Poly(vinylidene fluoride)-based dielectric materials are prospective candidates for high power density electric storage applications because of their ferroelectric nature, high dielectric breakdown strength and superior processability. However, obtaining a polar phase with relaxor-like behavior in poly(vinylidene fluoride), as required for high energy storage density, is a major challenge. To date, this has been achieved using complex and expensive synthesis of copolymers and terpolymers or via irradiation with high-energy electron-beam or γ-ray radiations. Herein, a facile process of pressing-and-folding is proposed to produce β-poly(vinylidene fluoride) (β-phase content: ~98%) with relaxor-like behavior observed in poly(vinylidene fluoride) with high molecular weight > 534 kg mol−1, without the need of any hazardous gases, solvents, electrical or chemical treatments. An ultra-high energy density (35 J cm−3) with a high efficiency (74%) is achieved in a pressed-and-folded poly(vinylidene fluoride) (670-700 kg mol−1), which is higher than that of other reported polymer-based dielectric capacitors to the best of our knowledge.

A B S T R A C TDielectric capacitors are very attractive for high power energy storage. However, the low energy density of these capacitors, which is mainly limited by the dielectric materials, is still the bottleneck for their applications. In this work, lead-free single-phase perovskite Sr x (Bi 1−x Na 0.97−x Li 0.03 ) 0.5 TiO 3 (x = 0.30 and 0.38) bulk ceramics, prepared using solid-state reaction method, were carefully studied for the dielectric capacitor application. Polar nano regions (PNRs) were created in this material using co-substitution at A-site to enable relaxor behaviour with low remnant polarization (P r ) and high maximum polarization (P max ). Moreover, P max was further increased due to the electric field induced reversible phase transitions in nano regions. Comprehensive structural and electrical studies were performed to confirm the PNRs and reversible phase transitions. And finally a high energy density (1.70 J/cm 3 ) with an excellent efficiency (87.2%) was achieved using the contribution of field-induced rotations of PNRs and PNR-related reversible transitions in this material, making it among the best performing lead-free dielectric ceramic bulk material for high energy storage.

The local electron density of an atom is one key factor that determines its chemical properties.R egulating electron density can promote the atomsr eactivity and so reduce the reaction activation energy,whichishighly desired in many chemical applications.H erein, we report an intracrystalline electron lever strategy,w hich can regulate the electron density of reaction centre atoms via manipulating ambient lattice states,f or Fenton activity improvement. Typically,with the assistance of ultrasound, the Mn 4+ ÀOÀFe 3+ bond in BiFe 0.97 Mn 0.03 O 3 perovskite nanocrystals can drive valence electrons and free electrons to accumulate on Fe atoms by apolarization electric field originated from the designed lattice strain. The increase of electron density significantly improves the catalytic activity of Fe,d ecreasing the activation energy of BiFe 0.97 Mn 0.03 O 3-mediated Fenton reaction by 52.55 %, and increasing the COH yield by 9.21-fold. This study provides an ew wayt ou nderstand the sono-Fenton chemistry,a nd the increased COH production enables ah ighly effective chemodynamic therapy.

0.94­(Bi0.5Na0.5TiO3)–0.06­(BaTiO3) (BNTBT) is a potential lead-free piezoelectric candidate to replace lead-based PZT ceramics. The thermal depoling temperature sets the upper limit for the high temperature application of piezoelectric materials. Recently, an interface model was proposed to explain the good resistance to thermal depoling of BNTBT-ZnO composite. However, we found that the presence of ZnO was not limited to the interface, but contributed intrinsically to the BNTBT lattice. This played a critical role in the structural changes of BNTBT, confirmed by a unit volume change supported by XRD, which was further proved by Raman, EDS, and dielectric characterization at different temperatures. The previous interface model is not correct because BNTBT shows thermally stable piezoelectric properties, even though there is no interface between BNTBT and ZnO. The thermal depoling behavior of BNTBT-based materials is directly related to the transition temperature from the rhombohedral phase to the tetragonal phase in our phase transition model, which is consistent with four current peaks in their ferroelectric loops close to the depoling temperature.

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of diseases. For example, inducing cancer cells from the aggressive and unrestricted growth state to a senescent state can limit their proliferation and reduce their resistance to treatments, [2] which can be realized by intracellular catalytic reduction of β-nicotinamide adenine dinucleotide (NAD + ). [3] However, it remains a challenge to realize highly efficient intracellular catalysis of nanocatalysts in the complex tumor microenvironment.Catalytic reaction is accompanied by electron transfer, and regulating the electronic structure of the catalyst has been an efficient way to improve the catalytic activity. [4] Heterostructures are superior in electron regulation owing to the spontaneous charge rearrangement at the interface driven by the difference in work function and Fermi level between materials, [5] thereby influencing the catalytic activities. [6] Moreover, the electron transfer tendency in heterostructures can be managed by integrating materials with different work functions. [7] By integrating Au nanoparticles with higher work function (work function = 5.27 eV) and Fe 2 C nanoparticles (work function = 4.89 eV) into a Janus-like Au-Fe 2 C heterostructure, we recently demonstrated a catalytic radiotherapy owing to enriched charges of Au. [8] However, its efficiency is insufficient. The key to further increasing the catalytic activity lies Intracellular catalytic reactions can tailor tumor cell plasticity toward highefficiency treatments, but the application is hindered by the low efficiency of intracellular catalysis.Here, a magneto-electronic approach is developed for efficient intracellular catalysis by inducing eddy currents of FePt-FeC heterostructures in mild alternating magnetic fields (frequency of f = 96 kHz and amplitude of B ≤ 70 mT). Finite element simulation shows a high density of induced charges gathering at the interface of FePt-FeC heterostructure in the alternating magnetic field. As a result, the concentration of an essential coenzyme-β-nicotinamide adenine dinucleotide-in cancer cells is significantly reduced by the enhanced catalytic hydrogenation reaction of FePt-FeC heterostructures under alternating magnetic stimulation, leading to over 80% of senescent cancer cells-a vulnerable phenotype that facilitates further treatment. It is further demonstrated that senescent cancer cells can be efficiently killed by the chemodynamic therapy based on the enhanced Fentonlike reaction. By promoting intracellular catalytic reactions in tumors, this approach may enable precise catalytic tumor treatment.

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Poly(vinylidene fluoride) (PVDF) and PVDF-based copolymers with trifluoroethylene (PVDF-TrFE) have attracted considerable academic and industrial interest due to their ferroelectric properties, which are only presented in very few polymers. However,...