The global energy crisis and water pollution drive the researchers to develop highly effective and less energy intensive water purification technologies. In this study, a highly active WO3@TiO2–SiO2 nanocomposite was synthesized and used for photocatalytic degradation of persistent organic pollutants under simulated solar light. The optimum WO3@TiO2–SiO2 prepared with 2 wt% WO3 loading and calcination at 800 °C exhibited higher photocatalytic activity, as the rate constant (k1) for phenanthrene degradation was ∼7.1 times of that for the commercial TiO2 (P25). The extremely large specific surface area (>400 m2/g) of WO3@TiO2–SiO2 afforded it with enlarged pollutants adsorption performance and abundant active surface sites. The heterojunction of anatase with SiO2 as well as loading of WO3 decreased the band gap energy (Eg) of TiO2, which extended the utilization spectrum of TiO2 to visible region. Formation of Ti–O–Si band indicated the excess charges can cause Brønsted acidity due to the absorption of protons to compensate the charges. Moreover, the migration of photo-excited electrons from the conduction band of anatase to WO3 and holes in the opposite direction restrained the electron-hole recombination. The photocatalytic degradation mechanism and pathway for phenanthrene degradation were proposed based on experimental analysis and density functional theory (DFT) calculation, and the toxicities of the degradation intermediates were evaluated by quantitative structure–activity relationship (QSAR) analysis. WO3@TiO2–SiO2 also showed good separation (settling) performance and high stability. Our work is expected to offer new insight into the photocatalytic mechanism for WO3, TiO2 and SiO2 based heterojunctions, and rational design and synthesis of highly efficient photocatalysts for environmental application.
Due to the difficulty in achieving high efficiency and high color purity simultaneously, blue emission is the limiting factor for the performance and stability of OLEDs. Since 2003, we have been working on organic light-emitting diodes (OLEDs), especially on blue light. After a series of molecular designs, novel strategies have been proposed from different aspects. At first, highly efficient deep blue emission could be achieved through molecular design with highly twisted structure to suppress fluorescence quenching and redshift. Deep blue emitters with high efficiency in solid state, a twisted structure with aggregation induced emission (AIE) characteristics was incorporated to inhibit molecular aggregation, and triplet-triplet fusion (TTF) and hybridized localized charge transfer (HLCT) were adopted to increase the ratio of triplet exciton used. Secondly, a highly efficient blue OLED could be achieved through improving charge transport. New electron transport materials (ETMs) with wide band gap were developed to control charge transport balance in devices. Thirdly, a highly efficient deep blue emission could be achieved through a mesoscopic structure of out-coupling layer. A mesoscopic photonic structured organic thin film was fabricated on the top of metal electrode by self-aggregation in order to improve the light out-coupling efficiency.
Due to the difficulty in achieving high efficiency and high color purity simultaneously, blue emission is the limiting factor for the performance and stability of OLEDs. Since 2003, we have been working on organic light-emitting diodes (OLEDs), especially on blue light. After a series of molecular designs, novel strategies have been proposed from different aspects. At first, highly efficient deep blue emission could be achieved through molecular design with highly twisted structure to suppress fluorescence quenching and redshift. Deep blue emitters with high efficiency in solid state, a twisted structure with aggregation induced emission (AIE) characteristics was incorporated to inhibit molecular aggregation, and triplet-triplet fusion (TTF) and hybridized localized charge transfer (HLCT) were adopted to increase the ratio of triplet exciton used. Secondly, a highly efficient blue OLED could be achieved through improving charge transport. New electron transport materials (ETMs) with wide band gap were developed to control charge transport balance in devices. Thirdly, a highly efficient deep blue emission could be achieved through a mesoscopic structure of out-coupling layer. A mesoscopic photonic structured organic thin film was fabricated on the top of metal electrode by self-aggregation in order to improve the light out-coupling efficiency.
Interface modification engineering has been widely used as a flexible and effective method to optimize the performance of perovskite photovoltaic devices. Herein, we adopt NiCl2 as a modifier to passivate the interface at the electron transporting layer (ETL) and perovskite layer to drive high-efficiency perovskite solar cells (PSCs) with increased open circuit voltage (V-oc) and neglectable hysteresis. The devices based on SnO2/NiCl2 ETL achieved a high V-oc (1.17 V) and power conversion efficiency (PCE) (19.46%). The improvement is attributed to the increased energy level of the conduction band minimum (E-CBM) and reduced defect states by NiCl2 interface modification. Our findings provide an effective way to obtain higher V-oc and PCE values as well as neglectable hysteresis for planar PSCs.
