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Lithium-sulfur (Li-S) batteries have gained considerable attention for high theoretical specific capacity and energy density. However, their development is hampered by the poor electrical conductivity of sulfur and the shuttle of polysulfides. Herein, the acidified bamboo-structure carbon nanotubes (BCNTs) were mixed with polyvinylidene difluoride and pyrolyzed at high-temperature to obtain the fluorinated bamboo-structure carbon nanotubes (FBCNTs), which were compounded with sulfur as the cathode. The prepared S@FBCNTs with sulfur loading reaching 74.2 wt.% shows a high initial specific capacity of 1407.5 mAh·g -1 at the discharge rate of 0.1 C. When the discharge rate was increased to 5 C, the capacity could be maintained at 622.3 mAh·g -1 . The electrical conductivity of carbon nanotubes is effectively improved by semi-ionic C-F bonds formed by the doped F atoms and carbon atoms. Simultaneously, the surface of the F-containing carbon tubes exhibits strong polarity and strong chemisorption effect on polysulfides, which inhibits the shuttle effect of Li-S batteries., (© 2023 IOP Publishing Ltd.)

Two-dimensional transition metal dichalcogenides (TMDs), as flexible and stretchable materials, have attracted considerable attention in the field of novel flexible electronics due to their excellent mechanical, optical, and electronic properties. Among the various TMD materials, atomically thin MoS 2 has become the most widely used material due to its advantageous properties, such as its adjustable bandgap, excellent performance, and ease of preparation. In this work, we demonstrated the practicality of a stacked wafer-scale two-layer MoS 2 film obtained by transferring multiple single-layer films grown using chemical vapor deposition. The MoS 2 field-effect transistor cell had a top-gated device structure with a (PI) film as the substrate, which exhibited a high on/off ratio (10 8 ), large average mobility (∼8.56 cm 2 V -1 s -1 ), and exceptional uniformity. Furthermore, a range of flexible integrated logic devices, including inverters, NOR gates, and NAND gates, were successfully implemented via traditional lithography. These results highlight the immense potential of TMD materials, particularly MoS 2 , in enabling advanced flexible electronic and optoelectronic devices, which pave the way for transformative applications in future-generation electronics., (© 2023 IOP Publishing Ltd.)

With the recent discovery of three dimensional Dirac semimetals, their integrations with the optoelectronic devices allow the novel optical effects and functionalities. Here, we theoretically report the photonic spin Hall effect in a periodic structure, where three dimensional Dirac semimetals and the dielectric materials are assembled into the stack. The incident angle and frequency dependent spin shift spectrum reveals that the spin shifts of the transmitted wave in this structure emerge the obvious peaks and valleys for the horizontal polarized wave and their magnitudes and positions display a distinct dependence on the incident angle around the specific frequency. These observations originate from its zero value of the effective perpendicular permittivity and its greatly reduced transmission in the multilayered structure, whose mechanism is different from those in the previous works. Moreover, both the peaks and valleys of the transmitted spin shift are significantly sensitive to the Fermi energy of three dimensional Dirac semimetals, whose magnitudes and positions can be tuned by varying it. Our results highlight the vital role of three dimensional Dirac semimetals in their applications of the spin photonic devices and pave the way to explore the tunable photonic spin Hall effect by engineering their Fermi energies., (© 2022 IOP Publishing Ltd.)

Negative refraction materials are indispensable building blocks in the optoelectric devices for their unique functionalities of controlling the light propagations, such as, superlens and transformation optics. However, material realizations of negative refraction are still limited to the conventional metals, semiconductors as well as magnetic materials. Here, we show that three dimensional Dirac semimetals have the opportunity to enable the negative refraction, which can be achieved through alternatively stacking three dimensional Dirac semimetals and the dielectric layers together. It is found that the effective perpendicular and parallel permittivities in this multilayered stack display the respective negative and positive values over a certain frequency region, which enables its negative group refractive angle and it can be controlled by the Fermi energy of Dirac semimetals. The spectra of transmittance in the multilayered structure for transverse magnetic wave also reveals an incident angle-independent transmittance dip, which originates from the zero value of the real part of the effective perpendicular permittivity. Our findings unveil the essential role of three dimensional Dirac semimetals in producing the negative group refraction responses and promise their applications in the metamaterial-based devices., (© 2022 IOP Publishing Ltd.)

