High-conductivity free-standing Li_(6)PS_(5)Cl/poly(vinylidene difluoride)composite solid electrolyte membranes for lithium-ion batteries

Bulk-type all-solid-state batteries(ASSBs)using sulfide solid electrolyte are considered as a promising alternative to commercial lithium-ion batteries owing to their high energy density and safety.However,cell energy density is often comparatively low due to use of a thick solid electrolyte separator and a lithium alloy as anode.For achieving high-performance ASSBs,creating a thin free-standing electrolyte with high-conductivity and good cycling stability against lithium anode is essential.In this work,we present Li_(6)PS_(5)Cl/poly(vinylidene difluoride)(LPSCl/PVDF)composite electrolytes prepared by a slurry method.The influence of the PVDF content on the microstructure,morphology,ionic conductivity and activation energy of the LPSCl/PVDF electrolytes is systematically investigated.Free-standing LPSCl/PVDF membranes with a thickness of 100-120 mm and a high ionic conductivity of about 1·10^(-3) S cm^(-1) at 25℃ are obtained.After adding PVDF to the LPSCl electrolyte,the cycling stability of the LPSCl electrolyte against lithium metal improves significantly.Therefore,LPSCl/PVDF composite electrolytes are promising candidates to be used in ASSBs.

Boron difluoride formazanate dye for high-efficiency NIR-Ⅱ fluorescence imaging-guided cancer photothermal therapy

The small molecular second near-infrared(NIR-Ⅱ, 1000–1700 nm) dye-based nanotheranostics can concurrently combine deep-tissue photodiagnosis with in situ phototherapy, which occupies a vital position in the early detection and precise treatment of tumors. However, the development of small molecular NIR-Ⅱ dyes is still challenging due to the limited electron acceptors and cumbersome synthetic routes.Herein, we report a novel molecular electron acceptor, boron difluoride formazanate(BDF). Based on BDF, a new small molecular NIR-Ⅱ dye BDF1005 is designed and synthesized with strong NIR-I absorption at 768 nm and bright NIR-Ⅱ peak emission at 1034 nm. In vitro and in vivo experiments demonstrate that BDF1005-based nanotheranostics can be applied for NIR-Ⅱ fluorescence imaging-guided photothermal therapy of 4T1 tumor-bearing mice. Under 808 nm laser irradiation, tumor growth can be effectively inhibited. This work opens up a new road for the exploitation of NIR-Ⅱ small molecular dyes for cancer phototheranostics.

DYNAMIC PROCESS OF VALENCE CHANGE OF EUROPIUM ION IN EUROPIUM DIFLUORIDE AT HIGH TEMPERATURE

The dynamic process of the ionic valence changing from Eu^(2+) to Eu^(3+) in EuF_2 at high temperature has been investigated by ESCA, high,temperature X-ray diffraction, high temperature spectrum, high temperature magnetic Isusceptibility and Mssbauer spectrum. It has been shown that the formed Eu^(3+) exists in different compounds when EuF_2 is heated to high temperature in different atmospheres. In air, Eu^(3+) exists in the form of hexagonal EuOF, in nitrogen, in the form of orthogonal EuF_3 and non-hexagon EuOF. This is because decomposition or disproportionation of EuF_2 is different with different atmospheres. The magnetic susceptibility measurement showed quantitatively that the change rate from Eu^(2+) to Eu^(3+) is about 95% in air, and about 75% in nitrogen when it is heated to 900℃. A small amount of Eu^(2+) coexists with Eu^(3+) in the final product.

A general method for one-step synthesis of monofluoroiodane(Ⅲ)reagents using silver difluoride

Herein we report a new general method for one-step synthesis of four kinds of fluoroiodane(Ⅲ)reagents by treating the corresponding aryl iodides with silver difluoride(AgF_(2)).This is the first method applicable for the synthesis of all four fluoroiodane(Ⅲ)reagents including p-iodotoluene difluoride(1),fluoro-benziodoxole(2),fluoro-benziodoxolone(3),and fluoro-N-acetylbenziodazole(4).AgF_(2)was firstly employed in the direct oxidative fluorination of iodobenzene and thus has shown its outstanding oxidation and fluorine-transfer ability.The use of AgF_(2)has improved the synthesis of fluoroiodane(Ⅲ)reagents by shortening the reaction steps,avoiding the use of hazardous reagents,and simplifying the experimental operations.It was worth noting that we have developed the first one-step direct synthetic method for 3,while 3 can only be synthesized through Cl→F ligand exchange reaction previously.

