J. Xiao

Ag/AgCl plasmonic cubes with ultrahigh activity as advanced visible-light photocatalysts for photodegrading dyes

Among numerous visible-light photocatalysts, plasmonic structure is a promising photocatalyst for photodegradation and energy generation. Ag/AgCl composite as an alternative visible-light photocatalyst has attracted extensive interests; however, its syntheses has many visible flaws, e.g. high temperature environment, requirement of various templates or additives, complicated synthetic procedures and impurities in the final products. For these issues, herein, we report, for the first time, a simple, facile, rapid and green technique to synthesize Ag/AgCl heterostructured cubes using a one-step process of laser irradiation in liquids. The fabricated Ag/AgCl cubes possess some active {111} facets and a high visible-light utilization efficiency induced by the localized surface plasmon resonance (SPR) from the Ag/AgCl heterostructure. As plasmonic photocatalysts, these Ag/AgCl cubes exhibited excellent photodegrading performance for dye molecules of methyl orange, Rhodamine B and methylene blue, and the photodegradation rates were about 0.268, 0.057, and 0.094 min−1, which are considerably higher than that of commercial Ag3PO4 by a factor of 29.8, 3.8 and 6.7, respectively. The high photo-stability of the Ag/AgCl cubes was also demonstrated. The SPR-mediated photocatalytic mechanism was proposed to address the ultrahigh activity of the Ag/AgCl heterostructure as an advanced visible-light photocatalyst. These results showed the broad applicability of the developed technique for accessing a new plasmonic photocatalyst with high-performance.

Ultrahigh relaxivity and safe probes of manganese oxide nanoparticles for in vivo imaging

Mn-based nanoparticles (NPs) have emerged as new class of probes for magnetic resonance imaging due to the impressive contrast ability. However, the reported Mn-based NPs possess low relaxivity and there are no immunotoxicity data regarding Mn-based NPs as contrast agents. Here, we demonstrate the ultrahigh relaxivity of water protons of 8.26u2005mM−1s−1 from the Mn3O4 NPs synthesized by a simple and green technique, which is twice higher than that of commercial gadolinium (Gd)-based contrast agents (4.11u2005mM−1s−1) and the highest value reported to date for Mn-based NPs. We for the first time demonstrate these Mn3O4 NPs biocompatibilities both in vitro and in vivo are satisfactory based on systematical studies of the intrinsic toxicity including cell viability of human nasopharyngeal carcinoma cells, normal nasopharyngeal epithelium, apoptosis in cells and in vivo immunotoxicity. These findings pave the way for the practical clinical diagnosis of Mn based NPs as safe probes for in vivo imaging.

Carbyne with finite length: The one-dimensional sp carbon

Carbyne with one-dimensional sp-hybridized carbon atoms is synthesized under ambient conditions in the laboratory. Carbyne is the one-dimensional allotrope of carbon composed of sp-hybridized carbon atoms. Definitive evidence for carbyne has remained elusive despite its synthesis and preparation in the laboratory. Given the remarkable technological breakthroughs offered by other allotropes of carbon, including diamond, graphite, fullerenes, carbon nanotubes, and graphene, interest in carbyne and its unusual potential properties remains intense. We report the first synthesis of carbyne with finite length, which is clearly composed of alternating single bonds and triple bonds, using a novel process involving laser ablation in liquid. Spectroscopic analyses confirm that the product is the structure of sp hybridization with alternating carbon-carbon single bonds and triple bonds and capped by hydrogen. We observe purple-blue fluorescence emissions from the gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital of carbyne. Condensed-phase carbyne crystals have a hexagonal lattice and resemble the white crystalline powder produced by drying a carbyne solution. We also establish that the combination of gold and alcohol is crucial to carbyne formation because carbon-hydrogen bonds can be cleaved with the help of gold catalysts under the favorable thermodynamic environment provided by laser ablation in liquid and because the unique configuration of two carbon atoms in an alcohol molecule matches the elementary entity of carbyne. This laboratory synthesis of carbyne will enable the exploration of its properties and applications.

A microfibre assembly of an iron-carbon composite with giant magnetisation.

Iron carbide is among the oldest known materials. The utility of this ancient advanced material is greatly extended in its nanostructured forms. We demonstrate for the first time that one-dimensional iron carbide microfibres can be assembled in liquid using strong magnetic field-assisted laser ablation. The giant saturation magnetisation of these particles was measured a 261u2005emu/g at room temperature, which is the best value reported to date for iron nitride and carbide nanostructures, is 5.5 times greater than the 47u2005emu/g reported for Fe3C nanoparticles, and exceeds the 212u2005emu/g for bulk Fe. The magnetic field-induced dipolar interactions of the magnetic nanospheres and the nanochains played a key role in determining the shape of the product. These findings lead to a variety of promising applications for this unique nanostructure including its use as a magnetically guided transporter for biomedicine and as a magnetic recording material.

