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Though the application of photochromic agents onto textile-based surfaces with the help of printing process or padding technique, their usability have been limited due to their low substantivity. In this study, 12 wt% polymer solutions were prepared with use of three different polyvinyl alcohol (PVA) pellets having identical hydrolysis degree but different molecular weights. Electrospinning was performed after addition of 4 wt% photochromic slurry (PCS) into these polymer solutions. Densities of photochromic slurry-loaded polymer solutions were measured and UV-Vis spectrophotometric analysis was performed for each polymer solution. Nanocomposite mats electrospun from these photochromic slurryloaded polymer solutions were characterized by FTIR, FESEM and UV-Vis spectrophotometry analysis in order to observe morphological, structural and photochromic properties. Thickness of these nanocomposite mats were also measured. Increase in polymer molecular weight lead to increase on average fiber diameter and mat thickness but fabrication of large pore-sized mat with high pore size variation. Even the finest nanofiber handling, surface imperfections were observed in nanocomposite mats electrospun from PVA 5-88 having the lowest molecular weight among the studied PVA polymers. PVA 14-88 polymer having moderate molecular weight exhibited optimum characteristic properties due to its appropriate polymer solution density, producibility of nano-scale electrospun fibers, possibility to make a consistent relationship among pore size, nanofiber diameter and photochromic efficiency. When UV-Vis spectrums of PCS loadedpolymer solutions and electrospun mats were compared, electrospinning technique caused to a differentiation in absorbence value, especially in PVA 17-88. [ABSTRACT FROM AUTHOR]

Diarylethenes (DAEs) are typical photochemically reversible type (P‐type) photochromic materials with excellent thermal stability and high fatigue resistance and are widely exploited as photo‐switches for various applications in molecular devices, data storage, photoresponsive materials, and bioimaging, etc. In recent years, there is an increasing number of reports using heat, acid, electrochemistry, etc. to drive the isomerization reaction of DAEs. The response to two or more different stimuli enables multi‐functionality within a single DAE molecule, which would facilitate complex logic‐gate operations, multimode data storage, and increased information density. Herein, the recent advances in DAE systems utilizing stimuli "beyond photo" to trigger the isomerization processes from three perspectives: acidochromism, thermochromism, and electrochromism are reviewed. Emphasis is placed on the molecule design strategies and the underlying mechanisms for cyclization and cycloreversion processes addressed by the alternative stimulus. Then the noticeable applications made in multi‐stimuli responsive DAE systems are summarized. Additionally, the challenges and opportunities of DAE switches driven by stimuli "beyond photo" in the future are also discussed. [ABSTRACT FROM AUTHOR]

Semiconductor oxides are widely used in the field of optical materials due to their broad spectral response, tunable structure, low cost, high chemical and thermal stability, among other advantages. The design and fabrication of photochromic materials in semiconductor oxides have shown tremendous potential in various fields such as optoelectronic displays, optical storage, and light-stimulated responses. In this work, we have designed and fabricated a novel inorganic photochromic material by doping Sm3+ ions into the semiconductor oxide CaBiNb2O9 (CBN). The introduction of Sm3+ ions induces the formation of oxygen vacancies and cationic vacancies in CBN, greatly enhancing the photochromic effect of the matrix. CaBiNb2O9: Sm3+ (CBN: Sm) can achieve reversible photochromic response through 254 nm light irradiation and 350 ℃ thermal stimulation, and exhibit excellent stability and fatigue resistance. The photochromic process and performance of the CBN: Sm materials were characterized, and the potential mechanisms were analyzed and discussed. The conducted research and insights will provide support for other researchers in the design and fabrication of photochromic materials based on semiconductor oxides. [ABSTRACT FROM AUTHOR]

Precise modulation of photoluminescence (PL) of nanomaterials by external control is of great interest in such diverse areas as photocatalysis, memory and sensing. Recent studies have combined colloidal quantum dots (QDs) with photochromic molecules to construct optically switchable PL systems. However, it still remains challenging to switch the PL on and off in the near-infrared (NIR) region with multi-stimuli such as light and heat. Here, we present light and heat triggered modulation of the NIR PL of PbS QDs using adjacent spiropyran derivatives. The NIR PL of PbS was reversibly switched on and off through the isomerization process of spiropyran molecules that can be triggered by either light irradiation or heating. The PL intensity of the off state is low enough to yield an on/off ratio as high as 54. Transient absorption measurements revealed ultrafast photoinduced hole transfer from PbS to spiropyran, the rate and efficiency of which depend critically on the driving force that can be deeply modulated through spiropyran isomerization. This study not only establishes a novel multi-stimuli switchable PL system in the NIR, but also provides fundamental guidelines for the design for such systems for a variety of emerging applications. [ABSTRACT FROM AUTHOR]

Photochromic materials are of great interest because they enable the fabrication of photo-activated switches. In this study, an experiment is proposed in which two chromene-based photochromic layers were inserted into the arms of a Mach–Zehnder interferometer. The chromene was studied from the perspective of optical absorption to determine the wavelength-dependent complex refractive index. Impinging ultraviolet light on one of the chromene layers induces a transition from the closed to the open form of the chromene, resulting in different phase shifts in the two arms of the interferometer. This results in a change in the probability of detecting a photon by the two detectors after the second mirror of the Mach–Zehnder interferometer. The experiment may be of interest to researchers working in the fields of quantum information and quantum communications. [ABSTRACT FROM AUTHOR]

Information storage and anti-counterfeiting are two very important applications of photochromic materials. Photochromic materials with both information storage and anti-counterfeiting should meet the requirements including fast coloration, good stability and reversibility, low storage cost, and practical application value. Herein, a novel viologen-based coordination polymer, Cd[(pbpy)0.5(HBTC)Cl]⋅2H2O (1) (pbpy = 1,1'-[1,4-phenylenebis-(methylene)]bis(4,4'-bipyridinium); HBTC2- = 1,3,5-benzenetricarboxylic acid), has been constructed. Compound 1 not only exhibits selective amine sensing properties, but also shows excellent photochromic properties, and the anti-counterfeiting of a two-dimensional code can be also realized through the color-changing behavior. Meanwhile, photochromic glass films of compound 1 were prepared, and compared to traditional optical information storage technology, these photochromic glass films have better water resistance and stability, improving their practical application stability. This work has further enriched the application of photochromic materials in the field of sensing, anti-counterfeiting and information storage. [ABSTRACT FROM AUTHOR]

