[en] The Cr(VI) pollutants are known to cause serious harm to the environment and human health. Chemical reduction is one of the efficient methods to eliminate the Cr(VI) pollutants. We synthesized polyvinylpyrrolidone-stabilized palladium (PVP-Pd) colloidal nanoparticles to catalytically reduce Cr(VI). The PVP-Pd colloidal nanocatalysts were active on the complete reduction of Cr(VI) to Cr(III) with a rate of 22.2 mol_Cr/(mol_Pd min) or a turn-over frequency (TOF) of 1,329 h⁻¹ at pH 4.0 and 45 °C. Magnetic Fe₃O₄ support was used for recycling the palladium nanocatalysts. The as-prepared Pd–Fe₃O₄ catalyst was easy to be separated from the reaction system by simply applying an external magnet and it exhibited efficient and stable reduction performance even after eight recycles.

[en] LED light bulbs that simulate solar spectrum were fabricated using CdSe core–shell quantum dots in combination with GaN blue-light chips. They exhibited excellent optical properties such as white CIE coordinates of (0.33, 0.33), high color rendering index (CRI) of 98 and correlated color temperature (CCT) of 5352 K. Moreover, a circuit system was used to control the LEDs so that the lighting spectrum changes with the time in a day to simulate the actual solar spectrum. The results show that the sun-like spectrum smart bulbs not only have good optical properties and high electrical stability, but also can automatically adjust their spectrum according to the time, making the lighting natural. This work makes sun-like lighting conditions for some special environments to promote the application of smart bulbs in smart lighting. (paper)

[en] This paper presents a new approach to nanosphere lithography, which overcomes undesirable manufacturing issues such as complex tilted-rotary evaporation and ion beam milling. A key innovation in this process is the use of non-conductive edge strips placed on top of the samples prior to metal removal. Such elements help to direct the flow of reactive ions during plasma etching and produce well-ordered arrays of metallic nanorings and nanocrescents over large areas of ∼1 cm². The obtained highly uniform nanocrescent array exhibits an electric resonance of 1.7 μm and a magnetic resonance of 3 μm. The absorption resonances of the fabricated nanorings depend on their diameters and shift toward shorter wavelengths (λ = 1.7 μm for d_o = 308 nm) as compared to larger rings (λ = 2.2 μm d_o = 351 nm). FDTD-based simulations match well with the experimental results. This ‘shaped nanosphere lithography’ approach creates opportunities to generate nanorings and nanocrescents that promise potential applications in chemical and biological sensing, for surface enhanced spectroscopy and in the field of infrared metamaterials. (paper)

[en] Transition metal dichalcogenides have unique physicochemical properties. Herein, a low-temperature facile method is demonstrated to synthesize ultrathin tungsten disulfide nanoflakes. They are loosely stacked between layers with highly exposed edges, which provide lots of active sites for electrochemical applications. The by-product of crystalline carbon improves their conductivity, which also enhances their performance in hydrogen evolution reaction. (paper)

[en] TiO₂ and ZnO nanomaterials are widely used to block ultraviolet radiation in many skin care products, yet product labels do not specify their dimensions, shape, or composition. The absence of this basic information creates a data gap for both researchers and consumers alike. Here, we investigate the structural similarity of pigments derived from actual sunscreen products to nanocrystals which have been the subject of intense scrutiny in the nanotoxicity literature. TiO₂ and ZnO particles were isolated from eight out of nine commercial suncare products using three extraction methods. Their dimension, shape, crystal phase, surface area, and elemental composition were examined using transmission and scanning electron microscopy, X-ray diffraction, Brunauer–Emmett–Teller (BET) specific surface area analysis, energy dispersive X-ray and inductively coupled plasma optical emission spectroscopy. TiO₂ pigments were generally rutile nanocrystals (dimensions ∼25 nm) with needle-like or near-spherical shapes. ZnO pigments were wurtzite rods with a short axes less than 40 nm and longer dimensions often in excess of 100 nm. We identify two commercial sources of TiO₂ and ZnO nanocrystals whose physical and chemical features are similar to the pigments found in sunscreens. These particular materials would be effective surrogates for the commercial product and could be used in studies of the health and environmental impacts of engineered nanomaterials contained in sunscreens.

