Luminescence Quenching Behavior of Oxygen Sensing ORMOSIL Films Based on Ruthenium Complex

An organically modified silicate(ORMOSIL) based optical sensor response to gaseous O2 or O2 dissolved in water is presented. The oxygen sensing film mechanism is based on the principle of fluorescence quenching of tris(4,7-diphenyl-l , 10-phenanthroline) ruthenium ( ) ([Ru(dpp)3]2+), which has been entrapped in a porous ORMOSIL film. In order to establish optimum film-processing parameters, comprehensive investigations, including the effects of the polarity and the hydrophobicity of the sensing film on oxygen quenching response and response time, were carried out. The film hydrophobicity increased as a function of dimethyl-dimethoxysilane (DiMe-DMOS) content, which is correlated with enhanced oxygen sensor performance. The sensor developed in the present work exhibits the advantages of fast response time and good reversibility. The detection limits are 0. 5 % and 0. 3 g/mL for O2 in the gaseous and the aqueous phases, respectively.     

Development of an integrated microfluidic platform for dynamic oxygen sensing and delivery in a flowing medium

This paper describes a platform for real-time sensing of dissolved oxygen in a flowing microfluidic environment using an oxygen-sensitive luminescent dye (platinum octaethylporphyrin ketone) integrated into a micro-oxygenator device. Using a phase-based detection method, the luminescent decay lifetime of the dye was consistent with the linear Stern-Volmer relationship using both gaseous and aqueous samples. Maximum sensor resolution varied between 120-780 ppb across a range of dissolved oxygen (DO) concentrations ranging from 0-42.5 ppm. The sensor was subsequently used to determine the convective mass-transfer characteristics of a multi-layer polydimethylsiloxane (PDMS) microfluidic oxygenator. The membrane-based oxygenator showed excellent agreement with an analytical convection model, and the integrated oxygen sensor was accurate across a wide range of tested flow rates (0.05-5 mL min(-1)). The device is unique for its ease of fabrication and highly flexible configuration, as well as the novel incorporation of oxygen delivery and detection in a single micro-device. Potential applications include tissue engineering, cell culturing, and miniaturized bio-assays that require the delivery and/or detection of precise quantities of oxygen within a microfluidic construct.     

An integrated optical oxygen sensor fabricated using rapid-prototyping techniques

This paper details the design and fabrication of an integrated optical biochemical sensor using a select oxygen-sensitive fluorescent dye, tris(2,2'-bipyridyl) dichlororuthenium(ii) hexahydrate, combined with polymeric waveguides that are fabricated on a glass substrate. The sensor uses evanescent interaction of light confined within the waveguide with the dye that is immobilized on an SU-8 waveguide surface. Adhesion of the dye to the integrated waveguide surface is accomplished using a unique process of spin-coating/electrostatic layer-by-layer formation. The SU-8 waveguide was chemically modified to allow the deposition process. Exposure of the dye molecules to the analyte and subsequent chemical interaction is achieved by directly coupling the fluid channel to the integrated waveguide. The completed sensor was linear in the dissolved oxygen across a wide range of interest and had a sensitivity of 0.6 ppm. A unique fabrication aspect of this sensor is the inherent simplicity of the design, and the resulting rapidity of fabrication, while maintaining a high degree of functionality and flexibility.     

八乙基卟啉膜/K~+交换玻璃光波导传感器的制备及对甲胺的气敏性研究

利用旋转-甩涂法(Spin-coating)将八乙基卟啉固定在K+交换玻璃光波导表面,制成八乙基卟啉膜/K+交换玻璃光波导敏感元件。利用该敏感元件考察不同有机挥发性气体的响应,同时优化了敏感元件的制备条件。结果表明,该敏感元件对甲胺具有较高的灵敏度,检出限(信噪比S/N=5.1)为1.0×10-8V/V0,响应时间为1.2 s,恢复时间为2.3 s,在平行试验中,其结果具有良好的线性关系,相对标准偏差为1.1%,证明了该元件对甲胺气体检测的准确性。     

Photochemical behaviour upon the inclusion for some volatile organic compounds in new fluorescent indolizine β-cyclodextrin sensors

The potentialities of three new fluorescent indolizine modified β-cyclodextrin have been investigated as molecular chemosensors. The pyridin-4-ylindolizine β-cyclodextrin derivatives were synthesised by an amidation between the fluorescent indolizine derivatives and 6-deoxy-6-amino-β-cyclodextrin. The multiconformational search by MM3 and AM1 method in gaseous state and in water respectively suggest the “open cavity” structure as the most probable. These compounds have been characterised spectroscopically by their emission spectra and their sensing ability towards 1-adamantanol, phenol and p-cresol. The fluorescent properties and sensitivity factor of the sensor containing an indolizine product with a perfluored aromatic fragment recommended it fairly as sensor for the detection of volatile organic compounds (VOCs), while the other two sensors, with an aliphatic fragment, can be utilised as biological markers. Finally, a significant bathochromic shift is observed for the sensor containing a t-butyl fragment, in such a way that this sensor may also lead to the detection of VOCs.     

