Photochromic Devices Research Articles

Photochromic and electrochromic dual-responsive devices: Integration of TiO2-Prussian blue composites and novel extended viologen

Photochromic and electrochromic devices have attracted remarkable attention due to their advantages of low power consumption, eye-friendliness, and broad application potential. However, developing dual-responsive devices with nice memory effect and rapid switching ability remains challenging. Here we report a novel strategy for fabricating dual-responsive photo-electrochromic device (PECD) based on TiO2-Prussian blue (PB) composite film and a novel extended viologen FHP. Exploiting the photocatalytic properties of TiO2, we successfully fabricated dual-responsive thin films and incorporated FHP as a complementary material to enhance the performance of the device. Notably, the resultant PECD exhibited remarkable performance, including long optical memory (33.91 h), fast response (4.6 s for coloring, 10.4 s for bleaching), high contrast (ΔT is 77.2 % at 692 nm), and excellent cycling stability (ΔT loss is smaller than 3.1 % after continuous working for 1000 cycles), highlighting their potential for advanced optical applications.

PH regulated two Zn(II) viologen-derived photochromic functional complexes

By adjusting pH, two zero-dimensional (0D) Zn(II)-based functional complexes, namely, [Zn(CEbpy)(TPDC)(H2O)4]·3H2O (1) and (CEbpy)2·[Zn(H2O)6](TPDC)·3H2O (2) have been successfully constructed from thiophene-2,5-dicarboxylic acid (H2TPDC) and 1-carboxyethyl-4,4′-bipyridine (CEbpy). Both 1 and 2 display electron transfer (ET)-mediated photochromic behaviors with different photoresponsive rates. Furthermore, the solid-state photo-controlled luminescence of two compounds is also examined at ambient temperature. Appealingly, upon UV illumination, compound 1 possesses potential as an inkless and erasable printing medium. These results provide potential avenues for rational design and synthesis of functional materials that can be used in photochromic devices by modulating pH.

Rhodamine 6G salicylaldehyde hydrazone-Zn complex: Synthesis, characterization, photochromism, understanding, and application

Zinc complex-based photochromic materials are gaining significant interest from their applications in various consumer products such as toys, cosmetic products, photochromic inks (for security marking), data storage, erasable optical memory media, etc. Here, the rhodamine 6G salicylaldehyde hydrazone-Zn complex was synthesized, characterized, and understood to develop a molecular device. The crystal structure analysis (CCDC number 2260405) confirms the synthesis of a new photo-ligand, rhodamine 6G salicylaldehyde hydrazone. The NMR, ESI-Mass, FT-IR, UV–Vis spectra (Job's and Benesi Hildebrand plots), chelation-enhanced fluorescence spectra (CHEF), and geometry optimization confirm the synthesis of the Zn-complex. We have studied photochromic behavior with absorption, emission, fatigue resistance, role of solvents, thermal bleaching kinetics, FMO computation, and vibrational analysis. The vibrational analysis has rationalized excited state intramolecular proton transfer (ESIPT) involved in photochromism. An attempt has been made to construct photochromic devices.

Exploring the chemical physics in tetraphenylporphyrin-N-methylfulleropyrrolidine supramolecular complex by spectroscopic investigations and quantum chemical calculations

The interaction between N-methylfulleropyrrolidine (A) and 5,10,15,20-tetraphenylporphyrin, i.e., D, is studied in solution. Absorption spectrophotometric study reveals formation of charge transfer (CT) absorption band for the DA complex from which CT transition energy (hνCT) is estimated to be 1.673 eV. Quenching of fluorescence of D in presence of A is utilized for determination of the binding constant of the DA complex as 13780 dm3⋅mol−1. DFT calculations generate both geometry optimized and electronic structures of the DA complex and the estimated HOMO-LUMO energy gap, i.e., 1.683 eV, correlates excellently well with the experimentally obtained value of hνCT. Proton NMR studies provide substantial support in favour of strong binding between D and A and provide a clear picture regarding orientation of bound guest (here A) with host (here D). The DA system reported in present work would certainly provide very good perspective for the construction of fulleropyrrolidine based photochromic devices in near future.

