1,720,958 research outputs found
Silver nanoparticles from orange peel extract: Colorimetric detection of Pb2+ and Cd2+ ions with a chemometric approach
Get PDFGreen silver nanoparticles (AgNPs@OPE) were obtained by using orange (citrus sinensis) peel water extract (OPE) that acts as a reducing and capping agent. This procedure permits the valorisation of waste as orange peel, and lowers the environmental impact of the process, with respect to the conventional synthetic procedure. The OPE extract reduced Ag(I) to Ag(0) in alkaline conditions, and stabilised the produced nanoparticles as a capping agent. The AgNPs@OPE were deeply characterized by UV–Vis spectroscopy, FT-IR, SEM analysis and DLS analysis and successively used as colorimetric sensors for different metals in aqueous solution. The colourimetric assay showed that AgNPs@OPE were able to detect Pb2+ and Cd2+, as demonstrated by the splits of surface plasmon resonance (SPR) band accompanied by the formation of a second new band; these spectral modification resulted in a colour change, from pristine nanoparticles’ yellow to brown, due to the aggregation process. For the quantification of each of the two target cations, a calibration was performed by using the univariate linear regression, within the linearity ranges, exploiting the absorbance ratio between the main SPR band and the new band relative to the aggregate formation. Then a multivariate approach was followed to perform both Cd2+ and Pb2+ quantification by means of Partial Least Square regression (PLS) and target cations distinction by Linear Discriminant Analysis (LDA) applied on Principal Components Analysis (PCA) outputs, in both cases using the entire UV–Vis spectra (350–800 nm) as input data. Finally, the ability to quantify and distinguish between Cd2+ and Pb2+ was tested in tap water samples spiked with the two cations in order to confirm the application of the AgNPs@OPE as selective sensor in real samples
Deferoxamine-Based Materials and Sensors for Fe(III) Detection
No full textDeferoxamine (DFO) is a siderophore widely studied for its ability to bind iron(III) strongly. Thanks to its versatility, it is suitable for several clinical and analytical applications, from the recognized iron(III) chelation therapy to the most recent applications in sensing. The presence of three hydroxamic functional groups enables Deferoxamine to form stable complexes with iron(III) and other divalent and trivalent metal ions. Moreover, the terminal amino group in the DFO molecule, not involved in metal ion complexation, allows modification or functionalization of solid phases, nanoobjects, biopolymers, electrodes and optical devices. This review summarizes and discusses deferoxamine-based applications for the chelation and recognition of Fe(III)
MIP-Based Screen-Printed Potentiometric Cell for Atrazine Sensing
No full textThis work presents the development of a MIP-based screen-printed potentiometric cell for sensing the pesticide atrazine. The cell comprises three screen-printed electrodes; the working and the counter are obtained by graphite-ink and the pseudo-reference by silver/silver chloride-ink. All electrodes are printed on the support of polyester. Obviously, only the working and the pseudo-reference electrodes are connected for potentiometric measurements. The prepolymeric mixture was composed of the reagents at the following molar ratio: 1 atrazine (ATZ):5 methacrylic acids (MAA):4 ethylene glycol dimethacrylate (EGDMA). An amount of 7 µL of the prepolymeric solution was drop coated on the graphite working electrode of the cell, and the polymerization was carried out in an oven at 70 °C overnight. The specific sites obtained after polymerization and template elution can be viewed as the ionophore of a usual ISE membrane. The active ion is the atrazine in its protonated form, positively charged, so the determination was carried out in aqueous solutions at pHs1.5. At these conditions, the potential increases linearly with atrazine concentration ranging from 5 × 10−7 to 5 × 10−6 M; the limit of detection obtained is 4 × 10−7 M. The slope of the calibration curve E vs. log c (obtained as an average value of the slope of different standardization performed with several electrodes) is 40(6) mV/dec; the sub-Nernstian behavior can be ascribed to the interference of the anions present in the solution media
Freshness Traffic Light for Fish Products: Dual-Optode Label to Monitor Fish Spoilage in Sales Packages
No full textFreshness and safety of fish products alongside the supply chain, from the harvest to the final consumers, represent an increasing concern due to the perishability of these foods. Therefore, there is an urgent need for low-cost, reliable, and easy-to-read devices to monitor fish products' freshness, directly implemented on sales packages. The here presented device consists of two colorimetric sensor units, in which a pH indicator, o-cresol red, is covalently bound to a plastic support, ethylene vinyl alcohol, and equilibrated at different pHs. The dual-optode label works as a freshness traffic light that turns color according to the spoilage byproducts and, thus, the real freshness. The naked-eye readout and the chemometric-assisted spoilage modeling are demonstrated and validated for a panel of fish products, simulating distribution and domestic storage conditions. The sensing performances and the versatility make this dual-optode label an interesting candidate to be implemented as smart labels in packed fish products
Screen-Printed Gold Electrode Functionalized with Deferoxamine for Iron(III) Detection
No full textDeferoxamine (DFO), a hydroxamic siderophore with a high affinity for Fe(III), is immobilized as a functionalized self-assembled monolayer of a thiol (SAM) on the gold surface of a screen-printed cell to develop a voltammetric sensor for iron(III). The surface of the working electrode was characterized, before and after functionalization, by determining surface properties such as the area and the double-layer capacitance. The Fe(III) detection was performed by DPV analysis after preconcentration of the cation at the open circuit potential in solution at pH = 1 for two minutes. The method was applied to the iron(III) quantification in water samples giving promising results
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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