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Multi-arm polymers prepared by atom transfer radical polymerization (ATRP) and their electrospun films as oxygen sensors and pressure sensitive paints
摘要： New oxygen and pressure sensitive paints (PSPs) with four-arm polymeric structures were prepared by using a kind of controlled living polymerizations - atom transfer radical polymerization (ATRP). The polymers composing of poly(isobutyl methacrylate)-co-poly(trifluoroethyl methacrylate)s (PolyIBMA-co-PolyTFEM)s act as the matrices for the platinum porphyrin-based phosphorescence probes, which were copolymerized in the matrices. The polymers were characterized by using 1H-NMR, 19F-NMR, and GPC to demonstrate their successful preparation. The influence of polymer structures on sensing activity including the sensitivity and response time to oxygen and/or pressure was investigated. Results showed that copolymers with suitable compositions (herein P3) can have highest sensitivity. Polymer structure's influence on response time to oxygen was also investigated. For increasing the polymer's surface area for further improving sensing sensitivity, electrospinning method was used for preparing films with micro-spherical or fibrous structures. The morphologies of electrospinning coated films were observed by SEM. Results showed that electrospinning coated films can respond much better to oxygen and pressure than their corresponding sprayed plates. This is the first time to apply the controlled living polymerization approach to prepare PSPs with multi-arm structures, which will broaden the PSP functional materials' design strategy.
关键词： oxygen sensing,pressure sensitive paints,electrospinning,multi-arm polymers,atom transfer radical polymerization
更新于2025-09-23 15:23:52
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Scale-variable region-merging for high resolution remote sensing image segmentation
摘要： In high resolution remote sensing imagery (HRI), the sizes of different geo-objects often vary greatly, posing serious difficulties to their successful segmentation. Although existent segmentation approaches have provided some solutions to this problem, the complexity of HRI may still lead to great challenges for previous methods. In order to further enhance the quality of HRI segmentation, this paper proposes a new segmentation algorithm based on scale-variable region merging. Scale-variable means that the scale parameters (SP) adopted for segmentation are adaptively estimated, so that geo-objects of various sizes can be better segmented out. To implement the proposed technique, 3 steps are designed. The first step produces a coarse-segmentation result with slight degree of under segmentation error. This is achieved by segmenting a half size image with the global optimal SP. Such a SP is determined by using the image of original size. In the second step, structural and spatial contextual information is extracted from the coarse-segmentation, enabling the estimation of variable SPs. In the last step, a region merging process is initiated, and the SPs used to terminate this process are estimated based on the information obtained in the second step. The proposed method was tested by using 3 scenes of HRI with different landscape patterns. Experimental results indicated that our approach produced good segmentation accuracy, outperforming some competitive methods in comparison.
关键词： Image segmentation,High resolution remote sensing imagery,Scale-variable,Region merging
更新于2025-09-23 15:23:52
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The upconversion photoluminescence and temperature sensing abilities of Pb(Zn1/3Nb2/3)O3-9PbTiO3 crystals induced by Er3+/Yb3+ doping
摘要： Er3+/Yb3+-doped Pb(Zn1/3Nb2/3)O3-9PbTiO3 ferroelectric crystals were grown by the high-temperature solution method. The micromorphology, phase structure, and upconversion photoluminescence of obtained crystals were analyzed and investigated. As the results suggest, the crystals displayed typical lamellar growth and possessed a pure perovskite structure. Excited by a 980 nm laser, the characteristic upconversion (UC) emissions of Er3+ were observed at room temperature. The luminescence intensity improved with the increasing of excitation power and reached its maximum at 1056 mW. Two-photon process was demonstrated at lower power range. As the temperature increased from 213 to 493 K, the luminescence intensity weakened continuously. An apparent difference in variation trend between two thermally coupled levels (2H11/2 and 4S3/2) was also observed, which was ascribed to the redistribution of electrons at two levels at the heating process. Based on this dependence, the temperature sensing abilities were examined with the help of the fluorescence intensity ratio (FIR) technique. The absolute sensitivity SA increased in the measurement temperature range and its maximum of 0.0033 K-1 was obtained at 493 K. Moreover, low conversion from incident light into heat was also demonstrated, which indicates the feasibility for crystal luminescence at high power pumping. These results make Er3+/Yb3+-doped Pb(Zn1/3Nb2/3)O3-9PbTiO3 crystals become a promising candidate in optical devices and temperature sensors.
