Fraction Of Charge Research Articles

Ultrasonic-Assisted Extraction, Structural Characteristics, and Antioxidant Activities of Polysaccharides from Alpinia officinarum Hance.

Alpinia officinarum Hance, a well known agricultural product in the Lei Zhou peninsula, is generally rich in polysaccharides. In order to enhance the use of A. officinarum Hance polysaccharides (AOP) in functional food, AOP was extracted using an ultrasonic-assisted extraction method, and the ultrasonic extraction parameters of AOP was optimized. Furthermore, this study investigated the physicochemical and antioxidant activities of AOPs. In addition, the structural properties were preliminarily determined using Fourier-transform infrared spectroscopy (FTIR), high performance size exclusion chromatography, and a Zetasizer. Ultimately, this study explored the mechanism underlying the antioxidant activities of AOP. The results showed that the optimal ultrasonic-assisted extraction parameters were as follows: ultrasonic time, 6 min; ratio of water to material, 12 mL/g; and ultrasonic power, 380 W. Under these conditions, the maximum yield of AOPs was 5.72%, indicating that ultrasonic-assisted extraction technology is suitable for extracting AOPs due to the reduced time and water usage. Additionally, AOPs were purified using graded alcohol precipitation, resulting in three fractions (AOP30, AOP50, and AOP70). AOP30 had the lowest molecular weight of 11.07 kDa and mainly consisted of glucose (89.88%). The half inhibitory concentration (IC50) value of AOP30 and AOP70 was lower than that of AOP50 in the ability to scavenge the ABTS radical, while a reverse trend was observed in reducing ferric ions. Notably, the antioxidant activities of AOPs were highly correlated with their polydispersity index (Mw/Mn) and Zeta potential. AOP30, a negatively charged acidic polysaccharide fraction, exhibited electron donating capacities. Additionally, it displayed strong antioxidant abilities through scavenging 2,2'-azinobis-(3-ethylbenzthiazoline-6-sulphonate) (ABTS) radicals and reducing ferric ions. In conclusion, the present study suggests that AOP30 could be developed as an antioxidant ingredient for the food industry.

Charge Transport Properties of a Protic Ionic Liquid studied by Dielectric Spectroscopy

Three simple models including the Debye type model, Cole-Cole type model and Einstein-Smoluchowski model are used to determine the number density ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> , charge carrier density) and the mobilities (μ) of the charge carriers separately from the dielectric spectroscopy. By comparing them, the Cole-Cole type model appears to evaluate charge transport properties very well while the Debye type model doesn’t work for a complex ionic system. The temperature dependence of the mobility exhibits a Vogel-Fulcher-Tammann (VFT) behavior, while the number density of mobile charges is almost insensitive to the temperature. However, the fraction of available (mobile) charge carriers is found to be surprisingly low (~6 % at 25 °C), which can be attributed to charge immobilization in molecular aggregates. A subtle step in the mobility and (mobile) charge density around -10 °C is discussed in terms of a “hidden” phase transition possibly affecting the molecular organization in such aggregates. Increasing the fraction of mobile ionic charges by preventing aggregation would be an effective strategy to enhance σ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DC</sub> of the protic ionic liquid trioctylammonium methanesulfonate ([TOA][OMs]).

Electrohydrodynamics of diffuse porous colloids.

The present article deals with the electrohydrodynamic motion of diffuse porous particles governed by an applied DC electric field. The spatial distribution of monomers as well as the charge distribution across the particle are considered to follow sigmoidal distribution involving decay length. Such a parameter measures the degree of inhomogeneity of the monomer distribution across the particle. The diffuse porous particles resemble several colloidal entities which are often seen in the environment as well as in biological and pharmaceutical industries. Considering the impact of bulk pH and ion steric effects, we modelled the electrohydrodynamics of such porous particulates based on the modified Boltzmann distribution for the spatial distribution of electrolyte ions and the Poisson equation for electric potential as well as the conservation of mass and momentum principles. We adopt regular perturbation analysis with weak field assumption and the perturbed equations are solved numerically to calculate the electrophoretic mobility and neutralization fraction of the particle charge during its motion as well as fluid collection efficiency. We further deduced the closed form relation between the drag force experienced by the charged porous particle and the fluid collection efficiency. In addition to the numerical results, we further derived the closed form analytical results for all the intrinsic parameters indicated above derived within the Debye-Hückel electrostatic framework and homogeneous distribution of monomers within the particle for which the decay length vanishes. The deduced mathematical results as indicated above will be useful to analyze several electrostatic and hydrodynamic features of a wide class of porous particulate and environmental entities.

