Effect Of Carboxyl Groups Research Articles

Effect of carboxyl group on photoelectrochemical performance of TiO2nanowire arrays for water splitting.

TiO2is one of the most studied semiconductor materials for the photoelectrochemical water splitting to hydrogen production, but it only responds to ultraviolet light. The introduction of organic compound is one of the common means to expand the visible light response of TiO2. In this work, rutile TiO2nanowire arrays (NWs) were grown on conductive glass by a modified solvothermal method using oleic acid as the key additive. The obtained TiO2NWs are characterized using x-ray diffraction, x-ray photoelectron spectroscopy, infrared spectroscopy and electrochemical characterization. The results show that the carboxyl groups arising from oleic acid are chemically bonded with the TiO2NWs in the form of chelating bidentate, which increases the visible light absorption range and active sites of TiO2, and reduces the transfer resistance between the photoelectrode and the electrolyte. The photocurrent density is doubled to 0.17 mA cm-2at 1.23 V vs. RHE. This work provides a novel idea for the design of metal oxide semiconductor photoanodes by adsorbing organic compounds.

Nanoscale mechanisms of carboxyl carbon preservation during Fe(II)-induced ferrihydrite transformation

The persistence of organic carbon (OC) in natural environments is widely attributed to OC associations with minerals such as iron (Fe) minerals. Carboxyl, a critical structure of OC, can form strong complexes with Fe minerals, but it is still largely unknown about the effects of carboxyl groups on the transformation of Fe oxides and the stabilization mechanisms of OC on Fe oxides at nanoscales. In this study, four carboxylic acids with varying numbers of carboxyl groups (2, 3, 4, and 27 carboxyls) and molecular weight (ranging from 100 to 2000 Da) were added during the coprecipitation of Fe oxides and OC. This approach was taken to systematically elucidate the nanoscale distribution and sequestration mechanisms of carboxyl-containing OC on Fe oxides over different aging periods. Results suggested that ferrihydrite transformed quickly into lepidocrocite, goethite, and magnetite with the presence of Fe(II). The transformation rate of lepidocrocite to goethite slowed with increasing carboxyl number in OC molecules for the low molecular weight carboxylic acids (100–300 Da), but the high molecular weight carboxylic acid (∼2000 Da) promoted ferrihydrite transformation into goethite. Meanwhile, the particle sizes of produced magnetite decreased with increasing carboxyl number in OC molecules. During the mineral transformation, the release of OC from Fe oxides to aqueous solution decreased with increasing numbers of carboxyl groups. Spherical aberration corrected scanning transmission electron microscopy (Cs-STEM) coupled with electron-energy-loss spectroscopy (EELS) suggested that carboxyl-rich OC promoted the formation of abundant defective or porous structures in goethite, resulting in OC accumulation in the bulk areas of goethite, which provided an effective way to sequester OC. The aggregation of high molecular weight OC containing more carboxyl groups with magnetite nanoparticles also played an important role in the preservation of OC. Furthermore, Fourier-transform infrared spectroscopy (FTIR) and near edge X-ray absorption fine structure spectroscopy (NEXAFS) indicated that OC may form bidentate binding with Fe oxides and the binding strength of Fe(III) and OC may change with varying numbers of carboxyl groups. Results in this study provided a comprehensive understanding of the dynamic interactions between OC with different numbers of carboxyl groups and Fe oxides, and shed insights into the nanoscale mechanisms of OC stabilization during Fe oxide transformation process.

Inhibition of cinnamic acid and its derivatives on polyphenol oxidase: Effect of inhibitor carboxyl group and system pH

Phenolic acids are promising inhibitors of polyphenol oxidase (PPO), but the effects of carboxyl group and pH on their inhibition effects are still unclear. In this study, methyl cinnamate, cinnamic acid and 4-carboxycinnamic acid were investigated by their inhibitory effects with pH varied from 6.8 to 5.0. Results showed that 4-carboxycinnamic acid had the strongest inhibitory effect on PPO, followed by cinnamic acid and methyl cinnamate. Acidic pH enhanced the inhibitory effects of cinnamic acid and its derivatives on PPO, and the enhancement degree, IC50 and Ki declining degree were followed as 4-carboxycinnamic acid > cinnamic acid > methyl cinnamate. Methyl cinnamate exhibited competitive inhibition on PPO, while cinnamic acid and 4-carboxycinnamic acid exhibited mixed-type inhibition. Inhibitors induced slight changes in the secondary and tertiary structures of PPO, which were enhanced by acidic pH. Molecular docking results showed that 4-carboxycinnamic acid exhibited the strongest binding ability, and the main interaction forces were around carboxyl groups, and acidic pH enhanced the binding effect through more interactions and lower binding energy. This study could provide new insights into industrial application of cinnamic acid and its derivatives for the control of enzymatic browning of fruits and vegetables.

