| The invention of nanogenerators provides a potential strategy to solve the critical problem of energy supplying in nanotechnology. Due to the presence of nanogenerators, the system of energy supplying and processing in nanodevices can work at nano levels, retaining the integrity of self-power and miniaturization of nanodevices. It not only lays the foundation for the miniaturization of nanodevices'working systems, but also can efficiently harvest the micro mechanical energy, which has been ignored and viewed as uselessness in the environment. Harvesting the ubiquitous mechanical energy has been proposed as an important and potential application, which will powerfully push the nanotechnology forward.To date, a number of reports on nanogenerators have been published, such as ZnO nanowires, which could realize the charge generation, separation, accumulation and transfer due to the unique coupling of semiconducting and piezoelectric effect. These devices involved various movable parts, causing the problem of stability. As a result, it is important to design a novel device structure with stability to harvest the vibrational energy in the environment, which will broaden the applications of nanogenerators. This thesis aims to the exploitation and optimization of the novel structure, resulting in the harvesting of vibrational energy and output of electricity. The main research works are listed as follows:(1) As an important1D semiconductor material, silicon nanowires (SiNWs) have been extensively used in chemistry, catalysis, biosensors, electronics and new energy resource, due to their unique electric and mechanics properties and compatibility to silicon industry. The SiNWs obtained from modified oxide-assisted growth contain alpha quartz, which is an excellent piezoelectric material. The existence of alpha quartz makes the as-prepared SiNWs exhibit an electret effect, and a series of experiments were carried out to explore the formation mechanism of the material. The SiNWs were utilized to fabricate a nanogenerator, which yielded an output current of2.8nA with a conversion efficiency of2.2%. These findings open up a novel application of SiNWs in micro energy.(2) The presence of numerous oxygen-containing functional groups makes graphene oxide (GO) substantially different from graphene in that the former exhibits versatile and unique properties. Within a GO sheet, isolated pockets of graphene are surrounded by amorphous regions of oxygen-containing functional groups. Charges can be stored either in the discrete, quantized levels of the nanosized graphene, or trapped in the amorphous GO dielectric, where oxygen functionalities like epoxy and hydroxyl groups have high electron affinity. A flexible nanogenerator based on GO film was fabricated to harvest acoustic energy, whose output current is about3.23nA with a high conversion efficiency of12.1%. The generated current of the flexible nanogenerator sensitively depends on the pH value of the suspensions for GO films production, which is a good clue for the optimization of the device.(3) Boron nitride nanosheet (BNNS) is an analogue of graphene in which alternating boron (B) and nitrogen (N) atoms substitute for C atoms in a honeycomb network with sp2bonding. BN is a promising material with a wide band gap (5.3-5.9eV). The as-prepared BNNSs were found to be charged, which were fabricated into a nanogenerator, yielding an output current of0.95nA with a load of1MQ, illustrating the practicality of the device.(4) It was found that the O-containing functional groups on diamonds'surface from carbon nanotubes as carbon source are more than those from graphite, although the diamonds are fabricated by high pressure high temperature catalytic method under the same conditions. These O-containing functional groups enhanced their combination with bio-material—dopamine (DA), achieving ultra-dispersed and more stable suspension. With a further modification, the as-prepared nanodiamonds may find new applications.
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