Plasmonic Sensor Based on Silver Nanoparticles for the Detection of Glucose

Plasmonics - Sensors for detecting glucose concentrations are crucial to medical testing. Here, we introduce silver nanoparticles (Ag NPs) uniformly distributed in space to investigate the sensing...     

Comparative Study of Plasmonic Properties of Cysteine-Functionalized Gold and Silver Nanoparticle Aggregates

The absorptance spectra of gold and silver nanoparticle (NP) aqueous dispersions were measured by UV–visible spectroscopy and computed numerically by finite element method. Both NPs were functionalized by l-cysteine amino acid (Cys) in order to develop aggregate-based localized surface plasmon resonance biosensors. Absorptance spectra measured at an analogous pH value of ～4.9 were compared, where Au-Cys conjugates have moderately split spectra with two commensurate maxima, while Ag-Cys conjugates exhibit the most pronounced secondary peak according to the highest degree of aggregation. The purpose of our theoretical study was to determine the simplest linear chain-like and wavy aggregate geometries, which result in maxima matching the measured peaks. The aggregates were characterized by N number and d diameter of NPs, g gap between the NPs, and t thickness of the l-cysteine covering. By tuning the angle of incidence and E -field oscillation direction in p-polarized light with respect to the aggregates, the contribution of longitudinal and transversal modes was varied. The comparison of measurements and computations revealed that spectra measured on bioconjugate dispersions include effects of numerous aggregates with various geometries, illuminated from different directions and are influenced by inter-aggregate coupling. Inspecting the normalized E -field distribution surrounding the aggregates, it was shown that fundamentally different multipolar modes can be identified at primary and secondary absorptance maxima, due to coupled plasmonic resonances on NPs.     

A Combined Zinc/Cadmium Sensor and Zinc/Cadmium Export Regulator in a Heavy Metal Pump

Heavy metal pumps (P1B-ATPases) are important for cellular heavy metal homeostasis. AtHMA4, an Arabidopsis thaliana heavy metal pump of importance for plant Zn²⁺ nutrition, has an extended C-terminal domain containing 13 cysteine pairs and a terminal stretch of 11 histidines. Using a novel size-exclusion chromatography, inductively coupled plasma mass spectrometry approach we report that the C-terminal domain of AtHMA4 is a high affinity Zn²⁺ and Cd²⁺ chelator with capacity to bind 10 Zn²⁺ ions per C terminus. When AtHMA4 is expressed in a Zn²⁺-sensitive zrc1 cot1 yeast strain, sequential removal of the histidine stretch and the cysteine pairs confers a gradual increase in Zn²⁺ and Cd²⁺ tolerance and lowered Zn²⁺ and Cd²⁺ content of transformed yeast cells. We conclude that the C-terminal domain of AtHMA4 serves a dual role as Zn²⁺ and Cd²⁺ chelator (sensor) and as a regulator of the efficiency of Zn²⁺ and Cd²⁺ export. The identification of a post-translational handle on Zn²⁺ and Cd²⁺ transport efficiency opens new perspectives for regulation of Zn²⁺ nutrition and tolerance in eukaryotes.     

Preparation of Luminescent Plasmonic Silver Nanoparticles for Electrochemical Detection of Sulphide and Thiourea in Aqueous Solution and Ab Initio DFT Study of the Chemical Affinity Towards Silver Nanoparticles

Plasmonics - A changing of the mole ratio of L-ascorbic acid: citrate is used to synthesize coloured luminescent silver nanoparticles (AgNPs) such as AgNPs green (G), reddish green (RG) and reddish...     

