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Abstract Background The spatiotemporal variation of observed trace gases (NO 2 , SO 2 , O 3 ) and particulate matter (PM 2.5 , PM 10 ) were investigated over cities of Yangtze River Delta (YRD) region including Nanjing, Hefei, Shanghai and Hangzhou. Furthermore, the characteristics of different pollution episodes, i.e., haze events (visibility < 7 km, relative humidity < 80%, and PM 2.5  > 40 µg/m 3 ) and complex pollution episodes (PM 2.5  > 35 µg/m 3 and O 3  > 160 µg/m 3 ) were studied over the cities of the YRD region. The impact of China clean air action plan on concentration of aerosols and trace gases is examined. The impacts of trans-boundary pollution and different meteorological conditions were also examined. Results The highest annual mean concentrations of PM 2.5 , PM 10 , NO 2 and O 3 were found for 2019 over all the cities. The annual mean concentrations of PM 2.5 , PM 10 , and NO 2 showed continuous declines from 2019 to 2021 due to emission control measures and implementation of the Clean Air Action plan over all the cities of the YRD region. The annual mean O 3 levels showed a decline in 2020 over all the cities of YRD region, which is unprecedented since the beginning of the China’s National environmental monitoring program since 2013. However, a slight increase in annual O 3 was observed in 2021. The highest overall means of PM 2.5 , PM 10 , SO 2 , and NO 2 were observed over Hefei, whereas the highest O 3 levels were found in Nanjing. Despite the strict control measures, PM 2.5 and PM 10 concentrations exceeded the Grade-1 National Ambient Air Quality Standards (NAAQS) and WHO (World Health Organization) guidelines over all the cities of the YRD region. The number of haze days was higher in Hefei and Nanjing, whereas the complex pollution episodes or concurrent occurrence of O 3 and PM 2.5 pollution days were higher in Hangzhou and Shanghai. The in situ data for SO 2 and NO 2 showed strong correlation with Tropospheric Monitoring Instrument (TROPOMI) satellite data. Conclusions Despite the observed reductions in primary pollutants concentrations, the secondary pollutants formation is still a concern for major metropolises. The increase in temperature and lower relative humidity favors the accumulation of O 3 , while low temperature, low wind speeds and lower relative humidity favor the accumulation of primary pollutants. This study depicts different air pollution problems for different cities inside a region. Therefore, there is a dire need to continuous monitoring and analysis of air quality parameters and design city-specific policies and action plans to effectively deal with the metropolitan pollution. 

Abstract Sensing of clinically relevant biomolecules such as neurotransmitters at low concentrations can enable an early detection and treatment of a range of diseases. Several nanostructures are being explored by researchers to detect biomolecules at sensitivities beyond the picomolar range. It is recognized, however, that nanostructuring of surfaces alone is not sufficient to enhance sensor sensitivities down to the femtomolar level. In this paper, we break this barrier/limit by introducing a sensing platform that uses a multi-length-scale electrode architecture consisting of 3D printed silver micropillars decorated with graphene nanoflakes and use it to demonstrate the detection of dopamine at a limit-of-detection of 500 attomoles. The graphene provides a high surface area at nanoscale, while micropillar array accelerates the interaction of diffusing analyte molecules with the electrode at low concentrations. The hierarchical electrode architecture introduced in this work opens the possibility of detecting biomolecules at ultralow concentrations. 

The rapid growth of point-of-care tests demands for biomolecule sensors with higher sensitivity and smaller size. We developed an optofluidic metasurface that combined silicon photonics and nanofluidics to achieve a lateral flow-through biosensor to fulfill the needs. The metasurface consists of a 2D array of silicon nanoposts fabricated on a silicon-on-insulator substrate. The device takes advantage of the high-Q resonant modes associated with the optical bound state and the nanofluidic delivery of analyte to overcome the problem of diffusion-limited detection that occurs in almost all conventional biosensors and offer a high refractive index sensitivity. We used rigorous coupled wave analysis and finite element analysis to design and optimize the device. We will present its photonic band diagram to identify the optical bound state and high-Q resonance modes near 1550 nm. The device was fabricated using e-beam lithography followed by a lift-off and reactive ion etching process. Reflectance of the sensor was measured using a tunable laser and a photodetector. The preliminary result shows a refractive index sensitivity of 720 nm/RIU. Furthermore, we implemented the optical metasurface as a lateral flow-through biosensor by covering the nanoposts using a PDMS cover. The nanofluidic channels are formed between the nanoposts for the flow of samples. The lateral flow-through sensor was used to detect the epidermal growth factor receptor (ErbB2), a widely used protein biomarker for breast cancer screening. The results show that the device can quantitatively measure the binding of ErBb2 antibody and ErBb2 by the continuous monitoring of the resonant wavelength shift.