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The aim of task 1.4 within the EMPIR project 18HLT01 MetVesII is to produce low-RI solid particles with an effective RI between 1.37 and 1.42. To prepare these low-RI solid particles, polymer cores will be coated with a silica shell. Although the bulk RI of polymers, such as polystyrene (RI = 1.59) and PMMA (RI = 1.49), and fused silica (RI = 1.46) are higher than desired, an effective RI below 1.42 will be achieved by using a mesoporous silica shell with tuneable shell-thickness and a polymer core with sufficiently small size. This approach has four advantages: (1) monodisperse commercial polymer particles and silica shell chemistry are available, (2) low-RI solid particles will have a tuneable size and RI, (3) fluorescence can be added by incorporating fluorescent dyes into the polymer cores via an established staining procedure, and (4) fluorescent dyes within the polymer cores are shielded against influences from the sample matrix, e.g. fluorescence quenching effects altering the emission properties of the reference materials.
This is a corrigendum to the original article "Determining the thickness and completeness of the shell of polymer core-shell nanoparticles by X-ray photoelectron spectroscopy, secondary ion mass spectrometry, and transmission scanning electron microscopy" that was published in "The journal of physical chemistry C", vol. 123 (2019), no. 49 pp. 29765-29775.
Controlling thickness and tightness of surface passivation shells is crucial for many applications of core–shell nanoparticles (NP). Usually, to determine shell thickness, core and core/shell particle are measured individually requiring the availability of both nanoobjects. This is often not fulfilled for functional nanomaterials such as many photoluminescent semiconductor quantum dots (QD) used for bioimaging, solid state lighting, and display technologies as the core does not show the applicationrelevant functionality like a high photoluminescence (PL) quantum yield, calling for a whole nanoobject approach. By combining high-resolution transmission electron microscopy (HR-TEM) and X-ray photoelectron spectroscopy (XPS), a novel whole nanoobject approach is developed representatively for an ultrabright oleic acid-stabilized, thick shell CdSe/CdS QD with a PL quantum yield close to unity. The size of this spectroscopically assessed QD, is in the range of the information depth of usual laboratory XPS. Information on particle size and monodispersity were validated with dynamic light scattering (DLS) and small angle X-ray scattering (SAXS) and compared to data derived from optical measurements. In addition to demonstrating the potential of this novel whole nanoobject approach for determining architectures of small nanoparticles, the presented results also highlight challenges faced by different sizing and structural analysis methods and method-inherent uncertainties.
Standardisation of concentration measurements of extracellular vesicles for medical diagnoses
(2020)
Extracellular vesicles (EVs) are cell-derived particles in body fluids, which have excellent potential as next generation biomarkers for the early diagnosis of common diseases, such as cancer and thrombosis. This project aims to tap into the clinical potential of EVs by developing traceable measurements of number concentration, size distribution, refractive index (RI) and fluorescence intensity of cell-specific EVs in human blood and urine.
To realise our aims, we will develop synthetic reference materials with physical properties resembling EVs (WP1), instrumentation and procedures to standardise EV measurements in clinical laboratories (WP2), and ready-to-use biological test samples (WP3). These will then be evaluated in an inter-laboratory comparison study across a range (>20) of standard flow cytometers in clinical labs (WP4).