Fiber‐based photochromic wearables have attracted growing attention in sustainable photo‐patterning information displays, information security encryption, and optical data recording/storage. Molybdenum trioxide (MoO3) is one of the key photochromic materials that possesses good photochromic performance, nevertheless, it faces considerable challenges in preparing photochromic textiles with stable, scalable, and long color‐retention properties. In this work, a new kind of fiber‐based photochromic wearables is designed and developed by combining cotton fabric with a MoO3‐based self‐adhesive polymer network and long chain silyl group. The prepared photochromic wearable has exhibited excellent fatigue resistance and favorable reversibility (> 40 cycles), rapid light response (reach color saturation with a UV dose of 60 kJ m−2), outstanding color retention capability (> 90 days), and desirable biocompatibility (cell viability > 100%). In addition, the prepared photochromic textiles could maintain a fast light response and excellent color retention even after experiencing repeated washing (20 cycles). Moreover, the photo‐patterning photochromic wearables are verified by resisting the deterioration of acid solution, alkali solution, and sweat (pH 2.0–9.0) as well as keeping clear patterns under sunlight irradiation. As a demonstration of the application, fiber‐based photochromic wearables are made and employed for the sustainable applications of rewritable photo‐patterning and information security encryption. [ABSTRACT FROM AUTHOR]

Viologen-based photochromic materials with photochromicity and photoluminescence have great advantages in anti-counterfeiting applications. Two novel viologen-based multifunctional Ln-MOFs Eu2Cl(m-bpybdc)L2(NO3)2·(H2O)5 (1) and Tb2Cl(m-bpybdc)L2(NO3)2·(H2O)6 (2) (m-bpybdc = 1,1′-bis(3-carboxyphenyl)-4,4′-bipyridinium and H2L = isophthalic acid) with three-dimensional structures were synthesized solvothermally. Both compounds exhibited reversible discoloration in response to external light and electrical stimulation. Notably, compound 1 presented strong fluorescence under ultraviolet light, showing the characteristic red emission of Eu3+. We further explored the application of these compounds in the field of anti-counterfeiting. These results provide useful data on the structure, luminescence, and light response of viologen-based lanthanide coordination polymers for their effective application. [ABSTRACT FROM AUTHOR]

In this paper, the structural, electronic, phonon, and optical properties of lanthanum (La)‐doped yttrium hydrogen selenide (YHSe), along with the effects of pressure variations on its optical properties, are investigated using the density functional theory method. Both the La‐doped and YHSe systems are dynamically stable, as indicated by phonon calculations showing no imaginary frequencies in the Brillouin zone (BZ). The influence of pressure on optical properties is examined, revealing that increased pressure enhances these properties, particularly by improving the absorption coefficient in the ultraviolet (UV) range. Moreover, the bandgap energy of both La‐doped YHSe and YHSe compounds is explored. Increasing La concentration reduces the bandgap and enhances the density of states (DOS) at Fermi energy, inducing metallic characteristics in YHSe. Furthermore, the optical properties are examined at various La concentrations, most of which exhibit a nonlinear relationship as the La concentration increases. Doping under extreme conditions significantly enhances the optical properties of La‐doped YHSe, particularly in the UV‐light wavelength range. Specifically, the absorption coefficient reaches its maximum value in the energy range of 6.678 −13.023 eV within the UV region for all concentrations, indicating strong absorption in this range. This suggests the material's effectiveness in absorbing electromagnetic radiation, particularly in the UV range, making it a promising candidate for photochromic applications. A thorough exploration of the optical properties under doping reveals prominent peaks, particularly in response to the UV spectrum, with a slight shift toward higher energies beyond the UV range. This suggests that the material under study holds promise as a candidate for sustained photochromic performance over time. [ABSTRACT FROM AUTHOR]

Poly(vinyl alcohol) (PVA)–phosphotungstic acid (PTA) nanocomposite films were prepared from aqueous solutions with added ethylene glycol (EG), which is a plasticizer for PVA and contains OH groups, capable of being electron donors in the photoreduction of PTA. Spectroscopic studies have shown that the addition of EG significantly enhances the photochromic properties of the resultant nanocomposites due to photoinduced electron transfer from the organic matrix of the nanocomposite to PTA molecules. [ABSTRACT FROM AUTHOR]

The rapid development of 3D printing has achieved considerable progress in architecture innovation, optical advancements, energy systems, dental care, pharmaceutical delivery, and personalized medical treatments. Nevertheless, the current technology of 3D printing is still limited to a single function. In recent years, the combination of photoresponsive materials and additive manufacturing has become a booming area for achieving intelligent photoresponsive 3D structures and stimulus‐responsive devices. By incorporating photoresponsive materials, 3D‐printed structures can change their shapes or colors under external stimuli. It is expected that the connection of photoresponsive materials and smart 3D printing will contribute to the development of adaptive camouflage, data retention, and molecular robotics. In this review, we summarize and discuss the current development of photoresponsive materials used in 3D printing, with an emphasis on photochromic materials, photodeformable materials, and photothermal materials. Additionally, the differences in the applications of these materials in 3D printing are compared. Finally, the current challenges and perspectives in the development of photoresponsive materials for additive manufacturing are also discussed. [ABSTRACT FROM AUTHOR]

Synthetic molecular photoswitches have taken center stage as high‐precision tools to introduce light‐responsiveness at the smallest scales. Today they are found in all areas of applied chemistry, covering materials research, chemical biology, catalysis, or nanotechnology. For a next step of applicability truly orthogonal photoswitching is highly desirable but to date such independent addressability of different photoswitches remains highly challenging. Herein we present the first example of all‐visible, all‐light responsive, and path‐ independent orthogonal photoswitching. By combining two recently developed indigoid photoswitches ‐ peri‐anthracenethioindigo and a rhodanine‐based chromophore ‐ a four‐state system is established and each state can be accessed in high yields completely independently and also with visible light irradiation only. The four states give rise to four different colors, which can be transferred to a solid polymer matrix to yield a versatile multi‐state photochromic material. Further, combination with a fluorescent dye as a third component is possible, demonstrating the applicability of this orthogonal photoswitching system in all‐photonic molecular logic behavior and information processing. [ABSTRACT FROM AUTHOR]

