Conformations in the solid state are typically fixed during crystallization. Transference of \"frozen\" C=C conformations in 3,5-bis((E)-2-(pyridin-4-yl)vinyl)methylbenzene (CH3-3,5-bpeb) by photodimerization selectively yielded cyclobutane and dicyclobutane isomers, one of which (Isomer 2) exhibited excellent in vitro anti-cancer activity towards T-24, 7402, MGC803, HepG-2, and HeLa cells.

Responsive organic luminescent aggregates have a wide range of application fields, but currently there is still a lack of reasonable molecular design strategies. Introducing ion-π interactions into molecules can effectively alter their luminescent properties. However, current research typically focuses on ion localization at luminescent conjugated groups with the strong interaction forces. In this work, we introduce the flexible alkoxy chain spacers between fluorescent conjugated groups and ion-π interaction sites, and then adjust the fluorescence performance of the molecule by changing the strength of ion-π interactions. Bromine ion-based molecules with strong ion-π interactions exhibit high and stable fluorescence quantum yields in crystals and amorphous powders under the external stimuli. Hexafluorophosphate ion-based molecules with weak ion-π interactions have the high fluorescence quantum yield in crystals and very low fluorescence quantum yield in amorphous powders, showing variable fluorescence intensities under external stimuli. This demonstrates a new class of responsive organic luminescent solid-state materials.

In this study, we demonstrate the feasibility of rapid volumetric additive manufacturing in the solid state. This additive manufacturing technology is particularly useful in outer space missions (microgravity) and/or for harsh environment (e.g., on ships and vehicles during maneuvering, or on airplanes during flight). A special thermal gel is applied here to demonstrate the concept, that is, ultraviolet crosslinking in the solid state. The produced hydrogels are characterized and the water-content-dependent heating/cooling/water-responsive shape memory effect is revealed. Here, the shape memory feature is required to eliminate the deformation induced in the process of removing the uncrosslinked part from the crosslinked part in the last step of this additive manufacturing process.

Solid-state anion exchange method is easy to handle and beneficial to improve stability of CsPbX3 (X = Cl, Br, I) perovskites nanocrystals (NCs) with respect to anion exchange in liquid phase. However, the corresponding exchange rate is rather slow due to the limited diffusion rate of anions from solid phases, resulting in mixed-halide perovskite NCs. Herein,  a fast and reversible post-synthetic quasi-solid-state anion exchange method in CsPbX3 NCs with inorganic potassium halide KX salts/polyvinylpyrrolidone (PVP) thin film is firstly reported. Original morphology of the exchanged NCs is well-preserved for all samples. Complete anion exchange from Br- to Cl- or I- is successfully achieved in CsPbX3 NCs within ≈20 min through possible vacancies-assisted ion exchange mechanism, under ambient conditions and vice versa. Particularly, Br- -exchanged CsPbCl3 and CsPbI3 NCs exhibit improved optical properties. Encouraged by the attractive fluorescence and persistent luminescence as well as good stability of the resulted CsPbX3 NCs, an effective dual-mode information storage-reading application is demonstrated.  It is believed that this method can open a new avenue for the synthesis of other direct-synthesis challenging quantum-confined perovskite NCs/nanoplates/nanodisks or CsSnX3 NCs/thin film and provide an opportunity for advanced information storage compatible for practical applications.

Poly(vinylidene fluoride)-based polymer electrolytes are being intensely investigated for solid-state lithium metal batteries. However, phase separation and porous structures are still pronounced issues in traditional preparing procedure. Herein, a bottom-to-up strategy is employed to design single-phase and densified polymer electrolytes via incorporating quasi-ionic liquid with poly(vinylidene fluoride-co-hexafluoropropylene). Due to strong ion/dipole-dipole interaction, the optimized polymer electrolyte delivers high room-temperature ionic conductivity of 1.55 × 10-3 S cm-1 , superior thermal and oxidation stability of 4.97 V, excellent stretchability of over 1500% and toughness of 43 MJ cm-3 as well as desirable self-extinguishing ability. Furthermore, the superb compatibility toward Li anode enables over 3000 h cycling of Li plating/stripping and ≈98% Coulombic efficiency in Li||Cu test at 0.1 mA cm-2 . In particular, lithium metal battery Li||LiNi0.6 Co0.2 Mn0.2 O2 exhibits a room-temperature discharge retention rate of 96% after 500 cycles under a rate of 0.1 C, which is associated with the rigid-flexible coupling electrodes/electrolytes interphase. This investigation demonstrates the potential application of quasi-ionic liquid/polymer electrolytes in safe lithium metal batteries.

