Formation of Au nanostructures through an alumina mask by laser-assisted deposition

We report a new method to produce ordered arrays of metal nanostructures on substrates. The method employs a through-hole nanoporous alumina membrane as a mask that is attached onto the substrate, silicon in this study. The material of deposition, Au in this study, was provided by pulsed laser ablation of a target gold. At an early stage of the deposition, a significant portion of Au penetrated the alumina through-holes and formed an ordered nanodot array on the silicon surface. At the later stage, the through-hole deposition was blocked by the growth of Au film on the top surface of the alumina, so that the heights of the Au nanodots were limited to about 10 nm under current experimental conditions. Subsequent attempts to clean up the top surface of the alumina with a lower power laser illumination resulted in the formation of new nanostructures around the alumina pores, nanospheres, or nanorings, depending on the fluence of the laser and the duration of the cleanup. We will discuss the underlying mechanism of the formation of these nanostructures.     

Three-dimensional mesoporous gold film to enhance the sensitivity of electrochemical detection

Cell-cell and cell-extracellular matrix (ECM) adhesion are fundamental and important in the development of a cell-based chip. In this study, a novel, simple, rapid, and one-step technique was developed for the fabrication of a uniform three-dimensional mesoporous gold thin film (MPGF) onto a gold (Au) coated glass plate based on an electrochemical deposition method. Scanning electron microscopy images demonstrated that the resulting MPGF electrode had uniformly distributed pores with diameters of about 20 nm. The cyclic voltammetric behavior of [Fe(CN)(6)](4-/3-) coupled onto MPGF and Au electrodes demonstrated that the MPGF electrode had a higher electrocatalytic sensitivity and reversibility than the bare Au electrode. The Arg-Gly-Asp (RGD) sequence containing the peptide was immobilized on the MPGF and bare Au substrates. HeLa cancer cells were then cultured on the RGD peptide layer. The successful immobilization of the peptide and cells was confirmed by atomic force microscopy. The cell proliferation and viability were evaluated by cyclic voltammetry and Trypan blue dyeing assay. These results indicated that the RGD/MPGF modified electrodes showed an electrochemical sensitivity in the detection of cancer cells which is approximately three times higher, especially at low cell density, than RGD/Au electrodes. This much improved sensitivity of the MPGF modified electrode demonstrates the potential for the fabrication of a highly sensitive and low-cost cell-based chip for rapid cancer detection.     

Tuning of localized surface plasmon resonance of well-ordered Ag/Au bimetallic nanodot arrays by laser interference lithography and thermal annealing

A novel hybrid approach to fabricate large-area well-ordered Ag/Au bimetallic nanodot arrays and its potential applications for biosensing is investigated. With the combination of laser interference lithography and the thermal annealing technique, Ag/Au bimetallic nanodots about ~50 nm are formed inside periodic nanodisk arrays at a dimension of ~530 nm on quartz substrates. Extinction spectra of the fabricated nanostructures show their localized surface plasmon resonance (LSPR) can be well controlled by Au concentration, which offers a means to flexibly tune the optical properties of the nanodot arrays. To study the sensitivity of the nanodot arrays, resonance wavelength changes per refractive index unit (RIU) are performed in different surrounding environments. This shows a 94% increase in peak shift per refractive index unit (nanometers/RIU) compared to the nanodot arrays formed only by thermal annealing. These results demonstrate a feasible approach to improve LSPR-based biosensor performance.     

Cell chip-based monitoring of toxic effects of cosmetic compounds on skin fibroblast cells

The present study estimated the efficacy of electrochemical detection of imidazolidinyl urea-induced cell toxicity in skin human fibroblast cells (HFF cells). The gold nanopunct structures were fabricated through a nanoporous alumina mask, and the structural formations were confirmed via scanning electron microscopy. The HFF cells were allowed to attach to RGD (Arg-Gly-Asp) peptide nanopatterned surfaces, and electrochemical tools were applied to skin cells attached to the chip surface. The HFF cells evidenced inflammation responses to allergens such as imidazolidinyl urea. The cells were subsequently treated with different concentrations of imidazolidinyl urea for 24 h in culture, which induced a change in the cyclic voltammetry (CV) current peak. Treatment with imidazolidinyl urea induced a loss of cell viability and accelerated inflammation in a concentration-dependent manner. The expression level of inflammation-related proteins such as IL-1 beta were increased in imidazolidinyl urea-treated cells. The CV results demonstrated that imidazolidinyl urea significantly reduced the current peaks in a dose-dependent manner. The results showed that the current peak was reduced in accordance with the increases in imidazolidinyl urea-induced inflammation. In conclusion, the results of this study suggest that the electrochemical-based chip provides crucial information for improvements to a cell chip system for drug screening applications.     