The explosive growth of information and its widespread availability underscores the need for robust encryption and anticounterfeiting measures. In this study, CdS quantum dots are engineered (QDs) to manifest multiple visual responses to a single trigger through strategic ligand design. The surface engineering method allows QDs to transition from yellow to black upon photoexcitation‐induced electron transfer from Cd(II) to Cd(0). Surface ligands desorption under hole injection, leading to an increase in QDs size and resulting in a redshift in photoluminescence. This photoexcitation‐induced redox reaction reveals unprecedented photochromism and photoluminescence phenomena, establishing a foundation for advanced information protection measures. Utilizing these QDs, excellent writing performance under UV irradiation is achieved in solid‐state substrates, while a dual‐mode encryption system is realized in gel matrices, opening up new avenues for information encryption as well as cumulative and interactive information protection. Furthermore, the redox reaction of CdS QDs is employed as ink for 3D printing, enabling for the creation of digitally programmable materials with distinct temporally evolving appearances by controlling the oxygen content in the ink to regulate the rate of photochromism. This advancement also sheds light on the progress in 3D printing technology. [ABSTRACT FROM AUTHOR]

The security monitoring of valuables is a crucial concern to ensure the stable development of human social business activities, scientific research, production, and daily life. The implementation of security precautions has traditionally involved the mere placement of items in safes. However, the formidable task of ascertaining whether valuables have been compromised during storage remains a significant challenge. Photochromic materials are important intelligent substances that can be employed as a potential candidates for security monitoring. However, previous studies have predominantly focused on achieving prominent photochromism by utilizing specific light sources such as ultraviolet, laser, and X‐ray radiation. In light of these existing challenges, a design strategy engaging high entropy is proposed to improve the photochromic performance. By selecting a diverse range of volatile metal elements, the A‐site high entropy is realized within the ABO3 perovskite structure, enabling the construction of various defects. This results in the successful realization of the material's sensitive response to sunlight, thereby validating the feasibility of the photochromism boosted by a high entropy strategy. The developed photochromic materials for intrusion indication demonstrate the capability to operate autonomously, making it a crucial component in high‐level security monitoring systems and presenting a novel approach toward enhancing security protection in traditional domains. [ABSTRACT FROM AUTHOR]

The combination of a microcavity and a microsphere has been proposed in this work to manipulate light in terms of emission wavelength and propagation direction. A microcavity with a layer of molecular photoswitch between two one-dimensional photonic crystals of polyvinyl carbazole and cellulose acetate has been designed. To tune the microcavity, the molecular photoswitch has been excited taking into account its cyclization upon irradiation at 313 nm and its cycloreversion at 450 nm. In this way, the emission peak of the microcavity switches from 508.5 nm to 525 nm. A polystyrene microsphere with a radius of 1 μ m is placed near the microcavity. With the detector at an angle of 8°, the emission at 525 nm is 1.73 times higher with respect to the emission at 508.5 nm, while at 10.8°, the emission at 508.5 nm is 1.45 times higher with respect to the emission at 525 nm. The value of these findings is that they offer the experimentalists a ready means to compare the optical data of these types of composites with theory. [ABSTRACT FROM AUTHOR]

2H-Naphthopyrans have become a crucial class of photochromic materials owing to their excellent sensitivity to sunlight and robust fatigue resistance. However, such compounds often display a relatively slow decoloration speed, which seriously limits their practical applications. How to tune the decoloration speed within about 10 seconds while maintaining good coloring ability is significant but challenging. In this work, two novel indeno-fused 2H-naphthopyrans (NP-a and NP-b) with a steric spirocycle have been synthesized, and their photochromic properties have been investigated. The results show that the spirocyclic groups can accelerate the decoloration speed with a half-life (t1/2) of 16 seconds for NP-a and 11 seconds for NP-b, respectively. In addition, both NP-a and NP-b exhibit higher colorability in the photostationary state compared to the parent compound 2,2-bis(4-methoxyphenyl)-2H-naphtho[1,2-b]pyran (NP). The solution of NP-a in chloroform also exhibits fluorescent properties with excellent fatigue resistance. [ABSTRACT FROM AUTHOR]

Photochromic materials are widely used in optical data storage, data encryption, and anti‐counterfeiting because of their ability to be written, erased, and read repeatedly. However, conventional information encryption and storage capabilities based on a "matrix" pattern in a 2D plane are limited to fewer storage dimensions, making information less secure. Here, a new concept of expanding the storage dimensions is presented by manipulating the rotation angle in 2D photochromic encoding disks based on the principle of the absolute encoder. For this purpose, a novel photochromic material, NaNbO3:xEu3+ is developed, with highly efficient red emission, a large luminescence switching contrast, and antithermal quenching behavior. The designed photochromic rotary encoder made with the NaNbO3‐based material exhibits higher‐level data encryption than that of conventional encoders and unlimited storage capability. This study presents exciting opportunities for information storage and encryption using luminescent photochromic materials. [ABSTRACT FROM AUTHOR]

The recyclable paper based on photochromic materials not only reduces the pollution in the paper manufacture process, but also reduces the pollution caused by the use of ink, which receives wide attention. In this paper, a series of phosphomolybdic acid–phosphotungstic acid/ZnO/polyvinylpyrrolidone (PMoA-PWA/ZnO/PVP) hybrid films, which had different ratio of PMoA/PWA, was prepared by the ultrasonic composite method. The results indicated that the hybrid film prepared when the ratio of PMoA to PWA was 3 had the best photochromic performance. In this system, ZnO was the photosensitizer, while PMoA/PWA was the chromophore. The photochromic mechanism of the PMoA-PWA/ZnO/PVP hybrid film was based on the photogenerated electron transfer mechanism. ZnO generated photoelectron under the excitation of visible light, then PMoA and PWA obtained the photoelectron and produced photoreduction reaction to generate heteropolyblue. The visible light photochromic paper was prepared by loaded PMoA-PWA/ZnO/PVP hybrid film (A3) on A4 paper. Application tests showed that the prepared paper had extremely stable, excellent and reversible visible light photochromic properties, whether it was printing patterns or words, and could replace ordinary paper to realize the reuse of paper. [ABSTRACT FROM AUTHOR]

