Journal Description
Photochem
Photochem
is an international, peer-reviewed, open access journal on photochemistry published quarterly online by MDPI.
- Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
- High Visibility: indexed within Scopus, ESCI (Web of Science), EBSCO, and other databases.
- Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 24.6 days after submission; acceptance to publication is undertaken in 6.8 days (median values for papers published in this journal in the first half of 2024).
- Recognition of Reviewers: APC discount vouchers, optional signed peer review, and reviewer names published annually in the journal.
Latest Articles
Photodynamic Therapy Review: Past, Present, Future, Opportunities and Challenges
Photochem 2024, 4(4), 434-461; https://doi.org/10.3390/photochem4040027 - 1 Oct 2024
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Photodynamic therapy (PDT) is a medical treatment that utilizes photosensitizing agents, along with light, to produce reactive oxygen species that can kill nearby cells. When the photosensitizer is exposed to a specific wavelength of light, it becomes activated and generates reactive oxygen that
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Photodynamic therapy (PDT) is a medical treatment that utilizes photosensitizing agents, along with light, to produce reactive oxygen species that can kill nearby cells. When the photosensitizer is exposed to a specific wavelength of light, it becomes activated and generates reactive oxygen that can destroy cancer cells, bacteria, and other pathogenic micro-organisms. PDT is commonly used in dermatology for treating actinic keratosis, basal cell carcinoma, and other skin conditions. It is also being explored for applications in oncology, such as treating esophageal and lung cancers, as well as in ophthalmology for age-related macular degeneration. In this study, we provide a comprehensive review of PDT, covering its fundamental principles and mechanisms, as well as the critical components for its function. We examine key aspects of PDT, including its current clinical applications and potential future developments. Additionally, we discuss the advantages and disadvantages of PDT, addressing the various challenges associated with its implementation and optimization. This review aims to offer a thorough understanding of PDT, highlighting its transformative potential in medical treatments while acknowledging the areas requiring further research and development.
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Open AccessReview
Metallic Nanoparticles for Surface-Enhanced Raman Scattering Based Biosensing Applications
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Jiro Karlo, Syed S. Razi, Mahamkali Sri Phaneeswar, Arunsree Vijay and Surya Pratap Singh
Photochem 2024, 4(4), 417-433; https://doi.org/10.3390/photochem4040026 - 26 Sep 2024
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Surface-enhanced Raman scattering (SERS) is a powerful tool for biosensing with high sensitivity, selectivity, and capability of multiplex monitoring for both in vivo and in vitro studies. This has been applied for the identification and detection of different biological metabolites such as lipids,
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Surface-enhanced Raman scattering (SERS) is a powerful tool for biosensing with high sensitivity, selectivity, and capability of multiplex monitoring for both in vivo and in vitro studies. This has been applied for the identification and detection of different biological metabolites such as lipids, nucleic acids, and proteins. The present review article explores the vast applications of metallic nanoparticles for SERS-based biosensing. We have summarized and discussed the fundamental principles, theories, developments, challenges, and perspectives in the field of SERS-based biosensing using different metal nanoparticle substrates namely gold, silver, copper, and bimetallic nanoparticles.
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Open AccessArticle
Ultrafast Excited State Dynamics of a Verdazyl Diradical System
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Caitlyn Clark, Filip Pawłowski, David J. R. Brook and Christopher Grieco
Photochem 2024, 4(4), 404-416; https://doi.org/10.3390/photochem4040025 - 24 Sep 2024
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While the photophysics of closed-shell organic molecules is well established, much less is known about open-shell systems containing interacting radical pairs. In this work, we investigate the ultrafast excited state dynamics of a singlet verdazyl diradical system in solution using transient absorption (TA)
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While the photophysics of closed-shell organic molecules is well established, much less is known about open-shell systems containing interacting radical pairs. In this work, we investigate the ultrafast excited state dynamics of a singlet verdazyl diradical system in solution using transient absorption (TA) spectroscopy for the first time. Following 510 nm excitation of the excitonic S0 → S1 transition, we detected TA signals in the 530–950 nm region from the S1 population that decayed exponentially within a few picoseconds to form a vibrationally hot S0* population via internal conversion. The dependence of the S1 decay rate on solvent and radical–radical distance revealed that the excited state possesses charge-transfer character and likely accesses the S0 state via torsional motion. The ultrafast internal conversion decay mechanism at play in our open-shell verdazyl diradicals is in stark contrast with other closed-shell, carbonyl-containing organic chromophores, which exhibit ultrafast intersystem crossing to produce long-lived triplet states as the major S1 decay pathway.
