Taking drug delivery as an example, manipulation of the unique chemical, physical, and electronic properties of colloidal gold enables researchers to develop drug-nanoparticle conjugates for targeted drug delivery, improving a drug’s biodistribution and pharmacokinetics within specific biological targets, such as diseased tissue or cancerous cells. Nanosized colloidal gold has great potential in multiple therapeutic and biotechnology applications. In commercial terms, the result of this carefully fostered research is that by 2015, the market for biomedical nanotechnology is expected to exceed $70 billion.1 In practical terms, this suggests a potentially transformative shift in the way diseases are targeted and treated. I and S refer to the scattering volume where S (q~,ω −ω) is the so-called dynamic structure factor.Today, the maturation of a decade’s worth of investment into nanotechnology is seeing nanomedical materials steadily emerge into clinical and medical practice. In this equation δn denotes the deviation of the local particle density from the average value ( δn := n(~r ,t ) − hni). The intensity is defined as the ensemble mean: In practice, however, the light intensity is obtained from the detectors. In principle, the relation describes the scattered light completely. The electrical field from all molecules in the scattering volume follows as: This eqation describes the electric field propagating from an elementary dipole originating from a molecule. With the electric field constant ε, and with R being the position of the detector. From the Maxwell-equations follows the light wave propagation in a detector direction kf: Hence, the molecules behave as Hertzian dipoles and provide a secondary light source. The field of the electromagnetic wave induces an oscillating electronic polarization. with the circular frequency ω and the normal vector n~. Index i stands for incident plane wave and index f stands for the outgoing waves (towards the detector). In light scattering experiments the incident electromagnetic wave may be written as: Where αL denotes the polarizability tensor. The relation between the dipole moment p~ of a molecule and the field E at the position ~r at time t is given by: For a general description of interactions between a light beam and molecules, it is appropriate to study the induced dipole moment of one molecule in an electrical field. With the refractive index nid of the fluid, the laser wavelength λ0 in vacuo, and the scattering angle Θ. The scattering vector is defined as q~ = k −k. However, with the help of scattering vector q~ follows from geometrical considerations, Fig.(3.1), the relationship between the wave vector ki that points in the direction of the incident plane wave, and kf which points in the direction of the outgoing waves. In principle, it is possible to vary the polarization of the incident light. In the following, the underlying theory of dynamic light scattering on fluids is briefly summarized. A typical scattering geometry for light scattering experiments is shown in Fig.(3.1). Also many constants listed in the text are vectors. Note:(Many calculation steps are skipped. With the aid of electromagnetic theory, statistical mechanics and hydrodynamics it is possible to gain information about the structural and dynamic properties of a sample. According to the semi-classical theory, when light interacts with matter, the electric field of the light induces an oscillating electronic polarization in the molecules or atoms. The dynamic light scattering is a very powerful technique to determine the size of particles or to study critical fluctuations in multi-component fluids. In the last decades, light scattering techniques have been used with increasing effort for investigations of the physical properties of pure fluids and multicomponent fluids.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |