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The discovery of superelastic organic crystals capable of phototwisting and photobending represents a significant advance in the field of light-responsive materials. This research focused on the synthesis and characterization of crystals derived from trifluoromethyl-substituted acylhydrazone derivatives, known as TBMP. These crystals exhibited remarkable superelasticity when subjected to mechanical forces along their (010) crystallographic plane while showing a tendency to fracture along the (001) plane. Single-crystal analysis revealed that hydrogen bonds, especially C–H···F, C–H···O, and C–H···N interactions, are crucial in providing the crystals with superelastic properties. In addition, reversible E↔ Zisomerization of TBMPmolecules occurred under UV irradiation and heating, resulting in photomechanical (twisting or bending) and thermal recovery behavior of the crystals. Due to their exceptional properties, these crystals possess significant potential for application in robotic arm technology.

Highly efficient persistent organic room temperature phosphorescence (RTP) has attracted increasing attention because of promising applications in fields of chemical sensors, optoelectronic devices, information security, and bioimaging, etc. Wherein, the crystal engineering of H-aggregation offers stabilization for long-lived triplet exciton for RTP, but the related research is rare because of the scarcity of ideal phosphorescent H-aggregate. Herein, we designed planar tricoordinate organoboron derivatives with molecular arrangement in ideal H-aggregation. The integration of Br atom can largely enhance RTP efficiency through increasing SOC effect, while the antiparallel molecular arrangement causes annihilation of triplet exciton. Thanks to good self-assembly property, their RTP can even be observed in PMMA matrix with doping ratio of merely 1 wt%. We further found that the cryogenic temperature contributes to stabilizing triplet exciton in H-aggregation, leading to red-shifted phosphorescence. By applying high hydrostatic pressure, the phosphorescence was largely enhanced and redshifted, demonstrating the crucial role of H-aggregation on RTP property. In phosphorescent tissue imaging of live mouse, nanoparticles of BrBA exhibited high contrast image viaeliminating the interference of autofluorescence.

The phenomenon that different molecular packing modes in aggregates result in different optical properties has attracted intense attention, since it can provide useful information to establish the relationship between the micro- and macro-world. In this paper, DBTDO-DMAC was designed with 9,10-dihydro-9,9-dimethylacridine (DMAC) as electron donor. DBTDO-DPA and DBTDO-Cz were designed for comparison, which adopted diphenylamine (DPA) with twisted structure and carbazole (Cz) with planar structure as donors, respectively. As expected, two polymorphs (Crystal G and Crystal Y) of DBTDO-DMAC were obtained and exhibited distinct properties. Crystal G originating from planar conformation exhibited mechanochromism (MC) phenomenon and the emission color changed from green to yellow with a redshift of 35 nm after grinding. Nevertheless, Crystal Y with folded conformation displayed obvious room-temperature phosphorescence (RTP) with yellow afterglow. Careful single crystal analyses, powder X-ray diffraction and theoretical calculation reveal that the different emissive behaviors are highly related to the molecular conformation and packing modes. The successful adjustment of molecular conformation provides some guidance in the design of other MC and/or RTP luminogens, broadens the molecule family with the tunable molecular conformation and opens up a new avenue for exploring possible adjustment of molecular packing in aggregates.

A flexible organic crystal with elastic bending characteristics has been constructed. Under hydrostatic pressure, the crystal exhibits excellent piezochromic behavior and a pressure-induced emission enhancement phenomenon, demonstrating further potential for application in flexible high-pressure sensors. [Display omitted]

There is still an urgent demand for novel smart materials that can achieve a diverse range of practical applications in the synthetic material area. Herein, we developed a simple but versatile aggregation-induced emission luminogen (AIEgen, 1). Compound 1was sensitive to an electric stimulus and displayed reversibly three-color switched electrochromism and on-to-off electroluminochromism. Such properties allowed the fabrication of high-performance non-doped OLEDs with a high external quantum efficiency of 5.22%. Due to its AIE property and remarkable sensitive color change in response to polarity change, it can serve as a unique imaging probe for detecting environmental polarity in cells and selective visualization of lipid droplets in live tissues. More impressively, compound 1exhibited a wide range of thermoresponsive behaviors with a ratiometric luminescence change and noticeable fluorescence color switching. As another remarkable feature, it can respond to anisotropic shearing force and isotropic hydrostatic pressure with prominent and contrasting luminescence conversion due to the distinct disturbance of the weak intermolecular interactions and charge transfer process. The present results may offer an important guideline for multifunctional molecular design and provide an important step forward to expand the real-life applications of smart materials.