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Open AccessArticle
Cyanobacterial Pigments as Natural Photosensitizers for Dye-Sensitized Solar Cells
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Tatiana Montagni, Mauricio Ávila, Sofía Fernández, Sylvia Bonilla and María Fernanda Cerdá
Photochem 2024, 4(3), 388-403; https://doi.org/10.3390/photochem4030024 - 12 Sep 2024
Cited by 1
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Three filamentous freshwater cyanobacterial strains were grown at high light intensity to produce lipidic dyes composed of xanthophylls, carotenes, and chlorophyll a. The properties of the pigments were evaluated as suitable natural compounds to be applied in dye-sensitized solar cells (DSSC). The assembled
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Three filamentous freshwater cyanobacterial strains were grown at high light intensity to produce lipidic dyes composed of xanthophylls, carotenes, and chlorophyll a. The properties of the pigments were evaluated as suitable natural compounds to be applied in dye-sensitized solar cells (DSSC). The assembled DSSC were characterized using the density current vs. potential profiles and electrochemical impedance spectroscopy. With an efficiency of 0.127%, our results are higher than those previously reported using similarly structured compounds from natural sources such as algae and cyanobacteria, among others. The best efficiencies were probably related to myxoxanthophyll-like derivates and aphanizophyll are carotenoids with many hydroxyl groups being able to interact with the semiconductor surface. The stability of the bonding between the dyes and the titanium oxide of the photoelectrode is crucial to ensuring the acceptable performance of the DSSC, which was successfully achieved in our experiments with carotenoids with many hydroxyl groups. Our results point to cyanobacterial pigments as a promising source of natural dyes for use in solar cells.
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Open AccessArticle
Riboflavin as a Coloring Agent of Tablets Affects the Photostability of Manidipine after the Change of Dosage Forms
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Kohei Kawabata, Minami Tsukimori, Kyoka Hirai, Shiori Akimoto, Naoto Uramaru, Masanori Inagaki and Hiroyuki Nishi
Photochem 2024, 4(3), 377-387; https://doi.org/10.3390/photochem4030023 - 10 Sep 2024
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Manidipine (MP) is widely used for reducing high blood pressure. Calslot® (CALS) tablets, which are the original MP medicines, and their generic medicines have been used for patients in clinical situations. The authors hypothesized that the photodegradability of MP drug substance in
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Manidipine (MP) is widely used for reducing high blood pressure. Calslot® (CALS) tablets, which are the original MP medicines, and their generic medicines have been used for patients in clinical situations. The authors hypothesized that the photodegradability of MP drug substance in CALS tablets might be enhanced when the tablets were photo-exposed after the change of the dosage form by the presence of riboflavin (RF), which is utilized as a coloring agent and a well-known photosensitizer. The present study clarified that RF enhanced the photodegradation of MP when the powders and the suspensions of CALS tablets were ultraviolet light (UV) irradiated. The addition of RF to the suspension of MP standard substances also promoted MP photodegradation along with the increase of the generation rate of its main photoproduct, benzophenone. Finally, the authors performed the photostabilization of MP suspensions based on the addition of quercetin (QU), which is one of polyphenols and has both the antioxidative potency and the UV filtering potency. It is summarized that QU has a protective potency for MP’s own photodegradation, and it partially suppresses the photocatalytic effect of RF. Further studies focused on the photochemical behaviors of utilized additives for medicines are needed for their safe use.
