Noble metal has chemical stability, biocompatibility, electric and thermal conductivity, surface plasmon property, and is widely used in catalysts, chemical/bio sensors, photoelectric devices, nano devices, surface enhanced Raman scattering (SERS) and so on.
Optical properties of the noble metal are largely influenced by the morphology thereof, and can be applied, when it is made to a single crystalline nanoplate, as plasmonics, bio sensors, molecular electronic devices and so on.
In general, a metal nanostructure can absorb molecules on a surface thereof using self-assembled monolayer (SAM), and it is possible to obtain a molecular layer uniformly absorbed on a surface of a noble metal nanostructure using this phenomenon.
Studies for developing biomolecule analysis technologies and optical devices can be performed by observing the SERS phenomenon of molecules using the noble metal nanoplate and the SAM and applying molecules that form the SAM as a linker, and particularly, utilization of uniformly produced noble metal nanoplate structure in the SERS detection can be used as a very sensitive analysis technology.
Existing studies for the optical device development using the plasmonics have been mostly performed by using metal nanoparticles. However, when using the metal nanoparticles, it is difficult to obtain the plasmonic structure and optical device having the desired stability since it is impossible to accurately control the structure of the metal nanoparticles.
However, the noble metal nanoplate which has no internal crystal defect and is made of high purity and high quality single crystal is a single crystalline metal nanoplate which has no defect and defined well at an atomic level. Therefore, this weakness can be solved by coupling synthesized the single crystalline noble metal nanoplate with the plasmonics.
Fabrication of the plasmonic structure by controlling a complete single crystalline metal nanoplate and control of molecular arrangement and Raman signal by applying external electric fields are expected to be a great turning point that will give major growth of a study for developing hybrid optical devices.
The metal nanostructure has been numerously studied and developed in earnest after 1990s and most of the studied and developed nanostructures were related to the form of a nanoparticle or a nanoplate. Studies for fabrication and application of a two-dimensional nanostructure such as a nanoplate were insignificant, and particularly, there has been no report on the fabrication of a metal (metal including noble metals) nanoplate, which has a size of several micrometer and made of a high purity and high quality single crystalline body, using a vapor-phase transport process.
Korean patent application publication No. 2006-0009735 discloses a fabrication method of a gold nanoplate using a liquid-phase process, but the method has a limitation in that it is difficult to control the morphology and size of the noble metal nanoplate, the fabricated noble metal nanoplate has low purity and a polycrystalline nanoplate having defects within the nanoplate is synthesized.
Therefore, the present applicants will provide a fabrication method of a high purity single crystalline metal nanoplate with no 2-dimensional defect including twin on a single crystalline substrate by a vapor-phase transport process using metal, metal halide or a mixture thereof as a precursor, a fabrication method of a metal nanoplate epitaxially with a single crystalline substrate, and an easily mass-producible method in which a side of a metal nanoplate has a length of several micrometers, a large amount of the nanoplates is arranged in parallel relation to each other and an orientation with respect to a substrate and a morphology can be controlled.