Synthesis and structure of free-standing germanium quantum dots and their application in live cell imaging

Ali Karatutlu (1) , Mingying Song (1) , Ann P. Wheeler (2) , Osman Ersoy (1) , William R. Little (1) , Yuanpeng Zhang (1) , Pascal Puech (3) , Filippo S. Boi (2) , Zofia Luklinska (4) , Andrei V. Sapelkin (1)

1 School of Physics and Astronomy [London]
2 QMUL - Queen Mary University of London
3 CEMES - Centre d'élaboration de matériaux et d'études structurales
4 SCU - Sichuan University [Chengdu]

Free-standing Ge quantum dots around 3 nm in size were synthesized using a bench-top colloidal method and suspended in water and ethanol. In the ethanol solution, the photoluminescence of the Ge quantum dots was observed between 650 and 800 nm. Structural and optical properties of these colloidal Ge quantum dots were investigated by utilizing X-ray diffraction, X-ray absorption spectroscopy, Raman spectroscopy, and photoluminescence spectroscopy and transmission electron microscopy. The structure of the as-prepared Ge quantum dots that were found is best described by a core-shell model with a small crystalline core and an amorphous outer shell with a surface that was terminated by hydrogen-related species. As-prepared Ge quantum dots were suspended in cell growth medium, and then loaded into cervical carcinoma (HeLa) cells. The fluorescent microscopy images were then collected using 405 nm, 488 nm, 561 nm and 647 nm wavelengths. We observed that, based on fluorescence measurements, as-prepared Ge quantum dots can remain stable for up to 4 weeks in water. Investigation of toxicity, based on a viability test, of as-prepared uncoated Ge quantum dots in HeLa cells was carried out and compared with the commercial carboxyl coated CdSe/ZnSe quantum dots. The viability tests show that Ge quantum dots are less toxic when compared to commercial carboxyl coated CdSe/ZnS quantum dots.

Mots clés: Cytology; Ethanol; Fluorescence; Germanium; Nanocrystals; Optical properties; Photoluminescence; Photoluminescence spectroscopy; Transmission electron microscopy; X ray absorption spectroscopy; X ray diffraction; CdSe/ZnS quantum dots; CdSe/ZnSe quantum dots; Cervical carcinoma; Fluorescence measurements; Fluorescent microscopy; Germanium quantum dots; Small-crystalline; Structural and optical properties; Semiconductor quantum dots

Domaines: Physique [physics]

Ali Karatutlu, Mingying Song, Ann P. Wheeler, Osman Ersoy, William R. Little, et al.. Synthesis and structure of free-standing germanium quantum dots and their application in live cell imaging. RSC Advances, 2015, 5 (26), pp.20566-20573. ⟨10.1039/c5ra01529d⟩. ⟨hal-01756982⟩