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M Franke, S Leubner, A Dubavik, A George, T Savchenko, C Pini, P Frank, D Melnikau, Y Rakovich, N Gaponik, A Eychmüller, A Richter
Microfluidic devices present the basis of modern life sciences and chemical information processing. To control the flow and to allow optical readout, a reliable sensor material that can be easily utilized for microfluidic systems is in demand. Here, we present a new optical readout system for pH sensing based on pH sensitive, photoluminescent glutathione capped cadmium telluride quantum dots that are covalently immobilized in a poly(acrylate) hydrogel. For an applicable pH sensing the generated hybrid material is integrated in a microfluidic sensor chip setup...
December 2017: Nanoscale Research Letters
Stephen C Warren-Smith, Mario Chemnitz, Henrik Schneidewind, Roman Kostecki, Heike Ebendorff-Heidepriem, Tanya M Monro, Markus A Schmidt
Intermodal third-harmonic generation using waveguides is an effective frequency conversion process due to the combination of long interaction lengths and strong modal confinement. Here we introduce the concept of tuning the third harmonic phase-matching condition via the use of dielectric nanofilms located on an open waveguide core. We experimentally demonstrate that tantalum oxide nanofilms coated onto the core of an exposed core fiber allow tuning the third harmonic wavelength over 30 nm, as confirmed by qualitative simulations...
May 1, 2017: Optics Letters
Jinxian Guo, L Q Chen, Peiyu Yang, Zhengjun Li, Yuan Wu, Xiaotian Feng, Chun-Hua Yuan, Z Y Ou, Weiping Zhang
In studying quantum correlation and quantum memory of continuous variables of light fields and atoms, a crucial step is the retrieval of the quantum fields by converting an atomic spin wave to light, and retrieval efficiency is a crucial parameter. In this Letter, we implement a double-pass Raman scheme in Rb87 by incorporating coherent feedback. We find that the transfer efficiency from an atomic spin wave, which is generated from a Raman process in a high gain regime, to light fields is enhanced by the double-pass scheme as compared to the commonly used single-pass scheme...
May 1, 2017: Optics Letters
D Valente, F Brito, T Werlang
The dynamic Stark shift results from the interaction of an atom with the electromagnetic field. We show how a propagating single-photon wave packet can induce a time-dependent dynamical Stark shift on a two-level system (TLS). A non-perturbative fully quantum treatment is employed, where the quantum dynamics of both the field and the TLS are analyzed. We also provide the means to experimentally access such time-dependent frequency by measuring the interference pattern in the electromagnetic field inside a 1D waveguide...
May 1, 2017: Optics Letters
Yu-Hui Huang, Guo-En Chang, Hui Li, H H Cheng
We report on Sn-based p-i-n waveguide photodetectors (WGPD) with a pseudomorphic GeSn/Ge multiple-quantum-well (MQW) active layer on a Ge-buffered Si substrate. A reduced dark-current density of 59  mA/cm<sup>2</sup> was obtained at a reverse bias of 1 V due to the suppressed strain relaxation in the GeSn/Ge active layer. Responsivity experiments revealed an extended photodetection range covering the O, E, S, C, and L telecommunication bands completely due to the bandgap reduction resulting from Sn-alloying...
May 1, 2017: Optics Letters
M Sendra, I Moreno-Garrido, M P Yeste, J M Gatica, J Blasco
Use of titanium dioxide nanoparticles (TiO2 NPs) has become a part of our daily life and the high environmental concentrations predicted to accumulate in aquatic ecosystems are cause for concern. Although TiO2 has only limited reactivity, at the nanoscale level its physico-chemical properties and toxicity are different compared with bulk material. Phytoplankton is a key trophic level in fresh and marine ecosystems, and the toxicity provoked by these nanoparticles can affect the structure and functioning of ecosystems...
April 25, 2017: Environmental Pollution
Tran Nguyen Lan, Dominika Zgid
Ab initio quantum chemistry calculations for systems with large active spaces are noto- riously difficult and cannot be successfully tackled by standard methods. In this letter, we generalize a Green's function QM/QM embedding method called self-energy embedding the- ory (SEET) that has the potential to be successfully employed to treat large active spaces. In generalized SEET, active orbitals are grouped into intersecting groups of few orbitals allowing us to perform multiple parallel calculations yielding results comparable to the full active space treatment...
