Preparation And Optical Properties Study Of Al Nanomaterials

In recent years,metal nano-materials,as a new type of plasmonic materials,have received extensive attentions.It has wide application prospect in catalysis,solar cell,optical sensing,biomarker,medical imaging and other fields.Under the excitation of light,there is a interaction between the photon and the outer electrons of metal nanomaterials,namely,local surface plasmon resonance(LSPR),which can be tuned by type,size,morphology and surrounding environment.Common plasmonic materials,with rich valence electrons and plenty of unoccupied electronic orbits,are usually noble metals,such as gold and silver.Recently,aluminum has also been found with unique plasmonic properties,which can range from deep ultraviolet to near infrared.Aluminum nano-materials have been widely applied in various fields,such as rocket propellant,explosives and solar cells.Aluminum nano-film prepared by the physical methods can be used for SERS detection with ultrahigh sensitivity under deep UV excitation,and the detection threshold for biological molecules and TNT can reach as low as attomolar.In comparation of classic noble plasmonic metals(gold and silver),aluminum is the most abundant metal element on the earth with cheap price,providing great application potentials.As mentioned above,the LSPR property is highly dependent on the morphology,which requires finely control of preparation.In this thesis,based on understanding of the preparation of noble metal plasmonic nanomaterials,we develop a suitable method for aluminium nanomaterials synthesis,andsuccessfully get a series of materials with outstanding optical properties.The main research work and the results are as follows:1.By using the one-step wet chemical method,a proposal of controlling the synthesis of aluminum nanomaterials by organic amines is evolved.Three main factors in preparation the aluminum nanoparticles:(1)reaction solvents;(2)reaction temperature;(3)organic amine.A series of aluminum nanoparticles with different sizes ranging from 20 to 1000 nm are prepared.The corresponding LSPR spectra are tunable at 250-285 nm.The best conditions are optimized as in mesitylene or toluene above 110 ?.In addition,the nitrogen atoms of the ammonium salt are found with strong intereaction with aluminum atoms,and the size of aluminum nanoparticles can be tuned accordingly.2.On the basis of successful synthesis of aluminum nanoparticles,we further prepared a series of aluminum nanosheets by reducing reactant concentration,reaction temperature and controlling oxygen concentration,which is controlled by different oxygen bubbling time.The thickness of nanosheets can be adjusted from 1.5 to 18 nm.As revealed by dark field microscope from scattering spectra of single particles,the corresponding LSPR is found to be located in the range of 632 to 825 nm.Using femtosecond pulse laser with 820 nm as the excitation wavelength,we found the two-photon emission is highly dependent on LSPR,and much better two-photon emission performance than gold nanorods(aspect ratio is 4).