# Role of Forster Resonance Energy Transfer in Graphene-Based Nanomaterials for Sensing
## 4 Conclusions and Perspectives  
In this review, we have summarized the significant progress in graphene-based nanomaterials such as GO, rGO, and GQDs, and discussed the synthesis, fluorescence properties, and FRET-based sensing of various target analytes. In the past 3 years, various methodologies have been developed to fabricate graphene-based pure and composite nanomaterials and their excellent photophysical performances, bringing them into practical applications. Despite this, various fabrication methodologies have been reported in graphene-related material research, but they are still at the primary stage in this field. For instance, atom-precise structures and well-defined protocols have not been developed to date. Therefore, start-of-the-art methodologies, structural relationships and properties, and technological fields of applications need to be well explored. In addition, graphene-based optical materials and their properties related to theoretical studies can be implemented in the future to obtain better-defined materials. In the field of sensing, we believe FRET-based sensors are less explored and most graphene-based nanomaterials are involved in fluorescence quenching. However, know \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**S.No** & **Sensors** & **Analytes** & **Mechanism** & **Binding Constant (M\({}^{-1}\))** & **LOD (M)** & **Ref.** \\ \hline
5 & GO & Zr\({}^{4+}\) & FRET & \(1.7\times 10^{4}\) M\({}^{-1}\) & 27 ng/mL & [58] \\ \hline
6 & GQDs & TNT & FRET & 1–20 nM & 0.6 nM & [60] \\ \hline
7 & Ag@AuNPs & H\({}_{2}\)O\({}_{2}\) & FRET & - & 0.4 uM & [62] \\ \hline
8 & GO-QDs & Theophylline & FRET & - & 4 nM & [64] \\ \hline
9 & GQDs-MnO\({}_{2}\) & Glutathione & FRET & - & 48 nM & [66] \\ \hline  & & & FRET & 0.01–0.1 uM & 2.4 nM & \\ \cline{3-6}  & & & FRET & 0.01–0.1 uM & & \\
10 & GQDs & Glutathione & 0.1–25 uM & 1.5 nM & & \\ \cline{3-6}  & & FRET & 0.01–0.1 uM & 4.2 nM & & \\ \cline{3-6}  & & FRET & 0.01–0.1 uM & 4.4 nM & & \\ \cline{3-6}  & & FRET & 0.1–30 uM & 4.4 nM & & \\ \hline
11 & GQDs & HE4 (Protein) & FRET & - & 4.8 pM–300 nM & [68] \\ \hline
12 & GO/aptamer & Antibiotics & FRET & - & (i) 1.997 ng/mL & [69] \\ \hline
13 & GQDs & Campylobacter & FRET & 10–10\({}^{6}\) CFU & 10 CFU/mL & [70] \\ \hline
14 & rGQDs & Digoxin & FRET & (i) 9.95 \(\pm\) 0.32 \(\times\) 10\({}^{-11}\) mol L\({}^{-1}\) &
\begin{tabular}{c} (i) 29.87 \(\pm\) 1.01 \(\times\) 10\({}^{-12}\) \\ mol L\({}^{-1}\) \\ (ii) 7.95 \(\pm\) 0.22 \(\times\) 10\({}^{-12}\) \\ mol L\({}^{-1}\) \\ \end{tabular} & [71] \\ \hline
15 & GQDs & Vi antigen & FRET & - & 1 pg/mL & [72] \\ \hline
16 & \
\begin{tabular}{c} GO/HA \\ aptamer \\ \end{tabular} &
\begin{tabular}{c} H5N1 IAV \\ hemagglutinin \\ (HA) \\ \end{tabular} & FRET & 0.1–15 ng mL\({}^{-1}\) & 60.9 pg mL\({}^{-1}\) & [73] \\ \hline
17 & GDQDs & miRNA-21 & FRET & 5 pM–200 nM & 0.5 pM & [74] \\ \hline
18 & GO &
\begin{tabular}{c} DNA-t and \\ DNA-c \\ \end{tabular} & FRET & - & 0.12 uM & [75] \\ \hline
19 & QD/GO & DNA-t & FRET & - & 1 nM & [76] \\ \hline
20 & GOQDs & DNA & FRET & - & 10\({}^{4}\) –10\({}^{10}\)\(\mu\)L & [77] \\ \hline \hline \end{tabular}
\end{table} 
Table 1: _Cont._ing how to avoid the quenching process and achieve better selectivity is far from our understanding. Moreover, a single sensor for multi-analyte-detection-approach-related investigations and their mechanisms are also less studied. Therefore, more understanding is required in the case of target sensing with high selectivity. On the other hand, doping and surface modifications are important, and there seems to be a long way to go before understanding the complex mechanism. Until now, some preliminary research has been carried out in this field, and major opportunities will be available in the future. More importantly, commercial-sensing-device-fabrication-related research is still at a basic level, and enormous efforts are required in order to achieve a final sensor device meeting industrial standards.