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1.
Sci Total Environ ; 792: 148543, 2021 Oct 20.
Artigo em Inglês | MEDLINE | ID: mdl-34465035

RESUMO

The preparation of an adsorbent with highest efficiency, selectivity and stability is usually a challenging task. Herein, we prepared a thio functionalized layered double hydroxide (LDH) denoted as S2O4 LDH by intercalating a strong reducing agent (S2O42-) in the interlayers of trimetallic LDH and was applied to capture vanadium (V(V)) oxyanions from aqueous medium of diverse conditions. The successful preparation of the adsorbent was first confirmed using XRD, FTIR, EDX and CHS analyses. The results revealed that the modified LDH showed excellent performance at a wider pH range which can avoid the tedious work of adjusting pH in actual industrial wastewater treatment. The adsorption capacity was increased with temperature and obtained 379.55 mg/g at 323 K comparing to 112.3 mg/g at 293 K. The adsorption isotherm was better fitted to Langmuir model which suggested monolayer adsorption behavior. At lower temperature (293 K), the sorption kinetics were fitted to a pseudo-first order reaction model which implied physisorption reaction while at higher temperatures (303 and 323 K), the reaction order fitted to pseudo-second order reaction model which highlighted the chemisorption reaction mechanism. As confirmed using XRD, FTIR, EDX and XPS instrumental techniques, the dominant removal mechanism of V(V) involved ion-exchange and partial reduction reactions to nontoxic and less soluble V(IV) and V(III) species due to the low valent sulfur group and followed adsorption in S2O4 LDH. The prepared adsorbent showed very good selectivity towards V(V) in the presence of different co-existing ions both in synthetic wastewater and spiked real water samples. This novel adsorbent also exhibited high recyclability and obtained >90.0% removal of V(V) after four consecutive adsorption-desorption cycles due to the unique memory effect of the LDH. We believe that this strategy provides a new direction to find highly efficient and selective materials for capturing vanadium ions from wastewater of diverse conditions.


Assuntos
Vanádio , Poluentes Químicos da Água , Adsorção , Elétrons , Concentração de Íons de Hidrogênio , Hidróxidos , Cinética , Sulfetos , Água , Poluentes Químicos da Água/análise
2.
Chemosphere ; 283: 131278, 2021 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-34467945

RESUMO

Production of MCFAs (Medium-chain fatty acids) from simple substrate (i.e., ethanol and acetate) and WAS with chain elongation microbiome was investigated in this study. The results showed that rapid production of MCFAs was observed when simple substrate was utilized. 1889 mg/L of caproate and 3434 mg/L of butyrate were achieved after 10 d's reaction. H2 proportion in the headspace could reach as high as 10.1% on day 8 and then declined quickly. However, when WAS was used, the bacterial consortia was not able to hydrolyze WAS efficiently, which resulted in poor MCFAs production performance. Presence of ethanol could improve the hydrolysis process to a limited degree, which resulted in solubilization of a small fraction of protein and carbohydrate. Around 33.8% and 36.9% of the total detected electrons on day 6 in the 50 mM and 100 mM tests were extracted from WAS respectively. Those results indicate that the chain elongation microbial consortia tended to receive electrons form ethanol directly other than the complex WAS.


Assuntos
Etanol , Esgotos , Elétrons , Ácidos Graxos , Fermentação
3.
Chemosphere ; 283: 131282, 2021 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-34467952

RESUMO

Carbon materials have been used to activate peroxydisulfate (PDS) for the degradation of organic pollutants. The mechanism involved, especially whether radicals are formed in these processes, is still under debate. In this research, multi-walled carbon nanotube (MWCNT) was employed to activate PDS for the removal of 2,4-dichlorophenol (2,4-DCP). The effects of solution pH, PDS concentration, 2,4-DCP concentration, and MWCNT loading on the degradation of 2,4-DCP were investigated. The mechanism was explored via radical scavenging experiments, electron paramagnetic resonance (EPR) and MWCNT surface characterization. The results showed that the rate of 2,4-DCP degradation increased with the increasing solution pH, PDS concentration and MWCNT loading. The presence of OH and SO4- signals in EPR studies, no inhibitory effect in radical scavenging experiments, and the chlorination of MWCNT observed by X-ray photoelectron spectroscopy (XPS) suggested that surface reactions involving both surface-bound radicals and direct electron transfer were responsible for 2,4-DCP degradation. Reusability tests showed that the surface sites responsible for surface-bound radical formation were poisoned after PDS activation, while those responsible for direct electron transfer remained active after five cycles. This research provided the first in-depth insights for the dual roles of MWCNT in the PDS activation process.


