Journal of Photochemistry and Photobiology最新文献

Recent publications have confirmed the ability of visible light from sunlight (in the absence of Ultraviolet A or B) to cause free radical formation in human skin, increases in metalloproteinases, induced pigmentation and even erythema from exposures within reasonable exposure periods (e.g. less than 8 h). This raises questions regarding the role of visible light on the formation of skin cancers and even the need for protection against visible light in general. Conducting such studies is a challenge, considering the doses of visible light required for observation of reactions, the difficulty in conducting animal studies with appropriate models in the current regulatory environment, and the lack of funding for basic photobiological research. A review of research from an earlier era in photobiology studies gives us some clues and suggests that there may in fact be detectable influences of visible radiation (for example on skin cancer induction) that warrant new approaches to photoprotection in this era.

We have demonstrated three LY-HTMs for perovskite solar cells in this report. These LY-HTMs embed cyclopentadithiophene (CPT) core that incorporates 2∼4 triphenylamine electron donor units. Designing LY-HTMs with Lewis-basic property of carbonyl or imine, can effectively passivate the defects of insufficiently coordinated Pb²⁺ in the perovskite layer. The LY-HTMs have good thermal stability and enhanced intermolecular interaction, thereby dense packing, due to the sulfur-sulfur interaction in the dithiophene structure. Moreover, the sulfur-sulfur interaction achieves a deeper HOMO energy level that can be well-matched to perovskite solar cells (PSCs). It also improves the charge mobility to enhance Voc and Jsc values. The best performance using LY-1 as a HTM in PSCs exhibited a Jsc of 23.1 mA∙cm⁻², a Voc of 1.06 V, and a fill factor of 0.78, corresponding to an overall conversion efficiency of 19.12% (the control device of spiro-OMeTAD, 17.69%). In addition, the PCEs of the LY-1 PSC devices underwent decays of only 90% and 74.8% of their original values after 10 and 30 days, respectively, under an Ar atmosphere.

Electron donor–acceptor (EDA) complexes are interesting chemical species that function as molecular complexes. In this context, chemists have actively studies the use of halogen bonding as a noncovalent interaction in photochemistry. This study focused on developing a direct arylation reaction using aryl radicals generated by photoinduced electron transfer (PET) through halogen-bonding interactions. The study also involves optimizing reaction conditions for a photo induced direct arylation reaction using phenols as halogen bonding acceptor and plausible reaction mechanism. Our results demonstrated that this method provides a facile and efficient approach for synthesizing complex biaryls containing heteroarens using readily available heteroarenes.

This review presents the main metrics developed so far to correlate physical properties of light and its effects on melatonin suppression. Melatonin is a hormone secreted at night and its production is suppressed by exposure to light. In this context, the negative effects of lighting at night and high exposure to light raise the need for a better quantification of these impacts on health. Different light action spectroscopy methodologies have been recently used to characterize the circadian response mediated by melatonin in humans, but there is so far no consensus on a main validated model. While complementary studies are still necessary to reach such an ideal model, here we analyze and compare the results of works that developed and tested metrics based on the absorption curves of human melanopsin, rods and cones, and on the dynamics of melatonin suppression in different light regimes. These studies reveal how the spectral composition, irradiance and temporality of light modulate the function of human melatonin. We present milestones in this research field, together with discussion on the advances, limitations and perspectives of application for distinct available models. Applied to different contexts, this knowledge can bring favorable changes to health in environmental lighting projects, production of ophthalmic lenses, screens, filters, films, and other optical devices.

Photocatalytic systems consisting of 2-substituted benzimidazoliums (BI⁺–R, R = polycyclic aryl, triarylamine or phenyl-sulfate) and stoichiometric hydride donor reagents were developed. Light emitting diode irradiation of these photocatalysts in the presence of NaBH₄ or picoline borane promotes desulfonylation reactions of an N-sulfonyl indole, N-sulfonyl amide and α-sulfonyl ketone. Absorption spectroscopic and redox potential measurements as well as density functional theory calculations were carried out to gain mechanistic information. Benzimidazolines (BIH–R), generated in situ by hydride reduction of BI⁺–R, serve as both an electron and hydrogen atom donor photocatalysts in these reductive desulfonylation reactions, which contrasts to ordinary reducing photocatalysts that simply donate electrons.

