Photochem, Volume 3, Issue 1 (March 2023) – 12 articles

Under simulated light irradiation, the aerobic oxidation of benzylamine to N,N-benzylidenebenzylamine was carried out as a model reaction to investigate the photocatalytic activity of a hydrothermally prepared composite based on BiOF and BiFeO₃ materials. The prepared photocatalysts were characterized using several spectroscopic techniques, such as powder X-ray diffraction (PXRD), diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and Fourier transform infrared spectroscopy (FTIR). Band gap analysis showed that the composite exhibits a band gap that lies in the UV region (3.5 eV). Nonetheless, pristine BiOF and BiFeO₃ exhibited band gaps of 3.8 eV and 2.15 eV, respectively. N,N-benzylidenebenzylamine was selectively achieved with a high conversion yield of ~80% under atmospheric conditions in which the product was confirmed using ¹H-NMR, ¹³C-NMR, and FTIR spectroscopic techniques. Various control experiments were conducted to further confirm the enhanced photocatalytic performance of the reported composite. Full article

Multidrug resistance of pathogenic microflora is a serious threat to the modern community looking for new approaches to treating superinfections. In this sense, antimicrobial photodynamic therapy (aPDT) is an effective and safe technique considered to be a promising alternative or an important supplement to the traditional clinically applied methods for inactivating antibiotic resistant pathogens. Macroheterocyclic photosensitizers (PS) of three generations are proposed for clinical practice. They are known as the key compounds for PDT able to be localized selectively in microbial cells and to be activated with the red light producing toxic reactive oxygen species (ROS). However, these neutral and anionic PSs possess low affinity towards the outer lipopolysaccharide membrane of Gram-negative bacteria and, consequently, poor ability to kill these pathogens under irradiation. In contrast, cationic PSs containing one or more charged groups, especially those bound to an appropriate carrier, provide efficient inactivation of microorganisms. In this paper, we focus on the study of photophysics, aggregation and photoinduced antimicrobial activity of the water-soluble derivative of deuteroporphyrin-IX, a blood group porphyrin, bearing two cationic trialkylammonium fragments. This potential photosensitizing agent is found to generate singlet oxygen in a non-polar environment and forms stable nano-sized molecular complexes with passive non-ionic carrier Tween 80, localizing in an aqueous surfactant solution as a non-aggregated form in the surface micellar layer. Two different modes of PS/Tween 80 binding characterized by their own stability constants and interaction stoichiometry are observed. Microbiological experiments clearly demonstrate that the increased permeability of the outer bacterial membrane caused by the application of the intramicellar form of the photosensitizer or addition of some potentiation agents leads to pronounced light phototoxicity of the pigment against antibiotic-resistant nosocomial strains of Gram-negative bacterial pathogens. Full article

The application domain of deep learning (DL) has been extended into the realm of nanomaterials, photochemistry, and optoelectronics research. Here, we used the combination of a computer vision technique, namely convolutional neural network (CNN), with multilayer perceptron (MLP) to obtain the far-field optical response at normal incidence (along cylinder axis) of concentric cylindrical plasmonic metastructures such as nanorods and nanotubes. Nanotubes of Si, Ge, and TiO₂ coated on either their inner wall or both their inner and outer walls with a plasmonic noble metal (Au or Ag) were thus modeled. A combination of a CNN and MLP was designed to accept the cross-sectional images of cylindrical plasmonic core-shell nanomaterials as input and rapidly generate their optical response. In addition, we addressed an issue related to DL methods, namely explainability. We probed deeper into these networks’ architecture to explain how the optimized network could predict the final results. Our results suggest that the DL network learns the underlying physics governing the optical response of plasmonic core-shell nanocylinders, which in turn builds trust in the use of DL methods in materials science and optoelectronics. Full article