Synergistic mechanism of formaldehyde adsorption by intrinsic defects and carboxyl groups on the surface of carbon materials

The adsorption of formaldehyde on the original carbon material is limited. Determining the synergistic adsorption of formaldehyde by different defects on the carbon material is necessary for comprehensively understanding the mechanism of formaldehyde adsorption on the surface of the carbon material. The synergistic effect of intrinsic defects and oxygen-containing functional groups on formaldehyde adsorption on the surface of carbon materials was simulated and verified by experiments. Based on the density functional theory, the adsorption of formaldehyde on different carbon materials was simulated by quantum chemistry. The synergistic adsorption mechanism was studied by energy decomposition analysis, IGMH, QTAIM, and charge transfer, and the binding energy of hydrogen bonds was estimated. The results showed that the energy for the adsorption of formaldehyde adsorbed by the carboxyl group on the vacancy defect was the highest, at −11.86 kcal/mol, the hydrogen bond binding energy was −9.05 kcal/mol, and a larger charge transfer was recorded. The mechanism of synergy was studied comprehensively, and the simulation results were verified at multiple scales. This study provides valuable insights into the effect of carboxyl groups on the adsorption of formaldehyde by activated carbon.

Removal Efficiency of Heavy Metals Such as Lead and Cadmium by Different Substrates in Constructed Wetlands

In order to find an efficient and economical wetland substrate to treat mine wastewater containing various heavy metals, and effectively realize the resource utilization of water treatment residuals, in this paper, the treatment efficiency of mine wastewater containing various heavy metals was investigated using unburned ceramsite prepared from water treatment residuals (UCWTR) and clay ceramsite. The continuous dynamic test results showed that the removal rate of Pb, Cd, Cu, Zn, and Fe can reach more than 98.5% after the UCWTR-based CWs runs for 56 days, and its concentration was 30.05%, 24.85%, 20.82%, 14.63%, and 7.91% lower than that of the clay ceramsite-based CWs, respectively. SEM, XPS, and FT-IR showed that the characteristic peaks of two ceramsites were basically similar. The ceramsite undergoes ion exchange, coordination complexation, and chelation reaction with Pb, Cd, Cu, Zn, and Fe under the action of the gel of internal groups -OH, C=O, Al-OH, Si-Fe-O and C-S-H. Compared with clay ceramsite, the ion exchange reaction and chelation reaction of -OH effect and the coordination reaction of C=O effect of carboxyl group in UCWTR were enhanced. In conclusion, using UCWTR as a CWs substrate can effectively enhance the adsorption capacity of heavy metals, providing a scientific basis for the application of UCWTR-based CWs in mine wastewater treatment.

Effects of Carboxyl Functionalized CNT on Electrochemical Behaviour of Polyluminol-CNT Composites

The effect of carboxyl groups on the redox activity of polyluminol-carbon nanotube composites was studied. Carboxyl groups were selected due to their known contributions toward surface wettability and pseudocapacitance while often present on naturally derived low-cost porous carbons. Density functional theory (DFT) predicted energetically favoured bonding and a significantly reduced band gap between the luminol and carboxylated graphene relative to that of bare graphene, suggesting improved charge storage for carboxylated carbon substrates. The prediction was validated using bare carbon nanotubes (CNTs) and carboxylated CNTs (COOH-CNTs) as the substrates for in situ chemical polymerized luminol (CpLum). Surface morphological studies showed a ca. 1.1 nm thick coating of CpLum on CNT (CpLum/CNT) and a ca. 1.3 nm on COOH-CNT (CpLum/COOH-CNT), while surface chemical analysis revealed ca. 10% nitrogen from CpLum on both CpLum/CNT and CpLum/COOH-CNT. However, with merely 4.4% of COOH functionalization, CpLum/COOH-CNT was able to store more charge (137.1 ± 17.1 C cm−3) relative to CpLum/CNT (86.1 ± 14.1 C cm−3) and had increased charge retention over 5000 cycles. The insights from these studies can be used to engineer the surface of carbons such as CNTs and ACs to improve the interfacial properties for redox active materials and composites.

