Cone-shaped Nanostructures Research Articles

초정밀 레이저를 이용한 연꽃잎 표면 자연 모사 연구

In a pilot natural super-hydrophobic surfaces study, a super-hydrophobic surface was made by coating, etching, laser ablation, chemical vapor deposition and lithography. In this study, cone-shaped periodic micro and nano-structures were constructed on a silica surface with femtosecond and picosecond laser, and the period of micro-structures between cone shape patterns was increased with 10 μm intervals. The contact angle and image of the super-hydrophobic surface were analysed and the cone (Aspect-ratio 1.27) shape model with micro-protrusion structure similar to the surface of the lotus leaf was made to measure the contact angle. To analyse the differences in the contact angles between the cone shapes and heights of the micro-protrusion, different samples with cone (Aspect-ratio 1.27), sphere (Aspect-ratio 1.00) shapes were made through laser micro-machining technology. To mimick the natural lotus leaves, the optimum condition was a cone shape. Samples of PDMS with different shapes and mixed micro/nano-structures were fabricated with a PDMS mold insert. The largest contact angle was measured at 170.42° which is similar to the contact angle of the lotus leaf. This mold insert could be used repeatedly. The molding process is advantageous for large areas and mass production.

Solvothermal synthesis of 3D hierarchical rutile TiO2 nanostructures for efficient dye-sensitized solar cells

3D hierarchical rutile TiO2 nanostructures were successfully prepared using the solvothermal method. X-ray diffraction (XRD) revealed the formation of the anatase phase. A high-resolution transmission electron microscope (HRTEM) shows that several hundred radially distributed nanofibers with a length of 1 μm were self-assembled to form a nanostructure. Current vs voltage (I-V) measurements for the cone-shaped nanostructure showed a short circuit current density (Isc) of 2.8 mA/cm2, an open circuit voltage (Voc) of 0.70 V, and the fill factor (FF) is 0.55. The efficiency obtained for cone-shaped hierarchical rutile TiO2 structures was 1.12 %.

Low-Frequency Dielectric Relaxation in Structures Based on Macroporous Silicon with Meso-Macroporous Skin-Layer.

The spectra of dielectric relaxation of macroporous silicon with a mesoporous skin layer in the frequency range 1–106 Hz during cooling (up to 293–173 K) and heating (293–333 K) are presented. Macroporous silicon (pore diameter ≈ 2.2–2.7 μm) with a meso-macroporous skin layer was obtained by the method of electrochemical anodic dissolution of monocrystalline silicon in a Unno-Imai cell. A mesoporous skin layer with a thickness of about 100–200 nm in the form of cone-shaped nanostructures with pore diameters near 13–25 nm and sizes of skeletal part about 35–40 nm by ion-electron microscopy was observed. The temperature dependence of the relaxation of the most probable relaxation time is characterized by two linear sections with different slope values; the change in the slope character is observed at T ≈ 250 K. The features of the distribution of relaxation times in meso-macroporous silicon at temperatures of 223, 273, and 293 K are revealed. The Havriliak-Negami approach was used for approximation of the relaxation curves ε″ = f(ν). The existence of a symmetric distribution of relaxers for all temperatures was found (Cole-Cole model). A discussion of results is provided, taking into account the structure of the studied object.

Polarized SERS Controlled by Anisotropic Growth on Ordered Curvature Substrate.

Colloidal lithography is an efficient and low-cost method to prepare an ordered nanostructure array with new shapes and properties. In this study, square-shaped and cone-shaped Au nanostructures were obtained by 70° angle deposition onto polystyrene bead array with the diameter of 500 nm when a space of 120 nm is created between the neighbor beads by plasma etching. The gaps between the units decrease when the Au deposition time increases, which leads to the polarized enhanced local field, in agreement with the surface-enhanced Raman scattering spectra (SERS) observations and finite-difference time-domain (FDTD) simulations. When the Au deposition time increased to 5 min, 5 nm gaps form between the neighbor units, which gave an enhancement factor of 5 × 109. The SERS chip was decorated for the detection of the liver cancer cell marker Alpha-fetoprotein (AFP) with the detection limit down to 5 pg/mL.

Molecular dynamics simulation on explosive boiling of thin liquid argon films on cone-shaped Al–Cu-based nanostructures

The aim of this study is to investigate the effects of Al and Cu nanostructures on the explosive boiling of a thin layer of liquid argon atoms on the Al and Cu substrates using molecular dynamics method. The results indicate that employing cone-shaped nanostructured surfaces leads to creation of thinner primary liquid layer as compared to the common Al or Cu smooth surfaces. Results show that using a cone-shaped nanostructured surface leads to a higher heat transfer rate and subsequently faster evaporating rate of the liquid layers due to increase in the solid–liquid contact area. In addition, it was found that Cu nanostructure has a more effective role in amplifying the explosive boiling, in comparison with Al nanostructure. The results further show that using the Al and Cu cone-shaped nanostructures on an Al smooth surface can increase the heat transfer by 29% and 38.7%, respectively.

