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Preparation of the Core-shell Nanocomposites and Their Application in Humidity Micro/Nanosensors

Author: YaoZuo
Tutor: ZhangJian
School: East China Normal University
Course: Microelectronics and Solid State Electronics
Keywords: Humidity Sensor Gold Nanoparticles polyvinyl alcohol (PVA) Polyvinylpyrrolidone (PVP) Core-shell Nanocomposites Relative Humidity
CLC: TB383.1
Type: Master's thesis
Year: 2010
Downloads: 232
Quote: 1
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Abstract


With the development of nanotechnology, more and more novel properties of nanostructured materials have been recognized.Nanomaterials would play an important role in semiconductor devices in the future. Among them, the core-shell nanocomposites had attracted lots of attentions in the past several years due to their unique properties and the potential applications.So far a lot of core-shell nanocomposites have been prepared. The research on how to put these core-shell nanocomposites into new nano devices application will be a focus in the future.In this thesis, the Au-polymer core-shell nanocomposites have been investigated. Two kinds of capacitive humidity sensors employed Au-polymer core-shell nanocomposites have been fabricated successfully. The main results are listed as bellows:1.In order to solve the problems of the conventional humidity sensors encountered currently such as the difficulties of adsorbption/desorbption and the slow response/recovery time, this work discussed a novel capacitive sensor using Au-polymer core-shell nanocomposites as sening material.The gold nanoparticles are chosen as the cores and polyvinyl alcohol (PVA) and Polyvinylpyrrolidone (PVP) are chosen as the shells to construct the core-shell nanocomposites, respectively. The adsorbption/desorbption of water can induce the dielectric constant change of these core-shell nanocomposites, so the humidity can be detected. Since the thickness of the polymer shells is only several hundreds nanometers with large specific suface area, it is believed that the sensors based on these core-shell nanocomposites will have the excellent sensitivity. And the humidity sensors’response/recovery time could be improved since the nanometer level polymer shell is benificial for uptake of water. The gold cores can also improve the dielectrical properties of nanocomposites.Both Polyvinyl alcohol and Polyvinylpyrrolidone are good humidity sensing materials.2.The preparation of Au-polymer core-shell nanocomposites has been studied in this thesis as well as their immobilization method in humidity sensor electrodes.The~10nm gold nanoparticles cores were firstly prepared by the citrate reduction of HAuCl4.Then Au-PVA and Au-PVP nanocomposites are prepared by sol-gel method. The as-received Au-PVA and Au-PVP core-shell nanocomposites are on the submicron level.Scanning electron microscope (SEM) and atom force microscopy (AFM), etc were used to characterize the structural and morphological property of the nanoparticles as well as nanocomposites.3 The Au-PVA and Au-PVP nanocomposites are grafted onto APTMS ((3-aminopropyl)-trimethoxysilane) treated P-silicon (p=1-20Ω·cm), respectively, to construct humidity sensors.A home-made testing system had been established to test humidity sensors and process the data collection. The results indicated that the capacitance changes of all capacitive humidity sensors are on the nF level.Both two kinds of developed sensors had the high sensitivity<-140Hz/%RH, the fast response time,00~236s, and the fast recovery time,<200s.The research also indicated that the sensor properties such as, stability, dynamic response, hysteresis,had been improved more or less.4.A new type of nano/micro trench electrodes were designed and fabricated for sensor testing.According to the thermal oxidation expansion theory, different shape of submicron electrodes were made successfully with minium gap~0.6μm. All these research provide a wild platform for discussing the structural and morphological property of Au-polymer between these submicron electrodes as well as making nano/micro humidity sensors to improve their performance.In conclusion, in this thesis, the application of the humidity sensors based on Au-polymer core-shell nanocomposites has been investigated. It is believed that the humidity sensors based on Au-polymer core-shell nanocomposites are potential to develop a new kind of humidity sensor with high performance and low cost.

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