Photochromic Activity Research Articles

Infiltration of glass nanofiber-reinforced polylactic acid into delignified hardwood toward photoluminescent and mechanically reliable smart windows

Ultraviolet-protective, mechanically reliable, and photoresponsive wood that can switch color under ultraviolet light was developed. A combination of alkaline earth-doped strontium aluminate (ASA) as a photoluminescent pigment and glass nanofiber-supported polylactic acid as a hosting agent was infused into a delignified wood, producing transparent wood with photochromic activity. The ASA phosphor has proven high thermal stability and photostability. A typical process for producing colorless photoluminescent wood includes the well-dispersion of ASA in glass nanofiber-supported polylactic acid without agglomeration. As proven by the coloration measurements, the current photoluminescent wood becomes green under ultraviolet light and remains transparent under daylight. Transmission electron microscopy (TEM) and scanning electron microscope (SEM) were employed to determine the morphology of the phosphor particles and glass fibers, demonstrating sizes of 12–21 nm and 50–125 nm, respectively. The luminescent wooden samples were studied by numerous microscopic and spectroscopic techniques, including SEM, X-ray fluorescence (XRF), and energy-dispersive X-ray (EDX). Upon excitation at 365 nm, the luminescence wood demonstrated an emission peak at 518 nm. When increasing the ASA concentration, the photoluminescent hardwoods displayed improved ultraviolet protection and better water resistance. The responsiveness of the luminescent wood to UV irradiation was fast and reversible.

Synthesis and Development of Inverse-Type Nucleoside Diarylethene Photoswitches.

Nucleosidic diarylethenes (DAEs) have evolved from an emerging class of photochromes into a well-established option for integrating photochromic functionalities into biological systems. However, a comprehensive understanding of how chemical structure influences their photochromic properties remains essential. While structural features, such as an inverse connection between the aryl residues and the ethene bridge, are well-documented for classical DAEs, their application to nucleosidic DAEs has been underexplored. In this study, we address this gap by developing three distinct types of inverse nucleosidic DAEs-semi-inverse thiophenes, semi-inverse uridines and inverse uridines. We successfully synthesized these compounds and conducted comprehensive analyses of their photostationary states, thermal stability, reversibility, and reaction quantum yields. Additionally, we conducted an in-depth comparison of their photochromic properties with those of their normal-type counterparts. Among the synthesized compounds, seven semi-inverse thiophenes exhibited the most promising characteristics. Notably, these compounds demonstrated excellent fatigue resistance, with up to 96 % retention of photochromic activity over 40 switching cycles, surpassing the performance of all comparable nucleosidic DAEs reported to date. These findings hold significant promise for future applications in various fields.

Fine-tuned photochromic WO3-x thin films: A detailed study from structural analysis to UV photo-sensing application

The oxygen substoichiometry of as-prepared WO3 (tungsten trioxide) nano-powders (NPs) from a polyol process was tuned via peptization of the NPs in aqueous solutions of different Cr2O72− oxidizing concentrations. The as-synthesized materials have been characterized by X-ray scattering (XRD and PDF), transmission electron microscopy (TEM), X-ray photoelectron (XPS), and UV-VIS photochromic activity. The local atomic structure of WO3-X was investigated using total scattering atomic pair distribution function (PDF) analysis based on X-ray total scattering data collected on powder at ambient conditions. The PDF analysis confirms that the crystal structure of all studied samples can be described in terms of very small crystallites with a P21/n space-group monoclinic framework but with anomalous unit cell distortion parameters, indicating that small crystallite sizes resulted in a larger monoclinic distortion (as measured by the beta angle of the unit cell). The nanometer dimension of the crystallites combined as well as the oxygen-tungsten stoichiometric ratio control, are key features for optimized photochromic properties. Moreover, we present the fabrication of a WO3-x thin film based UV photosensor, which was carried out on silica glass substrates via the dip-coating method. The obtained films exhibited a UV photoresponse and photoelectric characteristics at 5 V bias voltages able to detect very low UV doses, inferior to 10 W/m2. The photo-detection measurements prove the usability of our device as a UV photodetector with a good responsivity of 0.37 A/W and external quantum efficiency of more than 100% even at a very low power density (9.2 W/m2) of UV illumination.

