水稻化感材料的抑草作用及其机制

水稻化感材料PI312777和化感1号在田间能显著地抑制杂草,而且其抑草作用与栽培方式相关,抛秧和移栽方式对杂草的抑制作用明显地优于直播。结果表明,PI312777和化感1号植株产生和释放的化感物质(多酚、黄酮和羟基肟酸)显著高于非化感品种华粳籼1号,而且在6叶期植株中的化感物质含量达最大值。这种不同水稻材料植株在不同生育期产生并释放化感物质量的差异是导致它们在田间抑草效应强弱的重要原因之一。进一步研究发现,PI312777植株由地上部分合成化感物质后经根部分泌到环境中,根组织并不产生化感物质,且稗草能诱导PI312777植株产生和释放更大量的化感物质。在水培条件下,PI312777根分泌的化感物质明显地抑制稗草的生长,但水培液中加入活性碳能使水稻对稗草的抑制作用明显减弱。研究显示,水稻化感材料的抑草效应虽与化感作用、栽培方式和环境等多因素相关,但化感因子起着重要的作用,而且水稻和伴生稗草之间可能存在着化学识别机制。

化感物质提取与抑藻途径研究进展

湖泊水体富营养化问题一直受到国内外的高度重视,已成为全球性的水环境问题之一。但是一直未得到有效解决,利用植物所分泌的化感物质产生化感作用抑制水体藻类爆发,是公认的有效和生态友好手段。植物分泌的化感物质化学性质不同,作用机理也存在很大的差异,根据其作用的机理适当改变其抑藻的方式可以获得更好的作用效果。本文梳理了化感物质的作用机理,罗列了化感物质提取常见的方法即浸泡法、水提法和醇提法(有机物提取法),概述了当前几种主要的化感抑藻作用方式。本研究结果可为进一步深入研究水生生态系统中化感抑藻及相关技术应用提供科学依据。最后对化感物质研究和应用前景进行展望,以期为下一步工作打下认识基础并对控藻技术研究和开发提供指导意义。

Polarization insensitivity electromagnetically induced reflection in graphene metasurface

The electromagnetically induced reflection(EIR)effect of graphene metamaterials has been investigated by finite difference time domain(FDTD)method.In this study,a metamaterial sandwich structure composed of silica(SiO2),gold and graphene on terahertz band is designed.By changing the width of the two ribbons of graphene length and the incident angle of electromagnetic wave,the EIR effect of the structure is discussed,and it can be found that SiO2 is a kind of excellent dielectric material.The simulation results show that graphene metamaterial is not sensitive to polarized incident electromagnetic wave.Therefore,such EIR phenomena as insensitive polarization and large incident angle can be applied to optical communication filters and terahertz devices.

Magnetically induced micropillar arrays for an ultrasensitive flexible sensor with a wireless recharging system

Significant efforts have been devoted to enhancing the sensitivity and working range of flexible pressure sensors to improve the precise measurement of subtle variations in pressure over a wide detection spectrum. However,achieving sensitivities exceeding 1000 kPa^(-1) while maintaining a pressure working range over 100 kPa is still challenging because of the limited intrinsic properties of soft matrix materials. Here, we report a magnetic field-induced porous elastomer with micropillar arrays(MPAs) as sensing materials and a well-patterned nickel fabric as an electrode. The developed sensor exhibits an ultrahigh sensitivity of 10,268 kPa^(-1)(0.6–170 kPa) with a minimum detection pressure of 0.25 Pa and a fast response time of 3 ms because of the unique structure of the MPAs and the textured morphology of the electrode. The porous elastomer provides an extended working range of up to 500 kPa with long-time durability. The sophisticated sensor system coupled with an integrated wireless recharging system comprising a flexible supercapacitor and inductive coils for transmission achieves excellent performance. Thus, a diverse range of practical applications requiring a low-to-high pressure range sensing can be developed. Our strategy, which combines a microstructured high-performance sensor device with a wireless recharging system, provides a basis for creating next-generation flexible electronics.

