Silver nanocluster-based fluorescent sensors for sensitive detection of Cu(II)

In this work, we report the first application of water-soluble fluorescent Ag nanoclusters in fluorescent sensors. The fluorescence of poly(methacrylic acid) (PMAA)-templated Ag nanoclusters was found to be quenched effectively by Cu2+, but not when other common metal ions were present. By virtue of the specific response toward the analyte, a new, simple, and sensitive fluorescent method for detecting Cu2+ has been developed based on Ag nanoclusters.

Investigation of some critical parameters of buffer conditions for the development of quantum dots-based optical sensors

The unique surface-sensitive properties make quantum dots (QDs) great potential in the development of sensors for various analytes. However, quantum dots are not only sensitive to a certain analyte, but also to the surrounding conditions. The controlled response to analyte may be the first step in the designing of functional quantum dots sensors. In this study, taking the quenching effect of benzoquinone (BQ) on CdTe QDs as model, several critical parameters of buffer solution conditions with potential effect on the sensors were investigated. The pH value and the concentration of sodium citrate in the buffer solution critically influenced the quenching effects of BQ.

Flourescent Switch Constructed Based on Hemin-Sensitive Anionic Conjugated Polymer and Its Applications in DNA-Related Sensors

Here, a fluorescent switch is constructed combining hemin, hemin aptamer, and a newly synthesized anionic conjugated polymer (ACP), poly(9,9-bis(6'-phosphate-hexyl) fluorenealt-1,4-phenylene) sodium salt (PFHPNa/PFP). In the "off-state", the fluorescence of PFP is sensitively quenched by hemin, with a high K-sv value of similar to 10(7). While in the "on-state", the formation of the aptamer/hemin complex recovers the fluorescence intensity. The fluorescent switch is sensitive and selective to hemin. To testify the universality and practicality of the fluorescent switch, a series of label-free DNA-related sensing platforms are developed, containing three DNA sensing strategies and one ATP recognition strategy. The fluorescent switch developed is simple, sensitive, and universal, which extends applications of the anionic conjugated polymers.

Organic-inorganic hybrid material for the cells immobilization: Long-term viability mechanism and application in BOD sensors

In this paper, organic-inorganic hybrid material, which is composed of silica and the grafting copolymer of poly (vinyl alcohol) and 4-vinylpyridine (PVA-g-P(4-VP)), was employed to immobilize Trichosporon cutaneum strain 2.570 cells. Cells entrapped into the hybrid material were found to keep a long-term viability. The mechanism of such a long-term viability was investigated by using confocal laser scanning microscopy (CLSM). Our studies revealed that arthroconidia produced in the extracellular material might play an important role in keeping the long-term viability of the immobilized microorganism. After the arthroconidia were activated, an electrochemical biochemical oxygen demand (BOD) sensor based on cell/hybrid material-modified supporting membrane was constructed for verifying the proposed mechanism.

DNA based gold nanoparticles colorimetric sensors for sensitive and selective detection of Ag(I) ions

In this work, we reported both unlabeled and labeled sensing strategies for Ag(I) ions detection by using the DNA based gold nanoparticles (AuNPs) colorimetric method. In the unlabeled strategy, C-base riched single strand DNA (C-ssDNA) enwinded onto AuNPs to form AuNPs/C-ssDNA complex. In the labeled method, sulfhydryl group modified C-ssDNA (HS-C-ssDNA) was covalently labeled on AuNPs to produce AuNPs-S-C-ssDNA complex. In both strategies, C-ss DNA or HS-C-ssDNA could enhance the AuNPs stability against the salt-induced aggregation. However, the presence of Ag(I) ions in the obtained AuNPs/C-ssDNA or AuNPs-S-C-ssDNA complex would decrease such stability to display purple even blue colors due to the formation of Ag(I) ions mediated C-Ag(I)-C base pairs. Through this phenomenon, Ag(I) ions could be detected qualitatively and quantitatively using both unlabeled and labeled sensing strategies.

Antioxidant Sensors Based on Iron Diethylenetriaminepentaacetic Acid, Hematin, and Hemoglobin Modified TiO2 Nanoparticle Printed Electrodes

Antioxidant amperometric sensors based on iron-containing complexes and protein modified electrodes were developed. Indium tin oxide glass was printed with TiO2 nanoparticles, onto which iron-containing compounds and protein were adsorbed. When applied with negative potentials, the dissolved oxygen is reduced to H2O2 at the electrode surface, and the H2O2 generated in situ oxidizes Fe-II to Fe-III, and then electrochemical reduction of Fe-III therefore gives rise to a catalytic current. In the presence of antioxidants, H2O2 was scavenged, the catalytic current was reduced, and the decreased current signal was proportional to the quantity of existing antioxidants. A kinetic model was proposed to quantify the H2O2 scavenging capacities of the antioxidants. With the use of the sensor developed here, antioxidant measurements can be done quite simply: put the sensor into the sample solutions (in aerobic atmosphere), perform a cathodic polarization scan, and then read the antioxidant activity values. The present work can be complementary to the previous studies of antioxidant sensor techniques based on OH radicals and superoxide ions scavenging methods, but the sensor developed here is much easier to fabricate and use.

