Presence Of Quenchers Research Articles

Efficient catalytic activity of NiO and CeO2 films in benzoic acid removal using ozone.

This research focuses on the synthesis of NiO and CeO2 thin films using spray pyrolysis for the removal of benzoic acid using ozone as an oxidant. The results indicate that the addition of CeO2 films significantly enhances the mineralization of benzoic acid, achieving a rate of over 80% as the CeO2 films react with ozone to produce strong oxidant species, such as hydroxyl radicals, superoxide radicals, and singlet oxygen as demonstrated by the presence of quenchers in the reaction system. The difference in catalytic activity between NiO and CeO2 films was analyzed via XPS technique; specifically, hydroxyl oxygen groups in the CeO2 film were greater in number than those in the NiO film, thus benefitting catalytic oxidation as these species are considered active oxidation sites. The effects of nozzle-substrate distances and deposition time during the synthesis of the films on benzoic acid removal efficiency were also explored. Based on XRD characterization, it was established that the NiO and CeO2 films were polycrystalline with a cubic structure. NiO spherical nanoparticles were well-distributed on the substrate surface, while some pin holes and overgrown clusters were observed in the CeO2 films according to the SEM results. The stability of the CeO2 films after five consecutive cycles confirms their reusability. The retrieval of films is easy because it does not require additional separation methods, unlike the catalyst in powder form. The obtained results indicate that the CeO2 films have potential application in pollutant removal from water through catalytic ozonation.

Probing the Visible Light‐Driven Geometrical Isomerization of 4‐Arylbut‐3‐ene‐2‐amines

AbstractA series of thirteen 4‐arylbut‐3‐ene‐2‐amines were prepared and subjected to photosensitization experiments to interrogate their photostationary state (PS) composition of geometrical olefin isomers (E and Z). The amine PS compositions were found to depend on arene structure and temperature, while being largely independent of nitrogen substitution, solvent, or presence of triplet‐quenching oxygen. Photonic efficiency of isomerization (ζp) was found to depend on amine structure, solvent choice, and presence of quencher. With the proper choice of conditions, ζp was able to closely approach the theoretical maximum value of 0.5.

Metal plasmon-enhanced lanthanide fluorescent nanoparticles for monitoring aqueous copper ions

Lanthanide-doped nanomaterials displaying intense, explicit, and long-lasting photoluminescence (PL) have gained much attention in sensing and imaging applications. In this work, europium complex Eu(dibenzoylmethane)3(1,10-phenanthroline) was integrated into core-shell magnetoplasmonic nanoparticles (Ag@Fe3O4 MagPlas NPs), forming a photoluminescent MagPlas nanostructure with uniform morphology, sharp PL emission profile, and distinct magnetic response. The Eu-doped MagPlas NPs (Eu-MagPs) with Ag-core exhibited an enhancement of PL intensity and lifetime compared to the non-plasmonic counterpart, owing to the metal plasmon-induced fluorescence enhancement. Moreover, the quenching phenomenon of the Eu-MagP probe was utilized as a platform for active quantification of metal ion concentration, exclusively Cu2+, in aqueous samples. The luminescence intensity from the Eu-doped MagPlas NP was proportionally quenched by Cu2+ in the working range of 0–2 ppm with negligible influences of other common cations and anions. Static quenching was investigated as the main mechanism for selective detection, in which the presence of quenchers did not affect the luminescent lifetime of the hybrid nanostructure. Moreover, Eu-MagPs were integrated into polyacrylamide hydrogels with enhanced customizability toward the varied amounts of Cu2+. This fluorescent MagPlas structure, therefore, can be utilized as versatile, waste-free, fully recoverable testing assays or chemical sensors for on-site environmental analysis, and water quality control.

