Supramolecular Chemistry Approach To The Design Of A High-resolution Sensor Array For Multianion Detection In Water

Reliable sensing of structurally similar anions in water is a difficult problem, and analytical tests and sensor devices for reliable sensing of multiple anions are very rare. This study describes a method for fabrication of simple colorimetric array-based assays for aqueous anion solutions, including complex analytes encountered in real-life applications. On the fundamental level, this method shows how the discriminatory capacity of sensor arrays utilizing pattern recognition operating in multianalyte environments may be dramatically improved by employing two key features. The synergy between the sensor and hydrogel host resembles the cooperative effects of an apoenzyme and cofactor: the host hydrogel helps extract the target anions from the bulk analyte while stripping the solvate molecules off the anions. In addition, the supramolecular studies of the affinity and selectivity of the potential sensors for target analytes allow for constructing an array predesigned for a particular analyte. To illustrate both aspects, an eight-sensor array utilizing colorimetric sensor materials showing selectivity for fluoride and pyrophosphate while displaying significant cross-reactivity for other anions such as carboxylates, phosphate, or chloride was used to differentiate between 10 anions. The quantitative analyses were also performed to show that the eight-sensor array was found to operate across 4 orders of magnitude concentrations (0.20-360 ppm; 10 mu M to 20 mM). The applicability of this approach was demonstrated by analyzing several toothpaste brands. The toothpastes are complex analytes comprising both known and unknown anions in various concentrations. The fluoride-selective yet cross-reactive array is shown to utilize the fluoride content as the main differentiating factor while using the remaining anionic components for further differentiation between toothpaste brands

Benzothiadiazoles And Dipyrrolyl Quinoxalines With Extended Conjugated Chromophores-fluorophores And Anion Sensors

Stable fluorescent chromophores find use in a growing number of practical applications, including their utility as laser dyes,1 emitters in light-emitting diodes,2 photoconductors,3 optical data storage,4 and optical switches.5 Stable fluorophores with high quantum yields are widely used in fluorescent sensors6 and labels.7 These became very popular lately, owing to their potential for high sensitivity at low concentration coupled with decreased cost of the required equipment.8 Recently, we have described a new class of fluorescent anion sensors bearing extended conjugated chromophores9 with incorporated 2,3-di(1H-2-pyrrolyl)quinoxaline, (DPQ), as the anion recognition element.10 Literature shows that DPQ binds anions via hydrogen bonding between pyrrole NH and anions, the hydrogen bonding nature of the DPQ−anion complex was demonstrated by 1H NMR.10a In this paper, we provide a full account of our efforts including synthesis and photophysical properties of DPQ-based fluorescent anion sensors with extended conjugated chromophores S1−S6 (Figure 1), including their benzothiadiazole precursors F1−F6, which appears to be an interesting set of highly stable fluorescent chromophores

Fluorescence Sensor Array For Metal Ion Detection Based On Various Coordination Chemistries: General Performance And Potential Application

A sensor array containing 9 cross-reactive sensing fluorescent elements with different affinity and selectivity to 10 metal cations (Ca2+, Mg2+, Cd2+, Hg2+, Co2+, Zn2+, Cu2+, Ni2+, Al3+, Ga3+) is described. The discriminatory capacity of the array was tested at different ranges of pH and at different cation concentrations using linear discriminant analysis (LDA). Qualitative identification of cations can be determined with over 96% of accuracy in a concentration range covering 3 orders of a magnitude (5-5000 mu M). Quantitative analysis can be achieved with over 90% accuracy in the concentration range between 10 and 5000 mu M. The array performance was also tested in identification of nine different mineral water brands utilizing their various electrolyte compositions and their Ca2+, Mg2+, and Zn2+ levels. LDA cross-validation routine shows 100% correct classification for all trials. Preliminary results suggest that similar arrays could be used in testing of the consistency of the purification and manufacturing process of purified and mineral waters