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Open AccessArticle
Photo-Activated Carbon Dots as Catalysts in Knoevenagel Condensation: An Advance in the Synthetic Field
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Cinzia Michenzi, Francesca Scaramuzzo, Chiara Salvitti, Federico Pepi, Anna Troiani and Isabella Chiarotto
Photochem 2024, 4(3), 361-376; https://doi.org/10.3390/photochem4030022 - 27 Aug 2024
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Photoinduced chemical reactions and the development of new materials represent a current and significant topic. We present a sustainable and eco-friendly approach to the Knoevenagel condensation reaction involving carbonyl and active methylene compounds. Our method utilizes photo-activated carbon dots (CDs) derived from 5-hydroxymethylfurfural
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Photoinduced chemical reactions and the development of new materials represent a current and significant topic. We present a sustainable and eco-friendly approach to the Knoevenagel condensation reaction involving carbonyl and active methylene compounds. Our method utilizes photo-activated carbon dots (CDs) derived from 5-hydroxymethylfurfural (5HMF) within an aqueous medium and does not require acidic, basic, or thermal conditions. This protocol operates effectively with aromatic, aliphatic, and heteroaromatic aldehydes and ketones. The 5HMF-derived-CDs can be reused four times without significant loss of activity. Moreover, this methodology is suitable for scaling up reactions, thereby highlighting its potential for industrial applications.
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Open AccessArticle
Concurrent Photooxidation and Photoreduction of Catechols and Para-Quinones by Chlorophyll Metabolites
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Katherine Phan, Emily E. Lessard, Joseph A. Reed, Meredith G. Warsen, Soren Zimmer and Lisa M. Landino
Photochem 2024, 4(3), 346-360; https://doi.org/10.3390/photochem4030021 - 15 Aug 2024
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Photosynthesis is initiated when the sun’s light induces electron transfer from chlorophyll to plastoquinone, a para-quinone. While photosynthesis occurs in the intact chloroplasts of living plants, similar photochemical reactions between dietary chlorophyll metabolites and quinones are likely and may affect health outcomes. Herein,
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Photosynthesis is initiated when the sun’s light induces electron transfer from chlorophyll to plastoquinone, a para-quinone. While photosynthesis occurs in the intact chloroplasts of living plants, similar photochemical reactions between dietary chlorophyll metabolites and quinones are likely and may affect health outcomes. Herein, we continue our studies of the direct photoreduction of para-quinones and ortho-quinones that were generated by the photo-oxidation of catechols. Chlorophyll metabolites, including pheophorbide A, chlorin e6, and pyropheophorbide A, as well as methylene blue were employed as photosensitizers. We detected hydrogen peroxide using horseradish peroxidase following the photo-oxidation of the catechol dopamine, even in the presence of EDTA, a tertiary amine electron donor. Under ambient oxygen, hydrogen peroxide was also detected after the photoreduction of several para-quinones, including 2,3-dimethoxy-5-methyl-p-benzoquinone (CoQ0), methoxy-benzoquinone, and methyl-benzoquinone. The combinations of methylene blue and EDTA or pheophorbide A and triethanolamine as the electron donor in 20% dimethylformamide were optimized for photoreduction of the para-quinones. Chlorin e6 and pyropheophorbide A were less effective for the photoreduction of CoQ0 but were equivalent to pheophorbide A for generating hydrogen peroxide in photo-oxidation reactions with photosensitizers, oxygen, and triethanolamine. We employed dinitrophenylhydrazine to generate intensely colored adducts of methoxy-benzoquinone, methyl-benzoquinone, and 1,4-benzoquinone.
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Open AccessArticle
Optimization of CdSe Thin-Film Photoelectrochemical Cells: Effects of NaOH/Na2S/S Redox Couple Concentration and Activity on Cell Efficiency
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Ahed H. Zyoud
Photochem 2024, 4(3), 334-345; https://doi.org/10.3390/photochem4030020 - 10 Aug 2024
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This study investigates the relationships among redox couple activity, electrolyte concentration, and efficiency in CdSe thin-film photoelectrochemical solar cells. A CdSe photo-electrode was prepared using the electro-depositing technique to produce well-staged layering of CdSe, followed by chemical bath deposition to produce a layer
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This study investigates the relationships among redox couple activity, electrolyte concentration, and efficiency in CdSe thin-film photoelectrochemical solar cells. A CdSe photo-electrode was prepared using the electro-depositing technique to produce well-staged layering of CdSe, followed by chemical bath deposition to produce a layer with an acceptable thickness to absorb enough photons to create a suitable amount of photocurrent. The CdSe photo-electrochemical cell was tested under various concentrations of a NaOH/Na2S/S electrolyte solution. The results showed that the activity of the redox couple greatly affected the efficiencies of the solar cells. Correlation plots between ionic strength and PEC efficiency with the Debye–Hückel equation yielded an R² value of 0.96, while those between ionic strength and photocurrent density had an R² value of 0.92. The correlation between concentration and PEC efficiency was much weaker. This paper highlights how optimal ionic activity increases the performance of photoelectrochemical solar cells, which consequently improves the conversion efficiency of solar energy.
