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Multi-stimuli responsive polycyclic aromatic hydrocarbons offer advantages of high selectivity, sensitivity, and versatility as they can integrate multiple inputs and outputs to achieve the desired applications in a flexible manner. In this context, carbazole and its derivatives have been extensively studied due to their tunability, outstanding electrochemical properties and good environmental stability. However, most of the studies used the polymeric forms of carbazole derivatives which requires energy-intensive synthesis. Recently, it has been reported that the self-assembled monolayers of carbazole derivatives offer more advantages over their polymeric forms in terms of stability and efficiency. Herein, we introduce a carbazole-based low molecular weight gelator achieved with synthetic ease, exhibiting a multi-stimuli response behaviour, i.e. sensing of cyanide ions and electrochromism, in its solution state. Further, the compound forms a gel in dioxane–H2O and DMF–H2O mixtures and exhibits aggregation-induced emission (AIE). The mechanistic pathways of sensing have been investigated and the limit of detection is found to be 1.25 nM, which is significantly lower than the permissible limit established by the WHO. Furthermore, possibilities of extending the electrochromism and sensing in the gel state using carbazole derivatives have been explored and the results indicate that low molecular weight carbazole derivatives are promising candidates for electrochromism and sensing applications. [ABSTRACT FROM AUTHOR]

Functional materials revealing mechanochromism behaviors are in high demand for potential applications. Here, we report a 1 : 1 cocrystal of naphtho[2,1-b]benzofuran (BNF) and 1,2,4,5-tetracyanobenzene (TCNB) that displayed a reversible crystal transition (of α- and β-forms) with a resulting change in emission color. The slight differences in cell dimensions, slipping angles between stacking columns, and TCNB orientation enabled this cocrystal to be a sensitive mechanochromic luminescent material. The α-form cocrystal showed significant bathochromic shifts upon being subjected to grinding or isotropic compression, and returned to the original state upon subsequently being subjected to a heating or fuming treatment. Based on detailed spectroscopic and structural analyses, the observed changes in luminescence were mainly attributed to the crystal having undergone a transformation at low pressure and then having formed an amorphous state as a result of damage to its structure. [ABSTRACT FROM AUTHOR]

Recently, great advances have been made in the mechanochromic luminescence (MCL) of organic crystals that can switch their emission colors upon exposure to mechanical stimuli. Although several polymorphic crystals and solvates have exhibited multicolor MCL properties, a further deep understanding of the relationship between crystal structures and stimuli-responsive properties is required for rationally generating multicolor-emissive polymorphic crystals and solvates from a single luminescent compound. Herein, multicolor luminescence switching has been achieved for solvates of a phenanthroimidazolylbenzothiadiazole derivative with dianisyl groups. Four types of solvates with different luminescence properties changed their emission colors upon amorphization induced by mechanical stimuli. The amorphous state was recrystallized into solvates when exposed to solvent vapors. Furthermore, the solvate containing pyridine molecules showed a bathochromic shift in emission wavelength upon exposure to acid vapor. Typical acid-responsive luminescence switching is characterized by the protonation of the basic moiety of luminescent molecules, whereas in this study, the change in luminescence color could be induced by protonating non-luminescent pyridine molecules in the solvate. The present study potentially provides useful insights for the development of smart luminescent sensors. [ABSTRACT FROM AUTHOR]

A carboxylic acid-containing terpyridine-based hydrogelator (TPPCA) is synthesized to afford a self-assembly induced TPPCA hydrogel, which was used as an all-in-one electrochrome in electrochromic devices (ECDs) to demonstrate reversible transparent-to-black electrochromism with fast darkening and bleaching time of 8.3 s and 9.5 s, respectively, high photopic coloration efficiency of 65.8 cm2 C−1 and high optical memory. The ECD also revealed bluish-white to quenched emission simultaneously under the −3.5 V to 0 V voltage range. [ABSTRACT FROM AUTHOR]

A W18O49/[PEI/P5W30]20 film modulated for visible and near infrared light was prepared by a layer-by-layer method on an FTO glass substrate, and had a significant coloration efficiency (149.78 cm2 C−1), fast response time (2.62 and 0.94 s at 650 nm, and 1.98 and 1.92 s at 1167 nm, respectively), and good cycling stability (500 cycles) in 0.5 M AlCl3 electrolyte. Furthermore, the W18O49/[PEI/P5W30]20 film was successfully assembled into an electrochromic device, which can realize color reversibility conversion under a small voltage. Overall, the experimental results showed that W18O49/[PEI/P5W30]20 film preparation allows the production of an electrochromic film for next-generation smart windows, which are able to evenly control the solar light and heat gain in buildings. [ABSTRACT FROM AUTHOR]

