Analytical application of poly{methyl[3-(2-hydroxy-3,4-difluoro)phenyl]propyl siloxane} as a QCM coating for DMMP detection

A new material-poly{methyl[3-(2-hydroxy-3,4-difluoro)phenyl]propyl siloxane}(PMDFPS) sensitive to toxic organophosphate vapor was synthesized with 2,3-difluorophenol, allyl bromide and poly (methyl hydrosiloxane) as raw materials, via O-alkylation, Claisen rearrange reaction and hydrosilylation reaction. This novel material was then coated on a quartz crystal microbalance (QCM) to investigate its gas sensitive properties to the nerve agent simulant dimethyl methylphosphonate (DMMP) vapor, as well as known interfering vapors. When tested with competing vapors, the sensor was more than 10 times sensitive to DMMP than to other interfering vapors. Thus, high selectivity of poly{methyl[3-(2-hydroxy-3,4-difluoro)phenyl]propyl siloxane} to DMMP was demonstrated. The poly{methyl[3-(2-hydroxy-3,4-difluoro)phenyl]propyl siloxane}-QCM sensor responded linearly to DMMP vapor with a slope of 14 Hz/ppm in the 1-50 ppm range with a detection limit of 0.21 ppm (S/N=3).     

A Dual Read-out Molecularly Imprinted Composite Membrane Sensor Based on Zinc Porphyrin for the Detection of Dimethyl Methylphosphonate

Molecularly imprinted membrane-zinc porphyrin-mathacrylate(MIM-Zn-MAA), a dual read-out sensor based on a molecularly imprinted membrane, was developed to recognize and detect dimethyl methylphosphonate (DMMP) as an intermediate molecule of organophosphorus pesticides. The membranes were prepared via thermal polymerization of two functional monomers(zinc porphyrin and mathacrylate) on the surface of a glass slide functionalized with ethylene glycol dimethacrylate and azobisisobutyronitrile. The morphology of the as-synthesized MIM-Zn-MAA was determined with scanning electronic microscopy. The composite membranes exhibited macrovoid morphologies, which were affected by the functional monomers. These membranes were selectively adsorbed onto the template molecule and displayed higher adsorbing capacity toward DMMP compared with their structural analogs. Changes in the fluorescent spectra were qualitatively and quantitatively monitored via fluorescence photometry. Difference maps were also obtained using colorimetry before and after the reaction between MIM-Zn-MAA and DMMP at various concentrations. The maps showed a wide linear range varying from 0.1 μmol/L to 10 mmol/L with a low detection limit of 0.1 μmol/L. These preliminary results demonstrate that the as-fabricated dual read-out sensor displays good sensitivity and selectivity toward DMMP, indicating its considerable potential in DMMP detection in practical applications.     

Effect of humidity on the interaction of dimethyl methylphosphonate (DMMP) vapor with SiO2 and Al2O3 surfaces, studied using infrared attenuated total reflection spectroscopy

Infrared attenuated total reflection spectroscopy has been used to study the interaction of DMMP vapor with SiO(2), Al(2)O(3), and AlO(OH) vs relative humidity (RH) and DMMP partial pressure (P/P(0)). For SiO(2) the growth with increasing RH of ice-like and liquid-like layers is seen in agreement with previous work. H?D exchange during exposure to H(2)O and D(2)O indicates that the ice-like layer is more resistant to exchange, consistent with stronger H-bonding than in the liquid-like layer. Exposure of nominally dry SiO(2) to D(2)O indicates the existence of adsorbed H(2)O that does not exhibit an ice-like spectrum. The ice-like layer appears only at a finite RH. Exposure of SiO(2) to DMMP in the absence of intentionally added H(2)O shows the formation of a strongly bound molecular species followed by a liquid-like layer. The strong interaction involves SiO-H···O═P bonds to surface silanols and/or HO-H···O═P bonds to preadsorbed molecular H(2)O. At a finite RH the ice-like layer forms on SiO(2) even in the presence of DMMP up to P/P(0) = 0.30. DMMP does not appear to penetrate the ice-like layer under these conditions, and the tendency to form a such a layer drives the displacement of DMMP. Amorphous Al(2)O(3) and AlO(OH) do not exhibit an ice-like H(2)O layer. Both have a higher surface OH content than does SiO(2), which leads to higher coverages of H(2)O or DMMP at equivalent RH or P/P(0). At low P/P(0), for which adsorption is dominated by Al-OH···O═P bonding, a-Al(2)O(3) interacts with DMMP more strongly than does AlO(OH) as a result of the higher acidity of OH sites on the former. Up to RH = 0.30 and P/P(0) = 0.30, DMMP appears to remain bonded to the surface rather than being displaced by H(2)O. H(2)O appears to have little or no effect on the total amount of DMMP adsorbed on any of these surfaces, up to an RH of 0.30 and a P/P(0) of 0.30. The results have implications for the transport of DMMP and related molecules on oxide surfaces in the environment.     

