Publications

Abstract This work presents a new Knudsen effusion apparatus employing continuous monitoring of sample deposition using a quartz-crystal microbalance sensor with internal calibration by gravimetric determination of the sample mass loss. The apparatus was tested with anthracene and 1,3,5-triphenylbenzene and subsequently used for the study of sublimation behavior of several proteinogenic amino acids. Their low volatility and thermal instability strongly limit possibilities of studying their sublimation behavior and available literature data. The results presented in this work are unique in their temperature range and low uncertainty required for benchmarking theoretical studies of sublimation behavior of molecular crystals. The possibility of dimerization in the gas phase that would invalidate the effusion experiments is addressed and disproved by theoretical calculations. The enthalpy of sublimation of each amino acid is analyzed based on the contributions in two hypothetical sublimation paths involving the proton transfer in the solid and in the gas phase.

Abstract Spent coffee grounds (SCGs) are known for containing many organic compounds of interest, including carbohydrates, lipids, phenolic compounds and proteins. Therefore, we investigated them as a potential source to obtain carbon dots (CDs) via a nanotechnology approach. Herein, a comparison was performed between CDs produced by SCGs and classic precursors (e.g., citric acid and urea). The SCG-based CDs were obtained via the one-pot and solvent-free carbonization of solid samples, generating nanosized particles (2.1-3.9 nm). These nanoparticles exhibited a blue fluorescence with moderate quantum yields (2.9-5.8%) and an excitation-dependent emission characteristic of carbon dots. SCG-based CDs showed potential as environmentally relevant fluorescent probes for Fe(3+)in water. More importantly, life cycle assessment studies validated the production of CDs from SCG samples as a more environmentally sustainable route, as compared to those using classic reported precursors, when considering either a weight- or a function-based functional unit.

Abstract This work aims to apply photonic-crystal-based nanocoatings with unusual aesthetical orientation to wood application. Structural colors are currently a formula to achieve those colorful coatings including nonfading properties. They can be produced from self-assembled colloidal spheres into photonic crystals, which possess particular optical properties. Herein, photonic crystals with iridescent structural colors were prepared from the self-assembly of monodispersed nanospheres. Particle sizes can be adjusted from 308 to 196 nm, and well-ordered structures are arranged through self-assembly process into films, which exhibit brilliant colors over a wide visible spectrum, from red to violet. Color varies with the angle of observation of incidence light. The present study provided an effective and simple approach to prepare structural color films and their practical application to wood coating for an aesthetic appeal.

Abstract In this study, a homogeneous thin film growth of pentacene onto indium tin oxide (ITO) coated glass surfaces is explored using a high-resolution and reproducible vapor deposition methodology. Moreover, vacuum thermal evaporation of ionic liquids (ILs) ([C(2)C(1)im][NTf2] and [C(2)C(1)im][OTF]) onto ITO, gold/palladium (AuPd) and pentacene surfaces were performed. A greater wettability behavior of ILs is observed for surfaces containing AuPd. Sequential and simultaneous depositions of ILs and pentacene were explored. Simultaneous depositions lead to the formation of nanocomposites films, consisting of IL micro- and nanodroplets covered by pentacene layers. Plasma surface treatment was used to induce the ILs droplets coalescence and explore the dynamics and phase separation of the nanocomposites. The [C(2)C(1)im][OTF] droplets were found to be completely covered with pentacene, which suggests a great affinity between cation-anion pairs and the aromatic moiety. Pentacene films and their nanocomposites with ILs exhibit a typical optical band gap ofE(gap)=1.77 eV, indicating that the nanocomposite phase domains are large enough to behavior as the bulk.

