Nm For Mn Research Articles

THE ANTIBACTERIAL ACTIVITY OF GUM ARABIC-COATED Mn-DOPED CuS NANOPRISMS

Novel nanoprism-shaped manganese-doped copper sulfide (Mn–CuS) was fabricated by two-phase colloidal method (Mn percentages = 0%, 1%, 3%, and 5%). The Mn–CuS was analyzed by XRD, FTIR, UV–Vis spectrometer, and TEM. The XRD shows that the hexagonal covellite copper sulfide peaks appeared at 2[Formula: see text], and [Formula: see text] for 0%, 1%, 3%, and 5% respectively, and orthorhombic chalcocite copper sulfide appeared at the peaks that are corresponding the planes (412), (275), (029) and (106). According to UV–Vis analysis, the optical absorption of manganese-doped copper sulfide 0%, 1%, 3%, and 5% clearly appeared in the UV–Vis region at 518, 440, 478, and 477[Formula: see text]nm respectively, and there are broad peaks for localized surface plasmon resonances (LSPR) of CuS located at 970, 1061, 1002, and 1006[Formula: see text]nm for Mn–CuS 0%, 1%, 3%, and 5%, respectively. The favored nanoprism-shaped sample (manganese-doped copper sulfide 1%) was coated with gum Arabic (GA) in order to decrease the cytotoxicity and enhance the biocompatibility. The antibacterial activity of manganese-doped copper sulfide and GA@Mn–CuS 1% nanostructure toward Staphylococcus aureus and Escherichia coli bacteria was determined by inhibition zone. It was found that the fabrecated Mn–CuS 1% nanoprisms were more active toward both E. coli and S. aureus bacteria and the doping enhanced the antibacterial activity.

Nano-synthesis, characterization, theoretical, biological and catalytic studies of Mn(II), Cu(II), Cd(II), and Th(IV) complexes based on antipyrine azo dye ligand

The design and detailed characterization of the azo dye ligand obtained from the reaction of 4-aminoantipyrine diazonium salt with 3-hydroxybenzaldehyde (HL) and its novel metal chelates with Mn2+, Cu2+, Cd2+ and Th4+ ions have been presented. Utilizing modern spectroscopic and analytical techniques, these complexes were found to adopt an octahedral geometry, demonstrate inner sphere d2sp3 hybridization for Th(IV) complex and outer sphere sp3d2 hybridization for other complexes. Particle sizes calculated using the Debye-Scherrer equation on XRD patterns were 32.05 nm for Mn(II), 34.07 nm for Cu(II), 30.90 nm for Cd(II), and 22.05 nm for Th(IV). These substances' anticancer activity was assessed on human lung cancer cells (A-549) and pancreatic carcinoma cell lines (PANC-1). Cd(II) complex exhibited higher cytotoxicity against the A-549 cell line than the reference drug vinblastine sulfate (VinBLAStine Sulfate) which revealing its potential application as a new anticancer agent. Quantum chemical computations using the DMOL3 module's density functional theory (DFT) and molecular docking studies with the Schrödinger suite demonstrated significant inhibitory effects of the free organic compound and Cu(II) chelate on the FGFR1 protein, crucial for cell development and differentiation. Additionally, the study examined the catalytic activity of HL and its metal chelates in the oxidative degradation of methyl violet 2B dye in presence of H2O2. The order was followed by the pseudo-first-order rate constants: Th(IV) chelate (0.9556 min⁻¹) > HL (0.4911 min⁻¹) > Cu(II) chelate (0.5979 min⁻¹) > Mn(II) chelate (0.2645 min⁻¹) > Cd(II) chelate (0.2280 min⁻¹).

