柔性高灵敏单壁碳纳米管气体传感器研究

在柔性聚对二甲苯C基底上制作了基于单壁碳纳米管的小型化、高灵敏、反应快速的气体传感器。使用介质电泳集成碳管束,并利用单链脱氧核糖核酸修饰增强器件灵敏度。当传感器暴露在甲醇蒸气中时,会出现明显可重复的反应,它可以检测含量低至4.3×10-6的甲醇,并且在相当宽的体积分数范围有清晰的分辨能力。对于4.3×10-6的含量,未修饰的传感器对应电阻变化率是4.8%;经过脱氧核糖核酸修饰,电阻变化率增加到了12.3%。此外,该传感器还显示了很快的响应速度和很好的测试复验性。研究表明:这种柔性气体传感器在未来环境监测应用中有很好的前景。     

金(Au)/钯(Pd)复合膜表面等离子共振氢敏传感器基因优化

提出了一种新颖的基于波长调制的Au/Pd复合膜SPR氢敏传感器结构,采用遗传基因算法对Au/Pd复合膜氢敏传感器的灵敏度进行了数值计算和优化,优化结果表明:Au(2 nm)/Pd(27 nm)结构的复合膜氢敏传感器可获得最佳的灵敏度,与通常使用的单一纯Pd(20 nm)膜氢敏传感器相比,不仅氢敏传感器的敏感膜的稳定性得到改善,而且灵敏度也提高了近3倍.     

ZnO modified gold disc: A new route to efficient glucose sensing

Surface of a gold disc was modified by depositing ZnO film electrochemically. AFM analysis of the film shows c-axis oriented pillar like structures grown normal to the surface. Sensor surface was prepared by immobilizing glucose oxidase (GOD) on the ZnO modified gold disc. Different concentrations of glucose (50-1000 ng/ml) were taken to monitor the sensor response. Sensor was found to be highly sensitive to low concentrations of glucose and sensitivity increases linearly in the range of 50-250 ng/ml. The high sensitivity of the ZnO modified gold disc may be attributed to the SPR induced electron transfer between the two systems (i.e. Au and ZnO). The work indicates promising application of the system as a tool for studying sensitive bio-specific interactions, with further development of highly sensitive and selective bio-molecular and chemical SPR based optical sensors.     

多壁碳纳米管-Nafion/纳米金构建阻抗传感器研究

利用多壁碳纳米管（ MWNT）—Nafion和纳米金（ GNPs）修饰金电极构建了一种简单、灵敏检测人端粒DNA的电化学阻抗传感器。首先将Nafion分散的MWNT滴涂于Au电极表面,再利用电化学沉积法将GNPs沉积到MWNT—Nafion修饰Au电极表面,以GNPs为载体固定人端粒探针DNA制备DNA传感器。在最优实验条件下,将传感器用于人端粒DNA的检测中,结果表明：目标人端粒DNA的线性范围为1.0×10－13～5.0×10－11mol/L,检出限（S/N＝3）为2.5×10－14mol/L。采用MWNT为基底沉积GNPs修饰电极检测的灵敏度显著提高。     

基于纳米金颗粒放大的电化学传感器用于三聚氰胺的检测

三聚氰胺与胸腺嘧啶（T）之间能够通过三个氢键结合,以富T的DNA探针为识别元件,结合DNA修饰的纳米金颗粒放大技术,以电活性物质钌胺作为信号分子,发展了一种高灵敏检测三聚氰胺的电化学传感器,该传感器具有良好的特异性和灵敏度,检测下限低至0．5nmol／L。     

Integrated SWCNT sensors in micro-wind tunnel for air-flow shear-stress measurement

