Colorimetric sensor arrays for volatile organic compounds

The development of a low-cost, sensitive colorimetric sensor array for the detection and identification of volatile organic compounds (VOCs) is reported. Using an array composed of chemoresponsive dyes, enormous discriminatory power is possible in a simple device that can be imaged easily with an ordinary flatbed scanner. Excellent differentiation of closely related organic compounds can be achieved, and a library of 100 VOCs is presented. The array discriminates among VOCs by probing a wide range of intermolecular interactions, including Lewis acid/base, Br?nsted acid/base, metal ion coordination, hydrogen bonding, and dipolar interactions. Importantly, by proper choice of dyes and substrate, the array is essentially nonresponsive to changes in humidity.     

The function of a TiO2 compact layer in dye-sensitized solar cells incorporating "planar" organic dyes

We present a device based study into the operation of liquid electrolyte dye-sensitized solar cells (DSSC's) using organic dyes. We find that, for these systems, it is entirely necessary to employ a compact TiO2 layer between the transparent fluorine doped SnO2 (FTO) anode and the electrolyte in order to reduce charge recombination losses. By incorporation of a compact layer, the device efficiency can be increased by over 160% under simulated full sun illumination and more than doubled at lower light intensities. This is strong evidence that the more widely employed ruthenium based sensitizers act as to "insulate" the anode against recombination losses and that many planar organic dyes employed in DSSC's could greatly benefit from the use of a compact TiO2 blocking layer. This is in strong contrast to DSSC's sensitized with ruthenium based systems, where the introduction of compact TiO2 has only marginal effects on conversion efficiencies.     

Identification of yellow dye types in pre-columbian andean textiles

A number of pre-Columbian textiles, most discovered in northern Peru and dating to the Late Intermediate Period (ca. 1050-1200 AD), were analyzed by high-performance liquid chromatography with diode array and mass spectrometric detection (LC-DAD-MS), after extraction of the dyes with formic acid and methanol. The focus of this work was yellow dyes, most of which are present as glycosides of flavonoids and related compounds, with the objective of identifying the plants originally used for dyeing. Two major types of dyes were found in this set of specimens. The first type is characterized by the presence of flavonol 3-O-sulfates (never before reported as being present in dyes) and 3-O-glycosides; this type was probably derived from the plant Flaveria haumanii or a close relative. The second type is characterized by the presence of both chalcone (heretofore not reported in pre-Columbian textiles) and luteolin glycosides, though a specific plant source could not be identified. Two other yellow dye types appeared to be present, but there were not enough examples to allow conclusions to be drawn. Also present in some extracts were various hydroxybenzoic acids, which appear to be oxidation products of the respective unsubstituted flavonol (3-hydroxyflavone) dyes. Most yellow dyes are synthesized in plants as glycosides (or other derivatives), which are incorporated more or less intact into textile fibers during dyeing. Extraction of these derivatives and analysis by LC-DAD-MS yields distinctive profiles that, with appropriate plant reference materials, can aid in the identification of the original plant dyestuffs.     

Development of mild extraction methods for the analysis of natural dyes in textiles of historical interest using LC-diode array detector-MS

Analysis of dyes extracted from textiles of historical interest can give valuable information as to where, when, and how the textiles were made. The most widely used method for extraction of colorants involves heating with HCl, which frequently decomposes glycosidic dye components to their parent aglycons, with consequent loss of information about the source of the dye. This is particularly true for flavonoid dyes, many of which are glycosides. We have developed or improved upon two mild textile extraction methods that use ethylenediaminetetraacetic acid (EDTA) and formic acid and are efficient in extracting dyes, but preserve glycosidic linkages. The relative efficiencies of the HCl, EDTA, and formic acid extraction methods are compared by analyzing extracts of dyed samples of silk using HPLC coupled with diode array and mass spectrometric detection. HPLC profiles of EDTA or formic acid extracts of silk dyed, for example, with pagoda tree buds and onionskins are clearly distinguishable as to the plant material used, whereas profiles of HCl extracts are not. Thus, extraction of textiles with EDTA or formic acid reagents can yield significantly more information about the original dyestuff than can extraction with a strong acid.     

