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Constructing 3D skeletons modified with lithiophilic seeds has proven effective in achieving dendrite-free lithium metal anodes. However, these lithiophilic seeds are mostly alloy- or conversion-type materials, and they tend to aggregate and redistribute during cycling, resulting in the failure of regulating Li deposition. Herein, we address this crucial but long-neglected issue by using intercalation-type lithiophilic seeds, which enable antiaggregation owing to their negligible volume expansion and high electrochemical stability against Li. To exemplify this, a 3D carbon-based host is built, in which ultrafine TiO

Similarities in sizes, shapes, and physical properties between carbon dioxide (CO 2 ) and acetylene (C 2 H 2 ) make it a great challenge to separate the major impurity CO 2 from products in C 2 H 2 production. The use of porous materials is an appealing path to replace current very costly and energy-consuming technologies, such as solvent extraction and cryogenic distillation; however, high CO 2 /C 2 H 2 uptake ratio with minor adsorption of C 2 H 2 at standard pressure was only unexpectedly observed in scarce examples in recent years although the related research started early at 1950s, and general design strategies to realize this aim are still absent. This work has successfully developed an efficient PIET strategy and obtained the second highest CO 2 /C 2 H 2 adsorption ratio for porous materials in a proof-of-concept MOF with a photochromism-active bipyridinium zwitterion. An unprecedented photocontrollable gate effect, owing to change of interannular dihedral after photoinduced generation of radical species, was also observed for the first time. These findings will inspire design and synthesis of porous materials for high efficient gas adsorption and separation.

Charge-separated states with a lifetime scale of seconds or longer not only favor studies using various steady-state analysis techniques but are important for light-energy conversion and other applications. Through a steric-hindrance-induced method, unprecedented photoinduced generation of a partially charge separated (PCS) state with a lifetime of days has been detected in the "visual" mode during the decay of excited states to a commonly observed fully charge separated (FCS) state for viologen analogues. One pale yellow 4,4'-bipyridine-based metalloviologen compound, with an interannular dihedral angle of 1.84° in 4,4'-bipyridine, directly decays to the purple FCS state after photoexcitation. The other pale yellow compound, with a similar coordination framework but a larger interannular dihedral angle (33.74°), changes first to a yellow PCS state and then relaxes slowly (in the dark in Ar, ca. 2 days; 70 °C in Ar, ca. 1 h) to the purple FCS state. The two-step coloration phenomenon is unprecedented for viologen compounds and their analogues and also rather rare for other photochromic species. EPR and Raman data reveal that photoinduced charge separation first generates univalent zinc and radicals and then the received electron in Zn(I) slowly distributes further to 4,4'-bipyridine. Reduction of π-conjugation and a direct to indirect change in band gap account for the prolongation of the relaxation process and the capture of the PCS state. These findings help to understand and control decay processes of excited states and provide a potential design strategy for multicolor photochromism, light-energy conversion with high efficiency, or other applications.

By increasing contact between pre-existing paramagnetic centers and photoinduced radicals, a photochromic single-molecule magnet with large magnetization change (+20.9%) at room temperature and paramagnetic to ferromagnetic transition was successfully achieved. The increasing amplitude of magnetization was the largest among the radical-based photomagnetic systems.

Air-stability is one of the most important considerations for the practical application of electrode materials in energy-harvesting/storage devices, ranging from solar cells to rechargeable batteries. The promising P2-layered sodium transition metal oxides (P2-NaxTmO2) often suffer from structural/chemical transformations when contacted with moist air. However, these elaborate transitions and the evaluation rules towards air-stable P2-NaxTmO2 have not yet been clearly elucidated. Herein, taking P2-Na0.67MnO2 and P2-Na0.67Ni0.33Mn0.67O2 as key examples, we unveil the comprehensive structural/chemical degradation mechanisms of P2-NaxTmO2 in different ambient atmospheres by using various microscopic/spectroscopic characterizations and first-principle calculations. The extent of bulk structural/chemical transformation of P2-NaxTmO2 is determined by the amount of extracted Na+, which is mainly compensated by Na+/H+ exchange. By expanding our study to a series of Mn-based oxides, we reveal that the air-stability of P2-NaxTmO2 is highly related to their oxidation features in the first charge process and further propose a practical evaluating rule associated with redox couples for air-stable NaxTmO2 cathodes., Air-stability is a critical challenge faced by layered sodium transition metal oxide cathodes. Here, the authors depict a general and in-depth model of the structural/chemical evolution of P2-type layered oxides in air and propose an evaluation rule for the air-stability of layered sodium cathodes.

