Electrocatalytic oxidation of methanol on silica hollow spheres, loaded with platinum nanoparticles (Pt-SiO2-HS), is reported. The functionalized hollow silica spheres were prepared by the surfactant (lauryl ester of tyrosine) template-assisted synthesis. These spheres were loaded with platinum nanoparticles by γ-radiolysis. Energy-dispersive X-ray analysis (EDAX) and X-ray photoelectron spectroscopy (XPS) analyses confirmed presence of Si and Pt in the composite. High-resolution transmission electron microscopy showed the formation of uniformly deposited Pt nanoparticles over the hollow spheres with a predominant Pt(111) lattice plane on the surface. In spite of the poor conducting nature of the silica support, the oxidation potential and current density per unit mass for methanol oxidation were noted to be ca. 0.72 V vs NHE and 270 mA mg(-1), respectively, which are among the best values reported in its class. The composite did not show any sign of a degradation even after repeated use. In fact, the anodic current was found to increase under constant polarization, which is attributed to a facile reaction between adsorbed CO with a surface hydroxyl group present on the silica support. These results are in favor of Pt-SiO2-HS as a promising electrocatalyst material in the direct methanol fuel cell (DMFC) applications.
The toxicity levels of and exposure
to glyphosate, a widely used
herbicide and desiccant, are significant public health issues. In
this study, we aim to design a highly sensitive, label-free, portable
sensor for the direct detection of glyphosate in human urine. The
sensor platform consists of a portable, printed circuit board circular
platform with gold working and reference electrodes to enable nonfaradic
electrochemical impedance spectroscopy. The sensing platform was an
immunoassay-based, gold electrode surface immobilized with a monolayer
of dithiobis(succinimidyl propionate) (DSP), a thiol-based cross-linker,
which was then modified with a glyphosate antibody (Glyp-Ab) through
the bonding of the ester group of DSP with the amide of the antibody
(Glyp-Ab). The sensor was tested electrochemically, first using the
laboratory-based benchtop method for the glyphosate-spiked urine samples,
resulting in a dynamic response in the concentration range of 0.1–72
ng/mL with a limit of detection of 0.1 ng/mL. The platform showed
high selectivity in the presence of major interfering analytes in
urine [malathion (Mal), 3-phenoxybenzoic acid (PBA), and chlorpyrifos
(Chlp)] and high reproducibility. The sensing platform was then translated
into a portable device that showed a performance correlation (r = 0.994) with the benchtop (laboratory method). This developed
portable sensing approach can be a highly reliable alternate sensor
platform for the direct detection of pesticides in human bodily fluids.
Glyphosate and Glufosinate are widely used herbicides worldwide for controlling weeds in the agriculture field. The large increase in the herbicides tolerant plants has dramatically affected the level of usage of these herbicides recently. With the growing alarm about the associated toxicity to the environmental and human health, there is a need for direct low concentration detection of these herbicides present at the various food crops products and water. In this work, we present a simple electrochemical sensor to selectively detect glyphosate in presence of Glufosinate a structurally similar phosphorus containing amino acid group. The sensor substrate is made up of an interdigitated Au microelectrode, which was immobilized with glyphosate antibody, bounded with the help of the Dithiobis (succinimidyl propionate) (DSP) crosslinker. The data obtained using non-faradaic EIS method, showed a linear range across the whole dosing interval-10 ng ml−1 to 50 ug ml−1 for glyphosate in presence of the interfering component Glufosinate with the detection limit of 10 ng ml−1 and the sensitivity of 1.323% (change in impedance)/ppb. Further the sensor has been proven to measure the spiked pesticides doses in real oatmeal samples. Such micro-volume, high-sensitive, and selective platform which requires no prior sample preparation can be a potentially game-changing electrochemical on-field sensing device to measure the threshold limit, a precautionary step to alert the common man using the food products and farmers working in the agriculture field.
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