Polyaniline Synthesized by Different Dopants for Fluorene Detection via Photoluminescence Spectroscopy

The effects of different dopants on the synthesis, optical, electrical and thermal features of polyaniline were investigated. Polyaniline (PANI) doped with p-toluene sulfonic acid (PANI-PTSA), camphor sulphonic acid (PANI-CSA), acetic acid (PANI-acetic acid) and hydrochloric acid (PANI-HCl) was synthesized through the oxidative chemical polymerization of aniline under acidic conditions at ambient temperature. Fourier transform infrared light, X-ray diffraction, UV-visible spectroscopy, field emission scanning electron microscopy, photoluminescence spectroscopy and electrical analysis were used to define physical and structural features, bandgap values, electrical conductivity and type and degree of doping, respectively. Tauc calculation reveals the optical band gaps of PANI-PTSA, PANI-CSA, PANI-acetic acid and PANI-HCl at 3.1, 3.5, 3.6 and 3.9 eV, respectively. With the increase in dopant size, crystallinity is reduced, and interchain separations and d-spacing are strengthened. The estimated conductivity values of PANI-PTSA, PANI-CSA, PANI-acetic acid and PANI-HCl are 3.84 × 101, 2.92 × 101, 2.50 × 10−2, and 2.44 × 10−2 S·cm−1, respectively. Particularly, PANI-PTSA shows high PL intensity because of its orderly arranged benzenoid and quinoid units. Owing to its excellent synthesis, low bandgap, high photoluminescence intensity and high electrical features, PANI-PTSA is a suitable candidate to improve PANI properties and electron provider for fluorene-detecting sensors with a linear range of 0.001–10 μM and detection limit of 0.26 nM.

Cellulose Nanocrystals Obtained From Microcrystalline Cellulose by p-toluene Sulfonic Acid Hydrolysis, NaOH and Ethylenediamine Treatment

Cellulose nanocrystals (CNC) were first isolated from microcrystalline cellulose (MCC) by p-toluene sulfonic acid (p-TsOH) hydrolysis. Cellulose II nanocrystal (CNC II) and cellulose III nanocrystal (CNC III) were then formed by swelling the obtained cellulose I nanocrystal (CNC I) in concentrated sodium hydroxide solutions and ethylenediamine (EDA) respectively. The properties of CNC I, CNC II and CNC III were subjected to comprehensive characterization by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA). The results indicated that CNC I, CNC II and CNC III obtained in this research had high crystallinity index and good thermal stability. The degradation temperatures of the resulted CNC I, CNC II and CNC III were 300 ℃, 275 ℃ and 242 ℃, respectively. No ester bonds were found in the resulted CNC. CNC prepared in this research also had large aspect ratio and high negative zeta potential.

Synthesis of fatty 1,2,4-trioxanes by peracetalisation of β-hydroxy hydroperoxides

The peracetalisation of a β-hydroxy hydroperoxide derived from methyl oleate was studied using benzaldehyde as a model substrate to give the corresponding fatty 1,2,4-trioxane. The desired product was obtained as a mixture of regioisomers but only one diastereoisomer of each was formed. The nature of the acid catalyst was studied and both para-toluene sulfonic acid (PTSA) and Amberlyst A35 (A35) were found to be efficient homogeneous and heterogeneous catalysts, respectively. The nature of the solvent was also investigated and ethereal solvents such as 2-methyltetrahydrofuran (2-MeTHF), methyl tert-butyl ether (MTBE) and cyclopentyl methyl ether (CPME) gave the best NMR yield (85%) for the preparation of the fatty trioxane. The optimized conditions were applied to a range of aromatic and aliphatic aldehydes and the corresponding 1,2,4-trioxanes were isolated with 30-91% yields (21 examples). The antimalarial activity of 3 trioxanes was studied against Plasmodium falciparum, however, no significant activity was detected (IC50 > 1600 nM).