We report an atomic structure and property tailoring method that enables precise control of the diameter of individual double-walled carbon nanotubes (DWNTs), as well as the corresponding tuning of their tensile strength and electrical resistance. As demonstrated in a transmission electron microscope (TEM), this facile method involves the electron irradiation of DWNTs, followed by a thermal annealing process. The former process is responsible for the random atom loss and tube size reduction, whereas the latter allows for a complete structural recovery of defective nanotubes. The regarded DWNTs thus experience repeated disorder-order structural transitions, leading to the stepwise shrinkage in tube size, until the desired diameter is reached. Accordingly, these disorder-order transitions allow individual DWNTs to be controllably weakened and then strengthened, accompanied with the reversible changes in their breaking modes, as revealed by direct in-situ tensile tests. Differently, the resistance tuning of DWNTs upon irradiation/annealing does not follow the same trend, but depends significantly on the initial tube electrical characteristics and subsequent chirality transitions. These experimental results, combined with first-principles calculations, suggest that the change of tube chirality involved in the disorder-order transitions profoundly influences DWNT transport properties, but has a little impact on their mechanical strength.

Extending photoresponse ranges of semiconductors to the entire ultraviolet–visible (UV)–shortwave near-infrared (SWIR) region (ca. 200–3000 nm) is highly desirable to reduce complexity and cost of photodetectors or to promote power conversion efficiency of solar cells. The observed up limit of photoresponse for organic-based semiconductors is about 1800 nm, far from covering the UV–SWIR region. Here we develop a cyanide-bridged layer-directed intercalation approach and obtain a series of two viologen-based 2D semiconductors with multispectral photoresponse. In these compounds, infinitely π-stacked redox-active N-methyl bipyridinium cations with near-planar structures are sandwiched by cyanide-bridged MnII–FeIII or ZnII–FeIII layers. Radical–π interactions among the infinitely π-stacked N-methyl bipyridinium components favor the extension of absorption range. Both semiconductors show light/thermo-induced color change with the formation of stable radicals. They have intrinsic photocurrent response in the range of at least 355–2400 nm, which exceeds all reported values for known single-component organic-based semiconductors., Developing new materials with broadband photoresponse is highly desirable for realizing commercial photodetectors with extended detection ranges. Here, the authors report a cyanide-bridged layer-directed intercalation approach to design viologen compounds with enhanced broadband photoresponse.

Solid electrolytes hold the promise for enabling high-performance lithium (Li) metal batteries, but suffer from Li-filament penetration issues. The mechanism of this rate-dependent failure, especially the impact of the electrochemo-mechanical attack from Li deposition, remains elusive. Herein, we reveal the Li deposition dynamics and associated failure mechanism of solid electrolyte by visualizing the Li|Li7La3Zr2O12 (LLZO) interface evolution via in situ transmission electron microscopy (TEM). Under a strong mechanical constraint and low charging rate, the Li-deposition-induced stress enables the single-crystal Li to laterally expand on LLZO. However, upon Li “eruption”, the rapidly built-up local stress, reaching at least GPa level, can even crack single-crystal LLZO particles without apparent defects. In comparison, Li vertical growth by weakening the mechanical constraint can boost the local current density up to A·cm−2 level without damaging LLZO. Our results demonstrate that the crack initiation at the Li|LLZO interface depends strongly on not only the local current density but also the way and efficiency of mass/stress release. Finally, potential strategies enabling fast Li transport and stress relaxation at the interface are proposed for promoting the rate capability of solid electrolytes.

2,4,6-Tri(4-pyridyl)-1,3,5-triazine (tpt) is a widely used ligand for functional coordination compounds. In this work, tpt has shown unprecedented photochromism in the crystalline state. Experimental and theoretical data has revealed that the photocoloration of tpt very likely originates from intramolecular charge separation and the formation of a triplet diradical product. This finding demonstrates a new simple, neutral photochromic molecule and endows the tpt molecule and related compounds with potential optical applications.

Because of good planarity and a high degree of conjugation, two electron-transfer photochromic model compounds based on phenanthroline were rationally designed and synthesized. The result shows tha...

