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Along with the development of industrialization and urbanization, the pollution of the atmosphere increases and the air quality decreases gradually, especially in the developed regions such as Beijing, Tianjin and Hebei in China. The frequent occurrence of haze leads to the decrease of visibility day by day, which causes great inconvenience to people s mind and body. Therefore, an in-depth study of regional weather quality impact factors can improve the air quality in the regions, which is of important significance to haze warning. This study mainly explores the main causes of haze formation and forecasts the haze, and puts forward some suggestions on haze control. This study proposes a space-time prediction model of air pollutants based on artificial neural network. The selected research regions are cities in Beijing-Tianjin-Hebei region. The data are real-time daily data of monitoring stations published by Beijing Environmental Protection Monitoring Center and China Meteorological Administration, and the air environment changes of 13 cities in Beijing-Tianjin-Hebei region in 2017 are studied. The impact factors include PM2.5, PM10, SO2, NO2, CO and O3. Through collecting and visualizing the data, evaluating with air quality index (AQI), this study designs, establishes, trains, and simulates the backpropagation neural network, adjusts the corresponding parameters, obtains the optimal model and the main research conclusion, as well as provides scientific reasonable suggestion.

The recent steep rise in perovskite materials has triggered tremendous opportunities in the field of photonics and solar-cell technologies. As a direct bandgap semiconductor, perovskite exhibits the unique optical properties of bandgap tunability, charge-carrier mobility, defect tolerance, photoluminescence quantum efficiency and power conversion efficiency, which makes them as promising light-emitting materials for high optical gain, low-threshold and multicolor laser applications. Here, we begin with the investigation of structure growth and morphological control of perovskites, including thin films, nanoplatelets, nanowires and quantum dots. Next, fundamental photo-physical mechanisms, related with the charge-carrier recombination dynamical process, diffusion and radiative efficiencies, are discussed to elucidate perovskite light-emitting properties. Finally, we turn to discuss the light-emitting lasing with architectural innovations and the perovskite device performance in terms of optical gain, color-tuning, spectral coherence, and stability. The remaining challenges of perovskite light emitting materials and the potential future perovskite-based are heighten.

We theoretically investigate the hybridization of the elemental surface plasmons in umbrella-shape plasmonic nanostructures and experimentally demonstrate the implementation of plasmonic multicolor metasurfaces as well as their application in colorimetric sensing. The three-dimension metallic umbrella arrays consist of a periodic canopy-capped-nanopillars with metal-coated sidewall and a backplane metal-film to form vertical nanocavity of canopy and film. Plasmonic coupling and energy confinement in nanocavity induce a noticeably resonance narrowing of multispectral reflection. The metasurfaced nanostructures appeared in vibrant and tunable colors with broad gamut derived from color blending mechanism due to multiple, narrow-band resonances. Vivid colors varied from red, yellow, green, blue to violet are easily achieved. It is also shown that such plasmonic metasurfaces can work as the feasible and real-time colorimetric refractive index sensor by measuring the distinct color variation to glucose concentration changes. Our sensor scheme shows its spectral sensitivity in the periodic umbrella array with respect to the refractive index change to be 242.5 nm/RIU with a figure of merit of 7.3. Furthermore, a refractive index resolution of colorimetric sensing up to 0.025 RIU has been accomplished.

We report a type of plasmonic palettes formed by an array of cross-shaped cavity nanostructures for multicolor image generation. And the nanocross-shaped antennas actually act as plasmonic cavity resonators and could realize surface plasmon excitation, resonating and coupling, which can impart intriguing optical properties. These features enable the nanotexted metasurfaces to implement full-gamut palettes through spatially color blending and continuously tunable coloration. We also employ the dark-field scattering and near-field scanning analysis to experimentally study the circularly nanoscale optical scattering in the new cavity-nanopin photonic metasurfaces resulting from aperiodic Fibonacci spiral arrangements.

This paper reports a simple and convenient method to fabricate a surface-enhanced Raman scattering substrate. It includes a green chemistry synthesis of Ag nanoparticles(NPs) and a process of coating a monolayer of the Ag NPs on a polydimethylsiloxane(PDMS) elastomer film. Ultra-low concentration of Ag+(10−8M) was used in Tollens method to synthesis monodisperse and relatively uniform Ag NPs. With recovery of the stretched PDMS film, the distribution of Ag NPs gets concentrated, resulting in an improvement of SERS detection sensitivity. Due to the transparent and flexible property of this highly sensitive SERS substrate, it exhibits great potential in in-situ detection of solid or irregular objects.

This paper presents an ultrasensitive and inexpensive method for ricin detection by surface enhanced Raman scattering (SERS) on shape-controlled gold nanocrystals substrates fabricated by integrating electrodeposition with dielectrophoresis (DEP). The ricin is captured by the rabbit anti-ricin polyclonal antibody which immobilized on the substrates. It was show that the limit of detection(LOD) could reach 0.1ng/ml in phosphate buffered saline (PBS), which is 2000 times less than the minimum lethal dose(with 500ml liquor).

In view of the toxic potential of a bioweapon threat, rapid visual recognition and sensing of ricin has been of considerable interest while remaining a challenging task up to date. In this study, a gold nanopin-based colorimetric sensor is developed realizing a multicolor variation for ricin qualitative recognition and analysis. It is revealed that such plasmonic metasurfaces based on nanopin-cavity resonator exhibit reflective color appearance, due to the excitation of standing-wave resonances of narrow bandwidth in visible region. This clear color variation is a consequence of the reflective color mixing defined by different resonant wavelengths. In addition, the colored metasurfaces appear sharp color difference in a narrow refractive index range, which makes them especially well-suited for sensing applications. Therefore, this antibody-functionalized nanopin-cavity biosensor features high sensitivity and fast response, allowing for visual quantitative ricin detection within the range of 10–120 ng mL−1 (0.15 × 10−9–1.8 × 10−9 m), a limit of detection of 10 ng mL−1, and the typical measurement time of less than 10 min. The on-chip integration of such nanopin metasurfaces to portable colorimetric microfluidic device may be envisaged for the quantitative studies of a variety of biochemical molecules.

We report a new arrayed plasmonic nanopixels capable of producing a continuum of colors. The pixels are nanohelm-shaped metal-dielectric-metal resonators and could efficiently cause surface-plasmon coupling, resonances and hybridization to propagate enhanced electromagnetic energy to far-field and thus achieve highly sophisticated color generation. Moreover, the surface-plasmon resonance frequency, intensity and related reflection spectrum line-width are significantly dependent upon incident angle of light, also resulting in a broad color tuning. Such plasmonic nanohelm pixels could map white light to splendid colors and be thus used to engineer vivid color display beyond the diffraction limit.

Gold nanofilms consisting of networked, cross-linked nanowires were synthesised in large quantities by the integration of electrochemical deposition and dielectrophoresis. The resultant products were characterised by scanning electron microscopy and atomic force microscopy. On the basis of finite-element modelling of the electrode system in terms of the theory of dielectrophoresis and electromagnetism, the authors found that the growth of gold nanowires responded highly to the inhomogeneous electric fields. Also, the morphologies of the gold nanofilm evolve with the deposition time and frequency. Numerical simulations and theoretical analyses offer useful insights into the mechanism. The above study provides strong evidence that this electrochemical and template-free route is a powerful and universal technique to the synthesis for improving nanofilms performance. This strategy can be transplanted into the synthesis of other metallic nanofilms, such as silver and copper.