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Open AccessArticle
Facile Doping of 2,2,2-Trifluoroethanol to Single-Walled Carbon Nanotubes Electrodes for Durable Perovskite Solar Cells
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Naoki Ueoka, Achmad Syarif Hidayat, Hisayoshi Oshima, Yoshimasa Hijikata and Yutaka Matsuo
Photochem 2024, 4(3), 319-333; https://doi.org/10.3390/photochem4030019 - 14 Jul 2024
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Perovskite solar cells with an indium tin oxide (ITO)/SnO2/CH3NH3PbI3/Spiro-OMeTAD/2,2,2-trifluoroethanol (TFE) doped single-walled carbon nanotube (SWCNT) structure were developed by dropping TFE onto SWCNTs, which replaced the metal back electrode, and a conversion efficiency of 14.1%
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Perovskite solar cells with an indium tin oxide (ITO)/SnO2/CH3NH3PbI3/Spiro-OMeTAD/2,2,2-trifluoroethanol (TFE) doped single-walled carbon nanotube (SWCNT) structure were developed by dropping TFE onto SWCNTs, which replaced the metal back electrode, and a conversion efficiency of 14.1% was achieved. Traditionally, acidic doping of the back electrode, SWCNT, has been challenging due to the potential damage it may cause to the perovskite layer. However, TFE has facilitated easy doping of SWCNT as the back electrode. The sheet resistance of the SWCNTs decreased and their ionization potential shifted to deeper levels, resulting in improved hole transport properties with a lower barrier to carrier transport. Furthermore, the Seebeck coefficient (S) increased from 34.5 μV/K to 73.1 μV/K when TFE was dropped instead of EtOH, indicating an enhancement in the behavior of p-type charge carriers. It was observed that hydrophilic substances adhered less to the SWCNT surface, and the formation of PbI2 was suppressed. These effects resulted in higher conversion efficiency and improved solar cell performance. Furthermore, the decrease in conversion efficiency after 260 days was suppressed, showing improved durability. The study suggests that combining SWCNTs and TFEs improves solar cell performance and stability.
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Synthesis of Metallic and Metal Oxide Nanoparticles Using Homopolymers as Solid Templates: Luminescent Properties of the Eu+3 Nanoparticle Products
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María Ángeles Cortés, Carlos Díaz, Raquel de la Campa, Alejandro Presa-Soto and María Luisa Valenzuela
Photochem 2024, 4(3), 302-318; https://doi.org/10.3390/photochem4030018 - 14 Jul 2024
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Starting from poly(4-vinylpyridine) ((P4VP)n), poly(2-vinylpyridine) ((P2VP)n), and [N=P(O2CH2CF3)]m-b-P2VP20 block copolymers, a series of metal-containing homopolymers, (P4VP)n⊕MXm, (P2VP)n⊕MXm, and [N=P(O2
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Starting from poly(4-vinylpyridine) ((P4VP)n), poly(2-vinylpyridine) ((P2VP)n), and [N=P(O2CH2CF3)]m-b-P2VP20 block copolymers, a series of metal-containing homopolymers, (P4VP)n⊕MXm, (P2VP)n⊕MXm, and [N=P(O2CH2CF3)]m-b-P2VP20]⊕MXm MXm = PtCl2, ZnCl2, and Eu(NO3)3, have been successfully prepared by using a direct and simple solution methodology. Solid-state pyrolysis of the prepared metal-containing polymeric precursors led to the formation of a variety of different metallic and metal oxide nanoparticles (Pt, ZnO, Eu2O3, and EuPO4) depending on the composition and nature of the polymeric template precursor. Thus, whereas Eu2O3 nanostructures were obtained from europium-containing homopolymers ((P4VP)n⊕MXm and (P2VP)n⊕MXm), EuPO4 nanostructures were achieved using phosphorus-containing block copolymer precursors, [N=P(O2CH2CF3)]m-b-P2VP20]⊕MXm with MXm = Eu(NO3)3. Importantly, and although both Eu2O3 and EuPO4 nanostructures exhibited a strong luminescence emission, these were strongly influenced by the nature and composition of the macromolecular metal-containing polymer template. Thus, for P2VP europium-containing homopolymers ((P4VP)n⊕MXm and (P2VP)n⊕MXm), the highest emission intensity corresponded to the lowest-molecular-weight homopolymer template, [P4VP(Eu(NO3)3]6000, whereas the opposite behavior was observed when block copolymer precursors, [N=P(O2CH2CF3)]m-b-P2VP20]⊕MXm MXm= Eu(NO3)3, were used (highest emission intensity corresponded to [N=P(O2CH2CF3)]100-b-[P2VP(Eu(NO3)3)x]20). The intensity ratio of the emission transitions: 5D0 → 7F2/5D0 → 7F1, suggested a different symmetry around the Eu3+ ions depending on the nature of the polymeric precursor, which also influenced the sizes of the prepared Pt°, ZnO, Eu2O3, and EuPO4 nanostructures.