Light guide of Au nanostructures for color-filterness optoelectronic display devices

Au line nanostructures with different pitch distances from 500 nm to 950 nm on ITO coated glass substrates have been fabricated at room temperature for exploring the color light guide in all kinds of display system. The patterned Au line array is used as a light outcoupling and color-selection component due to the emission wavelength changed by the Au line arrays with different pitch distances that could achieve multi-color selections. The ITO coated glass substrates patterned with periodic Au line arrays with controlled line pitches has been demonstrated and used as a color filter in all display devices. Using a proper pitch distance of Au line nanostructures, the basic third colors of red, green, and blue (RGB) can be simply gained and controlled without a traditional color filter for future optoelectronic display devices.     

Magnetic dipolar interaction in NiFe nanodot arrays formed on vertical carbon nanotubes

A new and simple method for the fabrication of densely packed magnetic nanodot arrays was developed using conventional sputtering deposition at room temperature. An anodized alumina template was employed for the formation of nanodot assemblies, consisting of carbon nanotubes (CNTs) and magnetic nanodot arrays. Each nanodot was formed exactly on top of a CNT and was arranged with a well-ordered structure in a wide range of area. It was also found that the size of dots and the distance between dots can be tailored by changing the length of CNTs, inducing a change of strength of dipolar interaction between nanodots.     

Enhanced light output from the nano-patterned InP semiconductor substrate through the nanoporous alumina mask

A significant enhancement in the light output from nano-patterned InP substrate covered with a nanoporous alumina mask was observed. A uniform nanohole array on an InP semiconductor substrate was fabricated by inductively coupled plasma reactive ion etching (ICP-RIE), using the nanoporous alumina mask as a shadow mask. The light output property of the semiconductor substrate was investigated via photoluminescence (PL) intensity measurement. The InP substrate with a nanohole array showed a more enhanced PL intensity compared with the raw InP substrate without a nanohole structure. After ICP-RIE etching, the light output from the nanoporous InP substrate covered with a nanoporous alumina mask showed fourfold enhanced PL intensity compared with the raw InP substrate. These results can be used as a prospective method for increasing the light output efficiency of optoelectronic devices.     

Preparation and photovoltaic properties of the composite based on CdS nanorod arrays and PCPDTBSe

Vertically aligned CdS nanorod arrays (NRA) were synthesized through facile one-step and template-free hydrothermal approach directly on indium tin oxide (ITO)-coated glass substrates. A low band gap polymer, namely Poly[4,4-bis(2-ethylhexyl)cyclopenta[2,1-b:3,4-b’]dithiophene-2,6-diyl-alt-2,1,3-benzoselenadiazole-4,7-diyl] (PCPDTBSe) was synthesized by the Stille coupling reaction. An organic/inorganic hybrid solar cell prototype device was fabricated based on the as-prepared CdS NRA and PCPDTBSe (ITO/CdS arrays/PCPDTBSe/Au), showing a power conversion efficiency of 0.10 %.     

Nano barcoding cell-based biosensor using fluorophor-embedded silica nanotubes

A simple and reliable drug screening method was developed using peptide hydrogel cell beads coded by quantum dot-embedded silica nanotubes. Very long silica nanotubes were fabricated upon a nanoporous alumina template using sol-gel techniques. The physical shapes of the nanotubes were measured by TEM (Transmission Electron Microscope). Green and red quantum dots embedded in silica nanotubes were applied to peptide hydrogel cell beads as coding materials. This was confirmed by confocal microscopy that examined fluorescence levels and quantum dot shapes. The peptide hydrogel cell beads coded with silica nanotubes were loaded into a PDMS single chamber in order to assess the effect of doxorubicin on HMEC and MCF-7 cells, which was measured in hydrogel cell beads by live and dead cell staining using coding materials. As a result, MCF-7 cancer cells were more affected by doxorubicin than HMEC; however, doxorubicin induced HMEC cell death at a relatively high concentration (> 5 microg/ml).     

