Study On The Property And Application Of Gold Nanoparticle Array

Influence by the external force or strain, the mechanical structure as well as the resistance of conductors or semiconductors will be changed, which is defined as the strain resistance effect. Devices based on the strain resistance effect to measure the other physical quantities are called the strain sensors, which can be used to measure the variation of force, deformation, displacement, acceleration and torque, etc. Bonded strain gage is the main structure of resistive strain sensor, which is an accurate, sensitive, versatile, convenient, and economic sensor.Based upon the research status, titled of "Study on the response and the application of gold nanoparticle array based on electron tunneling effect", the response characteristics and the related applications of the self-assembled gold nanoparticles array and ultrathin gold film has been studied in this work, in order to have a good understanding of the sensing mechanism and expand the applications of the strain gauges based on the nanomaterials and nanostructures.The smooth-surface-spherical gold nanoparticle array was fabricated with the method of convective self-assembly. By tuning the assembly parameters during fabrication process, the order of the array distribution can be controlled. The strain response sensitivity of the array was measured and compared with the results mentioned in the documents, which indicates that the response characteristic is closely related to the arrangement of the array structure. The active units with higher order degree have higher strain response sensitivity.In order to improve the effective cross-section of tunneling, the gold nanoparticles with irregular morphology were selected to fabricate the strain gauge. Compared with the gauge with smooth surface nanoparticle, the conductivity of the irregular one’s can be improved by more than two orders of magnitude, which is helpful to improve its electrical performance characterization and operability of measurement. The response performance to the mechanical vibration caused by single frequency music and mixing speech voice has also been studied.To further improve the sensing properties of the two-dimensional gold nanoparticle system, the ultrathin gold film with strict monolayer structure was fabricated through the thermal evaporation method; meanwhile the evolution of morphology and the strain response characteristics of the film in various stages have been studied. The results indicate that the response sensitivity of the film decreases with the increase of the film thickness. Since the preparation technology of the ultrathin gold film is simple and easy to control, a new method of measuring the resistance change rate based on two sensing units is proposed in this paper to improve the response sensitivity. The detection limit of the ultrathin gold film with thickness of 4 nm was investigated, and the result shows that when the strain decreased to 0.00083%, the change in electrical resistance remained visible, in which case the signal-to-noise ratio is～1.9, demonstrating the ultrasensitive capability of the device. This detection limit is 10-100 times better than that of previously reported.We consult a number of literatures in the field of flexible sensors related to our study, to study the physical mechanism of the response charicater. Based on the previous achievements, this paper proposes a resistor network model based on the interaction of electron tunneling and free electron conductive, which can accurately explain the relationship between film thickness and resistance.In order to broaden the application of the ultrathin gold film, we studied the response performances of the cantilever beam made from ultrathin gold film to low frequency weak mechanical vibration. Our experimental results confirm that the strain sensor could achieve its applications in various areas such as droplet disturbance, intrusion alarm systemand pulse measurement and so on. In addition to the low frequency weak mechanical vibration, we also studied the response performances of the cantilever beam to high frequency mechanical vibration. Experiment results indicate that the gauge made from ultrathin gold film can detect vibrations with the frequency of 1-20 kHz in not only the contact mode but also the non-contact mode.The effect of temperature on resistivity of the ultrathin gold film has been studied. According to the experimental results, the temperature coefficient of resistance (TCR) is tunable by changing the thickness of the film, which is important to broaden its application. The fluence of the humidity to the resistance has also been studied and the results indicate that the resistance of the ultrathin gold film was sensitive to the environment humidity. Based on the experimental results, a possible mechanism was put forward to explain the influence of humidity on resistance of thatthe humidity causes the change of the dielectric constant of the medium filled in the adjacent nanoparticles, and which will change the electron tunneling probability and the resistance of the film system.