Toward a Unified Description of the Electrostatic Assembly of Microgels and Nanoparticles.

The interplay of soft responsive particles, such as microgels, with nanoparticles (NPs) yields highly versatile complexes that show great potential for applications, ranging from plasmonic sensing to catalysis and drug delivery. However, the microgel-NP assembly process has not been investigated so far at the microscopic level, thus hindering the possibility of designing such hybrid systems a priori. In this work, we combine state-of-the-art numerical simulations with experiments to elucidate the fundamental mechanisms taking place when microgel-NP assembly is controlled by electrostatic interactions and the associated effects on the structure of the resulting complexes. We find a general behavior where, by increasing the number of interacting NPs, the microgel deswells up to a minimum size after which a plateau behavior occurs. This occurs either when NPs are mainly adsorbed to the microgel corona via the folding of the more external chains or when NPs penetrate inside the microgel, thereby inducing a collective reorganization of the polymer network. By varying microgel properties, such as fraction of cross-linkers or charge, as well as NP size and charge, we further show that the microgel deswelling curves can be rescaled onto a single master curve, for both experiments and simulations, demonstrating that the process is entirely controlled by the charge of the whole microgel-NP complex. Our results thus have a direct relevance in fundamental materials science and offer novel tools to tailor the nanofabrication of hybrid devices of technological interest.

Monte Carlo simulation of electron emission from aluminum after low energy protons impact

A Monte Carlo (MC) simulation approach is developed to describe the proton-induced secondary electron emission in solids. First, we calculate the double differential cross-section (DDCS) of excited electrons for different charge fractions of the projectile resulting from electron screening. The DDCS parameter is used in MC calculations to describe electron transport in the medium. This parameter is calculated for electrons excited in the 1 eV − 100 eV energy range. The theoretical electron transport modeling is based on Mott’s elastic scattering cross-section and Lindhard’s dielectric function for inelastic scattering. The results obtained for aluminum describe the angular and energy distributions of backscattered electrons for incident protons with energy below 25 keV at normal incidence. Additionally, the total electron emission yield is also calculated, showing a good agreement with available measurements. Our predictions for energy and angular distributions could not be compared with experimental results due to a lack of data.

Tabulated equations of state from models informed by chiral effective field theory

Abstract We construct four equation of state (EoS) tables, tabulated over a range of temperatures, densities, and charge fractions, relevant for neutron star applications such as simulations of neutron star mergers. The EoS are computed from a relativistic mean-field theory constrained by the pure neutron matter EoS from chiral effective field theory, inferred properties of isospin-symmetric nuclear matter, and astrophysical observations of neutron star structure. To model nuclear matter at low densities, we attach an EoS that models inhomogeneous nuclear matter at arbitrary temperatures and charge fractions. The four EoS tables we develop are available from the CompOSE EoS repository https://compose.obspm.fr/eos/297 and gitlab.com/ahaber/qmc-rmf-tables.

Molecular electronic stopping cross section for H and He beams colliding with water: projectile charge state contribution

Abstract When an ion beam impinges on a target material, electron stripping and capture processes involve different charge fraction states in the beam, such that each projectile charge state produces a different energy-loss. In this work, the energy deposition of swift hydrogen and helium ion beams colliding with a water target in the gas phase is studied. The electronic structure of the molecular target is represented in terms of core, bond, and lone pair orbital decomposition within a Harmonic Oscillator representation. In this way, the stopping cross section becomes only a function of the orbital mean excitation energy, I 0i . The ion beam charge fraction compositions colliding on water is determined from the work of Wedlund et al (2019) Astronomy &amp; Astrophysics, 630, A36) by accounting for the electron transfer cross sections. We find that the larger the projectile charge state, the larger the electronic stopping cross section and that the beam charge fraction determines the position of the maximum of the electronic stopping curve. Also, in agreement with the experiment, evidence is given on the dominant role of the largest projectile charge state in defining the stopping cross section for high energy collisions, while for low collision energies it is the lowest charge state together with all possible charge states contributing at the maximum of the electronic stopping cross section curve. Our results are reported and compared to available experimental data showing an excellent agreement to the available literature.