A W18O49/[PEI/P5W30]20 film modulated for visible and near infrared light was prepared by a layer-by-layer method on an FTO glass substrate, and had a significant coloration efficiency (149.78 cm2 C−1), fast response time (2.62 and 0.94 s at 650 nm, and 1.98 and 1.92 s at 1167 nm, respectively), and good cycling stability (500 cycles) in 0.5 M AlCl3 electrolyte. Furthermore, the W18O49/[PEI/P5W30]20 film was successfully assembled into an electrochromic device, which can realize color reversibility conversion under a small voltage. Overall, the experimental results showed that W18O49/[PEI/P5W30]20 film preparation allows the production of an electrochromic film for next-generation smart windows, which are able to evenly control the solar light and heat gain in buildings. [ABSTRACT FROM AUTHOR]

Viologen (V)-modified asymmetric zinc(II) phthalocyanines (ZnPcs) were synthesized. Redox mechanisms of ZnPcs were determined with electrochemical and in situ spectroelectrochemical measurements. While ZnPc--Br illustrated common Pc-based electron transfer reactions, ZnPc--V and ZnPc--MV gave viologen and methyl-viologen (MV)-based reduction couples in addition to the Pc-based processes. During the reduction of dicationic viologen groups, ZnPc--V and ZnPc--MV complexes were electrodeposited on the electrode surface with repetitive cyclic voltammetry. The reduction processes of the V and MV groups considerably influenced the in situ spectroelectrochemical responses of the complexes. The distinct spectral changes during the redox reactions of ZnPc--V and ZnPc--MV indicated their possible use in electrochromic applications. Thus, ZnPc--V and ZnPc--MV were electrodeposited on indium tin oxide-coated glass electrodes (ITO) and investigated as potential electrochromophores. The electrochromic responses of these complexes are completely different from those of viologens and MPcs reported in the literature. Electrochromic measurements of the complexes indicated fast and reversible color changes with reasonable optical contrasts between various colors. Also, viologen groups extended the reduction reactions and considerably influenced the color changes of the complexes. Optical changes in the cyan color and low transmittance in the visible region indicated the functionality of the complexes for the construction of private places for the absolute proprietary. Moreover, the complexes have functionality for color changes from cyan to purple and pink as the anodes for electrochromic devices. [ABSTRACT FROM AUTHOR]

A Zr-based metal organic framework with naphthalene diimide teracarboxylate linkers is reported for its dual electrochromic and photochromic behavior. MOF crystals display reversible yellow to green photochromism upon exposure to visible light and colourless to dark-brown reversible electrochromism on applying a potential of 0 to −2.5 V. The MOF thin film shows good colouration efficiency at 550 nm, which is the highest sensitivity of the human eye. [ABSTRACT FROM AUTHOR]

An intriguing case of intramolecular and intervalence charge transfer-driven multistate electrochromism and electrofluorochromism in dibenzophenazin-(phenyl)methanone and arylamine-based redox-active donor–acceptor–donor molecules was elucidated. Tunable absorption from UV to NIR and on–off switching of fluorescence in a single-component all-organic molecular material by a subtle variation of electric potentials were demonstrated. [ABSTRACT FROM AUTHOR]

Electrochromic energy storage devices (EESDs) can directly reflect the level of energy storage via color changes, and the exploration of high-performance electrode materials is an important means to develop these devices. In this study, we report a nanocomposite film, NW/P2W17/Fe(phen)3, based on Dawson-type monolacunary polyoxotungstate K10P2W17O61 (abbreviated as P2W17) and a transition metal complex, [FeII(phen)3](ClO4)2 [abbreviated as Fe(phen)3], formed on a TiO2 nanowire (abbreviated as NW) array substrate combining a facile hydrothermal process and a layer-by-layer self-assembly method. The existence of TiO2 nanowire substrates significantly increased the active area of the nanocomposite film and facilitated the diffusion of ions during the electrochemical process. As bi-functional electrodes, the NW/P2W17/Fe(phen)3 films successfully achieved bridging electrochromic behavior with energy storage, realizing the multi-color transition from orange-red to light blue-violet and then to dark blue-violet during the charging and discharging process, with superior electrochemical properties of large optical modulation (34.3% at 600 nm), fast switching time (tc = 2.8, tb = 6.2 s), high coloring efficiency (194.5 cm2 C−1 at 600 nm) and volumetric capacitance (135.8 F·cm−3 at 0.2 mA cm−2). The charged EESD constructed based on NW/P2W17/Fe(phen)3 can light up an LED, indicating the feasibility of practical application of polyoxometalates for electrochromic and energy storage. [ABSTRACT FROM AUTHOR]

