Luminescence Switching Behaviors Research Articles

Photoinduced Multimodal Motions and Reversible Fluorescence Switching in an Elasto‐Plastic Crystal

AbstractMulti‐stimuli‐responsive materials have received widespread attention in the field of adaptive materials due to their ability to adapt to changes in the environment. However, fabricating multiple stimuli into a single component crystal still remains challenging. In this study, a polymorphic elasto‐plastic Schiff‐based crystal displaying morphology‐dependent photomechanical motions is designed and investigated. Both Form I and Form II of it exhibit dual plasticity and elasto‐plasticity along different facets, which is attributed to the slidable separating layers. Moreover, Form I retains its elastic bending ability even after being plastically twisted, owing to the well‐maintained strong π–π interactions, whereas Form II can not twist without fractures. In addition, the photomechanical motions of Form I including jumping, twisting to bending are realized by adjusting the crystal morphologies, while Form II is lacking in response to ultraviolet light irradiation. Theoretical calculation analysis reveals that lattice deformation induced by photoisomerization of Form I is the driving forces for crystal motions. Furthermore, reversible luminescence switching behaviors are realized in Form I and Form II upon acid‐base fumigation as well as heating. The synergistic multi‐stimuli‐responsive mode based on heat, acid, and solvent stimuli provides an alternative path for multi‐mode information encryption.

Advanced Optical Information Encryption Enabled by Polychromatic and Stimuli-Responsive Luminescence of Sb-Doped Double Perovskites.

The smart materials with multi-color and stimuli-responsive luminescence are very promising for next generation of optical information encryption and anti-counterfeiting, but these materials are still scarce. Herein, a multi-level information encryption strategy is developed based on the polychromatic emission of Sb-doped double perovskite powders (SDPPs). Cs2NaInCl6:Sb, Cs2KInCl6:Sb, and Cs2AgInCl6:Sb synthesized through coprecipitation methods exhibit broadband emissions with bright blue, cyan, and orange colors, respectively. The information transmitted by specific SDPP is encrypted when different SDPPs are mixed. The confidential information can be decrypted by selecting the corresponding narrowband filter. Then, an encrypted quick response (QR) code with improved security is demonstrated based on this multi-channel selection strategy. Moreover, the three types of SDPPs exhibit three different water-triggered luminescence switching behaviors. The confidential information represented by Cs2NaInCl6:Sb can be erased/recovered through a simple water spray/drying. Whereas, the information collected from the green channel is permanently erased by moisture, which fundamentally avoids information leakage. Therefore, different encryption schemes can be designed to meet a variety of encryption requirements. The multicolor and stimuli-responsive luminescence greatly enrich the flexibility of optical information encryption, which leaps the level of security and confidentiality.

MnOx In Situ Growth-Induced Luminescence and Oxidase-Like Feature Bimodulation of CePO4:Tb Nanorods: Toward Ascorbic Acid-Related Bioanalysis in a "One-Stone-Two-Birds" Manner.

Nanozyme-based multimode detection is a useful means to improve the accuracy and stability of analytical methods. However, both multifunctional nanozymes and related multimodal sensing strategies are still very scarce. Besides, they require complex processes to fabricate and operate. To fill this gap, here we propose a spontaneous interfacial in situ growth strategy to prepare a new bifunctional material (CePO4:Tb@MnOx) featuring good oxidase-like activity and green photoluminescence for the dual-mode colorimetric/luminescence determination of ascorbic acid (AA)-related biomarkers specifically. CePO4:Tb@MnOx was gained through the controllable redox reaction between KMnO4 and CePO4:Tb nanorods. It was interestingly found that MnOx in situ growth not only significantly enhanced the enzyme-like activity but also could reversibly regulate the luminescence of CePO4:Tb via a dual quenching mechanism. More interestingly, CePO4:Tb@MnOx exhibited a distinctive response toward AA against other reducing species. A double-coordination regulation mechanism was further verified to clarify the catalytic activity and luminescence switching behaviors in CePO4:Tb@MnOx. Based on these findings, a dual-mode colorimetric/luminescence approach was established for AA sensing in a "one-stone-two-birds" manner, providing excellent selectivity, sensitivity, and practicability. Furthermore, the determination of AA-related biomarkers, including acid phosphatase activity and organophosphorus residue, was also validated by the sensing principle. Our work not only deepens the understanding of the coordinated regulation of the luminescence and enzyme-like features in lanthanide-based materials but also offers a novel way to design and develop multifunctional nanozymes for advanced bioanalytical applications.

