A.C. Popescu

Radical modification of the wetting behavior of textiles coated with ZnO thin films and nanoparticles when changing the ambient pressure in the pulsed laser deposition process

Cotton/polyester woven fabrics were functionalized with ZnO thin films or nanoparticles by pulsed laser deposition, using a KrF* excimer laser source. Depending on the number of applied laser pulses, well-separated nanoparticles (for 10 pulses) or compact thin films (for 100 pulses) were deposited. The synthesized nanostructures were evaluated morphologically by scanning electron microscopy and atomic force microscopy, physico-chemically by x-ray diffraction and functionally by the contact angle method. By modifying the ambient gas nature and pressure in the deposition chamber, hydrophilic or hydrophobic surfaces were obtained. When using an oxygen flux, both the deposited thin films and nanoparticles were hydrophilic. After deposition in vacuum, the nanoparticles were hydrophobic, but the thin films were super-hydrophobic. This radical modification of wetting behavior was assigned to the differences in microstructure features and surface electrical charging in the two cases.

Enhanced gas sensing of Au nanocluster-doped or -coated zinc oxide thin films

We demonstrated that doping or covering with Au nanoclusters boosts gas sensing effectiveness of optical metal oxide sensors. The sensing response of pulsed laser deposited ZnO films as sensing element was tested by m-line technique for low concentration (1000ppm) of butane in environmental N2. The optical interrogation was performed for three types of coatings: undoped ZnO, undoped ZnO structures partially covered with Au nanoclusters, or obtained from Au (0.5wt%) doped ZnO targets. Nanocluster coating tripled the sensitivity, while doping resulted in an increase of up to 45% as compared with simple structures.

Analysis of indium zinc oxide thin films by laser-induced breakdown spectroscopy

We have performed spectroscopic analysis of the plasma generated by Nd:YAG (λ = 266 nm) laser irradiation of thin indium zinc oxide films with variable In content deposited by combinatorial pulsed laser deposition on glass substrates. The samples were irradiated in 5 × 104 Pa argon using laser pulses of 5 ns duration and 10 mJ energy. The plasma emission spectra were recorded with an Echelle spectrometer coupled to a gated detector with different delays with respect to the laser pulse. The relative concentrations of indium and zinc were evaluated by comparing the measured spectra to the spectral radiance computed for a plasma in local thermal equilibrium. Plasma temperature and electron density were deduced from the relative intensities and Stark broadening of spectral lines of atomic zinc. Analyses at different locations on the deposited thin films revealed that the In/(In + Zn) concentration ratio significantly varies over the sample surface, from 0.4 at the borders to about 0.5 in the center of the fil...

Estimation of polyethylene nanothin layer morphology by differential evanescent light intensity imaging

We investigated the morphology of polyethylene films by the Differential Evanescent Light Intensity (DELI) imaging method developed by us previously. The films were prepared by the Matrix Assisted Pulsed Laser Evaporation (MAPLE) technique. Rough or smooth organic layers were fabricated with thickness depending on the deposition conditions. We used the DELI imaging method here as a fast, low cost method for surface morphology diagnostics of large areas (i.e., hundreds of mm2) of nano layer polyethylene films.

ZnO Thin Films Deposited on Textile Material Substrates for Biomedical Applications

We report on the coating with ZnO adherent thin films of cotton woven fabrics by Pulsed laser deposition technique in order to obtain innovative textile materials, presenting protective effects against UV radiations and antifungal action.

Wettability of Nanostructured Surfaces

There are many studies in literature concerning contact angle measurements on different materials/substrates. It is documented that textiles can be coated with multifunctional materials in form of thin films or nanoparticles to acquire character‐ istics that can improve the protection and comfort of the wearer. The capacity of oxide nanostructures to inhibit fungal development and neutralize bacteria is a direct consequence of their wetting behavior [1–6]. Moreover, the radical modification of wetting behavior of nanostructures from hydrophilic to hydrophobic when changing the pulsed laser deposition (PLD) ambient will be thoroughly discussed. When an implant is introduced inside the human body, its surface is first wetted by the physiological fluids. This further controls the proteins adsorption followed by the attachment of cells to the implant surface. Hence, surface wettability is considered an important criterion that dictates biocompatibility of the implant and could stand for a decisive factor for its long-term stability inside the human body. In Section 1 of this chapter, the reader is briefly introduced to wetting phenomenon, and correlations between well-known Young, Cassie, and Wenzel approaches are made. Next, one of the most spread techniques to measure the wettability of surface, the contact angle measurement, is thoroughly explained and relevant examples are given. Section 2 begins with a summarized table about previous works on synthesis of hydrophobic or hydrophilic nanostructures with a special focus on ZnO, SiOx, TiO2, and DLC materials. A short presentation of the advantages of their synthesis by PLD, sol-gel, thermal evaporation, solution based on chemical approaches, sputtering, and plasma enhanced chemical vapor deposition will be introduced.

