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Wet chemical synthesis and magnetic properties of single crystal Co nanochains with surface amorphous passivation Co layers.

Zhou SM, Lou SY, Wang YQ, Chen XL, Liu LS, Yuan HL - Nanoscale Res Lett (2011)

Bottom Line: The as-synthesized Co samples do not include any other adulterants.Room-temperature-enhanced coercivity of NCs was observed, which is considered to have potential applications in spin filtering, high density magnetic recording, and nanosensors.PACS: 61.46.Df; 75.50; 81.07.Vb; 81.07.

View Article: PubMed Central - HTML - PubMed

Affiliation: Key Lab for Special Functional Materials of Ministry of Education, Henan University, 475004 Kaifeng, People's Republic of China. smzhou@henu.edu.cn.

ABSTRACT
: In this study, for the first time, high-yield chain-like one-dimensional (1D) Co nanostructures without any impurity have been produced by means of a solution dispersion approach under permanent-magnet. Size, morphology, component, and structure of the as-made samples have been confirmed by several techniques, and nanochains (NCs) with diameter of approximately 60 nm consisting of single-crystalline Co and amorphous Co-capped layer (about 3 nm) have been materialized. The as-synthesized Co samples do not include any other adulterants. The high-quality NC growth mechanism is proposed to be driven by magnetostatic interaction because NC can be reorganized under a weak magnetic field. Room-temperature-enhanced coercivity of NCs was observed, which is considered to have potential applications in spin filtering, high density magnetic recording, and nanosensors. PACS: 61.46.Df; 75.50; 81.07.Vb; 81.07.

No MeSH data available.


A typical (a) TEM and (b) HRTEM image of Co-NCs (inset: SAED pattern).
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Figure 2: A typical (a) TEM and (b) HRTEM image of Co-NCs (inset: SAED pattern).

Mentions: Figure 1a shows a typical SEM image, in which high dense (high-yield) chain-like nanostructures are observed. One can observe that the diameter and length of single NCs are approx. 60 nm and several micrometers, respectively. A high-resolution SEM image is demonstrated in the inset of Figure 1a where a nanoparticle array, taken from a single NC, is clearly seen. Based on SEM statistic analysis, the yield of the NCs is for approx. 60%. The XRD patterns of bulk Co NCs (Figure 1b) reveal that the two sharp diffraction peaks can be assigned to the Co face-centered cubic (FCC/Fm3m) structure (a = 0.354 nm) (see Card No. 15-0806, JCPDS-ICDD, June 2002). Two very broad peaks are noticed in 2 theta angles (20-40 and 45-60), which may result from the amorphous passivation Co layers and substrate. In addition, no impurity phases such as cobalt oxides or precursor compounds have been confirmed within instrumental error. More accurately, XPS was used to determine the composition of the bulk Co-NC samples. As shown Figure 1c, a range of XPS spectrum is indicated, in which the intensive peaks located at 778.3 eV (Co2p3/2) and 793.3 eV (Co2p1/2) correspond to the respective electronic states of metallic Co. As indicated with the arrows, these wide peaks (from 831 to 838 and from 777 to 698) originate from auger lines of monochromated Al for XPS characterization. It is clear that the NCs are high-pure Co0 with other elements absent, which is in very good agreement with the results of XRD. As shown in Figure 2a, a typical slight enlargement TEM image of the as-synthesized large-scale NCs is exhibited. From the TEM image, one can, by closer observation, conclude that perfectly aligned nanoparticles (chain-like nanostructures) were produced and the diameter of individual Co NCs is approx. 60 nm. For microanalysis, HRTEM, SAED, and EDS were employed for phase, and composition of single NCs. A HRTEM image taken from a single nanoparticle is shown in Figure 2b, in which the presence of the gray edge without any stripes and the center with perfect continuous lattice fringes reveals the amorphous passivation shell (marked with the large white arrow) and high-quality crystal core growth. The lattice spacing of 8.86 Å (5 × 1.772 Å) is consistent with that of the [200] planes of single-crystalline face-centered Co, which is compatible with the data of XRD. The SAED patterns (see the inset in Figure 2b) are composed of the regular, clear diffraction dots, which reveal the single crystalline nature and can be indexed to the FCC Co. Diffraction patterns taken from different parts along the NC axis show the same features, indicating the same periodical orientation along the single-crystalline Co NC. Based on micro-composition-analysis, Figure 3a gives a typical EDS pattern, in which only the Co peaks can be indexed within experimental error, and the peaks of elements Cu and C are attributable to copper grid with carbon film.