Anion exchange membranes with a semi-interpenetrating polymer network using 1,6-dibromohexane as bifunctional crosslinker

An anion exchange membrane(AEM)is generally expected to possess high ion exchange capacity(IEC),low water uptake(WU),and high mechanical strength when applied to electrodialysis desalination.Among different types of AEMs,semi-interpenetrating polymer networks(SIPNs)have been suggested for their structural superiorities,i.e.,the tunable local density of ion exchange groups for IEC and the restrained leaching of hygroscopic groups by insolubility for WU.Unfortunately,the conventional SIPN AEMs still struggle to balances IEC,WU,and mechanical strength simultaneously,due to the lack of the compact crosslinking region.In this work,we proposed a novel SIPN structure of polyvinylidene difluoride/polyvinylimidazole/1,6-dibromohexane(PVDF/PVIm/DBH).On the one hand,DBH with two cationic groups of imidazole groups are introduced to enhance the ion conductivity,which is different from the conventional monofunctional modifier with only one cationic group.On the other hand,DBH has the ability to bridge with PVIm,where the mechanical strength of the resulting AEM is increased by the increase of crosslinking degree.Results show that a low WU of 38.1%to 62.6%,high IEC of 2.12—2.22 mmol·g^(-1),and excellent tensile strength of 3.54—12.35 MPa for PVDF/PVIm/DBH membrane are achieved.This work opens a new avenue for achieving the high-quality AEMs.

Fluoride Processing of Titanium-Containing Minerals

Fluoride processing of natural ilmenite with the use of ammonium hydrogen difluoride (NH4HF2) as an effective fluorinating agent is suggested. Chemistry, composition, structure, thermal and hydrolytic properties of fluorination products were investigated. Ammonium fluoro- and oxofluorotitanates are suitable for preparing of titanium dioxide as pigmentary product or as doped by nitrogen and fluorine.

Electrical power generator from electrospun hybrid PVDF-BaTiO_(3)nanofiber membranes

To enhance the piezoelectric performance of piezoelectric polymer thin films in general,hybrid polyvinylidene difluoride(PVDF)and nanosized barium titanate(BaTiO_(3))piezoelectric films were prepared and their piezoelectric performance examined.The hybrid nanofibers were fabricated via electrospinning at an external voltage of 15 kV.The nonwoven fabrics were collected using a roller collection device,and their morphological structures were analyzed via scanning electron microscopy.The crystal structures of these piezoelectric films were characterized via micro-Raman spectroscopy.β-phase of the composite nanofiber membrane almost increased to twice owing to the addition of BaTiO_(3)nanoparticles.Compared with pure,electrospun PVDF piezoelectric film,the piezoelectric characteristics of the hybrid piezoelectric films were considerably enhanced because of the additional BaTiO_(3)nanoparticles.The maximum instantaneous open-circuit voltage of the hybrid PVDF-BaTiO_(3)nanofibers film can be high up to 80 V.The high-performance hybrid piezoelectric films exhibited notable prospects for applications in wearable electronic textiles.

High pressure responsive luminescence of flexible Eu^(3+) doped PVDF fibrous mats

Exploring lanthanide doped materials and their high-pressure optical properties is important from the perspective of designing pressure sensors, piezoelectric materials, scintillators, and optoelectronic devices, just to mention a few. Understanding the high-pressure optical properties of polymeric fibrous mats provides significant advantages in terms of flexibility, tunability, facile processability, and malleability. In this work, we have developed flexible polyvinylidene difluoride(PVDF) fibrous mats doped with an Eu^(3+) source of Eu(NO_(3))_(3)·5H_(2)O(EN-PF) or Eu_(2)(SO_(4))_(3)(ES-PF) by a Forcespinning■ method. Microstructural analysis of these two systems indicates that Eu(NO_(3))_(3)·5H_(2)O and Eu_(2)(SO_(4))_(3) are homogeneously distributed and dispersed into the PVDF matrix. Fiber formation promotes a β-phase PVDF. Eu^(3+) doping increases the β-phase. Its fraction is larger for the ES-PF mats. To understand their high-pressure optical properties, their photoluminescence spectra have been taken at various pressures up to 58 GPa in a diamond anvil cell. High-pressure luminescence illustrates a clear change in asymmetry ratio, peak intensity, peak breadth, color coordinate, and color temperature of Eu^(3+) ions from both EN-PF and ES-PF with a different extent of changes. Specifically, Eu^(3+) ions in the ES-PF mats switch from asymmetric to symmetric environment as pressure increases. Those in the EN-PF mats present symmetric environment for all tested pressures. Both of the Eu^(3+) doped PVDF systems present irreversible changes. Therefore,the EN-PF fibrous mats present an opportunity to make pressure induced red-orange-yellow tunable phosphors for multifunctional applications.

