Rumin Li

A graphene oxide/amidoxime hydrogel for enhanced uranium capture.

The efficient development of selective materials for the recovery of uranium from nuclear waste and seawater is necessary for their potential application in nuclear fuel and the mitigation of nuclear pollution. In this work, a graphene oxide/amidoxime hydrogel (AGH) exhibits a promising adsorption performance for uranium from various aqueous solutions, including simulated seawater. We show high adsorption capacities (Qm = 398.4 mg g−1) and high % removals at ppm or ppb levels in aqueous solutions for uranium species. In the presence of high concentrations of competitive ions such as Mg2+, Ca2+, Ba2+ and Sr2+, AGH displays an enhanced selectivity for uranium. For low uranium concentrations in simulated seawater, AGH binds uranium efficiently and selectively. The results presented here reveal that the AGH is a potential adsorbent for remediating nuclear industrial effluent and adsorbing uranium from seawater.

MnO2 Nanosheets Grown on Nitrogen-Doped Hollow Carbon Shells as a High-Performance Electrode for Asymmetric Supercapacitors.

A hierarchical hollow hybrid composite, namely, MnO2 nanosheets grown on nitrogen-doped hollow carbon shells (NHCSs@MnO2 ), was synthesized by a facile in situ growth process followed by calcination. The composite has a high surface area (251 m(2) g(-1) ) and mesopores (4.5 nm in diameter), which can efficiently facilitate transport during electrochemical cycling. Owing to the synergistic effect of NHCSs and MnO2 , the composite shows a high specific capacitance of 306 F g(-1) , good rate capability, and an excellent cycling stability of 95.2 % after 5000 cycles at a high current density of 8 A g(-1) . More importantly, an asymmetric supercapacitor (ASC) assembled by using NHCSs@MnO2 and activated carbon as the positive and negative electrodes exhibits high specific capacitance (105.5 F g(-1) at 0.5 A g(-1) and 78.5 F g(-1) at 10 A g(-1) ) with excellent rate capability, achieves a maximum energy density of 43.9 Wh kg(-1) at a power density of 408 W kg(-1) , and has high stability, whereby the ASC retains 81.4 % of its initial capacitance at a current density of 5 A g(-1) after 4000 cycles. Therefore, the NHCSs@MnO2 electrode material is a promising candidate for future energy-storage systems.

Core–shell structured Gd2O3:Ln@mSiO2 hollow nanospheres: synthesis, photoluminescence and drug release properties

Gd2O3:Ln@mSiO2 hollow nanospheres (Gd2O3:Ln hollow spheres coated by a mesoporous silica layer) were successfully synthesized through a self-template method using Gd(OH)CO3 as template to form hollow precursors (named HPs), which involved the incorporation of the rare earth compound into the interior of the hydrophilic carbon shell, followed by coating with a mesoporous silica shell, and subsequent calcination in air. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric and differential thermal analyses (TG-DTA), photoluminescence spectroscopy, kinetic decays as well as N2 adsorption/desorption were employed to characterize the composites. The results indicate that the uniform Gd2O3:Ln@mSiO2 composite with the particle size around 300 nm maintains the spherical morphology and good dispersibility of the precursor. Interestingly, the composite has a double-shell structure including an inner shell of Gd2O3 and an outer shell of mesoporous silica. Moreover, they also exhibit bright red (Eu3+, 5D0→7F2) down-conversion (DC) emission and characteristic up-conversion (UC) emissions of Yb3+/Er3+. Under beam excitation, the hollow structured sample emits, which should have potential applications in biomedicine and other fields.

Facile fabrication and electrochemical performance of flower-like Fe3O4@C@layered double hydroxide (LDH) composite

A novel core–shell structured Fe3O4@C@Ni–Al LDH composite containing a carbon-coated Fe3O4 magnetic core and a layered double hydroxide (LDH) has been successfully prepared by a combination of the hydrothermal method and a facile in situ growth process. The Fe3O4@C@Ni–Al LDH microspheres were characterized by X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM and TEM), high-resolution transmission electron microscopy (HRTEM), Fourier transformed infrared (FT-IR), X-ray photoelectron spectra (XPS), and N2 adsorption/desorption methods. Owing to the unique layered feature, the composite displays core–shell structure with flower-like morphology, ultra-high surface area (792 m2 g−1) and specific pore size distribution. Moreover, the as-synthesized Fe3O4@C@Ni–Al LDH microsphere as an electrode material was fabricated into a supercapacitor and characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic charge–discharge measurements. It turned out that the Fe3O4@C@Ni–Al LDH exhibits specific capacitance of 767.6 F g−1, good rate capability, and remarkable cycling stability (92% after 1000 cycling). Therefore, such a novel synthetic route to assemble the high-performance electrochemical capacitor may open a new strategy to prepare other materials with largely enhanced electrochemical properties, which can be of great promise in energy storage device applications.

Removal of uranium(VI) from aqueous solutions by surface modified magnetic Fe3O4 particles

We prepared surface modified magnetic Fe3O4 particles (Fe3O4@APTMS) which could efficiently remove uranium(VI) ions from aqueous solutions. Batch experiments have been conducted to study the effects of initial pH, adsorbent dosage, shaking time and temperature on uranium sorption efficiency. It is found that the maximum adsorption capacity of Fe3O4@APTMS toward uranium(VI) is 151.80 mg g−1, displaying a high efficiency for the removal of uranium(VI) ions. The metal-loaded Fe3O4@APTMS particles could be recovered readily from aqueous solution by magnetic separation and regenerated easily by alkali treatment. The present study suggests that magnetic Fe3O4@APTMS composite particles can be used as an effective and recyclable adsorbent for the removal of uranium(VI) from aqueous solutions.