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Open AccessSystematic Review
A Systematic Review of Heterogeneous Catalysis Applied to the Treatment of Pharmaceutical Wastewater: Operational Conditions and Statistical Analysis
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Raqueline Caldas do Nascimento, Arthur Cahino, Larissa Granjeiro Lucena, Inalmar D. Barbosa Segundo, Jonathan Cawettiere Espíndola and Elisângela M. R. Rocha
Photochem 2024, 4(3), 285-301; https://doi.org/10.3390/photochem4030017 - 29 Jun 2024
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The use of heterogeneous photocatalysis has garnered significant attention, mainly due to its remarkable efficacy in degrading recalcitrant compounds. The main objective of this research was to investigate this process applied to pharmaceutical treatment. For that, an analysis of a Final Bibliographic Portfolio
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The use of heterogeneous photocatalysis has garnered significant attention, mainly due to its remarkable efficacy in degrading recalcitrant compounds. The main objective of this research was to investigate this process applied to pharmaceutical treatment. For that, an analysis of a Final Bibliographic Portfolio (FBP), using the systematic review of the PRISMA and the ProKnow-C method, and a meta-analysis study in a historical series from 2010 to 2020, were performed for scientific works published in indexed journals from the Scopus and Web of Science databases and fully available in English. The works were filtered after a careful reading of the titles, followed by the exclusion of repeated documents and those that were not aligned with the research from 3498 articles, 40 of which were chosen to compose the FBP that addressed the classes of antibiotics, antihypertensives, analgesics, and anti-inflammatory drugs after scientific recognition and exclusion due to not fitting into one of the four FBP structured stages: (1) identification, (2) triage, (3) eligibility, and (4) inclusion. The following gaps were highlighted: (i) a limited number of studies working with interactions of the interfering variables; (ii) a large number of experiments not considering the natural constituents of wastewater; (iii) the use of drug concentrations high above the values found in aquatic matrices; (iv) little applicability of the process at the real scale. In this meta-analysis study, operational parameter optimization was fundamental to guarantee degradation efficiencies above 80% with a variety of pharmaceutical pollutants, the main representatives studied of which were tetracycline, nimesulide, diclofenac, ibuprofen, and atenolol. However, there is still a need to determine the best conditions for this technique when using real effluents, which have the utmost importance for the process on a large scale.
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Open AccessFeature PaperReview
Advances in Functional Ceramics for Water Splitting: A Comprehensive Review
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Julia Exeler and Thomas Jüstel
Photochem 2024, 4(2), 271-284; https://doi.org/10.3390/photochem4020016 - 12 Jun 2024
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The global demand for sustainable energy sources has led to extensive research regarding (green) hydrogen production technologies, with water splitting emerging as a promising avenue. In the near future the calculated hydrogen demand is expected to be 2.3 Gt per year. For green
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The global demand for sustainable energy sources has led to extensive research regarding (green) hydrogen production technologies, with water splitting emerging as a promising avenue. In the near future the calculated hydrogen demand is expected to be 2.3 Gt per year. For green hydrogen production, 1.5 ppm of Earth’s freshwater, or 30 ppb of saltwater, is required each year, which is less than that currently consumed by fossil fuel-based energy. Functional ceramics, known for their stability and tunable properties, have garnered attention in the field of water splitting. This review provides an in-depth analysis of recent advancements in functional ceramics for water splitting, addressing key mechanisms, challenges, and prospects. Theoretical aspects, including electronic structure and crystallography, are explored to understand the catalytic behavior of these materials. Hematite photoanodes, vital for solar-driven water splitting, are discussed alongside strategies to enhance their performance, such as heterojunction structures and cocatalyst integration. Compositionally complex perovskite oxides and high-entropy alloys/ceramics are investigated for their potential for use in solar thermochemical water splitting, highlighting innovative approaches and challenges. Further exploration encompasses inorganic materials like metal oxides, molybdates, and rare earth compounds, revealing their catalytic activity and potential for water-splitting applications. Despite progress, challenges persist, indicating the need for continued research in the fields of material design and synthesis to advance sustainable hydrogen production.
