Search Results (70)

A facile and versatile strategy to obtain NPs@ZnAlO nanocomposite materials, comprising controlled-size nanoparticles (NPs) within a ZnAlO matrix is reported. The mono-(Au, Ni) and bimetallic (Ni-Au) NPs serving as an active phase were prepared by the polyol-alkaline method, while the ZnAlO support was obtained via the thermal decomposition of its corresponding layered double hydroxide (LDH) precursors. X-ray diffraction (XRD) patterns confirmed the successful fabrication of the nanocomposites, including the synthesis of the metallic NPs, the formation of LDH-like structure, and the subsequent transformation to ZnO phase upon LDH calcination. The obtained nanostructures confirmed the nanoplate-like morphology inherited from the original LDH precursors, which tended to aggregate after the addition of gold NPs. According to the UV-Vis spectroscopy, loading NPs onto the ZnAlO support enhanced the light absorption and reduced the band gap energy. ATR-DRIFT spectroscopy, H₂-TPR measurements, and XPS analysis provided information about the functional groups, surface composition, and reducibility of the materials. The catalytic performance of the developed nanostructures was evaluated by the photodegradation of bisphenol A (BPA), under simulated solar irradiation. The conversion of BPA over the bimetallic Ni-Au@ZnAlO reached up to 95% after 180 min of irradiation, exceeding the monometallic Ni@ZnAlO and Au@ZnAlO catalysts. Its enhanced activity was correlated with good dispersion of the bimetals, narrower band gap, and efficient charge carrier separation of the photo-induced e⁻/h⁺ pairs. Full article

Photochemical degradation is a major removal pathway for pharmaceutical pollutants in water, and dissolved organic matter (DOM) in water is an important factor affecting this process. This study investigates the differential effects of seasonally-varied dissolved organic matter (DOM) from Songhua River and Liao River on the photodegradation of pharmaceutical pollutants, using levofloxacin (LFX), sulfamethoxazole (SMZ), and ibuprofen (IBP) as target compounds. The results demonstrated that summer and autumn DOM inhibited the photodegradation of LFX and SMZ through light screening and dynamic quenching effects, with inhibition rates of 35.1% and 55.5%, respectively, whereas winter DOM enhanced degradation through photo-oxidation mechanisms. DOM from Songhua River and Liao River significantly promoted the photodegradation of IBP. Quenching experiments showed differences in the contributions of photochemically reactive intermediates (PPRIs) to the photodegradation of different target pollutants, with hydroxyl radicals (•OH) dominating LFX photodegradation (48.79% contribution), excited triplet states of DOM (³DOM*) dominating SMZ photodegradation (85.20% contribution), and singlet oxygen (¹O₂) dominating IBP photodegradation (79.89% contribution). The photodegradation pathways were elucidated by measuring the photodegradation by-products of the target pollutants: LFX mainly underwent piperazine ring cleavage and oxidative decarboxylation, SMZ underwent isoxazole ring opening and deamination during photodegradation, and IBP underwent photodecarboxylation and oxidation reactions. Under the influence of the DOM from the Songhua River and Liao River, the generation of multiple photodegradation by-products led to an increasing trend in the acute toxicity of target pollutants to luminescent bacteria. This investigation elucidates the dual regulatory mechanisms of natural aquatic DOM on both photo-induced degradation pathways and toxicity evolution dynamics of pharmaceutical contaminants, which is of great significance for understanding the photochemical transformation behavior and risk assessment of pharmaceutical pollutants in aquatic environments. Full article

Green analytical chemistry represents a transformative approach to analytical science, emphasizing sustainability and environmental stewardship while maintaining high standards of accuracy and precision. This review highlights recent innovations in green analytical chemistry, including the use of green solvents, such as water, supercritical carbon dioxide, ionic liquids, and bio-based alternatives, as well as energy-efficient techniques like microwave-assisted, ultrasound-assisted, and photo-induced processes. Advances in green instrumentation, including miniaturized and portable devices, and the integration of automation and chemometric tools, have further enhanced efficiency and reduced the environmental footprint of analytical workflows. Despite these advancements, challenges remain, including the need to balance analytical performance with eco-friendliness and the lack of global standards to measure and promote sustainable practices consistently. However, the future of green analytical chemistry looks promising, with emerging technologies like artificial intelligence and digital tools offering new ways to optimize workflows, minimize waste, and streamline analytical processes. By focusing on these areas, green analytical chemistry is transforming analytical methodologies into tools that not only achieve high performance but also align with global sustainability goals. This review underscores how green analytical chemistry is more than just a scientific discipline, but a pathway for reducing the ecological impact of analytical processes while driving innovation in science and industry. With the continued commitment to research, collaboration, and the adoption of cutting-edge technologies, green analytical chemistry has the potential to shape a greener and more sustainable future for analytical chemistry and its diverse applications. Full article

