Measuring surface charge density and particle height using surface plasmon resonance technique.
We demonstrate a method to measure surface charge density and particle height using surface plasmon resonance (SPR) detection. It is based on two facts: (1) The equilibrium height of a charged particle over a charged surface depends on the electrostatic interaction between the particle and the surface; and (2) SPR is extremely sensitive to the height of the particle. We perform numerical simulations to establish the relations between the SPR signal and the particle height, and between the particle height and the surface charge density, and carry out systematic experiments, including effects of different buffer concentrations, particle sizes, and concentrations, to examine the relations. The simulation and experimental results are in good agreement with each other. Using the method, we determine surface charge density of gold surface functionalized with different molecules. If the surface charge density is known, the method can also be used to determine the charges of the particles.
Shan
Xiaonan
X
Department of Electrical Engineering, Center for Bioelectronics and Biosensors, Biodesign Institute, Arizona State University, Tempe, Arizona 85287-5801, USA.
Huang
Xinping
X
Foley
Kyle J
KJ
Zhang
Peiming
P
Chen
Kangping
K
Wang
Shaopeng
S
Tao
Nongjian
N
D055664:Electrochemical Techniques; D006863:Hydrogen-Ion Concentration; D009994:Osmolar Concentration; D010316:Particle Size; D020349:Surface Plasmon Resonance / Q000379:methods*; D013499:Surface Properties