Photochromic and photoswitchable magnetic (photomagnetic) properties of spin-crossover (SCO) metal complexes in the solid state were observed almost at cryogenic temperature. Here we present a new crystalline complex [FeII(TMPT)6](ClO4)8 (TMPT = 1-(1,2,4-triazol-4-yl)-2,4,6-trimethyl-pyridinium) showing photochromism and reversible hysteresis shift, with one direction being triggered by thermal annealing and the other by irradiation at room temperature. IR/Raman and single-crystal X-ray diffraction data revealed that these behaviors are very probably induced by thermal disorder of ClO4– anions, which change intermolecular interactions and the ligand field strength of the FeII center. This discovery may inspire the design and synthesis of new photochromic and photomagnetic compounds through controlling structural disorder.

Breaking the intrinsic rule of semiconductors that conductivity increases with increase of temperature and realizing a dramatic dropping of conductivity at high temperature may arouse new intriguing applications, such as circuit overload or over-temperature protecting. This goal has now been achieved through T-type electron-transfer photochromism of one organic semiconductor assembled by intermolecular cation⋅⋅⋅π interactions. Conductivity of the viologen-based model semiconductor (H2 bipy)(Hox)2 (H2 bipy=4,4'-bipyridin-1,1'-dium; ox=oxalate) increased by 2 orders of magnitude after photoinduced electron transfer (a record for photoswitchable organic semiconductors) and generation of radical cation⋅⋅⋅π interactions, and fell by approximately 81 % at 100 °C through reverse electron transfer and degeneration of the radical cation⋅⋅⋅π interactions. The model semiconductor has at least two different electron transfer pathways in the decoloration process.

Layered transition metal oxides are the most important cathode materials for Li/Na/K ion batteries. Suppressing undesirable phase transformations during charge-discharge processes is a critical and fundamental challenge towards the rational design of high-performance layered oxide cathodes. Here we report a shale-like NaxMnO2 (S-NMO) electrode that is derived from a simple but effective water-mediated strategy. This strategy expands the Na+ layer spacings of P2-type Na0.67MnO2 and transforms the particles into accordion-like morphology. Therefore, the S-NMO electrode exhibits improved Na+ mobility and near-zero-strain property during charge-discharge processes, which leads to outstanding rate capability (100 mAh g−1 at the operation time of 6 min) and cycling stability (>3000 cycles). In addition, the water-mediated strategy is feasible to other layered sodium oxides and the obtained S-NMO electrode has an excellent tolerance to humidity. This work demonstrates that engineering the spacings of alkali-metal layer is an effective strategy to stabilize the structure of layered transition metal oxides., Suppressing phase transitions is crucial for the layered lithium/sodium transition metal oxide cathodes in batteries. Here, the authors report a water-mediated strategy to mitigate the phase transitions and boost electrochemical performances of manganese-based layered cathodes for cost-effective Na-ion batteries.

A new design strategy through the synergy of Mo(VI)–Mo(V) intervalence charge transfer and π(radical)–π(radical/cation) interactions is proposed to obtain semiconductors with photoresponsive ranges covering the whole UV–SWIR (ultraviolet–shortwave near-infrared; ca. 250–3000 nm) region. With this strategy, a viologen-based molybdate semiconductor with a UV–SWIR photoresponsive range was obtained through UV/X-ray irradiation or thermal annealing. The thermally annealed semiconductor has the highest conversion and the best photocurrent response in the range of 355–2400 nm.

Metallic bismuth has drawn attention as a promising alloying anode for advanced potassium ion batteries (PIBs). However, serious volume expansion/electrode pulverization and sluggish kinetics always lead to its inferior cycling and rate properties for practical applications. Therefore, advanced Bi-based anodes via structural/compositional optimization and sur-/interface design are needed. Herein, we develop a bottom-up avenue to fabricate nanoscale Bi encapsulated in a 3D N-doped carbon nanocages (Bi@N-CNCs) framework with a void space by using a novel Bi-based metal-organic framework as the precursor. With elaborate regulation in annealing temperatures, the optimized Bi@N-CNCs electrode exhibits large reversible capacities and long-duration cyclic stability at high rates when evaluated as competitive anodes for PIBs. Insights into the intrinsic K+ -storage processes of the Bi@N-CNCs anode are put forward from comprehensive in situ characterizations.

