Exfoliated MXene-AuNPs hybrid in sensing and multiple catalytic hydrogenation reactions.

The increasing use of nanomaterials in consumer products is expected to lead to environmental contamination sometime soon. As water pollution is a pressing issue that threatens human survival and impedes the promotion of human health, the search for adsorbents for removing newly identified contaminants from water has become a topic of intensive research. The challenges in the recyclability of contaminated water continue to campaign the development of highly reusable catalysts. Although exfoliated 2D MXene sheets have demonstrated the capability towards water purification, a significant challenge for removing some toxic organic molecules remains a challenge due to a need for metal-based catalytic properties owing to their rapid response. In the present study, we demonstrate the formation of hybrid structure AuNPs@MXene (Mo2CTx) during the sensitive detection of Au nanoparticle through MXene sheets without any surface modification, and subsequently its applications as an efficient catalyst for the degradation of 4-nitrophenol (4-NP), methyl orange (MO), and methylene blue (MB). The hybrid structure (AuNPs@MXene) reveals remarkable reusability for up to eight consecutive cycles, with minimal reduction in catalytic efficiency and comparable apparent reaction rate constant (Kapp) values for 4-NP, MB, and MO, compared to other catalysts reported in the literature.

4-nitrophenol optical sensing with N doped oxidized carbon dots.

In this work, we report a facile strategy for 4-nitrophenol (4-NP) sensing using highly luminescent nitrogen-doped oxidized carbon dots. The quenching of fluorescence (turn OFF), with the addition of trace amounts of organic pollutant (4-NP) in NOCDs, has been attributed to the complete reduction of nitrogen-doped oxidized carbon dots (NOCDs) to reduced nitrogen-doped oxidized carbon dots (rNOCDs) and its formation was confirmed by infrared, X-ray diffraction and X-ray photoelectron spectroscopy measurements. The chemical changes in oxygen-containing functional groups of NOCDs, in the presence of 4-NP, are elucidated and corresponding characterization through XPS reveals the changes in the peak intensities of CC (284.5 eV) and OCO (288.6 eV), indicating a decrement in hydroxyl groups that hinder its complete reduction to NOCDs. The sensitivity of NOCDs towards 4-NP has been tested in spiked tap water in the concentration range 2 µM to 2 mM with the minimum detection limit of 2 µM (linear detection range from 2 to 100 µM with regression coefficient R2 =0.99). The proposed simple sensing platform can be used to reduce NOCDs and simultaneously sense low concentrations of 4-NP. Finally, an effective treatment to improve the reduction of nitrogen-doped graphene oxide is proposed.