4. Nanodiamond (ND)-cobalt oxide (Co3O4) nanoparticles

#### 4.1 Synthesis procedure

The ND-Co3O4 nanoparticles were synthesized by Syam Sundar et al. [19] using in situ and the chemical coprecipitation method. The synthesis route and TEM results are shown in Figure 11. The synthesis route contains dispersion of 0.5 g of ND particles and 0.5 g (0.003 M) of CoCl26H2O in 100 mL, adds 0.379 (0.01 M) g of NaBH4 gradually, and observes the formation of light black color precipitate. The XRD, VSM, and XPS results of ND-Co3O4 nanocomposite are reported in Figure 10.

because of the presence of nonmagnetic material of ND. The coercivity results of ND-Co3O4 and of pure Co3O4 nanoparticles are 334 and 490 Oe, respectively (Figure 12c). Based on the total sum rule, it is observed that there is 67% of ND and 33% of Co3O4 present in the ND-Co3O4 nanocomposite nanoparticles. The prepared ND-Co3O4 nanofluid's samples are shown in Figure 12d, and the final ND-Co3O4

The Cobalt Oxide-Based Composite Nanomaterial Synthesis and Its Biomedical and Engineering…

ND-Co3O4 nanoparticles: (a) XRD patterns, (b) M–H curve, (c) coercivity, and (d) the ND-Co3O4

The surface composition of ND-Co3O4 nanocomposite particles was measured

using X-ray photoelectron spectroscopy (XPS), and the results are shown in Figure 13a–c. The Co 2p spectra has two main peaks at binding energies (BEs) of 780.7 and 796.3 eV, which can be related to Co 2p3/2 and Co 2p1/2 spin-orbit lines, respectively (Figure 13a). The determination of oxidation state of the each and every component is very important, and also it is very difficult. The shape of the satellites and the energy gap between the satellites are the key parameters used to discriminate between different oxidation states of Co. For instance, the presence of

nanocomposite particles showing magnetic behavior are observed.

ND-Co3O4 nanoparticles: (a) synthesized method and (b) TEM image [19].

DOI: http://dx.doi.org/10.5772/intechopen.88272

Figure 11.

Figure 12.

41

nanofluids [19].

The XRD, VSM, and prepared nanofluids are shown in Figure 12a–d. From the XRD patterns (Figure 12a), the 2θ position for the ND nanoparticles for the plane (111) is 43.73° ; similarly, the 2θ position for the Co3O4 nanoparticles for the plane (311) is 36.81<sup>o</sup> , and the ND-Co3O4 nanocomposite nanoparticles contains both the ND and Co3O4 nanoparticles planes. The weight percentage of ND and Co3O4 present in the ND-Co3O4 nanocomposite was measured from vibrating sample magnetometer (Cryogenic, UK) instrument (Figure 12b). The total saturation magnetization of Co3O4 nanoparticles is 14.3 emu/g, whereas the total saturation magnetization of ND-Co3O4 nanocomposite is 4.7 emu/g. It is decreased

The Cobalt Oxide-Based Composite Nanomaterial Synthesis and Its Biomedical and Engineering… DOI: http://dx.doi.org/10.5772/intechopen.88272

Figure 11. ND-Co3O4 nanoparticles: (a) synthesized method and (b) TEM image [19].

Figure 12. ND-Co3O4 nanoparticles: (a) XRD patterns, (b) M–H curve, (c) coercivity, and (d) the ND-Co3O4 nanofluids [19].

because of the presence of nonmagnetic material of ND. The coercivity results of ND-Co3O4 and of pure Co3O4 nanoparticles are 334 and 490 Oe, respectively (Figure 12c). Based on the total sum rule, it is observed that there is 67% of ND and 33% of Co3O4 present in the ND-Co3O4 nanocomposite nanoparticles. The prepared ND-Co3O4 nanofluid's samples are shown in Figure 12d, and the final ND-Co3O4 nanocomposite particles showing magnetic behavior are observed.

