Cylindrical and Spherical Membranes of Anodic Aluminum Oxide with Highly Ordered Conical Nanohole Arrays

Nanoporous anodic aluminum oxide (AAO) with uniform and controllable pore diameters and periods over a wide range has been explored for various applications due to relatively easy fabrication processes. Moreover, one of the interesting possibilities afforded by the anodization process is that the anodization can take place on aluminum films with arbitrary shape, such as a section of cylinder or sphere, which has not yet been well studied or applied in nanofabrication. In this paper, we report that highly ordered conical nanohole arrays prepared by the anodization of cylindrical and spherical Al films have been fabricated. As can be seen by scanning electron microscopy (SEM), straight nanohole arrays have been grown along the radical directions of the cylindrical or spherical alumina membrane without bending or branching at all, the diameter of the conical nanoholes and the diameter change along individual channels can be tuned by changing the curvature of the membrane. These new types of templates may open new opportunities in optical, electronic and electrochemical applications.

Ultra-Stable and Durable Piezoelectric Nanogenerator with All-Weather Service Capability Based on N Doped 4H-SiC Nanohole Arrays

Ultra-stable piezoelectric nanogenerator(PENG)driven by environmental actuation sources with all-weather service capability is highly desirable.Here,the PENG based on N doped 4H-SiC nanohole arrays(NHAs)is proposed to harvest ambient energy under low/high temperature and relative humidity(RH)conditions.Finite element method simulation of N doped 4H-SiC NHAs in compression mode is developed to evaluate the relationship between nanohole diameter and piezoelectric performance.The density of short circuit current of the assembled PENG reaches 313 nA cm^(-2),which is 1.57 times the output of PENG based on N doped 4H-SiC nanowire arrays.The enhancement can be attributed to the existence of nanohole sidewalls in NHAs.All-weather service capability of the PENG is verified after being treated at-80/80℃and 0%/100%RH for 50 days.The PENG is promising to be widely used in practice worldwide to harvest biomechanical energy and mechanical energy.

Closed-Form Solution for a Circular Nanohole with Surface Effects Under Uniform Heat Flux

This paper investigates the steady-state thermoelastic problem of a circular nanohole embedded in an infinitely large elastic plane subjected to a uniform far-field heat flux.A lowly conductive surface model is used to account for the effects of surface phonon scattering,while the complete Gurtin–Murdoch model is utilized to characterize the effects of surface tension and surface elasticity.The closed-form solution to the temperature and stress field surrounding the hole is derived in the context of complex variable methods.Several numerical examples are presented to analyze the influence of surface effects on thermal stress fields.It is shown that surface effects induce notable increases in normal and shear stresses around the hole.Specifically,all three stress components(hoop,normal,and shear)in the vicinity of the hole exhibit substantial augmentation with increasing surface tension and surface modulus.In particular,it is found that the presence of surface effects amplifies the variation in stress gradients and intensifies stress concentration around the hole.

Propagation of elastic wave in nanoporous material with distributed cylindrical nanoholes

The effective propagation constants of plane longitudinal and shear waves in nanoporous material with random distributed parallel cylindrical nanoholes are studied. The surface elastic theory is used to consider the surface stress effects and to derive the nontraditional boundary condition on the surface of nanoholes. The plane wave expansion method is used to obtain the scattering waves from the single nanohole. The multiple scattering effects are taken into consideration by summing the scat- tered waves from all scatterers and performing the configuration averaging of random distributed scatterers. The effective propagation constants of coherent waves along with the associated dynamic effective elastic modulus are numerically evaluat- ed. The influences of surface stress are discussed based on the numerical results.

