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Nano Letters

Meng Liu, Shiyang Shen, Di Wen, Mengru Li, Teng Li, Xiaojie Chen, Zhen Gu, Ran Mo
Protein therapeutics hold increasing interest with promise of revolutionizing the cancer treatment by virtue of potent specific activity and reduced adverse effect. Nonetheless, the therapeutic efficacy of anticancer proteins is highly compromised by multiple successive physiological barriers to protein delivery. Concurrent elimination of bulk tumor cells and highly-tumorigenic cancer stem-like cells (CSCs) has been evidenced as a promising strategy to improve cancer therapy. Here we show that a hierarchically-assembled nanocomposite can self-adaptively transform its particulate property in response to endogenous tumor-associated signals to overcome the sequential barriers and achieve enhanced antitumor efficacy by killing CSCs and bulk tumor cells synchronously...
March 16, 2018: Nano Letters
Yu Liu, Yu Zhang, Silvia Ortega, Maria Ibáñez, Khak Ho Lim, Albert Grau Carbonell, Sara Martí-Sànchez, Ka Ming Ng, Jordi Arbiol, Maksym V Kovalenko, Doris Cadavid, Andreu Cabot
Bottom-up approaches for producing bulk nanomaterials have traditionally lacked control over the crystallographic alignment of nanograins. This limitation has prevented nanocrystal-based nanomaterials from achieving optimized performances in numerous applications. Here we demonstrate the production of nanostructured BixSb2-xTe3 alloys with controlled stoichiometry and crystallographic texture through proper selection of the starting building blocks and the adjustment of the nanocrystal-to-nanomaterial consolidation process...
March 16, 2018: Nano Letters
Sophie Meuret, Toon Coenen, Steffi Woo, Yong-Ho Ra, Zetian Mi, Albert Polman
Cathodoluminescence (CL) imaging spectroscopy provides two-dimensional optical excitation images of photonic nanostructures with deep-subwavelength spatial resolution. So far, CL imaging was unable to provide a direct measurement of the excitation and emission probabilities of photonic nanostructures in a spatially resolved manner. Here, we demonstrate that by mapping the cathodoluminescence autocorrelation function g(2) together with the CL spectral distribution the excitation and emission rates can be disentangled at every excitation position...
March 16, 2018: Nano Letters
Tao Jiang, Hao Hong, Can Liu, Wei-Tao Liu, Kaihui Liu, Shiwei Wu
Interactions between elementary excitations, such as carriers, phonons and plasmons, are critical for understanding the optical and electronic properties of materials. The significance of these interactions is more prominent in low-dimensional materials and can dominate their physical properties due to the enhanced interactions between these excitations. One-dimensional single-walled carbon nanotubes provide an ideal system for studying such interactions due to their perfect physical structures and rich electronic properties...
March 15, 2018: Nano Letters
Miguel A Marioni, Marcos Penedo, Mirko Baćani, Johannes Schwenk, Hans Josef Hug
Mallinson's idea that some spin textures in planar magnetic structures could produce an enhancement of the magnetic flux on one side of the plane at the expense of the other gave rise to permanent magnet configurations known as Halbach magnet arrays. Applications range from wiggler magnets in particle accelerators and free electron lasers, to motors, to magnetic levitation trains, but exploiting Halbach arrays in micro- or nanoscale spintronics devices requires solving the problem of fabrication and field metrology below 100 μm size...
March 15, 2018: Nano Letters
Zhao Xiaojuan, Leiming Tao, Hao Li, Wenchao Huang, Pengyu Sun, Jun Liu, Shuangshuang Liu, Qiang Sun, Zhifang Cui, Lijie Sun, Yan Shen, Yang Yang, Mingkui Wang
Organic-inorganic hybrid lead halide perovskites have been widely investigated in optoelectronics both experimentally and theoretically. The present work incorporates chemical modified graphene into nanocrystal SnO2 as electron transporting layer (ETL) for highly efficient planar perovskite solar cells. The modification of SnO2 with highly conductive two-dimensional naphthalene diimide-graphene can increase surface hydrophobicity and form van der Waals interaction between the surfactant and the organic-inorganic hybrid lead halide perovskite compounds...
March 14, 2018: Nano Letters
Jianbang Wang, Zhixin Zhou, Liang Yue, Shan Wang, Itamar Willner
The switchable reconfiguration of a mixture of two dimers of DNA origami tiles AB and CD into a mixture of two DNA origami dimers composed of AD and CB, using collection of fuel and anti-fuel strands, is presented. The reversible reconfiguration of the mixture of dimers AB/CD into AD/CB followed by labeling each of the tile with 0, 1, 2 and 3 4× hairpins labels and by imaging the dimer structures by AFM. Subjecting the reconfigurable dimer mixtures to a collection of Mg2+ -dependent DNAzyme subunits and the substrates consisting of the ROX/BHQ2-modified substrate and the FAM/BHQ1-modified substrate leads to the triggered and programmed switchable operation in the presence of appropriate fuel and anti-fuel strands...
