The Kinetics Of Charge Trapping In Polycrystalline Pentacene And Ion Migration In Light Emitting Electrochemical Cells Studied By Timeand Temperature-Resolved Electric Force Microscopy

The microscopic mechanisms by which charges trap in organic electronic materials are poorly understood. While trapping and bias stress in thin film transistors have been investigated through bulk techniques, these efforts cannot account for the known local variations of trap concentration and kinetics across the film. We show that electric force microscopy (EFM) can be used to follow local trap formation kinetics in working pentacene thin-film transistors. The trap formation rate we found was hole-concentration dependent, strongly suggesting a trapping mechanism involving one or more chemical reactions, or at least, we hypothesize, an activated process. Chemically modified pentacene also shows concentration dependent trapping despite the presence of functional groups that should inhibit the proposed chemical trap formation mechanisms. Furthermore, we found that electrons, injected by gate voltage in modified pentacene and by light in unmodified pentacene, clear trapped charges. When the trapped holes are cleared by electron injection, there is an uncharged intermediate species remaining which accelerates future charge trapping. Finally, we use variable temperature to show direct evidence that the trapping mechanism is an activated process. In light-emitting electrochemical cells (LEECs) the redistribution of ions assists the injection of electronic carriers and leads to efficient light emission. The mechanism of operation of LEECs has been controversial, and there is no consensus regarding the distribution of electric field in these devices. Here, we use EFM to directly observe ion motion within the channel of an operating LEEC. Initial results in a planar configuration show ion migration on top of the electrodes. To properly test the models, the organic material was patterned solely between the electrodes. The observed ion motion agrees with the electrodynamic surface potential model: ions move to the electrodes to assist injection

Purification of commercial 2,3-dimethyl phenol using supercritical fluid extraction

The commercial value of phenols is often reduced due to the presence of colored impurities. Several conventional techniques have been used for the purification of phenols. However, conventional purification techniques are tedious and make use of hazardous and expensive organic solvents. In this study, we present a new method for purification of an aged-discolored (orange) commercial 2,3-dimethyl phenol (2,3-DMP) reagent (~97%) using supercritical fluid CO2 (SCF CO2), as an extraction solvent. A supercritical fluid extraction (SFE)/purification apparatus was constructed and purification of the reagent under different extraction conditions was investigated. Based on the differential solubility of the 2,3-DMP and the impurities in SCF CO2, the commercial reagent was successfully purified by SFE; the purified 2,3-DMP was a white solid of high purity (\u3e 99.5%). The SFE method was also applied to purify a recently purchased batch of 2,3-DMP reagent. We found that the reagent purified by SFE was of a higher quality than a commercially available analytical standard. © Taylor & Francis Group, LLC

Delivering clinical trials at home: protocol, design and implementation of a direct-to-family paediatric lupus trial

Introduction Direct-to-family clinical trials efficiently provide data while reducing the participation burden for children and their families. Although these trials can offer significant advantages over traditional clinical trials, the process of designing and implementing direct-to-family studies is poorly defined, especially in children with rheumatic disease. This paper provides lessons learnt from the design and implementation of a self-controlled, direct-to-family pilot trial aimed to evaluate the effects of a medication management device on adherence to hydroxychloroquine in paediatric SLE.Methods Several design features accommodate a direct-to-family approach. Participants meeting eligibility criteria from across the USA were identified a priori through a disease registry, and all outcome data are collected remotely. The primary outcome (medication adherence) is evaluated using electronic medication event-monitoring, plasma drug levels, patient questionnaires and pill counts. Secondary and exploratory endpoints include (1) lupus disease activity measured by a remote SLE Disease Activity Index examination and the Systemic Lupus Activity Questionnaire; and (2) hydroxychloroquine pharmacokinetics and pharmacodynamics. Recruitment of the initial target of 20 participants was achieved within 10 days. Due to initial recruitment success, enrolment was increased to 26 participants. Additional participants who were interested were placed on a waiting list in case of dropouts during the study.Discussion and dissemination Direct-to-family trials offer several advantages but present unique challenges. Lessons learnt from the protocol development, design, and implementation of this trial will inform future direct-to-family trials for children and adults with rheumatic diseases. Additionally, the data collected remotely in this trial will provide critical information regarding the accuracy of teleresearch in lupus, the impact of adherence to hydroxychloroquine on disease activity and a pharmacokinetic analysis to inform paediatric-specific dosing of hydroxychloroquine.Trial registration number ClinicalTrials.gov Registry (NCT04358302)