Stress sensing is the basis of human-machine interface, biomedical engineering, and mechanical structure detection systems. Stress sensing based on mechanoluminescence (ML) shows significant advantages of distributed detection and remote response to mechanical stimuli and is thus expected to be a key technology of next-generation tactile sensors and stress recorders. However, the instantaneous photon emission in ML materials generally requires real-time recording with a photodetector, thus limiting their application fields to real-time stress sensing. In this paper, we report a force-induced charge carrier storage (FICS) effect in deep-trap ML materials, which enables storage of the applied mechanical energy in deep traps and then release of the stored energy as photon emission under thermal stimulation. The FICS effect was confirmed in five ML materials with piezoelectric structures, efficient emission centres and deep trap distributions, and its mechanism was investigated through detailed spectroscopic characterizations. Furthermore, we demonstrated three applications of the FICS effect in electronic signature recording, falling point monitoring and vehicle collision recording, which exhibited outstanding advantages of distributed recording, long-term storage, and no need for a continuous power supply. The FICS effect reported in this paper provides not only a breakthrough for ML materials in the field of stress recording but also a new idea for developing mechanical energy storage and conversion systems.
We report a simple metal ion-catechol coordination strategy to coat ruthenium-catechol polymer complex (TAC-Ru) on the surface of carbon nanotubes (CNT) to form a core-shell structure (abbreviated as CNT@TAC-Ru). This is achieved by firstly polymerizing catechol and boronic acid monomers on the surface of CNT to form a boronate ester polymer (BP) shell. Then, Ru3+is used to etch the BP shell, and cleave the dynamic boronate ester bond, leading to the formation of a CNT@ruthenium-catechol coordination complex based on the coordinative efficiency of the catechol group. The electrocatalytic property of the CNT@TAC-Ru composite can be activated through electrochemical cycling treatment. The as-activated CNT@TAC-Ru exhibits evidently improved hydrogen evolution reaction (HER) performance with an overpotential of 10 mV in 1.0 M KOH at a current density of 10 mA cm-2, which is better than that of commercial Pt/C (32 mV). And the long-term stability is also desirable. This work provides a pyrolysis-free method to form metal-polymer-carbon composite with high HER performance under the alkaline condition.
BiOCl has been actively explored as a promising material for photodetectors (PDs), but inefficient charge separation and narrow response spectral range limit the further development of BiOCl-based PDs. Herein, we show that coating BiOCl with a boronate polymer (BP) shell may provide a simple route to overcome the above limitations. The migration of Bi3+ from BiOCl to BP changes the energy level and enhances the light absorption of BP shell. Violent coordination at the core-shell interface, as well as Bi3+ migration induces the generation of Bi3+-O·-Bi3+ defects. Also, BP shell can reduce the darkcurrent of BiOCl@BPs PDs. The optimized PD assembled with BiOCl@BP1.9 (the subscript represents the shell thickness) shows fast photoresponse (rise time: 32, decay time: 52 ms, respectively), high on/off ratio, and responsivity of 119.77 μA/W under 365 nm light at 15 V. Moreover, BiOCl@BP PDs exhibit a gradually broadened spectral response range with the increase of BP shell thickness and show much higher photodetection performances. For example, under 940 nm light stimulation, the optimized PD (BiOCl@BP20.1) exhibits a high responsivity of 22.18 μA/W, 28 times that of BP PD. Our findings may provide a guideline for the design of high-performance PDs based on the precise construction of polymer-inorganic heterostructures.
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