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Photochemical multivariate curve resolution models for the investigation of photochromic systems under continuous irradiation
摘要： We propose a multivariate curve resolution approach for the investigation of photochromic systems using UV-Visible spectroscopy. The incorporation of photochemical hard-models as constraints in multivariate curve resolution alternating least squares (MCR-ALS) allows extracting reaction quantum yields in situations where a complete knowledge of the system is not available. We apply this approach to the study of the photochromism of CMTE (cis-1,2-dicyano-1,2-bis(2,4,5-trimethyl-3-thienyl)ethene) under continuous monochromatic irradiation. The mechanism, involving 3 species and 2 reversible reactions, is written and translated into a kinetic constraint that can be applied to the concentration profiles within ALS. First, ambiguity of the solution obtained for photochemical model(s) is calculated and discussed for single set analysis. Multiset analysis is then proposed combining data obtained under different irradiation wavelengths to provide more reliable results. Finally, the photochemical reactivity of CMTE is widely unraveled, and some description of the mechanism observed under irradiation at 365 nm is given.
关键词： Multivariate curve resolution,Quantum yield,Hard-soft modelling,Parameter ambiguity,Photochemical reaction
更新于2025-09-23 15:23:52
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Dynamics of dissolved organic matter in a wastewater effluent-impacted Japanese urban stream: characteristics, occurrence and photoreactivity of fluorescent components
摘要： We report the results of using the excitation–emission matrix (EEM) method combined with parallel factor analysis (PARAFAC) to investigate the characteristics and occurrence of dissolved organic matter (DOM) in an urban stream impacted by effluent from a wastewater treatment plant (WWTP). The PARAFAC model divides the bulk EEM spectra into six individual fluorescent components with three humic-like components (C1–C3), two protein-like components (C4 and C5) and a wastewater-derived component (C6). In general, intensities of fluorescent components are abundant in WWTP effluent impacted samples, thus showing that such an effluent is a major source of DOM in urban rivers, but C5 is considered to have autochthonous sources within the stream. In areas where the effluent is released, the fluorescent intensity from components (except C5) gradually decreases as these components are transported downstream. However, concentrations of dissolved organic carbon remain almost constant downstream of the release area. These results would be attributed to degradation and/or modification of fluorophore. Photolysis experiments confirmed that fluorescent intensities can decrease with increase of irradiation times. C6 particularly showed a rapid photodegradation, remaining only 24.1% after 48 h photolysis. These findings would be important when assessing DOM source and water quality in aquatic environments by EEM-PARAFAC.
关键词： dissolved organic matter,excitation–emission matrix,urban river,photochemical reaction
更新于2025-09-23 15:22:29
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Blue laser-induced photochemical synthesis of CuAg nanoalloys on h-BN supports with enhanced SERS activity for trace-detection of residual pesticides on tomatoes
摘要： The copper (Cu)-based nanoalloys loaded on graphene-like nanoplates have a great promise for boosting surface-enhanced Raman scattering spectroscopy (SERS), due to low-cost Cu species in comparison with noble metals and unique additional Raman enhancement originated from two-dimensional (2D) supports. Herein, we report an ingenious strategy to load highly dense and monodisperse CuAg nanoalloys (NAs) on hexagonal boron nitride (h-BN) by blue laser (405 nm) -induced photochemical reaction. Without the aid of any complex auxiliary reagents, the co-reduction of Cu and Ag ions is driven by photon-excited electron on semiconductor h-BN, resulting in the coalescence and overgrowth of “clean” CuAg NAs. As expected, the proposed h-BN/CuAg NAs provide ultrahigh SERS activity with the limit of detections (LODs) of crystal violet (CV) at femtomole level (~10?16 M), thiram and tricyclazole at pico-molar (10?12 M) and nanomolar levels (10?9 M), respectively. Most importantly, the as-prepared h-BN/CuAg NAs were also directly combined with polyethylene terephthalate (PET) by simple dripping and drying processes to form uniform flexible substrates. The low-cost Cu-based flexible substrates can be used to realize the ultrasensitive SERS detection of residual tricyclazole on tomato surfaces, thus facilitating the widespread precise assessment of pesticide residues in various practical applications.
关键词： CuAg nanoalloys,Pesticide detection,SERS analyses,Flexible SERS substrate,Photochemical reaction
更新于2025-09-23 15:19:57
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Automated generation of photochemical reaction data by transient flow experiments coupled with online HPLC analysis
摘要： The automated generation and acquisition of large-scale reaction data is crucial to recent progress in organic synthesis and pharmaceutical process development. To follow reaction progress over time, time-series of reaction data can be generated by transient flow experiments, which allow to investigate reactions in a short transient period between two steady-state operations of a continuous-flow microreactor. The acquisition of analytical data in this short transient period, however, remains challenging since separation techniques like HPLC – though able to cope with highly complex samples – are typically regarded as too slow for the required acquisition rates. We break the longstanding coupling between the timescale of the continuous-flow experiment and the acquisition rate of the analytical method with the introduction of the multiple heart-cutting interface, which allows for sample parking prior to sample analysis. Transient flow experiments are presented for the [2+2] cycloaddition between 1-methyl-2-quinolinone and coumarin. Competing homo- and crossdimerization reactions are quantitatively investigated in systematic reaction parameter screenings with more than 400 data points. Results provide precious insights into this complex photochemical system – not only for reaction optimization, but also for a more profound understanding of the involved chemical processes.
