Journal of Photochemistry and Photobiology最新文献

Solar powered conversion / reduction of carbon dioxide into value added chemicals has been identified as one of the foremost challenges for materials science in the 21st century. Despite extensive research, product yield remained low and one of the primary factors has been the issue of competing adsorption of CO₂ and water vapour on the catalyst surface. In this work we employ reduced graphene oxide wrapped TiO₂ nanotubes (TiO₂ - rGO) as a heterojunction photocatalyst and demonstrate that UV irradiation induces hydrophilicity on the TiO₂ surface and, hydrophobicity on the rGO surface. The resulting photocatalyst shows 25 % higher yield of methane over that of untreated photocatalyst. Hence, UV irradiation induced tailoring of the hydrophilicity yields selective adsorption sites for the CO₂ and water vapour leading to a significant enhancement of the methane yield through photocatalytic reduction process.

The structure and quality of eggshells (ES) vary around a mean value depending on different items, and these variations are important in their many industrial and technological applications as will be mentioned (vide infra). Five commercial egg brands of different laying hens are examined and their quality indices, morphological microstructure, elemental composition, and light absorbance at 200–700 nm UV/Vis spectra were compared. The ES layers include a limiting membrane, inner and outer shell membranes, a mammillary layer, a palisade layer, a surface vertical crystal layer, and a bilayer cuticle. The elemental composition of each layer reflects the proteinous or calcified nature of the layers, and various elements, C, O, N, Ca, Fe, Mg, Mn, Pb, Sr, Sc, Hf, Co, and La, were found. The weight difference between egg brands was significant, as well as the difference in ES percentage between white and colored eggs. ES weight possessed a positive relationship with the thickness of the calcified layer. So, the ES is heavier and the egg is larger and heavier when the calcified layer is thicker. The calculated average ES index was 7.99% ± 0.16 SE. In all ES samples, the absorbance in UV wavelength spectra (300–350 nm) was slightly higher than in Vis spectra (400 - 700 nm) and their difference was significant. The difference in absorbance of various treatments was significant and mean absorbance was the highest in the after-furnace (ash) samples and was the lowest for acid-treated ones. It seems that turning the ES into ash can improve the absorbance capability, especially in white ESs.

Exposure to ultraviolet (UV) radiation from the sun has both harms and benefits for human health. The best-known benefit of sun exposure is the generation of vitamin D within the skin and the best-known harm is malignant skin cancer. Australia and New Zealand have very high ambient UV radiation, resulting in high rates of skin cancer incidence and mortality, yet there is an appreciable prevalence of vitamin D deficiency (defined as blood 25-hydroxyvitamin D (25(OH)D) < 50 nmol/L) in both populations. The purpose of this study was to create a microsimulation model to replicate population 25(OH)D concentrations of people living in Australia and New Zealand, thus enabling the effect of different population-wide interventions to be estimated. We used large population datasets containing data on sun behaviours and socio-demographic variables, and environmental data on UV radiation, ozone, and solar zenith angle. Latitude, weather and time of day were accounted for. We simulated the conversion of daily UV radiation to a standard vitamin D dose (SDD) (100 J/m² vitamin D-weighted UV) and monthly accumulation of SDD to 25(OH)D concentration. The model was calibrated to match the seasonal prevalence of vitamin D deficiency. This report describes the Sun Exposure (SUNEX) microsimulation model, its development, data inputs and calibration against population prevalence of vitamin D deficiency.

The main flavonoid pigment in the petals of Kigelia Africana and the calyx of Hibiscus sabdariffa is anthocyanin, responsible for the vibrant red, maroon, and purple hues in flowers. This pigment can modulate incident light on flowers, prompting its selection for detailed investigation. TiO₂ nanostructures were synthesized using a one-step hydrothermal method, revealing the formation of nanorods and a single-phase rutile structure through FESEM and XRD analyses, respectively. The study aimed to assess the impact of various solvents on the extraction of natural dyes, which were subsequently sensitized on TiO₂ photoanodes for DSSC applications. Four solvents-water, water with HCl, ethanol, and citric acid were employed to extract natural dyes from Kigelia Africana's petals and Hibiscus sabdariffa's calyx. Notably, dyes extracted with citric acid demonstrated promising results. The conversion efficiency of DSSCs fabricated with Kigelia Africana dye and Hibiscus sabdariffa dye, extracted using citric acid as the solvent, was found to be 0.87 % and 0.92 %, respectively. The implications of these findings are discussed.