We have developed SWCNT sensors for air-flow shear-stress measurement inside a polymethylmethacrylate (PMMA) “micro-wind tunnel” chip. An array of sensors is fabricated by using dielectrophoretic (DEP) technique to manipulate bundled single-walled carbon nanotubes (SWCNTs) across the gold microelectrodes on a PMMA substrate. The sensors are then integrated in a PMMA micro-wind tunnel, which is fabricated by SU-8 molding/hot-embossing technique. Since the sensors detect air flow by thermal transfer principle, we have first examined the I–V characteristics of the sensors and confirmed that self-heating effect occurs when the input voltage is above ~1 V. We then performed the flow sensing experiment on the sensors using constant temperature (CT) configuration with input power of ~230 μW. The voltage output of the sensors increases with the increasing flow rate in the micro-wind tunnel and the detectable volumetric flow is in the order of 1 × 10⁻⁵m³/s. We also found that the activation power of the sensors has a linear relation with 1/3 exponential power of the shear stress which is similar to conventional hot-wire and polysilicon types of convection-based shear-stress sensors. Moreover, measurements of sensors with different overheat ratios were compared, and results showed that sensor is more sensitive to the flow with a higher overheat ratio.     

Caffeine as base analogue of adenine or guanine: A theoretical study

The results of quantum mechanical calculations, including binding energies and results of the population analysis show that the GC and AT base pair complexes are more stable than the CAF-X ones (where CAF is caffeine and X = adenine (A), thymine (T), cytosine (C) and guanine (G)). Structural similarity between the CAF molecule and purine bases (G and A) provides the possibility of incorporation of the CAF molecule into the DNA macromolecule. By comparing the CAF-A and CAF-T complexes with the AT base pair, and the CAF-G and CAF-C complexes with the GC base pair, it was found that the formation of the CAF-T complex is more probable than the other complexes. Thus, the CAF molecule acts as an analogue base of A and can be incorporated into the DNA macromolecule and paired with T and C in normal and rare state, respectively. Indeed, the results show that formation of the CAF-C complex is less probable than the CAF-T one and an AT to GC conversion is rarely occurred in the next DNA replication, so the CAF molecule may be considered as a weak mutagenic compound. To examine solvent effect, the binding energies have been calculated in solvent for the most important structures of the CAF-G, CAF-T, CAF-A and CAF-C complexes. The results in solvent are in agreement with those in the gas phase.     

Development of a screen-printed cholesterol biosensor: Comparing the performance of gold and platinum as the working electrode material and fabrication using a self-assembly approach

Gold (Au) and platinum (Pt) were used as the working electrode material to detect cholesterol in solution through enzymatically generated hydrogen peroxide (H₂O₂). Both gold and platinum were capable of detecting cholesterol through the electrochemical oxidation of H₂O₂, and could be used as the working electrode material. By comparison, however, Au was preferable over Pt in terms of higher response current and better sensitivity. Therefore, Au was chosen as the working electrode material for the fabrication of a thick-film screen-printed cholesterol biosensor consisting of three electrodes on an alumina substrate (working: Au, reference: Ag/AgCl, and counter: Au). The immobilization of the enzyme cholesterol oxidase (ChOx, E.C. 1.1.3.6) on the Au working electrode was achieved using a self-assembly approach. A thiol, 3-mercaptopropionic acid (MPA), was self-assembled onto the gold working electrode forming a thin organic layer that served as the anchor for the enzyme immobilization. 1-Ethyl-3(3-dimethylamino propyl)carbodiimide methiodide (EDC) was then used to immobilize the enzyme ChOx covalently on the gold working electrode through the carbodiimide coupling between the carboxyl (–COOH) groups of the self-assembled MPA layer and the amino (–NH₂) groups of the enzyme. Electrochemical measurements showed that this biosensor responded well to cholesterol, confirming that the self-assembly immobilization method was effective. The reproducibility, the interference, and the storage stability of the biosensor were studied and assessed.     

