Biocompatible and stable ZnOquantum dots generated by functionalization with siloxane-core PAMAM dendrons

Abstract

Despite the growing interest of quantum dots (QDs) in biological applications, there are many concerns regarding the potential accumulation and toxic effects of Cd-containg QDs in animals and humans. Zinc oxide QDs are promising alternatives for diagnosis and imaging but their aqueous instability has markedly limited their use. Generations 1, 2 and 3 (noted G1, G2, and G3, respectively) of new poly(amidoamine) (PAMAM) dendrons bearing a siloxane group at the focal point were prepared from 3-aminopropyltrimethoxysilane. Using tetramethylammonium hydroxide as cross-linking agent, hydrophobic oleate-capped ZnO QDs were functionalized with G1 or G2 dendrons, as evidenced by FT-IR, UV-visible and XPS analyses, and were successfully transferred in aqueous solution. AFM and TEM images show that ZnO@G1 and ZnO@G2 QDs have a spherical shape with average crystalline sizes of 5.3 and 5.1 nm, respectively. Immediately after dispersion in water, ZnO@G1 and ZnO@G2 QDs exhibit a broad and strong visible emission peak centered at 550 nm with a quantum yield of ca. 18%. A strong increase of photoluminescence quantum yields was observed over time and values up to 59% could be reached after ca. 20 days of storage in water at room temperature. The good quantum yields and the stabilities of PAMAMdendron capped ZnO QDs ensured their potential applications in cell imaging. ZnO@G2 were successfully used for the labelling of the Gram + bacterium Staphylococcus aureus. The biocompatibility of these QDs is markedly improved compared to Cd-based ones as growth inhibition tests showed that ZnO@G2 QDs could be used with concentrations up to 1 mM without altering the cell growth of the Escherichia coli bacterium while most Cd-containing QDs exhibit cytotoxicity already at the nM level. .

Applying Mechanochemistry for Bottom‐Up Synthesis and Host–Guest Surface Modification of Semiconducting Nanocrystals: A Case of Water‐Soluble β‐Cyclodextrin‐Coated Zinc Oxide

“…Moreover,w ater solubility of ZnO NCs, indispensable forb iomedical applications, is usually achieved in additional post-synthetic modifications teps involving complex hydrophilic ligands [17] or polymers. [18] Thus, undoubtedly,f urthere fforts in the development of new efficient synthetic procedures of ZnO nanostructures are highly desired.…”

Oriented Morphogenesis of ZnO Nanostructures from Water‐Soluble Zinc Salts under Environmentally Mild Conditions and Their Optical Properties

“…The O1 s spectrum shows the existence of oxygen in two different states, with binding energies at 530.2 and 531.5 eV that are assignable to the lattice-oxygen and the oxygen-deficient regions within the ZnO matrix, respectively (see the Supporting Information, Figure S1). [19] FT-IR spectroscopy showed a band at 474 cm…”

Effects of ZnO quantum dots on the photostability of acrylate photopolymers used as recording materials

“…were synthesized through a sol-gel route [39][40][41]. Anhydrous zinc acetate Zn(OAc) 2 The polymer samples were prepared by coating the photopolymerizable mixture onto a glass slide or a CaF 2 plate or, on a small aluminum rectangular crucible, followed by irradiation performed in an inert argon gas atmosphere using a conventional irradiation device (monochromator) at 488 nm with an intensity of 0.6 mW cm -2 , in the same conditions used for recording [23].…”