Assuntos
Clorofenóis , Nanotubos de Carbono , Elétrons , Oxirredução
4.
Sensors (Basel) ; 21(17)2021 Aug 30.
Artigo em Inglês | MEDLINE | ID: mdl-34502730

RESUMO

FLASH radiotherapy is an emerging radiotherapy technique used to spare normal tissues. It employs ultra-high dose rate radiation beams over 40 Gy/s, which is significantly higher than those of conventional radiotherapy. In this study, a fiber-optic radiation sensor (FORS) was fabricated using a plastic scintillator, an optical filter, and a plastic optical fiber to measure the ultra-high dose rate electron beams over 40 Gy/s used in FLASH radiotherapy. The radiation-induced emissions, such as Cherenkov radiation and fluorescence generated in a transmitting optical fiber, were spectrally discriminated from the light outputs of the FORS. To evaluate the linearity and dose rate dependence of the FORS, the outputs of the fiber-optic radiation sensor were measured according to distances from an electron scattering device, and the results were compared with those of an ionization chamber and radiochromic films. Finally, the percentage depth doses were obtained using the FORS as a function of depth in a water phantom. This study found that ultra-high dose rate electron beams over 40 Gy/s could be measured in real time using a FORS.


Assuntos
Elétrons , Fibras Ópticas , Tecnologia de Fibra Óptica , Imagens de Fantasmas , Radiometria , Dosagem Radioterapêutica
5.
Environ Pollut ; 286: 117564, 2021 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-34438491

RESUMO

Deca-brominated diphenyl ether (BDE-209) is shown to be persistent in soil and it's urgent to find an effective method to remove BDE-209 from contaminated soil. In this study, the investigation of BDE-209 degradation in three different rice-vegetable rotation soils induced by electron beam (E-beam) irradiation under flooded and non-flooded conditions was conducted. The reductive efficiency of 14C-BDE209 reached the highest level at 50 kGy and the values in flooded soils of rice-eggplant rotation soil (RES), rice-peanut soil (RPS), and rice-chili pepper soil (RCS) were 93.5%, 87.2%, and 73.8%, respectively. The reductive efficiencies in non-flooded soils of RES, RPS, and RCS were 73.4%, 81.0%, and 78%, respectively. The D0.5 values (dose required for reducing 50% BDE-209) of BDE-209 in non-flooded soils were lower than those in flooded soils, suggesting greater degradation efficiency of BDE-209 in non-flooded soils than in flooded soils. The BDE-209 was degraded into higher-brominated PBDEs and lower-brominated PBDEs by E-beam irradiation. The results demonstrate that BDE-209 in the soil can be degraded by E-beam irradiation, non-flooded condition is better than flooded condition for the removal of BDE-209, and the main degradation mechanism of BDE-209 by E-beam irradiation is debromination. This study provides a rapid and effective method for degrading BDE-209 that is persistent in soils, and has important implications for the remediation of soil contaminated by PBDEs in and around E-waste dismantling areas.


