National Institute Of Materials Physics - Romania

The main objective of this paper is to develop silver-doped hydroxyapatite suspensions (HApAg) with different concentrations of silver (x(Ag) = 0.05 and x(Ag) = 0.2) in order to obtain uniform and homogenous layers by spin-coating procedure. The colloidal properties of HApAg suspensions are evaluated by dynamic light scattering (DLS) analysis, zeta-potential (ZP), and ultrasound measurements. The ultrasound studies show that the HApAg20 sample revealed better stability than the HApAg5 sample. The structural and morphological analysis on suspensions and thin layers is also conducted. It is observed that the particles of the two samples have a similar shape and are uniform. The layers obtained present a homogeneous appearance of the surface without evidence of cracks or interruption of the coatings. The in vitro antifungal studies conducted on the two thin layers at two different time intervals (24 and 48 h) show that both HApAg5 (x(Ag) = 0.05) and HApAg20 (x(Ag) = 0.05) nanoparticles suspensions and composite layers inhibit the development of colony forming units (CFU) even after 24 h of incubation comparative to the control, represented by the Candida albicans (C. albicans) culture in a proper medium. The fungicidal effect was evident after 48 h of incubation in the case of both HApAg20 nanoparticles suspensions and composite layers.

The influence of Ag and Au nanoparticles and reduced graphene oxide (RGO) sheets on the photodegradation of alpha-lipoic acid (ALA) was determined by UV-VIS spectroscopy. The ALA photodegradation was explained by considering the affinity of thiol groups for the metallic nanoparticles synthesized in the presence of trisodium citrate. The presence of excipients did not induce further changes when ALA interacts with Ag and Au nanoparticles with sizes of 5 and 10 nm by exposure to UV light. Compared to the Raman spectrum of ALA powder, changes in Raman lines' position and relative intensities when ALA has interacted with films obtained from Au nanoparticles with sizes between 5 and 50 nm were significant. These changes were explained by considering the chemical mechanism of surface-enhanced Raman scattering (SERS) spectroscopy. The photodegradation of ALA that had interacted with metallic nanoparticles was inhibited in the presence of RGO sheets.

This work reports the effect of the Mn substitution, rapid solidification technique and heat treatments on the martensitic transformation, magnetic and magnetostrictive properties on the Fe70-xPd30Mnx (x = 1, 3) ferromagnetic shape memory ribbons. The samples were investigated by X-ray diffraction, differential scanning calorimetry, scanning electron microscopy, magnetic and magnetostrictive measurements. The thermal treatments induce significant changes in the microstructure and magnetocrystalline anisotropy of the martensitic phase, for Fe67Pd30Mn3 compared to Fe69Pd30Mn1. The competition between the magnetization orientation and twin boundary motion within martensitic variants under magnetic field evidenced in the magnetic-strain curves was discussed and correlated with the magnetic data.

Pb0.98Bi0.02Zr0.5Fe0.1Nb0.09Ti0.31O3 (PBiZFNT) powder obtained by a solid state reaction technique was uniaxial pressed and sintered at 1200 degrees C in order to fabricate dense thin disk ceramics with different thickness (200 mu up to 600 mu m). The pyroelectric response was influenced by the thickness of the ceramics. The thin ceramic disks of 250 mu m thickness show better pyroelectric signal (approximate to 35 mV) which recommend them for potential use in laser energy meters.

The latest decades presented a large development of various size and types of Unmanned Aerial Vehicles (UAVs). Nowadays, there are over 200 million UAVs used in various applications and there it is a large effort to adopt national and international regulation for using them. There it is a real need for the development of a reliable system for UAVs identity verification that can be implemented and used at global level. To this moment the software-based methods such as MAC address, IDs memorized on devices are prone to a large number of cyber-security vulnerabilities and attacks. This paper presents an innovative hardware-based identification solution which could be adapted to UAVs in a non-intrusive manner. The proposed solution is based on physical unclonable functions (PUF), which are implemented by using memristors. The proposed solution is very low cost and high performance. By using memristors, it is possible to generate a very large number of unclonable IDs, using only a few electrical components. This solution could be incorporated in any UAVs systems without major modifications and not affecting their flight parameters.