Investigation of the Growth Kinetics and Multipolar Plasmonic Properties of Silver Nanoparticle Cluster by Experiment and Numerical Simulations

Silver nanoparticle (AgNP) has wide-spread applications in photovoltaic cell, biological sensors, biomedical devices, surface enhanced Raman scattering (SERS) etc. which are intricately dependent on AgNP shape, size, concentration and aggregation states. Here, the particle size, shape and aggregation dependent dipole and quadrupole surface plasmon resonances are spectroscopically investigated by preparing AgNPs (diameter 10–110nm) using silver nitrate (AgNO₃) and sodium borohydride (NaBH₄ as reducing agent) in aqueous environment at 0 ^∘C. The AgNP UV-Visible spectra showing plasmon-induced dipole and quadrupole modes are corroborated by the theoretical framework of Mie-Gans model and discrete dipole scattering model DDSCAT and different particle sizes, shapes and possible aggregation or clusterization are predicted. All the samples show presence of spherical and nonspherical distribution of AgNP. However, the concentration of nonspherical particle is more for higher concentration of reducing agent as is evidenced by the appearance of quadrapole absorption maxima. The minimum particle size is found at a particular ratio of concentration of AgNO₃ and NaBH₄. The day variation of AgNP kinetics also signalled the onset of quadrupole deformation of clusters.

     

Hydrodynamic Analysis and Responsivity Improvement of a Metal/Semiconductor/Metal Plasmonic Detector

Characteristic improvements of photon/plasmon detectors have been the subject of several investigations in the area of plasmonic integrated circuits. Among different suggestions, silicon-based metal-semiconductor-metal (MSM) waveguides are one of the most popular structures for the implementation of high-quality photon/plasmon detectors in infrared wavelengths. In this paper, an integrated silicon-germanium (SiGe) core MSM plasmon detector is proposed to detect λ = 1550 nm with internal photoemission mechanism. Performance characteristics of the new sub-micron device are simulated with a simplified hydrodynamic model. In a specific bias point (V = 3 V and the incident optical power of 0.31 mW), the output current is 404.3 μA (276 μA detection current and 128.3 μA dark current), responsivity is 0.89 A/W, and the 3-dB electrical bandwidth is 120 GHz. Simulation results for the proposed plasmon detector, in comparison with the empirical results of a reported Si-based MSM device, demonstrate considerable responsivity enhancement.

     

Study on the Effect of Poly(Styrene 4-Sulfonic Acid-co-Maleic Acid) Toward Metallization and Plasmonic Tuning of Silver Nanoparticle Thin Films

Thin films with tunable optical properties from yellow to metallic were prepared from a monolayer coating of silver nanoparticles (AgNP) onto a polyelectrolyte multilayer (PEM) thin film. The AgNP were synthesized using various concentrations of stabilizing polyelectrolytes leading to a competitive adsorption concept in which AgNP compete with excess polyelectrolytes to coat the cationic PEM top layer. The AgNP were synthesized by chemical reduction of Ag salts using poly(styrene 4-sulfonic acid-co-maleic acid) (PSS-co-MA) as stabilizing agent to produce nanoparticles coated with both a strong acid (sulfonic) and a weak acid (carboxylic) moiety. Although all the nanoparticle solutions displayed a characteristic bright yellow due to the localized surface plasmon band around 420 nm, the monolayer films of nanoparticles obtained after dipping displayed striking different optical properties. When using a high PSS-co-MA content in the solution, a pale-yellow film was obtained which color shifted to orange and metallic when the capping concentration was decreased from 0.25 to 0.001 mM. The optical properties of the AgNP film could be further changed by galvanic replacement of the Ag with gold ions to produce a gold monolayer. These results are interesting to produce surface with tunable catalytic properties, tunable optical properties, or to be used as primer for the metallization of polymeric surfaces.

     

Analysis and Simulation of a Novel Localized Surface Plasmonic Highly Sensitive Refractive Index Sensor

Dividing a metal nanoparticle into smaller components and the occurrence of the plasmonic phenomenon in the gap between these components can improve the sensitivity of the detector to variation of the refraction coefficient of liquid. In this paper, in a constant volume of metal, a golden disk is divided into two rings and one smaller disk. With a proper arrangement of these components, the surface plasmon resonance phenomenon takes place at the wavelength of 945.7 nm. The occurrence of this phenomenon increases the field in the distance between nanoparticles surrounded by liquid. The sensitivity of the detector that designed using nanodisks is 300 nm/RIU while it increases to 500 nm/RIU for the new structure. The increase of LSPR displacement, for a variation of 0.01 in the liquid refraction coefficient, from 3 nm for a disk to 5 nm for a proposed structure verifies a 67% improvement in the sensitivity of the sensor.

