Single-Crystal α-Fe2O3 with Engineered Exposed (001) Facet for High-Rate, Long-Cycle-Life Lithium-Ion Battery Anode.

Designing electrode materials with engineered exposed facets provides a novel strategy to improve their electrochemical properties. However, the controllability of the exposed facet remains a daunting challenge, and a deep understanding of the correlation between exposed facet and Li+-transfer behavior has been rarely reported. In this work, single-crystal α-Fe2O3 hexagonal nanosheets with an exposed (001) facet are prepared with the assistance of aluminum ions through a one-step hydrothermal process, and structural characterizations reveal an Al3+-concentration-dependent-growth mechanism for the α-Fe2O3 nanosheets. Furthermore, such α-Fe2O3 nanosheets, when used as lithium-ion battery anodes, exhibit high specific capacity (1261.3 mAh g-1 at 200 mA g-1), high rate capability (with a reversible capacity of approximately 605 mAh g-1 at 10 A g-1), and excellent cyclic stability (with a capacity of over 900 mAh g-1 during 500 cycles). The superior electrochemical performance of α-Fe2O3 nanosheets is attributed to the pseudocapacitive behavior, Al-doping in the α-Fe2O3 structure, and improved Li+-transfer property across the (001) facet, as elucidated by first-principles calculations based on density functional theory. These results reveal the underlying mechanism of Li+ transfer across different facets and thus provide insights into the understanding of the excellent electrochemical performance.

Zinc Oxide Coating Effect for the Dye Removal and Photocatalytic Mechanisms of Flower-Like MoS2 Nanoparticles.

Flower-like MoS2 nanoparticles (NPs) consist of ultra-thin MoS2 nanosheets are synthesized via a facile one-pot hydrothermal method. The MoS2/ZnO p-n heterostructure is formed by coating n-type ZnO on the surface of flower-like MoS2 NPs through the seed-mediate route and post-annealing treatment. The effects for the dye removal and photocatalytic performances after ZnO coating are systematically investigated. The results demonstrated that the coating of ZnO nanoparticles has a positive promotion to the photodegrading properties while negative effect on the adsorption capacity of the MoS2/ZnO heterostructures. The related mechanisms on the relationship of adsorption capacity and photocatalysis are discussed in detail.

CTAB-assisted synthesis of novel ultrathin MoSe2 nanosheets perpendicular to graphene for the adsorption and photodegradation of organic dyes under visible light.

A novel nanostructure of perpendicular ultrathin MoSe2 nanosheets directly grown on graphene was produced by a facile hydrothermal method in the presence of CTAB. The vertically-oriented and ultrathin MoSe2 nanosheets distribute uniformly on the surface of graphene, and the nanosheets are typically 2-3 layers, which is confirmed by TEM and red shift of the A1g Raman peak. In comparison with pure MoSe2 and MoSe2 nanospheres on graphene, vertically oriented MoSe2 nanosheets on graphene show enhanced organic dye adsorption ability and photocatalytic performance in the degradation of MB, RhB and MO under dark conditions and visible light irradiation. The excellent photocatalytic activity may be contributed by the unique perpendicular MoSe2 nanosheets with fully exposed active edges and hybridized with graphene for reduced electron-hole pair recombination.

Shape control of inorganic nanoparticles from solution.

Inorganic materials with controllable shapes have been an intensely studied subject in nanoscience over the past decades. Control over novel and anisotropic shapes of inorganic nanomaterials differing from those of bulk materials leads to unique and tunable properties for widespread applications such as biomedicine, catalysis, fuels or solar cells and magnetic data storage. This review presents a comprehensive overview of shape-controlled inorganic nanomaterials via nucleation and growth theory and the control of experimental conditions (including supersaturation, temperature, surfactants and secondary nucleation), providing a brief account of the shape control of inorganic nanoparticles during wet-chemistry synthetic processes. Subsequently, typical mechanisms for shape-controlled inorganic nanoparticles and the general shape of the nanoparticles formed by each mechanism are also expounded. Furthermore, the differences between similar mechanisms for the shape control of inorganic nanoparticles are also clearly described. The authors envision that this review will provide valuable guidance on experimental conditions and process control for the synthesis of inorganic nanoparticles with tunable shapes in the solution state.

Low-Cost, Disposable, Flexible and Highly Reproducible Screen Printed SERS Substrates for the Detection of Various Chemicals.

Ideal SERS substrates for sensing applications should exhibit strong signal enhancement, generate a reproducible and uniform response, and should be able to fabricate in large-scale and low-cost. Herein, we demonstrate low-cost, highly sensitive, disposable and reproducible SERS substrates by means of screen printing Ag nanoparticles (NPs) on a plastic PET (Polyethylene terephthalate) substrates. While there are many complex methods for the fabrication of SERS substrates, screen printing is suitable for large-area fabrication and overcomes the uneven radial distribution. Using as-printed Ag substrates as the SERS platform, detection of various commonly known chemicals have been done. The SERS detection limit of Rhodamine 6G (R6G) is higher than the concentration of 1 × 10(-10) M. The relative standard deviation (RSD) value for 784 points on the detection of R6G and Malachite green (MG) is less than 20% revealing a homogeneous SERS distribution and high reproducibility. Moreover, melamine (MA) is detected in fresh liquid-milk without additional pretreatment, which may accelerate the application of rapid on-line detection of MA in liquid milk. Our screen printing method highlights the use of large-scale printing strategies for the fabrication of well-defined functional nanostructures with applications well beyond the field of SERS sensing.