The linear and nonlinear optical properties of two quadrupolar bithiophenes and two quadrupolar cyclopentadithiophenes have been investigated. At the 5,5′ positions of the central bi/dithiophene units, the molecules possess 1,4-phenylalkynyl groups that bear either electron-donating (NPh₂) or electron-withdrawing (SO₂CF₃) groups. The optical properties were experimentally studied and modelled via quantum chemistry computations of key configurations and conformations. All the compounds show good light harvesting efficiency due to their strong absorption in the visible range. These fluorescent compounds are also good two-photon absorbers in the NIR range that can photosensitize oxygen in toluene. DFT calculations reveal that the mixtures of conformers in a solution show similar linear optical properties. TD-DFT calculations reproduce the experimental spectroscopic data fairly well, including vibronic couplings in the fluorescence spectra. The lowest excited state for two-photon absorption corresponds to the S₂ state. The roles of the SO₂CF₃ and NPh₂ terminal groups on the nonlinear response were analyzed for possible bio-oriented applications, with the cyclopentadithiophenes showing the most promising figures of merit. Full article

Here we present simple fluorophores based on the pyridine core, obtained with straightforward synthetic methodologies. These compounds present in solution absorption maxima in the UV region and fluorescence emission of between 300 and 450 nm, depending on the solvent and chemical structure of the fluorophore. The nature of the solvent was shown to play a fundamental role in their excite-state deactivation, which allowed successful exploration of these compounds as optical sensors for benzene and fuel adulteration in gasoline. In ethanolic solution, upon the addition of benzene, in general the fluorophores presented fluorescence quenching, where a linear correlation between the emission intensity and the amount of benzene (quencher) was observed. In addition, the application of an optical sensor for the detection of fuel adulteration in commercial standard and premium gasoline was successfully presented and discussed. Theoretical calculations were also applied to better understand the solvent–fluorophore interactions. Full article

In the present study, we investigated the photooxidation of the biomimetic model of C-terminal methionine, N-Acetyl-Methionine (N-Ac-Met), sensitized by a 3-Carboxybenzophenone (3CB) excited triplet in neutral and basic aqueous solutions. The short-lived transient species that formed in the reaction were identified and quantified by laser flash photolysis and the final stable products were analyzed using liquid chromatography coupled with high-resolution mass spectrometry (LC-MS) and tandem mass spectrometry (MSMS). Based on these complementary methods, it was possible to calculate the quantum yields of both competing reactions, and the deprotonation was found to be favored over decarboxylation (for neutral pH: ϕ_-H = 0.23 vs. ϕ_-CO2 = 0.09, for basic pH: ϕ_-H = 0.23 vs. ϕ_-CO2 = 0.05). Findings on such a model system, which can possibly mimic the complex protein environment, are important in understanding complicated biological systems, for example, the studied compound, N-Ac-Met, can, to some extent, mimic the methionine in the C-terminal domain of β-amyloid, which is thought to be connected with the pathogenesis of Alzheimer’s disease. Full article

Gliosarcoma (GS) is a primary malignant neoplasm of the central nervous system, treated with an unfavorable prognosis with surgery, radiotherapy, and chemotherapy. The treatment for GS consists of surgical resection, almost always accompanied by radiotherapy and/or chemotherapy, given the invasive behavior of the tumor. Photodynamic Therapy (PDT) is studied as an alternative method that combines light, a photosensitizer (PS), and molecular oxygen. This study aimed to compare the effects of PDT using the photosensitizers Fotoenticine (FTC) and Photodithazine (PDZ) at low concentrations and fluences. For this study, 9 L/lacZ cells, concentrations of 1.55 µg mL⁻¹, 12.5 µg mL⁻¹, and 50 µg mL⁻¹ of chlorins and fluences of 1, 5, and 10 J/cm² were used. A test was also carried out with Trypan Blue in L929 cells at the mentioned concentrations at 5 J/cm². Both chlorins were internalized in the cytoplasm, with a significant reduction in viability (>95%) in almost all groups and altered cell adhesion and morphology after PDT. HSP70 expression decreased in both PS, while HSP27 increased only in PDT with FTC, and although there was a change in cell adhesion in the 9 L/LacZ lineage it was not observed in the L929 fibroblast lineage. Both chlorins were effective, highlighting the concentration of 50 µg mL⁻¹ at the fluence of 5 J/cm²; according to the present study, the PDZ showed better results. Full article