关键词： Two-photon process,Temperature sensing,FIR technique,Ferroelectric crystals,UC emissions
更新于2025-09-23 15:23:52
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Study of the effects of phytoplankton morphology and vertical profile on lidar attenuated backscatter and depolarization ratio
摘要： Propagation of a lidar beam in a coupled atmosphere-ocean model consisting of multiple atmospheric and upper oceanic layers and a rough ocean surface is studied by using a vectorized Monte Carlo radiative transfer solver optimized specifically for lidar-based remote sensing applications. The effects of assumed phytoplankton morphology variations and its vertical distribution on the lidar attenuated backscatter and depolarization ratio are studied. In this study, a phytoplankton particle is assumed to be a sphere, a sphere with a core, or a randomly distorted hexahedron with or without a core. The single-scattering properties of the nonspherical/inhomogeneous particles are computed using appropriate state-of-the-art light-scattering computational capabilities. Vertical variation of the phytoplankton distribution is derived explicitly using a PAR (photosynthetically active radiation) limited carbon biomass balance equation that is subsequently coupled with the Monte Carlo solver.
关键词： Radiative transfer,Lidar,Ocean optics,Monte Carlo,Phytoplankton,Net primary production,Remote sensing
更新于2025-09-23 15:23:52
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Light enhanced room temperature resistive NO2 sensor based on a gold-loaded organic–inorganic hybrid perovskite incorporating tin dioxide
摘要： A material is described for sensing NO2 in the gas phase. It has an architecture of type Au/MASnI3/SnO2 (where MA stands for methylammonium cation) and was fabricated by first synthesizing Au/MASnI3 and then crystallizing SnO2 on the surface by calcination. The physical and NO2 sensing properties of the composite were examined at room temperature without and with UV (365 nm) illumination, and the NO2-sensing mechanism was studied. The characterization demonstrated the formation of a p-n heterojunction structure between p-MASnI3 and n-SnO2. The sensor, best operated at a voltage of 1.1 V at room temperature, displays superior NO2 sensing performance. Figures of merit include (a) high response (Rg/Ra = 240 for 5 ppm NO2; where Rg stands for the resistance of a sensor in test gas, and Ra stands for the resistance of a sensor in air), (b) fast recovery (about 12 s), (c) excellent selectivity compared to sensors based on the use of SnO2 or Au/SnO2 only, both at room temperature under UV illumination; (d) a low detection limit (55 ppb), and (e) a linear response between 0.5 and 10 ppm of NO2. The enhanced sensing performance is mainly attributed to the high light absorption capacity of MASnI3, the easy generation and transfer of photo-induced electrons from MASnI3 to the conduction band of SnO2, and the catalytic effect of gold nanoparticles.
关键词： Light absorbing material,SPR effect,Photo generated electrons,Gas sensing,P-n junction,Catalytic effect,Heterojunction,SnO2,UV light,MASnI3
更新于2025-09-23 15:23:52
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Structural diversity, magnetic properties, and luminescent sensing of four coordination polymers based on 6-(3,5-dicarboxylphenyl)nicotinic acid
摘要： Four coordination polymers (CPs), namely, [Ni(HDNA)(bibp)(H2O)]n (1), [Co(HDNA)(bibp)]n (2), {[Co(HDNA)(bibp)]·H2O}n (3) and {[Zn(HDNA)(bibp)]·H2O}n (4), have been synthesized from the mixed-ligand strategy of 6-(3,5-dicarboxylphenyl)nicotinic acid (H3DNA) and 4,4′-bis(benzimidazo-1-ly)benzene (bibp). Structural analyses revealed that four CPs all feature 2D sheets with diverse nets from {44.62}-sql net (1), {Co2(COO)2} SBUs based {44.62}-sql net (2), to 4-connected {65.8} sheet (3 & 4). Besides, the temperature-dependent magnetic susceptibilities of CPs 1-3 were investigated. And the luminescent sensing indicated CP 4 is a good bifunctional sensor for Fe3+ and Cr2O7 2- ions.
