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Aura Higuera-Rodriguez, Bruno Romeira, Simone Birindelli, Lachlan E Black, Barry Smalbrugge, Peter J van Veldhoven, Wilhelmus Erwin M M Kessels, Meint K Smit, Andrea Fiore
The III-V semiconductor InGaAs is a key material for photonics since it provides optical emission and absorption in the 1.55 μm telecommunication wavelength window. However, InGaAs suffers from pronounced non-radiative effects associated with its surface states, which affect the performance of nanophotonic devices for optical interconnects, namely nanolasers and nanodetectors. This work reports the strong suppression of surface recombination of undoped InGaAs/InP nanostructured semiconductor pillars using a combination of ammonium sulfide, (NH4)2S, passivation and silicon oxide, SiOx, coating...
March 24, 2017: Nano Letters
Nandi Vrancken, Stefanie Sergeant, Guy Vereecke, Geert Doumen, Frank Holsteyns, Herman Terryn, Stefan De Gendt, XiuMei Xu
In situ characterization of the underwater stability of superhydrophobic micro- and nanostructured surfaces is important for the development of self-cleaning and anti-fouling materials. In this work, we demonstrate a novel ATR-FTIR (Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy) based method for large-area wetting characterization of silicon nanopillars. When air is present in between the structures, as is characteristic of the Cassie-Baxter state, the relative intensities of the water bands in the absorption spectrum are changed due to the wavelength-dependent attenuation of the evanescent wave...
March 24, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Fabian Schuster, Jonas Kapraun, Gilliard N Malheiros-Silveira, Saniya Deshpande, Connie J Chang-Hasnain
In this Letter, we report the site-controlled growth of InP nanolasers on a silicon substrate with patterned SiO2 nanomasks by low-temperature metal-organic chemical vapor deposition, compatible with silicon complementary metal-oxide-semiconductor (CMOS) post-processing. A two-step growth procedure is presented to achieve smooth wurtzite faceting of vertical nanopillars. By incorporating InGaAs multiquantum wells, the nanopillar emission can be tuned over a wide spectral range. Enhanced quality factors of the intrinsic InP nanopillar cavities promote lasing at 0...
March 23, 2017: Nano Letters
Parvathala Reddy Narangari, Siva Krishna Karuturi, Mykhaylo Lysevych, Hark Hoe Tan, Chennupati Jagadish
In this work, we report on the photoelectrochemical (PEC) investigation of n-GaN nanopillar (NP) photoanodes fabricated using metal organic chemical vapour deposition and the top-down approach. Substantial improvement in photocurrents is observed for GaN NP photoanodes compared to their planar counterparts. The role of carrier concentration and NP dimensions on the PEC performance of NP photoanodes is further elucidated. Photocurrent density is almost doubled for doped NP photoanodes whereas no improvement is noticed for undoped NP photoanodes...
April 18, 2017: Nanotechnology
Yuan-Ming Chang, Man-Ling Lin, Tung-Yen Lai, Chang-Hung Chen, Hsin-Yi Lee, Chih-Ming Lin, Yew-Chung Sermon Wu, Yen-Fu Lin, Jenh-Yih Juang
The photoluminescence (PL) and reflectivity characteristics of zinc oxide nanopillars (ZnO-NPs) grown on indium-tin-oxide (ITO)-coated glasses were investigated. The room temperature PL showed bright white-light emission for the undoped ZnO-NPs grown at 600 °C, suggesting the close relation between the optical characteristic and the growth conditions being carried out for obtaining the present ZnO-NPs. The reflectivity of the as-grown ZnO-NPs array was about ∼29% with the wavelength of the incident light ranging from 200 to 1800 nm...
March 27, 2017: ACS Applied Materials & Interfaces
Ferdi Hizal, Natthakan Rungraeng, Junghoon Lee, Soojin Jun, Henk J Busscher, Henny C van der Mei, Chang-Hwan Choi
Bacterial adhesion and biofilm formation on surfaces are troublesome in many industrial processes. Here, nanoporous and nanopillared aluminum surfaces were engineered by anodizing and postetching processes and made hydrophilic (using the inherent oxide layer) or hydrophobic (applying a Teflon coating) with the aim of discouraging bacterial adhesion. Adhesion of Staphylococcus aureus ATCC 12600 (Gram-positive, spherically shaped) and Escherichia coli K-12 (Gram-negative, rod-shaped) was evaluated to the nanoengineered surfaces under both static and flow conditions (fluid shear rate of 37 s(-1))...
March 27, 2017: ACS Applied Materials & Interfaces
Belén Sanz, Catalina von Bilderling, Jimena S Tuninetti, Lía Pietrasanta, Carmen Mijangos, Gabriel S Longo, Omar Azzaroni, Juan M Giussi
The surface properties of soft nanostructured hydrogels are crucial in the design of responsive materials that can be used as platforms to create adaptive devices. The lower critical solution temperature (LCST) of thermo-responsive hydrogels such as poly(N-isopropylacrylamide) (PNIPAm) can be modified by introducing a hydrophilic monomer to create a wide range of thermo-responsive micro-/nano-structures in a large temperature range. Using surface initiation atom-transfer radical polymerization in synthesized anodized aluminum oxide templates, we designed, fabricated, and characterized thermo-responsive nanopillars based on PNIPAm hydrogels with tunable mechanical properties by incorporating acrylamide monomers (AAm)...
