Decay Rate Constants Research Articles

Infrared Fingerprint and Unimolecular Decay Dynamics of the Hydroperoxyalkyl Intermediate (•QOOH) in Cyclopentane Oxidation.

A transient carbon-centered hydroperoxyalkyl intermediate (•QOOH) in the oxidation of cyclopentane is identified by IR action spectroscopy with time-resolved unimolecular decay to hydroxyl (OH) radical products that are detected by UV laser-induced fluorescence. Two nearly degenerate •QOOH isomers, β- and γ-QOOH, are generated by H atom abstraction of the cyclopentyl hydroperoxide precursor. Fundamental and first overtone OH stretch transitions and combination bands of •QOOH are observed and compared with anharmonic frequencies computed by second-order vibrational perturbation theory. An OH stretch transition is also observed for a conformer arising from torsion about a low-energy CCOO barrier. Definitive identification of the β-QOOH isomer relies on its significantly lower transition state (TS) barrier to OH products, which results in rapid unimolecular decay and near unity branching to OH products. A benchmarking approach is utilized to compute high-accuracy stationary point energies, most importantly TS barriers, for cyclopentane oxidation (C5H9O2), building on higher level reference calculations for ethane oxidation (C2H5O2). The experimental OH product appearance rates are compared with computed statistical microcanonical rates using RRKM theory, including heavy-atom tunneling, thereby validating the computed TS barrier. The results are extended to thermal unimolecular decay rate constants at temperatures and pressures relevant to cyclopentane combustion via master-equation modeling. The various torsional and ring puckering states of the wells and transition states are explicitly considered in these calculations.

Elucidating the dynamics and transfer pathways of photogenerated charge carriers in V2O5/BiVO4 heterojunction photoanodes: A transient absorption spectroscopy study

Pairing of bismuth vanadate (BiVO4) with vanadium pentoxide (V2O5) forms a Type II heterojunction photoanode, which has been proven to be a high-performance photoanode architecture for efficient photoelectrochemical (PEC) water oxidation. To further support for advanced rational design and improvement of the heterojunction photoanode, it is quintessential to understand the mechanics and properties of photogenerated charge carriers formed. This study aims to probe the dynamics of photogenerated electron-hole pairs formed in pristine photoanode as well as the heterojunction photoanodes using transient absorption spectroscopy (TAS). Relative to the BiVO4/V2O5 structure, modelling and quantification of the decay constant helps in explaining why the V2O5/BiVO4 heterojunction photoanode exhibited a longer lifetime of the photogenerated charge carriers with a lower decay rate constant that leads to a much-improved overall generation of photocurrent density. An oxygen evolving catalyst of nickel oxyhydroxide (NiOOH) was then anchored on the exterior surfaces of the heterojunction photoanode system to further investigate and modify the transfer pathways of the photogenerated charge carriers. Furthermore, the hole- and scavenger-assisted TAS measurements on the BiVO4/V2O5 heterojunction photoanode revealed that the majority of trapped holes species are accumulated within the BiVO4 layer. The findings suggested that the Type II heterojunction formation in V2O5/BiVO4 could effectively reduce its charge recombination process.

Persistence of respiratory, enteric, and fecal indicator viruses in fecal sludge from on-site sanitation in Dakar, Senegal

ABSTRACT As wastewater-based epidemiology (WBE) broadens to include prevalent diseases with significant global health impact, existing surveillance systems concentrate on sewer-based infrastructure, which excludes the 2.7 billion people using non-sewered systems. To address this gap, our study explores the potential of fecal sludge treatment plants for WBE, emphasizing the stability of virus RNA targets within pooled fecal sludge. We screened fecal sludge from a centralized treatment facility in Dakar, Senegal for SARS-CoV-2, human norovirus, and microbial source trackers pepper mild mottle virus and tomato brown rugose fruit virus (ToBRFV). Decay kinetics of viral genomic RNA markers were examined at 4, 15, and 30 °C over 70 days. Results indicate the high persistence of viral targets in fecal sludge (T90 value of 3.3 months for exogenous SARS-CoV-2 N1 and N2 and 6.2 months for ToBRFV), with all targets detected throughout the 70-day experiment under various temperatures with limited decay (<90% reduction). This study addresses a crucial gap in understanding virus persistence in on-site sanitation systems by providing essential decay rate constants for effective target detection. Our results indicate that sampling at centralized facilities treating fecal sludge from on-site sanitation could facilitate localized pathogen surveillance in low-income settings.

