A Zn-MOF-based mixed matrix membrane as an ultrastable luminescent sensor for selective and visual detection of antibiotics and pesticides in food samples.

The detection of antibiotics and pesticides are of great significance since their residues threaten the health of human beings by accumulation. However, most traditional solid chemical sensors are suffer from the limitations of low sensitivity and economic practicability because of the aggregating nature and unstable of solid sensors. Herein, a new luminescent sensor 1@PMMA (1, [(ZnL)·H2O]n (H2L = 5-(4-(pyridin-4-yl)benzamido)benzene-1,3-dioic acid); PMMA = poly(methyl methacrylate)) was successfully prepared. Notably, the polymer matrix provided the chemical protection for MOF particles. The as fabricated 1@PMMA was stable in milk, honey and egg as well as exhibited strong blue emission under ultraviolet light irradiation, which can act as luminescent probe for detecting antibiotics and pesticides. More interestingly, 1@PMMA exhibited visual, real-time and recyclable detection of antibiotics ornidazole (ODZ) and pesticides 2,6-dichloro-4-nitrobenzenamine (DCN) in real food samples. This work shows that the luminescent MOF-based mixed matrix membranes could be applied as good candidates for sensing analytes in practical application.

Temporal variations of 7Be and 210Pb activity concentrations in the atmospheric aerosols during 2018-2019 in Beijing, China and their correlations with meteorological parameters.

In order to establish a regional database on natural radioactivity, a series of measurements of 713 atmospheric aerosol samples collected on filters over a two-year period (2018-2019) in center of Beijing, northeastern China have been performed to analyze 7Be and 210Pb activity concentrations. The mean activity concentrations of 7Be and 210Pb were found to be 7.10 ± 2.44 mBq m-3 and 2.93 ± 1.52 mBq m-3, respectively. Both the radionuclides exhibited strong seasonal variations, with maximum concentration of 7Be occurring in the spring and that of 210Pb in the winter. The concentration of both the radionuclides was minimum in the rainy summer. Higher 7Be concentration in the spring was mainly caused by the stratosphere to troposphere exchange. Higher 210Pb concentration during winter was maybe attributed to the combustion processes in heating systems and the ingression of continental air masses resulted from winds originating from northwest. The dependence of the activity concentrations of 7Be and 210Pb with meteorological parameters such as rainfall, temperature, and humidity was studied through linear correlation analysis. Statistically significant negative correlations were observed between 7Be and 210Pb activity concentrations with rainfall, respectively, which suggested that the removal mechanisms of these two radionuclides were similar. Lead-210 showed statistically significant correlations with temperature, humidity and PM10. A comparison of the data obtained in the present study for Beijing with the northern hemisphere literature values of 7Be and 210Pb in the atmospheric aerosols showed that the values were smaller than the ones observed in the present study. Overall, the study provides an improved understanding of the temporal variability and correlation of 7Be and 210Pb concentrations in the atmosphere in center of Beijing, northeastern China.

SHOULD WE BEGIN REGULATING THE RADIATION SAFETY OF CABINET X-RAY SYSTEMS?

Radiation measurements were conducted at 22 cabinet X-ray systems in Beijing, China, between 2015 and 2019. The median dose rates in the closed-drapes position were 0.11, 0.14, 0.12, 0.14, 0.34 and 0.17 µGy h-1 at the operator position and 5 cm from the surface of the left side, right side, top, entrance and exit, respectively. When a scattering object was passed through the entrance/exit (open-drapes position), the dose rates of eight systems ranged from 1.19 to 6.72 µGy h-1 (median: 3.75 µGy h-1). From 2015 to 2019, we monitored the personal dose equivalent Hp (10) 589 times. The personal dose equivalent of three workers exceeded 1 mSv year-1. However, the integrity of equipment shielding needs to be checked regularly to ensure safe operation. The regulation of radiation protection by employers, technician support institutes or government departments is thus warranted to limit the radiation exposure of workers and the public.

Chemical content and source apportionment of 36 heavy metal analysis and health risk assessment in aerosol of Beijing.