A novel 0D organic–inorganic metal halide hybrid (C13H16N2O2)2InCl6·Cl (1) has been obtained by integrating the mono-viologen derivative with InCl3. Compound 1 exhibits reversible and ultrafast UV/sunlight/X-ray induced photochromic properties, as well as excellent electrochromic performance, which is the first example of an indium-based organic–inorganic chromic hybrid. [ABSTRACT FROM AUTHOR]

Luminescent materials with liquid-crystalline properties can form metastable structures and thus exhibit mechanochromic luminescence. Herein, we prepared a novel rod-like alkyltolane-terminated cyanostilbene luminophore, determined its solid structure, and investigated its mechanoresponsive photoluminescence. Although no mechanoresponsive behaviour was observed in the crystal state, the photoluminescence colour depended on the precipitation method, and a red or blue shift in the photoluminescence spectrum was observed upon mechanical grinding. This switch in mechanochromic luminescence behaviour was attributed to a change in the molecular packing of the metastable aggregated structure formed upon precipitation under different conditions. Given that materials exhibiting mechanochromic luminescence are expected to be broadly applicable as stimuli-responsive sensors, the obtained results facilitate the development of such sensors for a wide range of fields. [ABSTRACT FROM AUTHOR]

Herein, a Co(II)-based metallo-polymer (Co-tpy-L) with a three armed non-conjugated terpyridine ligand is synthesized using solvent–solvent interfacial polymerization. The thin film exhibits durable transmissive-to-blackish green electrochromism, selectively covering both the visible and NIR regions with a moderate voltage range of −1.4 to 0 V. [ABSTRACT FROM AUTHOR]

A new paddlewheel-type diruthenium complex with 2-amino-3-(trifluoromethyl)pyridine (amtfmp) [Ru2(amtfmp)4Cl2] ([1]), which shows intense and characteristic near-infrared (NIR) and visible absorption, has been developed and structurally characterized by single crystal X-ray diffraction (SCXRD) analyses. This complex exhibits reversible and dramatic NIR and visible electrochromic behavior from deep-blue ([1]) to pink ([1]−) due to the ON–OFF switching of its characteristic ligand-to-metal charge transfer (LMCT) and d–d absorption bands in response to an external voltage or chemical reagent such as decamethylcobaltocene (CoCp*2). The one-electron reduced species of [1], i.e., [CoCp*2][1], was successfully isolated and fully characterized via SCXRD, the temperature dependence of the magnetic susceptibility, and mass spectroscopy, proving that this electrochromic behavior occurs without significant structural reorganization of [1]. [ABSTRACT FROM AUTHOR]

Polyoxometalates (POMs) with their unique physical and electrochemical nature have been a promising class of electrochromic (EC) materials. Although extensive research has been conducted, much effort has been devoted to the enhancement of the EC properties. Among a variety of factors, the electrolytes exhibit great influences on the EC properties. In this paper, we fabricated a composite film based on nickel-substituted Dawson-type tungstophosphate (P2W17Ni) and TiO2 nanowires by a two-step process involving hydrothermal treatment and a layer-by-layer method (LbL). As a result, the composite film displays transparent to dark blue in both Li+-based non-aqueous and H+-based aqueous electrolytes. Compared to the H+-based electrolyte, the composite film in Li+-based media shows a larger optical modulation of 53.3% and higher coloration efficiency of 85.6 cm2 C−1. The fast switching times of 7.7 s for coloration and 2.2 s for bleaching in Li+-based solution are observed. In addition, the composite film remains almost stable even after 800 cycles in Li+-based solution. The enhancement of the EC properties may be due to the unique nanowire structure, high insolubility and applied potential in Li+-based solution. These results make POMs attractive candidates for EC devices in both non-aqueous and aqueous electrolytes. [ABSTRACT FROM AUTHOR]

