Nanoporous germanium prepared by a mechanochemical reaction with enhanced lithium storage properties.

The cost-effective and facile fabrication of nanostructured germanium for lithium-ion batteries (LIBs) remains a grand challenge. Herein, nanoporous Z-Ge was generated via a facile two-step mechanochemical-etching reaction with Mg2Ge and ZnCl2. The prepared nanoporous Ge nanoparticles, as the anode for Li-Ge half cells, showed superior LIB performance, in terms of a high capacity, good rate capability, and good long-term stability of 700 cycles. Significantly, the mechanochemical reaction was extended to produce other nanoporous Ge or Si materials such as A-Ge, Z-Si, and A-Si via the mechanochemical reaction between Mg2Ge and AlCl3, Mg2Si and ZnCl2, and Mg2Si and AlCl3.

Scalable synthesis of 3D porous germanium encapsulated in nitrogen-doped carbon matrix as an ultra-long-cycle life anode for lithium-ion batteries.

Germanium-based materials attract more interest as anodes for lithium-ion batteries, stemming from their physical and chemical advantages. However, these materials inevitably undergo capacity attenuation caused by significant volumetric variation in repeated electrochemical processes. Herein, we designed 3D porous Ge/N-doped carbon nanocomposites by the encapsulation of 3D porous Ge in a nitrogen-doped carbon matrix (denoted as 3D porous Ge/NC). The 3D porous structure can accommodate the volume change during alloying/dealloying processes and improve the penetration of the electrolyte. Furthermore, the doping of N in the carbon framework could introduce more defects and active sites, which can also contribute to electron transportation and lithium-ion diffusion. The half-cell test found that at a current density of 1 C (1 C = 1600 mA h g-1), the specific capacity stabilized at 917.9 mA h g-1 after 800 cycles; and the specific capacity remained at 542.4 mA h g-1 at 10 C. When assembled into a 3D porous Ge/NC//LiFePO4 full cell, the specific capacity was stabilized at 101.3 mA h g-1 for 100 cycles at a current density of 1 C (1 C = 170 mA h g-1), and the cycle specific capacity was maintained at 72.6 mA h g-1 at a high current density of 5 C. This work develops a low-cost, scalable and simple strategy to improve the electrochemical performance of these alloying type anode materials with huge volume change in the energy storage area.

A facile oxygen vacancy and bandgap control of Bi(OH)SO4·H2O for achieving enhanced photocatalytic remediation.

The development of highly efficient photocatalysts is crucial for the remediation of organic pollutants. Herein, we reported a facile synthesis of oxygen vacancy rich Bi(OH)SO4·H2O photocatalyst by the control of precursor. The samples were characterized by XRD, scanning electron microscope, electron paramagnetic resonance, X-ray photoelectron spectroscopy etc. With more oxygen vacancies introduced, the photocatalytic activity on the degradation of RhB and tetracycline was significantly boosted. Density functional theory calculation was used to further reveal the influence of oxygen vacancy on the band structure of Bi(OH)SO4·H2O. The results and finding of this work are helpful for the development of sustainable environmental protection.

High-efficiency solid-phase microextraction performance of polypyrrole enhanced titania nanoparticles for sensitive determination of polar chlorophenols and triclosan in environmental water samples.

In this work, a polypyrrole (PPy)/TiO2 nanocomposite coating was fabricated by the direct electropolymerization of pyrrole on annealed TiO2 nanoparticles and evaluated as a novel direct immersion solid phase microextraction (DI-SPME) fiber coating for extraction of trace amounts of pollutants in environmental water samples. The functionalized fiber is mechanically and chemically stable, and can be easily prepared in a highly reproducible manner. The effects of the pyrrole monomer concentration, polymerization voltage and polymerization time on the fiber were discussed. Surface morphological and compositional analyses revealed that the composite coating of nano polypyrrole and titanium dioxide nanoparticles (TiO2NPs) uniformly doped the Ti substrate. The as-fabricated fiber exhibited good extraction capability for phenolic compounds in combination with high performance liquid chromatography-UV detection (HPLC-UV). At the optimum SPME conditions, the calibration curves were linear (R 2 ≥ 0.9965). LODs and LOQs of less than 0.026 µg L-1 and 0.09 µg L-1 , respectively, were achieved, and RSDs were in the range 3.5-7.2%. The results obtained in this work suggest that PPy/TiO2 is a promising coating material for future applications of SPME and related sample preparation techniques.

Novel copper sulfide doped titania nanoparticles as a robust fiber coating for solid-phase microextraction for determination of polycyclic aromatic hydrocarbons.

