an independent optical device for information security is proposed by using silk fibroin materials with a quasiamorphous inverse structure. Given the reversible hydrogen bonds between silk fibroin materials and water molecules, a multicolor high-resolution pattern with a variable color can be obtained by using a simple spray coating method. Furthermore, a reversible water stimulus-response silk film with a laminated structure that consists of hidden and patterned layers and carries quick response (QR) code information is prepared. This device effectively hides (encryption) the QR code pattern in a normal environment and quickly displays the information (decryption) in water. Simultaneously, the silk film shows good mechanical strength, excellent biocompatibility, long-term structural stability, and a unique response mechanism, which make it a suitable carrier of optical information. Thus, this new preparation strategy of an optical device has a potential application value and is an important reference in the fields of information security and functional materials.

Real-Time Monitoring of Heavy Metals in Healthcare via Twistable and Washable Smartsensors.

The wearable and integrated sensing platform is a promising choice for developing real-time analytic electronics with clear advantages but still poses challenges, such as the realization of high precision, low limit of detection (LOD), moderate mechanical capacity, integration, and miniaturization. In this work, a simple printed wearable smartsensor has been fabricated with the aid of electrochemical plating methods with bismuth (Bi) films. The excellent sensing behaviors, including linear relationship, selectivity, stability, repeatability, and the LOD at ppb levels, have been obtained by this smartsensor. Additionally, the highly flexible textile-based sensor exhibits potential application on the substrates of daily cloth, sports T-shirt, and sports wristbands, and it maintains good stability under repeated deformations of washing and twisting. Importantly, integrated with printed circuit board, single chip micyoco, and Bluetooth modules, a smartsensing platform is successfully acquired for real-time detection of heavy metals (e.g., Zn, Cd, Pb, etc.). Finally, actual samples of human sweat, seawater, cosmetics, and drinking water have been remotely successfully demonstrated for detection by this smartsensor, enabling a great promise for fast on-site screening of samples in practical application.

Reflection and transmission two-way structural colors.

Management of reflection and transmission two-way structural colors is significant in color displays, projections, and anticounterfeiting. Here, inspired by the Lycurgus Cup, we fabricated photonic crystals with opal and inverse opal structures with controlled thickness, which show reflection and transmission two-way structural colors. In order to balance the reflection and transmission intensities, we first studied the effect of the order layer thickness on the reflection and transmission spectra and found that a thickness of about 5 µm can help the structural colors achieve high saturation in both directions. The photonic crystal film built with 295 nm SiO2 spheres shows bright red and green structural colors in the reflection and transmission directions, respectively. These two-way colors can be projected onto substrates, similar to a transflective color filter. The color displays can be tuned by adjusting the angle between the incident light and the sample. Furthermore, we also patterned the photonic crystal film with two-way structural colors, which shows clear patterns and rich colors in both directions. The photonic crystals assembled on a small wine glass display two-way structural colors similar to those of the Lycurgus Cup. More importantly, a flexible inverse opal photonic crystal film with two-way structural colors was also fabricated, which can be applied in multimode anticounterfeiting. This work will greatly expand the application field of photonic crystals in double sided displays, transflective color filters and anticounterfeiting.

Rotational Periodicity Display of the Tunable Wettability Pattern in a Photoswitch Based on a Response Bilayer Photonic Crystal.

Although the forward diffraction of the three-dimensional (3D) photonic crystal is easily applied to a photoswitch, backward diffraction rainbows are rarely reported. The first rotational photoswitch based on a bilayer 3D photonic crystal with backward diffractions similar to those of two-dimensional photonic crystals was fabricated by vertically combining different thicknesses of nanoparticle templates. When rotating the bilayer photonic crystal, the opening or closing of the rotational photoswitch shows periodic reproducibility values of 30 and 60°. Different periods are regulated by the thickness and scattering effect of the top layer. Moreover, invisible patterns can be encoded and erased by changing the wettability via pH. Because of the decreasing of the refractive index differentials, it will be revealed rapidly when immersed in water. The revealed pattern can be periodically turned on and off by rotating the bilayer photonic crystal. It has great application prospects in optical prism, warning board, anti-counterfeiting, steganography, watermarking, and complex information coding.