CoII mediates electronic coupling between two N-Me-pyridinium-terpyridine ligands that are related to redox-active N,N-dialkyl-4,4′-bipyridinium dications (viologens). Borderline Class II/III electronic delocalization imparts the cobaltoviologen complex with distinct electronic properties (e.g., 7 accessible redox states) relative to those of viologens, leading to enhanced electrochromism. [ABSTRACT FROM AUTHOR]

Transmissive-to-colored electrochromism has been achieved by combination of MLCT of transition metal complexes with the electrochromic properties of ligand molecules. The color transitions were from yellow to dark brown for the Fe(II) complex, yellow to orange to bluish-green for the Co(II) complex and yellow to green for the Zn(II) complex. By using a metal ion−ligand coordination approach, the self-assembly of hydrazone-based ligands containing a triphenylamine group with appropriate metal salts (FeCl2, Co(ClO4)2 and Zn(BF4)2) produced novel complexes of the general formula [ML2]X2. The isolated complexes were characterized by spectroscopic methods, and the Co(II) complex also by X-ray diffraction analysis. Thin films of the complexes have been obtained by a spray-coating method and they were used in the construction of electrochromic devices, which showed good electrochromic stability, a high color contrast of 47.5% for Fe(II), 37.2% for Co(II) and 33.7% for Zn(II) complexes and fast coloring and bleaching times. [ABSTRACT FROM AUTHOR]

A novel viologen-based multifunctional Eu-MOF was obtained by integrating a luminescent component Eu(NO3)3·6H2O and a viologen-functionalized ligand. The Eu-MOF not only exhibited reversible photochromic and electrochromic properties, but also displayed photoluminescent and electroluminochromic properties. [ABSTRACT FROM AUTHOR]

Recent advances in the practical applications of metallophthalocyanines (MPcs) in different technological fields have stimulated us to design and synthesize a new asymmetric AB3-type trimeric zinc(II)-phthalocyanine (1). This bulky and high molecular weight compound was characterized by elemental analysis, 1H, 13C DEPT, and 1H-1H NOESY NMR, HR MALDI-TOF mass spectrometry, UV-vis, and FT-IR (ATR) techniques. In-depth electrochemical studies show that 1 displays quasi-reversible three one-electron reductions and two one- or two-electron oxidation processes, rather than any redox processes including the transfer of three-electrons in one-step. Besides this, in situ spectroelectrochemical measurements suggest the good application potential of 1 as an electrochromic material in display technologies. A study of the nonlinear optical properties (NLOs) of 1 reveals that the poly(methylmethacrylate) (PMMA) composite film displays a much larger nonlinear absorption coefficient and a lower saturable absorption threshold for optical limiting when compared to the same Pc molecules in solution. Ultrafast transient absorption measurements reveal the intersystem crossing mechanism. Density functional theory (DFT) was used for the geometry optimizations and time dependent-DFT (TD-DFT) for HOMO/LUMO energies and electronic transitions for 1. [ABSTRACT FROM AUTHOR]

A mixed valence Cs⊂{Fe4–Fe4} cyanido-cube was synthesized and structurally characterized. The molecule, which is robust in solution, shows remarkable electronic versatility. Electrochromic properties associated with nine different electronic states are observed in solution together with a thermo-induced spin-transition in the solid state. [ABSTRACT FROM AUTHOR]

Two barbituric acid derivatives CB-Ph and CB-Me were synthesized, both of which show a strong aggregation induced emission (AIE) effect. It was found that these two compounds show almost the same absorption and emission spectra. As a result, they show the same yellow color in daylight and the same yellow-green color under UV at 365 nm. Upon grinding, CB-Ph exhibits superior mechanochromic fluorescence (MCF) properties, with its fluorescence color from yellow-green (555 nm) to brown (580 nm) and its emission intensity decreases by 93%. However, neither the fluorescence peak wavelength nor the intensity of CB-Me shows observable changes after being ground, indicating no MCF effect. The X-ray diffraction (XRD) data indicate that the CB-Ph powder changes from the crystalline to amorphous state after being ground, whereas CB-Me remains in its crystalline state. Molecular dynamics simulation (MDS) shows that CB-Ph takes a 3D conformation due to three phenyl groups on the periphery of the molecule, which hinders the molecules from aggregating closely and results in the change of the microstructure by external force stimuli. However, CB-Me aggregated more closely due to its better planarity and hydrophobic n-hexane group, which make it difficult to change the microstructure upon being ground. Based on the unique optical properties of CB-Ph and CB-Me, a new data encryption–decryption technology is developed. CB-Ph is used as cryptographic ink due to its excellent MCF effect upon grinding. CB-Me is used as a camouflage material as it shows the same color as CB-Ph in the daylight and under UV-365 nm; furthermore, its colors remain unchanged after being ground. [ABSTRACT FROM AUTHOR]