Spatial distribution of paddy field’s heavy metals diversity contamination in Samarinda using remote sensing imagery

Abstract. Palupi NP, Hardi EH, Fahrunsyah, Rahayu DE, Nugroho RA, Darma S, Idris SD. 2023. Spatial distribution of paddy field’s heavy metals diversity contamination in Samarinda using remote sensing imagery. Biodiversitas 24: 6743-6752. The adverse effects of heavy metal contamination on rice fields posing a significant threat to food safety. This study, conducted from May to July 2023 in Samarinda East Kalimantan, Indonesia, aims to determine the distribution of active rice fields and heavy metal contamination through Kriging's interpolation method. Aerial photographic interpretations, facilitated by ArcGIS 10.4, were performed with 144 sample points within 4 Districts. The content of heavy metals was assessed by Atomic Absorption Spectroscopy at specific wavelengths: 248.3 nm for Fe, 228.8 nm for Pb, 283.3 nm for Cd, 357.9 nm for Cr, 279.5 nm for Mn, 213.9 nm for Zn, and 324.7 nm for Cu, following guidelines of SNI 8910:2021. The research showed that existing rice fields were concentrated in North Samarinda District (380,416 ha), Loa Janan Ilir District (210,133 ha), Sambutan District (404,682 ha), and Palaran District (188,617 ha) with Fe content ranged from 4.976,45 ppm to 16.800,485 ppm, exceeding the critical Fe limit in soil of 500 ppm set by SNI. Mn content ranged from 22.65 ppm to 564.88 ppm, surpassing the critical soil threshold of 0.15 ppm for Mn according to SNI. Cu content varied from 3.32 ppm to 121.75 ppm, exceeding critical Cu limit of 0.04 ppm. Zn content ranged from 8.61 ppm to 223.12 ppm, surpassing the critical limit of Zn's pollution in the soil (0.06 ppm). Pb content ranged from 10.72 ppm to 32,84 ppm, categorized as intermediate compared to the threshold of 0.07 ppm for Pb in soil. Cd content ranged from 0.04 ppm to 0.739 ppm, exceeding the critical limit of 0.01 ppm set by SNI. Cr content was detected to be less than 0.032 ppm, falling into a very low category, with the critical limit for Cr content in soil set at 0.5 ppm according to SNI.

Quantum-dot-functionalized paper-based device for simultaneous visual detection of Cu(II), Mn(II), and Hg(II)

In this work, a new paper-based device (PAD) was developed for the colorimetric detection of multiple heavy metals. The sensing principle of this PAD is based on the analyte-regulated photocatalytic activity of quantum dots (QDs) to certain substrates. The PAD consisted of three filter paper layers, defining a sample area, three channels, and three testing areas. Three photocatalytic reactions between different QDs and their corresponding substrates could be performed in one device, achieving the simultaneous detection of Cu(II), Mn(II), and Hg(II). The detection limits are 7.3 nM for Cu(II), 5.4 nM for Mn(II), and 8.1 nM for Hg(II), respectively. This PAD was applied to analyze real samples and the results were consistent with those obtained by inductively coupled plasma-optical emission spectrometer. This approach may provide a promising colorimetric sensing platform for multi-target analysis.

Synthesis and Characterization of Pure and Manganese (Mn) Doped Zinc Oxide (ZnO) Nanocrystallites for Photocatalytic Applications

In this work, pure and manganese (Mn) doped zinc oxide (ZnO) nanocrystallites are synthesized using a sol-gel technique. 0.25 M solution of zinc nitrate hexahydrate is prepared in 50 ml of DI water with stirring condition. An equimolar citric acid (0.25 M) solution is added slowly into the above solution and stirred for 2 hrs. at 70oC. The obtained gel is dried for 3 hrs in hot air oven at 120°C. Further, the nanoparticles are annealed at 400°C and the samples are characterized by X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Fourier transform infrared (FTIR) spectroscopy, photoluminescence spectroscopy (PL) and photo catalytic studies. XRD analysis deciphered the polycrystalline hexagonal of the samples and the crystallites sizes are observed to be 18 nm and 42 nm for the pure and Mn doped ZnO particles, respectively. FE-SEM studies demonstrate that the crystallites are spherical in shape with agglomeration. PL studies reveal the emission bands at 490 nm for pure ZnO and 530 nm for Mn doped ZnO. The photocatalytic studies determine the photocatalytic performance of pure ZnO NPs and Mn doped ZnO NPs under the UV light irradiation (365 nm and 125 W) in which, the pure ZnO degrades MB dye more efficiently than Mn doped ZnO.

