Size detection limits of spICP-MS for analysis of nanoparticles in environmental media

Nanoparticles (NP) are widely integrated in our everyday lives, such as consumer products, health, agriculture, food, etc. This has resulted in a growing concern for their possible harmful effect on human health and the environment and the demand for characterization. To measure the emission of NPs and exposure levels in the environment, the methods have to be able of quantifying and sizing particles of interest at parts per billion (ppb) level concentrations or lower. However, their small size and expected low concentrations against high backgrounds of naturally occurring other particles make characterization impossible with non-specific measurement tech-niques. Single particle ICP-MS (spICP-MS) is a promising technique for quantifi-cation of both size and number concentration of NPs. The aim of this thesis is to evaluate the analytical capabilities of the Perkin Elmer Nexion 300 mass spectrometer for spICP-MS analysis. Gold nanoparticles were used as model NPs for all experiments and dissolved Au was added mimicking interferences or dissolved backgrounds often encountered in environmental samples. The particle size detection limit (DL) was determined and the factors determining the smallest measurable number concentration such as background count rate and particle contamination are discussed. Validation of outlier detection parameters has been done and it has been found that the more conservative n = 5 for + n* gives a smaller false positives count rate than the more common n = 3, while still not counting too many false negatives. Size detection limits vary between 22 and 32 nm and concentration limits of detection (LOD) are in the range of several ng L-1 for smaller (40 nm) particles to ca. 40 ng L-1 for bigger (60 and 100 nm) particles, which is at least 10 times higher than the theoretical LOD. This made it impossible to detect particles of the size 5, 10 and 20 nm. In general, there was a lot of variation between size DLs obtained with a published equation and DLs were sometimes lower than found possible. Setting the DL to an intensity of 2 counts gave more consistent and realistic results. Adding dissolved gold (50 and 75 ppb) to artificially increase the background showed it was impossible to separate the particle events from this high background. Dwell times of 50 s were used, but it was found that these needed to be merged to bigger dwell times to get correct results in the outlier detection algorithm. Further research to detect NPs in the presence of high dissolved back-grounds is required, as well as research for DLs and LODs of other types of nanoparticles, such as NPs with different isotopes and / or spectral in-terferences. Despite these shortcomings, spICP-MS has shown to be very promising for future quantification of nanoparticles in environmental media