The purpose of UV sensors is to detect ultraviolet radiation, which is crucial for various applications, such as skin protection, environmental monitoring, and industrial processes where UV exposure poses risks. These sensors provide real‐time data to ensure safety and optimize performance in relevant fields. In this context, the aim of this study was to develop easy‐to‐use UV sensors using photochromic nanofibrous materials. Photochromic nanofibers were obtained by electrospinning thermoplastic polyurethane and a spirooxazine dye. Two solvent systems (only dimethylformamide and a dimethylformamide:dichloromethane mixture) and three dye concentrations (0.5%, 2%, and 5%) were used to produce the nanofibers. Uniform and bead‐free nanofibers were obtained using a dimethylformamide:dichloromethane solvent system. The fatigue resistance of the photochromic nanofibers was tested, revealing a maximum color loss of 14% after 20 on‐off UV cycles. Nanofibers produced with a dimethylformamide:dichloromethane solvent system and a 0.5% dye concentration were chosen for UV sensor design due to their high total color difference. These photochromic nanofibers served as UV indicators, and a grayscale‐ adapted scale was used for evaluation. A UV sensor prototype capable of accurately determining UV exposure levels was successfully developed using photochromic nanofibers. This spectrally selective UV sensor can offer remarkable potential in managing the impact of UVR in our day‐to‐ day life. Highlights: Bead‐free, uniform nanofibers were obtained using a DMF:DCM solvent system.The nanofibers returned to their original colorless state in 5 min.The photochromic nanofibers showed high fatigue resistance.The nanofiber color indicated the UV intensity by comparing via adapted grayscale. [ABSTRACT FROM AUTHOR]

Photochromic glass shows great promise for 3D optical information encryption and storage applications. The formation of Ag nanoclusters by light irradiation has been a significant development in the field of photochromic glass research. However, extending this approach to other metal nanoclusters remains a challenge. In this study, we present a pioneering method for crafting photochromic glass with reliably adjustable dual‐mode luminescence in both the NIR and visible spectra. This was achieved by leveraging bimetallic clusters of bismuth, resulting in a distinct and novel photochromic glass. When rare‐earth‐doped, bismuth‐based glass is irradiated with a 473 nm laser, and it undergoes a color transformation from yellow to red, accompanied by visible and broad NIR luminescence. This phenomenon is attributed to the formation of laser‐induced (Bi+, Bi0) nanoclusters. We achieved reversible manipulation of the NIR luminescence of these nanoclusters and visible rare‐earth luminescence by alternating exposure to a 473 nm laser and thermal stimulation. Information patterns can be inscribed and erased on a glass surface or in 3D space, and the readout is enabled by modulating visible and NIR luminescence. This study introduces a pioneering strategy for designing photochromic glasses with extensive NIR luminescence and significant potential for applications in high‐capacity information encryption, optical data storage, optical communication, and NIR imaging. The exploration of bimetallic cluster formation in Bi represents a vital contribution to the advancement of multifunctional glass systems with augmented optical functionalities and versatile applications. [ABSTRACT FROM AUTHOR]

Luminescent materials responding to mechanical stimulation can visualize the strain and mechanical damage applied to objects. Mechanofluorochromism is a well‐known phenomenon induced by the mechanical force on fluorescent crystalline materials. However, simple application of the mechanofluorochromism is unsuitable for temporally and spatially detecting stress in detail because the fluorescent state is kept for rather long period. Here, the dynamic stress‐sensing luminescent solid material of a photochromic diarylethene with a fluorescent moiety is reported. Under the stress applied to the crystalline state, this material emitted cyan‐colored transient fluorescence that is rapidly diminished within a few second. This dynamic fluorescence phenomenon is well controlled by the combination of light irradiation and other external stimuli (organic solvent vapor and/or heat). In addition, the luminescence period is regulated by the excitation wavelength and magnitude of applied force. By utilizing these responses, the rewritable dynamic information encryption is successfully demonstrated. This material with transient fluorescence overcomes the persistence of fluorescence color of mechanochromism and present results provide a new principle for multifunctional light‐emitting materials responding to mechanical stimulation. [ABSTRACT FROM AUTHOR]

1, 4, 5, 8‐naphthalene diimide (NDI)‐based MOFs, due to their tunable structures and properties, have shown promising applications in photochromism, photocatalysis, electrocatalysis, photothermal therapy, etc. Herein, using an L‐alanine modified NDI ligand, i.e. N, N′‐bis(L‐alanine)naphthalenediimide (AlaNDI), a novel Cd‐NDI Cd (AlaNDI)(H2O)]·DMF·H2O (complex 1) was constructed under solvothermal conditions, which has an obvious different structure with the previously reported ones. Structural analysis shows that the packing structure of complex 1 consists of two adjacent Cd atoms sharing two AlaNDI ligands, forming a dimetallic building block [Cd2O8]. Each building block connects a total of four AlaNDI ligands, where two Cd atoms are bridged by two ligands. The building blocks are interconnected by ligands to form a two‐dimensional layered structure. Based on the features of the NDI skeleton, it was found that complex 1 possesses multiple stimulus responses involving sensitivity to light: a reversible photochromism property and good photocatalytic degradation activity against various dyes, especially against cationic dyes crystal violet (CV), methyl violet (MV), and Janus green B (JGB). In addition, the stimulus‐response mechanism was investigated by control experiments. It is revealed that the photocatalytic active species may be related to h+ and •OH. [ABSTRACT FROM AUTHOR]

Photochromic textiles have a wide range of applications in the field of fashion and smart textiles due to the qualities of rapid light responsiveness and reversibility of reaction. The principle and classification of photochromic materials are summarized. We discussed the latest research progress of photochromic textile preparation technology including direct grafting, dyeing and printing, spinning, layer-by-layer self-assembly, and microencapsulation, and summarized the advantages and disadvantages of each method. Direct grafting method can precisely control the number of materials, but some methods need professional technology and equipment. Dyeing and printing method is simple and economical, suitable for mass production, but the dyes are easy to fade and may pollute the environment. Spinning method spins photochromic substances into the fibers, but the preparation process is complicated. Layer-by-layer self-assembly method can accurately control the structure of the materials and improve stability, but the preparation cycle is long and cumbersome. Microencapsulation can effectively isolate the materials, improve stability, and has the potential for mass production. Finally, the research and application progress of photochromic textiles in the fields of optical information storage and solar ultraviolet detection were briefly introduced. [ABSTRACT FROM AUTHOR]