March 13, 2017: Soft Matter
Qiong Wu, Noritada Kaji, Takao Yasui, Sakon Rahong, Takeshi Yanagida, Masaki Kanai, Kazuki Nagashima, Manabu Tokeshi, Tomoji Kawai, Yoshinobu Baba
A millisecond micro-RNA separation of a mixture of total RNA and genomic DNA, extracted from cultured HeLa cells, was successfully achieved using a hybrid structure of nanopillars and nanoslits contained inside a microchannel. The nanopillars, 250-nm in diameter and 100-nm in height, were fabricated with a 750-nm space inside the nanoslits, which were 100-nm in height and 25-μm in width; the nanopillars were then applied as a new sieve matrix. This ultra-fast technique for the separation of miRNA can be an effective pretreatment for semiconductor nanopore DNA sequencing, which has an optimum reading speed of 1 base/ms to obtain effective signal-to-noise ratio and discriminate each base by ion or tunneling current during the passage of nucleic acids...
March 8, 2017: Scientific Reports
Lidia Morelli, Kinga Zór, Christian Bille Jendresen, Tomas Rindzevicius, Michael Stenbæk Schmidt, Alex Toftgaard Nielsen, Anja Boisen
The number of newly developed genetic variants of microbial cell factories for production of biochemicals has been rapidly growing in recent years, leading to an increased need for new screening techniques. We developed a method based on surface-enhanced Raman scattering (SERS) coupled with liquid-liquid extraction (LLE) for quantification of p-coumaric acid (pHCA) in the supernatant of genetically engineered Escherichia coli (E. coli) cultures. pHCA was measured in a dynamic range from 1 μM up to 50 μM on highly uniform SERS substrates based on leaning gold-capped nanopillars, which showed an in-wafer signal variation of only 11...
March 16, 2017: Analytical Chemistry
Sujung Kim, Eunah Kim, Yeon Ui Lee, Eunkyo Ko, Hyeong-Ho Park, Jeong Weon Wu, Dong-Wook Kim
We investigated the influence of metal coating on the optical characteristics of Si nanopillar (NP) arrays with and without thin metal layers coated on the sample surface. The reflection dips of the metal-coated arrays were much broader and more pronounced than those of the bare arrays. The coated metal layers consisted of two parts-the metal disks on the Si NP top and the holey metal backreflectors on the Si substrate. The Mie-like geometrical resonance in the NPs, the localized surface plasmons in the metal disks, and the propagation of surface plasmon polariton along the backreflector/substrate interface could contribute to the reflection spectra...
December 2017: Nanoscale Research Letters
Thomas Endlein, Aihong Ji, Shanshan Yuan, Iain Hill, Huan Wang, W Jon P Barnes, Zhendong Dai, Metin Sitti
Most studies on the adhesive mechanisms of climbing animals have addressed attachment against flat surfaces, yet many animals can climb highly curved surfaces, like twigs and small branches. Here we investigated whether tree frogs use a clamping grip by recording the ground reaction forces on a cylindrical object with either a smooth or anti-adhesive, rough surface. Furthermore, we measured the contact area of fore and hindlimbs against differently sized transparent cylinders and the forces of individual pads and subarticular tubercles in restrained animals...
February 22, 2017: Proceedings. Biological Sciences
Marina Radulaski, Matthias Widmann, Matthias Niethammer, Jingyuan Linda Zhang, Sang-Yun Lee, Torsten Rendler, Konstantinos G Lagoudakis, Nguyen Tien Son, Erik Janzén, Takeshi Ohshima, Jörg Wrachtrup, Jelena Vučković
Silicon carbide is a promising platform for single photon sources, quantum bits (qubits), and nanoscale sensors based on individual color centers. Toward this goal, we develop a scalable array of nanopillars incorporating single silicon vacancy centers in 4H-SiC, readily available for efficient interfacing with free-space objective and lensed-fibers. A commercially obtained substrate is irradiated with 2 MeV electron beams to create vacancies. Subsequent lithographic process forms 800 nm tall nanopillars with 400-1400 nm diameters...
March 8, 2017: Nano Letters
Youngjo Kim, Nguyen Dinh Lam, Kangho Kim, Won-Kyu Park, Jaejin Lee
Radial junction solar cells with vertically aligned wire arrays have been widely studied to improve the power conversion efficiency. In this work, we report the first Ge nanopillar solar cell. Nanopillar arrays are selectively patterned on p-type Ge (100) substrates using nanosphere lithography and deep reactive ion etching processes. Nanoscale radial and planar junctions are realized by an n-type Ge emitter layer which is epitaxially grown by MOCVD using isobutylgermane. In situ epitaxial surface passivation is employed using an InGaP layer to avoid high surface recombination rates and Fermi level pinning...
