Self-curled coral-like γ-Al2O3 nanoplates for use as an adsorbent.

Biomimetic self-curled nanoplates assembled coral-like nanoporous γ-Al2O3 has been prepared by a solvothermal method using ethylene glycol (EG)H2O as the mixed solvent, followed by the annealing process. The resulting samples are composed of micro/nanostructured units (∼1.5 µm) with self-curled porous nanoplates on the surface. The volume ratio of EG to water in precursor solution is crucial for the formation of coral-like structure. The formation process is investigated to be an assembly process with self-curled nanoplates driven by adsorption of EG. Importantly, the coral-like porous γ-Al2O3 has high surface area of 64.18 m(2)/g and exhibits enhanced adsorption performance for efficient removal of heavy metal Hg(II) (49.15 mg/g). The removal capacity is higher than (∼2.5 times) those of commercial Al2O3 nanoparticles and hollow structured γ-Al2O3 prepared without EG (∼2.7 times). Further investigation shows adsorption behaviors of the coral-like γ-Al2O3 and the alumina hollow structure can be well described by Langmuir isotherm model, whereas that of commercial Al2O3 nanoparticles fits Freundlich isotherm model. This work not only provides an inspiration for high efficient biomimetic adsorbent but also presents a facile route for coral-like γ-Al2O3 preparation.

High-performance ionic diode membrane for salinity gradient power generation.

Salinity difference between seawater and river water is a sustainable energy resource that catches eyes of the public and the investors in the background of energy crisis. To capture this energy, interdisciplinary efforts from chemistry, materials science, environmental science, and nanotechnology have been made to create efficient and economically viable energy conversion methods and materials. Beyond conventional membrane-based processes, technological breakthroughs in harvesting salinity gradient power from natural waters are expected to emerge from the novel fluidic transport phenomena on the nanoscale. A major challenge toward real-world applications is to extrapolate existing single-channel devices to macroscopic materials. Here, we report a membrane-scale nanofluidic device with asymmetric structure, chemical composition, and surface charge polarity, termed ionic diode membrane (IDM), for harvesting electric power from salinity gradient. The IDM comprises heterojunctions between mesoporous carbon (pore size ∼7 nm, negatively charged) and macroporous alumina (pore size ∼80 nm, positively charged). The meso-/macroporous membrane rectifies the ionic current with distinctly high ratio of ca. 450 and keeps on rectifying in high-concentration electrolytes, even in saturated solution. The selective and rectified ion transport furthermore sheds light on salinity-gradient power generation. By mixing artificial seawater and river water through the IDM, substantially high power density of up to 3.46 W/m(2) is discovered, which largely outperforms some commercial ion-exchange membranes. A theoretical model based on coupled Poisson and Nernst-Planck equations is established to quantitatively explain the experimental observations and get insights into the underlying mechanism. The macroscopic and asymmetric nanofluidic structure anticipates wide potentials for sustainable power generation, water purification, and desalination.