Revealing the structure–property relationships is crucial for promoting the development of photochromic materials and achieving the desired function in practical applications. Herein, a series of triphenylethylene photochromic materials (TP, TP-F, TP-Cl and TP-Br) have been synthesized and their photochromic properties were investigated. Monohalogenated TP-F, TP-Cl and TP-Br display obvious photochromic behaviors in solution, the solid state and polymer film. It is found that the halogen atoms with weak electron withdrawing ability can dramatically enhance the photocolorabilities of triphenylethylene. Moreover, TP-Cl and TP-Br exhibit different fatigue processes from TP-F. The further characterization reveals that the key factor leading to the diverse photochromic properties is cis/trans isomerization of triphenylethylene. The coloration of triphenylethylene mainly comes from the photo-triggered cyclization of cis-isomers. The initial attenuation of TP-Cl and TP-Br under UV irradiation is mostly caused by cis–trans photoisomerization, rather than the oxygen-involved photooxidation reactions. Based on the controllable "turn-on" and "turn-off" photobehaviors, TP-Cl and TP-Br were applied in the photoswitchable patterns, showing an enhanced signal-to-background ratio. [ABSTRACT FROM AUTHOR]

Photochromic materials have shown a wide range of applications. However, the development of new photochromic materials is still a great challenge. In this work, a photochromic functional ligand, 9,10-bis(di(pyridine-4-yl)methylene)-9,10-dihydroanthracene (L), was selected to construct a photochromic LMOF, [Ni2L(OBA)2(H2O)1.5·3.5i-PrOH]n (1) (LMOF = luminescent metal–organic framework; H2OBA = 4,4′-oxybisbenzoic acid; i-PrOH = isopropanol). 1 is composed of 4-connected Ni2+, 4-connected L and OBA2− bridges and exhibits a rare three-dimensional (3D) (4,4)-connected self-interpenetrated architecture and excellent water, pH and thermal stabilities. 1 and 1′ (1 after photochromism) can sense MnO4− in H2O by luminescence quenching effects. More importantly, this material after photochromism exhibits ultrahigh sensitivity for detecting MnO4− (the second highest Ksv of 6.11 × 105 M−1 and the nearly lowest LOD of 3.96 × 10−8 M) and can very efficiently recognize MnO4−. The sensing mechanism was explored in detail. [ABSTRACT FROM AUTHOR]

This research aimed to create a UV sensor using photochromic pigment in nonwoven form and analyse its fatigue resistance under continuous ultraviolet (UV) light. The photochromic polymeric matrices consist of a photochromic pigment, a polymer, and a photo stabilizer, which enhance the stability of the photochromic systems under light exposure. As a base matrix, we used polyvinyl butyral. Then, we added different amounts of the photochromic pigment 5-chloro-1,3,3-trimethylspiro [indoline-2,3′-(3H) naphtho (2,1-b) (1,4)-oxazine]. We produce photochromic nonwovens by electrospinning a polymeric matrix solution with varying pigment concentrations. The study aimed to create a UV sensor with photochromic nanofibers that are very sensitive to light. It also tested how well it can degrade under continuous UV radiation by looking at its photo fatigue resistance under constant UV irradiation for its final use as a UV sensor material. Using FTIR, CRM, SEM, and XRD techniques, this study investigates the physiochemical properties and photodegradation behaviour of photochromic nonwovens and writes a report on it. The photo-light stability of photochromic materials is a major problem concerning its external stimuli in different substrate forms. It also looks at how well they resist photo-chemically towards the UV light. The fatigue resistance measurements were carried out using a FOTOCHROM3 spectrophotometer under continuous UV irradiance using two different modes. This study evaluated and reported their photodegradation behaviour in cyclic and continuous UV irradiance modes. The tests showed that the prepared photochromic system works well with photostability and can go through more than 20 exposure cycles, each with 100 min of UV light and intensity equal to 1/3 of the sun's rays on a clear day. Given the PVB applications in our daily lives, it can serve as a UV sensor in numerous industrial applications. Photochromic nanofibers possessing excellent photosensitivity hold immense promise as optical rewritable devices and colourimetric-based UV sensors. [ABSTRACT FROM AUTHOR]

Photo‐triggered phase transition is a new type of phase transition in which a photochromic crystal with a thermal phase transition transforms into an identical high‐temperature phase in a temperature region lower than the thermal phase transition temperature upon light irradiation. Here, we report a second crystal that exhibits a photo‐triggered phase transition, thereby demonstrating that the photo‐triggered phase transition is a general phenomenon that occurs in crystals. When the chiral salicylidenephenylethylamine crystal was irradiated with ultraviolet (UV) light, the photo‐triggered phase transition occurred in the temperature range −30 to −10 °C. The photo‐triggered phase transition is induced by local stress due to trans‐keto molecules produced by photoisomerization near the irradiated surface. Crystal cantilevers exhibited stepwise bending by the combination of the photo‐triggered phase transition and photoisomerization. Alternate irradiation with UV and visible light achieved locomotion of single crystals driven by repeated stepwise bending. Finally, a detailed comparison of photo‐triggered and non‐photo‐triggered phase transition crystals revealed that a sufficient molecular conformation change in affordable crystal voids, smooth photoisomerization, and most likely a chiral molecular arrangement are required for inducing the photo‐triggered phase transition. [ABSTRACT FROM AUTHOR]

Photochromic circularly polarized luminescence (CPL) demonstrates broad application prospects in the field of advanced functional materials. However, the current photochromic CPL focuses predominantly on single‐band CPL adjustment, and how to achieve dynamically tunable CPL in multi‐band is still highly challenging. This work reports the success in utilizing reversible photochromism for realizing full‐color CPL emission. Photochromic flexible films are created consisting of triple components: spiropyran (SP) working as photochromic matter, polyurethane (PU) as matrix, and chiral helical polyacetylene as chiral component. Further introducing blue fluorophore 9‐anthracene carboxylic acid (ACA) in the film, blue CPL and red CPL are emitted respectively through selective absorption/transmission and circularly polarized fluorescence energy transfer (CPF‐ET). Doping the photochromic film with diverse fluorophores provides full‐color CPL emission. Adding Zn2+ further intensifies fluorescence and CPL via forming merocyanine (MC)‐Zn2+ complex. Taking advantage of the diverse fluorescence and CPL emission, anti‐counterfeiting, and secondary encryption application of the resulting photochromic CPL materials are demonstrated. [ABSTRACT FROM AUTHOR]

