Kuilin Deng

Most reported biomass-derived carbon electrode materials for supercapacitors are fabricated via single-step high-temperature activation with KOH or KCO3 at 700–800 °C, and their electrochemical performance primarily relies on the high specific surface area and porous structure of carbon materials, usually suffering from unregulated heteroatom doping and insufficient cycling stability.This work develops a facile two-step activation strategy to synthesize highly stable carbon electrodes from cheap waste Xanthoceras sorbifolium Bunge shells. Unlike traditional single-step activation, this method separates pore construction and heteroatom doping: KOH etching at 700 °C first forms a porous carbon skeleton, followed by low-temperature K₂CO₃ activation at 300 °C for controllable in-situ K doping. The optimized K7K-1:0.5 sample with abundant K active sites delivers remarkable electrochemical performance despite its moderate surface area, overturning the conventional view that capacitance only relies on high surface area. In 6 M KOH symmetric supercapacitors, it reaches 352 F g⁻¹ at 0.5 A g⁻¹ with 98% capacitance retention after 10,000 cycles. The as-fabricated zinc-ion hybrid supercapacitor achieves 168 mAh g⁻¹ at 0.5 A g⁻¹, a maximum energy density of 60 Wh kg⁻¹ at 279 W kg⁻¹, and 96% capacity retention over 60,000 cycles at 1 A g⁻¹. The synergistic effect of appropriate potassium doping is verified to be the critical factor for the prominent performance improvement of biomass carbon materials. This work provides an innovative and facile strategy for the design and preparation of ultra-stable biomass-derived carbon electrode materials for high-performance energy storage devices.

In this study, non‐conjugated fluorescent poly(amide amines) (PAMAs) are synthesized via three‐component Ugi polymerization using monomers containing piperazine structures as feedstock. The synthesized PAMA‐B exhibits strong fluorescence at 430 nm due to intramolecular aggregation of piperazine and amide groups along the macromolecular chain. PAMA‐B selectively detects Cu²⁺ ions even among common interfering ions, with a detection limit of 0.51 μM, much lower than the minimum permissible concentration of 30 μM for Cu²⁺ ions in drinking water as stipulated by the World Health Organization (WHO). The quenching mechanism involves the static quenching via 1:1 Cu²⁺ ions coordination. Recovery tests in tap and river water confirm PAMA‐B's specificity for Cu²⁺ ions in the real environments. Furthermore, fluorescent PAMA‐B is fabricated into a convenient test paper for Cu²⁺ ions detection in the experiment.

In this study, poly( 2, 4 ‐thiazolidinedione) (PTD) is prepared by oxidative polymerization using 2,4 ‐thiazolidinedione (TD) as monomer. PTD exhibits significant polymerization‐induced emission (PIE) at 540 nm, resulting from the intramolecular aggregation of thiazole heterocycles and the formation of electron‐space conjugation. The PIE‐active PTD demonstrates simultaneously specific detection of Cu ² ⁺/Co ² ⁺ with detection limits as low as 0.47 µ M and 68.9 nM, respectively, even in the presence of 14 common metal ions and 11 anions. Fluorescence quenching experiments reveal that Cu ² ⁺/Co ² ⁺ coordinates with PTD to form a 1:2 non‐fluorescent complex through a static quenching mode. Most importantly, the efficient differentiation between Cu ² ⁺ and Co ² ⁺ is achieved using dynamic color recognition technology based on smartphone APP and UV–vis absorption spectroscopy. This approach innovatively combines solution color gradient change with smartphone RGB to establish a semi‐quantitative and convenient detection method. The lower detection limits of Cu ² ⁺/Co ² ⁺ reached 36.2 and 37.8 nM m with naked eye recognition, which provides a technological solution for the rapid detection of Cu ² ⁺/Co ² ⁺ ions without the aid of large‐scale instruments. In brief, the successful preparation and detection application of PIE‐active PTD open up a straightforward and feasible path for molecular design of fluorescent non‐conjugated polymers from non‐fluorescent monomers.

Non‐conjugated fluorescent polymers have attracted much attention because of their simple preparation, unique properties and wide applications. In this investigation, we designed and synthesized the non‐conjugated fluorescent polyureas (PUAs) containing pyridine structure with three diaminopyridines as the monomers according to the cluster‐triggered emission (CTE). It was found that the fluorescence of PUAs depends heavily on the intramolecular aggregation of pyridine and urea groups along macromolecular chains, and the formation of a three‐dimensional hydrogen bond network between NH and OC bonds. Among three PUAs, PUA‐34 with excellent light stability and wide spectrum excitation characteristics has high selectivity for Cu ²⁺ detection even in the coexistence of 14 common cations and 11 anions. The detection limit is measured as low as 0.8 μM (linear range 1–100 μM), which is significantly superior to the traditional detection methods. The UV–Vis absorption spectroscopy, fluorescence lifetime and Stern–Volmer equation evaluation together confirm the dominated static quenching by the coordination between Cu ²⁺ ions and urea groups. The recovery rates of PUA‐34 for detecting Cu ²⁺ in water samples ranged from 99.2% to 101.6% (RSD < 5%), confirming its reliability in practical applications. This work provides a simple method to prepare the non‐traditional fluorescent polyurea, which shows the potential practical applications as fluorescent probes for Cu ²⁺ ion detection.