Highly stable sub-5 nm Sn6O4(OH)4 nanocrystals with ultrahigh activity as advanced photocatalytic materials for photodegradation of methyl orange

Among numerous active photocatalytic materials, Sn-based oxide nanomaterials are promising photocatalytic materials in environmental protection measures such as water remediation due to their excellent physicochemical property. Research on photocatalytic nanomaterials for photodegradation of methyl orange (MO) so far has focused on TiO₂-based nanostructures; e.g., TiO₂-P25 is recognized to be the best commercial photocatalyst to date, rather than Sn-based oxide nanomaterials, in spite of their impressive acid- and alkali-resistant properties and high stability. Here, we demonstrate very high photocatalytic activity of highly stable sub-5 nm hydromarchite (Sn₆O₄(OH)₄) nanocrystals synthesized by a simple and environmentally friendly laser-based technique. These Sn₆O₄(OH)₄ nanocrystals exhibit ultrahigh photocatalytic performance for photodegradation of MO and their degradation efficiency is far superior to that of TiO₂-P25. The detailed investigations demonstrated that the great photocatalytic activity results from the ultrafine size and unique surface activity induced by the laser-based technique. Mass production of reactive species of hydroxyl radicals was detected in the experiments due to the appropriate bandgap of Sn₆O₄(OH)₄ nanocrystals. These findings actually open a door to applications of Sn-based oxide nanomaterials as advanced photocatalytic materials.

Amorphous nickel hydroxide nanospheres by a green electrochemistry technique: structure, morphology and magnetism

The amorphous nickel hydroxide nanospheres have been prepared by a simple and green electrochemistry technique, and the magnetism measurements of the products show that the prepared amorphous nickel hydroxide nanospheres present ferromagnetism below the Curie temperature of 16.5 K, accompanied by high magnetization of 50 emu g−1 and high coercivity of 630 Oe at 5 K. These findings pave a way to applications of amorphous nickel hydroxide nanostructures as magnetic materials.

Ag2V4O11 nanostructures for highly ethanol sensitive performance

Ag2V4O11 brush-like nanostructures with a large specific surface area have been synthesized by a unique electrochemistry assisted laser ablation in liquids without any template or surfactant in an ambient environment. Considering the large surface-to-volume ratio of the as-synthesized nanostructures, an Ag2V4O11 brush-like nanostructured gas sensor was fabricated and exhibited an excellent performance in sensor response to ethanol concentrations in the range of 10 to 600 ppm under low working temperature. This high response was attributed to the highly crystalline and brush-like surface, which leads to the effective adsorption and desorption, and provides more active sites for gas molecules reacting. These findings show our desire to encourage the synthesis of new nanomaterials, e.g. ternary transition metal oxides, as gas sensors prepared by novel means.

Cubic boron nitride with an intrinsic peroxidase-like activity

Inorganic artificial enzymes have been developed as potential candidates to naturally occurring enzymes, and three inorganic enzyme mimics, noble metals, metal oxides and carbon materials, have been reported so far. Here, we reported the inorganic enzyme mimic of nitride-based materials. We demonstrated that cubic boron nitride (c-BN) as an enzyme mimic showed intrinsic peroxidase-like activity towards classical colorimetric substrates in the presence of hydrogen peroxide (H2O2). The Michaelis–Menten kinetics studies indicated that the catalytic efficiency of c-BN is superior to its natural peroxidase counterparts. We also established that the peroxidase-like activity of c-BN is induced by catalyzing the decomposition of H2O2 and generating hydroxyl radicals (˙OH). Based on the color reaction, a strategy was developed for H2O2 and glucose quantitative detection with high sensitivity. A reactor was constructed by entrapping c-BN in a porous platform and the peroxidase mimic immobilization for removal of organic pollutants was successfully conducted. Additionally, c-BN can be re-used up to 5 times and retain its catalytic activity after incubation at extremes of pH and temperature. These findings open the door for the application of c-BN as a catalyst and the development of nitride-based materials in the enzyme-mimics field.

Amorphous cobalt hydroxide nanostructures and magnetism from green electrochemistry

Amorphous cobalt hydroxide nanostructures have been synthesized by a simple and green electrochemistry technique. Magnetism measurements showed that the as-synthesized amorphous cobalt hydroxide nanoparticles are ferromagnetic under the Curie temperature of 10 K with high magnetization of 30 emu g−1 and an exchange bias field of 100 Oe at 5 K. These findings may lead to novel applications of the amorphous cobalt hydroxide nanostructures as magnetic materials.

Molecular Luminescence of White Carbon

Four-color emission modulated by the molecular chain length from white carbon (carbyne crystals) is observed. It is also established that a carbyne molecule with four carbon atoms is the basic unit or building block to construct carbyne crystals, where the chain length of the carbyne molecule in the synthesized carbyne crystals follows the rule of 4n (n = 1, 2, 3, …).