Photoinduced generation of stable radicals is important for photochromism, photoswitching and other applications, but was limited only to a few systems. An unprecedented series of triazole-based donor–acceptor organic molecules were found to form heat/air-stable triplet diradicals in the solid state and show a clear color change through photoinduced intramolecular charge separation, which was confirmed by electron spin resonance studies, ultrafast laser flash photolysis analyses and density functional theoretical calculations. In these molecules, electron-withdrawing substituents were more beneficial to the photoinduced charge separation than electron-donating ones. Moreover, a high molecular dipole moment was more conducive to photoinduced charge separation in the presence of an electron-withdrawing substituent.

Photoinduced electron transfer (PET) with the formation of stable radicals plays an important role in many areas. In this work, PET and color change of two sulfone-based donor–acceptor molecules were observed for the first time in the solid state. Generation of radicals was confirmed by experimental and theoretical data. The radicals could be stable in the air and at high temperature (e.g. 105 °C) in the solid state. Introducing an electron-donating substituent (such as –NH2) increases the molecular dipole moment and promotes the PET process. Sulfone-based molecules observed in this work and their analogs may be applied in several potential applications such as photoswitching, photochromism, energy conversion, and photocatalysis.

Irradiation with energetic particles has been recently demonstrated as an effective means to tailor the structures of a variety of materials with high precision, which, however, usually leading to irreversible degradation of the related properties due to defect introduction. Herein, we present a highly controllable defect handling approach, i.e. defect creation followed by their elimination in carbon nanotubes (CNTs). Technically, this can be accomplished by the alternate use of room-temperature electron irradiation and a separated heat treatment, as demonstrated here via in-situ transmission electron microscopy. The regarded CNTs thus undergo the order/disorder structural transition, which can be repeated up to at least 10 cycles with the CNT structural integrity largely retained. A temperature-dependent annealing experiment shows that the CNT recrystallization can be initiated at a surprisingly low temperature of ∼300 °C, and the irradiated CNTs can primarily regain their structural perfectness over 1000 °C. This technique allows for the reversible and repeatable tuning of a number of important CNT electrical properties, such as electron transport, as well as electron field emission that has never been achieved before. Furthermore, this defect handling technique has the potential as a general route for reversible tuning of other defect-dependent properties of sp2 carbon nanosystems.

Broad absorption, long-lived photogenerated carriers, high conductance, and high stability are all required for a light absorber toward its real application on solar cells. Inorganic-organic hybrid lead-halide materials have shown tremendous potential for applications in solar cells. This work offers a new design strategy to improve the absorption range, conductance, photoconductance, and stability of these materials. We synthesized a new photochromic lead-chloride semiconductor by incorporating a photoactive viologen zwitterion into a lead-chloride system in the coordinating mode. This semiconductor has a novel inorganic-organic hybrid structure, where 1-D semiconducting inorganic lead-chloride nanoribbons covalently bond to 1-D semiconducting organic π-aggregates. It shows high stability against light, heat, and moisture. After photoinduced electron transfer (PIET), it yields a long-lived charge-separated state with a broad absorption band covering the 200-900 nm region while increasing its conductance and photoconductance. This work is the first to modify the photoconductance of semiconductors by PIET. The observed increasing times of conductivity reached 3 orders of magnitude, which represents a record for photoswitchable semiconductors. The increasing photocurrent comes mainly from the semiconducting organic π-aggregates, which indicates a chance to improve the photocurrent by modifying the organic component. These findings contribute to the exploration of light absorbers for solar cells.

Viologen (N,N′-disubstituted bipyridinium) compounds are well known for their electron-transfer photochromic properties and many potential applications. However, viologen-based organic molecules, especially those with aliphatic hydrocarbon substituents, are inclined to be hygroscopic, and most of the known viologen compounds need dozens of seconds or even several minutes to exhibit photoinduced color change. The viologen–carboxylate zwitterion ligand, N,N′-dipropionate-4,4′-bipyridinium (L), is highly hygroscopic and its shortest coloration time is 5 s upon irradiation of a Xe lamp (ca. 110 mW cm−2). After coordination with ZnCl2, the obtained new compound [Zn2LCl4]n (ZnLCl) is highly stable in a wet environment (e.g. 60% relative humidity), and its shortest coloration time is 1 s upon irradiation of the same Xe lamp. X-ray diffraction analysis coupling with multiple experimental spectra (UV-vis, ESR, XPS, and IR) and density of states (DOS) calculations revealed that the photoinduced coloration of L and ZnLCl is contributed mainly by O → pyridinium and Cl → pyridinium electron transfer, respectively. The lower electronegativity of Cl over O and the shorter donor–acceptor separation may explain why ZnLCl has a shorter coloration time. Moreover, enhancement of molecular rigidity by the coordination structure may account for the improvement of moisture stability.

