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TaeWan Kim, Jihun Mun, Hyeji Park, DaeHwa Joung, Mangesh Diware, Won Chegal, Jonghoo Park, Soo-Hwan Jeong, Sang-Woo Kang
Semiconducting two-dimensional (2D) materials, particularly, extremely thin molybdenum disulfide (MoS2) films are attracting considerable attention from the academia and industry owing to their distinctive optical and electrical properties. Here, we present the direct growth of a MoS2 monolayer with unprecedented spatial and structural uniformity across an entire 8-inch SiO2/Si wafer. The influences of growth pressure, ambient gases (Ar, H2), and S/Mo molar flow ratio on the MoS2 layered growth were explored by considering the domain size, nucleation sites, morphology, and impurity incorporation...
March 27, 2017: Nanotechnology
Uksu Kim, Noboru Morita, Deug Lee, Martin Jun, Jeong Woo Park
Pulse electrochemical nanopatterning (PECN), a non-contact scanning probe lithography (NC-SPL) process using ultrashort voltage pulses, is based primarily on an electrochemical machining (ECM) process using localized electrochemical oxidation between a sharp tool tip and the sample surface. In this study, nanoscale oxide patterns were formed on silicon Si (100) wafer surfaces via electrochemical surface nanopatterning, by supplying external pulsed currents through non-contact atomic force microscopy. Nanoscale oxide width and height were controlled by modulating the applied pulse duration...
March 27, 2017: Nanotechnology
Yunhai Zhang, Huiru Lv, Can Cui, Lingbo Xu, Peng Wang, Hao Wang, Xuegong Yu, Jiangsheng Xie, Jiabin Huang, Zeguo Tang, Deren Yang
The solution-processed polycrystalline perovskite film contributes critically to the high photovoltaic performance of perovskite based solar cells (PSCs). The inevitable electronic trap states at grain boundaries and the intrinsic defects such as metallic lead (Pb0) and halide vacancies in perovskite film cause serious carrier recombination loss. Furthermore, the film can easily decompose into PbI2 in moisture atmosphere. Here, we introduce a simple strategy through a small increase in methylammonium iodide (CH3NH3I, MAI) molar proportion (5%) for perovskite fabrication in ambient air with a ~50% relative humidity...
March 27, 2017: Nanotechnology
Luigi Giacomazzi, Layla Martin-Samos, Aziz Boukenter, Youcef Ouerdane, Sylvain Girard, Antonino Alessi, Nicolas Richard, Stefano de Gironcoli
In this work we present an extensive investigation of nanoscale physical phenomena related to oxygen-deficient centers (ODC) in silica and Ge-doped silica by means of first-principles calculations, including nudged-elastic band (NEB), electron paramagnetic resonance (EPR) parameters calculations, and many-body perturbation theory (GW and Bethe-Salpeter Equation) techniques. We show that by neutralizing positively charged oxygen monovacancies we can obtain model structures of twofold Si and Ge defects of which the calculated absorption spectra and singlet-to-triplet transitions are in excellent agreement with the experimental optical absorption and photo-luminescence data...
March 27, 2017: Nanotechnology
Ning Li, Lei Feng, Fei Teng, Nan Lu
The plasmonic cavity arrays are ideal substrates for surface enhanced Raman scattering (SERS) analysis because they can provide large hot area for analyte molecules. The large area increases the probability to make more analyte molecules on hot spots and leads to a high reproducibility. Therefore, to develop a simple method for creating cavity arrays is important. Herein, we demonstrate how to fabricate a V and W shape cavity arrays by a simple method based on self-assembly. Briefly, the V and W shape cavity arrays are respectively fabricated by taking KOH etching on a nanohole and a nanoring array patterned silicon (Si) slides, which are generated by taking a reactive ion etching on a monolayer of polystyrene spheres patterned blank Si slide and a Si slide covered with a monolayer of octadecyltrichlorosilane...
March 27, 2017: Nanotechnology
Sijin Sung, Sooran Kim, Paengro Lee, Jingul Kim, Min-Tae Ryu, Heemin Park, Kyoo Kim, Byung Min, Jinwook Chung
We report europium (Eu)-induced changes in the π-band of graphene (G) formed on 6H-SiC(0001) surface by a combined study of photoemission measurements and density functional theory (DFT) calculations. Our photoemission data reveal that Eu intercalates upon annealing at 120 °C into the region between graphene and buffer layer (BL) to form a G/Eu/BL system, where a band gap of 0.29 eV opens at room temperature. This band gap is found to increase further to 0.48 eV upon cooling down to 60 K. Our DFT calculations suggest that the increased band gap originates from the enhanced hybridization between graphene π-Eu 4f band due to the increased magnetic ordering upon cooling...
