Temperature dependence of time-resolved luminescence spectra for 1D excitons in single-walled carbon nanotubes in micelles

Abstract We have investigated exciton luminescence spectra, decay behaviors, and their temperature dependence in singlewalled carbon nanotubes in micelles. The temperature dependence of luminescence spectra can be explained by the onephonon process associated with the radial breathing mode in the single-walled carbon nanotube. The luminescence decay behavior suggests that the signal is composed of various exponential decays with different decay times. These experimental results are explained by the existence of trapping centers on the nanotube.

Simple and Downsized Amplification System of a Femtosecond Laser Pulse using Dye Gain Media

A femtosecond laser pulse of a fiber laser is amplified in dye gain media. To evaluate the conditions for the amplification of a femtosecond laser pulse, the time-resolved measurements of gains in OXAZINE 750, DOTC, and LDS 821 dye solutions are carried out by using a TEA N2 laser (λ= 337.1 nm, FWHM= 0.6 ns), a TE N2 laser (λ= 337.1 nm, FWHM= 6 ns) and the second harmonic of a Nd:YAG laser (λ= 532 nm, FWHM= 5 ns), as the pump sources. The amplified output energy of the fs laser pulse is 1 μJ, and the pulse width is 180 fs (FWHM). These output energy and pulse width are comparable to those of a typical CPA laser system, and the cost performance is very high

Intra- and inter-tube exciton relaxation dynamics in high purity semiconducting and metallic single-walled carbon nanotubes

We have measured the exciton and carrier dynamics in the high purity semiconducting (S-) and metallic (M-) single-walled carbon nanotubes (SWNTs) in the isolated and aggregated (bundled) forms. The exciton relaxation decay times are measured by using the pump-probe spectroscopy. For bundled samples, the relaxation time becomes shorter than that for isolated SWNTs sample, because of the existence of inter-tube relaxation. We estimate the relaxation rates from S-SWNT to S-SWNT and S-SWNT to M-SWNT using the decay times for isolated SWNTs, high purity S-SWNTs bundle, and doped S-SWNTs in high purity M-SWNTs bundle. For S-SWNTs, inter-tube relaxation plays an important role in the relaxation dynamics. However, for M-SWNTs, the inter-tube relaxation is not so important, and the transition energy and intensity of exciton in M-SWNTs is strongly affected by the photoexcited carriers which plays like as photo doping

Effect of electron spin-spin exchange interaction on spin precession in coupled quantum well

Electron spin-spin interaction in an asymmetric coupled quantum well (CQW) was investigated through electron spin-precession measurements. Precession (Larmor) frequencies from electrons localized in two CQWs were measured by means of polarization- and time-resolved photoluminescence measurements under a high magnetic field. At a low excitation power density, the Larmor frequency of the CQW was same as that of a single quantum well. The Larmor frequency of electron spin in one well was shifted to that in the other well as the excitation power density was increased. These experimental results are quantitatively explained by an exchange interaction between electrons localized in the two wells.autho

Quality Control of High-Speed Photon Detectors

High-speed-photon detectors are some of the most important tools for observations of high energy cosmic rays. As technologies of photon detectors and their read-out electronics improved rapidly, the time resolution of some cosmic ray detectors became better than one nanosecond. To utilize such devices effectively, calibrations using a short-pulse light source are necessary. We have developed a pulsed laser of 80 picosecond width and adjustable peak intensity up to 100 mW. This pulsed laser is composed of a simple electric circuit and a laser diode. Details of this pulsed laser and its application for quality controls of photon detectors are reported in this contribution

Quality Control of High-Speed Photon Detectors

High-speed-photon detectors are some of the most important tools for observations of high energy cosmic rays. As technologies of photon detectors and their read-out electronics improved rapidly, the time resolution of some cosmic ray detectors became better than one nanosecond. To utilize such devices effectively, calibrations using a short-pulse light source are necessary. We have developed a pulsed laser of 80 picosecond width and adjustable peak intensity up to 100 mW. This pulsed laser is composed of a simple electric circuit and a laser diode. Details of this pulsed laser and its application for quality controls of photon detectors are reported in this contribution

Excitonic Photoluminescence from Nanodisc States in Graphene Oxides

The origin of near-infrared (NIR) luminescence from graphene oxide (GO) is investigated by photoluminescence (PL) excitation spectroscopy, time-resolved PL spectroscopy, and density functional theory based many body perturbation theories. The energy of experimentally observed NIR PL peak depends on the excitation energy, and the peak broadens with increasing excitation energy. It is found that the PL decay curves in time-resolved spectroscopy show build-up behavior at lower emission energies due to energy transfer between smaller to larger graphene nanodisc (GND) states embedded in GO. We demonstrate that the NIR PL originates from ensemble emission of GND states with a few nanometers in size. The theoretical calculations reveal the electronic and excitonic properties of individual GND states with various sizes, which accounts for the inhomogeneously broadened NIR PL. We further demonstrate that the electronic properties are highly sensitive to the protonation and deprotonation processes of GND states using both the experimental and theoretical approaches

Evaluation of ABCG2-mediated extra-renal urate excretion in hemodialysis patients

Abstract Two-thirds of urate is excreted via the renal pathway and the remaining one-third via the extra-renal pathway, the latter mainly via the intestine in healthy individuals. ABCG2, a urate exporter, is expressed in various tissues including the kidney and intestine, and its dysfunction leads to hyperuricemia and gout. ABCG2 is regarded as being responsible for most of the extra-renal urate excretion. However, the extra-renal urate excretion capacity via ABCG2 remains undefined in end-stage kidney diseases. Therefore, we evaluated the capacity of extra-renal ABCG2 using 123 anuric hemodialysis patients whose urate excretion depended on only the extra-renal pathway. ABCG2 function in each participant was estimated based on ABCG2 dysfunctional variants. We computed the uric acid pool (PoolUA) from bodyweight and serum urate level (SUA) using previously reported radio-isotopic data, and we analyzed the association between ABCG2 function and the PoolUA. SUA and PoolUA increased significantly with ABCG2 dysfunction, and extra-renal ABCG2 could excrete up to approximately 60% of the daily uric acid turnover in hemodialysis patients. Our findings indicate that the extra-renal urate excretion capacity can expand with renal function decline and highlight that the extra-renal pathway is particularly important in the uric acid homeostasis for patients with renal dysfunction