关键词： quinolinone,online HPLC analysis,photochemical reaction data,homo- and crossdimerization reactions,[2+2] cycloaddition,coumarin,automated generation,transient flow experiments
更新于2025-09-23 15:19:57
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Using density based indexes to characterize excited states evolution
摘要： With the aim of offering new computational tools helping in the description of photochemical reactions and phenomena occurring at the excited state, we present in this work the capability of a density based index (Π) in locating decay channels from higher to lower excited states. The Π index, previously applied to disclose non-radiative decay channels from the first excited state to the ground state, is very simple in its formulation and can be evaluated, practically with no extra computational cost, and coupled to any quantum method able to provide excited states densities. Indeed, this index relies only on the knowledge of energetics and electron densities of the different electronic states involved in the decay. In the present work, we show the proficiency of the Π index in the general case of decay between excited states by applying it to two model systems well characterized both theoretically and experimentally. In both cases, this descriptor was successful in spotting the regions where excited states are more likely to decay, thus suggesting its potential interest for further application in the design of new compounds.
关键词： density based indexes,excited states decay and crossing,funnel regions,quantum methods,photochemical reaction pathways
更新于2025-09-23 15:19:57
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A sensitive photochemical reaction-capacitively coupled contactless conductivity detection system for HPLC and its application in determination of Cyclosporin A
摘要： High performance liquid chromatography (HPLC) post-column photochemical reaction (PR) coupled capacitively coupled contactless conductivity detector (C4D) was used for the first time in analysis of weak ultraviolet (UV)-absorbing, non-fluorescence and nonpolar compound. A series of conditions including the radiation power of light source, the length of the reaction tube and the thickness of detection tube were investigated. HPLC-PR-C4D system was successfully applied to the determination of Cyclosporin A (CsA). Consequently, under optimal conditions, the detection system exhibited a detection limit of 0.04 μg/mL and wide linear range from 0.5 μg/mL to 100 μg/mL for CsA detection. Application of the HPLC-PR- C4D system to pharmaceutical formulation and biological samples revealed the system developed maybe reliably applied to clinical studies.
关键词： Photochemical reaction,Cyclosporin A,HPLC,Capacitively coupled contactless conductivity detection,Application
更新于2025-09-11 14:15:04
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Photoactive Nanocarriers for Controlled Delivery
摘要： Photoactive nanocarriers have emerged as robust and minimally invasive systems for the on-demand delivery of active payloads. The easy manipulation offered by light irradiation as an external stimulus allows precise spatiotemporal control of payload release based on the time, intensity, location, and wavelength of light exposure. Compared to conventional passive delivery systems, photoactive nanocarriers offer the possibility of tailoring the release kinetics of the encapsulated active molecules, which is of considerable clinical relevance for targeted delivery to desired sites of interest. In this progress report, the recent advances in the design and fabrication of photoactive nanoplatforms based on three main modes of mechanisms: photochemical reactions, the photothermal effect, and photosensitization mechanism mediated by reactive oxygen species are highlighted. The combination of these mechanisms provides additional flexibility for the effective delivery of therapeutics and improved synergistic therapeutic effects. Finally, challenges in future perspectives on the development of photoactive nanomaterials and their medical translation are discussed.
关键词： photothermal effects,photosensitization,photochemical reaction,nanocarriers,controlled delivery
更新于2025-09-11 14:15:04
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Numerical Demonstration of In-Tube Liquid-Column Migration Driven by Photoisomerization
摘要： Droplet manipulation by light-induced isomerization was numerically demonstrated and investigated regarding the driving mechanism. Such a non-invasive manipulation of a droplet in a microchannel can be realized, for example, by the use of watery solution of photoresponsive surfactant that exhibits the isomerization. Due to variable fluid properties between the cis and trans isomers, one-side light irradiation on a liquid column in a tube would lead to some kind of imbalance between the two ends of the liquid column and then drive droplet migration. The present numerical simulations of air–liquid two-phase flow and its scalar transport of the isomer, considering the variable static contact angle, agreed quantitatively with the experimental results in terms of the migration speed. This fact supports the contention that the droplet migration is more likely to be driven by an imbalance in the wettability, or the contact angle. The migration speed was found to be less dependent on the liquid-column length, but proportional to the tube diameter.
关键词： photochemical reaction,non-invasive control,wettability,surface tension,microfluidics,computational fluid dynamics,lab-on-a-chip,droplet manipulation,two-phase flow,photoresponsible surfactant
更新于2025-09-09 09:28:46