NANOPHOX

In general, the acquisition of scattered light intensities of particles under thermal motion is deployed for nanoparticle characterisation (principle of dynamic light scattering (DLS) ). The NANOPHOX CS combines photon cross-correlation spectroscopy (PCCS) with a innovative, patent pending polarisation-separated backscattering technology (Psb PCCS) , which allows for high resolution nanoparticle size analysis in high concentrated suspensions and emulsions ranging from 0.5 nm to 10,000 nm. With only small sample effort, meaningful and repeatable measurements below one minute of sample material in original concentration are realised. Particle size, distribution width and polydispersity are determined just as reliably as the stability of the dispersion with this variant of dynamic light scattering.

The goal of every particle analysis is to obtain unbiased measurement results. The foundation for reliable results lies in a product-specific analysis of the sample in its original state. The PsB PCCS implemented in the NANOPHOX CS offers concentration-independent particle characterisation of nanoparticles in opaque suspensions and emulsions. This measurement method eliminates multiple scattered light, raises the signal-to-noise ratio to a new level, allowing higher sample concentrations with shorter measurement times and improved repeatability and accuracy.

Similar results cannot be achieved with photon correlation spectroscopy (PCS) , which is traditionally used in dynamic light scattering. PCS uses the autocorrelation of the scattered light intensities to determine the particle size distribution. However, the traditional technique requires extremely dilute samples, as correct measurement of particle size is not possible due to the multiple scattering that occurs. The resulting sample preparation is time-consuming and error-prone, as this leads to changes in the particle size distribution and stability of the sample.

The application of the cross-correlation technique allows the calculation of the particle size distribution without the influence of multiple scattering. Comparability between conventional PCS and PCCS can be established by measuring a concentration series with monomodal suspensions of 100 nm polystyrene standards.

Five latex samples represent a spectrum ranging from the undiluted suspension with 1 % solids per volume to a dilution level of 1:10,000. For measurements in PCCS mode, the measured hydrodynamic diameter varies between 97 nm and 106 nm and is thus within specifications - regardless of dilution. The PCS results, on the other hand, deviate from the specifications for concentrated samples above a dilution of 1:1,000. The determination of reliable particle sizes with PCS starts at 5,000-fold dilution. PCCS achieves correct results already in the concentrated latex sample.