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Eva De Leo, Ario Cocina, Preksha Tiwari, Lisa V Poulikakos, Patricia Marqués-Gallego, Boris leFeber, David J Norris, Ferry Prins
Combining the ability to localize electromagnetic fields at the nanoscale with a directional response, plasmonic antennas offer an effective strategy to shape the far-field pattern of coupled emitters. Here, we introduce a family of directional multi-resonant antennas that allows for polarization-resolved spectral identification of fluorescent emission. The geometry consists of a central aperture surrounded by concentric polygonal corrugations. By varying the periodicity of each axis of the polygon individually, this structure can support multiple resonances that provide independent control over emission directionality for multiple wavelengths...
November 21, 2017: ACS Nano
Die Ling Zhao, Subhabrata Das, Tai-Shung Chung
Osmotic power generated by pressure-retarded osmosis (PRO) has attracted global attention as a clean, abundant and renewable energy resource. However, the substrates of PRO membranes are particularly prone to fouling because of their direct contact with various foulants in raw water. This leads to a significant decline in power density and impedes the commercialization of PRO technology. In this work, a facile surface modification method has been developed to obtain a new type of nanoparticle functionalized antifouling PRO membranes...
November 21, 2017: Environmental Science & Technology
Alice E A Allen, Michael C Payne, Daniel J Cole
A modification to the Seminario method [Int. J. Quantum Chem., 60, 1271-1277 (1996)] is proposed, which derives accurate harmonic bond and angle molecular mechanics force field parameters directly from the quantum mechanical Hessian matrix. The new method reduces the average error in the reproduction of quantum mechanical normal mode frequencies of a benchmark set of 70 molecules from 12.3% using the original method, to 6.3%. The modified Seminario method is fully automated and all parameters are computed directly from quantum mechanical data, thereby avoiding interdependency between bond and angle parameters and other components of the force field...
November 21, 2017: Journal of Chemical Theory and Computation
Leonel Paredes-Madrid, Arnaldo Matute, Jorge O Bareño, Carlos A Parra Vargas, Elkin I Gutierrez Velásquez
Force Sensing Resistors (FSRs) are manufactured by sandwiching a Conductive Polymer Composite (CPC) between metal electrodes. The piezoresistive property of FSRs has been exploited to perform stress and strain measurements, but the rheological property of polymers has undermined the repeatability of measurements causing creep in the electrical resistance of FSRs. With the aim of understanding the creep phenomenon, the drift response of thirty two specimens of FSRs was studied using a statistical approach. Similarly, a theoretical model for the creep response was developed by combining the Burger's rheological model with the equations for the quantum tunneling conduction through thin insulating films...
November 21, 2017: Materials
Anne Kathrine R Junker, Thomas Just Sørensen
The influence of an electron donating substituent on the photophysical properties of 1-azathioxanthone dyes has been investigated using optical spectroscopy and theoretical models. The motivation behind the study is based on the fact that thioxanthones are efficient triplet sensitizers, and thus promising sensitizers for lanthanide centered emission. By adding an aza group to one of the phenyl ring systems, direct coordination to a lanthanide center becomes possible, which makes azathoixanthones great candidates as antenna chromophores in lanthanide(III) based dyes...
November 21, 2017: Methods and Applications in Fluorescence
Michael A Famiano, Richard N Boyd, Toshitaka Kajino, Takashi Onaka
Previous work has suggested that the chirality of the amino acids could be established in the magnetic field of a nascent neutron star from a core-collapse supernova or massive collapsar. The magnetic field would orient the (14)N nuclei, and the alignment of its nuclear spin with respect to those of the electron antineutrinos emitted from the collapsing star would determine the probability of destruction of the (14)N nuclei by interactions with the antineutrinos. Subsequent work estimated the bulk polarization of the (14)N nuclei in large rotating meteoroids in such an environment...
November 21, 2017: Astrobiology
Weiwang Xu, Xiaoqi Hou, Yongjun Meng, Renyang Meng, Zhiyuan Wang, Haiyan Qin, Xiaogang Peng, Xue-Wen Chen
Upon photo- or electrical-excitation, colloidal quantum dots (QDs) are often found in multi-carrier states due to multi-photon absorption and photo-charging of the QDs. While many of these multi-carrier states are observed in single-dot spectroscopy, their properties are not well studied due to random charging/discharging, emission intensity intermittency, and uncontrolled surface defects of single QD. Here we report in-situ deciphering the charging status, and precisely assessing the absorption cross section, and determining the absolute emission quantum yield of mono-exciton and biexciton states for neutral, positively-charged, and negatively-charged single core/shell CdSe/CdS QD...
