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In order to achieve wearable displays, fiber-shaped supercapacitors have been widely explored. [5,6] Compared with the conventional planar structure, they could be woven into electronic clothes by the well-developed textile technology to achieve ventilating function. [7][8][9][10] Generally, in order to fabricate fiber-type device, a line-shaped electrode is necessary. There have been many kinds of alternative fiberlike electrode. For instance, electrochemically active materials are coated on fibrous structural supports (such as polymer fibers [11,12] and metal wires) [13] to fabricate the fiber-shaped electrode. However, the poor conductivity or the high cost of these supports restricts their further development. As an alternative approach, carbon materials (carbon nanotubes (CNTs), [14] graphene, [15] activated carbon) [16] have been made into fibers for potential wearable applications. Unfortunately, a constraint of these carbonaceous materials lies in their low capacitance, and these fibers are not mechanically tough to be weaved and knitted by machines. More recently, MXenes, a new 2D materials family of early transition metal carbides and carbonitrides, have shown much promise over other supercapacitor electrode materials. [17] The most widely studied MXene to date has been Ti 3 C 2 T x . It was obtained by selectively etching off the Al element from the host of layered carbide Ti 3 AlC 2 . [18] The surfaces of the etched resultant are typically terminated by O, OH, and/or F with a formula Ti 3 C 2 T x , where T x stands for a general surface termination. [19] In general, the rich chemistry and tunable surface termination, metallic conductivity, and surface hydrophilicity of MXenes make them attractive candidates for energy-storage applications, especially for supercapacitor electrode materials. Recent results have shown that Ti 3 C 2 T x electrodes have high capacitance and perform well at high rates, such as Ti 3 C 2 T x freestanding films, [17] self-assembled Ti 3 C 2 T x films with nickel foam, [20] sandwich-like MXene/CNT papers, [21] and so on. [22,23] Very recently, a wire-type supercapacitor based on Ti 2 CT x MXene in a basic electrolyte was demonstrated. [24] Its very low capacitance and energy density, and the rigid stainless steel wire support, make the fabricated supercapacitor not ideal for wearable purpose. Thus, exploring a strategy to fabricate fibertype MXene-based supercapacitors with high capacitance is very urgent, attractive, and challenging.Herein, we propose a solution-processed methodology to fabricate all-solid-state, flexible, and fiber-based supercapacitors employing Ti 3 C 2 T x MXene. We choose silver-plated nylon fibers

We have investigated the structure, adsorption energy, growth mode, diffusion barrier, magnetic property, dipole moment, and work function of Li, Na, Mg, Al, Cr, Fe, Co, Ni, Mo, Pd, Pt, and Au adsorption on phosphorene using firstprinciples density-functional theory. We have found that all the adatoms favor the hollow site of hexagonal. It seems that the Mg, Cr, Mo, and Au adatoms may have three-dimensional (3D) growth mode on phosphorene substrate, whereas all other adatoms prefer two-dimensional (2D) growth mode. The metallic state is observed in Li, Na, Al, and Cr doped systems, and the Cr doped phosphorene displays magnetic state. The other eight metal doped systems still preserve semiconducting band gap. Among them, we obtained spin polarized band structures in Fe, Co, and Au doped systems with a band gap. In particular, the Fe doped phosphorene can be a potential candidate for dilute magnetic semiconductor material because no clustering problem will take place. We found a variation in dipole moment and work functions in each impurity doped layer. Both dipole moment and the shift of the Fermi level could account for the change of work function semiquantitatively.

With the aim of understanding recent experimental data concerning noncovalent n/p-doping effects in graphene samples, we have investigated the interactions between two prototypical donor and acceptor molecules and graphene mono- and bilayer systems, by means of density functional theory calculations. We report and rationalize the structural, thermodynamical aspects, as well as charge transfers and the induced electronic structure modifications of the graphenic substrates in interaction with tetrathiafulvalene (TTF), an organic donor molecule, and tetracyanoethylene (TCNE), a typical acceptor. If the results show that p-doping of a graphene monolayer due to TCNE molecules can occur even at low concentration, n-doping of graphene requires either larger concentrations or cooperative adsorption of TTF molecules. In both cases, noncovalent doping only implies shifts of the Fermi level, and keeps the linear dispersion of the π and π* state around the Dirac point. Moreover, the intercalation of donor/acceptor molecules decouples the layers and doped them.

