MnO2 nanostructures of different morphologies from amino acids–MnO4− reactions in aqueous solutions

Fabrication and characterization of manganese dioxide (MnO2) nanoparticles and its degradation potential of benzene and pyrene

MnO2 nanoparticles have a wide range of applications, including catalytic abilities due to their oxygen reduction potential. Industrial processes and the burning of organic materials released PAHs into the biosphere which have adverse effects on living organisms when continually exposed. In this study, MnO2 nanoparticles were synthesized chemically using sodium thiosulphate as reducing agent. MnO2 nanoparticles were characterized using UV-visible adsorption spectroscopy and Fourier Transform Infrared Spectroscopy (FTIR). A X-Ray Diffraction Spectrophotometer (XRD), a Scanning Electron Microscopy - Energy Dispersive X-Ray Analyzer (SEM-EDAX), and Dynamic Light Scattering (DLS) were used to identify the crystalline nature and particle size of the fabricated MnO2 nanoparticles. Batch adsorption studies were conducted to identify the optimal conditions for better benzene and pyrene adsorption from aqueous solution using MnO2 nanoparticles. They are also effective in degrading benzene and pyrene by batch adsorption as determined by their adsorption isotherms and kinetics.

Photophysical Study of Heteroatom-Doped Carbon Dots-MnO2-Based Nanosensor: Selective Detection of Glutathione in the Nanomolar Level

Heteroatom doping on carbon dots (Cdots) has been developed as an efficient approach to modify its optical and electronic properties. The four different types of heteroatom-doped Cdots (undoped Cdots (u-Cdots, nitrogen-doped Cdots (N-Cdots), sulfur-doped Cdots (Cdots), nitrogen, sulfur codoped Cdots (N, S-Cdots)) have been synthesized through a simple heat treatment of 5 min. Among four different heteroatoms doped nanosensors, N, S-Cdots with MnO2 nanospheres (Mn NS) showed one of the best fluorescents "on-off-on" nanosensors for selective sensing of glutathione (GSH) and cell imaging. N, S-Cdots showed a high fluorescence quantum yield, good photostability, ionic strength, and pH stability. N, S-Cdots with Mn NS demonstrated extremely high fluorescence quenching efficiency and the maximum fluorescence recovery rate after adding GSH to the produced solution. The photophysical study of N, S-Cdots-Mn NS used as a sensor confirms the inner filter effect (IFE) quenching mechanism between them. The developed sensor has an 80 nM limit of detection (LOD) for GSH. The heteroatom-doped framework of Cdots plays a significant role in the sensitive detection of GSH. N, S-Cdots-Mn NS have good permeability, biocompatibility, and low toxicity, due to which it was used in the intracellular imaging of GSH in living cells. The prepared sensor is rapid, economical, less toxic, and highly applicable in diagnosing diseases.

T. J, Joseph A. Biogenic MnO2 nanoparticles derived from a Cedrus deodara pine needle extract and their composites with polyaniline/activated charcoal as an electrode material for supercapacitor applications

A ternary composite of phytogenic MnO2 nanoparticles with polyaniline (PA) and activated charcoal (AC) was designed and fabricated.

l-Cysteine directing synthesis of BiOBr nanosheets for efficient cefazolin photodegradation: The pivotal role of thiol

Cefazolin (CFZ) is widely present in the wastewater treatment effluents and in receiving waters and has caused severe impacts to the ecosystem. CFZ degradation by photocatalysis has attracted increasing attention due to its eco-friendly features. Herein, we presented a green synthesis strategy for a highly active BiOBr photocatalyst for CFZ removal with L-cysteine as a directing agent, and the role of thiol in cysteine for facets control and morphology regulation was discussed. We found that the photoactivity of cysteine-induced BiOBr nanosheet was much higher than those prepared by using arginine and glycine as directing agent. Further experiments showed that the cysteine preferentially coordinated Bi³⁺ with thiol rather than carboxyl. The strong interactions of thiol group with the external surface of the BiOBr crystals stabilize the small crystals that have high surface energy without the cysteine. Such a chemical environment favors forming BiOBr crystalline with small size of high surface area and oriented growth in [110] direction, which facilitates the photogenerated electron-hole separation to achieve significantly promoted photocatalytic activity. Moreover, the cysteine-directed BiOBr nanosheets displayed good photoreactivity to more pollutants (i.e. rhodamine B, cefradine and cefoperazone sodium) and excellent reusability as verified via seven consecutive recycle experiments. The proper photocatalyst dosage (0.4 g/L), relatively acidic water environment (pH 3.4) and high temperature (35 °C) would be beneficial to CFZ photodegrdation by BiOBr. Also, the CFZ photodegradation mechanism and degradation pathway were also proposed by combining radical trapping experiments and electron spin resonance (ESR) test with LC-MS analysis in the photocatalytic process.

Potential application of Micellar nanoreactor for electron transfer reactions mediated by a variety of oxidants: A review

Surfactant, either natural or synthetic, forms a different type of aggregates among which 'Micelle' is truly an important dynamic surfactant aggregate, having a different region to interact with several organic, inorganic, and biomolecules; therefore the practical use of micelle is rapidly growing day-to-day. Surfactant-micelle, looks like a reactor of nano-dimension, govern a variety of reactions in aqueous media extensively. Oxidation is one of the vital reaction, take a part in the course of several organic transformations which are not very easy to execute in water media alone due to the solubility problem. Moreover, in order to achieve a quick transformation overcoming several difficulties the utility of micellar media became an excellent innovation, that's why nowadays, the surfactant and its aggregates are a focus of interest to the researcher of synthetic field and thus its practical applicability has been tremendously cultivated over the few decades. It is, therefore, useful to introduce some basic concepts regarding the aggregation of surfactants. Subsequently, we emphasize the importance of micellar media on the kinetics of oxidation reactions mediated by several metal ions with a special emphasis on their catalytic role.

