Carboxylic Acid Functional Groups Research Articles

Fabricated copper catalyst on biochar nanoparticles for the synthesis of tetrazoles as antimicrobial agents

Biochar is a carbon-rich solid which its surface was covered by high density of carbonyl, hydroxyl and carboxylic acid functional groups. In this work, biochar nanoparticles were prepared from pyrolysis of chicken manure and further a new copper catalyst was supported on its surface (Cu-ABA@biochar) as reusable and environmental biocatalyst. The structure of this catalyst has been characterized by SEM, EDS, WDX, XRD, TGA, N2 adsorption–desorption isotherms, FT-IR and AAS techniques. SEM images of this catalyst demonstrate that particle size is less than 100 nm in diameter. The catalytic activity of this nanocatalyst was studied in the synthesis of tetrazole derivatives. Tetrazole products were obtained in high TOF and TON values in the presence of Cu-ABA@biochar, which indicate the high efficiency of this catalyst. The biological activity of obtained tetrazoles was screened against several Gram-positive & Gram-negative bacteria strains which these compounds were found to possess promising activity. This catalyst was reused for several runs without significant loss of its catalytic activity or copper leaching. Also, recovered catalyst was characterized by SEM, FT-IR, AAS and N2 adsorption–desorption isotherms. Heterogeneity and stability of this nanocatalyst was confirmed by hot filtration test and reusing of catalyst.

Probing Molecular Nanostructures of Aromatic Terephthalic Acids Triggered by Intermolecular Hydrogen Bonds and Electrochemical Potential.

Self-assembly provides unique routes to create supramolecular nanostructures at well-defined surfaces. In the present work, we employed scanning tunneling microscopy (STM) in combination with electrochemical techniques to explore the adsorption and phase formation of a series of aromatic carboxylic acids (ACAs) at Au(111)/0.1 M HClO4. Specific goals are to elucidate the roles of electrochemical potential and directional hydrogen-bonding on the structures and orientation of individual ACAs that form nanoarchitectures. ACAs are prototype materials for supramolecular self-assemblies via stereospecific hydrogen bonds between neighboring molecules. In this study, we mainly focus on a special ACA, terephthalic acid (TPA), which is almost insoluble in water, making the assembly of this molecule from aqueous solution challenging. Depending on the applied electric field, TPA molecules form distinctly different, highly ordered adlayers on Au(111) triggered by directional intermolecular hydrogen bonds. At low electrochemical potentials, TPA molecules are planar oriented, forming a potentially infinite hydrogen-bonded adlayer without any observed domain boundaries. The increase of the electrode potential triggers the deprotonation of one carboxylic acid functional group of TPA; additionally, this is accompanied by an orientation change of molecules from planar to perpendicular. In contrast, structural "defects" and multiple domain boundaries were found at this positively charged surface. The assembled nanostructures of TPA are compared with other ACAs (trimesic acid, benzoic acid, and isophthalic acid), and corresponding adsorption models were built for all molecular adlayers, showing that intermolecular hydrogen-bonding plays a determining role in the formation of two-dimensional ACA nanostructures.

Biochar as heterogeneous support for immobilization of Pd as efficient and reusable biocatalyst in C–C coupling reactions

Biochar is a stable and carbon‐rich solid which has a high density of carbonyl, hydroxyl and carboxylic acid functional groups on its surface. In this work, the surface of biochar nanoparticles (BNPs) was modified with 3‐choloropropyltrimtoxysilane and further 2‐(thiophen‐2‐yl)‐1H‐benzo[d]imidazole was anchored on its surface. Then, palladium nanoparticles were fabricated on the surface of the modified BNPs and further the catalytic application was studied as recyclable biocatalyst in carbon–carbon coupling reactions such as Suzuki–Miyaura and Heck–Mizoroki cross‐coupling reactions. The structure of the catalyst was characterized using scanning electron microscopy, transmission electron microscopy, energy‐dispersive X‐ray spectroscopy, thermogravimetric analysis, X‐ray diffraction and atomic absorption spectroscopy. The catalyst can be reused several times without a decrease in its catalytic efficiency. In addition to the several advantages reported, application of biochar as catalyst support for the first time is a major novelty of the present work.