Various integrated technologies have been investigated for the remediation of heavily polluted industrial dye effluent. Also, more than 70 % of these dyes are known to be solely azo dyes used in the textile industry with 5–30 % presence in the effluent as loose dye molecules which are recalcitrant to treatment. These challenges led to the investigation of energy-efficient processes (solar) and the fabrication of high-performance nano-photocatalysts for proficient photocatalysis of dye effluent while mediating the process with Fenton reagents. The study fabricated nanopolymeric catalyst composites (P-AKT) via novel in situ coupling and impregnation of the polyaniline (PANI) with surface-activated TiO₂ NPs. This fabrication is aimed at developing a high-performance catalyst with rapid and proficient photocatalytic activities to photons from sunlight irradiation. The photocatalytic process was mediated using a novel Fenton reagent to enhance the generation of radical species for dye degradation. Various instrumental characterization methods were used to study the structural, molecular, elemental, functional and optoelectronic properties of the fabricated nanocomposite photocatalysts. The result reveals functional groups aiding dye-catalyst bonding and morphological interaction reveal a surface-activated tetragonal crystalline mixture of anatase and rutile from TiO₂⁻Nps embedded in the macromolecular chain of PANI. It also reveals the optimal conditions of 20 mg dosage, 10 mg/L initial concentration with substantial effectiveness at pH of 5 and 7. However, the most efficient photocatalyst recorded was P-AKT-2 % and P-AKT-3 % having 95 % and 94 % efficiencies at 90 min of solar irradiation. The photocatalyst equally demonstrated its capacity for effluent treatability up to 4 cycles of use.

Near-infrared photoimmunotherapy (NIR-PIT) is a recently described method for cancer treatment that utilizes an antibody-conjugated phthalocyanine photosensitizer and NIR light. In NIR-PIT, light of 690 nm wavelength is used to activate a photosensitizer, IR700, while longer-wavelength light penetrates deeper into tissues. Thus, more effective NIR-PIT would be achieved by using photosensitizers that are activated by longer-wavelength light. The absorption wavelength would be red-shifted by destabilizing the highest occupied molecular orbital (HOMO) energy level by introducing electron donating groups at the α positions of a phthalocyanine ring. In this study, we developed a red-shifted photosensitizer for NIR-PIT, KA800, whose absorption wavelength was red-shifted by the introduction of ethoxy groups to IR700. As intended, the absorption maximum of KA800 was red-shifted compared to IR700 by 84 nm. Although phototoxicity of the antibody-KA800 (Ab-KA800) conjugate was observed in cultured cancer cells, no therapeutic effect was observed in mice. This is because the cytotoxicity of Ab-KA800 was mainly due to singlet oxygen, which can be quenched by abundant antioxidants in vivo. KA800 had low reactivity with respect to axial ligand cleavage required for inducing cell death via aggregate formation, a unique cytotoxic mechanism in NIR-PIT. The axial ligand cleavage proceeds via the anion radical formation of the photosensitizer, and KA800 was found to be less likely to receive an electron than IR700. This may be due to the destabilization of the HOMO energy level of KA800. Therefore, our findings suggest that stabilizing the lowest unoccupied molecular orbital (LUMO) energy level would be better than destabilizing the HOMO energy level for developing a red-shifted photosensitizer for NIR-PIT.