Stretchable Biaxial and Shear Strain Sensors Using Diffractive Structural Colors

Structural colors that can be changed dynamically, using either plasmonic nanostructures or photonic crystals, are rapidly emerging research areas for stretchable sensors. Despite the wide applications of various techniques to achieve strain-responsive structural colors, important factors in the feasibility of strain sensors-such as their sensing mechanism, stability, and reproducibility-have not yet been explored. Here, we introduce a stretchable, diffractive, color-based wireless strain sensor that can measure strain using the entire visible spectrum, based on an array of cone-shaped nanostructures on the surface of an elastomeric substrate. By stretching or compressing the substrate, the diffractive color can be tuned according to the changing grating pitch. Using the proposed method, we designed three types of strain-sensing modes: large-deformation (maximum 100%) tensile strain, biaxial 2D strain, and shear strain (maximum 78%). The strain sensors were fabricated, and applicability to strain-sensing was evaluated.

Synergistic effects on thermal growth of CuO nanowires

Growing cupric oxide (CuO) nanowires (NWs) through thermal oxidation of copper (Cu) in air is a facile and low-cost strategy. In a temperature range of 673–1073 K, single-crystal, bi-crystal NWs and cone-shaped nanostructure usually coexist. As far as the underlying mechanism is concerned, the stress-driven grain-boundary (GB) diffusion mechanism has been the most successful theory up to now. However, it did not include the influence of oxygen partial pressure and cannot explain the growth of long single-crystal CuO NWs of uniform diameters. Thus, the CuO NWs growth mechanism is yet to be fully understood. In this study, we present that synergistic effects of the Kirkendall effect, stress-driven GB diffusion, large surface free energy gap between Cu2O and CuO facets and an effective electric field along the CuO NWs originating from oxygen gradient are mainly involved in the thermal growth of CuO NWs.

Tapered Bottlebrush Polymers: Cone-Shaped Nanostructures by Sequential Addition of Macromonomers.

Tapered (cone-shaped) bottlebrush polymers were synthesized for the first time by ring-opening metathesis polymerization (ROMP) using a sequential-addition of macromonomers (SAM) strategy. Polystyrene macromonomers with molecular weights that increased from 1 to 10 kg mol-1 were polymerized in sequence to high conversion, yielding tapered bottlebrush polymers that could be visualized by atomic force microscopy (AFM).

Facile synthesis of double cone-shaped Ag4V2O7/BiVO4 nanocomposites with enhanced visible light photocatalytic activity for environmental purification

Abstract Ag4V2O7/BiVO4 photocatalysts with double cone-shaped nanostructure were successfully synthesized by a facile sodium polyphosphate-assisted hydrothermal method. The results demonstrate that coupling Ag4V2O7 with BiVO4 can promote the separation of photoinduced charge carriers and enhance the photon absorption efficiency. Experimental results indicate that Ag4V2O7/BiVO4 composites exhibit the enhanced photocatalystic activity for degradation of methylene blue (MB) and oxidation of NO in high concentrate (1600 ppb) compared to the pure BiVO4 under visible light irradiation (λ > 420 nm). The composite with 0.08 mol% Ag4V2O7 has the highest photocatalytic activity. MB degradation rate can reach 98.48% in 1 h and NO oxidation rate can reach 52.83% in 0.5 h on 0.08-Ag4V2O7/BiVO4, which are about 2.90 and 3.11 times higher than that of pure BiVO4 respectively. The excellent activity can be attributed to the efficient charge transfer between Ag4V2O7 and BiVO4, and active species h+ and O2− play important roles during MB degradation and NO oxidation. In addition, this composite exhibits favorable stability during the cycling experiment, suggesting it may be a promising visible light active photocatalyst for environmental applications.

Hierarchical Morphology-Dependent Gas-Sensing Performances of Three-Dimensional SnO2 Nanostructures.

Hierarchical morphology-dependent gas-sensing performances have been demonstrated for three-dimensional SnO2 nanostructures. First, hierarchical SnO2 nanostructures assembled with ultrathin shuttle-shaped nanosheets have been synthesized via a facile and one-step hydrothermal approach. Due to thermal instability of hierarchical nanosheets, they are gradually shrunk into cone-shaped nanostructures and finally deduced into rod-shaped ones under a thermal treatment. Given the intrinsic advantages of three-dimensional hierarchical nanostructures, their gas-sensing properties have been further explored. The results indicate that their sensing behaviors are greatly related with their hierarchical morphologies. Among the achieved hierarchical morphologies, three-dimensional cone-shaped hierarchical SnO2 nanostructures display the highest relative response up to about 175 toward 100 ppm of acetone as an example. Furthermore, they also exhibit good sensing responses toward other typical volatile organic compounds (VOCs). Microstructured analyses suggest that these results are mainly ascribed to the formation of more active surface defects and mismatches for the cone-shaped hierarchical nanostructures during the process of thermal recrystallization. Promisingly, this surface-engineering strategy can be extended to prepare other three-dimensional metal oxide hierarchical nanostructures with good gas-sensing performances.