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Open AccessReview
Excitation Wavelength-Dependent Photochemistry
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Mounir Maafi
Photochem 2024, 4(2), 233-270; https://doi.org/10.3390/photochem4020015 - 7 Jun 2024
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The dependence of photochemistry on excitation wavelength is not a recently observed phenomenon; nonetheless, it has, surprisingly enough, been largely ignored in the field. The reasons for this situation are not fully understood but might be related to a provisional extension of Kasha’s
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The dependence of photochemistry on excitation wavelength is not a recently observed phenomenon; nonetheless, it has, surprisingly enough, been largely ignored in the field. The reasons for this situation are not fully understood but might be related to a provisional extension of Kasha’s rule to photochemistry, or perhaps to a difficulty to justify the kind of short time-scales implied in such photochemistry, that challenges the usually held view giving predominance to fast internal conversion and vibrational relaxation. Regardless of the reasons, it is still a matter of fact that a complete and satisfactory interpretation for experimentally proven wavelength-dependent photochemistry is not yet available and the community endeavor to build a holistic understanding and a comprehensive view of the phenomenon. The present review is a non-exhaustive overview of the published data in the field, reporting on some of the most prominent features, issues, and interpretations.
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Open AccessArticle
Titanium Nanostructures: Advancing Photocatalysis in Complex Systems
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Alondra A. Lugo-Ruiz and Sonia J. Bailón-Ruiz
Photochem 2024, 4(2), 222-232; https://doi.org/10.3390/photochem4020014 - 6 May 2024
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The use of semiconductor materials, specifically TiO2, for photocatalysis of organic pollutants has gained global interest as an effective method for contaminant removal from wastewater. Titanium dioxide (TiO2) is a widely studied photocatalyst and is considered one of the
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The use of semiconductor materials, specifically TiO2, for photocatalysis of organic pollutants has gained global interest as an effective method for contaminant removal from wastewater. Titanium dioxide (TiO2) is a widely studied photocatalyst and is considered one of the best for wastewater treatments due to its high stability, affordability, and nontoxicity. The discharge of wastewater from the textile industries, which constitutes around 20% of total textile effluent, has become a significant environmental concern, posing a threat to both the aquatic ecosystem and human health. We aimed to investigate the photodegradation of organic dyes like Amaranth (AM), Methyl Orange (MO), and Quinoline Yellow (QY), individually and in combination, in an aqueous suspension with varying concentrations of TiO2. Results indicate a significant degradation of all three dyes in the multicomponent, with approximately 40% degradation in the presence of the 0.050 g/L TiO2 after 360 min. These findings suggest that TiO2 has a significant potential as a nanocatalyst in complex matrices.
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Open AccessEditorial
The Role of Photophysics in Photochemistry
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Dirk Poelman
Photochem 2024, 4(2), 219-221; https://doi.org/10.3390/photochem4020013 - 29 Apr 2024
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Photochemistry is a broad subject [...]
