Photochemical Properties Research Articles

Elementally Doped Carbonized Polymer Dots: Control of Optical Properties and Their Versatile Applications

AbstractCarbonized polymer dots (CPDs) are a class of luminescent nanomaterials formed through cross‐linking and polymerization. Owing to their excellent biocompatibility, ease of synthesis, good aqueous dispersion, high chemical stability, unique cross‐linking structure, and modifiable surface properties, CPDs have attracted significant attention. However, pure CPDs exhibit certain limitations in terms of optical performance, particularly in terms of fluorescence intensity, phosphorescence intensity, and emission wavelength tunability, which may not meet the requirements of specific applications. To address these limitations, doping CPDs with various elements, such as nitrogen (N), sulfur (S), and phosphorus (P) to modify their band structure and surface functionalization can significantly enhance their optical properties and photochemical stability, thereby expanding their application potential. This paper reviews the main synthesis methods for elementally doped CPDs, examines the effects of different types of elemental doping on their photochemical properties, and explores promising applications in optoelectronic devices, sensors, and catalysis. Finally, recent advancements in elementally doped CPDs are summarized, along with future development directions and challenges.

Integrating Two Photochromics into One Three-Dimensional Covalent Organic Framework for Synergistically Enhancing Multiple Photocatalytic Oxidations.

While photocatalytic oxidations are a category of important reactions in wide chemical synthesis, the fabrication of effective photocatalysts for broad oxidation reactions is still of a great challenge. Herein, by rationally integrating two photochromics, porphyrin and triphenylamine, a three-dimensional photoactive covalent organic framework (COF) is successfully constructed for photocatalytic oxidations. Characterization studies not only show the formation of a crystalline and three-dimensional porous framework, but also reveal its effective photochemical semiconductor properties derived from the porphyrin and triphenylamine moieties. Electron paramagnetic resonance measurements indicate that the COF is an effective photocatalyst for the generation of both singlet oxygen (1O2) and superoxide radical anions (·O2-). Synergistically enhanced efficiency in all photocatalytic reactions of photocatalytic aerobic oxidation of alkylbenzenes and silanes as well as thioanisoles, and cross-dehydrogenative coupling reaction of N-phenyltetrahydroisoquinoline and indole is confirmed by both experimental and theoretical studies, demonstrating its promising potential for broad photocatalytic oxidation reactions.

Integrating Two Photochromics into One Three‐Dimensional Covalent Organic Framework for Synergistically Enhancing Multiple Photocatalytic Oxidations

While photocatalytic oxidations are a category of important reactions in wide chemical synthesis, the fabrication of effective photocatalysts for broad oxidation reactions is still of a great challenge. Herein, by rationally integrating two photochromics, porphyrin and triphenylamine, a three‐dimensional photoactive covalent organic framework (COF) is successfully constructed for photocatalytic oxidations. Characterization studies not only show the formation of a crystalline and three‐dimensional porous framework, but also reveal its effective photochemical semiconductor properties derived from the porphyrin and triphenylamine moieties. Electron paramagnetic resonance measurements indicate that the COF is an effective photocatalyst for the generation of both singlet oxygen (1O2) and superoxide radical anions (·O2−). Synergistically enhanced efficiency in all photocatalytic reactions of photocatalytic aerobic oxidation of alkylbenzenes and silanes as well as thioanisoles, and cross‐dehydrogenative coupling reaction of N‐phenyltetrahydroisoquinoline and indole is confirmed by both experimental and theoretical studies, demonstrating its promising potential for broad photocatalytic oxidation reactions.

Fluorescent Rhodopsins: A Challenging Test for Cost-Effective QM/MM Approaches.

In this study, we evaluate the performance of two cost-effective models, namely, TD-DFT and ΔSCF methods, combined with different molecular mechanics models, to predict the photophysical and photochemical properties of a set of fluorescent mutants of the microbial rhodopsin Archaerhodopsin-3. We investigate absorption energies and excited-state isomerization barriers of the embedded retinal protonated Schiff-base chromophore by comparing different DFT functionals as well as different approximations of the embedding model. For absorption energies, CAM-B3LYP demonstrates the most consistent alignment with experiments among the functionals tested, whereas the embedding potentials exhibit similar accuracy. However, incorporating linear response corrections within the polarizable TD-DFT/MM framework enhances accuracy. The photoisomerization barriers, instead, exhibit a pronounced sensitivity to the choice of embedding model, underscoring the complex role that environmental factors play in modulating predictions of excited-state processes. For the two properties here investigated, ΔSCF/MM presents qualitatively similar behavior with respect to TD-DFT for all the tested embedding models.

