Excited state intramolecular proton transfer in 2-(2'-arylsulfonamidophenyl)benzimidazole derivatives: insights into the origin of donor substituent-induced emission energy shifts

Donor-substituted 2-(2'-arylsulfonamidophenyl)benzimidazoles undergo efficient excited-state intramolecular proton transfer (ESIPT) upon photoexcitation. The tautomer emission energy depends strongly on the substituent attachment position on the fluorophore pi-system. While substitution with a donor group in the para-position relative to the sulfonamide moiety yields an emission energy that is red-shifted relative to the unsubstituted fluorophore, fluorescence of the meta-substituted derivative appears blue-shifted. To elucidate the origin of the surprisingly divergent emission shifts, we performed detailed photophysical and quantum chemical studies with a series of methoxy- and pyrrole-substituted derivatives. The nature and contribution of solvent-solute interactions on the emission properties were analyzed on the basis of solvatochromic shift data using Onsager's reaction field model, Reichardt's empirical solvent polarity scale ET(30), as well as Kamlet-Abboud-Taft's empirical solvent index. The studies revealed that all ESIPT tautomers emit from a moderately polarized excited-state whose dipole moment is not strongly influenced by the donor-attachment position. Furthermore, the negative solvatochromic shift behavior was most pronounced in protic solvents presumably due to specific hydrogen-bonding interactions. The extrapolated gas-phase emission energies correlated qualitatively well with the trends in Stokes shifts, suggesting that solute-solvent interactions do not play a significant role in explaining the divergent emission energy shifts. Detailed quantum chemical calculations not only confirmed the moderately polarized nature of the ESIPT tautomers but also provided a rational for the observed emission shifts based on the differential change in the HOMO and LUMO energies. The results gained from this study should provide guidelines for tuning the emission properties of this class of ESIPT fluorophores with potential applications in analytical chemistry, biochemistry, or materials science.     

Chemical composition,antimicrobial and insecticidal activities of the essential oils of Conyza linifolia and Chenopodium ambrosioides

Two essential oil-containing plants growing wildly in Egypt: Conyza linifolia (Willd.) Täckh. (Asteraceae) and Chenopodium ambrosioides L. (Chenopodiaceae) were subjected to essential oil analysis and biological investigation. The essential oils from both plants were prepared by hydrodistillation, and GC/MS was employed for volatiles profiling. This study is the first to perform GC/MS analysis of C. linifolia essential oil growing in Egypt. C. linifolia essential oil contained mainly sesquiterpenes, while that of C. ambrosioides was rich in monoterpenes. Ascaridole, previously identified as the major component of the latter, was found at much lower levels. In addition, the oils were investigated for their antimicrobial activity against two Gram positive and two Gram negative bacteria, and one fungus. The insecticidal activities of both oils, including mosquitocidal and pesticidal potentials, were also evaluated. The results of biological activities encourage further investigation of the two oils as antimicrobial and insecticidal agents of natural origin.     

Parameters affecting carbofuran photocatalytic degradation in water using ZnO nanoparticles

Carbofuran photodegradation in water using zinc oxide nanoparticles as a catalyst was examined as well as some parameters influencing its percentage degradation rate such as zinc oxide load, initial concentration of carbofuran, the temperature of the reaction, the initial pH of the solution, and doping of zinc oxide nanoparticles with 5% (w:w) silver. Zinc oxide and Ag-doped zinc oxide nanoparticles were produced using solvothermal and photoreduction methods, respectively, and silver doping effects on the structural, optical, and photocatalytic properties of zinc oxide nanoparticles were investigated using XRD, UV-VIS spectrophotometer, TEM, SEM, SEM/EDX, and FTIR. The average diameter of the synthesized samples was 26.6, 30.55 nm for undoped zinc oxide and Ag-doped zinc oxide, respectively. Zinc oxide doping with silver did not change the shape of the zinc oxide crystal, but decreased the reflection in the visible region, as well as the energy of the bandgap, and increased the zinc oxide photocatalytic activity.     

Production and evaluation of second antibody for radioimmunoassay technique

Polyclonal antibody production in mammals is generally associated with multiple injections of antigens and adjuvant and repeated blood sampling procedures. In the production of second polyclonal antibodies, a number of critical steps can be identified that may influence the outcome of the animal experiment (immunological results and the pain and suffering of the animals). The goal of this work was to evaluate critical steps in the production of these antibodies, and to optimize production protocols that will ultimately result in effective antibody responses. This work was achieved through immunization of two healthy sheep by purified Alpha feto protein (AFP) antigen. Also, the present study involved the preparation of AFP standards from human cord blood. Furthermore, preparation of a radiolabeled AFP tracer of a high specific activity using ¹²⁵I isotope by chloramine T method was undertaken. Moreover, this study provides that there was no observable difference between the Scottish Antibody Production Unit (SAPU) and Sigma SAM IgG and the two second antibodies obtained from the local sheep sera.     

Sol-gel TiO2 decorated on eggshell nanocrystal as engineered adsorbents for removal of acid dye

Calcined eggshell (CES) food residue was modified by depositing sol-gel titanium dioxide (TiO₂) nanoparticles with narrow size distribution onto it through in situ precipitation and a novel hybrid nano biosorbent, namely TiO₂-CES, was obtained. The deposition was characterized and the TiO₂-CES nano network was used for efficient adsorption of single azo class anionic dye acid red nylon 57 (AN57) from aqueous solutions and the adsorption was pH dependent. Lower pH favored the sorption at the tested different pHs of 1.0–8.0. The calcination temperature had a cogent influence on the adsorption process. The sorption process reached equilibrium within 40?min, and the mathematical models were positively verified and could be described by a pseudo-second-order pattern, while equilibrium was described with Langmuir-type equation. In addition, the reusability study has proven that 0.5?M HNO₃ was efficient enough to desorb AN57 from the hybrid nano sorbent. All results validated that TiO₂-CES is Eco-Friendly adsorbent material practical treatment of dyes contaminated water.