Probing nanometal surface energy transfer between nanocopper and MoS2 for glutathione sensing

Cu nanoparticles and 2D-MoS2 nanosheets have been synthesised and the morphology of the prepared samples has been characterised using high-resolution transmission electron microscopy and field emission scanning electron microscopy. Steady-state fluorescence studies exhibit quenching of fluorescence intensity upon the addition of quencher in varying amounts. Time-resolved fluorescence studies show a reduction of fluorescence lifetime in the presence of quencher. A thorough investigation of energy transfer between MoS2 and copper nanoparticles has been accomplished using steady-state and time-resolved fluorescence studies. The results are more consistent with the nanometal surface energy transfer (NSET) theory, which follows a 1/d 4 distance dependence than the Förster resonance energy transfer theory exhibiting 1/d 6 distance dependence. For the MoS2–Cu pair, the NSET efficiency, the proximal distance between donor–acceptor pairs and the rate of energy transfer has been explored. Energy transfer-based fluorescent biosensors have been regarded as potential candidates in biosensing applications. Glutathione, an endogenous tripeptide compound, plays a vital role as an antioxidant in the human body. Irregular glutathione levels have been linked to several adverse illnesses. Henceforth, detection of glutathione levels is indispensable. The Cu–MoS2 pair was used for glutathione sensing in nanomolar concentration (nM), which demonstrated a turn-off sensing behaviour.

Assessment of solar-assisted electrooxidation of bisphenol AF and bisphenol A on boron-doped diamond electrodes

Bisphenol (BP) analogues in wastewater effluent and groundwater pose a potential threat to human health due to their ability to disrupt steroidogenesis. A new solar-assisted electrochemical process (SECP) was developed and evaluated for the degradation of BP analogues. The effects of quenchers, current density, initial pH, supporting electrolyte, and aqueous matrix on the removal kinetics of bisphenol AF (BPAF) and bisphenol A (BPA) were investigated. The kinetic constants of BPAF, BPA, and bisphenol S (BPS) in the SECP with irradiation intensity of 500 mW cm−2 were 0.017 ± 0.002 min−1, 0.022 ± 0.002 min−1, and 0.012 ± 0.001 min−1, respectively. The changes in the degradation rates of BPAF, BPA, and BPS in the presence of quenchers indicated the relative contribution of hydroxyl radical (●OH) oxidation, anodic electrolysis, and singlet (1O2) oxygenation in the degradation of BPs in the SECP. The enhanced rate of generation of ●OH and 1O2 was observed in the SECP compared with those in the conventional electrochemical system. The identification of the transformation products (TPs) of BPAF demonstrated that hydroxylation, ring cleavage, β-scission, and defluorination were the major processes during the oxidation in the SECP. The conversion to fluoride ions (76%) and mineralization of total organic carbon (72%) in the SECP indicated further degradation of TPs. The results from this study improved our understanding of the degradation of BP analogues in the electrooxidation irradiated by solar light and help to establish the application potential of the SECP for the effective degradation of emerging contaminants in wastewater.

Effect of anions on fluorescence quenching of Rhodamine B–Pluronic F127 complex

ABSTRACTPluronic F127 has been widely used for controlled release of drugs. The aggregation behaviour and solubilisation properties of pluronics can be affected by addition of salts. This work reports the studies on the changes in micellar assemblies of F127 due to addition of inorganic anions (KCl, KBr, KI and KNO3) in Pluronic F127–Rhodamine B system. This was monitored by using UV–vis spectroscopy, fluorescence spectroscopy and fluorescence lifetime spectra. The change in fluorescence spectrum due to the presence of quenchers was attributed to the change in microenvironment of the micelle. The quenching depends on the ability of the fluorophore to transfer energy to the quencher. Out of all four salts, KI was observed to be the best quencher for the above system.

