This presentation reports the use of nanostructured sapphire optical fiber (NSOF) with Au nanorods entrapped in anodized aluminum oxide (AAO) cladding for surface-enhanced Raman spectroscopy (SERS) sensing at elevated temperatures. Specifically, Au nanorods were fabricated in AAO pore channels by in-situ electroless reduction aided with Au nanoparticle catalysts. We show that the AAO pore channels endow the Au nanorods with enhanced thermal stability through geometrical confinement at up to 1000°C. The NSOF with entrapped Au nanorods was used for SERS measurements at temperatures ranging from room temperature to 800°C. The capacity of the novel fiber structure for sensing of hot gases in harsh environments was demonstrated.
Prostate cancer is a heterogenous disease that has a varied range from indolent to highly aggressiveness. The routinely used biomarker, Prostate Specific Antigen (PSA), is controversial due to over-diagnosis. A new approach is urgently needed to discriminate the indolent and lethal prostate cancer. We report the measurements of patient urine using surface-enhancement Raman scattering (SERS) as a potential means of differentiating aggressive and indolent prostate cancer types. To this end, urine samples from twenty prostate cancer patients with known clinical outcome are investigated in this study, with ten in each of the two groups: aggressive and indolent. SERS measurements, ten for each sample, are carried out in blind without revealing any clinical details to the investigators. Principal component analysis (PCA) and linear discriminant analysis (LDA) are used to statistically analyze the large number of Raman spectra to identify and classify the specific Raman features potentially associated with aggressive and indolent prostate cancer types. The experimental classifications are compared with the clinical outcome of the prostate cancer patients to demonstration the potential of SERS as an alternative method for patient screening and decision-making for the optimal treatment strategy.
Surface-enhanced Raman scattering (SERS) integrates high levels of sensitivity and spectroscopic precision with tremendous potential for chemical and biomolecular sensing. On the other hand, metal nanoparticles have been employed in catalysis with great promise for future energy technologies. Interactions between oxygen and gold surfaces are of fundamental importance in catalysis and other multiple and diverse areas of science and technology. We propose to synergistically integrate the two aspects of metal nanoparticles in dual-functional Ag@Au core-shell nanostructures to take advantage of high SERS enhancement factor of Ag and unique catalytic property of Au. Pure Au nanoparticles with specific size are also prepared to be a comparison with Ag@Au core-shell structures in terms of SERS enhancement and catalytic properties by in situ Raman detection during the decomposition of hydrogen peroxide.
This presentation reports our findings in the fabrication and evaluation of nanostructured sapphire optical fiber (NSOF) for surface-enhanced Raman spectroscopy (SERS) sensing at elevated temperatures. Specifically, we systematically investigated the morphological stability and the mechanical properties of the anodized aluminum oxide (AAO) cladding of NSOF after cyclic thermal treatment at temperatures ranging from 1000°-1500°C with the pore diameter, interpore distance, as well as the cladding thickness as parameters. The cladding/sapphire fiber interface integrity due to possible mismatch in the coefficient of thermal expansion between AAO and sapphire fiber was also examined. We also immobilized Ag nanoparticles in the pore channels of AAO cladding for in-situ SERS measurements in a hot furnace. We will show that Ag nanoparticles confined in the nanoscopic pore channels of AAO exhibit much better thermal stability, compared with those on a planar substrate, making high-temperature harsh environment SERS sensing possible with NSOF.
Current industrial technologies for selective oxidation of propene via a single-stage oxidation process in H2/O2 catalyzed by Au holds excellent prospect of green production of C3H6O. Fundamentals of the molecular mechanisms between catalytic Au and the oxidant remain unclear for decades, however, impeding the development of its rational design and implementation. We explore a multifunctional, highly organized nanoporous anodized aluminum oxide (AAO) substrate with immobilized Au nanoparticles (Au NPs) both as a catalytic reactor and an ultra-sensitive SERS probe to investigate the molecular level details during Au-catalyzed oxidation of propene in situ. Nanoporous AAO offers excellent thermal stability and enhanced particle coverage density for the immobilized Au NPs within to enable high temperature SERS interrogation, opening up new opportunities in the study of the catalytic reactions. Different size of Au NPs and pores of AAO are explored for improved SERS sensitivity and catalytic activity.
Single crystal sapphire fiber is an excellent candidate for fiber-optic sensing in harsh environments owing to its superior optical, mechanical and thermal properties at elevated temperatures up to 1500ºC. We have carried out an experimental and theoretical investigation on the mechanical properties of nanostructured sapphire optical fiber (NSOF) cladded with nanoporous anodized aluminum oxide (AAO). The threshold thickness beyond which the integrity of AAO cladding will be compromised due to tensile stress as growth of AAO extends radially outward is determined. Bending tests are conducted to explore relationship of NSOF mechanical properties with AAO porosity and thickness as parameters. Bending simulations using Finite Element Method will be compared with our experimental results. Parallel bending tests are conducted using AAO-clad silica fiber for comparison. Numerical and analytical simulations are also conducted to reveal the stress development during aluminum conversion to AAO on fiber geometry. The knowledge established on mechanical properties of NSOF will be of critical importance in its design, production, and utilization for a variety of demanding applications such as sensing for energy generation and energy production systems.
We describe an innovative and scalable strategy of transforming a commercial unclad sapphire optical fiber to an allalumina nanostructured sapphire optical fiber (NSOF) that overcomes decades-long challenges faced in the field of sapphire fiber optics. The strategy entails fiber coating with metal Al followed by subsequent anodization to form anodized alumina oxide (AAO) cladding of highly organized pore channel structure. We show that Ag nanoparticles entrapped in AAO show excellent structural and morphological stability and less susceptibility to oxidation for potential high-temperature surface-enhanced Raman Scattering (SERS). We reveal, with aid of numerical simulations, that the AAO cladding greatly increases the evanescent-field overlap both in power and extent and that lower porosity of AAO results in higher evanescent-field overlap. This work has opened the door to new sapphire fiber-based sensor design and sensor architecture.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.