关键词： Structural diversity,Coordination polymers,Luminescent sensing,Magnetic property,Polycarboxylic acid ligand
更新于2025-09-23 15:23:52
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Colorimetric and turn-on Fluorescence Chemosensor for Hg2+ Ion Detection in Aqueous Media
摘要： A new rhodamine 6G based fluorescent and colorimetric chemosensor, containing N-methyl imidazole nucleus, for the selective detection of Hg2+ ion was designed and synthesized. The results of UV-Vis and fluorescence spectral study indicated that the receptor is selective and sensitive towards Hg2+ with no noticeable interference with other competitive metal ions. The addition of Hg2+ to the receptor induced a rapid color change to pink from colorless and the turn-on fluorescence response toward Hg2+ among different cations was studied. The stoichiometric ratio of 1:1 between the receptor and Hg2+ was supported by Job’s plot. The color change and turn-on fluorescence response upon addition of Hg2+ ion was ascribed by the spirolactam ring-opening mechanism. The probable mode of binding between the receptor and Hg2+ was confirmed by 1H NMR and Mass spectral study. For the practical application, its electrospun nanofiber test strips successfully applied to recognize Hg2+ ion in aqueous media.
关键词： Sensing,Mercury ion,Nanofiber,Fluorescent
更新于2025-09-23 15:23:52
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Synthesis of water-soluble conjugated polymer, poly(N-3-sulfopropylaniline) and the study of its glucose sensing property
摘要： A water-soluble conjugated polymer, poly(N-3-sulfopropylaniline) (PSPA) with 7–10 controlled repeating units has been synthesized through oxidative polymerization of sulfopropylaniline (SPA) monomer, which is prepared by N-alkylation of aniline using 3-propane sultone. The glass transition temperature (Tg), thermal stability, molecular weight and size distribution of the synthesized polymer were investigated by DSC, TGA and MALDI TOFF respectively. The spectral (UV-Vis, PL, NMR, FTIR) analysis has been done to develop a facile colorimetric method to sense glucose (a biomarker of diabetes). The synthesized polymers could detect glucose up to nanomolar (10?9 M), which are 106 fold less than the level of a diabetic patient (4 × 10?3-9 × 10?3 M). It is also observed that the naked eye can sense up to decimolar (10?1 M) level. The polymerization process and the chemistry of colorimetric sensing are explained through spectral and cyclic voltammetry analysis. The polymerization and the sensing of glucose occurred through the electron transfer dependent color change processes.
关键词： Polymerization,Glucose sensing,Spectroscopy,Thermal analysis
更新于2025-09-23 15:23:52
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Remote sensing images super-resolution with deep convolution networks
摘要： Remote sensing image data have been widely applied in many applications, such as agriculture, military, and land use. It is difficult to obtain remote sensing images in both high spatial and spectral resolutions due to the limitation of implements in image acquisition and the law of energy conservation. Super-resolution (SR) is a technique to improve the resolution from a low-resolution (LR) to a high-resolution (HR). In this paper, a novel deep convolution network (DCN) SR method (SRDCN) is proposed. Based on hierarchical architectures, the proposed SRDCN learns an end-to-end mapping function to reconstruct an HR image from its LR version; furthermore, extensions of SRDCN based on residual learning and multi scale version are investigated for further improvement, namely Developed SRDCN(DSRDCN) and Extensive SRDCN(ESRDCN). Experimental results using different types of remote sensing data (e.g., multispectral and hyperspectral) demonstrate that the proposed methods outperform the traditional sparse representation based methods.
关键词： Convolution neural network,Remote sensing imagery,Super-resolution
更新于2025-09-23 15:23:52
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A top-down approach for semantic segmentation of big remote sensing images
摘要： The increasing amount of remote sensing data has opened the door to new challenging research topics. Nowadays, significant efforts are devoted to pixel and object based classification in case of massive data. This paper addresses the problem of semantic segmentation of big remote sensing images. To do this, we proposed a top-down approach based on two main steps. The first step aims to compute features at the object-level. These features constitute the input of a multi-layer feed-forward network to generate a structure for classifying remote sensing objects. The goal of the second step is to use this structure to label every pixel in new images. Several experiments are conducted based on real datasets and results show good classification accuracy of the proposed approach. In addition, the comparison with existing classification techniques proves the effectiveness of the proposed approach especially for big remote sensing data.
关键词： Neural networks,Remote sensing images,Big data,Semantic segmentation
更新于2025-09-23 15:23:52