Publications

A conductance zero that results from the destructive quantum interference of the electron states in quantum transport between two given sites of a molecular system persists or disappears depending on the location of an externally applied perturbation. The a priori knowledge of the perturbation site that destroys or preserves a zero is the basis of an algorithm that outlines the creation of logic gates having external perturbations as inputs and a given conductance as output. Using a graph of the possible conductance paths between the various sites, we showcase the several different scenarios that correspond to AND/OR/XOR logical functions for a given set of contacts. This setup is shown to be independent of the strength of the coupling to the leads and magnitude of the perturbation. We illustrate this approach in the case of bipartite and nonbipartite single carbon cycle molecules (fulvene and benzene) and double carbon cycle molecules (naphthalene and biphenyl).

The effectiveness of mesoporous SnO2 nickel-decoration as a method for obtaining active electrode materials for bioethanol electrochemical oxidation and the way in which the embedment of a small amount of Black Pearls (BP) affects the electrocatalytic performances of Ni/SnO2 systems were investigated. XPS analysis reveals the presence of NiO, Ni(OH)(2) and Ni2O3 chemical species which favors the oxidation of bioethanol and improves the COx tolerance. Nickel deposition in a reducing environment does not affect the Sn chemistry and the mesoporosity but significantly increases S-BET. A slight amount of BP enhances the S-BET value and a induces a small contribution of larger pores appears. Tafel slopes of 80 mV decade(-1) were estimated for bioethanol oxidation at Ni/SnO2, which favorably compare to those reported in the literature. It was also found that BP incorporation leads to a decrease of the Tafel slope to 70 mV decade(-1), without deleteriously affecting the stability of the electrocatalyst during long-term polarization. EIS results suggested that this improvement might be the combined effect of a lower electrical resistance, a higher specific surface area and a certain contribution from larger pores, which could lead to a better access of the bioethanol species to the electrocatalyst surface.

This study focused on investigating the optoelectronic properties of molybdenum trioxide (alpha-MoO3) thin films using the atomic layer deposition (ALD) technique through different cycle numbers and theoretical investigation. Initial band gap calculations using standard DFT with GGA-PBE resulted in a value of 1.19 eV, which deviated significantly from experimental measurements. The GGA + U method with Hubbard U corrections was applied for the first time to improve the accuracy. This refinement led to a more precise band gap value of 3.09 eV, closely matching previously reported experimental data. The electronic parameters of the alpha-MoO3 photodetector, such as ideality factor (n), barrier height (phi 0), and series resistance (Rs), were analyzed using the thermionic emission theory and confirmed by Cheung and Nord's methods. The results demonstrated that the sample deposited with 100 pulses exhibited higher photodetector performance under UV illumination, despite having a lower Rs.

Two hybrid materials, based on 7-amino-4-(trifluoromethyl)coumarin and 7-amino-4-methyl-coumarin that attach covalently to graphene oxide (GO) have been synthesized in two steps: i) increasing the number of carboxyl groups required for functionalization with aminocoumarin derivatives by derivatization of the hydroxyls groups with chloroacetic acid, transforming GO into GO-COOH material; ii) activation of carboxylic groups using the carbodiimide-promoted reaction. The obtained composites were characterized by numerous methods that highlighted their successful obtaining. The antimicrobial activity was evaluated on resistant Mycobacterium tuberculosis strains, as well as on ESKAPE pathogens ((Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp.) in planktonic and biofilm growth states. The biocompatibility of the materials has been assayed using 3-(4, 5-dimethylthiazol-2-yl)2, 5-diphenyltetrazolium bromide assay as well as by measuring the level of nitric oxide/total reactive oxygen species and superoxide release in treated cells. The results have shown that materials exhibited improved inhibitory activity against resistant M. tuberculosis strains in comparison with GO, but also against planktonic and adherent strains. Also, the tested composites have been proved to be biocompatible on the MRC-5 fibroblast cells, demonstrating their promising potential to develop novel agents effective against multidrug resistant pathogens, including M. tuberculosis, as well as by the activation of a pro-inflammatory and of an oxidative response in the mammalian cells.

Flexible porous materials have gained a high interest due to their impact on the development of electrochemical point-ofcare devices for monitoring the state of health of individuals. Among the porous materials, paper and textiles are most commonly used due to their innate capillary action on fluids. In this article, attention is paid to the retention of analytes in paper and textile porous substrates, and possible procedures to overcome this effect are discussed. The patterning of hydrophilic and hydrophobic regions for sample flow manipulation, and the folding properties of the flexible substrates for 3D architectures capable of transfer of analytes, are considered in relation to current electrode materials and detection methodologies.

