In this work, a paper-based electrochemical aptamer sensor was developed for the detection of aflatoxin B1 (AFB1) using a combination of MXene–Ti 3 C 2 T x and nucleic acid aptamers. The prepared single-layer or few-layer MXene suspension is suction-filtered onto MXene paper, which is cut to prepare MXene electrodes. To accomplish AFB1 specific detection, an amino-labeled AFB1 aptamer is mounted on the surface of the carboxy-functionalized MXene electrode. When AFB1 is present, it particularly binds to the aptamer to form a 3D structure, reducing the efficiency of electron transmission on the sensor surface. The difference in impedance signal change at the electrode/electrolyte interface is used to quantify AFB1. The results indicated that the detection range is 0.05–100 ng/mL, the detection limit is 0.04 ng/mL, and the recovery rate of AFB1 in corn samples is 97.8%–111.52% with the optimal detection conditions. The MXene paper-based label-free aptasensor is versatile and can detect different targets by simply swapping out the aptamers of different targets. The sensor also has a wide range of applications in food analysis and environmental testing. Practical applications A paper-based electrochemical aptamer sensor was developed to detect aflatoxin B1 using a combination of MXene–Ti 3 C 2 T x and nucleic acid aptamers.The design is based on the preparation of MXene electrodes by pumping and filtering monolayer or multilayer MXene suspensions onto MXene paper and cutting.The MXene paper-based label-free aptamer sensor was designed to be versatile, allowing the detection of different targets by simply replacing the aptamer with one from a different targets.
Lithium metal anode is the ideal candidate for high-energy–density rechargeable batteries. However, uncontrolled dendrite growth hampers its commercialization. Herein, a dendrite-free composite Li metal anode is realized by a flexible, freestanding, well-aligned and highly-lithiophilic MXene paper designed by a facile electrostatic self-assembly of the exfoliated MXene nanosheets and natural polysaccharide-chitosan (MX@CS). The MX@CS paper gets a well-aligned layered-3D structure with a micro-crumpled surface that can effectively decrease the local current density, guide even Li plating and suppress dendritic Li growth. More importantly, surface-adsorbed chitosan endows enhanced lithiophilicity for MXene substrate and thus reduces the Li nucleation overpotential, which is confirmed by the density functional theory calculations. Abundant lithiophilic groups on MX@CS surface provide high-concentration Li + anchoring site promoting Li nucleation and laterally inducing uniform Li deposition, which effectively avoids the formation of dendritic Li. As a result, the MX@CS-Li anode with a dendrite-free Li morphology shows a significantly improved cycling life in commercial carbonate-based electrolyte. When coupled with LiNi 0.8 Co 0.1 Mn 0.1 O 2 cathode, the full cell exhibits a low capacity decay and steady ultrahigh Coulombic efficiency of 99.6% at a current density of 5C. These findings develop a new approach for designing high-performance metal-based rechargeable batteries.
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