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This study explores novel nanoparticles used in environmental remediation of 4-nitrophenol and aniline from wastewater bodies. The Zn0.5Ni0.5FeCrO4 magnetic nanoparticles (MNPs) were synthesized using tragacanth gel as a green, low-cost, and easy sol-gel method. The MNPs were characterized by XRD, XPS, FT-IR, VSM, TEM, EDX, FESEM, BET, DRS, and elemental mapping. The analysis demonstrated that nanoparticles have a spinel cubic structure, spatial distribution of the elements, ferromagnetic activity, narrow bandgap, and uniform morphology. Furthermore, effectiveness of the developed MNPs to degrade recalcitrant organic pollutants such as 4-nitrophenol (4-NP) and aniline under visible light exposure were studied. The results indicated 95% aniline and 80% of 4-NP were successfully degraded in 180 and 150 min, respectively. The total organic carbon (TOC) analysis revealed 65% and 54% removal of aniline and 4-NP. LC-MS was employed to elucidate the photodegradation mechanism and to identify the degradation products, including small fragmented molecules.

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MgFe2O4@ZnAl2O4 magnetic nanocomposites were synthesized with the easy and green sol-gel method, and their photocatalytic efficiency was followed toward degradation of reactive blue 222 (RB222) dye under visible light irradiation. Prepared nanocomposites were fully characterized. The SEM and TEM images revealed the spherical morphology of the produced nanocomposites, with average size of 20-25 nm. The XRD pattern of sample exhibited the successful synthesis of the MgFe2O4@ZnAl2O4 MNCs with crystallite size 13 nm. The saturation magnetization (Ms) of the nanocomposites was examined using VSM, indicating a value of 6.59 emu/g. The absence of Hc and Mr values confirms the superparamagnetic nature of the nanoparticles. In addition, the surface area was calculated to be 78.109 m2/g utilizing BET analysis, and the band gap was determined to be 1.88 eV by DRS analysis. The photocatalytic, photolysis, and adsorption performance were investigated and result shown photodegradation activity was higher than others. These results confirm the synergetic effect between the MgFe2O4@ZnAl2O4 MNCs and visible light irradiation to degradation of organic dye. The results indicate that rapid degradation of 96% of RB222 dye occurred in just 10 min, with a TOC removal rate of approximately 59%. Furthermore, radical scavenger agents also clarified photodegradation of RB222 dye.

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In this study, green synthesis, characterizations, photocatalytic performance, and antibacterial applications of α-Mn2O3 nanoparticles are reported. The synthesized nanoparticles were characterized by Fourier transform infrared spectroscopy (FT-IR), powder X-ray diffraction (XRD), transmission electron microscope (TEM), Scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), Brunauer Emmett Teller (BET), Electrochemical Impedance Spectroscopy (EIS), Photoluminescence (PL), and Differential reflectance spectroscopy (DRS) analysis. The investigation verified that the α-Mn2O3 nanoparticles possessed a cubic structure, with a crystallite size of 23 nm. The SEM and TEM techniques were used to study the nanoscale morphology of α- Mn2O3 nanoparticles, which were found to be spherical with a size of 30 nm. Moreover, the surface area was obtained as 149.9 m2 g-1 utilizing BET analysis, and the band gap was determined to be 1.98 eV by DRS analysis. The photocatalysis performance of the α-Mn2O3 NPs was evaluated for degrading Eriochrome Black T (EBT) dye under visible light and degradation efficiency was 96% in 90 min. The photodegradation mechanism of EBT dye was clarified with the use of radical scavenger agents, and the degradation pathway was confirmed through Liquid Chromatography-Mass Spectrometry (LC-MS) analysis. Additionally, the produced nanoparticles could be extracted from the solution and continued to exhibit photocatalysis even after five repeated runs under the same optimal conditions. Also, the antibacterial activity of green synthesized α-Mn2O3 nanoparticles was investigated by using the broth microdilution method towards Enterococcus faecalis ATCC 29212 (Gram-positive), Staphylococcus aureus ATCC 29213 (Gram-positive), Salmonella typhimurium ATCC 14028 (Gram-negative), Klebsiella pneumoniae ATCC 7881 (Gram-negative), Escherichia coli ATCC 25922 (Gram-negative), Proteus mirabilis ATCC 7002 (Gram-negative), and Pseudomonas aeruginosa ATCC 27853 (Gram-negative) bacterial strains.

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Finding the DNA of the human immune deficiency virus (HIV) with simple and sensitive detection is the main challenge in early diagnosis of AIDS. Herein, two-point separation strategies based on the colorimetric and fluorescence are introduced. The naked-eye qualitative and semiquantitative colorimetric, and also accuracy fluorescence quantification of HIV-1 DNA were applied using label-free NiFe2O4@UiO-66 nanozyme with both functions of peroxidase-mimetic like and emitting fluorescence. The DNA probe-conjugated nanozyme is employed to hybridize a sequence of HIV-1. NiFe2O4@UiO-66 nanozymes catalyze the decomposition of H2O2 to •OH which can produce a remarkable fluorescent product 2-hydroxyterephthalic acid (TAOH) by the oxidation of the bridging ligand of weakly fluorescent terephthalic acid (TA). The accessibility of H2O2 toward confined-NiFe2O4 MNPs was reduced by increasing the HIV-1 target DNA concentration, resulting in the fluorescence intensity of TAOH being decreased. Meanwhile, remaining the unreacted H2O2 was transferred an acidic colorimetric solution containing FeSO4 and gold nanorods (AuNRs). Increasing the amount of H2O2 available for longitudinal etching of AuNRs due to •OH-generating Fe+2-catalyzed H2O2 is reponsible for different colors from brownish to colorless depending on the HIV-1 target DNA concentration. The fluorescence intensity and obtained colors have offered the sensitive biosensing methods with a linear range from 0.05 to 300 and 1-200 pM, respectively with a detection limit as low as 1 fM. Our study revealed that the applied sensing assay provides a cost-effective and straightforward qualitative, semiquantitative, and sensitive quantitation visible monitoring without the necessity of high-end instruments for HIV-1 detection in a human blood plasma/serum samples.

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