的模板导演电浆黄金纳米管的合成与可调谐红外吸收
Summary
解决方案悬浮黄金碳纳米管具有受控的尺寸，可以合成由电化学沉积在多孔阳极氧化铝（AAO）膜使用的疏水性聚合物的芯。黄金纳米管和纳米管阵列有希望在电浆生物传感，表面增强拉曼光谱，光热加热，离子和分子运输，微流体，催化和电化学传感应用。
Abstract
可以产生一个几乎平行阵列的孔，通过阳极氧化在酸性环境中1，2的铝箔。自1990年以来一直在开发的阳极氧化铝（AAO）膜的应用和模板合成的高宽比的纳米结构，主要是通过电化学增长或孔隙的润湿已成为一种常见的方法。最近，这些膜已成为市售在很宽的范围内的孔的尺寸和密度，从而导致被从阳极氧化铝膜的合成功能的纳米结构的一个广泛的图书馆。这些包括复合材料制成的金属，无机材料或聚合物3-10纳米棒，纳米线和纳米管的。纳米多孔膜已被用于合成纳米粒子和纳米管阵列，执行以及折射率传感器，电浆生物传感器，表面增强拉曼光谱（SERS）基板11-16，以及广泛的其他领域，如光热加热17日 ，：选择渗透运输18，19 20，催化，微流体21，和电化学传感器22，23。在这里，我们提出了一种新颖的程序，准备金的纳米管在AAO膜。空心纳米结构具有潜在的应用电浆和表面增强拉曼光谱感应，我们预计这些黄金纳米管将允许产生的高灵敏度和强大的等离子激元的信号，减少材料阻尼15。
Introduction
当它们的尺寸接近的光的穿透深度（约50 nm的纳米级），贵金属，和最重要的是金的，表现出精致的大小，形状和环境依赖性的光学特性24，25。在这个规模，直接照射会导致表面等离子体共振（SPR）被称为传导电子的相干振荡。 SPR是高度依赖于纳米结构的大小，形状，和周围介质的介电性能。有极大的兴趣特征SPR特性，在新材料，SPR为基础的设备不断涌现在亚波长光学，SERS基板，超灵敏的光学传感器，11-16，26-29。因此，开发的计算方法，更准确地预测规模和结构可以改变电浆反应仍然是一个主要的目标。 AAO膜的使用提供了一个方便的方式来改变颗粒的直径或长度，和几个重要的研究，使用此关联我消化率和计算的等离激元具有不同颗粒直径，长度，和纵横比为30，31的响应。也许最研究，并成功地利用电浆材料的折射率传感器。对于这一点，在红色，近红外（NIR）范围内（〜800 – 1300纳米）的共振是可取的，因为它们是更敏感的折射率变化，以及在于“水窗”，使得它们通过水和发送人体组织。在此范围内开放有趣的可能性， 在体内电浆生物传感与SPR峰的解决方案-悬浮纳米结构。
多孔阳极氧化铝已通过电化学合成或模板润湿用于制备聚合物纳米管或纳米线，并证明是适用于各种各样的材料。 AAO膜现在正在使用的综合解决方案悬浮的高纵横比的纳米棒和纳米结构阵列作为高性能电浆生物传感器或SER小号基板。虽然阳极氧化铝膜，大多被用作模板，用于合成固体棒，在某些情况下，它可能是可取的是中空的结构。电浆和SERS传感应用中，例如，基于表面，并具有大的表面面积与体积比的中空结构，可能会导致产生更强的信号和更高的灵敏度14，15，32。相对于这个已被合成，黄金碳纳米管从各种方法，包括电镀，无电解电镀34，35，模板孔隙36的表面变形，37次 ，溶胶-凝胶的方法38，和电沉积39-41银纳米棒33上的置换反应。这些合成通常留下不好的，多孔管或允许几乎没有控制权的大小和形态。的合成也有报道，其特征在于，淀积在金属壳在AAO膜42，43中的聚合物的核心。这些合成离开金nanotubes绑定到基板，并依赖于模板的蚀刻，以允许周围的聚合物增长的黄金，因此它们不能在溶液中进行研究。此外，模板刻蚀有一些潜在的缺点。首先，非均匀的孔蚀刻沿模板壁可能导致非均匀的金壳厚度。二，显着的蚀刻（ 即很厚的壁管）完全溶解毛孔壁。
最近，桥梁等人报道的腐蚀剂自由方法合成金的纳米管在阳极氧化铝膜，使用的牺牲的聚（3 -己基）噻吩的核心和产量溶液悬浮黄金碳纳米管具有非常高的折射率灵敏度15。从该和随后的工作中，它被发现未经化学蚀刻以沉积金壳聚合物纤芯周围，聚合物必须是管状的，例如，有它折叠的内部空间，并且该聚合物必须是疏水性的，使得其将关口失效到本身，而不是坚持的模板孔壁16。当亲水性聚合物的使用，一金“鞘”部分地覆盖的聚合物芯的观察，表明聚合物芯附着金沉积期间44的模板的壁之一。这里，中空黄金碳纳米管的合成，它允许长度和直径的控制协议，用于详细描述（ 图1）。这些解决方案悬浮的黄金纳米管是为广泛的应用，包括电浆生物感测或SERS衬底材料。
Protocol
1。形成的银工作电极 AAO膜基片的顶侧固定在玻璃板上，使用2 – 双面粘合。注意：与粘合剂接触的膜面积最小化，因为它会堵塞毛孔。 成的金属蒸发器的基板保持器，安装在玻璃板，关闭的腔室，并撤离到压力低于1.0μTorr。 使用一个电阻源，蒸发到衬底上的银颗粒（纯度> 99.99％），直到达到的层厚度为100nm，然后在0.8埃/秒的速率增加的蒸发速率的最终厚度为1.5埃/秒，直…
Representative Results
每个步骤之后，人们可以明显地确定是否合成是成功的，通过观察该膜的颜色。沉积铜（2.3）后的模板将出现紫色。在沉积镍（2.5）的模板会慢慢变成黑色。后的聚合物淀积（步骤3.3）模板应显得更暗紫色/黑色和更有光泽（ 图2）。成功聚合物和金的典型chronoapmerograms包括（ 图3）。在最后的蚀刻工序（5.2），该模板应出现紫色的和不透明的（ 图2），由于黄?…
Discussion
AAO膜纳米棒的模板合成已成为越来越流行，但是合成的纳米棒往往是对材料和合成条件的细微变化非常敏感。在这里，采用AAO膜的优点和局限性，列出一个全面的了解，以及使用阳极氧化铝膜的电化学合成纳米结构的一般准则。
购买AAO膜时，一般有两种类型可供选择：非对称和对称。非对称膜的有孔的直径从顶部向底部变化的。模板的底部通常包含支链的网络的孔，最终导?…
Acknowledgements
这项工作是由加拿大多伦多大学，自然科学和工程研究理事会，加拿大创新基金会，加拿大，安大略省研究基金支持。 DSS的早期研究者奖感谢安大略省。
Materials
| Reagent/Material | |||