March 14, 2018: Nano Letters
Zhimin Tao, Mandar Deepak Muzumdar, Alexandre Detappe, Xing Huang, Eric Xu, Yingjie Yu, Tarek H Mouhieddine, Haiqin Song, Tyler Jacks, P Peter Ghoroghchian
Human pancreatic ductal adenocarcinoma (PDAC) contains a distinctively dense stroma that limits the accessibility of anticancer drugs, contributing to its poor overall prognosis. Nanoparticles can enhance drug delivery and retention in pancreatic tumors and have been utilized clinically for their treatment. In preclinical investigations, various mouse models differentially recapitulate the microenvironmental features of human PDAC. Here, we demonstrate that through utilization of different organic co-solvents and by doping of a homopolymer of poly(ε-caprolactone), a diblock copolymer composition of poly(ethylene oxide)- block-poly(ε-caprolactone) may be utilized to generate biodegradable and nanoscale micelles with different physical properties...
March 13, 2018: Nano Letters
Lisa V Poulikakos, Prachi Thureja, Alexia Stollmann, Eva De Leo, David J Norris
Chiral metallic nanostructures can generate evanescent fields which are more highly twisted than circularly polarized light. However, it remains unclear how best to exploit this phenomenon, hindering the optimal utilization of chiral electromagnetic fields. Here, inspired by optical antenna theory, we address this challenge by introducing chiral antenna parameters: the chirality flux efficiency and the chiral antenna aperture. These quantities, which are based on chirality conservation, quantify the generation and dissipation of chiral light...
March 13, 2018: Nano Letters
Shawulienu Kezilebieke, Marc Dvorak, Teemu Ojanen, Peter Liljeroth
Magnetic impurities have a dramatic effect on superconductivity by breaking the time-reversal symmetry and inducing so-called Yu-Shiba-Rusinov (YSR) low energy bound states within the superconducting gap. The spatial extent of YSR states is greatly enhanced in 2D systems, which should facilitate the formation of coupled states. Here, we observe YSR states on single cobalt phthalocyanine (CoPC) molecules on a 2D superconductor NbSe2 using low-temperature scanning tunneling microscopy (STM) and spectroscopy (STS)...
March 13, 2018: Nano Letters
Huading Song, Yan-Fei Wu, Xin Yang, Zhaohui Ren, Xiaoxing Ke, Mert Kurttepeli, Gustaaf Van Tendeloo, Dameng Liu, Hanchun Wu, Baoming Yan, Xiaosong Wu, Chun-Gang Duan, Gaorong Han, Zhi-Min Liao, Dapeng Yu
Graphene, having all atoms on its surface, is favorable to extend the functions by introducing the spin-orbit coupling and magnetism through proximity effect. Here, we report the tunable interfacial exchange field produced by proximity coupling in graphene/BiFeO3 heterostructures. The exchange field has a notable dependence with external magnetic field, and it is much larger under negative magnetic field than that under positive magnetic field. For negative external magnetic field, interfacial exchange coupling gives rise to evident spin splitting for N≠0 Landau levels and a quantum Hall metal state for N=0 Landau level...
March 13, 2018: Nano Letters
Zhaosheng Zhang, Weihai Fang, Marina Tokina, Run Long, Oleg V Prezhdo
Two-dimensional (2D) Ruddlesden-Popper halide perovskites are appealing candidates for optoelectronics and photovoltaics. Nonradiative electron-hole recombination constitutes a major pathway for charge and energy losses in these materials. Surprisingly, experimental recombination is slower in multi-layers than mono-layer, even though multi-layer systems have smaller energy gaps and higher frequency phonons that should accelerate the recombination. Focusing on (BA)2(MA)n-1PbnI3n+1 with n=1 and 3, BA=CH3(CH2)3NH3 and MA=CH3NH3, we show that it is the enhancement of elastic electron-phonon scattering that suppresses charge recombination for n=3, by causing rapid loss of electronic coherence...
March 13, 2018: Nano Letters
Ekaterina Khestanova, John Birkbeck, Mengjian Zhu, Yang Cao, Geliang Yu, Davit Ghazaryan, Jun Yin, Helmuth Berger, László Forró, Takashi Taniguchi, Kenji Watanabe, Roman Vladislavovich Gorbachev, Artem Mishchenko, Andre K Geim, Irina V Grigorieva
It is well known that superconductivity in thin films is generally suppressed with decreasing thickness. This suppression is normally governed by either disorder-induced localization of Cooper pairs, weakening of Coulomb screening, or generation and unbinding of vortex-antivortex pairs as described by the Berezinskii-Kosterlitz-Thouless (BKT) theory. Defying general expectations, few-layer NbSe2 - an archetypal example of ultrathin superconductors - has been found to remain superconducting down to monolayer thickness...
