Quencher Concentration Research Articles

Predicting the quencher concentration of Er3+‐doped borate glasses via neighboring glassy compounds

AbstractThe quencher concentration (cmax) of rare‐earth (RE3+) doped laser glass plays a pivotal role in achieving high laser gain. However, it is still challenging to quantitatively calculate and predict the cmax of RE3+ ions in laser glass. Here, we propose and demonstrate a robust method in predicting the local environment and the cmax of RE3+ in laser glasses from their neighboring glassy compounds (NGCs). Specifically, the NGCs method capably predicts the local environment of Er3+ ions in borate glasses (B2O3–BaO binary and B2O3–BaO–Li2O ternary glasses). Moreover, the NGCs’ method accurately predicts the cmax of Er2O3 in borate glasses with an error of less than 5% compared to the experimental result, showing the promising prediction capability for the cmax of RE3+ ions. Based on the NGCs method, the cmax database of Er3+‐doped borate glasses is established for efficiently tailoring compositions with desired optical properties. This study offers a rapid and low‐cost route to design novel laser glasses.

Buffer-Dependent Photophysics of 2-Aminopurine: Insights into Fluorescence Quenching and Excited-State Interactions.

2-Aminopurine (2AP) is the most widely used fluorescent nucleobase analogue in DNA and RNA research. Its unique photophysical properties and sensitivity to environmental changes make it a useful tool for understanding nucleic acid dynamics and DNA-protein interactions. We studied the effect of ions present in commonly used buffer solutions on the excited-state photophysical properties of 2AP. Fluorescence quenching was negligible for tris(hydroxymethyl)aminomethane (TRIS), but significant for phosphate, carbonate, 3-(N-morpholino) propanesulfonic acid (MOPS), and 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) buffers. Results indicate that the two tautomers of 2AP (7H, 9H) are quenched by phosphate ions to different extents. Quenching by the H2PO4- ion is more pronounced for the 7H tautomer, while the opposite is true for the HPO42- ion. For phosphate ions, the results of the time-resolved fluorescence study cannot be explained using a simple collisional quenching mechanism. Instead, results are consistent with transient interactions between 2AP and the phosphate ions. We postulate that excited-state interactions between the 2AP tautomers and an H-bond acceptor (phosphate and carbonate) result in significant quenching of the singlet-excited state of 2AP. Such interactions manifest in biexponential fluorescence intensity decays with pre-exponential factors that vary with quencher concentration, and downward curvatures of the Stern-Volmer plots.

Nanomolar Protein Thermal Profiling with Modified Cyanine Dyes.

Protein properties and interactions have been widely investigated by using external labels. However, the micromolar sensitivity of the current dyes limits their applicability due to the high material consumption and assay cost. In response to this challenge, we synthesized a series of cyanine5 (Cy5) dye-based quencher molecules to develop an external dye technique to probe proteins at the nanomolar protein level in a high-throughput one-step assay format. Several families of Cy5 dye-based quenchers with ring and/or side-chain modifications were designed and synthesized by introducing organic small molecules or peptides. Our results showed that steric hindrance and electrostatic interactions are more important than hydrophobicity in the interaction between the luminescent negatively charged europium-chelate-labeled peptide (Eu-probe) and the quencher molecules. The presence of substituents on the quencher indolenine rings reduces their quenching property, whereas the increased positive charge on the indolenine side chain improved the interaction between the quenchers and the luminescent compound. The designed quencher structures entirely altered the dynamics of the Eu-probe (protein-probe) for studying protein stability and interactions, as we were able to reduce the quencher concentration 100-fold. Moreover, the new quencher molecules allowed us to conduct the experiments using neutral buffer conditions, known as the peptide-probe assay. These improvements enabled us to apply the method in a one-step format for nanomolar protein-ligand interaction and protein profiling studies instead of the previously developed two-step protocol. These improvements provide a faster and simpler method with lower material consumption.