Until now, the growth of periodic vertically aligned multi-walled carbon nanotube (VA-MWCNT) arrays was dependent on at least one lithography step during fabrication. Here, we demonstrate a lithography-free fabrication method to grow hexagonal arrays of self-standing VA-MWCNTs with tunable pitch and MWCNT size. The MWCNTs are synthesized by plasma enhanced chemical vapor deposition (PECVD) from Ni catalyst particles. Template guided dewetting of a thin Ni film on a hexagonally close-packed silica particle monolayer provides periodically distributed Ni catalyst particles as seeds for the growth of the periodic MWCNT arrays. The diameter of the silica particles directly controls the pitch of the periodic VA-MWCNT arrays from 600 nm to as small as 160 nm. The diameter and length of the individual MWCNTs can also be readily adjusted and are a function of the Ni particle size and PECVD time. This unique method of lithography-free growth of periodic VA-MWCNT arrays can be utilized for the fabrication of large-scale biomimetic materials., (© 2021 IOP Publishing Ltd.)

Talc is a van der Waals and naturally abundant mineral with the chemical formula Mg 3 Si 4 O 10 (OH) 2 . Two-dimensional (2D) talc could be an alternative to hBN as van der Waals dielectric in 2D heterostructures. Furthermore, due to its good mechanical and frictional properties, 2D talc could be integrated into various hybrid microelectromechanical systems, or used as a functional filler in polymers. However, properties of talcas one of the main representatives of the phyllosilicate (sheet silicates) group are almost completely unexplored when ultrathin crystalline films and monolayers are considered. We investigate 2D talc flakes down to single layer thickness and reveal their efficiency for solid lubrication at the nanoscale. We demonstrate by atomic force microscopy based methods and contact angle measurements that several nanometer thick talc flakes have all properties necessary for efficient lubrication: a low adhesion, hydrophobic nature, and a low friction coefficient of 0.10 ± 0.02. Compared to the silicon-dioxide substrate, 2D talc flakes reduce friction by more than a factor of five, adhesion by around 20%, and energy dissipation by around 7%. Considering our findings, together with the natural abundance of talc, we put forward that 2D talc can be a cost-effective solid lubricant in micro- and nano-mechanical devices., (Creative Commons Attribution license.)

The methylammonium (MA) and formamidinium (FA) are the most commonly used organic cations in perovskite solar cells (PSCs), whereas the impact of size and polarity differences between these two on the photovoltaic performances has been rarely revealed. Herein, we systematically investigated the phase distribution, optoelectronic and stability properties of FA-MA mixed perovskites. To identify the phase homogeneity, depth-dependent grazing-incidence wide-angle x-ray scattering measurements were employed, which demonstrates that the mixed cation perovskite possesses a FA-rich phase on the film surface and the bottom is comprised of MA-rich phase. Additionally, upon long-time illumination, a new PL peak is appeared at 778 nm, representing the generation of MA-rich phase induced by ion migration. It is worth noting that the phase splitting and inhomogeneous phase distribution would not bring any obvious detrimental effects to the photovoltaic performances and stability properties. Through judiciously tuning the cation proportion in pure-iodide perovskite, the additive-free PSCs achieve an efficiency as high as 20.7%. Furthermore, the PSCs with a broad range of FA/MA ratios show improved humidity/thermal/light stability despite the phase inhomogeneity. Therefore, the work shows that the MA and FA cations have a high compatibility in perovskite structure and the precise ratio control can further improve the performances.

We develop nano-bridged nanosphere lithography (NB-NSL), a modification to the widely used conventional nanosphere lithography (NSL). Nano-bridges between polystyrene (PS) spheres of a pristine NSL template are controllably formed in a two-step process: (i) spin-coating of a dilute styrene solution on top of the template, followed by (ii) oxygen plasma etching of the template. We show that the nanobridge dimensions can be precisely tuned by controlling the pre-processing conditions and the plasma etching time. The resulting lithography templates feature control over the shape and size of the apertures, which determine the morphology of the final nano-island arrays after material deposition and template removal. The unique advantage of NB-NSL is that PS particle templates based on a single PS particle diameter can be utilized for the fabrication of a variation of nano-island shapes and sizes, whereas conventional NSL yields only bowtie-shaped nano-islands, with their size being predetermined by the PS particle diameter of the template.

