Different Numbers Of Carboxyl Groups Research Articles

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.

One-step aromatic acids assisted synthesis of γ-Fe2O3 nanoparticles with large surface area by thermal decomposition of ferric nitrate

Maghemite (γ-Fe2O3) has attracted much attention due to its variety of applications in many areas. However, the current preparation methods of γ-Fe2O3 still involve complicated processes and a high cost, thereby needing improvement. In this study, a novel and facile one-step solid-state method for the preparation of γ-Fe2O3 nanoparticles (NPs) is performed through the thermal decomposition of ferric nitrate (Fe(NO3)3⋅9H2O) and the addition of aromatic acids. Three aromatic acids that have different numbers of carboxyl groups (i.e., benzoic acid, phthalic acid, and trimesic acid) are used as additives and their effects on the formation of γ-Fe2O3 NPs are investigated. Furthermore, the influence of the aromatic acid/Fe(NO3)3⋅9H2O mass ratio and calcination temperature on the structural properties of the products are investigated. The structural properties, morphology, and magnetic properties of the products are analyzed through X-ray diffraction, transmission electron microscopy, scanning electron microscopy, nitrogen adsorption/desorption measurements, and magnetic measurements. The results show that the addition of aromatic acids to Fe(NO3)3⋅9H2O leads to the formation of γ-Fe2O3 NPs, and has a significant influence on the morphology of γ-Fe2O3 NPs. When the aromatic acid/Fe(NO3)3⋅9H2O mass ratio is greater than 0.5, the addition of the three aromatic acids leads to the formation of pure γ-Fe2O3. The γ-Fe2O3 NPs obtained from benzoic acid/Fe(NO3)3⋅9H2O and phthalic acid/Fe(NO3)3⋅9H2O systems do not show a well-defined morphology. In contrast, the γ-Fe2O3 NPs obtained from the trimesic acid/Fe(NO3)3⋅9H2O system are composed of a porous three-dimensional hierarchical structure and have the largest Brunauer−Emmett−Teller surface area (100.0 m2 g−1).

Development of potent antipseudomonal β-lactams by means of polycarboxylation of aminopenicillins.

Pseudomonas aeruginosa is a Gram-negative opportunistic pathogen that presents a serious risk to immunosuppressed individuals and other extremely vulnerable patients such as those in intensive care units. The emergence of multidrug-resistant Pseudomonas strains has increased the need for new antipseudomonal agents. In this study, a series of amino group-modified aminopenicillin derivatives was synthesized that have different numbers of carboxyl groups and structurally resemble carboxypenicillin-ureidopenicillin hybrids, and their antipseudomonal activities were evaluated. Among the derivatives synthesized, diethylenetriaminepentaacetic acid (DTPA)-modified amoxicillin (DTPA-Amox) showed potent antipseudomonal activity, not only against the laboratory strain PAO1 but also against clinically isolated Pseudomonas strains that were resistant to piperacillin and carbenicillin. DTPA-Amox had no obvious cytotoxic effects on cultured mammalian cells. In addition, in an in vivo model of leukopenia, DTPA-Amox treatment produced a moderate but statistically significant improvement in the survival of mice with P. aeruginosa strain PAO1 infection. These data suggest that polycarboxylation by DTPA conjugation is an effective approach to enhance antipseudomonal activity of aminopenicillins.

Boosting Ethylene/Ethane Separation within Copper(I)-Chelated Metal-Organic Frameworks through Tailor-Made Aperture and Specific π-Complexation.

The development of new materials for separating ethylene (C2H4) from ethane (C2H6) by adsorption is of great importance in the petrochemical industry, but remains very challenging owing to their close molecular sizes and physical properties. Using isoreticular chemistry in metal–organic frameworks (MOFs) enables the precise design and construction of target materials with suitable aperture sizes and functional sites for gas separations. Herein, it is described that fine‐tuning of pore size and π‐complexation simultaneously in microporous copper(I)‐chelated MOFs can remarkably boost the C2H4/C2H6 adsorption selectivity. The judicious choice of organic linkers with a different number of carboxyl groups in the UiO‐66 framework not only allows the fine tuning of the pore size but also immobilizes copper(I) ions onto the framework. The tailor‐made adsorbent, CuI@UiO‐66‐(COOH)2, thus possesses the optimal pore window size and chelated Cu(I) ions to form π‐complexation with C2H4 molecules. It can rapidly adsorb C2H4 driven by the strong π‐complexation interactions, while effectively reducing C2H6 uptake due to the selective size‐sieving. Therefore, this material exhibits an ultrahigh C2H4/C2H6 selectivity (80.8), outperforming most previously described benchmark materials. The exceptional separation performance of CuI@UiO‐66‐(COOH)2 is validated by breakthrough experiments for 50/50 v/v C2H4/C2H6 mixtures under ambient conditions.