Assuntos
Oryza , Poluentes do Solo , Elétrons , Éteres Difenil Halogenados/análise , Rotação , Solo , Poluentes do Solo/análise , Verduras
6.
Int J Mol Sci ; 22(15)2021 Jul 23.
Artigo em Inglês | MEDLINE | ID: mdl-34360644

RESUMO

The complex physical and chemical reactions between the large number of low-energy (0-30 eV) electrons (LEEs) released by high energy radiation interacting with genetic material can lead to the formation of various DNA lesions such as crosslinks, single strand breaks, base modifications, and cleavage, as well as double strand breaks and other cluster damages. When crosslinks and cluster damages cannot be repaired by the cell, they can cause genetic loss of information, mutations, apoptosis, and promote genomic instability. Through the efforts of many research groups in the past two decades, the study of the interaction between LEEs and DNA under different experimental conditions has unveiled some of the main mechanisms responsible for these damages. In the present review, we focus on experimental investigations in the condensed phase that range from fundamental DNA constituents to oligonucleotides, synthetic duplex DNA, and bacterial (i.e., plasmid) DNA. These targets were irradiated either with LEEs from a monoenergetic-electron or photoelectron source, as sub-monolayer, monolayer, or multilayer films and within clusters or water solutions. Each type of experiment is briefly described, and the observed DNA damages are reported, along with the proposed mechanisms. Defining the role of LEEs within the sequence of events leading to radiobiological lesions contributes to our understanding of the action of radiation on living organisms, over a wide range of initial radiation energies. Applications of the interaction of LEEs with DNA to radiotherapy are briefly summarized.


Assuntos
Dano ao DNA , DNA/química , DNA/efeitos da radiação , Elétrons/efeitos adversos , Animais , Humanos
7.
Talanta ; 234: 122657, 2021 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-34364466

RESUMO

In this work, we report the construction of a direct electron transfer (DET) biosensor based on NAD-dependent formaldehyde dehydrogenase from Pseudomonas sp. (FDH) immobilized on the gold nanoparticle-modified gold electrode. To the best of our knowledge, a DET for FDH was achieved for the first time - the oxidation of formaldehyde started at a low electrode potential of -190 mV vs. Ag/AgCl and reached a maximum current density of 1100 nA cm-2 at 200 mV vs. Ag/AgCl. Also, the designed electrode was insensitive to substrate inhibition (in comparison to the free enzyme) and operated in solutions with formaldehyde concentrations up to 10 mM. The electrode was used and characterized as a mediatorless biosensor for the detection of formaldehyde. The biosensor demonstrated a limit of detection (0.05 mM), linear range from 0.25 to 2.0 mM, the sensitivity of 178.9 nA mM cm-2, high stability and selectivity. The biosensor has been successfully tested for the determination of added formaldehyde concentration in river water samples, thus the developed electrode could be applied for a fast, inexpensive and simple measurement of formaldehyde in various media.


Assuntos
Técnicas Biossensoriais , Nanopartículas Metálicas , Aldeído Oxirredutases , Eletrodos , Elétrons , Enzimas Imobilizadas , Formaldeído , Ouro , Rios , Água
8.
Nat Commun ; 12(1): 5092, 2021 08 24.
Artigo em Inglês | MEDLINE | ID: mdl-34429430

RESUMO

Development of a versatile, sustainable and efficient photosynthesis system that integrates intricate catalytic networks and energy modules at the same location is of considerable future value to energy transformation. In the present study, we develop a coenzyme-mediated supramolecular host-guest semibiological system that combines artificial and enzymatic catalysis for photocatalytic hydrogen evolution from alcohol dehydrogenation. This approach involves modification of the microenvironment of a dithiolene-embedded metal-organic cage to trap an organic dye and NADH molecule simultaneously, serving as a hydrogenase analogue to induce effective proton reduction inside the artificial host. This abiotic photocatalytic system is further embedded into the pocket of the alcohol dehydrogenase to couple enzymatic alcohol dehydrogenation. This host-guest approach allows in situ regeneration of NAD+/NADH couple to transfer protons and electrons between the two catalytic cycles, thereby paving a unique avenue for a synergic combination of abiotic and biotic synthetic sequences for photocatalytic fuel and chemical transformation.