The concentration levels of 36 airborne heavy metals and atmospheric radioactivity in total suspended particulate (TSP) samples were measured to investigate the chemical characteristics, potential sources of aerosols, and health risk in Beijing, China, from September 2016 to September 2017. The TSP concentrations varied from 6.93 to 469.18 µg/m3, with a median of 133.97 µg/m3. The order for the mean concentrations of heavy metals, known as hazardous air pollutants (HAPs), was as follows: Mn > Pb > As > Cr > Ni > Se > Cd > Co > Sb > Hg > Be; Non-Designated HAPs Metals: Ca > Fe > Mg > Al > K > Na > Zn > P > Ba > Ti > Cu > Sr > B > Sn > I > V > Rb > Ce > Mo > Cs > Th > Ag > U > Pt. The median concentration of As was higher than China air quality standard (6 ng/m3). The gross α and ß concentration levels in aerosols were (1.84 ± 1.59) mBg/m3 and (1.15 ± 0.85) mBg/m3, respectively. The enrichment factor values of Cu, Ba, B, Ce, Tl, Cs, Pb, As, Cd, Sb, Hg, Fe, Zn, Sn, I, Mo, and Ag were higher than 10, which indicated enriched results from anthropogenic sources. Pb, As, and Cd are considered to originate from multiple sources; fireworks released Ba during China spring festival; Fe, Ce, and Cs may come from stable emissions such as industrial gases. The health risks from anthropogenic metals via inhalation, ingestion, and dermal pathway were estimated on the basis of health quotient as well as the results indicated that children faced the higher risk than adults during the research period. For adults, the health risk posed by heavy metals in atmospheric particles was below the acceptable level.

Fixation of CO2 along with bromopyridines on a silver electrode.

Resulting from the drastic increase of atmospheric CO2 concentration day by day, global warming has become a serious environmental issue nowadays. The fixation of CO2 to obtain desirable, economically competitive chemicals has recently received considerable attention. This work investigates the fixation of CO2 along with three bromopyridines via a facile electrochemical method using a silver cathode to synthesize picolinic acids, which are important industrial and fine chemicals. Cyclic voltammetry is employed to investigate the cyclic voltammetric behaviour of bromopyridines. In addition, systematic study is conducted to study the relationships between the picolinic acids' yield and the electrolysis conditions and intrinsic parameters. The results show that the target picolinic acids' yields are strongly dependent on various conditions such as solvent, supporting electrolyte, current density, cathode material, charge passed, temperature and the nature of the substrates. Moreover, in the studied electrode materials such as Ag, Ni, Ti, Pt and GC, electrolysis and cyclic voltammetry show that Ag has a good electrocatalytic effect on the reduction and carboxylation of bromopyridine. This facile electrochemical route for fixation of CO2 provides an indispensable reference for the conversion and utilization of CO2 under mild conditions.

Synthesis, characterization, and CO2 capture study of micro-nano carbonaceous composites.

The micro-nano carbonaceous composite activated carbon fiber/carbon nanotube (ACF/CNTs) was obtained by chemical vapor deposition technology with CNTs growth on the substrate ACF, and the composite was further modified by branched polyethyleneimine (PEI). The morphological features of the as-grown ACF/CNTs and PEI-modified samples were analyzed by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy and thermal gravimetric analysis respectively. Physical properties of the samples were recorded by conducting N2 adsorption/desorption at 77K. CO2 capture tests indicated that both the presence of CNTs and PEI increased the CO2 adsorption capacity, due to the unique hollow tubular structure of CNTs and poly amino groups of PEI. The CO2 adsorption capacities of ACF/CNTs and ACF/CNTs-PEI were tested to be 66.2 mg/g and 98.8 mg/g, respectively at 30°C, which were much higher than that of unmodified ACF (42.4 mg/g). Increasing adsorption temperature up to 60°C further promoted the CO2 adsorption capacity of ACF/CNTs-PEI (121.2 mg/g) due to the maximum equilibrium adsorption between the chemical and physical adsorption at this temperature. Cyclic CO2 adsorption tests via thermal desorption proved that ACF/CNTs-PEI had a good regenerability of 96.2%, suggesting this material is a promising CO2 adsorbent for practical applications.

Survey on radioactive contamination in Beijing following the Japanese Fukushima nuclear accident.