Strong optical transmission through the ellipsoid metal-film nanohole arrays

The transmission characteristics of a metallic film with subwavelength ellipsoid nanohole arrays are investigated by using the three-dimensional finite-difference time-domain (3D-FDTD) method. The extraordinary transmission is attributed to the collaboration of localized waveguide resonance and surface plasmon resonance. The influences of the lattice constant and the hole shape on the transmission are studied. By analyzing the picture of electric field and electromagnetic energy distribution, we show the mechanisms of the two different resonances: Localized waveguide resonance mode can be confined inside the ellipsoid holes region, while electric field and electromagnetic energy are localized separately at the two ends of ellipsoid holes for the surface plasma resonance mode.

Large-scale highly ordered periodic Au nano-discs/graphene and graphene/Au nanoholes plasmonic substrates for surface-enhanced Raman scattering

In this paper,the study of using masks to directly generate large area,highly ordered and periodical nanostructure has been exhibited.Periodic Au nano-discs(NDs)arrays have been fabricated on top of graphene by using holey SigN4 mask which is directly fixed on top of graphene and Au metal is deposited through the holes in mask by thermal evaporation method under vacuum condition.This fabrication method provides an easy,fast and cost efficiency way to generate periodical nanostructure.Also,Au nanoholes(NHs)structure has been studied by using holey SigN4 as a template.The surface-enhanced Raman scattering(SERS)sensitvities of periodical Au NDs/graphene and graphene/Au NHs hybrid structures have been systematically studied.The internal mechanisms could be explained by chemical mechanism effect of graphene and electromagnetic mechanism effect of metallic nano-structures.The enhancement factors have been systematically investigated by varying the diameter and the thickness of Au discs and Au NHs.Raman mappings of Au NDs with 2.5 um diameter ilustrate that the larger SERS enhancements exist in the rim of NDs which has good agreement with the electric field simulation result.The SERE enhancement factors of fluorescein obtained from Au NDs/graphene substrates shows an improvement factor of 500%in comparison of graphene substrate.The calculated SERS enhancement factors of graphene/Au NHs achieve 1,200%in comparison of graphene/planar Au film substrate.

To increase more than 10% in efficiency of perovskite solar cells by using nanoholes SnO_(2)

The perovskite solar cells have been intensively investigated these years due to their premium electrical and optical properties as well as huge potential for application.In order to further increase the power conversion efficiency(PCE) of the thin film perovskite solar cells, light management should be taken into consideration. Herein, we apply a lithography method to transfer randomly distributed polystyrene(PS) nanospheres into the electron transporting SnO_(2) layer, by means of which, a nanoholes structure is formed. Finally, we get a nanostructured perovskite layer under low temperature(less than 150 ℃).The depth of SnO_(2) nanoholes is around 60 nm when the device is fabricated with 300-nm PS, and 150 nm in depth when 500-nm PS is used. The device gains PCE of 17.97%,which is 12.3% higher than that with planar electrontransporting SnO_(2) layer and 300-nm CH_(3)NH_(3)PbI_(3) layer.Our findings provide an applicable method to improve the light absorption, which can not only make the absorbing layer of lead-based perovskite solar cells thinner to help decrease the content of lead, but also increase the PCE of non-lead perovskite devices.

Large-area gold nanohole arrays fabricated by one-step method for surface plasmon resonance biochemical sensing

Surface plasmon resonance(SPR) nanosensors based on metallic nanohole arrays have been widely reported to detect binding interactions in biological specimens. A simple and effective method for constructing nanoscale arrays is essential for the development of SPR nanosensors. In this work, we report a one-step method to fabricate nanohole arrays by thermal nanoimprinting in the matrix of IPS(Intermediate Polymer Stamp). No additional etching process or supporting substrate is required. The preparation process is simple, time-saving and compatible for roll-to-roll process, potentially allowing mass production. Moreover, the nanohole arrays were integrated into detection platform as SPR sensors to investigate different types of biological binding interactions. The results demonstrate that our one-step method can be used to efficiently fabricate large-area and uniform nanohole arrays for biochemical sensing.