Nitric oxide turn-on fluorescent probe based on deamination of aromatic primary monoamines

The stable, water-soluble, and nonfluorescent FA-OMe can sense nitric oxide (NO) and form the intensely fluorescent product dA-FA-OMe via reductive deamination of the aromatic primary amine. The reaction is accompanied by a notable increase of the fluorescent quantum yield from 1.5 to 88.8%. The deamination mechanism of FA-OMe with NO was proposed in this study. The turn-on fluorescence signals were performed by suppression of photoinduced electron transfer (PeT), which was demonstrated by density functional theory (DFT) calculations of the components forming FA-OMe and dA-FA-OMe. Furthermore, FA-OMe showed water solubility and good stability at physiological pHs. Moreover, the selectivity study indicated that FA-OMe had high specificity for NO over other reactive oxygen/nitrogen species. In an endogenously generated NO detection study, increasing the incubation time of FA-OMe with lipopolysaccharide (LPS) pretreated Raw 264.7 murine macrophages could cause an enhanced fluorescence intensity image. In addition, a diffusion/localization cell imaging study showed that FA-OMe could be trapped in Raw 264.7 cells. These cell imaging results demonstrated that FA-OMe could be used as a turn-on fluorescent sensor for the detection of endogenously generated NO.     

Starch-iodine films respond to water vapor

Starch-iodine indicator films were found to have useful spectroscopic properties for the detection of water vapor. The large colorimetric response of these easily prepared films was easily detected by the absorption of 632.8 nm HeNe laser light, using a planar integrated optical waveguide (IOW) platform. The detection limit of a prototype sensor was found to be below 5% relative humidity (RH), with response times of the order of seconds.     

Multi-element optical waveguide sensor: General concept and design

A prototype of a self-contained multi-element optical waveguide sensor for detection and identification of the constituents of gaseous or liquid mixtures has been fabricated. The device consists of eight optical waveguides, each coated with a thin film known to react specifically with one or more components in a multicomponent system. An array of eight sequentially-activated light-emitting diodes is attached to the waveguide assembly in such a fashion as to activate each detection channel separately. Each waveguide is a fiber-optic coupled to a single high-gain, low-noise photomultiplier tube or photodiode/operational amplifier detector. The amplified signals can be displayed visually or input to a microprocessor pattern-recognition algorithm. CMOS analog switches/multiplexers are used in feedback loops to control automatic gain-ranging, light-level adjustment and channel-sequencing. Preliminary experiments involving the monitoring of redox/pH changes are discussed.     

氧化锌薄膜/锡掺杂玻璃光波导元件及其对氯苯的气敏性研究

建立了玻璃光波导气敏元件检测氯苯气体的方法.采用浸渍-提拉法将ZnO敏感膜固定在锡掺杂玻璃光波导表面,研制出了检测氯苯气体的ZnO薄膜/锡掺杂玻璃光波导气敏元件,并用该玻璃光波导气敏元件对挥发性有机气体进行了检测.实验结果表明,在室温下,气敏元件对氯苯气体有明显的响应,而对相同浓度的其它挥发性有机气体的响应相对较小,对...     

Microfluidic sorting system based on optical waveguide integration and diode laser bar trapping

Effective methods for manipulating, isolating and sorting cells and particles are essential for the development of microfluidic-based life science research and diagnostic platforms. We demonstrate an integrated optical platform for cell and particle sorting in microfluidic structures. Fluorescent-dyed particles are excited using an integrated optical waveguide network within micro-channels. A diode-bar optical trapping scheme guides the particles across the waveguide/micro-channel structures and selectively sorts particles based upon their fluorescent signature. This integrated detection and separation approach streamlines microfluidic cell sorting and minimizes the optical and feedback complexity commonly associated with extant platforms.     