The radioactive contamination in Beijing caused by the Japanese Fukushima nuclear accident was monitored. In this research, samples of air, rainwater, surface water and vegetables in Beijing were collected and measured to estimate the radioactive contamination levels in Beijing. During the period from the 15th to the 41st day after the first emission of radioactive material (first emission) from the Japanese Fukushima nuclear power station (NPS) on 12 March 2011, obvious radioactive contamination was found in the Beijing air samples. The maximum concentration of I-131 was 5.89 mBq m(-3) in the air samples detected on the 22nd day after the first emission, and the maximum concentration of Cs-137 and Cs-134 was found on the 20th day after the first emission. Except for one sample of rainwater, no artificial radionuclides associated with Fukushima were found in surface water. The measurement results showed that there was no harm to the health of local Beijing residents.

Ionic parachor and its application II. Ionic liquid homologues of 1-alkyl-3-methylimidazolium propionate {[C(n)mim][Pro] (n = 2-6)}.

Five propionic acid ionic liquids (PrAILs) [C(n)mim][Pro] (n = 2-6) (1-alkyl-3-methylimidazolium propionate) have been prepared by the neutralization method and characterized by (1)H NMR spectroscopy and differential scanning calorimetry (DSC). Their density, ρ, surface tension, γ, and refractive index, n(D), were measured at (298.15 ± 0.05) K, and the experimental values of parachor for the PrAILs were calculated. Using the parachor values of [C(n)mim](+) obtained by Guan et al., the anionic parachor values of [C(n)mim][Pro] (n = 2-6), [C(2)mim][RBF(3)] (R = N-C(n)H(2n+1) (n = 1-5)), [C(n)mim][Gly] (n = 2-6), and [C(n)mim][PF(3)(CF(2)CF(3))(3)] (n = 1-6) were determined. Then, the parachor, surface tension, and refractive index of the ILs investigated in this work were estimated. The estimated values correlate quite well with the corresponding experimental values.

n-Dodecyl-ammonium bromide monohydrate.

In the title compound, C(12)H(28)N(+)·Br(-)·H(2)O, the ionic pairs formed by n-dodecyl-ammonium cations and bromide anions are arranged into thick layers; these layers are linked in a nearly perpendicular fashion [the angle between the layers is 85.84 (5)°] by hydrogen-bonding inter-actions involving the water mol-ecules. The methyl-ene part of the alkyl chain in the cation adopts an all-trans conformation. In the crystal structure, mol-ecules are linked by inter-molecular N-H⋯Br, O-H⋯Br and N-H⋯O hydrogen bonds.

Low Temperature Heat Capacities and Standard Molar Enthalpy of Formation of 2-Pyrazinecarboxylic Acid (C5H4N2O2)(s).

Low-temperature heat capacities of 2-pyrazinecarboxylic acid (C5H4N2O2)(s) were measured by a precision automated adiabatic calorimeter over the temperature range from 78 to 400 K. A polynomial equation of heat capacities as a function of temperature was fitted by least squares method. Based on the fitted polynomial, the smoothed heat capacities and thermodynamic functions of the compound relative to the standard reference temperature 298.15 K were calculated and tabulated at 10 K intervals. The constant-volume energy of combustion of the compound at T = 298.15 K was measured by a precision rotating-bomb combustion calorimeter to be ΔcU = -(17839.40 ± 7.40) J g-1. The standard molar enthalpy of combustion of the compound was determined to be ΔcH0m = -(2211.39 ± 0.92) KJ mol-1, according to the definition of combustion enthalpy. Finally, the standard molar enthalpy of formation of the compound was calculated to be ΔfH0m = -(327.82 ± 1.13) kJ mol-1 in accordance with Hess law.

1,10-Phenanthrolinium 2,3,4,5,6-penta-fluoro-benzoate-2,3,4,5,6-penta-fluoro-benzoic acid (1/2).

In the title compound, C(12)H(9)N(2) (+)·C(7)F(5)O(2) (-)·2C(7)HF(5)O(2), the cation and anion are linked by an N-H⋯O hydrogen bond. The neutral mol-ecules bond to the anion via O-H⋯O hydrogen bonds to form associations of one cation, one anion and two neutral mol-ecules. Inter-molecular C-H⋯O, C-H⋯F, F⋯F [shortest contact = 2.768 (8) Å], F⋯π [shortest contact = 3.148 (13) Å] and π-π [shortest centroid-centroid separation = 3.689 (5) Å] inter-actions further link the components to form a three-dimensional network.