Assuntos
Etanol/química , Fotossíntese/fisiologia , Luz Solar , Catálise , Corantes , Elétrons , Hidrogênio/química , Hidrogenase/química , Cinética , Ligantes , Simulação de Acoplamento Molecular
9.
Water Res ; 202: 117490, 2021 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-34364064

RESUMO

Geobacter, as a typical electroactive microorganism, is the "engine" of interspecies electron transfer (IET) between microorganisms. However, it does not have a dominant position in all natural environments. It is not known what performs a similar function as Geobacter in coastal zones. Metagenomic and metatranscriptomic analysis revealed that Desulfovibrio and Methanobacterium species were the most abundant in electrochemically active aggregates. Metatranscriptomic analysis showed that Desulfovibrio species highly expressed genes for ethanol metabolism and extracellular electron transfer involving cytochromes, pili and flagella. Methanobacterium species in the aggregates also expressed genes for enzymes involved in reducing carbon dioxide to methane. Pure cultures demonstrated that the isolated Desulfovibrio sp. strain JY contributed to aggregate conductivity and directly transferred electrons to Methanothrix harundinacea, which is unable to use H2 or formate. Most importantly, further coculture studies indicated that Methanobacterium strain YSL might directly accept electrons from the Desulfovibrio strain JY for the reduction of carbon dioxide to methane in the aggregate. This finding suggested that the possibility of DIET by Desulfovibrio similar to Geobacter species in conductive methanogenic aggregates can not be excluded.


Assuntos
Desulfovibrio , Geobacter , Desulfovibrio/genética , Transporte de Elétrons , Elétrons , Geobacter/genética , Metano , Methanobacterium/genética
10.
Zhongguo Yi Xue Ke Xue Yuan Xue Bao ; 43(3): 429-434, 2021 Jun 30.
Artigo em Chinês | MEDLINE | ID: mdl-34238420

RESUMO

Objective To design a novel automatic dispensing and injecting system of positron radiopharmaceuticals,for precise dose dispensing,simplified operation,and reduction of occupational radiation exposure. Methods The automatic dispensing and injecting system was fabricated with tungsten alloy as the shielding material.The performance and radiation protection of the device were assessed. Results The total time of injection using the automatic dispensing and injecting system was about 60 s.The ratio of successful injection in stability test was 100%.The deviation of the dispensing dose with the system was ≤3%.With the tungsten alloy shield(40 mmPb of the cabinet,60 mmPb of the countertop,15 mmPb of the protective shield,and 50 mmPb of the inbuilt jar for radiopharmaceuticals),the average dose rate at 30 cm from the device was 1.44 µSv/h,and the radiation dose at the operator's extremity was reduced by 99%. Conclusions This automatic dispensing and injecting system of positron radiopharmaceuticals is easy to operate with precise dispensing dose.It is safe and meets the requirements of radiation protection.


Assuntos
Exposição Ocupacional , Proteção Radiológica , Elétrons , Exposição Ocupacional/análise , Doses de Radiação , Compostos Radiofarmacêuticos
11.
Molecules ; 26(13)2021 Jun 28.
Artigo em Inglês | MEDLINE | ID: mdl-34203564

RESUMO

The work is devoted to the study of the complementarity of the electronic structures of the ligands and SARS-CoV-2 RNA-dependent RNA polymerase. The research methodology was based on determining of 3D maps of electron densities of complexes using an original quantum free-orbital AlteQ approach. We observed a positive relationship between the parameters of the electronic structure of the enzyme and ligands. A complementarity factor of the enzyme-ligand complexes has been proposed. The console applications of the AlteQ complementarity assessment for Windows and Linux (alteq_map_enzyme_ligand_4_win.exe and alteq_map_enzyme_ligand_4_linux) are available for free at the ChemoSophia webpage.