A novel detector using a fluorescent sensor array and discrimination of pesticides

A novel, simple, and rapid detector using a fluorescent sensor array for discrimination and quantification of different concentrations (ppb level) of pesticides was proposed in this paper. Employing porphyrin, porphyrin derivatives, and chemically responsive dyes as the sensing elements, the developed sensor array based on a cross-responsive mechanism showed a unique pattern of fluorescence changes upon the reaction that lasted just 10 min. The eigenvalues from raw fluorescence spectra were analyzed via a pattern recognition algorithm, including hierarchical cluster analysis (HCA), principal component analysis (PCA), and back-propagation neural network (BPNN). The results showed that HCA, which were used to assess the feasibility and effectiveness of discrimination of the fluorescent sensor array, revealed a distinct separation between different pesticides. PCA and BPNN were used for automatically predicting the concentration of pesticides, and the recovery was 91.29–109.81 % while the lowest relative standard deviation was up to 3.12 %. It indicates a detector based on the fluorescent sensor array is a rapid and feasible sensing platform for the discrimination and quantitative analysis of pesticides, and also shows the possibilities in the related fields of pesticides identification and detection.     

An integrated optical leaky waveguide sensor with electrically induced concentration system for the detection of bacteria

An integrated, sensitive and rapid system was developed for the detection of bacteria. The system combined an optical metal-clad leaky waveguide (MCLW) sensor with an electric field. The electric field was used to concentrate Bacillus subtilis var. niger(BG) bacteria spores onto the immobilized anti-BG antibody on the MCLW sensor surface. This sensor combination has been characterised by detecting the scattering from bacterial spores, which are concentrated at the sensor surface, when they are illuminated at the coupling angle; and by detection of fluorescence from labelled antibodies added after the spores had been captured on the surface. The light scattering and fluorescence detection methods gave a detection limit of BG bacterial spores of 1 x 10(3) spores ml(-1) when the electric field was applied for 3 minutes.     

Sol-gel based optical carbon dioxide sensor employing dual luminophore referencing for application in food packaging technology

An optical sensor for the measurement of carbon dioxide in Modified Atmosphere Packaging (MAP) applications has been developed. It is based on the fluorescent pH indicator 1-hydroxypyrene-3,6,8-trisulfonate (HPTS) immobilised in a hydrophobic organically modified silica (ormosil) matrix. Cetyltrimethylammonium hydroxide was used as an internal buffer system. Fluorescence is measured in the phase domain by means of the Dual Luminophore Referencing (DLR) sensing scheme which provides many of the advantages of lifetime-based fluorometric sensors and makes it compatible with established optical oxygen sensor technology. The long-term stability of the sensor membranes has been investigated. The sensor displays 13.5 degrees phase shift between 0 and 100% CO2 with a resolution of better than 1% and a limit of detection of 0.08%. Oxygen cross-sensitivity is minimised (0.6% quenching in air) by immobilising the reference luminophore in polymer nano-beads. Cross-sensitivity towards chloride and pH was found to be negligible. Temperature effects were studied, and a linear Arrhenius correlation between ln k and 1/T was found. The sensor is stable over a period of at least seven months and its output is in excellent agreement with a standard reference method for carbon dioxide analysis.     

Fluorescent Determination of Mercury(II) Using Rhodamine B Immobilized on Polystyrene Microspheres

A novel microsphere-based fluorescent sensor 1 for determination of Hg(II) in food samples has been successfully synthesized and its fluorescent sensing properties were investigated in detail. Polystyrene microsphere was innovatively surface modified by a rhodamine derivative; therefore sensor 1 was a fluorescent sensor with high polymer material properties of polystyrene and the optical properties of a fluorescent probe. Sensor 1 displayed high selectivity, good anti-interference performance, and instantaneous response to Hg(II). The fluorescence intensity of sensor 1 showed a linear response to Hg(II) in the concentration range of 0?µM to 8?µM with a detection limit of 0.439?µM. The most valuable advantage was that sensor 1 was recyclable and environmentally-friendly. This proposed sensor 1 was applied to monitor the content of Hg(II) in real food samples, such as tap water, rice, and anglerfish. The recovery range of tap water was from 92.60 to 105.80%, the recovery range of rice was from 90.45 to 106.10%, and the recovery range of anglerfish was from 91.30 to 105.84%. The relative error was below 10% in spiked recovery studies, suggesting that fluorescent sensor 1 provides a simple, efficient, and promising method for determination of Hg(II) in complex matrices.     

DNA-directed protein immobilization on mixed self-assembled monolayers via a streptavidin bridge

The simultaneous detection of multiple analytes is an important consideration for the advancement of biosensor technology. Currently, few sensor systems possess the capability to accurately and precisely detect multiple antigens. This work presents a simple approach for the functionalization of sensor surfaces suitable for multichannel detection. This approach utilizes self-assembled monolayer (SAM) chemistry to create a nonfouling, functional sensor platform based on biotinylated single-stranded DNA immobilized via a streptavidin bridge to a mixed SAM of biotinylated alkanethiol and oligo(ethylene glycol). Nonspecific binding is minimized with the nonfouling background of the sensor surface. A usable protein chip is generated by applying protein-DNA conjugates which are directed to specific sites on the sensor chip surface by utilizing the specificity of DNA hybridization. The described platform is demonstrated in a custom-built surface plasmon resonance biosensor. The detection capabilities of a sensor using this protein array have been characterized using human chorionic gonadotropin (hCG). The platform shows a higher sensitivity in detection of hCG than that observed using biotinylated antibodies. Results also show excellent specificity in protein immobilization to the proper locations in the array. The vast number of possible DNA sequences combine with the selectivity of base-pairing makes this platform an excellent candidate for a sensor capable of multichannel protein detection.     