Theory of high-temperature superfluorescence in hybrid perovskite thin films.

The recent discovery of high-temperature superfluorescence in hybrid perovskite thin films has opened new possibilities for harnessing macroscopic quantum phenomena in nanotechnology. This study aimed to elucidate the mechanism that enables high-temperature superfluorescence in these systems. The proposed model describes a quasi-2D Wannier exciton in a thin film that interacts with phonons via the longitudinal optical phonon-exciton Fröhlich interaction. We show that the super-radiant properties of the coherent state in hybrid perovskites are stable against perturbations caused by the longitudinal optical phonon-exciton Fröhlich interaction. Using the multiconfiguration Hartree approach, we derive semiclassical equations of motion for a single-exciton wavefunction, where the vibrational degrees of freedom interact with the Wannier exciton through a mean-field Hartree term. Super-radiance is effectively described by a non-Hermitian term in the Hamiltonian. The analysis was then extended to multiple excited states using the semiclassical Hamiltonian as the basic model. We demonstrate that the ground state of the model exciton Hamiltonian with long-range interactions is a symmetric Dicke super-radiant state, where the Fröhlich interaction is nullified. The additional density matrix-based consideration draws an analogy between this system and stable systems, where the conservation laws determine the nullification of the constant (momentum-independent) decay rate part. In the exciton-phonon system, nullification is associated with the absence of a momentum-independent component in the Wannier exciton-phonon interaction coupling function.

Bimetallic complexation for significant fluorescence enhancement of faecal pigment towards water quality testing

Systematic spectroscopic investigations revealed bimetallic complexation of faecal pigments (FP) in waterthrough their multiple binding sites. FP-Zn(II)/Gd(III) complexes showed narrow emission (FWHM ∼ 26 nm) with maximum intensity compared to different bimetallic complexes in water. The fluorescence intensity of bimetallic Zn(II)/Gd(III) complexes of FP increased ∼3–5 fold in aqueous media compared to the FP-Zn(II) complexes, i.e. well-known as Schlesinger’s test. The optimum Zn(II): Gd(III) stoichiometry was observed at 3:2 for maximum FP fluorescence enhancement. The bimetallic FP-Zn(II)/Gd(III) complexes also exhibited higher fluorescence lifetimes and quantum yield than FP-Zn(II) complexes. The photophysical investigations demonstrated that bimetallic Zn(II)/Gd(III) complexation increased the rigidity of chromophores present in FP. Consequently, a decrease in non-radiative decay rate constants (knr) by ∼ 1.5 times was observed for bimetallic complexes compared to FP-Zn(II) in water. Hence, a detection limit of the nanomolar concentration range of FP could be achieved in the aqueous media. The effect of diverse interfering factors (humic acid, water hardness, pH) on the fluorescence behaviour of FP-Zn(II)/Gd(III) complexes was also investigated with an approach mimicking real water samples. Finally, a simple non-extraction analytical approach for sensitive detection of FP in water was demonstrated while also considering the fluorescence matrix interference problem.

Homomolecular Triplet-Triplet Annihilation in Metalloporphyrin Photosensitizers.

