This illustrates the formation of ferromagnetic specie consisting of the antiferromagnetic morphology of MnO2

LITERATURE REVIEW

            Ghorbani et al. (2017)   reported   that metal oxide nanoparticles are of great importance due to their unique properties. Due to their unique electrochemical properties, the manganese oxide nanoparticles are used considerably in field of technology. The electrochemical properties of manganese oxide nanoparticles have great importance to build the devices like capacitors. This due to the fact that these nanoparticles were very much ecofriendly, cost effective, excellent electrical properties and easy to prepare. The nanoparticles with two dimensions such as thin films and one dimensional nanoparticles in the form of nanowires are of great interest now a days due to their unique properties that are utilized to in different devices and applications. Flexible membranes were fabricated successfully by using manganese dioxide α-MnO2 (Zhao et al., 2014).

            Zhu et al. (2006) reported that the nanowires of α-MnO2 synthesized with the size range of 10-20 nm by using KMnO2 precursor with ultrasonic wave from the carbon nonporous source. The results revealed the formation process. A peak in the magnetization curve is observed at 100 K which indicates the formation of Nano porous carbon-MnO2. The results were in strong agreement with the transition temperature of the magnetization curve. This also has shown the magnetic transition of material at about 50 k temperature related to temperature-magnetization curve. This illustrates the formation of ferromagnetic specie consisting of the antiferromagnetic morphology of MnO2. Most important aspect of the experiment is the formation of nanowires of α-MnO2 in the controlled manner without ion, temperature and pH of the reactants. Another important advantage is the efficacy, controlled width and energy of the fabricated materials of nanowires of α-MnO2 in the pure form.

            Kumar et al. (2013) reported the manganese oxide nanoparticles have been synthesized due to their applications in the plenty of fields such as sensors, industries, piezoelectric devices, catalysis and electrodes. The size range of synthesized particles was 25-30 nm. The manganese oxide nanoparticles have attracted a great attention due to their application in lithium ion batteries as an anode because of the low cost preparation, cost effectiveness and other special properties. Nanoparticles of manganese oxides have been synthesized with different properties as well as different structures and morphologies.

            Toufiq et al. (2014) reported that the nanoparticles of manganese dioxide have been synthesized successfully by using hydrothermal method. The parent substances used were (NH4)2S2O8 and KMnO4. These nanoparticles were further characterized by using x-ray diffraction and TEM. The diameter of nanoparticles was calculated in the range of 15-20 nm with the tetragonal phase symmetry. The synthesized nanoparticles were super paramagnetic in nature as examined by VSM at room temperature. The ferromagnetic transition temperature of the nanoparticles was recorded 99 K by using temperature magnetization curve. The prepared nanoparticles were in the form of nanowire where the source used was KMnO4 by the hydrothermal route. The effect of temperature, concentration of precursors and reaction ratio has been reported to affect the size, structure and morphology of the synthesized nanoparticles. These nanowires were subjected to different characterizations for further studies.

            Kong et al. (2015) reported that the water bathing of facile material using hydrothermal route is opted to fabricate the manganese dioxide nanoparticles in the form of nanowires. The aging of the composite solution of KMnO4 and MnSO4 was done in the water bath. The dimension of the synthesized nanoparticles was controlled by controlling the time of aging, temperature and concentration of initial products. It has been observed that the change in temperature from 60 to 90 degree caused the change in the diameter of synthesized nanowires from 57 to 53 nanometers. On the other hand the diameter is also affected by the change of concentration of initial precursors. The change in 10 to 40 mole concentration of initial products results in the decrease in the diameter of nanowire from 104 to 35 nm. This change was done by keeping temperature and duration of time same. The variation of diameter from 0.58 micrometer to almost 35 nanometers has been observed by changing the aging time from 2 to 24 hours by keeping the temperature constant at 80 degree. Hence from this experimental result, it is proposed that the diameter and size of the nanowires can be modified according to the requirement of nanowires in the industry and other applied fields.

            Kumar et al. (2015) reported that the production of nano material by using hydrothermal method is reported.  In this work the nanowires of α-MnO2 were prepared. The acidic solution is used for this purpose and solutes were sodium nitrite and potassium manganite. There was no seed or template used. Further characterization of the synthesized nanowire was done using XRD, FTIR and HRTEM. The length of the wire fabricated was 0.1-2 µm and the diameter of the nanoparticles calculated was in the range of 10-40 nm. The field emission scanning electron microscopy is opted to study the variation in the size and length of nanowire due to temperature, concentration and aging time.

            Wang et al. (2016) reported that the α-MnO2 has been prepared by using CO3O4 coating. These nanoparticles were in form of nanowires and utilized in the lithium ion batteries. The diameter calculated was 5-20 nm in range with the length of 5-10 µm. the coating layer of CO3O4 was in diameter of 5 nm. The surface area of the 329 cm2 g-1 in range. These nanowires exhibited the strong catalyzing property. The batteries constructed can work efficiently and charging/discharging of the battery were 60 cycles. The morphology as well as size of synthesized hybrid α-MnO2/Co3O4 strongly affects the performance of the material in catalysis. On the other hand the different vacancies produced on the surface of MnO2 are also effective in catalysis such as vacancy of oxygen. The above results reveal that the synthesized nanoparticles in form of nanowires are effective for the construction of batteries.

            Julien et al. (2017) reported the production of inorganic materials of manganese oxide which were used in the industry for different purpose. These nanoparticles attracted the attentions of researches due to their unique applications and properties such as storage and conversion of energy. This study also revealed the production of nanoparticles of manganese oxide with different size and morphologies. Some other properties such as physical and electromagnetic applications were also reported in this aspect. Many evidences of the effect of size, morphology and the concentration have been reported. Some applications such as lithium ion batteries and super-capacitors have been reported.

            Shah et al. (2018) reported that the rectangular nanowires of the α-MnO2 were prepared hydrothermal process. The prepared nanowires were studied using XRD, FESEM, EDAX, FTIR and XPS techniques. The structures and morphology of the nanowire have been examined by above given techniques. The super-capacitor use of α-MnO2 is also confirmed by the study of electromagnetic properties. It has been reported that the synthesized nanowires of α-MnO2 have high value of capacitance with brilliant stability at the density of 1.0 Ag-1. The above results were in strong agreement of the need of industry and other fields in case of nanowires of manganese oxide. According to literature the effect of temperature, concentration of precursors and reaction ratio has been reported to affect the size, structure and morphology of synthesized nanoparticles. In the present work, MnO2 nanowires was prepared by simply changing the concentration of precursor and to investigate its effects on structural and optical properties of MnO2.

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