Effects of pyridinic N of carboxylic acid on the polymerization of polyaniline and its supercapacitor performances

Phthalic acid and 2,3-pyrazinedicarboxylic acid doped PANI were synthesized on carbon felt electrode by a simple hydrothermal method. A systematic study was done to show the effect of carboxylic acid groups and pyrazine moiety on the energy storage properties of polyaniline and the obtained electrodes were characterized using X-ray photoelectron spectroscopy, X-ray diffraction, Fourier Transform Infrared spectroscopy, Thermogravimetric analysis, Brunauer–Emmett–Teller surface area analysis and Scanning Electron Microscopy. Better specific capacitance of polyaniline (PANI) was observed in the presence of 2,3-pyrazinedicarboxylic (Pzdc) acid. The strengthening of electron delocalization of the PANI structure with pyridine N, the increase of π-π interactions and the formation of hydrogen bonds with the effect of carboxyl groups in the 2,3 pyrazine dicarboxylic acid contributed to the improvement of the energy storage properties of PANI. (Strengthening electron delocalization of the PANI structure with pyridine N, increased π-π interactions, and the formation of hydrogen bonds under the influence of carboxyl groups in the 2,3 pyrazine dicarboxylic acid contributed to the improvement of the energy storage properties of PANI.)Moreover, the study focused on showing the effect of the 2,3-pyrazinedi carboxylic acid ratio on its charge storage properties. Electrochemical measurements were carried out in 3.0 M KCl aqueous electrolyte solution. The results show that the high specific capacitance of 882.0 F g−1 is observed for Pzdc(0.02)/PANI electrode at the current density of 7 A g−1. Further, the supercapacitor electrode performed a good cycling test (96.7 %) after 2000 cycles with a high operating potential of 1.5 V. The fabricated symmetrical supercapacitor device has high cyclic stability and good electrochemical performance (energy density of 27.2 Wh kg−1 and 81.7 % at 2500 cycles).

Binding mechanism of functional moieties of a mixed-mode ligand in antibody purification

Functional moieties are critical in mixed-mode ligand design for separation and purification of biomolecules. This study investigated the role of carboxyl group and a hydrophobic moiety on a recently developed mixed-mode ligand (Phenylalanine-Tyrosine-Glutamate-“5-aminobenzimidazole”, FYE-ABI) for hIgG purification. The effects of carboxyl group were focused for its appearance in several commercial mixed-mode ligands. A ligand with glutamic acid on FYE-ABI substituted by glutamine (Phenylalanine-Tyrosine-Glutamine-“5-aminobenzimidazole”, FYQ-ABI) was first prepared to explore the binding mechanism of the FYE-ABI ligand. The selectivity (52.1%) of the FYQ-ABI ligand was found inferior comparing to the original design, which was gradually recovered during the hydrolysis process of glutamine (Gln) to glutamic acid (Glu). Meanwhile, a cationic exchange resin CM Bestarose Fast Flow with carboxyl group was used for comparison and the results demonstrated that other moieties such as aminobenzimidazole were helpful for elution processes. A new model mixed-mode ligand with such a design principle (a carboxyl group for binding and aminobenzimidazole for elution) was thus synthesized and comparable separation performance was achieved using the prepared resins. The model ligand had much simplified chemical structure and this study can help for the design of related mixed-mode ligands for antibody purification.

Confinement of Pt nanoparticles in cage-type mesoporous silica SBA-16 as efficient catalysts for toluene oxidation: the effect of carboxylic groups on the mesopore surface

In this work, 3D cage-type mesoporous SBA-16 materials functionalized with –COOH groups are used to support Pt metals and provide high catalytic activity for toluene oxidation.

Effect of carboxylic group on the compatibility with retarder and the retarding side effect of the fluid loss control additive used in oil well cement.

