Application Of Biochemical Sensors Using Rolled-up Noble Metal Composite Micro/Nano Tubes

Rolled-up nanotechnology, which involves releasing the internal stress of the nanomenbranes and self-rolling into three-dimensional micro- and nano-structures is considered as a simple and effective method to fabricate rolled-up microtube. During the past decade, various materials have been made into microtubes which can be implanted into the applications of optical detection, microengine, and biomedical field. Because of its unique physical and chemical properties, and great use of space in multiple areas, tubular micro-and nanostructure has become a focus of current research. In this paper, noble metal composited microtubes are fabricated by rolled-up nanotechnology, and the corresponding surface-enhanced Raman scattering properties are investigated. The main results are as followings:1. Perfect rolled-up noble metal composited microtubes including oxide nanomembranes and noble metal nanomembranes are obtained by designing the strain gradient in nanomembrane during the rolled-up process. Superior to the simple metal rolled-up microtubes which always accompany the disadvantages of disordered arrangements and rolled-up directions, these neatly arranged microtubes are demonstrated to have uniform rolled-up direction. Rolled-up nanotechnology offers impressive merits to control diameter and rotating times of rolled-up microtubes by tuning the parameters, such as material components, thickness of the deposited nanomembranes and sacrificial layers. The result indicates that with the same material component, the microtube diameter decreases with the increasing of the layer thickness. And we believe that this phenomenon results from the interactions of pre-strain and stress gradient of the deposited layers. Moreover, the patterns of the designed sacrificial layer also have an impact on the microtube diameter. That’s because the pre-strain of the nanomembranes will release simultaneously along axial derection and radial derection when the nanomembranes detach from the sacrificial layer.2. In this paper, rolled-up mivrotube have been proved to be an ideal surface- enhanced Raman scattering (SERS) substrate. The enhancement factor (EF) can reach up to 1.2×105. By measuring the Raman spectra intensity of the probe molecule under dirrerent concentrations, the effective measurement range is obtained to be 10-6-10-4 M. the intensities of Raman scattering spectra at different locations of microtube surface are also measured. It originates in local electromagnetic field enhancement which is generated from surface plasmon resonance. And both experimental results and theoretical simulations confirm the conclusion.3. Rolled-up microtube is a kind of hyperbolic metamaterials which has special morphology. Due to unique dispersion relation, it can control electromagnetic wave propagation in metamaterials. In this work, we explore a simple and effective method to tailor the SERS signal in surface of rolled-up microtubes. The distance between the probe molecules and the surface of nanostructures can be modulated by inserting a passivation layer (Al2O3 in this work) which is deposited by atomic layer deposition (ALD). When the thickness of the passivation layer is optimized to be 3nm, the intensity of characteristic peak (located at 1650 nm-1) is the strongest with the EF of about 4x 105. The result is also demonstrated by theoretical simulations, which is caused by the interactions between optical gain of dielectric and the distance dependence of electromagnetic field.