MXenes, 2D compounds generated from layered bulk materials, have attracted significant attention in energy‐related fields. However, most syntheses involve HF, which is highly corrosive and harmful to ...lithium‐ion battery and supercapacitor performance. Here an alkali‐assisted hydrothermal method is used to prepare a MXene Ti3C2Tx (T=OH, O). This route is inspired from a Bayer process used in bauxite refining. The process is free of fluorine and yields multilayer Ti3C2Tx with ca. 92 wt % in purity (using 27.5 m NaOH, 270 °C). Without the F terminations, the resulting Ti3C2Tx film electrode (ca. 52 μm in thickness, ca. 1.63 g cm−3 in density) is 314 F g−1 via gravimetric capacitance at 2 mV s−1 in 1 m H2SO4. This surpasses (by ca. 214 %) that of the multilayer Ti3C2Tx prepared via HF treatments. This fluorine‐free method also provides an alkali‐etching strategy for exploring new MXenes for which the interlayer amphoteric/acidic atoms from the pristine MAX phase must be removed.
High‐purity (92 wt %) Ti3C2Tx (T=OH, O) is obtained by an alkali‐assisted hydrothermal route that is totally free of HF. The obtained Ti3C2Tx terminated with OH/O shows a gravimetric capacitance (314 F g−1) that surpasses its HF‐etched counterparts by about 214 %. This method provides an alkali‐etching strategy for MXenes in which the interlayer amphoteric/acidic atoms from the pristine MAX phase must be removed.
Mixed anion compounds such as oxynitrides and oxychalcogenides are recognized as potential candidates of visible-light-driven photocatalysts since, as compared with oxygen 2p orbitals, p orbitals of ...less electronegative anion (e.g., N3–, S2–) can form a valence band that has more negative potential. In this regard, oxyfluorides appear unsuitable because of the higher electronegativity of fluorine. Here we show an exceptional case, an anion-ordered pyrochlore oxyfluoride Pb2Ti2O5.4F1.2 that has a small band gap (ca. 2.4 eV). With suitable modification of Pb2Ti2O5.4F1.2 by promoters such as platinum nanoparticles and a binuclear ruthenium(II) complex, Pb2Ti2O5.4F1.2 worked as a stable photocatalyst for visible-light-driven H2 evolution and CO2 reduction. Density functional theory calculations have revealed that the unprecedented visible-light-response of Pb2Ti2O5.4F1.2 arises from strong interaction between Pb-6s and O-2p orbitals, which is enabled by a short Pb–O bond in the pyrochlore lattice due to the fluorine substitution.
•A superhydrophobic and conductive nanofiber composite (SCNC) is prepared.•The SCNC possesses SiO2/graphene shell and polymer nanofiber core.•The SCNC possesses good anti-corrosive performance.•The ...SCNC strain sensor shows high stretchability, sensitivity and good durability.•The SCNC strain sensor can be used for full range detection of human body motions.
It is desirable and still challenging to develop flexible, breathable and anti-corrosive wearable strain sensors with high stretchability and sensitivity that can realize full range body motions. Here, a superhydrophobic and conductive nanofiber composites (SCNCs) with a hierarchical SiO2/graphene shell and polyurethane (PU) nanofiber core microstructure were fabricated by assembling graphene on PU nanofibers under the assistance of ultrasonication, followed by stretching-induced SiO2 nanoparticles decoration onto the graphene shell. The introduction of graphene and SiO2 nanoparticles improves both Young’s modulus, tensile strength and the elongation at break of PU nanofibrous membrane. The superhydrophobicity and conductivity can be almost maintained after the SCNCs are subject to cyclic stretching or abrasion or even exposed to harsh conditions. When used as strain sensors, the SCNCs show high stretchability, reliability and good durability and can be used in harsh environment including acid and salt conditions. The SCNCs are then assembled to monitor full range body motions including both subtle and large body movements, making it a promising candidate in wearable electronics.
Fluorinated ketones are widely prevalent in numerous biologically interesting molecules, and the development of novel transformations to access these structures is an important task in organic ...synthesis. Herein, we report the multicomponent radical acylfluoroalkylation of a variety of olefins in the presence of various commercially available aromatic aldehydes and fluoroalkyl reagents through N‐heterocyclic carbene organocatalysis. With this protocol, over 120 examples of functionalized ketones with diverse fluorine substituents have been synthesized in up to 99 % yield with complete regioselectivity. The generality of this catalytic strategy was further highlighted by its successful application in the late‐stage functionalization of pharmaceutical skeletons. Excellent diastereoselectivity could be achieved in the reactions forging multiple stereocenters. In addition, preliminary results have been achieved on the catalytic asymmetric variant of the olefin difunctionalization process.
Organocatalytic acylfluoroalkylation: A multicomponent radical acylfluoroalkylation of olefins through NHC organocatalysis was developed, and over 120 examples of fluoroketones were facilely accessed from simple materials. Moreover, a dearomative difunctionalization of indoles could be readily achieved in a highly diastereoselective manner. The generality and practicality were highlighted by the late‐stage modification of drug skeletons.
A reliable and precise method for determining the thorium (Th) and uranium (U) contaminants in 2,5-diphenyloxazole (PPO) to 10 ppq level was developed for Jiangmen Underground Neutrino Observatory ...(JUNO). The Th and U contaminants were separated from PPO by acid extraction and measured by inductively coupled plasma mass spectrometry (ICP-MS). The experimental conditions were optimized to improve extraction efficiencies and eliminate the interferences during the ICP-MS measurements. The 229Th and 233U isotopes were used as tracer, and nearly 100% recovery efficiencies of 229Th and 233U were obtained in both the spiked PPO samples and blanks. The method detection limits with 99% confidence level for 232Th and 238U in PPO were 3.3×10−14 g/g and 4.0×10−14 g/g, respectively. The measurements were consistent with the Th and U results obtained from a vaporization method. The method developed in this work can be extended to other fluors with minor adjustments.
