RESUMEN
The sensitization of surface-anchored organic dyes on semiconductor nanocrystals through energy transfer mechanisms has received increasing attention owing to their potential applications in photodynamic therapy, photocatalysis, and photon upconversion. Here, we investigate the sensitization mechanisms through visible-light excitation of two nanohybrids based on CsPbBr3 perovskite nanocrystals (NC) functionalized with borondipyrromethene (BODIPY) dyes, specifically 8-(4-carboxyphenyl)-1,3,5,7-tetramethyl-4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BDP) and 8-(4-carboxyphenyl)-2,6-diiodo-1,3,5,7-tetramethyl-4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (I2-BDP), named as NC@BDP and NC@I2-BDP, respectively. The ability of I2-BDP dyes to extract hot hole carriers from the perovskite nanocrystals is comprehensively investigated by combining steady-state and time-resolved fluorescence as well as femtosecond transient absorption spectroscopy with spectroelectrochemistry and quantum chemical theoretical calculations, which together provide a complete overview of the phenomena that take place in the nanohybrid. Förster resonance energy transfer (FRET) dominates (82%) the photosensitization of the singlet excited state of BDP in the NC@BDP nanohybrid with a rate constant of 3.8 ± 0.2 × 1010 s-1, while charge transfer (64%) mediated by an ultrafast charge transfer rate constant of 1.00 ± 0.08 × 1012 s-1 from hot states and hole transfer from the band edge is found to be mainly responsible for the photosensitization of the triplet excited state of I2-BDP in the NC@I2-BDP nanohybrid. These findings suggest that the NC@I2-BDP nanohybrid is a unique energy transfer photocatalyst for oxidizing α-terpinene to ascaridole through singlet oxygen formation.
RESUMEN
The introduction of an oxime group into indirubin (INR) derivatives, including INROx, MINROx, and 6-BrINROx, and its impact on the spectral and photophysical properties of INR was investigated using a combination of fast-transient absorption (fs-TA/fs-UC) and steady-state fluorescence techniques. The oxime group introduces structural modifications that promote a rapid keto-enol tautomeric equilibrium and enhance the excited-state proton transfer (ESPT) process compared to its analogue, INR. In the oxime-indirubin derivatives investigated, the ESPT process is notably more efficient than what is observed in INR and indigo, occurring extremely fast (<1 ps) in all solvents, except for the viscous solvent glycerol. The more rapid deactivation mechanism precludes the formation of an intermediate species (syn-rotamer), as observed with INR. These findings are corroborated by time-dependent density functional theory (TDDFT) calculations. The work demonstrates that introducing an oxime group to INR, whether in nature or in the laboratory, results in an enhancement of its photostability.
RESUMEN
This paper presents a comprehensive investigation of the synthesis and characterization of Zn1-xCoxO (0 ≤ x ≤ 0.05) nanopowders using a chemical co-precipitation approach. The structural, morphological, and vibrational properties of the resulting ZnO nanostructures were assessed through X-ray diffraction, scanning electronic microscopy, and Raman spectroscopy to examine the influence of cobalt doping. Remarkably, a notable congruence between the experimental results and the density functional theory (DFT) calculations for the Co-doped ZnO system was achieved. Structural analysis revealed well-crystallized hexagonal wurtzite structures across all samples. The SEM images demonstrated the formation of spherical nanoparticles in all the samples. The vibrational properties confirmed the formation of a hexagonal wurtzite structure, with an additional Raman peak corresponding to the F2g vibrational mode characteristic of the secondary phase of ZnCo2O4 observed at a 5% cobalt doping concentration. Furthermore, a theoretical examination of cobalt doping's impact on the elastic properties of ZnO demonstrated enhanced mechanical behavior, which improves stability, recyclability, and photocatalytic activity. The photocatalytic study of the synthesized compositions for methylene blue (MB) dye degradation over 100 min of UV light irradiation demonstrated that Co doping significantly improves photocatalytic degradation. The material's prolonged lifetime, reduced rate of photogenerated charge carrier recombination, and increased surface area were identified as pivotal factors accelerating the degradation process. Notably, the photocatalyst with a Zn0.99Co0.01O composition exhibited exceptional efficiency compared to that reported in the literature. It demonstrated high removal activity, achieving an efficiency of about 97% in a shorter degradation time. This study underscores the structural and photocatalytic advancements in the ZnO system, particularly at lower cobalt doping concentrations (1%). The developed photocatalyst exhibits promise for environmental applications owing to its superior photocatalytic performance.
RESUMEN
BACKGROUND: The induction of phototoxicity during photodynamic therapy (PDT) is dependent on oxygen availability. For this reason, the development of sensors to measure oxygen and oxygen consumption is extremely important. APPROACH: In this project we have used Fluorescence Lifetime imaging (FLIM) and Phosphorescence Lifetime Imaging/ delayed Fluorescence Lifetime Imaging (PLIM/dFLIM) to investigate the ability of bromine indirubin derivatives as oxygen sensors. RESULTS: The oxygen sensitivity of bromine indirubins was detected through PLIM/dFLIM. Moreover, we have observed, by measuring nicotinamide adenine dinucleotide (NADH) FLIM, that bromine indirubin has a significant impact on cellular metabolism by shifting the SCC-4 Cells metabolism from oxidative phosphorylation (OXPHOS) to glycolysis. CONCLUSIONS: In conclusion, this study successfully achieves its goals and provides important insights into the use of indirubin as a potential oxygen consumption sensor with the capability to identify and differentiate between normoxic and hypoxic regions within the cells.