Fast quenching of manganese emission in ZnS:Mn2+ nanoparticles

The Monte Carlo method was used to calculate static dipole-dipole (Förster) quenching of manganese luminescence in nanoparticles of various sizes in the semi-magnetic semiconductor Zn0.99Mn0.01S. For the first time, the quenching is stated to play insignificant role in sub-nanosecond huge drop of the emission transient. Parameter values of Förster's quenching stage of luminescence transient – characteristic quenching distance, concentration of quenchers, average quenching rate, probability of quencher absence in a nanoparticle, quenching amplitude, etc. − were found from a comparison of calculations with experimental transients. The values are dependent on nanoparticle growth technology. Calculations show that luminescence efficiency increases with a decrease in actual size of nanoparticles, while probability of obtaining nanoparticles without quenchers asymptotically approaches unity at smaller size. The latter condition together with agglomeration absence and greater intrinsic time decay are the main conditions for higher efficiency of manganese luminescence in ZnS:Mn2+ nanoparticles. The analysis of previous researches and our experiments showed that the most fast transient component originated from ZnS host.

Hydrogen-Mediated Photoelectrocatalysis with Nickel-Modified Poly(Heptazine Imides)

Polymeric carbon nitrides (C3N4) are photochemically active organic semiconductors that can be produced in a wide range of structural types. Here, a poly-(heptazine imide) containing nickel single atoms (Ni-PHI) is employed for photochemical hydrogen production and is compared to the non-nickel-doped semiconductor. Film deposits are formed on a platinum disk electrode (to detect hydrogen) and a coating of the molecularly rigid polymer of intrinsic microporosity PIM-1 is applied to (i) mechanically stabilize the photo-catalyst film without impeding photocatalysis and (ii) assist in the interfacial hydrogen capture/oxygen suppression process. In the presence of hole quenchers such as methanol or ethanol, anodic photocurrents linked to hydrogen production/oxidation are observed. A comparison with an experiment on glassy carbon confirms the formation of interfacial hydrogen as a mediator. The effects of hole quencher concentration are evaluated. The system Pt/Ni-PHI/PIM-1 is employed in a single-compartment photo-fuel cell.Graphical

Experimentally-measured rate parameters for vibrational quenching of CO by N2

Carbon monoxide is a trace species in Titan's atmosphere that is not consistently found in local thermodynamic equilibrium at all altitudes. Understanding how CO exchanges energy with atmospheric collision partners is therefore crucial for accurate atmospheric modelling. Particularly significant could be vibrational relaxation of CO by nitrogen due to the high collision frequency in Titan's N2-based atmosphere. Some CO(v)-N2 rate coefficients have never been experimentally measured while others were measured decades ago in low-precision experiments. In this work, we present precise experimental measurements of the rate coefficients for the quenching of CO(v = 1,2) by N2. To perform the experiment, an equilibrium mixture of CO, N2, O3, and bath gases was subjected to a temperature-jump, creating a small amount of vibrationally-excited CO. Transient diode laser absorption spectroscopy was then used to observe the evolving vibrational state populations as a function of time. The rate coefficients of interest were found by measuring quenching rate as a function of quencher concentrations. The rate coefficient for quenching of CO(v = 1) by N2 was measured to be k = (1.3 ± 0.2) x 10−14 cm3 molecule−1 s−1 and the rate coefficient for quenching of CO(v = 2) by N2 was measured to be k = (2.1 ± 0.5) x 10−13 cm3 molecule−1 s−1 at 315 K.

Protein – Metal ion Interaction: A Spectroscopic Study

This study reports on the spectroscopic interaction studies of mercuric chloride LYZ. The quencher concentration was maintained in the range of 0–6.25 µM. At the studied concentration range (10-6 M), LYZ did not have any variation in fluorescence intensity. Increase in LYZ concentration to 10-3 M showed a decrease in the fluorescence intensity due to the involvement of nucleophilic functional group. The fluorescence of LYZ was quenched to a large extent depending on the protein solution pH (2.2, 4.5, and 7.4).At all the studied pH, emission spectra showed blue shift. The onset and the shift varied with solution pH. Stern-Volmer analysis showed a three stage transition At pH 7.4, the presence of HgCl2 did not have much influence on the amide bands. But at pH 4.5, the amide I band showed a shift to lower wavenumber These confirmed that the quenching takes place through both static and energy transfer processes.