Assuntos
RNA-Polimerase RNA-Dependente de Coronavírus/química , Elétrons , SARS-CoV-2/enzimologia , Algoritmos , Amidas/química , Antivirais/química , Ligantes , Estrutura Molecular , Ligação Proteica , Pirazinas/química , Ribonucleosídeos/química
12.
Biomaterials ; 275: 120934, 2021 08.
Artigo em Inglês | MEDLINE | ID: mdl-34217019

RESUMO

Intersystem crossing (ISC) is of great significance in photochemistry, and has a decisive influence on the properties of photosensitizers (PSs) for use in photodynamic therapy (PDT). However, the rationally design PSs with efficient ISC processes to implement superb reactive oxygen species (ROS) production is still a very challenging work. In this contribution, we described how a series of high-performance PSs were constructed through electron acceptor and donor engineering by integrating the smaller singlet-triplet energy gap (ΔEST) and larger spin-orbit coupling (SOC)-beneficial functional groups into the PS frameworks. Among the yielded various PSs, TaTIC was confirmed as the best candidate for application in PDT, which was due to its most outstanding ROS generation capability, bright near-infrared (NIR) fluorescence with peak over 840 nm, as well as desired aggregation-induced emission (AIE) features. Importantly, the ROS generation efficiency of TaTIC was even superior to that of some popularly used PSs, including the most reputable PS of Rose Bengal. In order to further extend therapeutic applications, TaTIC was encapsulated with biocompatible amphiphilic matrix and formulated into water-dispersed nanoparticles (NPs). More excitedly, the as-prepared TaTIC NPs gave wonderful PDT performance on tumor-bearing mouse model, actualizing complete tumor elimination outcomes. Coupled with excellent biosecurity, TaTIC NPs would be a promising theranostic agent for practical clinical application.


Assuntos
Neoplasias , Fotoquimioterapia , Animais , Elétrons , Camundongos , Neoplasias/tratamento farmacológico , Fármacos Fotossensibilizantes/uso terapêutico , Espécies Reativas de Oxigênio
13.
Phys Med ; 88: 71-85, 2021 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-34198025

RESUMO

PURPOSE: To develop a particle transport code to compute w-values and stopping power of swift ions in liquid water and gases of interest for reference dosimetry in hadrontherapy. To analyze the relevance of inelastic and post-collisional processes considered. METHODS: The Monte Carlo code MDM was extended to the case of swift ion impact on liquid water (MDM-Ion). Relativistic corrections in the inelastic cross sections and the post-collisional Auger emission were considered. The effects of introducing different electronic excitation cross sections were also studied. RESULTS: The stopping power of swift ions on liquid water, calculated with MDM-Ion, are in excellent agreement with recommended data. The w-values show a strong dependence on the electronic excitation cross sections and on the Auger electron emission. Comparisons with other Monte Carlo codes show the relevance of both the processes considered and of the cross sections employed. W and w-values for swift electron, proton, and carbon ions calculated with the MDM and MDM-Ion codes are in very close agreement with each other and with the 20.8 eV experimental value. CONCLUSION: We found that w-values in liquid water are independent of ion charge and energy, as assumed in reference dosimetry for hadrontherapy from sparse experimental results for electron and ion impact on gases. Excitation cross sections and Auger emission included in Monte Carlo codes are critical in w-values calculations. The computation of this physical parameter should be used as a benchmark for micro-dosimetry investigations, to assess the reliability of the cross sections employed.


Assuntos
Elétrons , Prótons , Íons , Método de Monte Carlo , Reprodutibilidade dos Testes , Água
14.
Nano Lett ; 21(13): 5516-5521, 2021 07 14.
Artigo em Inglês | MEDLINE | ID: mdl-34228455

RESUMO

We present the discovery of a charge density wave (CDW) ground state in heavily electron-doped molybdenum disulfide (MoS2). This is the first observation of a CDW in any d2 (column 6) transition metal dichalcogenide (TMD). The band structure of MoS2 is distinct from the d0 and d1 TMDs in which CDWs have been previously observed, facilitating new insight into CDW formation. We demonstrate a metal-insulator transition at 85 K, a 25 meV gap at the Fermi level, and two distinct CDW modulations, (2√3 × 2√3) R30° and 2 × 2, attributable to Fermi surface nesting (FSN) and electron-phonon coupling (EPC), respectively. This simultaneous exhibition of FSN and EPC CDW modulations is unique among observations of CDW ground states, and we discuss this in the context of band folding. Our observations provide a route toward the resolution of controversies surrounding the origin of CDW modulations in TMDs.


