The Efficient K Ion Storage of M2P2O7/C (M=Fe,Co, Ni) Anode Derived from Organic-Inorganic Phosphate Precursors

Metal phosphates have been widely explored in lithium ion batteries and sodium ion batteries owing to high theoretical capacities, mild toxicity and low cost. However, their potassium ion battery applications are less reported due to the limited conductivity and the slow diffusion kinetics. Considering these drawbacks, novel structured M₂P₂O₇/C (M=Fe, Co, Ni) nanoflake composites are prepared through an organic-phosphors precursor-assisted solvothermal method and a subsequent high temperature annealing process. The designed Co₂P₂O₇/C composite exhibits the highest rate capacity with 502 mAh g⁻¹ at 0.1 A g⁻¹ and good cyclability for 900 cycles at 1 A g⁻¹ and 2 A g⁻¹ when compared with Ni and Fe based composites. The superior electrochemical performance can be attributed to their unique nanoparticle-assembled nanoflake structure, which can afford enough active sites for K⁺ intercalation. In addition, the robust pyrophosphate crystal structure and the in situ formed carbon composition also have positive effects on enhancing the long-term cycling performance and the electrode's conductivity. Finally, this organic-phosphors precursor induced simple approach can be applied for easy fabrication of other pyrophosphate/carbon hybrids as advanced electrodes.     

Screening of glycoside isomers in P. scrophulariiflora using ionic liquid‐based ultrasonic‐assisted extraction and ultra‐performance liquid chromatography/electrospray ionization quadrupole time‐of‐flight tandem mass spectrometry

A powerful ionic liquid‐based ultrasonic‐assisted extraction (ILUAE) method combined with ultra‐performance liquid chromatography coupled to electrospray ionization quadrupole time‐of‐flight tandem mass spectrometry (UPLC/ESI‐QTOFMSⁿ) was employed in the rapid simultaneous screening of iridoid glycosides, phenylethanoid glycosides, and cucurbitacin glycosides from P. scrophulariiflora. The ILUAE procedure was optimized over several ultrasonic parameters, including the ultrasonic power, concentration of the ionic liquid, and solid–liquid ratio. A comparison with conventional heat‐reflux extraction and regular UAE demonstrated that the optimized approach yielded a high extraction efficiency (Picroside I, 2.84%; Picroside II, 3.57%; 6‐O‐E‐feruloyl catalpol, 2.20%) within a short extraction time of 30 min. Negative ion mode ESI‐QTOFMS² analysis of the fragmentation reactions of the [M–H]^– ions was conducted to characterize the diagnostic ions related to the glycosyl moieties, aglycone units, and the type and substituted position of the ester groups. Interestingly, the positional isomers of the iridoid glycosides could be easily discriminated based on the characteristic ions. A total of 15 glycosides, including three groups of iridoid glycoside isomers and two groups of phenylethanoid glycoside isomers, were conveniently identified within 13.5 min. Moreover, 6'‐O‐vanilloyl catalpol was identified in P. scrophulariiflora for the first time. The method developed here was further validated by measuring the recovery, correlation coefficient (R²), and reproducibility (RSD, n = 5) of three iridoid glycosides: 89.60%–109.02%, 0.9991–0.9998, and 0.93%–1.44%, respectively. This study demonstrated the capabilities of ILUAE combined with UPLC/ESI‐QTOFMSⁿ for the rapid screening of glycosides in P. scrophulariiflora. This method offers an approach to similar studies on other natural plants. Copyright © 2012 John Wiley & Sons, Ltd.     

Synthesis and characterization of fluorine-containing cholesteric liquid crystalline polysiloxanes bearing trifluoromethyl-substituted mesogens

A series of side-chain liquid crystal (LC) polysiloxanes were synthesised with Poly(methylhydrogeno)siloxane, 4?-(undec-10-enoyloxy) biphenyl – 4 – yl 4- (trifluoromethyl) benzoate (M_th) and a chiral nematic (N*) LC monomer 1-allyl 10-(cholesteryl)-decanedioate (M_ch). The chemical structures and LC properties of the monomers and polymers were characterised by FTIR, ¹H-NMR, differential scanning calorimetry, thermogravimetric analysis, POM and X-ray diffractometer. M_ch is monotropic N* LC. The homopolymer derived from monomer M_ch is enantiotropic N* LC. Monomer M_th is a smectic A liquid crystal. The copolymers derived from M_ch and M_th are N* LCs. The temperatures at which 5% weight loss occurred are greater than 300°C for all the fluoro-containing polymers, and the residue weights of the samples at 600°C increased slightly as the content of trifluoromethyl mesogens increased in the polymers. The glass transition temperatures of the polymers increased as trifluoromethyl mesogens increased, too. The N*–I phase transition temperatures show a negative deviate from ideal or linear behaviour. The values of the enthalpy changes for the cholesteryl containing polymers are rather low and this is attributed to the biaxiality of cholesteryl moiety which tends to reduce the change in the orientational order at the N*–I transition. Compared to the monomers, the polymers show wider mesophase region.     

