NoFilter? No Signal: Measuring Fluorescent Compounds by DLS
Measuring the particle size of fluorescent nanomaterials by dynamic light scattering (DLS) can be challenging, especially when the fluorophore’s emission spectrum overlaps with the detection wavelength. This study demonstrates that, by applying a narrow band-pass filter between the sample and the detector, the Litesizer DLS can successfully measure fluorescent compounds, even when their emission occurs very close to the instrument’s laser wavelength.
Litesizer DLS instruments measure the particle size of nanomaterials using Dynamic Light Scattering (DLS), a well-established technique based on the temporal autocorrelation of intensity fluctuations caused by the Brownian motion of particles. However, when analyzing fluorescent samples, such as quantum dots or nanoparticles labeled with fluorescent dyes, the sample’s intrinsic fluorescence can significantly interfere with the detection of scattered light. When fluorescence overlaps with the detection wavelength, it elevates the background signal and degrades the quality of the autocorrelation function, compromising size accuracy and reproducibility.
To overcome this challenge, a narrow band-pass optical filter can be inserted into the detection path of the Litesizer DLS. This filter selectively transmits scattered light at the laser wavelength while effectively rejecting out-of-band fluorescence emission. Its use is particularly advantageous for strongly fluorescent samples, as it allows the instrument to discriminate between the coherent elastic scattering (i.e., the same wavelength and phase as the incident laser, required for DLS analysis) and the incoherent fluorescent background.
This application report demonstrates how the integration of a band-pass filter centered around the instrument’s laser wavelength (658 nm) into the optical setup enables high-quality DLS measurements of fluorescent species, including quantum dots, dye-labeled antibodies, and fluorescent latex polymer nanoparticles.
Get the document
To receive this document please enter your email below.