Gated Photochromism of Dithienylethene-Embedded Expanded Calixphyrins.

Dithienylethene (DTE)-embedded expanded porphyrins were synthesized and confirmed to be photochemically inactive due to the lowest excited state of the expanded porphyrins. On the other hand, DTE-embedded expanded calixphyrins exhibited reversible photochromism upon UV-irradiation to form colored closed forms, which reverted to colorless open forms upon red-light irradiation. The closed forms were oxidized with DDQ or the air to lock the recorded information by converting to photochemically inactive expanded porphyrins. This was unlocked by reduction with NaBH4 to restore expanded calixphyrins with photochromism activity. These gated photochromic behaviors were demonstrated in PMMA (polymethyl methacrylate) film.

Imparting cotton textiles glow-in-the-dark property along with other functional properties: photochromism, flame-retardant, water-repellency, and antimicrobial activity

Screen-printing and spray-coating methods were used to produce photoluminescent, water-repellent, and antimicrobial films on textile fibers. The cotton fabrics were firstly finished with a flame-resistant agent. There are a number of functional agents that have been applied during the textile finishing process, including strontium aluminate pigment as antibacterial and photoluminescent agent, flame-retardant organophosphate, and water-repellent silicone rubber. The current research investigated the surface morphologies and chemical compositions of the screen-printed and spray-coated fabric cottons using scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray (EDX), wavelength dispersive X-ray fluorescence (WDXRF), and Fourier-transform infrared spectroscopy (FT-IR). According to morphological analysis, the phosphor nanoparticles had sizes ranging from 2 to 12 nm. After excitation at 399 nm, the generated colorless photoluminescent layer deposited onto cotton surface showed an emission profile at 516 nm. The luminescence spectra and CIE Lab characteristics confirmed that the phosphor-coated textiles displayed a white color in visible spectrum and green emission in the presence of UV light. It has been shown by analysis that the tested colors are very stable over time. The measurements of static water contact and sliding angles were also explored. The self-extinguishing activity of the coated fabrics retained their flame-retardant properties over 24 laundry cycles. Antimicrobial activity, hydrophobicity, and luminous properties were improved without affecting the intrinsic physical and mechanical features of the treated textiles. Details on the CIE Lab colorimetric measurements were discussed. The stiffness and air permeability were examined to explore the flexibility and breathability of the treated textile fibers. Excellent reversibility and photostability were seen in the phosphor-coated materials.

Fabrication of photochromic and electrochromic (PVP-am)/WO3/MoO3 hydrogel composites and glass films with programmable shapes

Recently, the fabrication of functional and stimuli-responsive hydrogels using deep eutectic solvent derivatives is gaining tremendous scientific recognition owing to their unique self-switching properties. In this study, perfluorinated deep eutectic mixtures were prepared as the template for the synthesis of WO3/MoO3 composites. The metal oxide-based composites were further employed as a chemical crosslinking agent for the polymerization of polyvinyl pyrrolidine (PVP) and acrylamide (Am), for the construction of (PVP-Am)/WO3/MoO3 hydrogel composites. The hydrogels displayed unique morphologies and mechanical properties. The hydrophilic nature of hydrogels as well as the high concentration of dispersed WO3/MoO3 composites in the polymer network contributes to their photochromic activity and allows an immediate coloration upon exposure to light at a short time. Howbeit, the low concentration of the dispersed WO3/MoO3 composites in the dry glass membrane is responsible for the blue coloration and an extended time of photochromic response. In addition, the electrochromic behavior of the hydrogel composites displayed a strong quasi-rectangular shape potential window as well as a well-defined redox cyclic voltammetry curve when exposed to high voltage. This could be due to the photoredox property of the WO3/MoO3 composites responsible for charge transfer between the different oxidation states.