Assuntos
Elétrons , Molibdênio , Dissulfetos
15.
Anal Chem ; 93(29): 10084-10089, 2021 07 27.
Artigo em Inglês | MEDLINE | ID: mdl-34264066

RESUMO

We report for the first time on in situ transduction of electrochemical responses of ion-selective electrodes, operating under non-zero-current conditions, to emission change signals. The proposed novel-type PVC-based membrane comprises a dispersed redox and emission active ion-to-electron transducer. The electrochemical trigger applied induces a redox process of the transducer, inducing ion exchange between the membrane and the solution, resulting also in change of its emission spectrum. It is shown that electrochemical signals recorded for ion-selective electrodes operating under voltammetric/coulometric conditions correlate with emission intensity changes recorded in the same experiments. Moreover, the proposed optical readout offers extended linear response range compared to electrical signals recorded in voltammetric or coulometric mode.


Assuntos
Elétrons , Eletrodos Íon-Seletivos , Eletrodos , Oxirredução
16.
Chem Pharm Bull (Tokyo) ; 69(7): 608-611, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34193709

RESUMO

The coumarin skeleton has been a focus of attention for many years, and its fluorescence properties vary depending on the substituents. Fluorescent coumarin derivatives are useful tools for many strategies have been developed for their synthesis. Although 7-diethylaminocoumarin has excellent fluorescence properties, it is unstable. We have developed a facile strategy for the synthesis of 7-diethylaminocoumarin derivatives by increasing the electrophilicity of the ynone moiety to promote nucleophilic addition reactions and cyclization. The reaction tolerates a variety of substitutions at the 4-position.


Assuntos
Cumarínicos/química , Ciclização , Elétrons , Corantes Fluorescentes/química , Espectrometria de Fluorescência
17.
Biosens Bioelectron ; 191: 113475, 2021 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-34246895

RESUMO

A signal enhancement photoelectrochemical (PEC) immunoassay system induced by the composite (PTCs@Au) of electron donor-acceptor with Schottky heterojunction was designed. Carcinoembryonic antigen (CEA) was selected as a model target. Initially, the capture anibody (Ab1) was linked to gold nanoparticles electrodeposited on glassy carbon electrode and sealed by bovine serum albumin. Meanwhile, the organic semiconductor (PTCs) with the structure of electron donor-acceptor was synthetized from perylene tetracarboxylic dianhydride (acceptor) and dopamine (donor) via amidation reaction. Then PTCs@Au composite with Schottky heterojunction was formed through gold nanoparticles in situ reduction and functionalization with PTCs. Next, the detection antibody was labeled by PTCs@Au composite (Ab2-PTCs@Au) as an immuno-probe. The PTCs@Au was introduced via sandwich immune reaction leading to enhancement PEC signal without additional electron donor nor acceptor for achieving quantitative detection of CEA under external light. The proposed immunoelectrode showed dynamic ranges of 0.5 fg mL-1 to 10 pg mL-1 and 10 pg mL-1 to 1 µg mL-1 with the detection limit of 0.17 fg mL-1. In addition, this PEC strategy with acceptable selectivity and stability can be potentially applied to detect other targets by choosing appropriate target recognition unit.


Assuntos
Técnicas Biossensoriais , Nanopartículas Metálicas , Antígeno Carcinoembrionário , Técnicas Eletroquímicas , Elétrons , Ouro , Imunoensaio , Limite de Detecção
18.
Artigo em Inglês | MEDLINE | ID: mdl-34284694