Graphene oxide‐catalyzed CSp3–H activation of methylarenes in aqueous medium: A unified metal‐free access to amides and benzimidazoles

Graphene oxide (GO)‐catalyzed selective synthesis of amides via CSp3–H activation of methylarenes and consequent C–N bond formation with anilines under aqueous medium has been described. Oxygen functionality allied with GO surface played a dual role both as acid catalyst and oxidizing agent to some extent. However, GO has a copious effect on the reaction, shown by a high TOF value with TBHP as co‐oxidant. The decisive role of carboxylic acid functional groups on GO nanosheets in this metal‐free strategy has been confirmed and was monitored by various analytic techniques viz. Fourier transform‐infrared, UV–Vis, Raman and XPS. A plausible mechanism was proposed by control experiments and by the isolation of the intermediate. Over‐oxidation of methylarenes was not detected, and high recyclability of the carbocatalyst with its heterogeneous behavior facilitated the isolation and purification of the desired products. We have further explored the utility of this process for the chemoselective synthesis of benzimidazoles.

Gabapentin-based synthesis of novel oxo- and spiro-dihydroquinazoline derivatives

New series of gabapentin-based oxo- and spiro-1,4-dihydroquinazolins were synthesized through condensation reaction of isatoic anhydride, gabapentin and aromatic aldehydes or mono/1,3-dicarbonyl compounds. This procedure is environmentally safe due to the presence of water as a solvent. Also gabapentin acts as a catalyst via its carboxylic acid functional group. We hope these compounds to be useful for biological activities.

Film Formation of High Tg Latex Using Hydroplasticization: Explanations from NMR Relaxometry.

The film formation of acrylic latex dispersions, containing different amounts of carboxylic acid functional groups by the incorporation of methacrylic acid (MAA), was studied with GARField 1H NMR at various relative humidities (RH). Polymer particles with glass-transition temperatures in the range from 26 to 50 °C formed films at room temperature because of hydroplasticization. It was found that with an increased drying rate due to lower RH, the evaporation flux of water was limited by the latex polymer. Only in the second stage of drying this phenomenon was more obvious with increasing MAA content. 1H NMR relaxometry was used to study the change of hydrogen mobilities during film formation and hardening of the films. This showed that the drying rate itself had no impact on the hydrogen mobility in the latex films as measured via the T2 relaxation time. Hydrogen mobilities of water and the mobile polymer phase only significantly decrease after most water has evaporated. This implies that the rigidity of the polymers increases with the evaporation of water that otherwise plasticizes the polymer through hydrogen bonding with the carboxylic acid groups. This hardening of the polymer phase is essential for applications in a coating. The hydrogen mobilities were affected by the MAA concentration. Densities of mobile hydrogens increase with increasing MAA content. This is expected if the mobile protons are contained in the MAA groups. The result thus confirms the role of carboxylic acid groups in hydrogen bonding and plasticization of the copolymers. Hydrogen mobilities, however, decrease with increasing MAA content, which is hypothesized to be caused by the formation of dimers of carboxylic acid groups that still hold water. They still enable short-range polymer hydrogen mobility due to hydroplasticization but limit long-range polymer mobility due to interaction between the carboxylic acid groups.

Synthesis of poly[2-(3-butenyl)-2-oxazoline] with abundant carboxylic acid functional groups as a fiber-based sol–gel reaction supporter for catalytic applications

Polymer-based catalysts have been of special interest because of their several advantages such as easy processibility. Inorganic catalyst generally have been introduced into polymer-based media to endow catalytic activity. Surface decoration or sol–gel reaction have been performed so far, but inherent low affinity between organic/inorganic causes low efficiency in loading amount, resulting in low catalytic activity. Herein, we synthesized easily processible and highly functionalizable polyoxazoline as polymer nonwoven fiber-based catalytic supporter. Zr(OH)4 was grown on surface of fiber-web via sol–gel reaction. The Zr(OH)4 grown fiber exhibited not only excellent mechanical properties but also effective decontamination efficiency against organophosphate-based toxic agents.

