Geographical origin differentiation of Chinese Angelica by specific metal element fingerprinting and risk assessment.

Traceability offers significant information about the quality and safety of Chinese Angelica, a medicine and food homologous substance. In this study, a systematic four-step strategy, including sample collection, specific metal element fingerprinting, multivariate statistical analysis, and benefit-risk assessment, was developed for the first time to identify Chinese Angelica based on geographical origins. Fifteen metals in fifty-six Chinese Angelica samples originated from three provinces were analyzed. The multivariate statistical analysis model established, involving hierarchical cluster analysis (HCA), principal component analysis (PCA), and self-organizing map clustering analysis was able to identify the origins of samples. Furthermore, benefit-risk assessment models were created by combinational calculation of chemical daily intake (CDI), hazard index (HI), and cancer risk (CR) levels to evaluate the potential risks of Chinese Angelica using as traditional Chinese medicine (TCM) and food, respectively. Our systematic strategy was well convinced to accurately and effectively differentiate Chinese Angelica based on geographical origins.

Study on Tandem Polymer Light Emitting Devices.

We report tandem polymer light emitting devices by using the PEDOT∶PSS/ZnO/PEIE charge generation layer (CGL) and investigate the influences of the conductance and thickness of PEDOT∶PSS layer on the properties of the devices. The results indicate that the conductance and thickness of PEDOT∶PSS layer have marginal impact on the J-V characteristics of the devices, while significant influences of device efficiency upon utilization of different PEDOT∶PSS specimens mainly come from their different strengths on exciton quenching. Luminance efficiency of TOLEDs with the PEDOT∶PSS thickness of 60 nm in CGL is better than TOLEDs with the PEDOT∶PSS thickness of 30 nm in CGL, the reason is that PEDOT∶PSS thickness of 60 nm the surface topography is more even . Luminance efficiency and driving voltage of the tandem devices match the sum of the luminance efficiency and driving voltage of the component light-emitting units, respectively, indicating that charges generated in the CGL can be injected efficiently into the adjacent light-emitting units. Incorporation of a V2O5 layer into the CGL structure only slightly affects the J-V and LE-I characteristics of the tandem devices, suggesting that the utilization of the PEDOT∶PSS/ZnO/PEIE CGL enables the simplification of the CGL structure without compromising device performance. The luminescence spectra of TOLEDs obviously involves two light emitting unit of spectrum, which shows that two light emitting unit in TOLEDs is normal work. Measurements on the capacitance-voltage characteristics of the CGL-based devices confirm that under negative bias (ITO anode) charges are accumulated and displaced in the CGL, which is totally in line with the full operation of light emitting units in the tandem devices. PEDOT∶PSS/ZnO/PEIE layer is evidenced the effective CGL. On this basis, for the first time we report tandem polymer light emitting devices containing three SY-PPV light-emitting units，which show the mixture of luminance efficiency and external quantum efficiency of 21.7 cd·A-1 and 6.95%, similar to the total luminance efficiency and external quantum efficiency of constituent LEUs. At 5 000 cd·m-2, the luminance efficiency and external quantum efficiency of the tandem devices are 20.5 cd·A-1 and 6.6%. Thus, the increase in the number of light emitting units leads to almost no performance losses, implying the robustness of the PEDOT∶PSS/ZnO/PEIE CGL. Tandem polymer light emitting devices containing three SY-PPV light-emitting units of the luminescent spectra is close to the light emitting unit. Further efforts on the optimization of hole injection layer in the CGL to minimize exciton quenching are underlying to promote the luminance efficiency of tandem polymer light emitting devices.