When a sample of semiconducting material is illuminated by monochromatic light, in which the photon energy is higher than the energy gap of the semiconductor, part of the absorbed electromagnetic energy is spent on the generation of pairs of quasi-free charge carriers that are bound by Coulomb attraction. Photo-generated pairs diffuse through the material as a whole according to the density gradients established, carrying part of the excitation energy and charge through the semiconducting sample. This energy is indirectly transformed into heat, where the excess negatively charged electron recombines with a positively charged hole and causes additional local heating of the lattice. The dynamic of the photoexcited charge carrier is described by a non-linear partial differential equation of ambipolar diffusion. In moderate doped semiconductors with a low-level injection of charge carriers, ambipolar transport can be reduced to the linear parabolic partial differential equation for the transport of minority carriers. In this paper, we calculated the spectral function of the photoinduced charge carrier distribution based on an approximation of low-level injection. Using the calculated distribution and inverse Laplace transform, the dynamics of recombination photoinduced heat sources at the surfaces of semiconducting samples were studied for pulse optical excitations of very short and very long durations. It was shown that the photoexcited charge carriers affect semiconductor heating depending on the pulse duration, velocity of surface recombination, lifetime of charge carriers, and their diffusion coefficient. Full article

Ivermectin (IVM) is a pharmaceutical antiparasitic agent with a broad range of medicinal properties that are comparable in impact to those of penicillin and aspirin. The molecule’s structural composition includes functional groups that indicate the potential for photoreactivity. However, there is a paucity of information regarding its photostability, particularly in tropical regions where parasitic diseases and intense solar radiation intersect. It would be beneficial to investigate the chemical transformation of this compound in a variety of natural aqueous environments under different irradiation sources. This knowledge gap motivated this study. Therefore, the chemical alterations of IVM were investigated in various natural aqueous media when exposed to solar radiation (UVA-Vis). In particular, an evaluation of its photostability was conducted at wavelengths of 350 and 254.5 nm. It is noteworthy that photodegradation occurred primarily at 350 nm. Additionally, IVM demonstrated photohemolytic effects on human erythrocytes, indicating phototoxicity. This suggests the presence of photoinduced mechanisms by this drug for the generation of free radicals, including singlet oxygen (¹O₂, type II mechanism), superoxide anion, and hydroxyl radical (^.O₂ and ^.OH, type I mechanism). The latter would also entail the interaction of the IVM molecule with the membrane of human red blood cells, which would signify a considerable biological impact. Furthermore, through computational calculations, potential photoproducts formed during IVM irradiation were deduced, simulating experimental conditions. Our findings contribute to an enhanced comprehension of IVM’s behavior under solar exposure, particularly in tropical contexts. Additional research is imperative to address its emerging biological activity status and potential implications for biomedical applications. Full article

Due to their ability to reversibly isomerize under the influence of external stimuli, spiropyrans represent the most interesting class of organic photochromic molecules. The photochromic properties of the isomeric forms of spiropyrans differ significantly from each other, which makes it possible to use these photochromes as sensors, optoelectronic and holographic devices, memory elements, etc. Also, an undoubted advantage of spiropyrans compared to other classes of organic photochromes is the relative ease of their preparation and chemical transformation. At the same time, modification of the structure of spiropyrans by introducing various functional groups opens up great synthetic possibilities for obtaining new photochromic molecules with various spectral-kinetic characteristics. In the development of research aimed at expanding the boundaries of the use of spirophotochromic compounds, in order to obtain new light-controlled materials with different characteristics, as well as to study the influence of functional groups in the spirophotochromic molecule on the spectral and photochromic properties, we have synthesized a new spiropyran. In this work, we synthesized a new salt of photochromic spiropyran containing various functional groups (–CHO, –NO₂, –OCH₃, –(CH₂)₅N(CH₃)₂*HBr), capable of reversibly responding to external influences. Photoinduced transformations and the spectral and kinetic characteristics of the synthesized compound were studied. Full article

The photo-induced aerobic oxidation of C–H bonds has become an increasingly valuable strategy in organic synthesis, offering a green and efficient method for introducing oxygen into organic molecules. The utilization of molecular oxygen as an oxidant, coupled with visible-light photocatalysis, has gained significant attention due to its sustainability, atom economy, and environmentally benign nature. This review highlights the recent advancements in the field, focusing on the development of metal-free and transition-metal-based photocatalytic systems and novel photosensitizers capable of promoting selective C–H bond oxidation. The mechanistic pathways involved in various substrate oxidations, including benzylic, alkyl, alkene, and alkyne C–H bond transformations, are discussed. This review concludes with insights into the potential for integrating photocatalysis with renewable energy sources, positioning photo-induced aerobic oxidation as a cornerstone of sustainable chemical processes. Full article

