This study aimed to develop an irradiation strategy that would be able to maintain the validity of the Bunsen–Roscoe reciprocity law when exposing the aorta to ultraviolet A (UVA) radiation as a procedure to mechanically reinforce the blood vessels. Furthermore, it aimed to establish a research-based criterion for recommending optimal irradiance levels in a potential clinical setting. Aorta specimens were harvested postmortem from goat eyelids and exposed to UVA radiation (365 nm) in the specified conditions. Thermographic infrared analysis was carried out in order to determine the photothermal response. By performing irradiation in the presence of a photosensitizer (a riboflavin compound), which resulted in the crosslinking of vascular collagen, a photochemomechanical response was also determined based on the changes in mechanical properties as evaluated in a mechanical tester. Based on these radiation-induced photoresponses, a graphical method was employed to define the failure zones when applying the reciprocity law. Loss of the law’s validity was confirmed by the descending values of Schwarzschild’s p-coefficients. Both photoresponses showed that the law’s failure zone begins at an irradiance in the region of 70–75 mW/cm2 for radiant exposures between 6 and 18 J/cm2. Consequently, a higher irradiance is not beneficial when exposing vascular tissue to UVA radiation.
Polymer donors occupy a vital position within the active layer of organic solar cells (OSCs), and their rational molecular design and structural modulation are indispensable for the advancement of OSCs. Designing electron-withdrawing units with fused-ring skeletons is an effective strategy for constructing promising polymer donors. Herein, we report a wide-bandgap donor–acceptor (D-A)-type polymer donor, PBDQB-TF, constructed using a seven-membered fused-ring bis[1,2,5]thiadiazolo[3,4-a:3′,4′-c]dithieno[3,2-h:2′,3′-j]phenazine as the electron-withdrawing moiety. This fused aromatic skeleton exhibits strong electron-deficient character and a large conjugated plane. Benefiting from the structural merits, PBDQB-TF features a deep highest occupied molecular orbital (HOMO) energy level, broad visible-light absorption, and tunable aggregation behavior, enabling excellent spectral complementarity and energy-level alignment with classic non-fullerene acceptors BTP-eC9 and L8-BO. Photovoltaic devices fabricated from PBDQB-TF blended with either acceptor achieve promising power conversion efficiency near 10%. The PBDQB-TF:BTP-eC9 device delivers a favorable short-circuit current density of 20.03 mA cm−2, while the PBDQB-TF:L8-BO system affords a higher open-circuit voltage of 0.964 V and a fill factor of 52.15%. Overall, this work validates the great potential of this new seven-membered, fused-ring electron-withdrawing unit and offers a reliable design principle for the development of next-generation potential polymer donor materials.
The combination of Suzuki arylation and Buchwald–Hartwig amination provides a sequentially Pd-catalyzed pseudo-four-component strategy for the synthesis of symmetrically substituted 3,7,10-triarylphenothiazines in moderate to good yields. Using p-anisyl-derived donor units and p-benzonitrile-derived acceptor units, the electronic and photophysical properties of four representative derivatives were investigated by cyclic voltammetry, absorption and emission spectroscopy, and (TD-)DFT calculations. The calculated electronic transitions are in good agreement with the experimental absorption spectra and enable assignment of the underlying optical transitions, while the observed photophysical behavior is interpreted in the context of previous studies on related 3,10-diarylphenothiazines. A p-anisyl donor substituent at the phenothiazine nitrogen atom favors the intra-oriented ground-state conformation, resulting in intense low-energy absorption bands and high fluorescence quantum yields. In contrast, a p-benzonitrile substituent at this position shifts the conformational equilibrium toward the extra-oriented conformation, leading to altered electronic transitions and reduced fluorescence efficiency. Combined with p-anisyl donor units at the 3,7-positions, the extra-oriented conformation becomes predominant, resulting in pronounced emission quenching. These findings demonstrate that 3,7,10-triarylphenothiazines represent a class of redox-active luminophores in which electronic substitution and conformational preferences provide complementary handles for tuning ground- and excited-state properties.