Effects of atmospheric ozone on microarray data quality

A data anomaly was observed that affected the uniformity and reproducibility of fluorescent signal across DNA microarrays. Results from experimental sets designed to identify potential causes (from microarray production to array scanning) indicated that the anomaly was linked to a batch process; further work allowed us to localize the effect to the posthybridization array stringency washes. Ozone levels were monitored and highly correlated with the batch effect. Controlled exposures of microarrays to ozone confirmed this factor as the root cause, and we present data that show susceptibility of a class of cyanine dyes (e.g., Cy5, Alexa 647) to ozone levels as low as 5-10 ppb for periods as short as 10-30 s. Other cyanine dyes (e.g., Cy3, Alexa 555) were not significantly affected until higher ozone levels (> 100 ppb). To address this environmental effect, laboratory ozone levels should be kept below 2 ppb (e.g., with filters in HVAC) to achieve high quality microarray data.     

Arrays and cascades of fluorescent liquid-liquid waveguides: broadband light sources for spectroscopy in microchannels

This paper describes the fabrication and operation of fluidic broadband light sources for use "on-chip" in integrated microanalytical systems. These light sources consist of liquid-core, liquid-cladding (L2) microchannel waveguides with liquid cores containing fluorescent dyes, excited by incident light from an external halogen bulb. Simultaneous use of multiple fluorophores in a common solution, in a single L2 light source, is not possible, because energy transfer from fluorophores emitting at shorter wavelength to fluorophores emitting at longer wavelength is essentially complete. Two approaches circumvent this problem of energy transfer; both use spatial separation of the fluorophores in different streams. The first setup uses a cascade (series) of single-core, single-dye light sources of increasing absorption energy to generate a combined broadband output. The second approach uses a parallel array of single-core, single-dye light sources. The spectral content of the light output for both cascade and array light sources can be controlled through choice of flow rates and dyes. Output intensity from these light sources is comparable to standard fiber-optic spectrophotometer light sources. The paper also discusses the efficiency of energy transfer between parallel liquid cores as a function of the fluid medium (index of refraction, path length, and rate of flow).     

Solar/UV-induced photocatalytic degradation of three commercial textile dyes.

The photocatalytic degradation of three commercial textile dyes with different structure has been investigated using TiO(2) (Degussa P25) photocatalyst in aqueous solution under solar irradiation. Experiments were conducted to optimise various parameters viz. amount of catalyst, concentration of dye, pH and solar light intensity. Degradation of all the dyes were examined by using chemical oxygen demand (COD) method. The degradation efficiency of the three dyes is as follows: Reactive Yellow 17(RY17) > Reactive Red 2(RR2) > Reactive Blue 4 (RB4), respectively. The experimental results indicate that TiO(2) (Degussa P25) is the best catalyst in comparison with other commercial photocatalysts such as, TiO(2) (Merck), ZnO, ZrO(2), WO(3) and CdS. Though the UV irradiation can efficiently degrade the dyes, naturally abundant solar irradiation is also very effective in the mineralisation of dyes. The comparison between thin-film coating and aqueous slurry method reveals that slurry method is more efficient than coating but the problems of leaching and the requirement of separation can be avoided by using coating technique. These observations indicate that all the three dyes could be degraded completely at different time intervals. Hence, it may be a viable technique for the safe disposal of textile wastewater into the water streams.     

Matrix Discriminant Analysis With Application to Colorimetric Sensor Array Data

With the rapid development of nano-technology, a “colorimetric sensor array” (CSA) that is referred to as an optical electronic nose has been developed for the identification of toxicants. Unlike traditional sensors that rely on a single chemical interaction, CSA can measure multiple chemical interactions by using chemo-responsive dyes. The color changes of the chemo-responsive dyes are recorded before and after exposure to toxicants and serve as a template for classification. The color changes are digitalized in the form of a matrix with rows representing dye effects and columns representing the spectrum of colors. Thus, matrix-classification methods are highly desirable. In this article, we develop a novel classification method, matrix discriminant analysis (MDA), which is a generalization of linear discriminant analysis (LDA) for the data in matrix form. By incorporating the intrinsic matrix-structure of the data in discriminant analysis, the proposed method can improve CSA’s sensitivity and more importantly, specificity. A penalized MDA method, PMDA, is also introduced to further incorporate sparsity structure in discriminant function. Numerical studies suggest that the proposed MDA and PMDA methods outperform LDA and other competing discriminant methods for matrix predictors. The asymptotic consistency of MDA is also established. R code and data are available online as supplementary material.     