Spectroscopic and quantum chemical insights on supramolecular interaction between N-methylfulleropyrrolidine and designed porphyrins in solution

Present letter describes self-assembly of N-methylfulleropyrrolidine (A) with a designed free-base (H2Pr) and zinc porphyrin (ZnPr) in toluene. The binding constants (K) of A-H2Pr and A-ZnPr systems are estimated to be 5.92 × 103 dm3.mol–1 and 10.05 × 103 dm3⋅mol−1, respectively. DFT calculations by B3LYP (and MO6) method(s) extend very good support in favour of the K values of the A-H2Pr and A-ZnPr systems in terms of the heat of formation, i.e., 7.40 kcal⋅mol−1 (and 6.46 kcal⋅mol−1) and −128.25 kcal⋅mol−1 (and −125.05 kcal⋅mol−1), respectively. Present investigations envisage that A may be suitably employed as fulleropyrrolidine based photochromic devices in near future.

A Green-to-Near-Infrared Photoswitch Based on a Blended Subporphyrazine-Dithienylethene System.

A subporphyrazine (SubPz)-dithienylethene (DTE) photochromic device with 1o and 1c states, was developed and characterized. In this device, the DTE unit can reversibly switch the SubPz absorbance from green to near-infrared [λmax (o/c) = 527 nm/740 nm], as well as the SubPz fluorescence and singlet oxygen quantum yields. The core of this design involves using a highly tunable SubPz chromophore that shares its quasi-isolated ethene moiety with a DTE photoswitch.

Visible light photo catalytic and optical property evolution of combustion method prepared copper doped nickel ferrite nanoparticles

By using a simple microwave combustion technique, copper-doped NiFe2O4 spinel nanoparticles were formed. The XRD patterns demonstrated that Cu doping into NiFe2O4 spinel resulted in the creation of α-Fe2O3 secondary phase in addition to the cubic structure that already existed. Using SEM, morphological investigations revealed irregular shapes and severely agglomerated different grain boundaries. In an optical analysis, it was discovered that the band gap narrowed as the Cu2+ doping percentage raised. The octahedral site (Ni-O) and tetrahedral site (Fe-O) stretching modes of the Cu-doped nanoparticle structure were linked to bands at 548, 514, and 649cm-1 from FT-IR analysis. Cu-doped nanoparticles were examined for their enhanced photocatalytic degradation of RhB in visible light irradiation under atmosphere condition. The performance of pure NiFe2O4 as a photocatalyst was discovered to be greatly impacted by the Cu-doping. Additionally, the photo-catalytic effect was optimized (efficiency rose from 88.26 percent, x = 0-99.85 percent, x = 0.4) with the rise of Cu-doping into x=0.4. An in-depth discussion was had on the potential photocatalytic mechanism. The simultaneous improvement of photocatalytic activities serves as proof that Cu-doped NiFe2O4 spinel nanoparticles will perform well in multifunctional photochromic devices in future.

Novel extended viologen derivatives for photochromic and electrochromic dual-response smart windows

Smart windows, which could save building energy consumption by modulating indoor thermal and light intensity, have attracted considerable attention in recent years. Photochromic (PC) and electrochromic (EC) are two representative working modes of smart windows. Integrating PC and EC on a single smart window is beneficial for adapting to various environments and meeting individual needs. However, it remains challenging to develop PC and EC dual-responsive materials. In this work, we reported two extended viologen derivatives, EV-1 and EV-2, with both PC and EC properties. Photochromic devices (PCDs) and electrochromic devices (ECDs) based on these materials were fabricated successfully. Under UV light irradiation, the PCDs exhibited a significant color change from transparent to green (PCD-1) and blue (PCD-2) color, and the colored state can maintain a long time (2.73 h for PCD-1 and 41.72 h for PCD-2) after removing the UV light. Owing to the extension of the conjugate length of the chromophore as compared with traditional viologens using bipyridine as chromophores, the spectra response range of the devices was extended to the near-infrared (NIR) region. To obtain different light modulation capabilities, we fabricated electrochromic devices using propylene carbonate as solvent. These devices display different colored states (red for ECD-1 and purple for ECD-2) and spectra absorption compared to PCD-1 and PCD-2. Furthermore, a photo/electrochromic device (PECD) smart window system was developed to enhance light and thermal regulation. This system offers four working modes, including off mode, photochromic mode, electrochromic mode, and photo-electrochromic mode, which opens up new possibilities for expanding its applications.

