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Quantum yield

Jingqian Xie, Lu Zhao, Kai Liu, Fangjie Guo, Zunwei Chen, Weiping Liu
Chiral herbicides consist of two or more enantiomers, which usually differ in their biological properties and behave enantioselectively in biochemical process. Scant studies have been published in the past decades to characterize the enantiomers of herbicide lactofen. In this study, a laboratory method was developed to prepare the lactofen enantiomers using normal phase high performance liquid chromatography with an AD-H column, and μg level production yield was achieved in a single run. The two separated enantiomers had purity of ≫99%, with their absolute configurations assigned by experimental and calculated electronic and vibrational circular dichroism...
October 31, 2017: Chemosphere
Montaha Yassine, Laura Fuster, Marie-Hélène Dévier, Emmanuel Geneste, Patrick Pardon, Axelle Grélard, Erick Dufourc, Mohamad Al Iskandarani, Selim Aït-Aïssa, Jeanne Garric, Hélène Budzinski, Patrick Mazellier, Aurélien S Trivella
Kinetics of photodegradation of novel oral anticoagulants dabigatran, rivaroxaban, and apixaban were studied under simulated solar light irradiation in purified, mineral, and river waters. Dabigatran and rivaroxaban underwent direct photolysis with polychromatic quantum yields of 2.2 × 10(-4) and 4.4 × 10(-2), respectively. The direct photodegradation of apixaban was not observed after 19 h of irradiation. Kinetics of degradation of rivaroxaban was not impacted by the nature of the aqueous matrix while photosensitization from nitrate ions was observed for dabigatran and apixaban dissolved in a mineral water...
November 9, 2017: Chemosphere
Shiyang Shao, Jun Hu, Xingdong Wang, Lixiang Wang, Xiabin Jing, Fosong Wang
We demonstrate a novel molecular design concept for thermally activated delayed fluorescence (TADF) polymers based on a nonconjugated polyethylene backbone with through-space charge transfer effect between pendant electron donor (D) and electron acceptor (A) units. Different from conventional conjugated D-A polymers with through-bond charge transfer effect, the nonconjugated architecture avoids the direct conjugation between D and A units, enabling us to realize blue emission. Meanwhile, the spatial π-π interaction between the physically separated D and A units results in both small singlet-triplet energy splitting (0...
November 17, 2017: Journal of the American Chemical Society
Marco Deiana, Bastien Mettra, Lara Martinez-Fernandez, Leszek Mateusz Mazur, Krzysztof Pawlik, Chantal Andraud, Marek Samoc, Roberto Improta, Cyrille Monnereau, Katarzyna Matczyszyn
The implication of guanine-rich DNA sequences in biologically important roles such as telomerase dysfunction and the regulation of gene expression has prompted the search for structure-specific G-quadruplex agents for targeted diagnostic and therapeutic applications. To date, the number of two-photon absorbing fluorogenic dyes with intrinsically large two-photon absorption (TPA) cross-section (σ2) and quantum yield (φf), capable of specific detection of G-motifs over duplex DNAs is still limited. Herein, we report on a NIR two-photon poly(cationic) anthracene-based macromolecule able to selectively target G-quadruplexes (G4s) over genomic double-stranded DNA...
November 17, 2017: Journal of Physical Chemistry Letters
Chunchun Han, Yong Zhang, Peng Gao, Shulin Chen, Xinfeng Liu, Yang Mi, Jianqi Zhang, Yanhong Ma, Wenyu Jiang, Jinquan Chang
Mass production of two-dimensional quantum sheets (2D QSs) is highly desired to fully exploit their properties. Herein, we present a general strategy for the high-yield production of molybdenum disulfide (MoS2) and tungsten disulfide (WS2) QSs by a sequential combination of salt-assisted ball-milling and sonication-assisted solvent exfoliation of their bulk materials. Such strategy enables reproducible production of intrinsic and defect-free MoS2 and WS2 QSs with exceedingly high yield of 25.5 wt% and 20.1 wt% respectively...
November 17, 2017: Nano Letters
Mario Kock, Peter G Jones, Thomas Lindel
The first total synthesis of the bisindole alkaloid raputindole A from the rutaceous plant Raputia simulans is reported. The key step is a Au(I)-catalyzed cyclization that assembles the cyclopenta[f]indole tricycle from a 6-alkynylated indoline precursor. The isobutenyl side chain was installed by Suzuki-Miyaura cross-coupling, followed by a regioselective reduction employing LiDBB. Starting from 6-iodoindole, the sequence needs nine steps and provided (±)-raputindole A in 6.6% overall yield. The absolute configuration of the natural product (+)-raputindole A was determined by quantum chemical calculation of the ECD spectrum...