Synthesis, optical and fluorescence properties of Mn-doped ZnS Quantum Dots

ZnS and 3% Mn: ZnS QDs were prepared by the hydrothermal method. The samples are characterized by X-ray diffraction (XRD), UV-Vis spectroscopy, photoluminescence (PL) and Fourier-transform Infrared spectroscopy (IR). UV-Vis spectroscopy data showed that the peaks of the prepared ZnS and Mn: ZnS samples display a hypochromic shift compared to that of the bulk ZnS. The calculated band-gap value of the ZnS and Mn: ZnS QDs are found to be 4.5 and 4.3 eV, respectively, and larger than that of bulk ZnS (3.68 eV) owing to strong quantum confinement. The calculated particle sizes from bandgap energies are found to be1.8 nm and 1.7 nm for ZnS and Mn: ZnS, respectively. The PL measurements showed that the emission intensity of ZnS QDs increased by doping with Mn2+. The fluorescence quantum yield (FLQY) of ZnS and 3% Mn: ZnS QDs is found to be 0.86 and 0.85, respectively. The incident photon-to-electron conversion efficiency (IPCE) measurement was conducted to investigate the photovoltaic properties of ZnS and 3% Mn: ZnS QDs. At 370 nm, the measured IPCE (%) values are found to be 1.2 % and 2.1 % for ZnS and Mn: ZnS, respectively, suggesting that the Mn2+ dopant enhances the optical properties of the host crystal (ZnS QDs).

TM-doped B12N12 nano-cage (TM = Mn, Fe) as a sensor for CO, NO, and NH3 gases: A DFT and TD-DFT study

The DFT-D3 and TD-DFT calculations at B3lyp/6-311+g(d) level of the theory have been employed to study the impact of TM (TM = Mn, Fe) doping as well as the adsorption of CO, NO, and NH3 gases on the electrical and optical properties of the boron nitride nano-cage (B12N12). The binding energy, ionization potential, electron affinity, chemical hardness, and softness are estimated to emphasize the stability of the doped MnB11N12 and FeB11N12. The band gap for B12N12 is 6.748 eV while the Mn and Fe doping decrease its value to 2.199 and 2.333 eV, respectively. In addition, the doping increases the dipole moment and enhances the adsorptivity of the clusters as well as converts B12N12 from UV active material (λmax=195 nm) into visible active material (λmax=389 nm for Mn and 419 nm for Fe). Second order perturbation theory analysis of donor-acceptor interactions in the NBO basis suggests the donation-back donation mechanism for the gas-cluster interaction. The adsorption of CO, NO, and NH3 gases causes a noticeable change in the Eg of MnB11N12 (-14.37%, +22.51%, +26.6%, respectively) while affects less the Eg of B12N12 and FeB11N12, as well as leads to a considerable shift to the λmax of the UV-Vis spectra. These results may be helpful for designing a promising boron nitride gas sensor.

Investigation on the structural, optical and photocatalytic degradation properties of Zns/Mn:Zns thin films under visible light irradiation

Undoped and Manganese (Mn) doped Zinc Sulfide (ZnS) thin films have been prepared by using a simple sol–gel dip coating method and as-prepared ZnS thin films annealed at 400 °C at hot air furnace in order to improve crystallinity. The influence of Mn doping and annealing temperature on the structural, morphological, optical and photocatalytic behavior of the ZnS thin films under visible light irradiation has been scientifically investigated by using XRD, FESEM, UV–Visible and Photocatalytic analysis. XRD results suggest that prepared ZnS thin films formed hexagonal phase and crystallite size was calculated as 25 and 40 nm for ZnS and Mn:ZnS respectively. FESEM analysis shows that the nonoflake like morphology observed for undoped ZnS thin films annealed at 400 °C and this nonoflake like morphology further disappeared for Mn:ZnS thin films. An optical analysis confirm that the absorption edge shifts toward longer wavelength (red shift), which confirm that decreasing the band gap energy was observed for Mn:ZnS thin films. Besides, photocatalytic activity of methylene blue (MB) dye was investigated by using ZnS and Mn:ZnS thin films as catalyst under visible light irradiation. The result suggest that Mn:ZnS thin films exhibited excellent photocatalytic degradation efficiency (94%) and high stability towards MB dye than compared to pure ZnS thin films.

