| In recent years, environmental pollution has become more serious with increasing the economy development and the number of the population, how to deal with this problem has attracted a great attention. As a band gap of ?3.5 eV at room temperature, SnO2 is a n- type semiconductor, and has a good chemical, electrical and optical activity which offers a large potential application in photocatalyst, gas sensor, lithium ion battery, dye sensitive cell, super capacitor, transparent conducting film and other photoelectric devices. Meanwhile, graphene is composed of orthohexagonal monolayer carbon and also has a great potential application in photo-electric detector, optical modulating device, super-speed laser and other photoelectric devices due to its excellent electrical and optical property.As we know, the particle size, mophology, growing orientation and crystallinity of nano-material have a considerable effect on its optical and electrical property, thus designing and preparing various size and morphology about SnO2 and graphene have been carried out, and various nanostructures, such as, quantum dot, nanobelt, nanorod, nanosheet, hierarchical structure have been obtained.In this paper, the catalytic activity of flowerlike hetero tin oxide for R6G as well as its optical property has been investigated. Then, sandwich structured GO film decorated with Ag nano-particles has been successfully prepared and used to study the SERS activity on PCB77(3,3',4,4'-tetrachlorobiphenyl).The detailed discussions are presented as followsFirstly, hollow flowerlike nanostructure SnO and Sn3O4 II hetero-j unctions were synthesized through one step hydrothermal approaches at 180? in 18 hours, and then annealed at 300?, 400?,500?,600?,700?, respectively. Their phase transitions and photo-catalytic activity were studied either. The results indicated that the SnO gradually transformed into Sn3O4 with the increase of annealing temperature. When the annealing temperature was elevated to 500?, SnO and Sn3O4 type-II hetero-junction changed into Sn3O4/SnO2 type-I hetero-junction, when the annealing temperature went up to 700?, the product was almost composed of SnO2. Among those samples, SnO/Sn3O4 type-? hetero-junction had the best catalystic behaviour for P25s, its photocatalytic speed was 2.3×10-3 min-1. This may be due to its strong separation of electrons and holes via the interface between SnO and Sn3O4 type-II hetero-junction.Then, the optical properties of the prepared samples annealed at 400?,600? and 700? were investigated.moreover, we concentrated on its phase transition and optical property specifically. Discussion suggested that the in situ synthesized product consisted of SnO and Sn3O4 while containing traces of SnO2. With the annealing temperature increased, the product basically and largely transformed into Sn3O4 and SnO2. The Roman results indicated that the transformation temperature was about 420?; UV-Vis results suggested that the band gaps of SnO, Sn3O4 and SnO2 are approximately 2.8,2.1?2.3 and 3.4?3.6 eV; PL spectra revealed that all the product had the emission peaks at 420,450,470,495 and 530 nm, but the product annealed at 700? has additional two peaks centered at 377.5 and 399 nm. Flowerlike tin oxide will have a great potential application in li-ion battery and photo-catalyst due to their high surface-to-volume ratio and strong visible emissions.In this thesis, the other part of the work is concentrated on the preparations and Raman scattering effects of Ag nanoparticle/Graphene oxide (GO) sheet sandwich films using a laser ablation technique. Experimentally, the laser was used to irradiate the Ag target, which was immersed in the GO colloidal solutions, at the same time the solutions were continusly stiring with a stir bar, the Ag nanoparticles instantly were formed on the GO nanosheets homogeneiously. Then, the colloidal solution of Ag nanoparticle/GO sheet as-prepared was heated at 80? in oil bath for several hours so that the the 3D film was produced at the liquid surface. Such sandwich films exhibit very strong SERS activity due to the large coupling effects of the Ag nanoparticles along and between the nanosheets and the presence of more Ag nanoparticles in the films. The films allow for good stability and reproduction of the Raman signals. Additionally, they are ideal platforms for trace-detecting persistent organic pollutants in the environment. Also, the strategy is universal for fabricating other graphene-based sandwich films. |
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