Polariton-Assisted Singlet Fission in Acene Aggregates

Singlet fission is an important candidate to increase energy conversion efficiency in organic photovoltaics by providing a pathway to increase the quantum yield of excitons per photon absorbed in select materials. We investigate the dependence of exciton quantum yield for acenes in the strong light-matter interaction (polariton) regime, where the materials are embedded in optical microcavities. Starting from an open-quantum-systems approach, we build a kinetic model for time-evolution of species of interest in the presence of singlet quenchers and show that polaritons can decrease or increase exciton quantum yields compared to the cavity-free case. In particular, we find that hexacene, under the conditions of our model, can feature a higher yield than cavity-free pentacene when assisted by polaritonic effects. Similarly, we show that pentacene yield can be increased when assisted by polariton states. Finally, we address how various relaxation processes between bright and dark states in lossy microcavities affect polariton photochemistry. Our results also provide insights on how to choose microcavities to enhance similarly related chemical processes.

A Multiscale Model of Photosynthesis

Photosynthetic light harvesting, the conversion of photons into chemical energy, is responsible for all food and atmospheric oxygen on earth. Understanding the design principles underpinning light harvesting from the atomic to cellular length scales offers the potential of rationally engineering increased photosynthetic yield. The challenge, however, is bridging the large range of length and timescales involved. We have developed a model of excitation energy transfer and light harvesting that accurately spans from isolated pigment-protein complexes to the 100 nm length scale of the photosystem II (PSII) enriched portion of the thylakoid membrane. We explore the emergent features of PSII light harvesting in the presence of quenchers and demonstrate that the phenomenological models used historically fail to capture essential features of regulation by non-photochemical quenching, a process important for plant fitness. This work connects the structure of pigment-protein complexes to the resulting properties of photosystem II light harvesting in vivo, providing a first step towards a predictive model of photosynthesis.

A Comparative Study on “Turn‐off” Fluorimetric Nitro Aromatic Detection Using a Class of Dinulear Zinc (II) Schiff Base Complexes

AbstractFour “end‐off” compartmental ligands 2,6‐bis((E)‐((2‐(dimethylamino)ethyl)imino)methyl)‐4‐R‐phenol, where R= methyl/ isopropyl/ tertiary butyl/ chloro for HL1 – HL4 respectively, have been designed and four complexes of zinc(II) have been synthesized and structurally characterized with the aim to apply them as nitro aromatic detector by utilizing their fluorescent behavior. All the four complexes are found to be highly fluorescent in acetonitrile medium and their emission intensities are found to quench in presence of four nitro aromatics such as 2,6‐dinitrotoluene (2,6‐DNT), 4‐nitrobenzoic acid (4‐NBA), 1,3‐dinitrobenzene (1,3‐DNB), and 4‐nitrotoluene (4‐NT) with the complex 4 having the highest quenching capability. Fluorescence sensing ability and anti interference ability were done using complex 4 and 4‐NBA to establish their exclusive detection property. Stern‐Volmer experiments were performed to evaluate the quenching constants. Finally, photo physical experiments such as temperature dependent fluorescence titration study and TCSPC experiment in presence of quencher are carried out to prove the quenching mode as a dynamic.

Fluorescent silica nanoparticles with chemically reactive surface: Controlling spatial distribution in one-step synthesis

The encapsulation of fluorescent dyes inside silica nanoparticles is advantageous to improve their quality as probes. Inside the particle, the fluorophore is protected from the external conditions and its main emission parameters remains unchanged even in the presence of quenchers. On the other hand, the amine-functionalized nanoparticle surface enables a wide range of applications, as amino groups could be easily linked with different biomolecules for targeting purposes. This kind of nanoparticle is regularly synthesized by methods that employ templates, additional nanoparticle formation or multiple pathway process. However, a one-step synthesis will be an efficient approach in this sort of bifunctional hybrid nanoparticles.A co-condensation sol-gel synthesis of hybrid fluorescent silica nanoparticle where developed. The chemical and morphological characterization of the particles where investigated by DRIFTS, XPS, SEM and SAXS. The nanoparticle fluorescent properties were also assessed by excitation-emission matrices and time resolved experiments.We have developed a one-pot synthesis method that enables the simultaneous incorporation of functionalities, the fluorescent molecule and the amino group, by controlling co-condensation process. An exhaustive characterization allows the definition of the spatial distribution of the fluorescent probe, fluorescein isothiocyanate, inside the particle and reactive amino groups on the surface of the nanoparticle with diameter about 100nm.