     

合成生物学改造微生物及生物被膜用于重金属污染检测与修复

随着工业化进程不断加快,重金属污染日益加剧,尤其是水体的重金属污染,已严重威胁人类健康,迫切需要进行有效的污染修复.相比传统物理和化学修复,生物修复具有绿色环保和可持续性的特点.因为微生物生长繁殖迅速、生物被膜具有动态可调节和环境适应性好等特点,使其能更好耐受胁迫环境,在环境修复中有重要作用.合成生物学改造微生物及生物...     

Heavy Metal Pollution Characteristics of Surface Sediments in Different Aquatic Ecosystems in Eastern China: A Comprehensive Understanding

Aquatic ecosystems in eastern China are suffering threats from heavy metal pollution because of rapid economic development and urbanization. Heavy metals in surface sediments were determined in five different aquatic ecosystems (river, reservoir, estuary, lake, and wetland ecosystems). The average Cd, Cr, Cu, Ni, Pb, and Zn concentrations were 0.716, 118, 37.3, 32.7, 56.6, and 204 mg/kg, respectively, and the higher concentrations were mainly found in sediment samples from river ecosystems. Cd was the most anthropogenically enriched pollutant, followed by Zn and Pb, indicated by enrichment factors >1.5. According to consensus-based sediment quality guidelines, potential ecological risk indices, and risk assessment codes, all five types of aquatic ecosystems were found to be polluted with heavy metals, and the most polluted ecosystems were mainly rivers. Cd was the most serious pollutant in all five aquatic ecosystems, and it was mainly found in the exchangeable fraction (about 30% of the total Cd concentration, on average). The results indicate that heavy metal contamination, especially of Cd, in aquatic ecosystems in eastern China should be taken into account in the development of management strategies for protecting the aquatic environment.     

重金属抗性菌HQ-1生物吸附镉与银的比较研究

从北京市远郊东三岔地区一处废弃的铅锌尾矿中筛选到一株对铅、锌、铜、钴、银、镉等重金属均有很好抗性的蜡状芽胞杆菌Bacillus cereus HQ-1。特别是对镉的抗性高达1200mg/L,具有很高的应用价值。比较研究了HQ-1菌株吸附重金属银和镉的情况与机理,发现该菌株对两种重金属离子都有较强的吸附能力。对镉的吸附行为符合Langmuir模型,对银的吸附行为符合Freundlich模型。通过红外光谱和X射线能谱对其吸附机理做了初步推断。并通过质粒消除试验证明该菌株的重金属抗性与抗性质粒存在有关。     

Proposition and Numerical Analysis of a Plasmonic Sensing Structure of Metallo-Dielectric Grating and Silver Nano-slabs in a Metal-Insulator-Metal Configuration

Plasmonics - We propose and numerically investigate a near-infrared surface plasmon resonance-based refractive index sensor having in unison an extremely high sensitivity (1719 nm/RIU) and...     

微量蛋白检测中不同银染方法的比较与分析

随着生物化学技术的不断发展,作为检测SDS-聚丙烯酰胺凝胶电泳(SDS-PAGE)中微量蛋白的银染方法也在不断改进和发展.采用4种不同的银染方法检测不同含量的牛血清白蛋白,结果显示单纯的银染过程中如果使用戊二醛固定会使蛋白检出更快速灵敏,而结合考马斯亮蓝的复合银染则较单纯银染灵敏度提高了5～7个数量级.     

Design and Analysis of FBG Sensor for Explosive Detection Applications

In this paper, a simple uniform fiber Bragg grating (FBG) sensor is designed, and maximum reflection of 7.1 dB at 1.55 μm is obtained. As this FBG shows a better reflection, it deserves well for the purpose of sensing and communication predominantly as they are resistant to electromagnetic radiations, light weight, low cost, firm size, and ease of handling. The proposed FBG is used for explosive sensing applications to detect explosives like trinitrotoluene (TNT), nitroglycerin, and royal demolition explosive (RDX). The different strain and temperature wavelength shifts of the explosives also analyzed and plotted.

