Size-Dependent Properties of Solution-Processable Conductive MOF Nanocrystals.

The diverse optical, magnetic, and electronic behaviors of most colloidal semiconductor nanocrystals emerge from materials with limited structural and elemental compositions. Conductive metal-organic frameworks (MOFs) possess rich compositions with complex architectures but remain unexplored as nanocrystals, hindering their incorporation into scalable devices. Here, we report the controllable synthesis of conductive MOF nanoparticles based on Fe(1,2,3-triazolate)2. Sizes can be tuned to as small as 5.5 nm, ensuring indefinite colloidal stability. These solution-processable MOFs can be analyzed by solution-state spectroscopy and electrochemistry and cast into conductive thin films with excellent uniformity. This unprecedented analysis of MOF materials reveals a strong size dependence in optical and electronic behaviors sensitive to the intrinsic porosity and guest-host interactions of MOFs. These results provide a radical departure from typical MOF characterization, enabling insights into physical properties otherwise impossible with bulk analogues while offering a roadmap for the future of MOF nanoparticle synthesis and device fabrication.

Tunable Interlayer Interactions in Exfoliated 2D van der Waals Framework Fe(SCN)2(Pyrazine)2.

2D materials can be isolated as monolayer sheets when interlayer interactions involve weak van der Waals forces. These atomically thin structures enable novel topological physics and open chemical questions of how to tune the structure and properties of the sheets while maintaining them as isolated monolayers. Here, this work investigates 2D electroactive sheets that exfoliate in solution into colloidal nanosheets, but aggregate upon oxidation, giving rise to tunable interlayer charge transfer absorption and photoluminescence. This optical behavior resembles interlayer excitons, now intensely studied due to their long-lived emission, but which remain difficult to tune through synthetic chemistry. Instead, the interlayer excitons of these framework sheets can be modulated through control of solvent, electrolyte, oxidation state, and the composition of the framework building blocks. Compared to other 2D materials, these framework sheets display the largest known interlayer binding strengths, attributable to specific orbital interactions between the sheets, and among the longest interlayer exciton lifetimes. Taken together, this study provides a microscopic basis for manipulating long-range opto-electronic behavior in van der Waals materials through molecular synthetic chemistry.

Impact of late and prolonged working life on subjective health: the Swedish experience.

This paper explores the relationship between the prolongation of working life and subjective health. Drawing on a unique combination of longitudinal data and the results of a postal survey in Sweden, we investigate the health consequences of extending working life beyond the normal retirement age of 65. To do this, we compare the health status of two groups of retired people: one group who left the labour market completely at the age of 65, and a second group who remained in employment after the age of 65. Using a standard linear probability model and controlling for a range of socio-economic variables as well as previous labour market experiences, perceived life expectancy, pre-retirement income and health, our estimations show that those continuing to work after 65 on average display a 6.8% higher probability of reporting better health during retirement than those leaving at the age of 65. However, we find that this positive correlation between the extension of working life and health is only transitory. After 6 years of retirement, the health advantage of working after the normal retirement age disappears. Furthermore, we did not find any evidence that working after the age of 65 is positively correlated with physical fitness, self-reported depressive symptoms or well-being.

Gene expression analysis using single molecule detection.

Recent developments of single molecule detection techniques and in particular the introduction of fluorescence correlation spectroscopy (FCS) led to a number of important applications in biological research. We present a unique approach for the gene expression analysis using dual-color cross-correlation. The expression assay is based on gene-specific hybridization of two dye-labeled DNA probes to a selected target gene. The counting of the dual-labeled molecules within the solution allows the quantification of the expressed gene copies in absolute numbers. As detection and analysis by FCS can be performed at the level of single molecules, there is no need for any type of amplification. We describe the gene expression assay and present data demonstrating the capacity of this novel technology. In order to prove the gene specificity, we performed experiments with gene-depleted total cDNA. The biological application was demonstrated by quantifying selected high, medium and low abundant genes in cDNA prepared from HL-60 cells.