Methyl 5′-Chloro-8-formyl-5-hydroxy-1′,3′,3′-trimethyl-spiro-[chromene-2,2′-indoline]-6-carboxylate

Spiropyrans modified with reactive polyfunctional substituents are of great interest as building blocks for the creation of various smart systems with controllable properties for materials science and biomedicine. In this study, a new highly modified spiropyran of the indoline series, methyl 5′-chloro-8-formyl-5-hydroxy-1′,3′,3′-trimethyl-spiro[chromene-2,2′-indoline]-6-carboxylate, was obtained via the cyclocondensation reaction from 5-chloro-1,2,3,3-tetramethyl-3H-indolium perchlorate and methyl 3,5-diformyl-2,4-dihydroxy-benzoate. The molecular structure of the target compound was confirmed by 1H, 13C NMR, and IR spectroscopy, as well as LC/MS and elemental analysis. Photochemical studies revealed photochromic activity for the obtained spiropyran at room temperature. The photoinduced merocyanine form demonstrated an enhanced lifetime and fluorescent properties in the red region of the spectrum.

High selective adsorption of lithium by photochromic porous SP-C/PVDF membranes with the driven force of an external electric field

Efficient separation of lithium from salt lake brine with a high Mg/Li ratio remains a challenge and the design of functional materials is one of key points determining the selective recovery of lithium. In this work, a photochromic porous SP-C/PVDF membrane was prepared and its selective adsorption properties for Li+ with the driven force of an external electric field were studied. The SP-C embedded in membrane phase still kept stable photochromic activity and the SP-C/PVDF membrane showed sensitive colour-switching under the alternating irradiation of UV/visible light. The hydrophility and porosity of the SP-C/PVDF membranes could be controlled by changing added amount of TiO2 nanoparticles. The SP-C/PVDF membranes exhibited high selective adsorption of Li+ compared with Mg2+ under an external electric field. This work developed a new material and strategy for selective extraction of trace Li+ from aqueous solutions with high Mg/Li ratio, which might be expected to promote the development of lithium extraction from salt lake brines.

Construction of a novel self-bleaching photochromic hydrogel embraced within the Zn-MOF@WO3 junction for assembling UV-irradiated smart rewritable device

Photochromic hydrogels, which are dynamic in response to external light stimuli, have aroused increasing attentions due to their potential applications in intelligent devices. However, achieving excellent photochromic activity with fast photoresponse and self-bleaching rates still remains a huge challenge. Herein, a novel photochromic junction of zinc-based metal–organic framework (Zn-MOF) and tungsten oxide (WO3) was established as photochromic unit and embraced within hydrogel of poly(acrylic acid-co-polyethylene glycol) [P(AA/PEG)] via the interaction of ionic and hydrogen bonding (denoted as P(AA/PEG)-Zn-MOF@WO3), following by exploiting as self-bleaching photochromic agent for assembling UV-irradiated smart rewritable device. The photoinduced electrons can be efficiently separated and migrated from Zn-MOF to WO3 in the Zn-MOF@WO3 junction after UV irradiation, thereby increasing the coloration degree. Due to the enhanced fast response to light stimuli, the P(AA/PEG)-Zn-MOF@WO3-3 hydrogel prepared using 200 mg Zn-MOF demonstrated the fast responsive photochromic behavior of 10 s under UV lamp illumination and the self-fading process could be easily performed in room condition (within 20 min). Moreover, the coloration degree of P(AA/PEG)-Zn-MOF@WO3-3 photochromic hydrogel was precisely controlled and repeated by changing the UV irradiation time. Consequently, the fast photochromic and self-fading properties of P(AA/PEG)-Zn-MOF@WO3-3 afforded rapid and easy ‘‘writing’’ and “erasing” abilities. The present work proposes a new way for the construction of the reversibly responsive photochromic hydrogel with smart optical materials, further broadening their applications in intelligence sensors, smart windows, and flexible memory devices.