Detecting faulty sensors in an array using symmetrical structure and cultural algorithm hybridized with differential evolution

The detection of fully and partially defective sensors in a linear array composed of N sensors is addressed. First, the symmetrical structure of a linear array is proposed. Second, a hybrid technique based on the cultural algorithm with differential evolution is developed. The symmetrical structure has two advantages: (1) Instead of finding all damaged patterns, only (N–1)/2 patterns are needed; (2) We are required to scan the region from 0° to 90° instead of from 0° to 180°. Obviously, the computational complexity can be reduced. Monte Carlo simulations were carried out to validate the performance of the proposed scheme, compared with existing methods in terms of computational time and mean square error.     

A vertical structure photodetector based on all‐inorganic perovskite quantum dots

In this work, the vertical structure photodetector based on CsPbBr₃ quantum dots (QDs) with a structure of indium tin oxide (ITO)/zinc oxide (ZnO)/CsPbBr₃ QDs/Au is reported. In this device, CsPbBr₃ QDs film works as the light‐harvesting layer, and ZnO QDs film acts as the electron transport channel, which can extract the electron efficiently and improve the quality of CsPbBr₃ QDs film. As a result, the on/off ratio, detectivity and rise time (decay time) of CsPbBr₃/ZnO hybrid photodetector are measured to be 2.4 × 10⁶, 2.25 × 10¹¹, and 62 milliseconds (82 ms) under 0‐V bias. This work inspires the development of vertical structure photodetectors based on the all‐inorganic perovskite QDs.     

Selective detection of HCHO gas using mixed oxides of ZnO/ZnSnO3

Mixed oxides of ZnO/ZnSnO₃ doped with Au element were prepared by a hydrothermal process. The crystal structure, composition and ceramic microstructure of the powders obtained were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The results show that the product is the mixture of ZnO/ZnSnO₃; its particle size is about 500 nm with good dispersivity in shape. The sensitivity, selectivity, response and recovery properties of the ZnO/ZnSnO₃-based sensors were investigated by mixing a target gas in air. It is found that the sensors have remarkable sensitivity to HCHO vapor and satisfactory selectivity to other gases.     

基于抗体包被金磁纳米微粒修饰的磁性安培免疫传感器研制及对人血清癌抗原19-9的检测

在金电极表面修饰壳聚糖(CS)膜,并在酸性pH下利用CS上形成的-NH3+静电吸引Fe(CN)]3-6-(FeCN)到电极表面,制成了在pH 6.5磷酸盐缓冲液(PBS)中具有电活性的Au | CS-FeCN电极;再通过外加磁场吸引,在Au | CS-FeCN表面修饰一层血清癌抗原19-9单克隆抗体(anti CA19-9)包被的金磁纳米微粒(Fe3O4(核)／Au(壳),简称GMP),由此构建了一类快速检测CA19-9的无试剂安培免疫传感器(Au| CS-FeCN／GMP-anti CA19-9).用扫描电镜(SEM),X-射线荧光光谱(XFS)和X-射线光电子能谱(XPS)对电极表面进行了表征;并采用循环伏安法(CV),示差脉冲伏安法(DPV)、交流阻抗法(E1S)分 别研究了该传感器的电化学性质和对CAl9-9的检测性能.实验表明:Au I CS-FeCN／GMP-anti CAl9-9电极在含CAl9-9的pH 6.5 PBS中于35℃下温育25 min,其DPV还原电流下降值(AI)与CA19-9在0.1～10 U／mL和10~50 U／mL范围内成正比,检出下限为0.056 U／mL(3d).用于血清样本检测并和标准ELISA方法对照,结果一致.只需移去外加磁场,用PBS清洗电极表面即可实现电极更新.该磁性免疫传感器集分离、富集和测定于一身,灵敏度高、稳定性好、表面易更新,有望用于人血清中痕量CA19-9的快速检测.     

Electrochemical behavior of microfabricated thick-film electrodes

The possible chemical crosstalk between electrodes in microfabricated voltammetric oxygen sensors has been studied with an interdigitated electrode assembly. Experimental results show that significant amounts of hydrogen peroxide can be produced at the Au or Pt cathode and transferred to the surface of nearby counter and reference electrodes. Such chemical crosstalk may not only distort the sensing signal, but also affects the stability of the gold anode and the Ag/AgCl reference electrode.     

