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https://www.readbyqxmd.com/read/28324832/determination-of-the-interconversion-energy-barrier-of-three-novel-pentahelicene-derivative-enantiomers-by-dynamic-high-resolution-liquid-chromatography
#1
Pavel Majek, Jan Krupcik, Zachary S Breitbach, Milan K Dissanayake, Peter Kroll, Aaron A Ruch, LeGrande M Slaughter, Daniel W Armstrong
Dynamic high resolution liquid chromatography (DHPLC) was used to determine the kinetic and thermodynamic activation parameters of interconversion of three novel pentahelicene derivatives {3,5-bis(trifluoromethyl)benzo[i]pentahelicene, naphtho[1,2-i]pentahelicene and 4-methoxybenzo[i]pentahelicene}. DHPLC was performed on a chiral isopropyl - carbamate cyclofructan 6 (LARIHC CF6-P) column under normal phase conditions. Variation of the column temperature and flow rate was used to study the interconversion process...
December 21, 2016: Journal of Chromatography. B, Analytical Technologies in the Biomedical and Life Sciences
https://www.readbyqxmd.com/read/28324762/chrysanthemum-morphology-photosynthetic-efficiency-and-antioxidant-capacity-are-differentially-modified-by-light-quality
#2
Liang Zheng, Marie-Christine Van Labeke
The effect of light quality on leaf morphology, photosynthetic efficiency and antioxidant capacity of leaves that fully developed under a specific spectrum was investigated in Chrysanthemum cv. Four light treatments were applied at 100μmolm(-2)s(-1) and a photoperiod of 14h using light-emitting diodes, which were 100% red (R), 100% blue (B), 75% red with 25% blue (RB) and white (W), respectively. Intraspecific variation was investigated by studying the response of eight cultivars. Overall, red light significantly decreased the leaf area while the thinnest leaves were observed for W...
March 11, 2017: Journal of Plant Physiology
https://www.readbyqxmd.com/read/28324655/tracking-the-energy-flow-on-nanoscale-via-sample-transmitted-excitation-photoluminescence-spectroscopy
#3
Pavel Moroz, Natalia Razgoniaeva, Yufan He, Gregory Jensen, Holly Eckard, H Peter Lu, Mikhail Zamkov
Tracking the energy flow in nanoscale materials is an important yet challenging goal. Experimental methods for probing the intermolecular energy transfer (ET) are often burdened by the spectral crosstalk between donor and acceptor species, which complicates unraveling their individual contributions. This issue is particularly prominent in inorganic nanoparticles and biological macromolecules featuring broad absorbing profiles. Here, we demonstrate a general spectroscopic strategy for measuring the energy transfer efficiency between nanostructured or molecular dyes exhibiting a significant donor-acceptor spectral overlap...
March 21, 2017: ACS Nano
https://www.readbyqxmd.com/read/28324621/quantum-chemical-dissection-of-the-shortest-p-o%C3%A2-%C3%A2-%C3%A2-i-halogen-bond-the-decisive-role-of-crystal-packing-effects
#4
Milan Kivala, Tobias A Schaub, Rebecca Sure, Frank Hampel, Stefan Grimme
We report on a supramolecular arrangement comprising a bridged triarylphoshine oxide and an aryl iodide that features the shortest ever reported P=O···I halogen bond of 2.683(5) Å in the solid state. X-ray crystallographic analysis together with modern quantum chemical methods were enlisted to dissect the individual contributions that compelled this exceptionally short halogen bond pointing out the decisive role of crystal packing effects.
March 21, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28324593/phosphorescent-neutral-iridium-iii-complexes-for-organic-light-emitting-diodes
#5
REVIEW
Abd Rashid Bin Mohd Yusoff, Aron J Huckaba, Mohammad Khaja Nazeeruddin
The development of transition metal complexes for application in light-emitting devices is currently attracting significant research interest. Among phosphorescent emitters, those involving iridium (III) complexes have proven to be exceedingly useful due to their relatively short triplet lifetime and high phosphorescence quantum yields. The emission wavelength of iridium (III) complexes significantly depends on the ligands, and changing the electronic nature and the position of the ligand substituents can control the properties of the ligands...
