Intelligent piezoelectric polymers PVDF-PZT for biosensing applications

Nowadays a growing number of biosensing systems in micro- and nanoscale rely in expensive and bulky equipment that must capable accurately to resolve the angle or wavelength of optical interrogation. The costs, size, sensitivity, properties and etc which are required to assemble these biosensing tools, may limit the portability of such systems, and may restrict their usefulness in sensing applications outside of a controlled environment. This research covers creation and investigations of new piezoelectric materials based on PVDF and PZT with unique properties, i.e. synthesis, piezoelectric thin film formation, imprint of microperiodic structures, analysis of surface morphology by Atomic Force Microscopy, and analysis of diffraction efficiencies using laser diffractometer. These developments of new piezoelectric films have made it possible to understand the strengthening and deformation mechanisms in micro- and nanoscales together by bringing new insights in biosensing applications

Optical Properties of Black Silicon with Precipitated Silver and Gold Nanoparticles

Black porous silicon is a new material with low light reflectance and high light absorbance values. Black porous silicon layers are especially useful and important in solar energy conversion. In this work black porous silicon plates were prepared by wet chemical metal-assisted method. Silver and gold nanoparticles were precipitated from colloidal silver nitrate and chloroauric acid solutions. Obtained black porous silicon samples with precipitated nanoparticles were investigated by scanning electron microscope combined with energy dispersive X-ray spectrometer, ultraviolet and visible light spectrometer, the Fourier transformation infrared spectrometer. Scanning electron microscopy and energy dispersive X-ray analysis have revealed the presence of silver and gold nanoparticles on black porous silicon surface. Silver nanoparticles size varied from 30 to 100 nm, gold - from 20 to 70 nm. During UV-VIS analysis significant changes in reflectance of processed black porous silicon samples were obtained. Reflectance of black porous silicon samples was lower than 10%. The Fourier transform infrared analysis has revealed decrease in reflectance in far infrared region. Changes in the Fourier transform infrared spectra in "fingerprint" zone prove modification of the surface of black porous silicon layers after precipitation of metal nanoparticles

Micromechanical and tribological properties of nanocrystalline coatings of iron-tungsten alloys electrodeposited from citrate-ammonia solutions

The correlation between the composition, morphology, and properties of Fe-W alloy coatings containing up to 29 at % tungsten was investigated by means of scanning electron microscopy, X-ray diffraction analysis, and the wear resistance and nanohardness measurements. The coatings were deposited from the citrate-ammonia bath at a direct current, the current densities were ranged from 10 to 100 mA/cm². It is shown that, in contrast to metallurgical iron, the Fe-W coatings are nanocrystalline (amorphous, the grain size is 3.0–4.0 nm). This structure of alloys allows us to produce the coatings with a nanohardness of ∼13 GPa, which is comparable to the electrolytic chromium coatings. The study of wear resistance of thus obtained coatings reveals their oxidation in the course of dry friction; as a result, the oxygen content in the debris increases by 2–3 times, and the wear volume due to the tribooxidation exceeds that for similar hard Co-W and electrolytic chromium coatings.status: publishe

Polyvinylpyrrolidone surface modification with SiOx containing amorphous hydrogenated carbon (a-C:H/SiOx) and nitrogen-doped a-C:H/SiOx films using Hall-type closed drift ion beam source

In this study SiOx containing amorphous hydrogenated carbon (a-C:H/SiOx) and nitrogen-doped a-C:H/SiOx (a-C:H:N/SiOx) films were deposited on polyvinylpyrrolidone (PVP) templates of variable thickness using a Hall-type closed drift ion beam source with constant irradiation parameters. A detailed surface characterization was followed using atomic force microscopy (AFM) topography images, surface morphology parameters, height distribution histograms and bearing ratio curves with hybrid parameters. The AFM analysis directly showed that the a-C:H/SiOx/PVP and a-C:H:N/SiOx/PVP composite films represent different morphologies with characteristic surface textures. Surface adhesive properties were evaluated by measuring the force required to separate the AFM tip from the surface by means of AFM force-distance curves. The variance in adhesion force detected was lower for a-C:H/SiOx/PVP composite films due to lower structural homogeneity of the surfaces. Fourier transform infrared spectroscopy analysis was performed to study the blend behavior of PVP upon a-C:H/SiOx and a-C:H:N/SiOx direct ion beam deposition. It was determined that interfacial interactions of PVP with the direct ion beam induced changes in the carbonyl group of the PVP and are dependent on the carrier gas used for the synthesis of the amorphous hydrogenated carbon films

Failure analysis by indentation test of electrodeposited nanocrystalline CO-W and Fe-W thin films

