Intensive agricultural activities in the North China Plain (NCP) lead to substantial emissions of nitrogen oxides (NOx) from soil, while the role of this source on local severe ozone pollution is unknown. Here we use a mechanistic parameterization of soil NOx emissions combined with two atmospheric chemistry models to investigate the issue. We find that the presence of soil NOx emissions in the NCP significantly reduces the sensitivity of ozone to anthropogenic emissions. The maximum ozone air quality improvements in July 2017, as can be achieved by controlling all domestic anthropogenic emissions of air pollutants, decrease by 30% due to the presence of soil NOx. This effect causes an emission control penalty such that large additional emission reductions are required to achieve ozone regulation targets. As NOx emissions from fuel combustion are being controlled, the soil emission penalty would become increasingly prominent and shall be considered in emission control strategies.

Cross-reactive sensor arrays, known as "chemical noses", offer an alternative to time-consuming analytical methods. Here, we report a sensor array based on nanomaterial-assisted chemiluminescence (CL) for protein sensing and cell discrimination. We have found that the CL efficiencies are improved to varied degrees for a given protein or cell line on catalytic nanomaterials. Distinct CL response patterns as "fingerprints" can be obtained on the array and then identified through linear discriminant analysis (LDA). The sensing of 12 kinds of proteins at three concentrations, as well as 12 types of human cell lines among normal, cancerous, and metastatic, has been performed. Compared with most fluorescent or colorimetric approaches which rely on the strong interaction between analytes and sensing elements, our array offers the advantage of both sensitivity and reversibility.

Fluorescent gold nanoparticle (GNP) is an easily synthesized and biocompatible optical platform for sensing and imaging with tunable near-infrared (NIR) emission. However, the relatively low fluorescence (FL) quantum yield limits the further improvement of sensitivity and application. Here, we find that, on plasmonic substrates, the FL intensity of protein-directed synthesized GNPs can be enhanced significantly (~20-fold). Moreover, protein analytes can interact with GNPs and influence the enhanced fluorescence process so that we can obtain distinct FL image patterns. Then, using the array-based sensing strategy, protein discrimination can be achieved. In our present experiment, five GNPs were used as sensing elements and 10 kinds of proteins at three concentrations (0.2, 0.5, and 1 μM) were successfully identified. This array-based sensing strategy using enhanced-fluorescence from GNPs is highly sensitive and differentiable, expanding the application field of GNPs.

Identification of infectious bacteria responsible for biofilm-associated infections is challenging due to the complex and heterogeneous biofilm matrix. To address this issue and minimize the impact of heterogeneity on biofilm identification, we developed a gold nanoparticle (AuNP)-based multichannel sensor to detect and identify biofilms based on their physicochemical properties. Our results showed that the sensor can discriminate six bacterial biofilms including two composed of uropathogenic bacteria. The capability of the sensor was further demonstrated through discrimination of biofilms in a mixed bacteria/mammalian cell in vitro wound model.

The fluorescence, catalytic activity and assembly behavior of GO could be simultaneously changed after interaction with proteins, leading to distinct response patterns related to each specific protein. Based on the phenomenon, a triple-channel optical sensor has been proposed in the present communication for protein discrimination with GO as a single sensing element.