Plant extract-mediated biogenic synthesis of silver, manganese dioxide, silver-doped manganese dioxide nanoparticles and their antibacterial activity against food- and water-borne pathogens

Silver nanoparticles (AgNPs), manganese dioxide nanoparticles (MnO₂NPs) and silver-doped manganese dioxide nanoparticles (Ag-doped MnO₂NPs) were synthesized by simultaneous green chemistry reduction approach. Aqueous extract from the leaves of medicinally important plant Cucurbita pepo was used as reducing and capping agents. Various characterization techniques were carried out to affirm the formation of nanoparticles. HR-TEM analysis confirmed the size of nanoparticles in the range of 15-70 nm and also metal doping was confirmed through XRD and EDS analyses. FT-IR analysis confirmed that the presence of biomolecules in the aqueous leaves extract was responsible for nanoparticles synthesis. Further, the concentration of metals and their doping in the reaction mixture was achieved by ICP-MS. The growth curve and well diffusion study of synthesized nanoparticles were performed against food- and water-borne Gram-positive and Gram-negative bacterial pathogens. The mode of interaction of nanoparticles on bacterial cells was demonstrated through Bio-TEM analysis. Interestingly, AgNPs and Ag-doped MnO₂NPs showed better antibacterial activity against all the tested bacterial pathogens; however, MnO₂NPs alone did not show any antibacterial properties. Hence, AgNPs and Ag-doped MnO₂NPs synthesized from aqueous plant leaves extract may have important role in controlling various food spoilage caused by bacteria.

Biological synthesis of manganese dioxide nanoparticles by Kalopanax pictus plant extract

Manganese dioxide (MnO₂) nanoparticles were synthesised by the reduction of potassium permanganate (KMnO₄) using Kalopanax pictus leaf extract at room temperature. A transparent dark-brown colour appeared after the addition of K. pictus leaf extract to the solution of permanganate. The time course of the reduction of KMnO₄and synthesis of MnO₂ nanoparticles was monitored by means of UV-Vis spectra. The reduction of KMnO₄occurred after addition of plant extract with disappearance of KMnO₄specific peaks and emergence of peak specific for MnO₂nanoparticles. MnO₂nanoparticles showed absorption maxima at 404 nm. The electron dispersive X-ray spectroscopy analyses confirmed the presence of Mn and O in the sample. X-ray photoelectron spectroscopy revealed characteristic binding energies for MnO₂nanoparticles. Transmission electron microscopy micrographs revealed presence of uniformly dispersed spherical shaped particles with average size of 19.2 nm. The selected area electron diffraction patterns revealed the crystalline nature of MnO₂nanoparticles. Fourier transform-infrared spectroscopy spectra of pure MnO₂show the occurrence of O-Mn-O vibrational mode at around 518 cm⁻¹. The phyto-synthesised MnO₂nanoparticles showed degradation ability of dyes (congo red and safranin O) similar to chemically synthesised MnO₂nanoparticles. This study shows simple and eco-friendly synthesis of MnO₂nanoparticles by plant extract and their utilisation for dye degradation for the first time.

Comparative study of MnO2 nanoparticle synthesis by marine bacterium Saccharophagus degradans and yeast Saccharomyces cerevisiae

Microorganisms are one of the most attractive and simple sources for the synthesis of different types of metal nanoparticles. The synthesis of manganese dioxide nanoparticles (MnO2 NPs) by microorganisms from reducing potassium permanganate was investigated for the first time in the present study. The microbial supernatants of the bacterium Saccharophagus degradans ATCC 43961 (Sde 2-40) and of the yeast Saccharomyces cerevisiae showed positive reactions to the synthesis of MnO2 NPs by displaying a change of color in the permanganate solution from purple to yellow. KMnO4-specific peaks also disappeared and MnO2-specific peaks emerged at an absorption maximum of 365 nm in UV-visible spectrophotometry. The washed Sde 2-40 cells did not show any ability to synthesize MnO2 NPs. The medium and medium constituents of Sde 2-40 showed similar positive reactions as supernatants, which indicate the role of the Sde 2-40 medium constituents in the synthesis of MnO2 NPs. This suggests that microorganisms without nanoparticle synthesis ability can be misreported for their abilities to synthesize nanoparticles. S. cerevisiae washed cells showed an ability to synthesize MnO2 NPs. The strategies of keeping yeast cells in tea bags and dialysis membranes showed positive tests for the synthesis of MnO2 NPs. A Fourier transform-infrared spectroscopy study suggested roles for the proteins, alcoholic compounds, and cell walls of S. cerevisiae cells in the synthesis of MnO2 NPs. Electron-dispersive X-ray spectroscopy analyses confirmed the presence of Mn and O in the sample. X-ray photoelectron spectroscopy revealed characteristic binding energies for MnO2 NPs. Transmission electron microscopy micrographs revealed the presence of uniformly dispersed hexagonal- and spherical-shaped particles with an average size of 34.4 nm. The synthesis approach using yeast is possible by a simple reaction at low temperature without any need for catalysts, templates, or expensive and precise equipment. Therefore, this study will be useful for the easy, cost-effective, reliable, and eco-friendly production of nanomaterials.