April 2017: Topics in Current Chemistry (Journal)
https://www.readbyqxmd.com/read/28323410/zno-quantum-dots-decorated-zn2sno4-nanowire-heterojunction-photodetectors-with-drastic-performance-enhancement-and-flexible-ultraviolet-image-sensors
#6
Ludong Li, Leilei Gu, Zheng Lou, Zhiyong Fan, Guozhen Shen
Here we report fabrication of high-performance ultraviolet photodetectors based on a unique heterojunction device structure in which ZnO quantum dots were used to decorate Zn2SnO4 nanowires. Systematic investigations have shown their ultrahigh light-to-dark current ratio (up to 6.8 × 104), specific detectivity (up to 9.0×1017 Jones), photoconductive gain (up to 1.1 × 107), fast response, and excellent stability. Compared with a pristine Zn2SnO4 nanowire, a quantum dots decorated nanowire demonstrated about 10 times higher photocurrent and responsivity...
March 21, 2017: ACS Nano
https://www.readbyqxmd.com/read/28319899/molecular-imprinting-sensor-based-on-quantum-weak-measurement
#7
Dongmei Li, Qinghua He, Yonghong He, Meiguo Xin, Yilong Zhang, Zhiyuan Shen
A new type of sensing protocol, based on a high precision metrology of quantum weak measurement, was first proposed for molecularly imprinted polymers (MIP) sensor. The feasibility, sensitivity and selectivity of weak measurement based MIP (WMMIP) sensor were experimentally demonstrated with bovine serum albumin (BSA). Weak measurement system exhibits high sensitivity to the optical phase shift corresponding to the refractive index change, which is induced by the specific capture of target protein molecules with its recognition sites...
March 10, 2017: Biosensors & Bioelectronics
https://www.readbyqxmd.com/read/28319838/graphene-oxide-quantum-dot-sensitized-porous-titanium-dioxide-microsphere-visible-light-driven-photocatalyst-based-on-energy-band-engineering
#8
Yu Zhang, Fuyuan Qi, Ying Li, Xin Zhou, Hongfeng Sun, Wei Zhang, Daliang Liu, Xi-Ming Song
We report a novel graphene oxide quantum dot (GOQD)-sensitized porous TiO2 microsphere for efficient photoelectric conversion. Electro-chemical analysis along with the Mott-Schottky equation reveals conductivity type and energy band structure of the two semiconductors. Based on their energy band structures, visible light-induced electrons can transfer from the p-type GOQD to the n-type TiO2. Enhanced photocurrent and photocatalytic activity in visible light further confirm the enhanced separation of electrons and holes in the nanocomposite...
March 11, 2017: Journal of Colloid and Interface Science
https://www.readbyqxmd.com/read/28319781/systematic-study-of-imidazoles-inhibiting-ido1-via-the-integration-of-molecular-mechanics-and-quantum-mechanics-calculations
#9
Yi Zou, Fang Wang, Yan Wang, Wenjie Guo, Yihua Zhang, Qiang Xu, Yisheng Lai
Indoleamine 2,3-dioxygenase 1 (IDO1) is regarded as an attractive target for cancer immunotherapy. To rationalize the detailed interactions between IDO1 and its inhibitors at the atomic level, an integrated computational approach by combining molecular mechanics and quantum mechanics methods was employed in this report. Specifically, the binding modes of 20 inhibitors was initially investigated using the induced fit docking (IFD) protocol, which outperformed other two docking protocols in terms of correctly predicting ligand conformations...
March 14, 2017: European Journal of Medicinal Chemistry
https://www.readbyqxmd.com/read/28319663/2h-ws2-quantum-dots-produced-by-modulating-the-dimension-and-phase-of-1t-nanosheets-for-antibody-free-optical-sensing-of-neurotransmitters
#10
Man-Jin Kim, Su-Ji Jeon, Tae Woog Kang, Jong-Min Ju, DaBin Yim, Hye-In Kim, Jung Hyun Park, Jong-Ho Kim
Modulating the dimensions and phases of transition metal dichalcogenides is of great interest to enhance their intrinsic properties or to create new physicochemical properties. Herein, we report an effective approach to synthesize 2H-WS2 quantum dots (QDs) via the dimension and phase engineering of 1T-WS2 nanosheets. The solvothermal reaction of chemically-exfoliated 1T-WS2 nanosheets in N-methyl-2-pyrrolidone (NMP) under an N2 atmosphere induced their chopping and phase transition at lower temperature to produce 2H-WS2 QDs with a high quantum yield (5...