Recent Progress in g-C3N4-Based Photocatalysts for Organic Pollutant Degradation: Strategies to Improve Photocatalytic Activity

With unique photochemical properties, graphitic carbon nitride (g-C3N4) has gained significant attention for application in photocatalytic degradation of a wide range of organic pollutants. However, its performance is limited by the rapid electron–hole recombination and the relatively weak redox capability. Substantial progress has been made in the preparation of g-C3N4-based photocatalysts with enhanced photocatalytic activity. This review summarizes the recent advances in strategies to improve the photocatalytic activity of g-C3N4-based photocatalysts and their application in the photocatalytic degradation of organic pollutants. Morphology control, doping, functionalization, metal deposition, dye sensitization, defect engineering, and construction of heterojunctions can be used to improve the photocatalytic activity of g-C3N4 through promoting charge carrier separation, reducing the bandgap, and suppressing charge recombination. Furthermore, a range of oxidants, such as hydrogen peroxide and persulfate, can be coupled with g-C3N4-based photocatalysts to enhance the generation of reactive oxygen species and boost the photocatalytic degradation of organic pollutants. Precise control over the g-C3N4 structure during the synthesis process remains a challenge, and further improvements are required in photocatalyst stability and the mineralization rates of organic pollutants. More research and development effort is needed to address the existing challenges, refine the design of g-C3N4-based photocatalysts to improve their activity, and promote their practical application in pollutant degradation.

Investigation photophysical, photochemical and aggregation properties of A3B type Zn(II) and In(III) phthalocyanines containing tert-butyl and benzodioxane groups

Investigation photophysical, photochemical and aggregation properties of A3B type Zn(II) and In(III) phthalocyanines containing tert-butyl and benzodioxane groups

Constructing Ti3C2/SnS2 Schottky heterojunctions photocatalyst with a superior efficiency for RhB degradation

In this study, SnS2/Ti3C2 was synthesized by combining SnS2 (synthesized via oil bath method) with Ti3C2 (prepared from etching of Al layers from Ti3AlC2 MAX phase). The morphology, structure and photochemical properties of the catalyst were analyzed by various characterization methods. The photocatalytic performance of sample was studied by the degradation of Rhodamine B (RhB) under xenon lamp irradiation. Results showed that SnS2/Ti3C2 could achieve 99% photocatalytic degradation of RhB within 60 min, which was much higher than the 38% photocatalytic degradation of SnS2. In addition, the RhB degradation rate of SnS2/Ti3C2 still reached 93% after 5 cycles. The excellent photocatalytic activity and durability were mainly attributed to the formation of Schottky heterojunction between SnS2 and Ti3C2, which is very advantageous for efficiently separating and transferring charge carriers. The work functions of SnS2 and Ti3C2Tx were calculated through the DFT calculations, which were 5.22 eV and 5.69 eV respectively. According to barder charge analysis, the charge transfer between SnS2 and Ti3C2 was 0.04 e. Meanwhile, radical trapping experiments confirmed that h+ and •O2− were the main active species in the reaction system. As a visible light-responsive catalyst, SnS2/Ti3C2 can be effectively applied to the degradation of organic dye pollutants, and which has broad application prospects.

Photochemical Conversion of Indazoles into Benzimidazoles.

Fragment-based drug discovery relies on preparing diverse libraries of advanced building blocks, often incorporating heteroaromatic motifs. Altering the core of heteroaromatics to maximise library diversity typically requires de novo synthesis of each system. This can be often challenging when specific substitution patterns are needed. Here, we introduce a photochemical strategy for the direct permutation of 1H- and 2H-indazoles into benzimidazoles. This transformation exploits the distinct photochemical properties of these heteroaromatics and proceeds under mild conditions. Through systematic experimental and computational studies, we have elucidated a two-step mechanism involving excited-state tautomerization of 1H-indazoles, followed by photochemical rearrangement of the resulting 2H-isomers. This approach demonstrates broad substrate scope, high yields, and compatibility with a variety of functional groups. This method can expand the structural diversity of heterocycle-based libraries through the concept of chemical permutation for heteroaromatic interconversion.

