Conductive carbon nanotubes (CNTs) obtained by dotting carboxylated CNTs with metal nanocrystals by chemical functional groups, are described by KAIST LG Chem Chair Professor Dept. of Chemical & Biomolecular Engineering, Sang Yup Lee (Daejeon, KR), Hee Tae Jung , Dae Hwan Jung , Young Koan Ko , Do Hyun Kim, Seok Jae Lee, Byung Hun Kim and Jae Shin Lee in U.S. Patent Application 20100009432. The inventors also describe a method for fabricating a pattern or film of the conductive CNTs which involves repeatedly depositing conductive CNTs on a substrate to achieve high surface density.
A biosensor is detailed in which bioreceptors that bind to target biomolecules are selectively attached to conductive CNTs or a conductive CNT pattern or film. In order to improve the electrical properties of the existing CNTs, CNTs are dotted with metal nanoparticles. The CNTs dotted with the metal nanoparticles are repeatedly deposited on a solid substrate coated with chemical functional groups, by chemical binding, to fabricate a conductive CNT pattern (or film) having high surface density. Also, various bioreceptors having functional groups that react with the gold nanocrystals present in the high-density CNT pattern are attached to the CNT pattern or film, to fabricate a biosensor that can detect various target biomaterials directly or by electrochemical signals.
By use of the conductive biosensor, various target biomaterials that bind or react with the bioreceptors can be precisely measured directly or by electrochemical signals in large amounts in one step. Additionally, the biosensor can be used for an electrical detection method capable of providing precise measurement results even with a small amount of source material.
FIG. 1 is a schematic diagram showing a process for producing carbon nanotubes (CNTs) dotted with gold nanoparticles according to the process developed at KAIST.
FIG. 2 is a schematic diagram showing a process for making a polymer mask pattern having a given shape for the integration of CNTs of FIG. 1 on a silicon substrate by photolithography.
FIG. 3 is a flow chart illustrating a method for fabricating a pattern of CNTs dotted with gold nanoparticles. FIG. 3a is a schematic diagram showing that a thiol (--SH) group is exposed to a substrate surface having a pattern formed thereon, and a CNT monolayer dotted with gold nanocrystals is immobilized to the substrate surface. FIG. 3b is a schematic diagram showing other CNTs dotted with gold nanocrystals immobilized to the CNT monolayer of FIG. 3a by a chemical substance having two thiol groups.
FIG. 3c is a schematic diagram showing a method for increasing the surface density of gold nanoparticle-dotted CNT by repeating the method of FIG. 3b. FIG. 3d is a schematic diagram showing a method for depositing gold nanoparticle-dotted CNTs to high density, by repeating the method of FIG. 3c.
FIG. 3e is a schematic diagram showing CNTs dotted with gold nanoparticles deposited on the substrate at high density to form a CNT pattern.
FIG. 9a is a TEM photograph showing a gold crystal-dotted CNT obtained by forming thiol (--SH) groups on a CNT and reacting the thiol groups with gold colloids, and FIG. 9b is a TEM photograph showing a CNT obtained by reacting gold colloids with a CNT having no thiol (--SH) groups.
FIG. 10 is a HR-TEM photograph of FIG. 9 enlarged to high magnification.
FIG. 13 is a photograph showing that DNAs having thiol functional groups are attached to CNTs dotted with gold nanoparticles. FIG. 13a is a photograph showing the comparison of the results of interaction between various DNAs and CNTs, and FIG. 13b is a photograph showing the results of comparison to determine if DNA complementarily binds to a CNT pattern
KAIST is the Korea Advanced Institute of Science and Technology.