With the rapid development of intelligent materials in recent years, intelligent hydrophobic materials have become a new research direction, and hydrophobic surfaces with adjustable wettability have enormous application potential in many fields. Generally speaking, surface wettability is determined by the combined effect of surface chemical composition and surface morphology. Therefore, the photoresponsive wettability of azobenzene-modified surfaces can be achieved by constructing rough surface of micro-nano scale and reducing the surface free energy. In this paper, we synthesized two photo responsive hydrophobic azobenzene derivatives (AAAB-PFDT and UAAB-PFDT), characterized their structure, thermal degradation behavior, and microscopic morphology. The light conversion performance of the two materials in dispersion was also studied using a UV–Vis spectrometer. By depositing the materials on the glass slide, the measurements of the water contact angle (WCA) under different lighting conditions were performed, demonstrating that both materials exhibit excellent photoswitchable hydrophobicity and reversibility. [ABSTRACT FROM AUTHOR]

Photogenerated radicals are an indispensable member of the state‐of‐the‐art photochromic material family, as they can effectively modulate the photoluminescence and photothermal conversion performance of radical‐induced photochromic complexes. Herein, two novel radical‐induced photochromic metal–organic frameworks (MOFs), [Ag(TEPE)](AC) ⋅ 7/4H2O ⋅ 5/4EtOH (1) and [Ag(TEPE)](NC) ⋅ 3H2O ⋅ EtOH (2), are reported. Distinctly different topological networks can be obtained by judiciously introducing alternative π‐conjugated anionic guests, including a new topological structure (named as sfm) first reported in this work, describing as 4,4,4,4‐c net. EPR data and UV–Vis spectra prove the radical‐induced photochromic mechanism. Dynamic photochromism exhibits tunability in a wide CIE color space, with a linear segment from yellow to red for 1, while a curved coordinate line for 2, resulting in colorful emission from blue to orange. Moreover, photogenerated TEPE* radicals effectively activate the near‐infrared (NIR) photothermal conversion effect of MOFs. Under 1 W cm−2 808 nm laser irradiation, the surface temperatures of photoproducts 1* and 2* can reach ~160 °C and ~120 °C, respectively, with competitive NIR photothermal conversion efficiencies η=51.8 % (1*) and 36.2 % (2*). This work develops a feasible electrostatic compensation strategy to accurately introduce photoactive anionic guests into MOFs to construct multifunctional radical‐induced photothermal conversion materials with tunable photoluminescence behavior. [ABSTRACT FROM AUTHOR]

Inorganic photochromic luminescent materials hold immense promise as potential candidates for optical information storage applications. Unfortunately, static and single reading mode of photochromic luminescent materials in bright and dark environments pose a security threat to the stored information. Here, a novel material La2MgSnO6:Er3+,Fe3+ is developed, possessing both reversible photochromic and adjustable upconversion/downconversion photoluminescent (PL) properties. Upon exposure to 275 nm ultraviolet (UV) light, the sample changes in color from white to brown. And this transformation rapidly reverses when exposed to 365 nm UV light, resulting in a corresponding alteration in luminescence intensity. Notably, when combined with photochromic, the 980 nm excited upconversion PL maintains stable luminescence, while the 365 nm excited downconversion PL exhibits significant intensity changes. Inspired by this unique feature, a dark‐field selective dual‐mode reading is proposed that depends on the excitation wavelength, including static decrypt in long‐time cases and dynamic reading in time‐limited situations. These findings have the potential to revolutionize high‐security data storage applications and drive advancements in the field. [ABSTRACT FROM AUTHOR]

Photochromic materials have drawn enormous attention for their potential applications in optical memory storage and photoswitchable molecular devices. Although great achievements for photochromic materials have been fulfilled, it is still a big challenge to realize gated photochromism for ready tunable photochromic properties. In previous studies, rare examples of gated photochromism are reported. Herein, three triarylethylene derivatives FTrPE‐oI, ClTrPE‐oI and BrTrPE‐oI with reversible thermally activated photochromic characteristics are designed and synthesized, whose crystalline powders show no photochromism until thermally activated treatments to relative temperature. Temperature acts as a gate to switch the photochromic properties by switching the aggregation state from crystalline to melted amorphous. With this progress, a broader structural realm becomes accessible for gated photochromic materials, which can now be synthetically tailored for advanced future applications, e.g., in research on gated molecular machines and switches, in studies of photoisomerization mechanisms, or in the generation of thermal tracing materials. To showcase the potential of these distinct thermally activated photochromic materials, their applications in encrypted thermal printing, thermal trace monitoring as well as multi‐level anticounterfeiting are demonstrated, in addition to a comprehensive photochemical study of all compounds. [ABSTRACT FROM AUTHOR]

Photoluminescence (PL) colour-changing materials in response to photostimulus play an increasingly significant role in intelligent applications for their programmability. Nevertheless, current research mainly focuses on photochemical processes, with less attention to PL transformation through uniform aggregation mode adjustment. Here we show photochromic luminescence in organic crystals (e.g. dimethyl terephthalate) with PL varying from dark blue to purple, then to bright orange-red, and finally to red. This change is attributed to the emergence of clusters with red emission, which is barely achieved in single-benzene-based structures, thanks to the subtle molecular rearrangements prompted by light. Crucial to this process are the through-space electron interactions among molecules and moderate short contacts between ester groups. The irradiated crystals exhibit reversible PL transformation upon sufficient relaxation, showing promising applications in information storage and smart optoelectronic devices. This research contributes to the development of smart photochromic luminescent materials with significant PL colour transformations through molecular rearrangement. Color-changing emissions in organic crystals are often realized via photochemical reactions of their molecules. Here, the authors demonstrate reversible color change through more simple molecular rearrangements with application in encryption and data storage. [ABSTRACT FROM AUTHOR]

