was observed upon addition of ATP-binding aptamer due to the host-guest interaction between aptamer and β-CD. The addition of ATP to β-CD-CuInS 2 QDs/aptamer
system further enhanced the fluorescence emission, which due to the aptamer-ATP
complexes formed and included into the cavity of β-CD.
15.4.2 CD-Functionalized QDs as a Chiral Recognition Sensing
Platform
Due to the CD cavity’s inherent chirality, luminescence sensing of CD-conjugated
QDs for chiral recognition has been widely investigated [85–89]. In one example,
Willner et al. have designed β-CD-modified CdSe/ZnS QDs for optical sensing and
chiroselective sensing of different organic substrates based on a fluorescence resonance energy transfer (FRET) or an electron transfer (ET) mechanism [85]. The
β-CD coated on the surface of CdSe/ZnS QDs was used to accommodate rhodamine
B dye that acted as an optical label. Such systems were utilized for direct sensing of
organic substrates exhibiting electron-acceptor or electron-donor properties via
electron transfer quenching of the luminescence of the QDs. Moreover, the β-CDfunctionalized QD/dye system was used for the chiroselective optical discrimination
between D, L-phenylalanine and D, L-tyrosine enantiomers. The specific selection
of aromatic chiral amino acid was explained by favored interactions of the
phenylring with the β-CD receptor. The same β-CD-functionalized QDs were also
used as direct luminescence sensors for the optical detection of p-nitrophenol using
an ET quenching route. In a similar manner, water-soluble CD-modified CdSe/ZnS
QDs were utilized as selective fluorescent assays for the recognition of amino acid
enantiomers [86, 87]. The selective enantiorecognition of L-penicillamine and
D-penicillamine was accomplished by host-guest interaction between the penicillamines and the β-CD pockets on the QDs.
Wei et al. reported a photoluminescence chiral assay for tryptophan enantiomers
based on mono-6-SH-β-cyclodextrin capped Mn-doped ZnS quantum dots (β-CDMn-ZnS QDs) (Fig. 8) [88]. The β-CD-Mn-ZnS QDs have been prepared by
hydrothermal process and exhibited dual photoluminescence (PL) at 430 nm and
598 nm. The PL intensity of β-CD-Mn-ZnS QDs responded to tryptophan enantiomers differently: L-Tryptophan enhances the PL intensity of β-CD-Mn-ZnS QDs
drastically, whereas the D-isomer barely affects it. In addition, L-tryptophan can be
detected in the presence of its stereoisomer with a detection limit of 5.4 nM in a
linear range of 0–6.0 mM.
15.5 Cyclodextrin-Functionalized Noble Metal Nanoparticles
Noble metal nanoparticles (NPs), such as Au NPs, Ag NPs, and Pd NPs, have
attracted a growing interest of researchers due to their wide spectrum of potential
applications in fields such as sensing, catalysis, or nanomedicine. The utility of metal
NPs for any particular application strongly depends upon their physicochemical
15 Cyclodextrin Hybrid Inorganic Nanocomposites for Molecular Recognition. . .
441
system further enhanced the fluorescence emission, which due to the aptamer-ATP
complexes formed and included into the cavity of β-CD.
15.4.2 CD-Functionalized QDs as a Chiral Recognition Sensing
Platform
Due to the CD cavity’s inherent chirality, luminescence sensing of CD-conjugated
QDs for chiral recognition has been widely investigated [85–89]. In one example,
Willner et al. have designed β-CD-modified CdSe/ZnS QDs for optical sensing and
chiroselective sensing of different organic substrates based on a fluorescence resonance energy transfer (FRET) or an electron transfer (ET) mechanism [85]. The
β-CD coated on the surface of CdSe/ZnS QDs was used to accommodate rhodamine
B dye that acted as an optical label. Such systems were utilized for direct sensing of
organic substrates exhibiting electron-acceptor or electron-donor properties via
electron transfer quenching of the luminescence of the QDs. Moreover, the β-CDfunctionalized QD/dye system was used for the chiroselective optical discrimination
between D, L-phenylalanine and D, L-tyrosine enantiomers. The specific selection
of aromatic chiral amino acid was explained by favored interactions of the
phenylring with the β-CD receptor. The same β-CD-functionalized QDs were also
used as direct luminescence sensors for the optical detection of p-nitrophenol using
an ET quenching route. In a similar manner, water-soluble CD-modified CdSe/ZnS
QDs were utilized as selective fluorescent assays for the recognition of amino acid
enantiomers [86, 87]. The selective enantiorecognition of L-penicillamine and
D-penicillamine was accomplished by host-guest interaction between the penicillamines and the β-CD pockets on the QDs.
Wei et al. reported a photoluminescence chiral assay for tryptophan enantiomers
based on mono-6-SH-β-cyclodextrin capped Mn-doped ZnS quantum dots (β-CDMn-ZnS QDs) (Fig. 8) [88]. The β-CD-Mn-ZnS QDs have been prepared by
hydrothermal process and exhibited dual photoluminescence (PL) at 430 nm and
598 nm. The PL intensity of β-CD-Mn-ZnS QDs responded to tryptophan enantiomers differently: L-Tryptophan enhances the PL intensity of β-CD-Mn-ZnS QDs
drastically, whereas the D-isomer barely affects it. In addition, L-tryptophan can be
detected in the presence of its stereoisomer with a detection limit of 5.4 nM in a
linear range of 0–6.0 mM.
15.5 Cyclodextrin-Functionalized Noble Metal Nanoparticles
Noble metal nanoparticles (NPs), such as Au NPs, Ag NPs, and Pd NPs, have
attracted a growing interest of researchers due to their wide spectrum of potential
applications in fields such as sensing, catalysis, or nanomedicine. The utility of metal
NPs for any particular application strongly depends upon their physicochemical
15 Cyclodextrin Hybrid Inorganic Nanocomposites for Molecular Recognition. . .
441