1,720,978 research outputs found
Recent advances in electrochemical chitosan-based chemosensors and biosensors: applications in food safety
Full text linkChitosan is a biopolymer derived from chitin. It is a non-toxic, biocompatible, bioactive, and biodegradable polymer. Due to its properties, chitosan has found applications in several and different fields such as agriculture, food industry, medicine, paper fabrication, textile industry, and water treatment. In addition to these properties, chitosan has a good film-forming ability which allows it to be widely used for the development of sensors and biosensors. This review is focused on the use of chitosan for the formulation of electrochemical chemosensors. It also aims to provide an overview of the advantages of using chitosan as an immobilization platform for biomolecules by highlighting its applications in electrochemical biosensors. Finally, applications of chitosan-based electrochemical chemosensors and biosensors in food safety are illustrated
Extending substrate sensing capabilities of zinc tris(2-pyridylmethyl)amine-based stereodynamic probe
No full textTripodal metal complexes have been widely used for catalysis and more recently also for molecular recognition applications. Their ability in recognition and signal amplification of chiral substrates is because of the setup of the ligand around the metal in a propeller shape. Within this subject, we have recently reported tris(2-pyridylmethyl)amine- and triphenolamine-based complexes for the determination of the enantiomeric excess of various substrates. Herein, we show the versatility of the zinc tris(2-pyridylmethyl)amine-based stereodynamic probe by performing a detailed study of the imine formation process, by the extension of the sensing capabilities to other chiral compounds. A principal component analysis study of the system together with TD-DFT studies highlights the molecular origin of the observed chiroptical properties
Superior transport behavior of gold nanoparticles/P3HT blends by tuning optical and structural properties
Full text linkOrganic materials and blends have received a great deal of interests for application in large area, flexible, and low-cost organic/hybrid electronics. In this work the optical, structural and the electrical behaviors of a new active layer system composed by functionalized gold nanoparticles (AuNPs) and conjugated polymers, were investigated. For this purpose, gold nanoparticles with diameter of about 5 nm were chosen, coated with the bifunctional π-conjugated ligand (9,9-didodecyl-2,7-bis(acetylthio)fluorene, FL) for their high stability and easy dispersibility in organic solvents. The blends based on AuNPs and regioregular poly-3-hexylthiophene (P3HT) were prepared by adding an increasing percentage by weight of nanoparticles, i.e. from 10% to 90 wt%, in the P3HT polymeric matrix. The presence of nanoparticles was confirmed by UV-Vis spectroscopy, electron microscopy and X-ray diffraction techniques. The optical characterization of the composites demonstrated the possibility to tune the optical behavior of the P3HT by adding increasing percentages of AuNPs into the polymer matrix. Their inclusion results in a loss of P3HT crystallinity and in a simultaneous increase of the π-π interaction between the polythiophene chain and fluorene ligand. To better investigate the films, Grazing Incident X-ray Diffraction (GIXD) measurements were carried out and the blend containing 30 wt% of AuNPs in P3HT reveals an optimal condition, combining good structural order and interconnectivity in the polymer matrix. The electrical characterization of the AuNPs/P3HT blends reveals an improvement of the electrical conductivity in all the prepared blends, that show higher conductivity values compared to the pristine AuNPs and P3HT materials. The best performance is achieved adding 30 wt% of AuNPs to P3HT resulting in an enhancement of conductivity by about 350% compared to that of the pure polymer. This result could be of great interest for the realization of new conductive film composites to use in opto-electronic devices
Review - multiscale characterization of Li-Ion batteries through the combined use of atomic force microscopy and X-ray microscopy and considerations for a correlative analysis of the reviewed data
No full textThe present review analyses the recent literature on the combined use of X-ray microscopy (XRM) and atomic force microscopy (AFM) for the multiscale characterization of Li+ (or Li) batteries (LiBs) with the aim of developing guidelines for their correlative analysis. The usefulness of XRM resides in the capability of affording non invasively in situ images of the inner parts of a LiB (an encapsulated device) with spatial resolution of dozens of nm during LiB operation. XRM is non destructive and affords the early diagnosis of LiBs degradation causes when these manifest themselves as microdeformations. The multiscale characterization of LiBs also requires AFM for visualizing the morphological/physical alterations of LiB components (anodes, cathodes, electrolyte) at the sub-nanometer level. Different to XRM, AFM necessitates of a modification of LiB working configuration since AFM uses a contacting probe whereas XRM exploits radiation-matter interactions and does not require the dissection of a LiB. A description of the working principles of the two techniques is provided to evidence which technical aspects have to be considered for achieving a meaningful correlative analysis of LiBs. In delineating new perspectives for the analysis of LiBs we will consider additional complementary techniques. Among various AFM-based techniques particular emphasis is given to electrochemical AFM (EC-AFM)
