This book describes different aspects of characterization and detection of nanomaterials in liquid disperse systems, such as suspensions, emulsions and suspoemulsions. Natural and technical particulate nanomaterials (NMs) are often present in formulations and products consisting of several disperse phases and complex dispersion media. Specific interfacial properties of the particles, their interactions with each other and with the dispersion medium, have to be considered. For example, the interfacial properties determine whether the particles tend to be arranged in aqueous or lipid phases or at their phase boundaries. The interfacial properties are significantly influenced by the adsorption of dissolved species, i.e., they depend on the composition of the dispersion medium. This poses great challenges for the characterization of these nanoparticle systems and requires adequate preparation methods. The nanoparticle measurement techniques aim at a deep physico-chemical understanding of the dispersity state of nanoparticle systems. Since the dispersity state of nanoparticle systems in an application usually does not correspond to their original manufacturing process, the formulation of new or improved product properties is of decisive importance. The characterization of nanoparticles in complex formulations or matrices requires an adequate sample preparation based on an existing or yet to be developed Standard Operating Procedure (SOP). The structure of the SOPs includes the dispersion regulations, which are of essential importance for comparing reproducible results of nanoparticle measurement with respect to comparability and transferability worldwide. The aim is to separate and isolate relevant NMs with knowledge of the interrelationships.

Autorentext

Dr. Retamal Marín studied Mechanical Engineering at the University of Talca (Chile), where he obtained his degree in 2011. In 2021, he obtained a Ph.D. degree on the field of particle technology at the Technische Universität Dresden (Germany). Dr. Retamal Marín's research focused on dispersing and stabilizing of nanoparticle suspensions, the characterization of multi-component materials containing nanostructured materials in complex matrices, the electrokinetic characterization of colloidal systems and the development as well as the implementation of particle measurement techniques for process analysis.

Inhalt

Preface 1_ Introduction and classification

1.1 Dispersity state of nanomaterials

1.2 Scope of the book

1.3 Analysis tasks and structure

2_ State of the art and knowledge about (nanoparticles) disperse systems The characterization of NM with respect to their dispersity state and stability behavior requires profound knowledge of colloid chemistry fundamentals of disperse systems, physical understanding of measurement methods and engineering methods. A unifying interface of the above knowledge in the form of reproducible and comparable SOPs for the study of NM is necessary to achieve a satisfactory state of the art. When studying NM in dispersed systems, particle interactions are present, which should be considered in the characterization of NM. The dispersity state of NM in heterodisperse substance systems is influenced by interactions of particles and dissolved ions in dispersed media, which take place at the interfacial particle continuum of nanoparticle systems.

2.1 Characterization of liquid nanoparticle systems in particle metrology

2.1.1 Classification of core concepts of nanoparticle measurement technology

2.1.2 Formulation types of nanoparticle systems in liquid phases

2.1.3 Regulatory assessment of nanomaterials

2.1.4 Challenges and content of the characterization

2.2 Physico-chemical Properties of "nano"-particles systems

2.2.1 Electrochemical double layer - model

2.2.2 Stability of liquid disperse systems

2.2.3 Theory of solubility parameters

2.2.4 Nanoparticle wettability

2.3 Emulsification process with contained nanomaterials

2.3.1 Preparation of emulsions containing nanomaterials

2.3.2 Stabilization and destabilization mechanisms of emulsions

2.3.3 Dispersing (emulsifying) processes of suspoemulsions and emulsions

2.4 Theory of the characteristics of the dispersing processes

2.4.1 Mechanical dispersing methods

2.4.2 Application of the volume-based energy density concept

2.4.3 Energy density concept in nanoparticle metrology- and research

3_ Main principles of the characterization of liquid nanoparticle systems

The different purposes of a material characterization cannot all be fulfilled with one analytical specification but require appropriate procedures. Consequently, the need arises for the elaboration of a principled methodology for the characterization of NM, centered on purpose-specific sample preparation. The characterization of NM requires in-depth knowledge relevant to the interpretation and comparison of studies. Particle measurement technology offers a wide range of methods used to determine the physical and chemical properties of nanoparticle systems. However, there are gaps in the development of preparation techniques and characterization methods. In order to be able to obtain comparable results in the characterization of NM in liquid dispersed systems, the present work aims to highlight the influence of analytical methodology (including preparation, measurement and data analysis) on NM characterization results. Furthermore, guidance on the design of characterization specifications is given to fill some gaps in the field of analysis and data interpretation.

3.1 Analysis of liquid nanoparticle systems

3.1.1 Objectives, fundamentals and obstacles

3.1.2 Development and application of standard operating procedures

3.1.3 Granulometric methods of nanoparticle metrology

3.2 Possibilities for the representation of distribution functions

3.2.1 Normalized distribution functions

3.2.2 Non-normalized distribution functions

3.2.3 Transformed density function

3.2.4 Component balance of the distribution

3.3 Selected characterization techniques

3.3.1 Laser Diffraction Spectroscopy - LDS

3.3.2 Dynamic light scattering - DLS

3.3.3 Dynamic ultramicroscopy - DUM

3.3.4 Analytical photocentrifuge

3.3.5 Acoustophoretic mobility

3.3.6 Electrophoretic mobility

4 Knowledge generating experiments

In this chapter, results of experimental research are presented. These results provide the basis for SOP guidelines regarding sample preparation for the characterization of the dispersive state of nanoparticle systems. The dispersing process during sample preparation should be reproducible. A reproducible dispersion means that the dispersing of nanoparticle systems is performed at arbitrary locations, by different operators, and ideally with different equipment and sample volumes. Therefore, the dispersion effectiveness of different mechanical dispersing techniques (ultrasonic dispersers, rotor-stator systems) for different nanostructured materials will be investigated. The focus here is also on the sample contamination problem (abrasion) for the mentioned mechanical dispersion methods.Another important pillar for sample preparation is the characterization of the interfacial properties of liquid dispersed NM in the experimental determination of the zeta potential value. In order to make the results for the evaluation of the stability of disperse systems measured by zeta potential comparable, the influence of the dilution medium and the estimation of the morphology of the particles should be taken into account. In addition, preparation methods for the extraction of NM from cosmetic formulations (such as suspoemulsions) are proposed in this chapter. Under discussion is which aspects of the obtained experimental results can be adopted for the SOP guidelines (development of preparation methods).

4.1 Reproducible …