Metalloporphyrins are ubiquitous in their applications as triplet photosensitizers, particularly for promoting sensitized photochemical upconversion processes. In this study, bimolecular excited state triplet-triplet quenching kinetics, termed homomolecular triplet-triplet annihilation (HTTA), exhibited by the traditional triplet photosensitizers-zinc(II) tetraphenylporphyrin (ZnTPP), palladium(II) octaethylporphyrin (PdOEP), platinum(II) octaethylporphyrin (PtOEP), and platinum(II) tetraphenyltetrabenzoporphyrin (PtTPBP)─were revealed using conventional transient absorption spectroscopy. Nickel(II) tetraphenylporphyrin was used as a control sample as it is known to be rapidly quenched intramolecularly through ligand-field state deactivation and, therefore, cannot result in triplet-triplet annihilation (TTA). The single wavelength transients associated with the metalloporphyrin triplet excited state decay─measured as a function of incident laser pulse energy in toluene─were well modeled using parallel first- and second-order kinetics, consistent with HTTA being operable. The combined transient kinetic data enabled the determination of the first-order rate constants (kT) for excited triplet decay in ZnTPP (4.0 × 103 s-1), PdOEP (3.6 × 103 s-1), PtOEP (1.2 × 104 s-1), and PtTPBP (2.1 × 104 s-1) as well as the second-order rate constant (kTT) for HTTA in ZnTPP (5.5 × 109 M-1 s-1), PdOEP (1.1 × 1010 M-1 s-1), PtOEP (7.1 × 109 M-1 s-1), and PtTPBP (1.6 × 1010 M-1 s-1). In most instances, triplet excited state extinction coefficients are either reported for the first time or have been revised using ultrafast transient absorption spectroscopy and singlet depletion: ZnTPP (78,000 M-1 cm-1) at 470 nm, PdOEP (67,000 M-1 cm-1) at 430 nm, PtOEP (51,000 M-1 cm-1) at 418 nm, and PtTPBP (100,000 M-1 cm-1) at 460 nm. The combined experimental results establish competitive time scales for homo- and heteromolecular TTA rate constants, implying the significance of considering HTTA processes in future research endeavors harnessing TTA photochemistry using common metalloporphyrin photosensitizers.

Predicting Nonradiative Decay Rate Constants of Cyclometalated Ir(III) Complexes.

The theoretical calculation of the temperature-dependent nonradiative decay rate constant is fundamental for predicting the usefulness of transition-metal complexes for technological applications. Such a computation implies the determination of the barriers separating the emitting triplet state from metal-centered states, which are key mediators of this type of radiationless relaxation. We here do so for the two green-emitting cyclometalated Ir(III) complexes, [Ir(ppy)2(pyim)]+ and [Ir(diFppy)2(dtb-bpy)]+, of general formula [Ir(C∧N)2(N∧N)]+, performing DFT calculations with both B3LYP and PBE0 functionals. On the basis of the obtained results and the comparison with the experimental nonradiative decay rate constants, we conclude that B3LYP provides too low energy barriers to the metal-centered states, while the PBE0 provides reasonable values. We consequently recommend to avoid the use of the commonly employed B3LYP functional for the evaluation of such an energy barrier for cyclometalated Ir(III) complexes.

Phosphine Oxide‐Containing Gold(III) Complexes with Tunable Emission Color and Thermally Enhanced Luminescence Behavior

AbstractA series of phosphine oxide‐containing gold(III) complexes with tunable emission colors spanning from sky‐blue to near‐infrared region is reported. This is accomplished by the switching of the excited state characters from intraligand to ligand‐to‐ligand charge transfer through the replacement of the auxiliary ligand from aryl to nitrogen‐based ligands. In addition to high photoluminescence quantum yields in both solution and solid‐state thin films, these complexes exhibit large radiative decay rate constants of the order of 106 s−1, much larger than those commonly found for other gold(III) complexes. The origin of such enhanced performance is believed to be arising from the occurrence of both thermally activated delayed fluorescence and thermally stimulated delayed phosphorescence processes within the emitters. This is probed by ns‐ and fs‐transient absorption spectroscopy, time‐resolved, and temperature‐dependent emission spectroscopy. In particular, the direct observation of the upconversion processes and the determination of the activation barriers are achieved in the variable‐temperature fs‐transient absorption spectroscopic studies. Solution‐processed organic light‐emitting devices with satisfactory external quantum efficiencies of up to 15.2% are achieved, which could be ascribed to the presence of thermally activated delayed fluorescence and/or thermally stimulated delayed phosphorescence processes.

