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Recently, much effort has been dedicated to ultra-thin two-dimensional metal–organic framework (2D MOF) nanosheets due to their outstanding properties, such as ultra-thin morphology, large specific surface area, abundant modifiable active sites, etc. However, the preparation of high-quality 2D MOF nanosheets in good yields still remains a huge challenge. Herein, we report 2D cadmium-based metal–organic framework (Cd-MOF) nanosheets prepared in a one-pot polyvinylpyrrolidone (PVP)-assisted synthesis method with high yield. The Cd-MOF nanosheets were characterized with good stability and dispersion in aqueous systems, and were highly selective and sensitive to the antibiotic metronidazole (MNZ) with low limit of detection (LOD: 0.10 μM), thus providing a new and promising fluorescent sensor for rapid detection of MNZ in aqueous solution.

Fe-Doped Co-Mo-S microtubes were successfully synthesized through a multistep synthetic route, employing MoO3 microrods as the sacrificial template, Co(NO3)2·6H2O and Fe(SO4)2·7H2O as the metal sources, 2-methylimidazole (2-MI) as the ligand and thioacetamide (TAA) as the S2- ion source. The as-prepared products were characterized by X-ray powder diffraction (XRD), energy dispersive spectrometry (EDS), inductively coupled plasma mass spectrometry (ICP-MS), X-ray photoelectron spectroscopy (XPS), (high-resolution) transmission electron microscopy (TEM/HRTEM) and HAADF-STEM-EDS elemental mapping. Experiments showed that the as-obtained Fe-doped Co-Mo-S microtube catalyst demanded overpotentials of ∼105 and 268 mV to afford the current density of -10 mA cm-2 for hydrogen evolution reaction (HER) and 10 mA cm-2 for oxygen evolution reaction (OER) with a durability of 60 h in 1.0 M KOH solution, respectively. In a two-electrode water-splitting device, the as-prepared Fe-doped Co-Mo-S microtubes acted as both anode and cathode simultaneously. To deliver a current density of 10 mA cm-2, a cell voltage of 1.605 V was required in 1.0 M KOH solution. After continuously catalyzing the overall water splitting for 60 h, the overpotential hardly changed, implying remarkable long-term stability. Obviously, the present Fe-doped Co-Mo-S microtubes have potential applications as bifunctional catalysts for electrochemical water splitting.

Ultrathin Tb3+-doped Zinc metal-organic-framework two-dimensional (2D) nanosheets (Tb3+@Zn-AIP-NS, AIP = 5-aminoisophthalic acid) were synthesized by an ultrasonic exfoliation method at room temperature, employing Tb3+@Zn-AIP microrods prepared in advance as the raw material. Experiments revealed that the as-prepared ultrathin Tb3+@Zn-AIP-NS could be dispersed homogeneously in deionized water to obtain a stable sol, and emit the strong characteristic fluorescence of Tb3+ ions. Since the above strong luminescence of Tb3+ ions was quenched by nitrofurazone (NFZ) antibiotic without the interference from other antibiotics, anions, cations and amino acids in aqueous systems, the ultrathin Tb3+@Zn-AIP-NS could be employed as a sensitive probe for visualized fluorescence detection of NFZ with a high Ksv of 4.59 × 105 M−1, a low LOD of 0.24 μM and a quick response time of 20 s. Systematic investigations on the sensing mechanism suggested that the synergistic action between the inner filter effect and the fluorescence resonance energy transfer resulted in the selective detection of NFZ. Moreover, the practical application of the present Tb3+@Zn-AIP-NS sensor was also investigated.

Mesoporous composite TiO2-ZrO2 (TZ) having enhanced surface area was synthesized by sol-gel process. The structure of the prepared samples was characterized by X-ray diffraction, transmission electron microscope, energy dispersive spectrometer, scanning electron microscope, N2 sorption techniques, etc. Electrocatalytic reduction of 2-pyridinaldehyde in 1-ethyl-3-methylimidazolium tetrafluoroborate (EMI-BF4) on the mesoporous TZ composite film electrode was investigated by cyclic voltammetry (CV). A comparison of the CV recorded in the absence and presence of 2-pyridinaldehyde confirmed the catalytic reduction of 2-pyridinaldehyde produced 2-piperidinemethanol by Ti(III)/Ti(IV) redox couple on the surface of mesoporous TZ composite film. The mechanism of this electrode reaction is called catalytic (EC′) mechanism.

