The electrical transport properties of CHNHPbBr (MAPbBr) polycrystals were in situ investigated by alternating-current impedance spectroscopy under high pressures up to 5.6 GPa. It is confirmed that ionic and electronic conductions coexist in MAPbBr. As pressure below 3.3 GPa ions migration is the predominant process, while above 3.3 GPa electronic conduction becomes the main process. An obvious ionic-electronic transition can be observed. The pressure dependent photo responsiveness of MAPbBr was also studied by in situ photocurrent measurements up to 3.8 GPa. The mixed conduction can be clearly seen in photocurrent measurement. Additionally, the photocurrents remain robust below 2.4 GPa, while they are suppressed with pressure-induced partial amorphization. Interestingly, the photoelectric response of MAPbBr can be enhanced by high pressure, and the strongest photocurrent value appears in the high-pressure phase II at 0.7 GPa, which is similar to previous results in both MAPbI and MASnI.

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The study on the thermal transport properties of matter under high pressure is important but is hard to fulfill in a diamond anvil cell (DAC) because the accurate measurement of the temperature gradient within the sample of DAC is very difficult. In most cases, the sample temperature can be read accurately from the thermocouples that are directly attached to the lateral edges of diamond anvils because both the sample and diamond anvils can be uniformly heated up to a given temperature. But for the thermal transport property studies in DAC, an artificial temperature distribution along the compression axis is a prerequisite. Obviously, the temperature of the top or bottom surface of the sample cannot be substituted by that of diamond anvils although diamond anvils can be considered as a good medium for heat conduction. With temperature field simulation by finite element analysis, it is found that big measurement errors can occur and are fatal to the correct analysis of thermal transport properties of materials. Thus, a method of combining both the four-thermocouple configuration and temperature field analysis is presented for the accurate temperature distribution measurement in DAC, which is based on the single-function relationship between temperature distribution and sample thermal conductivity.

Quantitative nuclear magnetic resonance (qNMR), as a primary approach used to characterize SI (International System of Units)-traceable organic compounds, is based on the proportionality of intensities from analyte and standard, which implies a fundamental requirement that the peaks to be used for quantitation are isolated from impurities. Therefore, sufficient dispersion or a data analysis method has to be used to enable isolation of the peaks for quantitation of impurities. This technique offers many metrological advantages, though significant challenges associated with factors such as calibration reference materials, experimental parameter optimization and isolation of quantitative peaks must be considered to ensure confidence in the results. This review focuses on the development of advanced qNMR methods (including combined qNMR methods), especially those that enhance measurement selectivity and mitigate biases associated with chemical interferences, aiming to satisfy this requirement. For this aim, in recent years, different advanced qNMR approaches have been developed to remove interferences spatially, mathematically, spectroscopically, etc. The principles, advantages, challenges and future prospects of these approaches are introduced in this review. These advanced approaches aim to improve qNMR accuracy for analytes with molecular weight up to ~6000 g/mol. The approaches are aimed at removing potential systematic errors in qNMR to improve its trueness and its application as primary metrolgical method and routine analysis method.

The ionic transport and dielectric behaviors in NaNbO3 were studied under pressures up to 29.1 GPa by in situ impedance spectroscopy measurements. The transport process consists of the ionic transfer and the Warburg diffusion process between sample/electrode diffusion layers. A dielectric relaxation with a giant dielectric constant at low frequencies is observed, which is attributed to the “Maxwell-Wagner” interfacial polarization. In the Pbcm phase, the increase in the interaction between the Na+ ions and the NbO6 octahedra results in the enhancement of vibration resonance damping. In the high-pressure phases, the decrease in the relative permittivity with pressure indicates the existence of space charge polarization of the interface layer besides the ionic polarization.

Metconazole (MEZ) is widely used in prevention and control of fruit and vegetable diseases. Here, a simple and reliable gas chromatography–tandem mass spectrometry (GC-MS/MS) method, using modified QuEChERS (“quick, easy, cheap, effective, rugged and safe”) extraction method, was developed for determining the dissipation and residue of MEZ in grapes and soil, and the dietary risk of MEZ residues in grapes was evaluated for Chinese people. The average recoveries of MEZ in two matrices were 80.72–100.36% with relative standard deviations of 1.56–6.16%. The same limits of detection and quantification in grapes and soil were 0.0006 mg/kg and 0.002 mg/kg, respectively. Under field conditions, the half-life of MEZ dissipation in grapes ranged from 11.75 to 20.39 days. The final residues of MEZ in grapes and soil ranged from 0.002 mg/kg to 0.19 mg/kg at pre-harvest intervals of 7, 14 and 21 days. The whole dietary risk assessment indicated acute hazard index and hazard quotient to be less than 1, implying the risk of MEZ was acceptable. This is the first study conducted on the dissipation, residue analysis and risk assessment of MEZ in grapes, thus providing reference for the detection and risk assessment of MEZ in other agricultural products.

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