Researchers are turning to innovative techniques to accurately measure the size of nanoparticles, which are too small for conventional optical microscopes. One such approach is the dynamic light scattering (DLS) system known as OpenDLS, developed by Etienne. This method leverages a laser beam to analyze particle motion in a suspension, allowing for size estimation even in laboratories without access to advanced equipment like scanning electron microscopes.
Dynamic light scattering operates by directing a laser into a suspension of fine particles. The light sensor then measures the intensity of light scattered from the particles. As these particles exhibit Brownian motion, the scattered light’s intensity fluctuates based on their movement. The variation in this intensity enables researchers to calculate the particles’ speeds and, consequently, their sizes.
The OpenDLS setup features a 3D-printed and laser-cut frame that securely holds a small laser diode. This diode shines light into a cuvette, where a light sensor is positioned to capture the scattered light. Various sensor options were initially explored, including a photoresistor and an Arduino-compatible light sensor. Ultimately, a photodiode paired with a two-stage transimpedance amplifier was selected for its enhanced performance. An Arduino captures data at a rate of 67 kHz and transmits it to a host computer. The computer then employs SciPy and NumPy libraries to analyze the acquired data.
Despite its effectiveness, the OpenDLS system has some limitations. Researchers noted an underestimation of nanoparticle size when measuring a standard 188 nm polystyrene dispersion, which was recorded at 167 nm. This discrepancy is likely due to multiple scattering events occurring within the sample. While further dilution of the suspension could improve accuracy, it would also diminish the signal strength, placing the system near its operational limits.
Innovative approaches to measuring nanoparticle sizes are vital, especially as these tiny particles play significant roles across various scientific fields. While OpenDLS presents a promising solution for less-equipped laboratories, it is not the only optical method available. For those with access to more sophisticated tools, electron microscopes offer another effective means to investigate nanoparticles.
As research advances, the demand for accurate measurement techniques will only grow. The potential for widespread adoption of dynamic light scattering systems like OpenDLS could democratize access to nanoparticle research, making these crucial measurements available to a broader range of laboratories. With ongoing developments, even those without extensive resources can engage in vital scientific inquiries, ultimately contributing to the broader understanding of nanotechnology.