Direct Double Electrophilic Fluorination of Allenoic Acids and Tosylamides to Give 1,1-Difluoroallylic Heterocyclic Compounds

A novel and facile preparation of l,l-difluoroallyl substituted five-membered lactones or pyrrolidines in mod- erate yields through direct double electrophilic fluorination of 4,5-allenoic acids or tosylamides with SelectfluorTM F-TEAD-BF4 is described.

Near-infrared Aza-BODIPY Dyes Through Molecular Surgery for Enhanced Photothermal and Photodynamic Antibacterial Therapy

The widespread use of high-dose antibiotics will not only lead to the rapid acquisition of antibiotic resistance and increased incidence of drug-resistant bacterial infections, but also produce toxic side effects on normal tissues. Herein, two near-infrared dyes BDP-4PTZ and BDP-4DPA were synthesized, and the electron donors of diphenylamine and phenothiazine with the only difference of sulphur(S)-lock between the two phenyl rings were introduced onto the electron acceptor aza-dipyrromethene boron difluoride(aza-BODIPY) through molecular surgery. Through co-precipitation into nanoparticles(NPs), BDP-4PTZ NPs and BDP-4DPA NPs were fabricated with good biocompatibility. Upon 660 nm photoirradiation, BDP-4PTZ NPs and BDP-4DPA NPs showed excellent photothermal conversion efficiency(43% and 50%, respectively) and reactive oxygen species(ROS) production performance(ca. 3.6 and 6 times higher than that of indocyanine green, respectively). In vitro antibacterial experiments indicated that both NPs could effectively destroy the bacteria’s membrane to eradicate drug-resistant bacteria. Furthermore, the bacterial abscess was effectively eliminated after treatment with BDP-4DPA NPs under 660 nm photoirradiation without adverse effects. Thus, through molecular surgery, BDP-4DPA without the S-lock demonstrates synergistic photothermal and photodynamic antimicrobial activities, which is promising for further molecular design towards effective neo-antimicrobial phototherapy.

The past,present,and future of piezoelectric fluoropolymers:Towards efficient and robust wearable nanogenerators

Polyvinylidene difluoride(PVDF)derivatives in metal/PVDF/metal(MPM)sandwich structures have been studied extensively since 1969.Cousin copolymers of the same family have been discovered with fascinating piezoelectric,pyroelectric,electrocaloric,and ferroelectric properties.Solution processing,flexibility,lightweight,and thermal stability make this class of materials complementary to inorganics.Thus,PVDF based polymers potentially compete with inorganic materials for a broad range of technologies such as energy generators,loudspeakers,coolers,and memories.However,the stable non-electroactiveα-phase and hydrophobic nature of PVDF are the main barriers for developoing high performing and robust MPM devices in electronic applications.In this review,we present an up-to-date overview on different methods to induce the electroactiveβ-phase and improve the adhesion strength with metals to ensure robust and durable MPM devices.We go through advantages and disadvantages of several methods and pinpoint future opportunities in this research area.A special attention is paid to wearable piezoelectric nanogenerators for energy harvesting from human body motion,where flexible PVDF derivatives are compared with rigid piezoelectric ceramics.While the piezoelectric coefficient of PVDF(d_(33)~24–34 pm/V)is one order lower than ceramic materials,novel co-polymers of PVDF display d_(33)>1000 pm/V upon bias.This shows promise to bring piezoelectrics to flexible and large-area applications such as smart textiles.We also discussed challenges to improve wearability,such as light weight,breathability,and flexibility.

Valency and Its Change Process of Samarium Ion in Samarium Fluoride System

Nonstoichiometric series SmF_x (2.0≤x≤3.0) have been synthesized by reduction of samarium trifluoride with hydrogen for several times, and the stoichiometric samarium difluoride has been obtained. The structure of nonstoichiometric samarium fluoride series and the valency of samarium ion are briefly discussed. The valent change process of samarium ion at high temperatures in different atmospheres is investigated.