Thermal quenching of fluorescence in condensed media

Abstract Environmental factors strongly affect the features of the electromagnetic spectra of fluorescent compounds hosted by material media. The shape of the absorption and emission peaks, their characteristic asymmetry and breadth, the Stokes shift and quantum yield are generally temperature dependent and heavily influenced by both the local and extended physical properties of the medium. The theoretical method used before to obtain the lineshape function is extended here to other terms of the interaction energy between the optically sensitive orbital and the hosting medium, which become significant when the spectral feature is broad. An analytical expression for the temperature dependent decay rate by non-radiative processes is obtained by this way. Comparison with experiment on thermal quenching gives agreement within the experimental uncertainty. The solvent polarity, its protic or aprotic character, hydrogen bonds, proximity effects and presence of quenchers are expected to enter through the coupling constants of the corresponding energy terms.

Synthesis, characterization and photoinduced charge separation of carbon nanohorn-oligothienylenevinylene hybrids.

The covalent coupling between oligo(thienylenevinylenes) (nTVs) and carbon nanohorns (CNHs) has been investigated. The resulting nanohybrids have been characterized by a combination of several techniques, including thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HR-TEM) and Raman spectroscopy. The photophysical properties of the new hybrids were investigated by steady-state and time-resolved spectroscopic techniques. A transient signal characterized by two kinetic regimes, one short decay within 0.5 μs corresponding to around 80% of the total signal and another much longer-lived decay of 10 μs, has been detected. The transient absorption spectra are characterized by a continuous absorption that increases in intensity towards shorter wavelengths, with a maximum at 430 nm. These transient signals have been assigned to the charge-separated state delocalized on CNHs based on the quenching behavior and by comparison with the photophysical properties of nTV in the absence and presence of quenchers. The photophysical behavior of covalent nTV-CNH conjugates with microsecond transients due to electrons and holes on CNHs contrasts with the absence of any transient for analogous nTV-C60 conjugates, for which charge separation was not observed at timescales longer than nanoseconds. The photochemical behavior of CNHs is believed to derive from the amphoteric (electron donor and acceptor) properties of CNHs and from the larger number of carbon atoms (efficient delocalization) in CNHs compared with C60.

Radionuclide, scintillation cocktail and chemical/color quench influence on discriminator setting in gross alpha/beta measurements by LSC

Gross alpha/beta measurements in drinking waters enable radiochemical composition analysis in environmental studies providing efficient screening method that can indicate whether water contains elevated levels of any radionuclide. Routine gross alpha/beta activity monitoring in drinking waters has been carried out for a few years in laboratory for low-level radioactivity measurements in Novi Sad according to ASTM method, performing measurements on liquid scintillation counter Quantulus 1220 which can simultaneously generate alpha/beta spectra of samples by Pulse Shape Analysis (PSA circuit). In this paper, PSA discriminator impact was investigated to ensure obtaining of accurate and reliable alpha/beta activities. One novelty of presented work is PSA parameter setup with two combinations of radionuclides (241Am, 226Ra and 90Sr/90Y) with varying activity concentrations. Performed experiments also make contribution to investigations on the manner in which chemical and color quench affect optimal PSA parameter setting and further on, their altogether influence on gross alpha/beta activity measurements. Nitromethane, 15.8 M nitric acid and water, as well as yellow and yellow-orange dye, were used as quenching agents in order to test PSA/interference factor behavior in the presence of quenchers with different quenching strengths. Variation of PSA setting in quenched samples with two different commercially available cocktails (Ultima Gold LLT and OptiPhase HiSafe 3) was also tested. Lastly, application i.e. assessment of obtained PSA-SQP(E) correlation on the obtained results of activity concentrations of few artesian well water samples and colored spiked samples, based on the measured SQP(E) value of samples, has been demonstrated.