Wet chemical synthesis and magnetic properties of single crystal Co nanochains with surface amorphous passivation Co layers.

Zhou SM, Lou SY, Wang YQ, Chen XL, Liu LS, Yuan HL - Nanoscale Res Lett (2011)

A typical (a) TEM and (b) HRTEM image of Co-NCs (inset: SAED pattern).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211350&req=5

Figure 2: A typical (a) TEM and (b) HRTEM image of Co-NCs (inset: SAED pattern).
Mentions: Figure 1a shows a typical SEM image, in which high dense (high-yield) chain-like nanostructures are observed. One can observe that the diameter and length of single NCs are approx. 60 nm and several micrometers, respectively. A high-resolution SEM image is demonstrated in the inset of Figure 1a where a nanoparticle array, taken from a single NC, is clearly seen. Based on SEM statistic analysis, the yield of the NCs is for approx. 60%. The XRD patterns of bulk Co NCs (Figure 1b) reveal that the two sharp diffraction peaks can be assigned to the Co face-centered cubic (FCC/Fm3m) structure (a = 0.354 nm) (see Card No. 15-0806, JCPDS-ICDD, June 2002). Two very broad peaks are noticed in 2 theta angles (20-40 and 45-60), which may result from the amorphous passivation Co layers and substrate. In addition, no impurity phases such as cobalt oxides or precursor compounds have been confirmed within instrumental error. More accurately, XPS was used to determine the composition of the bulk Co-NC samples. As shown Figure 1c, a range of XPS spectrum is indicated, in which the intensive peaks located at 778.3 eV (Co2p3/2) and 793.3 eV (Co2p1/2) correspond to the respective electronic states of metallic Co. As indicated with the arrows, these wide peaks (from 831 to 838 and from 777 to 698) originate from auger lines of monochromated Al for XPS characterization. It is clear that the NCs are high-pure Co0 with other elements absent, which is in very good agreement with the results of XRD. As shown in Figure 2a, a typical slight enlargement TEM image of the as-synthesized large-scale NCs is exhibited. From the TEM image, one can, by closer observation, conclude that perfectly aligned nanoparticles (chain-like nanostructures) were produced and the diameter of individual Co NCs is approx. 60 nm. For microanalysis, HRTEM, SAED, and EDS were employed for phase, and composition of single NCs. A HRTEM image taken from a single nanoparticle is shown in Figure 2b, in which the presence of the gray edge without any stripes and the center with perfect continuous lattice fringes reveals the amorphous passivation shell (marked with the large white arrow) and high-quality crystal core growth. The lattice spacing of 8.86 Å (5 × 1.772 Å) is consistent with that of the [200] planes of single-crystalline face-centered Co, which is compatible with the data of XRD. The SAED patterns (see the inset in Figure 2b) are composed of the regular, clear diffraction dots, which reveal the single crystalline nature and can be indexed to the FCC Co. Diffraction patterns taken from different parts along the NC axis show the same features, indicating the same periodical orientation along the single-crystalline Co NC. Based on micro-composition-analysis, Figure 3a gives a typical EDS pattern, in which only the Co peaks can be indexed within experimental error, and the peaks of elements Cu and C are attributable to copper grid with carbon film.

Bottom Line: The as-synthesized Co samples do not include any other adulterants.Room-temperature-enhanced coercivity of NCs was observed, which is considered to have potential applications in spin filtering, high density magnetic recording, and nanosensors.PACS: 61.46.Df; 75.50; 81.07.Vb; 81.07.

View Article: PubMed Central - HTML - PubMed

Affiliation: Key Lab for Special Functional Materials of Ministry of Education, Henan University, 475004 Kaifeng, People's Republic of China. smzhou@henu.edu.cn.

ABSTRACT
: In this study, for the first time, high-yield chain-like one-dimensional (1D) Co nanostructures without any impurity have been produced by means of a solution dispersion approach under permanent-magnet. Size, morphology, component, and structure of the as-made samples have been confirmed by several techniques, and nanochains (NCs) with diameter of approximately 60 nm consisting of single-crystalline Co and amorphous Co-capped layer (about 3 nm) have been materialized. The as-synthesized Co samples do not include any other adulterants. The high-quality NC growth mechanism is proposed to be driven by magnetostatic interaction because NC can be reorganized under a weak magnetic field. Room-temperature-enhanced coercivity of NCs was observed, which is considered to have potential applications in spin filtering, high density magnetic recording, and nanosensors. PACS: 61.46.Df; 75.50; 81.07.Vb; 81.07.

No MeSH data available.