Effect of Temperature and Magnetic Dopants on Particle size and Electrical Properties of ZnO Ceramic Varistor

We report here structural and electrical properties of Zn0.95 M0.05O ceramic, M = Zn, Co and Mn. It is found that addition of magnetic doping did not influence the hexagonal wurtzite structure of ZnO. Furthermore, the lattice parameters ratio c/a for hexagonal distortion and the length of the bond parallel u to the c axis were nearly unaffected. The average crystalline diameters, deduced from XRD analysis are 83.75, 72.86 and 70.97 nm for Zn, Mn and Co, which are 15 times lower than those obtained from FESEM micrographs (1570, 1380 and 1150 nm). The breakdown field EB was decreased as the temperature increased, in the following order: Mn> Zn > Co. The nonlinear region was observed for all samples as the temperature increased up to 400 K and completely disappeared with further increase of temperature up to 500 K. The values of nonlinear coefficient, α were between 1.65 and 56 for all samples, in the following order: Mn> Zn > Co. Moreover, the electrical conductivity σ was gradually increased as the temperature increased up to 500 K, in the following order: Co > Zn > Mn. On the other hand, the activation energies were 0.194, 0.155 eV and 0.231 eV for all samples, in the following order Mn, Zn and Co. These results have been discussed in terms of valence states, magnetic moment and thermo-ionic emission which were produced by the doping, and controlling the potential barrier of ZnO.

Investigation on microstructure and improved supercapacitive performance of Mn doped CuO thin films prepared by reactive radio frequency magnetron sputtering

A reactive radio frequency magnetron sputtering technique was adopted to synthesize un-doped copper oxide and manganese doped copper oxide thin films. XRD analysis confirmed the formation of monoclinic phase of CuO with average crystallite size of about 19 and 15.5 nm for CuO and Mn doped CuO thin films respectively. Field emission scanning electron microcopy investigation indicated that doping of CuO with Mn influences the microstructure of the doped films. The electrochemical measurements using cyclic voltammetry (CV) and galvanostatic charging with potential limited (GCPL) techniques were carried out to study the electrochemical supercapacitive performance of the Mn doped CuO film electrodes. An areal capacitance of the Mn doped CuO film electrode obtained from CV measurements was 81 mF cm−2 measured at 10 mV s−1. The galvanostatic charge–discharge (GCD) measurements exhibited the areal capacitance of 87 mF cm−2 at constant current density of 1 mA cm−2 in 3 M KOH. These GCD profiles were linear and symmetric in nature with the maximum columbic efficiency of about 96%. The electrochemical performance of the Mn doped CuO has indicated that the as-prepared Mn doped CuO film electrodes could be good candidate electrodes for supercapacitor applications.

Room temperature ferromagnetic behavior of Mn doped NiO nanoparticles: a suitable electrode material for supercapacitors

Magnetism in Ni1 −xMnxO (x = 0.0, 0.1, 0.2, 0.3) nanoparticles synthesized by Sol–gel technique has been reported. X-ray diffraction (XRD), FESEM with EDAX, Fourier transform infrared spectroscopy (FTIR) and Vibrating Sample Magnetometer (VSM) were employed to understand the influence of Mn in the structural, functional and magnetic properties of NiO nanoparticles. XRD analysis confirmed the formation of single phase cubic structure. The average particle size was measured to be 29 and 23 nm for NiO and Mn doped NiO nanoparticles respectively. FESEM results revealed that particles were spherical in shape. The elemental composition was analyzed by EDAX and it was in good agreement with the starting stoichiometries. FTIR spectra confirmed the existence of NiO. Room temperature ferromagnetism was observed for pure and Mn doped NiO nanoparticles. Pure NiO particles show ferromagnetic behavior with high coercivity and it reduces gradually when doping ratio increases. Higher saturation magnetization was obtained for the sample 0.1% of Mn doped NiO nanoparticles. Electrochemical properties of Mn doped NiO was investigated regarding its performance as electrodes in supercapacitors. Pure NiO shows the maximum specific capacitance of 134.46 Fg−1 at a scan rate of 20 m Vs−1. It reveals that it is a good electrode material for super capacitor.