Preparation of Sulfur-doped PANI/TiO2 Nanowires and Its Sensing Properties to Mercury

TiO₂ nanowires were successfully prepared via a simple hydrothermal method and a layer of sulfurized polyaniline(PANI) was loaded onto their surface to prepare a sensor of elemental mercury at room temperature. The sulfurized PANI/TiO₂ composite sensor has a high sensitivity to mercury in a range of density from 5.57 mg/m³ to 126.18 mg/m³ at room temperature. The response time and recovery time are relatively short. We also investigated the sensitivity and response time to other interfering gases, such as NO₂, SO₂ and NH₃. And the sulfurized PANI/TiO₂ composite material shows a good selectivity for element mercury. The microscopic structure of the sensor was investigated via X-ray diffraction(XRD), scanning electron microscopy(SEM) and energy dispersive X-ray analysis (EDAX). The sulfurized PANI/TiO₂ composite material shows a high sensitive response, and good selectivity to element mercury, which is promising for the application in the detection of element mercury.     

平面型乙醇快速响应气敏传感器的制备

采用水热法合成了纳米In₂O₃颗粒,将其旋涂于陶瓷基片上经氮化处理获得InN基片,再对InN基片进行氧化,合成出气敏材料并在一种微型平面电极片上制备了传感器件.采用扫描电子显微镜（SEM）、透射电子显微镜（TEM）、X射线衍射（XRD）仪、X射线光电子能谱（XPS）等手段对材料的形貌、组成进行了表征与分析,结果表明,最终获得了松枝状结构的InN-In₂O₃纳米复合材料.对器件的气敏性能进行了测试,发现基于此材料制备的平面型气敏传感器对乙醇气体具有良好的气敏性能：检测浓度为1.025 mg/m³（500 ppb）的乙醇蒸汽的灵敏度可达18;检测2.05 mg/m³（1 ppm）的乙醇的响应-恢复时间最快仅为1 s;最佳工作温度低,仅为50℃.     

Collection method for chemical particulates on surfaces with detection using thermal desorption-ion trap mass spectrometry

Successful analysis of particulate/low vapor pressure analytes such as explosives and toxic chemicals, and commercial pesticides require new sampling tools that enable detection of these analytes using current vapor phase detection instruments. We describe a sampling approach that uses stainless steel screens coated with a sticky polydimethyl siloxane (PDMS) coating to capture particulates from surfaces. Preliminary results for the collection of dimethyl methylphosphonate (DMMP) sorbed onto silica gel (SG) particulates (DMMP/SG) from a surface with subsequent analysis by thermal desorption-cylindrical ion trap mass spectrometry (TD-CITMS) are reported.     

Electrocatalytic Sensor for Hydrogen Peroxide Based on Immobilized Benzoquinone

An amperometric chemosensor for the detection of hydrogen peroxide is reported. The sensor is based on 1,4-benzoquinone immobilized on the gold electrode using self-assembled monolayer of short chain symmetrical dithiol as an anchor layer. Sensor analysis was performed by cyclic voltammetry at the potential range from −0.6 V till +0.9 V as well as in the anodic or cathodic potential ranges only. The results indicate oxidative electrochemical decomposition of hydrogen peroxide at the potential of ∼+0.4 V leading to the formation of oxygen while at cathodic potentials a reduction of the formed oxygen as well as of the hydrogen peroxide occur. A decrease in the oxidation potential of hydrogen peroxide on the gold electrode coated by self-assembled monolayer with 1,4-benzoquinone in comparison with that measured on the electrodes coated by the same self-assembled monolayer without 1,4-benzoquinone, indicates electrocatalytic effect of this moiety on oxidative decomposition of hydrogen peroxide. Analytical evaluation of the sensor performance was done in the voltammetric as well as in the chronoamperometric mode. The sensor exhibited linear response over the concentration range till 2.5 mM with a limit of detection ∼4 μM.     