In the present study, sage-coated zinc-doped hydroxyapatite was incorporated into a dextran matrix (7ZnHAp-SD), and its physico-chemical and antimicrobial activities were investigated. A 7ZnHAp-SD nanocomposite suspension was obtained using the co-precipitation method. The stability of the nanocomposite suspension was evaluated using ultrasound measurements. The stability parameter calculated relative to double-distilled water as a reference fluid highlights the very good stability of the 7ZnHAp-SD suspension. X-ray diffraction (XRD) experiments were performed to evaluate the characteristic diffraction peak of the hydroxyapatite phase. Valuable information regarding the morphology and chemical composition of 7ZnHAp-SD was obtained via scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS) studies. Fourier-transform infrared spectroscopy (FTIR) measurements were performed on the 7ZnHAp-SD suspensions in order to evaluate the functional groups present in the sample. Preliminary studies on the antimicrobial activity of 7ZnHAp-SD suspensions against the standard strains of Staphylococcus aureus 25923 ATCC, Enterococcus faecalis 29212 ATCC, Escherichia coli 25922 ATCC, and Pseudomonas aeruginosa 27853 ATCC were conducted. More than that, preliminary studies on the biocompatibility of 7ZnHAp-SD were conducted using human cervical adenocarcinoma (HeLa) cells, and their results emphasized that the 7ZnHAp-SD sample did not exhibit a toxic effect and did not induce any noticeable changes in the morphological characteristics of HeLa cells. These preliminary results showed that these nanoparticles could be possible candidates for biomedical/antimicrobial applications.

High density samples (92-94.5 %) of MgB2 were prepared by Spark Plasma Sintering (SPS). The on-off pulsed current patterns of SPS processing were 8-4, 12-2, 24-2, 99-1. Patterns with more on pulses favor formation of a higher amount of the secondary MgB4 phase through the decomposition of MgB2. They also promote enhancement of larger MgO crystallites without a strong increase in the amount of this phase. Densification rate and pressure in the SPS chamber show a similar behavior, but their amplitude varies and the temperatures defining different stages present some shifts. As-revealed differences induced by pulsed patterns impact superconducting properties in a complex manner. An attempt to assess correlations between the pattern and different superconducting parameters is presented.

The effect of the demagnetizing factor, regarding the determination of the de-pairing current density Jdep, has been studied in the case of a Fe(Se,Te) crystal, using DC magnetic measurements as a function of a magnetic field (H) at different temperatures (T). First, the lower critical field Hc1(T) values were obtained, and the demagnetization effects acting on them were investigated after calculating the demagnetizing factor. The temperature behaviors of both the original Hc1 values and the ones obtained after considering the demagnetization effects (Hc1demag) were analyzed, and the temperature dependence of the London penetration depth lambda L(T) was obtained in both cases. In particular, the lambda L(T) curves were fitted with a power law dependence, indicating the presence of low-energy quasiparticle excitations. Furthermore, by plotting lambda L-2 as a function of T, we found that our sample behaves as a multigap superconductor, which is similar to other Fe-11 family iron-based compounds. After that, the coherence length xi values were extracted, starting with the Hc2(T) curve. The knowledge of lambda L and xi allowed us to determine the Jdep values and to observe how they are influenced by the demagnetizing factor.

Rare-earth-free permanent magnets with the L1(0) phase are actively researched for their potential as a future class of magnetic materials, capable of operating at higher temperatures and in challenging corrosion environments such as renewable energy applications. Among these classes, MnGa shows potential, being cost effective and having interesting magnetic properties. A MnGa magnetic alloy, with composition Mn73.6Ga26.4 in atomic percent, was produced via the out-of-equilibrium method, and its structural and magnetic properties were assessed using X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED) and extended magnetic characterization. We show that the MnGa alloy submitted to thermal annealing in optimal conditions exhibits a two-phase microstructure, where small nanocrystals of tetragonal L1(0)/D0(22) magnetic phase are embedded within a D0(19) MnGa matrix of a non-collinear antiferromagnetic nature. These co-existing, magnetically different phases produce an optimal set of promising magnetic properties, larger than the values reported in the literature for single-phase MnGa alloys and thin films. Such large values are explained by the exchange coupling between competing non-collinear magnetic sublattices of the D0(19) MnGa with the net moment of the small magnetic nanocrystals of tetragonal symmetry.

Technological progress has led to the development of analytical tools that promise a huge socio-economic impact on our daily lives and an improved quality of life for all. The use of plant extract synthesized nanoparticles in the development and fabrication of optical or electrochemical (bio)sensors presents major advantages. Besides their low-cost fabrication and scalability, these nanoparticles may have a dual role, serving as a transducer component and as a recognition element, the latter requiring their functionalization with specific components. Different approaches, such as surface modification techniques to facilitate precise biomolecule attachment, thereby augmenting recognition capabilities, or fine tuning functional groups on nanoparticle surfaces are preferred for ensuring stable biomolecule conjugation while preserving bioactivity. Size optimization, maximizing surface area, and tailored nanoparticle shapes increase the potential for robust interactions and enhance the transduction. This article specifically aims to illustrate the adaptability and effectiveness of these biosensing platforms in identifying precise biological targets along with their far-reaching implications across various domains, spanning healthcare diagnostics, environmental monitoring, and diverse bioanalytical fields. By exploring these applications, the article highlights the significance of prioritizing the use of natural resources for nanoparticle synthesis. This emphasis aligns with the worldwide goal of envisioning sustainable and customized biosensing solutions, emphasizing heightened sensitivity and selectivity.