Mechanisms of arsenite oxidation and arsenate adsorption by a poorly crystalline manganese oxide in the presence of low molecular weight organic acids

Manganese oxides are considered as one of the effective oxides capable of oxidizing arsenite and reduce the toxicity of arsenic. Since low molecular weight organic acids (LMWOAs) commonly found in nature can act as reducing and chelating agents for manganese oxides, it is particularly important to investigate how these organic acids with different numbers of carboxyl groups like citrate and EDTA affect oxidation and adsorption of arsenic by manganese oxides. In this study, low As(V) adsorption on manganese oxide is slightly enhanced by citrate and EDTA, which results from the increase in active sites via reduction of manganese oxide by LMWOAs. However, citrate and EDTA have different effects on the oxidation of As(III). MnIII/II citrate autocatalytic cycle as a manganese-based redox system decreases As(III) oxidation rate, but EDTA does not yield autocatalysis, which slightly increases the oxidation rate of As(III). Reduction of manganese oxide by EDTA and chelation between Mn(II) and EDTA lead to exposure of more active sites. Our research highlights the different effects of low molecular weight organic acids on the reactions between arsenic and manganese oxide.

Enumeration of carboxyl groups carried on individual components of humic systems using deuteromethylation and Fourier transform mass spectrometry.

Here, we report a novel approach to enumeration of carboxylic groups carried by individual molecules of humic substances using selective chemical modification and isotopic labeling (deuteromethylation) and high-resolution electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FTICR MS). Esterification was conducted with a use of thionyl chloride-deuteromethanol reagent under mild conditions to avoid transesterification. The deuteromethylated products were subjected to solid phase extraction using PPL Bond Elute cartridges prior to FTICR MS analysis. An amount of carboxyl groups in the individual molecular component was estimated from the length of identified deuteromethylation series. The method allowed for discerning between compounds with close elemental compositions possessing different protolytic properties. We found that different carboxylic moieties occupy distinct regions in molecular space of humic substances (HS) projected onto Van Krevelen diagram. These locations do not depend on the source of the humic material and can be assigned to carboxyl-rich alicyclic molecules (5 to 6 COOH), hydrolyzable tannins (3-4 COOH), lignins (1 to 2 COOH), condensed tannins and lignans (0 to 1 COOH), and carbohydrates (0 COOH). At the same time, the alignment pattern of these carboxylated species along the structural evolution lines in Van Krevelen diagrams was characteristic to the specific transformation processes undergone by the humic materials in the different environments. The obtained data enable mapping of molecular ensemble of HS with regards to their specific acidic compartments and might be used for directed fractionation of HS. Graphical abstract Selective isotopic labeling followed by FTICR MS enables discerning between humic molecules with close elemental compositions carrying different numbers of carboxylic groups.

Supramolecular Self-Assembly of Hexaphenylbenzene Derivatives with Different Symmetry and Number of Carboxylic Acid at Liquid/Solid Interfaces

Functional molecules, especially with carboxyl groups are crucial in building supramolecular structures. It is great important to study the effect of the symmetry, number of carboxyl groups on the self-assembly behavior of corresponding molecules. A series of hexaphenylbenzene (HPB) derivatives (HPB-1,3,5-3A, HPB-1,2,4-3A, and HPB-1,4-2A) substituted with different number of carboxyl groups at different position have been synthesized and their self-assembled structures were investigated at both 1-phenyloctane/HOPG and heptanoic acid/HOPG interfaces by using scanning tunneling microscopy (STM) technique. The self-assembled mechanisms of these HPB-based compounds were further studied with the help of density functional theory (DFT) calculations. The results indicate that symmetry and number of carboxyl groups as well as solvent play a significant role on the tuning self-assemble process resulting in various structures.

