Thickness dependant characterization of chemically exfoliated TiS2 nanosheets

Monolayer TiS2 is the lightest member of the transition metal dichalcogenides family with promising application in energy storage and conversion systems. Use of TiS2 has been limited by the lack of rapid characterisation of layer number via Raman spectroscopy and its easy oxidation in wet environment. Here, we demonstrate layer number dependent Raman modes for TiS2. 1T-TiS2 presents two characteristics Raman active modes, A1g (out-of-plane) and Eg (in-plane). We identified a characteristic peak frequency shift of the Eg mode with the layer number and an unexplored Raman mode at 372 cm-1 whose intensity changes relative to the A1g mode with the thickness of TiS2 sheets. These two characteristic features of the Raman spectra allow the determination of layer numbers between 1 and 5 in exfoliated TiS2. Further, we develop a method to produce oxidation-resistant inks of micron sized mono- and few-layered TiS2 nanosheets at concentrations up to 1 mg/mL .These TiS2 inks can be deposited to form thin films with controllable thickness and nanosheet density over cm2 areas. This opens up pathways for a wider utilization of exofliated TiS2 towards a range of applications

Comb-like pseudopeptides enable very rapid and efficient intracellular trehalose delivery for enhanced cryopreservation of erythrocytes

Cell cryopreservation plays a key role in development of reproducible and cost-effective cell-based therapies. Trehalose accumulated in freezing and desiccation tolerant organisms in nature has been sought as an attractive non-toxic cryoprotectant. Herein, we report a co-incubation method for very rapid and efficient delivery of membrane-impermeable trehalose into ovine erythrocytes through reversible membrane permeabilization using pH-responsive, comb-like pseudopeptides. The pseudopeptidic polymers containing relatively long alkyl side chains were synthesized to mimic membrane-anchoring fusogenic proteins. The intracellular trehalose delivery efficiency was optimized by manipulating the side chain length, degree of substitution and concentration of the pseudopeptides with different hydrophobic alkyl side chains, the pH, temperature and time of incubation, as well as the polymer-to-cell ratio and the concentration of extracellular trehalose. Treatment of erythrocytes with the comb-like pseudopeptides for only 15 min yielded an intracellular trehalose concentration of 177.9 ± 8.6 mM, which resulted in 90.3 ± 0.7% survival after freeze-thaw. The very rapid and efficient delivery was found to be attributed to the reversible, pronounced membrane curvature change as a result of strong membrane insertion of the comb-like pseudopeptides. The pseudopeptides can enable efficient intracellular delivery of not only trehalose for improved cell cryopreservation, but also other membrane-impermeable cargos

Realization of ground state in artificial kagome spin ice via topological defect-driven magnetic writing

Arrays of non-interacting nanomagnets are widespread in data storage and processing. As current technologies approach fundamental limits on size and thermal stability, enhancing functionality through embracing the strong interactions present at high array densities becomes attractive. In this respect, artificial spin ices are geometrically frustrated magnetic metamaterials that offer vast untapped potential due to their unique microstate landscapes, with intriguing prospects in applications from reconfigurable logic to magnonic devices or hardware neural networks. However, progress in such systems is impeded by the inability to access more than a fraction of the total microstate space. Here, we demonstrate that topological defect-driven magnetic writing—a scanning probe technique—provides access to all of the possible microstates in artificial spin ices and related arrays of nanomagnets. We create previously elusive configurations such as the spin-crystal ground state of artificial kagome dipolar spin ices and high-energy, low-entropy ‘monopole-chain’ states that exhibit negative effective temperatures

Direct solution-phase synthesis of 1T’ WSe2 nanosheets

Crystal phase control in layered transition metal dichalcogenides is central for exploiting their different electronic properties. Access to metastable crystal phases is limited as their direct synthesis is challenging, restricting the spectrum of reachable materials. Here, we demonstrate the solution phase synthesis of the metastable distorted octahedrally coordinated structure (1T’ phase) of WSe2 nanosheets. We design a kinetically-controlled regime of colloidal synthesis to enable the formation of the metastable phase. 1T’ WSe2 branched few-layered nanosheets are produced in high yield and in a reproducible and controlled manner. The 1T’ phase is fully convertible into the semiconducting 2H phase upon thermal annealing at 400 °C. The 1T’ WSe2 nanosheets demonstrate a metallic nature exhibited by an enhanced electrocatalytic activity for hydrogen evolution reaction as compared to the 2H WSe2 nanosheets and comparable to other 1T’ phases. This synthesis design can potentially be extended to different materials providing direct access of metastable phases