Improving Dynamic Light Scattering Measurements Through Detector Performance

Detector performance in dynamic light scattering: why it matters for accurate particle sizing

Dynamic light scattering (DLS) is widely used to estimate the size of nanoparticles, proteins, and other macromolecular systems in solution, but for demanding measurements such as dilute samples, very small particles, or complex formulations, detector performance can become a major factor in measurement quality.

Key takeaways: detector performance and DLS measurement accuracy

Detector performance has a direct effect on DLS measurement quality because the technique depends on resolving fast, low-amplitude fluctuations in scattered light.
SPAD detectors are widely used in modern DLS instruments because they combine sensitivity, timing performance, and robustness.
The three SPAD parameters with the most direct impact on DLS results are afterpulsing probability, photon detection efficiency (PDE), and maximum count rate (MCR).
Strong detector performance helps maintain reliable measurements across weakly scattering, low-concentration, and more complex sample conditions.

Why detector performance is critical for accurate dynamic light scattering measurements

DLS translates Brownian-motion-driven intensity fluctuations into size through the intensity autocorrelation function (how scattered light correlates with itself over time). Monodisperse samples typically show a clean exponential decay; polydisperse samples produce broader, more complex behavior.

Because the correlation signal comes from fast, low-amplitude changes, detector noise and artifacts directly affect results. This is why single-photon detectors such as SPADs are widely used for their timing and sensitivity.

Three SPAD detector specifications that influence DLS particle sizing results

These three SPAD parameters most strongly influence autocorrelation fidelity and, therefore, sizing results.

1. Reducing false counts in DLS measurements

Afterpulsing Probability: Afterpulsing is a spurious detection event that can follow a genuine photon detection, caused by trapped charge carriers in the detector. These false counts can introduce artificial correlations, especially when measuring small, weakly scattering particles where the true signal is close to the noise floor. In the highest‑performance SPAD models, Hamamatsu achieves afterpulsing levels as low as 0.1%.

2. Improving sensitivity for weak DLS signals

Photon detection efficiency (PDE): This describes how reliably incoming photons are registered. Higher PDE improves measurement statistics, supports low-signal samples, and can reduce the need for repeated acquisitions.

3. Preventing saturation in high-signal DLS applications

Maximum count rate (MCR): At high photon flux (concentrated samples, large particles, or higher laser power), a limited maximum count rate (MCR) can lead to saturation or extended dead time, distorting the correlation function. Higher MCR preserves data fidelity and supports faster acquisition of robust correlation data.

DLS applications where detector performance has the biggest impact

These parameters become critical when signals are weak, losses are higher, or samples are challenging. For example:

Proteins and biomolecules at very low concentration: where strong detector performance helps support reliable measurements at nanomolar or subnanomolar concentrations.
Weak scatterers in native buffers: extracellular vesicles, lipid nanoparticles, and viral particles.
Biopharmaceutical formulations: where detector performance supports early-stage aggregate detection in challenging sample conditions.
Higher-loss measurement geometries: backscatter (~173°) and multi-angle DLS where optical throughput is lower and signals are weaker.

Hamamatsu's single photon detectors for high accuracy DLS instruments

Hamamatsu Photonics has long-standing expertise in single-photon detection, from photomultiplier tubes (PMTs) to silicon photomultipliers (MPPCs) and SPAD detectors. For DLS applications, Hamamatsu offers high-performance SPAD detectors and modules designed to support accurate photon counting under demanding conditions, including low afterpulsing, high maximum count rates, and strong photon detection efficiency at wavelengths commonly used in DLS.

We offer both SPAD sensors and complete detection modules with control electronics, temperature stabilization, and digital outputs, helping simplify integration into DLS instrument designs.

Explore SPADs

Explore the details on detector performance in dynamic light scattering further:

Read the article [431 KB/PDF]

If you are evaluating detector options for a DLS instrument, our engineers can help you identify the right solution for your setup.

Detector performance in dynamic light scattering: why it matters for accurate particle sizing

Key takeaways: detector performance and DLS measurement accuracy

Why detector performance is critical for accurate dynamic light scattering measurements

Three SPAD detector specifications that influence DLS particle sizing results

1. Reducing false counts in DLS measurements

2. Improving sensitivity for weak DLS signals

3. Preventing saturation in high-signal DLS applications

DLS applications where detector performance has the biggest impact

Hamamatsu's single photon detectors for high accuracy DLS instruments

For more information, please contact us.

1. What are cookies?

2. What are the different types of cookies?

3. How do we use cookies?

4. Which cookies do we use?

5. What are Internet tags and how do we use them with cookies?

6. Analytics and Advertisement Cookies