Hydroxy-terminated organic semiconductor-based field-effect transistors for phosphonate vapor detection

Organic field-effect transistors (OFETs) with a hydroxy-functionalized semiconductor incorporated into a receptor layer were fabricated and shown to respond strongly to the analyte dimethyl methylphosphonate (DMMP) that simulates phosphonate nerve agents. Large and reproducible source-drain current changes were observed upon exposure to DMMP vapor. Compared to single component transistors, OFETs with a mixed hydroxylated and nonhydroxylated semiconductor upper layer exhibited higher sensitivity. We further investigated the selectivity of the heterostructured OFETs by comparing responses upon exposure to different interference vapors with response to DMMP exposure. Much higher response was observed in the case of DMMP, even when the concentration of DMMP vapor was much lower than other analytes. Microstructures of OSC were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD), revealing that the organic mixture has similar crystal structure and surface morphology to those of single component OSC films, indicating that the enhanced performance of the mixture is due to its chemical properties, rather than microstructural effects.     

有序介孔碳/石墨烯/镍泡沫的制备及其对多巴胺的高灵敏度和高选择性检测

柔性生物传感器在可穿戴电子设备中有着广泛的应用前景. 为了获得柔性电化学多巴胺传感器,作者在本工作中首先在镍泡沫表面通过化学气相沉积生长石墨烯,随后通过高温碳化嵌段共聚物与酚醛树脂在石墨烯表面共组装形成的薄膜制备了有序介孔碳/石墨烯/镍泡沫（OMC/G/Ni）复合材料. 其中,镍泡沫可以为复合材料提供具有高导电性和良好柔韧性的金属骨架,而具有垂直排列介孔阵列的有序介孔碳层为复合材料提供了高的电活性表面积,且有利于活性位点的暴露. 值得注意的是,夹在有序介孔碳层和镍泡沫之间的石墨烯极大地增强了各组分之间的相容性,有利于进一步提升复合材料的电化学性能. 作为电化学传感器中的工作电极,OMC/G/Ni体现出优异的多巴胺检测能力. 不但具有宽的线性检测范围（0.05 ~ 58.75 μmol·L^-1）和低检测限（0.019 μmol·L^-1）,还具有良好的选择性、重现性和稳定性. 此外,OMC/G/Ni在弯曲状态下依旧能够保持对多巴胺的高检测能力,证明了其在柔性生物传感器中的应用潜力.     

二氧化钛纳米颗粒/还原氧化石墨烯修饰玻碳电极在对硝基苯酚检测中的应用

本文报道了用二氧化钛纳米颗粒（TiO₂NPs）/还原氧化石墨烯（RGO）的复合物修饰玻碳电极检测微量对硝基苯酚（4-NP）的电化学方法. 本研究用扫描电子显微镜（SEM）对该复合材料形貌进行表征,用循环伏安法和交流阻抗谱对该复合物电极的电化学性能进行检测,表现出良好的电化学特性,采用差分脉冲伏安法对4-NP进行微量检测,结果令人满意,这主要得益于TiO2NPs/RGO复合物对4-NP有较高的催化活性,其电流峰值与浓度呈较高的线性关系,DPV的检测范围为10μmol·L^-1 ~ 350μmol·L^-1,检测限为0.13 μmol·L^-1. 与其他报道的一些电化学传感器相比,该传感器检测范围大,检测限低,且工作稳定,成本低,分析简单快速,具有很好的应用前景.     

A resistive-type humidity sensor using composite films prepared from poly(2-acrylamido-2-methylpropane sulfonate) and dispersed organic silicon sol

A composite material of dispersed organic silicon sol and poly(2-acrylamido-2-methylpropane sulfonate) (poly-AMPS) was used to make humidity sensor without protective film or complicated chemical procedures. The organic silicon sol was dispersed well in the poly-AMPS without using dispersion agent. Parameters that may affect the water-resistive but humidity-sensitive characteristic of composite material, the adding amount of organic silicon sol solution and the film of thermal treatment time, were investigated. The microstructure of the material was analyzed, and the humidity sensing and electrical properties of the sensor were measured. The sensor well responded to humidity with a relatively good linearity, though it depended on the applied frequency. The temperature influence between 15 and 35 °C was within −0.17 % relative humidity (RH)/°C in the range of 30–90% RH. The activation energy was maximum around 40% RH. The sensor showed the hysteresis within 5.9%, fast response time, long-term stability (75 days at least) and satisfactory resistance to high humidity atmosphere (97% RH) and chemical environment (20% C₂H₅OH vapor). Analyzing the structure and complex impedance plots of organic silicon sol/poly-AMPS was used to explain improvement in humidity sensing properties in comparison with nano-sized SiO₂ powder/poly-AMPS films.     

