Effect of Solvent Polarity on Excited-State Double Proton Transfer Process of 1,5-Dihydroxyanthraquinone

The excited-state double proton transfer(ESDPT)properties of 1,5-dihydroxyanthraquinone(1,5-DHAQ)in various solvents were investigated using femtosecond transient absorption spectroscopy and the DFT/TDDFT method.The steady-state fluorescence spectra in toluene,tetrahydrofuran(THF)and acetonitrile(ACN)solvents presented that the solvent polarity has an effect on the position of the ESDPT fluorescence emission peak for the 1,5-DHAQ system.Transient absorption spectra show that the increasing polarity of the solvent accelerates the rate of excited state dynamics.Calculated potential energy curves analysis further verified the experimental results.The ESDPT barrier decreases gradually with the increase of solvent polarity from toluene,THF to ACN solvent.It is convinced that the increase of solvent polarity can promote the occurrence of the ESDPT dynamic processes for the 1,5-DHAQ system.This work clarifies the mechanism of the influence of solvent polarity on the ESDPT process of 1,5-DHAQ,which provides novel ideas for design and synthesis of new hydroxyanthraquinone derivatives.

Effects of Hydrogen-bonding Interaction and Polarity on Emission Spectrum of Naphthalene-Triethylamine in Mixed Solvent

The effects of the protic and aprotic polar solvents on the emission spectrum of the naphthalene-triethyl-amine system in THF were studied under conditions of steady-state illumination. The fluorescence spectrum of the naphthalene-triethylamine system consists of two emission bands, the fluorescence band of naphthalene(band A, 329 nm) and the emission band of the exciplex(band B, 468 nm). The intensities of both the emission bands decrease with increasing the solvent polarity. The intensity of band B also decreases due to the hydrogen-bonding interaction between triethylamine and protic solvent, while that of band A increases. It is thus suggested that the quenching of naphthalene fluorescence by triethylamine in THF occurs through the charge transfer and electron transfer reactions. The spectral changes upon the increase of solvent polarity can be explained by the dependences of the equilibrium constant between exciplex and ion-pair and the rate constant for the electron transfer reaction from triethylamine to the excited naphthalene on the relative permittivity of solvent. It is shown that the formation of intermolecular hydrogen-bonding between triethylamine and protic solvent suppresses the quenching reaction by the decrease in free amine. Acetonitrile has only a polar effect and trichloroacetic acid only a hydrogen-bonding(or protonation) effect, while alcohols have both the effects. The effects of alcohols could be separated into the effects of solvent polarity and intermolecular hydrogen-bonding interaction quantitatively.

Advancements in Polymer Science: Synthesis, Characterization, and Biomedical Applications of Homopolymers and Copolymers

Polymer science encompasses a different range of materials critical to industries spanning from packaging to biomedicine. Understanding the synthesis, characterization, and applications of common homopolymers and copolymers is fundamental to advancing polymer research and development. In this comprehensive review, we explore various preparation methods, including free radical, anionic, and cationic polymerization, utilized for synthesizing homopolymers and copolymers. Furthermore, we investigate solvent choices commonly employed for polymer characterization, ranging from neat conditions, polar protic and polar aprotic solvents. We also explored characterization techniques, including Fourier Transform Infrared Spectroscopy (FTIR), Nuclear Magnetic Resonance (NMR), Atomic Force Microscopy (AFM), Differential Scanning Calorimetry (DSC), and Thermogravimetric Analysis (TGA). In addition to industrial applications, we highlight the diverse biological applications of homopolymers, poly(2-hydroxyethyl methacrylate) (pHEMA) and polystyrene, which find its extensive use in biomedicine. By synthesizing and analyzing this wealth of information, this review aims to provide a comprehensive understanding of the synthesis, characterization, and applications of homopolymers and copolymers, with a particular focus on their biological applications. This holistic approach not only contributes to advancements in polymer science and technology but also fosters innovation in biomedicine, ultimately benefiting human health and well-being.

Lipid extraction and CO_(2)capture with switchable polarity solvent

In this study,lipid extraction and CO_(2)capture are combined using N,N-dimethylcyclohexylamine(DMCHA)as switchable polarity solvent.The effects of operation parameters are discussed according to the CO_(2)absorption/desorption and lipid/DMCHA recovery results.A triphasic models considering lipid,water,and gas phases are established to analyze the kinetic behaviors.The results show that DMCHA is reversible through CO_(2)absorption/desorption,and the enhanced dispersion of droplets and bubbles in water phase improves the lipid/DMCHA recovery and CO_(2)absorption/desorption.The triphasic kinetic models fit well with experimental data,and gas-liquid mass transfer is regarded as the rate-determining step.The lower interfacial areas result in the poorer gas-liquid mass transfer for the DMCHA recovery than lipid recovery process.