The photocatalytic degradation of Acid Orange 7 (AO7) in aqueous solution in the presence of exfoliated C3N4 (n-C3N4) as a photocatalyst was investigated under simulated solar light irradiation. The n-C3N4 photocatalyst was synthesized by polymerization of urea as a precursor and characterized by UV/Vis and FTIR spectroscopy, and transmission electron microscopy. Degradation products were identified by high-performance liquid chromatography with high-resolution mass spectrometry (LC–HRMS). It was found that AO7 undergoes a series of oxidation steps mediated by radicals generated during light absorption by n-C3N4, as well as through a photosensitization process initiated by light absorption by AO7. This results in decolorization and the formation of aromatic and aliphatic intermediates, which undergo further oxidation to simpler compounds.
The conformational composition and ultraviolet photochemistry of neutral valine isolated in solid parahydrogen were investigated using high-resolution infrared spectroscopy, ultraviolet photolysis, and density functional theory calculations. The observed infrared spectrum was analyzed by combining calculated vibrational frequencies, relative infrared intensities, and conformer-specific photolysis kinetics. Four distinct photolysis-rate categories were identified experimentally, providing direct evidence for the presence of at least four valine conformers in the parahydrogen matrix. The combined spectroscopic and kinetic analysis enabled assignment of the major absorption bands to the six lowest-energy conformers and revealed pronounced conformer-dependent photostability of valine. Upon irradiation at 213 nm, valine undergoes predominantly α-carbonyl C–C bond cleavage, producing the hydrocarboxyl (HOCO) radical and 2-methylpropan-1-imine as the major photoproducts. The formation of HOCO is consistent with previous studies of amino acids isolated in solid parahydrogen and supports a common photodissociation pathway among aliphatic amino acids. The hydrogen-bonded Type II conformer exhibits significantly slower photodepletion than the Type I conformers, indicating that intramolecular hydrogen bonding enhances ultraviolet photostability of valine. These results establish a direct relationship between molecular conformation and photochemical stability in isolated amino acids while further demonstrating the unique capability of solid parahydrogen matrix isolation for conformer-specific photochemical investigations.
Three types of meso-substituted manganese(III) porphyrin complexes with phenyl, propyl, and isopropyl substituents were synthesized to examine their photochemical and electrochemical properties. The distortion of the porphyrin rings and redox potentials depended on the substituents. The fluorescence quantum yields of these porphyrins were significantly low, indicating the rapid deactivation of their singlet excited states. Although weak emissions attributed to higher singlet excited states and charge-transfer states were observed, their quantum yields remained low. Redox potential measurements showed the relatively strong photooxidative ability of these porphyrins from a thermodynamic standpoint. However, photosensitized protein oxidation was barely observed. The rapid deactivation of photoexcited states decreases the probability of photochemical reactions including biomolecule oxidation. These porphyrins suppressed the self-oxidation of photo-irradiated 1-benzyl-1,4-dihydronicotinamide and catalyzed the decomposition of hydrogen peroxide. In conclusion, these manganese(III) porphyrin complexes barely showed photooxidation activity toward biomolecules and demonstrated protective action against phototoxic reactions.
This work investigates the photo-Fenton degradation of azo dyes in an aqueous medium rich in sodium dodecyl sulfate (SDS), using methyl orange (MO) as a model contaminant. Chemometric modeling was integrated with mechanistic analysis to elucidate the role of the micellar pseudophase in radical distribution, dye partitioning, and overall reaction efficiency. A sequential experimental design strategy was applied, combining fractional factorial design and response surface methodology (RSM) to evaluate the individual and interactive effects of key operational variables and determine the optimal operating conditions for maximum degradation efficiency. Under optimized conditions (pH 2.85, [H₂O₂] = 100 mM, [Fe²⁺] = 0.5 mM, [SDS] = 13 mM, [MO] = 0.01 mM), MO degradation reached 98.4% in 5 minutes. Spectroscopic and partitioning studies revealed a strong affinity of MO for the micellar interface, indicating preferential localization in a microheterogeneous environment. Radical scavenging experiments confirmed that hydroxyl radicals are the dominant oxidizing species in water, while the reduction observed in the presence of SDS suggested secondary radical pathways derived from the surfactant under micellar conditions. Kinetic analyses highlighted the role of intermolecular interactions and micellar compartmentalization in radical generation. The optimized system was successfully extended to other azo dyes, underscoring the potential of surfactant-rich organized media to enhance photo-Fenton reactions in complex aqueous environments.