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Open AccessReview
A Review of Visible Light Responsive Photocatalysts for Arsenic Remediation in Water
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Isabella Natali Sora, Francesca Fontana, Renato Pelosato and Benedetta Bertolotti
Photochem 2024, 4(2), 198-218; https://doi.org/10.3390/photochem4020012 - 17 Apr 2024
Cited by 1
Abstract
This review summarizes the progress over the last fifteen years in visible light reactive photocatalysts for environmental arsenic remediation. The design and performance of several materials including (1) doped and surface functionalized TiO2, (2) binary composites combining TiO2 with another
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This review summarizes the progress over the last fifteen years in visible light reactive photocatalysts for environmental arsenic remediation. The design and performance of several materials including (1) doped and surface functionalized TiO2, (2) binary composites combining TiO2 with another semiconductor that absorbs visible light radiation or a metal (Pt), (3) ternary composites incorporating TiO2, a conductive polymer that can retard electron-hole recombination and an excellent adsorbent material for the removal of As(V), (4) tungsten, zinc, and bismuth oxides, (5) g-C3N4 based catalysts, and (6) M@AgCl core–shell structures. These results show that long reaction time remains a major challenge in achieving high As(III) oxidation.
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(This article belongs to the Special Issue Exclusive Papers of the Editorial Board Members of the Journal Photochem)
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Open AccessArticle
Excited-State Dynamics of Carbazole and tert-Butyl-Carbazole in Thin Films
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Konstantin Moritz Knötig, Domenic Gust, Kawon Oum and Thomas Lenzer
Photochem 2024, 4(2), 179-197; https://doi.org/10.3390/photochem4020011 - 9 Apr 2024
Abstract
Thin films of carbazole (Cz) derivatives are frequently used in organic electronics, such as organic light-emitting diodes (OLEDs). Because of the proximity of the Cz units, the excited-state relaxation in such films is complicated, as intermolecular pathways, such as singlet–singlet annihilation (SSA), kinetically
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Thin films of carbazole (Cz) derivatives are frequently used in organic electronics, such as organic light-emitting diodes (OLEDs). Because of the proximity of the Cz units, the excited-state relaxation in such films is complicated, as intermolecular pathways, such as singlet–singlet annihilation (SSA), kinetically compete with the emission. Here, we provide an investigation of two benchmark systems employing neat carbazole and 3,6-di-tert-butylcarbazole (t-Bu-Cz) films and also their thin film blends with poly(methyl methacrylate) (PMMA). These are investigated by a combination of atomic force microscopy (AFM), femtosecond and nanosecond transient absorption spectroscopy (fs-TA and ns-TA) and time-resolved fluorescence. Excitonic J-aggregate-type features are observed in the steady-state absorption and emission spectra of the neat films. The S1 state shows a broad excited-state absorption (ESA) spanning the entire UV–Vis–NIR range. At high S1 exciton number densities of about 4 × 1018 cm−3, bimolecular diffusive S1–S1 annihilation is found to be the dominant SSA process in the neat films with a rate constant in the range of 1–2 × 10−8 cm3 s−1. SSA produces highly vibrationally excited molecules in the electronic ground state (S0*), which cool down slowly by heat transfer to the quartz substrate. The results provide relevant photophysical insight for a better microscopic understanding of carbazole relaxation in thin-film environments.
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(This article belongs to the Special Issue Feature Papers in Photochemistry II)
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Open AccessArticle
Excited-State Dynamics of Carbazole and tert-Butyl-Carbazole in Organic Solvents
by
Konstantin Moritz Knötig, Domenic Gust, Thomas Lenzer and Kawon Oum
Photochem 2024, 4(2), 163-178; https://doi.org/10.3390/photochem4020010 - 30 Mar 2024
Cited by 1
Abstract
Carbazole-based molecular units are ubiquitous in organic optoelectronic materials; however, the excited-state relaxation of these compounds is still underexplored. Here, we provide a detailed investigation of carbazole (Cz) and 3,6-di-tert-butylcarbazole (t-Bu-Cz) in organic solvents using femtosecond and nanosecond UV–Vis–NIR
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Carbazole-based molecular units are ubiquitous in organic optoelectronic materials; however, the excited-state relaxation of these compounds is still underexplored. Here, we provide a detailed investigation of carbazole (Cz) and 3,6-di-tert-butylcarbazole (t-Bu-Cz) in organic solvents using femtosecond and nanosecond UV–Vis–NIR transient absorption spectroscopy, as well as time-resolved fluorescence experiments upon photoexcitation in the deep-UV range. The initially prepared Sx singlet state has a (sub-)picosecond lifetime and decays to the S1 state by internal conversion (IC). The S1 state exhibits absorption peaks at 350, 600 and 1100 nm and has a lifetime of 13–15 ns, which is weakly dependent on the solvent. Energy transfer from vibrationally hot S1 molecules (S1*) to the surrounding solvent molecules takes place with a time constant of 8–20 ps. The T1 triplet state is populated by intersystem crossing (ISC) from S1 with a typical quantum yield of 51–56% and shows a lifetime which is typically in the few microseconds regime. The S1 and T1 states of both carbazole compounds in solution are strongly quenched by O2. Two-photon excitation leads to the formation of a small amount of the respective radical cation. The influence of the tert-butyl substituents on the photophysics is relatively weak and mainly reflects itself in a small increase in the Stokes shift. The results provide important photophysical information for the interpretation of carbazole relaxation in more complex environments.