Potassium niobate nanolamina: a promising adsorbent for entrapment of radioactive cations from water.

Processing and managing radioactive waste is a great challenge worldwide as it is extremely difficult and costly; the radioactive species, cations or anions, leaked into the environment are a serious threat to the health of present and future generations. We report layered potassium niobate (K4Nb6O17) nanolamina as adsorbent to remove toxic Sr(2+), Ba(2+) and Cs(+) cations from wastewater. The results show that K4Nb6O17 nanolamina can permanently confine the toxic cations within the interlayer spacing via a considerable deformation of the metastable layered structure during the ion exchange process. At the same time, the nanolaminar adsorbent exhibits prompt adsorption kinetics, high adsorption capacity and selectivity, and superior acid resistance. These merits make it be a promising material as ion exchanger for the removal of radioactive cations from wastewater.

Significantly enhanced dye removal performance of hollow tin oxide nanoparticles via carbon coating in dark environment and study of its mechanism.

Understanding the correlation between physicochemical properties and morphology of nanostructures is a prerequisite for widespread applications of nanomaterials in environmental application areas. Herein, we illustrated that the uniform-sized SnO2@C hollow nanoparticles were large-scale synthesized by a facile hydrothermal method. The size of the core-shell hollow nanoparticles was about 56 nm, and the shell was composed of a solid carbon layer with a thickness of 2 ~ 3 nm. The resulting products were characterized in terms of morphology, composition, and surface property by various analytical techniques. Moreover, the SnO2@C hollow nanoparticles are shown to be effective adsorbents for removing four different dyes from aqueous solutions, which is superior to the pure hollow SnO2 nanoparticles and commercial SnO2. The enhanced mechanism has also been discussed, which can be attributed to the high specific surface areas after carbon coating.

Tube-like ternary α-Fe2O3@SnO2@Cu2O sandwich heterostructures: synthesis and enhanced photocatalytic properties.

Heterogeneous photocatalysis is of great interest for environmental remediation applications. However, fast recombination of photogenerated electron-hole pair and a low utilization rate of sunlight hinder the commercialization of currently available semiconductor photocatalysts. In this regard, we developed a unique ternary single core-double shell heterostructure that consists of α-Fe2O3@SnO2@Cu2O. This heterostructure exhibits a tube-like morphology possessing broad spectral response for the sunlight due to the combination of narrow bandgap and wide bandgap semiconductors forming a p-n heterojunction. To fabricate such a short nanotube (SNT), we used an anion-assisted hydrothermal route for deposition of α-Fe2O3, a seed-mediated deposition strategy for SnO2, and finally an aging process to deposit a Cu2O layer to complete the tube-like ternary α-Fe2O3@SnO2@Cu2O single core-double shell heterostructures. The morphology, composition, and photocatalytic properties of those ternary core-shell-shell heterostructures were characterized by various analytical techniques. These ternary heterostructures exhibited enhanced photocatalytic properties on the photodegradation of the organic dye of Rhodamine B (RhB) under simulated sunlight irradiation. The origin of enhanced photocatalytic activity is due to the synergistic effect of broad spectral response by combining narrow bandgap and wide bandgap semiconductors and, hence, an efficient charge separation of photogenerated electron-hole pairs facilitated through the p-n heterojunction. Furthermore, our unique structure provides an insight on the fabrication and controlled preparation of multilayer heterostructural photocatalysts that have intriguing properties.

Template and silica interlayer tailorable synthesis of spindle-like multilayer α-Fe2O3/Ag/SnO2 ternary hybrid architectures and their enhanced photocatalytic activity.

Our study reports a novel iron oxide/noble metal/semiconductor ternary multilayer hybrid structure that was synthesized through template synthesis and layer-by-layer deposition. Three different morphologies of α-Fe2O3/Ag/SiO2/SnO2 hybrid architectures were obtained with different thicknesses of the SiO2 interlayer which was introduced for tailoring and controlling the coupling of noble metal Ag nanoparticles (NPs) with the SnO2 semiconductor. The resulting samples were characterized in terms of morphology, composition, and optical property by various analytical techniques. The as-obtained α-Fe2O3/Ag/SiO2/SnO2 nanocomposites exhibit enhanced visible light or UV photocatalytic abilities, remarkably superior to commercial pure SnO2 products, bare α-Fe2O3 seeds, and α-Fe2O3/SnO2 nanocomposites. Moreover, the sample of α-Fe2O3/Ag/SiO2/SnO2 also exhibits good chemical stability and recyclability because it has higher photocatalytic activity even after eight cycles. The origin of enhanced photocatalytic activity on the multilayer core-shell α-Fe2O3/Ag/SiO2/SnO2 nanocomposites was primarily ascribed to the coupling between noble metal Ag and the two semiconductors Fe2O3 and SnO2, which are proven to be applied in recyclable photocatalysis.

Fabrication, characterization and screen printing of conductive ink based on carbon@Ag core-shell nanoparticles.

The large-scale synthesis and characterization of carbon-core/Ag-shell (C@Ag) nanoparticles by the successive reduction of silver ammonia are described. The resultant C@Ag nanoparticles had a mean core diameter of 360 nm and a controllable shell thickness from 10 to 40 nm by simple adjustments of repeat coating times. Various analysis techniques confirmed that the carbon cores were fully covered by Ag nanoshells. The results also show that C/Ag composite nanomaterials-based conductive inks, which can be easily produced on a large scale and possess outstanding electronic properties, have great potential for the convenient fabrication of flexible and low-cost carbon-based electronic devices and replace the traditional pure silver paste, by using a simple screen printing technique.