Solvent Effects on Nonradiative Relaxation Dynamics of Low-Energy Ligand-Field Excited States: A CuCl42- Complex

Revealing the Photophysical and Photochemical Reaction Processes of Carprofen in Different Solutions via Ultrafast Femtosecond to Nanosecond Transient Absorption

Carprofen (CP), one kind of a nonsteroidal anti-inflammatory drug, exhibits phototoxic side effects in physiology, while its phototoxic mechanism is ambiguous. To uncover CP's photophysical and photochemical reaction processes, femtosecond to nanosecond transient absorption spectroscopies were employed to directly detect excited states and transient intermediates of CP upon UV irradiation in pure acetonitrile (MeCN), MeCN/water 1:1, and acid/alkaline buffer solutions. The transient absorption data together with DFT calculations were integrated to elucidate mechanisms for photochemical reactions of CP in different solutions. The associated photophysical and photochemical reaction pathways are dependent on various solution environments. In a pure MeCN solvent, CP is excited to a singlet state (S₁) and rapidly interacts with the solvent to proceed solvent rearrangement (SR). It then undergoes vibrational cooling (VC) and proceeds intersystem crossing (ISC) to produce the lowest triplet state (³CP). ³CP finally decays to the ground state. While in a MeCN/water 1:1 solution, deprotonated S₁ of CP experiences SR and VC processes, and then it is promoted to a deprotonated triplet state (³CP^-). ³CP^- undergoes the parallel reactions: dechlorination to a phenyl radical (²CP^-) and decarboxylation to a T₁ anion (³CP^-(de-CO₂)). Finally, both intermediates produce the radical anion species ²CP^-(de-CO₂). In a pH = 7.4 (MeCN/PBS 1:1) solution, ³CP^- can be converted into ²CP^-(de-CO₂) more quickly. Interestingly, we found that the dechlorination step can be promoted in an alkaline solution. Phenyl and chlorine radicals produced in an aqueous solution may be the root cause of the drug's harmful side effects on the human body. This may be useful to guide the design of related CP drugs with minimal phototoxicity in the pharmaceutical process.

Sensitization of TiO2 nanosheets with Cu-biphenylamine framework to enhance photocatalytic degradation performance of toxic organic contaminants: synthesis, mechanism and kinetic studies

TNS/Cu(X) composite materials were firstly synthesized via simple overnight stirring of TNS in the methanolic solution of Cu complexes. The developed TNS/Cu(X) composites had a well-designed nanostructure, in which the TNS and Cu complexes were closely bounded with each other. The biphenylamine complexes fixed on the TNS surface in form of nanocapsules, which were confirmed by TEM and SEM, thus improving the surface area and subsequently charge separation. Innovatively merged photocatalysts of Cu complexes with TNS were successfully verified for photocatalytic mineralization of colored and colorless organic contaminants under the visible light degradation. As compared to original TNS, TNS/Cu(BA) showed prominent improvement in the catalytic actions. Kinetics i.e. t _1/2 (half-life times period), K _app, and R ² (linear regression co-efficient) were also studied. The amended materials created charge separation, by means of electrons gathering at the higher CB, and holes gathering at the lower level valence band of the Cu complex, therefore improving mineralization efficiency of the electrons and holes. TNS/Cu(BA) degrade 99%-99.6% of methyl orange (MO) and rhodamine B (RhB) dyes at 120 min, and 160 min, respectively, and 68% of phenol and 53% of TCP were destroyed in 180 min. The resilient holes can directly destroy MO, RhB, phenol, and TCP.

Encapsulating nano rods of copper–biphenylamines framework on g-C3N4 photocatalysts for visible-light-driven organic dyes degradation: promoting charge separation efficiency

For the first time we have successfully constructed semi conductive copper–biphenylamines framework hybrid photocatalysts to degrade organic pollutants.