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Nano Letters

Andreas Bayer, Marcel Pozimski, Simon Schambeck, Dieter Schuh, Rupert Huber, Dominique Bougeard, Christoph Lange
Achieving control over light-matter interaction in custom-tailored nanostructures is at the core of modern quantum electrodynamics. In strongly and ultrastrongly coupled systems, the excitation is repeatedly exchanged between a resonator and an electronic transition at a rate known as the vacuum Rabi frequency ΩR. For ΩR approaching the resonance frequency ωc, novel quantum phenomena including squeezed states, Dicke superradiant phase transitions, the collapse of the Purcell effect, and a population of the ground state with virtual photon pairs are predicted...
September 22, 2017: Nano Letters
Filip Krizek, Thomas Kanne, Davydas Razmadze, Erik Johnson, Jesper Nygård, Charles M Marcus, Peter Krogstrup
Epitaxially connected nanowires allow for the design of electron transport experiments and applications beyond the standard two terminal device geometries. In this Letter, we present growth methods of three distinct types of wurtzite structured InAs nanocrosses via the vapor-liquid-solid mechanism. Two methods use conventional wurtzite nanowire arrays as a 6-fold hexagonal basis for growing single crystal wurtzite nanocrosses. A third method uses the 2-fold cubic symmetry of (100) substrates to form well-defined coherent inclusions of zinc blende in the center of the nanocrosses...
September 22, 2017: Nano Letters
Shoujun Zheng, Jinkyu So, Fucai Liu, Zheng Liu, Nikolay I Zheludev, Hong Jin Fan
Monolayer two-dimensional transitional metal dichalcogenides, such as MoS2, WS2 and WSe2, are direct band gap semiconductors with large exciton binding energy. They attract growing attentions for opto-electronic applications including solar cells, photo-detectors, light-emitting diodes and photo-transistors, capacitive energy storage, photodynamic cancer therapy and sensing on flexible platforms. While light-induced luminescence has been widely studied, luminescence induced by injection of free electrons could promise another important applications of these new materials...
September 21, 2017: Nano Letters
Yu Wang, Johannes B Woehrstein, Noah Donoghue, Mingjie Dai, Maier S Avendano, Ron C J Schackmann, Jason Zoeller, Shan Shan H Wang, Paul W Tillberg, Demian Park, Sylvain W Lapan, Edward S Boyden, Joan S Brugge, Pascal S Kaeser, George Church, Sarit S Agasti, Ralf Jungmann, Peng Yin
To decipher the molecular mechanism of biological function, it is critical to map the molecular composition of individual cells or even more importantly tissue samples in the context of their biological environment in situ. Immunofluorescence (IF) provides specific labeling for molecular profiling. However, conventional IF methods have finite multiplexing capabilities due to spectral overlap of the fluorophores. Various sequential imaging methods have been developed to circumvent this spectral limit, but are not widely adopted due to the common limitation of requiring multi-rounds of slow (typically over 2 hours at room temperature to overnight at 4 °C in practice) immunostaining...
September 21, 2017: Nano Letters
Alexander Schlaich, Julian Kappler, Roland R Netz
The viscous properties of nanoscopically confined water are important when hydrated surfaces in close contact are sheared against each other. Numerous experiments have probed the friction between atomically flat hydrated surfaces in the subnanometer separation regime and suggested an increased water viscosity, but the value of the effective viscosity of ultraconfined water, the mechanism of hydration layer friction, and the crossover to the dry friction limit are unclear. We study the shear friction between polar surfaces by extensive nonequilibrium molecular dynamics simulations in the linear-response regime at low shearing velocity, which is the relevant regime for typical biological applications...
September 21, 2017: Nano Letters
Warren Fon, Matthew H Matheny, Jarvis Li, Lev Krayzman, Michael C Cross, Raissa M D'Souza, James P Crutchfield, Michael L Roukes
Control of the global parameters of complex networks has been explored experimentally in a variety of contexts. Yet, the more difficult prospect of realizing arbitrary network architectures, especially analog physical networks that provide dynamical control of individual nodes and edges, has remained elusive. Given the vast hierarchy of time scales involved, it also proves challenging to measure a complex network's full internal dynamics. These span from the fastest nodal dynamics to very slow epochs over which emergent global phenomena, including network synchronization and the manifestation of exotic steady states, eventually emerge...
September 21, 2017: Nano Letters
Joshua McGraw, Antoine Niguès, Alexis Chennevière, Alessandro Siria
Friction at the nanoscale differs markedly from that between surfaces of macroscopic extent. Characteristically, the velocity dependence of friction between apparent solid/solid contacts can strongly deviate from the classically assumed velocity independence. Here, we show that a non-destructive friction between solid tips with radius on the scale of hundreds of nanometers, and solid, hydrophobic selfassembled monolayers has a strong velocity dependence. Specifically, using laterally oscillatingquartztuningforks,weobservealinearscaling in the velocity at the lowest accessed velocities, typically hundreds of micrometers per second, crossing over into a logarithmic velocity dependence...