A combined spectroscopic and computational approach has been used to study in detail the complexation between Ga(III) and ARS in solution. The NMR results revealed the formation of four Ga(III)/ARS complexes, at pH 4, differing in their metal:ligand stoichiometries or configuration, and point to a coordination mode through the ligand positions C-1 and C-9. For equimolar metal:ligand solutions, a 1:1 [Ga(ARS)(H₂O)₄]⁺ complex was formed, while for 1:2 molar ratio solutions, a [Ga(ARS)₂(H₂O)₂]⁻ complex, in which the two ligands are magnetically equivalent, is proposed. Based on DFT calculations, it was determined that this is a centrosymmetric structure with the ligands in an anti configuration. For solutions with a 1:3 molar ratio, two isomeric [Ga(ARS)₃]³⁻ complexes were detected by NMR, in which the ligands have a mer and a fac configuration around the metal centre. The DFT calculations provided structural details on the complexes and support the proposal of a 1,9 coordination mode. The infrared spectroscopy results, together with the calculation of the infrared spectra for the theoretically proposed structures, give further support to the conclusions above. Changes in the UV/vis absorption and fluorescence spectra of the ligand upon complexation revealed that ARS is a highly sensitive fluorescent probe for the detection of Ga(III). Full article

Electrocatalysis is a promising way to treat water contaminated by harmful organic compounds. The combination of nanoparticles supported on a conductive substrate allows degradation to occur under less energetic conditions. This work evaluated the effect of deposition of bismuth vanadate (BVO) particles on pencil-type graphite electrodes. BVO particles were obtained by ultrasonic irradiation with coprecipitation. Then, they were deposited on the surface of a graphite electrode by the impregnation method. A 2³-design was used to optimize electrode fabrication. Matter Dispersion Spectroscopy (SEM/EDS), X-Ray Diffraction (XRD) and Dynamic Light Scattering (DLS) were used for characterization. Electrochemical characterization was performed by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The results confirmed the synthesis of BVO@C (BVO/graphite). Furthermore, BVO@C significantly increased the electroactive surface area of the electrode, decreased the electron transfer resistance, and significantly increased the electron transfer rate to a greater extent than the electrode without any modification. To prove that the performance of BVO@C is better than the pure electrode, photoelectrocatalysis (PEC) and electrocatalysis (EC) were performed in a rhodamine B (RhB) solution. The results showed that in 5 min of treatment with unmodified electrode, BVO@C EC system and BVO@C PEC system, there was degradation of 31.53%, 46.09% and 58.17% respectively, reaching 95%, 98% and 99.64%, respectively, in 30 min. The reaction rate constants were calculated and to be found k = 0.10272 m⁻¹, k = 0.12221 m⁻¹ and k= 0.15022 m⁻¹ for the unmodified graphite, BVO@C EC System and BVO@C PEC system, respectively. These results demonstrate that the BVO@C electrodes are efficient for application in a wide range of treatments, including the treatment of organic pollutants. Full article

Due to their excellent properties and unique structures, transition metal sulfides play an important role in the development of efficient and stable photoelectric catalysts. In recent years, their potential applications have expanded from photoelectric catalysis to energy storage, especially as materials for key components of electrochemical energy storage. As a typical multifunctional metal sulfide catalyst, Co₉S₈ is highly attractive due to its high conductivity, better stability, suitable band structure, enhanced performance and wide applications. A large number of studies have shown that strategically modified Co₉S₈-based materials have greater advantages in various applications compared with pure Co₉S₈. Therefore, this review will evaluate the physicochemical properties and the preparation of different dimensions of Co₉S₈-based materials, and the influence of different structures on the photoelectrochemical energy of materials will be described. In addition, the research progress regarding the evolution of hydrogen photocatalytic, electrocatalytic water splitting and various electrochemical energy storage materials will be emphasized. Finally, the challenges faced by Co₉S₈-based materials and the research directions for their future applications will be discussed. Full article

In this work, we monitored the fluorescence quantum efficiency (η) and the fluorescence lifetime (τ) of natural dye extracts from the leaves of Tradescantia pallida purpurea. The natural dye was extracted from leaves in aqueous solutions as a function of the potential of hydrogen (pH). The η was determined from conical diffraction (CD) pattern measurements due to thermally-driven self-phase modulation. The fluorescence spectra and time-resolved fluorescence measurements corroborate the CD results, and the average η ≈ 0.28 and τ ≈ 3.1 ns values were obtained in the pH range 3.96–8.02. In addition, the extracted natural dye was tested as a possible colorimetric and/or fluorometric pH indicator in milk. Full article