Thin Surface Layer of Plasma Treated Polyethylene

This paper reports on the effect of argon plasma on the high density polyethylene surface. The aim is to alter the surface in a manner and scale resulting in a stronger metal/polymer valence. The specimens are exposed to the direct current discharge, the irradiation time and power being variables. Electron paramagnetic resonance and X-ray photoelectron spectroscopy (EPR and XPS, respectively) are employed to determine the plasma effect. The surface wettability is studied by goniometry. The plasma treatment leads to radical generation and activation of such agents as oxygen, thus the surface wettability is significantly increased. The evolution ofthe treated surface in different media is studied. The influence of an increased oxygen concentration and the storage medium on the concentration gradient within the surface monolayers is proved. The EPR data show a gradual and very slow decrease in the number of radicals present on the treated surface after 2000 h. Also evidence is given for partial dissolution of the treated surface in water.Представлены результаты изучения влияния плазмы аргона на поверхность полиэтилена высокой плотности. Целью исследования является изменение поверхности таким образом, чтобы увеличить валентность ме­талла/полимера. Образцы подвергали воз­действию разряда постоянного тока, при этом время воздействия и мощность являлись переменными величинами. Для опре­деления влияния плазмы использовали электронный парамагнитный резонанс (ЭПР) и фотоэлектронную рентгеновскую спектроскопию. Смачиваемость поверхнос­ти изучали с использованием гониометрии. Плазменная обработка ведет к образованию радикалов и активизации таких реагентов, как кислород и таким образом, значительно увеличивается смачиваемость поверхности. Исследована эволюция обработанной по­верхности в различных средах. Приведено подтверждение влияния повышенной кон­центрации кислорода и среды на градиент концентрации в поверхностных монослоях. Данные ЭПР свидетельствуют о постепен­ном и очень медленном уменьшении коли­чества радикалов на обработанной поверхности после 2000 ч. Приведены также дан­ные о частичном растворении обработанной поверхности в воде

Chiral plasmonic response of 2D Ti3C2Tx flakes: realization and applications

The circularly polarized light sensitive materials response can be reached at plasmon wavelengths through the coupling of intrinsically non-chiral plasmonic nanostructure with chiral organic molecules. As a plasmonic background, the different types of metal nanoparticles of various shapes and sizes are successfully tested and an apparent circular dichroism (CD) signal is measured in both, nanoparticles suspensions and after nanoparticle immobilization in substrate. In this work, the creation of plasmon-active 2D flakes of MXenes (Ti3C2Tx) is proposed, with the apparent CD response at plasmon wavelength, through the coupling of intrinsically non-chiral flakes with helically shaped helicene enantiomers. This work provides the first demonstration of chiral and plasmon-active 2D material, which shows the absorption sensitive to light intrinsic circular polarization even in plasmon wavelengths range. The appearance of the induced CD signal is additionally confirmed by several theoretical calculations. After the experimental and theoretical confirmation of the optical chirality at plasmon wavelengths, the flakes are utilized for the polarization sensitive conversion of light to heat, as well as for polarization dependent triggering of plasmon-assisted chemical transformation

Enhanced Growth and Osteogenic Differentiation of Human Osteoblast-Like Cells on Boron-Doped Nanocrystalline Diamond Thin Films

Intrinsic nanocrystalline diamond (NCD) films have been proven to be promising substrates for the adhesion, growth and osteogenic differentiation of bone-derived cells. To understand the role of various degrees of doping (semiconducting to metallic-like), the NCD films were deposited on silicon substrates by a microwave plasma-enhanced CVD process and their boron doping was achieved by adding trimethylboron to the CH4:H2 gas mixture, the B∶C ratio was 133, 1000 and 6700 ppm. The room temperature electrical resistivity of the films decreased from >10 MΩ (undoped films) to 55 kΩ, 0.6 kΩ, and 0.3 kΩ (doped films with 133, 1000 and 6700 ppm of B, respectively). The increase in the number of human osteoblast-like MG 63 cells in 7-day-old cultures on NCD films was most apparent on the NCD films doped with 133 and 1000 ppm of B (153,000±14,000 and 152,000±10,000 cells/cm2, respectively, compared to 113,000±10,000 cells/cm2 on undoped NCD films). As measured by ELISA per mg of total protein, the cells on NCD with 133 and 1000 ppm of B also contained the highest concentrations of collagen I and alkaline phosphatase, respectively. On the NCD films with 6700 ppm of B, the cells contained the highest concentration of focal adhesion protein vinculin, and the highest amount of collagen I was adsorbed. The concentration of osteocalcin also increased with increasing level of B doping. The cell viability on all tested NCD films was almost 100%. Measurements of the concentration of ICAM-1, i.e. an immunoglobuline adhesion molecule binding inflammatory cells, suggested that the cells on the NCD films did not undergo significant immune activation. Thus, the potential of NCD films for bone tissue regeneration can be further enhanced and tailored by B doping and that B doping up to metallic-like levels is not detrimental for cells