Photostability Study of Avobenzone in Commercial Sunscreen SPF 45 with Additional SolaStay® Quencher Upon Sun Exposure

Avobenzone combined with various concentrations of Ethylhexyl Methoxycrylene (SolaStay® S1 quenchers) aims to see photostability studies. So that in this study tested the effect of SolaStay® S1 quenchers, SolaStay® quencher concentration, and the effect of irradiation time with sunlight on the photostability of avobenzone in commercial sunscreen formulations SPF 45. As well as determining the best SPF 45 commercial sunscreen formulations with the addition of Quenchers. The method used in this study is the spectroscopic method which uses two UV-VIS and HPLC spectrophotometer analyser. Based on the research data obtained in the presence of a quencher showed good photostability to avobenzone at certain quencher concentrations. Compared to F0, the effect of the addition of the quencher was very good, as seen from the relatively low decrease in the photodegradation rate compared to without the addition of the quencher. Viewed from the overall results, FSOL1 with the addition of 3% SolaStay® is the best SPF 45 sunscreen formulation of all formulations. This is seen from the small photodegradation results every time and the effect of skin effects was low. Keywords: Avobenzone, Quencher, Photostability, Photodegradation, SolaStay®, Sunscreen

Study of Photophysical Properties of Thiol-capped CdS Quantum Dots Doped with Gold Nanoparticles.

In this study, CdS quantum dots (QDs) capped with benzyl mercaptan (thiol) were prepared by microwave irradiation technique. The shape, size, morphology, and spectral properties of thiol-capped CdS QDs were characterized with transmission electron microscopy (TEM), scanning electron microscopy (SEM), UV-vis absorption, and photoluminescence (PL) spectrometry. The photophysical properties of synthesized thiol-capped CdS QDs in the presence of different amounts of gold nanoparticles (AuNPs) have been investigated, exhibiting strong PL quenching. The amount of fluorescence quenching was found to be dependent on the concentration of metal nanoparticles. A Stern-Volmer kinetics model was used to analyze the observed quenching mechanism as a function of the quencher (AuNPs) concentration. The Stern-Volmer plot along with the absorption spectra of thiol-capped CdS QDs in the absence and presence of AuNPs suggest the dynamic (collision) nature of quenching and rule out the possibility of static quenching. The energy transfers from QDs to Au NPs, and hence the quenching of QDs emissions provides new insight into designing novel optical-based materials and the development of FRET-based bionanosensors and phototherapeutic applications.

Orange Pomace-Derived Fluorescent Carbon Quantum Dots: Detection of Dual Analytes in the Nanomolar Range.

Green-emissive carbon quantum dots (CQDs) with exclusive chemosensing aspects were synthesized from orange pomace as a biomass-based precursor via a facile microwave method without using any chemicals. The synthesis of highly fluorescent CQDs with inherent nitrogen was confirmed through X-ray diffraction, X-ray photoelectron, Fourier transform infrared, Raman, and transmission electron microscopic techniques. The average size of the synthesized CQDs was found to be 7.5 nm. These fabricated CQDs displayed excellent photostability, water solubility, and outstanding fluorescent quantum yield, i.e., 54.26%. The synthesized CQDs showed promising results for the detection of Cr6+ ions and 4-nitrophenol (4-NP). The sensitivity of CQDs toward Cr6+ and 4-NP was found up to the nanomolar range with the limit of detection values of 59.6 and 14 nM, respectively. Several analytical performances were thoroughly studied for high precision of dual analytes of the proposed nanosensor. Various photophysical parameters of CQDs (quenching efficiency, binding constant, etc.) were analyzed in the presence of dual analytes to gain more insights into the sensing mechanism. The synthesized CQDs exhibited fluorescence quenching toward incrementing the quencher concentration, which was rationalized by the inner filter effect through time-correlated single-photon counting measurements. The CQDs fabricated in the current work exhibited a lower detection limit and a wide linear range through the simple, eco-friendly, and rapid detection of Cr6+ and 4-NP ions. To evaluate the feasibility of the detection approach, real sample analysis was conducted, demonstrating satisfactory recovery rates and relative standard deviations toward the developed probes. This research paves the way for developing CQDs with superior characteristics utilizing orange pomace (biowaste precursor).