Solvent Effects on Spectral Property and Dipole Moment of the Lowest Excited State of Coumarin 343 Dye

Steady-state absorption and fluorescence spectra, and time-resolved fluorescence spectra of coumarin 343 （C343） were measured in different solvents. The effect of the solvent on the spectral properties and dipole moment of the lowest excited state of C343 were investigated. It was found that the absorption and fluorescence spectra red-shifted slightly and strongly with increasing solvent polarity, respectively, because the charge distribution of the excited state leaded to the increasing difference between the absorption and fluorescence spectra with increasing solvent polarity. The dipole moment of the lowest excited state of C343 was determined from solvatochromic measurements and the quantum chemical calculation, and the results obtained from these two methods were fully consistent. Investigations of the time-resolved fluorescence of C343 in different solvents indicated that the fluorescence lifetimes increased nearly linearly with 4.45 ns in water. This can be ascribed between C343 and hydrogen donating increasing solvent polarity from 3.09 ns in toluene to to the intermolecular hydrogen bonding interactions solvents

Molten salt as ultrastrong polar solvent enables the most straightforward pyrolysis towards highly efficient and stable single-atom electrocatalyst

Currently,pyrolysis as the most widely used method still has some key issues not well resolved for synthesis of carbon-supported single-atom catalysts(C-SACs),e.g.,the sintering of metal atoms at high temperature as well as the high cost and complicated preparations of precursors.In this report,molten salts are demonstrated to be marvellous medium for preparation of C-SACs by pyrolysis of small molecular precursors(ionic liquid).The ultrastrong polarity on one hand establishes robust interaction with precursor and enables better carbonization,resulting in largely enhanced yield.On the other hand,the aggregation of metal atoms is effectively refrained while no nanoparticle or cluster is formed.By this strategy,a C-SAC with atomically dispersed Fe-N_(4) sites and a high specific area over 2000 m^(2) g^(-1) is obtained,which illustrates high ORR activity in both acid and alkaline media.Moreover,this SAC exhibits superior methanol tolerance and stability after acid soaking at 85℃ for 48 h.It is believed that the molten-salts-assisted pyrolysis can be developed into a routine strategy as it not only can largely simply the synthesis of C-SACs,but also can be extended to prepare other types of SACs.

Effects of Polar Organic Solvent on Separation of Y(edta)^-/Nd(edta)^- Complexes on Polyacrylic Anion Exchangers

The use of polar organic solvents for the separations of rare earth elements (Ⅲ) is effective especially for their extensive separations despite the solubility limitations. The study shows that polyacrylate anion exchangers, particularly the weakly basic, gel anion exchanger Amberlite IRA 68, can be applied to the separation of rare earth complexes with EDTA in H_2O-methanol and H_2O-ethanol systems. In most cases the determined distribution coefficients of Ln^(3+) complexes with EDTA in mixed media like water-methanol on polyacrylate anion exchangers are larger than those in pure water (media.)

Probing the Impact of Solvent on the Strength of Lewis Acids via Fluorescent Lewis Adducts

Various methods have been developed to measure the strength of a Lewis acid.A major challenge for these measurements lies in the complexity that arises from variable solvent interactions and perturbations of Lewis acids as their reaction environment changes.Herein,we investigate the impact of solvent effects on Lewis acids for the first time as measured by the fluorescent Lewis adduct(FLA)method.The binding of a Lewis acid in various solvents reveals a measurable dichotomy between both polarity and donor ability of the solvent.While not strictly separable,we observe that the influence of solvent polarity on Lewis acid unit(LAU)values is distinctly opposite to the influence of donor ability.This dichotomy was confirmed by titration data,illustrating that solvation effects can be appropriately and precisely gauged by the FLA method.

Redshift of Excitation Wavelength Caused by the Concentration of L-Tryptophan in Water: A Theoretical and Experimental Study

A redshift in the wavelength of excitation spectra is experimentally measured as a function of the concentration parameter for tryptophan solutions in water. To understand the microscopic causes of this behavior, theoretical calculations obtained from four model clusters are carried out: (Trp)1 - (H2O)9, (Trp)2 - (H2O)18, (Trp)3 - (H2O)27 and (Trp)4 - (H2O)36, where there are interactions among 1, 2, 3 and 4 molecules of tryptophan. According to the literature, each interaction occurred with nine molecules of water to stabilize its expected zwitterionic form. In these models, the molecules of tryptophan appear at an adjacent distance among them to generate an analogous behavior when there is an experimental increase in the concentration. It is evident that the distance between adjacent molecules of tryptophan decreases as their concentration increases. The optical properties of these clusters are obtained by studying the corresponding excited states and the molecular orbitals involved, showing charge transfers by using time-dependent density functional theory (TD-DFT) methods. The experimental spectroscopic data are obtained by using the clusters proposed, and good agreement is found by drawing a comparison with the theoretical data.