We report the first demonstration of a high-efficiency photoelectrochemical (PEC) water splitting reaction using a novel Si NWs/WO 3 core/shell photoanode prepared by a mild and inexpensive metal-catalyzed electroless etching process followed by dip-coating, airing and annealing methods. The dense and vertically aligned Si NWs/WO 3 core/shell nanostructure were characterized by scanning electron microscopy, transmission electron microscopy and x-ray diffraction. In comparison to planar n-Si, Si NWs and planar Si/WO 3 , the Si NWs/WO 3 samples showed significantly enhanced photocurrent over the entire potential sweep range. More significantly, the Si NWs/WO 3 samples have an exceptionally low photocurrent onset potential of -0.6393 V versus reversible hydrogen electrode (RHE), indicating very efficient charge separation and charge transportation processes. The as-prepared electrode also has a photocurrent density of 2.7 mA cm -2 at 0.6107 V versus RHE in 0.5 M Na 2 SO 4 solution under simulated solar light irradiation (100 mW cm -2 from 300 W Xenon lamp coupled with an AM 1.5 G filter). An optimal solar-to-hydrogen efficiency of about 1.9% was achieved at 0.2676 V versus RHE. Electrochemical impedance spectroscopy was conducted to investigate the properties of the charge transfer process, and the results indicated that the enhanced PEC performance may due to the increased charge separation. The x-ray photoelectron spectroscopy measurements indicated the chemical composition of the Si NWs/WO 3 nanostructure. Our work has provided an efficient strategy to improve the energy conversion efficiency and photocurrent of water splitting materials.

Surfaces with a periodic nanostructure and controllable feature size are sought after for optical applications, and the fabrication of such surfaces in large areas with high reproducibility, good stability and low deviation is very important. We present a strategy to fabricate large-area nanoslit arrays with controllable pitches and gaps. Au nanoslit arrays with gaps down to around 10 nm and a high gap density of 2.0 × 10 4 cm -1 have been fabricated, which can greatly enhance the near-field electromagnetic field to achieve localized surface plasmon resonance (LSPR). An averaged surface-enhanced Raman scattering analytical enhancement factor of 8.0 × 10 7 has been achieved on the substrate using a 633 nm laser source and the 'coupling effect' of LSPR of the nanoslits.

Sensitive detection of a specific deoxyribo nucleic acid (DNA) sequence is important for biomedical applications. In this report, a two-step amplification strategy is developed based on magnetic nanoparticles (MNPs) to achieve ultrasensitive DNA fluorescence detection. The first level amplification is obtained from multiple binding sites on MNPs to achieve thousands of probe DNA molecules on one nanoparticle surface. The second level amplification is gained by enzymatic reaction to achieve fluorescence signal enhancement. MNPs functionalized by probe DNA (DNAp) are bound to target DNA (t-DNA) molecules with a ratio of 1:1 on a substrate with capture DNA (DNAc). After the MNPs with DNAp are released from the substrate, alkaline phosphatase (AP) is labelled to MNPs via hybridization reaction between DNAp on MNPs and detection DNAs (DNAd) with AP. The AP on MNPs catalyses non-fluorescent 4-methylumbelliferyl phosphate (4-MUP) to fluorescent 4-methylumbelliferone (4-MU) with high intensity. Finally, fluorescence intensity of the 4-MU is detected by a conventional fluorescence spectrophotometer. With this two-step amplification strategy, the limit of detection (LOD) of 2.8 × 10(-18) mol l(-1) for t-DNA has been achieved.

A multilayer coated paper substrate, combining barrier and printability properties was manufactured utilizing a pilot-scale slide curtain coating technique. The coating structure consists of a thin mineral pigment layer coated on top of a barrier layer. The surface properties, i.e. smoothness and surface porosity, were adjusted by the choice of calendering parameters. The influence of surface properties on the fine line printability and conductivity of inkjet-printed silver lines was studied. Surface roughness played a significant role when printing narrow lines, increasing the risk of defects and discontinuities, whereas for wider lines the influence of surface roughness was less critical. A smooth, calendered surface resulted in finer line definition, i.e. less edge raggedness. Dimensional stability and its influence on substrate surface properties as well as on the functionality of conductive tracks and transistors were studied by exposure to high/low humidity cycles. The barrier layer of the multilayer coated paper reduced the dimensional changes and surface roughness increase caused by humidity and helped maintain the conductivity of the printed tracks. Functionality of a printed transistor during a short, one hour humidity cycle was maintained, but a longer exposure to humidity destroyed the non-encapsulated transistor.