All forms of neural communications, from cognition to emotion, are regulated by neurotransmitters, which are otherwise the chemical language of the brain. Precise detection of these neurotransmitters is essential for the perception of neurophysiology and diagnosis of neurodegenerative diseases as well. Among the existing techniques for the detection of these molecules, fluorescence sensing is evolving as a powerful approach in terms of high sensitivity, rapid response, and real-time visualization of the chemical events occurring in the neural system. In recent years, nanomaterials have transformed this field by integrating tunable optical properties, excellent photostability, and modifiable surface chemistry into biocompatible nanostructures. We summarize the recent advances of these architectures to show how the material type and dimensionality, as well as the surface functionality, play roles in sensing through the mechanisms of Förster resonance energy transfer (FRET), photoinduced electron transfer (PET), inner filter effect (IFE), and aggregation-induced emission (AIE). The discussion has also been extended to the correlation of fluorescence modulation with the selectivity and sensitivity in the mechanism-to-function relationship. The potential utility of such innovative technologies, including artificial intelligence, spectral deconvolution analysis via big data algorithms, and chip-integrated sensing, was explored as a means to enable real-time neurochemical detection. This converging area of nanotechnology and neuroscience leaves a mark not just in analytical accuracy, but also parallels human brain rhythms.
Xanthophylls are oxygenated carotenoids widely distributed in photosynthetic microorganisms, plants, algae, and certain invertebrates, where they function as key photoprotective and antioxidant pigments. Among them, xanthophylls containing vicinal 1,2-diol moieties exhibit unique chemical reactivity that enables reversible coordination with boron species naturally present in marine and terrestrial environments. The formation of cyclic borate esters between boron and diol-containing xanthophylls induces structural and electronic modifications that may enhance pigment stability and functional performance. Emerging evidence suggests that boron–xanthophyll complexes display improved resistance to photooxidative degradation, enhanced singlet oxygen quenching capacity, and increased radical-scavenging activity compared with their uncomplexed counterparts. In addition, boron coordination can influence molecular conformation, polarity, and supramolecular organization within lipid bilayers, thereby promoting membrane stabilization under conditions of high light exposure and oxidative stress. Together, these effects indicate a cooperative role of boron complexation in amplifying the intrinsic photoprotective and antioxidant properties of xanthophylls. A deeper understanding of the structural basis and biological implications of boron–xanthophyll interactions may provide new insights into adaptive stress tolerance in marine and photosynthetic organisms, as well as guide the development of advanced photoprotective systems for biomedical and technological applications.
4-Dimethylamino-2′-hydroxy chalcone (DHC) 1 is an important natural compound that is nearly non-fluorescent in solution but highly fluorescent in its crystalline state. At room temperature, the weak fluorescence from the DHC solution is exclusively from its keto tautomer, without notable contribution from its enol tautomer. By using low-temperature fluorescence, the study found that the enol emission could be detected upon cooling with liquid N2 in a protic solvent (e.g., EtOH). This led to observation of the fluorescence vibronic structure of enol tautomer, in addition to its enol emission λem ≈ 473 nm that is well separated from its keto tautomer emission (λem ≈ 600 nm). By freezing DHC in a solvent matrix, the study revealed the fluorescent characteristics of a single molecule in a rigid environment. Further comparison of DHC in a solvent matrix and crystalline state disclosed that the emission of crystalline DHC was primarily from the keto tautomer, along with some minor contribution from the enol tautomer, despite the tight packing environment in the crystalline state.