Photocontrolled reversible modulation of lanthanide luminescence in mesoporous silica nanospheres by photochromic diarylethenes

The as-prepared SiO2@diarylethene/lanthanide complex hybrid material exhibits reversible luminescence switching behavior under alternating UV and visible light irradiation.

Photoresponsive Luminescence Switching of Metal‐Free Organic Phosphors Doped Polymer Matrices

AbstractA new type of luminescence switching behavior based on phosphorescence enhancement from a series of metal‐free organic phosphors doped polymers by UV‐irradiation is investigated. This phenomenon is observed only from pairs of organic phosphors and polymer matrices having a combination of appropriate triplet exciton lifetime and oxygen permeability. Systematic investigation reveals that the luminescence switching behavior of organic phosphors embedded in a specific polymeric matrix stems from the conversion of triplet oxygens to singlet oxygens by UV‐irradiation, leading to the unique phosphorescence enhancement of organic phosphors. Visualization of latent information by UV‐irradiation is demonstrated toward novel secure information communication applications.

Synthesis, structure and dual-stimulus-responsive luminescence switching of a new platinum(II) complex based on 3-trimethylsilylethynyl-1,10-phenanthroline

A new diimine-platinum(II) complex, Pt(PhenC≡CSiMe3)(C≡C-C6H4-3-F)2 (1) based on 3-trimethylsilylethynyl-1,10-phenanthroline (PhenC≡CSiMe3), was synthesized and characterized. Two solvated crystals, 1·1/2(ClCH2CH2Cl) and 1·CHCl3 exhibited dual-stimulus-responsive color and luminescence switching behaviors triggered by heating or mechanical grinding. Upon heating, the color and luminescence of both complexes were changed to red with luminescence red-shifting to 656 for 1·1/2(ClCH2CH2Cl) and 691 nm for 1·CHCl3, corresponding to the thermo-triggered luminescence red-shifts of 112–142 nm and 156–189 nm, respectively. The different heated samples confirm that the original stacking structure can accurately affect the luminescence switching properties of luminescent switching materials. Under the mechanical grinding, both complexes were converted to the same red amorphous product with red emission peaked at 702 nm. Interestingly, once exposure to ClCH2CH2Cl or CHCl3 vapor, the heated and ground samples could be thoroughly reverted to crystalline 1·1/2(ClCH2CH2Cl) and 1·CHCl3. Such reversible thermo- and mechanical-grinding-triggered luminescence switching properties of the complexes are attributed to the interconversions of the lowest energy excited states between metal-to-ligand charge transfer (MLCT) and metal-metal-to-ligand charge transfer (MMLCT) transitions during the heating/grinding-vapor absorbing processes. Furthermore, 1·CHCl3 was successfully used for rewritable data recording.

Facile and Equipment-Free Data Encryption and Decryption by Self-Encrypting Pt(II) Complex.

Luminescence switching materials are vital to various data security-related techniques, including data encryption-decryption. Here, we report a family of pseudopolymorphs based on a diimine-platinum(II) complex, Pt(Me3SiC≡CbpyC≡CSiMe3)(C≡CC6H4Br-3)2 (1), and systematically studied the influence of stacking modes on luminescence switching behaviors. Upon exposure to heat or tetrahydrofuran vapor, these pseudopolymorphs exhibit unusual stacking mode-intervened luminescence switching (SMILS) property that non-columnar and quasi-columnar pseudopolymorphs undergo single- and multi-step conversion processes, respectively, to the same non-columnar products. Systematic studies revealed that the unique SMILS behavior is caused by the existence of stable intermediate products as well as different conversion processes of pseudopolymorphs with distinct stacking modes. Such a new property leads to the self-encryption function of 1, which is very important for improving the existing data encryption-decryption technique. On this basis, we developed a facile, reusable, equipment-free technique with 1 as the only starting material and realized data encryption-decryption successfully.

Reversible luminescence switching and non-destructive optical readout behaviors of Sr3SnMO7: Eu3+ (M = Sn, Si, Ge, Ti, Zr, and Hf) driven by photochromism and tuned by partial cation substitution

Here, we report a series of Eu3+-doped Sr3SnMO7 (M = Sn, Si, Ge, Ti, Zr, or Hf) phosphors, which exhibited both photochromism and luminescence switching. Under alternating UV (254 nm) light irradiation and visible light/thermal stimulus, the obtained samples showed a reversible color change from the initial white color to brown. Based on photochromism and red luminescence, the red emission could be effectively modulated. Most interestingly, the Eu3+ red emission could be reversibly modulated by alternating UV and visible light/thermal treatment with excellent reproducibility, which can be used as non-destructive optical information write-in and read-out. In the case of the Sr3SnMO7 host, the band gap could be clearly changed from 3.64 to 4.41 eV through partial cation substitution, resulting in an evident effect on the photochromism and photoluminescence modulation performance. This provides a new method for tuning the photochromism and photoluminescence modulation properties. These results suggest that Sr3SnMO7:Eu3+ phosphors with photochromism and luminescence switching properties constitute a class of promising candidates for the development of optical data storage devices. On the basis of their luminescence modulation behavior, a model with non-radiative energy transfer from the luminescent centers to the color center was developed.

