The photophysical properties of polar molecules in solution with an intramolecular charge-transfer effect in the excited state depend strongly on the polarity and proticity of the solvents. UV-visible spectra of 1,8-naphthalimide and some N-substituted derivatives in acetic acid, acetonitrile, dichloromethane, and p-dioxane were carried out. Several molecular cluster geometries formed with N-substituted 1,8-naphthalimide derivatives and a large set of random positioning of some solvent molecules in their environment were optimized by a semiempirical method. It provided a complete screening of possible solute-solvent configurations and resulted in a multiple minima hypersurface of the supramolecular systems. With such local minima energies, the main thermodynamic association functions were found. They also provided selected cluster geometries for calculations of vertical electronic transitions with a time-dependent density functional theory (TD-DFT), if the lowest energy structures were considered. Calculated vertical electronic transition energies at the TD-DFT level were compared with experimental data. The experimental absorption UV-visible spectra for the six compounds in the four solvents were performed in our laboratory. Moreover, X-ray photoelectron spectroscospy of the 1,8-naphthalimide was carried out in the ICP-CSIC laboratory. Thermodynamic function values show different association energies between each solvent and the molecules, in correlation with the possibility of hydrogen bond formation and the polarity and dielectric constant of the solvents. The 3- and 4-acetamide 1,8-naphthalimide derivatives have the highest conformer number and the most negative Gibbs free association energy values for a determined solvent. This indicates the importance of the entropic factors.

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Cerium (Ce) oxide nanoparticles (CNPs) have attracted attention due to their high bioactivity and unique redox-chemistry. The oxygen vacancies at the surface of the nanoparticle explain the autocatalytic properties of CNPs in which the Ce atoms occupy the center of the oxygen vacancies surrounded by Ce atoms. Until now, CNPs have been associated with organic molecules at the synthesis stage to extend their applications or improve their stability. However, there is a lack of information regarding the post-synthesis interaction of CNPs and organic molecules that could enhance or induce new properties. Due to their unique optical properties and their many uses in different areas such as supramolecular chemistry or biomedicine, we have chosen a derivative from the family of naphthalimides (the 4-amino-1,8-naphthalimide-N-substituted; ANN) to study the interaction with different CNPs (CNP1-4) and their joint bioactivity compared to that of the same compounds alone. ANN-CNP complexes were formed as revealed by spectroscopic studies, but, the interaction was markedly different depending on the physicochemical properties of CNPs and their surface content of Ce sites. The ANN adsorption on all CNPs involved the amino group in the naphthalene moiety as shown by NMR spectroscopy, while the pyrrolidine ring was mainly involved in the specific interaction between ANN and CNP1. The biological effect of each CNP and ANN individually and forming complexes was assessed using a bioluminescent model bacterium. The results showed that ANN and CNP with the higher content of surface Ce (CNP1) when combined acted additively towards the used model organism. In the opposite, ANN-CNP2, ANN-CNP3 and ANN-CNP4 complexes were antagonistic when the nanoparticles dominated the mixture. The results of this study contribute to expand the knowledge of the interaction between nanoparticles and organic molecules which may be useful for understanding the behavior of nanoparticles in complex matrices.

Currently, resistance to antibiotics has become a problem for the treatment of infectious diseases. In this study, silver nanoparticles were synthesized using the aqueous extract of Palo santo (Burseragraveolens), for its biocide action, in order to determine its antimicrobial effect on Escherichia coli and Staphylococcus aureus. Different concentrations of nanoparticles (100 until1000 ppm) were evaluated at contact times of 1, 2, 5 and 10 minutes for 1500 and 15000 CFU/mL. Additionally, to determine effectiveness, disc diffusion tests using various concentrations of nanoparticles (500-1000 ppm) were performed on S.aureus and K. pneumoniae. According to the results of antimicrobial effect for E.coli, the effectiveness of nanoparticles can be established at all contact times for 1500 CFU from 800 ppm and for 15000 CFU from 400 ppm. With S.aureus, total inhibition was showed from 800 ppm in 1500 CFU at 5 minutes of contact and between 500-1000 ppm with 15000 CFU at minute one. S. aureus and K.pneumoniae tests showed sensitivity with nanoparticles. The average of susceptibility for S.aureus had the lowest inhibition between 500-600 ppm and the highest at 700-800 ppm. The average susceptibility for K. pneumoniae is more constant in terms of inhibition at 600-1000 ppm. This study demonstrated the antimicrobial effect of silver nanoparticles synthesized under the specified conditions.