Photochromic inks have been a tempting authentication method to make commercial items more resistant to counterfeiting. However, recent studies have shown that photochromic inks have major drawbacks, such as expensiveness and low durability. Herein, we report the development of new photochromic nanofibers for cutting‐edge anti‐counterfeiting uses. Lanthanide‐doped strontium aluminate nanoparticles (LSAN) were synthesized and immobilized onto electrospun polyurethane nanofibers (PUNF). Anti‐counterfeiting materials encapsulated with inorganic photochromic agent can guarantee photostability and durability. LSAN function as an efficient inorganic photochromic agent whereas PUNF function as a hosting matrix. Both of photostability and reversibility of the prepared UV‐induced photochromic LSAN@PUNF were found to be rather high. Applying varying ratios of LSAN resulted in the development of polyurethane nanofibers with distinct emission properties depending on the LSAN content. The nanofibrous films showed green emission under UV illumination, and whereas no traces were detected in visible daylight. LSAN displayed diameters of 3–6 nm, whereas LSAN@PUNF nanofibers had diameters of 150–450 nm. Transparency was indicated by an excitation peak at 347 nm, and a green color was indicated by an emission peak of 530 nm. The current approach can be presented as an efficient technology to prevent forgery of commercial products. [ABSTRACT FROM AUTHOR]

High-performance organic devices with dynamic and stable modulation are essential for building devices adaptable to the environment. However, the existing reported devices incorporating light-activated units exhibit either limited device stability or subpar optoelectronic properties. Here, we synthesize a new optically tunable polymer dielectric functionalized with photochromic arylazopyrazole units with a cis-isomer half-life of as long as 90 days. On this basis, stable dual-mode organic transistors that can be reversibly modulated are successfully fabricated. The trans-state devices exhibit high carrier mobility reaching 7.4 square centimeters per volt per second and excellent optical figures of merit, whereas the cis-state devices demonstrate stable but starkly different optoelectronic performance. Furthermore, optical image sensors are prepared with regulatable nonvolatile memories from 36 hours (cis state) to 108 hours (trans state). The achievement of dynamic light modulation shows remarkable prospects for the intelligent application of organic optoelectronic devices. [ABSTRACT FROM AUTHOR]

Alkaline earth stannate is characterized by good physicochemical stability. It has been applied in the field of optical information storage by coupling photoluminescence intensity modulation and photochromic performance, which has attracted the attention of researchers. The development of alkaline earth stannate ceramics with high light intensity modulation properties and non-destructive reading of optical information is of great research value. In this study, Er3+-doped Ca 2 SnO 4 photochromic ceramics were prepared by high-temperature solid-phase reaction method. Alternating UV light irradiation and thermal stimulation, the ceramics achieve a reversible transition between light and dark gray. Er3+ doping gives the ceramics dual-mode luminescence light intensity modulation performance. When the doping amount of Er3+ is 0.01 mol, there is a maximum down-conversion luminous intensity modulation ratio of 93%, which is higher than most of the same type of photochromic materials. The photochromic behavior is explained using the capture-release model of traps for carriers, and the dual-mode luminescence light-intensity modulation behavior is analyzed through the energy transfer mechanism. The optical radiation response properties were investigated and the optimum light response wavelength is found to be 290 nm, which is related to the optical band gap E g. And the selection of the optimal light response wavelength can effectively improve the performance of photochromic and light intensity modulation. This study provides a promising strategy for performance enhancement of photochromic materials. [ABSTRACT FROM AUTHOR]

Highly transparent inorganic photochromic materials have several promising applications, especially for anti‐counterfeiting application. Enriching and enhancing the luminescent properties of perovskite by doping transition metals and rare earth elements into the host is a feasible and attractive route. Codoping of Mn2+ and Er3+ can realize novel anti‐counterfeiting properties with upconversion emission and photochromic ability within a double perovskite structure of Cs2AgInCl6.The Cs2AgInCl6: Mn2+, Er3+ single crystal can be observed in a reversible color variation from yellow to dark violet by implementing under 365, 520 nm illumination or thermal treatment. In addition, the crystal emits red and green light under the excitation of 365 nm ultraviolet and 980 nm laser, respectively. The introduction of Mn2+ endowed Cs2AgInCl6 with photochromic ability, and Mn2+ acted as a bridge for energy transfer from host excitons to Er3+, facilitating emission in the visible region. Er3+ achieve upconversion luminescence in the material through its abundant energy levels and acting synergistically with Mn2+. Herein, the Cs2AgInCl6:Mn2+, Er3+ combines various optical properties and has applications for specific anti‐counterfeiting demands. [ABSTRACT FROM AUTHOR]

In daily life, counterfeit and substandard products, particularly currency, medicine, food, and confidential documents, are capable of bringing about very serious consequences. The development of anti-counterfeiting and authentication technologies with multilevel securities is a powerful means to overcome this challenge. Among various anti-counterfeiting technologies, fluorescent anti-counterfeiting technology is well-known and commonly used to fight counterfeiters due to its wide material source, low cost, simple usage, good concealment, and simple response mechanism. Spiropyran is favored by scientists in the fields of anti-counterfeiting and information encryption due to its reversible photochromic property. Here, we summarize the current available spiropyran-based fluorescent materials from design to anti-counterfeiting applications. This review will be help scientists to design and develop fluorescent anti-counterfeiting materials with high security, high performance, quick response, and high anti-counterfeiting level. [ABSTRACT FROM AUTHOR]

This review paper provides a comprehensive overview of recent advancements in the synthesis, reactivity, and applications of N-isoindoline-1,3-dione heterocycles. These aromatic compounds, characterized by an isoindoline nucleus and carbonyl groups at positions 1 and 3, have gained significant attention for their potential use in diverse fields such as pharmaceutical synthesis, herbicides, colorants, dyes, polymer additives, organic synthesis, and photochromic materials. The review focuses on the period from 2015 to 2024, highlighting the diverse synthetic strategies employed to access N-isoindoline-1,3-diones derivatives. This review discusses the innovative methodologies and transformations that have enabled the efficient construction of these compounds with various substitution patterns. Furthermore, the reactivity of N-isoindoline-1,3-diones and their potential applications in different fields are explored. The paper emphasizes the importance of understanding the structure–activity relationships and biological properties of N-isoindoline-1,3-dione derivatives, with the aim of unlocking their potential as therapeutic agents. Additionally, the review underscores the need for sustainable and environmentally friendly synthetic approaches in this field. [ABSTRACT FROM AUTHOR]

