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Gold Nanoparticles For Sensor Application

Posted on:2013-02-08Degree:DoctorType:Dissertation
Country:ChinaCandidate:X J ChenFull Text:PDF
GTID:1118330374468012Subject:Microelectronics and Solid State Electronics
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Recently, gold nanoparticles (AuNPs) have been extensively investigated due to their unique electronic, optical and biocompatible properties. They are attracting more and more attention in the field of physics, chemistry and life sciences. To date, a lot of techniques including physical and chemical methods for synthesis of AuNPs have been reported. In our work, AuNPs were successfully prepared by the reduction of HAuCl4in a boiling sodium citrate solution, and then applied for the study in different kinds of sensors.Firstly, we introduced the preparation of gold-polymer core-shell material and its application in humidity sensors. By analyzing the mechanism of polymer-coated core-shell humidity sensing material and capacitive-type humidity sensors, we used wet chemistry technique to synthesize Au-PVP nanocomposites successfully and then incorporate them into a capacitive-type humidity sensor as humidity sensing element. Due to the adsorption/desorption of water molecule, the capacitance variations under different humidity levels, in terms of the frequency shift, were examined by the capacitance-frequency conversion circuit and recorded by LabVIEW system. As relative humidity increased from11.3%RH to93%RH, the output frequencies decreased monotonically, and the sensitivity was about-136Hz/%RH. And also the good reproducibility, stability, fast response and low hysteresis make the Au-PVP nanocomposites the suitable candidate for humidity sensing materials. The as-prepared Au-PVP capacitive-type humidity sensor will have great potential in the field of humidity sensing with easy fabrication, low cost, compatibility with traditional IC process and good humidity sensing properties.Secondly, we designed the micro/nano-gap gold electrodes and explored their application in electrical DNA sensors. By analyzing the theory of silicon oxidation, we used the combination of lithography and thermal oxidation processes to realize the transition of electrodes gaps from micro-to submicron-or nano-scale. The submicron-gap electrodes were prepared successfully and studied by SEM and electrical testing. The result shows the electrodes with different shapes have different oxidation effect, among which the flat-to-flat ones have the best oxidation effect. Their gap distance can decrease from1.4μm to500nm. Then three kinds of electrodes with flat-to-flat arrays (i.e. interdigitated) were applied for DNA detection by measuring the I-V characteristics before and after hybridization. The gap distance is1.8μm,1.3μm and600nm respectively. The result shows that the as-prepared electrical DNA sensor can distinguish the matched and mismatched target DNA by comparing the I-V characteristics. The sensitivity of the three interdigitated electrodes is0.11,1.75and2.5μA/nM, which means narrower electrode gap leads to higher sensitivity. The calculated detection limit of our DNA sensor is~60fM. This method we proposed may enable batch-production and low-cost DNA biosensors. The sensors based on micro/nano-gap electrodes are in favor of devices'miniaturization and integration.Thirdly, we introduced the preparation of silicon nanowires (SiNWs) with gold nanoparticles'modification and their application in electrochemistry DNA sensor. SiNWs were prepared successfully by wet chemistry method, and gold nanoparticles were self-assembled onto the surface of SiNWs by APTMS, then silver paste was used to connect the lead to Au/SiNWs to construct the detection electrodes, i.e. electrochemistry DNA sensor. After the immobilization of capture DNA onto Au/SiNWs, the sensor was put into the target DNA solution for detection. By means of electrochemistry work station, Cyclic Voltammetry (CV) was used for measuring the sample's electrochemical characteristics. The results shows the as-prepared Au/SiNWs DNA sensor can successfully distinguish the matched and mismatched target DNA without the interference of phosphate buffered saline (PBS). The sample we proposed with the advantages of low cost, good compatibility with IC process, batch-production and real-time monitoring will be a good candidate for DNA detection.In conclusion, the main content of our subject is to apply AuNPs into different sensors by different methods for study, based on their excellent characteristics. And we hope these ideas, designs and studies will be useful for sensors'miniaturization, integration and multi-parameter testing.
Keywords/Search Tags:Gold Nanoparticles (AuNPs), Core-Shell Structure, Humidity Sensors, Submicron-gap Electrodes, DNA Detection, Biosensor, Silicon Nanowires (SiNWs), Surface Modification, Photolithography, Thermal Oxidation
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