A metal complex nanosheet was synthesized by the liquid–liquid interface self-assembly method from a star-shaped ligand of tris[4-(4′-2,2′:6′,2′′-terpyridyl)-phenyl]amine in organic solvents and metal ion Fe(II) in water solution. The as-prepared nanosheet possessed excessively smooth morphology with a thickness of hundreds of nanometers. Adhering to an ITO glass, the nanosheet showed noticeable electrochromism from purplish red at 0 V to orange-yellow at 1.4 V and green at 1.6 V. Besides, the nanosheet exhibited outstanding stability with the optical contrast maintained at almost 100% of its original electrochemical activity over 500 cycles. The liquid–liquid interface self-assembly method was proven to be promising to prepare a polymeric metal complex for potential electrochromic applications. [ABSTRACT FROM AUTHOR]

Two bilayer polymer films (pTPAT/pPHT and pPHT/pTPAT), derived from two star-shaped thiophene derivatives (TPAT and PHT) with central cores of triphenylamine and phenyl respectively, were successfully fabricated on ITO-glasses by electrochemical polymerization. The difference between the two bilayer polymer films pTPAT/pPHT and pPHT/pTPAT is just the layer configuration due to different sequential deposit orders of the pPHT and pTPAT layers during the electrochemical polymerization process. In the systems of bilayer films, the pPHT layer shows no electrochromism, a low HOMO level and a high impedance value, while the pTPAT layer shows obvious electrochromism, a high HOMO level and a low impedance value in contrast. The electrochromic properties showed that the optical contrast and cyclic stability of bilayer films are similar to those of the single pTPAT films, while the switching rate is relatively slower. Furthermore, in comparison with the pTPAT film, a higher ion-diffusion resistance was found in the bilayer film pTPAT/pPHT, and an obvious interface resistance was observed in the bilayer film pPHT/pTPAT. The existence of the pPHT layer in bilayer films may serve as a charge transport barrier and hinder the ion-diffusion or hole-injection process, depending on the layer structural arrangement in bilayer films. The investigation of the electrochromic properties of two bilayer films also provides unambiguous evidence for a fact that both ion-diffusion and charge-injection processes exerted great influences on the electrochromic switching rate of a polymer. [ABSTRACT FROM AUTHOR]

We demonstrated the electrochromism of photochromic radical complexes containing triaryl imidazole: fast photoswitchable pentaarylbiimidazole (PABI) and the phenoxyl–imidazolyl radical complex (PIC). Cyclic voltammetry and spectroelectrochemistry revealed that PABI and PIC generate the highly stable radical cation by one-electron oxidation accompanied by a color change from colorless to green. The stability of the radical cation is strongly affected by the dihedral angle between the imidazole ring and the phenyl ring at the 2-position of the imidazole ring. [ABSTRACT FROM AUTHOR]

In this work, a series of multifunctional polyurethane (PU) materials containing three kinds of different triarylamine (TAA) units was prepared. These polymers show good solubility in common organic solvents and excellent thermal stability under a N2 atmosphere. The PU films show reversible color changes with high contrast ratios and electrochromic stability. Moreover, they have good memory storage performance. The ON/OFF current ratio is about two orders of magnitude. Meanwhile, they can be used as detectors for 2,4,6-trinitrotoluene (TNT) and 2,4,6-trinitrophenol (TNP). The polymer solutions rapidly exhibit fluorescence-quenching phenomena when exposed to trace amounts of TNT and TNP. The PU films also have mechanical properties that make them suitable for use in stretchable devices. [ABSTRACT FROM AUTHOR]

Two triphenylamine derivatives, N,N,N′,N′-tetrakis(4-methoxyphenyl)-1,4-phenylenediamine TPPA and N,N,N′,N′-tetrakis(4-methoxyphenyl)-1,1′-biphenyl-4,4′-diamine TPB, were successfully prepared and combined with HV to fabricate the electrochromic device as a panchromatic shutter for the application of transparent display. The obtained electrochromic device exhibits exceptional novel electrochromic properties, including enhanced color contrast, switching time, and long-term stability. Furthermore, it is worth mentioning that the most important contribution of this ambipolar system approach is that no supporting electrolyte is added into the device. [ABSTRACT FROM AUTHOR]