The aim of this paper is to study the failure of the electrodeposited Co-W and Fe-W alloys onto copper and steel substrates by the indentation technique, examine plastic strain distributions around indentations and evaluate behaviour of the system "coating-substrate". The alloys of Co-W and Fe-W obtained electrodeposited from citrate-ammonia baths are nanocrystalline. The values of grain size were evaluated based on the XRD spectrum and show values 30-37 Å. An experimental investigation into the Vickers indentation hardness and associated plastic deformation in electrochemically performed coatings was conducted. The methodology applied for this study allows obtaining the qualitative data to describe the behaviour of the system "coating-substrate", when both are deforming plastically. Implications of this study in understanding the mechanical behaviour of coatings and their derivatives are discussed.status: publishe

Iron-tungsten alloys electrodeposited under direct current from citrate-ammonia plating baths

Fe–W alloys containing ~23–30 at.% tungsten were electrodeposited from citrate–ammonia solutions at different cathodic current densities. A characterization of the structural properties of these coatings is reported. The 8 to 15 μm thick Fe–W coatings obtained are smooth and nano-crystalline. The structure of such aselectrodeposited coatings evolves slightly with increasing cathodic current densities. Above 5 A dm⁻², micro-cracks appear in electrodeposited Fe–W coatings, and the oxygen content in the coatings increases. A nano-crystalline structure and a high tungsten content result in nanohardness of 13 GPa. The electrodeposited Fe–W alloys remain “nanocrystalline” after annealing up to 800 °C. After heating at 1000 °C, the nano-crystalline structure transforms into a microcrystalline one, and up to three phases are formed, namely FeWO₄, Fe, and possibly Fe₂W.status: publishe

Characterization of Plasma Polymerized Hexamethyldisiloxane Films Prepared by Arc Discharge

Herein, we present a simple method for fabricating plasma polymerized hexamethyldisiloxane films (pp-HMDSO) possessing superhydrophobic characteristics via arc discharge. The pp-HMDSO films were deposited on a soda–lime–silica float glass using HMDSO monomer vapor as a precursor. A detailed surface characterization was performed using scanning electron microscopy and atomic force microscopy. The growth process of the pp-HMDSO films was investigated as a function of deposition time from 30 to 300 s. The non-wetting characteristics of the pp-HMDSO films were evaluated by means of contact angle (CA) measurements and correlated with the morphological characteristics, as obtained from microscopy measurements. The deposited films were found to be nano-structured and exhibited dual-scale roughness with the static CA values close to 170°. Fourier transform infrared spectroscopy analysis was carried out to investigate chemical and functional properties of these films. Methyl groups were identified spectroscopically to be present within the pp-HMDSO films and were proposed to result in the low surface energy of material. The synergy between the dual-scale roughness and low surface energy resulted in the superhydrophobic characteristics of the pp-HMDSO films. A possible mechanism for the pp-HMDSO film formation is propose

Water droplet behavior on superhydrophobic SiO2 nanocomposite films during icing/deicing cycles

This work investigates water droplet behavior on superhydrophobic (water contact angle value of 162 ± 1°) SiO2 nanocomposite films subjected to repetitive icing/deicing treatments, changes in SiO2 nanocomposite film surface morphology and their non-wetting characteristics. During the experiment, water droplets on SiO2 nanocomposite film surface are subjected to a series of icing and deicing cycles in a humid (~ 70% relative humidity) atmosphere and the resulting morphological changes are monitored and characterized using atomic force microscopy (AFM) and contact angle measurements. Our data show that the formation of the frozen or thawed water droplet, with no further shape change, on superhydrophobic SiO2 nanocomposite film, is obtained faster within each cycle as the number of the icing/deicing cycles increases. After 10 icing and deicing cycles, the superhydrophobic SiO2 nanocomposite film had a water contact angle value of 146 ± 2° which is effectively non-superhydrophobic. AFM analysis showed that the superhydrophobic SiO2 nanocomposite film surface area under the water droplet undergoes gradual mechanical damage during the repetitive icing/deicing cycles. We propose a possible mechanism of the morphological changes to the film surface that take place during the consecutive icing/deicing experiments

Water droplet behavior on superhydrophobic SiO2 nanocomposite films during icing/deicing cycles

This work investigates water droplet behavior on superhydrophobic (water contact angle value of 162 ± 1°) SiO2 nanocomposite films subjected to repetitive icing/deicing treatments, changes in SiO2 nanocomposite film surface morphology and their non-wetting characteristics. During the experiment, water droplets on SiO2 nanocomposite film surface are subjected to a series of icing and deicing cycles in a humid (~ 70% relative humidity) atmosphere and the resulting morphological changes are monitored and characterized using atomic force microscopy (AFM) and contact angle measurements. Our data show that the formation of the frozen or thawed water droplet, with no further shape change, on superhydrophobic SiO2 nanocomposite film, is obtained faster within each cycle as the number of the icing/deicing cycles increases. After 10 icing and deicing cycles, the superhydrophobic SiO2 nanocomposite film had a water contact angle value of 146 ± 2° which is effectively non-superhydrophobic. AFM analysis showed that the superhydrophobic SiO2 nanocomposite film surface area under the water droplet undergoes gradual mechanical damage during the repetitive icing/deicing cycles. We propose a possible mechanism of the morphological changes to the film surface that take place during the consecutive icing/deicing experiments