A novel organ-like MXene-Ti 3 C 2 nanomaterial was successfully prepared by etching Al from Ti 3 AlC 2 in HF at room temperature and then used to immobilise hemoglobin (Hb) to fabricate a mediator-free biosensor with an oxidized surface. MXene-Ti 3 C 2 and its morphology were well characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), and the physical and electrochemical properties of as-obtained samples were studied by UV-vis diffuse reflectance spectra (DRS) and the electrochemical workstation. Spectroscopic and electrochemical results confirmed that MXene-Ti 3 C 2 exhibited an excellent enzyme immobilization ability with biocompatibility for redox protein, displaying good protein bioactivity and stability. Due to the special structure and properties of MXene-Ti 3 C 2 , the direct electron transfer of Hb is facilitated and the prepared biosensors displayed good performance for the detection of H 2 O 2 with a wide linear range of 0.1-260 μM for H 2 O 2 , as well as an extremely low detection limit of 20 nM (based on a signal-to-noise ratio of 3) for H 2 O 2 . The immobilization of proteins onto the surface of MXene-Ti 3 C 2 is shown to be an efficient method for the development of a new class of sensitive, stable, and promising electrochemical biosensors.To accomplish the direct electron transfer (DET) between an enzyme and an electrode is of great importance in fabrication of mediator-free electrochemical biosensors. 1 Because the redox-active center of proteins is embedded in its protein shell deeply, DET between the protein and the electrode surface is generally difficult. 2-6 Moreover, the enzyme usually loses its bioactivity that adsorbed directly onto the electrode surface. 1,7 These problems make it difficult to transfer electrons directly at traditional electrodes. 1 Therefore, to employ nanomaterials is an efficient way to facilitate the direct electron transfer and retain the bioactivity of immobilized enzymes. 1,[8][9][10][11][12][13][14][15][16][17] And among them, two-dimensional layered nanomaterials such as graphene 18-26 and MoS 2 , 27-29 have attracted extensive attention to being used for immobilization of biomolecules onto electrode surface due to large specific surface areas, excellent electronic transport properties, and good biocompatibility.However, as far as we know, the application of the novel graphene-like MXene-Ti 3 C 2 nanomaterial, for constructing mediatorfree biosensor has rarely been reported. In our study, MXene-Ti 3 C 2 was successfully prepared by etching Al from Ti 3 AlC 2 in HF at room temperature. [30][31][32] In general, Ti 3 AlC 2 is a promising member of a large family of layered hexagonal (space group P6 3 /mmc) ternary metal carbides and nitrides referred to as the M n+1 AX n phases, where "M" is an early transition metal, "A" is an A-group element (mostly groups 13 and 14), "X" is carbon or nitrogen, and n = 1, 2, 3, 4, 5 or 6. 33,34 This structure comprises Ti 6 C octahedra, interleaved with layers of Al atoms. Immersing Ti 3 AlC 2 phase in ...

Membrane‐based reverse electrodialysis (RED) is considered as the most promising technique to harvest osmotic energy. However, the traditional membranes are limited by high internal resistance and low efficiency, resulting in undesirable power densities. Herein, we report the combination of oppositely charged Ti3C2Tx MXene membranes (MXMs) with confined 2D nanofluidic channels as high‐performance osmotic power generators. The negatively or positively charged 2D MXene nanochannels exhibit typical surface‐charge‐governed ion transport and show excellent cation or anion selectivity. By mixing the artificial sea water (0.5 m NaCl) and river water (0.01 m NaCl), we obtain a maximum power density of ca. 4.6 Wm−2, higher than most of the state‐of‐the‐art membrane‐based osmotic power generators, and very close to the commercialization benchmark (5 Wm−2). Through connecting ten tandem MXM‐RED stacks, the output voltage can reach up 1.66 V, which can directly power the electronic devices.

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Membranes. In their Research Article (e202206152), Jian Xue, Jürgen Caro, Haihui Wang et al. report a bioinspired Ti3C2Tx MXene‐based ionic diode membrane for osmotic energy conversion with extraordinary ionic rectification.

An ion-selective membrane can directly convert the osmotic energy to electricity through reverse electrodialysis. However, developing an advanced membrane that simultaneously possesses high power density, excellent mechanical strength, and convenient large-scale production for practical osmotic energy conversion, remains challenging. Here, the fabrication of ultrathin and ultrastrong Kevlar aramid nanofiber (KANF) membranes with interconnected three-dimensional (3D) nanofluidic channels via a simple blade coating method is reported. The negatively charged 3D nanochannels show typical surface-charge-governed nanofluidic ion transport and exhibit excellent cation selectivity. When applied to osmotic energy conversion, the power density of the KANF membrane-based generator reaches 4.8 W m -2 (seawater/river water) and can be further increased to 13.8 W m -2 at 328 K, which are higher than most of the state-of-the-art membranes. Importantly, a 4-μm-thickness KANF membrane shows ultrahigh tensile strength (565 MPa) and Young's modulus (25 GPa). This generator also exhibits ultralong stability over 120 days, showing great potential in practical energy conversions.

Membrane‐based reverse electrodialysis (RED) is considered as the most promising technique to harvest osmotic energy. However, the traditional membranes are limited by high internal resistance and low efficiency, resulting in undesirable power densities. Herein, we report the combination of oppositely charged Ti3C2Tx MXene membranes (MXMs) with confined 2D nanofluidic channels as high‐performance osmotic power generators. The negatively or positively charged 2D MXene nanochannels exhibit typical surface‐charge‐governed ion transport and show excellent cation or anion selectivity. By mixing the artificial sea water (0.5 m NaCl) and river water (0.01 m NaCl), we obtain a maximum power density of ca. 4.6 Wm−2, higher than most of the state‐of‐the‐art membrane‐based osmotic power generators, and very close to the commercialization benchmark (5 Wm−2). Through connecting ten tandem MXM‐RED stacks, the output voltage can reach up 1.66 V, which can directly power the electronic devices.

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