A novel single organic molecule–carborane conjugate, CAN, was synthesized in a high yield via a modified nickel-catalyzed cross-coupling reaction incorporating an anthracene unit and an o-carborane moiety. CAN exhibits multiple functions of tricolored mechanochromism and mechanically triggered thermochromism. The fluorescence could be switched from blue to bright yellow then to pink by grinding. The robust and reversible thermochromic process was triggered by the mechanical force. The locally excited (LE) state emission, intermolecular excimer formation and twisted intermolecular charge transfer (TICT) are the primary origins of this tricolor switching property. High temperature sensitivity of the heavily ground CAN powders contribute to the mechanical force induced TICT emission enhancement and color switching.

Picric acid (PA) is an organic substance widely used in industry and military, which poses a great threat to the environment and security due to its unstable, toxic, and explosive properties. Trace detection of PA is also a challenging task because of its highly acidic and anionic character. In this work, silver nanoparticles (AgNPs)-decorated porous silicon photonic crystals (PS PCs) were controllably prepared as surface-enhanced Raman scattering (SERS) substrates using the immersion plating solution. PA and Rhodamine 6G dye (R6G) were used as the analyte to explore the detection performance. As compared with single layer porous silicon, the enhancement factor of PS PCs substrates is increased to 3.58 times at the concentration of 10⁻⁶ mol/L (R6G). This additional enhancement was greatly beneficial to the trace-amount-detection of target molecules. Under the optimized assay condition, the platform shows a distinguished sensitivity with the limit of detection of PA as low as 10⁻⁸ mol/L, the linear range from 10⁻⁴ to 10⁻⁷ mol/L, and a decent reproducibility with a relative standard deviation (RSD) of ca. 8%. These results show that the AgNPs-modified PS PCs substrates could also find further applications in biomedical and environmental sensing.

Inspired by the enhanced gas-sensing performance by the one-dimensional hierarchical structure, one-dimensional hierarchical polyaniline/multi-walled carbon nanotubes (PANI/CNT) fibers were prepared. Interestingly, the simple heating changed the sensing characteristics of PANI from p-type to n-type and n-type PANI and p-type CNTs form p–n hetero junctions at the core–shell interface of hierarchical PANI/CNT composites. The p-type PANI/CNT (p-PANI/CNT) and n-type PANI/CNT (n-PANI/CNT) performed the higher sensitivity to NO₂ and NH₃, respectively. The response times of p-PANI/CNT and n-PANI/CNT to 50 ppm of NO₂ and NH₃ are only 5.2 and 1.8 s, respectively, showing the real-time response. The estimated limit of detection for NO₂ and NH₃ is as low as to 16.7 and 6.4 ppb, respectively. After three months, the responses of p-PANI/CNT and n-PANI/CNT decreased by 19.1% and 11.3%, respectively. It was found that one-dimensional hierarchical structures and the deeper charge depletion layer enhanced by structural changes of PANI contributed to the sensitive and fast responses to NH₃ and NO₂. The formation process of the hierarchical PANI/CNT fibers, p–n transition, and the enhanced gas-sensing performance were systematically analyzed. This work also predicts the development prospects of cost-effective, high-performance PANI/CNT-based sensors.

o-Carborane–anthracene triads were synthesized and characterized with anthracene and o-carborane acting as the chromophore and electron acceptor, respectively. Two functional groups were linked by an acetylene unit. The influence of the alkyl substituents in the cage carbon on the aggregation-caused quenching (ACQ) characteristics of the anthracene core was investigated. The results showed that the fluorescence quantum yield of the triads could be modulated from 7.0 to 42.9% in the solid state as the cage C substituents changed from H to methyl to ethyl. Mechanistic investigation indicated that the alkyl substitutes in the cage carbon could effectively suppress the C_cage–C_cage vibration, o-carborane unit rotation and intermolecular π–π stacking interactions. In addition, the 2-Me-o-carboranyl moiety could obviously twist the anthracene backbone, which was in favor of the twisted intramolecular charge transfer (TICT) state emission. These were responsible for the high fluorescence quantum yield in solid state.