Luminescence Intermittency and Quantum Efficiency of Individual Porous Si Nanoparticles.

1999 ◽  
Vol 560 ◽  
Author(s):  
Michael D. Mason ◽  
Grace M. Credo ◽  
Paul J. Carson ◽  
Steven K. Buratto
Keyword(s):  
Quantum Efficiency ◽  
Colloidal Suspension ◽  
Porous Si ◽  
Time Resolved ◽  
High Quantum Efficiency ◽  
Si Nanoparticles ◽  
Shear Force Microscopy ◽  
Spectrally Resolved ◽  
Single Particle Spectroscopy ◽  
Microscopy Techniques

ABSTRACTWe have recently observed spectrally resolved vibronic structure and luminescence intermittency from nanometer-size porous silicon nanocrystals. In this study we examine the quantum efficiency of a single nanoparticle and show that emitting nanoparticles do so with near unity quantum efficiency. This result suggests that the emission from porous Si nanoparticles, and thus bulk porous Si, results from a small number of high quantum efficiency emitters. In our previous work we have shown that our nanoparticles contain more than one coupled chromophore. In order to examine these effects more closely we employ several spectroscopy and microscopy techniques including: 1) single-particle spectroscopy, 2) shear-force microscopy, and 3) time-resolved spectroscopy, on a colloidal suspension of size-selected, surface-oxidized nanoparticles. In addition we apply statistical techniques to provide a more complete picture of the coupling between chromophores in a given nanoparticle.

Energy transfer dynamics and time resolved photoluminescence in BaWO4:Eu3+ nanophosphors synthesized by mechanical activation

2017 ◽  
Vol 41 (17) ◽  
pp. 8947-8958 ◽  
Author(s):  
Paramananda Jena ◽  
Santosh K. Gupta ◽  
Narendra Kumar Verma ◽  
Akhilesh Kumar Singh ◽  
R. M. Kadam
Keyword(s):  
Energy Transfer ◽  
Mechanical Activation ◽  
Quantum Efficiency ◽  
Time Resolved ◽  
High Quantum Efficiency ◽  
Red Phosphor ◽  
White Leds ◽  
High Quantum ◽  
Time Resolved Photoluminescence

Red purity and high quantum efficiency of BaWO4:Eu3+ projects it as a new red phosphor for application in white LEDs.

scholarly journals Photocatalytic CO2 reduction with a quantum efficiency exceeding 60%: time-resolved spectroscopic and X-ray studies on Cu(I) photosensitizers in coordinative interaction with Co(II) phthalocyanine catalysts

2022 ◽  
Author(s):  
Jia-Wei Wang ◽  
Xian Zhang ◽  
Michael Karnahl ◽  
Zhi-Mei Luo ◽  
Zizi Li ◽  
...  
Keyword(s):  
Excited State ◽  
Quantum Efficiency ◽  
Absorption Spectroscopy ◽  
High Performance ◽  
Transient Absorption Spectroscopy ◽  
Torsional Angle ◽  
Time Resolved ◽  
Free System ◽  
High Quantum Efficiency ◽  
X Ray

Abstract The utilization of a fully noble-metal-free system for photocatalytic CO2 reduction remains a fundamental challenge, demanding the precise design of photosensitizers and catalysts, as well as the exploitation of their intermolecular interactions to facilitate electron delivery. Herein, we have implemented triple modulations on catalyst, photosensitizer and coordinative interaction between them for high-performance light-driven CO2 reduction. In this study, heteroleptic copper and cobalt phthalocyanine complexes were selected as photosensitizers and catalysts, respectively. An over ten-fold improvement in light-driven reduction of CO2 to CO is achieved for the catalysts with appending electron-withdrawing substituents for optimal CO-desorption ability. In addition, pyridine substituents were implanted at the backbone of the phenanthroline moiety of the Cu(I) photosensitizers and the effect of their axial coordinative interaction with the catalyst was tested. The combined results of 1H NMR titration experiment, steady-state/transient photoluminescence, and transient absorption spectroscopy confirm the coordinative interaction and reductive quenching pathway in photocatalysis corroboratively. It has been found that the catalytic performances of the coordinatively interacted systems are unexpectedly reverse to those with the pyridine-free Cu(I) photosensitizers. Moreover, the latter system enables a very high quantum efficiency up to 63.5% at 425 nm with a high selectivity exceeding 99% for CO2-to-CO conversion. As determined by time-resolved X-ray absorption spectroscopy and DFT calculation, the replacement of phenyl by pyridyl groups in the Cu(I) photosensitizer favors a stronger flattening and larger torsional angle change of the overall excited state geometry upon photoexcitation, which explains the decreased lifetime of the triplet excited state. Our work promotes the systematic multi-pathway optimizations on the catalyst, photosensitizer and their interactions for advanced CO2 photoreduction.