A hexa-quinoline based C3-symmetric chemosensor for dual sensing of zinc(ii) and PPi in an aqueous medium via chelation induced "OFF-ON-OFF" emission.

A quinoline-based C3-symmetric fluorescent probe (1), N,N',N''-((2,4,6-trimethylbenzene-1,3,5-triyl)tris(methylene))tris(1-(quinolin-2-yl)-N-(quinolin-2-ylmethyl)methanamine), has been developed which can selectively detect Zn2+ without the interference of Cd2+via significant enhancement in emission intensity (fluorescence "turn-ON") associated with distinct fluorescence colour changes and very low detection limits (35.60 × 10-9 M in acetonitrile and 29.45 × 10-8 M in 50% aqueous buffer (10 mM HEPES, pH = 7.4) acetonitrile media). Importantly, this sensor is operative with a broad pH window (pH 4-10). The sensing phenomenon has been duly studied through UV-vis, steady-state, and time-resolved fluorescence spectroscopic methods indicating 1 : 3 stoichiometric binding between 1 and Zn2+ which is further corroborated by 1H NMR studies. Density functional theoretical (DFT) calculations provide the optimized molecular geometry and properties of the zinc complex, 1[Zn(ClO4)]33+, which is proposed to be formed in acetonitrile. The results are in line with the solution-state experimental findings. The single crystal X-ray study provides the solid state structure of the trinuclear Zn2+ complex showing solubility in an aqueous buffer (10 mM HEPES, pH = 7.4). Finally, the resulting trinuclear Zn2+ complex has been utilized as a fluorescence "turn-OFF" sensor for the selective detection of pyrophosphate in a 70% aqueous buffer (10 mM HEPES, pH = 7.4) acetonitrile solvent with a nanomolar detection limit (45.37 × 10-9 M).

Up-conversion luminescence switching of (K0.5Na0.5)0.995Er0.005NbO3 ferroelectric ceramic based on photochromic reaction

Inorganic luminescence switching ferroelectrics based on photochromic reactions have great potential applications in optoelectronic devices. In this paper, (K0.5Na0.5)0.995Er0.005NbO3 ferroelectric ceramic is found to show a strong photochromic reaction by visible irradiation, and its color turns from initial milky white to gray. And up-conversion luminescence intensity can be greatly quenched by the light irradiation. The luminescence switching behavior upon photochromic reactions in (K0.5Na0.5)0.995Er0.005NbO3 ceramic as a function of irradiation wavelength and irradiation time has been investigated, and it is found that a high decrease of 79.47% is obtained after irradiation of 407-nm light for 4min. The color and up-conversion luminescence of the irradiated ceramic can recover to its initial state by a 200°C stimulus. However, the exciting 980-nm light has little effect on the up-conversion emission and photochromic reaction of the (K0.5Na0.5)0.995Er0.005NbO3 ceramic. These results demonstrate that the ceramic is promising in the applications such as luminescence switching and optical storage materials. In addition, the (K0.5Na0.5)0.995Er0.005NbO3 ceramic shows strong ferroelectric and piezoelectric properties.

Optically Switchable Luminescent Hydrogel by Synergistically Intercalating Photochromic Molecular Rotor into Inorganic Clay

Photomodulated luminescent hydrogels are of great potential for construction of functional soft materials. Herein a simple yet effective approach, by synergistically intercalating the dithienylethene‐bridged bispyridinium dye into the inorganic clay of Laponite, is proposed to immobilize the dye's molecular conformation and then to activate the hydrogel's fluorescence emission. The incorporation with dithienylethene unit can not only increase the π‐conjugation of organic dye but also endow the obtained supramolecular hydrogel with desirable photoswitchable capability. It can be envisioned that this organic–inorganic hybrid hydrogel featuring reversible luminescence switching behavior, high water content, good transparency, and mouldability may offer a practical strategy to create more advanced intelligent materials.

Cyclometalated Ir(iii) complexes based on 2-(2,4-difluorophenyl)-pyridine and 2,2'-(2-phenyl-1H-imidazole-4,5-diyl)dipyridine: acid/base-induced structural transformation and luminescence switching, and photocatalytic activity for hydrogen evolution.