The electron transfer reaction between C₆₀ and SWCNTs in D₂O was investigated. Repeated laser irradiation of water-soluble C₆₀ encapsulated in γ-cyclodextrin and SWCNTs with carboxymethylcellulose dispersed in D₂O resulted in the accumulation of C₆₀ anion radicals and a decrease in the E₁₁ absorption band of SWCNTs, strongly suggesting electron transfer between C₆₀ and SWCNTs. Transient absorption techniques revealed that this electron transfer occurred through the excited triplet of C₆₀.

Mammals use social thermoregulation to maintain the core body temperature (Tc) at a lower energy cost. Brown adipose tissue (BAT) plays a crucial role in thermoregulation. This study tested the hypothesis that social isolation induces alterations in thermogenesis and metabolism to maintain the rhythm of Tc throughout the day. Adult male mice (C57BLJ/6) were maintained in groups of 4–5 (group-housed) or isolated (single-housed) for 28 days. Telemetric probes recorded spontaneous locomotor activity (SLA) and Tc to analyze SLA and Tc daily rhythms. Body weight was measured weekly. VO2 consumption was analyzed at zeitgeber time (ZT) 1–3 (beginning of light phase) or ZT10–14 (beginning of dark phase). The expression of thermogenic-related and clock genes in the BAT occurred at ZT2, ZT8, ZT14, and ZT20. The β3 adrenergic agonist CL-316,243 was i.p. injected in the group- or single-housed mice. Social isolation increased the amplitude of Tc rhythm but decreased the amplitude of SLA oscillation. Nevertheless, in single-housed mice, the circadian peak of Tc and SLA was unaltered, with reduced body weight gain, increased VO2 consumption, and BAT Ucp1 expression at ZT14. Isolation advanced the BAT Rev-erb-ɑ peak of expression and phased-shift the peak of expression in BAT Bmal1, while it abolished the daily BAT Per2 oscillation. Isolation also abolished the BAT Ucp1 and hormone-sensitive lipase (Hsl) expression induced by stimulation of the β3ADR, but it increased Rev-erb-ɑ and Pgc1α. Thus, alterations in Ucp1, Reverb-α, Bmal1, and Per2 daily expression may favor an increased metabolic rate at the beginning of the dark, which, in turn, contributes to maintaining the daily Tc rhythm at the expense of reduced body weight gain in isolated mice. In addition, at least at the transcription level, the response of BAT from isolated mice to adrenergic agonist seems to be via a non-canonical mechanism involving Rev-erb-α and Pgc1α.

The reactions involving aryl radicals is an efficient strategy for the synthesis of a wide variety of important molecules. We have highlighted here recent developments on the generation of aryl radicals from various substrates by visible light mediated photocatalysis and their reactions with different substrates to produce a library of arylated and het-arylated compounds. These reactions are performed at room temperature using LED bulbs. Thus, this strategy is green involving less energy.

Covalently linked peptide-porphyrin compounds are most suitable systems for fundamental studies aiming to the comprehension of the mechanisms driving photoinduced energy/electron transfer processes. Mimicking photosynthetic units, the porphyrin groups act as antenna moieties while the peptide chain is the active medium through which energy and/or electron funneling occur. In this contribution we studied the transfer of excitation between two identical tetraphenylporphyrin groups connected by short peptide chains of different length formed by non-coded conformationally constrained α-amino acids, i.e., C^α-methylvaline. The photophysical events following porphyrin photoexcitation were characterized from the microsecond to the picosecond time region by time-resolved spectroscopy techniques. Ultrafast transient absorption measurements revealed the presence of a transient species that we assign to a self-trapped exciton migrating through the peptide chain. The exciton species propagates the electronic coupling between the two porphyrin groups giving rise to a characteristic bisignate band measured by circular dichroism experiments. Molecular dynamics simulations strongly suggest that the long lifetime (hundreds of picoseconds) of the exciton species is determined by the rigidity of the C^α-methylvaline residues, that inhibited energy relaxation pathways coupled to torsional motions of the peptide chain.

Seaweeds play an important role for the environment, since they are photosynthetic organisms, contributing to the cycling of nutrients and to the protection and feeding of several animals. The potential for biotechnological applications of marine macroalgae biomass is enormous, and to attend the demand of the current market, the knowledge of the physiological characteristics of these organisms is essential to ensure a high productivity in cultivation systems. In this review, we contribute to the knowledge about the photosynthetic characteristics of seaweeds, describing relevant aspects of marine macroalgae and photosynthesis, and the biotechnological use of these organisms.