Tunable surface chemistry and wettability of octafluorocyclobutane and acrylic acid copolymer combined LDPE substrate by pulsed plasma polymerization

Octafluorocyclobutane and acrylic acid (C4F8-co-AA) are plasma copolymerized onto low-density polyethylene (LDPE) and glass slides under various pulsation periods of radio frequency pulsed plasma. The surface wettability of plasma polymer coating is traditionally considered as a substrate-independent property. The combined effect of ultrathin C4F8-co-AA coatings and LDPE substrate on surface wettability is presented. The high concentration of the carboxylic acid functional groups gives rise to hydrophilicity via lowering duty cycle, and substrate impact gives rise to hydrophobicity for ultrathin coatings. The X-ray photoelectron spectroscopy and coating thickness measurements confirmed that the sudden increase in water contact angle for the lower duty cycle is influenced by the hydrophobic substrate for ultrathin polymer coatings. It is highlighted that the precise control over the surface wettability is attained by tuning the plasma parameters. The substrate-dependent wettability for flat substrate persisted for longer than 8 weeks, which demonstrates wetting stability for ultrathin coatings.

Therapeutic Effects of Amino Acids in Liver Diseases: Current Studies and Future Perspectives.

Hepatocellular carcinoma (HCC) is the most common primary malignant tumor of the liver and the third most common cause of cancer-related death worldwide. HCC is caused by infection of hepatitis B/C virus and liver dysfunctions, such as alcoholic liver disease, nonalcoholic fatty liver disease, and cirrhosis. Amino acids are organic substances containing amine and carboxylic acid functional groups. There are over 700 kinds of amino acids in nature, but only about 20 of them are used to synthesize proteins in cells. Liver is an important organ for protein synthesis, degradation and detoxification as well as amino acid metabolism. In the liver, there are abundant non-essential amino acids, such as alanine, aspartate, glutamate, glycine, and serine and essential amino acids, such as histidine and threonine. These amino acids are involved in various cellular metabolisms, the synthesis of lipids and nucleotides as well as detoxification reactions. Understanding the role of amino acids in the pathogenesis of liver and the effects of amino acid intake on liver disease can be a promising strategy for the prevention and treatment of liver disease. In this review, we describe the biochemical properties and functions of amino acids and to review how they have been applied to treatment of liver diseases.

Acetic-Acid Plasma-Polymerization on Polymeric Substrates for Biomedical Application.

Cold plasma is an emerging technology offering many potential applications for regenerative medicine or tissue engineering. This study focused on the characterization of the carboxylic acid functional groups deposited on polymeric substrates using a plasma polymerization process with an acetic acid precursor. The acetic acid precursor contains oxygen and hydrocarbon that, when introduced to a plasma state, forms the polylactide-like film on the substrates. In this study, polymeric substrates were modified by depositing acetic acid plasma film on the surface to improve hydrophilic quality and biocompatibility. The experimental results that of electron spectroscopy for chemical analysis (ESCA) to show for acetic acid film, three peaks corresponding to the C–C group (285.0 eV), C–O group (286.6 eV), and C=O group (288.7 eV) were observed. The resulting of those indicated that appropriate acetic acid plasma treatment could increase the polar components on the surface of substrates to improve the hydrophilicity. In addition, in vitro cell culture studies showed that the embryonic stem (ES) cell adhesion on the acetic acid plasma-treated polymeric substrates is better than the untreated. Such acetic acid film performance makes it become a promising candidate as the surface coating layer on polymeric substrates for biomedical application.

Toward Advanced Functional Systems: Honeycomb-Like Polymeric Surfaces Incorporating Polyoxovanadates with Surface-Appended Copper-Cyclam Complexes.