Fabrication of Metallic Crescent-shaped Nanohole Arrays by Combination of Nanoimprint Lithography and Nanotransfer Printing

Molecular detection techniques based on localized surface plasmon resonances shift, surfaced-enhanced Raman spectroscopy, surface-enhanced fluorescence, and plasmon resonance energy transfer are all highly dependent on the intensity of localized electromagnetic fields. Many different nano- structures were fabricated for sensing. Ebbesen and his co-workers discovered that hole-based ＂hot spots＂ could act as optical antennae, which could concentrate the electromagnetic fields into extremely small regions. Many efforts have been devoted to understanding this unique transmission phenomenon in the past decade. The most widely used methods for hole array fabrication are e-beam lithography（EBL） and focused ion beam. The serial nature of these techniques allows only small regions to be patterned, and it is difficult to integrate such structures into integrated sensing architecture. To improve the fabrication efficiency, several other methods have been deve- loped. Wu et al. presented a process to fabricate 2D arrays via a self-assembled monolayer of hexagonally close packed silica and polystyrene microspheres. Li et al. reported a technique based on a combination of colloidal lithography and parallel imprinting for fabricating crescent-shaped nanohole structures. Through soft interference lithography, Henzie et al.

Aluminium nanohole arrays enhanced resonance Raman scattering spectra in the near ultraviolet region

Aluminium nanohole arrays with fixed diameter were fabricated by focused ion beam and the periodicities were turned.Aluminium nanohole arrays enhanced resonance Raman scattering spectra in the near ultraviolet region were studied experimentally and theoretically,which revealed that the SERRS enhancement factor was as high as 6 orders.

Deep-elliptical-silver-nanowell arrays (d-EAgNWAs) fabricated by stretchable imprinting combining colloidal lithography: A highly sensitive plasmonic sensing platform

Elliptical metallic nanohole arrays possess much higher transmission and enhanced sensitivity compared with circular nanohole arrays.However,fabricating elliptical metallic nanohole arrays in large area with highly tunable aspect ratio remains a challenge.Herein,a brand-new method combining stretchable imprinting with colloidal lithography is figured out to fabricate deep-elliptical-silver-nanowell arrays (d-EAgNWAs).In this method,large area highly ordered silicon nanopillar arrays fabricated by colloidal lithography were taken as a master to transfer large area polydimethylsiloxane (PDMS) nanohole arrays.Benefit from the high elasticity of PDMS mold,the aspect ratio of d-EAgNWAs achieved can be facilely regulated from 1.7 to 5.0.Through optimization of polarization direction and the structural parameters including nanowell depth,aspect ratio,and hole size,the sensing performance of d-EAgNWAs was finally improved up to 1,414.1 nm/RlU.The best sensing behaved d-EAgNWAs were employed as an immunoassay platform finally to prove their great potential in label-free biosensing.

Highly sensitive deep-silver-nanowell arrays （d-AgNWAs） for refractometric sensing

Large-area deep-silver-nanowell arrays （d-AgNWAs） for plasmonic sensing were manufactured by combining colloidal lithography with metal deposition. In contrast to most previous studies, we shed light on the outstanding sensitivity afforded by deep metallic nanowells （up to 400 nm in depth）. Using gold nanohole arrays as a mask, a silicon substrate was etched into deep silicon nanowells, which acted as a template for subsequent Ag deposition, resulting in the formation of d-AgNWAs. Various geometric parameters were separately tailored to study the changes in the optical performance and further optimize the sensing ability of the structure. After several rounds of selection, the best sensing d-AgNWA, which had a Ag thickness of 400 nm, template depth of 400 nm, hole diameter of 504 nm, and period of 1 ~m, was selected. It had a sensitivity of 933 nm.RIU-1, which is substantially higher than those of most common thin metallic nanohole arrays. As a proof of concept, the as-prepared structure was employed as a substrate for an antigen-antibody recognition immunoassay, which indicates its great potential for label-free real-time biosensing.