ABSTRACT
In electrides, interstitial anionic electrons (IAEs) in the quantized energy levels at cavities of positively charged lattice framework possess their own magnetic moment and interact with each or surrounding cations, behaving as quasi-atoms and inducing diverse magnetism. Here, we report the reversible structural and magnetic transitions by the substitution of the quasi-atomic IAEs in the ferromagnetic two-dimensional [Gd2C]2+·2e- electride with hydrogens and subsequent dehydrogenation of the canted antiferromagnetic Gd2CHy (y > 2.0). It is demonstrated that structural and magnetic transitions are strongly coupled by the presence or absence of the magnetic quasi-atomic IAEs and non-magnetic hydrogen anions in the interlayer space, which dominate exchange interactions between out-of-plane Gd-Gd atoms. Furthermore, the magnetic quasi-atomic IAEs are inherently conserved by the hydrogen desorption from the P[Formula: see text] 1m structured Gd2CHy, restoring the original ferromagnetic state of the R[Formula: see text]m structured [Gd2C]2+·2e- electride. This variable density of magnetic quasi-atomic IAEs enables the quantum manipulation of floating electron phases on the electride surface.
ABSTRACT
A high-performance gas sensor operating at room temperature is always favourable since it simplifies the device fabrication and lowers the operating power by eliminating a heater. Herein, we fabricated the ammonia (NH3) gas sensor by using Au nanoparticle-decorated TiO2 nanosheets, which were synthesized via two distinct processes: (1) preparation of monolayer TiO2 nanosheets through flux growth and a subsequent chemical exfoliation and (2) decoration of Au nanoparticles on the TiO2 nanosheets via hydrothermal method. Based on the morphological, compositional, crystallographic, and surface characteristics of this low-dimensional nano-heterostructured material, its temperature- and concentration-dependent NH3 gas-sensing properties were investigated. A high response of ~ 2.8 was obtained at room temperature under 20 ppm NH3 gas concentration by decorating Au nanoparticles onto the surface of TiO2 nanosheets, which generated oxygen defects and induced spillover effect as well.
ABSTRACT
Heavy metals in groups 3-16 in periods 4 and greater. They exist naturally in the earth's crust. People are exposed to heavy metals by the inhalation of polluted air and via the intake of contaminated food. People are exposed to lead (Pb), one of heavy metals, by consuming foods that are contaminated from the environment. Pb is ubiquitous in the environment and accumulates in plants and animals that eat contaminated plants. The Pb in foods before and after processing were analyzed via Inductively coupled plasma with mass spectrometry to determine the effects of the procedures on the Pb migration and residue. This analytical method was verified to have a limit of detection of 0.011-0.859 µg/kg, acceptable linearity with the regression coefficient of 0.999, relative recoveries of 78.1-89.9% and repeatability of 1.4-7.7%. The amount of Pb was reduced during the following processes: more than 79.6% by extracting ginseng, extracting red ginseng and balloon flower roots via alcohol, more than 47.9% by blanching Chwinamul, more than 18.2% by brewing coffee with cold and hot water, more than 22.2% by extracting juices from fruits and peeling fruits. Therefore, proper cooking and food processing can be advantageous in terms of reducing exposure to Pb.
ABSTRACT
BACKGROUND: There are two methods for quantifying methylmercury (MeHg) in fish using GC-electron capture detection (ECD): AOAC INTERNATIONAL Official Method 988.11 and the Korean Food Code (KFC) method. Both of these methods consume a large amount of chemicals and require long pretreatment times because of several complicated MeHg extraction steps. OBJECTIVE: In this study, a new method for the simple and rapid determination of MeHg in fish has been developed. The method is based on the investigation of oxygen combustion-gold amalgamation using a direct mercury analyzer (DMA) after the complete removal of MeHg by organic extraction and back-extraction to an aqueous medium. METHODS: The DMA is suitable for the analysis of both solid and liquid materials and has a good detection limit. The developed method was validated by comparing the MeHg recoveries (%) of both certified reference materials and the market-purchased fish samples with the MeHg concentration obtained using the KFC method. RESULTS: The following parameters pertaining to the developed method were established: detection limit, 1.02 µg/kg; LOQ, 3.09 µg/kg; linearity (r), 0.9998; range, 0.1-300 µg/kg; and recovery, 95-97%. CONCLUSIONS: Our method is a promising alternative by virtue of its much simpler and faster sample pretreatment procedure, with a MeHg recovery as high as that of the KFC method. HIGHLIGHTS: The developed method enables the simultaneous analysis of total Hg and MeHg with only DMA equipment.