Nanoprofiles evaluation of ZnO thin films by an evanescent light method.

The extraction efficiency of evanescent light from ZnO nanolayers and their thickness profiles in the range of (1–105) nm was evaluated by a new microscopy technique, differential evanescent light intensity imaging method. It is based on capturing the evanescent light scattered by the layer of the material deposited on glass substrates. The analyzed ZnO films were obtained by pulsed laser deposition at 27°C and 100°C, using a nanosecond UV laser source. Microsc. Res. Tech., 76:992–996, 2013.

Polymer-Bioglass Composite Coatings: A Promising Alternative For Advanced Biomedical Implants

Human bone can easily regenerate in normal conditions, so in case of fractures some support devices are used to take the load from the new forming bone. However, in case of diseases, ageing and large traumas, the bone has to be helped to regenerate. Usually, large bone defects are filled with natural material from a donor site from the same patient (‘‘autografting”). Unfortunately the transplantable bone is limited and the procedure requires the extension of the operating site (Lahav et al., 2006). The concept of an artificial device able to help human parts to regenerate or to replace entirely one of the body functions, stimulated numerous research teams around the globe to test materials and combinations of materials aiming towards the “holly grail” of biocompatibility: the biomimetism. There are evidences that prove early tests on bone repair using metal parts, dating from antiquity (Bliquez, 1996). Up to present time, metals have been the elements of choice for manufacturing implants or prostheses in various shapes and dimensions. Tests and clinic reports have all agreed in time, that the best metal for such devices is Ti (Emsley, 2001). It is bio tolerated by the human body and it has a low density and mechanical properties that do not negatively affect the bone (Oshida, 2006). Orthopedics as a medicine branch does not consider bio tolerated devices as satisfactory. The general aim of an orthopedic device is to stimulate the bone to regenerate, in other words it has to be bioactive. Ceramic materials made of calcium phosphates (CaP) in various formulas, pure or doped have been extensively studied in literature for their resemblance to the mineral part of the bone (Leon & Jansen, 2010). Because ceramics brittle when submitted to high tensions, devices made completely out of these materials are not convenient. The common consensus is to use for the bulk implant metals as main components, covered by a very thin and adherent ceramic layer, thus making the surface bioactive (Park, 2008). This chapter is dedicated to bioactive glasses (BG), “intelligent materials” superior in bioactivity to CaP, made of various metal oxide combinations. They change their composition in vivo after prolonged contact with body fluids, transforming in an equivalent of the mineral bone (Hench & Wilson, 1993).

Thickness Influence on In Vitro Biocompatibility of Titanium Nitride Thin Films Synthesized by Pulsed Laser Deposition

We report a study on the biocompatibility vs. thickness in the case of titanium nitride (TiN) films synthesized on 410 medical grade stainless steel substrates by pulsed laser deposition. The films were grown in a nitrogen atmosphere, and their in vitro cytotoxicity was assessed according to ISO 10993-5 [1]. Extensive physical-chemical analyses have been carried out on the deposited structures with various thicknesses in order to explain the differences in biological behavior: profilometry, scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction and surface energy measurements. XPS revealed the presence of titanium oxynitride beside TiN in amounts that vary with the film thickness. The cytocompatibility of films seems to be influenced by their TiN surface content. The thinner films seem to be more suitable for medical applications, due to the combined high values of bonding strength and superior cytocompatibility.

Deposition and surface modification of thin solid structures by high-intensity pulsed laser irradiation

Abstract This chapter focuses on the permanent modification of structure and surface morphology of thin solid structures by high-intensity pulsed laser irradiation. Structure modification with deposition parameters by pulsed and matrix-assisted laser evaporation are presented for two examples: ambient gas that transforms ZnO from transparent to dark and carbon structures that convert from very soft to quite hard. Emphasis is also put on the experimental results of surface processing in air or under liquid using femtosecond laser. The advantage in using liquids is the possibility to employ all types of light-induced processes for direct single-step surface patterning.