Polymeric pH indicators immobilized PVA membranes for optical sensors of high basicity based on a kinetic process

Two kinds of polymeric pH indicators PPF (phenolphthalein-formaldehyde product) and CPF (o-cresolphthalein-formaldehyde product) immobilized cross-linked poly(vinyl alcohol) membranes (PPF-PVA and CPF-PVA) for optical intermittent determination of high basicity ([OH-] = 1-8 M) based on a kinetic process were developed. In our previous work, we had demonstrated that PPF-PVA and CPF-PVA could perform the determination of high pH values from pH 10.0 to 14.0. Here the discoloring kinetic behaviors of PPF-PVA and CPF-PVA were compared with those of free phenolphthalein, o-cresolphthalein and thymolphthalein. Experimental results and theoretical analysis indicated that the response behaviors of the optodes' membranes in concentrated NaOH solutions were diffusion-independent and still complied with the pseudo-first-order kinetics. In addition, two data analysis methods for determination were presented. One was directly based on the reduced absorbance: the other was based on the discoloring kinetic constant. It was found that the latter could perform a rapid (60 s) and reliable (relative standard deviation: 2.6%) determination for high basicity.

Electrogenerated chemiluminescence sensors using Ru(bpy)(3)(2+) doped in silica nanoparticles

A novel electrogenerated chemiluminescence (ECL) sensor based on Ru(bpy)(3)(2+)-doped silica (RuDS) nanoparticles conjugated with a biopolymer chitosan membrane was developed. These uniform RuDS nanoparticles ( similar to 40 nm) were prepared by a water-in-oil microemulsion method and were characterized by electrochemical and transmission electron microscopy technology. The Ru( bpy)(3)(2+)-doped interior maintained its high ECL efficiency, while the exterior nanosilica prevented the luminophor from leaching out into the aqueous solution due to the electrostatic interaction. This is the first attempt to branch out the application of RuDS nanoparticles into the field of ECL, and since a large amout of Ru(bpy)(3)(2+) was immobilized three-dimensionally on the electrode, the Ru( bpy)(3)(2+) ECL signal could be enhanced greatly, which finally resulted in the increased sensitivity. This sensor shows a detection limit of 2.8 nM for tripropylamine, which is 3 orders of magnitude lower than that observed at a Nafion-based ECL sensor. Furthermore, the present ECL sensor displays outstanding long-term stability.

K+ sensors based on supported alkanethiol/phospholipid bilayers

A novel kind of K+ sensor with valinomycin-incorporated bilayers supported on a gold electrode consisting of self-assembled alkanethiol monolayers (SAMs) and a lipid monolayer has been fabricated successfully. The lipid monolayer is deposited on the alkylated surface of the first alkanethiol monolayer through three different methods, such as the Langmuir-Blodgett (LB) technique, painted method and painted-frozen method. The response of K + sensors produced by a painted or painted-frozen lipid monolayer on an alkanethiol alkylated gold electrode is larger than that by the LB method, which is due to the difference in fluidity of the three kinds of bilayers. Selectivity coefficients KK+, Na+, KK+, Li+, KK+, Ca2+ and KK+, Mg2+ are 10(-4), 10(-4), 2 x 10(-5) and 3 x 10(-5) respectively, and there is no obvious difference among different fabricating methods. A linear response toward the potassium ion was found in the range from 10(-1) M to 10(-5) M with the detection limit of 10(-6) M. The sensor has a slope of 60 mV per decade. Meanwhile, the longevity of the sensor was improved obviously for at least two months at about -10 degrees C. The higher stability shows the possibility to fabricate a practical biosensor.

AMPEROMETRIC DETECTION AT A CARBON-FIBER ARRAY RING GLASSY-CARBON DISK ELECTRODE IN A WALL-JET CELL

A wall-jet cell incorporating a carbon fibre array ring/glassy-carbon disk electrode has been constructed, and characterized by the cyclic voltammetry and flow-injection techniques. The ring (composed of several microdisks) and glassy-carbon disk electrode, can be used separately for different purposes, e.g., detection in solution without a supporting electrolyte, collection/shielding detection with dual-electrode and voltammetric/amperometric detection with series dual-electrode. The electrode shows better collection and shielding effects than usual ring-disk electrode in quiescent solution and the series dual-electrode in a thin-layer flow-through cell. The detection limit at the ring electrode is comparable with that at a conventional-size electrode, and has been used in the mobile phase without a supporting electrolyte, proving to be a promising detector for normal-phase liquid chromatography.

基于证据理论的虚拟力机器人网络控制

将网络与机器人相连,延伸网络的应用领域,可以实现价格低廉的远程监视与操作,而远程控制成功实现的关键在于信息的正确获得。利用Dempster-Shafer对六个超声波传感器所获取的距离信息进行融合,而后连同速度信息提供给弹簧-阻尼器系统以构建虚拟力;力的信息通过编程映射到游戏杆上,变成操纵方向的约束力。通过采用微软公司的带有力反馈的操纵杆作为力觉提示装置控制移动机器人在结构化环境下顺利运行,验证了虚拟力信息获取方法的有效性。

全地形移动机器人轮-地几何接触角估计

研究全地形移动机器人在不平坦地形中轮-地几何接触角的实时估计问题.本文以带有被动柔顺机构的六轮全地形移动机器人为对象,抛弃轮-地接触点位于车轮支撑臂延长线上这一假设,通过定义轮-地几何接触角δ来反映轮-地接触点在轮缘上位置的变化和地形不平坦给机器人运动带来的影响,将机器人看成是一个串-并联多刚体系统,基于速度闭链理论建立考虑地形不平坦和车轮滑移的机器人运动学模型,并针对轮-地几何接触角δ难以直接测量的问题,提出一种基于模型的卡尔曼滤波实时估计方法.利用卡尔曼滤波对机器人内部传感器的测量值进行噪声处理,基于机器人整体运动学模型对各个轮-地几何接触角进行实时估计,物理实验数据的处理结果验证了本文方法的有效性,从而为机器人运动学的精确计算和高质量的导航控制奠定了基础.