The photoreceptor bacteriorhodopsin (HsBR) from Halobacterium salinarum is a model system for studying ultrafast photoinduced reactions in proteins. Recent time-resolved serial femtosecond crystallography (TR-SFX) experiments require high pump energies, raising concerns about nonlinear excitation and multi-photon effects. Here, we systematically investigate the influence of excitation energy, pulse duration and the sign of the chirp on the initial HsBR photo-reaction using femtosecond Vis-pump IR-probe spectroscopy in the retinal C=C stretching region. An acousto-optic programmable dispersive filter enabled independent control of pulse energy and chirp. Within the tested range, the retinal dynamics were independent of pulse duration and chirp, indicating that fluence alone does not fully describe excitation conditions. Increasing excitation energy leads to nonlinear saturation of the retinal signals and the appearance of an additional band near 1550 cm−1. However, this band rises linearly with the excitation energy. Hence, the additional band is not directly caused by non-resonant multi-photon absorption. Spectral decomposition reveals two components: a low-energy contribution consistent with the known retinal isomerization dynamics and a high-energy contribution attributed to a small population of photo-damaged HsBR likely formed via a resonant two-photon process. These findings clarify the role of excitation conditions in ultrafast HsBR spectroscopy and suggest that spectral changes at high pump energies mainly arise from damaged species upon resonant two-photon excitation.
TiO2 is normally a preferred photocatalyst; however, its photocatalytic performance is constrained by its low surface area, wide band gap, and high electron–hole pair recombination rates. The objective of this study was to optimize the photocatalytic efficiency of TiO2 by impregnating it onto activated carbon derived from Senegalia mellifera biomass. The quantitative study involved synthesizing TiO2 using the precipitation technique and preparing AC through both chemical and physical activation methods. The prepared AC samples were impregnated with TiO2 NPs using the wet impregnation method. The physicochemical properties of the samples were examined using several characterization techniques, namely, FTIR, EDS, Raman, UV reflectance, STA, SEM, and BET. The photocatalytic efficiency of AC/TiO2 composites was evaluated through methyl orange degradation. The results showed significant improvement in photocatalytic performance when TiO2 was supported on AC. The modified photocatalyst exhibited enhanced surface area, thus increased active sites for photocatalysis, improving electron–hole separation and reducing recombination. The 50%CO2/AC-0.5TiO2 composite demonstrated superior photocatalytic activity under both UV and visible light irradiation. It showed 52.1% MO removal under visible light and 76.1% MO removal under UV light. The study concludes that biomass-derived AC/TiO2 composites present a promising, cost-effective and sustainable approach of enhancing photocatalytic activities.
The increasing prevalence of antimicrobial resistance, together with recurring infectious disease outbreaks, has intensified the need for alternative strategies to control microbial infections beyond conventional antibiotic therapies. Antimicrobial photodynamic therapy has emerged as a promising non-antibiotic approach in which light-activated photosensitising compounds generate reactive oxygen species that induce oxidative damage to microbial cells. Plant-derived photosensitisers have attracted increasing attention due to their structural diversity, biocompatibility, natural abundance, and potential for sustainability. Natural compounds such as curcumin, hypericin, chlorophyll derivatives, flavonoids, anthraquinones, and riboflavin exhibit favourable photochemical properties that enable efficient production of reactive oxygen species upon irradiation with visible light. Through radical- and singlet-oxygen-mediated photochemical pathways, these molecules exhibit broad-spectrum antimicrobial activity against bacteria, fungi, viruses, and biofilm-associated microorganisms. This review examines the photophysical properties and mechanisms of reactive oxygen species generation associated with plant-derived photosensitisers, together with key factors influencing their antimicrobial performance. Recent advances in nanocarrier-based delivery systems, dual-wavelength activation strategies, and synergistic combination therapies are also discussed for their potential to improve photostability, enhance reactive oxygen species generation, and increase microbial inactivation efficiency. Finally, current progress, challenges, and future research directions for advancing plant-derived photosensitisers in antimicrobial photodynamic therapy are discussed.