Ultraviolet (UV) irradiation has been identified as a key trigger for skin photoaging, characterized by the overproduction of matrix metalloproteinases (MMPs) and reactive oxygen species (ROS), along with the accelerated decomposition of extracellular matrix (ECM) proteins, ultimately contributing to the development of wrinkles. Persicaria senticosa (PS) extracts are recognized for their antioxidative properties and their importance in skin health. Nevertheless, there is a paucity of studies investigating the potential of PS in protecting the skin against photoaging. The present study aimed to assess the effectiveness of PS extracts in preventing photoaging and elucidating the molecular mechanisms involved in using immortalized human keratinocytes (HaCaT) and hairless mice. The major bioactive constituents of PS were identified as p-coumaric acid, isoquercitrin, quercetin-3-O-glucuronide, and quercetin. Aqueous extracts of PS exhibited the ability to mitigate UVB-induced cellular damage and diminished ROS generation in HaCaT cells. Moreover, treatment with PS effectively attenuated the upregulated expression of matrix metalloproteinase-1 (MMP-1) and collagen degradation induced by UVB exposure. The property of PS to counteract photoaging was related to its capacity to inhibit the UVB-induced phosphorylation of mitogen-activated protein kinase (MAPK) and suppress the subsequent activation of activator protein 1 (AP-1) signaling pathways. Moreover, in hairless mice exposed to UVB radiation, the application of PS significantly alleviated the development of skin wrinkles, diminished epidermal thickening, and mitigated collagen degradation. Notably, PS treatment resulted in the downregulation of the UVB-activated MAPK/AP-1/MMP-1 pathway in mouse skin tissues. These findings suggest that PS has the potential to serve as a therapeutic agent for treating photoaging, holding promises in both cosmeceutical and pharmaceutical applications.

It is known that cell culture micropatterns have the ability to facilitate stem cell differentiation induced by specialized chemical factors and different differentiation directions have different optimal micropattern shapes. In this study, by utilizing extrinsic photobiomodulation (EPM) with verteporfin as photosensitizer and light irradiation of 690 nm wavelength as a universal, unbiased, and synchronizing way of inducing differentiation of human umbilical cord Wharton's Jelly mesenchymal stem cells (WJ-MSCs), the topographic cue for cell type specification conveyed in microislands is investigated. It is found that the topographic cues are encoded in the symmetry and aspect ratio of microislands and conformation of cells to microislands is necessary for acquiring the cue. F-actin vertical columns form and cell thickness increases for cells on microislands, and the two effects are enhanced by EPM and correlate with cell differentiation. EPM treatment poises cells in a stationary state to initiate differentiation and the process of making commitment takes two days. Our findings reveal the way to fully exploit topographic cues for promoting and controlling cell differentiation.

Photobiomodulation (PBM) is emerging as a promising non-invasive approach for managing inflammatory skin conditions. However, its precise molecular mechanisms, especially within the green light spectrum, remain elusive. In this study, we investigated the anti-inflammatory mechanisms of 520 nm green light in primary human keratinocytes (KCs) exposed to the contact sensitizer 2,4-dinitrochlorobenzene (DNCB). Our data revealed that green light effectively reduces the mRNA expression of pro-inflammatory cytokines IL-6, IL-8, and TNF-α, comparably to the effect of dexamethasone, a conventional anti-inflammatory agent. As Nuclear factor erythroid-2-related factor 2 (Nrf2) is involved in the red light response, we explored Nrf2′s role in green light anti-inflammatory activity. Green light exposure activated the Nrf2 pathway, leading to Nrf2 increased accumulation in KCs and the induction of Nrf2 target genes, including HO-1 and GCLC. Invalidation of Nrf2 with si-RNA diminished the green light's regulatory effect, indicating Nrf2′s essential role in the green light's anti-inflammatory action. As the Transient Receptor Potential Vanilloid 1 (TRPV1) channel is a potential target for green light, we investigated its role in PBM response. Blocking TRPV1 with capsazepine (CPZ) abolished the anti-inflammatory effect of green light and prevented the upregulation of Nrf2 target genes. This finding highlights TRPV1′s integral role in green light beneficial activity via the activation of the Nrf2 pathway. Overall, our study identifies TRPV1 and Nrf2 as critical players in the green light response, highlighting the versatility of PBM in controlling skin inflammation.

A simple method for obtaining triplet-triplet absorption (TTA) spectra and triplet state (T₁) lifetimes of long-lived triplets is presented and demonstrated with the polycyclic aromatic hydrocarbon coronene (both normal and perdeuterated forms) in a polymer matrix at room temperature. The TTA spectra obtained with a camera flash and a spectrophotometer are noisier but otherwise identical to those obtained with a state-of-the-art flash photolysis apparatus. The triplet lifetimes obtained from transient absorption are identical to the phosphorescence lifetimes of the same samples.