|
|
Study of photocatalytic activity of Zn.sub.x./sub.Cd.sub.1-x./sub.S quantum dots in dependence on their composition using methylene blue
Praus, P. ; Svoboda, L. ; Hospodková, Alice ; Mamulová Kutláková, K.
ZnCdS quantum dots (QDs) with the different composition were prepared by precipitation of zinc and cadmium acetates with sodium sulphide in the presence of cetyltrimethylammonium bromide (CTAB) used for stabilization of their aqueous colloid dispersions. Transition energies of these quantum dots were determined from the UV-VIS spectra of QDs colloid dispersions and consequently used for calculation of the QDs sizes according to the Schrodinger equation. The ZnCdS QDs size was found to be significantly influenced by their composition: the QDs size decreased with the increasing Zn content. The photocatalytic activity of the ZnCdS QDs was studied using the methylene blue decomposition under UV irradiation. Different photocatalytic activity depending on the composition x was observed and explained. The maximal photocatalytic activity was achieved for x = 0.6 when the energy of the irradiation photons was still sufficient to generate electron-hole pairs in majority of the QDs and at the same time the photocatalytic surface area was maximal.\n
|
|
|
Polymeric nanofibrous scaffolds reinforced with diamond and ceramic nanoparticles for bone tissue engineering
Bačáková, Lucie ; Pařízek, Martin ; Staňková, Ľubica ; Novotná, Katarína ; Douglas, T.E.L. ; Brady, M. A. ; Kromka, Alexander ; Potocký, Štěpán ; Stránská, D.
Three types of nanofibrous scaffolds were prepared by electrospining: (1) poly(lactide-co-glycoside) (PLGA) scaffolds reinforced with 23 wt.% of diamond nanoparticles (DNPs), (2) poly(L-lactide) (PLLA) scaffolds with DNPs in concentration ranging from from 0.4 wt.% to 12.3 wt.%, and (3) PLLA scaffolds with 5 wt.% or 15 wt.% of hydroxyapatite (HAp) nanoparticles. The diameter of the nanofibers ranged between 160 and 729 nm. The nanofibers with nanoparticles were thicker and the void spaces among them were smaller. Mechanical properties of the nanoparticle-loaded scaffolds were better, as demonstrated by a rupture test in scaffolds with DNPs and by a creep behavior test in scaffolds with HAp. On PLGA scaffolds with DNPs, the human osteoblast-like MG-63 cells adhered in similar numbers and grew with similar kinetics as on pure PLGA scaffolds. Human bone marrow mesenchymal stem cells grew faster and reached higher population densities on PLGA-DNP scaffolds. However, on PLLA-based scaffolds, the activity of mitochondrial enzymes and concentration of osteocalcin in MG-63 cells decreased with increasing DNP concentration. On the other hand, the metabolic activity of MG-63 cells and content of osteocalcin in these cells were positively correlated with the HAp concentration in PLLA scaffolds. Thus, PLGA nanofibers with 23 wt% of DNPs and PLLA nanofibers with 5 and particularly 15 wt.% of HAp seem to be promising for bone tissue engineering.
|
|
|
(100) substrate processing optimization for fabrication of smooth boron doped epitaxial diamond layer by PE CVD
Mortet, Vincent ; Fekete, Ladislav ; Ashcheulov, Petr ; Taylor, Andrew ; Hubík, Pavel ; Trémouilles, D. ; Bedel-Pereira, E.
Boron doped diamond layers were grown in an SEKI AX5010 microwave plasma enhanced chemical vapour deposition system. Effect of surface preparation, i.e. polishing and O2/H2 plasma etching on epitaxial growth on type Ib (100) HPHT synthetic diamonds were investigated. Using optimized substrate preparation, smooth (RRMS ~ 1 nm) boron doped diamond layers with metallic conduction and free of un-epitaxial crystallites were grown with a relatively high growth rate of 3.7 μm/h. Diamond were characterized by optical microscopy, optical profilometry, atomic force microscopy and Hall effect.
|
|
| |
|
|
Fabrication of 3D diamond membranes for microfluidic systems
Varga, Marián ; Babchenko, Oleg ; Bauerová, Pavla ; Hruška, Karel ; Jurka, Vlastimil ; Kromka, Alexander ; Rezek, Bohuslav
Perfusion of cell medium, especially in microfluidic devices, can provide in-vivo-like conditions for cell cultures. The most recent demand on such systems is to include electronically active artificial cell support for in-situ monitoring. Diamond thin films exhibit advantageous combination of physical, mechanical, chemical, biocompatible and electronic properties for this purpose. In this work we explore two strategies for fabrication of self-standing three-dimensional nanocrystalline diamond membrane for implementation in microfluidic invivo like experiments: i) nucleation and chemical vapour deposition (CVD) growth of diamond on porous 3D carbon foam (with 80 pores per inch) and ii) selective diamond growth predefined by photolithographic processing using copper grid mask. The morphology and material quality of the fabricated membranes are characterized by scanning electron microscopy and Raman spectroscopy.
|
|
|
Photocatalytic activity of ZnxCd.sub.1-x./sub.S quantum dots in dependence on their composition
Praus, P. ; Svoboda, L. ; Hospodková, Alice ; Mamulová-Kutláková, K.