Recyclable photoluminescent elastomer incorporating carboxyl‐functionalized fluorescent powder via dynamic covalent cross‐linking

AbstractThe rapid development of photochromic devices has stimulated great enthusiasm for the design and preparation of luminescent materials. Introducing fluorescent powder ZnS:Cu into the cross‐linked polymer matrix is an efficient and simple method to obtain photochromic materials with excellent comprehensive performance. However, the traditional method is to directly introduce fluorescent powder into the polymer matrix by physical mixing. This not only increases the internal defects of the polymer and reduces the mechanical properties, but also hinders the fluorescent powder from absorbing external energy and reduces its luminescence efficiency. In addition, few studies have focused on recyclable photochromic luminescent materials. Inspired by dynamic covalent cross‐linking technology, this paper first modified fluorescent powder with 3‐mercaptopropionic acid and then introduced it into epoxy silicone rubber to prepare recyclable luminescent elastomer. Compared with traditional physical blending, the mechanical properties and luminescence performance of the covalently bonded luminescent elastomer were improved. Excellent mechanical properties and luminescence performance were maintained in multiple recycling processes. This paper provides a feasible and simple scheme for the preparation of recyclable luminescent elastomers, paving the way for the recycling and long‐term utilization of photochromic luminescent materials.

Nb, Ta and Hf – The tri-dopant tournament for the enhancement of TiO2 photochromism

TiO2 quantum dot (QD) size nanoparticle colloids have shown tremendous photochromic response. Here we show that the of the photochromic response of TiO2 QDs can be further enhanced by doping. Our synthesis approach allows to reach high nominal doping level by substituting up to 20 % of Ti in TiO2 without phase segregation simultaneously keeping particles in ultra-small. We compare the effect of different dopants (Nb5+, Hf4+ and Ta5+) on photochromic properties of TiO2 QDs. We show all dopants in study enhance the response kinetics and total transmittance change. From all three dopants, Nb5+ provides strongest response and fastest coloration while Hf4+ doped TiO2 QDs exhibit fastest recovery when the UV light is off. The presented insight in photochromic properties of doped TiO2 QDs will allow to develop photochromic devices and materials with better performance.

The thermal spin molecular logic gates modulated by light

Digital electronics and spintronics are based on logic operations. Here, nonequilibrium Green’s functions are incorporated with the density functional theory to evaluate the thermal spin transportation features of the photochromic molecule spintronic devices constructed by dihydropyrene/cyclophanediene (DDP/CPD) molecule in alone, series, or parallel, connected with graphene nanoribbons electrodes. Based on calculations, the spin-polarized currents can be manipulated by light. Then, a complete set of thermal spin molecular logic gates is proposed, including AND, OR, and NOT gates. The above logic gates can be employed to perform complex thermal spin molecular logic operations and facilitate all-optical control of thermal spin molecular devices.

Recyclable photoluminescent composites via incorporating ZnS‐based phosphors into dynamic crosslinking elastomeric matrixes

AbstractThe rapid advances in photochromic devices have spurred great enthusiasm in the design and preparation of luminescent materials. It is an efficient and facile strategy to incorporate ZnS‐based phosphors into crosslinking polymer substrates, obtaining photochromic materials with excellent comprehensive properties. However, crosslinking polymeric ZnS‐based phosphor luminous materials are unable to be recycled and reprocess at the end of service, limiting their long‐term utilization and burdening the environment. Besides, few reported works have explored photoluminescent properties of samples during multiple reprocessing and recycling. Herein, enlightened by the intriguing dynamic covalent crosslinking technology, recyclable and photoluminescent elastomers, employed polymeric flexible matrixes with dynamic covalent joints integrated with ZnS:Cu and ZnS:Cu,Mn phosphors, were prepared in this work. Due to the breakage and reformation of exchangeable crosslinking connections and intensive interfacial interactions between polar elastomeric matrixes and luminophores, the original and recycled composites exhibit excellent recyclable, photoluminescent, and mechanical properties. We anticipate that the strategy of this work, inserted phosphors into dynamic crosslinking polymer matrixes with a facile fabrication process, paves the way for the recycling and long‐term utilization of photoluminescent materials.

