Photon Correlation Spectroscopy (PCS,) also known as Dynamic Light Scattering (DLS) or Quasi-elastic Light Scattering (QELS,) is a technique used to measure the size and distribution of small particles or molecules in a suspension or solution.
It works by illuminating a sample of particles or molecules in solution and then analyzing the fluctuations in the intensity of scattered light caused by the Brownian motion of particles over time.
How it works:
- A laser beam is directed into the sample containing suspended particles.
- Particles scatter the incident light in many directions.
- Due to the particles’ random thermal motion (Brownian motion), the scattered light intensity fluctuates over time.
- A detector (such as an avalanche photodiode, a semiconductor device that converts light into electrical signals) captures these fluctuations.
- An autocorrelator processes the signal to interpret the fluctuations over time. The autocorrelation function measures how the intensity at one time point correlates with the intensity at a later time, providing insights into the dynamics of the particles. Specifically, it quantifies how similar the scattered light signal is to itself after a certain delay, revealing information about particle size and diffusion behavior.
- A computer analyzes the autocorrelation function.
- From this analysis, the diffusion coefficient of the particles is determined.
- Using the Stokes-Einstein equation, the particle size (usually the hydrodynamic radius) is calculated.
There are many applications of PCS or DLS including:
- Nanoparticle Characterization: Determining the size, size distribution, and stability of nanoparticles such as liposomes, polymer nanoparticles, and quantum dots.
- Protein and Biomolecule Analysis: Measuring the hydrodynamic radius of proteins, peptides, and other biomolecules to study their conformational states, aggregation, and interactions.
- Pharmaceutical Development: Assessing the size and stability of drug delivery systems, including liposomes, micelles, and polymeric carriers, to ensure quality and efficacy.
- Polymer and Colloidal Suspension Studies: Evaluating the size and dispersity of polymers, colloids, and emulsions in various formulations.
- Monitoring Aggregation and Stability: Tracking changes in particle size over time to study aggregation phenomena, stability of suspensions, and formulation stability.
- Quality Control: Used in manufacturing environments to ensure consistency and quality of nanoscale materials and formulations.
- Research in Material Science: Studying the self-assembly, crystallization, and phase behavior of colloidal and nanostructured materials.
There are several advantages to using PCS, or dynamic light scattering. The technique is non-invasive and non-destructive and requires minimal sample preparation. Also, the technique is usually quite rapid and capable of analyzing a wide range of particle sizes, typically from ~1 nm to several micrometers.
Brookhaven Instruments are pioneers in the field of PCS, or dynamic light scattering. For over 40 years we have been innovating new advances in the field. We are trusted experts, and we are also caring people who treat our customers with respect. Our modular instrument designs offer flexibility. We listen first to understand our customers’ challenges and then configure appropriate light scattering systems to meet our customers’ needs, and our instruments have always been designed and built in the USA.
Contact us today to learn more about our light scattering solutions for particle size and zeta potential analysis.