Noble-Metal-Free ZnII-Anchored Pyrene-Based Covalent Organic Framework (COF) for Photocatalytic Fixation of CO2from Dilute Gas into Bioactive 2-Oxazolidinones.

Photocatalytic conversion of CO2 into value-added chemicals offers a propitious alternative to traditional thermal methods, contributing to environmental remediation and energy sustainability. In this respect, covalent organic frameworks (COFs), are crystalline porous materials showcasing remarkable efficacy in CO2 fixation facilitated by visible light owing to their excellent photochemical properties. Herein, we employed Lewis acidic Zn(II) anchored pyrene-based COF (Zn(II)@Pybp-COF) to facilitate the photocatalytic CO2 utilization and transformation to 2-oxazolidinones. Notably, Zn-COF displayed absorption of visible light, with an optimal band gap of 1.8 eV, effectively catalyzing light-mediated functionalization of propargylic amines to 2-oxazolidinones under green conditions. Detailed experimental and theoretical mechanistic investigations demonstrated that light plays a crucial role in enhancing the efficacy of the photocatalyst, as it activates inert CO2 molecule to radical anion and thereby, lowers the energy barrier for its subsequent cyclization reaction with propargylic amine. Additionally, Zn-COF demonstrates promising catalytic performance utilizing dilute gas as the CO2 source. This is the first report regarding noble metal-free, Zn-COF exhibiting excellent photocatalytic carboxylative cyclization of CO2 with propargyl amines to prepare 2-oxazolidinones using dilute gas (13% CO2). This study offers a new direction for rationally constructing noble metal-free eco-friendly photocatalysts for achieving CO2 fixation reactions under eco-friendly conditions.

Novel BODIPY Dyes with a Meso-Benzoxadiazole Substituent: Synthesis, Photophysical Studies, and Cytotoxic Activity Under Normoxic and Hypoxic Conditions

Background/Objectives: Novel boron dipyrromethene derivatives with a heterocyclic, benzoxadiazole substituent were obtained as potential candidates for the photodynamic therapy (PDT) of cancers. Photochemical properties (e.g., singlet oxygen generation quantum yields (ΦΔ), absorption, and emission spectra) and cytotoxic activity studies in normoxic and hypoxic conditions were performed to verify the potential of novel BODIPYs as photosensitizers for PDT. Methods: Obtained dyes were characterized using mass spectrometry and various NMR techniques. The relative method with Rose Bengal as a reference and 1,3-diphenylisobenzofuran as a singlet oxygen quencher was used to determine ΦΔ values. The in vitro studies were conducted on human ovarian carcinoma (A2780) and human breast adenocarcinoma (MDA-MB-231) cells. Results: Photochemical studies showed that the presence of benzoxadiazole moiety only slightly affected the localization of the absorption maxima but resulted in fluorescence quenching compared with meso-phenyl-substituted analogs. In addition, brominated and iodinated analogs revealed a high ability to generate singlet oxygen. Anticancer studies showed high light-induced cytotoxicity of BODIPYs containing heavy atoms with very low IC50 values in the 3.5–10.3 nM range. Further experiments revealed that both compounds also demonstrated phototoxic activity under hypoxic conditions. The most potent cytotoxic effect in these conditions was observed in the iodinated BODIPY analog with IC50 values of about 0.3 and 0.4 μM for A2780 and MDA-MB-231 cells, respectively. Conclusions: The results of this study highlighted the advantages and some potential drawbacks of BODIPY compounds with heavy atoms and benzoxadiazole moiety as a useful scaffold in medicinal chemistry for designing new photosensitizers.

Chalcone-containing phthalocyanines: Determination of photophysical and photochemical properties and cytotoxicity on breast cancer cell models

Chalcone-containing phthalocyanines: Determination of photophysical and photochemical properties and cytotoxicity on breast cancer cell models

Unraveling Crystal Phase-Driven Activity and Selectivity of WO3 for Photoelectrochemical Biomass Valorization.

