Wide energy-window view on the density of states and hole mobility of poly(p-phenylene vinylene)

Using an electrochemically gated transistor, we achieved controlled and reversible doping of poly(p-phenylene vinylene) in a large concentration range. Our data open a wide energy-window view on the density of states (DOS) and show, for the first time, that the core of the DOS function is Gaussian, while the low-energy tail has a more complex structure. The hole mobility increases by more than four orders of magnitude when the electrochemical potential is scanned through the DOS.Comment: 4 pages, 4 figure

Loosening the reins or tightening them?:Complex relationships between parenting, effortful control, and adolescent psychopathology

Background Adolescents face major developmental tasks such as increasing individuation and establishing autonomy. These developmental tasks increase demands on adolescent self-control, hereby putting youth with poor effortful control at risk for psychopathology. Specific parenting behaviors might be warranted to buffer against this risk. Objective This study was designed to examine parenting-related risk and protective factors in the associations between effortful control and adolescent psychopathology. We hypothesized that youth with poor effortful control require more parental involvement (i.e., lower autonomy granting) to help complete these developmental tasks and subsequently avoid psychopathology. Methods Via adolescent self-reports (N = 809), associations between effortful control, perceived parenting (i.e., psychological control and autonomy support), and externalizing (i.e., interpersonal aggression and rule-breaking) and internalizing problems (i.e., depressive and anxiety problems) were examined. Results Regression analyses supported our hypothesis in boys: higher levels of autonomy support exacerbated the negative association between effortful control and rule-breaking. In contrast, in girls this was the case for lower levels of autonomy support. For both genders, low autonomy support and psychological control exacerbated negative associations between effortful control and internalizing problems. No buffering effects of parenting were found. Conclusions Low effortful control is associated with psychopathology in adolescents, but parenting can affect this association in several ways, depending on the type of psychopathology and the adolescent’s gender. Future research should focus on finding ‘optimal’ levels of parental control that can help avoid psychopathological problems in youth with poor effortful control

Tunable band structure in core-shell quantum dots through alloying of the core

Integrated optics have a wide range of applications in telecommunications, information treatment and lab-on-chip analysis. Nowadays, light is in most cases generated outside of the photonic device, coupled with it through optical fibers. The integration of reliable light sources would make these devices more efficient, more robust and would allow the integration of active components. In that view, core-shell quantum dots (QDs) show unique properties: their emission wavelength can be tuned, they present high quantum yield and their integration in photonic devices is based on classical fabrication process. Moreover, the band structure of core shell QDs give rise to interesting features. In type II QDs, such as CdS/ZnSe, one type of charge carrier is confined in the core and the other in the shell, what allows single exciton gain. On the contrary, in type I QDs, such as CdSe\ZnSe, both charge carriers are strongly confined in the core, what results in high emission quantum yield and single photon emitter behaviour. Here, we present an original method to finely tune the band structure of visible emitting core\shell QDs between type I and type II. We study CdSe(1-x)Sx\ZnS\ZnS QDs with various compositions of the alloyed core and we show that, by changing the ratio between sulfur and selenium, one can shift continuously from type I to type II. Based on transient absorption spectroscopy measurements, we also analyse the evolution of gain with the proportion of selenium in the core