Photochem, Volume 1, Issue 3 (December 2021) – 15 articles

The effect of foam-like 3D graphene (3DG) in an electron transport material (ETM), viz. ZnO thin film, on the steady-state photoluminescence (PL), light-harvesting efficiency (LHE), photocurrent density (J_SC), photovoltage (V_OC), and charge transport parameters of perovskite solar cells (PSCs) are systematically investigated. The ETM is developed by spin coating a ZnO precursor solution containing varying amounts of 3DG on conducting glass substrates and appropriate annealing. A significant improvement in the photoconversion efficiency of PSCs is observed for a low concentration of 3DG in ZnO. The current–voltage and electrochemical impedance spectroscopy measurements show that the addition of 3DG enhances the V_OC due to efficient electron–hole separation and charge transport compared to the pristine ZnO. These studies offer a route for further advances in enhancing the optoelectronic properties of ETM for artificial photosynthesis and photocatalysis devices. Full article

Photocytotoxic activity sensitized by 5,10,15,20-tetrakis[4-(3-N,N-dimethylaminopropoxy)phenyl]chlorin (TAPC) was investigated in Candida albicans under different culture conditions. Planktonic cells incubated with 2.5 μM TAPC were eradicated after 5 min irradiation with white light. Studies in the presence of reactive oxygen species scavengers indicated the involvement of mainly a type II mechanism. Furthermore, cell growth of C. albicans was suppressed in the presence of 5 μM TAPC. A decrease in pseudohyphae survival of 5 log was found after 30 min irradiation. However, the photokilling of this virulence factor reached a 1.5 log reduction in human serum. The uptake of TAPC by pseudohyphae decreased in serum due to the interaction of TAPC with albumin. The binding constant of the TAPC-albumin complex was ~10⁴ M⁻¹, while the bimolecular quenching rate constant was ~10¹² s⁻¹ M⁻¹, indicating that this process occurred through a static process. Thus, the photoinactivation of C. albicans was considerably decreased in the presence of albumin. A reduction of 2 log in cell survival was observed using 4.5% albumin and 30 min irradiation. The results allow optimizing the best conditions to inactivate C. albicans under different culture conditions. Full article

This study investigated the decolorization of Remazol Black (RBB) using a TiO₂ photocatalyst modified by S and Co co-doped TiO₂ (S-Co-TiO₂) from a single precursor. X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and UV–Vis specular reflectance spectroscopy were used to characterize the photocatalysts. The results revealed that the band-gap energy of the doped and co-doped TiO₂ decreased, with the S-Co-TiO₂ 8% showing the greatest one, and was found to be 2.78 eV while undoped TiO₂ was 3.20 eV. The presence of S and Co was also identified through SEM-EDX. An activity study on RBB removal revealed that the S-Co-TiO₂ photocatalyst showed the best result compared to undoped TiO₂, S-TiO₂, and Co-TiO₂. The S-Co-TiO₂ 8% photocatalyst reduced RBB concentration (20 mg L⁻¹) up to 96% after 90 min of visible light irradiation, whereas S-TiO₂, Co-TiO₂, and undoped TiO₂ reduced it to 89%, 56%, and 39%, respectively. A pH optimization study showed that the optimum pH of RBB decolorization by S-Co-TiO₂ was 3.0, the optimum mass was 0.6 g L⁻¹, and reuse studies show that S-Co-TiO₂ 8% has the potential to be used repeatedly to remove colored pollutants. The results obtained indicate that the modification of S, Co co-doped titania synthesized using a single precursor has been successfully carried out and showed excellent characteristics and activity compared to undoped or doped TiO₂. Full article

The search of new organic emitters is receiving a strong motivation by the development of ORTP materials. In the present study we report on the preparation, optical and photophysical characterization, by both steady state and time resolved techniques, of two pyrene-functionalized cyclic triimidazole derivatives. Together with the already reported mono-substituted derivative, the di- and tri-substituted members of the family have revealed as intriguing emitters characterized by impressive quantum yields in solution and RTP properties in the solid state. In particular, phosphorescence lifetimes increase from 5.19 to 20.54 and 40.62 ms for mono-, di- and trisubstituted compounds, respectively. Based on spectroscopical results and theoretical DFT/TDDFT calculations on the di-pyrene molecule, differences in photophysical performances of the three compounds have been assigned to intermolecular interactions increasing with the number of pyrene moieties appended to the cyclic triimidazole scaffold. Full article