Simple Molecule-based Fluorescent Sensors For Vapor Detection Of Tnt

1,4-Diarylpentiptycenes (1a-e) were synthesized from 1,4-dichloro- or 1,4-difluoro-2,5-diarylbenzene derivatives by double base-promoted dehydrohalogenation to give corresponding arynes, which in the presence of anthracene undergo cycloaddition providing 1,4-diarylpentiptycenes in moderate overall yields. The resulting 1,4-diarylpentiptycenes show fluorescence modulated by the 1,4-aryl residues. The fluorescence is quenched in the presence of vapors of nitroaromatic compounds suggesting potential application in sensing of explosives

Synthesis, Structure, Anion Binding, And Sensing By Calix[4] Pyrrole Isomers

The synthesis, structure, and anion binding properties of chromogenic octamethylcalix[4] pyrroles (OMCPs) and their N-confused octamethylcalix[4] pyrrole isomers (NC-OMCPs) containing an inverted pyrrole ring connected via alpha\u27- and beta-positions are described. X-ray diffraction analyses proved the structures of two synthesized isomeric pairs of OMCPs and NC-OMCPs. The addition of anions to solutions of chromogenic OMCPs and NC-OMCPs resulted in different colors suggesting different anion-binding behaviors. The chromogenic NC-OMCPs showed significantly stronger anion-induced color changes compared to the corresponding chromogenic OMCP, and the absorption spectroscopy titrations indicated that chromogenic OMCPs and NC-OMCPs also possess different anion binding selectivity. Detailed NMR studies revealed that this rather unusual feature stems from a different anion-binding mode in OMCPs and NC-OMCPs, one where the beta-pyrrole C-H of the inverted pyrrole moiety participates in the hydrogen-bonded anion-NC-OMCP complex. Preliminary colorimetric microassays using synthesized chromogenic calixpyrroles embedded in partially hydrophilic polyurethane matrices allow for observation of analyte-specific changes in color when the anions are administered in the form of their aqueous solutions and in the presence of weakly competing anions

Rational Design Of A Minimal Size Sensor Array For Metal Ion Detection

The focus of this study was to demonstrate that, in the luminescent sensors, the signal transduction may possibly be the most important part in the sensing process. Rational design of fluorescent sensor arrays for cations utilizing extended conjugated chromophores attached to 8-hydroxyquinoline is reported. All of the optical sensors utilized in the arrays comprise the same 8-hydroxyquinoline (8-HQ) receptor and various conjugated chromophores to yield a different response to various metal cations. This is because the conjugated chromophores attached to the receptor are partially quenched in their resting state, and upon the cation coordination by the 8-HQ, the resulting metalloquinolinolate complex displays a change in fluorescence. A delicate balance of conjugation, fluorescence enhancement, energy transfer, and a heavy metal quenching effect results in a fingerprint-like pattern of responses for each sensor-cation complex. Principal component analysis (PCA) and linear discriminant analysis (LDA) are used to demonstrate the contribution of individual sensors within the array, information that may be used to design sensor arrays with the smallest number of sensor elements. This approach allows discriminating between 10 cations by as few as two or even one sensor element. Examples of arrays comprising various numbers of sensor elements and their utility in qualitative identification of Ca2+, Mg2+, Cd2+, Hg2+, Co2+, Zn2+, CU2+, Ni2+, Al3+, and Ga3+ ions are presented. A two-member array was found to identify 11 analytes with 100% accuracy. Also the best two of the sensors were tested alone and both were found to be able to discriminate among the samples with 99% and 96% accuracy, respectively. To illustrate the utility of this approach to a real-world application, identification of enhanced soft drinks based on their Ca2+, Mg2+, and Zn2+ cation content was performed. The same approach to reducing array elements was used to construct three- and two-member arrays capable of identifying these complex analytes with 100% accuracy

Web 2.0 en el proceso de enseñanza-aprendizaje. Aplicación a la enseñanza de Economía de la Empresa