Abstract Background: The increasing demand of effective pharmaceutical products directed to fight against malaria lead to the combination of at least two antimalarial drugs. This combination aims to minimize the Plasmodium falciparum resistance which is found when the most frequently used drugs are taken individually. Within this context, proguanil hydrochloride and chloroquine phosphate which have independent modes of action are taken together to prevent malaria. This paper aims to develop a fast and powerful analytical method for the simultaneous determination of proguanil hydrochloride and chloroquine phosphate in the commercial Paludrine/Avloclor dosage forms using a multi-way chromatographic calibration based on high-performance liquid chromatography with diode array detection (HPLC-DAD) and multivariate curve resolution - alternating least-squares (MCR-ALS). Methods: A rapid and powerful analytical method based on HPLC-DAD and MCR-ALS was developed for the simultaneous quantification of proguanil hydrochloride and chloroquine phosphate in the commercial Paludrine/Avloclor antimalarial drugs. An isocratic mobile phase composed by 0.2 M ammonium acetate, acetonitrile, and methanol (40:25:35) and a flow rate of 1.2 mL min(-1) were employed in the chromatographic runs with an elution time about 5 min. Results: This approach demonstrates that chromatographic analysis may become considerably simpler and economical in terms of time, cost, and organic solvent consumption when coupled to multiway calibration models such as MCR-ALS. In fact, this multi-way chromatographic calibration based on second-order HPLC-DAD data matrices (with extremely low chromatographic resolution) and MCR-ALS allows the development of greener analytical methods for complex samples. The proposed analytical method allowed the simultaneous quantification of two antimalarial APIs present in the commercial Paludrine/Avloclor drugs with low REP values below 8% for the simultaneous determination of proguanil hydrochloride and chloroquine phosphate. Conclusion: The proposed multi-way chromatographic strategy can be used for routine control of pharmaceutical dosage forms. It should be highlighted that MCR-ALS allowed to: (a) achieve the second-order advantage and the quantification of analytes in the presence of uncalibrated compounds such as coeluted profile measured in different magnitude of the signal in each successive chromatographic run and significant overlapping profiles and (b) separate the contribution of several components from chromatographic runs with extremely low separation of peaks through the deconvolution of the signal obtained, performing the so-called mathematical chromatography.

Abstract The west coast of Tangier, in northern Morocco, has been affected by industrial wastewater discharge that reaches the ocean through the Boukhalef river. Therefore, the Jbila and Sidikacem beaches near to the Boukhalef river mouth have been classified as polluted for many years. With the aim of determining the COVID-19 pandemic consequences on the Tangier coastal environment, a linear model using Sentinel 3 water surface temperature (WST) has been tested in several locations. Data from April 2019 and April 2020, before and during the COVID-19 pandemic related emergency status in Morocco, were compared. The results from April 2019 showed high WST values and consequently, the poorest water quality in the sites closest to the Boukhalef river mouth. On the other hand, the results from April 2020 showed normal WST values and high water quality in the same study area. These results illustrate the usefulness of Sentinel 3 WST for the estimation of bathing water quality on the west coast of Tangier. The study shows the positive impact of the COVID-19 pandemic consequences on the coastal environment quality in the study area and indicates the importance of decreasing the industrial discharge on the west coast of Tangier. The same methodology could be used in decision-making processes and to reduce cost, time and human resources for coastal monitoring systems. We demonstrate the potential of using the Sentinel 3 data for coastal waters monitoring, as well as the need for stricter controls of pollutant discharges into the world's rivers.

Abstract Swept-source optical coherence tomography (SSOCT) is a noncontact, noninvasive bioimaging tool that uses various probes to obtain high contrast images. Rare-earth based upconversion particles (UCPs) provide a unique platform to enhance the capabilities of bioimaging techniques. The UCPs can act as contrast enhancers for the SSOCT with additional optical functionality, and hence in this work upconversion emission optimized polyvinylpyrrolidone (PVP)/NaGdF4:Er3+/Yb3+ UCPs were synthesized and then injected into chicken breast tissues to enhance the SSOCT images. As-synthesized samples have shown good biocompatibility toward HEK293, HeLa cell lines and showed apparent enhancement in contrast to SSOCT images. Additionally, compared to the bare NaGdF4:Er3+/Yb3+ UCPs the polyvinylpyrrolidone-stabilized UCPs have shown 3-fold enhancement in the frequency of upconverted green and red light intensity under 976 nm diode laser excitation (26 W/cm(2)).