November 21, 2017: Nano Letters
Brigitte Stucki-Buchli, Philip J M Johnson, Olga Bozovic, Claudio Zanobini, Klemens L Koziol, Peter Hamm, Adnan Gulzar, Steffen Wolf, Sebastian Buchenberg, Gerhard Stock
We explore the capability of the non-natural amino acid azidohomoalanine (AHA) as an IR label to sense relatively small structural changes in proteins with the help of 2D IR difference spectroscopy. To that end, we AHA-labelled an allosteric protein (the PDZ2 domain from human tyrosine-phosphatase 1E) and furthermore covalently linked it to an azobenzene-derived photoswitch as to mimic its conformational transition upon ligand binding. To determine the strengths and limitations of the AHA label, in total six mutants have been investigated with the label at sites with varying properties...
November 21, 2017: Journal of Physical Chemistry. A
Amy L Stevens, Neeraj Kumar Joshi, Matthew F Paige, Ronald Paul Steer
Dimeric and multimeric aggregates of a model metalloporphyrin, zinc tetraphenylporphyrin (ZnTPP), have been produced in a controlled manner by incrementally increasing the water content of dilute aqueous ethanol solutions. Steady state absorption, fluorescence emission and fluorescence excitation spectra have been measured to identify the aggregates present as a function of solvent composition. The dynamics of the excited states of the aggregates produced initially by excitation in the Soret region have been measured by ultrafast fluorescence upconversion techniques...
November 21, 2017: Journal of Physical Chemistry. B
Nils Schulz, Pandian Sokkar, Elric Engelage, Severin Schindler, Mate Erdelyi, Elsa Sanchez-Garcia, Stefan Matthias Huber
We performed a comparative study on the interaction mode of 2-haloimidazolium salts with anions in solution, particularly with regard to halogen bonding, hydrogen bonding and anion-π interactions. The syntheses and solid-state analyses of a series of sterically and electronically modified 2-haloimidazolium structures is presented. Detailed isothermal titration calorimetry (ITC) measurements, quantum mechanics/molecular mechanics (QM/MM MD), classical molecular dynamics simulations (MD) and free energy calculations together with NMR were used to elucidate the binding mode in solution...
November 21, 2017: Chemistry: a European Journal
Huimei He, Bing Tang, Ying Ma
Room temperature recrystallization is a simple and convenient method for synthesis of all-inorganic perovskite nanomaterials with excellent luminescent properties. However, the fast crystallization usually brings the colloidal stability and uncontrollable synthesis issues in the formation of all-inorganic perovskite. In the present study, we present a new strategy to prepare the quantum confined CsPbBr3 nanocrystals with controlled morphology under ambient condition. With the assist of fatty acid-capped precursor, the crystallization and the following growth rate can be retarded...
November 21, 2017: Nanotechnology
Elena V Shornikova, Louis Biadala, Dmitri R Yakovlev, Donghai Feng, Victor F Sapega, Nathan Flipo, Aleksandr A Golovatenko, Marina A Semina, Anna V Rodina, Anatolie Mitioglu, Mariana V Ballottin, Peter C M Christianen, Yuri G Kusrayev, Michel Nasilowski, Benoit Dubertret, Manfred Bayer
We address spin properties and spin dynamics of carriers and charged excitons in CdSe/CdS colloidal nanoplatelets with thick shells. Magneto-optical studies are performed by time-resolved and polarization-resolved photoluminescence, spin-flip Raman scattering and picosecond pump-probe Faraday rotation in magnetic fields up to 30 T. We show that at low temperatures the nanoplatelets are negatively charged so that their photoluminescence is dominated by radiative recombination of negatively charged excitons (trions)...
November 21, 2017: Nano Letters
Qi Zhao, Weifeng Yao, Cunping Huang, Qiang Wu, Qunjie Xu
This research reports for the first time that single cobalt atoms anchored nitrogen-doped graphene (Co-NG) can serve as a highly effective and durable cocatalyst for visible light photocatalytic hydrogen production from water. Results show that under identical conditions the hydrogen production rate (1382 µmol/h) for 0.25 wt.% Co-NG loaded CdS photocatalyst (0.25 wt.% Co-NG/CdS) is 3.42 times greater than that of nitrogen-doped graphene (NG) loaded CdS photocatalyst (NG/CdS) and about 1.3 times greater than the greatest hydrogen production rate (1077 µmol/h) for 1...