轮型多金属氧酸盐复合物膜的制备及在检测亚硝酸盐中的应用

利用自组装和电沉积交替的方法制备了基于磷钨酸盐K₂₈Li₅H₇P₈W₄₈O₁₈₄·92H₂O(P₈W₄₈)、 碳纳米管和Ni纳米颗粒的复合膜电极, 用于NO₂^- 的检测. 由于复合膜中P₈W₄₈, CNTs和Ni纳米颗粒3种活性成分的协同作用, 所制备的传感器表现出低的检出限、 宽的线性范围和较高的选择性. 将该传感器用于检测果汁中的NO₂^- , 所得到的回收率在允许的误差范围内. 这种复合膜电极传感器有望在实际应用中高度灵敏地检测NO₂^- .     

碘氧铋/二氧化钛纳米棒复合材料的制备及其对双酚A的光电化学检测

采用简易的两步水热法在FTO导电玻璃表面合成碘氧铋/二氧化钛纳米棒(BiOI/TiO₂ NRAs)复合材料。通过扫描电子显微镜、X射线单晶衍射仪对该复合材料进行了表征,基于电流-时间法考察了其光电化学行为。 BiOI的负载不仅成功地将TiO₂的光吸收范围拓展到可见光区,同时二者结合形成的p-n异质结构有效地促进光生电子空穴分离,增强了光催化能力。 基于该复合材料对双酚A的光催化氧化作用,建立了一种新型检测双酚A的方法。 结果表明,420 nm可见光激发下,利用电流-时间法,在外加偏压为0.0 V时,光电流密度与双酚A浓度在0.0047~14.7 μmol/L范围内呈线性关系,检测限为0.93 nmol/L(S/N=3)。 该传感器具有高的灵敏度、良好的稳定性及重现性,将其应用于塑料制品和牛奶中的双酚A检测,获得令人满意的结果,回收率为98.0%~107.1%。     

碱性橙Ⅱ印迹传感器的制备及其应用

以纳米石墨烯和纳米银作为修饰材料修饰工作电极,制备一种以碱性橙Ⅱ为模板分子,邻氨基苯酚和邻苯二胺为复合功能单体的新型快速检测碱性橙Ⅱ的印迹传感器。运用紫外光谱法选择最佳功能单体,并研究了模板分子与功能单体之间的作用形式和作用强度,采用电化学分析法优化各种制备条件,用甲醇?0.4 mol/L NaOH水溶液（体积比2∶1）洗脱模板分子,得到分子印迹电极,并对印迹电极的分析性能进行了研究。实验结果表明,该印迹传感器对碱性橙Ⅱ具有高选择性,样品加标平均回收率为88.45%～101.40%,相对标准偏差（RSD）在1.31%～2.83%之间（n=5）,线性范围为3.0×10^-9～5.0×10^-5 mol/L,检出限为1.0×10^-9 mol/L。该传感器成功应用于食品中碱性橙Ⅱ残留的快速检测。     

Ag/ZIF-90自组装薄膜的制备及SERS活性研究

合成了金属有机框架化合物沸石咪唑框架-90(ZIF-90)溶胶和ZIF-90晶体薄膜,分别以这2种材料为基底,制备出了Ag@ZIF-90复合材料和Ag/ZIF-90自组装薄膜。通过傅里叶变换红外(FT-IR),X射线衍射(XRD),扫描电子显微镜(SEM)对产物进行表征,分析了它们的形貌和结构特征。以罗丹明6G(R 6G)作为检测分子,对所制备材料的表面增强拉曼散射(SERS)性能进行测试。结果表明制备出的Ag/ZIF-90自组装薄膜具有好的SERS性能,而ZIF-90本身的拉曼峰并不会对Ag/ZIF-90自组装薄膜对目标分子的SERS检测效果产生影响。这种材料可以作为一种良好的SERS检测基底,在农药残留检测方面具有很好的应用前景。     