Tuning the triplet population of arylselanyl-BODIPY photosensitizers through substituents engineering for triplet-triplet annihilation photon upconversion with perylene

Organic triplet-triplet annihilation photon upconversion (TTA-UC) systems have attracted considerable attention owing to their promising applicability in solar energy harvesting, optoelectronic devices, photocatalysts, and bio-imaging. In this study, a series of BODIPYs prepared by incorporating substituted/ unsubstituted arylselenium groups, 1 (R = H), 2 (R = OMe), and 3 (R = F), were evaluated as triplet photosensitizers for TTA-UC. Direct Se-C bond formation on the BODIPY core provided a facile intersystem crossing (ISC) channel from the excited singlet state to the metastable triplet state, being the most effective in 2, as inferred from the singlet oxygen generation experiments, possibly because of the n-electron arising from the OMe group. The UC behavior of systems comprising the sensitizers and perylene as the acceptor in deaerated toluene was investigated using a 524 nm-wavelength laser to detect upconverted emission at 449 nm; thus, the UC yield decreased in the order of 21% for 3 > 16% for 2 > 12% for 1. This trend is consistent with the Stern-Volmer constants calculated from the quenched triplet state lifetimes of the sensitizers as a function of the concentration of the perylene quencher. This suggests that the UC efficiency was mainly governed by the intermolecular triplet-triplet energy transfer (TTET) process between arylselanyl-BODIPY photosensitizers and the perylene acceptor. This result was rationalized by the efficient population of the long-lived triplet excited state of the sensitizer, which is advantageous for diffusion-controlled TTA-UC behavior.

Sudan Black B treatment for reducing autofluorescence in human glioma tissue and improving fluorescent signals of bacterial LPS staining.

The 3D visualization based on tissue clearing technology allows us to have a deeper understanding of the 3D spatial information of deep molecules in the tissue. Tissue clearing and bacterial labeling methods have been used for in situ 3D microbiota imaging, and we have developed a pipeline for 3D visualization of in situ microbiota in human gliomas. Anti-LPS antibodies are appropriate to label and characterize bacteria in situ within tumors. However, autofluorescence (AF) is common in biological tissues, especially in brain tissues filled with lipofuscin-like (LF) substances. This natural fluorescent signal is usually considered to be a problem because it affects the 3D visualization of fluorescent signals in bacterial LPS staining. Here, we used Sudan Black B (SBB) to mask the AF of human glioma tissue and explored in detail the optimal quencher concentration, which allows 3D visualization of intratumoral bacteria to reduce AF and maintain the intensity of intratumoral bacteria-specific LPS fluorescent signals.

Electronic Energy Migration in Microtubules.

The repeating arrangement of tubulin dimers confers great mechanical strength to microtubules, which are used as scaffolds for intracellular macromolecular transport in cells and exploited in biohybrid devices. The crystalline order in a microtubule, with lattice constants short enough to allow energy transfer between amino acid chromophores, is similar to synthetic structures designed for light harvesting. After photoexcitation, can these amino acid chromophores transfer excitation energy along the microtubule like a natural or artificial light-harvesting system? Here, we use tryptophan autofluorescence lifetimes to probe energy hopping between aromatic residues in tubulin and microtubules. By studying how the quencher concentration alters tryptophan autofluorescence lifetimes, we demonstrate that electronic energy can diffuse over 6.6 nm in microtubules. We discover that while diffusion lengths are influenced by tubulin polymerization state (free tubulin versus tubulin in the microtubule lattice), they are not significantly altered by the average number of protofilaments (13 versus 14). We also demonstrate that the presence of the anesthetics etomidate and isoflurane reduce exciton diffusion. Energy transport as explained by conventional Förster theory (accommodating for interactions between tryptophan and tyrosine residues) does not sufficiently explain our observations. Our studies indicate that microtubules are, unexpectedly, effective light harvesters.