The purpose of this study was to investigate the effects of microwave power and additives on the microwave-assisted pyrolysis of cotton stalk. Pyrolysis temperature profiles, product yields, and bio-oil components were analyzed. The results indicated that as the microwave power increased, so did the final temperature and heating rate. When microwave power increased from 800 to 1200 W, the yield of the solid residue decreased and gas yield increased, but the maximum bio-oil yield of 26.7% was achieved under a microwave power of 1000 W. All three of the additives (NaOH, Na2CO3, and H3PO4) increased the yields of solid residue and gas, while the yield of the bio-oil decreased. Gas chromatography-mass spectrometry (GC-MS) analysis indicated that the main components of bio-oil from microwave-assisted pyrolysis of pure sample were acetol, furfural, 2-methoxy-phenol, and 4-methyl-2-methoxy-phenol. Sodium hydroxide and sodium carbonate (NaOH and Na2CO3) greatly favor the formation of acetol. Phosphoric acid (H3PO4) remarkably promoted the formation of furfural and 4-methyl-2-methoxy-phenol, while H3PO4 inhibited the formation of acetol.

Hierarchical core-shell NiCo2S4@CoNi-LDH nanoarrays grown on carbon cloth (CC) with outstanding electrocatalytic activity for oxygen evolution reaction (OER) were successfully constructed by a three-step hydrothermal strategy. The as-prepared hierarchical core-shell NiCo2S4@CoNi-LDH nanoarrays were characterized by powder X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), energy dispersive spectrometry (EDS) and EDS mapping technologies. Electrochemical measurements showed that the OER catalytic activity of as-obtained NiCo2S4@CoNi-LDH catalyst could be tuned by the molar ratio of Co/Ni in CoNi-LDH. Experiments uncovered that NiCo2S4@Co1Ni4-LDH catalyst prepared at the Co/Ni molar ratio of 1:4 exhibited the strongest OER electrocatalytic activity. To deliver the current densities of 100 mA cm−2, the as-obtained NiCo2S4@Co1Ni4-LDH catalyst required the overpotential of 337 mV in 1.0 M KOH solution. After continuously catalyzing for 40 h, the voltage curve hardly waved, presenting excellent long-term stability. The present work is a useful attempt for constructing highly active and cost-effective OER catalyst.

Nanoporous TiO2 having enhanced surface area was synthesized by sol–gel method. On the nanoporous TiO2 film electrode, electrocatalytic reduction of the 2-pyridineethanol in the ionic liquid electrolyte of 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMI]BF4) was investigated by cyclic voltammetry (CV). It was found that the indirect electroreduction of 2-pyridineethanol produced 2-piperidinoethanol by Ti(IV)/Ti(III) redox system on the nanoporous TiO2 film surface. The current of cathodic reduction peak increased along with the increase of reactant concentration. The electrode reaction mechanism is called catalytic (EC′) mechanism.

In this paper, we have demonstrated that carbon-doped nanostructured TiO2 (CD ns-TiO2) films could be prepared simply and cheaply with oxalic acid and tetrabutylammonium bromide (Bu4N·Br) as the carbon sources. The surface morphology of the films was a multiple-porous network structure.The average size of nanoparticle was about 40 nm. Carbon doped into substitutional sites of TiO2 has also proven to be indispensable for band-gap narrowing and photovoltaic effect. Carbon doping lowered the band gap of n-TiO2 to 1.98, 1.64, and 1.26 eV. The CD ns-TiO2 film was first used as photoanode for solar cells, exhibiting high photocurrent densities (l.34 mA/cm2) and yielding an overall conversion efficiency (η) of 4.42 %.