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In this work, we have successfully synthesized pure and Cobalt (2.5% and 5%) doped-MnO2 nanorods via a simple hydrothermal route. The morphological, structural, optical, and antibacterial effects, were studied using advanced analytical techniques. The grain sizes of as-prepared nanorods, were calculated in the range of 21–26 nm. The UV–Visible absorption spectroscopy shows a broad absorption band, centered at ~ 450 nm for pure, and ~ 465 nm for cobalt-doped MnO2 nanorods, respectively. The reduction in band gap was observed from 2.36 to 1.96 eV with the increase in the dopant concentration. The antimicrobial activities of synthesized samples were studied against gram-negative (E. coli and P.aeruginosa) bacteria and a gram-positive (S.aureus) bacteria. The antimicrobial studies show inhibition zones in the range of 9–16 mm for pure and cobalt-doped MnO2. The maximum inhibition zone (MIC) was observed for 5% Co-MnO2 doping against E. coli. We believe that the synthesized nanorods can be used as antimicrobial agent, and that could be used for antibacterial drug applications. [ABSTRACT FROM AUTHOR]

We report the hydrothermal growth of pure and doped TiO2 nanoparticles with different concentrations of carbon. The microstructure of the as-synthesized samples is characterized by x-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive x-ray spectroscopy (EDX), and Raman spectroscopy to understand the structure and composition. The XRD patterns confirm the formation of anatase phase of TiO2 with the average crystallite size is calculated to be in the range of 13 nm to 14.7 nm. The functional groups of these nanostructures are characterized by Fourier transformed infrared (FT-IR) spectroscopy, which further confirms the single anatase phase of the synthesized nanostructures. UV-visible absorption spectroscopy is used to understand the absorption behavior, which shows modification in the optical bandgap from 3.13 eV (pure TiO2) to 3.74 eV (1.2 mol% C-doped TiO2). Furthermore, the Ti3+ centers associated with oxygen vacancies are identified using electron paramagnetic resonance spectroscopy (EPR). [ABSTRACT FROM AUTHOR]

In this paper, 1D single-crystalline MnO2 nanowires have been synthesized using facile hydrothermal growth method using KMnO4 and Na2S2O8 as starting reaction reagents. The morphology, phase structure and composition of the as-prepared nanomaterial were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) with selected area electron diffraction (SAED), and energy dispersive X-ray spectroscopy (EDX). FESEM and TEM analysis shows that the as-prepared MnO2 nanowires have diameters of 25-35 nm. The structural features of as-synthesized MnO2 nanowires are studied to analyze the near-neighbor environment of oxygen coordination around manganese cations using Raman scattering (RS) spectroscopy. Photoluminescence Spectrophotometer was employed to study the optical properties of the synthesized material at room temperature which exhibits prominent emission bands located in green-violet spectral region. [ABSTRACT FROM AUTHOR]

In this paper, three-dimensional (3D) Cu0.45Mn0.55O2 nanoflowers self-assembled by interconnecting dense stacked single-crystalline nanoplates have been prepared using the template-free hydrothermal growth method. The morphology, phase structure and composition of the as-prepared nanomaterial were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) with selected area electron diffraction (SAED) and energy-dispersive X-ray spectroscopy (EDX). FESEM and TEM analyses show that the size of 3D Cu0.45Mn0.55O2 nanoflowers is in the range of 1–1.5 μm and the thickness of interconnected nanoplates is about 40 nm on the average. The photoluminescence (PL) spectra of the as-prepared Cu0.45Mn0.55O2 nanostructures at room temperature exhibits prominent emission bands located in red–violet spectral region. Moreover, magnetic investigations revealed the weak ferromagnetic behavior of the as-prepared Cu0.45Mn0.55O2 nanoflowers and reported for the first time using vibrating sample magnetometer (VSM). [ABSTRACT FROM AUTHOR]

In this paper, single crystalline ID tetragonal MnO2 pen-type nanorods were synthesized by varying the dwell time through a facile hydrothermal route at a reaction temperature of 250°C. X-ray diffraction (XRD) and transmission electron microscopy (TEM) studies showed that the diameter of MnO2 nanorods decreases from 460 nm to 250 nm with the increase in hydrothermal reaction time from 5 h to 15 h. Field-emission scanning electron microscopy (FESEM) and TEM studies revealed the evolution of improved surface morphology of MnO2 nanorods that are prepared with longer hydrothermal reaction time. The magnetic properties of the products were evaluated using vibrating sample magnetometer (VSM) at room temperature, which showed that the as-prepared samples exhibit weak ferromagnetic behavior. The effect of diameter on the magnetization values was observed and discussed in detail. [ABSTRACT FROM AUTHOR]