Polyaniline and Copper based nanometal surface energy transfer probe for efficient turn-on bovine serum albumin sensing

In the present study, we have investigated the energy transfer mechanism owing to the interaction between colloidal Cu nanorods and polyaniline as a function of varying amounts of Cu. XRD, FESEM, and HRTEM examined the sample's structural and morphological characteristics, and the optical characteristics were explored by UV–Vis absorbance, photoluminescence, and time-resolved photoluminescence measurements. The steady-state photoluminescence exhibits quenching behaviour and time-resolved photoluminescence measurements exhibit lifetime reduction in accordance with the nanometal surface energy transfer theory, following 1/d4 distance dependency from polyaniline to the surface of Cu. With the increasing quencher (Cu) concentration, quenching efficiency and rate of energy transfer increase, whereas a decrease in the distance between Cu and polyaniline has been observed. Our research attempts to see if such nanohybrid comprising polymer–noble metal nanoparticles could be used as sensitive biosensors. Hence, the nanohybrid system consisting of Cu and polyaniline has been employed in the potential bovine-serum albumin sensing, which showed an excellent detection limit of 15.3 nM. The Cu- PANI pair also exhibits excellent selectivity amidst the other possible interfering compounds.

Interaction of the birch-bark terpenoids with human and bovine serum albumins

Abstract Interactions between pentacyclic triterpenes isolated from white birch (Betula pendula Roth.) bark samples from Northeast Bulgaria and bovine serum albumin or human serum albumin were investigated using fluorescence techniques. The experimental results show the formation of complexes between the isolated triterpenes with serum albumins. Quenching of the intrinsic fluorescence of human serum albumins was monitored by emission spectra of varied quencher concentration solutions. By analysing the fluorescence spectra and fluorescence intensity, some parameters of the serum albumins - quencher interaction were determined to evaluate the type of quenching. An extract containing the isolated triterpenes formed complexes with both bovine serum albumin and human serum albumin, leading to quenching the fluorescence of both albumins by a combined quenching mechanism.

Plasmonic Surface of Metallic Gold and Silver Nanoparticles Induced Fluorescence Quenching of Meso-Terakis (4-Sulfonatophenyl) Porphyrin (TPPS) and Theoretical–Experimental Comparable

Colloidal metallic nanoparticles have attracted a lot of interest in the last two decades owing to their simple synthesis and fascinating optical properties. In this manuscript, a study of the effect of both gold nanoparticles (Au NPs) and silver nanoparticles (Ag NPs) on the fluorescence emission (FE) of TPPS has been investigated utilizing steady-state fluorescence spectroscopy and UV–Vis spectrophotometry. From the observed electronic absorption spectra, there is no evidence of the ground state interaction between metallic Au NPs or Ag NPs with TPPS. On the other side, the FE spectra of TPPS have been quenched by both Ag and Au NPs. Via applying quenching calculations, Ag NPs showed only traditional static fluorescence quenching of TPPS with linear Stern–Volmer (SV) plots. On the contrary, quenching of TPPS emission by Au NPs shows composed models. One model is the sphere of action static quenching model that prevails at high quencher concentrations leading to non-linear SV plots with positive deviation. However, at low Au NPs concentrations, traditional dynamic quenching occurs with linear SV plots. The quantum calculations for TPPS structure have been obtained using Gaussian 09 software: in which the TPPS optimized molecular structure was achieved using DFT/B3LYP/6-311G (d) in a gaseous state. Also, the calculated electronic absorption spectra for the same molecule in water as a solvent are obtained using TD/M06/6-311G + + (2d, 2p). Furthermore, the theoretical and experimental results comparable to UV–Vis spectra have been investigated.

FLUORESCENT STUDIES OF LYSOZYME IMMOBILISED CHITOSAN/POLYSTYRENE SULPHONATE MULTILAYER MEMBRANES

The fluorescence emission properties of lysozyme immobilized at selected pH 5, 8.8 and 10.6 on chitosan/polystyrene sulfonate (CHI/PSS) multilayer membranes were investigated. The tryptophanyl fluorescence was selectively excited at 290 nm. The emission maximum and fluorescence intensity were found to be dependent on the pH of lysozyme solution. The fluorescence intensity was highest at pH 8.8. A slight red shift was observed as the pH changes from 5 to 10.6. Quenching of lysozyme fluorescence by iodide was used to study the effect of pH on the adsorption pattern of lysozyme to multilayers. For lysozyme (pH 10.6) adsorbed membrane, the fluorescence intensity was found to decrease progressively with quencher concentration. Almost complete quenching of fluorescence was observed when the iodide concentration was 1 M suggesting full accessibility of quencher to tryptophanyl residues. A linear Perrin plot was obtained suggesting a static mechanism for quenching under the experimental conditions. Fluorescence quenching studies were also carried out with lysozyme (pH 5) adsorbed membranes prepared by normal adsorption methods and also under ultrafiltration conditions. The quenching efficiency was different for the two sets of membranes. The fluorescence quenching studies reveals that adsorption pattern of proteins on multilayers strongly depend on pH and immobilization method.

Using Lifetime and Quenching Rate Constant to Determine Optimal Quencher Concentration.

ABSTRACT Excited state quenching is a key step in photochemical reactions that involve energy or electron transfer. High reaction quantum yields require sufficiently high concentrations of a quencher to ensure efficient quenching. The determination of quencher concentrations is typically done through trial and error. Using kinetic modeling, however, a simple relationship was developed that predicts the concentration of quencher necessary to quench 90% of excited states, using only the photosensitizer lifetime and the rate constant for quenching as inputs. Comparison of the predicted quencher concentrations and quencher concentrations used in photoredox reactions featuring acridinium-based photocatalysts reveals that the majority of reactions used quencher concentrations significantly below the predicted concentration. This suggests that these reactions exhibit low quantum yields, requiring long reaction times and/or intense light sources.

EFFECT OF HYDROGEN BONDING ON FLUORESCENCE QUENCHING OF QUINOLIN-8-OL - ANALYSIS USING NEGATIVE STERN-VOLMER PLOTS

Photophysics of fluorescent organic compounds give a better knowledge of the excited state properties which in turn will help in the design of newer molecules and understanding their performance in specific applications. Here we present the fluorescence quenching study of a Quinolin-8-ol (QO) in toluene and butanol solvents by steady state fluorescence measurements. Anilineis the quencher. Negative deviation in the Stern – Volmer (S-V) plots has been observed with moderate quencher concentration. The downward curvature in the S-V plot is interpreted in terms of existence of different conformers of the solute in the ground state. The formation of intermolecular and intra molecular hydrogen bonding is found to be responsible for the conformational changes in the ground state of the solute. Quenching data is analyzed by modified Stern-Volmer equation or Lehrer equation.

Overlooked Factors Required for Electrolyte Solvents in Li-O2 Batteries: Capabilities of Quenching 1 O2 and Forming Highly-Decomposable Li2 O2.

Although sufficient tolerance against attack by superoxide radicals (O2 - ) has been mainly recognized as an important property for Li-O2 battery (LOB) electrolytes, recent evidence has revealed that other critical factors also govern the cyclability, prompting a reconsideration of the basic design guidelines of LOB electrolytes. Here, we found that LOBs equipped with a N,N-dimethylacetamide (DMA)-based electrolyte exhibited better cyclability compared with other standard LOB electrolytes. This superior cyclability is attributable to the capabilities of quenching 1 O2 and forming highly decomposable Li2 O2 . The 1 O2 quenching capability is equivalent to that of a tetraglyme-based electrolyte containing a several millimolar concentration of a typical chemical quencher. Based on these overlooked factors, the DMA-based electrolyte led to superior cyclability despite its lower O2 - tolerance. Thus, the present work provides a novel design guideline for the development of LOB electrolytes.