![]() If the liquid is a pure solvent like toluene, the purest solvent possible should be sourced. A concentration of 10 mM KNO3 is ideal for all concentrations of particles. We recommend the use of KNO3 for aqueous diluents. A general salt like NaCl can be used but often the chloride ions are too aggressive and may react with the particles or adsorb to their surface. The ions with opposite charge will condense around the particle, screening long distance electrostatic interactions. To screen any charge on the particles, it is a good idea to measure in water with a trace amount of salt. The size measured in DI water will usually be too big by 2 to 10 nm due to the electrostatic interaction between the particles. Particle size measurements by Dynamic Light Scattering should not be conducted in pure de-ionized (DI) water, as the electrical double layer surrounding the particles will have long distance interaction. Although there are differences, the terms suspended and dissolved will be used interchangeably in this document. The solution or suspension to be measured is the sample in the liquid. The samples to be analyzed by DLS will be prepared in the liquid. Diluents are solvent with additives, for example a 10% by weight methanol in water or a 10 mM KNO3 salt in DI water solution. The diluent may also be referred to as the liquid in DLS textbooks. Examples of solvents are toluene or water. The term solvent refers the pure solvent used to prepare the diluent. ![]()
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