Cell chip with nano-scale peptide layer to detect dopamine secretion from neuronal cells

A cell chip with a nano-scaled thin film of cysteine modified synthetic oligopeptide C(RGD)4 was fabricated to detect dopamine secretion from neuronal cells. Thin C(RGD)4 peptide layer was fabricated on chip surface for increasing the binding affinity of cells to gold electrode surface, which is essential for the electrochemical detection of dopamine released from PC12 cells. The structural formation of the peptide thin film was confirmed by both atomic force microscopy (AFM) and scanning electron microscopy (SEM). Redox characteristics of chemical dopamine were firstly characterized by voltammetric tool to compare the dopamine released from PC12 cells. Cells grown on the chip were then subjected to cyclic voltammetric (CV) analysis after 48 hours of incubation. The intensities of reduction peaks were found to be increased with increasing the concentrations of PC12 cells. In addition, the electrochemical redox signal increased more in the cells treated with glucose and potassium compared to the control group. Hence, the developed cell chip can be used to determine the effects of drugs on living cells electrochemically.     

Preparation of regularly structured nanotubular TiO2 thin films on ITO and their modification with thin ALD-grown layers

Nanotubular titanium dioxide thin films were prepared by anodization of titanium metal films evaporated on indium tin oxide (ITO) coated glass. A facile method to enhance the adhesion of the titanium film to the ITO glass was developed. An optimum thickness of 550 nm for the evaporated titanium was found to keep the film adhered to ITO during the anodization. The films were further modified by growing amorphous titania, alumina and tantala thin films conformally in the nanotubes by atomic layer deposition (ALD). The optical, electrical and physical properties of the different structures were compared. It was shown that even 5 nm thin layers can modify the properties of the nanotubular titanium dioxide films.     

铝栅极降低氧化铟锡薄膜表面电阻

大面积钙钛矿电池组件效率一直比小面积电池最高效率低10%左右,其中透明导电氧化物(TCO)电极的横向电阻是构成串联电阻增加的主要因素。本文采用湿法刻蚀的方法在超白玻璃上制备了深达1-2 μm的凹槽,横向宽度最小为10 μm,随后蒸镀金属铝,射频溅射沉积氧化铟锡(ITO)薄膜,通过调控刻蚀各参数,得到良好的铝栅极形状。对比分析有无铝栅极的ITO薄膜,结果表明,有铝栅极的ITO薄膜相较无铝栅极的ITO薄膜,平均透过率下降约3.5%,横向电阻从17.4Ω降至2.4Ω,得到明显改善。并可通过调控刻蚀厚度,可使横向电阻进一步降低,从而显著提升ITO薄膜在太阳能电池领域里作为透明导电电极时横向电子收集能力,对以玻璃为基底的薄膜太阳能电池大面积产业化应用提供了可能。     

Molding of hydrogel microstructures to create multiphenotype cell microarrays

The fabrication of mammalian cell-containing poly(ethylene glycol) (PEG) hydrogel microstructures on glass and silicon substrates is described. Using photoreaction injection molding in poly(dimethylsiloxane) microfluidic channels, three-dimensional hydrogel microstructures encapsulating cells (fibroblasts, hepatocytes, macrophage) were fabricated with cells uniformly distributed to each hydrogel microstructure, and the number of cells in each hydrogel microstructure was controlled by changing the cell density of the precursor solution. PEG hydrogels were modified using an Arg-Gly-Asp (RGD) peptide sequence, with the incorporation of RGD into the hydrogel matrix promoting the spreading of encapsulated fibroblasts over a 24-h period in culture. Cells remained viable encapsulated in these hydrogel microstructures for a period in excess of 1 week in culture. Arrays of hydrogel microstructures encapsulating two or more phenotypes on a single substrate were successfully fabricated using multimicrofluidic channels, creating the potential for multiphenotype cell-based biosensors.     

Nanopatterned silicon emitters of a solar cell fabricated by anodic aluminum oxide masks

We investigated the nanopattern transferring process by a template of anodic aluminum oxide and the formation of a nanoporous aluminum oxide layer on a Si solar cell by the anodization process of Al thin films. The anodization process provided a template to transfer the nanopattern onto the Si surface. The small-sized nanoporous alumina template was attached to be covered on the textured surface and played the role of etching mask in the F-based dry etching process. Furthermore, we deposited an Al thin film onto the Si surface and the subsequent anodization process was performed. The alumina formulated on the deposited Al thin film did not show the array of nanoporous structure and no nanopatterns were transferred onto the surface. The large-areal alumina deposited on the Si surface showed enhanced photo-absorption in the ultraviolet spectral region of 243 nm, but increased the photo-reflectance in the visible and infrared spectral regions when compared to the Si-bare sample.     

