Reported detection limits for MXene biosensors now extend from micromolar to attomolar concentrations. These values are impressive, but they do not show which part of a sensing architecture produces the improvement or whether the device remains reliable in a biological sample. Electrochemical and optical platforms for detecting metabolites, proteins, and nucleic acids are compared here using the same criteria: MXene composition, surface chemistry, bioreceptor attachment, signal generation, analytical performance, and experimental validation. The discussion includes Ti₃C₂Tₓ and less frequently studied MXenes containing Nb, V, or Mo, together with electrochemical, fluorescence, FRET, SPR-LSPR, SERS, colorimetric, and photothermal readouts.The comparison shows that performance is rarely determined by the MXene phase alone. Noble-metal nanoparticles often provide catalytic activity and anchoring sites, while polymers and carbon materials can limit restacking or improve mechanical stability. Molecular amplification contributes substantially to the lowest LODs reported for nucleic-acid sensors. In these systems, MXenes serve mainly as conductive interfaces, adsorption surfaces, fluorescence quenchers, or supports for other signal-generating components. Electrochemical devices are readily connected to compact electronics but remain sensitive to fouling, oxidation, and interfacial drift. Optical systems support label-free or spectrally resolved measurements, although their reliability depends on the optical configuration and reproducibility of the nanostructured surface.The evidence for clinical use is still limited. Many devices have been tested only in buffers, spiked samples, or small clinical cohorts, while stability and recovery were measured under different and often poorly comparable conditions. Further work should prioritize controlled surface chemistry, reproducible fabrication, untreated clinical samples, and comparison with established diagnostic methods rather than further reductions in LOD alone.
The transition toward sustainable carbon materials requires synthesis strategies that simultaneously deliver advanced structural performance, resource efficiency, and reduced environmental impact. Herein, we develop a closed-loop salt-templating strategy for the activation-free production of hierarchical porous carbon from sodium lignosulfonate (SLS), an abundant lignin-derived by-product of the sulfite pulping industry, using recyclable sodium chloride (NaCl) as the sole hard template. Unlike conventional chemical activation and irreversible hard-templating methods, this recrystallization–carbonization approach eliminates corrosive activating agents and integrates template recovery and reuse into the synthesis cycle. By optimizing the precursor/template ratio, recrystallization conditions, and carbonization temperature, sulfur-doped porous carbon with a high specific surface area of 1831 m² g⁻¹, interconnected hierarchical meso/macroporous architecture, and excellent structural uniformity was obtained. The NaCl template was recovered with an efficiency above 90% and successfully reused in multiple cycles with negligible changes in the physicochemical properties of the resulting carbons, demonstrating the circularity and robustness of the proposed process. The optimized porous carbon further enabled highly efficient Ni-based catalytic applications, achieving 99.2–99.8% conversion in guaiacol hydrodeoxygenation, high benzene selectivity, and stable continuous-flow operation for 6 h without detectable deactivation. This study presents a scalable and resource-efficient pathway for valorizing sodium lignosulfonate into high-value hierarchical porous carbons and highlights recyclable salt templating as a promising alternative to conventional chemically activated carbon manufacturing.
Understanding friction in graphene is essential for its applications in nanoelectromechanical systems and solid lubrication. However, establishing a direct relationship between tribological properties and local graphene properties requires correlative measurements using multiple experimental techniques. Here, we investigate the thickness-dependent tribological behavior of epitaxial graphene on SiC by combining atomic force microscopy, low-energy electron microscopy, and Raman spectroscopy. LEEM enables unambiguous identification of monolayer, bilayer, and trilayer graphene domains, while Raman spectroscopy provides statistical characterization of the same regions. Raman analysis reveals layer-dependent spectral fingerprints, including systematic variations in 2DFWHM, I2D/IG, and strain-dominated correlations between the G and 2D band positions. AFM friction measurements show a monotonic decrease in the friction coefficient from monolayer graphene to trilayer graphene. This decreasing friction trend is accompanied by a layer-dependent evolution of the Raman-derived strain state, while the measured RMS roughness and D band area remain approximately constant. The combined AFM–LEEM–Raman approach reveals a spatial correlation between graphene thickness, Raman spectroscopic signatures, and nanoscale friction in epitaxial graphene on SiC.