The controllable of BODIPY dimers without installing blocking groups as both fluorescence and singlet oxygen generators

AbstractWe compared a range of BODIPY dimer derivatives without installing blocking groups by optimizing geometry structures and analyzing energies, frontier molecular orbitals, Chole&Cele map, electron density difference, spin‐orbit coupling (SOC) matrix and decay rate constants from excited states. The dihedral angles of the β‐β‐linked BODIPY dimer and the α‐α‐linked BODIPY dimer tend to flatten in the T1 state, which is detrimental to the occurrence of the intersystem crossing (ISC). Conversely, the dihedral angle of the meso‐β‐linked BODIPY dimer, the meso‐meso‐linked BODIPY dimer and α‐γ‐linked BODIPY dimer is within the range of 125°–143° in the T1 state, facilitating ISC and the generation of singlet oxygen. Notably, the transition from S1 to S0 involving lowest unoccupied molecular orbital to highest occupied molecular orbital with long‐wavelength emission and moderate oscillator strength underpins the remarkable long emission peaks observed experimentally for α‐γ‐linked BODIPY dimer. Moreover, the apparent SOC matrix enhances the ISC process, resulting in a respectable efficiency in generating singlet oxygen for this dimer. In meso‐β‐linked BODIPY, meso‐meso‐linked BODIPY, and α‐γ‐linked BODIPY, the S1→T1 process is characterized by a significant charge transfer, specifically transitioning from the 1CT state to the 3LE state, indicative of a spin‐orbit charge transfer ISC (SOCT‐ISC) mechanism. The ability to regulate the photosensitivity of BODIPY dimers by adjusting the dihedral angle between the two units in the T1 state unveils new avenues for designing high‐performance photosensitizers for both therapeutic and imaging applications.

Room‐Temperature Afterglow Nanostructures via Block Copolymer Self‐Assembly

AbstractMiniaturization of organic afterglow materials has shown promising application in biomedical and other areas. Current technologies, such as nanoprecipitation, mechanical treatment, and emulsion polymerization, lack the capability of facile control on the morphology and dimension of the miniaturized organic afterglow materials. Here we report the fabrication of organic afterglow nanostructures via block copolymer self‐assembly at room temperature. The fabrication is based on two‐component design strategy where hydrophobic luminescent emitters with small rate constants of phosphorescence decay or reverse intersystem crossing are designed as the first component. Amphiphilic block copolymers that can form spherical core‐shell micelles and worm‐like micelles with glassy hydrophobic cores are used as the second component. Upon addition of water into a dimethylformamide solution that contains the two components, the amphiphilic block copolymers self‐assemble into well‐defined nanostructures and accommodate the hydrophobic luminescent emitters in nanostructure's hydrophobic cores. After switching to pure water by dialysis, room‐temperature afterglow nanostructures have been obtained because of the excellent protection of organic triplets by the glassy hydrophobic cores. The afterglow nanostructures exhibit intriguing afterglow mechanism modulated by the types of luminescent emitters, controlled dimensions and morphologies by the structural parameters of the block copolymers.

Bipolar ionization-mediated airborne virus inactivation and deposition rates

Bipolar ionization (BPI) of indoor air has emerged as a widely implemented bulk-air disinfection technology to reduce human exposure to airborne viruses. This study presents BPI-mediated decay rate constants for the inactivation and deposition of infectious viral aerosols. Rate constants are estimated for the enveloped bacteriophage Ф6, a common SARS-CoV-2 surrogate, at low (∼25 %), medium (∼50 %) and high (∼75 %) relative humidity (RH) levels under bipolar ion concentrations of 106 ions/cm3. Enhanced BPI-facilitated viral inactivation rate constants of 4.6, 6.9, and 7.6 h −1 under low, middle, and high RH, respectively, are reported. BPI-mediated infectious decay and deposition rates for aerosolized Ф6 were RH-dependent, with significant increases from low to high RH (p < 0.05). Calculated BPI susceptibility constants, that account for ion concentrations, reveal limited airborne viral inactivation (<0.1 h −1) at bipolar ion levels (103 ions/cm3) that are common in bulk air where BPI is applied.