The retarding side effect and the compatibility with other additives are the main problems that limit the field application of the synthesized fluid loss control additive (FLCA). The effect of the type and content of carboxylic acid groups on the retarding side effect of FLCA and the compatibility between FLCA and the retarder AMPS-IA synthesized using 2-acrylamido-2-methyl propane sulfonic acid (AMPS) and itaconic acid (IA) was studied in this paper. The type and content of carboxylic acid group have a great influence on the fluid loss control ability, the compatibility with retarder and the retarding side effect of FLCA. FLCA containing IA or maleic acid (MA) shows better compatibility with retarder than FLCA containing acrylic acid, but the retarding side effect of FLCA containing MA is weaker than that of FLCA containing IA. Thus, MA is the most suitable monomer for synthesizing FLCA having good compatibility with retarder AMPS-IA.

Molecular understanding of the interaction of amino acids with sulfuric acid in the presence of water and the atmospheric implication

Amino acids are important components of atmospheric aerosols. Despite the diversity of amino acids structures, however, the role of amino acids with additional non-characteristic functional groups in new particle formation (NPF) has almost remained unexplored. Herein, the interaction of serine (Ser) and threonine (Thr), which feature a hydroxyl group and differ by a methyl-substitution, with sulfuric acid (SA) and up to three water (W) molecules has been investigated at the M06-2X/6-311++G (3df, 3pd) level of theory. The effects of structural differences of amino acids on the structure and properties of clusters were also pointed out. Results show that serine may play more important role in stabilizing sulfuric acid to promote NPF in initial steps compared with threonine, glycine and alanine. Meanwhile, threonine may participate in ion-induced nucleation due to the high dipole moment of (Thr) (SA) isomers. Moreover, the effects of structure differences of amino acids can be seen in several aspects. Firstly, methyl substitution and hydroxyl group of amino acids have great influence on the structure of clusters. Secondly, hydrated (Ser) (SA) and (Tur) (SA) clusters could retain water even at low relative humidity, which may due to the hydroxyl group in serine and threonine. In addition, the Rayleigh light scattering intensities of amino acid-containing clusters are higher than trimethylamine, monoethanolamine and oxalic acid-involved counterparts. The effect of carboxyl group and methyl substitution on optical properties of clusters is also discussed. This study may bring new insight into the role of amino acids with additional non-characteristic functional groups in initial steps of NPF.

New α-Glucosidase inhibitors from the resins of Boswellia species with structure–glucosidase activity and molecular docking studies

Phytochemical investigation of the oleo-gum resins from Boswellia papyrifera afforded one new triterpene, named 3α-hydroxyurs-5:19-diene (1) together with twelve known compounds including eight triterpenoids (2–9), two diterpenoids (10 and 11) and two straight chain alkanes (12 and 13). Similarly ten more known compounds were isolated from the resin of Boswellia sacra including one triterpene (20) and nine boswellic acids (14–19 and 21–23). Herein the compound 2 was first time reporting from natural source along with complete NMR assignment, while compounds 3–11 are known, but reported for the first time from the resin of B. papyrifera. The structure elucidation was done by advance spectroscopic 1D and 2D NMR techniques viz., 1H, 13C, DEPT, HSQC, HMBC, and COSY, and NEOSY, ESI-MS and compared with the reported literature. All compounds were evaluated for their α-glucosidase inhibitory activity and as result eight of them 1, 3, 10, 11, 15, and 17–19 were found significantly active against α-glucosidase with an IC50 value ranging from 15.0 ± 0.84 to 80.3 ± 2.33 µM, while 21 exhibited moderate activity with IC50 of 799.9 ± 4.98 µM. Furthermore, two compounds 24 and 25 were synthesised from 16 and 17 to see the effect of carboxyl group in structural-activity relationship (SAR) study. Compounds 24 and 25 retained good α-glucosidase inhibition as compared to 16 and 17, indicating that carboxylic group play a key role in SAR. In addition, the aforementioned activity of all the active compounds was first time reported for their α-glucosidase inhibition potential. The molecular docking studies showed that all the active compounds well accommodate in the active site of the enzyme. Moreover pharmacokinetic properties of the compounds were predicted in silico, suggesting that the compounds possess drug like properties and excellent ADMET profile.