Modulating the crystal phase of a photocatalyst significantly impacts its surface and photochemical properties, allowing for the adjustment of catalytic activity and selectivity, particularly in the electrooxidation reactions of biomass-derived chemicals. Herein, monoclinic and hexagonal phases of WO3 are employed as photoanodes for the photoelectrochemical conversion of 5-hydroxymethylfurfural (HMF) to 2,5-diformylfuran (DFF). The monoclinic phase demonstrated exceptional performance in photoelectrocatalytic HMF oxidation, achieving remarkable photocurrent densities (1.1 mA cm-2), which were 5.5 times greater than those observed for hexagonal WO3. Moreover, the yield of DFF products obtained over monoclinic WO3 was approximately 2.5 times higher compared to that of hexagonal WO3. A combination of experiments and theoretical calculations indicates that the superior performance of monoclinic WO3 for HMF oxidation mainly originates from enhanced light harvesting efficiency, better charge separation and utilization, balanced adsorption energy, and stronger oxidative ability of photogenerated holes. This study emphasizes the potential of crystal phase engineering to regulate the reaction activity and selectivity and provides insights into how to design next-generation high-performance photoelectrodes for sustainable chemical production from biomass.

Furan-Indole-Chromenone-Based Organic Photocatalyst for α-Arylation of Enol Acetate and Free Radical Polymerization Under LED Irradiation.

In this study we report on the efficiency of a furane-indole-chromenone-based organic derivative (FIC) as a photocatalyst in the α-arylation of enol acetate upon LED irradiation at 405 nm, and as a photoinitiator/photocatalyst in the free radical polymerization of an acrylate group in the presence of bis-(4-tert-butylphenyl)iodonium hexafluorophosphate (Iod) as an additive, or in the presence of both Iod and ethyl-4-(dimethyl amino) benzoate (EDB) under LED irradiation at 365 nm. The photochemical properties of this new light-sensitive compound are described, and the wide redox window (3.27 eV) and the high excited-state potentials FIC*/FIC●- (+2.64 V vs. SCE) and FIC●+/FIC* (-2.41 V vs. SCE) offered by this photocatalyst are revealed. The chemical mechanisms that govern the radical chemistry are discussed by means of different techniques, including fluorescence-quenching experiments, UV-visible absorption and fluorescence spectroscopy, and cyclic voltammetry analysis.

Prediction of Thermodynamic Properties of C60-Based Fullerenols Using Machine Learning.

Traditional machine learning methods face significant challenges in predicting the properties of highly symmetric molecules. In this study, we developed a machine learning model based on graph neural networks (GNNs) to accurately and swiftly predict the thermodynamic and photochemical properties of fullerenols, such as C60(OH)n (n = 1 to 30). First, we established a global method for generating fullerenol isomers through isomer fingerprinting, which can generate all possible isomers or produce diverse structural types on demand. Significantly, by incorporating interpretable descriptors such as atomic labels, bond lengths, and bond angles from highly symmetric isomers, our multilayer GNN model achieved over 90% accuracy in predicting the thermodynamic stability of fullerenols. The model also performed excellently in predicting electronic properties, including the highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO), and the energy gap. Overall, this work demonstrates a new strategy using interpretable descriptors for accurately predicting the properties of highly symmetric structures, offering theoretical chemists a valuable tool for studying these materials.

Design and Construction of a Porphyrin-Based Samarium(III)-Metal-Organic Framework for Antibiotic Detection.

Porphyrins bearing the unique 18π electron tetrapyrrolic macrocycles exhibit interesting photophysical and photochemical properties and have been considered as promising ligands for the construction of functionalized metal-organic frameworks (MOFs). The combination of porphyrin-type ligands with lanthanide metals featured with diverse coordination environments to realize the novel functions as well as the diversity of the MOF is thus attractive but challenging. Herein, an unprecedented porphyrin-based samarium MOF (Sm-BCPP) composed of a 5,10-bis(4-carboxyphenyl)-10,20-diphenyl porphyrin (H2BCPP) ligand and samarium-formed one-dimensional clusters has been constructed via a solvothermal approach, and the synthesized Sm-BCPP has excellent chemical stabilities, exhibiting red luminescence. Interestingly, Sm-BCPP demonstrated excellent fluorescence quenching against commonly used antibiotics, showing an ultrahigh fluorescence quenching constant (KSV) and ultralow detection limit (LOD), among which the detection limit of rifampicin (LOD = 0.33 nM) and nitrofurazone (LOD = 0.24 nM) was found to be lower than most reported MOF materials. Encouragingly, the Sm-BCPP MOF exhibited excellent stability in aqueous solutions at different pH environments, and the detection capability in the natural water environment indicated its practical application potential. The in-depth studies suggested that the mechanism of the fluorescence quenching against antibiotics involved internal filtration effect and photoinduced electron transfer.