Quantitative prediction of rate constants and its application to organic emitters

Many phenomena in nature consist of multiple elementary processes. If we can predict all the rate constants of respective processes quantitatively, we can comprehensively predict and understand various phenomena. Here, we report that it is possible to quantitatively predict all related rate constants and quantum yields without conducting experiments, using multiple-resonance thermally activated delayed fluorescence (MR–TADF) as an example. MR–TADFs are excellent emitters because of its narrow emission, high luminescence efficiency, and chemical stability, but they have one drawback: slow reverse intersystem crossing (RISC), leading to efficiency roll-off and reduced device lifetime. Here, we show a quantum chemical calculation method for quantitatively obtaining all the rate constants and quantum yields. This study reveals a strategy to improve RISC without compromising other important factors: radiative decay rate constants, photoluminescence quantum yields, and emission linewidths. Our method can be applied in a wide range of research fields, providing comprehensive understanding of the mechanism including the time evolution of excitons.

Study of the degradation behavior of enisamium iodide, tilorone dihydrochloride, morpholinium thiazotate in the soil by the GC-Fid method

The aim. To study the behaviour of enisamium iodide, thiloron dihydrochloride, morpholinium thiazotate, and the suitability of the previously developed GC-FID methodology in soil. Materials and methods. The determination of the Enisamium iodide, Tilorone dihydrochloride, and Morpholinium thiazotate in soil gas chromatography with a flame ionization detector using the Rxi-5 ms (30 m long, 0.25 mm outer diameter and 0.25 μm liquid stationary phase thickness). Results. A study was conducted on the behaviour of enisamium iodide, thiloron dihydrochloride, and morpholinium thiazotate in soil, along with the assessment of the suitability of the developed GC-FID methodology for determination in soil. The half-life in soil was investigated, which amounted to 45 days for enisamium iodide, 30 days for thilorone dihydrochloride, and 7 days for morpholinium thiazotate, with corresponding decay rate constants of 0.001 mg/mL, 0.001 mg/mL, and 0.0005 mg/mL, respectively. Conclusions. The previously developed GC-FID methodology is suitable for the determination of enisamium iodide, thilorone dihydrochloride, and morpholinium thiazotate in soil, with necessary analysis conditions established. Under aerobic conditions, the selected pharmaceutical preparations' dispersion rate followed the following decreasing order: enisamium iodide &gt; thilorone dihydrochloride &gt; morpholinium thiazotate in soil

Isomer-resolved unimolecular dynamics of the hydroperoxyalkyl intermediate (•QOOH) in cyclohexane oxidation

The oxidation of cycloalkanes is important in the combustion of transportation fuels and in atmospheric secondary organic aerosol formation. A transient carbon-centered radical intermediate (•QOOH) in the oxidation of cyclohexane is identified through its infrared fingerprint and time- and energy-resolved unimolecular dissociation dynamics to hydroxyl (OH) radical and bicyclic ether products. Although the cyclohexyl ring structure leads to three nearly degenerate •QOOH isomers (β-, γ-, and δ-QOOH), their transition state (TS) barriers to OH products are predicted to differ considerably. Selective characterization of the β-QOOH isomer is achieved at excitation energies associated with the lowest TS barrier, resulting in rapid unimolecular decay to OH products that are detected. A benchmarking approach is employed for the calculation of high-accuracy stationary point energies, in particular TS barriers, for cyclohexane oxidation (C6H11O2), building on higher-level reference calculations for the smaller ethane oxidation (C2H5O2) system. The isomer-specific characterization of β-QOOH is validated by comparison of experimental OH product appearance rates with computed statistical microcanonical rates, including significant heavy-atom tunneling, at energies in the vicinity of the TS barrier. Master-equation modeling is utilized to extend the results to thermal unimolecular decay rate constants at temperatures and pressures relevant to cyclohexane combustion.