Based on ligands dfppyH and pidpyH, cyclometalated Ir(iii) complexes [Ir(dfppy)2(pidpyH)](PF6) (1·PF6) and [Ir(dfppy)2(pidpy)] (2) have been synthesized. The crystal structures indicate that each {Ir(dfppy)2}+ unit is coordinated by a neutral ligand pidpyH in 1·PF6, while by a pidpy- anion in 2. The packing structure of 1·PF6 only exhibits electrostatic interactions and van der Waals interactions among [Ir(dfppy)2(pidpyH)]+ cations and PF6- ions. In contrast, the neighboring molecules in 2 are linked into a supramolecular chain structure through aromatic stacking interactions between two dfppy- ligands. In solution, 1·PF6 and 2 show acid/base-induced structural transformation due to the protonation/deprotonation of their pyridyl groups and/or imidazole units, which can be confirmed by their 1H NMR spectra. At room temperature, compounds 1·PF6, 2 and pidpyH in CH2Cl2 reveal TFA-induced luminescence switching behaviors, from a non-luminescence state to a luminescence state with an emission at 582 nm for both 1·PF6 and 2, and emission switching from 392 nm to 502 nm for pidpyH. These switching behaviors are associated with the protonation of pyridyl groups and/or imidazole units in 1·PF6, 2 and pidpyH. Moreover, compounds 1·PF6 and 2 were used as photosensitizers (PS) for reduction of water to hydrogen under the same experimental conditions. It was found that the amount of evolved hydrogen and the PS turnover number are 512 μmol and 102 for 1·PF6, and 131 μmol and 26 for 2, respectively. Thus, compound 1·PF6 has better photocatalytic activity than 2. In this paper, we discuss the modulation of luminescence and photocatalytic activities of 1·PF6 and 2 by varying the coordination mode and/or protonation extent of pidpyH/pidpy- ligands.

(K,Na)NbO3ferroelectrics: a new class of solid-state photochromic materials with reversible luminescence switching behavior

A kind of new photosensitive material, Sm doped K0.5Na0.5NbO3(KNN) ceramics, exhibits excellent photochromism and reversible luminescence switching properties.

First Orange Fluorescence Composite Film Based on Sm-Substituted Tungstophosphate and Its Electrofluorochromic Performance.

We chose a Sm-containing sandwich-type tungstophosphate K3Cs8[Sm(PW11O39)2]·10H2O (SmPW11) as a molecular dyad, which contains photoluminescence and electrochromism components in a skeletal structure, and investigated its electrofluorochromic performance both in solution and in composite films. First, the electrochemical activity and luminescence property of SmPW11 were studied in different pH solutions to determine the optimal pH solution medium; and then, the electrofluorochromic performance of SmPW11 was investigated under the optimized pH solution medium. Subsequently, the composite films containing SmPW11 were prepared on quartz substrates and conductive ITO substrates through a layer-by-layer (LbL) assembly method, using PDDA and PEI as molecular linkers. Characterization methods of the composite films include UV-vis spectra, fluorescence spectroscopy, cyclic voltammetry (CV), bulk electrolysis with coulometry, chronoamperometry, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). Finally, in situ UV-vis and fluorescence spectroelectrochemical systems were used to research electrofluorochromic properties for the composite films under electrochemical modulation. The results indicate that the composite films display not only orange luminescence emission but also reversible orange luminescence switching behaviors manipulated by the redox process of tungstophosphate species PW11 via the energy transfer between the orange luminescence component Sm and electroreduced species of tungstophosphate PW11.

Fabrication of white luminescence composite films containing Dy-polyoxometalate and the study of their luminescence switching behaviors.

White luminescence composite films containing Dy-polyoxometalate (Dy-POM) were firstly constructed by a layer-by-layer assembly method for the realization of electrically controlled luminescence switching. Additionally, blue-white luminescence could be switched by the choice of POM structural types and control of the concentration ratio of POM/Dy-POM in solution and composite films.

Reversible On–Off Luminescence Switching in Self-Healable Hydrogels

We present herein an easy way to prepare novel responsive hydrogels by simply doping lanthanide complexes into a polymer hydrogel, poly(2-acrylamido-2-methyl-1-propanesulfonicacid) (PAMPSA). The resulting hybrid hydrogels can be readily processed into a range of shapes. Both the on-off luminescence switching and the healable properties are simultaneously achieved in the resulting responsive hybrid hydrogels. They exhibit effectively self-healing performance without any external stimulus and reversible "on-off" luminescence switching triggered by exposure to acid-base vapor. The key to this on-off luminescence switching behavior is that the protonation of the organic ligands compete with full coordination to Ln(3+) and that incomplete coordination affects the luminescence yield. The high proton strength in the resulting hydrogels makes the doped lanthanide complexes unstable, and ammonia (or triethylamine) vapor can dramatically decrease the proton strength through neutralization, driving the full coordination of the ligand to Ln(3+).