Ultrasonic humidifier aerosols: Observed high heavy metal enrichment and a new emission control method

Ultrasonic humidifiers are commonly used in households to maintain indoor humidity and generate a large number of droplets or spray aerosols. However, there have been various health concerns associated with humidifier use, largely due to aerosols generated during operation. Here, we investigated the size distribution, chemical composition, and charged fraction of aerosol particles emitted from commercial ultrasonic humidifiers. Heavy metals in water used for humidifiers were found to be highly enriched in the ultrasonic humidifier aerosols (UHA), with the enrichment factors ranging from 102 to 107. This enrichment may pose health concerns for the building occupants, as UHA concentrations of up to 106 particles/cm3 or 3 mg/m3 were observed. Furthermore, approximately 90% of UHA were observed to be electrically charged, for the first time according to our knowledge. Based on this discovery, we proposed and tested a new method to remove UHA by using a simple electrical field. The designed electrical field in this work can efficiently remove 81.4% of UHA. Therefore, applying this electrical field could be an effective method to significantly reduce the health risks by UHA.

A Molecular Thermodynamic Model of Coacervation in Solutions of Polycations and Oppositely Charged Micelles.

To guide the rational design of personal care formulations, we formulate a molecular thermodynamic model that predicts coacervation from cationic polymers and mixed micelles containing neutral and anionic surfactants and added salt. These coacervates, which form as a result of dilution of conditioning shampoos during use, deposit conditioning agents and other actives to the scalp or skin and also provide lubrication benefits. Our model accounts for mixing entropy, hydrophobic interactions of polycation with water, free energies of bindings of oppositely charged groups to micelles and polycations, and electrostatic interactions that capture connectivity of charged groups on the polycation chain and the micelle. The model outputs are the compositions of surfactants, polycation, salt, and water in the coacervate and in its coexisting dilute phase, along with the binding fractions and coacervate volume fraction. We study the effects of overall composition (of surfactant, polycation, and added salt), charge fractions on micelles and polycations, and binding free energies on the phase diagram of coacervates. Then, we perform coacervation experiments for three systems: sodium dodecyl sulfate (SDS)-JR30M, sodium methyl cocoyl taurate (Taurate)-JR30M, and sodium lauryl alaninate (Alaninate)-JR30M, where JR30M is a cationic derivative of hydroxyethylcellulose (cat-HEC), and rationalize their coacervation data using our model. For comparison with experiment, we also develop a parametrization scheme to obtain the requisite binding energies and Flory-Huggins χ parameter. We find that our model predictions agree reasonably well with the experimental data, and that the sulfate-free surfactants of Taurate and Alaninate display much larger 2-phase regions compared to SDS with JR30M.

Frequencies of f - and p -oscillation modes in cold and hot compact stars

A large collection of equations of state (EOSs) built within the covariant density functional theory of hadronic matter and allowing for density dependent couplings is employed to study polar $f$- and $p$-oscillations of cold and hot compact stars. Correlations between oscillation frequencies of cold purely nucleonic neutron stars (NSs), their global parameters as well as properties of nuclear matter (NM) are investigated by considering a set of models from Beznogov and Raduta, [Phys. Rev. C 107, 045803 (2023)], where a number of constraints on the saturation properties of NM, pure neutron matter and the lower bound of the maximal NS mass were imposed within a Bayesian framework. The roles of finite temperature and exotic particle degrees of freedom, e.g., hyperons, $\mathrm{\ensuremath{\Delta}}$-resonances, antikaon condensates or a hadron to quark phase transition, are addressed by employing a family of models publicly available on compose and assuming idealized profiles of temperature or entropy per baryon and charge fraction. We find that finite temperature effects reduce the oscillation frequencies of nucleonic stars while the opposite effect is obtained for stars with exotic particle degrees of freedom. When the $\mathrm{\ensuremath{\Gamma}}$-law is employed to build finite temperature EOSs, errors in estimating oscillation modes frequencies are of the order of 10% to 30%, depending on the mass. Throughout this work the Cowling approximation is used.

