tailieunhanh - Báo cáo hóa học: " Excitonic Transitions and Off-resonant Optical Limiting in CdS Quantum Dots Stabilized in a Synthetic Glue Matrix"

Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: Excitonic Transitions and Off-resonant Optical Limiting in CdS Quantum Dots Stabilized in a Synthetic Glue Matrix | Nanoscale Res Lett 2007 2 561-568 DOI S11671-007-9099-8 NANO EXPRESS Excitonic Transitions and Off-resonant Optical Limiting in CdS Quantum Dots Stabilized in a Synthetic Glue Matrix Pushpa Ann Kurian C. Vijayan K. Sathiyamoorthy C. S. Suchand Sandeep Reji Philip Received 1 August 2007 Accepted 5 October 2007 Published online 25 October 2007 to the authors 2007 Abstract Stable films containing CdS quantum dots of mean size nm embedded in a solid host matrix are prepared using a room temperature chemical route of synthesis. CdS synthetic glue nanocomposites are characterized using high resolution transmission electron microscopy infrared spectroscopy differential scanning calorimetry and thermogravimetric analysis. Significant blue shift from the bulk absorption edge is observed in optical absorption as well as photoacoustic spectra indicating strong quantum confinement. The exciton transitions are better resolved in photoacoustic spectroscopy compared to optical absorption spectroscopy. We assign the first four bands observed in photoacoustic spectroscopy to 1se-1sh 1pe-1ph 1de-1dh and 2pe -2ph transitions using a non interacting particle model. Nonlinear absorption studies are done using z-scan technique with nanosecond pulses in the off resonant regime. The origin of optical limiting is predominantly two photon absorption mechanism. Keywords Exciton Nanomaterials Optical limiting Nonlinearity Photoacoustics Introduction Semiconductor nanocrystals have been receiving considerable attention over the past several years as model systems exhibiting quantum confinement effects and hence P. A. Kurian C. Vijayan El K. Sathiyamoorthy Indian Institute of Technology Madras Chennai 600036 India e-mail cvijayan@ C. S. Suchand Sandeep R. Philip Raman Research Institute Bangalore 560080 India as potential candidate materials for device applications such as optical limiting and optical switching 1-6 . Optical limiting has been reported for .