# Theranostic Nanoplatforms of Thiolated Reduced Graphene Oxide Nanosheets and Gold Nanoparticles
## 3 Results and Discussions
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & \multicolumn{2}{c}{**Step 1**} & \multicolumn{2}{c}{**Step 2**} & \multicolumn{2}{c}{**Step 3**} \\
**Sample** & **(\(\Delta^{\circ}\)C)** & \begin{tabular}{c} **Weight** \\ **Loss (\%)** \\ \end{tabular} & **(\(\Delta^{\circ}\)C)** & \
\begin{tabular}{c} **Weight** \\ **Loss (\%)** \\ \end{tabular} & **(\(\Delta^{\circ}\)C)** &
\begin{tabular}{c} **Weight** \\ **Loss (\%)** \\ \end{tabular} & **Residue** \\ \hline arGO & 50–110 & 4.2 & 111–300 & 44.5 & 360–450 & 10.7 & 34.0 \\ bwGO & 50–110 & 7.6 & 120–300 & 22.8 & 460–610 & 11.6 & 40.6 \\ rGO-SH & 50–110 & 2.9 & 150–340 & 7.6 & 430–800 & 51.0 & 34.5 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Characteristic weight loss (%) as function of temperature steps calculated from TGA analyses for as-received GO, base-washed GO, and thiolated reduced GO. Figure 2: TGA curves recorded under nitrogen flow for the lyophilized powers of as-received GO (solid line), base-washed GO (dashed line), and thiolated reduced GO (dotted line). In Figure 3a, the experimental ATR-FTIR spectra of arGO, bwGO, and rGOSH samples are shown. The IR spectrum of pristine GO demonstrates the presence of -OH (at 3392 cm\({}^{-1}\)), carboxyl -C=O and -C-O (stretching modes at 1737 cm\({}^{-1}\) and 1425 cm\({}^{-1}\), respectively), aromatic -C=C (at 1622 cm\({}^{-1}\)), epoxy O-C-O (bending modes at 874 cm\({}^{-1}\)), and C-OH phenolic stretching (at 1050 cm\({}^{-1}\)), indicating the existence of oxygen-containing groups on the GO sheets [88]. The C-H stretching modes at 3222 cm\({}^{-1}\) are also visible. Upon the base-wash treatment of GO, a diminished intensity in both the epoxy (at 874 cm\({}^{-1}\)) and the hydroxy (at 1050 cm\({}^{-1}\)) vibrational mode bands were observed, concomitantly with the appearance of a band at 1228 cm\({}^{-1}\), attributed to the C-O-C stretching, and a redshift to 1580 cm\({}^{-1}\) and to 1716 cm\({}^{-1}\) of the aromatic -C=C and of C=O stretching modes, respectively. These findings are characteristic of the deoxygenated surface, which occurred with the removal of OD and subsequent restoration of conjugation in the \(\pi\)-aromatic system [89]. After the brominating and thiolation treatments, it was expected that the hydroxyl (-OH) and carboxylic (-COOH) functional groups of GO would be transformed into sulphur-containing moieties, including thiol (-SH), for the most part, but also thiocarbboxylic (-COSH) or dithiocarbonylic (-CSSH) groups [32]. Accordingly, for rGOSH sample, the absorption broadband in the wavenumber region around 3400 cm\({}^{-1}\) disappeared, which revealed the absence of OH group after reduction. In general, all C-O vibrational modes were no longer observed in the rGOSH spectrum and the peak belonging the -C=C vibrational mode was redshifted to 1565 cm\({}^{-1}\)[90]. The weak S-H stretching band was barely visible at 2667 cm\({}^{-1}\)[89]. The calculated IR spectra in Figure 3b confirmed the trend observed in the experimental spectra, i.e., the disappearance in rGOSH sample of the peaks due to the O-H stretch modes (3600-3400 cm\({}^{-1}\) region), the appearance of S-H stretching at 2770 cm\({}^{-1}\), and the redshift of C=C stretching mode (1570 cm\({}^{-1}\) vs. 1580 cm\({}^{-1}\) in GO sample). Moreover, in the fingerprint region, 2000-800 cm\({}^{-1}\), where several convoluted bands were superimposed on a broader absorbance, significant changes in  
Figure 3: Infrared spectra of rGOSH in the comparison with GO: (**a**) Experimental attenuated total reflection-FTIR (ATR-FTIR) spectra of pristine GO, base-washed GO, and thiolated reduced GO; (**b**) calculated IR spectra of GO and thiolated reduced GO. the spectral feature were visible for rGOSH compared to GO, including the decrease of epoxide stretch at 1260 cm\({}^{-1}\)[91] and a significant absorption by C-S stretching modes at 720 cm\({}^{-1}\)[92].