Synthesis and Photoluminescence Enhancement of Silver Nanoparticles Decorated Porous Anodic Alumina

Silver nanoparticles(Ag NPs) were successfully assembled in porous anodic alumina(AAO) templates via a green silver mirror reaction.The Ag NPs/AAO composite templates then were characterized by field emission scanning electron microscopy(FESEM),energy-dispersive X-ray microanalysis(EDX),and X-ray diffraction(XRD).Furthermore,the photoluminescence(PL) properties were also investigated.Compared with the blank AAO,the PL intensity of Ag NPs/AAO templates are enhanced and the maximum enhancement is 2.58 times.Based on the local electric field enhancement effect,the theoretical values were also deduced,which are basically coincident with the experimental.     

Silver nanoparticles deposited on anodic aluminum oxide template using magnetron sputtering for surface-enhanced Raman scattering substrate

Low-cost and highly sensitive surface-enhanced Raman scattering (SERS) substrates have been fabricated by a simple anodizing process and a magnetron sputtering deposition. The substrates, which consist of silver nanoparticles embedded on anodic aluminum oxide (AAO) templates, are investigated by a scanning electron microscope and a confocal Raman spectroscopy. The SERS activities are demonstrated by Raman scattering from adsorbed solutions of methylene blue and pyridine on the SERS substrate surface. The most optimized SERS substrate contains the silver nanoparticles, with a size distribution of 10-30 nm, deposited on the AAO template. From a calculation, the SERS enhancement factor is as high as 8.5 × 10⁷, which suggests strong potentials for direct applications in the chemical detection and analyses.     

Reflectivity spectra and colors of porous anodic aluminum oxide containing silver nanoparticles by plasmonic absorption

The reflectivity spectra and color of porous anodic aluminum oxide (AAO) nanostructures containing the assembly of silver (Ag) nanoparticles (NPs) with a diameter of -10 nm were investigated. The Ag NPs were assembled inside the pores of AAO with a diameter of -60 nm by dip-coating process during which Ag NPs adsorbed on the surface of AAO and driven inside the pores by capillary force upon the evaporation of solvent. The reflectivity spectra and associated colors of AAO with Ag NPs were determined by the plasmonic absorption of light by Ag NPs. Even with the monolayer coverage of Ag NPs in the pores of AAO, the reflectivity is significantly reduced specifically at -465 nm wavelength by a strong plasmonic absorption, resulting in its golden color. Aggregating Ag NPs by post-annealing at 300 and 400 degrees C changed the color to pink due to the red-shift of absorption. These results are indicative of potential color-engineering of NPs/AAO platform by wavelength-selective reduction of reflected light intensity and using it in direct optical read-out of change of surface and morphology conditions.     

Fabrication and characterization of Ag nanoparticles based on plasmid DNA as templates

Ag nanoparticles have been synthesized successfully by using plasmid DNA as templates based on photoinduced method at room temperature. The plasmid DNA with an average size of 3980 base pairs was separated from Bacillus by using molecular biology methods. The morphology and composition of the samples were characterized by Transmission electron microscopy (TEM) and Energy dispersive spectroscopy (EDS). The UV-vis spectrum was applied to study the different stages of the synthesis processes. The results showed that the Ag was successfully deposited on the surface of plasmid DNA and formed the Ag nanoparticles with average sizes of ~ 30 nm. It was suggested that this high efficiency approach has promising application for the synthesis of other metal or alloy nanoparticles.     

Tunable amorphous carbon nanotubes prepared by a simple template

An easy versatile method is reported to synthesize tunable amorphous carbon nanotubes (a-CNTs) with different pore diameter, length and orientation of graphene layers at a low temperature of 450 °C in the absence of metal catalysts by using porous anodic aluminum oxide (AAO) as a template and citric acid as a precursor. Since citric acid was adsorbed by hydrogen bonds with the -OH groups at the walls of the AAO templates, which can be influenced by the concentration of H⁺ ions in the solution, the pH leads to the change of the orientation of graphene layers and the graphitization degree.     

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.     

Tailoring defect structure and optical absorption of porous anodic aluminum oxide membranes

Defects influence the optical and electronic properties of nanostructured materials that may be relevant for applications. In self-organized anodic aluminum oxide (AAO) templates we have investigated the effect of annealing, doping and nanoscale metal deposition. Optical absorption spectroscopy has been used as a sensitive probe for the defect density in AAO templates. The electronic spectra are found to be dominated by bands which originate from oxygen-deficient color centers (F⁺, F and F₂). In annealing studies, the integrated absorption of the bands changes non-monotonically with annealing temperature and annealing time. This demonstrates that the concentration of defects can be optimized to tailor the optical properties of the AAO. Metallic Au wires are deposited in the template to establish a plasmonic template or array. The investigations provide an interesting insight into the interplay of reactivity and diffusivity on nanoscales.     