Valorization of Rice Straw via Hydrotropic Lignin Extraction and Its Characterization

Rice straw hydrotropic lignin was extracted from p-Toluene sulfonic acid (p-TsOH) fractionation with a different combined delignification factor (CDF). Hydrotropic lignin characterization was systematically investigated, and alkaline lignin was also studied for the contrast. Results showed that the hydrotropic rice straw lignin particle was in nanometer scopes. Compared with alkaline lignin, the hydrotropic lignin had greater molecular weight. NMR analysis showed that β-aryl ether linkage was well preserved at low severities, and the unsaturation in the side chain of hydrotropic lignin was high. H units and G units were preferentially degraded and subsequently condensed at high severity. High severity also resulted in the cleavage of part β-aryl ether linkage. 31P-NMR showed the decrease in aliphatic hydroxyl groups and the increasing carboxyl group content at high severity. The maximum weight loss temperature of the hydrotropic lignin was in the range of 330–350 °C, higher than the alkaline lignin, and the glass conversion temperature (Tg) of the hydrotropic lignin was in the range of 107–125 °C, lower than that of the alkaline lignin. The hydrotropic lignin has high β-aryl ether linkage content, high activity, nanoscale particle size, and low Tg, which is beneficial for its further valorization.

Molecular structure of poplar lignin obtained by p-Toluene sulfonic acid (p-TsOH) and formic acid delignification

Poplar wood sawdust was chemically modified and separated into fractions using a mixture of p-toluene sulfonic acid (p-TsOH) and formic acid under different conditions. The optimum conditions of poplar lignin separation were determined by single-factor experiment. The mixed acid lignin (MAL) and the solid residues were subjected to comprehensive structural characterization by Fourier-transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (1H-NMR), X-ray diffraction (XRD), and scanning electron microscope (SEM). At the mass ratio of 5:1 of p-TsOH and formic acid, temperature of 80 °C, acid concentration of 75%, and reaction time of 20 min, more than 80% of lignin was removed, and almost all of the cellulose was retained in the solid residue. The results indicated that the p-TsOH/formic acid achieved rapid and nearly-complete dissolution of wood lignin below the water boiling temperature by enhancing the cleavage of interunitary bonds in lignin (β-O-4′ bond) and the 4-hydroxy-3-methoxy cinnamic acid structure in the lignin.

Bicyclic [1,3,4]Thiadiazolo[3,2-α]Pyrimidine Analogues: Novel One-Pot Three-Component Synthesis, Antimicrobial, and Antioxidant Evaluation

A novel one-pot three-component synthesis of 1-(7-methyl-2,5-diphenyl-5H-[1,3,4]thiadiazolo(3,2-α)pyrimidine-6-yl)ethanone (4a-i) derivatives via cyclo-condensation of substituted 2-amino-[1,3,4]thiadiazole (1a-c), acetylacetone (2) and various aromatic aldehydes (3a-c) in the presence of p-toluene sulfonic acid (PTSA) in acetonitrile. Spectral data and elemental analysis have characterized the newly synthesized compounds. The new analogs were screened for their antibacterial and antifungal activities. The majority of the tested compounds displayed significant to moderate efficacy against most of the designated organisms. Among the tested compounds, 4b, 4e, and 4h showed noteworthy efficacy against selected microbes, and compounds 4c and 4i were found to be exceptionally efficient against selected fungal strains. Compound 4c, 4e, 4f, 4i were also designated as best antioxidants against NOx.

Hybrid composites with low reflection of IR radiation

The conditions of formation and properties of hybrid organic-inorganic composites based on epoxy polymer matrix and a mixture of magnetic and polymeric fillers are studied. Based on the study of physicochemical properties of fillers and composites, it was found that the introduction of a dispersion of magnetite modified with polymer shells and polyaniline doped with toluene sulfonic acid in the thermosetting epoxy composition in the amount of 2-6 wt.% provides the ability of composites to significant absorption and low reflection of IR and microwave range. It was found that the optimal content of the composition corresponds to the best mechanical properties of the obtained coatings, in particular, high microhardness. This makes it possible to use the proposed composition to obtain on its basis composite films and coatings for anti-radar purposes, which reduce the intensity of microwave radiation acting on the object and at the same time act as protective coatings on the surface of metals.