Bo Zhi

Ordered mesoporous MnO2 as a synergetic adsorbent for effective arsenic(III) removal

Ordered mesoporous MnO2 nanoarrays were successfully prepared via a vacuum-assisted nanocasting route from an SBA-15 template. To achieve better purification performance for As(III), iron oxides with varied ratios were dispersed into the 2D hexagonal channels, and a series of FeMn-x adsorbents were obtained. Consisting of both iron and manganese oxides, these adsorbents could realize powerful oxidation and effective adsorption of As(III) simultaneously, revealing a synergetic arsenic removal process. The saturation adsorption capacity was 10.55 mg g−1 and >95% adsorption stability could be reached within a relatively short time. Furthermore, owing to the optimum Fe/Mn ratio, the FeMn-2 sample could easily bring the residual concentration down to below 10 ppb, when dealing with trace As(III) concentrations as low as 300 ppb, which provides a convenient method to efficiently capture trace As(III) from water for in-depth purification.

Effect of cationic surfactants on structure and morphology of mesostructured MOFs

Cooperative self-assembly of metal ions, bridging ligands and surfactants is an effective method to prepare mesostructured metal–organic frameworks (MOFs). In this study, we use quaternary ammonium surfactants with different head groups as templates to examine their effects on the structure and morphology of mesostructured MOFs formed by Cu2+ and 5-hydroxy-1,3-benzenedicarboxylic acid. In the presence of low surfactant concentrations, mesostructured MOFs with a variety of morphologies have been synthesized, having disordered, lamellar, p6mm or Pmn structure accordingly by increasing surfactant charge density. The particle size of mesostructured MOFs can be controlled from 200 to 600 nm by adjusting the molar ratio of ligand to surfactant. Comparing our experimental results with the synthesis of mesoporous silicas, we find that they follow a similar assembly process and the charge matching between surfactant and MOF framework plays a key role in the formation of mesostructures.

Improving the properties of β-galactosidase from Aspergillus oryzae via encapsulation in aggregated silica nanoparticles

In this study, a new immobilization method was exploited to encapsulate β-galactosidase (β-gal) from Aspergillus oryzae using aggregated core–shell silica nanoparticles as a matrix. Transmission electron microscopy (TEM) and Fourier transform infrared (FTIR) spectroscopy were used to characterize the material encapsulated β-gal. Compared to the free β-gal, the encapsulated β-gal shows a broader pH tolerance and thermal stability. Furthermore, the encapsulated β-gal shows better storage stability over 30 days. After nine cycles of hydrolytic reaction, the encapsulated β-gal still maintains 94.2% of its initial activity, which indicates that the β-gal exhibits excellent reusability after encapsulation.

Anion-templated assembly of three indium–organic frameworks with diverse topologies

[In(bpydc)(NO3)(DMA)0.5]·(DMA)(H2O)4.5 (JLU-Liu8), [In(bpydc)(HCOO)H2O]·(DMF)2(H2O)3 (JLU-Liu9) and [In(bpydc)Cl]·(DMF)2(H2O)3 (JLU-Liu10), three novel 3D monoatomic indium–organic frameworks, have been synthesized from the 2,2′-bipyridine-5,5′-dicarboxylic acid (H2bpydc) ligand under solvothermal conditions. These three compounds are constructed from the same ligand, but templated using three different anions (NO3−, HCOO− and Cl−), and they exhibit three different 4-connected ung, crb and cbo network topologies. JLU-Liu8 exhibits two types of single-helical chains with opposite helical directions (left-handed and right-handed), all of the left-handed and right-handed helical chains alternate together. In the structure of JLU-Liu9, there are two types of metal–ligand channels: the smaller square channels with dimensions 3.45 A × 4.03 A and the bigger square channels with dimensions of 11.5 A × 11.5 A. JLU-Liu10 displays an interesting feature of double-helical chains: both helical chains are interconnected with each other by sharing indium ions which entangle one spiral shaft. Furthermore, the role of anions in assisting the formation of distinct structures has been discussed. These three compounds display strong luminescence in the solid state at room temperature.

Release, detection and toxicity of fragments generated during artificial accelerated weathering of CdSe/ZnS and CdSe quantum dot polymer composites

Next generation displays and lighting applications are increasingly using inorganic quantum dots (QDs) embedded in polymer matrices to impart bright and tunable emission properties. The toxicity of some heavy metals present in commercial QDs (e.g. cadmium) has, however, raised concerns about the potential for QDs embedded in polymer matrices to be released during the manufacture, use, and end-of-life phases of the material. One important potential release scenario that polymer composites can experience in the environment is photochemically induced matrix degradation. This process is not well understood at the molecular level. To study this process, the effect of an artificially accelerated weathering process on QD–polymer nanocomposites has been explored by subjecting CdSe and CdSe/ZnS QDs embedded in poly(methyl methacrylate) (PMMA) to UVC irradiation in aqueous media. Significant matrix degradation of QD–PMMA was observed along with measurable mass loss, yellowing of the nanocomposites, and a loss of QD fluorescence. While ICP-MS identified the release of ions, confocal laser scanning microscopy and dark-field hyperspectral imaging were shown to be effective analytical techniques for revealing that QD-containing polymer fragments were also released into aqueous media due to matrix degradation. Viability experiments, which were conducted with Shewanella oneidensis MR-1, showed a statistically significant decrease in bacterial viability when the bacteria were exposed to highly degraded QD-containing polymer fragments. Results from this study highlight the need to quantify not only the extent of nanoparticle release from a polymer nanocomposite but also to determine the form of the released nanoparticles (e.g. ions or polymer fragments).