Full exploitation of graphene's superior properties requires the ability to precisely control its morphology and edge structures. We present such a structure-tailoring approach via controlled atom removal from graphene edges. With the use of a graphitic-carbon-capped tungsten nanoelectrode as a noncontact "milling" tool in a transmission electron microscope, graphene edge atoms approached by the tool tip are locally evaporated, thus allowing a freestanding graphene sheet to be tailored with high precision and flexibility. A threshold for the tip voltage of 3.6 ± 0.4 V, independent of polarity, is found to be the determining factor that triggers the controlled etching process. The dominant mechanisms involve weakening of carbon-carbon bonds through the interband excitation induced by tunneling electrons, assisted with a resistive-heating effect enhanced by high electric field, as elaborated by first-principles calculations. In addition to the precise shape and size control, this tip-based method enables fabrication of graphene edges with specific chiralities, such as "armchair" or "zigzag" types. The as-obtained edges can be further "polished" to become entirely atomically smooth via edge evaporation/reconstruction induced by in situ TEM Joule annealing. We finally demonstrate the potential of this technique for practical uses through creating a graphene-based point electron source, whose field emission characteristics can effectively be tuned via modifying its geometry.

Changing N-substituents to modify energy gaps is important for the diverse applications (photochromism, photocatalysis, etc.) of viologen-based compounds. In situ N-substitution using alcohols under solvothermal and acidic conditions is an effective and common synthetic method for viologen-templated metal halides. In this work, we found that replacing alcohols with alkenes could reduce the reaction temperature dramatically to room temperature. A new cis/trans-viologen-templated bromoplumbate with a novel 1-D chain structure built by edge-sharing planar [Pb3Br9]3− oligomers was successfully obtained. This bromoplumbate hybrid has a narrower energy gap compared with bulk PbBr2, which has been well explained by linear optical response spectra calculations and PDOS analysis.

Nonlinear optical (NLO) switchable materials are important for photonic and optoelectronic technologies. One important issue for NLO photoswitching, the most studied physical switching approach, is how to improve the switching contrast of second harmonic generation (SHG) in crystals, because the known values are generally below 3 times. Thermoswitching, as another approach, has shown impressive high SHG-switching contrasts (4–∞ times), but the fast decay of thermally induced states demands constant heat sources to maintain specific SHG intensities. We have synthesized a photochromic and thermochromic bistable acentric compound, β-[(MQ)ZnCl3] (MQ+ = N-methyl-4,4′-bipyridinium), which represents the first crystalline compound with both photo- and heat-induced SHG-switching behavior and the first example of a thermoswitchable NLO crystal that can maintain its expected second-order NLO intensity without any heat source. The SHG-switching contrast can reach about 8 times after laser irradiation or 2 times after thermal annealing. The former value is the highest recorded for photoswitchable NLO crystals. This work also indicates that higher SHG-switching contrasts may be obtained through increasing electron-transfer efficiency, variation of permanent dipole moment, and self-absorption.

Electron-transfer (redox) thermochromism was successfully used for switching the conductance of semiconductors, by introducing a thermally active organic component into an inorganic semiconducting framework. A moisture-resistant semiconductor {(MV)2[Pb7Br18]}n (MV2+=methyl viologen cation) has been prepared through an in situ synthetic method for MV2+. It features a rare 3D haloplumbate open framework and unprecedented electron-transfer thermochromic behavior in haloplumbates. The electrical conductivity of this compound dropped significantly after coloration and restored after decoloration, which was satisfactorily explained by valence band XPS and theoretical data. This work not only offers a new approach to modify electrical properties of semiconductors without altering components or structures, but may lead to the development of over-temperature color indicators, circuit overload protectors or photovoltaic materials.

The past years have evidenced the rapid development of photochromic coordination compounds; however, the impact of coordination on the photochromic behavior of organic dyes has never been explored in the pyridinium derivative photochromic system. In this work, two new coordination compounds with a photoactive pyridinium-based inner salt, [Zn(H2O)6](PTA)·(CEbpy)2·2H2O (1, PTA = terephthalate, CEbpy = 1-carboxyethyl-4,4′-bipyridine) and [Zn(H2O)2(CEbpy)2]nBr2n·[Zn(H2O)4(PTA)]n (2), were selected as model compounds for this purpose. Compound 1 features an isolated structure, where uncoordinated photoactive CEbpy ligands connect to hexahydrated zinc ions through hydrogen bonds. Compound 2 features a 1-D chain structure with CEbpy ligands coordinating to zinc ions. Compound 1 shows faster coloration speed upon irradiation than 2, demonstrating that coordination of the electron donor in CEbpy is not in favor of photochromic behavior. Both compounds show significant photoluminescence quenching after coloration, ...