Structural, Electrochemical, DNA Binding and Cleavage Properties of Nickel(II) Complex [Ni(H2biim)2(H2O)2]2+of 2,2'-Biimidazole

A nickel(II) complex <TEX>$[Ni(H_2biim)_2(H_2O)_2</TEX><TEX>]</TEX><TEX>(ClO_4)_2{\cdot}H_2O$</TEX> (1) of biimidazole ligand has been synthesized and characterized (Where <TEX>$H_2biim$</TEX> = 2,2'-biimidazole). The single crystal X-ray diffraction of the complex shows a dimeric structure with six coordinated psudo-octahedral geometry. The cyclic voltammograms of complex exhibited one quasireversible reduction wave (<TEX>$E_{pc}=-0.61V$</TEX>) and an irreversible oxidation wave (<TEX>$E_{pa}=1.28V$</TEX>) in DMF solution. The interaction of the complex with Calf-Thymus DNA (CT-DNA) has been investigated by absorption and fluorescence spectroscopy. The complex is an avid DNA binder with a binding constant value of <TEX>$1.03{\times}10^5M^{-1}$</TEX>. The results suggest that the nickel(II) complex bind to CT-DNA via intercalative mode and can quench the fluorescence intensity of EB bind to CT-DNA with <TEX>$K_{app}$</TEX> value of <TEX>$3.2{\times}10^5M^{-1}$</TEX>. The complex also shown efficient oxidative cleavage of supercoiled pBR322 DNA in the presence of hydrogen peroxide as oxidizing agent. The DNA cleavage by complex in presence of quenchers; viz. DMSO, KI, <TEX>$NaN_3$</TEX> and EDTA reveals that hydroxyl radical or singlet oxygen mechanism is involved. The complex showed invitro antimicrobial activity against four bacteria and two fungi. The antimicrobial activity was nearer to that of standard drugs and greater than that of the free ligand.

Theoretical Study on Acid Diffusion Length in Chemically Amplified Resists Used for Extreme Ultraviolet Lithography

Acid diffusion length has been regarded as the most important factor in the development of chemically amplified resists used for ultrafine patterning. In this study, the acid diffusion length in chemically amplified extreme ultraviolet (EUV) resists was investigated by a Monte Carlo method in the presence of quenchers. The acid diffusion length corresponding to the highest chemical gradient, which results in the lowest line edge roughness, was investigated by varying the exposure dose, the acid generator concentration, and the effective reaction radius for deprotection. Although the optimum acid diffusion length was decreased with the increase of effective reaction radius for deprotection, it did not depend on the exposure dose or acid generator concentration.

Indications of the reactive species in a heterogeneous Fenton-like reaction using Fe-containing zeolites

Heterogeneous Fenton-like reactions have potential applications in wastewater treatment. Recently, the use of zeolites containing iron species as catalysts in Fenton-like processes has gained increasing interest. While it has been assumed in the literature that hydroxyl radicals (OH ) are the dominant reactive species formed from H 2O 2 in the presence of Fe-zeolites, no direct evidence for this hypothesis exists so far. This work aims at the elucidation of the type of reactive species involved in the heterogeneous Fenton reaction using the Fe-containing zeolites Fe-ZSM5 and Fe-Beta. Electron paramagnetic resonance (EPR) measurements using dimethyl pyrroline-N-oxide (DMPO) as spin trap were carried out; the formation of the complex DMPO-OH was observed, which is often ascribed to a reaction with OH . However, significant differences were found in the kinetic deuterium isotope effect (KDIE) for methanol oxidation between the heterogeneous Fenton-like reaction and genuine OH reactions initiated by the homogeneous Fenton reaction. The KDIE for methanol oxidation in the heterogeneous reaction increased from 1.33 to 1.41 with increasing concentration of the OH scavenger bicarbonate, whereas the KDIE in the classical Fenton reaction is 1.07 and unaffected by the presence of quenchers. The significantly different values are a clear indication for the participation of additional oxidants beside OH . In addition, Fe-zeolites catalyzed the epoxidation of cyclohexene by H 2O 2. This type of reaction suggests the participation of a high-valent oxoiron complex (ferryl) in the wet peroxide oxidation of organic compounds catalyzed by Fe-zeolites.

