**7. Cyclodextrin-nanocarbon hybrids as chemical sensors**

Over the past several decades, carbon nanomaterials for instance carbon nanotubes, fullerene and nanodiamonds, and other polyaromatic hydrocarbons because their unique electrical, structural, and mechanical properties have riveted a significant interest of the researchers across the globe to meet the challenge of

*Cyclodextrin-Based Sensors for the Recognition of Small Molecules DOI: http://dx.doi.org/10.5772/intechopen.108500*

#### **Figure 14.**

*Schematic depiction of fluorescence quenching upon the addition of adamantane functionalized viologen derivative (53) to π-conjugated fluorescent polymer (49).*

#### **Figure 15.**

*Schematic representation of hyodeoxycholic acid (56) assisted structural variation of* β*-CD-peptide hybrid polymeric conjugate (55).*

constructing the CD-based sensors through hybridization with carbon nanomaterials [78–81]. In this context, Fujita and Yuan *et al.* have reported a *β*-CD-fullerene hybrid conjugate (**63**), which has the ability to quench the fluorescence of rhodamine B (**64**),

#### **Figure 16.**

*Schematic representation of guest (59) assisted structural variation of methylated* β*-CD-DNA hybrid fluorescent polymeric conjugate (58).*

after its capture in the hydrophobic cavity of *β*-CD (**Figure 18**) [82]. On the other hand, Harada and co-workers have constructed pyrene-functionalized *β*-CD-SWCNT hybrid conjugate (**67**) and utilized it in the development of stimuli-responsive supramolecular hydrogel (**Figure 19**). It has been observed that the addition of sodium adamantane carboxylate as a competitive guest leads toward the conversion of a gel to sol [83]. Remarkably, the Stoddart's group has decorated pyrene-functionalized *β*-CDs on SWCNT hybridized with field-effect transistors (FETs) in order to sense typical organic guest molecules *viz*. 1-adamantanol, sodium cholate, 1-adamantane carboxylic acid. It was observed that the FET characteristics of these hybrid nano-conjugates are highly sensitive and dependent on the association constants between *β*-CDs and competitive organic guest molecules [84].
