Photoluminescence of dense nanocrystalline titanium dioxide thin films: effect of doping and thickness and relation to gas sensing

The photoluminescence (PL) of dense nanocrystalline (anatase) TiO(2) thin films is reported as a function of calcination temperature, thickness, and tungsten and nickel doping. The dependence of the optical absorption, Raman spectra, and PL spectra on heat treatment and dopants reveals the role of oxygen vacancies, crystallinity, and phase transformation in the performance of TiO(2) films used as gas sensors. The broad visible PL from defect states of compact and undoped TiO(2) films is found to be much brighter and less sensitive to the presence of oxygen than that of mesoporous films. The dense nanocrystalline grains and the nanoparticles comprising the mesoporous film are comparable in size, demonstrating the importance of film morphology and carrier transport in determining the intensity of defect photoluminescence. At higher calcination temperatures, the transformation to rutile results in the appearance of a dominant near-infrared peak. This characteristic change in the shape of the PL spectra demonstrates efficient capture of conduction band electrons by the emerging rutile phase. The W-doped samples show diminished PL with quenching on the red side of the emission spectrum occurring at lower concentration and eventual disappearance of the PL at higher W concentration. The results are discussed within the context of the performance of the TiO(2) thin films as CO gas sensors and the chemical nature of luminescent defects.     

Predicting time to recovery among depressed adolescents treated in two psychosocial group interventions.

Aims were to identify the demographic, psychopathology, and psychosocial factors predicting time to major depressive disorder (MDD) recovery and moderators of treatment among 114 depressed adolescents recruited from a juvenile justice center and randomized to a cognitive behavioral treatment (CBT) condition or a life skills-tutoring control condition. Nine variables predicted time to recovery over 1-year follow-up (e.g., earlier MDD onset, attention-deficit/hyperactivity disorder, functional impairment, hopelessness, negative thoughts, low family cohesion, coping skills); suicidal ideation and parental report of problem behaviors were the best predictors. CBT resulted in faster recovery time relative to control treatment, specifically among adolescents of White ethnicity, with recurrent MDD, and with good coping skills. Results suggest that psychopathology plays a more prominent role in maintaining adolescent depression than demographic or psychosocial factors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)