Trace-fiber color discrimination by electrospray ionization mass spectrometry: a tool for the analysis of dyes extracted from submillimeter nylon fibers

The application of electrospray ionization mass spectrometry (ESI-MS) to trace-fiber color analysis is explored using acidic dyes commonly employed to color nylon-based fibers, as well as extracts from dyed nylon fibers. Qualitative information about constituent dyes and quantitative information about the relative amounts of those dyes present on a single fiber become readily available using this technique. Sample requirements for establishing the color identity of different samples (i.e., comparative trace-fiber analysis) are shown to be submillimeter. Absolute verification of dye mixture identity (beyond the comparison of molecular weights derived from ESI-MS) can be obtained by expanding the technique to include tandem mass spectrometry (ESI-MS/MS). For dyes of unknown origin, the ESI-MS/MS analyses may offer insights into the chemical structure of the compound-information not available from chromatographic techniques alone. This research demonstrates that ESI-MS is viable as a sensitive technique for distinguishing dye constituents extracted from a minute amount of trace-fiber evidence. A protocol is suggested to establish/refute the proposition that two fibers--one of which is available in minute quantity only--are of the same origin.     

Extending the longevity of fluorescence-based sensor arrays using adaptive exposure

Fluorescent microbead sensor arrays were prepared to determine sensor array longevity. Sensor longevity is limited by photobleaching of the dyes attached to the microbeads and presents one of the biggest drawbacks of most fluorescent dye-based arrays. Responses of an array of organic vapor sensors were acquired for 2 weeks to evaluate the sensor performance over time. Photobleaching effects were overcome in two ways: (1) by limiting the excitation light power and gradually increasing the power at a rate comparable to the sensor photobleaching rates and (2) by illuminating subsections of the array through an optical slit. Both approaches extended the longevity of a sensor array. During the longevity study, the sensor arrays were employed to test their ability to correctly distinguish between responses to seven vapors. A high classification accuracy (99.8%) was obtained after 17,700 exposures for vapor responses collected over two weeks using only approximately 8% of the array's surface area.     

头发中9种碱性染料的HPLC-DAD检测方法

文中建立了HPLC-DAD同时测定头发中碱性橙31等9种碱性染料的方法。方法以甲醇为提取溶剂,采用xB—c18柱,以乙腈-0．02mol／L乙酸铵（含0．05％甲酸）为流动相进行梯度洗脱,二极管阵列检测器检测。试验的平均回收率为93．9％～102．5％,相对标准偏差为1．2％～3．5％,最低检测浓度为0．15～0．60mg／kg。结果表明该方法前处理简单、快速,适用于测定头发中碱性橙3l等9种碱性染料组分的含量。     

Capillary Assembly of Liquid Particles

Capillary assembly is a versatile method for depositing colloidal particles within templates, resulting in nano/microarrays and colloidal superstructures for optical, plasmonic, and sensory applications. Liquid particles (LPs), comprised of oligomerized 3‐(trimethoxysilyl)propyl methacrylate, are herein shown to deposit into patterned cavities via capillary assembly. In contrast to solid colloids, LPs coalesce upon solvent evaporation and assume the geometry of the template. Incorporating small molecules such as dyes followed by LP solidification generates fluorescent polymer microarrays of any geometry. The LP size is inversely proportional to the quantity of deposited material and the convexity of the final polymer array. Cavity filling can be tuned by increasing the assembly temperature. Extraction of the polymerized regions produces solidified particles with faceted shapes including square prisms, trapezoids, and ellipsoids with sizes up to 14 µm that retain the shape of the cavity in which they are initially held. LP deposition thus presents a highly controllable fabrication scheme for geometrically diverse polymer microarrays and anisotropic colloids of any conceivable polygonal shape due to space filling of the template. The extension of capillary assembly to LPs that can be doped with small molecule dyes and analytes invaluably expands the synthetic toolbox for top‐down, scalable, hierarchically engineered materials.     