The effect of carboxylate groups on the complexation of metal ion with oligopeptides – Potentiometric investigation

Iron(II), iron(III), cobalt(II), zinc(II) cadmium(II) and lead(II) complexes of Asp2 and Asp3 and other Asp/Glu containing ligands were studied by potentiometry. Our goal was to study the influence of β- and γ-carboxylate groups as well as the increased negative charge of the ligands on the complex formation processes. Mainly 1:1 species are present, the formation of bis(ligand) complexes is not typical for these systems. It can be concluded that the effect of side chain carboxylate groups on the stability of complexes is especially significant in the case of lead(II) and cadmium(II). The greater the number of carboxylic groups there are in the system, the more stable complexes are formed with the studied metal ions. The influence of β-carboxylate groups of aspartic acid is unambiguous, they are directly bounded to the metal ion, which results in increased stability of the complexes. On the other hand, the repulsion between the negative charged residues becomes conspicuous resulting less stable species in the case of peptides containing glutamic acid.

Effects of humic acids with different polarities on the photocatalytic activity of nano-TiO2 at environment relevant concentration

Large volume production and application of nano-TiO2 make it inevitably release to natural waters and its environmental behaviors would be affected by natural organic matters. In this study, the mechanisms of humic acid (HA) affecting the photocatalytic performance of nano-TiO2 were elucidated by using three HA fractions from the same source but with different polarities. Bulk HA was fractionated on a silica gel column to get three fractions with polarity increasing in the order of FA, FB and FC. FA was fulvic acid-like while FB and FC were humic acid-like. All the three fractions (at 0.1 mg/L) promoted the generation of hydroxyl radicals (OHs) by nano-TiO2, and thus in turn facilitated the photocatalytic degradation of bispheol A (BPA). FA and FC displayed a stronger promotion effect than FB and the bulk HA. Online in situ flow cell ATR-FTIR and XPS analyses indicated that HA fractions could form charge-transfer complex with nano-TiO2 surface through the phenolic hydroxyl and carboxylic groups, which favored the separation of photogenerated electron-hole pairs. Through step methylation experiments, it was verified that the phenolic hydroxyl and carboxylic groups of HA fractions played important roles in promoting the photocatalytic performance of nano-TiO2, and the effect of carboxylic group was more significant than the phenolic hydroxyl group.

Effect of differently terminal groups of poly(amido-amine) dendrimers on dispersion stability of nano-silica and ab initio calculations

To investigate the effect of differently terminal groups of the lowest-order generation poly(amido-amine) dendrimers on dispersion stability of nano-silica, the four types of G0-CH2CH3 (G0E), G0-CH2CH2CH2CH3 (G0B), G0-NH2 (G0N), and G0-COOH (G0C) dendrimer molecules are used to modify the silica based on the dry modification. The zeta potential, the surface charge density, and the storage stability of kinds of modified SiO2 dispersion systems have been studied. The results show that the effect of carboxyl groups on dispersion stability is stronger than that of the other groups such as the amine and alkyl groups. Mulliken charge distributions of the main active sites are analyzed through the conductor-like polarizable calculation model (CPCM) on basis of the density functional theory (DFT) method, indicating the formation of chemical bonding between the modifiers and SiO2 particles. The most stable SiO2 dispersion system modified by G0-COOH dendrimer molecule is obtained due to the combined effect including the hydrogen bonding, electrostatic repulsive force, and the steric hindrance of the terminal groups. Copyright © 2015 John Wiley & Sons, Ltd.

Surface passivated carbon nanodots prepared by microwave assisted pyrolysis: effect of carboxyl group in precursors on fluorescence properties

Carbon sources with different numbers of carboxyl groups greatly affect the photoluminescence and quantum yield of carbon nanodots.

Effect of carboxyl group on the visible-light photocatalytic activity of SrTiO3 nanoparticles

SrTiO3 nanoparticles modified with a carboxyl group were successfully prepared by microwave-assisted solvothermal reaction of SrCl2·6H2O and Ti(OC3H7)4 in methanol–organic acid solution. The as-prepared products were characterized using X-ray diffraction (XRD), diffuse reflectance spectroscopy, and Fourier-transform infrared (FTIR) spectroscopy. The photocatalytic activity was determined by DeNOx ability using a mercury arc with filters to control irradiation wavelengths to >290, >400, and >510 nm. Nanoparticles of perovskite-type SrTiO3 were successfully synthesized above pH 12. The photocatalytic activity of SrTiO3 under visible-light (>510 nm) irradiation could be promoted by surface modification of SrTiO3 with the carboxyl group (–COO), especially from oleic acid.