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(This article belongs to the Special Issue Feature Papers in Photochemistry II)
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Open AccessArticle
Charge-Selective Photocatalytic Degradation of Organic Dyes Driven by Naturally Occurring Halloysite Nanotubes
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Ashim Pramanik, Martina Maria Calvino, Luisa Sciortino, Pooria Pasbakhsh, Giuseppe Cavallaro, Giuseppe Lazzara, Fabrizio Messina and Alice Sciortino
Photochem 2024, 4(2), 151-162; https://doi.org/10.3390/photochem4020009 - 28 Mar 2024
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This study explores the use of Halloysite NanoTubes (HNTs) as photocatalysts capable of decomposing organic dyes under exposure to visible or ultraviolet light. Through a systematic series of photocatalytic experiments, we unveil that the photodegradation of Rhodamine B, used as a model cationic
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This study explores the use of Halloysite NanoTubes (HNTs) as photocatalysts capable of decomposing organic dyes under exposure to visible or ultraviolet light. Through a systematic series of photocatalytic experiments, we unveil that the photodegradation of Rhodamine B, used as a model cationic dye, is significantly accelerated in the presence of HNTs. We observe that the extent of RhB photocatalytic degradation in 100 min in the presence of the HNTs is ~four times higher compared to that of bare RhB. Moreover, under optimized conditions, the as-extracted photodegradation rate of RhB (~0.0022 min−1) is comparable to that of the previously reported work on the photodegradation of RhB in the presence of tubular nanostructures. A parallel effect is observed for anionic Coumarin photodegradation, albeit less efficiently. Our analysis attributes this discrepancy to the distinct charge states of the two dyes, influencing their attachment sites on HNTs. Cationic Rhodamine B molecules preferentially attach to the outer surface of HNTs, while anionic Coumarin molecules tend to attach to the inner surface. By leveraging the unique properties of HNTs, a family of naturally occurring nanotube structures, this research offers valuable insights for optimizing photocatalytic systems in the pursuit of effective and eco-friendly solutions for environmental remediation.
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Open AccessArticle
Torsional Disorder in Tetraphenyl [3]-Cumulenes: Insight into Excited State Quenching
by
David Bain, Julia Chang, Yihuan Lai, Thomas Khazanov, Phillip J. Milner and Andrew J. Musser
Photochem 2024, 4(1), 138-150; https://doi.org/10.3390/photochem4010008 - 9 Feb 2024
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Cumulenes are linear molecules consisting of consecutive double bonds linking chains of sp-hybridized carbon atoms. They have primarily been of interest for potential use as molecular wires or in other nanoscale electronic devices, but more recently, other applications such as catalysis or even
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Cumulenes are linear molecules consisting of consecutive double bonds linking chains of sp-hybridized carbon atoms. They have primarily been of interest for potential use as molecular wires or in other nanoscale electronic devices, but more recently, other applications such as catalysis or even light harvesting through singlet fission have been speculated. Despite the recent theoretical and experimental interest, the photoexcitation of cumulenes typically results in quenching on the picosecond timescale, and the exact quenching mechanism for even the simplest of [3]-cumulenes lacks a clear explanation. In this report, we perform transient absorption spectroscopy on a set of model [3]-cumulene derivatives in a wide range of environmental conditions to demonstrate that the planarization of phenyl groups ultimately quenches the excited state. By restricting this intramolecular motion, we increase the excited state lifetime by a few nanoseconds, strongly enhancing photoluminescence and demonstrating an approach to stabilize them for photochemical applications.
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