March 27, 2017: Nanotechnology
Ramathasan Thevamaran, Deepika Saini, Mehmet Karakaya, Jingyi Zhu, Ramakrishna Podila, Apparao Rao, Chiara Daraio
We describe the super compressible and highly recoverable response of bucky sponges as they are struck by a heavy flat-punch striker. The bucky sponges studied here are structurally stable, self-assembled mixtures of multiwalled carbon nanotubes (MWCNTs) and carbon fibers (CFs). We engineered the microstructure of the sponges by controlling their porosity using different CF contents. Their mechanical properties and energy dissipation characteristics during impact loading are presented as a function of their composition...
March 24, 2017: Nanotechnology
Wenqi Xiong, Congxin Xia, Juan Du, Tianxing Wang, Yuting Peng, Zhongming Wei, Jingbo Li
As a fast developing field, van der Waals (vdW) heterostructure can overcome the weakness of single two-dimensional (2D) layered material and extend its electronic and optoelectronic applications. Through first-principles methods, the studied MoS2/stanene heterostructure preserves high-speed carrier characteristics and opens the direct band gap. Meanwhile, the band alignment shows that the electrons transfer from stanene to MoS2, which forms an internal electric field. As an effective strategy, the out-of-plane strain remarkably change the band gaps of heterostructure and enhances its carrier concentration...
March 23, 2017: Nanotechnology
Ming-Lin Li, Haili Huang, Liping Tu, Weidong Wang, Peifeng Li, Yang Lu
The nonlocal scale parameter of the nonlocal Euler-Bernoulli beam theory is evaluated for the static bending of single layer molybdenum disulfide (SLMoS2) without the predetermined bending rigidity. The evaluation activity is performed by matching the fitted curve between the maximum deflection and the beam length obtained from molecular mechanics simulations. It was observed that the fitted curves have an abnormal sign in the second order term of the maximum deflection for SLMoS2, opposite to that for graphene and regardless of the used interatomic interaction potentials...
March 23, 2017: Nanotechnology
Michal Krupinski, Marcin Perzanowski, Alexey Maximenko, Yevhen Zabila, Marta Marszalek
In this work, we propose a new method for a large-scale production of flexible, periodic alumina arrays with well-ordered pores. We show the incorporation of pre-patterning based on a polystyrene (PS) nanosphere lithography into aluminium anodization process. We prepared ordered monolayers of PS spheres with average diameters of (510 ± 10) nm, and (430 ± 10) nm on a large area (1.5 x 1.5 cm<sup>2</sup>) of the Si substrate. Next, we deposited the 5 μm aluminium layer on arrays of PS nanospheres using the sputtering technique...
March 23, 2017: Nanotechnology
Cameron Olsen, Jacob Embley, Kameron Hansen, Andrew Henrichsen, J Peterson, John S Colton, Richard Watt
This study uses the formation of a mixed metal oxide inside ferritin to tune the band gap energy of the ferritin mineral. The mixed metal oxide is composed of both Co and Mn, and is formed by reacting aqueous Co2+ with MnO4- in the presence of apoferritin. Altering the ratio between the two reactants allowed for controlled tuning of the band gap energies. All minerals formed were indirect band gap materials, with indirect band gap energies ranging from 0.52 to 1.30 eV. The direct transitions were also measured, with energy values ranging from 2...
March 23, 2017: Nanotechnology
Cameron Olsen, Trevor Smith, Jacob Embley, Jake Maxfield, Kameron Hansen, J Peterson, Andrew Henrichsen, Stephen Erickson, David Buck, John S Colton, Richard Watt
This paper investigates the comproportionation reaction of MnII with MnO4- as a route for manganese oxide nanoparticle synthesis in the protein ferritin. We report that MnO4- serves as the electron acceptor and reacts with MnII in the presence of apoferritin to form manganese oxide cores inside the protein shell. Manganese loading into ferritin was studied under acidic, neutral, and basic conditions and the ratios of MnII and permanganate were varied at each pH. The manganese-containing ferritin samples were characterized by transmission electron microscopy, UV/Vis absorption, and by measuring the band gap energies for each sample...
