Year: 2018

Antibacterial and Antibiofouling Properties of Light Triggered Fluorescent Hydrophobic Carbon Quantum Dots Langmuir-Blodgett Thin Films

Posted on by Mario Kotlár

STANKOVIČ, Nenad K – BODIK, Michal – ŠIFFALOVIČ, Peter – KOTLÁR, Mário – MICUŠÍK, M. – ŠPITÁLSKY, Zdenko – DANKO, Martin – MILIVOJEVIČ, Dušan D. – KLEINOVÁ, Angela – KULBAT, Pavel – CAPÁKOVÁ, Zdenka – HUMPOLIČEK, Petr – LEHOCKY, Marian – MARKOVIČ, Biljana – MARKOVIČ, Zoran

In ACS Sustainable Chemistry and Engineering. Vol. 6, iss. 3 (2018)

Abstract

Inimitable properties of carbon quantum dots as well as a cheap production contribute to their possible application in biomedicine especially as antibacterial and antibiofouling coatings. Fluorescent hydrophobic carbon quantum dots are synthesized by bottom-up condensation method and used for deposition of uniform and homogeneous Langmuir–Blodgett thin films on different substrates. It is found that this kind of quantum dots generates singlet oxygen under blue light irradiation. Antibacterial and antibiofouling testing on four different bacteria strains (Escherichia coli, Staphylococcus aureus, Bacillus cereus, and Pseudomonas aeruginosa) reveals enhanced antibacterial and antibiofouling activity of hydrophobic carbon dots thin films under blue light irradiation. Moreover, hydrophobic quantum dots show noncytotoxic effect on mouse fibroblast cell line. These properties enable potential usage of hydrophobic carbon quantum dots thin films as excellent antibacterial and antibiofouling coatings for different biomedical applications.

Chemical Oxidation of Graphite: Evolution of the Structure and Properties

Posted on by Viliam Vretenár

SKÁKALOVÁ, Viera – KOTRUSZ, Peter – JERGEL, Matej – SUSI, Toma – MITTELBERGER, Andreas – VRETENÁR, Viliam – ŠIFFALOVIČ, Peter – KOTAKOSKI, J. – MEYER, Jannik C. – HULMAN, Martin

In Journal of Physical Chemistry C. Vol. 122, iss. 1 (2018)

https://doi.org/10.1021/acs.jpcc.7b10912

Abstract

Graphene oxide is a complex material whose synthesis is still incompletely understood. To study the time evolution of structural and chemical properties of oxidized graphite, samples at different temporal stages of oxidation were selected and characterized through a number of techniques: X-ray photoelectron spectroscopy for the content and bonding of oxygen, X-ray diffraction for the level of intercalation, Raman spectroscopy for the detection of structural changes, electrical resistivity measurements for probing charge localization on the macroscopic scale, and scanning transmission electron microscopy for the atomic structure of the graphene oxide flakes. We found a nonlinear behavior of oxygen uptake with time where two concentration plateaus were identified: Uptake reached 20 at % in the first 15 min, and after 1 h a second uptake started, reaching a highest oxygen concentration of >30 at % after 2 h of oxidation. At the same time, the interlayer distance expanded to more than twice the value of graphite and the electrical resistivity increased by seven orders of magnitude. After 4 days of chemical processing, the expanded structure of graphite oxide became unstable and spontaneously exfoliated; more than 2 weeks resulted in a significant decrease in the oxygen content accompanied by reaggregation of the GO sheets. These correlated measurements allow us to offer a comprehensive view into the complex oxidation process.