A new metal–organic framework with excellent water stability, {H[(N(CH3)4)2][Gd3(NIPA)6]}·3H2O (1, H2NIPA = 5-nitroisophthalic acid), displays a proton conductivity of 7.17 × 10−2 S cm−1 (at 75 °C and 98% relative humidity), which is among the highest values for proton-conducting MOFs.

Lanthanide(III) ion (Ln(III)) sensing has become a major research area owing to its intriguing prospect in clinic, biology, and environmental studies. However, the existing methods have limitations like requirement of expensive instrumentation, long analytical times, and sample pretreatments, revealing the necessity of other methods. In this work, by using N-methyl-4-pyridinium tetrazolate (mptz) zwitterion as an electron acceptor, we obtained several new Ln(III) compounds with electron-transfer (ET) photochromic properties: [Ln(NO3)3(H2O)4]·mptz [Ln = Sm (1), Eu (2), Gd (3), La (4), Ce (5), Pr (6), Nd (7), Tb (8), Dy (9), Ho (10), Er (11), Tm (12), Yb (13), Lu (14)]. Notably, different Ln(III) ions in these compounds can be visually identified by their different photoinduced color changes related to the ET process. This work may not only contribute to the more understanding of the structure–photosensitivity relationships of pyridinium-based compounds, but also provide a new approach for Ln(III) ion sensing.

One of the crucial challenges for applying Sn as an anode of lithium-ion batteries (LIBs) is the dramatic volume change during lithiation/delithiation process, which causes a rapid capacity fading and then deteriorated battery performance. To address this issue, herein, we report the design and fabrication of Sn encapsulated carbon nanoboxes (denoted as Sn@C) with yolk@shell architectures. In this design, the carbon shell can facilitate the good transport kinetics whereas the hollow space between Sn and carbon shell can accommodate the volume variation during repeated charge/discharge process. Accordingly, this composite electrode exhibits a high reversible capacity of 675 mAh g−1 at a current density of 0.8 A g−1 after 500 cycles and preserves as high as 366 mAh g−1 at a higher current density of 3 A g−1 even after 930 cycles. The enhanced electrochemical performance can be ascribed to the crystal size reduction of Sn cores and the formation of polymeric gel-like layer outside the electrode surface after long-term cycles, resulting in improved capacity and enhanced rate performance.

A radiochromic material with energy-dependent X-ray-induced photochromism was obtained by incorporating a radiosensitive glycolate ligand into an electron-transfer photochromic metalloviologen system. It is highly promising for detecting soft X-rays with energies less than 2 keV and may find application in qualitatively and visually distinguishing the energy range of X-rays.

A photochromic compound with fast response to Mo-Kα (4 min) and Al-Kα (1 s) X-rays was synthesized using a cluster of high-Z atoms and a flexible viologen zwitterion. The coloration time of 1 s when exposed to soft X-rays is the recorded minimum for X-ray-induced photochromic materials, indicating a potential to detect low-energy X-rays.

Long-lived charge-separated states and photoswitchable photoluminescence are important for many photochemical and photophysical applications. Recent studies have demonstrated the effectiveness of MOFs to achieve long-lived charge-separated states; however, the related studies are still rather rare owing to the limited numbers of photoresponsive MOFs. In this work, a new electron-transfer photochromic MOF compound, encapsulating photoactive viologen cations, was found to exhibit a charge-separated state with a lifetime value of more than 2 months, exceeding the reported values of the analogues. In addition, the photochromic process can afford a luminescence contrast up to 10 times between two stable states, which is higher than those of most known pyridine derivative-based photochromic compounds.

Using a hydrothermal reaction of SmCl3•6H2O, ZnBr2 and TPPS, a crystalline metalloporphyrinic compound (MPC), [SmZn(TPPS)H3O][Formula: see text]•2[Formula: see text]H2O (1), was synthesized. The crystal structure of the MPC exhibits a condensed and robust 3-D porous open framework. We studied the adsorption and desorption isotherms for N2, H2 and CO2 conducted at 77 K and 273 K. They show different isotherms such as Type I, II and III isotherm behaviors. We found that low temperature is propitious for the title complex to adsorb more H2, but less N2. Compound 1 showed remarkably high selectivity for CO2–N2 separation, and good thermal stability. The temperature dependent magnetic susceptibility shows an antiferromagnetic-like behavior for 1.