Fluorescently tuned nitrogen-doped carbon dots from carbon source with different content of carboxyl groups

In this study, fluorescent nitrogen-doped carbon dots (NCDs) were tuned via varying the sources with different number of carboxyl groups. Owing to the interaction between amino and carboxyl, more amino groups conjugate the surface of the NCDs by the source with more carboxyl groups. Fluorescent NCDs were tuned via varying the sources with different content of carboxyl groups. Correspondingly, the nitrogen content, fluorescence quantum yields and lifetime of NCDs increases with the content of carboxyl groups from the source. Furthermore, cytotoxicity assay and cell imaging test indicate that the resultant NCDs possess low cytotoxicity and excellent biocompatibility.

Novel ruthenium sensitizers having different numbers of carboxyl groups for dye-sensitized solar cells: effects of the adsorption manner at the TiO₂ surface on the solar cell performance.

Two novel ruthenium sensitizers having multiple carboxyl groups ((TBA)[Ru{4'-(3,4-dicarboxyphenyl)-4,4″-dicarboxyterpyridine}(NCS)3] (TUS-21) and (TBA)[Ru{4'-(3-carboxyphenyl)-4,4″-dicarboxyterpyridine}(NCS)3] (TUS-37); TBA = tetrabutylammonium) have been synthesized as improved model sensitizers for the previously reported ruthenium sensitizer TUS-20 ((TBA)[Ru{4'-(3,4-dicarboxyphenyl)terpyridine}(NCS)3]). The absorption maxima of two MLCT bands and the absorption onsets of TUS-21 and TUS-37 were shifted to longer wavelengths of about 30 nm in comparison to those of TUS-20 by introducing a carboxyl group to the each terminal pyridine ring of the terpyridine ligand. TUS-21 and TUS-37 showed quite similar adsorption behaviors to the TiO2 surface, and this adsorption behavior was found to be different from that of TUS-20. ATR-IR measurements revealed that TUS-21 and TUS-37 bind to the TiO2 surface by using two carboxyl groups at the 3-position of the phenyl ring and at one of the terminal pyridine rings of the terpyridine ligand, while TUS-20 is reported to bind by using two carboxyl groups at the 3,4-dicarboxyphenyl unit. The dye-sensitized solar cell (DSC) with TUS-21 exhibited 10.2% conversion efficiency, which is much higher than that of the DSC with TUS-20 (7.5%), under AM 1.5 (100 mW/cm(2)) irradiation.

WO3 nanorods created by self-assembly of highly crystalline nanowires under hydrothermal conditions.

WO3 nanorods and wires were obtained via hydrothermal synthesis using sodium tungstate as a precursor and either oxalic acid, citric acid, or poly(methacrylic acid) as a stabilizing agent. Transmission electron microscopy images showed that the organic acids with different numbers of carboxylic groups per molecule influence the final sizes and stacking nanostructures of WO3 wires. Three-dimensional electron diffraction tomography of a single nanocrystal revealed a hexagonal WO3 structure with preferential growth along the c-axis, which was confirmed by high-resolution transmission electron microscopy. WO3 nanowires were also spin-coated onto an indium tin oxide/glass conducting substrate, resulting in the formation of a film that was characterized by scanning electron microscopy. Finally, cyclic voltammetry measurements performed on the WO3 thin film showed voltammograms typical for the WO3 redox process.

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.

Atomic Force Microscopy Study of the Effects of Water‐Soluble Fullerenes on the Elasticity of Living Plant Cells

In this work, atomic force microscopy (AFM) was employed to characterize the elastic properties of a living suspension of Nicotiana tabacum L. cv. Bright Yellow (BY-2) cells and to investigate the changes in plant-cell elasticity that were induced by water-soluble C70 fullerene derivatives. The results revealed different effects of the three fullerene derivatives that had different numbers of carboxylic groups on the cell elasticity. BY-2 cells that were repressed by dimalonic-acid-modified C70 fullerenes (DiF70) and trimalonic-acid-modified C70 fullerenes (TriF70) showed a clear decrease in their Young's modulus. However, the Young's modulus of cells that were treated with tetramalonic-acid-modified C70 fullerenes (TetraF70) increased. Disruption of the actin cytoskeleton arrangement was observed following treatment with DiF70 and TriF70, but not with TetraF70. Moreover, the fullerene-induced cell-elasticity change was consistent with the change in cell-proliferation rate. This work provides a new approach and valuable information for the study of the biological effect of nanomaterials on plant cells.