Effect of chromium substitution on crystal and lattice structure of soft manganese zinc ferrites

Chromium-doped manganese–zinc ferrite samples were prepared by solid-state reaction route to probe the effect of chromium ion on the crystal and lattice structure of mixed manganese–zinc ferrite. X-ray diffraction patterns reveal that Mn[Formula: see text]Zn[Formula: see text]Cr[Formula: see text]Fe[Formula: see text]O[Formula: see text] ([Formula: see text] = 0.0, 0.1, 0.2, 0.3, 0.4 and 0.5) ferrite has polycrystalline cubic spinel structure with some secondary phase of [Formula: see text]–Fe[Formula: see text]O[Formula: see text]. The Raman spectra reveal four Raman active phonon modes in the measurement range of 200–750 cm[Formula: see text] with small shift in Raman modes towards higher wave number. The average particle size for Mn[Formula: see text]Zn[Formula: see text]Fe[Formula: see text]O[Formula: see text] is found to be 37.28 nm which reduces to 33.64 nm for Mn[Formula: see text]Cr[Formula: see text]Fe[Formula: see text]O[Formula: see text]. As the ion doping of chromium increases, the modes of vibration are found to shift towards higher wavelength and blueshift is attributed to the higher ionic radii of Cr[Formula: see text] as compared to Zn[Formula: see text].

Ca(II) Binding Regulates and Dominates the Reactivity of a Transition-Metal-Ion-Dependent Diesterase from Mycobacterium tuberculosis.

The diesterase Rv0805 from Mycobacterium tuberculosis is a dinuclear metallohydrolase that plays an important role in signal transduction by controlling the intracellular levels of cyclic nucleotides. As Rv0805 is essential for mycobacterial growth it is a promising new target for the development of chemotherapeutics to treat tuberculosis. The in vivo metal-ion composition of Rv0805 is subject to debate. Here, we demonstrate that the active site accommodates two divalent transition metal ions with binding affinities ranging from approximately 50 nm for Mn(II) to about 600 nm for Zn(II) . In contrast, the enzyme GpdQ from Enterobacter aerogenes, despite having a coordination sphere identical to that of Rv0805, binds only one metal ion in the absence of substrate, thus demonstrating the significance of the outer sphere to modulate metal-ion binding and enzymatic reactivity. Ca(II) also binds tightly to Rv0805 (Kd ≈40 nm), but kinetic, calorimetric, and spectroscopic data indicate that two Ca(II) ions bind at a site different from the dinuclear transition-metal-ion binding site. Ca(II) acts as an activator of the enzymatic activity but is able to promote the hydrolysis of substrates even in the absence of transition-metal ions, thus providing an effective strategy for the regulation of the enzymatic activity.

4-(2-Pyridylazo)-resorcinol Functionalized Thermosensitive Ionic Microgels for Optical Detection of Heavy Metal Ions at Nanomolar Level.

4-(2-Pyridylazo)-resorcinol (PAR) functionalized thermosensitive ionic microgels (PAR-MG) were synthesized by a one-pot quaternization method. The PAR-MG microgels were spherical in shape with radius of ca. 166.0 nm and narrow size distribution and exhibited thermo-sensitivity in aqueous solution. The PAR-MG microgels could optically detect trace heavy metal ions, such as Cu(2+), Mn(2+), Pb(2+), Zn(2+), and Ni(2+), in aqueous solutions with high selectivity and sensitivity. The PAR-MG microgel suspensions exhibited characteristic color with the presence of various trace heavy metal ions, which could be visually distinguished by naked eyes. The limit of colorimetric detection (DL) was determined to be 38 nM for Cu(2+) at pH 3, 12 nM for Cu(2+) at pH 7, and 14, 79, 20, and 21 nM for Mn(2+), Pb(2+), Zn(2+), and Ni(2+), respectively, at pH 11, which was lower than (or close to) the United States Environmental Protection Agency standard for the safety limit of these heavy metal ions in drinking water. The mechanism of detection was attributed to the chelation between the nitrogen atoms and o-hydroxyl groups of PAR within the microgels and heavy metal ions.