Ruthenium(II)‐catalyzed meta‐selective C−H (di)fluoromethylation was accomplished by phosphine and carboxylate cooperation. The remote C−H functionalization was characterized by ample substrate ...scope, thereby setting the stage for meta‐(di)fluoromethylation through facile C−H cleavage.
2 for meta: meta‐C−H mono‐ and difluoromethylation reactions with ample scope and excellent levels of remote selectivity were accessed with a ruthenium(II) catalyst bearing cooperative electron‐deficient triarylphosphine and carboxylate ligands.
•A bio-inspired flexible and superhydrophobic fabric is prepared for electromagnetic interference shielding.•The conductivity of the composite fabric could reach 4000 S/m.•The composite fabric ...possesses a high specific shielding effectiveness of 209.6 dB cm3 g−1.•The excellent EMI shielding performance could be maintained after multiple abrasion and cyclic bending tests.
Electromagnetic pollution often causes disturbances to nearby electronic apparatus and also severely threatens people’s health, and it is therefore urgent to develop electromagnetic interference (EMI) shielding materials. However, preparation of EMI shielding materials with lightweight, good flexibility, superior corrosion-resistance, excellent EMI shielding performance remains challenging. Here, a facile method is proposed to prepare flexible, superhydrophobic and highly conductive polymer composite fabrics for the EMI shielding. The polydopamine (PDA) is first decorated onto the fabric surface, and the functional groups in the PDA could promote the Ag precursor adsorption. The electrically conductive PP fabric becomes superhydrophobic and anti-corrosive after further treatment with a fluorine containing molecule. The average shielding effectiveness (SE) and specific SE (SSE) of the composite fabric could reach as high as 48.2 dB and 209.56 dB cm3 g−1 at the frequency of 8.2–12.4 GHz, respectively, which could even be maintained after the composite fabric undergoes cyclic abrasion and bending tests. Furthermore, the superhydrophobic surface ensures the reliability of the conductive fabric as shielding materials when they are used in harsh conditions.
Over the last two decades, fluorine substitution has become one of the essential structural traits in modern pharmaceuticals. Thus, about half of the most successful drugs (blockbuster drugs) contain ...fluorine atoms. In this review, we profile 17 fluorine‐containing drugs approved by the food and drug administration (FDA) in 2018. The newly approved pharmaceuticals feature several types of aromatic F and CF3, as well as aliphatic (CF2) substitution, offering advances in the treatment of various diseases, including cancer, HIV, malarial and smallpox infections.
Fluorinated drugs: This Review outlines 17 fluorine‐containing drugs approved by the food and drug administration (FDA) in 2018. These newly developed fluorinated pharmaceuticals are recommended for the treatment of various diseases, including cancer, HIV, malarial and smallpox infections.
Activation of the sp3 C−F bond in 2‐trifluoromethyl‐1‐alkenes was accomplished through treatment with a Lewis acid. In the presence of an equimolar amount of EtAlCl2, the (trifluoromethyl)alkenes ...readily underwent an SN1′‐type reaction with arenes through a Friedel–Crafts‐type mechanism via elimination of a fluoride ion to afford 3,3‐difluoroallylated arenes in good yields. This selective activation of one C−F bond of the CF3 group provides a synthetic method for accessing biologically and synthetically important 1,1‐difluoro‐1‐alkenes.
A clean break: C−F bond activation in 2‐trifluoromethyl‐1‐alkenes was accomplished through treatment with a Lewis acid. In the presence of EtAlCl2, the (trifluoromethyl)alkenes readily undergo elimination of a F− ion and SN1′‐type reaction with arenes through a Friedel–Crafts‐type mechanism to give 3,3‐difluoroallylated arenes in good yields. This selective activation of just one sp3 C−F bond of the CF3 group provides facile access to 1,1‐difluoro‐1‐alkenes.
MXene (e.g., Ti3C2) represents an important class of two‐dimensional (2D) materials owing to its unique metallic conductivity and tunable surface chemistry. However, the mainstream synthetic methods ...rely on the chemical etching of MAX powders (e.g., Ti3AlC2) using hazardous HF or alike, leading to MXene sheets with fluorine termination and poor ambient stability in colloidal dispersions. Here, we demonstrate a fluoride‐free, iodine (I2) assisted etching route for preparing 2D MXene (Ti3C2Tx, T=O, OH) with oxygen‐rich terminal groups and intact lattice structure. More than 71 % of sheets are thinner than 5 nm with an average size of 1.8 μm. They present excellent thin‐film conductivity of 1250 S cm−1 and great ambient stability in water for at least 2 weeks. 2D MXene sheets with abundant oxygen surface groups are excellent electrode materials for supercapacitors, delivering a high gravimetric capacitance of 293 F g−1 at a scan rate of 1 mV s−1, superior to those made from fluoride‐based etchants (<290 F g−1 at 1 mV s−1). Our strategy provides a promising pathway for the facile and sustainable production of highly stable MXene materials.
An iodine‐assisted method has been developed for etching bulk Ti3AlC2 in anhydrous acetonitrile (CH3CN), resulting in 2D MXene sheets (Ti3C2Tx, T=O, OH) with intact lattice, high yield (71 %), large size (1.8 μm) and ultimate thickness (<5 nm). 2D MXene sheets present great ambient stability in water for at least 2 weeks and high gravimetric capacitances of 293 F g−1 at 1 mV s−1 when serving as electrode materials for supercapacitors.
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