Sensitive analysis of glutathione in bacteria and HaCaT cells by polydopamine/gold nanoparticle-coated microchip electrophoresis via online pre-concentration of field-amplified sample stacking

In this paper, polydopamine/gold nanoparticles (PDA/Au NPs) were used to construct a functional film on a glass microfluidic channel surface in microchip electrophoresis (MCE) for the separation of reduced glutathione (GSH) and oxidized glutathione (GSSH). The formation of the PDA/Au NPs was characterized by scanning electron microscopy, transmission electron microscope, UV–Vis spectra and ATR-FTIR. An online pre-concentration strategy involving field-amplified sample stacking was used to determine the sensitivity of the assay for measuring GSH and GSSH in bacteria (Escherichia coli, Staphylococcus aureus and Salmonella enterica serovar Typhimurium) and HaCaT cells samples by MCE with laser-induced fluorescence detection. The influences of the separation voltage, the concentration of the running buffer and the pH value of running buffer, were carefully investigated. Using this studied method, GSH and GSSH could be simultaneously pre-concentrated and separated within 70 s. The limits of detection of GSH and GSSH were as low as 0.81 and 0.91 nM, respectively (S/N = 3), which corresponded to approximately 180–301-fold improvements in peak height. Moreover, this method was successfully applied to the analysis of bacteria (E. coli, S. aureus and S. typhimurium) and HaCaT cell samples with a satisfactory recovery rate.     

Shrink-induced ultrasensitive mercury sensor with graphene and gold nanoparticles self-assembly

Here we report an ultrasensitive trace mercury(II) micro sensor based on heat-shrinkable polymer (polyolefins, PO). The layer-by-layer self-assembly (LBL SA) method was employed to modify mixed gold nanoparticle (Au NPs) and graphene solution on a micro gold electrode with PO substrate. The unique wrinkle structure of the electrode surface and superior properties of modification film enhanced the performance of LBL SA graphene–Au NPs shrink sensor greatly in determination of Hg(II) using anodic stripping voltammetry (ASV): compared with a shrink gold electrode without surface modification, the sensitivity was improved for about 3.7 times from 0.197 to 0.721 μA/ppb; compared with a same-sized sensor without surface modification nor shrink, the sensitivity was improved for over 50 times. This sensor’s detection limit of Hg(II) was achieved as 0.931 ppb with a sensitivity of 0.721 μA/ppb. This simple but highly sensitive sensor can be widely used in applications of on-line environmental monitoring of Hg(II).

     

A novel amperometric biosensor for oxalate determination using multi-walled carbon nanotube-gold nanoparticle composite

An amperometric oxalate biosensor using nanohybrid film of multi-walled carbon nanotubes (MWCNTs) and gold colloidal nanoparticles (GNPs) via carbodiimide chemistry by forming amide linkages between carboxylic acid groups on the CNTs and amine residues of cysteamine self-assembled monolayer (SAM) has been prepared. The c-MWCNTs were immobilized on the gold (Au) electrode and characterized by FTIR. The morphologies of the c-MWCNT/Au and GNPs/MWCNT/Au electrodes were investigated by scanning electron microscopy (SEM) and the electrochemical performance of the Au, c-MWCNT/Au and GNPs/c-MWCNT/Au electrodes were also studied amperometrically. The Cl⁻ and NO₃⁻ insensitive oxalate oxidase from grain sorghum was finally immobilized on this electrode. The influence of pH, temperature and oxalate concentration on electrode activity was studied. The electrode showed optimum response within 7 s. The electrocatalytic response showed a linear dependence on the oxalic acid concentration ranging from 1 to 800 μM with a detection limit of 1 μM. The K_m value for the oxalic acid sensor was 444.44 μM. The enzyme electrode retained 30% of its initial activity after 5 months, when stored at 4 °C. The electrode was employed for measurement of oxalic acid in serum, urine and foodstuffs.     

