# Role of Forster Resonance Energy Transfer in Graphene-Based Nanomaterials for Sensing
## 3 Application of Graphene-Based Nanomaterials in Sensing
### DNA and RNA Sensor  
Recently, [PERSON] et al. [74] developed a GDQDs (**G17**) probe for the sensing of miRNA-21 via the FRET process (Figure 19). Hence, GDQDs acted as a donor and GQDs behaved as an acceptor. During the sensing process, GDQDs conjugated with DNA showed a high fluorescence intensity in the presence of GQDs via the FRET process. In the presence of miRNA with conjugated GDQDs with DNA, the distance between the GDQDs and GQDs increased, which was confirmed through the average lifetime analysis. The LOD was noted to be 0.5 pM (S/N = 3). Moreover, **G17** could be used to detect miRNA-21 in human serum, biological cell lines, and MDA-MB231 living cancer cells. [PERSON] et al. [75] developed a fluorescence magnetic nanoparticle (FMNP) modified with target DNA-t (**G18**), which was bound onto the modified GO (Figure 20). The **G18** probe could act as a fluorescence quencher, and was further used for the detection of DNA-t and DNA-c through fluorescence techniques. The detection of hybridization occurred between DNA-t and DNA-c, due to \(\pi\)-\(\pi^{*}\)/n-\(\pi^{*}\) transitions and the sp\({}^{2}\) hybridization of GO, which led to a decrease in the fluorescence intensity of **G18** through the FRET quenching mechanism (LOD = 0.12 uM). Figure 18: Schematic representation of UCNPs (**G16**) and their sensing of HA of influenza via the FRET process. Reprinted from [73] with permission from the American Chemical Society. To overcome antibiotic resistance, [PERSON] et al. [76] synthesized a ZFP-GO (**G19**) probe through the interconnection of zinc finger proteins (ZFPs) and 2D nanosheet GO. ZFP-labeled quantum dots (QD) were applied over the GO nanosheet, which quenched the fluorescence intensity via the FRET mechanism (Figure 21). In the selective detection of the antibiotic resistance gene (ARG) in bacteria, the probe **G19** behaved as a turn OFF and ON in the presence and absence of ARG. During this process, engineered DNA took 10 min to detect the DNA-t, as per the detection system. Notably, **G19** was modified with GO-ZFP, which could detect ARG quickly with a LOD of 1 nM. Furthermore, **G19** DNA-binding domains could be utilized for the specific detection of dsDNA. [PERSON] and [PERSON] et al. [77] fabricated GOQDs (**G20**) for the detection of DNA sequences (Figure 22). Briefly, **G20** was treated with three different fluorescent dyes to check the photoluminescence properties and quenching effect. The selected fluorescent dyes were tested against prepared **G20** at different wavelengths to observe the quenching effect. Many hydroxyl groups in **G20** exhibited weak fluorescence and behaved as a fluorescent quencher for conjugated dyes in the real-time fluorescence quantitative polymerase chain reaction  
Figure 19: Schematic representation of the preparation of (**a**) GQD and (**b**) GDQD, Reprinted from [74] with permission from Elsevier. Figure 20: A plausible mechanism for the detection of DNA (**G18**) using the FRET quenching process. Reprinted from [75] with permission from MDPI. (qRT-PCR) via the FRET process. Furthermore, GOQDs combined with the qRT-PCR system could detect DNA sequences, with a high detection rate of 10\({}^{4}\)-10\({}^{10}\) copies per \(\upmu\)L range. The comparison of all essential properties, such as sensors, analytes, LOD, binding constants, and sensing mechanisms, is specified in Table 1. \begin{table}
\begin{tabular}{c c c c c c} \hline
**S.No** & **Sensors** & **Analytes** & **Mechanism** & **Binding Constant (M\({}^{-1}\))** & **LOD (M)** & **Ref.** \\ \hline
1 & GO aptasensor & Pb\({}^{2+}\) & FRET & 0.07–20 nM. & 0.5 pM & [54] \\ \hline
2 & GO aptasensor & Ag\({}^{+}\) and Hg\({}^{2+}\) & FRET & 0.05–50 nM & 1.33 pM & [55] \\ \hline
3 & GQD (NGQD) & Ag\({}^{+}\) & FRET & - & 0.05–0.02 nM & [56] \\ \hline
4 & GSH-AuNCs & Cd\({}^{2+}\) & FRET & 0.1–100 \(\upmu\)M & 42.0 nM & [57] \\ \hline \end{tabular}
\end{table} 
Table 1: Comparison of properties based on different analytes.