April 28, 2017: Journal of Physical Chemistry Letters
David R Hanson, Imanuel Bier, Baradan Panta, Coty N Jen, Peter H McMurry
Computational fluid dynamics simulations (CFD) of a flow reactor provided 3D spatial distributions of its temperature and flow profiles and abundances of sulfuric acid, nitrogeneous base and the acid-base clusters formed from them. Clusters were simulated via their kinetic formation and decomposition involving sulfuric acid and base molecules. Temperature and flow profiles and the base and sulfuric acid distributions are characterized and the latter is compared to mass spectrometer measurements. Concentrations of simulated clusters of sulfuric acid with either NH3 or dimethylamine were compared to experimentally measured particle concentrations...
April 28, 2017: Journal of Physical Chemistry. A
Yong He
We utilize surface plasmon field of a metal nanoparticle (MNP) to detect strain-mediated coupling in a quantum dot-mechanical resonator hybrid system including a quantum dot (QD) embedded within a conical nanowire (NW) and a MNP in the presence of an external field. Based on the numerical solutions of the master equation, we find that a slow oscillation originating from the strain-mediated coupling between the QD and the NW, appears in the time evolution of the plasmon field enhancement. The results show that the period (about 2 μs) of the slow oscillation is equal to that of the mechanical resonator of NW, which suggests the time-resolved measurement of the plasmon field enhancement can be achieved easily based on the current experimental conditions...
April 28, 2017: Nanotechnology
Joseph M Zadrozny, Audrey T Gallagher, T David Harris, Danna E Freedman
The command of atomic-level spatial control over qubits, the fundamental units of both quantum information processing systems and quantum sensors, constitutes a crucial cross-field challenge. Toward this end, embedding electronic spin based qubits within the framework of a crystalline porous material is a promising approach to create precise arrays of qubits. Realizing porous hosts for qubits would also impact the emerging field of quantum sensing, whereby porosity enables analytes to infuse into a sensor matrix...
April 28, 2017: Journal of the American Chemical Society
Dachao Hong, Yuto Tsukakoshi, Hiroaki Kotani, Tomoya Ishizuka, Takahiko Kojima
A Ni(II) complex bearing a S2N2-type tetradentate ligand inspired by the active site of carbon monoxide dehydrogenase was found to selectively catalyze CO2 reduction to produce CO in a photocatalytic system using [Ru(bpy)3](2+) (bpy = 2,2'-bipyridine) as a photosensitizer and BIH (1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzo[d]-imidazole) as an electron donor. The Ni(II) complex shows high TON over 700 with the high CO selectivity of > 99% and quantum yield of 1.42% in the photocatalytic system.
April 28, 2017: Journal of the American Chemical Society
Fred Ka-Wai Kong, Man-Chung Tang, Yi-Chun Wong, Maggie Ng, Mei-Yee Chan, Vivian Wing-Wah Yam
A new class of highly luminescent bipolar alkynylplatinum(II) complexes has been synthesized, characterized, and applied as phosphorescent dopants in the fabrication of solution-processable organic light-emitting devices (OLEDs). Through the incorporation of a delicate balance of electron-donating carbazole moieties and electron-accepting phenylbenzimidazole or oxadiazole moieties into the platinum(II) core, the platinum(II) complexes have been demonstrated to exhibit bipolar charge transport character with high photoluminescence quantum yields of up to 0...
April 28, 2017: Journal of the American Chemical Society
Hiroki Ito, Atsushi Iio, Katsutoshi Tokuhara, Hiroyuki Sakaue, Yutaka Kadoya, Hitoshi Suzuki
Quantum dots (QDs) were immobilized on an ultra-flat Au surface by using amide binding between the carboxyl groups on the QDs and the amino groups of the self-assembled monolayer on the surface. The number density of the QDs estimated by atomic force microscopy (AFM) agreed with the quantity of QDs estimated by X-ray photoelectron spectroscopy and fluorescence microscopy. QDs were also immobilized on dot patterns fabricated by e-beam lithography. AFM was able to identify clusters of just a few QDs on the dot patterns, whose minimum designed size was 50 nm × 50 nm per dot...
December 2017: Nanoscale Research Letters
Carlos Cabezas, Yasuki Endo
Pulsed Fourier-transform microwave experiments have been performed to probe the products resulting from the reaction between HCl and the simplest Criegee intermediate, CH₂OO, where the reaction is considered to be important in atmospheric chemistry. The experimentally determined rotational parameters interpreted with the help of quantum chemical calculations support the identification of chloro-methyl hydroperoxide molecule as the primary product of this reaction.