Filter-free integrated sensor array based on luminescence and absorbance measurements using ring-shaped organic photodiodes

An optical waveguiding sensor array featuring monolithically integrated organic photodiodes as integrated photo-detector, which simplifies the readout system by minimizing the required parts, is presented. The necessity of any optical filters becomes redundant due to the proposed platform geometry, which discriminates between excitation light and sensing signal. The sensor array is capable of measuring luminescence or absorption, and both sensing geometries are based on the identical substrate. It is demonstrated that background light is virtually non-existent. All sensing and waveguide layers, as well as in- and out-coupling elements are assembled by conventional screen-printing techniques. Organic photodiodes are integrated by layer-by-layer vacuum deposition onto glass or common polymer foils. The universal and simple applicability of this sensor chip is demonstrated by sensing schemes for four different analytes. Relative humidity, oxygen, and carbon dioxide are measured in gas phase using luminescence-based sensor schemes; the latter two analytes are also measured by absorbance-based sensor schemes. Furthermore, oxygen and pH in aqueous media were enabled. The consistency of calibration characteristics extending over different sensor chips is verified.

Patterning, integration and characterisation of polymer optical oxygen sensors for microfluidic devices

This paper describes a process for the layer-by-layer fabrication and integration of luminescent dye-based optical oxygen sensors into microfluidic devices. Application of oxygen-sensitive platinum(ii) octaethylporphyrin ketone fluorescent dye dissolved in polystyrene onto glass substrates by spin-coating was studied. Soft lithography with polydimethylsiloxane (PDMS) stamps and reactive ion etching in oxygen plasma were used to produce sensor patterns with a minimum feature size of 25 microm. Sensors patterns were integrated into a PDMS microfluidic device by plasma bonding. No degradation of the sensor response as a result of the lithography and pattern-transfer processes was detected. Gaseous and dissolved oxygen (DO) detection was characterised using fluorescence microscopy. The intensity signal ratio of the sensor films was found to increase almost two-fold from 3.6 to 6.8 by reducing film thickness from 1.3 microm to 0.6 microm. Calibration of DO measurement showed linear Stern-Volmer behaviour that was constant for flow rates from 0.5 to 2 mL min(-1). The calibrated sensors were subsequently used to demonstrate laterally resolved detection of oxygen inside a microfluidic channel. The fabrication process provides a novel, easy to use method for the repeatable integration of optical oxygen sensors into cell-culture and lab-on-a-chip devices.     

Detection of Exhaled Volatile Organic Compounds Improved by Hollow Nanocages of Layered Double Hydroxide on Ag Nanowires

To detect biomarkers from human exhalation, air flow dynamics on the nanoparticle surface were explored by a surface‐enhanced Raman scattering (SERS) sensor. A hollow Co‐Ni layered double hydroxide (LDH) nanocage on Ag nanowires (Ag@LDH) was prepared. Ag nanowires provided amplified Raman signals for trace determination; hollow LDH nanocages served as the gaseous confinement cavity to improve capture and adsorption of gaseous analytes. The Raman intensity and logarithmic analyte concentration exhibit an approximately linear relationship; the detection limit of SERS sensors for aldehyde is 1.9×10^?9 v/v (1.9 ppb). Various aldehydes in mixed mimetic gas are distinguished by Raman spectra statistical analysis assisted by multivariate methods, including principal component analysis and hierarchical cluster analysis. The information was recorded in a barcode, which can be used for the design and development of a desktop SERS sensor analysis system for large‐scale lung cancer detection.     

A water-soluble, small molecular fluorescent sensor with femtomolar sensitivity for zinc ion

A water-soluble fluorescent sensor, 1, based on the quinoline platform, demonstrates femtomolar sensitivity for zinc ion with a 14-fold enhanced quantum yield upon chelation to zinc ion and also exhibits high selectivity to zinc ion over other physiological relevant divalent metals in the presence of EDTA. X-ray crystal structure of zinc complex reveals that an acetic carboxylic group participates in coordination, which significantly enhances the affinity of 1 for zinc ion.     

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%。