Nanosphere-Aggregation-Induced Reflection and Its Application in Large-Area and High-Precision Panchromatic Inkjet Printing.

Artificial structural colors have attracted more and more attention due to their high photostability, low toxicity, and brilliant colors. Inkjet printing of photonic crystals or amorphous photonic structures can realize large-scale structural color patterns, while plasma printing of metals can achieve high-precision color images. However, still no method is available to fabricate structural color patterns on both a large scale and with high precision. Here, nanosphere-aggregation-induced reflection (NAIR) is first theoretically and experimentally demonstrated and vivid full-spectrum structural color can be generated based on NAIR. Dramatically different from photonic crystals, the accumulation of only a few monodisperse dielectric spheres with an appropriate refractive index and diameter can produce bright structural colors, which makes high resolution possible. By introducing commercial inkjet printers, this aggregate structure can be constructed at high speed in a large scale. Importantly, the color mixing is easily performed by simultaneously applying spheres with different sizes, which allow us to sophisticatedly control the generated color. The demonstrated NAIR printing paves the way toward a full-spectrum, large-scale, and high-precision structural color, offering great potential for daily commercial utilization.

Asymmetric structural colors based on monodisperse single-crystal Cu2O spheres.

Structural colors have attracted broad attention owing to their anti-photobleaching capability and brilliant metallic color. In particular, the asymmetric structural colors generated by a simple material will have great practical significance in the fields of biomimetic materials, double-side display and anti-counterfeiting. The asymmetric optical effects were usually achieved by the plasmonic effects of Ag or Au nanocrystals. Here, for the first time, we realized the asymmetric structural colors based on the asymmetric scattering of Cu2O single-crystal spheres. By spray-coating Cu2O spheres on a glass slide, different structural colors were viewed from the Cu2O film side and the glass slide side. The FDTD simulations confirmed that the asymmetric colors were ascribed to the inhomogeneous distribution of the electric field intensity. The film built by 200 nm Cu2O spheres on a glass slide shows green and cyan structural colors from the front and back sides, respectively. The colors on both sides of the Cu2O films were proved to be tuned by changing the diameters of the Cu2O single-crystal spheres. Different substrates were used to examine the influence of substrates on the asymmetric colors. Finally, inspired by different brilliant colors from the front and back of natural creatures, the patterns of butterfly and petals were fabricated by Cu2O spheres. Impressively, similar to nature, the patterns show completely different colors viewed from the front and back sides. The asymmetric structural colors of Cu2O single-crystal spheres will open up new avenues to realize multi-mode color output and pave their applications in display, biomimetic materials and anti-counterfeiting materials.

Bilayer Heterostructure Photonic Crystal Composed of Hollow Silica and Silica Sphere Arrays for Information Encryption.

Utilizing photonic crystals to fabricate information encryption materials has attracted widespread interest due to their tunable optical properties and responsiveness to external stimuli. In most of the previously reported systems, the information is hidden at a specific angle and the angle-dependent invisibility is a limitation. Meanwhile, poor structural stability is still a key issue that needs to be solved for potential applications. In this paper, a bilayer heterostructure photonic crystal containing ordered hollow silica inverse opal arrays, amorphous silica opal arrays, and poly(vinyl alcohol) (adhesive) is successfully constructed. It makes the information highly invisible at any angle and also achieves information encryption. With this strategy, the information can be hidden by the noniridescent structural color derived from the strong scattering effect of light from the top layer of amorphous silica sphere arrays. After wiping with ethanol or a refractive-index-matching solvent, the scattering effect vanishes and the amorphous silica sphere arrays become transparent. The reflected light of the bottom layer caused by the increasing refractive index contrast between the inside and outside of the hollow silica spheres could rapidly reveal the hidden information. The bilayer photonic crystal exhibits robust structural stability, and the hiding/revealing process is completely reversible, which shows great potential applications in steganography and information encryption.