Synthesis and characterization of layered oriented hydrogen titanate micro-tube films

Continuous and uniform films of oriented hydrogen titanate tubes with diameters, c.a. 200 nm, were prepared directly via porous anodic aluminum oxides (AAO) templates without any further removal of templates. Simple impregnation method was applied with aqueous solution titanium tetrafluoride (TiF₄) as the precursor to form the titania sol-gel. Scanning electron microscope (SEM) results show that the films are uniform, tubes highly oriented and even in length, diameter and morphology. Hydrogen trititanate (H₂Ti₃O₇) phase is proved by X-ray diffraction (XRD) patterns. Layered films of oriented tubes are fabricated when impregnation time is well controlled. The formation mechanism is drawn with the help of energy dispersion spectra (EDS). Due to the existence of F ⁻, the hydrolysis of Ti⁴⁺ is relatively slow along inner channel walls of AAO, which eventually forms compact tube arrays. The solubility among different parts of AAO template is of big difference in acidic surrounding. Layered films of oriented tubes are, therefore, fabricated when impregnation time is well controlled. The channel size of the AAO template takes control in deciding the pore size of the titania micro-tubes and reaction time, the length of the tubes.     

Niobium and hafnium grown on porous membranes

In this work we report on a method for fabricating highly ordered nanostructures of niobium and hafnium metals by physical vapour deposition using two different templates: anodized aluminum oxide membranes (AAO) and zirconium onto AAO membranes (Zr/AAO). The growth mechanism of these metal nanostructures is clearly different depending on the material used as a template. A different morphology was obtained by using AAO or Zr/AAO templates: when the metal is deposited onto AAO membranes, nanospheres with ordered hexagonal regularity are obtained; however, when the metal is deposited onto a Zr/AAO template, highly ordered nanocones are formed. The experimental approach described in this work is simple and suitable for synthesizing nanospheres or nanoholes of niobium and hafnium metals in a highly ordered structure.     

Photoluminescence properties of TiO2: Eu3 + thin films deposited on different substrates

Strong photoluminescence of Eu^3 + due to intra 4f transitions are obtained from amorphous xerogel TiO₂: Eu^3 + films prepared by sol–gel method and treated at a low temperature of 100 °C. The films are deposited on four different substrates: Si, Al, AAO (anodic alumina oxide) and porous silicon. We find that the luminescence intensity on AAO substrate increased 4 times comparing with that of Si or Al, and luminescence intensity decreases obviously on porous silicon substrate. Energy transfer mechanism from TiO₂ host to Eu^3 + is deduced through analysis of photoluminescence and photoluminescence excitation spectrum. Concentration quenching of Eu^3 + does not appear even at high atomic concentration of 7.69%.     

Pb(Zr0.52Ti0.48)O3 nanotubes synthesis and infrared absorption properties

Herein a useful methodology to synthesize the lead zirconate titanate (PZT) nanotubes via a dip-coating deposition process with anodic aluminum oxide (AAO) template is proposed. The nano-porous AAO templates were produced using a controlled two-step electrochemical anodization technique. The PZT/AAO composite was formed using the dip-coating wetting technique. The prepared PZT precursor solution was driven into the nanopore channels of AAO template under the driving force of capillary action, subsequently the sintering process of the as-filled templates was carefully tuned to obtain Pb(Zr_0.52Ti_0.48)O₃ nanotubes of crystalline tetragonal phase with uniform pore size and ordered arrange. Fourier transform infrared spectroscopy (FTIR) results show that in the 1200–1900 cm⁻¹ band, the composite structure of PZT/AAO has obvious absorption peaks at 1471.56 cm⁻¹ and 1556.09 cm⁻¹, the absorption intensity of the composite structure is about six times of pure AAO template. The unusual optical properties found in PZT/AAO composite will stimulate further theoretical and experimental interests in ferroelectric nanostructures.     