Characterization of core-shell oxide nanoparticles

The growing amount of applications of nanoparticles (NP) have led to concern for their possible harmful effect on human health and the leakage in the environment. Characterization and quantification of the content of NPs are of prime importance, especially methods to relate size, composition and morphology of the particles with the possibility of their detection and quantification. Magnetic iron oxide core-shell nanoparticles, coated with a protective silica layer have been proven to be successful as adsorbents for water purification and hydromet-allurgy of rare earth elements. Their growing applications in catalysis, medicine and protection of the environment make them highly interesting for further characterization. The goal of this thesis project was to analyze and characterize these NPs for future applications and quantification with single particle ICP-MS (spICP-MS). Instrument difficulties made quantification with spICP-MS impossible, but the particles have been characterized in the solid state using environmental scanning microscopy with energy dispersion X-ray spectroscopy analysis (ESEM-EDS), atomic force micros-copy (AFM), powder X-ray diffraction (PXRD) and Fourier transform infrared spec-troscopy (FTIR). The nanoparticles in solution are also investigated with nanoparticle tracking analysis (NTA), dynamic light scattering (DLS), inductively coupled plasma mass spectroscopy (ICP-MS) and again with ESEM-EDS and AFM. The mean size results of these different methods were compared. It was concluded that the iron oxide core-shell NPs were successfully encapsulated by a silica layer. The core consists mostly of magnetite (Fe3O4), but some oxidation to maghemite (gg-Fe2O3) has taken place. The particles are very polydisperse and the dispersion aggregates quickly, so no 'right' size can be determined. Further research needs to be done for development of applications. External inves-tigation for separation based on magnetic properties to determine the fraction Fe3O4 that has been oxidized to gg-Fe2O3 and method development with single particle ICP-MS is required.Het steeds groeiende aantal van toepassingen met nanopartikels (NP) heeft geleid tot bezorgdheid voor hun mogelijk schadelijk effect op de menselijke gezondheid en lekkage in het milieu. Karakterisatie en kwantificatie van de inhoud van NPs zijn van voornaam belang, hoofdzakelijk methodes waarmee grootte, compositie en morfologie van de partikels gelinkt worden aan hun mogelijkheid voor detectie en kwantificatie. Magnetische ijzeroxide kern-schil nanopartikels, bedekt met een beschermende silica laag zijn succesvol toegepast als absorbentia voor waterzuivering en hydrometallurgie van zeldzame aarden. Hun groeiende applicaties in katalyse, geneeskunde en bescherming van het milieu maken hen zeer interessant voor verdere karakterisering. Het doel van dit thesis project was om deze NPs te analyseren en te karakteriseren voor verdere applicaties en om ze te kwantificeren met single particle ICP-MS (spICP-MS). Instrument moeilijkheden maakten kwantificering via spICP-MS onmogelijk, maar de partikels zijn gekarakteriseerd in de vaste vorm met environmental scanning microscopie met energie dispersie X-straal spectroscopie analyse (ESEMEDS), atoomkrachtmicroscopie (AFM), poeder X-straal diffractie (PXRD) en Fouriertransformatie infraroodspectroscopie (FTIR). De nanopartikels in oplossing zijn ook onderzocht met nanoparticle tracking analyse (NTA) en dynamische lichtstrooiing (DLS), inductief gekoppeld plasma massaspectrometrie (ICP-MS) en opnieuw met ESEM-EDS en AFM. De gemiddelde groottes verkregen met deze verschillende methoden werden onderling vergeleken. Er werd geconcludeerd dat de ijzeroxide kern-schil NPs met succes zijn omvat door een silica laag. De kern bestaat voornamelijk uit magnetiet (Fe3O4), maar gedeeltelijke oxidatie naar maghemiet (g-Fe2O3) heeft plaatsgevonden. De partikels zijn zeer polydispers en de dispersie aggregeert snel, waardoor geen 'juiste' grootte kan bepaald worden. Verder onderzoek moet gebeuren voor de ontwikkeling van applicaties. Extern onderzoek voor separatie gebaseerd op magnetische eigenschappen om de fractie Fe3O4 die geoxideerd is naar g-Fe2O3 te bepalen en ontwikkeling van een methode voor single particle ICP-MS is vereist

Fatty acid capped, metal oxo clusters as the smallest conceivable nanocrystal prototypes

Metal oxo clusters of the type M6O4(OH)4(OOCR)12 (M = Zr or Hf) are valuable building blocks for materials science. Here, we synthesize a series of zirconium and hafnium oxo clusters with ligands that are typically used to stabilize oxide nanocrystals (fatty acids with long and/or branched chains). The fatty acid capped oxo clusters have a high solubility but do not crystallize, precluding traditional purification and single-crystal XRD analysis. We thus develop alternative purification strategies and we use X-ray total scattering and Pair Distribution Function (PDF) analysis as our main method to elucidate the structure of the cluster core. We identify the correct structure from a series of possible clusters (Zr3, Zr4, Zr6, Zr12, Zr10, and Zr26). Excellent refinements are only obtained when the ligands are part of the structure model. Further evidence for the cluster composition is provided by nuclear magnetic resonance (NMR), infrared spectroscopy (FTIR), thermogravimetry analysis (TGA), and mass spectrometry (MS). We find that hydrogen bonded carboxylic acid is an intrinsic part of the oxo cluster. Using our analytical tools, we elucidate the conversion from a Zr6 monomer to a Zr12 dimer (and vice versa), induced by carboxylate ligand exchange. Finally, we compare the catalytic performance of Zr12-oleate clusters with oleate capped, 5.5 nm zirconium oxide nanocrystals in the esterification of oleic acid with ethanol. The oxo clusters present a five times higher reaction rate, due to their higher surface area. Since the oxo clusters are the lower limit of downscaling oxide nanocrystals, we present them as appealing catalytic materials, and as atomically precise model systems. In addition, the lessons learned regarding PDF analysis are applicable to other areas of cluster science as well, from semiconductor and metal clusters, to polyoxometalates