Mixed Organic Counterion Strategy Modulates the Self-Assembly of Polyoxometalate Hybrids into Toroids and Affects Their Photochromic and Photocatalytic Properties.

A series of five mixed-counterion polyoxometalate (POM) hybrids 1-5 have been developed starting from the [SiW12O40]4- cluster and two different aryl sulfonium counterions (ASCIs), (4-hydroxyphenyl)dimethylsulfonium (HPDS) and (4-formylphenyl)dimethylsulfonium (FPDS), bearing different functional groups -OH and -CHO, respectively. The HPDS/FPDS counterion ratio in hybrids 1-5 varied as 4:0 (1), 3:1 (2), 2:2 (3), 1:3 (4), and 0:4 (5), and it resulted in a morphological transition of the self-assembly of these hybrids. Hybrid 1 exhibited spherical self-assembly, while hybrid 5 exhibited large toroidal self-assembly predominantly. The hybrids 2-4 gave a mixture of spherical, dimpled spherical, and toroidal self-assemblies in varying amounts, indicating a gradual transition of self-assembly from spherical to toroidal as the percentage of FPDS increases in the system. A plausible explanation for the differences in the self-assembly properties of these hybrids has been proposed based on the differences in the H-bonding interactions of the two counterions with the dispersion medium. The HPDS and FPDS counterions exhibited different HOMO-LUMO gaps, and their varying percentages in hybrids 1-5 led to differences in optical band gaps and photochromic activities. Hybrid 2 showed the lowest band gap value and the best photochromic activity (t1/2 = 0.72 min) in the series. The influence of the mixed-counterion strategy in catalysis has been demonstrated by evaluating the photocatalytic activity of these hybrids toward rhodamine B dye degradation. The hybrid 4, exhibiting stable toroidal self-assembly, showed the best catalytic activity in the series, probably due to a combination of reasons such as the enhanced surface area due to toroid formation and also the presence of H-bonding -OH functionality on the counterion. Therefore, the present study suggests a new method for altering the self-assembly and the materials and catalytic properties of POM hybrids through a mixed-counterion strategy.

Dithienylethene‐Containing Cyclometalated Platinum(II) Complexes with Tunable Photochromic and Photophysical Properties

AbstractA series of cyclometalated platinum(II) complexes with a dithienylethene‐containing N^C and an ancillary O^O ligand have been synthesized and characterized. All the complexes, [Pt(thpy‐DTE)(dtpd)] (1), [Pt(CF3‐thpy‐DTE)(dtpd)] (2) and [Pt(Me‐thpy‐DTE)(dtpd)] (3), exhibit photochromism that can be triggered by photoexcitation at 420 nm into the metal‐to‐ligand charge transfer (MLCT)/intraligand charge transfer (ILCT) band at the visible region, which is accompanied with colour changes from yellow to green, as well as the quenching of red phosphorescence originated from the emissive triplet intraligand (3IL) excited state. The photophysical and photochromic properties can be readily tuned by varying the ligands. Moreover, the fatigue resistance and thermal irreversibility of this series of complexes have also been demonstrated by the representative complex 1 with persistence of the photochromic activity after six photoswitching cycles and a thermal decay half‐live of 4.8 days even at 308 K.

(Invited, Digital Presentation) Substituent Effect on Fluorescent Probes: Photophysical- and Electrochemical Properties and Their Application As Chemosensors

Stimulus-responsive materials have great potential for sensing applications, and their photophysical- and electrochemical properties can be finely tuned as modifying molecular structure. In this presentation, two series of fluorescent probes, BF2dbm and CzPyr, will be introduced as nitro-explosive and acid chemosensors, respectively. Both series of compounds showed different sensing abilities, varying from electron-withdrawing to electron-donating abilities in the peripheral phenyl groups. The photophysical- and electrochemical properties of these compounds, along with density functional theory and time-dependent density functional theory calculations, are systematically investigated to study the structure-property relationships. For BF2dbm, the emissions in chloroform solution are quenched exponentially by adding o-nitroaniline, with quenching constants up to 17,800 M−1. For CzPyr, an evaluation of the emission properties in the solid-state revealed the photochromic activity, and reversibly switched on and off by controlling the pH conditions.