The surface composition of ND-Co3O4 nanocomposite particles was measured using X-ray photoelectron spectroscopy (XPS), and the results are shown in Figure 13a–c. The Co 2p spectra has two main peaks at binding energies (BEs) of 780.7 and 796.3 eV, which can be related to Co 2p3/2 and Co 2p1/2 spin-orbit lines, respectively (Figure 13a). The determination of oxidation state of the each and every component is very important, and also it is very difficult. The shape of the satellites and the energy gap between the satellites are the key parameters used to discriminate between different oxidation states of Co. For instance, the presence of

anode. So, it is understood that the composite material exhibits synergistic (superior

GO/Co3O4 nanomaterial: (a) charge-discharge curves at the current density of 0.5 A=g, (b) charge-discharge curves at different current densities (0.5, 1.0, and 2.0 A=g), (c) cycling stability at varying the current density,

The ND-Co3O4 nanoparticles were synthesized by Syam Sundar et al. [19] using

The XRD, VSM, and prepared nanofluids are shown in Figure 12a–d. From the

the ND and Co3O4 nanoparticles planes. The weight percentage of ND and Co3O4

sample magnetometer (Cryogenic, UK) instrument (Figure 12b). The total satura-

saturation magnetization of ND-Co3O4 nanocomposite is 4.7 emu/g. It is decreased

; similarly, the 2θ position for the Co3O4 nanoparticles for the

, and the ND-Co3O4 nanocomposite nanoparticles contains both

in situ and the chemical coprecipitation method. The synthesis route and TEM results are shown in Figure 11. The synthesis route contains dispersion of 0.5 g of ND particles and 0.5 g (0.003 M) of CoCl26H2O in 100 mL, adds 0.379 (0.01 M) g of NaBH4 gradually, and observes the formation of light black color precipitate. The XRD, VSM, and XPS results of ND-Co3O4 nanocomposite are reported in

XRD patterns (Figure 12a), the 2θ position for the ND nanoparticles for the

present in the ND-Co3O4 nanocomposite was measured from vibrating

tion magnetization of Co3O4 nanoparticles is 14.3 emu/g, whereas the total

electrical) properties compared to the single-phase nanoparticles.

and (d) long-term stability at a current density of 2.0 A=g [21].

4. Nanodiamond (ND)-cobalt oxide (Co3O4) nanoparticles

4.1 Synthesis procedure

Cobalt Compounds and Applications

Figure 10.

40

Figure 10.

plane (111) is 43.73°

plane (311) is 36.81<sup>o</sup>

Figure 13. ND-Co3O4 nanocomposite—XPS spectra: (a) Co 2P, (b) O 1s, and (c) C 1s core levels [19].

a pronounced satellite like that founded in the present sample at 785.7 eV can be ascribed to CoO. For the case of Co3O4 compounds, the satellite is generally detected at BEs higher than 10 eV with respect to the main peak. It is observed from the XPS analysis that the Co3O4 particles are covered by a thin layer of CoO.

The O 1s core level is presented in Figure 13b for the cobalt nanoparticles (bottom) and for the nanocomposite (upper). The first component, centered at a BE = 529.5 eV (gray), is ascribed to oxygen atoms in the cobalt particles, while the others are related to different oxygen species. In particular, the components at 531.6 eV (red) and 533.7 eV (green) are ascribed to OH and C▬O/O=C▬O, respectively. Moreover, in the case of the nanocomposite, the C 1s core level (Figure 13c) shows interesting features. Four components were needed for fitting this peak, appearing at BEs of 284.6 eV (gray), 286.5 eV (red), 287.8 eV (green), and 289.6 eV (blue), which can be ascribed to C▬C, C▬OH or C▬O▬C, C=O, and O=C▬O, respectively. Thus, XPS indicates that the cobalt particles are integrated with the treated nanodiamonds.

#### 4.2 Thermal properties

The water- and ethylene glycol-based ND-Co3O4 nanofluid's thermal conductivity and viscosity were measured by Syam Sundar et al. [19], and the data is shown in Figure 14a and b at different particle weight concentrations and temperatures. The water-based ND-Co3O4 nanofluid's samples are shown in Figure 14b, and particle size distribution is shown in Figure 14c. They observed thermal conductivity enhancement of 2 and 6% for 0.05 wt.% of water-based ND-Co3O4 nanofluid and the thermal conductivity enhancement of 8.7 and 15.7% for 0.15 wt.% of water-based ND-Co3O4 nanofluid at temperatures of 20 and 60°C, respectively, compared with water data (Figure 14a). They also observed thermal conductivity enhancement of 1.16 and 3.97% for 0.05 wt.% of EG-based ND-Co3O4 nanofluid and the thermal conductivity enhancement of 4.68 and 8.71% for 0.15 wt.% of EGbased ND-Co3O4 nanofluid at temperatures of 20 and 60°C, respectively, compared with EG data (Figure 14d).