An ultrahigh-sensitivity and selective sensing material for ethanol： α-/γ-Fe2O3 mixed-phase mesoporous nanofibers

A process for synthesizing Fe2O3 based on electrospinning and the hard-template method was proposed such that the crystal phase of Fe2O3 could be tailored with precision. Mesoporous γ-Fe2O3, α-/γ-Fe2O3, and α-Fe2O3 nanofibers could be fabricated successfully by changing the synthesis parameters. Scanning electron microscopy, transmission electron microscopy, X-ray diffraction analyses, Raman spectroscopy, and nitrogen adsorption-desorption analyses were used to characterize the structures of the synthesized products. The optimal calcination conditions for preparing α-/γ-FeaO3 nanofibers with the highest ethanol response were determined through ethanol-sensing measurements. The mixed-phase material exhibited a significantly higher sensitivity than the corresponding purephase ones. The superior ethanol-sensing performance of the α-/γ-Fe2O3 nanofibers suggested that they may be suitable for use in alcohol sensing. Hence, a novel strategy for improving the sensing performance of metal oxide semiconductors is to assemble the different crystalline forms of the same metal oxide in one structure. Finally, the mechanism responsible for the sensing performance of α-/γ-Fe2O3 being higher than those of γ-Fe2O3 and α-Fe2O3 was elucidated on the basis of data from X-ray photoelectron spectroscopy and resistance measurements.

Recent advances in ionic liquid-based electrochemical biosensors

Ionic liquids （ILs） have been generally described as molten salts which are composed of asymmetric cations and anions. They exist in liquid state below 100 ℃. Both ILs and their composite materials have been widely used in various fields. Attributed to the outstanding properties including the thermal and chemical stabilities, the negligible volatility, the high ionic conductivity, the wide electrochemical window, and the easy design in the construction, ILs have been applied in electrochemical applications including the electrocatalysis, the electrosynthesis, the electrodeposition, the electrochamical devices and sensors. In addition to the application in electrochemical sensors, ILs have also been used in biosensors because of their biocompatibiciy. Here, we review the recent devel- opments for the applicaitons of ILs in electrochemical sensors and biosensors, including the corresponding properties of ILs suitable for electrochemical sensors. Electrochemical biosensors constructed by numorous composites are the emphasis in the review.

TiO_2-functionalized mesoporous materials for sensitive analysis of multi-phosphopeptides

Protein phosphorylation as one of the most important post-translational modifications in mammalian cells regulates numerous biological processes. Here we propose a novel strategy for the selective isolation and sensitive analysis of mul- ti-phosphopeptides based on TiO2-gratfed mesoporous materials, in which MCM-41 and SBA-15 were chosen as the hard templates. The commercialized IMAC and TiO2 nanopartices were further investigated in the phosphopeptide analysis for comparison. The enrichment efficiency was evaluated and measured by MALDI-TOF mass spectrometry. The results indicated that both TiO2-SBA-15 and TiO2-MCM-41 exhibited the preferential affinity to multi-phosphopeptides compared with the other two widely used strategies. The mesoporous TiO2 based protocol showed highly selective and sensitive properties, where phosphopepddes could be identified at femtomole.

High-efficiency room temperature phosphorescence from amorphous metal-free copolymers

Photofunctional materials with room-temperature phosphorescence（RTP）commonly appeared in expensive metal-coordination complexes and rare-earth-based compounds.Recently,the metal-free organic RTP materials have been paid growing attention from scientific community because of the ease of molecular design,low cost as well as potential applications in molecular switches,chemical sensors and biological imaging.To date,efficient RTP materials with high quantum yield are still very limited due to the T_1-S_0 spinforbidden process and weak spin-orbital coupling.Current mechanism based on crystallization-induced or aggregationinduced phosphorescence may serve as an effective way to enhance the RTP[1,2];

Side-chain effect of organic semiconductors in OFET-based chemical sensors

Organic field-effect transistors（OFETs） offer great potential applications in chemical and biological sensing for homeland security,environmental monitoring,industry manufacturing,and medical/biological detection. Many studies concentrate on sensitivity and selectivity improvement of OFET-based sensors. We report four organic semiconductors with different alkyl side chain lengths but the same π-conjugated core structure for OFETs. Our work focuses on the molecular structure of organic semiconductors（OSCs）. Alkyl side chains can hinder the diffusion of ammonia into the OSCs layer,which blocks the interaction between ammonia and conducting channel. The result also reveals the relationship between the alky chain and the film thickness in sensitivity control. These results are expected to be a guide to the molecular design of organic semiconductors and the choice of OSCs.

