Transition metal carbides, known as MXenes, are generated via the selective etching of "A" layers from their layered, ternary parent compounds, MAX phases, where M corresponds to early d-transition metal, A being a main group sp-element from either Group 13 or 14 and carbon or nitrogen being denoted by X. MXenes are being recognized as a new and uprising class of 2D materials with extraordinary physical and electrochemical properties. The huge specific surface area and outstanding electrical conductivity of MXenes, make them ideal candidates for sensing and energy applications. Herein, we demonstrated the successful incorporation of pristine MXene, Ti 3 C 2 produced via HF etching and subsequent delamination with TBAOH, as a transducer platform toward the development of a second generation electrochemical glucose biosensor. Chronoamperometric studies demonstrate that the proposed biosensing system exhibits high selectivity and excellent electrocatalytic activity toward the detection of glucose, spanning over wide linear ranges of 50−27 750 μM and possess a low limit of detection of 23.0 μM. The findings reported in this study conceptually proves the probable applications of pristine MXenes toward the field of biosensors and pave ways for the future developments of highly selective and sensitive electrochemical biosensors for biomedical and food sampling applications.
Electrochemical and electrocatalytic properties of a class of layered materials known as MAX and MAB phases have yet to gain interest in the scientific community. Herein, electrochemical and toxicity studies of six MAX and MAB phases (Ti 2 AlC, Ti 2 AlN, Ti 3 AlC 2 , Ti 3 SiC 2 , Cr 2 AlB 2 , and MoAlB) were explored. The materials were found to possess high heterogeneous electron transfer (HET) rates, enhanced electrochemical sensing of ascorbic acid and uric acid, and promising electrocatalytic performances toward hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR). MAB phases possessed better electrochemical properties than did MAX phases. In addition, in vitro cytotoxicity studies toward various human cells found near negligible toxicity toward the cells tested deeming them safe for handling and biocompatible for future biological applications. Therefore, MAX and MAB phases can be regarded as safe layered materials for potential electrochemical applications.
Two-dimensional transition-metal
dichalcogenides (TMDs) are lately
in the scope within the scientific community owing to their exploitation
as affordable catalysts for next-generation energy devices. Undoubtedly,
only precise tailoring and control over the catalytic properties can
ensure high efficiency and successful implementation of such devices
in day-to-day practical utilization. However, contrary to theoretical
predictions, systematic experimental work dealing with the doped materials
and their impact to electrocatalysis are relatively underrated despite
the considerable effect that it could bring into this field. Herein,
we investigate the effect of four different dopants (i.e., Ti, V,
Mn, and Fe) incorporated to both layered MoS2 and WS2 as solid-state solution toward their electrocatalytic performance
through their evaluation as catalysts for oxygen reduction reaction
(ORR) and hydrogen evolution reaction (HER). Our results pointed out
that doping by Mn and Fe can enhance the electrocatalytic performance
toward ORR, whereas doping by Ti and V revealed poor electrocatalytic
effects (inhibition) compared to both undoped MoS2 and
WS2. Surprisingly, none of the dopants contributed to the
improvement of either MoS2 or WS2 toward HER
activity. Therefore, in addition to the experimental data, density
functional theory calculations were performed to further investigate
the role of the dopants in the performance of MoS2 toward
HER. According to these calculations, all dopants preferably occupied
the edges of the crystal structure and thus could affect the electrocatalytic
properties of the initial material. However, the observed ΔG values for hydrogen adsorption revealed that MoS2 is the best catalyst with a subsequent trend for doped materials
following the less negative binding energies V < Ti < Mn <
Fe, which was in good agreement with experimentally obtained overpotentials
of the respective samples. This study thus elucidates the reasons
for negative effects of doping in TMDs. This study brings an insight
that not all dopants are beneficial and not all reactions are affected
in the same way by dopants in TMDs.
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