Casimir Forces in CFT with Defects and Boundaries

We investigate the quantum forces occurring between the defects and/or boundaries of a conformal field theory (CFT). We propose to model imperfect defects and boundaries as localized relevant double-trace operators that deform the CFT. Our focus is on pointlike and codimension-one planar defects. In the case of two parallel membranes, we point out that the CFT 2-point function tends to get confined and develops a tower of resonances with a constant decay rate when the operator dimension approaches the free field dimension. Using a functional formalism, we compute the quantum forces induced by the CFT between a variety of configurations of pointlike defects, infinite plates and membranes. Consistency arguments imply that these quantum forces are attractive at any distance. Forces of the Casimir–Polder type appear in the UV (ultraviolet), while forces of the Casimir type appear in the IR (infrared), in which case the CFT gets repelled from the defects. Most of the forces behave as a non-integer power of the separation, controlled by the dimension of the double-trace deformation. In the Casimir regime of the membrane–membrane configuration, the quantum pressure behaves universally as 1/ℓd; however, information about the double-trace nature of the defects still remains encoded in the strength of the pressure.

A data-driven approach for simplifying the estimation of time for contaminant plumes to reach their maximum extent

Globally there exist a very large number of contaminated or possibly contaminated sites where a basic preliminary assessment has not been completed. This is largely, among others, due to limited simple methods/models available for estimating key site quantities such as the maximum plume length, further denoted as Lmax and the corresponding time T=TLmax, at which the plume reaches its maximum extent L=Lmax. An approach to easily obtain an estimate of TLmax in particular is presented in this work. Limited availability of high-quality field data, particularly of TLmax, necessitates the use of synthetic data, which constrains the overall model development works. Taking BIOSCREEN-AT (transient 3D model) as a base model, this work proposes second-order polynomial models, with only two parameters, for estimating Lmax and TLmax. This reformulation of the well established solution significantly reduces data requirement and workload for initial site assessment purposes. A global sensitivity analysis (Morris, 1991), using a large number of random synthetic data, identifies the first-order decay rate constants in the plume λEFF and at the source γ as dominantly most influential for TLmax. For Lmax, the first-order decay rate constant λEFF and groundwater velocity v are the two important parameters. The sensitivity analysis also identifies that these parameters non-linearly impact TLmax or Lmax. With this information, the proposed polynomial models (each for Lmax and TLmax) were trained to obtain model coefficients, using a large amount of synthetic data. For verification, the developed models were tested using four datasets comprising over 100 sample sets against the results obtained from BIOSCREEN-AT and the developed BIOSCREEN-AT-based steady-state model. Additionally, the developed models were evaluated against two well documented field sites. The proposed models largely simplify estimation, particularly, of TLmax, for which only very limited field or literature information is available.

Persistence of human respiratory viral RNA in wastewater-settled solids.

Wastewater-based epidemiology has emerged as a valuable tool for monitoring respiratory viral diseases within communities by analyzing concentrations of viral nucleic-acids in wastewater. However, little is known about the fate of respiratory virus nucleic-acids in wastewater. Two important fate processes that may modulate their concentrations in wastewater as they move from household drains to the point of collection include sorption or partitioning to wastewater solids and degradation. This study investigated the decay kinetics of genomic nucleic-acids of seven human respiratory viruses, including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), respiratory syncytial virus (RSV), human coronavirus (HCoV)-OC43, HCoV-229E, HCoV-NL63, human rhinovirus (HRV), and influenza A virus (IAV), as well as pepper mild mottle virus (PMMoV) in wastewater solids. Viruses (except for PMMoV) were spiked into wastewater solids and their concentrations were followed for 50 days at three different temperatures (4°C, 22°C, and 37°C). Viral genomic RNA decayed following first-order kinetics with decay rate constants k from 0 to 0.219 per day. Decay rate constants k were not different from 0 for all targets in solids incubated at 4°C; k values were largest at 37°C and at this temperature, k values were similar across nucleic-acid targets. Regardless of temperature, there was limited viral RNA decay, with an estimated 0% to 20% reduction, over the typical residence times of sewage in the piped systems between input and collection point (<1 day). The k values reported herein can be used directly in fate and transport models to inform the interpretation of measurements made during wastewater surveillance.IMPORTANCEUnderstanding whether or not the RNA targets quantified for wastewater-based epidemiology (WBE) efforts decay during transport between drains and the point of sample collection is critical for data interpretation. Here we show limited decay of viral RNA targets typically measured for respiratory disease WBE.