Charge breeding experiment of stable ion beams in EBIS charge breeder for RAON facility

The Electron Beam Ion Source (EBIS) charge breeder is used to produce highly charged ions in the Isotope Separation On-Line (ISOL) system of the Rare isotope Accelerator complex for ON-line experiments (RAON). Beam tests of the EBIS are performed using stable Cs and Sn ion beams. 133Cs1+ ions from a test ion source were injected into the EBIS to measure the breeding effect with the electron beam. The resulting relative abundance of 133Cs27+ was 25.0%, and the extraction energy was 49.3 keV/q. A charge breeding test of the 120Sn ions from the Target Ion Source (TIS) of the ISOL system was also carried out. The charge fraction of 120Sn24+ was 23.0%, and the energy was 50 keV/q. These results fulfilled the input beam condition of the RFQ accelerator (A/q < 6 and 10 keV/u). Additionally, 133Cs27+ ions were extracted with a pulse length up to 10 ms (FWHM) by the preliminary pulse-stretching experiment.

Hippocampal versus cortical deletion of cholinergic receptor muscarinic 1 in mice differentially affects post-translational modifications and supramolecular assembly of respiratory chain-associated proteins, mitochondrial ultrastructure, and respiration: implications in Alzheimer's disease.

Introduction: In a previous retrospective study using postmortem human brain tissues, we demonstrated that loss of Cholinergic Receptor Muscarinic 1 (CHRM1) in the temporal cortex of a subset of Alzheimer's patients was associated with poor survival, whereas similar loss in the hippocampus showed no such association. Mitochondrial dysfunction underlies Alzheimer's pathogenesis. Therefore, to investigate the mechanistic basis of our findings, we evaluated cortical mitochondrial phenotypes in Chrm1 knockout (Chrm1-/-) mice. Cortical Chrm1 loss resulted in reduced respiration, reduced supramolecular assembly of respiratory protein complexes, and caused mitochondrial ultrastructural abnormalities. These mouse-based findings mechanistically linked cortical CHRM1 loss with poor survival of Alzheimer's patients. However, evaluation of the effect of Chrm1 loss on mouse hippocampal mitochondrial characteristics is necessary to fully understand our retrospective human tissue-based observations. This is the objective of this study. Methods: Enriched hippocampal and cortical mitochondrial fractions (EHMFs/ECMFs, respectively) derived from wild-type and Chrm1-/- mice were used to measure respiration by quantifying real-time oxygen consumption, supramolecular assembly of oxidative phosphorylation (OXPHOS)-associated proteins by blue native polyacrylamide gel electrophoresis, post-translational modifications (PTMs) by isoelectric focusing (IEF), and mitochondrial ultrastructure by electron microscopy. Results: In contrast to our previous observations in Chrm1-/- ECMFs, EHMFs of Chrm1-/- mice significantly increased respiration with a concomitant increase in the supramolecular assembly of OXPHOS-associated proteins, specifically Atp5a and Uqcrc2, with no mitochondrial ultrastructural alterations. IEF of ECMFs and EHMFs from Chrm1-/- mice showed a decrease and an increase, respectively in a negatively charged (pH∼3) fraction of Atp5a relative to the wild-type mice, with a corresponding decrease or increase in the supramolecular assembly of Atp5a and respiration indicating a tissue-specific signaling effect. Discussion: Our findings indicate that loss of Chrm1 in the cortex causes structural, and physiological alterations to mitochondria that compromise neuronal function, whereas Chrm1 loss in the hippocampus may benefit neuronal function by enhancing mitochondrial function. This brain region-specific differential effect of Chrm1 deletion on mitochondrial function supports our human brain region-based findings and Chrm1-/- mouse behavioral phenotypes. Furthermore, our study indicates that Chrm1-mediated brain region-specific differential PTMs of Atp5a may alter complex-V supramolecular assembly which in turn regulates mitochondrial structure-function.

