Understanding the mechanism of Nb-MXene bioremediation with green microalgae

Abstract

Rapidly developing nanotechnologies and their integration in daily applications may threaten the natural environment. While green methods of decomposing organic pollutants have reached maturity, remediation of inorganic crystalline contaminants is major problem due to their low biotransformation susceptibility and the lack of understanding of material surface-organism interactions. Herein, we have used model inorganic 2D Nb-based MXenes coupled with a facile shape parameters analysis approach to track the mechanism of bioremediating 2D ceramic nanomaterials with green microalgae Raphidocelis subcapitata. We have found that microalgae decomposed the Nb-based MXenes due to surface-related physicochemical interactions. Initially, single and few-layered MXene nanoflakes attached to microalgae surfaces, which slightly reduced algal growth. But with prolonged surface interaction, the microalgae oxidized MXene nanoflakes and further decomposed them into NbO and Nb2O5. Since these oxides were nontoxic to microalgal cells, they consumed Nb-oxide nanoparticles by an uptake mechanism thus enabling further microalgae recovery after 72 h of water treatment. The uptake-associated nutritional effects were also reflected by cells’ increased size, smoothed shape and changed growth rates. Based on these findings, we conclude that short- and long-term presence of Nb-based MXenes in freshwater ecosystems might cause only negligible environmental effects. Notably, by using 2D nanomaterials as a model system, we show evidence of the possibility of tracking even fine material shape transformations. In general, this study answers an important fundamental question about the surface interaction-associated processes that drive the mechanism of 2D nanomaterials’ bioremediation as well as provides the fundamental basis for further short- and long-term investigations on the environmental effects of inorganic crystalline nanomaterials.

In Situ Self-Oxidation of Few-Layered Nb2CTx Nanosheets in Aqueous Solution for Achieving Improved Humidity Sensitivity and Selectivity

“…FTIR was further performed to check the surface chemical constituents of the three samples. As shown in Figure (g), these are most likely vibrations located at 597.8 cm –1 (Nb–O), 1062.5 cm –1 (C–O), 1221.2 cm –1 (C–F), 1309.9 cm –1 , 1404.8 cm –1 (C–H), 1523.0 cm –1 , 1593.3 cm –1 (CC), 1692.7 cm –1 (CO), 2851.7 cm –1 , 2938.9 cm –1 (C–H), and 3301.5 cm –1 (O–H) for the as-prepared few-layered Nb 2 CT x nanosheets. − With the increase of incubation duration, most of the vibrational modes of the bonds are eradicated, while the Nb–O and CC bonds are preserved and even enhanced for few-layered Nb 2 CT x nanosheets after 17 and 37 days incubation. The FTIR results exhibit similarity to those obtained from XPS and Raman spectroscopy.…”

Photocatalytic Activity of the Oxidation Stabilized Ti3C2Tx MXene in Decomposing Methylene Blue, Bromocresol Green and Commercial Textile Dye

“…8692. [ 66,78 ] Analysis was performed using TMAOH‐, MILD‐MXenes, and MB. After photocatalysis, this work removed the MXene by centrifugation and prepared the remaining supernatant with a serial dilution technique to obtain serial concentrations of 5.4, 4.3, 3.2, 2.2, 0.5, and 0.3 mg L −1 .…”

“…One of the best bioindicators are producers such as microalgae. [65,66] They act as food base and interact with the whole ecosystem by producing a variety of chemical products due to their photosynthetic action. Therefore, we evaluated the potential influence of decomposed dye by-products on green microalgae Raphidocelis subcapitata.…”

Cleaning the environment with MXenes

“…This effect was revealed for green microalgae Raphidocelis subcapitata challenged by Nb-MXenes. 75 The microalgae could decompose Nb-MXenes via surfacerelated physicochemical interactions, oxidation into NbO and Nb 2 O 5 , and subsequent oxide consumption (Figure 6). An uptake-associated nutritional effect allowed any microalgae recovery and normal growth.…”