Abu Hatab Nahla A, Oran Jenny M, Sepaniak Michael J
Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996-1600, USA.
ACS Nano. 2008 Feb;2(2):377-85. doi: 10.1021/nn7003487.
The development of quantitative, highly sensitive surface-enhanced Raman spectroscopy (SERS) substrates requires control over size, shape, and position of metal nanoparticles. Despite the fact that SERS has gained the reputation as an information-rich spectroscopy for detection of many classes of analytes, in some isolated instances down to the single molecule detection limit, its future development depends critically on techniques for nanofabrication. Herein, an unconventional nanofabrication approach is used to produce efficient SERS substrates. Metallic nanopatterns of silver disks are transferred from a stamp onto poly(dimethysiloxane) (PDMS) to create nanocomposite substrates with regular periodic morphologies. The stamp with periodic arrays of square, triangular, and elliptical pillars is created via electron beam lithography (EBL) of ma-N 2403 resist. A modified cyclodextrin is thermally evaporated onto the stamp to overcome the adhesive nature of the EBL resist and to function as a releasing layer. Subsequently, Ag is physically vapor deposited onto the stamp at a controlled rate and thickness and used directly for nanotransfer printing (nTP). Stamps, substrates, and the efficiency of the nTP process were explored by scanning electron microscopy. Transferred Ag nanodisk-PDMS substrates are studied by SERS using Rhodamine 6G as the probe analyte. There are observed optimal conditions involving both Ag and cyclodextrin thickness. The SERS response of metallic nanodisks of various shapes and sizes on the original stamp is compared to the corresponding nTP created substrates with similar trends observed. Limits of detection for crystal violet and Mitoxantrone are approximately 10(-8) and 10(-9) M, respectively. As an innovative feature of this approach, we demonstrate that physical manipulation of the PDMS post-nTP can be used to alter morphology, e.g., to change internanodisk spacing. Additionally, stamps are shown to be reusable after the nTP process, adding the potential to scale-up regular morphology substrates by a stamp-and-repeat methodology.
定量、高灵敏度表面增强拉曼光谱（SERS）基底的开发需要对金属纳米颗粒的尺寸、形状和位置进行控制。尽管SERS已被誉为一种用于检测多种分析物的信息丰富的光谱技术，在某些孤立情况下甚至可达到单分子检测限，但其未来发展关键取决于纳米制造技术。在此，采用一种非常规的纳米制造方法来制备高效的SERS基底。银盘的金属纳米图案从印章转移到聚二甲基硅氧烷（PDMS）上，以创建具有规则周期性形态的纳米复合基底。通过对ma-N 2403光刻胶进行电子束光刻（EBL），制作出具有方形、三角形和椭圆形柱体周期性阵列的印章。将一种改性环糊精热蒸发到印章上，以克服EBL光刻胶的粘性并用作脱模层。随后，以可控的速率和厚度将银物理气相沉积到印章上，并直接用于纳米转移印刷（nTP）。通过扫描电子显微镜对印章、基底和nTP工艺的效率进行了研究。使用罗丹明6G作为探针分析物，通过SERS对转移的银纳米盘-PDMS基底进行了研究。观察到了涉及银和环糊精厚度的最佳条件。将原始印章上各种形状和尺寸的金属纳米盘的SERS响应与通过nTP创建的具有相似趋势的相应基底进行了比较。结晶紫和米托蒽醌的检测限分别约为10^(-8)和10^(-9) M。作为该方法的一个创新特点，我们证明了在nTP之后对PDMS进行物理操作可用于改变形态，例如改变纳米盘间距。此外，印章在nTP过程后可重复使用，这增加了通过印章重复方法扩大具有规则形态基底规模的潜力。
