Biophysical Chemistry of Biointerfaces

Hiroyuki Ohshima

• Publisher: Wiley
• Year: 2011
• ISBN:
  9781118057858
• Edition: 1
• Topic: Ciencias físicas
• Subtopic: Química física y teórica

The first book on the innovative study of biointerfaces using biophysical chemistry

The biophysical phenomena that occur on biointerfaces, or biological surfaces, hold a prominent place in the study of biology and medicine, and are crucial for research relating to implants, biosensors, drug delivery, proteomics, and many other important areas. Biophysical Chemistry of Biointerfaces takes the unique approach of studying biological systems in terms of the principles and methods of physics and chemistry, drawing its knowledge and experimental techniques from a wide variety of disciplines to offer new tools to better understand the intricate interactions of biointerfaces. Biophysical Chemistry of Biointerfaces:

• Provides a detailed description of the thermodynamics and electrostatics of soft particles
  
  

• Fully describes the biophysical chemistry of soft interfaces and surfaces (polymer-coated interfaces and surfaces) as a model for biointerfaces
  
  

• Delivers many approximate analytic formulas which can be used to describe various interfacial phenomena and analyze experimental data
  
  

• Offers detailed descriptions of cutting-edge topics such as the biophysical and interfacial chemistries of lipid membranes and gel surfaces, which serves as good model for biointerfaces in microbiology, hematology, and biotechnology
  
  

Biophysical Chemistry of Biointerfaces pairs sound methodology with fresh insight on an emerging science to serve as an information-rich reference for professional chemists as well as a source of inspiration for graduate and postdoctoral students looking to distinguish themselves in this challenging field.

Part I

Potential and Charge at Interfaces

Chapter 1

Potential and Charge of a Hard Particle

1.1 Introduction

The potential and charge of colloidal particles play a fundamental role in their interfacial electric phenomena such as electrostatic interaction between them and their motion in an electric field [1–4]. When a charged colloidal particle is immersed in an electrolyte solution, mobile electrolyte ions with charges of the sign opposite to that of the particle surface charges, which are called counterions, tend to approach the particle surface and neutralize the particle surface charges, but thermal motion of these ions prevents accumulation of the ions so that an ionic cloud is formed around the particle. In the ionic cloud, the concentration of counterions becomes very high while that of coions (electrolyte ions with charges of the same sign as the particle surface charges) is very low, as schematically shown in Fig. 1.1, which shows the distribution of ions around a charged spherical particle of radius a. The ionic cloud together with the particle surface charge forms an electrical double layer. Such an electrical double layer is often called an electrical diffuse double layer, since the distribution of electrolyte ions in the ionic cloud takes a diffusive structure due to thermal motion of ions. The electric properties of charged colloidal particles in an electrolyte solution strongly depend on the distributions of electrolyte ions and of the electric potential across the electrical double layer around the particle surface. The potential distribution is usually described by the Poisson–Boltzmann equation [1–4].

Figure 1.1 Electrical double layer around a positively charged colloidal particle. The particle is surrounded by an ionic cloud, forming the electrical double layer of thickness 1/κ, in which the concentration of counterions is greater than that of coions.

1.2 The Poisson–Boltzmann Equation

Consider a uniformly charged particle immersed in a liquid containing N ionic species with valence z_i and bulk concentration (number density)

(i = 1, 2,…, N) (in units of m⁻³). From the electroneutrality condition, we have

(1.1)

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