Search results for "quench"
showing 10 items of 306 documents
Effect of surface impurities on downconversion luminescence of Pr3+, Yb3+ activated SrF2 nanoparticles
2020
Abstract Pr3+,Yb3+ activated SrF2 nanoparticles synthesized by low-temperature hydrothermal method were studied. The composition and size of nanoparticles were intentionally changed by controlling synthesis conditions. After structural and morphological characterization, the spectroscopic properties of the nanoparticles were analyzed in the visible and near infrared spectra ranges. The results show correlation between the gradual change of the amount of carboxylate and hydroxyl moieties on the nanoparticle surface, varied by the size nanoparticles and the quenching of the luminescence. The size-related amount of surface quenchers is strongly connected to the decrease of the downconversion e…
Light-responsive hybrid material based on luminescent core-shell quantum dots and steroidal organogel
2016
We report the synthesis of a smart novel hybrid with reversible photoswitchable luminescence properties modulated by light. The combination of a low molecular weight organogelator (LMOG) and CdSe/ZnS core-shell semiconductor nanoparticles capped with trioctylphosphine oxide ligands produces a luminescent, stable and transparent material. Modulation of the luminescence properties was successfully achieved using a diarylethene photochromic compound, with good resistance to fatigue ca. 22 cycles. Interestingly, the morphology of the organogel fibers was preserved in the hybrid, while a partial luminescence quenching of the nanoparticle was observed. This material could have implication for on-…
Insight into the defect-molecule interaction through the molecular-like photoluminescence of SiO2 nanoparticles
2016
Luminescence properties due to surface defects in SiO2 are the main keystone with particles that have nanoscale dimensions, thus motivating their investigation for many emission related applications in the last few decades. A critical issue is the role played by the atmosphere that, by quenching mechanisms, weakens both the efficiency and stability of the defects. A deep knowledge of these factors is mandatory in order to properly limit any detrimental effects and, ultimately, to offer new advantageous possibilities for their exploitation. Up to now, quenching effects have been interpreted as general defect conversion processes due to the difficulty in disentangling the emission kinetics by…
Luminescence of natural α-quartz crystal with aluminum, alkali and noble ions impurities
2019
This work was supported by the Latvian Science Council Grant No lzp-2018/1–0289 .
Platinum( ) and palladium( ) complexes with electron-deficient -diethoxyphosphorylporphyrins: synthesis, structure and tuning of photophysical prope…
2019
The luminescence quenching by O and photodegradation of Pt( ) and Pd( ) phosphorylporphyrins are reported.
The interaction of photoexcited carbon nanodots with metal ions disclosed down to the femtosecond scale
2017
Fluorescent carbon nanodots are a novel family of carbon-based nanoscale materials endowed with an outstanding combination of properties that make them very appealing for applications in nanosensing, photonics, solar energy harvesting and photocatalysis. One of the remarkable properties of carbon dots is their strong sensitivity to the local environment, especially to metal ions in solution. These interactions provide a testing ground for their marked photochemical properties, highlighted by many studies, and frequently driven by charge transfer events. Here we combine several optical techniques, down to femtosecond time resolution, to understand the interplay between carbon nanodots and aq…
Time resolved luminescence spectroscopy of CsPbBr3 single crystal
2020
Abstract The work reports the results of spectroscopic and luminescence-kinetic studies of CsPbBr3 single crystal over 14–300 K temperature range. It is shown that at low temperatures the luminescence spectrum contains three narrow bands at 534, 537, and 541.5 nm exhibiting a fast decay and a broad emission band at ca. 560 nm with long decay. The evolution of the luminescence bands and their temporal characteristics with temperature are discussed from the viewpoint of possible emission mechanisms. The origin of the luminescence bands is discussed in relation with the observed features of their temporal characteristics. The mechanism of luminescence quenching for different emission band is s…
Efficient and Long-Living Light-Emitting Electrochemical Cells
2010
Three new heteroleptic iridium complexes that combine two approaches, one leading to a high stability and the other yielding a high luminescence efficiency, are presented. All complexes contain a phenyl group at the 6-position of the neutral bpy ligand, which holds an additional, increasingly bulky substituent on the 4-position. The phenyl group allows for intramolecular π–π stacking, which renders the complex more stable and yields long-living light-emitting electrochemical cells (LECs). The additional substituent increases the intersite distance between the cations in the film, reducing the quenching of the excitons, and should improve the efficiency of the LECs. Density functional theory…
Fluorescent Carbon Nanodots as Sensors of Toxic Metal Ions and Pesticides
2021
Carbon nanodots (CDs) are a new class of fluorescent carbon-based nanomaterials characterized by a plethora of morphologies and sizes. Among these, we can include two different types of CDs, namely, graphitic and diamond-like. This wide range of structures opens up the possibility to design different CDs, with tunable optical properties accordingly to the synthesis method and precursors used. We prepared two different CDs following a bottom-up approach by thermally induced decomposition of organic precursors (namely, citric acid and urea in different molar ratios), and using purification by Size Exclusion Chromatography (SEC). Obtained CDs were characterized by Raman, absorption and fluores…
Ein neuartiges Verfahren der Sauerstoffdetektion für Medizin, Biologie, Umweltforschung und Biotechnik auf Basis der Lumineszenzlöschung - An Innovat…
1996
For most (aerobic) animal organisms, oxygen is a mandatory and global substrate. The accurate measurement of oxygen is therefore of importance in the fields of medicine, biology, environmental research and biotechnology. The fact that oxygen is not readily soluble in aqueous media makes its detection more difficult. In contrast to the technique of polarography, the use of luminescence quenching by paramagnetic oxygen, does not consume the oxygen. Another problem of oxygen detection in connection with respiration is the need for very short response times. A third problem, which is associated with luminescence itself, is the fading of the dyes, which results in long-term signal instability. T…