High resolution transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction studies of nanocrystalline manganese borohydride (Mn(BH4)2) after mechano-chemical synthesis and thermal dehydrogenation

Abstract In order to synthesize manganese borohydride, Mn(BH4)2, mechano-chemical activation synthesis (MCAS) of the (2LiBH4 + MnCl2) powder mixture was carried out by ball milling in a magneto ball mill. Both X-ray diffraction and TEM selected area electron diffraction patterns (SAEDPs) clearly confirm the presence of the Mn(BH4)2 and LiCl phases in the synthesized nanocomposite. No other phases were detected. Bright field high-resolution TEM imaging of the synthesized composite powder particles reveals the presence of nanograins consistent with LiCl and Mn(BH4)2 within the powder particles. Their respective grain sizes, estimated as the equivalent circle diameters (ECD) from the high-resolution TEM micrographs with the corrected sample standard deviations, are within the range of 14.1 ± 3.7 nm and 10.0 ± 2.9 nm for LiCl and Mn(BH4)2, respectively. The XRD patterns of the thermally dehydrogenated (Mn(BH4)2 + 2LiCl) nanocomposite do not exhibit any Bragg diffraction peaks belonging to either crystalline Mn or B. In contrast, the SAED patterns and EDS elemental maps provide strong evidence that both Mn and B exist in the dehydrogenated powder as crystalline phases α-Mn and β-B, respectively. The results show that the lack of XRD Bragg diffraction peaks is insufficient evidence that the Mn and B elemental products of Mn(BH4)2 thermolysis can be classified as being amorphous.

Photocatalytic studies of crystal violet dye using mn doped and PVP capped ZnO nanoparticles.

Mn (0.5%, 1%, 1.5% and 2%) doped and undoped ZnO nanoparticles (NPs) capped with PVP (1.0%) were successfully synthesized via co-precipitation approach using zinc acetate, sodium hydroxide and manganese acetate as precursors. Structural analysis was performed by XRD confirming phase purity and crystalline wurtzite structure. TEM results show average particle size 15-20 nm and 22-25 nm for Mn (1%) and Mn (2%) doped ZnO NPs respectively. Manganese (Mn) doping has led to reduction in band gap which facilitate the absorption of radiation in visible region. The Photocatalytic activity of undoped and Mn (0.5%,1%,1.5% and 2%) doped NPs was analyzed via degradation of crystal violet (CV) dye. The crystal violet decomposition rate of undoped and Mn doped NPs were studied under UV-visible region. It is observed from degradation studies that the doping has a pronounced effect on the photocatalytic activity of ZnO NPs. Kinetic studies shows that photo degradation of CV follow a pseudo first-order kinetic law. Experiments for reusability of Mn (1%) doped with PVP (1%) capped ZnO were also performed to determine the stability of as prepared sample. It shows an increase in catalytic activity of NPs by small amount when exposed to UV irradiation for 3 h. Photoluminescence and UV-Visible absorption spectroscopy studies were also performed for studying the effect of UV irradiation on the surface of ZnO NPs.

Study on the efficiency of nanosized magnetite and mixed ferrites in magnetic hyperthermia

Magnetic materials, which have the potential for application in heating therapy by hyperthermia, were prepared. This alternative treatment is used to eliminate cancer cells. Magnetite, magnesium-calcium ferrites and manganese-calcium ferrites were synthesized by sol-gel method followed by heat treatment at different temperatures for 30 min in air. Materials with superparamagnetic behavior and nanometric sizes were obtained in all the cases. Thus, these nanopowders may be suitable for their use in human tissue. The average sizes were 14 nm for magnetite, 10 nm for both Mg(0.4)Ca(0.6)Fe(2)O(4) and Mg(0.6)Ca(0.4)Fe(2)O(4) and 11 nm for Mn(0.2)Ca(0.8)Fe(2)O(4). Taking into account that the Mg(0.4)Ca(0.6)Fe(2)O(4) and Mg(0.6)Ca(0.4)Fe(2)O(4) treated at 350 °C showed the lower coercivity values, these nanoparticles were selected for heating tests and cell viability. Heating curves of Mg(0.4)Ca(0.6)Fe(2)O(4) subjected to a magnetic field of 195 kHz and 10 kA/m exhibited a temperature increase up to 45 °C in 15 min. A high human osteosarcoma cell viability of 90-99.5% was displayed. The human osteosarcoma cell with magnesium-calcium ferrites exposed to a magnetic field revealed a death cell higher than 80% in all the cases.