直流电沉积法制备单晶Ag纳米棒阵列

在较低温条件下,采用直流电沉积法在AAO模板中成功制备出了大面积生长均匀的单晶Ag蚋米棒阵列.利用扫描电子显微镜(SEM),能谱仪(EDS),透射电子显微镜(TEM),选区电子衍射(SAED)和XRD等分析手段对样品进行形貌表征及成分分析.结果表明,阵列中的Ag纳米棒尺寸均匀,保持着良好的平行度,直径接近200nm,与AAO模板的孔径大小相当,且可以通过控制沉积时间来实现对Ag纳米棒长度的控制.     

Synthesis and photocatalytic properties of BiOCl nanowire arrays

Bismuth oxychloride (BiOCl) nanowire arrays have been successfully prepared employing the Anodic Aluminum Oxide (AAO) template assisted sol-gel method. Nanowires of 100 nm diameter and length 2-6 μm, assembled in the porous of AAO templates, were formed. XRD and HRTEM results show that the nanowires are pure BiOCl polycrystal phase without Bi₂O₃ or BiCl₃. The photocatalytic activity of BiOCl nanowire arrays was investigated by the degradation of Rhodamine B dye solution under UV irradiation.     

Morphological evolution of porous nanostructures grown from a single isolated anodic alumina nanochannel

Porous anodic aluminum oxide (AAO) membranes have been widely used as templates for growing nanomaterials because of their ordered nanochannel arrays with high aspect ratio and uniform pore diameter. However, the intrinsic growth behavior of an individual AAO nanochannel has never been carefully studied for the lack of a means to fabricate a single isolated anodic alumina nanochannel (SIAAN). In this study, we develop a lithographic method for fabricating a SIAAN, which grows into a porous hemispherical structure with its pores exhibiting fascinating morphological evolution during anodization. We also discover that the mechanical stress affects the growth rate and pore morphology of AAO porous structures. This study helps reveal the growth mechanism of arrayed AAO nanochannels grown on a flat aluminum surface and provides insights to help pave the way to altering the geometry of nanochannels on AAO templates for the fabrication of advanced nanocomposite materials.     

装甲铝合金显微硬度及微动磨损对其影响的研究

利用MH-6型显微硬度仪和MGW-01高频往复式微动磨损试验机进行7A52装甲铝合金的显微硬度测试和微动磨损试验，分析不同取向表面显微硬度及微动磨损试验对显微硬度的影响。结果表明不同取向表面显微硬度基本相同，试验范围内微动磨损表面显微硬度比基体表面显微硬度增加。     

AAO模板快速制备方法探究

为了快速制备出高度有序且孔径可调控的AAO(阳极氧化铝)模板应用于工业生产,通过改进传统的两步阳极氧化法,采用逐步提高电解液浓度的硬氧氧化法制备了AAO模板,并确定了最佳制备工艺为初始电解液浓度0.15mol/L,添加电解液浓度0.40mol/L,温度保持在5℃左右,无水乙醇添加比例为1:1,从而使铝片的击穿电压从40V上升到130V左右(模板面积1.5cm×4.5cm),采用DimensionEdge型号的原子力显微镜(AFM)对多孔氧化铝模板进行了表征。结果表明:未经退火处理的铝片,也可以制备出高度有序的AAO模板,但其粗糙度略有增加,并与在高压条件下二次氧化、三次氧化、四次氧化制备AAO模板进行了比较,发现二次氧化制备的AAO模板有序度、孔径、孔间距均优于三次、四次氧化法。     

Fabrication of oriented arrays of porous gold microsheaths using aligned silver nanowires as sacrificial template

A simple one-step process for preparation of oriented arrays of porous gold microsheaths has been developed by dissolution of sacrificial templates of aligned Ag nanowires in a mixture solution of HAuCl₄ and NaCl at room temperature. The morphology and crystal structure of the product were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and selected area electron diffraction (SAED). Its composition was estimated by energy dispersive X-ray spectroscopy (EDX). The results indicated that the gold microsheaths had generally preserved the original orientation of Ag nanowires and their orientation was robust enough to survive the centrifugal process. The gold microsheaths consist of nanoparticles (ca. 100 nm) that form nanovoids (tens to hundreds of nanometers) between them, giving them a porous nature. Such arrays of well oriented gold microsheaths are expected to show interesting anisotropic optical and electronic properties, and their hollow porous structures might find broad potential applications in surface plasma resonance (SPR), catalysis and chemical sensing.     