Development of a microchamber array for picoliter PCR

A microchamber array for PCR was developed by semiconductor microfabrication technology. The microchambers were designed to be of picoliter quantity. To optimize fluid retention, the surface states of the substrate and the inner walls were examine for four different types of microchamber. The substrate was silicon, while silicon dioxide was selected for the inner walls. PCR was performed in the microchamber array, and the amplification of DNA was detected using a technique based on the energy transfer of fluorescent dyes. The lower volume limit for PCR was investigated using various sizes of microchambers. Microchambers with volume greater than 86 pL gave successful PCR. In addition, the system was improved in order to take up the PCR product. To prevent mixing of the samples, the samples were dried after PCR using a membrane that permeates only vapor.     

A real-time ratiometric method for the determination of molecular oxygen inside living cells using sol-gel-based spherical optical nanosensors with applications to rat C6 glioma

The first sol-gel-based, ratiometric, optical nanosensors, or sol-gel probes encapsulated by biologically localized embedding (PEBBLEs), are made and demonstrated here to enable reliable, real-time measurements of subcellular molecular oxygen. Sensors were made using a modified St?ber method, with poly(ethylene glycol) as a steric stabilizer. The radii of these spherical PEBBLE sensors range from about 50 to 300 nm. These sensors incorporate an oxygen-sensitive fluorescent indicator, Ru(II)-tris(4,7-diphenyl-1,10-phenanthroline) chloride ([Ru(dpp)3]2+), and an oxygen-insensitive fluorescent dye, Oregon Green 488-dextran, as a reference for the purpose of ratiometric intensity measurements. The PEBBLE sensors have excellent reversibility, dynamic range, and stability to leaching and photobleaching. The small size and inert matrix of these sensors allow them to be inserted into living cells with minimal physical and chemical perturbations to their biological functions. Applications of sol-gel PEBBLEs inserted in rat C6 glioma cells for real-time intracellular oxygen analysis are demonstrated. Compared to using free dyes for intracellular measurements, the PEBBLE matrix protects the fluorescent dyes from interference by proteins in cells, enabling reliable in vivo chemical analysis. Conversely, the matrix also significantly reduces the toxicity of the indicator and reference dyes to the cells, so that a wide variety of dyes can be used in optimal fashion.     

The effectiveness of the exciton mechanism in superconducting layered compounds

The excitonic interaction resulting from an array of adsorbed dyes on a plane conducting metallic sheet is considered. We show that only with the appropriate choice of dye and with certain constraints on the structure and properties of the metallic system can this interaction be strong enough to influence the superconducting properties of the sheet.     

Nanodroplet‐Containing Polymers for Efficient Low‐Power Light Upconversion

Sensitized triplet–triplet‐annihilation‐based photon upconversion (TTA‐UC) permits the conversion of light into radiation of higher energy and involves a sequence of photophysical processes between two dyes. In contrast to other upconversion schemes, TTA‐UC allows the frequency shifting of low‐intensity light, which makes it particularly suitable for solar‐energy harvesting technologies. High upconversion yields can be observed for low viscosity solutions of dyes; but, in solid materials, which are better suited for integration in devices, the process is usually less efficient. Here, it is shown that this problem can be solved by using transparent nanodroplet‐containing polymers that consist of a continuous polymer matrix and a dispersed liquid phase containing the upconverting dyes. These materials can be accessed by a simple one‐step procedure that involves the free‐radical polymerization of a microemulsion of hydrophilic monomers, a lipophilic solvent, the upconverting dyes, and a surfactant. Several glassy and rubbery materials are explored and a range of dyes that enable TTA‐UC in different spectral regions are utilized. The materials display upconversion efficiencies of up to ≈15%, approaching the performance of optimized oxygen‐free reference solutions. The data suggest that the matrix not only serves as mechanically coherent carrier for the upconverting liquid phase, but also provides good protection from atmospheric oxygen.     