cells showed a mitotic index of 71.3 2.2%. However, a dose-dependent effect on mitotic index was noted for Co3O4 and Co3O4-cND. In particular, the mitotic indices were found to be 58.07 1.7, 37.8 1.2, and 28.6 0.8% upon exposure

The Cobalt Oxide-Based Composite Nanomaterial Synthesis and Its Biomedical and Engineering…

DOI: http://dx.doi.org/10.5772/intechopen.88272

Thermal conductivity of ND-Co3O4 nanofluids: (a) water-based nanofluids, (b) sample nanofluids,

insignificant at these concentrations of cND with values of 68.3 2.0, 65.7 1.9, and 59.0 1.7, respectively. The ameliorative effect of Co-accrued impacts is demonstrated by low (5 μg/mL) and moderate (10 μg/mL) concentration values of cND-Co3O4. This indicates that, if accidentally released into the environment, cND-Co3O4 would be safe for biotic life to a maximum concentration of 10 μg/mL. The observed Co-accrued cyto-genotoxic consequences coincide with similar earlier studies, where Co oxide nanoparticles were reported to spoil the whole cellular metabolism and stages of cell division mainly by blocking water channels through

to 5, 10, and 20 μg/mL Co, respectively. Notably, decreases in MI were

(c) particle size distribution, and (d) EG-based nanofluids [19].

Figure 14.

43

#### 4.3 Toxicity of ND-Co3O4 nanoparticles

The toxicity of ND-Co3O4 nanoparticles was studied by Syam Sundar et al. [24] on Allium cepa, and the results are shown in Figure 15. The untreated root tip

The Cobalt Oxide-Based Composite Nanomaterial Synthesis and Its Biomedical and Engineering… DOI: http://dx.doi.org/10.5772/intechopen.88272

#### Figure 14.

a pronounced satellite like that founded in the present sample at 785.7 eV can be ascribed to CoO. For the case of Co3O4 compounds, the satellite is generally

ND-Co3O4 nanocomposite—XPS spectra: (a) Co 2P, (b) O 1s, and (c) C 1s core levels [19].

with the treated nanodiamonds.

Cobalt Compounds and Applications

4.2 Thermal properties

Figure 13.

with EG data (Figure 14d).

42

4.3 Toxicity of ND-Co3O4 nanoparticles

detected at BEs higher than 10 eV with respect to the main peak. It is observed from the XPS analysis that the Co3O4 particles are covered by a thin layer of CoO. The O 1s core level is presented in Figure 13b for the cobalt nanoparticles (bottom) and for the nanocomposite (upper). The first component, centered at a BE = 529.5 eV (gray), is ascribed to oxygen atoms in the cobalt particles, while the others are related to different oxygen species. In particular, the components at 531.6 eV (red) and 533.7 eV (green) are ascribed to OH and C▬O/O=C▬O, respectively. Moreover, in the case of the nanocomposite, the C 1s core level (Figure 13c) shows interesting features. Four components were needed for fitting this peak, appearing at BEs of 284.6 eV (gray), 286.5 eV (red), 287.8 eV (green), and 289.6 eV (blue), which can be ascribed to C▬C, C▬OH or C▬O▬C, C=O, and O=C▬O, respectively. Thus, XPS indicates that the cobalt particles are integrated

The water- and ethylene glycol-based ND-Co3O4 nanofluid's thermal conductivity and viscosity were measured by Syam Sundar et al. [19], and the data is shown in Figure 14a and b at different particle weight concentrations and temperatures. The water-based ND-Co3O4 nanofluid's samples are shown in Figure 14b, and particle size distribution is shown in Figure 14c. They observed thermal conductivity enhancement of 2 and 6% for 0.05 wt.% of water-based ND-Co3O4 nanofluid and the thermal conductivity enhancement of 8.7 and 15.7% for 0.15 wt.% of water-based ND-Co3O4 nanofluid at temperatures of 20 and 60°C, respectively, compared with water data (Figure 14a). They also observed thermal conductivity enhancement of 1.16 and 3.97% for 0.05 wt.% of EG-based ND-Co3O4 nanofluid and the thermal conductivity enhancement of 4.68 and 8.71% for 0.15 wt.% of EGbased ND-Co3O4 nanofluid at temperatures of 20 and 60°C, respectively, compared