April 27, 2017: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
Vladan Bajić, Biljana Spremo-Potparević, Lada Živković, Andrea Čabarkapa, Jelena Kotur-Stevuljević, Esma Isenović, Dušan Sredojević, Ivana Vukoje, Vesna Lazić, S Phillip Ahrenkiel, Jovan M Nedeljković
The antigenotoxic and antioxidative properties of surface-modified TiO2 nanoparticles (NPs) with ascorbic acid (AA) were compared with those of constituents (free AA and bare TiO2 NPs). Colloids consisting of the TiO2 NPs with anatase crystal structure were prepared by acidic hydrolysis of TiCl4. The synthesized TiO2 NPs were characterized using transmission electron microscopy and X-ray diffraction analysis. The charge transfer (CT) complex formation between surface Ti atoms and AA is indicated by immediate appearance of red color...
April 14, 2017: Colloids and Surfaces. B, Biointerfaces
Stoyan I Karakashev, Stoyan K Smoukov
The critical micelle concentration (CMC) of various surfactants is difficult to predict accurately, yet often necessary to do in both industry and science. Hence, quantum-chemical software packages for precise calculation of CMC were developed, but they are expensive and time consuming. We show here an easy method for calculating CMC with a reasonable accuracy. Firstly, CMC0 (intrinsic CMC, absent added salt) was coupled with quantitative structure - property relationship (QSPR) with defined by us parameter "CMC predictor" f1...
April 18, 2017: Journal of Colloid and Interface Science
Keun Man Song, Do Hyun Kim, Jong Min Kim, Chu-Young Cho, Jehyuk Choi, Ka Hee Kim, Jinsub Park, Hogyoung Kim
We demonstrated an InGaN/GaN-based, monolithic, white light-emitting diode (LED) without phosphors by using morphology-controlled active layers formed on multi-facet GaN templates containing polar and semipolar surfaces. The nanostructured surface morphology was controlled by changing the growth time, and distinct multiple photoluminescence peaks were observed at 360, 460, and 560 nm; these features were caused by InGaN/GaN-based multiple quantum wells (MQWs) on the nanostructured facets. The origin of each multi-peak was related to the different indium (In) compositions in the different planes of the quantum wells grown on the nanostructured GaN...
April 27, 2017: Nanotechnology
Brent A Koscher, Joseph K Swabeck, Noah D Bronstein, A Paul Alivisatos
We demonstrate post-synthetic modification of CsPbBr3 nanocrystals by a thiocyanate salt treatment. This treatment improves the quantum yield of both freshly synthesized (PLQY~90%) and aged nanocrystals (PLQY~70%) to within measurement error (2-3%) of unity, while simultaneously maintaining the shape, size, and colloidal stability. Additionally, the luminescence decay kinetics transform from multi-exponential decays typical of nanocrystalline semiconductors with a distribution of trap sites, to a monoexponential decay, typical of single energy level emitters...
April 27, 2017: Journal of the American Chemical Society
Naoyuki Koiso, Yuichi Kitagawa, Takayuki Nakanishi, Koji Fushimi, Yasuchika Hasegawa
A luminescent Eu(III) chiral coordination polymer with a structural transformation system, [Eu(hfa)3((R)-bidp)]n (hfa: haxafluoroacetylacetonato, (R)-bidp: (R)-1,1'-binaphthyl-2,2'-bis(diphenylphosphinate), is reported. Single-crystal X-ray analysis revealed a characteristic helical polymer structure of [Eu(hfa)3((R)-bidp)]n with hydrogen-fluorine/π interactions. [Eu(hfa)3((R)-bidp)]n shows high thermostability (decomposition temperature = 320 °C) and strong luminescence properties (the 4f-4f emission quantum yield = 76%) in the solid state due to its tight packing and asymmetric structure...
April 27, 2017: Inorganic Chemistry
Jiaming Li, Leonardo F de Melo, Le Luo
We present a cooling method for a cold Fermi gas by parametrically driving atomic motions in a crossed-beam optical dipole trap (ODT). Our method employs the anharmonicity of the ODT, in which the hotter atoms at the edge of the trap feel the anharmonic components of the trapping potential, while the colder atoms in the center of the trap feel the harmonic one. By modulating the trap depth with frequencies that are resonant with the anharmonic components, we selectively excite the hotter atoms out of the trap while keeping the colder atoms in the trap, generating parametric cooling...
March 30, 2017: Journal of Visualized Experiments: JoVE
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