CASPT2 study of the electronic structure and photochemistry of protonated N -nitrosodimethylamine (NDMA-H+ ) at 453 nm

In this work, we have studied the photodissociation of the protonated derivatives of N-nitrosodimethylamine [(CH3)2N–NO] with the CASPT2 method. It is found that only one of the four possible protonated species of the dialkylnitrosamine compound absorbs in the visible region at 453 nm, that is, N-nitrosoammonium ion [(CH3)2NH-NO]+. This species is also the only one whose first singlet excited state is dissociative to directly yield the aminium radical cation [(CH3)2NHN·]+ and nitric oxide. In addition, we have studied the intramolecular proton migration reaction {[(CH3)2N–NOH]+ → [(CH3)2NH–NO]+} both in the ground and excited state (ESIPT/GSIPT); our results indicate that this process is not accessible neither in the ground nor in the first excited state. Furthermore, as a first approximation, MP2/HF calculations on the nitrosamine–acid complex indicate that in acidic solutions of aprotic solvents, only [(CH3)2NH–NO]+ is formed.This work was supported by the Spanish Ministry of Science and Innovation (Grant No. MCIN/AEI/10.13039/501100011033) through Project No. PID2021-122613OB-I00. Funding for open access charge: Universidad de Málag

Determination of fluorene in sea-water by room temperature phosphorescence in organised media †

Fluorene, insoluble in water, forms an inclusion compound in aqueous media with b-cyclodextrin, with an equilibrium constant of 2290 ± 150 l mol 21 at 15°C. The inclusion phenomenon was studied by fluorimetric and phosphorimetric techniques. A schematic host-guest model to explain the inclusion complex structure is reported. The phosphorescence spectra showed maximum excitation and emission wavelengths at 304 and 460 nm, respectively. The phosphorescence lifetimes were calculated employing different organic and inorganic perturber atoms, and was 185 ms for 3-bromopropan-1-ol. Optimum conditions of the method were [b-cyclodextrin] = 8 3 10 23 m, pH = 6.65, 3-bromopropan-1-ol as heavy atom, sodium sulfite-sulfurous acid as oxygen scavenger, b-cyclodextrin, heavy atom and buffer as addition order, temperature 15°C and t d and t g 0.1 and 13 ms, respectively. The main figures of merit were linear dynamic range 15-2000 ng ml 21 , detection limit 4.5 ng ml 21 and RSD 2.5%. The method has a moderate selectivity against other PAHs and aromatic molecules and a considerable increase in selectivity in comparison with fluorimetric measurements is observed. An application of this technique to fluorene determination in environmental sea-water samples with successful results is described

Synthesis of porous graphene/TiO2 by use of recycled graphite

Graphene-based nanomaterials are a kind of new technological materials with high interest for physicists, chemists and materials scientists. Graphene is a two-dimensional (2-D) sheet of carbon atoms in a hexagonal configuration with atoms bonded by sp2 bonds. These bonds and this electron configuration provides the extraordinary properties of graphene, such as very large surface area, a tunable band gap, high mechanical strength and high elasticity and thermal conductivity [1]. Graphene has also been investigated for preparation of composites with various semiconductors like TiO2, ZnO, CdS aiming at enhanced photocatalytic activity for their use for photochemical reaction as water splitting or CO2 to methanol conversion [2-3]. In this communication, the synthesis of porous graphene@TiO2 obtained from a powder graphite recycled, supplied by ECOPIBA, is presented. This graphite was exfoliated, using a nonionic surfactant (Triton X-100) and sonication. Titanium(IV) isopropoxide was used as TiO2 source. After removing the surfactant with a solution HCl/n-propanol, a porous solid is obtained with a specific area of 358 m2g-1. The solid was characterized by XRD, FTIR, XPS, EDX and TEM. Figure 1 shows the graphene 2D layer bonded with nanoparticles of TiO2. When a water suspension of this material is exposed with UV-vis radiation, water splitting reaction is carried out and H2/O2 bubbles are observed (Figure 2)Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