A novel strategy for immobilization of thionine based on calcium carbonate-gold nanoparticles inorganic hybrid composite and its application in hydrogen peroxide sensor

A novel strategy for efficient immobilization of electroactive Thionine(Th)on the gold(Au)electrode surface based on calcium carbonate-gold nanoparticles(CaCO3-AuNPs)inorganic hybrid composite was proposed and conducted by the strong electrostatic interaction between positively charged Th and negatively charged CaCO3-AuNPs composite.The hybrid composite was obtained by the adsorption of AuNPs onto the surface of CaCO3 microspheres through electrostatic interaction.Due to the microporous architecture,large surface area,and good biocompatibility of CaCO3-AuNPs composite,the amount and stability of the immobilized Th were highly strengthened.The application of the resulting Th modified electrode in the hydrogen peroxide(H2O2)sensor was also investigated.It exhibited rapid response to H2O2 within 3 s.The linear calibration ranged from 8.00×107to 1.06×10 -3mol/L with a detection limit of 2.00×10 -7mol/L.

Non-stoichiometry in Ca2Al2SiO7 enabling mixedvalent europium toward ratiometric temperature sensing

Eu^2+/Eu^3+ mixed-valence couple co-doped material holds great potential for ratiometric temperature sensing owing to its different electronic configurations and electron-lattice interaction. Here, the correlation of nonstoichiometry in chemical composition, phase structures and luminescence propertis of Ca2 Al2 Si1-xO7:Eu is discussed, and controlled Eu^2+/Eu^3+ valence and tunable emission appear with decreasing Si content. It is found that the 2 Ca^2++ Si^4+←→ Eu^2++ Eu^3++ Al^3+ cosubstitution accounts for the structural stability and charge balance mechanism. Benefiting from the diverse thermal dependent emission behaviors of Eu^2+ and Eu^3+, Ca2 Al2 Si1-xO7:Eu thermometer exhibits excellent temperature sensing performances with the maximum absolute and relative sensitivity being 0.024 K-1(at 303 K) and 2.46% K-1(at 443 K) and good signal discriminability. We propose that the emission quenching of Eu^2+ is ascribed to 5 d electrons depopulation through Eu^2+/Eu^3+ intervalence charge transfer state, while the quenching of Eu^3+ comes from multiphonon relaxation. Our work demonstrates the potential of Ca2 Al2 Si1-xO7:Eu for noncontact optical thermometry, and also highlights mixed-valence europium-containing compounds toward temperature sensing.

A novel hydrogen peroxide biosensor based on the BPT/AuNPs/graphene/HRP composite

A novel hydrogen peroxide biosensor based on the BPT/AuNPs/graphene/HRP composite was developed. Firstly, graphene was prepared under the protection of polyvinylpyrrolidone (PVP), and then the AuNPs/graphene composite was synthesized via in situ decoration. Using biphenyldimethanethiol (BPT) as a connector, the AuNPs/graphene composite was immobilized on the surface of the Au electrode, and whereafter the horseradish peroxidase (HRP) was decorated on the surface of the composite by adsorption. The morphology and structure of the products were characterized by XRD, SEM, TEM and UV-visible spectroscopy. The electrocatalytic performance of the resulting BPT/AuNPs/grapheme/HRP composite (namely, biosensor) was studied by electrochemical instrument. The results show that the biosensor has high sensitivity and fast response to H2O2. In the solution of pH 7.4 with potential -0.2V, the linear response of the biosensor to H2O2 ranges from 5.0×10-6 to 2.5×10-3M with the detection limit of 1.5×10-6M.