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Synthesis and magnetic properties of single-crystalline Na2-xMn8O16 nanorods.

Lan C, Gong J, Liu S, Yang S - Nanoscale Res Lett (2011)

Bottom Line: The synthesis of single-crystalline hollandite-type manganese oxides Na2-xMn8O16 nanorods by a simple molten salt method is reported for the first time.The magnetic measurements indicated that the nanorods showed spin glass behavior and exchange bias effect at low temperatures.The low-temperature magnetic behaviors can be explained by the uncompensated spins on the surface of the nanorods.

View Article: PubMed Central - HTML - PubMed

Affiliation: Nanjing National Laboratory of Microstructures and Department of Physics, Nanjing University, 22 Hankou Road, Nanjing, 210093, China. sgyang@nju.edu.cn.

ABSTRACT
The synthesis of single-crystalline hollandite-type manganese oxides Na2-xMn8O16 nanorods by a simple molten salt method is reported for the first time. The nanorods were characterized by powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and a superconducting quantum interference device magnetometer. The magnetic measurements indicated that the nanorods showed spin glass behavior and exchange bias effect at low temperatures. The low-temperature magnetic behaviors can be explained by the uncompensated spins on the surface of the nanorods.

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SEM and TEM images. (a) Low-magnification SEM image of Na2-xMn8O16 nanorods; (b) high-magnification SEM image of Na2-xMn8O16 nanorods; (c) TEM image of Na2-xMn8O16 nanorods; (d) TEM image of a single Na2-xMn8O16 nanorod; (e) HRTEM image of the Na2-xMn8O16 nanorod, the inset of (e) is the corresponding SAED pattern of the nanorod. (f) EDS spectrum of the Na2-xMn8O16 nanorods. C peak originates from conductive adhesive, Cu peak originates from Cu sheet, and Pt peaks originate from sputtered Pt layer. (a) scale bar 10 μm, (b) scale bar 5 μm, (c) (d) scale bar 500 nm, (e) 5 nm
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Figure 2: SEM and TEM images. (a) Low-magnification SEM image of Na2-xMn8O16 nanorods; (b) high-magnification SEM image of Na2-xMn8O16 nanorods; (c) TEM image of Na2-xMn8O16 nanorods; (d) TEM image of a single Na2-xMn8O16 nanorod; (e) HRTEM image of the Na2-xMn8O16 nanorod, the inset of (e) is the corresponding SAED pattern of the nanorod. (f) EDS spectrum of the Na2-xMn8O16 nanorods. C peak originates from conductive adhesive, Cu peak originates from Cu sheet, and Pt peaks originate from sputtered Pt layer. (a) scale bar 10 μm, (b) scale bar 5 μm, (c) (d) scale bar 500 nm, (e) 5 nm

Mentions: A low-magnified scanning electron microscopy (SEM) image of Na2-xMn8O16 nanorods is shown in Figure 2a. From the SEM image, it can be found that large quantity of nanorods was obtained. The average diameter of the nanorods is about 200 nm from the high-magnified SEM image as shown in Figure 2b. The transmission electron microscopy (TEM) image shown in Figure 2c indicates that the product mainly consists of solid-rod-like structures and the average diameter of the nanorods is about 200 nm, consisting with the SEM results. The TEM image of a single nanorod is shown in Figure 2d. The high-resolution TEM (HRTEM) image taken from a part of the single nanorod is shown in Figure 2e. Clear lattice fringes in Figure 2e indicate a high crystallinity of the nanorod. The lattice spacings of 0.481 and 0.274 nm are recognized and ascribed to the (002) and (011) (or (01-1)) planes of the monoclinic phase of Na2-xMn8O16, respectively. The corresponding selected area electron diffraction (SAED) pattern taken from the same nanorod can be indexed to the reflections of the monoclinic phase of Na2-xMn8O16 as shown in the inset of Figure 2e. The clear diffraction spots indicate the high crystallinity of the nanorod, which is consistent with HRTEM result. Combing the HRTEM and SAED results, it can be concluded that the growth direction of the nanorod is along [010], which is the tunnel direction of the compound. The composition of the as-synthesized nanorods was determined by EDS. Figure 2f shows the EDS spectroscopy. The chemical components of the nanorods are Na, Mn, and O with the ratio 7.24:33.38:59.38. The ratio of O/Mn is close to 2, which is consistent with the chemical formula. The chemical formula calculated from the EDS result is Na1.74Mn8O16.