Surface modification of starch based biomaterials by oxygen plasma or UV-irradiation

Radiation is widely used in biomaterials science for surface modification and sterilization. Herein, we describe the use of plasma and UV-irradiation to improve the biocompatibility of different starch-based blends in terms of cell adhesion and proliferation. Physical and chemical changes, introduced by the used methods, were evaluated by complementary techniques for surface analysis such as scanning electron microscopy, atomic force microscopy, contact angle analysis and X-ray photoelectron spectroscopy. The effect of the changed surface properties on the adhesion of osteoblast-like cells was studied by a direct contact assay. Generally, both treatments resulted in higher number of cells adhered to the modified surfaces. The importance of the improved biocompatibility resulting from the irradiation methods is further supported by the knowledge that both UV and plasma treatments can be used as cost-effective methods for sterilization of biomedical materials and devices.I. P. thanks the FCT for providing her a postdoctoral scholarship (SFRH/BPD/8491/2002). This work was partially supported by FCT, through funds from the POCTI and/or FEDER programs, The European Union funded STREP Project HIPPOCRATES (NNM-3-CT-2003-505758) and the European NoE EXPERTISSUES (NMP3-CT-2004-500283)

Controlled biopolymer roughness induced by plasma and excimer laser treatment

A new method for biopolymer poly-L-lactic-acid (PLLA) surface nanostructuring with surface plasmon resonance appearance is proposed. The motivation of this work is to determine optimal conditions for rough or flat biopolymer surface which may find broad application in tissue engineering as biocompatible carrier for various types of cell lines. A combination of plasma pre-treatment with consequent excimer laser exposure is proposed as a method for increasing the roughness of PLLA surface and changing its morphology. The focus of this paper is to determine morphology changes in combination with mass loss changes. The ablation loss and morphology of PLLA was induced by excimer laser exposure of plasma pre-treated PLLA with different laser fluencies and number of pulses. The combination of a certain input parameters of plasma pre-treatment together with laser exposure induces extensive physico-chemical changes (morphology, contact angle, optical properties) on polymer surface with dramatic roughness increase. Gravimetric studies have revealed an extensive polymer ablation after excimer laser application. The effect of surface plasmon resonance was observed in laser modified PLLA. Conditions for PLLA surface flattening are also proposed

Repeated Temperature and Humidity Stability of SERS-active Periodical Silver Nanostructure

In this work the effect of physical aging on the plasmonic properties of surface plasmon-polariton supported silver grating was studied. As physical treatment the periodical variation of external temperature, humidity and their combination was applied. It was previously expected, that the physical aging will results in the silver oxidation, redistribution, and potential worse of plasmonic properties. The oxidation processes were studied using the XPS technique, the changes of surface morphology were examined by AFM, and finally, the shift of plasmonic efficiency was checked using the SERS test

Emission of volatile degradation products from polymers irradiated with heavy ions to different fluences

Polyimide (Upilex), polyethyleneterephtalate, polystyrene and polyethylene were irradiated with 20-200 KeV C+, N+, F+, Ar and Xe+ ions to the fluences up to 10(17) cm(-2) and the depth profiles of hydrogen and oxygen atoms in the polymer surface layer were determined using standard Rutherford Back-Scattering (RBS) and Elastic Recoil Detection (ERD) techniques. The H and O depth profiles are structureless with no local extremes and with the concentration monotonically increasing from the sample surface to the bulk value typical for pristine polymer. The H and O contents in the irradiated surface layer remain unchanged up to a critical fluence, which is a decreasing function of the energy density deposited by an ion. Then they decline rather rapidly and converge to 50-70% of their original values of unirradiated polymer. The decline rate is roughly the same for all ion/polymer combinations regardless of the ion mass and energy