In this work the immobilization of hybrid polyoxometalates (POMs) onto functional polymeric surfaces is exposed and discussed. Thus, various hybrid polymer‒inorganic films were prepared by anchoring selected hybrid POMs onto tailored polymeric surfaces that consisted of breath figures (BFs) made of polystyrene-b-poly(acrylic acid)/polystyrene (PS-b-PAA/PS) blends. Functionalization of the BF films was performed by selective arrangement of acrylic acid groups of the amphiphilic block copolymer on the surface pores because of their affinition for the water condensed during breath figure formation. These carboxylic acid functional groups contained within the PAA blocks were then employed to anchor [Cu(cyclam)][{Cu(cyclam)}2(V10O28)]·10H2O (1-CuV10) and [{Cu(cyclam)}(VO3)2]·5H2O (1-CuV1), hybrid POMs by immersing the films into aqueous solutions of the in situ formed hybrid clusters, resulting in the hybrid films BF1 and BF2, respectively. Superficial analysis of these hybrid polymeric films was carried out by the sophisticated ion beam-based technique time-of-flight secondary ion mass spectrometry (ToF-SIMS) that was revealed to be an excellent method for the superficial compositional mapping of patterned surfaces.

Amidic succinic acid moiety anchored silica gel for the extraction of UO22+ from aqueous medium and simulated sea water

A solid phase adsorbent containing amidic carboxylic acid functional group on the surface of the silica gel was prepared by organo-surface modification reactions and characterized the product, Si-SUC, by FT-IR, Raman, thermogravimetry, X-ray diffraction, SEM-EDX and pH titration techniques. The extraction behaviour of U(VI) from aqueous solution was studied as a function of various parameters such as the aqueous phase pH, duration of equilibration, presence of interfering ions and concentration of U(VI) in aqueous phase to evaluate the feasibility using Si-SUC for the recovery of U(VI) from sea water. The kinetic data on the extraction of U(VI) was fitted into second order rate equation, and the U(VI) extraction isotherm was fitted using Langmuir, Freundlich, Dubinin- Radushkevich and Temkin adsorption models. The performance of Si-SUC was evaluated under dynamic conditions by following a break-through behaviour of U(VI) in the column study. The effect of flow-rate and concentration of U(VI) in the feed solution, on the break-through behaviour of U(VI) was studied and fitted the breakthrough curve using Thomas model.

Insight on the Sequential Vapor Infiltration Mechanisms of Trimethylaluminum with Poly(methyl methacrylate), Poly(vinylpyrrolidone), and Poly(acrylic acid)

The sequential vapor infiltration (SVI) method, based on atomic layer deposition chemistry, allows the creation of a polymer–inorganic hybrid material through the diffusion of metal–organic vapor reagents into a polymer substrate. This study investigates the reactivity of the ester, amide, and carboxylic acid functional groups of poly(methyl methacrylate) (PMMA), poly(vinylpyrrolidone) (PVP), and poly(acrylic acid) (PAA), respectively, in the presence of trimethylaluminum (TMA) vapor. This work explores the possible reaction mechanisms of these functional groups through in situ Fourier transform infrared spectroscopy and ab initio quantum chemical analysis. At temperatures of ≤100 °C, TMA physisorbs to the carbonyl groups of PMMA. As the temperature is increased, TMA forms a covalent bond with PMMA. TMA physisorbs to PVP and then partially desorbs in the presence of water for all studied temperatures of ≤150 °C. PAA readily reacts with TMA to form a covalent bond with the carbonyl group at 60 °C. This inc...

Thermomechanical behavior and thermal stability of polyurethane rigid nanocomposite foams containing binary nanoparticle mixtures