Optimizing retinal Imaging: Evaluation of ultrasmall TiO2 Nanoparticle- fluorescein conjugates for improved Fundus fluorescein angiography

Fundus Fluorescein Angiography (FFA) has been extensively used for the identification, management, and diagnosis of various retinal and choroidal diseases, such as age-related macular degeneration, diabetic retinopathy, retinopathy of prematurity, among others. This exam enables clinicians to evaluate retinal morphology and the pathophysiology of retinal vasculature. However, adverse events, including from mild to severe reactions to sodium fluorescein, have been reported. Titanium dioxide nanoparticles (NPTiO2) have shown significant potential in numerous biological applications. Coating or conjugating these nanoparticles with small molecules can enhance their stability, photochemical properties, and biocompatibility, as well as increase the hydrophilicity of the nanoparticles, making them more suitable for biomedical applications. This work demonstrates the potential use of ultrasmall titanium dioxide nanoparticles conjugated with sodium fluorescein to improve the quality of angiography exams. The strategy of conjugating fluorescein with NPTiO2 successfully enhanced the fluorescence photostability of the contrast agent and increased its retention time in the retina. Preliminary in vivo and in vitro safety tests suggest that these nanoparticles are safe for the intended application demonstrating low tendency to hemolysis, and no significant changes in the retina thickness or in the electroretinography a-wave and b-wave amplitudes. Overall, the conjugation of fluorescein to NPTiO2 has produced a nanomaterial with favorable properties for use as an innovative contrast agent in FFA examinations. By providing a clear description of our methodology of analysis, we also aim to offer better perspectives and reproducible conditions for future research.

Optical properties and photobleaching of wildfire ashes aqueous extracts.

Wildfires can severely degrade soils and watersheds. Post-fire rain events can leach ashes and altered dissolved organic matter (DOM) into streams, impacting water quality and carbon biogeochemistry. The photochemical properties and persistence of DOM from wildfire ash leachates are not well understood. To establish a range of properties, wildfire DOM leachates were generated from (i) surficial [grey and black] wildfire ashes, (ii) mineral soils below ash, and (iii) unimpacted soils from two Colorado wildfire scars. Subsequently, the leachates were studied under simulated sunlight. Photochemical properties of absorbance, fluorescence and 1O2 quantum yield (ΦF and Φ1O2) were determined for thirteen wildfire leachates. Φ1O2 of ash leachates was greatest (7.6 ± 3.4%), followed by underlying mineralized soil leachates (4.6 ± 0.7%), and control soil leachates (Φ1O2 = 3.9 ± 1%). Correlations between increasing E2 : E3, ΦF, Φ1O2 suggest that surface ash leachates with elevated molar absorptivity may play an important role in 1O2 production that is not well documented. Interestingly, photobleaching experiments comparing ash DOM to unimpacted soil DOM revealed ash leachates lost fluorescence, absorbance, while producing CO2 at rates ∼3 fold greater than soils. This suggests that aromatic features of ashes may cause degradation of wildfire DOM faster than unimpacted DOM in the environment.

Investigation on photophysical and photochemical properties of Ir and Ru complexes featuring sulfurated pyridine-1,2,3-triazole based ligands

Investigation on photophysical and photochemical properties of Ir and Ru complexes featuring sulfurated pyridine-1,2,3-triazole based ligands

Synthesis, characterization and evaluation of the photochemical properties and photothermal conversion capacities of Mo2CTx-MXene@Fuc nanohybrids

Synthesis, characterization and evaluation of the photochemical properties and photothermal conversion capacities of Mo2CTx-MXene@Fuc nanohybrids

Evaluation of indocyanine green antimicrobial photodynamic therapy in radical species elimination: an in vitro study.

Antimicrobial photodynamic therapy (aPDT) utilizes light-sensitive materials to inactivate pathogens. Indocyanine green (ICG) is an FDA-approved photosensitizer known for its effective photo-thermal and photo-chemical properties.