The vast majority of reports of self-assembled monolayers (SAMs) on metals focus on the use of gold. However, other metals, such as palladium, platinum, and silver offer advantages over gold as a substrate. In this work, palladium is electrochemically deposited from PdCl2 solutions on glassy carbon electrodes to form a substrate for alkanethiol SAMs. The conditions for deposition are optimized with respect to the electrolyte, pH, and electrochemical parameters. The palladium surfaces have been characterized by scanning electron microscopy (SEM) and the surface roughness has been estimated by chronocoulometry. SAMs of alkane thiols have been formed on the palladium surfaces, and their ability to suppress a Faradaic process is used as an indication for palladium coverage on the glassy carbon. The morphology of the Pd deposit as characterized by SEM and the blocking behavior of the SAM formed on deposited Pd delivers a consistent picture of the Pd surface. It has been clearly demonstrated that, via selection of experimental conditions for the electrochemical deposition, the morphology of the palladium surface and its ability to support SAMs can be controlled. The work will be applied to create a mixed monolayer of metals, which can subsequently be used to create a mixed SAM of a biocomponent and an alkanethiol for biosensing applications.
In this study, locally available biomasses obtained from avocado kernel seeds (AKS), Juniperus procera sawdust (JPS) and papaya peels (PP) were investigated as adsorbents for the removal of Cr (
Surface nanostructuring with metal nanoparticles has gained importance because of the unique physicochemical properties of the nanoparticles. We have fabricated nanostructured surfaces on the basis of the sequential electrochemical deposition of palladium nanoparticles (Pd NPs) onto glassy carbon electrodes (GCEs). To increase the number density of the Pd NPs at the GC electrode surface, successive rounds of deposition/protection cycles were realized. Freshly deposited Pd NPs were immediately capped with 6-ferrocenylhexanethiol (Fc-C(6)SH) to prevent secondary nucleation processes from occurring during subsequent deposition rounds. This approach allowed us to maintain a narrow size distribution and, as such, the inherent properties of the deposited Pd NPs. Scanning electron microscopy (SEM) was used to confirm the successful deposition as well as to measure the size and spatial distribution of the deposited Pd NPs. SEM image analysis results showed that the number density of Pd NPs increased in each sequential deposition stage. The anodic peak current signal recorded for the electroactive SAM of Fc-C(6)SH following six consecutive deposition/protection cycles was found to be 75 times higher than that formed on a bulk palladium electrode. Finally, for comparison, gold NPs were deposited on GCEs following the same approach and exhibited considerably reduced signal enhancement properties as compared to the Pd NPs. The work presented here should find wide applicability for enhancing sensor signals by specifically structuring transducer surfaces on the nanoscale.
Simple, fast, and
sensitive molecularly imprinted composite thin-film-based
electrochemical sensor developed by using in situ co-electropolymerization
of aniline and acrylic acid in the presence of melamine as a template
is described here. The prepolymerization complex formation was studied
by using Fourier transform infrared (FTIR) spectrophotometry, while
the film formation was performed and characterized by cyclic voltammetry,
Fourier transform infrared (FTIR), and scanning electron microscopy
(SEM). The optimization of important parameters and removal of melamine
generated the binding sites in the polymer matrix, which can recognize
melamine specifically. Electrochemical measurements were performed
to achieve the linear range, the limit of quantification, and limit
of detection of 0.1–180, 0.0573, and 0.0172 nM, respectively.
The sensitivity of the sensor was attributed to the synergistic effects
of amine from aniline and the carboxylic group from acrylic acid to
form multiple noncovalent interactions with the template. Melamine-spiked
infant formula and raw milk were analyzed by the developed sensor,
and the recovery range of 95.87–105.63% with a relative standard
deviation of 1.11–2.23% was obtained. The results showed that
the developed sensor using the new composite polymer receptor is promising
for the online monitoring of melamine in the food industries in the
future.
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