Incorporation of Si-N inducing white light of SrAl 2Si 2O 8:Eu 2+,Mn 2+ phosphor for white light emitting diodes

Photoluminescence (PL) and colorimetric properties of white-light emission SrAl 2Si 2O 8:Eu 2+,Mn 2+ phosphor were tuned effectively through incorporating Si-N bond to the host in the form of Si 3N 4. A maximum solubility of Si-N bond in SrAl 2 -x Si 2+ x O 8 -x N x was estimated theoretically to be in a value of x=1.0. Under 365 nm irradiation, a distinct red-shift of blue band emission from 406 to 473 nm for Eu 2+ and an enhancement of yellow band emission peaked at ∼565 nm for Mn 2+ were observed with the increase of Si-N content. These effects resulted from partial substitution of Si-N for Al1-O1 and Al4-O2 sites in SrAl 2Si 2O 8 lattice. Eventually, a white emission with CIE chromaticity coordinates (0.287, 0.337) and color rendering index (CRI) 78.3 for SrAl 2Si 2O 8:Eu 2+,Mn 2+ phosphor were achieved upon optimization to a suitable amount of Si-N.

Studies on the preparation and ethanol gas sensing properties of spinel Zn 0.6Mn 0.4Fe 2O 4 nanomaterials

Zn 1− x Mn x Fe 2O 4 ( x = 0, 0.2 and 0.4) nanomaterials were synthesized by sol–gel citrate method and studied structural and gas sensing properties. The structural characteristics of synthesized nanomaterials were studied by X-ray diffraction measurement (XRD) and transmission electron microscope (TEM). The results revealed that the particle size is in the range of 30–35 nm for Mn–Zn ferrite with good crystallinity. The gas sensing properties were studied towards reducing gases like LPG, CH 4, CO and ethanol and it is observed that Mn–Zn ferrite shows high response to ethanol at relatively lower operating temperature. The Zn 0.6Mn 0.4Fe 2O 4 nanomaterial shows better sensitivity towards ethanol at an operating temperature 300 °C. Incorporation of 1.5 wt.% Pd improved the sensitivity, selectivity, response time and reduced the operating temperature from 300 °C to 230 °C for ethanol sensor. The response time of 200 ppm ethanol in air is about 10s.

Manganese in coastal rainwater: speciation, photochemistry and deposition to seawater

Concentrations of manganese in 56 rain events in Wilmington, NC, USA rainwater from April 1, 2005 to March 31, 2006 were 11 ± 3 nM for dissolved Mn and 1.2 ± 0.4 nM for particulate Mn. Concentrations of both forms of Mn were higher in terrestrial storms relative to marine events. This observation along with the positive correlation of Mn with pollutant indicators suggests anthropogenic inputs to rain at this location, as has been observed at other locations. The ratio of Mnpart/Mndiss was threefold larger in summer relative to winter rain, which matched the increase of particulate to dissolved Fe in rainwater suggesting influence of Saharan dust during the summer. Like Fe in rain, Mn undergoes photoreduction in rainwater, which has also been shown to be important in Mn cycling in seawater. The flux of Mn removed from the atmosphere via wet deposition is 1.5 × 10−5 moles m−2 yr−1 at this location, which is approximately twice the flux reported from two rainwater studies conducted in the early 1980s on Bermuda. Atmospheric input of Mn to the oceans is important because Mn like Fe is an essential and potentially limiting nutrient. Experiments mixing authentic rainwater and seawater demonstrate that rainwater dissolved Mn does not rapidly precipitate in seawater suggesting wet deposition is an important source of soluble, stable Mn to surface seawater.