ChemPhotoChem最新文献

The improvement of photodynamic inactivation (PDI) significantly depends on the development of new families of photosensitizers (PSs). In this sense, three BOPHY derivatives (BP, BP-Br and BP-I) were synthetized, studied, and compared to assess their antimicrobial photodynamic properties. BP is an interesting fluorescent probe for cell imaging, while the halogenated analogs (BP-Br and BP-I) are excellent oxygen photosensitizing agents. BP compound presented a fluorescence quantum yield close unity and showed no reactive oxygen species (ROS) production. In contrast, BP-I did not show emission properties but exhibited a high production of ROS through both photodynamic mechanisms, generating singlet oxygen (type II) and superoxide radical anion (type I) under aerobic light irradiation. BP-Br presented an adequate balance between ROS production and emission properties. The photokilling action and the binding to bacterial cells of these macrocycles were evaluated in vitro against methicillin-resistant Staphylococcus aureus (MRSA) and Escherichia coli bacteria. Our results demonstrated that the halogenated BOPHY derivatives were effective PSs in inactivating MRSA using shorter irradiation periods. In addition, the antimicrobial action sensitized by these BOPHYs was potentiated by adding KI. The combination of halogenated BOPHY and KI led to a complete elimination of both Gram-positive and Gram-negative bacteria. Hence, BP-Br and BP-I prove to be potent broad-spectrum antimicrobial PSs. To the best of our knowledge, this is the first time that BOPHY derivatives have been applied to photokill pathogenic microorganisms.

The reactions occurred at excited states are promising and flourished. Many strategies have been discovered reactions initiated by visible light and without transition metals and organic dyes. Diboron ester (B₂cat₂) has special activity towards unsaturated bonds at excited states. In this work, azobenzene and derivatives are reduced to hydrazo with high yield and high selectivity by a very convenient and rapid reaction. Only three factors, B₂cat₂, water and 400 nm lighting or sunlight are necessary. Density functional theory (DFT) studies and NMR results show that azobenzene is excited and a trans to cis isomerization occurs under 400 nm and B₂cat₂ reacts with cis azobenzene through B−B bond cleavage rather than with ground state trans azobenzene. Hydrazo compounds are obtained after hydrolysis with water. Gram level hydrazobenzenes are obtained under sunlight with moderate yields. This strategy is benefit to sustainable chemistry.

The (6–4) photolesion is a key photodamage that occurs when two adjacent pyrimidine bases in a DNA strand bond together. To better understand how the absorption of UVB and UVA radiation by the 2-pyrimidinone moiety in a (6–4) lesion can damage DNA, it is important to study the electronic deactivation mechanism of its 2-pyrimidinone chromophore. This study employs theoretical (MS-CASPT2/cc-pVDZ level) and experimental (steady state and femtosecond broadband spectroscopic) methods to elucidate the photochemical relaxation mechanisms of 2-(1H)-pyrimidinone and 1-methyl-2-(1H)-pyrimidinone in aqueous solution (pH 7.4). In short, excitation at 320 nm leads to the population of the S₁ ¹(ππ*) state with excess vibrational energy, which relaxes to the S₁ ¹(ππ*) minimum in one picosecond or less. A trifurcation event in the S₁ ¹(ππ*) minimum ensued, leading to radiative and nonradiative decay of the population to the ground state or the population of the long-lived and reactive T₁ ³(ππ*) state in hundreds of picoseconds. Collectively, the theoretical and experimental results support the idea that in DNA and RNA, the T₁ ³(ππ*) state of the 2-pyrimidinone moiety in the (6–4) lesion can further participate in photosensitized chemical reactions increasing DNA and RNA damage.

Defect-enriched mesoporous CuO nanosheets (NSs) were constructed to investigate the cooperative photo-Fenton and photothermal-Fenton catalysis on degradation of fluoroquinolones (FQ) antibiotics. The oxygen vacancies provide abundant active sites to bind the substrates and inhibit charge recombination, by all means to enhance Fenton-like activity. Two disparate spectral selective functions of photoexcitation and photothermal conversion were achieved on CuO NS, which to promote the Fenton activity synergistically. Visible light induced photoexcitation to facilitate the generation of Cu⁺ and ⋅OH, while near-infrared light converted into heat to promote charge separation and accelerate medium transport. Ultimately, as a unitary catalyst system, the CuO NS integrated the Lewis acid catalysis, Fenton-like catalysis and photothermal catalysis that rapidly and sustainably degraded antibiotics under near-neutral conditions.