November 17, 2017: Organic Letters
Yi Yuan, Xiaocan Zhao, Sainan Wang, Liming Wang
Atmospheric oxidation mechanism of furan and methyl furans (MFs) initiated by OH radicals is studied using high-level quantum chemistry and kinetic calculations. The reaction starts mainly with OH addition to C2/C5-position, forming highly chemically activated adduct radical R2*/R5*, which would either be stabilized by collision or promptly isomerize to R2B*/R5B* by breaking the C2-O/C5-O bond and then isomerize to other conformers of R2B/R5B by internal rotations. Under the atmospheric conditions, the ring-retaining radical R2/R5 would recombine with O2 and be converted to a 5-hydroxy-2-furanone compound and a compound containing epoxide, ester, and carbonyl functional groups, while the ring-opening radicals R2B/R5B would react with O2 and form unsaturated 1,4-dicarbonyl compounds...
November 17, 2017: Journal of Physical Chemistry. A
Meiquan Cai, Peizhe Sun, Liqiu Zhang, Ching-Hua Huang
Peracetic acid (PAA) is a widely used disinfectant, and combined UV light with PAA (i.e. UV/PAA) can be a novel advanced oxidation process for elimination of water contaminants. This study is among the first to evaluate the photolysis of PAA under UV irradiation (254 nm) and degradation of pharmaceuticals by UV/PAA. PAA exhibited high quantum yields (Φ254nm = 1.20 and 2.09 mol·Einstein-1 for the neutral (PAA0) and anionic (PAA-) species, respectively) and also showed scavenging effects on hydroxyl radicals (k•OH/PAA0 = (9...
November 17, 2017: Environmental Science & Technology
Yasunari Tamai, Yeli Fan, Vincent O Kim, Kostiantyn Ziabrev, Akshay Rao, Stephen Barlow, Seth R Marder, Richard H Friend, S Matthew Menke
Rapid, long-range charge separation in polymer-fullerene organic solar cells (OSCs) enables electrons and holes to move beyond their Coulomb capture radius and overcome geminate recombination. Understanding the nature of charge generation and recombination mechanisms in efficient, nonfullerene-acceptor-based OSCs are critical to further improve device performance. Here we report charge dynamics in an OSC using a perylene diimide (PDI) dimer acceptor. We use transient absorption spectroscopy to track the time evolution of electroabsorption caused by the dipolar electric field generated between electron-hole pairs as they separate after ionization at the donor-acceptor interface...
November 17, 2017: ACS Nano
Rongqin Ye, Qianling Cui, Chuang Yao, Ronghua Liu, Lidong Li
In this work, we developed a supramolecular fluorescent system based on host-guest interactions between a fluorene derivative carrying two bispyridinium units (FPy) and cucurbit[8]uril (CB[8]). In aqueous solution, the system showed outstanding tunable emission properties. After being encapsulated into the rigid hydrophobic cavity of the CB[8] host, the fluorescence emission of fluorene had an obvious red-shift with enhanced quantum yield. Interestingly, the emission behavior of the FPy/CB[8] complex showed a two-step self-assembly process when the molar ratio of FPy to CB[8] changed from 1 : 1 to 1 : 2...
November 17, 2017: Physical Chemistry Chemical Physics: PCCP
Ben Yiu-Wing Wong, Hok-Lai Wong, Yi-Chun Wong, Vonika Ka-Man Au, Mei-Yee Chan, Vivian Wing-Wah Yam
A new class of donor-acceptor type luminescent bis(alkynyl)gold(iii) N⁁C complexes has been synthesized and characterized. These gold(iii) complexes not only exhibit high photoluminescence quantum yields of up to 0.81, but also interesting mechanochromic luminescence behaviors that are reversible. Upon grinding, a dramatic luminescence color change from green to red can be observed in solid samples of the gold(iii) complexes, and the mechanochromic luminescence can be readily tuned via a judicious selection of substituents on the pyridine ring...
October 1, 2017: Chemical Science
Heming Zhang, Xiaoxuan Wei, Xuedan Song, Shaheen Shah, Jingwen Chen, Jianhui Liu, Ce Hao, Zhongfang Chen
For organic pollutants, photodegradation, as a major abiotic elimination process and of great importance to the environmental fate and risk, involves rather complicated physical and chemical processes of excited molecules. Herein, we systematically studied the photophysical and photochemical processes of a widely used antibiotic, namely sulfapyridine. By means of density functional theory (DFT) computations, we examined the rate constants and the competition of both photophysical and photochemical processes, elucidated the photochemical reaction mechanism, calculated reaction quantum yield (Φ) based on both photophysical and photochemical processes, and subsequently estimated the photodegradation rate constant...
October 7, 2017: Chemosphere
Han-Wei Chu, Ju-Yi Mao, Chia-Wen Lien, Pang-Hung Hsu, Yu-Jia Li, Jui-Yang Lai, Tai-Chia Chiu, Chih-Ching Huang
Carbon quantum dots (CQDs) have attracted enormous interest in recent years owing to their low cytotoxicity, excellent biocompatibility and strong fluorescence. They have been successfully employed in sensor, bio-imaging, and drug carrier applications. A complete understanding of their core-surface structure is essential for tuning their physical and chemical properties for various applications. Conventional characterizations of CQDs are conducted with electron microscopy or spectroscopy, such as transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and Raman spectroscopy...