The structural origin of the efficient photochromism in natural minerals

SignificanceNatural photochromic minerals have been reported by geologists for decades. However, the understanding of the photochromism mechanism has a key question still unanswered: What in their structure gives rise to the photochromism's reversibility? By combining experimental and computational methods specifically developed to investigate this photochromism, this work provides the answer to this fundamental question. The specific crystal structure of these minerals allows an unusual motion of the sodium atoms stabilizing the electronic states associated to the colored forms. With a complete understanding of the photochromism mechanism in hand, it is now possible to design new families of stable and tunable photochromic inorganic materials-based devices.

Construction of polymer materials with specific responses to violet and green lights and their potential applications in an artificial visual memory system

Novelty: a revisable binary to ternary memory behavior is achieved by photoelectric synergy controls in one photochromic polymer device, which greatly enhances storage density and has great potential in optical recognition for artificial retinas.

Novel flexible photochromic device with unprecedented fast-bleaching kinetic via platinum decoration on WO3 layer

Photochromic devices (PC) are considered as ideal candidates for integrated building applications because of their ability to control light and heat transfer into/out of building inner spaces without any external power supply. However, several issues restrict their practical application, including long-term stability concerns due to the volatile nature of the commonly used liquid electrolyte, the high replacement/installation cost associated with their rigid device architecture, and an extremely slow bleaching speed during reversion to their original state due to the lack of an external stimulus such as electricity. The present study aimed to resolve these bottlenecks. Firstly, we exploited a highly stable and conductive polymer-gel electrolyte based on UV-curable trivalent acrylate instead of using organic liquid-based electrolytes. Secondly, we explored a low-temperature UV-curing procedure to deposit the chromogenic WO3 and TiO2 layers, suitable for fabricating a flexible PC device. Finally, a catalytic amount of Pt nanoparticles was successfully incorporated on the surface of the WO3 layer using an identical UV-curing route, which was found to significantly enhances the bleaching speed of the resulting PC device. Thanks to the combined positive effects, the fabricated PC device displayed a deep contrast in coloration (approximately 60 %), unprecedented bleaching kinetic with 90 % recovery of its original transmittance value within 45 min in the dark condition, and prolonged long-term operation for over 1000 coloration-bleaching cycles. These results open way to making efficient PCs for not only smart windows but also for other bendable or wearable applications.

Chemiluminescence-Derived Self-Powered Photoelectrochemical Immunoassay for Detecting a Low-Abundance Disease-Related Protein.

Early diagnosis of cancers relies on the sensitive detection of specific biomarkers, but most of the current testing methods are inaccessible to home healthcare due to cumbersome steps, prolonged testing time, and utilization of toxic and hazardous substances. Herein, we developed a portable self-powered photoelectrochemical (PEC) sensing platform for rapid detection of prostate-specific antigen (PSA, as a model disease-related protein) by integrating a self-powered photoelectric signal output system catalyzed with chemiluminescence-functionalized Au nanoparticles (AuNPs) and a phosphomolybdic acid (PMA)-based photochromic visualization platform. TiO2-g-C3N4-PMA photosensitive materials were first synthesized and functionalized on a sensor chip. The sensor consisted of filter paper modified with a photocatalytic material and a regional laser-etched FTO electrode as an alternative to a conventional PEC sensor with a glass-based electrode. The targeting system involved a monoclonal anti-PSA capture antibody-functionalized Fe3O4 magnetic bead (mAb1-MB) and a polyclonal anti-PSA antibody (pAb2)-N-(4-aminobutyl)-N-ethylisoluminol-AuNP (ABEI-AuNP). Based on the signal intensity of the chemiluminescent system, the photochromic device color changed from light yellow to heteropoly blue through the PMA photoelectric materials integrated into the electrode for visualization of the signal output. In addition, the electrical signal in the PEC system was amplified by a sandwich-type capacitor and readout on a handheld digital multimeter. Under optimum conditions, the sensor exhibited high sensitivity relative to PSA in the range of 0.01-50 ng mL-1 with a low detection limit of 6.25 pg mL-1. The flow-through chemiluminescence reactor with a semiautomatic injection device and magnetic separation was avoid of unstable light source intensity inherent in the chemiluminescence process. Therefore, our strategy provides a new horizon for point-of-care analysis and rapid cost-effective clinical diagnosis.

3D-Printable Nanocellulose-Based Functional Materials: Fundamentals and Applications.