Force Regulation by Sequence-Defined Polyelectrolytes

In order to achieve multifunctional adhesive materials with water and salt tolerance, it is crucial to understand the electrostatic mechanism of nanoconfined polyelectrolytes (PEs) with specific monomer sequences. Here, using density functional theory (DFT), self-consistent field theory (SCFT), and molecular dynamics (MD) simulation, we analyzed the microstructures of sequence-defined PEs confined in a nanoscale slit and the relationship between sequences and the attractive forces induced by the nanoconfined PEs. Among three sequence-defined (alternating [A], tapered [T], and reversely tapered [R] sequence) PEs, due to the formation of stable multibridge conformations, [A]-sequence PEs induce the strongest attractive forces even in the case with high salt concentrations, i.e., the best salt tolerance. It is worth emphasizing that salt enhancement of attractive forces occurs in systems with [A]-sequence PEs due to the screening of repulsive interactions between PE chains. In contrast, in systems with [T]-sequence PEs, the shielding of the attractive interactions between surfaces and charged monomers significantly attenuates the attractive forces between surfaces at high salt concentrations. In addition, the strength of attractive forces can be regulated by block number Nb. At high charge fractions such as fc = 0.5, the attractive forces induced by [A]-sequence PEs become stronger with Nb, while at low charge fractions such as fc = 0.2, the attractive forces vary nonmonotonically with Nb due to the electrostatic correlations.

Role of Complexation Strength on the Photophysical and Transport Properties of Semiconducting Charged Polymer Complexes

The high polymer fraction in complexes of conjugated and insulating polyelectrolytes offers unique opportunities for the fabrication of conductive thick films and bulk structures. The electrostatic interactions in these systems further provide a handle for controlling their structure and properties. The impact of charge-mediated complexation strength on the photophysical and electronic transport properties in blends of conjugated polyelectrolytes (CPEs) with oppositely charged polymeric ionic liquids (PILs) was examined. Complexes were formed with varying frequency of charged repeat units, from 50 to 100%, on an anionic polythiophene-based CPE and a complimentary cationic PIL. In highly charged complexes, the intimate mixing between the CPE and the PIL reduced the structural disorder along the CPE backbone, enhancing its intrachain conjugation and interchain stacking. In weakly charged complexes (<90%), these chain planarization effects were absent and microphase separation occurred. At all charge fractions examined, the electrical conductivity of an acid-doped complex was higher than that of the unblended constituent CPE. The highest electrical conductivity, near 1 S cm–1, was found for a charge fraction of 100%. These results demonstrate the potential for designing effective polymeric conductors using electrostatic complexation.

Revealing the sources and sinks of negative cluster ions in an urban environment through quantitative analysis

Abstract. Atmospheric cluster ions are important constituents in the atmosphere, and their concentrations and compositions govern their role in atmospheric chemistry. However, there is currently limited quantitative research on atmospheric ion compositions, sources, and sinks, especially in the urban atmosphere where pollution levels and human populations are intense. In this study, we measured the compositions of negative cluster ions and neutral molecules using an atmospheric pressure interface high-resolution time-of-flight mass spectrometer (APi-TOF) and a chemical ionization mass spectrometer in urban Beijing. Quantitative analysis of cluster ions was performed by their comparison with condensation sink (CS), reagent ions, and neutral molecules. We demonstrate the feasibility of quantifying cluster ions with different compositions using in situ-measured ion mobility distributions from a neutral cluster and air ion spectrometer (NAIS). The median concentration of negative cluster ions was 85 (61–112 for 25 %–75 %) cm−3 during the measurement period, which was negatively correlated with CS. The negative cluster ions mainly consisted of inorganic nitrogen-containing ions, inorganic sulfur-containing ions, and organic ions in the form of adducts with NO3- or HSO4-. The CHON-related organic ions accounted for over 70 % of the total organic ions. Although the molecules clustered with NO3- and HSO4- had similar compositions, we found that HSO4- clustered more efficiently with CHO and CHONnonNPs species (CHON excluding nitrated phenols), while NO3- clustered more efficiently with nitrated phenols (CHONNPs). Additionally, most organic ions were positively correlated with neutral molecules, resulting in similar diurnal cycles of organic ions and neutral molecules. However, an exception was found for CHONNPs, the concentration of which is also significantly influenced by the reagent ions NO3-. The charge fractions are generally higher for molecules with higher molecular weight and a higher oxidation state, and the opposite diurnal variations in charging fractions between H2SO4 and organic species indicate a charging competition between them. Finally, we choose HSO4- and C3H3O4- as representatives to calculate the contribution of different formation and loss pathways. We found their losses are condensational loss onto aerosol particles (73 %–75 %), ion–molecule reaction losses (19 %), and ion–ion recombination losses (6 %–8 %).