A multi-center naturalistic study of a newly designed 12-sessions group psychoeducation program for patients with bipolar disorder and their caregivers

Background: Psychoeducation (PE) for bipolar disorder (BD) has a first-line recommendation for the maintenance treatment phase of BD. Formats vary greatly in the number of sessions, whether offered individually or in a group, and with or without caregivers attending. Due to a large variation in formats in the Netherlands, a new program was developed and implemented in 17 outpatient clinics throughout the country. The current study investigated the feasibility of a newly developed 12-sessions PE group program for patients with BD and their caregivers in routine outpatient practice and additionally explored its effectiveness. Methods: Participants in the study were 108 patients diagnosed with BD, 88 caregivers and 35 course leaders. Feasibility and acceptance of the program were investigated by measures of attendance, and evaluative questionnaires after session 12. Preliminary treatment effects were investigated by pre- and post-measures on mood symptoms, attitudes towards BD and its treatment, levels of self-management, and levels of expressed emotion. Results: There was a high degree of satisfaction with the current program as reported by patients, caregivers, and course leaders. The average attendance was high and 83% of the patients and 75% of the caregivers completed the program. Analyses of treatment effects suggest positive effects on depressive symptoms and self-management in patients, and lower EE as experienced by caregivers. Conclusions: This compact 12-sessions psychoeducation group program showed good feasibility and was well accepted by patients, caregivers, and course leaders. Preliminary effects on measures of self-management, expressed emotions, and depressive symptoms were promising. After its introduction it has been widely implemented in mental health institutions throughout the Netherlands

Introducing psychological control in the context of teaching style: Its costs for learning and well-being

12status: publishe

The synergistic relationship of perceived autonomy support and structure in the prediction of self-regulated learning

Background. Self-determination theory defines two important dimensions of teaching style: autonomy support and structure. Aims. The purpose of the present study was to investigate the synergistic relationship of perceived teacher autonomy support and the provision of structure in the prediction of self-regulated learning. Sample and method. Students (N = 526) completed questionnaires assessing perceived autonomy support, structure, and self-regulated learning. Results. First, autonomy support and structure were found to be positively correlated, suggesting that the support of student autonomy generally goes hand in hand with the provision of structure and order in the classroom. Second, moderated regression analyses indicated that structure but not autonomy support yielded a main effect on self-regulated learning, although this main effect was qualified by a structure by autonomy support interaction. Conclusion. The interaction suggests that structure was associated with more self-regulated learning under conditions of moderate and high autonomy support only. Therefore, when teachers want their students to evaluate themselves, to plan their study activities, and to think about themselves as learners, the teachers are encouraged to provide help, instructions, and expectations in an autonomy-supportive way

Psychologically controlling teaching: examining outcomes, antecedents, and mediators

Psychologically controlling teaching (PCT) refers to the use of intrusive behaviors that pressure students to act, think, and feel in particular ways. The goal of the present research was to examine the dynamics involved in PCT. Study 1 examined self-regulated learning and achievement outcomes of PCT, whereas Study 2 examined antecedents (i.e., individual and environmental pressures). In Study 1, we found that PCT was related negatively to students' use of self-regulation strategies, which, in turn, was positively related to academic achievement. Students' relative autonomy for studying played an intervening role in these associations. Findings of Study 2 revealed that both pressure from above (i.e., a pressuring school environment) and pressure from within (i.e., teachers' low relative autonomy for teaching) were related to PCT, whereas pressure from below (i.e., students' low relative autonomy for studying) was not. These associations could be accounted for by depersonalization, one component of teacher burnout. The discussion focuses on how PCT represents one aspect of the "dark side" of teaching, which is understudied in educational psychology

Psychologie en verloskunde: het belang van 'sense of coherence'

status: publishe