Colour‐switchable and photoluminescent polyvinyl chloride for multifunctional smart applications

Recycled polyvinyl chloride (PVC) waste was used to prepare transparent materials with long-lasting phosphorescence, photochromic activity, hydrophobicity, strong optical transmission, ultraviolet (UV) light protection, and stiffness. Lanthanide-activated aluminate (LaA) microparticles were prepared using a high temperature solid-state procedure, and were subjected to top-down grinding technology to produce lanthanide-aluminate nanoparticles (LaAN). Laminated PVC bottles were shredded into a transparent plastic matrix, which was combined with LaAN and drop casted to produce smart materials for various applications. Smart windows and photochromic film for smart packaging can be made from recycled PVC waste by immobilizing it with various ratios of LaAN. Long-lasting phosphorescent translucent PVC smart windows and films need LaAN to be evenly dispersed in PVC without clumping. Different analytical methods were used to assess the material's morphological structure and chemical composition. Photoluminescence and decay spectra were all used to investigate the luminescence characteristics. In addition, the mechanical performance was studied. According to Commission Internationale de l'Éclairage laboratory colour measurements, this transparent PVC smart material becomes bright green under UV rays and turns a greenish-yellow in the dark. The PVC luminescence was observed to exhibit apparent emission bands at 429 and 513 nm when excited at 367 nm. Improvements were monitored in UV shielding and hydrophobicity when increasing the phosphor concentration. LaAN-immobilized PVC exhibited reversible photochromism. The present approach can be applied to various applications such as anticounterfeiting films for smart packaging, smart windows, and warning light marks.

Photoluminescent and photochromic smart window from recycled polyester reinforced with cellulose nanocrystals.

Smart windows with long-persistent phosphorescence, ultraviolet (UV) light protection, high transparency, and high rigidity were developed by easily immobilizing varying ratios of lanthanide-activated aluminate phosphor nanoscale particles within a composite of recycled polyester/cellulose nanocrystals (RPET/CNC). Cellulose nanocrystals were prepared from rice straw waste. Cellulose nanocrystals were used at low concentration as both crosslinker and drier to improve both transparency and hardness. The phosphor nanoscale particles must be distributed into the recycled polyester/cellulose nanocrystals composite bulk without agglomeration to produce transparent RPET/CNC substrates. Photoluminescence characteristics were also studied using spectroscopic profiles of excitation/emission and decay/lifetime. The hardness efficiency was also examined. This transparent recycled polyester waste/cellulose nanocrystals nanocomposite smart window has been shown to change colour under UV light to strong green and to greenish-yellow when it is dark, as proved by Commission Internationale de l'éclairage (CIE) laboratory colour parameters. It was found that the afterglow RPET/CNC smart window had phosphorescence intensities of 428, 493, and 523 nm upon excitation at 368 nm. There was evidence of improved UV shielding, photostability, and hydrophobic activity. In the presence of a low phosphor ratio, the luminescent RPET/CNC substrates showed quick and reversible fluorescence photochromic activity when exposed to UV radiation.

Modulation of the fading kinetics of lactone-fused naphthopyran UV photoswitches

A set of new lactone-fused naphthopyrans substituted with aryl or arylethynyl groups were synthesized using an acid-catalyzed one-pot reaction. These colorless dyes exhibit photochromic activity at 20 °C acquiring intense reddish hues under UV light, that fades completely, in the dark within a few minutes. The introduction of the arylethynyl group increases the thermal stability of the reddish photoisomers, resulting in darker shades, while the discoloration process remains under 6 min.

Authentication of documents using polypropylene immobilized with rare-earth doped aluminate nanoparticles.