Covalent organic frameworks (COFs), newly developed materials, exhibit considerable promise in the field of catalysis. COFs exhibit captivating catalytic characteristics, including thermal and chemical stability, customizable porosities, and the ability to place active sites flexibly with tunable functions. To establish a connection between structure and activity, this paper provides a thorough justification of the planned creation of covalent organic frameworks for photocatalysis, encompassing H₂ production, carbon dioxide reduction, pollutants reduction and transformation of organic substances. We have investigated the catalytic sites that are active within covalent organic frameworks, encompassing the metals, molecular catalysts, and catalyst with single atom (SACs); the reactive skeleton/linkages; and the reactive pendant groups. This exploration aims to establish the benefits of using COF-based catalysts compared to traditional catalysts. Despite the new advantages, numerous difficulties have also been noted with regard to the future. The objective of this review is to make it easier to design COF-based composite materials for practical uses.

Two π-extended derivatives of boron-dipyrromethene (BODIPY) – unsymmetrical benzo[b]-fused BODIPY 1 and symmetrical naptho[b]-fused BODIPY 2 – were synthesized. Spectroscopic and photophysical properties of the synthesized fluorescent dyes were investigated in various organic media. Both BODIPY 1 and BODIPY 2 distinguished by bathochromically shifted absorption and emission bands compared to their non-fused derivatives, while possessing green (526–543 nm) and red (664–708 nm) absorbance and fluorescence, respectively. Spectral characteristics of the investigated fluorescent dyes were found to be weakly depended on solvent polarizability in case of BODIPY 1 and greatly influenced by both solvent polarizability and dipolarity in case of BODIPY 2. Quantum chemical calculations were used to clarify the relationships between geometry/electronic structure and spectral properties/solvatochromic behavior of BODIPY 1 and BODIPY 2.

With the rise of antibiotic resistance within clinical settings, combating the growth of microbial biofilms presents a unique challenge. Biofilm-inhabiting bacteria are embedded within a self-produced, protective matrix, which can reduce the efficacy of treatment. The naturally derived product β-lapachone is an appealing therapeutic agent that has been reported to inhibit biofilm growth. However, its off-target toxicity and poor metabolic stability pose a significant hurdle for its application in vivo. Using a photo-pharmacological approach via a coumarin-based photocage, the reactivity of β-lapachone can be tuned so it only becomes active once the photocage is removed. Here we report both the photo-uncaging efficiency and the effective inhibition concentration of photocaged β-lapachone within model Bacillus subtilis biofilms. Additionally, the mechanism of action is analyzed with results supporting catalase inhibition. This novel light-activatable anti-microbial has potential applications in medical settings to inhibit biofilm growth and provide synergistic treatment with traditional antibiotics.

Constructing a catalyst capable of reducing CO₂ through photoreduction in aqueous environments presents a significant challenge. In this study, we present the synthesis of BiVO₄@NiCo₂O₃ heterojunction using a straightforward hydrothermal method for CO₂ photoreduction. The sample with the optimal loading ratio demonstrates a CO generation rate of 7.202 μmol ⋅ g⁻¹ ⋅ h⁻¹, which is twice that of pure BiVO₄ (3.626 μmol ⋅ g⁻¹ ⋅ h⁻¹) and 1.5 times that of pure NiCo₂O₃ (4.726 μmol ⋅ g⁻¹ ⋅ h⁻¹). Analysis using XPS and EPR techniques suggests that electron transfer at the interface of the heterojunction facilitates the separation of photogenerated charge carriers, thereby enhancing the efficiency of the photocatalytic process. This investigation offers a viable approach for developing photocatalysts for CO₂ reduction in aqueous environments.

Visible light-mediated photocatalytic approach for the radical functionalization of alkenes bearing the fluorinated aryl sulfide fragment is described. The process occurs in the presence of organic photocatalyst using sulfinates as sources of radicals. The key step of the reaction is the intramolecular 1,4-migration of the polyfluoroaryl group. In the reaction, three new bonds are formed (two C−C and one C−S bond). The decisive role of fluorine atoms in the reaction efficiency was confirmed by DFT calculations.

Photoelectrocatalytic (PEC) reduction of nitrobenzene (NB) is an extremely promising technology for renewable energy utilization and conversion. PEC reduction of NB to produce higher-value azobenzene (AZB) instead of aniline (AN), which is now commonly reported, is not currently achievable. In this work, we fabricated Ag nanoparticles (AgNPs)-decorated silicon nanocone (SiNC) array photocathodes with which the PEC reduction of NB to azobenzene (AZB) was realized for the first time. The SiNC array structure constructed by cryogenic dry etching greatly improved the light absorption ability of the photoelectrode. Ag was chosen as the cocatalyst because of its larger potential difference for the NB reduction reaction and the competing side reaction hydrogen evolution reaction. The Schottky junction formed by AgNPs with Si facilitates the rapid extraction of photogenerated electrons to participate in the PEC reaction. Under the optimized conditions, the PEC reduction of NB was achieved with a conversion of more than 90 %, with the reduction products being mainly AZB (9 : 1 ratio of AZB to AN) as well as excellent stability. The present work provides a photoelectrode that highly selectively PEC reduction of NB to AZB, and also provides insights into the design and preparation of high-performance silicon-based photoelectrodes.