Polysulfide solution effects on Li[sbnd]S batteries performances
No full textRecently, rechargeable Li[sbnd]S batteries, a next-generation energy storage system, are deeply studied due to their theoretical specific energy density. However, to produce batteries comparable to those already available on the market some drawbacks must be overcome, including essentially self-discharge, high internal resistance and rapid capacity fading upon cycling. In this work the use of polysulfide solutions either as additives or as active material in Li[sbnd]S batteries is proposed. The addition of polysulfides to the electrolytic solution improves the cell performances in terms of specific capacity and coulombic efficiency, passing from a capacity of about 150 mAh/g with a coulombic efficiency of about 0.85 to a capacity of 600 mAh/g with a coulombic efficiency of about 0.99 after 10 cycles. In batteries where polysulfide solutions are used as cathodic material, the obtained performances are even higher, reaching specific capacities of 420–450 mAh/g after about 70 cycles. Moreover, the cells tested with carbon paper as electrode support shows a greater reversibility, with a coulombic efficiency very close to 1. Finally, reducing the potential window from 3 to 1.5 V to 2.8–1.7 V, the cells show high stability and efficiency, reaching specific capacity values of about 600 mAh/g after 200 cycles
X-Ray microscopy: a non-destructive multi-scale imaging to study the inner workings of batteries
No full textX-ray microscopy (XRM) is a non-destructive characterization technique that provides quantitative information regarding the morphology/composition of the specimen and allows to perform multiscale and multimodal 2D/3D experiments exploiting the radiation-matter interactions. XRM is particularly suitable to afford in situ images of inner parts of a battery and for the early diagnosis of its degradation in a non-invasive way. Since traditional characterization techniques (SEM, AFM, XRD) often require the removal of a component from the encapsulated device that may lead to non-desired contamination of the sample, the non-destructive multi-scale potential of XRM represents an important improvement to batteries investigation. In this work, we present the advanced technical features that characterize a sub-micron X-ray microscopy system, its use for the investigation of hidden and internal structures of different types of batteries and to understand their behavior and evolution after many charge/discharge cycles
Divalent metal ion depletion from wastewater by RVC cathodes: a critical review
No full textIn this paper, a critical review of results obtained using a reticulated vitreous carbon (RVC) three-dimensional cathode for the electrochemical depletion of various divalent ions, such as Cu+2, Cd+2, Pb+2, Zn+2, Ni+2, and Co+2, often present in wastewater, has been carried out. By analyzing the kinetics and fluid dynamics of the process found in literature, a general dimensionless equation, Sh = f(Re), has been determined, describing a general trend for all the analyzed systems regardless of the geometry, dimensions, and starting conditions. Thus, a map in the log(Sh) vs. log(Re) plane has been reported by characterizing the whole ion electrochemical depletion process and highlighting the existence of a good correlation among all the results. Moreover, because in recent years, the interest in using this three-dimensional cathode material seems to have slowed, the intent is to revive it as a useful tool for metal recovery, recycling processes, and water treatments
Magnetic force microscopy characterization of core–shell cobalt-oxide/hydroxide nanoparticles
No full textCobalt-based nanoparticles directly synthesized on conductive substrates through electrodeposition find application in a broad range of scientific and technological fields.The capability to characterize both morphological parameters (e.g., shape, size, structure, and numerical density per unit of area) and magnetic properties (e.g., magnetic moment, saturation magnetization, or coercivity) directly on the substrate on which they are grown is fundamental for many of those applications. In this work, we report on the use of magnetic force microscopy (MFM) to characterize Co-based nanoparticles synthesized through electrodeposition on Al substrates using two different counter electrodes, i.e., Co and Pt. Morphological analysis using AFM and scanning electron microscopy (SEM) was used to assess differences in size and number density of the nanoparticles obtained using the two counter electrodes, while MFM was employed to measure the remanent magnetization of single isolated nanoparticles, to asses the presence of a nonmagnetic shell on the nanoparticles and to estimate their thickness
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