Pure g-C₃N₄ sample was prepared by thermal treatment of melamine at 520 °C, and iron-modified samples (0.1, 0.3 and 1.1 wt.%) were prepared by mixing g-C₃N₄ with iron nitrate and calcination at 520 °C. The photocatalytic activity of the prepared materials was investigated based on the photocatalytic reduction of CO₂, which was conducted in a homemade batch reactor that had been irradiated from the top using a 365 nm Hg lamp. The photocatalyst with the lowest amount of iron ions exhibited an extraordinary methane and hydrogen evolution in comparison with the pure g-C₃N₄ and g-C₃N₄ with higher iron amounts. A higher amount of iron ions was not a beneficial for CO₂ photoreduction because the iron ions consumed too many photogenerated electrons and generated hydroxyl radicals, which oxidized organic products from the CO₂ reduction. It is clear that there are numerous reactions that occur simultaneously during the photocatalytic process, with several of them competing with CO₂ reduction. Full article

A Photoinduced dearomative nucleophilic addition to N-Boc indoles mediated by two-molecule organic photoredox catalysts such as phenanthrene and 1,4-dicyanobenzene with UV irradiation furnished 2-substituted indolines in moderate to quantitative yields. Hydroxide, alkoxide, and cyanide ions can be used as a nucleophile to provide 2-hydroxy, 2-alkoxy, and 2-cyanoindolines, respectively. Both electron-rich and -deficient indoles, including tryptophan derivatives, can be employed in the photoreaction to provide various indolines. This method provides transition-metal-free access to 2-subsituted indolines from indoles using organic photoredox catalysts under mild conditions. Full article

Cancer is considered one of the major public health problems worldwide. Among the therapeutic approaches investigated and used so far, the combined use of photothermal (PTT) and photodynamic (PDT) therapies have shown promising results for in vivo studies. The mechanisms of actions of both therapies are based on use of a chemical entity and a source light with an appropriate wavelength, and, in PDTs case, also molecular oxygen (O₂). Moreover, the combined use of PTT and PDT may present a synergic effect on the elimination of solid tumor and metastasis. Herein, we review the past 5 years (2016–2020) regarding the combined use of PTT and PDT and carbon nanomaterial platforms as photosensitizers and photothermal agents against cancer (in vivo evaluation). We intend to highlight the most important and illustrative examples for this period. Additionally, we report the mechanisms of action of PTT and PTT and the general physical/chemical properties of carbon nanomaterial platforms used for this therapeutic approach. Full article

More than three decades of research efforts have yielded powerful methodologies based on transition metal template-directed syntheses for the assembly of a huge number of interlocked systems, molecular knots, machines and synthesizers. Such template techniques have been applied in the preparation of mechanically linked electron donor–acceptor artificial photosynthetic models. Consequently, synthetic challenging photoactive rotaxanes and catenanes have been reported, in which the chromophores are not covalently linked but are still associated with undergoing sequential energy (EnT) and electron transfer (ET) processes upon photoexcitation. Many interlocked photosynthetic models produce highly energetic, but still long-living charge separated states (CSS). The present work describes in a historical perspective some key advances in the field of photoactive interlocked systems assembled by transition metal template techniques, which illustrate the usefulness of rotaxanes and catenanes as molecular scaffolds to organize electron donor–acceptor groups. The effects of molecular dynamics, molecular topology, as well as the role of the transition metal ion used as template species, on the thermodynamic and kinetic parameters of the photoinduced energy and electron transfer processes in the interlocked systems are also discussed. Full article

Titanium dioxide (TiO₂) is one of the stable and potential metal oxide semiconductor nanomaterials with flexible properties which allows them to be used in a variety of applications (i.e., environmental remediation, energy storage and production, and also as a pigment in personal care products, etc.). However, its low surface area, poor adsorption capacity and high bandgap energy (~3.2 eV) prevents its full potency. Especially, TiO₂ with high bandgap (~3.2 eV) reduces its visible light absorption capacity and catalytic efficiency. Various modification processes (i.e., metal and non-metal doping, composite materials (mixed metal oxide, high surface area adsorbents), and dye sensitization etc.) have been accomplished for stimulating the characteristics of TiO₂ and the associated catalytic efficiency. Among the modifications, the non-metal doping process in TiO₂, specifically nitrogen doping, is one of the efficient dopants for enhancing the photocatalytic efficiency of TiO₂ in the presence of visible light irradiation. However, the morphology of TiO₂, structural changes in TiO₂ during N-doping, properties (e.g., morphology and electronic) of N-doped TiO₂ and also reaction operational parameters (e.g., doping concentration) hold a greater impact for enhancing the photocatalytic properties of TiO₂ either positively or negatively. Furthermore, the synthesis methodologies have a major influence on the synthesis of stable N-TiO₂ with pronounced photocatalytic efficiencies. Nevertheless, the methodologies for highly stable N-TiO₂ synthesis, properties evaluation and their correlation with photocatalytic efficiencies are still not appropriately stabilized to accomplish the commercial utilization of N-TiO₂. Therefore, this review article focuses on the synopsis of various synthesis methodologies and either their efficiencies or inefficiencies, the mechanism involved in the doping processes, changes in the structural, electronic and morphological properties observed due to the N-doping along with the photocatalytic capacity. Furthermore, the opportunities, challenges and future requirements linked to the development of durable N-doped TiO₂-based semiconductor nanomaterials for efficient catalytic performance is also represented. Full article

