Using Research and Planning to Develop Community Outreach: A Case Study in Helping Clientele Cope with Stress

Extension educators collaborated with local agencies to conduct a survey on sources of stress in the lives of local residents. Results reveal that five variables emerge as statistically significant factors associated with reported stress levels: financial problems, stress on the job, having too little time, number of major life changes in the past year, and being a woman. Educators followed with a Vision to Action Program that identified specific goals aimed at helping community residents cope with and reduce stress levels. Combining applied research with existing Extension programming is an effective way to engage the public on issues of local concern

Understanding the photophysical properties of methylammonium lead halide perovskites

Photostability is important for current organometal halide perovskites being used as materials in light emitting devices, lasers, quantum dots and solar cells. Illumination from different sources such as the sun, lamps, and lasers can alter the physical and PL stability of nanocrystalline perovskites. This instability can be problematic for the use of perovskite quantum dots as molecular probes and lead to deterioration of perovskite-based solar cells. Here, different synthetic pathways are being analyzed using luminescence microscopy to determine the most stable method(s) for preparing physically and PL λmax stable MA lead halide perovskite nanocrystals. Dimensionality is controlled by capping with octylammonium ligands. Two different precursor ratios are evaluated to determine which provide the highest photostability. It is determined that the 1:1.5:1.5 PbX2:CH3NH3X:CH3(CH2)7X precursor ratio provides the most photo-stable MA lead halide perovskite nanocrystals

A Comparison of Young Children\u27s Writing Products in Skills-Based and Whole Language Classrooms

Whole language instruction and an emphasis on the writing process have had a significant impact on the teaching of writing. Many whole language teachers are already in practice, and more educators are moving toward this kind of teaching. However, comparative research on the value of whole language curriculum is limited. It is important to study children\u27s interpretations (Erickson and Shultz, 1992) as they are reflected in the written products they generate in different kinds of classrooms. We need to know more about the sense children make of their instruction, what they are learning about written language, and the kinds of writing they produce. The purpose of this article is to report on a two-year, descriptive study of eight, low-income children\u27s writing in skills-based and whole language instruction during kindergarten and first grade. Our focus was on the development of emergent writers in these two different kinds of instruction

Nanosecond, Time-Resolved Shift of the Photoluminescence Spectra of Organic, Lead-Halide Perovskites Reveals Structural Features Resulting from Excess Organic Ammonium Halide

The effort to drive solution-based perovskite solar cells towards higher efficiency has been considerable, reaching over 24%. Such progress has been made possible by the low-energy barrier to crystallization. The low-energy barrier in the reverse direction, however, also renders them susceptible to dissociation from heat, moisture, and photoexcitation. Consequently, studies that provide information on the stability of perovskites are of considerable importance. It has been reported that perovskite crystals formed using different stoichiometries of the organic precursors and metal halide are equivalent. Our findings, however, suggest that the difference in reaction pathways affects the quality of the final crystal and that changes in morphology and the production of any defects can lead to differences in behavior under illumination. Here, we present photoluminescence spectra subsequent to nanosecond photoexcitation of perovskites synthesized under various conditions. Our results indicate that the presence of excess precursors (i.e., CH3NH3X, X= I and surfactant) gives rise to an ~20-nanosecond relaxation time with which the photoluminescence spectrum achieves its equilibrium value. This relaxation is absent in bulk, polycrystalline material. This is, to our knowledge, the first report of the ~20-ns relaxation time, which we attribute to cation migration. These structural changes are not detectable subsequent to photoexcitation by x-ray diffraction, nor are they detectable by in situ x-ray diffraction during photoexcitation

Synthetic Control of the Photoluminescence Stability of Organolead Halide Perovskites

An optimized synthetic procedure for preparing photostable nanocrystalline methylammonium lead halide materials is reported. The procedure was developed by adjusting the lead halide to methylammonium/octylammonium halide precursor ratio. At a high precursor ratio (1:3), a blue-shifted photoinduced luminescence peak is measured at 642 nm for CH3NH3PbI3 with 0.01 to 12 mJ pulsed-laser irradiation. The appearance of this peak is reversible over 300 min upon blocking the irradiation. In order to determine if the peak is the result of a phase change, in situ x-ray diffraction measurements were performed. No phase change was measured with an irradiance that causes the appearance of the photoinduced luminescence peak. Luminescence microscpectroscopy measurements showed that the use of a lower precursor ratio (1:1.5) produces CH3NH3PbI3 and CH3NH3PbBr3 perovskites that are stable over 4 min of illumination. Given the lack of a measured phase change, and the dependence on the precursor ratio, the photoinduced luminesce peak may derive from surface trap states. The enhanced photostability of the resulting perovskite nanocrystals produced with the optimized synthetic procedure supports their use in stable optoelectronic devices