Carlos Alberto Huerta-Aguilar

Fluorescent organic nanoparticles (FONs) for selective recognition of Al3+: application to bio-imaging for bacterial sample

The development of a novel chemo-sensor for the detection of Al3+ with high sensitivity in aqueous solution is widely considered an important research goal because of the importance of such probes in medicine, living systems and the environment. In this work, we describe a new fluorescent probe, a Schiffs base N,N′-propylenebis(salicylimine) (salpn) as fluorescent organic nanoparticles for Al3+. The study shows that salpn detects Al3+ with the detection limit as low as 1.24 × 10−3 mM, indicating that the chemo-sensor has high sensitivity in aqueous medium, and the fluorescence intensity increases with the increasing Al3+ concentration in the presence of the salpn-ONPs which act as chemo-sensors. The interference of common coexistent metal ions such as Mn2+, Mg2+, Co2+, Fe3+, Ni2+, Zn2+, Sr2+, Ag+, Sm3+, Al3+, Cd2+, Ba2+, Na+ and K+ was tested, showing that salpn-ONPs efficiently detect Al3+ ions with small interference from Cu2+ and Cr3+. Finally, the efficiency of salpn to as a fluorescent probe for Al ion in living systems was evaluated in Gram-negative and Gram positive bacteria, and con-focal laser scanning microscopy confirms its utility that this chemo-sensor efficiently detects Al3+ ion in Staphylococcus aureus enclosed by a single membrane.

A ruthenium(III) complex derived from N,N′-bis(salicylidene)ethylenediamine as a chemosensor for the selective recognition of acetate and its interaction with cells for bio-imaging: experimental and theoretical studies

A ruthenium(III) complex of N,N′-bis(salicylidene)ethylenediamine (L1) was prepared to give a compound of composition [RuL1(H2O)(PPh3)]PF6, which was examined using spectroscopic methods and single-crystal X-ray diffraction analysis. The geometric analysis was accomplished by DFT studies, which enabled a comparative analysis with related Ru(III) complexes. Sensing studies by means of fluorescence spectroscopy revealed that [RuL1(H2O)(PPh3)]+ performs the selective detection of acetate without interference from the presence of other anions (F−, Cl−, Br−, I−, CN−, ClO4−, NO3−, HSO4−, H2PO4−), with a detection limit of 1.20 × 10−7 M. The stoichiometry of the complex formed between the ruthenium complex and acetate is 1 : 1, as determined by Jobs method. Molecular orbital analysis based on DFT calculations revealed that the energy of the orbital, which is responsible for the Photo Electron Transfer (PET) mechanism, is lowered for [RuL1(H2O)(AcO)] when compared to that for [RuL1(H2O)(PPh3)]+, resulting in an enhanced fluorescence intensity after addition of acetate. Furthermore, the recognition of acetate ions with the ruthenium complex in Saccharomyces cerevisiae cells was studied, and the absorption of the substrate (host) within the cells and the subsequent addition of the guest (acetate anion) were carefully examined through fluorescence spectroscopy.

Visible light driven photo-degradation of Congo red by TiO2ZnO/Ag: DFT approach on synergetic effect on band gap energy

In this paper, we report the combination of two metal oxides (TiO2ZnO) that allows mixed density of states to reduce band gap energy, facilitating the photo-oxidation of Congo red dye under visible light. For the oxidation, a possible mechanism is proposed after analyzing the intermediates by GC-MS, and it is consistent with Density Functional Theory (DFT). The nanohybrids were characterized comprehensibly by several analytical techniques such as X-Ray diffraction (XRD), Transmission Electron Microscopy (TEM), Atomic Force Microscopy (AFM), and X-ray Photoelectron Spectroscopy (XPS). For the addition of ZnO to TiO2, a dominance of anatase phase was found rather than other phases (rutile or brookite). A broad band (∼550 nm) is observed in UV-Visible spectra for TiO2ZnO/Ag NPs nm because of Surface Plasmon properties of Ag NPs. The band gap energy was calculated for TiO2ZnO/Ag system, and then it has been further studied by DFT in order to show why the convergence of two semiconductors allows a mixed density of states, facilitating the reduction of the energy gap between occupied and unoccupied bands; ultimately, it improves the performance of catalysts under visible light. Significantly, the interaction of crystal planes (0 0 Ī) of TiO2 anatase and (0 0 1) of ZnO crucially plays as an important role for the reduction of energy band-gap. Additionally, TiO2ZnOAg NPs were used recognize Saccharomyces cerevisiae cells by con-focal fluorescence microscope, showing that it develops bright bio-images for the cells; while for TiO2 or ZnO or TiO2ZnO NPs, no fluorescent response was seen within the cells.