     

光谱和微量热法分析柑橘苷与BSA分子间作用及构建其理论模型

光谱和微量热法分析柑橘苷(naringin,NAR)与牛血清白蛋白（bovine serum albumin, BSA）分子间作用,构建NAR与BSA分子间作用的理论模型。采用紫外-荧光光谱法解析Fōrster方程求得NAR与BSA分子间作用及分子间作用的临界距离r,等温滴定微量热技术测定NAR与BSA分子间作用的积分量热曲线,获得Δ H并通过Gibbs-Helmholtz方程获取Δ S和Δ G。基于光谱和微量热辅助分析,构建NAR与BSA分子间作用的理论模型。结果表明,光谱法测出NAR与BSA发生分子间作用,NAR与BSA分子间作用的临界距离为2.06 nm,表明NAR与BSA分子间作用为短程分子间作用。微量热法成功测定出NAR与BSA分子间的热力学参数Δ H<0,Δ S>0,Δ G<0,说明NAR与BSA分子间作用是自发进行的放热相互作用。依据Ross理论分析NAR与BSA分子间作用力主要是疏水作用力和静电作用力。模型构建结果说明,NAR与BSA分子间作用主要发生在BSA的domain IIA区域,NAR与BSA分子间作用力主要是静电作用力,兼有范德华作用力和氢键。实验与理论模型构建结果基本一致。本研究工作可为深入了解蛋白质与大分子化合物间的作用以及研究微观药理学机制提供有益的参考。     

Experimental and Theoretical Analysis of Connector Offset Optical Fiber Refractive Index Sensor

Plasmonics - In this paper, a high sensitive connector offset optical fiber sensor is employed to detect the refractive index of liquid. The configuration chosen for this experiment is formed by...     

The Adsorption Properties of Agricultural and Forest Soils Towards Heavy Metal Ions (Ni,Cu, Zn,and Cd)

Adsorption of Cu, Cd, Ni, and Zn in single and multi-metal solutions by agricultural and forest soils was investigated in batch sorption experiments. The results showed significant differences in sorption capacities of the studied soils. The selectivity order was as follows: agricultural soil? top forest soil > bottom forest soil. The adsorption sequence Cu > Zn > Ni > Cd was established for the agricultural and bottom forest soil, while the order for the top forest soil was Cu > Ni > Zn > Cd. The experimental isotherms for the metal sorption were described satisfactorily by the Freundlich and Langmuir models. The competitive adsorption experiment indicated a reduction in the amount of metals adsorbed by the soils from the multi-metal solution compared to the single metal solution. Properties of the soils, such as pH, content of clay and organic matter, exchangeable bases and hydrolytic acidity, showed a significant influence on adsorption capacities of the studied soils.     

黄瓜MTP基因家族分析及重金属胁迫下表达特征

该研究以模式物种(拟南芥、水稻、玉米)的MTP序列作为种子序列,对黄瓜MTP基因家族(CsMTP)成员进行了系统鉴定和分析;并以Zn2、Cd2+、Mn2+、Cu2+、Fe2+和Mo2+处理后的黄瓜叶片和根系为材料,对CsMTP响应金属离子的表达模式进行了研究,为探究该基因家族对黄瓜重金属胁迫调控机制提供理论依据.结果 ...     

辽宁省不同地区几种食用菌重金属含量测定及质量评价

对食用菌重金属含量测定和污染状况分析,探讨环境污染因素对食用菌吸收重金属的影响。采用微波消解法对食用菌进行处理,应用ICP-AES法测定了Ni、Cr、Pb、Cd、As、Hg六种重金属元素的含量。结果表明,调查的51份样品中香菇、平菇、杏鲍菇、茶树菇、双孢菇、黑木耳、鸡腿菇、蛹虫草重金属合格率均为97%以上;Ni、As含量在个别香菇和黑木耳中超标,但超标量很小;个别平菇、香菇、黑木耳、鸡腿菇有Pb的检出但不超标;平菇、香菇、茶树菇、黑木耳有Cd的检出但不超标;平菇、香菇、杏鲍菇、茶树菇、黑木耳、鸡腿菇有Cr的检出但不超标;所有样品中Hg均未检出。辽宁市场上食用菌大部分是安全的。