Needle-like cobalt phosphide arrays grown on carbon fiber cloth as a binder-free electrode with enhanced lithium storage performance

Cobalt phosphide(CoP) is a promising anode candidate for lithium-ion batteries(LIBs) due to its high specific capacity and low working potential.However,the poor cycling stability and rate performance,caused by low electrical conductivity and huge volume variation,impede the further practical application of CoP anode materials.Herein,we report an integrated binder-free electrode featuring needle-like CoP arrays grown on carbon fiber cloth(CC) for efficient lithium storage.The as-prepared CoP/CC electrode integrates the advantages of 1 D needle-like CoP arrays for efficient electrolyte wettability and fast cha rge transpo rtation,and 3 D CC substrate for superior mechanical stability,flexibility and high conductivity.As a result,the CoP/CC electrode delivers an initial specific capacity of 1283 mAh/g and initial Coulombic effeciencies of 85.4%,which are much higher than that of conventional CoP electrode.Notably,the Co P/CC electrode shows outstanding cycling performance up to 400 cycles at 0.5 A/cm² and excellent rate performance with a discharge capacity of 549 mAh/g even at 5 A/cm².This work demonstrates the great potential of integrated CoP/CC hybrid as efficient bind-free and freestanding electrode for LIBs and future flexible electronic devices.     

DMAO-activated Rare-earth Metal Catalysts for Styrene and Its Derivative Polymerization

The catalytic performance of rare-earth metal dialkyl complexes in combination with DMAO(dry methylaluminoxane)is explored.In the presence of 60 equivalents of DMAO,the half-sandwich complex(C13H8CH2Ph)Sc(CH2SiMe3)2(THF)(1)is inert for styrene polymerization,but(C5Me4Ph)Sc(CH2C6H4NMe2-o)2(2)converts 18％styrene into syndiotactic polystyrene.Under the same conditions,the constrained-geometry configuration sandium complex(C13H8CH2Py)Sc(CH2SiMe3)2(3a)displays extremely high catalytic activity(＞6420 kg·molSC-1·h-1)and perfect syndiospecific(rrrr＞99％)for styrene polymerization,while its lutetium(3b)and yttrium(3c)analogues are nearly inactive.Although the binary catalytic system 3a/DMAO exhibits very low activity for 4-methoxystyrene polymerization,it is an efficient catalyst for the syndioselective polymerization of other styrene derivatives such as 2-methoxystyrene,4-methylthiostyrene,4-fluorostyrene,4-dimethylhydrosilylstyrene,alkyne-susbstituted styrenes and 4-methylstyrene.In addition,the binary system 3a/DMAO can copolymerize ethylene and styrene to give alternating copolymers with a single glass transition at 80℃and 0.4 MPa ethylene pressures.By increasing styrene feed amount from 20 mmol to 60 mmol,the styrene content slight increases from 48.2 mol％to 53.8 mol％,but the polymerization activity is obviously promoted from 240 kg·molSc-1·h-1 to 532 kg·molSc-1·h-1.     

Comprehensive characterization of natural organic matter by MALDI- and ESI-Fourier transform ion cyclotron resonance mass spectrometry

Natural organic matter (NOM) is a complex and non-uniform mixture of organic compounds which plays an important role in environmental processes. Due to the complexity, it is challenging to obtain fully detailed structural information about NOM. Although Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) has been demonstrated to be a powerful tool for providing molecular information about NOM, multiple ionization methods are needed for comprehensive characterization of NOM at the molecular level considering the ionizing selectivity of different ionization methods. This paper reports the first use of matrix assisted laser desorption/ionization (MALDI) method coupled with FT-ICR-MS for molecular characterization of NOM within a mass range of 200–800 Da. The mass spectral data obtained by MALDI were systematically compared with data generated by electrospray ionization (ESI). It showed that complementary molecular information about NOM which could not be detected by ESI, were provided by MALDI. More unsaturated and aromatic constituents of NOM with lower O/C ratio (O/C ratio < 0.5) were preferentially ionized in MALDI negative mode, whereas more polar constituents of NOM with higher O/C ratio were preferentially ionized in ESI negative mode. Molecular anions of NOM appearing at even m/z in MALDI negative ion mode were detected. The results show that NOM molecules with aromatic structures, moderate O/C ratio (0.7 > O/C ratio > 0.25) and lower H/C ratio were liable to form molecular anions at even m/z, whereas those with higher H/C ratio are more likely to form deprotonated ions at odd m/z. It is speculated that almost half of the NOM molecules identified by MALDI may be aromatic or condensed aromatic compounds with special groups which are liable to absorb electron from other molecules to generate free radical anions during MALDI ionization.     

