Autor Mario Kotlár

Characterization of the chips generated by the nanomachining of germanium for X-ray crystal optics

Posted on by Mario Kotlár

ZÁPRAŽNÝ, Zdenko – KORYTÁR, Dušan – JERGEL, Matej – HALAHOVETS, Yurily – KOTLÁR, Mário – MATKO, Igor – HAGARA, Jakub – ŠIFFALOVIČ, Peter – KECKES, Jozef – MAJKOVÁ, Eva

In International Journal of Advanced Manufacturing Technology. Vol. 102, iss. 9-12 (2019)

https://doi.org/10.1007/s00170-019-03392-z

Abstract

Micro-Raman spectroscopy, scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HR-TEM) were used to study the effect of cutting speed and cutting depth on the mode of the single-point diamond fly cutting of Ge(110) surface via crystallinity of the chips. Reducing the cutting depth from 15 to 2 μm and concurrently cutting speed from 10 to 2 mm/min at 2000 rpm, the content of amorphous phase in the chips increased at the expense of the crystalline one from 28 to 46%. Simultaneously, the chip morphology visible by SEM suggested transition from a brittle to a mixed brittle-ductile mode of nanomachining. The damage transition line indicates 1/3 portion of the ductile component at 2-μm cutting depth that produced twisted lamellae of a width of 18–20 μm without any signs of a fracture. As the feed rate here was 1 μm/rev, the tool made 18–20 revolutions while passing the same point of the nanomachined surface that was enough to gradually remove the surface region damaged by the brittle cutting component along with the entire amorphous region beneath, both being delaminated by the chips. This explains the dislocation-free single-crystal lattice beneath the Ge(110) surface machined under these conditions. A close relationship between the brittle mode of nanomachining and crystallinity of the chips observed by micro-Raman spectroscopy and SEM was confirmed by HR-TEM showing dense occurrence of nanocrystals in the chips coming from the nanomachinings with 5-μm and 15-μm cutting depths. These results demonstrate potential of the single-point diamond machining for the preparation of high-quality X-ray surfaces with undistorted single-crystal lattice beneath for next-generation X-ray crystal optics.

On the formation of hydrophobic carbon quantum dots Langmuir films and their transfer onto solid substrates

Posted on by Mario Kotlár

BODIK, Michal – ŠIFFALOVIČ, Peter – NÁDAŽDY, Peter – BENKOVIČOVÁ, Monika – MARKOVIČ, Zoran – CHLPÍK, Juraj – CIRÁK, Július – KOTLÁR, Mário – MICUŠÍK, M. – JERGEL, Matej – MAJKOVÁ, Eva

In Diamond and Related Materials. Vol. 83, (2018)

https://doi.org/10.1016/j.diamond.2018.02.011

Abstract

In this work, we present a study of the Langmuir film formation composed of hydrophobic carbon quantum dots (hCQDs). We studied the kinetics of hCQDs pyrolysis and optimized the reaction time for maximum photoluminescence. The resulting hCQDs were analyzed by transmission electron microscopy, X-ray photoemission spectroscopy and grazing-incidence X-ray diffraction. The process of monolayer formation was studied by monitoring surface pressure, surface potential, elastic modulus and Brewster angle microscopy in real time under continuous compression conditions. The monolayer transferred onto a silicon wafer was examined on the nano- and micro-scales by means of atomic force microscopy and confocal fluorescence microscopy, respectively.

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)

https://doi.org/10.1021/acssuschemeng.7b04566

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.