Metal-organic frameworks (MOFs) have great potential to become innovative heterogeneous supports for immobilizing catalytically active noble metal nanoparticles (NPs). However, unlike metal oxide supports, the interfacial interactions between noble metal NPs and MOFs are currently neglected, thus dramatically diminishing the advantage of MOFs as supports. Herein, ZIFs(Co/Zn)@M (M = Pd, Pt or Au) nanocomposites with well-defined interfaces are synthesized and used as catalysts in gas-phase CO oxidation and liquid-phase C6H5CHO oxidation. Notably, in both reactions, ZIF-67(Co)@M samples exhibit better catalytic activity than ZIF-8(Zn)@M samples, and moreover, the catalytic activity of ZIFs@Pd is higher than that of ZIFs@Pt and ZIFs@Au samples. Experimental and theoretical results reveal that the enhanced catalytic activity originates from the interfacial electron transfer from ZIFs to noble metal NPs as well as the coupling between d band of noble metal in NPs and metal node in ZIFs.

A high-quality field emission electron source made of a highly ordered array of carbon nanotubes (CNTs) coated with a thin film of hexagonal boron nitride (h-BN) is fabricated using a simple and scalable method. This method offers the benefit of reproducibility, as well as the simplicity, safety, and low cost inherent in using B(2)O(3) as the boron precursor. Results measured using h-BN-coated CNT arrays are compared with uncoated control arrays. The optimal thickness of the h-BN film is found to be 3 nm. As a result of the incorporation of h-BN, the turn-on field is found to decrease from 4.11 to 1.36 V μm(-1), which can be explained by the significantly lower emission barrier that is achieved due to the negative electron affinity of h-BN. Meanwhile, the total emission current is observed to increase from 1.6 to 3.7 mA, due to a mechanism that limits the self-current of any individual emitting tip. This phenomenon also leads to improved emission stability and uniformity. In addition, the lifetime of the arrays is improved as well. The h-BN-coated CNT array-based field emitters proposed in this work may open new paths for the development of future high-performance vacuum electronic devices.

Volatile organic compounds (VOCs) are widely used as constituents of household chemicals. Although adverse health effects have been reported, long-term exposure to low-level VOCs mixture has not been studied. Especially, there is a lack of substantial information on the sensitive biomarkers and carcinogenic markers. In the present study, we examined oxidative stress and genotoxic effects of sub-chronic low-dose VOCs mixture (formaldehyde, benzene, toluene and xylene). Male Kunming mice were exposed to 0 (control) and three different doses of VOCs mixture (group 1S, 5S and 10S) for 90 d (2 h/d). Group 1S is 0.10, 0.11, 0.20 and 0.20 mg/m³, group 5S is 0.50, 0.55, 1.00 and 1.00 mg/m³, group 10S is 1.00, 1.10, 2.00 and 2.00 mg/m³, which, respectively, corresponded to 1, 5 and 10 times of indoor air quality standard (IAQS) in China. One day following VOCs exposure, oxidative stress markers in lung, 8-hydroxy-2'-deoxyguanosine in bronchoalveolar lavage fluid and genotoxicity (DNA damage) in liver were examined. Results showed that exposure to VOCs (IAQS dose) resulted in oxidative damages of lung, which were supported by the significant changes on reactive oxygen species, reduced glutathione (GSH), GSH S-transferase, total antioxidative capacity, malondialdehyde, protein carbonyl and nitric oxide (NO). Moreover, oxidative stress markers in group 5S and 10S (except NO) in lung were affected significantly. In addition, VOCs exposure also induced significantly DNA damage in liver. Our study suggested long-term VOCs inhalation at low levels caused oxidative stress and genotoxicity response in mice. Since effects were seen at the current IAQS level, further studies below this level are necessary.

Manipulation of oxygen vacancies via electric-field-controlled ionic liquid gating has been reported in many model systems within the emergent fields of oxide electronics and iontronics. It is then significant to investigate the oxygen vacancy formation/annihilation and migration across an additional ferroelectric layer with ionic liquid gating. Here, we report that via a combination of ionic liquid and ferroelectric gating, the remote control of oxygen vacancies and magnetic phase transition can be achieved in SrCoO 2.5 films capped with an ultrathin ferroelectric BaTiO 3 layer at room temperature. The ultrathin BaTiO 3 layer acts as an atomic oxygen valve and is semitransparent to oxygen-ion transport due to the competing interaction between vertical electron tunneling and ferroelectric polarization plus surface electrochemical changes in itself, thus resulting in the striking emergence of new mixed-phase SrCoO x . The lateral coexistence of brownmillerite phase SrCoO 2.5 and perovskite phase SrCoO 3−δ was directly observed by transmission electron microscopy. Besides the fundamental significance of long-range interaction in ionic liquid gating, the ability to control the flow of oxygen ions across the heterointerface by the oxygen valve provides a new approach on the atomic scale for designing multistate memories, sensors, and solid-oxide fuel cells.