Interface modification engineering has been widely used as a flexible and effective method to optimize the performance of perovskite photovoltaic devices. Herein, we adopt NiCl2 as a modifier to passivate the interface at the electron transporting layer (ETL) and perovskite layer to drive high-efficiency perovskite solar cells (PSCs) with increased open circuit voltage (V-oc) and neglectable hysteresis. The devices based on SnO2/NiCl2 ETL achieved a high V-oc (1.17 V) and power conversion efficiency (PCE) (19.46%). The improvement is attributed to the increased energy level of the conduction band minimum (E-CBM) and reduced defect states by NiCl2 interface modification. Our findings provide an effective way to obtain higher V-oc and PCE values as well as neglectable hysteresis for planar PSCs.
TROPOspheric Monitoring Instrument (TROPOMI), on-board the Sentinel-5 Precurser satellite, is a nadir-viewing spectrometer measuring reflected sunlight in the ultraviolet, visible, near-infrared, and shortwave infrared. From these spectra several important air quality and climate-related atmospheric constituents are retrieved, including nitrogen dioxide (NO2) at unprecedented spatial resolution from a satellite platform. We present the first retrievals of TROPOMI NO2 over the Canadian Oil Sands, contrasting them with observations from the Ozone Monitoring Instrument satellite instrument, and demonstrate TROPOMI's ability to resolve individual plumes and highlight its potential for deriving emissions from individual mining facilities. Further, the first TROPOMI NO2 validation is presented, consisting of aircraft and surface in situ NO2 observations, and ground-based remote-sensing measurements between March and May 2018. Our comparisons show that the TROPOMI NO2 vertical column densities are highly correlated with the aircraft and surface in situ NO2 observations, and the ground-based remote-sensing measurements with a low bias (15-30 %); this bias can be reduced by improved air mass factors. Plain Language Summary Nitrogen dioxide (NO2) is a pollutant that is linked to respiratory health issues and has negative environmental impacts such as soil and water acidification. Near the surface the most significant sources of NO2 are fossil fuel combustion and biomass burning. With a recently launched satellite instrument (TROPOspheric Monitoring Instrument [TROPOMI]), NO2 can be measured with an unprecedented combination of accuracy, spatial coverage, and resolution. This work presents the first TROPOMI NO2 measurements near the Canadian Oil Sands and shows that these measurements have an outstanding ability to detect NO2 on a very high horizontal resolution that is unprecedented for satellite NO2 observations. Further, these satellite measurements are in excellent agreement with aircraft and ground-based measurements.
ABSTRACT Tag quality is an important factor to the success of social tagging systems and platforms. Users' domain expertise may influence they perceive tag quality. This study aims to explore how users of different domain experience (frequent user, occasional user, and non-user) perceive the quality of the same tags. We examined an online video community, Bilibili, which specializes in Anime, Comic and Games (ACG) subculture. We asked 60 users to watch 15 videos and rate the 95 tags of these videos, and found that: 1) Users with more domain expertise give higher ratings for tags' relevance to the videos and their retrieval value; 2) Occasional users have the lowest understandability rating, followed by non-users, and frequent users; 3) users think high-frequency tags are less suitable for retrieval. These results may provide insights to high quality tag selection for personalized recommendation and retrieval.
A system based on incoherent broadband cavity-enhanced absorption spectroscopy (IBBCEAS) has been developed for simultaneous measurement of nitrogen dioxide (NO2), glyoxal (GLY), and methylglyoxal (MGLY). In this system, the measured light absorption at around 460 nm is spectrally resolved. The concentration of absorbers is determined from a multicomponent fit. At an integration time of 100 s, the measurement sensitivity (2 sigma) for NO2, GLY, and MGLY is 18, 30, and 100 ppt, respectively. The measurement uncertainty, which mainly originates from path length calibration, sampling loss, and uncertainty of absorption cross sections is estimated to be 8% for NO2, 8% for GLY, and 16% for MGLY. When deploying the instrument during field observations, we found significant influence of NO2 on the spectra fitting for retrieving GLY and MGLY concentrations, which is caused by the fact that NO2 has a higher absorption cross section and higher ambient concentration. In order to minimize such an effect, a NO2 photolytic convertor (NPC), which removes sampled NO2 at an efficiency of 76 %, was integrated on the IBBCEAS system. Since sampled GLY and MGLY are mostly (>= 95 %) conserved after passing through the NPC, the quality of the spectra fitting and the measurement accuracy of ambient GLY and MGLY under NO2-rich environments could be improved.