Characterization and gas sensitivity study of polyaniline/SnO2 hybrid material prepared by hydrothermal route

A polyaniline (PAni)/SnO₂ hybrid material was prepared by a hydrothermal method and characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). The XRD pattern suggested that PAni did not modify the crystal structure of SnO₂, but SnO₂ affected the crystallization of PAni to some extent. The gas sensitivity of the PAni/SnO₂ hybrid was also studied to ethanol and acetone at operation temperatures of 30, 60 and 90 °C. It was found that the PAni/SnO₂ hybrid material had gas sensitivity only when operated at 60 and 90 °C, and it showed a linear relationship between the responses and the concentrations of ethanol and acetone at 90 °C. The sensing mechanism was also discussed.     

Fabrication of micro sensors on a flexible substrate

Flexible micro temperature and humidity sensors on parylene thin films were designed and fabricated using a micro-electro-mechanical-systems (MEMS) process. Based on the principles of the thermistor and the ability of a polymer to absorb moisture, the sensing device comprised gold wire and polyimide film. The flexible micro sensors were patterned between two pieces of parylene thin film that had been etched using O₂ plasma to open the contact pads. The sacrificial Cr spacer layer was removed from the Cr etchant to release the flexible temperature and humidity sensors from the silicon substrate. Au was used to form the sensing electrode of the sensors while Ti formed the adhesion layer between the parylene and Au. The thickness of the device was 7 ± 1 μm, so the sensors attached easily to highly curved surfaces. The sensitivities of the temperature and humidity sensor were 4.81 × 10⁻³ °C⁻¹ and 0.03 pF/%RH, respectively. This work demonstrates the feasibility and compatibility of thin film sensor applications based on flexible parylene. The sensor can be applied to fuel cells or components that must be compressed.     

Label-free detection of DNA hybridization using gold-coated tapered fiber optic biosensors (TFOBS) in a flow cell at 1310 nm and 1550 nm

We had previously reported the detection of a model protein bovine serum albumin (BSA) using antibody-immobilized tapered fiber optic biosensors (TFOBS) at 1310 nm and 1550 nm under stagnant and flow conditions. Because of recent interest in pathogen detection based on DNA, in this work we explore the application of these sensors for the detection of single stranded DNA (ssDNA). We show that it is feasible to directly detect the hybridization of a 10-mer ssDNA to its complementary strand immobilized on the sensor surface. Detection was performed under flow conditions because flow reduces non-specific binding to sensor surface, eliminates optical transmission changes due to mechanical movements, and allows for instantaneous switching of samples when needed.

TFOBS were fabricated with waist diameters of 5–10 μm and total lengths of 1000–1200 μm. The taper regions were coated with 50 nm of gold and housed in a specially constructed holder which served as a flow cell. The TFOBS was immobilized with 15-mer ssDNA with a C₆ extension and a thiol group, which attaches to Au1 1 1 sites. Then, the complementary 10-mer ssDNA samples were allowed to flow in from low to high concentration (750 fM to 7.5 nM) and the resulting transmission changes were recorded. It is shown that 750 fM of complementary DNA can be detected. This sensor was able to distinguish between complementary DNA from DNA with a single nucleotide mismatch in the middle position.     

基于纳米金修饰丝网印刷电极的乙醇生物传感器

在丝网印刷电极上利用吸附法固定乙醇脱氢酶,并用纳米金进行修饰,以铁氰化钾为介体制作了用于酒精检测的一次性乙醇脱氢酶电极试纸.纳米金颗粒修饰酶电极,极大地改善了电极电流响应,提高了传感器的灵敏度.此乙醇传感器的响应时间仅为25 s,灵敏度为0.06 μA(mmol/L)~(-1),线性浓度测量范围为1.0 mmol/L至10 mmol/L.