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Biomass‐based porous carbon (BPC) with renewability and flexible nano/microstructure tunability has attracted increasing attention as efficient and cheap electrode materials for supercapacitors. To meet commercial needs, high mass‐loading electrodes with high areal capacitance are preferred when designing supercapacitors. The increased mass percentage of active materials can effectively improve the energy density of supercapacitors. However, as the thickness of the electrode increases, it will face the following challenges including severely blocked ion transport channels, poor charging dynamics, poor electrode structural stability, and complex preparation processes. A bridge between theoretical research and practical applications of BPC electrodes for supercapacitors needs to be established. In this review, the advances of high mass‐loading BPC electrodes for supercapacitors are summarized based on different biomass precursors. The key performance evaluation parameters of the high mass‐loading electrodes are analyzed, and the performance influencing factors are systematically discussed, including specific surface area, pore structure, electrical conductivity, and surface functional groups. Subsequently, the promising optimization strategies for high mass‐loading electrodes are summarized, including the structure regulation of electrode materials and the optimization of other supercapacitor components. Finally, the major challenges and opportunities of high mass‐loading BPC electrodes in the future are discussed and outlined.

A simple and low-cost fluorescence signal-on sensing strategy has been developed based on functional nucleic acids (FNAs) via energy transfer between DNA-templated silver nanoclusters (DNA-AgNCs) and gold nanorods (GNRs). FNAs were used as highly selective recognition probes, in which an aptamer was used to detect small molecules represented by tetracycline, and DNAzyme was used to detect heavy metal ions represented by Pb2+. The fluorescent DNA-AgNCs were synthesized by the designed oligonucleotide sequences, which consisted of three parts: AgNCs synthesis template C6G5C6, spacer T5, and complementary sequences of the aptamer or enzyme strand. The difference in electrostatic interactions between ss/dsDNA and positively charged GNRs leads to energy transfer with different efficiencies. The analytes represented by tetracycline and Pb2+ can destroy the dsDNA structure and reduce the energy-transfer efficiency between DNA-AgNCs and GNRs, thus achieving fluorescence recovery and a signal-on analytical strategy. This strategy has excellent specificity and sensitivity with limit of detections of 4.411 nM for tetracycline and 1.416 nM for Pb2+ and has been successfully applied to detect tetracycline in milk and Pb2+ in river water. Using DNA-AgNCs formed in situ as signal probes, this strategy does not require labels or modifications and can be completed without complex analytical instruments. Moreover, this strategy can be extended to detect other targets by replacing FNA sequences. Therefore, it has promising prospects in the sensitive, simple, and rapid detection of contaminants in food and environment samples.

Lead contamination has posed a potential threat to the environment and food safety, arousing extensive concern. In this work, we fabricated a novel fluorescent sensing platform based on zeolitic imidazolate framework-8 (ZIF-8) and DNAzyme for monitoring Pb 2+ in water and fish samples. ZIF-8 was proposed as a fluorescence quencher with the advantages of simple synthesis, low cost, and high quenching efficiency. The Pb 2+ -dependent GR5 DNAzyme containing the large ssDNA loop can be adsorbed onto ZIF-8 accompanied by fluorescence quenching. Upon binding with Pb 2+ , GR5 DNAzyme was activated and cleaved, leading to the release of FAM-labeled 5-base ssDNA, which restored the fluorescence. The "turn-on" assay can detect Pb 2+ through the one-pot procedure in the range of 0.01−10.0 nM with a detection limit of 7.1 pM. The platform is promising for on-site monitoring of Pb 2+ owing to the excellent performance of high sensitivity, low background, strong anti-interference ability, and simple operation.

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