March 20, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28319662/optimizing-charge-injection-across-transition-metal-dichalcogenide-heterojunctions-theory-and-experiment
#11
Jie Guan, Hsun-Jen Chuang, Zhixian Zhou, David Tomanek
In search of an improved strategy to form low-resistance contacts to semiconducting transition metal dichalcogenides, we combine ab initio density functional electronic structure calculations for an NbSe2/WSe2 interface with quantum transport measurements of the corresponding heterojunction between a few-layer WSe2 semiconductor and a metallic NbSe2 layer. Our theoretical results suggest that, besides a rigid band shift associated with charge transfer, the presence of NbSe2 does not modify the electronic structure of WSe2...
March 20, 2017: ACS Nano
https://www.readbyqxmd.com/read/28319661/atomistic-insights-into-nucleation-and-formation-of-hexagonal-boron-nitride-on-ni-from-first-principles-based-reactive-molecular-dynamics-simulations
#12
Song Liu, Adri C T van Duin, Diana M van Duin, Bin Liu, James H Edgar
Atomistic-scale insights into the growth of a continuous, atomically thin hexagonal boron nitride (hBN) lattice from elemental boron and nitrogen on Ni substrates were obtained from multi-scale modeling combining density functional theory (DFT) and reactive molecular dynamics (rMD). The quantum mechanical calculations focused on the adsorption and reaction energetics for the hBN building-block species, i.e., atomic B, N, BxNy (x, y = 1-2), on Ni(111) and Ni(211), and the diffusion pathways of elemental B and N on these slab model surfaces and in the sublayer...
March 20, 2017: ACS Nano
https://www.readbyqxmd.com/read/28319388/visualizing-intramolecular-vibrational-redistribution-in-cyclotrimethylene-trinitramine-rdx-crystal-by-multiplex-coherent-anti-stokes-raman-scattering
#13
Guoyang Yu, Yangyang Zeng, Wencan Guo, Honglin Wu, Gangbei Zhu, Zhaoyang Zheng, Xianxu Zheng, Yunfei Song, Yanqiang Yang
The femtosecond time-resolved multiplex coherent anti-Stokes Raman scattering (CARS) technique has been performed to investigate the intramolecular vibrational redistribution (IVR) through vibrational couplings in RDX molecules. In the multiplex CARS experiment, the supercontinuum (SC) was used as broadband Stokes light to coherently and collectively excite multiple vibrational modes, and quantum beats arising from vibrational couplings among these modes were observed. The IVR of RDX is visualized by a topological graph of these vibrational couplings...
March 20, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28319374/mechanisms-of-energy-transfer-and-enhanced-stability-of-carbidonitride-phosphors-for-solid-state-lighting
#14
Christopher Grieco, Kurt F Hirsekorn, Andrew T Heitsch, Alan C Thomas, Mark H McAdon, Britt A Vanchura, Michael M Romanelli, Lora L Brehm, Anne Leugers, Anatoliy Sokolov, John B Asbury
Phosphor-converted light emitting diodes (pcLEDs) produce white light through the use of phosphors that convert blue light emitted from the LED chip into green and red wavelengths. Understanding the mechanisms of degradation of the emission spectra and quantum yields of the phosphors used in pcLEDs is of critical importance to fully realize the potential of solid state lighting as an energy efficient technology. Toward this end, time-resolved photoluminescence spectroscopy was used to identify the mechanistic origins of enhanced stability and luminescence efficiency that can be obtained from a series of carbidonitride red phosphors with varying degree of substitutional carbon...
March 20, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28319223/kinetics-and-heterogeneity-of-energy-transfer-from-light-harvesting-complex-ii-to-photosystem-i-in-the-supercomplex-isolated-from-arabidopsis
#15
Stefano Santabarbara, Tania Tibiletti, William Remelli, Stefano Caffarri
State transitions are a phenomenon that maintains the excitation balance between photosystem II (PSII) and photosystem I (PSI-LHCI) by controlling their relative absorption cross-sections. Under light conditions exciting PSII preferentially, a trimeric LHCII antenna moves from PSII to PSI-LHCI to form the PSI-LHCI-LHCII supercomplex. In this work, the excited state dynamics in the PSI-LHCI and PSI-LHCI-LHCII supercomplexes isolated from Arabidopsis have been investigated by picosecond time-resolved fluorescence spectroscopy...
