Ultrafast Interlayer Charge Transfer Outcompeting Intralayer Valley Relaxation in Few-Layer 2D Heterostructures.

While 2D transition metal dichalcogenides (TMDs) feature interesting layer-tunable multivalley band structures, their preeminent role in determining the photoexcitation charge transfer dynamics in 2D heterostructures (HSs) is yet to be unraveled, as previous charge transfer studies on TMD HSs have been mostly focused on monolayers with a direct bandgap at the K valley. By ultrafast transient absorption spectroscopy and deliberately designed few-layer WSe2/WS2 HSs, we have observed an ultrafast interlayer electron transfer from photoexcited few-layer WSe2 to WS2, prior to intralayer relaxation to lower lying dark valleys. More interestingly, we have identified an unconventional ∼0.5 ps electron back-transfer process after the initial interlayer electron transfer in HSs with WSe2 layers ≥ 3, regenerating indirect intralayer excitons. The result reveals an ielectron and valley relaxation pathway mediated by interlayer charge transfer in 2D HSs, faster than intralayer relaxation. It also sheds light on the origin of generally observed robust ultrafast interlayer charge transfer in TMD HSs and provides guidance toward optoelectronic and valleytronic devices using few-layer TMDs.

Fish-Wearable Piezoelectric Nanogenerator for Dual-Modal Energy Scavenging from Fish-Tailing.

Aiming to develop a self-powered bioelectric tag for fish behavioral studies, here we present a fish-wearable piezoelectric nanogenerator (FWPNG) that can simultaneously harvest the strain energy and the flow impact energy caused by fish-tailing. The FWPNG is fabricated by transferring a 2 µm-thick Nb0.02-Pb(Zr0.6Ti0.4)O3 (PZT) layer from a silicon substrate to a spin-coated polyimide film via a novel zinc oxide (ZnO) release process. The open-circuit voltage of the strain energy harvester reaches 2.3 V under a strain of 1% at an ultra-low frequency of 1 Hz, and output voltage of the impact energy harvester reaches a 0.3 V under a pressure of 82.6 kPa at 1 Hz, which is in good agreement with our theoretical analysis. As a proof-of-concept demonstration, an event-driven underwater acoustic transmitter is developed by utilizing the FWPNG as a trigger switch. Acoustic transmission occurs when the amplitude of fish-tailing is larger than a preset threshold. The dual-modal FWPNG device shows the potential application in self-powered biotags for animal behavioral studies and ocean explorations.

Cobalt doped iron oxychloride as efficient heterogeneous Fenton catalyst for degradation of paracetamol and phenacetin.

Cobalt doped iron oxychloride (Co-FeOCl) was synthesized and employed as catalyst in Fenton degradation of paracetamol (APAP) and phenacetin (PNCT) for the first time. The catalytic performance was evaluated by means of various parameters including catalyst load, hydrogen peroxide (H2O2) dose and pH value. The high removal of APAP (87.5%) and PNCT (76.0%) was obtained under conditions of 0.2 g/L Co-FeOCl and 0.5 mM H2O2 at pH 7.0, with calculated pseudo-first order kinetic constants of 0.031 min-1 for APAP and 0.023 min-1 for PNCT. Particularly, quenching tests and in situ electron spin resonance (ESR) tests were employed for the identification of the reactive oxygen species (ROS) in system. Hydroxyl radical (·OH) and superoxide radical (O2-·) were the primary ROS in Co-FeOCl/H2O2 system. A possible mechanism for H2O2 activation by Co-FeOCl catalyst was proposed as well. Finally, the formation of typical disinfection by-products (DBPs) decreased slightly in Co-FeOCl/H2O2 pre-oxidation. However, stability and reusability of Co-FeOCl were deactivated in the consecutive three cycles.

Reactive oxygen species generation in FeOCl nanosheets activated peroxymonosulfate system: Radicals and non-radical pathways.

Iron oxychloride (FeOCl) is utilized as a activator of peroxymonosulfate (PMS) for the degradation of paracetamol (APAP) and phenacetin (PNCT) in response to the water pollution by persistent pharmaceuticals. The degradation process was well fitted with a pseudo-first order kinetic pattern, and the excellent catalytic performance towards APAP (100 % removal) and PNCT (86.5 % removal) was obtained in the presence of 0.2 g/L FeOCl and 2.0 mM PMS at pH 7.0 in 30 min. In-situ electron spin resonance (ESR) and scavenging tests revealed the generation of a series of ROS (·OH, SO4-, O2-, 1O2), which was highly dependent on pH. Besides, the non-radical pathways process involved 1O2 was dominant in APAP oxidation, while both ·OH and 1O2 are significant in PNCT removal. Furthermore, the formation of disinfection by-products (DBPs) during post-chlorination showed neglectable increment at neutral and alkaline condition with FeOCl/PMS pre-oxidation, and the calculated cytotoxicity would experience a continuous deterioration with pH increase. These results displayed high efficiency of FeOCl/PMS system in micropollutants degradation and a relatively comprehensive activation process of PMS, which may promote practical application in environmental remediation.