September 20, 2017: Nano Letters
Menghao Wu, Xiao Cheng Zeng
Atomically thin Bi2O2Se has been recently synthesized and it possesses ultra-high mobility (Nat Nanotech. 2017, 12, 530; Nano Lett. 2017, 17, 3021). Herein, we show first-principles evidence that Bi2O2Se and a related class of bismuth oxychalcogenides, such as Bi2O2S and Bi2O2Te, not only are novel semiconductors with ultra-high mobility but also possesses previously unreported ferroelectricity/ferroelasticity. Such a unique combination of semiconducting with ferroelectric/ferroelastic properties enables bismuth oxychalcogenides to potentially meet a great challenge, that is, integration of room-temperature functional non-volatile memories into future nanocircuits...
September 20, 2017: Nano Letters
Alexander Kerelsky, Ankur Nipane, Drew Edelberg, Dennis Wang, Xiaodong Zhou, Abdollah Motmaendadgar, Hui Gao, Saien Xie, Kibum Kang, Jiwoong Park, James Teherani, Abhay Pasupathy
High quality electrical contact to semiconducting transition metal dichalcogenides (TMDCs) such as MoS2 is key to unlocking their unique electronic and optoelectronic properties for fundamental research and device applications. Despite extensive experimental and theoretical efforts reliable ohmic contact to doped TMDCs remains elusive and would benefit from a better understanding of the underlying physics of the metal-TMDC interface. Here we present measurements of the atomic-scale energy band diagram of junctions between various metals and heavily doped monolayer MoS2 using ultrahigh vacuum scanning tunneling microscopy (UHV-STM)...
September 20, 2017: Nano Letters
Andreas Johansson, Pasi Myllyperkiö, Pekka Koskinen, Jukka Aumanen, Juha Tapio Koivistoinen, Hung-Chieh Tsai, Chia-Hao Chen, Lo-Yueh Chang, Vesa-Matti Hiltunen, Jyrki Manninen, Wei-Yen Woon, Mika Pettersson
Atomically thin materials, such as graphene, are the ultimate building blocks for nanoscale devices. But although their synthesis and handling today are routine, all efforts thus far have been restricted to flat natural geometries, since the means to control their three-dimensional (3D) morphology has remained elusive. Here we show that, just as a blacksmith uses a hammer to forge a metal sheet into 3D shapes, a pulsed laser beam can forge graphene sheet into controlled 3D shapes in the nanoscale. The forging mechanism is based on laser-induced local expansion of graphene, as confirmed by computer simulations using thin sheet elasticity theory...
September 19, 2017: Nano Letters
Raju Regmi, Pamina Martina Winkler, Valentin Flauraud, Kyra Borgman, Carlo Manzo, Juergen Brugger, Herve Rigneault, Jerome Wenger, Maria F Garcia-Parajo
Optical nano-antennas can efficiently confine light into nanoscopic hotspots enabling single-molecule detection sensitivity at biological relevant conditions. This innovative approach to breach the diffraction limit offers a versatile platform to investigate the dynamics of individual biomolecules in living cell membranes and their partitioning into cholesterol-dependent lipid nanodomains. Here, we present optical nano-antenna arrays with accessible surface hotspots to study the characteristic diffusion dynamics of phosphoethanolamine (PE) and sphingomyelin (SM) in the plasma membrane of living cells at the nanoscale...
September 19, 2017: Nano Letters
David Shicheng Li, Soon Joon Yoon, Ivan Pelivanov, M Frenz, Matthew O'Donnell, Lilo D Pozzo
A new contrast agent for combined photoacoustic and ultrasound imaging is presented. It has a liquid perfluorocarbon (PFC) core of about 250 nm diameter coated by a 30 nm thin polypyrrole (PPy) doped polymer shell emulsion which represents a broadband absorber covering the visible and near-infrared ranges (peak optical extinction at 1050 nm). When exposed to a sufficiently high intensity optical or acoustic pulse, the droplets vaporize to form microbubbles providing a strong increase in imaging sensitivity and specificity...
September 19, 2017: Nano Letters
Richard Hobbs, William Putnam, Arya Fallahi, Yujia Yang, Franz Kaertner, Karl K Berggren
Understanding plasmon-mediated electron emission and energy transfer on the nanometer length scale is critical to controlling light-matter interactions at nanoscale dimensions. In a high-resolution lithographic material, electron emission and energy transfer lead to chemical transformations. In this work, we employ such chemical transformations in two different high-resolution electron-beam lithography resists, poly(methyl methacrylate) (PMMA) and hydrogen silsesquioxane (HSQ), to map local electron emission and energy transfer with nanometer resolution from plasmonic nanoantennas excited by femtosecond laser pulses...
