Zhi Xie

Thermodynamic analysis on the binding of heavy metals onto extracellular polymeric substances (EPS) of activated sludge

Metal binding to microbial extracellular polymeric substances (EPS) greatly influences the distribution of heavy metals in microbial aggregates, soil and aquatic systems in nature. In this work, the thermodynamic characteristics of the binding between aqueous metals (with copper ion as an example) and EPS of activated sludge were investigated. Isothermal titration calorimetry was employed to estimate the thermodynamic parameters for the binding of Cu²⁺ onto EPS, while three-dimensional excitation-emission matrix (EEM) fluorescence spectroscopy with parallel factor analysis was used for quantifying the complexation of Cu²⁺ with the EPS. The binding mechanisms were further explored by X-ray absorption fine structure (XAFS) and Fourier transform infrared (FTIR) spectroscopy analysis. The results show that the proteins and humic substances in EPS were both strong ligands for Cu²⁺. The binding capacity N, binding constant K, binding enthalpy ΔH were calculated as 5.74 × 10⁻² mmol/g, 2.18 × 10⁵ L/mol, and -11.30 kJ/mol, respectively, implying that such a binding process was exothermic and thermodynamically favorable. The binding process was found to be driven mainly by the entropy change of the reaction. A further investigation shows that Cu²⁺ bound with the oxygen atom in the carboxyl groups in the EPS molecules of activated sludge. This study facilitates a better understanding about the roles of EPS in protecting microbes against heavy metals.

Aligned Fe2TiO5-containing nanotube arrays with low onset potential for visible-light water oxidation

There remains a pressing challenge in the efficient utilization of visible light in the photoelectrochemical applications of water splitting. Here, we design and fabricate pseudobrookite Fe2TiO5 ultrathin layers grown on vertically aligned TiO2 nanotube arrays that can enhance the conduction and utilization of photogenerated charge carriers. Our photoanodes are characterized by low onset potentials of ~0.2u2009V, high photon-to-current efficiencies of 40-50% under 400-600u2009nm irradiation and total energy conversion efficiencies of ~2.7%. The high performance of Fe2TiO5 nanotube arrays can be attributed to the anisotropic charge carrier transportation and elongated charge carrier diffusion length (compared with those of conventional TiO2 or Fe2O3 photoanodes) based on electrochemical impedance analysis and first-principles calculations. The Fe2TiO5 nanotube arrays may open up more opportunities in the design of efficient and low-cost photoanodes working in visible light for photoelectrochemical applications.

Half-unit-cell α-Fe2O3 semiconductor nanosheets with intrinsic and robust ferromagnetism.

The synthesis of atomically thin transition-metal oxide nanosheets as a conceptually new class of materials is significant for the development of next-generation electronic and magnetic nanodevices but remains a fundamental chemical and physical challenge. Here, based on a template-assisted oriented growth strategy, we successfully synthesized half-unit-cell nanosheets of a typical transition-metal oxide α-Fe2O3 that show robust intrinsic ferromagnetism of 0.6 μB/atom at 100 K and remain ferromagnetic at room temperature. A unique surface structure distortion, as revealed by X-ray absorption spectroscopy, produces nonidentical Fe ion environments and induces distance fluctuation of Fe ion chains. First-principles calculations reveal that the efficient breaking of the quantum degeneracy of Fe 3d energy states activates ferromagnetic exchange interaction in these Fe(5-co)-O-Fe(6-co) ion chains. These results provide a solid design principle for tailoring the spin-exchange interactions and offer promise for future semiconductor spintronics.

Self-doping effect and successive magnetic transitions in superconducting Sr2VFeAsO3

We have studied a quinary Fe-based superconductor

Cu and Co codoping effects on room-temperature ferromagnetism of (Co,Cu):ZnO dilute magnetic semiconductors

{text{Sr}}_{2}{text{VFeAsO}}_{3}

Influence of p-type and n-type dopants on the magnetic properties of ZnCuO based diluted magnetic semiconductor thin films

by the measurements of x-ray diffraction, x-ray absorption, Mossbauer spectrum, resistivity, magnetization, and specific heat. This apparently undoped oxyarsenide is shown to be self-doped via electron transfer from the

Unidirectional Thermal Diffusion in Bimetallic Cu@Au Nanoparticles

{text{V}}^{3+}

Realizing Ferromagnetic Coupling in Diluted Magnetic Semiconductor Quantum Dots

ions. We observed successive magnetic transitions within the

Interfacial intermixing of TiN/Si3N4 super-hard multilayer films studied by fluorescence x-ray absorption fine structure

{text{VO}}_{2}

Defect-induced ferromagnetism in insulating Mn-P codoped ZnO grown in oxygen-rich environment

layers: an antiferromagnetic transition at 150 K followed by a weak ferromagnetic transition at 55 K. The spin orderings within the