[en] Semiconductor nanocrystals are 1-10 nm inorganic particles with unique size-dependent optical and electrical properties due to quantum confinement (so they are also called quantum dots). Quantum dots are new types of fluorescent materials for biological labeling with high quantum efficiency, long-term photostability, narrow emission, and continuous absorption spectra. Here, we discuss the recent development in making water-soluble quantum dots and related cytotoxicity for biomedical applications

[en] Perovskite white light-emitting devices (WLEDs) without intercalation layers have not been achieved due to the ion exchange. Although the intercalation layers prevent ion exchange between perovskite nanocrystals (NCs), it also creates a new problem of charge imbalance and the structure becomes more complex. In this study, blue emitting ZnCdS/ZnS NCs with high quantum yield and stability are introduced to work with the yellow emission from CsPb(Br/I)₃ perovskite NCs for WLEDs. The WLEDs are constituted of ITO/ZnO/PEI/ZnCdS/ZnS NCs/CsPb(Br/I)₃ NCs/TCTA/MoO₃/Au. This design avoids ion exchange between different perovskites NCs, and realizes white light emission by simple fabrication. As a result, we achieved the white light coordinates of (0.34, 0.34) and a correlated color temperature of 5153 K. (paper)

[en] I–VI chalcogenide low-toxicity semiconductors and their near-infrared optical property are of great importance for solar cell and biological probe applications. Here, we report the synthesis of Ag₂S _x Se_{1− x} ( x  = 0–1) ternary nanocrystals (NCs) and their photoelectrochemical properties, using a refined simple hot-injection reaction recipe. The ICP-MS results show the change of non-metallic composition in products and precursors, which can be well fitted with Vegard’s equation. Ternary alloying broadens the absorption spectrum region of Ag₂S NCs. It can also balance the transfer of photo-excited electrons through the interfaces of TiO₂/Ag₂S _x Se_{1− x} and Ag₂S _x Se_{1− x} /electrolyte by minimizing electron–hole recombination. By tuning the compositions, an increase in power conversion efficiency (PCE) was observed with the increase of S composition and the size of the NCs. The photoelectrochemical results reveal that Ag₂S _x Se_{1− x} ternary NCs exhibit higher conversion efficiency than pure binary NCs. The drop in PCE of the binary NCs is mainly attributed to the decreases of the charge separation following exciton transition. (paper)

[en] Highlights: • The visible photocatalyst WSe₂/NG were synthesized via hydrothermal route. • WSe₂/50NG exhibited the efficient and rapid visible photocatalytic activity. • WSe₂/NG showed higher stability and good reusability. Nitrogen doped graphene oxide (NG) modified WSe₂ nanorod composites (WSe₂/NG) were prepared by a hydrothermal synthesis route. The synthesized samples were characterized by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), transmission electron microscopy (TEM), UV–vis diffuse reflectance spectroscopy(DRS) and elemental analysis. Using methylene blue (MB) as a target organic dye, WSe₂/NG nanocomposites exhibited significant enhancement in photocatalytic degradation of MB under visible light irradiation compared with WSe₂. That was mainly attributed to the strong adsorption of MB, excellent electrical conductivity and charge separation features of the NG, leading to effectively restrained electron-hole pair recombination of WSe₂ nanorods. Among the hybrid photocatalysts, WSe₂/50NG (50 wt% of NG) exhibited the highest photocatalytic activity with a rate constant of 0.0572 min⁻¹ for the degradation of the MB in aqueous solution under visible light irradiation, and the removal efficiency reached 99.3% which was 2.4 times higher than that of WSe₂. In addition, WSe₂/NG also showed higher stability and good reusability.

[en] Highlights: • Visualization of AIE process was illustrated by molecular dynamics simulation. • Long alkyl and cyclohexane substituents are introduced into the AIE molecule as hydrophobic groups. • Hydrophobic groups enhances the AIE fluorescence stability in the aggregate state in water. • The CSB-2 still exhibited a superior performance in detecting TNT in aqueous media after placed for a week. Since the aggregation induced emission (AIE) phenomenon was reported, many research groups have used this unique AIE effect to develop chemo- or bio-sensors for detecting ions, gases, explosives, proteins, and enzymes. Most of these sensors work in their aggregate state, therefore, fluorescence stability has become one of the important problem, and unfortunately, as far as we know, there is no paper to discuss what factors can improve the fluorescence stability of AIE compounds in the aggregate state, if the fluorescence stability of the sensors are poor, there will seriously affect the detection result. In this article, we found that compounds with hydrophobic long alkyl substituents can maintain stable fluorescence intensity for a long time in the aggregate state. In addition, cyclohexane is introduced as a hydrophobic substituent. Therefore, the fluorescence stability of the aggregates also increased by 90% within 1800s. The aggregation solutions of CB-3 and CSB-2 were left for two weeks, and no significant changes were found in the fluorescence intensity. Molecular dynamics simulation (MDS) shows that the presence of hydrophobic substituents in compounds cause the molecules to be closely interspersed with each other, hence, making it difficult to change the optical properties, microstructure and stacking mode of the AIE aggregates by external stimulations. The introduction of hydrophobic substituents improves the fluorescence stability of AIE compounds, and makes the AIE phenomenon more valuable in the fields of biological/chemical sensing and imaging.