March 23, 2017: Nanotechnology
Concepcion Cascales, Carlos Paino, Eulalia Bazán, Carlos Zaldo
This work presents the synthesis by coprecipitation of diamond shaped Yb:Er:NaGd(WO<sub>4</sub>)<sub>2</sub> crystalline nanoparticles (NPs) with diagonal dimensions in the 5-7 nm × 10-12 nm range which have been modified with TWEEN80 for their dispersion in water, and their interaction with mesenchymal stem cells (MSCs) proposed as cellular NP vehicles. These NPs belong to a large family of tetragonal Yb:Er:NaT(XO<sub>4</sub>)<sub>2</sub> (T=Y, La, Gd, Lu; X= Mo, W) compounds with green (<sup>2</sup>H<sub>11/2</sub>+<sup>4</sup>S<sub>3/2</sub>→<sup>4</sup>I<sub>15/2</sub>) Er-related upconversion (UC) efficiency comparable to that of Yb:Er:β-NaYF<sub>4</sub> reference compound, but with a ratiometric thermal sensitivity (S) 2...
March 21, 2017: Nanotechnology
Michael Boutilier, Nicolas Hadjiconstantinou, Rohit Karnik
Graphene membranes have the potential to exceed the permeance and selectivity limits of conventional gas separation membranes. Realizing this potential in practical systems relies on overcoming numerous scalability challenges, such as isolating or sealing permeable defects in macroscopic areas of graphene that can compromise performance and developing methods to create high densities of selective pores over large areas. This study focuses on a centimeter-scale membrane design, where leakage is reduced by substrate selection, permeable polymer film coating, and stacking of three independent layers of graphene, while (selective) pores are created by high density ion bombardment...
March 21, 2017: Nanotechnology
Lei Liu, Yazhou Huang, Jingjie Sha, Yunfei Chen
Monolayer and/or atomically thin transition metal dichalcogenides cover a wide range of two-dimensional (2-D) materials, whose fascinating semiconducting and optical properties have made them being promising candidate materials for optoelectronic device. Controllable growth of these materials is critical for their device applications. By using MoCl5 and H2S as precursors, monolayer and ultrathin molybdenum disulfide (MoS2) films with controlled lamellar structure have been directly built layer by layer on SiO2 substrates without followed high-temperature annealing...
March 21, 2017: Nanotechnology
Nancy Rahbany, Wei Geng, Renaud Bachelot, Christophe Couteau
Overcoming the diffraction limit to achieve high optical resolution is one of the main challenges in the fields of plasmonics, nanooptics and nanophotonics. In this work, we introduce novel plasmonic structures consisting of nanoantennas (nanoprisms, single bowtie nanoantennas and double bowtie nanoantennas) integrated in the center of ring diffraction gratings. Propagating surface plasmon polaritons (SPPs) are generated by the ring grating and coupled with localized surface plasmons (LSPs) at the nanoantennas exciting emitters placed in their gap...
March 21, 2017: Nanotechnology
Rafael Salas-Montiel, Martin Berthel, Josslyn Beltrán-Madrigal, Serge Huant, Aurélien Drezet, Sylvain Blaize
One of the most explored single quantum emitters for the development of nanoscale fluorescence lifetime imaging is the nitrogen-vacancy (NV) color center in diamond. Indeed, a NV center does not experience fluorescence bleaching and blinking at room temperature. Furthermore, its optical properties are preserved when embedded into nanodiamond hosts. This letter focuses on the modeling of the local density of states (LDOS) in a plasmonic nanofocusing structure with NV center acting as local illumination sources...
March 21, 2017: Nanotechnology
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
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
Maria Sarno, Lucia Baldino, Carmela Scudieri, Stefano Cardea, Paolo Ciambelli, Ernesto Reverchon
Energy density, safety, simple and environmentally friendly preparation methods are very significant aspects in the realization of a compact supercapacitor. Herein we report the use of a supercritical CO2 assisted gel drying process (SC-CO2) for the preparation of porous electrodes containing dispersed graphene in a Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) binder membrane to sandwich in a new portable supercapacitor based on graphene oxide (GO). A GO loading of 60 wt.% has been found to give the better combination of factors (porosity, wettability, mechanical and electrochemical properties,...
March 20, 2017: Nanotechnology
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