**4. Characterization experiments for CNOs**

Under condition described in **Table 1** we obtain in our laboratories high quality CNOs [33].

### **4.1. Micro-Raman experiments**

In **Figure 18** the induced defects and disorder are related to D band (1350 cm−1), G band (1550– 1620 cm−1) represents vibrations in graphene plane and Dʹ band (2500–3000 cm−1) correspond to secondary order Raman scattering (second order of D and G bands).

**Figure 18.** Raman band characteristics to CNOs.

with Eq. (1). For all gases two diameters distribution of 1.31 and 1.47 nm were calculated see **Figure 16(b)** (black lines) in great agreement with the result obtained from statistically HR-

302 Applications of Laser Ablation - Thin Film Deposition, Nanomaterial Synthesis and Surface Modification

As can be seen in **Figure 17** we found different yields of SWCNTs versus the gas carrier. In **Table 3** using the yields and collected mass we calculate the mass of SWCNTs contained in the soot and the highest value was obtained in helium, almost 10 times more than in argon.

**Figure 17.** TGA curves of the ablation product, i.e., SWCNTs, obtained in different inert gases (Gas: air, *T* = 100–850°C).

Under condition described in **Table 1** we obtain in our laboratories high quality CNOs [33].

In **Figure 18** the induced defects and disorder are related to D band (1350 cm−1), G band (1550– 1620 cm−1) represents vibrations in graphene plane and Dʹ band (2500–3000 cm−1) correspond

He 44 75.3 33.1 Ne 28.7 88.3 25.3 N2 8.6 53.7 4.6 Ar 8.4 43.2 3.6

to secondary order Raman scattering (second order of D and G bands).

**Percentage of SWCNTs in the deposition from TGA curves**

**Mass of SWCNTs produced**

**[mg]**

STEM measurements 1.25–1.35 nm (**Figure 13**).

*3.7.4. TGA experiments*

**Carrier gas Mass of deposition onto cold finger [mg]**

**4.1. Micro-Raman experiments**

**Table 3.** SWCNTs mass calculated from the TGA curves.

**4. Characterization experiments for CNOs**

The ratio of the D and G band intensity (*I*D/*I*G), which is related with the crystalline perfection was calculated and is 0.63. This value indicates that the CNOs synthesized by laser ablation shown a high crystallinity. Pimenta proposed an empirical formula (2) for determine in-plane crystallite size *La* in nm [34].

$$L\_a = \frac{560}{E^4} \frac{I\_G}{I\_D} \tag{2}$$

where *E* is the excitation energy in eV (2.33 eV). Thus, resulting *La* value based on this formula is about 30 nm.

### **4.2. SEM experiments**

As can be observed in **Figure 19** by ablating the target under conditions for CNOs we obtain totally different material comparing with SWCNTs images from **Figure 10**. The raw material looks as well defined spherical shapes.

**Figure 19.** SEM images of CNOs.

### **4.3. HR-TEM experiments**

The products obtained by ablating the pure graphite target using conditions for CNOs synthesis in **Table 1**, look like well-defined nano-onions, both individual and clustered through a matrix of amorphous carbon. As can be seen in **Figure 20(a)** the diameter is between 10 and 25 nm which is in good agreement with the dimensions obtained from micro-Raman spectroscopy using Pimenta formula (2).

**Figure 20.** (a) CNOs clustered; (b) CNOs profile perpendicular to shells (c) CNOs profile along of the shell.

If we measure the graphitic interlayer distance of the CNOs from perpendicular direction to shells profile we found 0.35 nm in great agreement with the graphene monolayer thickness (**Figure 20(b)**). On the other hand if we analyze the profile in along of shell we found the distance between two consecutive atoms to be 0.24 nm, in good agreement with the atomic lattice on graphene **Figure 20(c)**.

### **4.4. TGA experiments**

In order to measure the purity of obtained CNOs we perform thermo-gravimetric analysis (TGA) as can be seen in **Figure 21**. The percentage of weight lost has been measured using a constant heating rate of 5°C/min under a 20 mL/min Ar flux that limited the oxygen content in the furnace.

The mass loss between 350 and 600°C was assigned to the oxidation of the CNOs and is about 94%.

**Figure 21.** TGA curves of the CNOs (Gas: argon, *T* = 50–1200°C).