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Understanding the convection flows driven by the uneven temperature distribution in heated aqueous solutions is fascinating and meaningful both in fundamental and industrial aspects. Therefore, it is desirable to develop a simple and convenient method for real‐time tracking of surface temperature distribution and the solvent flow state. Herein, we designed and screened a water‐soluble spiropyran derivative (BS‐SP1) that contains benzothiazole and sulfonic acid groups. The BS‐SP1 molecule was found to exceptionally maintain the reversible photochromic characteristics in water, and then served as a photo‐responsive indicator for visualizing the temperature distribution and flow behavior on water surface with high resolution. This study provides feasible guidance on the dynamic self‐assembly and thermodynamics occurring in the water evaporation system and offers a practical tool for investigating these behaviors. [ABSTRACT FROM AUTHOR]

Photochromic materials are of great interest because they enable the fabrication of photo-activated switches. In this study, an experiment is proposed in which two chromene-based photochromic layers were inserted into the arms of a Mach–Zehnder interferometer. The chromene was studied from the perspective of optical absorption to determine the wavelength-dependent complex refractive index. Impinging ultraviolet light on one of the chromene layers induces a transition from the closed to the open form of the chromene, resulting in different phase shifts in the two arms of the interferometer. This results in a change in the probability of detecting a photon by the two detectors after the second mirror of the Mach–Zehnder interferometer. The experiment may be of interest to researchers working in the fields of quantum information and quantum communications.

Mechanically reliable photoluminescent bricks were prepared from polyurethane (PUR) by reinforcement with electrospun glass nanofibers (EGNF). To enhance the mechanical qualities of the PUR sheets, EGNF were electrospun and applied to the PUR sheets as a reinforcement agent. We physically incorporated nanoparticles of rare-earth doped strontium aluminate (NRSA) into EGNF@PUR bricks to create photoluminescent and photochromic properties. In order to confirm the transparency of EGNF@PUR with the ability to change color to greenish beneath ultraviolet irradiation, both photoluminescence spectra and CIE (Commission Internationale de l'Eclairage) Lab coordinates were examined. When irradiated at 365 nm, an emission peak was monitored at 519 nm. With low concentrations of NRSA, the emission characteristic of the EGNF@PUR hybrid bricks was immediately reversible, revealing fluorescence emission. Persistent emission with delayed reversibility was observed in EGNF@PUR when using high concentrations of NRSA. Examining the morphological properties of NRSA and EGNF using transmission electron microscopy (TEM) revealed diameters of 4-9 nm and 75-125 nm, respectively. Both EGNF and EGNF@PUR bricks were subjected to morphological analysis using different analytical methodologies. As the concentration of NRSA rose, the material became more hydrophobic and more ultraviolet-protective. When compared to NRSA-free EGNF@PUR bricks, those containing NRSA had superior scratch resistance. [ABSTRACT FROM AUTHOR]

Strongly differing static dipole moments of the trans and cis isomers of photochromic azobenzene allow for optical switching of the work function of azobenzene-functionalized self-assembled monolayers (SAMs). We apply these properties in a fundamental experiment to manipulate the area size of the switched SAM. Azobenzene molecules were excited by ultraviolet laser illumination, and the transient isomerization profile of the SAM was spatially resolved recording photoemission electron microscopy images. Thereby, we demonstrate the spatial tuning of the SAM's work function and discuss the role of the laser spot profile in generating sharp edges or gradual changes of the work function. [ABSTRACT FROM AUTHOR]

Ionogels, composed of ionic liquids and supporting networks, possess a plethora of exceptional properties, including nonvolatility, remarkable thermal and electrochemical stability, elevated mechanical strength, as well as outstanding ionic conductivity. Based on these extraordinary characteristics, ionogels have found extensive applications in diverse fields encompassing functional materials, sensors, soft electronics, solid electrolytes, and biomedicine. In recent years, ionogels have witnessed significant advancements and emerged as a highly popular subject matter. Consequently, this review provides a comprehensive overview of the latest progress made in the realm of ionogels. The preparation methods of ionogels are initially introduced following a concise introduction. Subsequently, the properties of ionogels, encompassing mechanical properties, high and low temperature resistance, ionic conductivity, stimuli-response properties, self-healing properties, recyclability and their structure-property relationships, are comprehensively discussed. Moreover, recent advancements in the utilization of ionogels in solid electrolytes, ionic skins, soft electronics, adhesions and other domains are also elaborated upon extensively. Finally, after a succinct summary, challenges and prospects regarding the future development of ionogels are thoroughly deliberated. [ABSTRACT FROM AUTHOR]

Good transparency and color contrast are difficult to obtain at the same time, which is a pressing problem for photochromic ceramics. Lanthanum oxide doping improved the transmittance and color-changing characteristics of the sample. In this study, the photochromism and reversible luminescence modulation of 0.94(K0.5Na0.5)NbO3-0.06Sr(Bi0.5Nb0.5)O3:2.0 wt% La3+ (KNN–SBN + La2.0) transparent ferroelectric ceramics with different sintering temperatures were investigated. KNN–SBN + La2.0 has good light transmittance and color contrast characteristics, as well as a certain degree of photoluminescence characteristics. The sample that was sintered at 1162°C has a relatively high dielectric constant (εr) and a high transmittance (1100 nm). The diffuse reflection spectra of the sample that was sintered at 1182°C has a wide absorption band at 400 nm, while, after ultraviolet irradiation, the reflectivity of the sample is significantly reduced. The color rendering rate of the sample at the sintering temperature of 1182°C is high, the color rendering contrast (ΔRT) is 60.01%, and the high fluorescence luminescence contrast (ΔRI) is 82.42% under 150 s of 365-nm light. Based on these results, KNN–SBN + La2.0 ceramics have a good application prospect in data storage and electronic goods. [ABSTRACT FROM AUTHOR]

In this concept, we showcase the upsurge in the studies of dynamic ultralong room‐temperature phosphorescence (RTP) materials containing inorganic and/or organic components as versatile photo‐responsive platforms. The goal is to provide a comprehensive analysis of photo‐controllable RTP, and meanwhile delve into the underlying RTP properties of various classes of photochromic materials including metal‐organic complexes, organic‐inorganic co‐crystals, purely organic small molecules and organic polymers. In particular, the design principles governing the integration of the photochromic and RTP moieties within a single material system, and the tuning of dynamic RTP in response to light are emphasized. As such, this concept sheds light on the challenges and opportunities of using these tunable RTP materials for potential applications in optoelectronics, particularly highlighting their use of reversible information encryption, erasable light printing and rewritable smart paper. [ABSTRACT FROM AUTHOR]