Recently, an emergent layered material T d -WTe 2 was explored for its novel electron-hole overlapping band structure and anisotropic inplane crystal structure. Here, the photoresponse of mechanically exfoliated WTe 2 flakes is investigated. A large anomalous current decrease for visible (514.5 nm), and mid-and far-infrared (3.8 and 10.6 µm) laser irradiation is observed, which can be attributed to light-induced surface bandgap opening from the first-principles calculations. The photocurrent and responsivity can be as large as 40 µA and 250 A W −1 for a 3.8 µm laser at 77 K. Furthermore, the WTe 2 anomalous photocurrent matches its in-plane crystal structure and exhibits light polarization dependence, maximal for linear laser polarization along the W atom chain a direction and minimal for the perpendicular b direction, with the anisotropic ratio of 4.9. Consistently, first-principles calculations confirm the angle-dependent bandgap opening of WTe 2 under polarized light irradiation. The anomalous and polarization-sensitive photoresponses suggest that linearly polarized light can significantly tune the WTe 2 surface electronic structure, providing a potential approach to detect polarized and broadband lights up to far infrared range.

Chiral nanostructures exhibit strong coupling to the spin angular momentum of incident photons. The integration of metal nanostructures with semiconductor nanoparticles (NPs) to form hybrid plasmon-exciton nanoscale assemblies can potentially lead to plasmon-induced optical activity and unusual chiroptical properties of plasmon-exciton states. Here we investigate such effects in supraparticles (SPs) spontaneously formed from gold nanorods (NRs) and chiral CdTe NPs. The geometry of this new type of self-limited nanoscale superstructures depends on the molar ratio between NRs and NPs. NR dimers surrounded by CdTe NPs were obtained for the ratio NR/NP = 1:15, whereas increasing the NP content to a ratio of NR/NP = 1:180 leads to single NRs in a shell of NPs. The SPs based on NR dimers exhibit strong optical rotatory activity associated in large part with their twisted scissor-like geometry. The preference for a specific nanoscale enantiomer is attributed to the chiral interactions between CdTe NP in the shell. The SPs based on single NRs also yield surprising chiroptical activity at the frequency of the longitudinal mode of NRs. Numerical simulations reveal that the origin of this chiroptical band is the cross talk between the longitudinal and the transverse plasmon modes, which makes both of them coupled with the NP excitonic state. The chiral SP NR-NP assemblies combine the optical properties of excitons and plasmons that are essential for chiral sensing, chiroptical memory, and chiral catalysis.

Carbon vacancies are commonly present in two-dimensional (2D) MXenes that hold promise in a variety of applications whereas their behavior remains unknown. Here we report on the influence of carbon vacancies on the structural stability, electronic properties and stiffness of MXenes by taking TiCT (T = O, F, and OH) as an example. According to the first-principles calculations, the formation energies of carbon vacancies in MXenes are lower than those in other typical 2D materials including graphene and MoS, in combination with high migration energies. These two features mean that carbon-vacant MXenes are thermodynamically and dynamically stable as further evidenced by the absence of structural reconstruction both in the ground state and at ambient temperature. Interestingly, carbon vacancies that are usually considered as defects substantially offer a new opportunity on at least two aspects: enhanced electronic conduction and reduced stiffness corresponding to improved flexibility. The localized states in the vicinity of the Fermi level introduced by carbon vacancies account for the prominent metallic characteristics in carbon-vacant TiCT MXenes.

Phosphorene is receiving great research interests because of its peculiar physical properties. Nonetheless, the phosphorus has a trouble of degradation due to oxidation. Hereby, we propose that the electrical and optical anisotropic properties can be preserved by encapsulating into hexagonal boron nitride (h-BN). We found that the h-BN contributed to enhancing the band gap of the phosphorene layer. Comparing the band gap of the pristine phosphorene layer, the band gap of the phosphorene/BN(1ML) system was enhanced by 0.15 eV. It was further enhanced by 0.31 eV in the BN(1ML)/phosphorene/BN(1ML) trilayer structure. However, the band gap was not further enhanced when we increased the thickness of the h-BN layers even up to 4 MLs. Interestingly, the anisotropic effective mass and optical property were still preserved in BN/phosphorene/BN heterostructures. Overall, we predict that the capping of phosphorene by the h-BN layers can be an excellent solution to protect the intrinsic properties of the phosphorene.