Two commonly used techniques to determine the sizes of nanoparticles are dynamic light scattering (DLS), available in many different laboratories preparing or working with nanoparticles, and the more sophisticated small angle X-ray scattering (SAXS), that can be made traceable to the International System of Units (SI). 10 Whereas SAXS depends on the scattering of X-rays based upon the electron density of the particles, which should be independent of any fluorescence signals, DLS relies on light scattering and may thus be affected by the absorption and emission of labelled dyes or self-luminescent nanomaterials. Depending on the optical properties and the wavelength of the laser used for the DLS measurements, absorption can result in a partial loss of the coherent incident light and the subsequently emitted non-coherent fluorescence may also affect the measured signal. Moreover, strong absorption can cause unwanted side effects such as local sample heating, beam expansion, and convection, that interfere with the sample characterization. 11 Thus, DLS measurements of strongly absorbing samples and highly turbid colloidal systems can be challenging. To overcome the limitations of common DLS, modified and improved optical scattering techniques have been developed, such as 3D cross-correlation DLS, 12–15 DLS using a flat cell light scattering instrument, 16 diffusing wave spectroscopy, 17 or photon density wave spectroscopy. 18,19 However, many researcher that work with fluorescent nanoparticles for bioanalytical applications still use common DLS systems to characterize their particle samples, due to the wide availability and broad application range of this established technique. There are several publications on the comparison of DLS and SAXS size measurements for different particle systems such as micelles, proteins, and polymers. #DYNAMIC LIGHT SCATTERING INSTRUMENT USING MALVERN ZETASIZER SERIES#Ģ0–25 However, until today there exists no systematic investigation on the influence of fluorescence on these particle size measurement techniques.Once understood, it is often possible to change measurement procedures to extend the potential range of applications suitable for the technique.įurther information on DLS, the Zetasizer range and other particle measurement systems can be found at: Related Articles: It is therefore necessary to ensure that the limits for reliable measurements for each sample type are fully understood. Too few particles in the scattering volume will cause undesirable intensity fluctuations. This means that very small objects scatter very little light, eventually limiting the size or concentration measureable, while large particles may sediment and affect the result.
Particles scatter light with an intensity proportional to size to the 6th power. Malvern's Zetasizer Nano systems use light scattering techniques to measure the hydrodynamic size, zeta potential and molecular weight of proteins and nanoparticles. In the seminar, biophysical characterization specialist Dr Ulf Nobbmann explores the limits of each system in the Malvern Zetasizer Nano range and examines best practice methodologies for measuring nanoparticle and protein samples at the extreme ends of the particle size scale. A recording of a recent Malvern Instruments web seminar addressing the question of "What is the real sensitivity of DLS for nanoparticle and protein measurements?" is now freely available on line.
0 kommentar(er)