Anticounterfeiting of commercial products has been improved using photochromism as an intriguing approach. In order to develop a mechanically reliable nanocomposite, the engineering procedure of the anticounterfeiting nanocomposite must be improved. Rare-earth doped aluminate/polypropylene (REA/PP) hybrid nanofibers were successfully made by electrospinning, and they were shown to be mechanically stable and highly photoluminescent, making them ideal for anticounterfeiting applications. UV-induced photochromic anticounterfeiting properties were monitored in the synthesized nanocomposite films. In order to ensure that the REA-PP film is completely transparent, REA must be embedded into the polypropylene nanofibers in nano-sized particle shape to facilitate a better dispersion without agglomeration of REA particles in polypropylene matrix. The morphology and structure of REA were studied by transmission electron microscopy and X-ray diffraction. The morphologies and chemical contents of the polypropylene nanofibrous films were studied by scanning electron microscopy, X-ray fluorescence, and energy-dispersive X-ray spectroscopy. The REA-PP nanofibrous film showed absorbance and emission maxima at 365 and 517 nm, respectively. When exposed to UV light, the photochromic activity of the transparent nanofibrous substrates to greenish-yellow was rapid and reversible without fatigue. Hydrophobicity of REA-PP films increased without affecting their original look or mechanical properties, while increasing the REA content. It was possible to produce ultraviolet-induced photochromic nanofibrous films that were transparent, flexible, and cost-effective. As a result of this method, numerous anticounterfeiting materials could be developed toward a better marketplace with both economy and community values. HIGHLIGHTS: Rare-earth aluminate/polypropylene (REA/PP) electrospun nanofibers were prepared. The photochromic transparent nanofibers displayed green emission under UV light. The nanofibrous films were flexible, mechanically stable and highly luminescent. Films showed absorbance and emission maxima at 365 and 517 nm, respectively. Hydrophobicity was improved without affecting the films original properties.

Immobilization of lanthanide doped aluminate phosphor onto recycled polyester toward the development of long-persistent photoluminescence smart window.

Smart window can be defined as switchable material whose light transmission is altered upon exposure to light, voltage, or heat. However, smart windows are usually produced from expensive and breakable glass materials. Herein, transparent smart window with long-persistent phosphorescence, high optical transmittance, ultraviolet (UV) protection, rigid, high photostability and durability, an d superhydrophobicity was developed from recycled polyester (PET). Recycled polyester waste (RBW) was simply immobilized with different ratios of lanthanide-doped aluminate nanoparticles (LdAN) to provide a long-persistent phosphorescent polyester smart window (LdAN@PET) with an abili ty to persist emitting light for extended time periods. The solid-state high temperature technique was used to prepare lanthanide-doped aluminate (LdA) micro-scale powder. Then, the top-down technique was applied to afford the corresponding LdAN. Recycled shredded recycled polyester bottles were charged into a hot bath to provide a clear plastic shred bulk, which was then well-mixed with LdAN and drop-casted to provide long-persistent luminescent smart window. In order to improve the phosphor dispersion in the PET bulk, LdAN was synthesized in the nanoparticle form which was characterized utilizing transmission electron microscopy (TEM). For better preparation of translucent smart window of long-persistent phosphorescent polyester, LdAN must be homogeneously dispersed in the PET matrix without agglomeration. The morphology and chemical composition were studied by Fourier-transform infrared (FTIR) spectra), X-ray fluorescence (XRF) analysis, scanning electron microscopy (SEM), and energy-dispersion X-ray spectroscopy (EDX). In addition, spectral profiles of excitation and emission, and decay and lifetime were used to better understand the photoluminescence properties. The hardness properties were also investigated. The developed phosphorescent transparent polyester smart window demonstrated a color switch to intense green underneath UV irradiation and greenish-yellow under darkness as verified by CIELab color parameters. The afterglow polyester smart window showed an absorption wavelength at 365 nm and two phosphorescence intensities at 442 and 512 nm. An enhanced UV protection, photostability and hydrophobic activity were detected. The luminescent polyester substrates with lower LdAN ratios demonstrated rapid and reversible fluorescent photochromic activity beneath the UV light. The luminescent polyester substrates with higher LdAN contents displayed long-persistent phosphorescence afterglow. The current strategy can be simply applied for the production of smart windows, low thickness anti-counterfeiting films and warning signs.