Polyurethane (PU) rigid nanocomposite foams containing binary nanoparticle mixtures were prepared via reactive foaming process by using the synergy of mixing based on H-bonding interactions between nanofillers and polymer matrix. Using a very high surface area hydrophilic fumed nanosilica with a primary particle size of 7 nm and a concentration of less than 0.2 wt% in addition to carboxylic acid functionalized multiwalled carbon nanotubes (MWCNTs-COOH) in PU rigid foams leads to improved thermal stability, thermomechanical and mechanical properties. Particularly, the system containing both 0.4 wt % CNT and 0.1 wt% nanosilica has a much higher value in terms of T g , storage modulus value at T g , reduced compressive strength, thermal stability and cell density compared to the sample containing only 0.5 wt% CNT. Based on FT-IR results, favorable and enhanced H-bonding interactions of N–H and carbonyl functional groups of the urethane linkage in PU chains with surface silanols of hydrophilic nanosilica particles and carboxylic acid functional groups of MWCNT-COOH were shown to be the main reasons for the reinforcement effect in PU rigid foams. • H-bonding interactions induced synergy of mixing between nanoparticles and PU rigid foam. • The addition of 0.4 wt % CNT and 0.1 wt % nanosilica maximized H-bonding. • The addition of 0.4 wt % CNT and 0.1 wt % nanosilica improved thermomechanical properties. • The addition of 0.4 wt % CNT and 0.1 wt % nanosilica improved reduced compressive strength, thermal stability. • The addition of CNT and more than 0.2 wt % nanosilica decreased thermomechanical properties, thermal stability.

Novel Copper(II)-Selective Potentiometric Sensor Based on a Folic Acid-Functionalized Carbon Nanotube Material

A folic acid-functionalized carbon nanotube nanomaterial was prepared by immobilizing folic acid molecules on the carbon nanotubes through covalent bonds. The material was characterized using Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy and scanning electron microscopy. Fourier transform infrared spectroscopy confirmed that folic acid molecules were grafted on the carbon nanotube surfaces through the amide bonds between the carboxylic acid functional groups of the oxidized carbon nanotubes and the amine groups of the folic acid molecules. The folic acid molecules bonded to carbon nanotube surfaces led to appreciable changes in the morphology. By using currently obtained folic acid-functionalized carbon nanotube nanomaterial as electroactive material in a polyvinyl chloride membrane, a potentiometric copper (II)-selective sensor was developed. Membrane optimization studies showed that the composition exhibiting the best potentiometric properties was 4.0% (w/w) folic acid–carbon nanotube, 64.0% (w/w) o-nitrophenyl octylether, and 32.0% (w/w) polyvinyl chloride. The developed sensor displayed a linear response in the copper (II) concentration ranging from 1.0 × 10–6 to 1.0 × 10–1 M with a correlation coefficient of 0.9993 and a slope of 29.8 ± 0.6 mV/decade of activity. The response time, detection limit, and pH working range were determined to be 4 s, 3.8 × 10–7 M and 4.0–8.0, respectively. The developed sensor showed highly selective and satisfactory potentiometric response for the determination of copper (II) in a Turkish coin.

Revealing the Structural Complex of Adsorption and Assembly of Benzoic Acids at Electrode–Electrolyte Interfaces Using Electrochemical Scanning Tunneling Microscopy

Self-assembly of benzenecarboxylic acids on well-defined noble metals has been intensively investigated using surface-sensitive techniques. However, most studies were focused on the formation of nanostructures via benzenetricarboxylic and benzenedicarboxylic acids, which are composed of multiple carboxylic acid functional groups in either the meta or para positions of the benzene ring, allowing the formation of long-range ordered molecular arrays through −COOH-mediated intermolecular hydrogen bonds. Two-dimensional nanostructures of benzoic acid molecules that are composed of a single carboxylic acid functional group on the phenyl ring at metal–electrolyte interfaces were rarely reported using scanning tunneling microscopy (STM) because there is only one carboxylic acid functional group for each benzoic acid available to form intermolecular hydrogen bonds, making it difficult to construct long-range ordered nanoarchitectures. In this work, we employed electrochemical scanning tunneling microscopy (EC-STM)...