The Cu-MOF-199/single-walled carbon nanotubes modified electrode for simultaneous determination of hydroquinone and catechol with extended linear ranges and lower detection limits

A novel electrochemical sensor based on Cu-MOF-199 [Cu-MOF-199 = Cu₃(BTC)₂ (BTC = 1,3,5-benzenetricarboxylicacid)] and SWCNTs (single-walled carbon nanotubes) was fabricated for the simultaneous determination of hydroquinone (HQ) and catechol (CT). The modification procedure was carried out through casting SWCNTs on the bare glassy carbon electrode (GCE) and followed by the electrodeposition of Cu-MOF-199 on the SWCNTs modified electrode. Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM) were performed to characterize the electrochemical performance and surface characteristics of the as-prepared sensor. The composite electrode exhibited an excellent electrocatalytic activity with increased electrochemical signals towards the oxidation of HQ and CT, owing to the synergistic effect of SWCNTs and Cu-MOF-199. Under the optimized condition, the linear response range were from 0.1 to 1453 μmol L⁻¹ (R_HQ = 0.9999) for HQ and 0.1–1150 μmol L⁻¹ (R_CT = 0.9990) for CT. The detection limits for HQ and CT were as low as 0.08 and 0.1 μmol L⁻¹, respectively. Moreover, the modified electrode presented the good reproducibility and the excellent anti-interference performance. The analytical performance of the developed sensor for the simultaneous detection of HQ and CT had been evaluated in practical samples with satisfying results.     

New Monoterpenoids from Fruits of Gardenia jasminoides var. radicans

One new lactone, cyclopentanepyrone A ( 1 ), and two new monoterpenoids, gardeterpenone A ( 2 ) and jasminoside V ( 3 ), were isolated from the fruits of Gardenia jasminoides var. radicans, along with four known monoterpenoids, 4 – 7 , which were isolated from this plant for the first time. The structures of the isolates were elucidated by extensive spectroscopic studies, including UV, IR, 1D‐ and 2D‐NMR, ESI‐MS, HR‐ESI‐MS, and CD experiments.     

Structure and Absolute Configuration of Aspergilumamide A,a Novel Lumazine Peptide from the Mangrove‐Derived Fungus Aspergillus sp.

A novel lumazine peptide, aspergilumamide A ( 1 ), as well as a known analog penilumamide ( 2 ), were isolated from the mycelia of a marine‐derived fungus Aspergillus sp. (33241), obtained from the mangrove Bruguiera sexangula var. rhynchopetala collected from the South China Sea. The structure of 1 was identified by comprehensive spectroscopic analysis, including 1D‐ and 2D‐NMR, ESI‐MS, and MS/MS experiments. The absolute configuration of 1 was determined by Marfey's method.     

Ultrasensitive non-enzymatic glucose sensing at near-neutral pH values via anodic stripping voltammetry using a glassy carbon electrode modified with Pt3Pd nanoparticles and reduced graphene oxide

We describe an anodic stripping voltammetric (ASV) method for glucose sensing that widely expands the typical amperometric i-t response of glucose sensors. The electrode is based on a working electrode consisting of a glassy carbon electrode modified with Pt-Pd nanoparticles (NPs; in an atomic ratio of 3:1) on a reduced graphene oxide (rGO) support. The material was prepared via the spontaneous redox reaction between rGO, PdCl₄ ²⁻ and PtCl₄ ²⁻ without any additional reductant or surfactant. Unlike known Pt-based sensors, the use of Pt₃Pd NPs results in an ultrasensitive ASV approach for sensing glucose even at near-neutral pH values. If operated at a working voltage as low as 0.06 V (vs. SCE), the modified electrode can detect glucose in the 2 nM to 300 μM concentration range. The lowest detectable concentration is 2 nM which is much lower than the LODs obtained with other amperometric i-t type sensing approaches, most of which have LODs at a μM level. The sensor is not interfered by the presence of 0.1 M of NaCl.

We describe an anodic stripping voltammetric method for glucose sensing that widely expands the typical amperometric i-t response of glucose sensors (2 nM to 300 μM). The electrode is based on a glassy carbon electrode modified with Pt-Pd nanoparticles on a reduced graphene oxide (rGO) support.

     

Two Uranyl Complexes with Pyromellitic Acid. A Heterometallic Complex with U=O–CuII Interaction

Two uranyl complexes based on pyromellitic acid were hydrothermally synthesized, and their X‐ray single‐crystal diffraction structures were determined. Complex [UO₂(Hbtec)]^–(Himd)⁺ · H₂O ( 1 ) (H₄btec = pyromellitic acid, imd = imidazole), is an ionic complex, which shows a typical (4, 4) topological structure in the space. A heterometallic complex, UO₂Cu(btec)(phen) ( 2 ) (phen = 1,10‐phenanthroline) results from the reaction of uranyl nitrate and copper(II) bromide with pyromellitic acid. The structure of complex 2 revealed that the chains of UO₇ and CuO₃N₂ units were connected to each other through the carboxyl groups and U=O–Cu interactions to create a two‐dimensional framework.