Synthesis and magnetic properties of single-crystalline Na2-xMn8O16 nanorods.

Lan C, Gong J, Liu S, Yang S - Nanoscale Res Lett (2011)

SEM and TEM images. (a) Low-magnification SEM image of Na2-xMn8O16 nanorods; (b) high-magnification SEM image of Na2-xMn8O16 nanorods; (c) TEM image of Na2-xMn8O16 nanorods; (d) TEM image of a single Na2-xMn8O16 nanorod; (e) HRTEM image of the Na2-xMn8O16 nanorod, the inset of (e) is the corresponding SAED pattern of the nanorod. (f) EDS spectrum of the Na2-xMn8O16 nanorods. C peak originates from conductive adhesive, Cu peak originates from Cu sheet, and Pt peaks originate from sputtered Pt layer. (a) scale bar 10 μm, (b) scale bar 5 μm, (c) (d) scale bar 500 nm, (e) 5 nm
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Figure 2: SEM and TEM images. (a) Low-magnification SEM image of Na2-xMn8O16 nanorods; (b) high-magnification SEM image of Na2-xMn8O16 nanorods; (c) TEM image of Na2-xMn8O16 nanorods; (d) TEM image of a single Na2-xMn8O16 nanorod; (e) HRTEM image of the Na2-xMn8O16 nanorod, the inset of (e) is the corresponding SAED pattern of the nanorod. (f) EDS spectrum of the Na2-xMn8O16 nanorods. C peak originates from conductive adhesive, Cu peak originates from Cu sheet, and Pt peaks originate from sputtered Pt layer. (a) scale bar 10 μm, (b) scale bar 5 μm, (c) (d) scale bar 500 nm, (e) 5 nm
Mentions: A low-magnified scanning electron microscopy (SEM) image of Na2-xMn8O16 nanorods is shown in Figure 2a. From the SEM image, it can be found that large quantity of nanorods was obtained. The average diameter of the nanorods is about 200 nm from the high-magnified SEM image as shown in Figure 2b. The transmission electron microscopy (TEM) image shown in Figure 2c indicates that the product mainly consists of solid-rod-like structures and the average diameter of the nanorods is about 200 nm, consisting with the SEM results. The TEM image of a single nanorod is shown in Figure 2d. The high-resolution TEM (HRTEM) image taken from a part of the single nanorod is shown in Figure 2e. Clear lattice fringes in Figure 2e indicate a high crystallinity of the nanorod. The lattice spacings of 0.481 and 0.274 nm are recognized and ascribed to the (002) and (011) (or (01-1)) planes of the monoclinic phase of Na2-xMn8O16, respectively. The corresponding selected area electron diffraction (SAED) pattern taken from the same nanorod can be indexed to the reflections of the monoclinic phase of Na2-xMn8O16 as shown in the inset of Figure 2e. The clear diffraction spots indicate the high crystallinity of the nanorod, which is consistent with HRTEM result. Combing the HRTEM and SAED results, it can be concluded that the growth direction of the nanorod is along [010], which is the tunnel direction of the compound. The composition of the as-synthesized nanorods was determined by EDS. Figure 2f shows the EDS spectroscopy. The chemical components of the nanorods are Na, Mn, and O with the ratio 7.24:33.38:59.38. The ratio of O/Mn is close to 2, which is consistent with the chemical formula. The chemical formula calculated from the EDS result is Na1.74Mn8O16.

Bottom Line: The synthesis of single-crystalline hollandite-type manganese oxides Na2-xMn8O16 nanorods by a simple molten salt method is reported for the first time.The magnetic measurements indicated that the nanorods showed spin glass behavior and exchange bias effect at low temperatures.The low-temperature magnetic behaviors can be explained by the uncompensated spins on the surface of the nanorods.

View Article: PubMed Central - HTML - PubMed

Affiliation: Nanjing National Laboratory of Microstructures and Department of Physics, Nanjing University, 22 Hankou Road, Nanjing, 210093, China. sgyang@nju.edu.cn.

ABSTRACT
The synthesis of single-crystalline hollandite-type manganese oxides Na2-xMn8O16 nanorods by a simple molten salt method is reported for the first time. The nanorods were characterized by powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and a superconducting quantum interference device magnetometer. The magnetic measurements indicated that the nanorods showed spin glass behavior and exchange bias effect at low temperatures. The low-temperature magnetic behaviors can be explained by the uncompensated spins on the surface of the nanorods.

No MeSH data available.


Related in: MedlinePlus