In this paper, single crystalline tetragonal MnO2 nanorods have been synthesized by a simple hydrothermal method using MnSO4 • H2O and Na2S2O8 as precursors. The crystalline phase, morphology, particle sizes and component of the as-prepared nanoma-terial were characterized by employing X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED) and energy-dispersive X-ray spectroscopy (EDS). The photoluminescence (PL) emission spectrum of MnO2 nanorods at room temperature exhibited a strong ultraviolet (UV) emission band at 380 nm, a prominent blue emission peak at 453 nm as well as a weak defect related green emission at 553 nm. Magnetization (M) as a function of applied magnetic field (H) curve showed that MnO2 nanowires exhibited a superparamagnetic behavior at room temperature which shows the promise of synthesized MnO2 nanorods for applications in ferrofluids and the contrast agents for magnetic resonance imaging. The magnetization versus temperature curve of the as-obtained MnO2 nanorods shows that the Néel transition temperature is 94 K. [ABSTRACT FROM AUTHOR]

Silicon dioxide-doped tetragonal MnO2 single crystalline prismatic nanorods have been successfully synthesized through a facile hydrothermal route at a temperature of 250 ° C with a reaction time as quick as 5 h. The synthesized MnO2 prismatic nanorods were characterized by x-ray diffraction, field emission scanning electron microscopy, energy dispersive x-ray analysis, transmission electron microscopy, high resolution transmission electron microscopy with selected area electron diffraction and Raman spectroscopy. Experimental results show that single crystalline tetragonal MnO2 nanorods have been successfully synthesized at all doping concentrations and that nanorods with a prismatic surface morphology have been obtained at 20 mass% of SiO2. The diameter of as-prepared MnO2 nanorods increases from 125 to 250 nm on increasing the dopant concentration. X-ray photoelectron spectroscopy analysis confirms the presence of valence Si (2p) of SiO2 in the as-prepared MnO2 nanostructures. The intensity of Raman modes clearly increases with increasing doping concentration, indicating an improvement in the structural aspects of the MnO2 nanorods. The magnetic properties of the products have been evaluated using a vibrating sample magnetometer, revealing that the as-prepared MnO2 nanorods exhibit weak ferromagnetic behavior at room temperature. The Néel temperature of the as-obtained products is calculated as 97 K. On the basis of the structural information, a growth mechanism is proposed for the formation of prismatic-like 1D MnO2 nanorods. [ABSTRACT FROM AUTHOR]

We have reported new magnetic and optical properties of Mn2O3 nanostructures. The nanostructures have been synthesized by the hydrothermal method combined with the adjustment of pH values in the reaction system. The particular characteristics of the nanostructures have been analyzed by employing X-Ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), Raman spectroscopy (RS), UV-visible spectroscopy, and the vibrating sample magnetometer (VSM). Structural investigation manifests that the synthesized Mn2O3 nanostructures are orthorhombic crystal. Magnetic investigation indicates that the Mn2O3 nanostructures are antiferromagnetic and the antiferromagnetic transition temperature is at TN = 83 K. Furthermore, the Mn2O3 nanostructures possess cantedantiferromagnetic order below the Neel temperature due to spin frustration, resulting in hysteresis with large coercivity (1580 Oe) and remnant magnetization (1.52 emu/g). The UV-visible spectrophotometry was used to determine the transmittance behaviour of Mn2O3 nanostructures. A direct optical band gap of 1.2 eV was acquired by using the Davis-Mott model. The UV-visible spectrum indicates that the absorption is prominent in the visible region, and transparency is more than 80% in the UV region. [ABSTRACT FROM AUTHOR]

Abstract: Novel square nanosheets of Cu1.4Mn1.6O4 have been successfully synthesized by auto-thermal growth technique using KMnO4 and Cu (NO3)2·3H2O as precursors. High Resolution Transmission Electron Microscopy (HRTEM) analysis revealed that the synthesized square nanosheets are phase sensitive as exposed to electron beam irradiation. UV-visible spectrophotometer was used to determine the transmittance behavior of synthesized square nanosheets. Optical direct bandgap of 1.37eV was acquired by applying Davis-Mott model. Magnetic investigations using Vibrating Sample Magnetometer (VSM) revealed the soft ferromagnetic behavior of synthesized Cu1.4Mn1.6O4 square nanosheets. [Copyright &y& Elsevier]

Abstract: The structural, electronic and optical properties of tungsten-doped TiO2 have been investigated using density functional theory with plane wave basis sets and ultrasoft pseuodopotential. Substitutional W doping at Ti sites create W 5d states just below the conduction band minimum while interstitial W doping gives isolated W 5d states in the middle of forbidden region. Averaged bond lengths show that W doping at Ti sites produce minimum structural distortion as compared to the interstitial W-doped TiO2. Substitutional W-doped TiO2 has better visible light absorption compared to interstitial W-doped TiO2 and has stable configuration which provide reasonable explanation for the experimental findings. Tungsten doping in TiO2 with different doping concentrations is investigated as an enabling concept for enhancing the visible light absorption. Optical properties show that optimal W doping concentration would improve the visible light absorption. 2.08% W doping concentration gives strong visible and ultraviolet light absorption among all doped models found consistent with experiments. [Copyright &y& Elsevier]