Magnet-activatable nanoliposomes as intracellular bubble microreactors to enhance drug delivery efficacy and burst cancer cells.

To address the thereapeutic challenges in clinical cancer treatment and guarantee efficient and rapid intracellular delivery of drugs while evading efflux and chemotherapy resistance, herein, we designed a liposomal nanostructure equipped with superparamagnetic iron oxide nanoparticles (SPIOs) and anethole trithione (ADT, a hydrogen sulfide (H2S) donor drug). At first, by spatially focused manipulation of the external static magnetic field (SMF), the SPIOs and ADT-loaded liposomes (SPIOs-ADT-LPs) could rapidly overcome the cell membrane barrier to enter the cytoplasm, which could be imaged by magnetic resonance imaging (MRI). Sequentially, the intracellular release of ADT drugs was triggered by enzymatic catalysis to generate acoustic-sensitive H2S gas. At the beginning, during the production of H2S at low concentrations, the cell membrane could be permeabilized to further increase the cellular uptake of SPIOs-ADT-LPs. The continued generation of H2S gas bubbles, imaged by ultrasound (US) imaging, further enhanced the intracellular hydrostatic pressure (above 320 pN per cell) to physically unfold the cytoskeleton, leading to complete cell death. The magneto-acoustic approach based on SPIO-ADT-LPs as intracellular bubble reactors leads to improved anticancer cell efficacy and has potential applications for novel MRI/US dual image-guided bubble bursting of cancer cells.

Role of TGF-ß-activated kinase 1 (TAK1) activation in H5N1 influenza A virus-induced c-Jun terminal kinase activation and virus replication.

Activation of c-Jun terminal kinase (JNK) by the nonstructural protein 1 (NS1) of the H5N1 subtype of influenza A virus (IAV) plays an important role in inducing autophagy and virus replication. However, the mechanisms of NS1-induced JNK activation remain elusive. Here we first confirmed the ability of H5N1 (A/mallard/Huadong/S/2005) to activate JNK and to induce autophagy in 293T cells, a human embryonic kidney cell line. We further showed that TAK1, MAP kinase kinase 4 (MKK4), and JNK were activated in 293T cells transfected with the NS1 gene of the H5N1 virus. JNK activation by the NS1 protein or by H5N1 virus was blocked by 5Z-7-Oxozeaenol (5Z), a TAK1-specific inhibitor, and by TAK1 siRNA. Further study showed that 5Z and TAK1 siRNA suppressed H5N1 virus-induced autophagy and inhibited virus replication. Our study unveiled a previously unrecognized role of TAK1 in IAV replication, IAV-induced JNK activation, and autophagy.

Highly efficient and giant negative electrocaloric effect of a Nb and Sn co-doped lead zirconate titanate antiferroelectric film near room temperature.

Adiabatic temperature variation (ΔT), coefficient of performance (COP) and electrocaloric coefficient (ΔT/ΔE) play important roles in evaluating the comprehensive performance of solid-state cooling technology based on the electrocaloric effect (ECE). A Nb and Sn co-doped lead zirconate titanate antiferroelectric film, Pb0.99Nb0.02(Zr0.85Sn0.13Ti0.02)O3 (PNZST), shows a highly efficient and giant negative ECE. The ΔT, |ΔT/ΔE| and COP are about -9.8 K, 0.0488 K cm kV-1 and 35.53 at around 50 °C, respectively. The full width at half maximum of the ΔT peak is about 37 °C. Phenomenological analysis indicates that the highly efficient and giant negative ECE is associated with the first-order transition that has a discontinuous polarization change with increasing temperature.

Role of c-Jun terminal kinase (JNK) activation in influenza A virus-induced autophagy and replication.

The non-structural protein 1 (NS1) of different influenza A virus (IAV) strains can differentially regulate the activity of c-Jun terminal kinase (JNK) and PI-3 kinase (PI3K). Whether varying JNK and PI3K activation impacts autophagy and IAV replication differently remains uncertain. Here we report that H5N1 (A/mallard/Huadong/S/2005) influenza A virus induced functional autophagy, as evidenced by increased LC3 lipidation and decreased p62 levels, and the presence of autolysosomes in chicken fibroblast cells. H9N2 (A/chicken/Shanghai/F/98) virus weakly induced autophagy, whereas H1N1 virus (A/PR/8/34, PR8) blocked autophagic flux. H5N1 virus activated JNK but inhibited the PI-3 kinase pathway. In contrast, N9N2 virus infection led to modest JNK activation and strong PI-3 kinase activation; whereas H1N1 virus activated the PI-3 kinase pathway but did not activate JNK. SP600125, a JNK inhibitor, inhibited H5N1 virus-induced autophagy and virus replication in a DF-1 chicken fibroblast cell line. Our study uncovered a previously unrecognized role of JNK in IAV replication and autophagy.