March 20, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28319040/modelling-plexcitons-of-periodic-gold-nanorod-arrays-with-molecular-components
#16
Bo Liu, Hongdan Yan, Rainer Stosch, Benedikt Wolfram, Martin Bröring, Andrey Bakin, Meinhard Schilling, Peter Lemmens
Plasmonic or exciton/plasmon (plexcitonic) systems are presently described based on electromagnetic models, ignoring the need for an improved microscopic understanding. This is based on the fact that a full quantum mechanical approach on a micrometer scale still represents a considerable challenge. In this paper we report on the experimental observation of plexcitons in 2D gold nanorod array systems coupled to dye molecules and we provide a description of the experimental data using a quantum model. We show that treating the collective behavior in the array as being represented by a single quasiparticle is a suitable approximation that offers the opportunity to avoid the complicated calculation of long-distance interactions between the individual nanoparticles of the plexcitonic, periodic system...
March 20, 2017: Nanotechnology
https://www.readbyqxmd.com/read/28319039/tunable-amplified-spontaneous-emission-in-graphene-quantum-dots-doped-cholesteric-liquid-crystals
#17
Mingxuan Cao, Siwei Yang, Yating Zhang, Xiaoxian Song, Yongli Che, Haiting Zhang, Yu Yu, Gu Ding, Guizhong Zhang, Jianquan Yao
Graphene quantum dots (GQDs) have received great attention owing to their unique structure and novel phenomena of optical absorption/emission. In this letter, we observed the tunable amplified spontaneous emission (ASE) in GQDs doped cholesteric liquid crystals (CLC) for the first time. The GQDs are dispersed in CLC homogeneously with the weight ratio of 0.5 wt%. Under optical excitation, a typical ASE is triggered in the system above a 1.25 mJ/cm2 threshold. In addition, the emission peak at the long wavelength edge of the photonic bandgap shifts from 662 nm to 669 nm with the change of working temperature...
March 20, 2017: Nanotechnology
https://www.readbyqxmd.com/read/28318263/deterministic-coupling-of-quantum-emitters-in-2d-materials-to-plasmonic-nanocavity-arrays
#18
Toan Trong Tran, Danqing Wang, Zaiquan Xu, Ankun Yang, Milos Toth, Teri W Odom, Igor Aharonovich
Quantum emitters in two dimensional materials are promising candidates for studies of light-matter interaction and next generation, integrated on-chip quantum nanophotonics. However, realization of integrated nanophotonic systems requires coupling of emitters to optical cavities and resonators. In this work, we demonstrate hybrid systems in which quantum emitters in 2D hexagonal boron nitride (hBN) are deterministically coupled to high quality plasmonic nanocavity arrays. The plasmonic nanoparticle arrays offer a high quality, low loss cavity in the same spectral range as the quantum emitters in hBN...
March 20, 2017: Nano Letters
https://www.readbyqxmd.com/read/28318255/excited-state-decay-paths-in-tetraphenylethene-derivatives
#19
Yuan-Jun Gao, Xue-Ping Chang, Xiang-Yang Liu, Quan-Song Li, Ganglong Cui, Walter Thiel
The photophysical properties of tetraphenylethene (TPE) compounds may differ widely depending on the substitution pattern, for example with regard to the fluorescence quantum yield phi_f and the propensity to exhibit aggregation-induced emission (AIE). We report combined electronic structure calculations and nonadiabatic dynamics simulations to study the excited-state decay mechanisms of two TPE derivatives with four methyl substituents, either in meta-position (TPE-4mM, phi_f = 0.1%) or in ortho-position (TPE-4oM, phi_f = 64...
March 20, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28318239/trapping-experiments-on-a-trichlorosilanide-anion-a-key-intermediate-of-halogenosilane-chemistry
#20
Julian Teichmann, Markus Bursch, Benedikt Köstler, Michael Bolte, Hans-Wolfram Lerner, Stefan Grimme, Matthias Wagner
Treatment of Si2Cl6 with [Et4N][BCl4] in CH2Cl2 furnished the known products of a chloride-induced disproportionation reaction of the disilane, such as SiCl4, [Si(SiCl3)3](-), and [Si6Cl12·2Cl](2-). No Si-B-bonded products were detectable. In contrast, the addition of Si2Cl6 to [Et4N][BI3Cl] afforded the Si-B adduct [Et4N][I3SiBI3]. Thus, a quantitative Cl/I exchange at the silicon atom accompanies the trihalogenosilanide formation. [Et4N][I3SiBI3] was also accessible from a mixture of Si2I6, [Et4N]I, and BI3...
March 20, 2017: Inorganic Chemistry
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