Characterization of Nanomaterials in Liquid Disperse Systems

ISBN-13: 9783030998806 / Angielski / Twarda / 2022

R. R. Retamal Marín

Opis

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.

Spis treści

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 dispersing with defined energy input                                                               

4.1.1 Dispersing techniques in practice                                                                

4.1.2 Calibration specification of mechanical dispersing methods                        

4.1.3 Validation of mechanical dispersing - practical test                                      

4.1.4 Sample contamination during dispersion                                                                

4.1.5 Discussion of the results on dispersing                                                        

 

4.2 Electrokinetic properties and stability behavior of nanoparticle systems                        

4.2.1 Conservation of the dispersity and interfacial state of the suspension       

4.2.2 Comparability of zeta potential methods                                                     

4.2.3 From fractal-like aggregates to spherical SiO₂ particles                                    

4.2.4 Measurement of the zeta potential of different silica types                                         

4.2.5 Discussion of the results and consequences for SOPs                                    

 

4.3 Extraction of nanomaterials from cosmetic formulations                                                       

4.3.1 Procedure for the development of extraction methods                                    

4.3.2 Research of the emulsification process with contained nanomaterials   

4.3.3 Discussion of the results and consequences for SOPs                                    

 

5_ Demonstration experiments                                                                                                            

In this chapter, different scenarios with defined SOPs are elaborated to analyze the dispersity state of nanoparticle systems. Developed SOPs are applied to better answer open research questions as well as analytical challenges in the context of nanoparticle metrology. First, the load-dependent dispersity state of NM is considered, with specific statements on material behavior. These statements include a consequent observance of the dispersing SOPs as well as the documentation of all relevant parameters that influence a reproducible characterization of NM. The adjustment of the power inputs according to uniform calibration rules (protocols) is an elementary part of the NM characterization. Likewise, the production of disperse material systems in a comprehensive sense is part of the SOP development. Therefore, NM are investigated in complex dispersed systems, where the state of dispersity in physiological media differs from that in cosmetic formulations. In this context, NM fractions in complex disperse substance systems are separated from other particulate components. This separation is a relevant focus in particle metrology because most characterization methods concentrate on particle systems with only one dispersed phase – preferably with not very broad size distributions. Thus, to make a concrete statement about the dispersity state of nanoparticle systems, separation is essential. The separation is either real (physical), as in extraction, or theoretical, as in data analysis (e.g., by using non-normalized density functions). Whereas physical separation is sometimes unavoidable with respect to the conservation of the dispersity and interface state of NM in liquid disperse systems. Consequently, the consideration of the absolute signal strength in the characterization of suspensions and emulsions is considered to be of essential importance.

 

5.1 Load-dependent dispersity state of nanomaterials                                                                

5.1.1 Influence on the measured particle size distribution of SiO₂                          

5.1.2 Dispersing effectiveness of direct dispersing methods                                              

5.1.3 Discussion on dispersing effectiveness of nanostructured oxides                                           

 

5.2 Dispersity state of nanomaterials in physiological media                                                                   

5.2.1 Nanomaterials in simulated lung fluid                                                                     

5.2.2 Nanomaterials in simulated gastrointestinal passage                                               

5.2.3 Discussion                                                                                                                          

 

5.3 Consideration of the absolute signal strength of optical measurement methods                                  

5.3.1 Component balance of the distribution and possibilities for representation                

5.3.2 Granulometric data analysis of complex nanoparticle systems                                    

5.3.3 Discussion on characterization of complex nanoparticle systems                                    

 

6_Summary, discussion and outlook                                                                                                               

7.1 Summary of the results                                                                                                     

7.2 Discussion                                                                                                                        

7.3 Outlook                                                                                                                            

7.4 Conclusion                                                                                                                       

 

References                                                                                                                                                             

Nomenclature                                                                                                                                                         

Latin Letters                                                                                                                           

Greek Letters                                                                                                                        

Indices                                                                                                                                   

Mathematical Symbols and Operators                                                                                     

Constants                                                                                                                              

Abbreviations                                                                                                                         

 

Appendix A Applied materials                                       

A.1 Powder particle systems and their general properties                                              

A.1.1 Synthetic Amorphous Silica (SAS) – SiO₂                                                 

A.1.2 Fumed nanostructured oxides – TiO₂ und Al₂O₃                                                    

 

Appendix B Validation and parameterization of the ultramicroscopic analyses                                                

B.1 General properties of the reference materials                                                          

B.2 Parameterization of image acquisition and analysis with reference materials                     

B.3 Parameterization of image acquisition and analysis for SAS samples                                    

 

Appendix C Turbidity measurements of silicas in physiological media                                                      

C.1 Comparison of the sedimentation rate                                                                     

C.2 Transmission profiles for selected SAS samples in physiological media                          

C.3 Investigation of the long-term stability of formulated SAS-suspoemulsions           

 

Appendix D Sample preparation of SAS nanomaterials for SEM and TEM/EDX analyses                                  

D.1 Dispersion behavior of carbohydrates in water                                                         

D.2 Sample preparation of fumed and precipitated silica on a TEM grid/perforated film using membrane filtration                                                                                                  

 

Appendix E Composition of the physiological media                                                                               

E.1 Cell culture medium – F-12K                                                                                    

E.2 Fed-State Simulated Intestinal Fluid – FeSSIF                                                            

 

Appendix F Chemicals and analytical technology in the laboratory                                                                       

F.1 Instruments for controlling the physicochemical properties of nanoparticle systems    

F.2 Instruments for the separation of disperse and continuous phases                                    

F.3 Material database – Chemicals                                                                                 

 

Appendix G Study of the abrasion of mechanical dispersing techniques.                                                  

G.1 Image capture of nanoparticle suspensions with sedimented abrasion                      

G.2 Abrasion image capture with microscop for RSD                                                       

G.3 Abrasion image capture with microscop for dUSD                                                    

 

Appendix H Technical data of mechanical dispersing techniques                                                             

H.1 Blade or propeller stirrer systems                                                                            

H.2 Ultrasonic disperser                                                                                                           

H.3 Rotor-Stator-Systems                                                                                                          

O autorze

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.