Correction: Corrigendum: Observation of strongly enhanced photoluminescence from inverted cone-shaped silicon nanostructures

Silicon nanowires (SiNWs) attached to a wafer substrate are converted to inversely tapered silicon nanocones (SiNCs). After excitation with visible light, individual SiNCs show a 200-fold enhanced integral band-to-band luminescence as compared to a straight SiNW reference. Furthermore, the reverse taper is responsible for multifold emission peaks in addition to the relatively broad near-infrared (NIR) luminescence spectrum. A thorough numerical mode analysis reveals that unlike a SiNW the inverted SiNC sustains a multitude of leaky whispering gallery modes. The modes are unique to this geometry and they are characterized by a relatively high quality factor (Q ~ 1300) and a low mode volume (0.2 < (λ/neff)3 < 4). In addition they show a vertical out coupling of the optically excited NIR luminescence with a numerical aperture as low as 0.22. Estimated Purcell factors Fp ∝ Q/Vm of these modes can explain the enhanced luminescence in individual emission peaks as compared to the SiNW reference. Investigating the relation between the SiNC geometry and the mode formation leads to simple design rules that permit to control the number and wavelength of the hosted modes and therefore the luminescent emission peaks.

Observation of strongly enhanced photoluminescence from inverted cone-shaped silicon nanostructures. [corrected

Silicon nanowires (SiNWs) attached to a wafer substrate are converted to inversely tapered silicon nanocones (SiNCs). After excitation with visible light, individual SiNCs show a 200-fold enhanced integral band-to-band luminescence as compared to a straight SiNW reference. Furthermore, the reverse taper is responsible for multifold emission peaks in addition to the relatively broad near-infrared (NIR) luminescence spectrum. A thorough numerical mode analysis reveals that unlike a SiNW the inverted SiNC sustains a multitude of leaky whispering gallery modes. The modes are unique to this geometry and they are characterized by a relatively high quality factor (Q ~ 1300) and a low mode volume (0.2 < (λ/neff)3 < 4). In addition they show a vertical out coupling of the optically excited NIR luminescence with a numerical aperture as low as 0.22. Estimated Purcell factors Fp ∝ Q/Vm of these modes can explain the enhanced luminescence in individual emission peaks as compared to the SiNW reference. Investigating the relation between the SiNC geometry and the mode formation leads to simple design rules that permit to control the number and wavelength of the hosted modes and therefore the luminescent emission peaks.

Haze-Free Highly Transparent Glass Substrates with Nanostructured Surface by Using Self-Assembled Ag Etch Masks

Nano- or micro-structured glass substrates have been widely used for displays, but have a significant drawback called haze that blurs the images. To eliminate haze while maintaining high total optical transmittance (Ttotal), the optimized design of textured structures on single- and double-side glass substrates was investigated using a rigorous coupled-wave analysis method. With optimized truncated cone-shaped nanostructures having period (Λ) = 200 nm, top-diameter to bottom-diameter ratio (R) = 0.4 and height (h) ≥ 150 nm on both sides of glass substrates, we achieved a haze-free substrate with an average Ttotal = 99.5% in the wavelength (λ) range 300–800 nm.

A novel method for synthesis of well-aligned hexagonal cone-shaped ZnO nanostructures in field emission applications

Well-aligned and high-density ZnO nanocone arrays were prepared on Si substrates using an electric field-assisted chemical bath deposition (FECBD) method. The photoluminescence (PL) spectra of ZnO nanostructures indicate that near-band-edge (NBE) emission shifted slightly toward lower wavelengths with the increase in procedure temperature, and the intensity increased with improved ZnO crystallization. The cone-shaped ZnO nanorods had the lowest turn-on electric field, largest field-enhancement factor, and good stability, which were attributed to the small emitter radius at the tip, uniform density distribution, and high aspect ratio. These results indicate that the cone-shaped ZnO nanostructures fabricated by FECBD are promising for application as field emission (FE) electron sources.

Nanocones to study initial steps of endocytosis.