September 19, 2017: Nano Letters
Chia-Yen Huang, Jing-Jie Lin, Tsu-Chi Chang, Che-Yu Liu, Tzu-Ying Tai, Kuo-Bin Hong, Tien-Chang Lu, Hao-Chung Kuo
We demonstrated a monolithic GaN-InGaN core-shell nanorod lattice lasing under room temperature. The threshold pumping density was as low as 140 kW/cm2 with a quality factor as high as 1940. The narrow mode spacing between lasing peaks suggested a strong coupling between adjacent whisper gallery modes (WGM), which was confirmed with the far-field patterns. Excitation area dependent photoluminescence revealed that the long-wavelength lasing modes dominated the collective lasing behavior under a large excitation area...
September 19, 2017: Nano Letters
Zhengmao Lu, Kyle L Wilke, Daniel John Preston, Ikuya Kinefuchi, Elizabeth F Chang-Davidson, Evelyn N Wang
Evaporation is a ubiquitous phenomenon found in nature and widely used in industry. Yet fundamental understanding of interfacial transport during evaporation remains limited to date owing to the difficulty of characterizing the heat and mass transfer at the interface, especially at high heat fluxes ( > 100 W/cm(2)). In this work, we elucidated evaporation into an air ambient with an ultra-thin (≈ 200 nm thick) nanoporous (≈ 130 nm pore diameter) membrane. With our evaporator design, we accurately monitored the temperature of the liquid-vapor interface, reduced the thermal-fluidic transport resistance and mitigated the clogging risk associated with contamination...
September 19, 2017: Nano Letters
Daniela Y Santiesteban, Diego S Dumani, Daniel Profili, Stanislav Y Emelianov
We have developed laser-activated perfluorocarbon nanodroplets containing copper sulfide nanoparticles (CuS NPs) for contrast-enhanced ultrasound and photoacoustic imaging. As potential clinical contrast agents, CuS NPs have favorable properties including biocompatibility, biodegradability and enhance contrast in photoacoustic images at clinically relevant depths. However, CuS NPs are not efficient optical absorbers when compared to plasmonic nanoparticles and therefore, contrast enhancement with CuS NPs is limited, requiring high concentrations to generate images with sufficient signal-to-noise ratio...
September 19, 2017: Nano Letters
Mahfujur Rahaman, Raul D Rodriguez, Gerd Plechinger, Stefan Moras, Christian Schüller, Tobias Korn, Dietrich R T Zahn
Tip-enhanced Raman spectroscopy (TERS) has been rapidly improved over the last decade and opened up opportunities to study phonon properties of materials at the nanometer scale. In this contribution we report on tip-enhanced Raman spectroscopy (TERS) of an ultra-thin MoS2 flake on a nanostructured Au on silicon surface forming a two-dimensional (2D) crystal/plasmonic heterostructure. Au nanostructures (shaped in triangles) are prepared by nanosphere lithography and then MoS2 is mechanically exfoliated on top of them...
September 19, 2017: Nano Letters
Qijing Zheng, Wissam A Saidi, Yu Xie, Zhenggang Lan, Oleg V Prezhdo, Hrvoje Petek, Jin Zhao
The van der Waals (vdW) interfaces of two-dimensional (2D) semiconductor are central to new device concepts and emerging technologies in light-electricity transduction where the efficient charge separation is a key factor. Contrary to general expectation, efficient electron-hole separation can occur in vertically stacked transition-metal dichalcogenide heterostructure bilayers through ultrafast charge transfer between the neighboring layers despite their weak vdW bonding. In this report, we show by ab initio nonadiabatic molecular dynamics calculations, that instead of direct tunneling, the ultrafast interlayer hole transfer is strongly promoted by an adiabatic mechanism through phonon excitation occurring on 20 fs, which is in good agreement with the experiment...
September 19, 2017: Nano Letters
Benjamin T Diroll, Xuedan Ma, Yaoting Wu, Christopher B Murray
The synthesis colloidal nanocrystals in non-polar organic solvents has led to exceptional size- and shape-control, enabling the formation of nanocrystal superlattices isostructural to atomic lattices built with nanocrystals rather than atoms. The long aliphatic ligands (e.g. oleic acid) used to achieve this control separate nanocrystals too far in the solid-state for most charge-transporting devices. Solid-state ligand exchange, which brings particles closer together and enhances conductivity, necessitates large changes in the total volume of the solid (compressive stress), which leads to film cracking...
September 18, 2017: Nano Letters
Steven J Brown, Ryan A DeCrescent, David M Nakazono, Samuel H Willenson, Niva A Ran, Xiaofeng Liu, Guillermo C Bazan, Thuc-Quyen Nguyen, Jon A Schuller
Due to strong electric field enhancements, surface plasmon polaritons (SPPs) are capable of drastically increasing light-molecule coupling in organic optoelectronic devices. The electric field enhancement, however, is anisotropic, offering maximal functional benefits if molecules are oriented perpendicular to the interface. To provide a clear demonstration of this orientation dependence, we study SPP dispersion and SPP-mediated photoluminescence at a model Au/small-molecule interface where identical molecules can be deposited with two very different molecular backbone orientations depending on processing conditions...
September 18, 2017: Nano Letters
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