Immobilized TiO2 nanoparticles modified by nanoscale CuS (CuS@TiO2NPs) were successfully synthesized and used as fibers for solid-phase microextraction (SPME) for the determination of some polycyclic aromatic hydrocarbons (PAHs) in water samples. A novel fiber has been developed by postprecipitation of CuS coated the titania nanoparticles in situ grown on a titanium wire annealed at 550 °C in a nitrogen ambient atmosphere. Its morphology and surface properties were characterized by scanning electron microscopy and energy dispersive X-ray spectrometry. It was connected to high performance liquid chromatography-ultraviolet detector (HPLC-UV) equipment by replacing the sample loop of a six-port injection valve, building the online SPME-HPLC-UV system. Variables affecting extraction procedures, including desorption time, stirring speed, extraction temperature, extraction time and ionic strength were investigated and the parameters were optimized. The SPME fiber exhibits high selectivity for the five PAHs studied. The linear ranges varied between 0.15 µg L-1 and 200 µg L-1 with correlation coefficients ranging from 0.9913 to 0.9985. LODs and LOQs ranged from 0.02-0.04 µg L-1 and 0.07-0.13 µg L-1. RSDs for one fiber and fiber-to-fiber were in the range of 3.2-4.3% and 4.6-6.8%, respectively. Additionally, the fiber possessed advantages such as resistance to organic solvent, high mechanical strength and difficult breakage, making it have strong potential applications in the selective extraction of PAHs from complex water samples at trace levels.

[Fabrication and application of polyaniline/titanium dioxide nanotube solid phase microextraction fiber].

A novel solid phase microextraction fiber of polyaniline coated titania composite nanotube (PANI@TiO2NTs/Ti) array was fabricated on a titanium wire by in situ oxidation. The effects of the inorganic acid medium, aniline concentration, and oxidation voltage on the electropolymerization of aniline were discussed. The best forming conditions for the composite fiber obtained by analyzing the surface morphology and composition of the fibers were as follows:electrolyte composing, 0.5 mol/L aniline-1 mol/L H2SO4; electropolymerization, 10 V for 60 min. The developed fibers were used in conjunction with high performance liquid chromatography for the extraction and determination of ultraviolet filters in samples, and the extraction conditions optimized were as follows:extraction time 40 min, desorption time 4 min, extraction temperature 40℃, stirring rate 600 r/min. The average recoveries of the target analytes spiked in real samples ranged from 78.2% to 118%, and the relative standard deviations ranged from 4.4% to 8.9%. The developed method is simple, rapid, and accurate, and it is suitable for the sensitive determination of UV filters in environmental water samples.

Visible light activity of Bi2WO6@TCNQ with core-shell structure in phenol degradation.

Bi2WO6@TCNQ visible light photocatalyst with a core-shell structure was synthesized by adsorption methods. The core-shell structure results in the fast transfer of photogenerated carriers, reduced carrier recombination and photogenerated holes on the HOMO level of TCNQ can be injected into the VB of Bi2WO6 under visible light irradiation, resulting in the direct oxidation of organic pollutants. The photocatalytic activity of Bi2WO6@TCNQ was gradually enhanced with an increasing proportion of TCNQ. When the mass fraction of TCNQ reaches 0.5%, it exhibits the highest visible light activity. The apparent rate constant k of Bi2WO6@TCNQ-0.5% is almost 2.2 times as high as that of pure Bi2WO6.

Development of nitrogen-enriched carbonaceous material coated titania nanotubes array as a fiber coating for solid-phase microextraction of ultraviolet filters in environmental water.

A novel solid-phase microextraction (SPME) fiber was fabricated by direct electrodeposition of polyaniline (PANI) coated the titania nanotube arrays in situ grown on the titanium wire followed by carbonization at 500°C under nitrogen atmosphere. The resulting titanium-based fiber with nitrogen-enriched carbonaceous material coated titania nanotubes (N-C/TiO2NTs/Ti) showed better extraction performance for ultraviolet (UV) filters among model aromatic compounds compared with common PANI as well as commercial polydimethylsiloxane and polyacrylate coatings. The influence of various experimental parameters on the extraction efficiency of UV filters were investigated and optimized. The calibration curves were linear from 0.2 to 200µgL-1 for each analyte with correlation coefficients above 0.9980. Limits of detection (LODs) and limits of quantitation (LOQs) ranged from 0.03 to 0.05µgL-1 and from 0.11 to 0.18µgL-1 for UV filters, respectively. Relative standard deviations (RSDs) for single fiber repeatability ranged from 3.3% to 4.1% (n=5) and RSDs for fiber-to-fiber reproducibility (n=3) varied from 5.7% to 7.7%. The proposed method was successfully applied to the preconcentration and determination of target UV filters in river water and wastewater samples with good recoveries from 86.2% to 113%. Moreover this novel Ti-based fiber is mechanically and chemically stable, and can be easily prepared in a highly reproducible manner.