Calcium copper titanate (CaCu3Ti4O12, abbreviated as CCTO) has emerged as a versatile, high-performance material distinguished by its remarkable dielectric, photocatalytic, and environmental properties, positioning it at the forefront of ongoing research and technological innovation. This review provides a comprehensive analysis of CCTO, emphasizing its growing relevance in catalytic and environmental applications. Beginning with an overview of its unique structural and dielectric properties, we discuss how these attributes underpin CCTO’s multifunctionality. Various synthesis methods are examined for their effects on CCTO’s microstructure and performance. Furthermore, we investigate the photocatalytic potential of CCTO under visible light, particularly for applications such as water splitting, CO2 reduction, and degradation of organic pollutants. Environmental applications, including gas sensing and wastewater treatment, are also evaluated, highlighting CCTO’s chemical robustness and suitability under diverse operating conditions. Lastly, key challenges in scalability, cost, and environmental adaptability are discussed, along with future directions, including hybrid composite development and machine-learning-assisted material design. Together, these insights position CCTO as a promising material for advancing sustainable technologies in energy and the environment.
Seminaphtofluorones (SNAFRs) are a family of benzannulated xanthene dyes that exhibit strong fluorescence in both neutral and anionic states and can reach emission wavelengths in the deep-red to near-infrared region. Their optical response is highly sensitive to regioisomerism and functionalization, making them attractive candidates for systematic structure–property investigations. Here, we computed the photophysical properties of six SNAFR regioisomers for both neutral and anionic species and correlate the calculated results with available experimental data. From the six dyes, we further chose two of them, SNAFR4 and SNAFR6, to further investigate how phenyl-ring functionalization modulates SNAFR properties by introducing methyl (–CH3) and carboxyl (–COOH) substituents at the ortho (o), meta (m), and para (p) positions. The calculations indicate that substitution induces measurable changes in geometries, as well as in excitation and emission energies, with particularly pronounced effects for the anionic derivatives. Overall, these results provide a computational framework for the rational tuning of SNAFRs’ optical properties and the design of derivatives with tailored optical characteristics for fluorescence imaging and applications in photodynamic therapy.
In this study, we combined lead-free inorganic perovskite, CsSnI3, with a transition metal chalcogenide, MoS2, to develop a hybrid architecture for photodetectors utilizing the SCAPS-1D simulation tool. The performance of the photodetector was investigated across various thicknesses, doping concentrations, light intensities, and temperatures. An in-depth analysis of built-in potential, recombination rate, generation rate, quantum efficiency, I-V characteristics, and other performance parameters showed that the ideal thickness, doping density, bulk defect density, and interface defect density for enhanced photodetector performance are 800 nm, 1 × 1019 cm−3, 1 × 1014 cm−3, and 1 × 1010 cm−3, respectively. The photodetector exhibits optimal performance within the wavelength range of 200–500 nm and under illumination levels of 500–700 mW/m2, maintaining a consistent responsivity of 0.59 A/W, a detectivity of 4.28 × 1013 Jones, a photocurrent of 34.50 mA/cm2, and a low dark current of 10−6 mA/cm2, with good thermal stability over a wide range of temperatures. The findings indicate that the CsSnI3/MoS2 heterojunction photodetector exhibits superior performance characterized by enhanced sensitivities throughout a broad operational range within the UV–blue visible spectrum and paves the way for the development of cost-effective, high-performance photodetectors in future optoelectronic applications.