声表面波分子印迹技术检测甲基膦酸二甲酯的研究

以分子印迹(MIP)电聚合的成膜方法,在声表面波(SAW)双通道延迟线上制备了对甲基膦酸二甲酯(DMMP)有选择性的分子印迹薄膜(纳米级),并证实了分子印迹的明显效果,所研制的声表面波分子印迹传感器／(SAW—MIP)对甲基膦酸二甲酯的检出限为5mg／m^3。     

Ag/ZIF-90自组装薄膜的制备及SERS活性研究

合成了金属有机框架化合物沸石咪唑框架-90(ZIF-90)溶胶和ZIF-90晶体薄膜,分别以这2种材料为基底,制备出了Ag@ZIF-90复合材料和Ag/ZIF-90自组装薄膜.通过傅里叶变换红外(FT-IR),X射线衍射(XRD),扫描电子显微镜(SEM)对产物进行表征,分析了它们的形貌和结构特征.以罗丹明6G(R 6G)作为检测分子,对所制备材料的表面增强拉曼散射(SERS)性能进行测试.结果表明制备出的Ag/ZIF-90自组装薄膜具有好的SERS性能,而ZIF-90本身的拉曼峰并不会对Ag/ZIF-90自组装薄膜的SERS检测效果产生影响.这种材料可以作为一种较好的表面增强拉曼(SERS)活性基底,在农药残留检测方面具有很好的应用前景.     

POMs as Active Center for Sensitively Electrochemical Detection of Bisphenol A and Acetaminophen

A new type of electrochemical sensor based on multi-walled carbon nanotubes(MWCNTs), K2H4SiW11CuO39-6H2O(SiW11Cu) and gold nanoparticles(AuNPs) was prepared for the simultaneous detection of bisphenol A and acetaminophen. Differential pulse voltammetry(DPV), cyclic voltammetry(CV) and electrochemical impedance spectroscopy(EIS) were used for electrochemical characterization, and Fourier transfonn infrared spectroscopy(FTIR) was used to characterize the structure of polyoxometalates. Electrochemical experimental results show that the composite modified electrodes have good electrochemical activity as well as current response values of bisphenol A and acetaminophen when pH=7.0. At the same time, the modified electrode exhibits good stability and reproduction, and has good anti-interference ability to other substances. In practical application, the sensor obtained satisfactory results.     

Adsorption on carbon nanotubes studied using polarization-modulated infrared reflection-absorption spectroscopy

Single-wall carbon nanotubes (SWNTs), deposited onto an Al substrate from a liquid suspension, have been cleaned by annealing in ultrahigh vacuum. The effects of exposing the sample in situ to atomic H (or D) and/or to dimethyl methylphosphonate [DMMP, (CH(3)O)(2)(CH(3))P=O] were then studied using polarization-modulated infrared reflection-absorption spectroscopy. Atomic H reacts preferentially near strained or defective regions in the nanotube wall to produce a spectrum consistent with alkane-like species (>CH(2) and -CH(3)). Only a small fraction of the >C=C< sites in the nanotube wall react with H, and there is no clear evidence for monohydride >C(H)-C(H)< species. For DMMP, data were obtained under steady-state conditions in reagent pressures in excess of half the room-temperature vapor pressure. Adsorption occurs via the P=O group with a coverage that depends on the ambient pressure. Varying the DMMP coverage by changing the pressure causes changes in the spectrum that can be related to the strength of the DMMP/SWNT interaction. Preadsorbed H is seen to have little or no effect on the subsequent adsorption of DMMP. For DMMP, the molecular features are superimposed on a broad, smoothly varying background that can be related to adsorption-induced changes in the Drude parameters characterizing the SWNT free-carrier density and scattering lifetime.     

Gold nanoparticles-enhanced bisphenol A electrochemical biosensor based on tyrosinase immobilized onto self-assembled monolayers-modified gold electrode

A novel electrochemical sensor based on the immobilization of tyrosinase(tyr) onto gold nanoparticles(nano-Au) and thioctic acid amide(T-NH2) self-assembled monolayers(SAMs)-modified gold electrode has been developed for the determination of bisphenol A(BPA).It was found that the nano-Au could significantly enhance the electrochemical response of tyr/nano-Au/T-NH2/Au electrode to BPA,and the enhancement effect of nano-Au on the current response was also related to the enzyme.The results indicated that the biosensor could be used as a detector for BPA determination with a linear range from3.99 ×10-7mol/L to 2.34 ×10-4mol/L and a detection limit of 1.33×10-7mol/L.In addition,this biosensor showed good reproducibility.