A. Kromka

Chemical modifications and stability of diamond nanoparticles resolved by infrared spectroscopy and Kelvin force microscopy

Chemically modified 5-nm detonation diamond nanoparticles (DNPs) are characterized by grazing angle reflectance (GAR) Fourier transform infrared spectroscopy (FTIR), Kelvin force microscopy (KFM), and X-ray photoelectron spectroscopy (XPS). Using GAR-FTIR we discuss the surface chemistry and stability of the as-received DNPs, and compare them with DNPs modified by annealing in air or by oxygen plasma treatment. Infrared spectra of the as-received DNPs are dominated by C–H bonds and carboxylic groups (COOH), probably related to the wet chemical treatment in acids. Annealing in air and oxygen plasma lead to a significant enhancement of C=O groups and vanishing C–H groups. After short-term (10xa0min) oxygen plasma treatment, infrared peaks change in intensity and position indicating a spontaneous reactivity of DNPs, probably due to the partial erosion of the graphitic shell. Prolonged oxygen plasma treatment (40xa0min) or annealing in air at 450xa0°C for 30xa0min provides a stable DNPs surface. Surface potentials of DNPs obtained by KFM are well correlated with the GAR-FTIR measurements. XPS characterization corroborates DNPs compositional changes after the modification procedures.

Silicon nanocrystals and nanodiamonds in live cells: photoluminescence characteristics, cytotoxicity and interaction with cell cytoskeleton

The number of newly developed nanomaterials is steadily increasing but only a few are suitable for applications in biology. These nanomaterials are often made from harmful compounds and there is no convenient technique to remove them from the body after application. This study is focused on silicon nanocrystals and nanodiamonds, which are two promising nanomaterials for bio-applications. Silicon nanocrystals (Si-NCs) are exceptional since they provide several desired properties: low cytotoxicity, suitability for chemical activation, efficient photoluminescence, and bio-degradability. All these parameters promote application of Si-NCs in living organisms and even human medicine. Nanodiamonds (NDs), on the other hand, are non-biodegradable which limits their use to mostly long term in vitro studies. However, when using these nanomaterials one needs to address the effect of accumulation and aggregation of such materials in cells and how it contributes to the overall cytotoxicity. Here, we present studies on the interaction of two promising nanomaterials Si-NCs and NDs with actin structure of mammalian cells, evaluation of their cytotoxicity by various methods, and observation of single nanoparticle luminescence spectra within living cells. According to our results Si-NCs are more promising for application in nanomedicine compared to NDs.

Electrochemically grafted polypyrrole changes photoluminescence of electronic states inside nanocrystalline diamond

Hybrid diamond-organic interfaces are considered attractive for diverse applications ranging from electronics and energy conversion to medicine. Here we use time-resolved and time-integrated photoluminescence spectroscopy in visible spectral range (380–700 nm) to study electronic processes in H-terminated nanocrystalline diamond films (NCD) with 150 nm thin, electrochemically deposited polypyrrole (PPy) layer. We observe changes in dynamics of NCD photoluminescence as well as in its time-integrated spectra after polymer deposition. The effect is reversible. We propose a model where the PPy layer on the NCD surface promotes spatial separation of photo-generated charge carriers both in non-diamond carbon phase and in bulk diamond. By comparing different NCD thicknesses we show that the effect goes as much as 200 nm deep inside the NCD film.

Nanofibrous Scaffolds as Promising Cell Carriers for Tissue Engineering

Nanofibers are promising cell carriers for tissue engineering of a variety of tissues and organs in the human organism. They have been experimentally used for reconstruction of tissues of cardiovascular, respiratory, digestive, urinary, nervous and musculoskele‐ tal systems. Nanofibers are also promising for drug and gene delivery, construction of biosensors and biostimulators, and wound dressings. Nanofibers can be created from a wide range of natural polymers or synthetic biostable and biodegradable polymers. For hard tissue engineering, polymeric nanofibers can be reinforced with various ceramic, metal-based or carbon-based nanoparticles, or created directly from hard materials. The nanofibrous scaffolds can be loaded with various bioactive molecules, such as growth, differentiation and angiogenic factors, or funcionalized with ligands for the cell adhesion receptors. This review also includes our experience in skin tissue engineering using nanofibers fabricated from polycaprolactone and its copolymer with polylactide, cellulose acetate, and particularly from polylactide nanofibers modified by plasma activation and fibrin coating. In addition, we studied the interaction of human bone-derived cells with nanofibrous scaffolds loaded with hydroxyapatite or diamond nanoparticles. We also created novel nanofibers based on diamond deposition on a SiO2 template, and tested their effects on the adhesion, viability and growth of human vascular endothelial cells.

The Application of Nanodiamond in Biotechnology and Tissue Engineering

Diamond in the allotrope form consists of carbon atoms arranged in a cubic crystal structure covalently bonded in sp3 hybridization. Diamond has emerged as a very promising material for various biomedical applications due to its excellent mechani‐ cal properties (hardness, low friction coefficient, good adhesiveness to the underlying substrate, good interlayer cohesion), optical properties (the ability to emit intrinsic luminescence), electrical properties (good insulator in the pristine state and semicon‐ ductor after doping), chemical resistance (low chemical reactivity and resistance to wet etching) and biocompatibility (little if any toxicity and immunogenicity). For ad‐ vanced biomedical applications, diamond is promising particularly in its nanostruc‐ tured forms, namely nanoparticles, nanostructured diamond films and composite scaffolds in which diamond nanoparticles are dispersed in a matrix (mainly nanodia‐ mond-loaded nanofibrous scaffolds). This chapter summarizes both our long-term experience and that of other research groups in studies focusing on the interaction of cells (particularly bone-derived cells) with nanodiamonds as nanoparticles, thin films and composites with synthetic polymers. Their potential applications in bioimaging, biosensing, drug delivery, biomaterial coating and tissue engineering are also reviewed.

Schottky contact metallization stability on AlGaN/GaN heterostructure during the diamond deposition process

The issue of gate metallization stability on AlGaN/GaN heterostructure during the diamond deposition process has been studied. Among tested Ni, Ir, NiO and IrO2 materials the iridium-based has the most promising characteristic to be used. The diamond growth in focused microwave plasma system on transistors with Ir and IrO2 Schottky contact metallization has been demonstrated and discussed.

Nanocrystalline diamond films for electronic monitoring of gas and organic molecules

Nowadays, implementation of specific materials for (bio) sensors is one of the most rapidly developing micro-electronic field. Synthetic diamond thin films exhibit an extraordinary combination of intrinsic properties which make it an attractive material for investigation of solid state interaction with (bio) molecules or complex biological systems. Hydrogen terminated intrinsic diamond films reveal a phenomenological property — induced p-type surface conductivity which has been found as suitable for fabrication of various electronic devices, mainly impedance elements and field effect transistors. This study draws on research conducted by employing hydrogen terminated nanocrystalline diamond as the functional layer for (bio) sensoric uses and point out recent models for the detection principles.