Neoplastic disease has multifactorial etiology and insidious evolution which make it unlikely to be detected in early stages and very difficult to treat at later times. The effectiveness of standard therapeutic approaches is limited by severe adverse effects, metastasis, and tumor capacity to develop multidrug resistance. The success of inorganic nanomaterial-based therapeutic agents depends on the degree to which these nanostructures satisfy general requirements for drug safety regarding biocompatibility, biodegradability, and stability and on their antitumor efficacy. Fabrication of such nanomedicines requires adequate assessment and engineering of nanomaterial physicochemical characteristics like particle size, specific surface area, surface charge, hydrodynamic size, and magnetic, optical, and photocatalytic properties. Together with surface functionalization and delivery method, these properties dictate the in vivo "biological identity" of the nanomaterial and its fate with respect to cellular uptake and distribution/accumulation inside the body. We reviewed recent literature on interdisciplinary studies regarding applications of inorganic nanomaterials in the treatment of cancer. The major functions that inorganic nanomaterials can play in cancer therapy are: 1. Nanocarriers for therapeutic agents and active targeting ligands for molecules overexpressed on tumor tissues as well as for altered signal transduction pathways. Inorganic nanomaterial-based therapeutic agents are able to reduce tumor growth acting on neoplastic vasculature (by inhibiting angiogenesis, vasculogenesis, and vasculogenic mimicry) or on malignant cells (blocking activation of overexpressed receptors and their specific signaling pathways, inducing oxidative stress, and reducing multidrug resistance). Moreover, inorganic nanomaterials are able to inhibit tumor invasiveness and metastasis by reducing degradation of extracellular matrix, exosome secretion, and cell proliferation at the secondary site. 2. Contrast agents and medical adhesives in cancer surgery: (i). Vital staining of sentinel lymph nodes (SLNs) where the first metastasis appears - the use of carbon nanoparticles, single-walled and multilayer carbon nanotubes, or superparamagnetic iron oxide nanoparticles was associated with a significantly higher number of harvested SLNs in breast and cervical tumors, lung cancer, papillary thyroid carcinoma, and prostate carcinoma. (ii). Nanoparticle-based medical adhesives used for surgical wound closure aqueous suspensions of iron oxide and silicon dioxide nanoparticles were shown to rapidly connect highly vascularized tissues (e.g., liver). 3. Inorganic sensitizers for radiotherapy - gold nanoparticles were reported to significantly enhance the efficiency of ionizing radiation and induce targeted cancer cell apoptosis, tumor growth inhibition, and increases of survival rates in tumor-bearing mice. 4. Antitumor agents based on specific material properties like surface plasmon resonance (photothermal heating), magnetic responsiveness (magnetic hyperthermia), and photocatalysis (photodynamic therapy) - heat generated by plasmonic (gold-based) or magnetic (iron oxide-based) nanomaterials exposed to laser light or alternating magnetic fields, respectively, was shown to efficiently destroy tumors in mouse models or leads to promising results in clinical trials; the antitumor action of photoactivated TiO2-based nanomedicines was assessed in numerous in vitro and several in vivo studies. 5. Adjuvant therapy (iron replacement therapy) - iron oxide colloids (IOC) are more efficient than free iron in treating iron-deficient anemia associated with cancer. Overall, inorganic-organic therapeutic nanoplatforms provide enhanced treatment efficiency, reduced adverse effects, multiple antitumor action mechanisms, facile cell internalization, and diminished multidrug resistance.

Thin nanostructured films are the state-of-the-art materials for detection of very low limits of toxic gases. The work presents a comparison between the properties of WO3 thin films obtained by two different deposition techniques: Advanced Gas Deposition (AGD) and DC Reactive Sputtering. Films have been characterized by XRD, SEM and XPS. WO3-based sensors have selective sensitivity in H2S detection at operating temperature of 200 degrees C and relative humidity specific to field applications. The potential interferences with CO2, SO2 and NH3 are negligible, highlighting the application potential of WO3.

MgB2 bulk superconductors are expected to be utilized as rare-earth-free and lightweight trapped field magnets. However, the flux jumps frequently happen during the magnetizing processes, and heavily degrade the field-trapping performances. We have investigated the effect of additives to the MgB2 bulk samples prepared by spark plasma sintering process, and observed various flux jumps during the pulsed field magnetizing processes, which were carried out at 14 K which was obtained by the 2-stage GM cryocooler. The authors classified the flux motions as three categories as "no flux flow", "fast flux flow", and "flux jump" regions, and investigated the conditions where the flux jumps happen. We observed some drastic flux jumps in the pristine and clarified the effect of graphene addition to the flux jumps. The experimental results showed us a possible expansion of no flux jump region, and suggested us the improvement of field trapping capability.

Carbon-Titanium multilayer thin films were obtained by Thermionic Vacuum Arc (TVA) method. The nanostructured films consisting by 100nm Carbon base layer and seven 40nm alternatively Titanium and Carbon layers were deposed on Silicon substrate. As well, to give C-Ti multilayer films with different percentages in Ti and C of layers, a 100nm thick Carbon base layer was deposed on Si substrate, and then seven Ti-C layers, each of these having thickness of 40nm. In order to achieve the successively layers with C, and Ti different percentages, were adjusted the discharge parameters of C and Ti plasma sources to obtain the desired composition of layers. Also, were obtained composite films having a variable C: Ti atomic ratio 9:1 at interface to 1:9 at the surface. By changing of substrate temperature from room temperature to 100 degrees C, 200 degrees C, 300 degrees C, 400 degrees C respectively, and on the other hand the bias potential up to -700V, different batches of samples were obtained. Characterization of structural properties of films was achieved by Electron Microscopy technique (TEM, STEM) and GIXRD techniques. The measurements show that increase of the substrate temperature reveal changes in TixCy lattice parameters. Thus, according to GIXRD analysis it was found out that the Ti:C atomic ratio changes with increase of synthesis temperature. Also, in the case of composite films an increase of amount and sizes of TiC nanocrystals with the increase of energy of Ti ions determined by increase of bias voltage was observed. The tribological measurements were performed using a ball-on-disk system with normal forces of 0.5, 1, 2, 3N respectively. Was found that the coefficient of friction depends on the synthesis temperature and on the bias voltage. It is also noted that the friction coefficient depends on the pure C content, Ti content and amount of TiC nanocrystallites. These results are due to atomic diffusion at Ti/C interfaces and also are associated with amount of TiC nanocrystallites. To characterize the electrical conductive properties, the electrical surface resistance versus temperature have been measured, and then the electrical conductivity is calculated. Using the Wiedemann-Frantz law was obtained the thermal conductivity.