Vesicle endocytosis at the plasma membrane is associated with a precise temporal choreography in the recruitment of cytosolic proteins that sense, generate, or stabilize locally curved membrane regions. To dissect the role of membrane curvature sensing from other co-occurring events during the initial steps of endocytosis, we developed a method to artificially induce nanoscale deformations of the PM in living cells that is based on cone-shaped nanostructures (i.e., Nanocones). When cultured on Nanocones, cells create stable inward plasma membrane deformations to which curvature-sensing proteins are recruited. Here, we provide a detailed protocol how to use Nanocones to study recruitment during the initial steps of endocytosis in cells by fluorescence and electron microscopy.

Investigations on Diamond Nanostructuring of Different Morphologies by the Reactive-Ion Etching Process and Their Potential Applications

We report the systematic studies on the fabrication of aligned, uniform, and highly dense diamond nanostructures from diamond films of various granular structures. Self-assembled Au nanodots are used as a mask in the self-biased reactive-ion etching (RIE) process, using an O2/CF4 process plasma. The morphology of diamond nanostructures is a close function of the initial phase composition of diamond. Cone-shaped and tip-shaped diamond nanostructures result for microcrystalline diamond (MCD) and nanocrystalline diamond (NCD) films, whereas pillarlike and grasslike diamond nanostructures are obtained for Ar-plasma-based and N2-plasma-based ultrananocrystalline diamond (UNCD) films, respectively. While the nitrogen-incorporated UNCD (N-UNCD) nanograss shows the most-superior electron-field-emission properties, the NCD nanotips exhibit the best photoluminescence properties, viz, different applications need different morphology of diamond nanostructures to optimize the respective characteristics. The optimum diamond nanostructure can be achieved by proper choice of granular structure of the initial diamond film. The etching mechanism is explained by in situ observation of optical emission spectrum of RIE plasma. The preferential etching of sp(2)-bonded carbon contained in the diamond films is the prime factor, which forms the unique diamond nanostructures from each type of diamond films. However, the excited oxygen atoms (O*) are the main etching species of diamond film.

Fabrication and photoelectrochemical properties of cone-shaped CdSe nanorod arrays

Vertically aligned, cone-shaped CdSe nanorods (NRs) have been synthesized on fluorine-doped tin oxide (FTO) glass by a simple one-step, template-free electrochemical deposition at room temperature. The preparation took advantage of the wurtzite structure characteristics and current density. The experiments had been conducted with different current densities at the zero time (j) in order to investigate the morphology dependence on j. Photoelectrochemical measurements indicated that the novel CdSe photoelectrode had a potential application in photovoltaic devices. The cone-shaped nanostructure presented here could be a model system for fabricating shape-controlled NRs of other wurtzite structural materials.

Enhanced light output from light emitting diodes with two-dimensional cone-shape nanostructured surface

A simple, inexpensive and high throughput approach for creating two-dimensional cone-shaped nanostructures is reported. A self-assembled array of polystyrene nanospheres is employed as the primary mask to fabricate such structures on AlGaInP red light emitting diodes, resulting in over two times increase of light output power. An orderly array of cones show higher intensity emitted in the forward direction than one that is randomly arranged.

A facile fabrication process for polystyrene nanoring arrays

Polystyrene nanoring arrays with outer diameters ranging from 130 to 230 nm were fabricated using low cost and simple fabrication techniques, including nanosphere lithography, argon plasma treatment, immersion in organic solvents and sonication. These nanorings were developed from polystyrene nanospheres pre-assembled on substrates. Scanning electron microscopy revealed that the argon plasma treatment transformed polystyrene nanospheres into hollow cone-shaped nanostructures. X-ray photoelectron and Raman spectroscopy found that the argon plasma changed the composition of the polystyrene nanospheres by forming graphitic materials. The nanoring formation mechanism was discussed based on the instrument analyses.

Increased Light Extraction From Vertical GaN Light-Emitting Diodes With Ordered, Cone-Shaped Deep-Pillar Nanostructures

In this paper, improved light extraction using cone-shaped deep-pillar nanostructures is demonstrated on the Honeycomb-type vertical GaN light-emitting diodes (VLEDs). In order to produce ordered, cone-shaped deep-pillar patterns on the surface of an n-type GaN, double-layered polystyrene (PS) nanospheres of 500-nm size were coated onto the n-GaN layer by a simple spin-coating. Then, immediately after the O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> plasma ashing for double-layered PS beads, the Ni metal was deposited and lifted off to form a hard mask for deep pillar etching. Then, the three VLEDs-the reference VLED with no patterns and the two VLEDs with ordered, cone-shaped pillar patterns of 1.0 and 1.5 μm depth on the n-type GaN surface-were prepared for comparison. As a result, the output power for the proposed VLEDs with 1.0- and 1.5-μm-deep cone-shaped patterns has been increased by 200% and 214%, respectively, at 350 mA as compared to the reference VLED. There was a slight sacrifice of operational voltage and leakage current. The improved optical properties are attributed to the multiple scattering of light from the sidewall of the cone-shaped patterns and the increased surface dimension.