Methods for in situ reversible control over ligand binding processes at transition metal complexes can enable advances in switchable and tunable catalysis. After a brief overview of different approaches to controlling ligand binding, this Perspective details the development of “pincer-crown ether” ligands that contain a rigid pincer backbone and a hemilabile aza-crown ether unit that enables cation-modulated hemilability. Applications of pincer-crown ether complexes in small molecule activation and catalysis are discussed, culminating in a set of design principles for ligands capable of cation-modulated ligand binding. [ABSTRACT FROM AUTHOR]

A ferrocene–viologen linked “bipolar” type redox-active ionic liquid ([FcC11VC1][TFSI]2) was synthesized as an electrochromic (EC) material that functions without any other additives: solvents, supporting electrolytes and sacrificial agents. The efficiency of a prototype symmetrical EC cell was 70 cm2 C−1 at 1.0 V. The EC process was stable even after over 10 000 potential cycles. [ABSTRACT FROM AUTHOR]

A micro-porous network thin film of core-tetrachlorinated perylene bisimide (PBI) was deposited by electrochemical polymerization, which showed reversible n-doping/dedoping processes at rather low potentials, accompanied by color changes from an orange red (neutral) state to a transparent (radical anion) state and further to an aquamarine (dianion) state. The film possesses preferable coloration efficiency and cycling stability (＞10 000 cycles). [ABSTRACT FROM AUTHOR]

The choice of the metal ion M and the terminal Y and donor X chalcogen species (M = Ni, Pt; and X, Y = S, Se) in square-planar complexes deriving from 1,3-dimethyl-2-chalcogenoxo-imidazoline-4,5-dichalcogenolates allows fine-tuning of both the redox stability and the energy of the particularly intense NIR electrochromic absorption, thanks to the subtle contribution of M, X, and Y to the relevant frontier molecular orbitals, investigated at the IEF-PCM DFT and TD-DFT level. [ABSTRACT FROM AUTHOR]

An aqueous suspension of WO3/poly(4-(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl-methoxy)-1-butanesulfonic acid) (PEDTS) hybrid nanoparticles (NPs) is prepared by air-assisted oxidative polymerization and simultaneous attachment of PEDTS on WO3-NPs, and used for electrochromic (EC) film fabrication via air-brush spraying. The hybrid EC device exhibits enhanced EC properties compared to the ones based on WO3-NP or PEDTS alone. [ABSTRACT FROM AUTHOR]

Tetraruthenium macrocycles with 1,4-divinylphenylene and diarylamine-substituted isophthalic acids as the sides display up to eight one-electron redox steps and rich electrochromic behaviour with strong absorptions of the dications in the near infrared and of the tetra- and hexacations at low energies in the visible. [ABSTRACT FROM AUTHOR]

In this study, we demonstrate the enhancement of the electrochromic performance of tungsten oxide (WO3) by crystal network topology modification. This is achieved by constructing various crystalline morphologies and patterns of the films. Different mesoscopic crystalline networks of WO3 were acquired on transparent conducting fluorine-doped tin oxide (FTO) by a crystal-seed-assisted hydrothermal process. The modification of the crystal network topology and crystal growth habit of WO3 films was achieved by adding different concentrations of oxalic acid and HCl, and controlling the growth time. The influence of the topological patterns on the corresponding electrochromic performance of WO3 films was examined by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and in situ reflectance spectroscopy. It follows that four different topological patterns of WO3 microstructures, namely random “rocks” of the seed layers, micro-urchin, small peony, and blooming peony were obtained by adding different concentrations of oxalic acid and hydrochloric acid. It is found that pH and oxalic acid are both the key modifying factors of the habit and topology of the crystal networks. Consequently, the urchin-like pattern gives rise to a high efficiency in optical modulation and coloration due to its similarity to micro-sized antennas, which may facilitate the emission and absorption of charged particles and electrochemical reactions at the WO3 surfaces. [ABSTRACT FROM AUTHOR]