Single-cell metabolomics could be used to discover the chemical strategies of cells for coping with chemical or environmental stress because metabolomics provides a more immediate and dynamic picture of cell functionality. However, these small-molecule metabolites are the most difficult to measure because they characterize rapid metabolic dynamics, structural diversity, and incapacity to achieve signal amplification or labeling. In order to solve above problems, we presented a surface-enhanced Raman scattering (SERS)-microfluidic droplet platform to realize the label-free simultaneous analysis of multiplexed metabolites at the single-cell level via a versatile magnetic SERS substrate composed by silver nanoparticles (AgNPs, 30 nm)-decorated 400 nm Fe3O4magnetic microspheres. This metal-magnetic composite substrate is beneficial to efficient adsorption of single cell metabolites, fast separation from complex matrixes, and high SERS sensitivity. Also, the endocytosis effect can be fully prohibited due to its relatively large size. This work achieves label-free, nondestructive, simultaneous determination of three single-cell metabolites, pyruvate, adenosine triphosphate (ATP), and lactate, owing to their intrinsic SERS fingerprints. The “hotspots” effect induced by the magnetic aggregation of Fe3O4@AgNPs allows highly sensitive SERS detection. Encapsulating metabolites in such a limited and isolated droplet accelerates the process of diffusion and adsorption equilibriums. Activation with saponin for metabolites was assessed on different cell lines. The SERS-microdroplet platform is a powerful tool for exploring single-cell heterogeneity at the metabolic level.

A novel single crystal, PyB, is produced in a high yield by the simple method of connecting a pyrene unit and a rhodamine B moiety together. PyB shows multiple functions of aggregation-induced emission, low-loss optical waveguiding, and tricolored mechanochromism. The crucial point for fabricating such a multifunctional single crystal is selecting the CN group as a spacer, which simplifies the synthetic procedure, confines the molecular conformation to develop single crystals, and allows one to dynamically observe the color variation in situ and quantitatively analyze the effect of applied pressures. Such a simple approach may be extended to other fluorophores, thus providing a new opportunity for the real world application of mechanochromic materials for mechanical sensors, optical encoding, and optoelectronic devices, etc.

In recent years, semiconductor-based surface-enhanced Raman scattering (SERS) substrates have received considerable attention and led to a forefront in the SERS field. However, the lack of electromagnetic (EM) enhancement contributions highly precludes the development of semiconductive-substrate-based SERS. In this study, Ga-doped ZnO nanoparticles (NPs) were fabricated and employed as novel SERS substrates based on the EM enhancement contribution of surface plasmon resonance (SPR). The obtained Ga-doped ZnO NPs exhibited obvious SPR absorptions in the visible and near- and mid-infrared regions. SPR absorption can be readily tuned by changing the doping ratios of Ga3+ions. The SERS spectra of Ga-doped ZnO/4-mercaptopyridine (MPy) were investigated at different excitation wavelengths of 488, 532, 633, and 785 nm. The spectral enhancement of Ga-doped ZnO substrates depended on the doping ratios, excitation wavelengths, and nearby SPR absorption. Ga-doped ZnO NPs with the highest free charge carrier density and the doping ratio of 5% showed the strongest SERS spectra. For the fixed doping ratio of 5%, the better is the match between excitation wavelengths and SPR absorption, the higher is the SERS spectral enhancement. This study showed the feasibility of EM contributions to SERS by using semiconductive substrates and can contribute to the development of the semiconductor-based EM mechanism.