Hemocompatibility of cellulose phosphate aerogel membranes with potential use in bone tissue engineering.

Cellulose is an appealing material for tissue engineering. In an attempt to overcome some obstacles with cellulose II cell scaffolding materials related to insufficient biomineralization, lack of micron-size porosity, and deficiency in surface charge, respective solutions have been proposed. These included covalent phosphorylation of different cellulose materials targeting relatively low degrees of substitution (DS 0.18-0.23) and processing these cellulose derivatives into scaffolding materials by a dissolution/coagulation approach employing the hitherto rarely used TBAF/DMSO/H2O system for cellulose dissolution. Here, we report bioactivity and preliminary hemocompatibility testing of dual-porous cellulose phosphate aerogels (contrasted with the phosphate-free reference) obtained via coagulation (water/ethanol), solvent exchange and scCO2 drying. Deposition of hydroxyapatite from simulated body fluid (7 days of immersion) revealed good bioactivity (1.5-2.2mg Ca2+ per mg scaffold). Incubation of the scCO2-dried and rehydrated scaffolding materials in heparin anticoagulated human whole blood was conducted to study selected parameters of hemostasis (prothrombin F1+2 fragment, PF4, count of thrombocyte-leukocyte conjugates) and inflammatory response (C5a fragment, leukocyte activation marker CD11b). Adhesion of leukocytes on the surface of the incubated substrates was assessed by scanning electron and fluorescence microscopy (DAPI staining). The results suggest that phosphorylation at low DS does not increase platelet activation. However, a significant increase in platelet activation and thrombin formation was observed after a certain fraction of the negative surface charges had been compensated by Ca2+ ions. The combination of both phosphorylation and calcification turned out to be a potent means for controlling the inflammatory response, which was close to baseline level for some of the studied samples.

Triboelectric polymer with excellent enhanced electrical output performance over a wide temperature range

Due to thermionic emission of triboelectric charge and degradation of mechanical stability of polymer tribomaterials (PTMs), PTMs based TENG (PTM-TENG) cannot maintain efficient electrical output and operate stably at high temperatures. Herein, a series of fatty acid doped PVDF-HFP (PH-FA) PTMs are fabricated. The introduction of FA lubricants dramatically increases the β-phase relative fraction, dielectric constant and surface charge potential of PTMs. Therefore, the PH-SA (stearic acid) based TENG shows improved electrical output over a wide temperature range, extraordinary stability, and durability. Particularly, the VT/VRoom, IT/IRoom and QT/QRoom of PH-SA at 100 °C are separately up to 231.10%, 251.46% and 234.01%, the output efficiency of PH-SA is still higher than 100% at 120 °C. This study not only provides pioneering reference for the development of advanced PTM-TENG with enhanced output performance over a wide temperature range, but also greatly promotes the application of PTM-TENG devices in harsh environments.

