Chemical etching method shows potential for large-scale and low-cost processed MXenes but incorporates surface terminations such as F&OH that probably deteriorate the lithium storage characteristics. Herein, we propose that tailoring appropriate surface functionalization and the intrinsic electrical properties can dramatically enhance the lithium storage capability of Ti3C2T x (T stands for F, OH, and O) MXene materials. By carefully controlling the annealing process, the Ti3C2T x films  possess fewer F&OH elements so that with higher conductivity, they are still freestanding and flexible. Density functional theory computations of the low-F&OH-containing Ti3C2T x show low-ion-diffusion barrier values of 0.34–0.43 eV and a significant increase of Li adsorption energy by 6–30 times compared to those of high-F&OH-containing Ti3C2T x , suggesting high Li-ion storage and transfer capabilities can be achieved in low-F&OH-containing Ti3C2T x MXenes. Dramatically, the heteroatom-controlled Ti3C2T x MXene films show reversible capacities of 221 mAh g–1 for lithium-ion batteries at a current density of 0.1 C (1 C = 320 mAh g–1), which is the highest up to now for pure Ti-based MXenes. These results demonstrate the importance of surface chemistry and electronic structure of MXene in the lithium storage capability, which provides valuable information on designing high-performance MXene-based materials for energy storage, optoelectronic, thermoelectric, and magnetic applications.

The origin of the contrast in noncontact atomic force microscopy (NC-AFM) images which is interpreted as intramolecular and intermolecular bonds is still under debate. Based on the ab initio approach and explicitly including the tilt effect of the flexible CO tip, we reveal that the outermost electron density of the sample dominates the AFM contrast, by corrugating of the repulsive force which determines the frequency shift and the lateral behavior of the flexible tip.Consequently, we find that various aspects of bond images in AFM are governed by features of the electron density residing between nuclei: e.g., in a π-conjugated system the brightness of bonds is similar to that of atoms in AFM images due to the gently undulating π electron density; bright lines can arise between two bonded atoms (e.g. in a hydrogen bond), and also between "non-bonded" atoms (e.g. between two Xe atoms) due to the spatial overlapping of the outermost electrons.

We employed a scanning probe-based lithography process on single-crystalline Si(100), Si(110), and Si(111) surfaces and studied the effects of crystallographic surface structures on mechanochemical etching of silicon in liquid water. The facet angle and etching rate of the mechanochemical process were different from those of the purely chemical etching process. In liquid water, the shape of the mechanochemically etched nanochannel appeared to be governed by thermodynamics of the etched surface, rather than stress distribution. Analyzing the etch rate with the mechanically assisted Arrhenius-type kinetics model showed that the shearinduced hydrolysis activity varies drastically with the crystallographic structure of silicon surface.

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Carbon doped into Bi2Se3 as substitution for Se was reported inducing simultaneous magnetic and hole doping. In this work, based on theoretical and experimental approaches, we find that carbon doped Bi2Se3 is indeed spin polarized, while the magnetic moments are small and hole doping is little. Most carbon atoms energetically favor to be dimer- and trimer-substitutions for Se which induce neither magnetism nor charge doping. A few isolated carbon atoms doped at interstitial sites in the vdW gap or at Se vacancies result in spontaneous spin polarization and charge doping. The diffusion of a single carbon dopant into Bi2Se3 is difficult, while if dopants are close, carbon clusters can easily form, which means that the isolated, pairwise, and trimeric carbon dopants should coexist. These studies suggest that to obtain strong ferromagnetic C-Bi2Se3, experiments need careful design to dope single carbon atoms into bulk dispersedly.