Molecular Design, Characterization, and Application of Multiinformation Dyes for Multidimensional Optical Chemical Sensings. 2. Preparation of the Optical Sensing Membranes for the Simultaneous Measurements of pH and Water Content in Organic Media

Optical chemical sensing of pH and water content in organic solvents is proposed, using multiinformation dyes (MIDs) based on the support matrixes for the dyes. In this investigation, four kinds of merocyanine-type dyes having a polymerizable olefin unit as the MIDs were synthesized. These dyes were copolymerized with hydrophilic monomer molecules to obtain dye-immobilized optical chemical sensor (optode) membranes. In this case, selection of the monomer molecule gave optode membranes having different color change properties, because different monomer molecules provided different chemical environments around the immobilized dye. These optode membranes were used for the measurement of pH and water content in organic solvents. These membranes offered two-dimensional sensing information in one spectrum when they were employed for water content sensing in organic solvents, in which the maximum wavelength represents the water content and the absorbance at this wavelength represents the pH of the water present. These polymer membranes have a long lifetime, which can be adequate for practical use.     

Photoactive curcumin-derived dyes with surface anchoring moieties used in ZnO nanoparticle-based dye-sensitized solar cells

Photoactive, eco-friendly and high molar extinction coefficient, curcumin-derived dyes (BCMoxo and BCtCM) have been explored in ZnO nanoparticles (NPs)-based dye-sensitized solar cells (DSSCs). The boron complex curcumin dyes modified with di-carboxylic anchor groups (BCtCM) provided surface attachment with a strong UV–vis region absorption than the dye molecule without anchor groups (BCMoxo). Photoanodes primed with poly-dispersive ZnO NPs (∼80–50 nm) specifically devised for these dyes and optimized for the critical thickness, sensitization time and concentration using a solvent-free ionic electrolyte so as to get current density as high as 1.66 mA/cm² under 80 mW/cm² irradiation. Therefore, a successful conversion of visible light into electricity by using these curcumin-derived dyes (natural derived photoactive molecules) as photosensitizer in DSSCs would be a great interest in future studies for enhancing further conversion efficiencies.     

Multicolor FRET silica nanoparticles by single wavelength excitation

Fluorescent nanoparticles with multiple emission signatures by a single wavelength excitation are needed in multiplex bioanalysis and molecular imaging. We have prepared silica nanoparticles encapsulated with three organic dyes using a modified St?ber synthesis method. By varying the doping ratio of the three tandem dyes, fluorescence resonance energy transfer (FRET)-mediated emission signatures can be tuned to have the nanoparticles exhibit multiple colors under one single wavelength excitation. These nanoparticles are intensely fluorescent, highly photostable, uniform in size, and biocompatible. The acceptor emission of the FRET nanoparticles has generated a large Stokes shift, which implicates broad applications in biological labeling and imaging. Molecular recognition moieties, such as biotin, can be covalently attached to the nanoparticle surface to allow for specific binding to target molecules. These multicolor FRET silica nanoparticles can be used as barcoding tags for multiplexed signaling. By using these NPs, one can envision a dynamic, multicolor, colocalization methodology to follow proteins, nucleic acids, molecular machines, and assemblies within living systems.     

High-efficiency fast scintillators for "optical" soft x-ray arrays for laboratory plasma diagnostics

Scintillator-based "optical" soft x-ray (OSXR) arrays have been investigated as a replacement for the conventional silicon (Si)-based diode arrays used for imaging, tomographic reconstruction, magnetohydrodynamics, transport, and turbulence studies in magnetically confined fusion plasma research. An experimental survey among several scintillator candidates was performed, measuring the relative and absolute conversion efficiencies of soft x rays to visible light. Further investigations took into account glass and fiber-optic face-plates (FOPs) as substrates, and a thin aluminum foil (150 nm) to reflect the visible light emitted by the scintillator back to the optical detector. Columnar (crystal growth) thallium-doped cesium iodide (CsI:Tl) deposited on an FOP, was found to be the best candidate for the previously mentioned plasma diagnostics. Its luminescence decay time of the order of approximately 1-10 micros is thus suitable for the 10 micros time resolution required for the development of scintillator-based SXR plasma diagnostics. A prototype eight channel OSXR array using CsI:Tl was designed, built, and compared to an absolute extreme ultraviolet diode counterpart: its operation on the National Spherical Torus Experiment showed a lower level of induced noise relative to the Si-based diode arrays, especially during neutral beam injection heated plasma discharges. The OSXR concept can also be implemented in less harsh environments for basic spectroscopic laboratory plasma diagnostics.