| UniKera Standard Membrane | Synkera Technologies Inc. | SM-X-Y-13 | Anodic aluminum oxide membranes are available from synkera in various pore sizes ranging from 13 – 150 nm, and thicknesses from 50 to 100 μm. We use the 50 μm ones. They are symmetric, meaning the pore size is uniform from top to bottom. |
| Anopore Inorganic Membranes | Whatman | 6809-7023 | 13 mm diameter, 200 nm pore size. These membranes are very fragile. The pore diameters are not uniform throughout, so it is important to always use the bottom of the membrane as the working electrode |
| Silver Pellets %99.99 | Kurt J. Lesker | EVMAG40EXE-D | |
| Copper(II) sulfate pentahydrate | Sigma-Aldrich | 209189 | |
| Sulfuric acid | ACP | S8780 | Caution: corrosive liquid |
| Hydrogen peroxide (30%) | ACP | H7000 | Caution: oxidizing liquid |
| Nitric Acid | ACP | N2800 | Caution: corrosive fuming liquid |
| Sodium Hydroxide | Fisher Scientific | S318-1 | Caution: caustic powder |
| Watts Nickel Pure | Technic Inc. | 130859 | Product is no longer available from Technic inc., however other commercial nickelplating solutions will work. |
| Techni-Gold 434HS | Technic Inc. | X6763600 | Contains cyanide, do not acidify |
| Boron trifluoride diethyl etherate | Sigma-Aldrich | 175501-100ML | Must be stored and used under inert atmosphere |
| 3-hexylthiophene | Sigma-Aldrich | 399051-5G | |
| Deuterium Oxide | Sigma-Aldrich | 151880-100G | |
| Acetonitrile (anhydrous) | Sigma-Aldrich | 271004 | |
| Ethanol (anhydrous) | Caledon Labs | 1500-1-05 | |
| Equipment | |||
| EC Epsilon potentiostat/galvanostat | BASi (Bioanalytical Systems, Inc.) | N/A | Reference electrodes and platinum wires were included with the potentiostat, and replacements can be purchaes from BASi http://www.basinc.com/products/ec/epsilon/features.html |
| Cary 5000 UV-Vis-NIR spectrophotometer | Agilent Technologies | N/A | http://www.chem.agilent.com/en-US/products-services/Instruments-Systems/Molecular-Spectroscopy/Cary-5000-UV-Vis-NIR/Pages/default.aspx |
| Thermomixer R | Eppendorf | N/A | http://www.eppendorf.com/int/index.php?action=products&contentid=1&catalognode=9832 |
| Branson 2510 Ultrasonic Cleaner | Bransonic | Z244810 (From Sigma Aldrich) | http://www.sigmaaldrich.com/catalog/product/aldrich/Z244910?lang=en®ion=CA |
| Covap 2 thermal evaporator | Angstrom Engineering | N/A | http://www.angstromengineering.com/covap.html |
| Millipore Synergy water purification system | Millipore | N/A | http://www.millipore.com/catalogue/module/c9209 |
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Cite This Article
Bridges, C. R., Schon, T. B., DiCarmine, P. M., Seferos, D. S. Template Directed Synthesis of Plasmonic Gold Nanotubes with Tunable IR Absorbance. J. Vis. Exp. (74), e50420, doi:10.3791/50420 (2013).