Nanostructured Materials for Microfluidic Sensing Application
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Nanostructured Materials for Microfluidic Sensing Application Nancy N. Kariuki, Laura Moussa, Tanya Menard, Asif Hassan, Li Han, Elizabeth Crew, Jin Luo, and Chuan-Jian Zhong* Department of Chemistry, State University of New York at Binghamton, Binghamton, New York 13902. * [email protected] ABSTRACT Nanostructured thin films were assembled on interdigited microelectrode (IME) arrays as sensitive interfacial materials of an electrochemical detector, which can be integrated into microfluidic sensor devices. The goal is to produce sensor devices at extremes of miniaturization. The IME were created on glass wafers using conventional lithographic techniques. Open channels were etched on quartz or glass, and covered by PDMS materials, which were created using soft-lithography. The capability of chemical recognition was provided by the ligand framework structures of the nanostructured thin films on the electrode surface. A model system for such nanostructures involved the use of monolayer-capped gold nanoparticles of ~2 nm core sizes which were assembled by carboxylic acid functionalized alkyl thiol linkers. The detection of dopamine was studied as a redox probe to test the feasibility of the microfluidic device. Results of cyclic voltammetric and chronoamperometric experiments are presented. Implications of the findings to the development of sensitive, selective, rapid and portable microanalytical devices for chemical/biological sensing are also discussed.
INTRODUCTION Nanoparticles in the size range of 1-100 nm have become increasingly important in several technological fields such as chemical sensors, electronic, optical and mechanical devices, drug delivery and bio-encapsulation1-2. The use of nanoparticles as building blocks for the construction of highly responsive materials at electrodes with nanoscopic dimensions constitutes one of the increasingly important areas in interfacial electrochemistry3-6. Some of the current research areas are directed at manipulating nanostructured thin films to create interfacial recognition properties for chemical and biological species using miniaturized devices. Among different miniaturization technologies, microfluidic technology has shown great potential in analytical miniaturization due to high-throughput capabilities7 with significant applications in medical diagnostics as well as environmental monitoring8. One recent development of microfluidic systems combines advantages of flow injection analysis and electrochemical detection on microelectrodes. The surface modification of the electrode with nanostructured ligand framework as sensing materials can lead to enhancement of selectivity, sensitivity and detection limit. We have been exploring a general strategy that entails core-shell manipulation of gold and alloy nanoparticles as building blocks towards responsive or fine-tunable interfacial materials for electroanalytical applications. One example for the preparation
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of nanostructured sensing materials involves the assembly of gold nanoparticles and car
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