March 12, 2018: Nano Letters
Ziwei Dou, Sei Morikawa, Alessandro Cresti, Shu-Wei Wang, Charles G Smith, Christos Melios, Olga Kazakova, Kenji Watanabe, Takashi Taniguchi, Satoru Masubuchi, Tomoki Machida, Malcolm Richard Connolly
Van der Waals structures formed by aligning monolayer graphene with insulating layers of hexagonal boron nitride exhibit a moiré superlattice that is expected to break sublattice symmetry. Despite an energy gap of several tens of millielectronvolts opening in the Dirac spectrum, electrical resistivity remains lower than expected at low temperature and varies between devices. While subgap states are likely to play a role in this behavior, their precise nature is unclear. We present a scanning gate microscopy study of moiré superlattice devices with comparable activation energy but with different charge disorder levels...
March 12, 2018: Nano Letters
Xu Wang, Yinchu Ma, Xing Sheng, Yucai Wang, Hangxun Xu
Extensive efforts have been devoted to synthesizing photothermal agents (PTAs) that are active in the first near-infrared (NIR) region (650~950 nm). However, PTAs for photothermal therapy (PTT) in the second NIR window (1000~1350 nm) are still rare. Here, we show that two-dimensional ultrathin polypyrrole (PPy) nanosheets prepared via a novel space-confined synthesis method could exhibit unique broadband absorption with a large extinction coefficient of 27.8 L g-1 cm-1 at 1064 nm and can be used as an efficient PTA in the second NIR window...
March 12, 2018: Nano Letters
Mohammad Mahdi Tavakoli, Fabrizio Giordano, Shaik M Zakeeruddin, Michael Grätzel
The solar to electric power conversion efficiency (PCE) of perovskite solar cells (PSCs) has recently reached 22.7 % exceeding that of competing thin film photovoltaics and the market leader polycrystalline silicon. Further augmentation of the PCE towards the Shockley-Queisser limit of 33.5 % warrants suppression of radiationless carrier recombination by judicious engineering of the interface between the light harvesting perovskite and the charge carrier extraction layers. Here, we introduce a mesoscopic oxide double layer as electron selective contact consisting of a scaffold of TiO2 nanoparticles covered by a thin film of SnO2, either in amorphous (a-SnO2), crystalline (c-SnO2) or nanocrystalline (quantum dot) form (SnO2-NC)...
March 12, 2018: Nano Letters
Tomáš Neuman, Ruben Esteban, David Casanova, Francisco J Garcia-Vidal, Javier Aizpurua
As the size of a molecular emitter becomes comparable to the dimensions of a nearby optical resonator, the standard approach that considers the emitter to be a point-like dipole breaks down. By adopting a quantum description of the electronic transitions of organic molecular emitters, coupled to a plasmonic electromagnetic field, we are able to accurately calculate the position-dependent coupling strength between a plasmon and an emitter. The spatial distribution of excitonic and photonic quantum states is found to be a key aspect in determining the dynamics of molecular emission in ultrasmall cavities both in the weak and strong coupling regimes...
March 9, 2018: Nano Letters
Joseph DuChene, Giulia Tagliabue, Alex J Welch, Wen-Hui Cheng, Harry A Atwater
Harvesting non-equilibrium hot carriers from plasmonic-metal nanostructures offers unique opportunities for driving photochemical reactions at the nanoscale. While examples of hot electron-driven processes abound, the realization of plasmonic systems capable of harvesting hot holes from metal nanostructures has eluded the nascent field of plasmonic photocatalysis. Here, we fabricate gold/p-type gallium nitride (Au/p-GaN) Schottky junctions tailored for photoelectrochemical studies of plasmon-induced hot hole capture and conversion...
March 9, 2018: Nano Letters
V G Deepagan, Hyewon Ko, Seunglee Kwon, N Vijayakameswara Rao, Sang Kyoon Kim, Wooram Um, Sohee Lee, Jiwoong Min, Jeongjin Lee, Ki Young Choi, Sol Shin, Minah Suh, Jae Hyung Park
Conventional cancer targeting with nanoparticles has been based on the assumed enhanced permeability and retention (EPR) effect. The data obtained in clinical trials to date, however, have rarely supported the presence of such an effect. To address this challenge, we formulated intracellular nitric oxide-generating nanoparticles (NO-NPs) for the tumor site-specific delivery of NO, a well-known vasodilator, with the intention of boosting EPR. These nanoparticles are self-assembled under aqueous conditions from amphiphilic copolymers of poly(ethylene glycol) and nitrated dextran, which possesses inherent NO release properties in the reductive environment of cancer cells...
March 9, 2018: Nano Letters
Shan Zhang, Baojin Ma, Feng Liu, Jiazhi Duan, Shicai Wang, Jichuan Qiu, Dong Li, Yuanhua Sang, Chao Liu, Duo Liu, Hong Liu
Numerous studies have determined that physical cues, especially the nanotopography of materials, play key roles in directing stem cell differentiation. However, most research on nanoarrays for stem cell fate regulation are based on non-biodegradable materials, such as silicon wafers, TiO2, and poly (methyl methacrylate), which are rarely used as tissue engineering biomaterials. In this study, we prepared biodegradable poly-lactic acid (PLA) nanopillar arrays with different diameters but the same center-to-center distance using a series of anodic aluminum oxide nano-well arrays as templates...
March 8, 2018: Nano Letters
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