Liquid-phase exfoliation of bismuth telluride iodide (BiTeI): structural and optical properties of single-/few-layer flakes

Bismuth telluride halides (BiTeX) are Rashba-type crystals with several potential applications ranging from spintronics and nonlinear optics to energy. Their layered structures and low cleavage energies allow their production in a two-dimensional form, opening the path to miniaturized device concepts. The possibility to exfoliate bulk BiTeX crystals in the liquid represents a useful tool to formulate a large variety of functional inks for large-scale and cost-effective device manufacturing. Nevertheless, the exfoliation of BiTeI by means of mechanical and electrochemical exfoliation proved to be challenging. In this work, we report the first ultrasonication-assisted liquid-phase exfoliation (LPE) of BiTeI crystals. By screening solvents with different surface tension and Hildebrandt parameters, we maximize the exfoliation efficiency by minimizing the Gibbs free energy of the mixture solvent/BiTeI crystal. The most effective solvents for the BiTeI exfoliation have a surface tension close to 28 mN m(-1) and a Hildebrandt parameter between 19 and 25 MPa0.5. The morphological, structural, and chemical properties of the LPE-produced single-/few-layer BiTeI flakes (average thickness of & SIM;3 nm) are evaluated through microscopic and optical characterizations, confirming their crystallinity. Second-harmonic generation measurements confirm the non-centrosymmetric structure of both bulk and exfoliated materials, revealing a large nonlinear optical response of BiTeI flakes due to the presence of strong quantum confinement effects and the absence of typical phase-matching requirements encountered in bulk nonlinear crystals. We estimated a second-order nonlinearity at 0.8 eV of |chi((2))| & SIM; 1 nm V-1, which is 10 times larger than in bulk BiTeI crystals and is of the same order of magnitude as in other semiconducting monolayers (e.g., MoS2)

Identification and characterization of novel ETV4 splice variants in prostate cancer

Abstract ETV4, one of ETS proteins overexpressed in prostate cancer, promotes migration, invasion, and proliferation in prostate cells. This study identifies a series of previously unknown ETV4 alternatively spliced transcripts in human prostate cell lines. Their expression has been validated using several unbiased techniques, including Nanopore sequencing. Most of these transcripts originate from an in-frame exon skipping and, thus, are expected to be translated into ETV4 protein isoforms. Functional analysis of the most abundant among these isoforms shows that they still bear an activity, namely a reduced ability to promote proliferation and a residual ability to regulate the transcription of ETV4 target genes. Alternatively spliced genes are common in cancer cells: an analysis of the TCGA dataset confirms the abundance of these novel ETV4 transcripts in prostate tumors, in contrast to peritumoral tissues. Since none of their translated isoforms have acquired a higher oncogenic potential, such abundance is likely to reflect the tumor deranged splicing machinery. However, it is also possible that their interaction with the canonical variants may contribute to the biology and the clinics of prostate cancer. Further investigations are needed to elucidate the biological role of these ETV4 transcripts and of their putative isoforms

Sulfonated NbS2-based proton-exchange membranes for vanadium redox flow batteries

In this work, novel proton-exchange membranes (PEMs) based on sulfonated poly(ether ether ketone) (SPEEK) and two-dimensional (2D) sulfonated niobium disulphide (S-NbS2) nanoflakes are synthesized by a solution-casting method and used in vanadium redox flow batteries (VRFBs). The NbS2 nanoflakes are produced by liquid-phase exfoliation of their bulk counterpart and chemically functionalized with terminal sulfonate groups to improve dimensional and chemical stabilities, proton conductivity (sigma) and fuel barrier properties of the as-produced membranes. The addition of S-NbS2 nanoflakes to SPEEK decreases the vanadium ion permeability from 5.42 x 10(-7) to 2.34 x 10(-7) cm(2) min(-1). Meanwhile, it increases the membrane sigma and selectivity up to 94.35 mS cm(-2) and 40.32 x 10(4) S min cm(-3), respectively. The cell assembled with the optimized membrane incorporating 2.5 wt% of S-NbS2 nanoflakes (SPEEK:2.5% S-NbS2) exhibits high efficiency metrics, i.e., coulombic efficiency between 98.7 and 99.0%, voltage efficiency between 90.2 and 73.2% and energy efficiency between 89.3 and 72.8% within the current density range of 100-300 mA cm(-2), delivering a maximum power density of 0.83 W cm(-2) at a current density of 870 mA cm(-2). The SPEEK:2.5% S-NbS2 membrane-based VRFBs show a stable behavior over 200 cycles at 200 mA cm(-2). This study opens up an effective avenue for the production of advanced SPEEK-based membranes for VRFBs