Cu-Doped and Un-Doped WO3 Photochromic Thin Films

In this work, 0%, 0.5%, 1%, and 2% Cu-doped WO3 nanoparticles were synthesized via a polyol method. The as-synthesized materials were characterized by x-ray diffraction, scanning electron microscopy (SEM), electron paramagnetic resonance (EPR), x-ray photoelectron spectroscopy (XPS), and UV-Vis photochromic activity. A bond valence model was adopted to explain the relationship between the lattice parameter and Cu percentage. Additionally, two films (1% Cu-doped and un-doped samples) obtained by dip-coating from a well-dispersed suspension were optically investigated using ex situ and in situ UV-Vis spectrometry; coloring/bleaching kinetics were thoroughly studied. The Cu-doped WO3 film was found to have a high-quality bleaching mechanism (five times as fas as the un-doped WO3 film). Finally, the high bleaching performance of the doped films was confirmed by successive cycling, showing that the as-prepared compounds are of great interest for smart window applications, for example.

Diarylethenes in Optically Switchable Organic Light‐Emitting Diodes: Direct Investigation of the Reversible Charge Carrier Trapping Process

AbstractThe design, fabrication, and characterization of optically switchable organic light‐emitting diodes (OSOLEDs) based on the combination of the commercially available light‐emitting polymer poly(9,9′‐dioctylfluorene‐alt‐benzothiadiazole), F8BT, doped with a diarylethene derivative is reported. The photochromic activity of the dopant in the solid state has been investigated both via UV/vis absorption and photoluminescence spectroscopy, whereas the morphology of different blends is investigated via atomic force microscopy. OSOLEDs embedding dopant loadings of 1, 5, and 10 wt% exhibit optical responsivity with a maximum reversible optical threshold voltage shift of 4 V. The best performing devices containing 5 wt% dopant show a maximum current density and luminance ON/OFF ratio of ≈20 and ≈90, respectively. For the first time, the impact of the diarylethene isomerization on hole and electron transport has been decoupled and directly investigated, via the design, fabrication, and characterization of single‐carrier switchable devices based on the same blends. Not only do these results confirm the photo‐responsive trapping activity of the diarylethenes on both charge carriers, but they also demonstrate its asymmetry, with a predominant effect on electron transport that is over 3.4 times larger as compared to hole transport.

Synthesis of lanthanide-doped strontium aluminate nanoparticles encapsulated in polyacrylonitrile nanofibres: photoluminescence properties for anticounterfeiting applications.

Photochromism has been applied as an interesting technique in order to improve the anticounterfeiting of commercial commodities. To build up a mechanically reliable anticounterfeiting nanocomposite, it has been vital to enhance the engineering process of the anticounterfeiting material. In the current study, we developed mechanically reliable and highly photoluminescent lanthanide-doped strontium aluminate nanoparticles (LSAN)/polyacrylonitrile (PAN) hybrid nanofibres successfully fabricated using an electrospinning technique for anticounterfeiting applications. The produced nanocomposite films exhibited ultraviolet-induced photochromic anticounterfeiting properties. To guarantee the transparency of the LSAN-PAN film, LSAN must be immobilized onto the nanoparticle size to allow better dispersion without aggregation in the polyacrylonitrile matrix. The LSAN-PAN nanofibrous film demonstrated absorbance intensity that exhibited at 354 nm and associated with an emission intensity at 424 nm. The produced LSAN-PAN films demonstrated an enhanced hydrophobicity when increasing the ratio of LSAN, without adversely influencing their native appearance and mechanical performance. Upon excitation with ultraviolet light, the translucent nanofibrous substrates exhibited fast and reversible photochromic activity to greenish-yellow without exhaustion. The nanofibrous films exhibited stretchability, transparency, flexibility, and ultraviolet light-induced photochromism at low cost. The current strategy can be considered as an efficient technique towards the development of various anticounterfeiting materials for a better market with economic and social values.