Polycyanometallate compounds with both photochromism and photomagnetism have appealing applications in optical switches and memories, but such optical behaviors were essentially restricted to the cryogenic temperature. We realized, for the first time, the photochromism and photomagnetism of 3d-4f hexacyanoferrates at room temperature (RT) in [Eu(III)(18C6)(H2O)3]Fe(III)(CN)6·2H2O (18C6 = 18-crown-6). Photoinduced electron transfer (PET) from crown to Fe(III) yields long-lived charge-separated species at RT in air in the solid state and also weakens the magnetic susceptibility significantly. The PET mechanism and changing trend of photomagnetism differ significantly from those reported for known 3d-4f hexacyanoferrates. This work not only develops a new type of inorganic-organic hybrid photochromic material but opens a new avenue for RT photomagnetic polycyanometallate compounds.

The hollow core of a carbon nanotube (CNT) provides a unique opportunity to explore the physics, chemistry, biology, and metallurgy of different materials confined in such nanospace. Here, we investigate the nonequilibrium metallurgical processes taking place inside CNTs by in situ transmission electron microscopy using CNTs as nanoscale resistively heated crucibles having encapsulated metal nanowires/crystals in their channels. Because of nanometer size of the system and intimate contact between the CNTs and confined metals, an efficient heat transfer and high cooling rates (similar to 10(13) K/s) were achieved as a result of a flash bias pulse followed by system natural quenching, leading to the formation of disordered amorphous-like structures in iron, cobalt, and gold. An intermediate state between crystalline and amorphous phases was discovered, revealing a memory effect of local short-to-medium range order during these phase transitions. Furthermore, subsequent directional crystallization of an amorphous iron nano wire formed by this method was realized under controlled Joule heating. High-density crystalline defects were generated during crystallization due to a confinement effect from the CNT and severe plastic deformation involved.

Two new isostructural coordination compounds exhibit the rare difunctional properties of both electron-transfer (ET) photochromism and ET thermochromism, which are significantly affected by halogen atoms. The thermocrystallographic studies of the same single crystal have elucidated the electron-donating nature of the halogen atoms.

Two tunable white light emitting compounds with high CRI values of 96 and 88 were obtained using an inorganic–organic hybrid strategy., Single-component white light materials may create great opportunities for novel conventional lighting applications and display systems; however, their reported color rendering index (CRI) values, one of the key parameters for lighting, are less than 90, which does not satisfy the demand of color-critical upmarket applications, such as photography, cinematography, and art galleries. In this work, two semiconductive chloroplumbate (chloride anion of lead(ii)) hybrids, obtained using a new inorganic–organic hybrid strategy, show unprecedented 3-D inorganic framework structures and white-light-emitting properties with high CRI values around 90, one of which shows the highest value to date.

White light emission from single-component small organic triazole molecules in the solid state was observed for the first time. This unusual intrinsic broadband emission, stemming from the supramolecular aggregate instead of the excimer, can be tuned by controlling the degree of electron delocalization and intensities of intermolecular interactions.

We have studied the electron-transfer photochromism of the crystalline adducts of 4,4′-bipyridine (Bpy) and carboxylic acids and revealed the key structural parameters that decide whether the photochromism can happen for the first time. Experimental and theoretical analyses on nine known examples showed that the hydrogen bonds, instead of π–π stacking interactions, are the defining factor to the photochromism. Only the presence of N–H···O hydrogen bonds can fulfill the electron transfer from the carboxylate group to the Bpy part, although both the N···O separations of O–H···N and N–H···O hydrogen bonds are suitable for the so-called through-space electron transfer. These results can not only help to screen out the photochromic species from the known hundreds of Bpy–carboxylic acid adducts deposited in the Cambridge Crystallographic Data Centre (CCDC) database but also guide the design and syntheses of new adducts using diverse N-heterocyclic aromatic molecules and carboxylic acids.