El uso de Internet y su evolución acelerada en el tiempo no afecta exclusivamente a las empresas, sino que su ritmo viene marcado precisamente por los que se han de considerar nuevos productores de contenido en la Red. La Universidad no puede quedarse atrás en el uso de las TIC pero tampoco puede centrarse exclusivamente en plataformas de aprendizaje on-line de sofisticación elevada –OCW, Moodle, entre otros-, pero sin otorgar poder para modificar y generar contenidos a los usuarios. La Unidad Docente de Organización de Empresas del Departamento de Economía y Gestión Forestal de la Escuela Técnica Superior de Ingenieros de Montes de la Universidad Politécnica de Madrid propone el uso de plataformas Web 2.0 con el objeto de desarrollar competencias tradicionales y competencias 2.0. Estas plataformas tienen una gran acogida entre el alumnado, presentan utilidad tanto en el presente como en el futuro, y se puede utilizar como plataforma de Learning 2.0 de la Economía y Organización de Empresa

Ultrafast Energy Transfer In Oligofluorene-aluminum Bis(8-hydroxyquinoline)acetylacetone Coordination Polymers

Understanding the excited-state dynamics in conjugated systems can lead to their better utilization in optical sensors, organic photovoltaics (OPVs), and organic light-emitting diodes (OLEDs). We present the synthesis of self-assembled coordination polymers comprising two types of fluorescent moieties: discrete fluorene oligomers of a well-defined length (n = 1-9) connected via aluminum(III) bis(8-quinolinolate)acetylacetone joints. Due to their well-defined structure, these materials allowed for a detailed study of energy migration processes within the materials. Thus, femtosecond transient spectroscopy was used to study the ultrafast energy transfer from the oligofluorene to the quinolinolate moieties, which was found to proceed at a rate of 10(11) s(-1). The experimental results were found to be in agreement with the behavior predicted according to the Beljonne\u27s improved Forster model of energy transfer. In addition, the solid-state and semiconductor properties of these coordination polymers allowed for the fabrication of OLEDs. Preliminary experiments with simple two- and three-layer devices fabricated by spin-coating yield bright yellow electroluminescence with maximum brightness of 6000 cd/m(2), with a turn-on voltage of similar to 6 V and a maximum external quantum efficiency of up to 1.2%, suggesting their potential for use in PLED applications

Images of Science Linked to Labwork: A Survey of Secondary School and University Students

This paper presents findings about the images of science drawn upon in laboratory work, by upper secondary and university students, in academic streams with a science focus. Data were collected through four written questions, administered to a total of 368 students. The questions all required students to comment on laboratory investigations carried out by research scientists or by science students. We show that students’ reasoning has an epistemological and an ontological dimension, and that it often differs significantly from accepted perspectives on the nature of science. The issue for teaching appears to be showing students what counts (and what does not count) as appropriate reasoning in actual situations. In other words, explicit teaching about the various relationships that can exist between theory and data would transform labwork towards a more critical process that involves making and justifying decisions

Production, Processing, Commercialization and Analysis of Costumer Preferences of Sheep Cheese in Chile

The constant increase in the demand for dairy products and their derivatives has generated a higher consumption of dairy products (113.5 t/year). Chile has not been the exception; in 2017, it presented an average per capita consumption of 11.1 kg of cheese, making it the largest consumer in Latin America, followed by Argentina (7.5 kg) and Uruguay (5 kg). Although Chile does not have a strong tradition of consuming sheep’s milk cheese compared with other (European) countries, in recent years, there have been changes in the demands and expectations of cheese consumers, who demand higher quality and a wider range of varieties, thus establishing the potential for further products to enter the market. The global cheese industry has taken charge of these trends through the phenomenon of granting a premium value to certain products, adding new ingredients and flavors, producing limited editions of certain products, favoring traditional recipes and craft methods, and highlighting specific localities of origin. Given a greater appreciation for and popularity of locally produced cheeses and value-added products, particularly those with the highly valued “Designation of Origin” label, this would offer a potential for expansion in the Chilean market