Disorder in charge-transport in doped polymers

Charge transport in molecular doped polymers has important applications in xerography, as well as being a theoretical challenge. Its investigation by determination of transient photocurrents is reviewed, with experiments and pertinent theories, such as hopping in a Gaussian density of states and the small polaron model, being outlined. The temporal features of the photocurrents, the field and temperature dependence of the charge carrier mobilities, and the influence of molecular properties—and what can be inferred from these—are discussed. Copyright © 1994 Verlag GmbH & Co. KGaA, Weinheimstatus: publishe

Emission from zeolite-occluded manganese-diimine complexes

Manganese complexes of 2,2'-bipyridine (bpy) and 1,10-phenantroline (phen) have been synthesised in the supercages of cubic NaX and NaY and in the hypercages of the hexagonal NaEMT faujasites. The coordination and redox chemistry were studied with ESCA, CA, FT-IR, FT-Raman, diffuse reflectance and emission techniques. FT-IR:FT-Raman shows cis coordination for all complexes and a high Mn-N stretching frequency in the phen complexes as a result of steric constraints imposed by the ligand, (Mn(bpy)(2)](2+) in the different zeolites shows metal-to-ligand charge transfer (MLCT; at 495 nm); for [Mn(phen)(2)](2+)-NaY the MLCT is broadened owing to complex distortion, On MLCT excitation [Mn(bpy)(2)](2+) complexes show an ipsochromic shift in the emission and an increase in quantum field with increasing steric restrictions imposed by the zeolite, The ipsochromic shift of the emission band of [Mn(phen)(3)](2+) in NaY results from the combined effect of the ligand field (this suggests emission from a CT state) and of coordinative distortion, The key factor influencing the emission properties is found to be the overall matrix-induced complex distortion. Cation stabilisation of the ligand anion affects emission indirectly. The decay times for [Mn-bpy)(2)](2+)-NaY are in the millisecond range (7.5-11.5 ms). A proposed model for excitation and emission properties of zeolite-occluded Mn-II complexes involves excitation of a quartet CT state, intersystem crossing and subsequent emission. The enhanced stability of the coordination sphere in the zeolite allows complexes to luminesce from a CT state, which is not detected in solution. The zeolite behaves as a supramolecular cryptating agent, protecting complexes from photodissociation

Drugs - a study in post-primary schools situated outside Dublin 1981.

The article reports on a survey of a random sample of pupils attending post-primary schools outside Dublin city and county. The survey of 5,408 students from 16 schools was conducted between September and December 1981. Information on the availability, use and knowledge of illicit drugs was gathered by means of self administered questionnaires. Some of the survey results were compared with those from a study of Irish rural post-primary school-children dating from 1970/71, and another carried out among Dublin post-primary school-children in 1981. A three- to eight-fold increase in the numbers of respondents who said they had taken a drug was found when the results were compared to the 1970/71 survey, and these students occurred with one-third to one-half the frequency to the Dublin 1980/81 survey. The authors suggested that their findings exposed the need to improve the drugs education available in schools