Maleimides serve as crucial components in various synthetic processes and are of significant interest to researchers in bioorganic chemistry and biotechnology. Although thermal reactions involving maleimides have been studied extensively, light-mediated reactions with maleimides remain relatively underutilized. This review focuses on understanding the behavior of maleimides in their excited state, particularly their role as synthetic scaffolds for excited-state reactions. Specific emphasis is placed on the diverse photoreactions involving maleimides and photophysical evaluation from our research group. Full article

For the first time, the Z₁ and Z₂ defects with closely spaced energy levels having negative-U properties are revealed in high-purity semi-insulating (HPSI) 4H-SiC using Laplace-transform photoinduced transient spectroscopy (LPITS). In this material, after switching off the optical trap-filling pulse, either the one-electron or the two-electron thermally stimulated emission from these defects is observed at temperatures 300–400 K. It is found that the former corresponds to the Z₁^0/+ and Z₂^0/+ transitions with the activation energies of 514 and 432 meV, respectively, and the latter is associated with the Z₁^−/+ and Z₂^−/+ transitions with the activation energies of 592 meV and 650 meV, respectively. The Z₁ and Z₂ defect concentrations are found to increase from 2.1 × 10¹³ to 2.2 × 10¹⁴ cm⁻³ and from 1.2 × 10¹³ to 2.7 × 10¹⁴ cm⁻³, respectively, after the heat treatment of HPSI 4H-SiC samples at 1400 °C for 3 h in Ar ambience. Using the electrical trap-filling pulse, only the thermal two-electron emission from each defect was observed in the epitaxial 4H-SiC through Laplace-transform deep level transient spectroscopy (LDLTS). The activation energies for this process from the Z₁ and Z₂ defects are 587 and 645 meV, respectively, and the defect concentrations are found to be 6.03 × 10¹¹ and 2.64 × 10¹² cm⁻³, respectively. It is postulated that the Z₁ and Z₂ defects are the nearest-neighbor divacancies involving the carbon and silicon vacancies located at mixed, hexagonal (h), and quasi-cubic (k) lattice sites. Full article

A visible-light photochromic hybrid film was synthesized based on combining phosphomolybdic acid (PMoA) with the polythiophene (PTh) matrix. The microstructure and photochromic properties of the materials were analyzed through atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and ultraviolet-visible spectra (UV-vis). According to FTIR spectra, the geometries of PMoA and PTh were well preserved in hybrid film and there exists a strong interaction at the interface of PMoA and PTh. The XPS spectra revealed the change in the chemical microenvironment and the reduction of Mo⁶⁺ atoms in the photoreduction reaction. Under visible light irradiation, the composite film changed from transparent to blue and deepened gradually, generating heteropoly blue. The hybrid film also shows reversibility in the presence of oxygen. The results indicated that the photochromic reaction was inconsistent with photoinduced electron transfer mechanism. Full article

The formation of intrinsic point defects in the N-sublattice of semi-insulating Mg-doped GaN crystals grown by the ammonothermal method (SI AT GaN:Mg) was investigated for the first time. The grown-in defects produced by the displacement of nitrogen atoms were experimentally observed as deep traps revealed by the Laplace transform photoinduced transient spectroscopy in the compensated p-type crystals with the Mg concentrations of 6 × 10¹⁸ and 2 × 10¹⁹ cm⁻³ and resistivities of ~10¹¹ Ωcm and ~10⁶ Ωcm, respectively. In both kinds of materials, three closely located traps with activation energies of 430, 450, and 460 meV were revealed. The traps, whose concentrations in the stronger-doped material were found to be significantly higher, are assigned to the (3+/+) and (2+/+) transition levels of nitrogen vacancies as well as to the (2+/+) level of nitrogen split interstitials, respectively. In the material with the lower Mg concentration, a middle-gap trap with the activation energy of 1870 meV was found to be predominant. The results are confirmed and quantitatively described by temperature-dependent Hall effect measurements. The mechanism of nitrogen atom displacement due to the local strain field arising in SI AT GaN:Mg is proposed and the effect of the Mg concentration on the charge compensation is discussed. Full article

