## 3 Results and Discussion  
EDX was used to examine the carbon and oxygen percentages in the functionalized CNTs. The degree of functionalization is shown in Table 1. As functionalization time increased, oxygen  
Figure 1: Structural formula for (**a**) griseofulvin (GF) and (**b**) sulfamethoxazole (SMZ). percentage increased and the C:COOH ratio decreased. After 40 min of functionalization, the oxygen percentage did not increase significantly and therefore treatment times beyond 40 minutes were not studied. The oxygen content of the different f-CNTs varied from 6.1 to 13.6% while the C:COOH ratio could be as low as 16:1. The f-CNTs were labeled based on the C:COOH ratio. The concentrations of f-CNTs in GF were calculated from the TGA (Figure 2). The amount of f-CNTs in the GF crystals prepared from f-CNT\({}_{23,2}\), f-CNT\({}_{19,8}\), and f-CNT\({}_{16.0}\) suspensions were found to be 3.9, 4.2, and 3.8%, respectively. The values were calculated based on the weight percent at the temperatures from which f-CNTs started to burn out (around 300 \({}^{\circ}\)C) for each composite minus the corresponding weight percent of pure GF at the same temperature. Since the behavior of the f-CNTs was similar to SMZ during thermogravimetric analysis, it was difficult to predict the composition of the SMZ-CNT samples by TGA. The concentrations of f-CNTs in the SMZ-CNTs were measured based on elemental analysis. The sulfur content was used to calculate the amount of SMZ in the composite, from which the amount of f-CNTs could be predicted. The amount of f-CNTs in the SMZ crystals prepared from f-CNT\({}_{23,2}\), f-CNT\({}_{19,8}\), and f-CNT\({}_{16.0}\) suspensions were found to be 2.9, 1.3, and 1.4%, respectively. These samples are referred to as SMZ-CNT\({}_{\mathrm{X}}\) or GF-CNT\({}_{\mathrm{X}}\), where x is the C:COOH ratio. It appears that the degree of functionalization did not significantly affect the weight percent of f-CNTs in the drug crystals formed during the anti-solvent precipitation. The GF-CNT and SMZ-CNT sample morphologies were studied using SEM. Figure 3a-c show SEM images of GF-CNT\({}_{23,2}\), GF-CNT\({}_{19,8}\), and GF-CNT\({}_{16}\) at 25 K magnification. Figure 3d-f show SEM images of SMZ-CNT\({}_{23,2}\), SMZ-CNT\({}_{19,8}\) and SMZ-CNT\({}_{16}\) at the same magnification. The SEM images show that the f-CNTs were present on the crystal surface. Compared to the SEM images of pure GF and pure SMZ in Figure 3g,h, the crystal shape and size did not depend on CNT functionalization or incorporation. The TEM images (Figure 3i,j) show that the f-CNTs were also partially embedded in the drug crystals. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Treatment Time (min)**} & \multicolumn{2}{c}{**\% by Weight**} & \multirow{2}{*}{**C:COOH**} \\ \cline{2-3} \cline{3-4}  & **C** & **O** & \\ \hline
0 & 92.7 & 6.1 & 39.5 \\ \hline
5 & 89.7 & 9.9 & 23.2 \\ \hline
10 & 87.9 & 11.2 & 19.8 \\ \hline
40 & 86.3 & 13.6 & 16.0 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Analysis of carboxylated carbon nanotubes (f-CNTs) with different levels of functionalization. Figure 2: Thermogravimetric analysis (TGA) of GF-CNT\({}_{\mathrm{x}}\). Figure 3: _Cont._  
Figure 3: Scanning electron microscope (SEM) images of (**a**) GF-CNT\({}_{23,2}\), (**b**) GF-CNT\({}_{19,8}\), (**c**) GF-CNT\({}_{16}\), (**d**) SMZ-CNT\({}_{23,2}\), (**e**) SMZ-CNT\({}_{19,8}\), (**f**) SMZ-CNT\({}_{16}\), (**g**) pure GF, (**h**) pure SMZ, and Transmission electron microscopy (TEM) images of (**i**) GF-CNT\({}_{16}\), (**j**) SMZ-CNT\({}_{16}\). Figure 4a shows the Raman spectra of f-CNTs, pure GF, and GF-CNTs with various degrees of functionalization. The typical spectral features of f-CNTs were overlaid with peaks from GF. The Raman spectra for pure GF and GF-CNT composites remained the same, indicating that the presence of the f-CNTs didn't change the chemical nature of the GF or its polymorphism, which are important considerations in drug development.