An sp2 and sp3 hybrid nanocrystalline carbon film electrode for anodic stripping voltammetry and its application for electrochemical immunoassay.
A hybridized nanocrystalline carbon film electrode consisting of sp(2) and sp(3) bonds was investigated to reveal the reduction properties of Cd(2+) and for application as a highly sensitive and reliable electrochemical immunoassay.  Conductive nanocrystalline carbon film consisting of about 60% sp(2) and 40% sp(3) bonds was fabricated using electron cyclotron resonance (ECR) sputtering equipment, and then the Cd(2+) concentrations were measured with an ECR sputtered carbon (ECR nano-carbon) electrode by employing an anodic stripping voltammetry (ASV) technique.  The preconcentrated Cd was analyzed with Kelvin probe force microscopy and energy dispersive X-ray spectroscopy while observing the morphology change with an atomic force microscope and a scanning electron microscope.  The preconcentrated Cd on the ECR nano-carbon electrode was revealed to be a thin sheet structure, which was significantly different from the Cd on a conventional carbon material that grows with a coralloid structure.  The background current during an ASV measurement maintains a low level equivalent to that found with boron-doped diamond because the surface of the ECR nano-carbon is robust and angstrom-level flat.  The carbon-electrode performance for ASV was improved by controlling its structure at a nanometer scale without any metal doping or coating.  Finally, the ECR nano-carbon was used for biomolecular determination by electrochemical immunoassay with a CdSe nanoparticle label.  Electrochemical immunoassay results were successfully obtained with the ECR nano-carbon, and they correlated well with fluorescence results obtained for CdSe nanoparticles.
National Institute of Advanced Industrial Science and Technology, Tsukuba Central, Higashi, Ibaraki, Japan. r.kurita@aist.go.jp
Ryoji
R
Kurita
Kohei
K
Nakamoto
Yuko
Y
Sato
Tomoyuki
T
Kamata
Akio
A
Ueda
Dai
D
Kato
Shigeru
S
Hirono
Osamu
O
Niwa
D019187:Cadmium Compounds / Q000032:analysis; D002244:Carbon / Q000737:chemistry*; D017357:Cyclotrons; D055664:Electrochemical Techniques; D004566:Electrodes; D007118:Immunoassay; D053758:Nanoparticles / Q000032:analysis; D049329:Nanostructures / Q000737:chemistry*; D010316:Particle Size; D018036:Selenium Compounds / Q000032:analysis; D013499:Surface Properties
D019187:Cadmium Compounds; D018036:Selenium Compounds; D002244:Carbon; C058667:cadmium selenide