N,N'-Disubstituted bipyridinium (viologen) and N-monosubstituted bipyridinium compounds are well known for their electron-transfer (ET) photochromic behavior. Their modification has exclusively focused on the N-substituents to date. For the first time, we have studied the photochromic behavior when one pyridyl ring of the bipyridinium is substituted with a multifunctional azole group, and have found that two new coordination compounds based on N-methyl-4-pyridinium tetrazolate (mptz) zwitterion, [Zn(mptz)2 Br2 ] (1) and [Cd3 (mptz)2 Cl6 ]n ⋅4n H2 O (2), exhibit typical ET photochromic behavior owing to photoinduced ET from halogen anion to the mptz ligand. This work demonstrates a new simple, neutral photoactive molecule with electron-accepting ability, which may act as a photoactive component for materials with potential photoswitching and photocatalysis applications.

Mechanical properties and fracture behaviors of multiwalled WS2 nanotubes produced by large scale fluidized bed method were investigated under uniaxial tension using in situ transmission electron microscopy probing; these were directly correlated to the nanotube atomic structures. The tubes with the average outer diameter ∼40 nm sustained tensile force of ∼2949 nN and revealed fracture strength of ∼11.8 GPa. Surprisingly, these rather thick WS2 nanotubes could bear much higher loadings than the thin WS2 nanotubes with almost "defect-free" structures studied previously. In addition, the fracture strength of the "thick" nanotubes did not show common size dependent degradation when the tube diameters increased from ∼20 to ∼60 nm. HRTEM characterizations and real time observations revealed that the anomalous tensile properties are related to the intershell cross-linking and geometric constraints from the inverted cone-shaped tube cap structures, which resulted in the multishell loading and fracturing.

Light-emitting diodes (LEDs) and organic light-emitting diodes (OLEDs) have brought about a revolution in lighting and display. A very hot field in recent years has been to develop white-light phosphors, aiming to achieve better colour stability, better reproducibility, and a simpler fabrication process for LEDs and OLEDs. This feature article reviews the development of inorganic–organic hybrid white-light phosphors, including coordination compounds of small organic molecules, organically templated inorganic compounds (phosphates, borates, sulfides, halides), metal-functionalized organic polymers, and organically coated nanoparticles.

The structural defects that inevitably exist in real-world carbon nanotubes (CNTs) are generally considered undesirable because they break the structural perfection and may result in drastically degraded CNT properties. On the other hand, the deliberate defect introduction can provide a possibility to tailor the tube mechanical properties. Herein, we present a fully controllable technique to handle defects by using in situ transmission electron microscopy (TEM). Young's modulus, quality factor of the resonation and tensile strength of CNTs can be controllably, reversibly, and repeatedly tuned. Parallel high-resolution visualizing of structural defects suggests that the property tuning cycles are primarily attributed to the reversible conversion of defects at the atomic scale: the defects are created in the form of vacancies and interstitials under electron irradiation, and they vanish through the recombination via current-induced annealing. For applications, such as reversible frequency-tuned CNT resonators, this defect-engineering technique is demonstrated to be uniquely precise; the frequency may be tuned with 0.1%/min accuracy, improved by 1 order of magnitude compared with the existing approaches. We believe that these results will be highly valuable in a variety of property-tunable CNT-based composites and devices.

We synthesized monodisperse Pd nanocrystals with exposed (111) and (100) facets through preferentially oriented facet growth technology. We then supported them on α-Al2O3 as catalysts for application in CO oxidative coupling to dimethyl oxalate (DMO) and find, for the first time, that the (111) facets of Pd nanocrystals are active planes for CO oxidative coupling to DMO. This conclusion is based on experiment results, reaction mechanism, and density functional theory calculation. Directed by this shape effect, a high-performance and long-lived nanocatalyst with much lower Pd load for CO oxidative coupling to DMO was successfully prepared by a new wet impregnation–solution chemical reduction method, which can well control the exposure of (111) facets and sizes of Pd nanocrystals.

Growth of semiconducting nanostructures on graphene would open up opportunities for the development of flexible optoelectronic devices, but challenges remain in preserving the structural and electrical properties of graphene during this process. We demonstrate growth of highly uniform and well-aligned ZnO nanowire arrays on graphene by modifying the graphene surface with conductive polymer interlayers. On the basis of this structure, we then demonstrate graphene cathode-based hybrid solar cells using two different photoactive materials, PbS quantum dots and the conjugated polymer P3HT, with AM 1.5G power conversion efficiencies of 4.2% and 0.5%, respectively, approaching the performance of ITO-based devices with similar architectures. Our method preserves beneficial properties of graphene and demonstrates that it can serve as a viable replacement for ITO in various photovoltaic device configurations.