Luminescence of Polyethylene Glycol Coated CdSeTe/ZnS and InP/ZnS Nanoparticles in the Presence of Copper Cations

Abstract

The use of click chemistry for quantum dot (QD) functionalization could be very promising for the development of bioconjugates dedicated to in vivo applications. Alkyne-azide ligation usually requires copper(I) catalysis. The luminescence response of CdSeTe/ZnS nanoparticles coated with polyethylene glycol (PEG) is studied in the presence of copper cations, and compared to that of InP/ZnS QDs coated with mercaptoundecanoic acid (MUA). The quenching mechanisms appear different. Luminescence quenching occurs without any wavelength shift in the absorption and emission spectra for the CdSeTe/ZnS/PEG nanocrystals. In this case, the presence of copper in the ZnS shell is evidenced by energy-filtered transmission electron microscopy (EF-TEM). By contrast, in the case of InP/ZnS/MUA nanocrystals, a redshift of the excitation and emission spectra, accompanied by an increase in absorbance and a decrease in photoluminescence, is observed. For CdSeTe/ZnS/PEG nanocrystals, PL quenching is enhanced for QDs with 1) smaller inorganic-core diameter, 2) thinner PEG shell, and 3) hydroxyl terminal groups. Whereas copper-induced PL quenching can be interesting for the design of sensitive cation sensors, copper-free click reactions should be used for the efficient functionalization of nanocrystals dedicated to bioapplications, in order to achieve highly luminescent QD bioconjugates.

Quantum dots–DNA bioconjugates: synthesis to applications

“…The reaction is often catalysed by Cu þ . However, Cu þ cations are known to quench the photoluminescence of QDs [16]. In order to circumvent this issue, Cu-free click chemistry has been employed to conjugate DNA to QD while maintaining high fluorescent quantum yield [85].…”

An Interactive Quantum Dot and Carbon Dot Conjugate for pH‐Sensitive and Ratiometric Cu2+ Sensing

“…The Cu 2+ ions preferentially bound to the Qdot surfaces rather than Cdots, which resulted in gradual quenching of Qdot emission but left the Cdot emission nearly intact. The very low solubility product of CuS ( K s =6×10 −16 ) compared with ZnS ( K s (wurtzite)=3×10 −2 and K s (zinc blend)=2×10 −4 ) and the similar ionic radius of Cu 2+ and Zn 2+ could facilitate the chemical displacement of surface Zn 2+ ions by Cu 2+ . The Cu 2+ ions possibly displaced the surface Zn 2+ ions to form nonfluorescent CuS due to the lower solubility product, which led to quenching of the Qdot emission through surface annihilation.…”

Revisiting 30 years of biofunctionalization and surface chemistry of inorganic nanoparticles for nanomedicine

“…QDs need to be coated to other chemical species if they are to be used as biomarkers, therapeutic agents or sensors. In fact, water soluble and water QDs have been successfully coated with polymers via click-chemistry reactions (Beaune et al, 2011; Janczewski et al, 2011; Lai and Guan, 2011; Petryayeva and Krull, 2012; Zhang et al, 2012a). Jańczewski et al reported the use of click-QDs by producing water solubilization of hydrophobic CdSe/ZnS QDs using amphiphilic polymeric coatings.…”