Morphological Control of Hydroxyapatite Particles by Homogeneous Precipitation Method in the Co-Presence of Various Carboxylic Acids

We focused on the investigation of the influence of carboxylic acid additives on the morphology of hydroxyapatite (Ca10(PO4)6(OH)2, HAp) particles synthesized by a homogeneous precipitation method. Three types of carboxylic acids with different number of carboxyl groups, that is, acetic acid, succinic acid and citric acid, were used as additives to control the nucleation, growth and alignment of HAp crystals. The powder properties of resulting particles were examined by powder X-ray diffractometry, fourier-transform infrared spectroscopy, and scanning electron microscopy. All resulting particles were identified to be single-phase carbonate-containing calcium-deficient HAp. The resulting particles synthesized by using acetic acid as an additive were strip-like morphology. In the case of succinic acid addition, the resulting particles exhibited irregular plate-like or spherical morphology. Wheileas, in the case of citric acid addition, the obtained particles became regular spherical shape. These results indicate the numbers of carboxyl groups of carboxylic acid give an influence of the morphology of the HAp particles.

Aggregation of ε-caprolactone polymers containing at one chain end different number of carboxyl groups in the presence of calcium cations

The aggregation of poly(ε-caprolactone) containing different number of carboxyl groups at one chain end in the presence of Ca2+ cations was investigated by viscosity measurements. With increasing number of carboxyl groups, aggregation is strongly enhanced as evidenced by the viscosity-time profiles. The formation of long cylindrical structures was observed by scanning electron microscopy.

Flame retardant finishing of cotton fleece: part VII. Polycarboxylic acids with different numbers of functional group

In our previous research, multifunctional carboxylic acids have been used as flame retardants to reduce the flammability of cotton fleece so that the garment made of cotton fleece can pass the US mandatory requirement specified by the government regulation “Standard for the Flammability of Clothing Textiles” (16 CFR 1610). In this research, we studied and compared the effectiveness of the polycarboxylic acids having different numbers of carboxylic groups as the durable flame retardants for cotton fleece. The cotton fabrics were treated with 1,2,3,4-butanetetracarboxylic acid (BTCA), citric acid (CA), succinic acid (SUA) and malic acid (MLA). We compared the reactivity of those polycarboxylic acids to esterify cotton cellulose and their effectiveness to reduce the flammability of the cotton fleece. The data indicated that the polycarboxylic acids with higher functionalities (BTCA and CA) form more esterlinkages on cotton and are more durable to home launderings than that treated with their bifunctional counter parts (SUA and MLA, respectively). In addition, the cotton fabrics treated with BTCA and CA have higher dimensional stability and higher strength loss. All those differences can be attributed to the fact that only those acids with three or more carboxylic groups, i.e., BTCA and CA, are able to crosslink cotton cellulose whereas the bifunctional acids (SUA and MLA) only form single esterlinkage with cotton.

Star-Shaped Oligofluorenes End-Capped with Carboxylic Groups: Syntheses and Self-Assembly at the Liquid–Solid Interface

A series of star-shaped oligofluorenes end-capped with carboxylic acid groups were synthesized. Different numbers of carboxyl groups that can form hydrogen bonds, and long alkane chains that have stabilizing effects, were intentionally introduced. The resulting molecular architectures of the so-prepared star-shaped oligofluorenes at the liquid-solid interface were investigated by scanning tunneling microscopy. It is found that the number of hydrogen-bonding groups and the symmetry of the target molecules have crucial influences on the structures of the ordered assemblies.

Trityl Radicals as Persistent Dual Function pH and Oxygen Probes for in Vivo Electron Paramagnetic Resonance Spectroscopy and Imaging: Concept and Experiment

Triarylmethyl radicals, TAMs, have been the popular choice for electron paramagnetic resonance (EPR) spectroscopy and imaging applications because of their extraordinary stability in cells and tissues, narrow linewidths resulting in high analytical resolution at μM concentrations, and enhanced sensitivity to O2. In this Communication we propose a general approach and provide experimental data allowing for improvement of the functionality of TAM radicals by developing pH sensitive derivatives. The magnetic resonance parameters, both g-factor and hydrogen hyperfine splitting, of several TAM radicals containing different number of carboxyl groups and hydrogen atoms attached to the aryl substituents were found to be pH dependent. This pH effect was measured using X-band and Q-band EPR spectroscopy and is related to reversible protonation of carboxyl groups. Taking into account that both oxygen and pH play key roles in cellular metabolism and homeostasis, dual function pH and oxygen probes based on TAM radical...