Solvothermal synthesis of nanoscaled LiFePO4 with thinner thickness along [010] direction

Single-phased nanosized LiFePO₄ with thinner thickness along [010] crystallographic direction were successfully fabricated under solvothermal condition by using glycerol as co-solvent. The as-obtained product with thinner thickness is beneficial for fast migration of Li ions in the olivine-structured LiFePO₄, hence exhibiting excellent electrochemical performance.     

驻波教学中的初相问题

从推导驻波方程的一般形式出发,讨论了入射波和反射波的初相在驻波形成中的作用和关系.     

A mitochondrial-targeted ratiometric probe for detecting intracellular H2S with high photostability

Based on 4-bromo-1,8-naphthalic anhydride, one novel ratiometric fluorescence H₂S-probe (IDNA) was designed and synthesized. Further studies indicate that IDNA can sensitively recognize H₂S (detection limit of 7 μmol/L) with good selectivity and anti-interference ability. In addition, IDNA has satisfactory photostability in HeLa cells, ability of mitochondrial co-localization, and can be utilized in fluorescence imaging of H₂S.     

Superresolution imaging of DNA tetrahedral nanostructures in cells by STED method with continuous wave lasers

DNA tetrahedral nanostructures are considered to be uew nanocarriers because they can be precisely controlled and hold excellent penetration ability to the cellular membrane. Although the DNA tetrahedral nanostructure is extensively studied in biology and medicine, its behavior in the cells with nanoscale resolution is not understood clearly. In this letter, we demonstrate superrcsolution fluorescence imaging of the distribution of DNA tetrahedral nanostructures in the cell with a simulated emission depletion （STED） microscope, which is built based on a conventional eonfocal microscope and can t）rovide a resolution of 70 nm.     

Synthesis and Characterization of Hydrophilic Trityl Radical TFO for Biomedical and Biophysical Applications

Tetrathiatriarylmethyl (TAM, trityl) radicals have found wide applications as spin probes/labels for EPR spectroscopy and imaging, and as polarizing agents for dynamic nuclear polarization. The high hydrophilicity of TAM radicals is essential for their biomedical applications. However, the synthesis of hydrophilic TAM radicals (e.g., OX063) is extremely challenging and has only been reported in the patent literature, to date. Herein, an efficient synthesis of a highly water-soluble TAM radical bis(8-carboxyl-2,2,6,6-tetramethylbenzo[1,2-d:4,5-d′]bis([1,3]dithiol-4-yl)-mono-(8-carboxyl-2,2,6,6-tetrakis(2-hydroxyethyl)benzo[1,2-d:4,5-d′]bis([1,3]dithiol-4-yl)methyl (TFO), which contains four additional hydroxylethyl groups, relative to the Finland trityl radical CT-03, is reported. Similar to OX063, TFO exhibits excellent properties, including high water solubility in phosphate buffer, low log P, low pK_a, long relaxation times, and negligible binding with bovine serum albumin. On the other hand, TFO has a sharper EPR line and higher O₂ sensitivity than those of OX063. Therefore, in combination with its facile synthesis, TFO should find wide applications in magnetic resonance related fields and this synthetic approach would shed new light on the synthesis of other hydrophilic TAM radicals.     

Enhanced Sensitive Electrochemical Sensor for Simultaneous Catechol and Hydroquinone Detection by Using Ultrasmall Ternary Pt-based Nanomaterial

The simple and effective method for the novel synthesis of Pt-based nanoparticle was presented with high efficiency. The sensitive catalyst for the simultaneous detection of catechol and hydroquinone was prepared by depositing ternary metal complex on fluorine-doped tin-oxide (FTO). The composition and morphology of nanomaterials were characterized by TEM, HRTEM, XRD, XPS, and EDS (energy dispersive spectroscopy). The size of the Pt-based nanomaterial was about 5±1 nm. The electrochemical performance of the modified catalyst was studied by CV, DPV, and EIS. The modified PtNiCu@FTO catalyst possessed good electro-oxidation activity for hydroquinone and catechol and used for simultaneous detection of catechol and hydroquinone at scan rate of 20 mV s⁻¹ (vs. Ag/AgCl). Detection responses were found in the ranges of 5–2900 μM for hydroquinone and 5–3000 μM for catechol. The detection limits (LOD) for HQ and CC were observed as 0.35 and 0.29 μM, respectively. The sensitivity of HQ and CC were 1515.55 and 1485 μA mM⁻¹ cm⁻², respectively. The prepared nanomaterial were effectively applied for the determination of CC and HQ in real samples.