The influence of Ni nanoparticles and Ni (II) on the growth of Ag dendrites immobilized on the chelating copolymer membrane

Preparation of Ag dendrites on the surface of chelating copolymer membranes (PBAGI), which was synthesized by using the soap-free emulsion copolymerization of n-butylacrylate (BA) and acrylonitrile (AN), as well as 2-methacrylic acid 3-(bis-carboxymethylamino)-2-hydroxy-propyl ester (GMA-IDA) that was used as a chelating group, is presented in this study. The characteristics of polymer membranes were investigated by Fourier transform infrared (FTIR) spectroscopy and elementary analysis (EA). The weight fraction of GMA-IDA in the polymer was 4.2 wt% as revealed by elemental analysis. The chelating group, –N(CH₂COO⁻Na⁺)₂ on the polymer was used to coordinate different amounts of Ni(II), controlled by different chelating times and subsequently reduced to Ni nanoparticles, as templates for growing Ag nanocrystals from 1.67 wt% AgNO₃ aqueous solution with 55.7 ppm poly(vinyl pyrrolidone) (PVP) added. In addition, the effect of Ni²⁺ concentration on the growth of the Ag dendrites was studied. Crystallinity and morphology of Ag dendrites were examined with X-ray diffraction (XRD) and scanning electronic microscopy (SEM), respectively. Amount of Ag dendrites increased with the increasing of Ni nanoparticles on the PBAGI membrane or the dose of Ni²⁺ present in the aqueous solution. Notable, under higher amount of Ni nanoparticles (over 200 mmol Ni²⁺/g PBAGI membrane), Ag dendrites could be successful grown on the membrane. However, higher dose of Ni²⁺ (over 41.3 ppm) might inhibit the growth of Ag dendrites.     

Effects of temperature and voltage mode on nanoporous anodic aluminum oxide films by one-step anodization

Many conventional anodic aluminum oxide (AAO) templates were performed using two-step direct current anodization (DCA) at low temperature (0–5 °C) to avoid dissolution effects. This process is relatively complex. Pulse anodization (PA) by switching between high and low voltages has been used to improve wear resistance and corrosion resistance in barrier type anodic oxidation of aluminum or hard anodization for current nanotechnology. However, there are only few investigations of AAO by hybrid pulse anodization (HPA) with normal-positive and small-negative voltages, especially for the one-step anodization, to shorten the running time. In this article, the effects of temperature and voltage modes (DCA vs. HPA) on one-step anodization have been investigated. The porous AAO films were fabricated using one-step anodization in 0.5 M oxalic acid in different voltage modes including the HPA and DCA and the environment temperature were varied at 5–15 °C. The morphology, pore size and oxide thickness of AAO films were characterized by high resolution field emission scanning electron microscope. The pore size distribution and circularity of AAO films can be quantitatively analyzed by image processing of SEM. The pore distribution uniformity and circularity of AAO by HPA is much better than DCA due to its effective cooling at relatively high temperatures. On the other hand, increasing environment temperature can increase the growth rate and enlarge the pore size of AAO films. The results of one-step anodization by hybrid pulse could promote the AAO quality and provide a simple and convenient fabrication compared to DCA.     

Synthesis and enhanced light absorption of alumina matrix nanocomposites containing multilayer oxide nanorods and silver nanoparticles

In this paper, multilayer oxide nanorods were deposited in the nanopores of anodic aluminum oxide (AAO) via solution infiltration followed by heat treatment. The nanorods have a core–shell structure. First, the shell (nanotube) with the thickness of about 40 nm was made of TiO₂ through the hydrolysis of (NH₄)₂TiF₆. Second, silver nanoparticles with the diameter of about 3 nm were added into the TiO₂ layer through thermal decomposition of AgNO₃ at elevated temperatures. Then, cylindrical cores (nanorods) of CoO and ZnO with 200 nm diameter were prepared, respectively. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to characterize the structure and composition of the nanorods. UV–vis light absorption measurements in the wavelength range from 350 to 1000 nm were performed to study the effect of nanorod and nanoparticle addition on the light absorption property of the alumina nanocomposites. It is found that CoO nanorods increase the light absorption of the alumina matrix composite in the wavelength range from 500 nm to 800 nm, but the TiO₂ shell does not increase the light absorption much. The ZnO nanorods do not change the light absorption either. However, the addition of silver nanoparticles significantly enhances light absorption of both AAO/TiO₂/Ag/CoO and AAO/TiO₂/Ag/ZnO nanocomposites. This increase in the visible light absorption reveals that there exists surface plasmon around the fine silver nanoparticles in the nanorods.