Effects of the density of carboxyl groups in organic compounds on the photocatalytic reduction of Cr(VI) in a TiO2 suspension

Photocatalytic reduction (PCR) of Cr(VI) in a TiO2 suspension was studied at pH 4 in the presence of organic compounds containing different numbers of carboxyl groups. The compounds studied were glycine (Gly), iminodiacetic acid (IDA), nitrilotriacetic acid (NTA), ethylenediaminetetraacetic acid (EDTA). In all the cases, near complete Cr(VI) removal was observed after 60 minutes. During PCR process, the aqueous Cr(VI) concentration measured with both Ion Chromatography and Atomic Absorption Spectrophotometery was different in the presence of IDA and EDTA as reaction proceeded while little difference was observed in a control test. This result suggests that a greater portion of reduced Cr(III) species was possibly dissolved through complex formation with IDA (Cr(III)-IDA) and EDTA (Cr(III)-EDTA) or with reaction intermediates (Cr(III)-organic complexes) during PCR compared to the control test. As the number of carboxyl group increased Cr(VI) reduction increased and showed a good linear relationship between initial rates of Cr(VI) reduction and adsorption density of carboxyl group of the surface of TiO2. The initial rate of Cr(VI) reduction in the presence of EDTA was 5 times greater than that in control. When the PCR process was applied in the treatment of real wastewater, an effective Cr(VI) reduction was observed with addition of EDTA.

Photoelectrochemical properties of TiO 2 electrodes sensitized by porphyrin derivatives with different numbers of carboxyl groups

The photochemical and photoelectrochemical properties of two porphyrin derivatives with different numbers of carboxyl groups were investigated. The two porphyrin derivatives are 5-(4-carboxyphenyl)-10,15,20-tritolylporphyrin (H 2TC1PP) and 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin (H 2TC4PP). The interaction between the porphyrin and TiO 2 is determined by the UV–vis spectra. Differences in adsorption behavior of the two porphyrin derivatives on the TiO 2 electrode surface were observed. The IR data suggest that both of the porphyrins adsorb by bridging or bidentate chelate coordination on the TiO 2 surface. Comparing the luminescence spectra of the two porphyrins in solution and the solid state, no spectral difference was observed. However, we found that the variation in the number of carboxyl groups has an influence on the fluorescence spectra of the adsorbed TiO 2 electrode. Furthermore, we measured and compared the incident photon-to-current conversion efficiency (IPCE) and the light-to-electrical conversion efficiency of the porphyrin-sensitized solar cell. These results revealed that the number of functional groups influenced the photoelectrochemical properties of the cell.

New Ru(II) phenanthroline complex photosensitizers having different number of carboxyl groups for dye-sensitized solar cells

We have prepared and characterized four carboxylated Ru(II) phenanthroline complexes with different number of carboxyl groups, cis-dithiocyanato bis(4,7-dicarboxy-1,10-phenanthroline) ruthenium(II) [Ru(dcphen)2(NCS)2, DCP2], cis-dithiocyanato bis(4-monocarboxy-1,10-phenanthroline) ruthenium(II) [Ru(mcphen)2(NCS)2, MCP2], cis-dithiocyanato (4,7-dicarboxy-1,10-phenanthroline) (1,10-phenanthroline) ruthenium(II) [Ru(dcphen)(phen)(NCS)2, DCPP], and cis-dithiocyanato (4-monocarboxy-1,10-phenanthroline)(1,10-phenanthroline) ruthenium(II) [Ru(mcphen)(phen)(NCS)2, MCPP], as photosensitizers for nanocrystalline dye-sensitized solar cells. All complexes exhibit a broad MLCT absorption band around 500 nm in ethanol and an emission band around 700 nm in ethanol–methanol (4:1) at 77 K. The excited state lifetime of these complexes at 77 K was 1.5–2.9 μs and the oxidation potential, 0.90–1.12 V vs. NHE, was obtained by cyclic voltammetry in solution. The best solar-energy-to-electric conversion efficiency under AM 1.5 irradiation was obtained for DCPP which has two carboxyl groups on one phenanthroline ligand. The performance of photosensitizer of MCPP which has only one carboxyl group is lower than that for the other complexes, indicating that the number of carboxyl groups as anchor is very important for efficient solar cell performance.