February 17, 2017: Scientific Reports
Shuang Shuang, Zheng Xie, Zhengjun Zhang
CdS nanoparticles (NPs) decorated α-Fe2O3 nanopillar arrays (NPAs) were fabricated through several steps. Fe NPAs were firstly fabricated by glancing angle deposition technique and oxidized in air to gain α-Fe2O3 NPAs. Then these NPAs were decorated by CdS NPs through successive ion layer adsorption and reaction (SILAR). Here we have tested photodegredation of methylene blue (MB) and photoelectrochemical properties under visible light. Especially, when SILAR cycle number reaches to 10, it shows the highest degradation efficiency (94% in 75min on MB) which improves 72% comparing with pure one and the highest photocurrent density (2...
May 15, 2017: Journal of Colloid and Interface Science
V Dolores-Calzadilla, B Romeira, F Pagliano, S Birindelli, A Higuera-Rodriguez, P J van Veldhoven, M K Smit, A Fiore, D Heiss
Nanoscale light sources using metal cavities have been proposed to enable high integration density, efficient operation at low energy per bit and ultra-fast modulation, which would make them attractive for future low-power optical interconnects. For this application, such devices are required to be efficient, waveguide-coupled and integrated on a silicon substrate. We demonstrate a metal-cavity light-emitting diode coupled to a waveguide on silicon. The cavity consists of a metal-coated III-V semiconductor nanopillar which funnels a large fraction of spontaneous emission into the fundamental mode of an InP waveguide bonded to a silicon wafer showing full compatibility with membrane-on-Si photonic integration platforms...
February 2, 2017: Nature Communications
Nicholas J Hestand, Frank C Spano
The transport and photophysical properties of organic molecular aggregates, films, and crystals continue to receive widespread attention, driven mainly by expanding commercial applications involving display and wearable technologies as well as the promise of efficient, large-area solar cells. The main blueprint for understanding how molecular packing impacts photophysical properties was drafted over five decades ago by Michael Kasha. Kasha showed that the Coulombic coupling between two molecules, as determined by the alignment of their transition dipoles, induces energetic shifts in the main absorption spectral peak and changes in the radiative decay rate when compared to uncoupled molecules...
February 1, 2017: Accounts of Chemical Research
Chaturanga D Bandara, Sanjleena Singh, Isaac O Afara, Annalena Wolff, Tuquabo Tesfamichael, Kostya Ostrikov, Adekunle Oloyede
Nanotextured surfaces (NTSs) are critical to organisms as self-adaptation and survival tools. These NTSs have been actively mimicked in the process of developing bactericidal surfaces for diverse biomedical and hygiene applications. To design and fabricate bactericidal topographies effectively for various applications, understanding the bactericidal mechanism of NTS in nature is essential. The current mechanistic explanations on natural bactericidal activity of nanopillars have not utilized recent advances in microscopy to study the natural interaction...
March 1, 2017: ACS Applied Materials & Interfaces
C Bran, Yu P Ivanov, J Kosel, O Chubykalo-Fesenko, M Vazquez
Arrays of multisegmented Co/Au nanowires with designed segment lengths and diameters have been prepared by electrodeposition into aluminum oxide templates. The high quality of the Co/Au interface and the crystallographic structure of Co segments have determined by high-resolution transmission electron microscopy. Magnetic hysteresis loop measurements show larger coercivity and squareness of multisegmented nanowires as compared to single segment Co nanowires. The complementary micromagnetic simulations are in good agreement with the experimental results, confirming that the magnetic behavior is defined mainly by magnetostatic coupling between different segments...
March 3, 2017: Nanotechnology
M Khorasaninejad, Z Shi, A Y Zhu, W T Chen, V Sanjeev, A Zaidi, F Capasso
In this Letter, we experimentally report an achromatic metalens (AML) operating over a continuous bandwidth in the visible. This is accomplished via dispersion engineering of dielectric phase shifters: titanium dioxide nanopillars tiled on a dielectric spacer layer above a metallic mirror. The AML works in reflection mode with a focal length independent of wavelength from λ = 490 to 550 nm. We also design a metalens with reverse chromatic dispersion, where the focal length increases as the wavelength increases, contrary to conventional diffractive lenses...
March 8, 2017: Nano Letters
Waleed A Hassanain, Emad L Izake, Michael S Schmidt, Godwin A Ayoko
A highly sensitive nanosensing method for the combined selective capture and SERS detection of Microcystin-LR (MC-LR) in blood plasma has been developed. The new method utilizes gold coated magnetic nanoparticles that are functionalized with anti MC-LR antibody Fab' fragments for the selective capture of MC-LR from aqueous media and blood plasma. Using an oriented immobilization approach, the Fab' fragments are covalently attached to gold surface to form a monolayer with high capture efficiency towards the toxin...
May 15, 2017: Biosensors & Bioelectronics
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