Singlet oxygen (1O2) is a key mediator in photodynamic therapy (PDT), and its generation and reactivity in biological systems have been extensively studied. It has been shown that laser radiation at near-infrared (NIR) regions can be used to directly generate 1O2. In this work, we investigated photosensitizer-free 1O2 generation using an original all-fiber pulsed laser operating at 1066 nm and 1241 nm and evaluated its impact on mitochondrial activity in U-87 MG glioblastoma cells. Singlet oxygen was evaluated using the 1,3-diphenylisobenzofuran (DPBF) chemical probe and confirmed with argon-purging controls, demonstrating clear oxygen- and wavelength-dependent effects. Laser irradiation of glioblastoma cells demonstrated distinct effects depending on the wavelength, although decrease in cellular metabolic activity was observed in both cases. Interestingly, some inhibitory effect was also observed when the culture medium was pre-irradiated at 1241 nm and subsequently added to intact cells. These results demonstrate that laser radiation at both studied wavelengths can elicit measurable biological effects, although the relative efficiency in chemical versus cellular systems varies. Collectively, these findings provide a foundation for further systematic studies of wavelength-specific NIR interactions with cellular and molecular components in biological environments.
We report the use of σ-alkynyl d6 electron-rich transition metal complexes as electron-releasing end-groups in octupolar molecules designed for nonlinear optical (NLO) applications, specifically, N,N′,N″-triarylisocyanurates (5,7,8,10,12) and 1,3,5-triarylbenzenes (6,9,11) functionalized by Fe(II) and Ru(II) organometallic moieties, and their NLO properties, as assessed by hyper-Rayleigh scattering (HRS) and Z-scan. The redox properties are briefly investigated through isolation of the corresponding Fe(III) trications 5[PF6]3 and 6[PF6]3. The second-harmonic generation (SHG) or two-photon absorption (2PA) performance of the Fe(II) and Ru(II) parents is compared with the help of TD-DFT calculations performed on models. Comparison with tris-ferrocenyl isocyanurate 4 reveals that the σ-connection of the metallic centers to the π-manifold is superior to the η5-connection for enhancing NLO properties. The positive effect of organometallic end-groups on NLO properties relative to purely organic electron-releasing substituents is established. The mechanism by which NLO enhancement occurs is complex and possibly connected to the polarizable π-electrons in the ligands surrounding the metal alkynyl units, but in most cases, the observed NLO enhancement must arise from the transition metal centers interacting with the central π-manifold.
Hollow fibers (HFs) have recently gained attention as an advantageous photocatalyst immobilizer for heterogeneous catalysis. Depending on their fabrication method, they can come up, or not, with a porous network within their structure. In this case, they are sometimes referred to as membranes, although they are not applied in liquid flow applications as filters. This work provides a concise overview of all the studies encountered in the literature on photocatalytic hollow fibers (HFs) and hollow fiber membranes (HFMs), clarifying the prevailing confusion about the topic. All publications are categorized with respect to their reported applications in batch liquid, flow, or gas experiments.
Titanium dioxide (TiO2) thin films were deposited by DC magnetron sputtering and subsequently treated in hot water at 50, 70, and 95 °C for 72 h to investigate the influence of low temperature on their structural optical and functional properties. XRD analysis revealed a progressive transformation from amorphous to anatase phase with increasing treatment temperature, accompanied by an increase in crystallite size from 5.2 to 15.1 nm. FT-IR spectroscopy confirmed enhanced surface hydroxylation and contact angle measurements showed a decrease from 77.4° to 19.7°, indicating a significant improvement in superior wettability. The transmittance spectroscopy revealed a slight narrowing of the optical band gap from 3.34 to 3.21 eV, consistent with improved visible-light absorption. Photocatalytic tests using the Resazurin indicator demonstrated that the film treated at 95 °C exhibited the highest activity, achieving a bleaching time of 245 s three times faster than treated at 50 °C and twice as fast as treated at 70 °C. Under low-intensity solar irradiation, the same sample achieved complete E. coli inactivation within 90 min. These improvements are attributed to increased crystallinity, surface hydroxyl density, and enhanced ROS generation. Overall, this study demonstrates that mild hot-water treatment is an effective, substrate-friendly route to enhance TiO2 film wettability and multifunctional performance, enabling the fabrication of self-cleaning and antibacterial coatings on fragile materials such as plastics and textiles.