水基性透明液体剂型的加工、性能和差异(Ⅱ)

4微乳剂早在20世纪40年代,Hoar和Schulman等人发现油-水混合物借助表面活性剂可以自发地形成透明的分散体系,由于所形成的液滴粒径非常小,后来将这种体系命名为微乳液。此后证明,它是一个热力学上稳定的、均相的水包油型乳液可溶体系,加工的微乳液剂型即为微乳剂。微乳液存在3种结构类型,即O/W型。

Electron transport in solution-grown TIPS-pentacene single crystals:Effects of gate dielectrics and polar impurities

The n-channel behavior has been occasionally reported in the organic field-effect transistors （OFETs） that usually exhibit p-channel transport only. Reconfirmation and further examination of these unusual device performances should deepen the understanding on the electron transport in organic semiconductors. 6,13-bis（triisopropyl-silylethynyl） pentacene （TIPS-pentacene）, a widely examined p-channel material as Au is used for source-drain electrodes, has recently been reported to exhibit electron transport when grown from non-polar solvent on divinyltetramethyldisiloxanebis （benzocy- clobutene） （BCB） dielectric, spurring the study on this unusual electron transport. This paper describes FET characteristics of solution-grown TlPS-pentacene single crystals on five polymer gate dielectrics including polystyrene （PS）, poly（methyl methacrylate） （PMMA）, poly（4-vinyl phenol） （PVP）, poly（vinyl alcohol） （PVA） and poly（vinylidene fluoride-trifluoroethylene-chlorofluoroethylene） （P（VDF-TrFE-CFE））. In addition to the p-channel behavior, electron transport occurs in the crystals on PMMA, PS, thick PVA （40 nm） and a bilayer dielectric of PMMA on P（VDF-TrFE-CFE）, while does not on PVP and thin PVA （2 nm）. The two distinct FET characteristics are consistent with the previous reported trap effect of hydroxyl groups （in PVP and PVA） and reduced injection barrier by Na~ ions （as impurity in PVA）. The highest electron mobility of 0.48 cm2 V-1 s-1 has been achieved in the crystals on PMMA. Furthermore, the electron transport is greatly attenuated after the crystals are exposed to the vapor of a variety of polar solvents and the attenuated electron transport partially recovers if the crystals are heated, indicating the adverse effect of polar impurities on electron transport. By reconfirming the n-channel behavior in the OFETs based on TIPS-pentacene, this work has implications for the design of n-channel and ambipolar OFETs.

Antibacterial activity of starfish Stellaster equestris from Southeast Coast of India

Objective:To isolate and characterize the antibacterial compounds from starfish Stellaster equestris(S.equestris).Methods:The whole body was extracted with high polar and medium polar solvents such as methanol and ethanol.The antibacterial activity has been tested against human bacterial pathogens using standard disc diffusion method.Results:The starfish S.equestris was collected from Mudasalodai,southeast coast of India.the maximum zone inhibition[(9.7±0.3)mm]against Escherichia coli(E.coli)and Vibrioparahaemolyticus at 100%concentration and minimum was Staphylococcus aureus[(4.0±0.6)mm].The crude ethanol extract showed maximum zone of inhibition in E.coli[(9.70±0.33)mm]and the lowest concentration exhibited the minimum inhibition activity against all bacterial pathogens.The fractions showed the maximum inhibition zone in Klebsiella oxytoca(5.00±0.82 mm),Salmonella typhi(S.typhi)(5.00±0.82)and Staphylococcus aureus[(3.0±2.3)mm].One way ANOVA analysis of antibacterial activity showed no significant difference at 0.05%level(P>0.05).The crude ethanol extract showed the minimum inhibitory concentration against E.coli(100%),Klebsiella pneumoniae The present investigation exhibited that the crude methanol extract showed the minimum inhibitory concentration against Klebsiella pneumonia,Proteus mirabilis,S.typhi,Staphylococcus aureus and Vibrio cholerae at 100%whereas E.coli was at 75%concentration.No bacterial growth was observed against Klebsiella oxytoca at 100%concentration.Conclusions:(75%),S.typhi(100%)and Vibrio cholerae(100%).The fraction exhibited equestris have remarkable antimicrobial activities against human bacterial pathogens.Further fraction has been characterised by using GC-MS and ^(1)H and ^(13)NMR spectroscopy analysis.The result of the present study indicates that the crude and fractions of starfish S.

Synthesis and orientational assemblies of MgO nanosheets with exposed(111) facets

MgO nanosheets with exposed（111） facets were obtained through the preparation of Mg（OH）2 precursor by a hydrothermal method in the presence of oleylamine and subsequent calcination in air. The different preferred orientational assemblies of Mg O nanosheets, achieved by adjusting the polarity of dispersing solvents（ethanol and cyclohexane） during the sample preparation, show different structural and spectral features.