The toxicity of ND-Co3O4 nanoparticles was studied by Syam Sundar et al. [24]

on Allium cepa, and the results are shown in Figure 15. The untreated root tip

Thermal conductivity of ND-Co3O4 nanofluids: (a) water-based nanofluids, (b) sample nanofluids, (c) particle size distribution, and (d) EG-based nanofluids [19].

cells showed a mitotic index of 71.3 2.2%. However, a dose-dependent effect on mitotic index was noted for Co3O4 and Co3O4-cND. In particular, the mitotic indices were found to be 58.07 1.7, 37.8 1.2, and 28.6 0.8% upon exposure to 5, 10, and 20 μg/mL Co, respectively. Notably, decreases in MI were insignificant at these concentrations of cND with values of 68.3 2.0, 65.7 1.9, and 59.0 1.7, respectively. The ameliorative effect of Co-accrued impacts is demonstrated by low (5 μg/mL) and moderate (10 μg/mL) concentration values of cND-Co3O4. This indicates that, if accidentally released into the environment, cND-Co3O4 would be safe for biotic life to a maximum concentration of 10 μg/mL. The observed Co-accrued cyto-genotoxic consequences coincide with similar earlier studies, where Co oxide nanoparticles were reported to spoil the whole cellular metabolism and stages of cell division mainly by blocking water channels through

conducted using Allium cepa (Figure 15A–D). For comparison purpose, similar tests are also performed for various concentrations of cobalt oxide nanoparticles

The Cobalt Oxide-Based Composite Nanomaterial Synthesis and Its Biomedical and Engineering…

The zeolite Y/cobalt oxide (Co3O4) nanoparticles were synthesized by Davar

nanocomposite was synthesized by an ion exchange of cobalt ions and zeolite Y in the presence of sodium hydroxide and calcination treatment; the synthesized zeolite

et al. [25], and the schematic diagram is depicted in Figure 16. The Co3O4

(Figure 15E–G) and cND-Co3O4 (H–K) (Figure 15H–K).

DOI: http://dx.doi.org/10.5772/intechopen.88272

5. Zeolite Y/cobalt oxide (Co3O4) nanoparticles

Y/Co3O4 has a paramagnetic behavior at room temperature.

6. Carbon nanotubes/cobalt oxide (Co3O4) nanoparticles

using the electrostatic coprecipitation route. They noted that the specific

The f-SWCNT/Co3O4 nanocomposite was prepared by Abdolmaleki et al. [26]

6.1 Synthesis procedure

Synthesis procedure of zeolite Y/Co3O4 nanoparticles [25].

Figure 16.

45

5.1 Synthesis procedure

#### Figure 15.

Toxicity tests on Allium cepa of ND-Co3O4 nanoparticles (A–D), various concentrations of cobalt oxide (E–G), and cND-Co3O4 (H–K). A = prophase, B = metaphase, C = anaphase, D = telophase, E = chromosomal break, F = cytoplasmic bridge, G = disturbed anaphase, H = laggard, I = sticky anaphase, J = scattered anaphase, K = prophase nuclei with micronucleus in interphase, L = binucleate cells [24].

adsorption and/or by impacting genetic material by causing various types of chromosomal aberrations.

In summary, insignificant changes in MI with moderate concentration (10 μg/mL) of cND-Co3O4 also confirm that cND-Co3O4 was unable to interfere with the normal development of mitosis mainly by its incapacity to prevent cells from entering the prophase and blocking the mitotic cycle during interphase inhibiting DNA/protein synthesis. Moreover, 20 μg/mL of cND-Co3O4 compared to 5, 10, and 20 μg/mL of Co3O4 and 10 μg/mL of cND-Co3O4 presents insignificant and infrequent chromosome aberrations (such as stickiness, breaks, disturbed, and scattered metaphase); therefore, these results strongly support the environment-friendly nature of the cND-Co3O4 nanocomposite, as demonstrated by the toxicity tests

The Cobalt Oxide-Based Composite Nanomaterial Synthesis and Its Biomedical and Engineering… DOI: http://dx.doi.org/10.5772/intechopen.88272

conducted using Allium cepa (Figure 15A–D). For comparison purpose, similar tests are also performed for various concentrations of cobalt oxide nanoparticles (Figure 15E–G) and cND-Co3O4 (H–K) (Figure 15H–K).