One-pot synthesis of green-emitting nitrogen-doped carbon dots from xylose

Carbon dots (CDs) are interesting carbon nanomaterials that exhibit great photoluminescent features, low cytotoxicity, and excellent water stability and solubility. For these reasons, many fields are starting to integrate their use for a variety of purposes. The catalytic performance of VOPO4 has been evaluated in the synthesis of nitrogen-doped carbon dots (N-CDs). The synthesis reaction was carried out at 180 °C using VOPO4 as a heterogeneous catalyst for 2 to 4 h of reaction time. After reaction, the N-CDs were purified using a novel method for the protection of the functional groups over the surfaces of the N-CDs. The morphological, superficial, and photoelectronic properties of the N-CDs were thoroughly studied by means of TEM, HRTEM, XPS, and photoluminescence measurements. The conversion of the carbon precursor was followed by HPLC. After three catalytic runs, the catalyst was still active while ensuring the quality of the N-CDs obtained. After the third cycle, the catalyst was regenerated, and it recovered its full activity. The obtained N-CDs showed a great degree of oxidized groups in their surfaces that translated into high photoluminescence when irradiated under different lasers. Due to the observed photoelectronic properties, they were then assayed in the photocatalytic degradation of methyl orange.This research was funded by the Spanish Ministry of Science and Innovation (PID2021-122736OB-C42, PID2021-122613OB-I00) and FEDER (European Union) funds (PID2021-122736OB-C42, P20-00375, UMA20-FEDERJA88)

Fe(II) complexes of pyridine-substituted thiosemicarbazone ligands as catalysts for oxidations with hydrogen peroxide

La reacción de tres complejos [FeII(TSC)2], donde TSC es una ligando de tipo tiosemicarbazona sustituido por piridina, con H2O2 en acetonitrilo no permitía acumular los correspondientes complejos de Fe(III), [FeIII(TSC)2]+. En su lugar, se generaba una mezcla de especies de Fe(II) diamagnéticas de bajo espín. Según los espectros obtenidos por espectrometría de masas, estas especies eran el resultado de la adición secuencial de hasta cinco átomos de oxígeno al complejo. Esta capacidad para la adición de átomos de oxígeno sugirió que dichas especies podrían ser activas para la transferencia de átomos de oxígeno a sustratos externos. Por ello, se evaluó la capacidad de estos complejos para la oxidación de tioanisol y estireno empleando H2O2 como oxidante inicial. Los complejos fueron activos tanto en la oxidación de tioanisol a su sulfóxido como en la de estireno a benzaldehído, con escalas temporales que indicaban la participación de las especies intermedias que contenían los átomos de oxígeno añadidos. Curiosamente, los ligandos libres y el complejo [Zn(Dp44mT)2] también catalizaban la sulfoxidación selectiva del tioanisol, pero eran ineficaces para catalizar la oxidación del estireno a benzaldehído. Estos hallazgos abren nuevas vías para el desarrollo de catalizadores metálicos basados en tiosemicarbazonas en procesos de oxidación de gran interés

Monitoring oocyte-based human pluripotency acquisition using synchrotron-based FTIR microspectroscopy reveals specific biomolecular trajectories

