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Quantum dots (QDs) are fluorescent nanocrystals with superb photo-physical properties. Applications of QDs have been exponentially increased during the past decade. They can be employed in several disciplines, including biological, optical, biomedical, engineering, and energy applications. This review highlights the structural composition and distinctive features of QDs, such as resistance to photo-bleaching, wide range of excitations, and size-dependent light emission features. Physical and chemical preparation of QDs have prominent downsides, including high costs, regeneration of hazardous byproducts, and use of external noxious chemicals for capping and stabilization purposes. To eliminate the demerits of these methods, an emphasis on the latest progress of microbial synthesis of QDs by bacteria, yeast, and fungi is introduced. Some of the biomedical applications of QDs are overviewed as well, such as tumor and microRNA detection, drug delivery, photodynamic therapy, and microbial labeling. Challenges facing the microbial fabrication of QDs are discussed with the future prospects to fully maximize the yield of QDs by elucidating the key enzymes intermediating the nucleation and growth of QDs. Exploration of the distribution and mode of action of QDs is required to promote their biomedical applications.

In this work, a novel adsorbent called magnetite/MXene (Fe3O4/Ti3C2) nanocomposite was prepared, characterized, and applied for the removal of organic dye, malachite green dye (MG), from both real water and model solutions. Numerous techniques were used to characterize the prepared Fe3O4/Ti3C2 nanocomposite: XRD, SEM, TEM, FTIR, and surface area analysis. The outcomes showed that the Al layer had been selectively etched, that the MAX phase (Ti3AlC2) had been transformed into layered Ti3C2 MXene, that the cubic Fe3O4 phase had been prepared, and that the prepared Fe3O4 NPs had been evenly distributed on the MXene surface. Also, SEM pictures showed the successful etching of the MAX phase and the formation of the ultrathin multi-layered MXene, which the Fe3O4 NPs covered upon forming the Fe3O4/Ti3C2 nanocomposite at the surface and inside the ultrathin multi-layered MXene. The effect of different operational parameters affecting the removal process was explored and optimized. The MG dye was removed mostly within 60 min, with a 4.68 mg/g removal capacity using 5 mg of the Fe3O4/Ti3C2 nanocomposite. The removal was examined from both kinetic and thermodynamic perspectives, and the findings demonstrated the spontaneity of the removal process as well as the applicability of fractal-like pseudo-first-order and fractal-like pseudo-second-order kinetics when compared to other kinetics models. The Fe3O4/Ti3C2 nanocomposite was used to remove MG dye from real spiked environmental water samples, and the results revealed the successful remediation of the real samples from the organic dye by the Fe3O4/Ti3C2 nanocomposite. Accordingly, Fe3O4/Ti3C2 nanocomposite could be considered a potential adsorbent for the environmental remediation of polluted water.

In this research work, a hematite (α-Fe2O3) nanoparticle was prepared and then mixed with oxidized multi-walled carbon nanotubes (O-MWCNT) to form a stable suspension of an α-Fe2O3/O-MWCNTs nanocomposite. Different characterization techniques were used to explore the chemical and physical properties of the α-Fe2O3/O-MWCNTs nanocomposite, including XRD, FT-IR, UV-Vis, and SEM. The results revealed the successful formation of the α-Fe2O3 nanoparticles, and the oxidation of the MWCNT, as well as the formation of stable α-Fe2O3/O-MWCNTs nanocomposite. The electrochemical behaviour of the α-Fe2O3/O-MWCNTs nanocomposite was investigated using cyclic voltammetry (CV) and linear sweep voltammetry (LSV), and the results revealed that modification of α-Fe2O3 nanoparticles with O-MWCNTs greatly enhanced electrochemical performance and capacitive behaviour, as well as cycling stability.