Solid-state lithium batteries using solid polymer electrolytes can improve the safety and energy density of batteries. Smoother lithium-ion channels are necessary for solid polymer electrolytes with high ionic conductivity. The porosity and channel structure of the polymer film affect the transfer of lithium ions. However, their controllable synthesis remains a big challenge. Here, we developed a simple synthesis approach toward wrinkled microporous polymer electrolytes by combining the amphoteric (water solubility and organic solubility) polymer in three polymer blends. The homogeneous blend solution spontaneously wrinkled to vertical fold channels as the solvent evaporated. Two minor polymers, poly(vinyl pyrrolidone) (PVP) and polyetherimide (PEI), formed close stacks, and Janus PVP was dispersed in the poly(vinylidene fluoride) (PVDF) matrix. The interfacial tensions between the three polymers were different, so stress was produced when they solidified. The solvent was evaporated to the top layer of the polymers when the temperature increased. The bottom layer wrinkled owing to the stress during solidification. The evaporation of the solvent generated micropores to form the lithium-ion channel. They helped Li+ transference and created a wrinkled microporous PVDF-based polymer electrolyte, which achieved an ionic conductivity of 5.1 × 10-4 S cm-1 and a lithium-ion transference number of 0.51 at room temperature. Meanwhile, the good flame retardancy and tensile strength of the polymer electrolyte film can improve the safety of the battery. At 0.5C and room temperature, the batteries with a LiFePO4 cathode and the wrinkled microporous LiTFSI/PEI/PVP/PVDF electrolyte reached a high discharge specific capacity of 122.1 mAh g-1 at the 100th cycle with a Coulombic efficiency of above 99%. The results of tensile and self-extinguishing tests show that the polymer electrolyte film has good safety application prospects.

Although polymer electrolytes have been regarded as potential separator materials for high energy density solid-state lithium-based batteries, their applications were significantly restricted by the low ionic conductivity, poor mechanical strength, and thermostability. Herein, a highly conductive and thermostable hybrid polymer electrolyte was developed by combining poly(vinylidene fluoride-co-hexafluoropropylene)-grafted polyrotaxane and nano-Al2O3 particles. In this unique hybrid, not only the Lewis acid-type Al2O3 and the fluorine groups of polyrotaxane branches exhibited strong integration with ionic species to accelerate the dissociation of lithium salt, improving the Li ionic conductivity, but also the abundant hydroxy functional groups on the surface of Al2O3 hydrogen-bonded with fluorine-containing branches, enhancing the mechanical strength. More importantly, the hybrid electrolyte exhibited superior thermal stability due to the heat resistance of the ceramic filler and the unique bead string structure of polyrotaxane. Consequently, a polymer electrolyte with a comprehensively improved performance was obtained, including high ionic conductivity and Li+ transfer number and superior tensile strength and thermostability. The hybrid electrolyte provided a dendrite-free lithium anode with a long life up to 1800 h and stable solid-state lithium-metal batteries at a high temperature of 80 °C.

Developing an effective and green method toward organic functional cocrystals based on the solubility-mismatched coformers is highly desirable and very important. Herein, we applied a green two-step liquid-assisted-grinding coassembly (LAGC) in fabricating tetracene-octafluoronaphthalene (TC-OFN) cocrystals from solubility-mismatched pairs of tetracene (TC, poorly soluble, 0.2 mg mL-1) and octafluoronaphthalene (OFN, highly soluble, 0.2 × 104 mg mL-1). Such cocrystals are extremely difficult to prepare through the common solution-processing strategies. More importantly, this two-step LAGC process could allow us to efficiently prepare TC-OFN cocrystals in gram scale. The as-prepared cocrystals displayed the intrinsic green emission of TC with much higher photoluminescence quantum yield (13.75%) comparing with the pure solid TC with the almost-quenched emission (0.41%, aggregation-caused quenching (ACQ)). The ultrafast spectra study on these cocrystals verifies the successful barrier function of OFN molecules in interrupting the well-known singlet fission (SF) in TC solids. Furthermore, this method can allow us to easily fabricate fluorescent TC-OFN water inks, which can be employed to prepare luminescent paintings or highly emissive ultratransparent/flexible films.

Solid-state photochromic materials with reversible and adjustable optical properties are very appealing because of their wide prospects in advanced functional materials. Yet, it remains a significant challenge to develop such materials in the solid state. In this study, a tetraphenylethene derivative (SP-TPE-SP)-based solid-state photoswitch, which exhibits reversible photochromism in the solid state, was constructed. Efficient photoswitching between SP-TPE-SP and its photoisomer MC-TPE-MC is assisted by the large free volumes caused by the nonplanar molecular structures of the TPE1 moieties and the intramolecular π-π stackings between the two MC moieties. The free volumes are large enough to allow for the transport of HCl gas molecules for an acidochromic response. Furthermore, the morphology of the SP-TPE-SP solid surface can be regulated by ultraviolet light irradiation. The contact angles of the SP-TPE-SP solid surface can be decreased, changing from 97 to 82°. Therefore, SP-TPE-SP with a rather simple molecular structure is appealing for advanced multifunctional materials.

The emerging carbon quantum dots (CQDs) have been attracting significant attention for their prominent fluorescence, excellent stability and outstanding biocompatibility. Here, we report a facile one-step synthesis of highly fluorescent CQDs by using phthalic acid and triethylenediamine hexahydrate as precursors through a simple microwave-assisted method. The reaction time needed is only 60 s, which is less time-consuming than most previous reports. The phthalic acid with a benzene ring can improve the photoluminescence properties of CQDs as it can provide foreign sp2 conjugating units, and then finally result in long-wavelength emission. The synthesized CQDs were fully characterized by transmission electron microscopy, X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. Besides, the impacts of different freed ratio on physical and chemical properties of CQDs were investigated in detail. The prepared CQDs exhibited strong green fluorescence with a broad maximum emission wavelength. The quantum yields of the CQDs can reach 16.1% in aqueous solution and they were successfully used in cell imaging with good biocompatibility. Moreover, in solid state, the CQDs with the feed ratio of 1 : 0.5 showed a strong green-yellow fluorescence which may have great potential to fabricate optoelectronic devices. Furthermore, the prepared CQDs also showed high pH sensitivity and can act as a fluorescence nanosensor for pH sensing.