Modulation of optical properties of ZnS QDs embedded glasses through aluminum and manganese doping

2021 ◽  
Author(s):  
Kai Li ◽  
Ying Ye ◽  
Wenchao Zhang ◽  
Yuzhou Hu ◽  
Ying Yang ◽  
...  
Keyword(s):  
Optical Properties ◽  
Quantum Efficiency ◽  
High Quantum Efficiency ◽  
Information Display ◽  
Manganese Doping ◽  
High Quantum

Nontoxic cadmium-free ZnS and ZnSe QDs QDs with high quantum efficiency have drawn considerable attention for information display. Applications of ZnS and ZnSe QDs are limited by their short emission...

scholarly journals Review of time-resolved non-contact electrostatic force microscopy techniques with applications to ionic transport measurements

2019 ◽  
Vol 10 ◽  
pp. 617-633 ◽  
Author(s):  
Aaron Mascaro ◽  
Yoichi Miyahara ◽  
Tyler Enright ◽  
Omur E Dagdeviren ◽  
Peter Grütter
Keyword(s):  
Atomic Force Microscopy ◽  
Electrostatic Force ◽  
Oscillation Period ◽  
Electrostatic Force Microscopy ◽  
Time Varying ◽  
Time Resolved ◽  
Battery Materials ◽  
Force Microscopy ◽  
Atomic Force ◽  
Microscopy Techniques

Recently, there have been a number of variations of electrostatic force microscopy (EFM) that allow for the measurement of time-varying forces arising from phenomena such as ion transport in battery materials or charge separation in photovoltaic systems. These forces reveal information about dynamic processes happening over nanometer length scales due to the nanometer-sized probe tips used in atomic force microscopy. Here, we review in detail several time-resolved EFM techniques based on non-contact atomic force microscopy, elaborating on their specific limitations and challenges. We also introduce a new experimental technique that can resolve time-varying signals well below the oscillation period of the cantilever and compare and contrast it with those previously established.

scholarly journals Highly Efficient Near-Infrared Detector Based on Optically Resonant Dielectric Nanodisks

Nanomaterials ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 428
Author(s):  
Reza Masoudian Saadabad ◽  
Christian Pauly ◽  
Norbert Herschbach ◽  
Dragomir N. Neshev ◽  
Haroldo T. Hattori ◽  
...  
Keyword(s):  
Quantum Efficiency ◽  
High Speed ◽  
Near Infrared ◽  
Infrared Detector ◽  
High Quantum Efficiency ◽  
Fast Detection ◽  
High Quantum ◽  
Resonant Modes ◽  
Infrared Wavelengths ◽  
Dielectric Metasurface

Fast detection of near-infrared (NIR) photons with high responsivity remains a challenge for photodetectors. Germanium (Ge) photodetectors are widely used for near-infrared wavelengths but suffer from a trade-off between the speed of photodetection and quantum efficiency (or responsivity). To realize a high-speed detector with high quantum efficiency, a small-sized photodetector efficiently absorbing light is required. In this paper, we suggest a realization of a dielectric metasurface made of an array of subwavelength germanium PIN photodetectors. Due to the subwavelength size of each pixel, a high-speed photodetector with a bandwidth of 65 GHz has been achieved. At the same time, high quantum efficiency for near-infrared illumination can be obtained by the engineering of optical resonant modes to localize optical energy inside the intrinsic Ge disks. Furthermore, small junction capacitance and the possibility of zero/low bias operation have been shown. Our results show that all-dielectric metasurfaces can improve the performance of photodetectors.

A novel high quantum efficiency SiGe Phototransistor detector

2021 ◽  
Author(s):  
Yang Xiang ◽  
Hongyun Xie ◽  
Yin Sha ◽  
Ruilang Ji ◽  
Fu Zhu ◽  
...  
Keyword(s):  
Quantum Efficiency ◽  
High Quantum Efficiency ◽  
High Quantum
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