Study on characteristic and mechanism involved in the formation of N-nitrosodimethylamine precursors during microbial metabolism of amino acids

Amino acid metabolism by microorganisms is a new but important pathway for the formation of NDMA precursors in water. We investigated the properties of nitrosamine precursors produced through microbial metabolism of amino acids by polarity rapid assessment method and molecular weight fractionation by ultrafiltration method. The PRAM results showed that the positively charged fraction and the non-polar fraction accounted for most (45 %–79 % and 6 %–82 %, respectively) of the NDMA precursors. The MW fractionation results also indicate the dominant precursors had MWs <1 kDa or over 10 kDa. NDMA precursors produced through amino acid metabolism were identified and quantified. Dimethylamine, N-methyl-alanine and alanine methyl ester were produced during the metabolism of alanine and peptone. Together, N-methyl-alanine and dimethylamine averagely contributed 24 % (12 %–44 %) of the NDMA precursors in the alanine medium. The NDMA precursor formation pathway during alanine metabolism involves the methylation of alanine to form N-methyl-alanine and the decomposition of alanine anabolism products to form dimethylamine. Nitrosamine precursors are generally formed through anabolism or methylation, but biogenic amines or NH3 can be produced through catabolism before nitrosamine precursor synthesis. Microbial community analysis was performed and Ralstonia was found to be a likely key genus contributing to NDMA precursor formation during alanine metabolism.

Iridium nanoclusters for highly efficient p-nitroaniline fluorescence sensor

A facile strategy was proposed for the preparation of two fluorescent iridium nanoclusters of IrNCs-1 and IrNCs-2 by heating IrCl3 in N,N-dimethylacetamide (DMA) and N-Methylformanilide (MFA), respectively. The DMA and MFA are amide compounds and contain electron-rich oxygen and nitrogen atoms. They can be used as electron donors and a fraction of electron charge was transferred to Ir atom to form ligand-to-metal charge transfer (LMCT) complexes. The Ir atoms can be stabilized in LMCT complexes via accepting and localizing the electron density. These LMCT complexes with excellent fluorescent property were defined as the IrNCs. They exhibited obvious excitation wavelength-dependent emission behavior. The emission bands of two IrNCs showed red-shifting with the increasing of excitation wavelength based on the effect of “inhomogeneous broadening”. The IrNCs-1 possessed concentration-dependent emission behavior. With the decreasing of IrNCs-1 concentrations, the fluorescence spectra showed remarkable blue-shifting due to the destruction of intermolecular hydrogen bonds between IrNCs-1. In the presence of p-nitroaniline (p-NA), the fluorescence of IrNCs-1 was significantly quenched and the fluorescence bands red-shifted strongly. According to the Stern-Volmer quenching behavior under different reaction temperature and absorbance spectra of IrNCs-1 in the presence and absence of p-NA, the dynamic quenching mechanism was included. Based on these findings, the fluorescence sensor for p-NA determination was developed with the linear range of 0.1–40 μM and the limit of detection (LOD) of 50 nM. The proposed sensor was successfully applied in the p-NA determination of tap water and lake water samples, suggesting that the novel IrNCs will be a promising candidate as a luminescence sensor.

Band gap structure - Lewis acid/base feature correlation for potassium/sodium polyniobates and polytitanates

Polyniobates and Polytitanates are extensively studied because of their characteristic structure, electronic and acid/alkali feature as perovskite oxide based materials. Based on the experimental data from references and theoretical results calculated by density functional theory (DFT), respectively, the qualitative correlation between band gap structure and Lewis acid/base feature is investigated in the present paper. When it comes to band gap structure, the bond angle θ and bond length are considered as the quite influential factors. As the M-O-M bond angle deviates from 180° and the bond length elongates, the band gap energy increases. The conduction band potential and valence band potential are associated with Sanderson charge fraction δi. It can be drawn from this study that the conduction band potential is positively correlated with Lewis acid (Nbδ+ or Tiδ+) strength and valence band potential is negatively correlated with Lewis base (Oδ−) strength for potassium polyniobates and polytitanates with different phase structure. The conduction band potential and valence band potential are positively correlated with Lewis acid (Nbδ+ or Tiδ+) strength and Lewis base (Oδ−) strength for sodium polyniobates and polytitanates with same phase structure. Sanderson electronegativity and the charge for the O 1s confirm the correlation between band gap structure and Lewis acid and base. In addition, the phase structures of polyniobates and polytitanates affect the Lewis acid feature of the conduction band and Lewis base feature of valence band respectively, resulting in changes in their band gap structure.