Novel insights into the mechanism of laccase-driven rhizosphere humification for alleviating wheat 17β-estradiol contamination

Global-scale crop contamination with environmental estrogens has posed a huge risk to agri-food safety and human health. Laccase is regarded as an unexceptionable biocatalyst for regulating pollution and expediting humification, but the knowledge of estrogen bioremediation and C storage strengthened by laccase-driven rhizosphere humification (LDRH) remains largely unknown. Herein, a greenhouse microcosm was performed to explore the migration and fate of 17β-estradiol (E2) in water-wheat (Triticum aestivum L.) matrices by LDRH. Compared to the non-added laccase, the pseudo-first-order decay rate constants of E2 in the rhizosphere solution after 10 and 50 μM exposures by LDRH increased from 0.03 and 0.02 h−1 to 0.36 and 0.09 h−1, respectively. Furthermore, LDRH conferred higher yield, polymerizability, O-containing groups, and functional-C signals in the humified precipitates, because it accelerated the formation of highly complex precipitates by radical-controlled continuous polymerization. In particular, not only did LDRH mitigate the phytotoxicity of E2, but it also diminished the metabolic load of E2 in wheat tissues. This was attributed to the rapid attenuation of E2 in the rhizosphere solution during LDRH, which limited E2 uptake and accumulation in each subcellular fraction of the wheat roots and shoots. Although several typical intermediate products such as estrone, estriol, and E2 oligomers were detected in roots, only small-molecule species were found in shoots, evidencing that the polymeric products of E2 were unable to be translocated acropetally due to the vast hydrophobicity and biounavailability. For the first time, our study highlights a novel, eco-friendly, and sustainable candidate for increasing the low-C treatment of organics in rhizosphere microenvironments and alleviating the potential risks of estrogenic contaminants in agroenvironments.

Temperature effect on spectral characters and dipole moment in short-lived excited singlet S1 state of 3HBI-7D-2HChromen-2-one laser dye in non-associative and highly viscous glycerol solvent

Steady state method is employed to study the effect of temperature on the absorption and emission characteristics of 3-(1H-benzo[d]imidazol-2-yl)-7-(diethylamino)-2H-chromen-2-one(3HBI-7D-2HChromen-2-one) laser dye in glycerol solvent. Temperature induces thermal effect on maxima absorption, emission wavelength, fluorescence intensity etc. Radiative and non-radiative transition probabilities mechanism, fluorescence lifetime, frequency assisted parameters decay rate constants, and activation energy is estimated. Advance thermochromic shift method is adopted to determine the ground and excited state dipole moments.

On the mechanism of luminescent YVO4:Eu3+ as turn-off luminescent probe for selective detection of Cu2+ ions

Poly(acrylic acid) (PAA) funtionalized luminescent YVO4:Eu3+ nanocrystals could be successfully prepared by polyol method. The surface functionalization of YVO4:Eu3+ nanocrystal is ascertained from the Fourier transform infrared spectroscopy. Photoluminescence studies confirm the occurrence of resonant energy transfer from vanadate (VO43−) to the excited states of Eu3+ resulting in strong red emission. Luminescent YVO4:Eu3+ nanocrystals shows the selective detection of Cu2+ among various metal ions. The intensity of Eu3+ emission could be reduced to ∼92 % with 9 μM of Cu2+. The behavior of quenching is dominant by dynamic nature. The detection limit could be achieved ∼17 nM. With the calculated decay rate constants, the excited photon migration from Eu3+ to Cu2+ ions is ascertained which leads in quenching of Eu3+ emission. While, from VO43− to Cu2+ is insignificant. Alkaline medium is more sensitive towards Cu2+ detection. This nanocrystal has a response time of ∼7 min.