RESUMO

Arsenic (As) mobilization in alluvial aquifers is facilitated by microbially catalyzed redox transformations that depend on the availability of electron acceptors (EAs). In this study, the response of an As-contaminated groundwater microbial community from West Bengal, India towards varied EAs was elucidated through microcosm based 16S rRNA gene amplicon sequencing. Acinetobacter, Deinococcus, Nocardioides, etc., and several unclassified bacteria (Ignavibacteria) and archaea (Bathyarchaeia, Micrarchaeia) previously not reported from As-contaminated groundwater of West Bengal, characterized the groundwater community. Distinct shifts in community composition were observed in response to various EAs. Enrichment of operational taxonomic units (OTUs) affiliated to Denitratisoma (NO3-), Spirochaetaceae (Mn4+), Deinococcus (As5+), Ruminiclostridium (Fe3+), Macellibacteroides (SO42-), Holophagae-Subgroup 7 (HCO3-), Dechloromonas and Geobacter (EA mixture) was noted. Alternatively, As3+ amendment as electron donor allowed predominance of Rhizobium. Taxonomy based functional profiling highlighted the role of chemoorganoheterotrophs capable of concurrent reduction of NO3-, Fe3+, SO42-, and As biotransformation in As-contaminated groundwater of West Bengal. Our analysis revealed two major aspects of the community, (a) taxa selective toward responding to the EAs, and (b) multifaceted nature of taxa appearing in abundance in response to multiple substrates. Thus, the results emphasized the potential of microbial community members to influence the biogeochemical cycling of As and other dominant anions/cations.


Assuntos
Arsênio , Água Subterrânea , Microbiota , Poluentes Químicos da Água , Arsênio/análise , Elétrons , Sequenciamento de Nucleotídeos em Larga Escala , Microbiota/genética , RNA Ribossômico 16S/genética , Poluentes Químicos da Água/análise
19.
J Phys Chem Lett ; 12(27): 6431-6438, 2021 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-34236197

RESUMO

Organic room temperature phosphorescent (ORTP) compounds have recently emerged as a promising class of emissive materials with a multitude of potential applications. However, the number of building blocks that give rise to efficient ORTP materials is still limited, and the rules for engineering phosphorescent properties in organic solids are not well understood. Here, we report ORTP in a series of N-substituted acridone derivatives with electron-donating, electron-withdrawing, and sterically bulky substituents. X-ray crystallography shows that the solid-state packing varies progressively between coparallel and antiparallel π-stacking and separated π-dimers, depending on the size of the substituent. The detailed photophysical studies supported by DFT calculations reveal complex dynamics of singlet and triplet excited states, depending on the electronic effects of substituents and solid-state packing. The programmable molecular packing provides a lever to control the triplet-triplet annihilation that is manifested as delayed fluorescence in acridone derivatives with continuous (both parallel and antiparallel) π-stacking.


Assuntos
Acridonas/química , Luminescência , Temperatura , Elétrons , Modelos Moleculares , Conformação Molecular
20.
J Phys Chem B ; 125(30): 8550-8557, 2021 08 05.
Artigo em Inglês | MEDLINE | ID: mdl-34286993

RESUMO

In the heterobiaryl cross-coupling reaction between aryl halides (Ar-X) and N-methylpyrrole (N-MP) catalyzed by rhodamine 6G (Rh6G+) under irradiation with visible light, a highly active and long-lived (millisecond time range) rhodamine 6G radical (Rh6G•) is formed upon electron transfer from N,N-diisopropylethylamine (DIPEA) to Rh6G+. In this study, we utilized steady-state and time-resolved spectroscopy techniques to demonstrate the existence of another electron-transfer process occurring from the relatively electron-rich N-MP to photoexcited Rh6G+ that was neglected in the previous reports. In this case, the radical Rh6G• formed is short-lived and undergoes rapid recombination (nanosecond time-range), rendering it ineffective in reducing Ar-X to aryl radicals Ar• that can subsequently be trapped by N-MP. This is further demonstrated via two model reactions involving 4'-bromoacetophenone and 1,3,5-tribromobenzene with insignificant product yields after visible-light irradiation in the absence of DIPEA. The unproductive quenching of photoexcited Rh6G+ by N-MP leads to a lower concentration of photocatalyst available for competitive charge transfer with DIPEA and hence decreases the efficiency of the cross-coupling reaction.


Assuntos
Elétrons , Pirróis , Rodaminas
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