November 21, 2017: ACS Applied Materials & Interfaces
A Kostopoulou, M Sygletou, K Brintakis, A Lappas, E Stratakis
A facile, low-temperature precipitation-based method is utilized for the synthesis of ultra-thin and highly uniform cesium lead bromide perovskite nanowires (NWs). The reactions facilitate the NWs' crystalline nature over micron-size lengths, while they impart tailored nanowire widths that range from the quantum confinement regime (∼7 nm) down to 2.6 nm. This colloidal synthesis approach is the first of its kind that is carried out on the work-bench, without demanding chemical synthesis equipment. Importantly, the NWs' photoluminescence is shown to improve over time, with no requirement for tedious post-synthesis surface treatment...
November 21, 2017: Nanoscale
Sebastian Deffner
Quantum entanglement is among the most fundamental, yet from classical intuition also most surprising properties of the fully quantum nature of physical reality. We report several experiments performed on IBM's Quantum Experience demonstrating envariance - entanglement assisted invariance. Envariance is a recently discovered symmetry of composite quantum systems, which is at the foundational origin of physics and a quantum phenomenon of pure states. These very easily reproducible and freely accessible experiments on Quantum Experience provide simple tools to study the properties of envariance, and we illustrate this for several cases with "quantum universes" consisting of up to five qubits...
November 2017: Heliyon
Thomas F Watson, Bent Weber, Yu-Ling Hsueh, Lloyd L C Hollenberg, Rajib Rahman, Michelle Y Simmons
Scaling up to large arrays of donor-based spin qubits for quantum computation will require the ability to perform high-fidelity readout of multiple individual spin qubits. Recent experiments have shown that the limiting factor for high-fidelity readout of many qubits is the lifetime of the electron spin. We demonstrate the longest reported lifetimes (up to 30 s) of any electron spin qubit in a nanoelectronic device. By atomic-level engineering of the electron wave function within phosphorus atom quantum dots, we can minimize spin relaxation in agreement with recent theoretical predictions...
March 2017: Science Advances
Ignacio J Melero-Jiménez, A Enrique Salvo, José C Báez, Elena Bañares-España, Andreas Reul, Antonio Flores-Moya
The canopy-forming, intertidal brown (Phaeophyceae) seaweed Fucus guiryi is distributed along the cold-temperate and warm-temperate coasts of Europe and North Africa. Curiously, an isolated population develops at Punta Calaburras (Alboran Sea, Western Mediterranean) but thalli are not present in midsummer every year, unlike the closest (ca. 80 km), perennial populations at the Strait of Gibraltar. The persistence of the alga at Punta Calaburras could be due to the growth of resilient, microscopic stages as well as the arrival of few-celled stages originating from neighbouring localities, and transported by the permanent Atlantic Jet flowing from the Atlantic Ocean into the Mediterranean...
2017: PeerJ
Dominyka Dapkute, Simona Steponkiene, Danute Bulotiene, Liga Saulite, Una Riekstina, Ricardas Rotomskis
Purpose: Cell-mediated delivery of nanoparticles is emerging as a new method of cancer diagnostics and treatment. Due to their inherent regenerative properties, adult mesenchymal stem cells (MSCs) are naturally attracted to wounds and sites of inflammation, as well as tumors. Such characteristics enable MSCs to be used in cellular hitchhiking of nanoparticles. In this study, MSCs extracted from the skin connective tissue were investigated as transporters of semiconductor nanocrystals quantum dots (QDs)...
2017: International Journal of Nanomedicine
Kyoung-Duck Park, Tao Jiang, Genevieve Clark, Xiaodong Xu, Markus B Raschke
Excitons, Coulomb-bound electron-hole pairs, are elementary photo-excitations in semiconductors that can couple to light through radiative relaxation. In contrast, dark excitons (XD) show anti-parallel spin configuration with generally forbidden radiative emission. Because of their long lifetimes, these dark excitons are appealing candidates for quantum computing and optoelectronics. However, optical read-out and control of XD states has remained challenging due to their decoupling from light. Here, we present a tip-enhanced nano-optical approach to induce, switch and programmably modulate the XD emission at room temperature...
November 20, 2017: Nature Nanotechnology
Bing Yang, Shixue Liu, Zijing Lin
Quantum chemistry calculations play a fundamental role in revealing the molecular structures observed in gas-phase spectroscopic measurements. The supersonic jet cooling widely used in single molecular spectroscopy experiment is a non-equilibrium process and often causes confusion on the theoretical and experimental comparison. A computational approach is proposed here to account for the effect of the non-equilibrium cooling on the experimental spectra and applied to the cases of tyrosin-glycine (YG), tryptophane-glycine (WG) and glycine-tryptophane (GW)...
November 20, 2017: Scientific Reports
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