Thermal, magnetic, photo sensitive properties and surface stability of nanoparticle are different from that of block material in normal condition because of properties of large specific surface area, number of surface atoms, surface energy and surface tension and small size effect, surface effect, quantum scale effect and macroscopic quantum tunnel effect, etc. Thus, it has widely application in photology, non-linear photology, electrology, magnetology and chemistry fields. Therefore, Nanotechnology has been sprung up like mushrooms. Relative products also have been introduced into daily life.
In numerous nanomaterial, inorganic nanopolymer obtains more and more attention. Although inorganic metal or ceramic material has properties of high strength, high rigidity, good thermal property and high hardness; it has disadvantages of poor moldability and difficult to process. The conventional inorganic nanomaterial is agglomeration easily because of low melting point and large specific surface area. As to the organic polymer material, it has good moldability and toughness; although thermal and mechanical properties are not as good as inorganic material. Therefore, mixing and dispersing the inorganic nanomaterial into the polymer substrate to form an inorganic nanopolymer composite material is applicable since it has improved properties of photology, thermal and activity of nanoparticles. Moreover, properties of toughness and easy process of the polymer are maintained.
However, nanoparticles need to be fabricated and fixed in the polymer base material or on the surface of the base material when preparing the inorganic nano-polymer composite material. For example, nanoparticles need to be fabricated in the polymer film or sol-gel film for photology, non-linear photology and sensor application. Solid base material is better for stable the nanoparticles comparing to the colloidal dispersion system, especially at high temperature. The interaction between nanoparticles and solid base material not only change the electronic state of the nanoparticles thereby changing physicochemical property, such as the surface plasma resonant absorption and catalytic activity, but also improve self-function of the base material (photo catalytic activity).
Currently, methods for preparing inorganic nanometal particles can be divided into physical method and chemical method. Nanometal particles can be obtained by the physical method directly; but special equipment and high vacuum environment are required. For example, the nanoparticals can be prepared by physical polishing the metal agglomerate, by metal ablation with laser to ablate the nanometal particle or deposited by physical vapor deposition (PVD). Nanoparticles prepared by the physical method have narrower particles distribution. However, more power are consumed for maintaining the reduce voltage, laser energy and vacuity during fabrication process. Thus, the chemical method was developed.
The Chemical method typically includes gas phase reaction and liquid precipitation. Gas phase reaction includes spraying method, which is preparing nanometal particles by spraying high pressure gas; pyroly decomposition method, which is preparing nanometal particles by decomposing the metal compound and gas reducing agent; and vapor/aggregation method, which is preparing nanometal particles by heating and evaporating the volatility material. Liquid precipitation includes sol-gel, hydrothermal, ultrasonic decomposition, micro emulsion and chemical reduction. Recently, the chemical reduction method, using a reducing agent, is widely used because of low pollution, high efficiency, low reaction temperature, simply procedure and easily to control the shape of the particles.
Chemical reduction method reduces the metal oxide to nanometal particles efficiently by the reducing agent at room temperature. Typical metal oxide includes copper chloride, nickel chloride, iron chloride, silver nitrate and chlorauric acid, for example. Typical reducing agent includes sodium citrate, ethylene diamine tetraacetic acid (EDTA), ethylene glycol, sodium borohydride, ascorbic acid, ethanol, dimethyl formamide (DMF), dimethyl acetamide (DMA), etc. However, nanoparticles, which is prepared by the chemical method, aggregated easily due to the coalescence between particles. Thus, a dispersing agent needs to be introduced to control the dispersibility and stability of the nanometal particles.
Currently, the dispersing agent can be divided into two types: surfactant and polymer. Surfactant is used to stabilize the nanometal particles by combining the functional group, such as amine, thiol, acid and alcohol, with the nanometal particles. Comparing to the surfactant, the structure and the functionality of the polymer are variable and easy to control. For example, the structure of the polymer includes linear, comb and branch, etc. The functionality of the polymer includes hydrophilic/hydrophobic, anion/cation, emulsibility and self-assembly. The nanometal particles can be grown stably and efficiently through the specific characteristics of the polymer. Some of the polymer and the solvent, such as polyvinyl alcohol (PVA), polyethylene glycol (PEG), polyvinyl pyrrolidone (PVP), ethylene glycol or DMF, etc., can be induced by thermal or light to have its own reducing ability. No additional reducing agent is needed. The nanometal particles can be prepared through its owned dispersing and stable effect. According to the research, the nanoparticles, obtained by utilizing the polymer as a dispersing agent, have advantage of uniform particle distribution, controllable particle size and easy to film.
Nanomaterial, which is recently developed rapidly and has important application, is AgNPs composite. It has widely application includes photoelectric, catalyst, conductive, bio-medical sensor, drug release and quantum dot. However, the bottleneck of the applications is particles agglomeration easily and the concentration increasable inefficiently during fabrication. Therefore, the aspect of research is to minimum the agglomeration of the nanoparticles and prepare silver nanoparticle composite with variety shape.
Therefore, this invention desired to disclose a method dispenses with any reducing agent or dispersing agent but allows nanometallic particles to be formed in situ and thereby reduces surface resistance of the polymer film efficiently.