Abstract In this investigation, hybrid-biocomposites "ZnO-Chitosan" were synthesized using a chitosan biomaterial and various amounts of ZnO particles (7 and 93 wt percent). The chitosan was obtained from the exoskeletons of shrimp shells, which were collected from the fishmongers in Meknes city (Morocco). Several techniques including X-ray diffraction, Fourier transform infrared spectroscopy, differential thermal analysis and thermogravimetric analysis, diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy and scanning electron microscopy coupled with energy dispersive spectroscopy were used for the characterization of the synthesized hybrid-biocomposites. The obtained experimental results showed the existence of a strong interaction between Zn-2(+), and the amino and hydroxyl groups of chitosan only for the hybrid-biocomposite containing 7 wt percent of ZnO. This suggests that the structure of this sample is probably formed via a complexation between Zn-2(+) ions which are linked to -NH2, -OH groups of chitosan, and H2O molecules. The photocatalytic activity of the asprepared hybrid-biomaterials was then evaluated by measuring the degradation efficiency of methyl orange (MO) and paranitrophenol (pNP) under both UV-A and visible light irradiation. The obtained results indicated that the photocatalytic performance was significantly improved by adding an optimum amount of ZnO (7 wt %) to the chitosan biomaterial, and suggested that the photocatalytic activity depended closely on the ZnO weight percent. The role of the active species (electrons, holes and hydroxyl radicals) in the photocatalytic process has been studied and the probable degradation mechanisms of MO and pNP under both UV-A and visible light illuminations were proposed.

Abstract In this work, we combined electrochemical techniques with SPR (eSPR) for the label-free detection of cancer biomarker miRNA-145. Detection was performed in a simple two-step assay. In the first step, the gold sensor surface, previously functionalized with a self-assembled monolayer (SAM) of thiolated RNA probes is incubated with the sample containing the target RNA biomarker. In this step, hybridization of RNA fragments with complementary immobilized probes was monitored in real-time by SPR. In the second step, eSPR measurements were performed to improve the sensitivity of the hybridization assay. Potential-induced deposition of a redox probe at the sensor surface resulted in enhanced SPR response promoted by the electrochemical process, thereby allowing the detection of miRNA-145 at femtomolar level (LOD = 0.56 fM), without sample derivatization or post-hybridization treatment for signal amplification. Good linearity was achieved (R-2 = 0.984) over the concentration range from 1.0 fM and 10 nM. Furthermore, the developed eSPR biosensor showed high selectivity towards single-base and two-base mismatch sequences and detection of target miRNA-145 in synthetic human serum was successful achieved.

Abstract In this work, three universally used redox probes in amperometric biosensing devices, [Fe(CN)(6)](3-)/[Fe(CN)(6)](4-), Ru[(NH3)(6)](3+), and ferrocenedimethanol (FDM), were selected to evaluate the stability of electrochemical signals provide by the reporting systems. Studies were carried out at disposable gold screen-printed electrode (AuSPE) biosensing platforms, commonly used for screening chemical and biological relevant biomolecules. Firstly, electrochemical combined-surface plasmon resonance (eSPR) studies were performed to evaluated adsorption reversibility and/or formation of redox probe complexes at the bare gold surface when routinely used electrochemical techniques, namely cyclic voltammetry (CV) and square-wave voltammetry (SWV), are recorded. Then, the results obtained were compared with those obtained at the AuSPE under the same electrochemical conditions. Based on our findings, best experimental conditions, including the type of electrochemical technique used, are speculated for each reporting system in order to improve the analytical signal stability. Finally, a methodology based on SWV technique was applied to modified electrodes to provide a simple and easy tool to ensure diffusion controlled permeability of probes thorough the films to electrode surface.