Hierarchical porous CNTs@NCS@MnO2 composites: rational design and high asymmetric supercapacitor performance

In this contribution, we present a novel and rational strategy for preparing hierarchical porous CNTs@NCS@MnO2 core–shell composites via a facile in situ chemical polymerization coating method, followed by a hydrothermal process. An intermediate nitrogen-doped carbon shell (NCS) with mesoporous structure and favorable chemical durability is obtained by utilizing resorcinol–formaldehyde resin as the carbon source and L-cysteine as the nitrogen source. Benefiting from a unique structure and considerable combination, the composites exhibit a highly comprehensive electrochemical performance: high specific capacitance (312.5 F g−1 at a current density of 1 A g−1), good rate capability (76.8% retention with the charge–discharge rate increasing from 1 A g−1 to 10 A g−1), superior reversibility and cycling stability (92.7% capacitance retention after 4000 cycles at 8 A g−1). In order to increase the energy density and voltage window, an asymmetric supercapacitor (ASC) was assembled using CNTs@NCS@MnO2 and activated carbon (AC) as the positive and negative electrodes, respectively. The as-fabricated asymmetric supercapacitor achieved a high specific capacitance with a stable operating voltage of 1.8 V and a maximum energy density of 27.3 W h kg−1. Such a synthetic route to prepare capacitor materials can thoroughly motivate the synergistic effect between electrical double layer capacitors and pseudocapacitors for obtaining high comprehensive performance electrodes in energy storage fields.

Fabrication of ZIF-8@SiO2 Micro/Nano Hierarchical Superhydrophobic Surface on AZ31 Magnesium Alloy with Impressive Corrosion Resistance and Abrasion Resistance

Superhydrophobic coatings are highly promising for protecting material surfaces and for wide applications. In this study, superhydrophobic composites, comprising a rhombic-dodecahedral zeolitic imidazolate framework (ZIF-8@SiO2), have been manufactured onto AZ31 magnesium alloy via chemical etching and dip-coating methods to enhance stability and corrosion resistance. Herein, we report on a simple strategy to modify hydrophobic hexadecyltrimethoxysilan (HDTMS) on ZIF-8@SiO2 to significantly improve the property of repelling water. We show that various liquids can be stable on its surface and maintain a contact angle higher than 150°. The morphologies and chemical composition were characterized by means of scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FI-IR). In addition, the anticorrosion and antiattrition properties of the film were assessed by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization and HT, respectively. Such a coating shows promising potential as a material for large-scale fabrication.

Controllable synthesis of nanostructured TiO2 by CTAB-assisted hydrothermal route

In this study, steerable nanosized TiO2 was prepared by a novel and facile cetyltrimethyl ammonium bromide (CTAB)-assisted hydrothermal process. Different from traditional hydrothermal methods, diverse amounts of CTAB and TiO2 nanopowders were added into a NaOH aqueous solution for hydrothermal reaction. The products were characterized by thermogravimetric differential scanning calorimetry (TG-DSC), X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and N2 adsorption–desorption. The results show that adding 0.04 mol L−1 CTAB in the hydrothermal reaction contributes to the efficient preparation of TiO2 nanotubes. It is found that the length of TiO2 nanotubes can be tuned from 50 nm to several hundred nanometers by simply adjusting the CTAB concentration from 0.01 to 0.04 mol L−1. It is noteworthy that the as-prepared TiO2 consists of nanosheets with the further increased amount of CTAB to 0.2 mol L−1. Furthermore, the possible formation mechanism of nanosized TiO2 with controllable morphology obtained from the CTAB-assisted hydrothermal method was also proposed.

Facile synthesis of magnetic carboxymethylcellulose nanocarriers for pH-responsive delivery of doxorubicin

The design of a single nanosystem with multifunctional surface properties via selecting the appropriate materials and synthesis methods was shown to be crucial for the development of drug delivery systems. In this work, modified magnetic nanocarriers have been successfully constructed using carboxymethylcellulose as the stabilization agents through a facile one-step hydrothermal method. The modified magnetic nanocarriers exhibited a high magnetic saturation of 54.6 emu g−1 and excellent biocompatibility which was detected by a standard MTT cell assay with L929 cell lines; the nanomaterials proved reusable for drug delivery. Subsequently, doxorubicin (DOX) was loaded onto the surface of the nanocarriers and a high loading efficiency of 92.5% was attained. The results from the release characteristics of the DOX-loaded nanocarriers demonstrated that these modified magnetic nanocarriers were highly stable at neutral pH (blood plasma) and strongly pH-responsive for drug delivery in an acidic environment (tumor tissue). The as-prepared multi-functional nanocarriers showed promising potential as drug carriers to improve the therapeutic efficacy of drugs.

Hierarchically structured layered-double-hydroxides derived by ZIF-67 for uranium recovery from simulated seawater

Under the background of increasing and sustainable development of nuclear industry, it is significant to develop materials with high adsorption capacity and high selectivity of uranium as adsorbents. In this work, novel Mg-Co layered-double-hydroxide (LDH) with hierarchical structure was synthesized successfully via self-sacrifice template by ZIF-67. X-ray diffraction (XRD) technique, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FT-IR), Brunauer-Emmett-Teller surface area measurement (BET) and X-ray photoelectron spectroscopy (XPS) characterization were conducted, which confirmed the specifically hollow structured material possesses high surface area and abundant mesopores that makes uranium ions diffuse into it more easily. In typical batch adsorption experiments, varieties of parameters were investigated in details. In addition, adsorption of trace concentration of uranium (ppb level) in simulated seawater was also studied. The results showed as-prepared Mg-Co LDHs are promising adsorbents for extraction of uranium from simulated seawater.