ZnxCd1-xS quantum dots (QDs) with the different composition x were prepared by precipitation of Zn and Cd acetates with sodium sulphide from aqueous colloid dispersions. Transition energies of these QDs were determined from UV-VIS spectra of the QDs colloid dispersions and consequently used for calculation of the QDs sizes according to the Schrödinger equation. The ZnCdS QDs size was found to be significantly influenced by their composition, decreased with increasing the Zn content. The QDs were also characterized by TEM, X-ray powder diffraction and PL. The photocatalytic activity of the QDs was studied using the methylene blue decomposition under UV irradiation with the maximum intensity of 365 nm. Different photocatalytic activity depending on the composition x was observed. Quantum levels of the QDs have important influence on their photocatalytic activity as a result of quantum size effect. The maximal photocatalytic activity was achieved for x=0.6.
|
|
|
Influence of incorporated nanodiamond particles on mechanical properties of composite material based on multi-layer PVA nanofiber textiles
Prošek, Zdeněk ; Indrová, K. ; Rácová, Z. ; Ryparová, Pavla ; Nežerka, V. ; Topič, J. ; Tesárek, Pavel ; Kromka, Alexander
The present study investigates the influence of NDP on mechanical properties of multi-layer PVA nanofiber textiles. The particles of a diameter equal to 5 nm were incorporated into double- and triple-layer textiles, while the single-layer samples were prepared as the reference. The diameter of PVA nanofibers varied from 100 to 300 nm. We characterized the tensile strength, stiffness and ductility of fabricated nanofibers by using a conventional method – a tensile test. We found that the NDP-enriched nanofibers reveal antibacterial character. However, none or negligible influence of NDP additions on the tested mechanical properties was observed.
|
|
|
Microscopic characterization of graphene material and electronic quality across neighbouring, differently oriented copper grains
Čermák, Jan ; Yamada, T. ; Ganzerová, Kristína ; Rezek, Bohuslav
We study graphene grown across the boundary of three such grains having bright, medium, and dark color in reflection. Raman micro-spectroscopy proves presence of mostly a monoor bi-layer graphene on all the grains. Yet intensity of Raman 2D band is grain-dependent: highest at the darkest grain and lowest at the brightest one. Contrary, conductive atomic force microscopy detects the highest conductivity at the brightest grain and the lowest current at the darkest grain. This is attributed to dominant electrical current path through graphene and underlying oxide thickness of which also depends on the type of copper grain. We correlate and discuss the results with view to better understanding of graphene growth and electronic properties on large area copper substrates.
|
|
|
Computational study of cellular assembly on hydrophobic/hydrophilic micro-patterns
Ukraintsev, Egor ; Brož, A. ; Kalbáčová, M.H. ; Kromka, Alexander ; Rezek, Bohuslav
We develop simple onedimensional stochastic model of cell behavior on chemically patterned surfaces that is based on three key parameters: speed of cell movement (motility) across substrate, probability of cell adhesion to substrate, and probability of cell division on substrate when adhered on substrate. Amount of adhered cells on hydrophobic and hydrophilic regions is calculated as function of time (number of cycles up to 2000). The model is correlated with in-vitro data obtained within 48 h in real time. We show that this simple stochastic model with the three parameters (where cell motility is the most important one) can describe with high accuracy the experimental data and thereby explain the observed preferential cell assembly on hydrophilic/hydrophobic micro-patterns (up to 200 um width).
|
|
|
Interpretation of the C=O band of modified diamond nanoparticles by means of DFT theory
Jirásek, Vít ; Kozak, Halyna ; Remeš, Zdeněk ; Kromka, Alexander
Diamond nanoparticles (DNPs) are an interesting class of nanomaterials, which has many unique properties. Their applications in medicine and molecular biology have been mentioned. The DNPs were reviewed in sense of their surface chemistry and a range of analytic techniques was pointed out. The experimental analysis can be enhanced by theoretical models based on the first principles. An approach to theoretical analysis of infrared spectra was introduced. As an example, a part of FTIR spectra of the oxidized DNPs was interpreted by means of the DFT theory. The calculation of the C=O stretch vibrational frequencies of carboxylic and anhydride groups on certain model clusters enabled to explain the shift and splitting of the measured spectral bands.
|
guest ::