The reprogramming of human somatic cells to induced pluripotent cells (iPSCs) has become a milestone and a paradigm shift in the field of regenerative medicine and human disease modeling including drug testing and genome editing. However, the molecular processes occurring during reprogramming and affecting the pluripotent state acquired remain largely unknown. Of interest, different pluripotent states have been described depending on the reprogramming factors used and the oocyte has emerged as a valuable source of information for candidate factors. The present study investigates the molecular changes occurring in somatic cells during reprogramming with either canonical (OSK) or oocyte-based (AOX15) combinations using synchrotron-radiation Fourier transform infrared (SR FTIR) spectroscopy. The data acquired by SR FTIR indicates different representation and conformation of biological relevant macromolecules (lipids, nucleic acids, carbohydrates and proteins) depending on the reprogramming combination used and at different stages during the reprogramming process. Association analysis based on cells spectra suggest that pluripotency acquisition trajectories converge at late intermediate stages while they diverge at early stages. Our results suggest that OSK and AOX15 reprogramming operates through differential mechanisms affecting nucleic acids reorganization and day 10 comes out as a candidate hinge point to further study the molecular pathways involved in the reprogramming process. This study indicates that SR FTIR approach contribute unpaired information to distinguish pluripotent states and to decipher pluripotency acquisition roadmaps and landmarks that will enable advanced biomedical applications of iPSCs.The authors thank ALBA Synchrotron facility for beamtime allocation and financial support from the Proposal No. 2021085254 and excellent working conditions. E.G-M acknowledge financial support from Ministerio de Ciencia e Innovaci´on del Gobierno de Espa˜na (grant number PID2021-124033OB-I00) and from Consejería Economía y Conocimiento Junta de Andalucía-FEDER (grant number UMA18-FEDERJA-107). Funding for open access charge was provided by Universidad de Málaga / CBUA

Nanoporous alumina support covered by imidazole moiety-based ionic liquids: optical characterization and application

This work analyzes chemical surface and optical characteristics of a commercial nanoporous alumina structure (NPAS) as a result of surface coverage by different imidazolium-based ionic liquids (1-butyl-3-metylimidazolium hexafluorophosphate, 3-methyl-1-octylimidazolium hexafluorophosphate, or 1-ethyl-3-methylimidazolium tetrafluoroborate). Optical characteristics of the IL/NPAS samples were determined by photoluminescence (at different excitation wavelengths (from 300 nm to 400 nm), ellipsometry spectroscopy, and light transmittance/reflectance measurements for a range of wavelengths that provide information on modifications related to both visible and near-infrared regions. Chemical surface characterization of the three IL/NPAS samples was performed by X-ray photoelectron spectroscopy (XPS), which indicates almost total support coverage by the ILs. The IL/NPAS analyzed samples exhibit different photoluminescence behavior, high transparency (<85%), and a reflection maximum at wavelength ~380 nm, with slight differences depending on the IL, while the refractive index values are rather similar to those shown by the ILs. Moreover, the illuminated I–V curves (under standard conditions) of the IL/NPAS samples were also measured for determining the efficiency energy conversion to estimate their possible application as solar cells. On the other hand, a computational quantum mechanical modeling method (DFT) was used to establish the most stable bond between the ILs and the NPAS support.M.A. thanks the SpanishMinistry of Science and Innovation (MCIN/AEI/10.13039/ 501100011033) through project PID2021-122613OB-I00

CDs and N-CDs preparation from xylose and xylose-enriched biomass liquors for methyl orange photocatalytic degradation.

CDs are newly discovered carbon nanoparticles that present unique properties. Each nanoparticle consists of a graphitic lattice core covered by a functionalized surface composed by several polar functional groups attached1,2. Due to this functionalization, CDs exhibit photoinduced electronic transference, fluorescence and up-conversion photoluminescence3. CDs have raised increasing attention for their undemanding synthesis procedure combined with the fact that they have been proved to be non-toxic and can be modified to reach satisfactory quantum yield values. A current tendency in the obtention of CDs is the pursuit of a synthesis method that fulfils the requirements of green chemistry but keeps production costs low. Therefore, CDs obtained from green precursors coming from biomass is an emergent research topic4,3,5,6,7. The most frequent and best-known method for CDs production is hydrothermal or solvothermal method7,3,2.The acidic conditions required by this method are commonly achieved using mineral acids such as HCl; nonetheless, the hydrothermal method is compatible with heterogeneous catalysis, which have been proved in this work. As a consequence of their photoluminescence and electron transfer properties, CDs can work as electron mediators, photosensitizers, as well as photocatalysts by themselves 10. It has been proved that CDs when photo excited are outstandingly good electron donors and electron acceptors, since either electron acceptors or electron donors are able to quench the photoluminescence emitted by CDs effectively 9.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech