Mihaela Mindroiu

DNA-based membranes for potential applications

In this paper, we present results of our research on developing of new deoxyribonucleic acid (DNA)-based conducting membranes for application in electrochromic devices. Improvements of performances of DNA-based solid bioelectrolyte in smart windows were achieved by adding plasticizer like glycerol and different amounts of photosensitive chromophores, such as Nile Blue. The results were obtained and analyzed by a variety of experimental tools and techniques such as FT-IR, UV–VIS spectroscopy, fluorescence, electric conductivity, contact angle, charge density measurements, and cyclic voltammetry. The biomembranes with the highest ionic conductivity values were successfully applied in smart windows with glass/ITO/WO3/DNA-based membranes/CeO2–TiO2/ITO/glass configuration which have shown a good change of transmittance under the applied electric field. The obtained results suggest that DNA-based electrolytes are very promising materials to be applied in electrochromic devices.

Enhancing the Stability of PPy Film on Ti by PEG Incorporation

Composite films based on polypyrrole (PPy) and polyethylene glycol (PEG) were synthesized on titanium electrode, using various percentages of PEG, as the insulating material in order to enhance surface properties of the polymer composite films. The Fourier transform infrared spectroscopy (FT-IR) was performed to demonstrate the formation of a PPy-PEG composite film. The corrosion behaviour of coatings has been studied by Tafel tests and cyclic voltammetry. The PPy-PEG films/electrolyte interface was analyzed by electrochemical impedance spectroscopy (EIS) and the specific parameters of corresponding equivalent circuits were calculated. The polymeric layer morphology on titanium substrate has been evaluated using atomic force microscopy (AFM) and enhanced properties of the PPy-PEG films are discussed as the effect of PEG incorporation in the polypyrrole structure.

Electrodeposition of Polypyrrole/Poly(Styrene Sulphonate) Composite Coatings on Ti6Al7Nb Alloy

The aim of this work is to study the influence of surfactants concentration on pyrrole polimerization on Ti6Al7Nb alloy in order to improve the surface performance of such biomaterials. The electrochemical stability of the polypyrrole based composite coatings were evaluated in Hanks Balanced Salt Solution by Tafel tests, cycle voltammetry and electrochemical impedance spectroscopy (EIS). The surface analysis of composite coating type atomic force microscopy (AFM), was completed with an infrared structure evaluation. The coating properties such as electrochemical parameters, wettability and roughness can be controlled by changing the pyrrole/poly(styrene sulphonate) polymerization ratio.

DNA- and DNA-CTMA: novel bio-nanomaterials for application in photonics and in electronics

Functionalization of deoxyribonucleic acid (DNA) with surfactants, photosensitive and conductivity increasing molecules as well as thin film processing is reviewed and discussed. The comparative spectroscopic studies of chemical and photothermal stability of several chromophores show a better stability in DNA-cetyltrimethylammonium (CTMA) surfactant complexes than in polycarbonate (PC) or poly(ethylene glycol) (PEG) matrices. Also the optical damage threshold in nanosecond pulsed laser illumination is higher in thin films of bio-macromolecules such as DNA, DNACTMA, collagen than in PC. The electrical conductivity of doped DNA based systems exhibits a typical ionic character and can be improved by an appropriate doping. Practical applications of DNA based complexes are reviewed and discussed.

Electrochemical testing of a novel alloy in natural and artificial body fluids

There is a recent trend in tissue engineering and regenerative medicine to use nanotechnology and bionanomaterials to obtain materials that mimic the surface properties of a natural tissue. From this perspective, nanolevel tissue engineering can be viewed as a novel anatomy of the future. In this paper, a novel titanium-based alloy is studied following this strategy. The alloy nanostructuration is proposed as an improved alternative for restorative prosthodontics or an implantable biomaterial. Tests in (i) standard solution of simulated body fluid (SBF) and (ii) natural saliva were performed to investigate the alloys electrochemical stability. The results show that nanochannel growth on the alloy surface confers a higher stability than that of the untreated one in both natural and simulated environments.

The Roll of NaPSS Surfactant on the Ceria Nanoparticles Embedding in Polypyrrole Films

Cerium oxide nanoparticles CeO2 NPs in crystalline form have been synthesized by a coprecipitation method. CeO2 nanoparticles were then embedded in polypyrrole PPy films during the electropolymerization of pyrrole Py on titanium substrate. The influence of polysodium 4-styrenesulfonate NaPSS surfactant used during polymerization on the embedding of CeO2 NPs in polypyrrole films was investigated. The new films were characterized in terms of surface analysis, wettability, electrochemical behaviour, and antibacterial effect. The surface and electrochemical characterization revealed the role of surfactant on PPy doping process cerium oxide incorporation. In the presence of surfactant, CeO2 NPs are preferentially embedded in the polymeric film while, without surfactant, the ceria nanoparticles are quasiuniformly spread as agglomerates onto polymeric films. The antibacterial effect of studied PPy films was substantially improved in the presence of cerium oxide and depends by the polymerization conditions.