Nondestructive replication of self-ordered nanoporous alumina membranes via cross-linked polyacrylate nanofiber arrays

Ordered nanofiber arrays are a promising material platform for artificial adhesive structures, tissue engineering, wound dressing, sensor arrays, and self-cleaning surfaces. Their production via self-ordered porous alumina hard templates serving as shape-defining molds is well-established. However, their release requires the destruction of the hard templates, the fabrication of which is costly and time-consuming, by wet-chemical etching steps with acids or bases. We report the nondestructive mechanical extraction of arrays of cross-linked polyacrylate nanofibers from thus recyclable self-ordered nanoporous alumina hard templates. Silica replicas of the latter were synthesized using the extricated nanofiber arrays as secondary molds that could be mechanically detached from the molded material. The approach reported here, which can be combined with microstructuring, may pave the way for the high-throughput production of both functional nanofiber arrays and ordered nanoporous membranes consisting of a broad range of material systems.     

Micropatterned arrays of porous silicon: toward sensory biointerfaces

We describe the fabrication of arrays of porous silicon spots by means of photolithography where a positive photoresist serves as a mask during the anodization process. In particular, photoluminescent arrays and porous silicon spots suitable for further chemical modification and the attachment of human cells were created. The produced arrays of porous silicon were chemically modified by means of a thermal hydrosilylation reaction that facilitated immobilization of the fluorescent dye lissamine, and alternatively, the cell adhesion peptide arginine-glycine-aspartic acid-serine. The latter modification enabled the selective attachment of human lens epithelial cells on the peptide functionalized regions of the patterns. This type of surface patterning, using etched porous silicon arrays functionalized with biological recognition elements, presents a new format of interfacing porous silicon with mammalian cells. Porous silicon arrays with photoluminescent properties produced by this patterning strategy also have potential applications as platforms for in situ monitoring of cell behavior.     

Dual desorption electrospray ionization-laser desorption ionization mass spectrometry on a common nanoporous alumina platform for enhanced shotgun proteomic analysis

A gold coated nanoporous alumina surface was used for dual ionization mode mass spectrometric analysis using desorption electrospray ionization (DESI) and laser desorption ionization (LDI). DESI and LDI mass spectrometry (MS) from the nanoporous alumina surface were compared with conventional electrospray ionization (ESI) mass spectrometry and matrix assisted laser desorption ionization (MALDI) for analysis of tryptic digests of proteins. Combined use of DESI and LDI offer greater peptide coverage than either method alone and comparable peptide coverage as with dual MALDI and ESI. This dual ionization technique using a common platform with same sample spot demonstrates a potential time and cost-effective tool for improved shotgun proteomic analysis.     

RGD修饰钛表面对人牙龈成纤维细胞初期黏附和铺展的影响

用羰基二咪唑(1,1'-carbonyldiimidazole,CDI)将含RGD的短肽共价连接到纯钛表面,研究接枝后的钛表面对原代培养的人牙龈成纤维细胞(human gingival fibroblasts,HGF)初期黏附和铺展的影响.结果表明,RGD修饰的纯钛表面粘附的细胞数比未修饰钛表面多,细胞铺展面积比钛表面的大,应力纤维的形成比钛表面早.RGD接枝钛表面更有利于人牙龈成纤维细胞的粘附,改善了纯钛的生物相容性.     

Preparation and Magnetic Properties of FePt Nanodot Arrays Sputtering on AAO Templates

FePt nanodot arrays are the promising recording media for future super-high density magnetic recording because of their huge uniaxial magneto-crystalline anisotropy and good signal noise ratio. In this article, FePt nanodot arrays were successfully prepared on anodic aluminum oxide (AAO) templates by magnetron sputtering, and an Ag underlayer was proposed to improve the magnetic properties of FePt nanodot arrays. The dependences of Ag underlayer, annealing temperature, and pore diameter on the magnetic properties of FePt nanodot arrays were investigated. Using the AAO templates with pore diameter of 80 nm and annealing temperature of 600°C, the coercivity of Ag/FePt nanodot arrays is improved significantly to 10262 Oe.     

ITO用作铁电薄膜电极的研究

研究了sol-gel掺锡氧化铟（ITO溶胶在SiO2/Si衬底和光学玻璃衬底上的成膜及结晶性能,并与CVD法生长的ITO薄膜作了对比。结论是：sol-gelITO膜,虽然具有与CVD ITO膜相似的结晶性能和较高的导电性,但以sol-gel ITO膜作下电极,无法使PLT、PZT的sol-gel膜具有明显的结晶取向。因漏电太大,sol-gel ITO也无法作sol-gel铁电膜（如PLT,PZT）的上电极。但在CVD ITO膜上,sol-gel铁电膜能很好结晶,且Au/PLT/ITO电容,具有良好的电学性能。