Search results for "luminescence."

Luminescence of the surface nonbridging oxygen hole center in silica: Spectral and decay properties

2008

We investigated the red luminescence in a porous film of silica nanoparticles, originating from surface nonbridging oxygen hole centers. The excitation spectrum was measured from 1.8 to 8.0 eV by a tunable laser system and a synchrotron radiation source; this spectrum evidences a peak at 2.0 eV, nearly overlapping with the emission, and an ultraviolet broadband with peaks at 4.8 and 6.0 eV. The emission is characterized by a spectrum with two subbands split by 0.07 eV, its decay occurs with lifetime longer than 30 microsec and undergoes a thermal quenching by a factor aboout 2 with increasing temperature from 10 to 290 K. The optical characteristics of surface and bulk centers are discussed…

Disclosing the emissive surface traps in green-emitting carbon nanodots

2021

Abstract The bright photoluminescence of surface-functionalized carbon nanoparticles, known as carbon nanodots (CDs), has been studied for more than a decade because of its fundamental photo-physical interest and strong technological potential. However, the essential nature of the electronic states involved in their typical light emission remains very elusive. Here, we provide conclusive evidence that surface carboxylic moieties are the key to CD fluorescence. The synergy of nanosecond and femtosecond optical studies, cryogenic fluorescence, computational investigations and chemical engineering of a strategically chosen model CD system, allows to demonstrate that their visible-light transit…

Detailed photoluminescence study of vapor deposited Bi2S3 films of different surface morphology (Phys. Status Solidi B 11/2014)

2014

Dynamic carrier distribution in quantum wells modulated by surface acoustic waves

2001

We have investigated the dynamics of photogenerated carriers under surface acoustic wave (SAW) fields in GaAs quantum wells using spatially and time-resolved photoluminescence (PL). The frequency and phase of the PL oscillations under a SAW yield information about the carrier distribution and the band-gap modulation induced by the SAW. We directly prove that the transport properties of the carriers ultimately control their distribution, storage and, subsequent recombination in the modulated potential.

Feasibility of an induced metabolic bioluminescence imaging technique in ovarian cancer: Results of a pilot study.

2016

e17093Background: The precise determination of energy metabolites is challenged by the heterogeneity of their distribution, their rapid changes after surgical resection and the architectural comple...

Effect of donor substituents on thermally activated delayed fluorescence of diphenylsulfone derivatives

2019

This research was funded by the European Social Fund according to the activity ‘Improvement of researchers’ qualification by implementing world-class R&D projects’ of Measure No. 09.3.3-LMT-K-712. DG acknowledges to the ERDF PostDoc project No. 1.1.1.2/VIAA/1/16/177;

Diphenylsulfone-based hosts for electroluminescent devices: Effect of donor substituents

2020

DG acknowledges to the ERDF PostDoc project No. 1.1.1.2/VIAA/1/16/177. This work was supported by the project of scientific co-operation program between Latvia, Lithuania and Taiwan ?Polymeric Emitters with Controllable Thermally Activated Delayed Fluorescence for Solution-processable OLEDs? (grant No. S-LLT-19-4). Support of the Lithuanian Academy of Sciences is gratefully acknowledged; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART²

Shedding Light on Graphene Quantum Dots: Key Synthetic Strategies, Characterization Tools, and Cutting-Edge Applications

2021

During the last 20 years, the scientific community has shown growing interest towards carbonaceous nanomaterials due to their appealing mechanical, thermal, and optical features, depending on the specific nanoforms. Among these, graphene quantum dots (GQDs) recently emerged as one of the most promising nanomaterials due to their outstanding electrical properties, chemical stability, and intense and tunable photoluminescence, as it is witnessed by a booming number of reported applications, ranging from the biological field to the photovoltaic market. To date, a plethora of synthetic protocols have been investigated to modulate the portfolio of features that GQDs possess and to facilitate the…

Luminescence of ZrO<sub>2</sub> Nanocrystals

2005

The luminescence of nanocrystalline tetragonal and cubic ZrO2 has been investigated. The tetragonal undoped ZrO2 revealed two luminescence bands, at ~2.0 eV and 2.7 eV , but only one band at ~2.7 eV was observed from cubic ZrO2. This luminescence was shown to be intrinsic. The regular zirconium-oxygen complex excited state is suggested as being responsible for intrinsic luminescence.

Transition metal ions luminescence in neutron irradiated magnesium oxide

2010

The results of investigation of the photoluminescence (PL), its excitation and optical absorption of MgO crystals doped with different concentrations of transition metals exposed to fast neutron irradiation and after annealing are presented. It is suggested that the 440 nm photoluminescence band belongs to the complex V−OH-Fe3+ center with tetragonal symmetry, the ~730 nm PL band observed in the irradiated MgO crystals is connected with defects, generated as a result of decay of the complex V−OH-Fe3+ centers. The near infrared luminescence bands in MgO crystals are connected with Fe3+-Fe3+ exchange coupled pairs.