Investigating the Stabilisation Effect of Carboxylic vs. Hydroxyl Groups on Fe3O4 and Fe3O4@Au Nanoparticles

The high-temperature solution phase reaction of iron(III) acetylacetonate, Fe(acac)3 and 1,2-hexadecanediol was used to synthesise iron oxide and gold-coated iron oxide nanoparticles. Different surface functionalities, such as sebacic acid (SA) and 1, 10–Decanediol (DD), were introduced on the surface of the particles to investigate the stabilising effect of carboxylic groups (SA) in comparison to the hydroxyl groups (DD). Nanoparticle thermal stability, composition, state of aggregation, size and morphology were investigated and the results from techniques such as Fourier Transform-Infra Red spectroscopy (FT-IR), Ultraviolet visible spectroscopy (UV-vis), Transmission Electron Microscopy (TEM) and thermal analysis are discussed.

The electrochemical behaviour of [Co(sep)]3+ bound with p-sulfonatothiacalix[4]arene and tetracarboxy-p-sulfonatocalix[4]arene in correlation with inclusive and non-inclusive binding modes

The comparative study of the ion-pairing of Co(III) sepulchrate ([Co(sep)]3+) with p-sulfonatothiacalix[4]arene and p-sulfonatocalix[4]arene tetracarbonic acid by 1H NMR and pH-metric data in solution and X-ray data in solid state elucidates pH dependent effect of carboxylate groups on the stoichiometry and the mode of the ion pairing. The electrochemical data of [Co(sep)]3+ bound with both calix[4]arenes have been analyzed in the correlation with stoichiometry and the mode of their binding. The pH-dependent effect of tetracarboxy-p-sulfonatocalix[4]arene on the electrochemical behavior of [Co(sep)]3+ has been found to correlate with the participation of carboxylate groups in the host–guest binding.

Determination of the crystallinity of cephalexin in pharmaceutical formulations by chemometrical near-infrared spectroscopy

Background: Near-infrared (NIR) spectroscopy has gained wide acceptance in the pharmaceutical industry as a rapid and non destructive method for drug identification and the determination of the drug content of preparations. Aim: The crystallinity of cephalexin (CEX) in microcrystalline cellulose (MCC) was determined using a nondestructive NIR reflectance spectroscopic technique. The molecular interaction of a ground amorphous solid of CEX was investigated by the method. Method: Six kinds of standard material with various degrees of crystallinity were prepared by the physical mixing of crystalline, amorphous CEX, and MCC. X-ray powder diffraction profiles and NIR spectra were recorded for standard samples. A chemometric analysis of the NIR spectral data sets was conducted using principal component regression (PCR). Results: The correlation between the actual crystallinity of CEX and that predicted using the conventional X-ray diffraction method showed a straight line with a slope of 1.000, an intercept of −2.071 × 10−5 and a correlation coefficient of determination (R2) of 0.974. The NIR spectrum of amorphous CEX showed significantly different peaks at 1176 and 1206 nm because of the CH3 group from those of CEX. PCR was performed on various kinds of pretransformed NIR spectral data sets of standard samples of CEX. To minimize the SE of cross-validation (SECV), the spectral data sets were subjected to the leave-one-out method. The second derivative treatment in the range of 1176–1206 nm yielded the lowest SECV values. Based on a two-component model, a plot of the calibration data between the actual crystallinity of CEX and that predicted by the NIR method was obtained. The plot showed a straight line (Y = 0.995X + 0.117 and R2 = 0.994; n = 18). The mean bias for the NIR and X-ray powder diffraction methods was calculated to be 1.52% and 2.26%, and mean accuracy was 3.06% and 7.14%, respectively. Conclusion: NIR spectral changes of crystalline CEX during grinding suggested that the intermolecular hydrogen bonds between the amino and carboxyl groups are destroyed and the binding of methyl groups is heightened by the resonance effect of carboxyl groups, and the crystals are transformed into amorphous CEX.