Preparation of green luminescence composite film and study of electrofluorochromic performance

Abstract A novel hybrid consisting of 8-hydroxypyrene-1,3,6-trisulfonic acid trisodium salt (HOPTS) and graphene oxide (GO) was firstly synthesized as GO@HOPTS, which was confirmed to exhibit green luminescence emission. Then, GO@HOPTS and heteropolyanion NaP5W30O11014 − (P5W30) were utilized to fabricate the composite films {(PDDA/P5W30)5/[(PDDA/P5W30)5/PDDA/GO@HOPTS]15/(PDDA/P5W30)5} on quartz substrate and conductive ITO-coated glass electrode by the layer-by-layer (LBL) assembly deposition technique based on the electrostatic attraction of oppositely charged species. The composite films were characterized by cyclic voltammetry (CV), fluorescence spectroscopy, UV–vis spectroscopy and X-ray photoelectron spectroscopy (XPS). The electrofluorochromic performance of the composite film was investigated by in situ UV–vis spectroelectrochemical and fluorescence spectroelectrochemical measurements under electrochemical modulation. The results indicate that the composite film displays not only green luminescence emission but also reversible green luminescence switching behaviors manipulated by the redox process of P5W30 via the energy transfer between the green luminescence component HOPTS and electroreduced species of P5W30.

An effective combination of electrodeposition and layer-by-layer assembly to construct composite films with luminescence switching behavior.

This article presents a combination strategy of electrodeposition and a layer-by-layer assembly to fabricate functional composite films with luminescence switching behavior. Firstly, a novel green luminescence film consisting of 8-hydroxypyrene-1,3,6-trisulfonic acid trisodium salt (HOPTS) was first obtained on ITO by a facile electrodeposition method. Then, the multilayer films containing different layers of tungstophosphate K12.5Na1.5[NaP5W30O110]·15H2O (P5W30) were further fabricated on the green luminescence film to form the composite films [(HOPTS)50/(PDDA/P5W30)n] (n = 10, film 1; n = 27, film 2; n = 57, film 3). Cyclic voltammetry and fluorescence spectroscopy were used to characterize the electrochemical activity of P5W30 and the luminescence property of HOPTS in the composite films, respectively. Lastly, in situ UV-Vis spectroelectrochemical and fluorescence spectroelectrochemical measurements were applied to investigate the luminescence switching behaviors of the composite films controlled by the electrochromism component of P5W30 upon electrochemical modulation. In summary, the investigation results revealed that the electrodeposition method is convenient and rapid, and thus-prepared composite films showed improved luminescence switching performance in terms of switching process, activation cycles, coloration efficiency, and bleached-state transparency as well as good stability, wide voltage range and good reversibility. Therefore, the present study offers a new fabrication route for the multifunctional composite films through an effective combination of electrodeposition and layer-by-layer assembly technique.

Study on effects of tungstophosphate structures on electrochemically induced luminescence switching behaviors of the composite films consisting of tris(1,10-phenanthroline) ruthenium

A series of composite films consisting of different tungstophosphates were fabricated and their electrochemically induced fluorescence switchable behaviors were investigated.

Ce3+-Sensitized GdPO4:Tb3+ Nanorods: An Investigation on Energy Transfer, Luminescence Switching, and Quantum Yield

Herein we report the enhanced green emission from Tb3+-doped GdPO4 nanorods sensitized with Ce3+. The increase in the rate of nonradiative transition processes in sensitizer due to efficient energy transfer to activator is realized from steady-state and dynamic luminescence studies. Luminescence quenching due to cross relaxation is least significant up to 20 at. % Ce3+ and 7 at. % Tb3+ concentration. The quantum yield of the sample with maximum luminescence, i.e., GdPO4:Tb3+ (5 at. %)/Ce3+ (7 at. %), is found to be 28%. Also, samples are readily redispersible in water and could be easily incorporated in polymer-based films that show strong green light emission under UV excitation. The luminescence switching (ON and OFF) behavior is examined using alternately an oxidizing agent (KMnO4) and then a reducing agent (ascorbic acid) through a redox reaction (Ce3+/Ce4+). Both GdPO4:Tb3+ and GdPO4:Tb3+/Ce3+ are observed to be paramagnetic.