In this study, molybdenum disulfide (MoS₂) decorated on graphitic carbon nitride (g-C₃N₄) heterostructure catalysts at various weight ratios (0.5%, 1%, 3%, 10%, w/w) were successfully prepared via a two-step hydrothermal synthesis preparation method. The properties of the synthesized materials were studied by X-ray diffraction (XRD), attenuated total reflectance–Fourier transform infrared spectroscopy (ATR-FT-IR), UV–Vis diffuse reflection spectroscopy (DRS), scanning electron microscopy (SEM) and N₂ porosimetry. MoS₂ was successfully loaded on the g-C₃N₄ forming heterojunction composite materials. N₂ porosimetry results showed mesoporous materials, with surface areas up to 93.7 m²g⁻¹, while determined band gaps ranging between 1.31 and 2.66 eV showed absorption over a wide band of solar light. The photocatalytic performance was evaluated towards phenol oxidation and of Cr(VI) reduction in single and binary systems under simulated sunlight irradiation. The optimum mass loading ratio of MoS₂ in g-C₃N₄ was 1%, showing higher photocatalytic activity under simulated solar light in comparison with bare g-C₃N₄ and MoS₂ for both oxidation and reduction processes. Based on scavenging experiments a type-II photocatalytic mechanism is proposed. Finally, the catalysts presented satisfactory stability (7.8% loss) within three catalytic cycles. Such composite materials can receive further applications as well as energy conversion. Full article

For the first time, heterostructures of electrospun carbon nanofibers decorated with Ag₃PO₄ nanoparticles (Ag₃PO₄/CNFs) were successfully fabricated by the combination of simple and versatile electrospinning technique followed by carbonization and incorporation of Ag₃PO₄ nanoparticles via colloidal and precipitation synthesis approaches. The as-fabricated heterostructures were characterized by FESEM with EDS, XRD, TEM with HRTEM, FTIR and UV-vis diffuse reflectance spectroscopy. Experimental results revealed that the heterostructure obtained by colloidal synthesis approach (Ag₃PO₄/CNFs-1) was decorated with small-sized (~20 nm) and uniformly distributed Ag₃PO₄ nanoparticles on the surface of CNFs without any evident agglomeration, while in the heterostructure obtained by the precipitation synthesis approach (Ag₃PO₄/CNFs-2), CNFs were decorated with agglomerated and bigger-sized Ag₃PO₄ nanoparticles. The visible-light-driven photocatalytic investigation signified that the Ag₃PO₄/CNFs-1 heterostructure can exhibit higher performance towards the photodegradation of MB dye solution compared to the Ag₃PO₄/CNFs-2 heterostructure, which could be attributed to the synergistic effect between the uniformity and small size of Ag₃PO₄ nanoparticles and CNFs that can serve as a conductivity network to prevent the recombination of charge carriers. Moreover, the mechanism of the photocatalytic activity as-prepared heterostructure is proposed. Full article

This mini review summarizes the preparation and testing of polymeric composites with a N-doped TiO₂ photocatalyst to effectively design a photocatalytic system for water pollutant degradation under visible light. In detail, the various N-doped TiO₂/polymer composites reported in the literature are briefly discussed along with some examples dealing with the use of N-doped TiO₂ particles, both supported on the external surface of polymers and dispersed within the structure of visible-light-transparent polymeric aerogels. Finally, the scope for future works and challenges for the commercialization of such materials are highlighted. Full article

This article covers the structural and optical property analysis of the sillenite Bi₁₂NiO₁₉ (BNO) in order to characterize a new catalyst that could be used for environmental applications. BNO crystals were produced by the combustion method using Polyvinylpyrrolidone as a combustion reagent. Different approaches were used to characterize the resulting catalyst. Starting with X-ray diffraction (XRD), the structure was refined from XRD data using the Rietveld method and then the structural form of this sillenite was illustrated for the first time. This catalyst has a space group of I23 with a lattice parameter of a = 10.24 Å. In addition, the special surface area (SSA) of BNO was determined by the Brunauer-Emmett-Teller (BET) method. It was found in the range between 14.56 and 20.56 cm²·g⁻¹. Then, the morphology of the nanoparticles was visualized by Scanning Electron Microscope (SEM). For the optical properties of BNO, UV-VIS diffusion reflectance spectroscopy (DRS) was used, and a 2.1 eV optical bandgap was discovered. This sillenite′s narrow bandgap makes it an effective catalyst for environmental applications. The photocatalytic performance of the synthesized Bi₁₂NiO₁₉ was examined for the degradation of Basic blue 41. The degradation efficiency of BB41 achieved 98% within just 180 min at pH ~9 and with a catalyst dose of 1 g/L under visible irradiation. The relevant reaction mechanism and pathways were also proposed in this work. Full article