Chromium complexes containing a bis(diphenylphosphino) ligand have attracted significant interest over many years due to their potential as active catalysts for ethylene oligomerisation when combined with suitable co-catalysts such as triethylaluminium (TEA) or methylaluminoxane (MAO). While there has been considerable attention devoted to the possible reaction intermediates and the nature of the Cr oxidation states involved, the potential UV photoactivity of the Cr(I) complexes has so far been overlooked. Therefore, to explore the photoinduced transformations of bis(diphenylphosphino) stabilized Cr(I) complexes, we used continuous-wave (CW) EPR to study the effects of UV radiation on a cationic [Cr(CO)₄(dppp)]⁺[Al(OC(CF₃)₃)₄]⁻ complex (1), where dppp represents the 1,3 bis-(diphenylphosphino)propane ligand, Ph₂P(C₃H₆)PPh₂. Our preliminary investigations into the photochemistry of this complex revealed that [Cr(CO)₄(dppp)]⁺ (1) can be readily photo-converted into an intermediate mer-[Cr(CO)₃(κ¹-dppp)(κ²-dppp)]⁺ complex (2) and eventually into a trans-[Cr(CO)₂(dppp)₂]⁺ complex (3) in solution at room temperature under UV-A light. Here, we show that the intermediate species (2) involved in this transformation can be identified by EPR at much lower temperature (140 K) and at a specific wavelength (highlighting the wavelength dependency of the reaction). In addition, small amounts of a ‘piano-stool’-type complex, namely [Cr(CO)₂(dppp-η⁶-arene)]⁺ (4), can also be formed during the photoconversion of [Cr(CO)₄(dppp)]⁺ using UV-A light. There was no evidence for the formation of the [Cr(L-bis-η⁶-arene)]⁺ complex (5) in these UV irradiation experiments. For the first time, we also evidence the formation of a 1-hexene coordinated [Cr(CO)₃(dppp)(1-hexene)]⁺ complex (6) following UV irradiation of [Cr(CO)₄(dppp)]⁺ in the presence of 1-hexene; this result demonstrates the unprecedented opportunity for exploiting light activation during Cr-driven olefin oligomerisation catalysis, instead of expensive, difficult-to-handle, and hazardous chemical activators. Full article

Previous biological tests have shown that some resveratrol analogs exhibited significant antioxidative and cholinesterase inhibitory potential, as evidenced by lower IC₅₀ values compared to the established standards, resveratrol and galantamine, respectively. Photochemical transformations were made in parallel on these compounds in the presence of porphyrin photocatalysts in batch and microreactor, showing the significant advantage of flow photochemistry concerning productivity, selectivity, and yields. In this research, the products of photocatalysis and direct irradiation (photolysis) of resveratrol analogs were compared to elucidate how the types and ratios of the products depend on the excitation energy, to reveal the effects of the substituent on the photoinduced reactions and to rationalize experimentally and computationally the nature and ratio of the obtained products. Thus, two main paths were computed in agreement with the experimental results: isomerization with the participation of triplet state intermediates to yield the experimentally detected cis-isomers and subsequent cyclization following a pathway not available for the trans-isomers. The investigation of five model compounds confirmed the advantages of the flow photoreactor in the photochemical reactions of heterocyclic resveratrol analogs. Full article

Heterogeneous photocatalysts incorporating metal halide perovskites (MHPs) have garnered significant attention due to their remarkable attributes: strong visible-light absorption, tuneable band energy levels, rapid charge transfer, and defect tolerance. Additionally, the promising optical and electronic properties of MHP nanocrystals can be harnessed for photocatalytic applications through controlled crystal structure engineering, involving composition tuning via metal ion and halide ion variations, dimensional tuning, and surface chemistry modifications. Combination of perovskites with other materials can improve the photoinduced charge separation and charge transfer, building heterostructures with different band alignments, such as type-II, Z-scheme, and Schottky heterojunctions, which can fine-tune redox potentials of the perovskite for photocatalytic organic reactions. This review delves into the activation of organic molecules through charge and energy transfer mechanisms. The review further investigates the impact of crystal engineering on photocatalytic activity, spanning a diverse array of organic transformations, such as C–X bond formation (X = C, N, and O), [2 + 2] and [4 + 2] cycloadditions, substrate isomerization, and asymmetric catalysis. This study provides insights to propel the advancement of metal halide perovskite-based photocatalysts, thereby fostering innovation in organic chemical transformations. Full article

S- and Se-based chalcogenide glasses are intrinsically metastable and exhibit a number of photo-induced effects unique to this class of materials, reversible photostructural changes and photo-induced anisotropy being major examples. These effects are usually interpreted in terms of the formation of valence alternation pairs and ‘wrong’ bonds. In this work, using density functional theory simulations, we demonstrate for the case example of ${\mathrm{As}}_2{\mathrm{S}}_3$ that a strong decrease in the optical band gap can be achieved if a polymorphic transformation of the local structure from orpiment to that of tetradymite takes place. For the formation of the latter, the presence of lone-pair electrons in near-linear atomic configurations is crucial. Our results represent a novel approach to understanding the photo-induced structural changes in chalcogenide glasses as being due to the presence of polymorphism, and will lead to their wider use in various photonic devices. Full article