Electro-catalytic Activity of Carbon Nanofibers Supported Palladium Nanoparticles for Direct Alcohol Fuel Cells in Alkaline Medium

Carbon nanofibers (CNFs) were successfully prepared employing a chemical vapor deposition method using chicken oil as a starting material. CNFs acquired from waste chicken fat represent a fascinating alternative to produce low-cost/cheap fuel cell electro-catalysts. The Pd/CNF electro-catalyst was synthesized using carbon nanofibers as a support material without adjusting the pH of the solution. The synthesized nanomaterials were studied using Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, Transmission electron microscopy (TEM), X-ray diffractometry (XRD), and X-ray photoelectron spectroscopy (XPS). The FTIR outcomes confirmed that the prepared carbon nanofibers are functionalized with carboxylic acid functional groups which enhance the dispersion of Pd nanoparticles. The Raman spectrum revealed that the synthesized CNFs contain two peaks D and G bands, which correspond to a disordered carbon peak (D) and graphite peak (G). TEM pictures confirmed that the synthesized nanomaterials were of the nanoscale and not uniformed in size. XRD peaks confirmed that the carbon nanofibers were amorphous and Pd (111) was observed in the Pd/CNF electro-catalyst. XPS results showed the composition of the prepared samples and the oxidation states of Pd in Pd/CNF electro-catalyst. The Pd/CNF electro-catalyst prepared by CVD method exhibits superior performance towards the electro-oxidation of ethanol and methanol as compared to the commercial palladium electro-catalyst.

Fluorenone Based Anolyte for an Aqueous Organic Redox-Flow Battery

As renewable energy sources (e.g. solar, wind) are increasingly incorporated into our electrical grid, adequate large-scale energy storage is necessary to smooth out the intermittency of these renewable sources. Redox-flow batteries (RFBs) are an attractive energy storage solution with several attributes, most notably their decoupling of power and energy. Recently, organic RFBs have gained widespread attention over their inorganic counterparts due to the ability to synthetically tune and tailor the molecular structure of the active material for improved performance. Here, we present the first aqueous organic RFB utilizing a fluorenone based negative electrolyte (anolyte). With the addition of a carboxylic acid functional group, solubility of the fluorenone anolyte is enabled under alkaline conditions with a maximum solubility of 1M. Paired with a ferro/ferricyanide redox couple in the positive electrolyte (catholyte), this RFB can achieve an open circuit potential of 1.18V which rivals many other aqueous organic RFB chemistries that have previously been reported. Galvanostatic charge/discharge cycling has shown coulombic efficiencies in excess of 90% with energy and voltaic efficiencies above 80%. Moreover, the cost of this material has been quoted to be as low as $2/kg compared with the current state-of-the-art inorganic vanadium RFBs at greater than $80/kg. This work will show the potential for fluorenone based anolytes as promising candidates to further promote widespread commercialization of RFBs.

Evolution of C-Terminal Modification Tolerance in Full-Length and Split T7 RNA Polymerase Biosensors.

T7 RNA polymerase (RNAP) is a powerful protein scaffold for the construction of synthetic biology tools and biosensors. However, both T7 RNAP and its split variants are intolerant to C-terminal modifications or fusions, thus placing a key limitation on their engineering and deployment. Here, we use rapid continuous-evolution approaches to evolve both full-length and split T7 RNAP variants that tolerate modified C termini and fusions to entire other proteins. Moreover, we show that the evolved split C-terminal RNAP variants can function as small-molecule biosensors, even in the context of large C-terminal fusions. This work provides a panel of modified RNAP variants with robust activity and tolerance to C-terminal fusions, and provides insights into the biophysical requirements of the C-terminal carboxylic acid functional group of T7 RNAP.

Fluorenone Based Anolyte for an Aqueous Organic Redox-Flow Battery

Here we present the first aqueous organic redox-flow battery based on a fluorenone anolyte. The use of polar carboxylic acid functional groups on the core fluorenone molecule enables good solubility under alkaline conditions. Three isomers of carboxyl functionalized fluorenone were screened, with the most promising, 9-fluorenone-2-carboxylic acid, achieving a maximum solubility of 0.8M in 1M KOH with a redox potential of -690 mV vs SHE. When paired with a ferro/ferricyanide redox couple, an open cell potential of 1.18 V was achieved. However, during charge/discharge cycling significant capacity loss was observed within the first few cycles. In addition, flow-battery tests showed low limiting current densities and peak power densities. Subsequent analysis revealed that the redox reversibility of the fluorenone molecules is strongly dependent on pH and potential, which can lead to undesired irreversible redox reactions.