A facile and green method to synthesize stable Ag nanoparticles (Ag NPs) with a narrow size distribution in water is reported. Water-soluble quaternized carboxymethyl chitosan (QCMC) with a surfactant-like structure was used as both a reducing and stabilizing agent under microwave irradiation via the modified Tollens reaction. In order to study the preparation mechanism, carboxymethyl chitosan (CMC) and quaternized chitosan (QCS) were compared as both reducing and stabilizing agents. Full characterization was performed using UV-vis, XRD, TEM, AAS, FT-IR, NMR and TGA. The results revealed that the prepared Ag NPs were mostly spherical with a small proportion being cylinders or cuboids; they were stable due to the package of the macromolecules; the diameters were 10.24 ± 3.13 nm. The Tollens reaction followed first order kinetics, and the Ea was 102.4 kJ mol(-1) for QCMC/Ag NP composite. During the growth of the Ag NPs, some quaternary ammonium groups and carboxymethyl groups were respectively oxidized to -CH2COCH3 and -CH3 groups, and the quaternary ammonium groups were more helpful for the growth of Ag NPs than the carboxymethyl groups. In addition, QCMC/Ag NP composite had much higher thermal stability than QCMC.

In this study, an attempt was made to prepare novel D-glucosamine hydrochloride-rectorite (DGH-REC) nanocomposites with improved antioxidant and anti-ultraviolet activity via the solution-intercalation method. The structure and morphology of DGH-REC nanocomposites were characterized by XRD, TEM, (13)C CP/MAS NMR, FT-IR, XPS and SEM. The results showed that the interlayer distance of REC was enlarged after intercalation of DGH; the largest value reached 11.76 nm, and in this case exfoliation of the REC layer was observed. Moreover, most strong crystals of DGH were greatly disrupted while two other weak crystals of DGH were stronger after intercalation of DGH into REC. More importantly, it was found that DGH-REC nanocomposites showed pronounced antioxidant activity, in contrast with DGH, and the nanocomposites had anti-ultraviolet capacity, which was not observed in DGH. Furthermore, the nanocomposites did not show apparent cytotoxicity. Therefore, DGH-REC nanocomposites have great potential in health or functional food application as compared to DGH.

Cyclic tensile and compressive deformation is applied to cellulose nanowhisker-epoxy resin based model nanocomposites. The molecular deformation of the cellulose nanowhiskers within the epoxy resin matrix is followed using a Raman spectroscopy technique, whereby shifts in the position of a band located at ∼ 1095 cm(-1) are shown to correlate directly with a breakdown in the interfaces between the resin and the nanowhiskers and between nanowhiskers themselves. A theoretical model is used to determine the dissipation of energy at the interfaces between whiskers and at the whisker-matrix interface. This approach is shown to be useful for interpreting the local micromechanics of these materials by providing a quantitative measure of the quality of the interface.

Non-viral vectors have gained increasing attention in gene therapy because of their safety, but with the shortcoming of low transfection efficiency. We have developed a hybrid material as a novel non-viral vector, which combines the advantages of both biopolymer and clay in a gene delivery system. Quaternized chitosan was intercalated into the interlayers of rectorite to obtain a new polymer/layered silicate nanocomposite. In vitro and in vivo toxicity studies revealed that the nanocomposites were biocompatible and non-toxic. At the nanocomposite:pDNA mass ratio of 8:1, they achieved 100% pDNA adsorption capacity. In vitro cell transfection revealed a transfection efficiency of 32.1% at 96 h as shown by a flow-cytometric study, and the intensive green fluorescence protein (GFP) expression could last for up to 120 h. Furthermore, an in vivo transfection study showed that the most prominent GFP expression was observed in the gastric and duodenum mucosa, and good transfection efficiency was also obtained when injected into the muscle. All the results suggest that quaternized chitosan/rectorite nanocomposite is a novel and potential non-viral gene carrier.