Link to publication in University of Groningen/UMCG research database Citation for published version (APA): Molen, S.

No abstract

Well ordered nanoparticle arrays were prepared on Si/SiO 2 surfaces from alkanethiol-coated Au nanoparticles via self-assembly and micro-contact printing. We study the insertion of conjugated molecular species within the nanoparticle arrays via spectroscopic and electrical transport measurements. Upon exchange of the alkanethiol chains with the conjugated oligomers, the conductance of the network increases by one to 3 orders of magnitude. In addition, the absorption spectra in the visible light range show a red-shift of the surface plasmon resonance (SPR). The latter shift, which is due to the difference in permittivity between alkanes and conjugated oligomers, can be understood within Mie and Maxwell-Garnett theory. Finally, infrared absorption spectra provide direct spectroscopic evidence that the conjugated oligomers can be not only inserted but also, subsequently, fully removed from the nanoparticle arrays via place-exchange. The reversibility of the exchange process demonstrates the potential of these structures as a platform for molecular electronics.

Impact of silver nanoparticles (AgNP) on aquatic algae has largely been studied with model species that possess a rigid cell wall. Here we explored the interactions of AgNP with Euglena gracilis, a green alga having no cell wall but a pellicle. The toxicity and silver uptake upon 1-2 h exposures to various concentrations of AgNO3 and AgNP, having a mean size of 47 nm measured in the exposure medium, were examined. The photosynthetic yield decreased in a concentration-dependent manner and AgNP were less toxic than AgNO3 based on total silver added. Cell morphology was significantly altered by AgNP and AgNO3. Damaging effects of AgNP on photosynthesis and morphology were completely prevented by cysteine, suggesting that the toxicity of AgNP was mediated by dissolved Ag. Indeed, the maximal cell-associated silver was higher in AgNP compared to AgNO3 exposures, amounting to 5.1 × 10 -4 mol Lcell -1 and 1.4 × 10 -4 mol Lcell -1 for AgNP and AgNO3, respectively. However, the difference was not caused by cellular uptake of AgNP, but strong sorption of AgNP to the pellicle. Nano ImpactOne of the most controversial issues in algal nanotoxicology is whether nanoparticles can be internalized and if internalization is a prerequisite for toxicity. Here, we examined the interactions of AgNP with the algae, Euglena gracilis, possessing a proteinaceous pellicle instead of a typical cell wall, which we considered as a barrier against nanoparticle uptake. This study provides evidence that AgNP were not internalized but strongly adsorbed on the pellicle. The toxicity of AgNP to algae merely resulted from the dissolved silver released from the nanoparticles.

We compare the adsorption, bonding, and electronic structure of closo-1,2 dicarbadodecaborane (orthocarborane, C2B10H12) and closo-1,7 dicarbadodecaborane (metacarborane, C2B10H12) on metal surfaces. The electronic structure (molecular orbitals) of these two isomer molecules are calculated to be very similar, but there are significant differences in the experimental binding energies for each isomer as an adsorbed species. Metacarborane adsorbs on both Co and Au with the Fermi level (chemical potential) placed closer to the lowest unoccupied molecular orbital than is observed with orthocarborane adsorbed on Co and Cu.