November 16, 2017: Nanoscale
Zhiyuan Huang, Zihao Xu, Melika Mahboub, Xin Li, Jordan Taylor, Hill Harman, Tianquan Lian, MingLee Tang
Here, we observe that a sub-monolayer CdS shell on PbS quantum dots (QDs) enhances triplet energy transfer (TET) by suppressing competitive charge transfer from QDs to molecules. The CdS shell increases the linear photon upconversion quantum yield (QY) from 3.5% for PbS QDs to 5.0% for PbS/CdS QDs when functionalized with a tetracene acceptor, 5-CT. While transient absorption spectroscopy reveals that both PbS and PbS/CdS QDs show the formation of the 5-CT triplet (with rate constants of 5.91 ±0.60 ns-1 and 1...
November 15, 2017: Angewandte Chemie
Nopondo N Esemoto, Andrius Satraitis, Linda Wiratan, Marcin Ptaszek
A series of a rigid meso-meso directly linked chlorin-chlorin, chlorin-bacteriochlorin, and bacteriochlorin-bacteriochlorin dyads, including free bases as well as Zn(II), Pd(II), and Cu(II) complexes, has been synthesized, and their absorption, emission, singlet oxygen ((1)O2) photosensitization, and electronic properties have been examined. Marked bathochromic shifts of the long-wavelength Qy absorption band and increase in fluorescence quantum yields in dyads, in comparison to the corresponding monomers, are observed...
November 15, 2017: Inorganic Chemistry
Fang-Xin Wang, Mu-He Chen, Yan-Nan Lin, Hang Zhang, Cai-Ping Tan, Liang-Nian Ji, Zongwan Mao
Four phosphorescent cyclometalated iridium(III) complexes containing benzimidazole moiety have been designed and synthesized. These Ir(III) complexes can inhibit several cancerous processes including cell migration, invasion, colony formation and angiogenesis effectively. Interestingly, they show much higher singlet oxygen quantum yield in acidic solution than in neutral solution. Upon irradiation at 425 nm with low energy (1.2 J·cm(-2)), they can induce apoptosis through lysosomal damage, evaluation of ROS level and activation of caspase-3/7...
November 15, 2017: ACS Applied Materials & Interfaces
Ruilin Xu, Chen Liao, Yanqing Xu, Chunfeng Zhang, Min Xiao, Lei Zhang, Changgui Lu, Yiping Cui, Jiayu Zhang
Mn(2+) ions were introduced as exciton couplers to enhance the quantum yield (QY) of type-II photoluminescence (PL) from CdS/ZnSe/ZnS quantum dots (QDs) with slow hot-exciton cooling and low radiative rate. Transient absorption spectroscopy verifies the faster bleach recovery and faster peak red-shifting at the charge-transfer state. And the transient PL peak of the QDs changes from blue-shifting to red-shifting due to Mn(2+) doping. The QY of type-II PL can be enhanced from ∼35% to ∼60% by Mn(2+) doping...
November 15, 2017: Nanoscale
Wei Zheng, Yan-Ming Xu, Dan-Dan Wu, Yue Yao, Zhan-Ling Liang, Heng Wee Tan, Andy T Y Lau
Quantum dots (QDs) are semiconducting nanocrystals with unique optical properties. When coated with shell/capping, QDs are not deleterious to cells and organisms. However, when QDs are retained in the cellular environment for a certain period of time, their coatings may be degraded, yielding "naked" QDs. Although some studies have documented the acute effects of QDs in various cell lines, however, to our knowledge, there are no published studies on the chronic effects of QDs in normal lung cells. In this study, we therefore sought to study the effects of cadmium telluride (CdTe) QDs of various particles sizes on their cytotoxicity and carcinogenicity in normal human bronchial epithelial cells (BEAS-2B)...
November 11, 2017: Biochemical and Biophysical Research Communications
Mihaela Savin, Carmen-Marinela Mihailescu, Iulia Matei, Dana Stan, Carmen Aura Moldovan, Marian Ion, Ion Baciu
We describe the preparation and validation of a novel lateral flow immunoassay test for the detection of human heart fatty acid binding protein (hFABP). Water-soluble CdTe quantum dots (QDs) were selected as the fluorescent label and were linked covalently to anti-hFABP antibodies. Upon conjugation, the secondary structure of the anti-hFABP was preserved and the fluorescence quantum yield of the CdTe QDs increased. The labelled antibodies were transferred to the immunoassay test strip and the antigen-antibody reaction was successfully performed...
February 1, 2018: Talanta
Hongyan Zeng, Li Li, Yaping Ding, Qi Zhuang
In this work, a new selective and simple fluorescence probe based on polyethylenimine(PEI) functionalized carbon dots (PEI-CDs) for fast determination of 6-thioguanine (6-TG) was developed. We successfully prepared the highly fluorescent PEI-CDs by hydrothermal method, and completed the synthesis and modification processes in one step. The fluorescence quantum yield (QY) of the as-synthesized CDs was 38% and higher than that of most previous reports (5-30%). The fluorescence intensity of PEI-CDs decreased obviously with gradually increased concentration of 6-TG...
February 1, 2018: Talanta
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