Nucleobindin 1 Is a Calcium-regulated Guanine Nucleotide Dissociation Inhibitor of Gαi1

Nucleobindin 1 (NUCB1) is a widely expressed multidomain calcium-binding protein whose precise physiological and biochemical functions are not well understood. We engineered and heterologously expressed a soluble form of NUCB1 (sNUCB1) and characterized its biophysical and biochemical properties. We show that sNUCB1 exists as a dimer in solution and that each monomer binds two divalent calcium cations. Calcium binding causes conformational changes in sNUCB1 as judged by circular dichroism and fluorescence spectroscopy experiments. Earlier reports suggested that NUCB1 might interact with heterotrimeric G protein α subunits. We show that dimeric calcium-free sNUCB1 binds to expressed Gα(i1) and that calcium binding inhibits the interaction. The binding of sNUCB1 to Gα(i1) inhibits its basal rate of GDP release and slows its rate and extent of GTPγS uptake. Additionally, our tissue culture experiments show that sNUCB1 prevents receptor-mediated Gα(i)-dependent inhibition of adenylyl cyclase. Thus, we conclude that sNUCB1 is a calcium-dependent guanine nucleotide dissociation inhibitor (GDI) for Gα(i1). To our knowledge, sNUCB1 is the first example of a calcium-dependent GDI for heterotrimeric G proteins. We also show that the mechanism of GDI activity of sNUCB1 is unique and does not arise from the consensus GoLoco motif found in RGS proteins. We propose that cytoplasmic NUCB1 might function to regulate heterotrimeric G protein trafficking and G protein-coupled receptor-mediated signal transduction pathways.

Photoinduced electron transfer reactions of pyrylium derivatives with organic sulfides in acetonitrile

The photochemistry and photophysics of pyrylium derivatives with organic sulfides in acetonitrile medium are investigated. A steady decrease in the fluorescence intensity and fluorescence lifetime of the dyes was observed with increase in the quencher concentration. Bimolecular quenching constants were evaluated and correlated with the free energy of electron transfer. Laser flash photolysis investigations on the dyes in presence of quenchers were done. Observation of pyranyl radical and sulfide cation radicals as intermediates clearly illustrates the electron transfer mechanistic pathway for this reaction. The radical pair energies were calculated and found to be lower than the triplet energy of the sensitisers and hence we do not see any triplet induction in the present system.

Preparation and physicochemical studies of new multiple rings s-tetrazines

Several new supramolecular s-tetrazines have been prepared and studied. Their electrochemical and spectroscopic properties have been investigated, especially in the presence of quenchers. Fluorescence quenching has been shown to occur as expected through a charge transfer mechanism and the cyclophane structure has been shown to lead to an acceleration of the quenching process.

Impact of Nonconstant Diffusion Coefficient on Latent Image Quality in 22 nm Fabrication using Extreme Ultraviolet Lithography

In chemically amplified resists, acids catalyze pattern formation reactions with acid diffusion in the presence of quenchers, starting with the initial acid distribution as a boundary condition. Diffusion coefficients have been intensively investigated and reported to depend on the condition of the matrix. In this study, the effect of nonconstant diffusion coefficients was investigated using a simulation based on the reaction mechanisms of chemically amplified extreme ultraviolet resists. It was found that nonconstant diffusion coefficients have a significant impact on the resolution, sensitivity, and image quality (line edge roughness) in 22 nm fabrication.