Nanomaterials obtained from sustainable and natural sources have seen tremendous growth in recent times due to increasing interest in utilizing readily and widely available resources. Nanocellulose materials extracted from renewable biomasses hold great promise for increasing the sustainability of conventional materials in various applications owing to their biocompatibility, mechanical properties, ease of functionalization, and high abundance. Nanocellulose can be used to reinforce mechanical strength, impart antimicrobial activity, provide lighter, biodegradable, and more robust materials for packaging, and produce photochromic and electrochromic devices. While the fabrication and properties of nanocellulose are generally well established, their implementation in novel products and applications requires surface modification, assembly, and manufacturability to enable rapid tooling and scalable production. Additive manufacturing techniques such as 3D printing can improve functionality and enhance the ability to customize products while reducing fabrication time and wastage of materials. This review article provides an overview of nanocellulose as a sustainable material, covering the different properties, preparation methods, printability and strategies to functionalize nanocellulose into 3D-printed constructs. The applications of 3D-printed nanocellulose composites in food, environmental, and energy devices are outlined, and an overview of challenges and opportunities is provided.

Nano-3D-Printed Photochromic Micro-Objects.

Molecular photoswitches that can reversibly change color upon irradiation are promising materials for applications in molecular actuation and photoresponsive materials. However, the fabrication of photochromic devices is limited to conventional approaches such as mold casting and spin-coating, which cannot fabricate complex structures. Reported here is the first photoresist for direct laser writing of photochromic 3D micro-objects via two-photon polymerization. The integration of photochromism into thiol-ene photo-clickable resins enables rapid two-photon laser processing of highly complex microstructures and facile postmodification using a series of donor-acceptor Stenhouse adduct (DASA) photoswitches with different excitation wavelengths. The versatility of thiol-ene photo-click reactions allows fine-tuning of the network structure and physical properties as well as the type and concentration of DASA. When exposed to visible light, these microstructures exhibit excellent photoresponsiveness and undergo reversible color-changing via photoisomerization. It is demonstrated that the fluorescence variations of DASAs can be used as a reporter of photoswitching and thermal recovery, allowing the reading of DASA-containing sub-micrometric structures in 3D. This work delivers a new approach for custom microfabrication of 3D photochromic objects with molecularly engineered color and responsiveness.

Advances in Electrochemical Energy Devices Constructed with Tungsten Oxide-Based Nanomaterials.

Tungsten oxide-based materials have drawn huge attention for their versatile uses to construct various energy storage devices. Particularly, their electrochromic devices and optically-changing devices are intensively studied in terms of energy-saving. Furthermore, based on close connections in the forms of device structure and working mechanisms between these two main applications, bifunctional devices of tungsten oxide-based materials with energy storage and optical change came into our view, and when solar cells are integrated, multifunctional devices are accessible. In this article, we have reviewed the latest developments of tungsten oxide-based nanostructured materials in various kinds of applications, and our focus falls on their energy-related uses, especially supercapacitors, lithium ion batteries, electrochromic devices, and their bifunctional and multifunctional devices. Additionally, other applications such as photochromic devices, sensors, and photocatalysts of tungsten oxide-based materials have also been mentioned. We hope this article can shed light on the related applications of tungsten oxide-based materials and inspire new possibilities for further uses.

Rational design of the electrolyte systems for the photochromic device

A photochromic (PC) device, a simplified version of the photoelectrochromic (PEC) device without the transparent conducting oxide (TCO) layer, can modulate the intensity of transmitted light by automatically changing its transmittance. To effectively regulate the transmittance of sunlight, the PC device should possess a high optical contrast and reasonable transition time. However, these properties cannot be achieved simultaneously due to the competitive coloring and bleaching reactions. In this study, the effects of the concentration ratio of redox couples (tetramethylthiourea/tetramethylformaminium disulfide (TMTU/TMFDS2+)) and the concentration of lithium source on the performance of the PC device were systematically investigated. The results confirmed that the intrinsic limitation can be overcome by the rational design of the electrolyte system. The PC device containing an optimized TMTU/TMFDS2+ (0.05 M/0.1 M) redox couple and 1 M LiClO4 provided excellent coloration depth (~51% transmission change at 670 nm) and fast bleaching speed (80% recovery in under 1.5 h). In addition, long-term durability (>100 h) tests of the PC device revealed the high stability of the investigated electrolyte system. The in-depth discussion in combination with the experimental results provided in this work can pave the way for the future rational design of PC devices.