WO3 nanostructures with various morphologies and crystallinity (such as cylinder-like WO3 nanorod arrays (WNRs-1), porous WO3 nanofibers, WO3 nanoflake arrays, sharp cone-like nanorod arrays (WNRs-2) and annealed cylinder-like WNRs-1) were prepared on FTO substrates by using a hydrothermal method without organic additives. The effects of morphology, size and crystallinity on the electrochromic properties of WO3 nanostructures were systematically investigated by scanning electron microscopy, X-ray diffraction, cyclic voltammetry and chronoamperometry. WNRs-1 exhibited excellent cyclic stability, wide optical modulation (64%), and relatively high coloration efficiency (61 cm2 C−1). Fast switching speeds of 5 s and 6 s for bleaching and coloration are achieved for WNRs-1 after annealing. Moreover, the relationship between the micro-morphologies/structures and electrochromic performance of WO3 nanostructures was also discussed. [ABSTRACT FROM AUTHOR]

Lactobacillus fermentum, a bacterium of human microbiota, acts as an electron donor for the electrochromic [P2MoVI18O62]6−. Since the reductive capacity of L. fermentum correlates with its metabolic activity, the reaction with [P2MoVI18O62]6− affords a means of evaluating its activity. Following this logic, we have concluded that vancomycin severely affects the activity of L. fermentum whereas omeprazole does not. [ABSTRACT FROM AUTHOR]

A vertically aligned hierarchical WO3 nanosheet array on a transparent conducting substrate is produced via a template-free and capping-agent-free hydrothermal method. Due to its high porosity among the nanosheets and good contact with the conductive substrate, the WO3 nanosheet film exhibits advantageous electrochemical abilities. For example, fast switching speed (5.2 and 2.2 s for coloration and bleaching, respectively), significant optical modulation (62% at 633 nm and 67% at 2000 nm), high coloration efficiency of 55.6 cm² C-1 at 700 nm and excellent cycling stability (95.4% after 3000 cycles) are achieved for the WO3 nanosheet array film in electrochromic application. In addition, the nanosheet film also shows outstanding electrocatalytic ability for chemical reduction of H2O2. [ABSTRACT FROM AUTHOR]

A p-extended tetrathiafulvalene-boradiazaindacene chimera, ex-TTFBODIPY, has been prepared. The resulting system undergoes sequential one-electron oxidations, allowing access to both the mono-oxidized radical cationic and dicationic states. Additionally, ex-TTF-BODIPY displays electrochromic and electrofluorochromic behaviour in the near-IR portion of the electromagnetic spectrum and functions as a redox switched ''on-off-on'' emissive system. [ABSTRACT FROM AUTHOR]

A series of conjugated azomethines end-capped with phenylamides and consisting of different aromatic cores of varying π-donor strength were prepared. Their optical and electrochemical properties were investigated to assess the suitability of the azomethines as electrochromic materials. The azomethines were found to undergo both electrochemical oxidation and reduction in the window of −1.60 and +1.35 V vs. Ag/Ag+. The color of the ambipolar compounds could be dramatically changed when switched between their reduced, neutral, and oxidized states. The color of the different states was contingent on the π-donor strength of the central aromatic unit. The largest spectral difference of 350 nm between the reduced and oxidized states was observed when the central aromatic group was 3,4-ethylenedioxythiophene (EDOT). The colors detectable by the eye for this EDOT derivative were blue, red, and bleached for the reduced, neutral, and oxidized states, respectively. The multichromatic azomethine was used as an electrochromic layer in a functioning device. The proof-of-concept ambipolar electrochromic device could be repeatedly switched between its orange (neutral) and purple (reduced) states. The device could also be switched to its oxidized (bleached) state. [ABSTRACT FROM AUTHOR]

Selective detection of cyanide anions is realized via electrofluorochromism of a benzothiadiazole-containing conjugated copolymer because oxidative fluorescence quenching induced by positive potentials can be significantly weakened by interaction between nucleophilic cyanide and electron-deficient benzothiadiazole. [ABSTRACT FROM AUTHOR]

By a facile curing reaction, novel electrochromic triarylamine-based thermosetting epoxy materials could be readily prepared for the first time. The resulting multielectrochromic epoxy materials exhibited good electrochemical stability and large optical changes in transmittance between their bleached and colored states with tunable intervalence charge transfer behavior. [ABSTRACT FROM AUTHOR]

Correction for 'Multi-color electrochromism from coordination nanosheets based on a terpyridine-Fe(II) complex' by Yu Kuai et al., Dalton Trans., 2019, DOI: 10.1039/c9dt02980j. [ABSTRACT FROM AUTHOR]