Effect Of Surface Functional Groups Research Articles

Exploring a New Method to Study the Effects of Surface Functional Groups on Adsorption of CO2 and CH4 on Activated Carbons

The commercial coconut shell-activated carbon was modified to change the number of oxygen-containing functional groups. N2 adsorption/desorption isotherms, Fourier transform infrared (FT-IR), and Boehm titration were adopted to describe the physical and chemical properties of the samples. The adsorption isotherms of CO2 and CH4 on both the unmodified and modified samples were measured. To better understand the effects of surface oxygen-containing functional groups on adsorption of CO2 and CH4, the overall adsorption could be considered as the result of adsorption within the pores and adsorption onto the oxygen-containing functional groups. Thus, a new way to understand different adsorption mechanisms by calculation was proposed. On the basis of the results, there is a significant correlation between the saturation adsorption capacity of CO2 and the number of oxygen-containing functional groups, especially carboxyl and hydroxyl. According to the values of enthalpy (-12.2 to -20 kJ/mol), it can be known that the adsorption caused by oxygen-containing functional groups is exothermic and belongs to physisorption. A semiempirical relationship between the variation of the surface oxygen-functional groups and the variation of the adsorbed amount was established. The method proposed in this paper provides a new way to study the effects of surface functional groups on the adsorption of CO2 and CH4 and can be even promoted in studying the adsorption mechanism of other adsorbates.

Interactions of emerging contaminants with model colloidal microplastics, C60 fullerene, and natural organic matter - effect of surface functional group and adsorbate properties.

Surface adsorption of two commonly detected emerging contaminants, amlodipine (AMP) and carbamazepine (CBZ), onto model colloidal microplastics, natural organic matter (NOM), and fullerene nanomaterials have been investigated. It is found that AMP accumulation at these colloidal-aqueous interfaces is markedly higher than that of CBZ. Measurements of surface excess and particle zeta potential, along with pH-dependent adsorption studies, reveal a distinct influence of colloidal functional group on the adsorption properties of these pharmaceuticals. AMP shows a clear preference for a surface containing carboxylic group compared to an amine modified surface. CBZ, in contrast, exhibit a pH-dependent surface proclivity for both of these microparticles. The type of interactions and molecular differences with respect to structural rigidity and charge properties explain these observed behaviors. In this work, we also demonstrate a facile approach in fabricating uniform microspheres coated with NOM and C60 nanoclusters. Subsequent binding studies on these surfaces show considerable adsorption on the NOM surface but a minimal uptake of CBZ by C60. Adsorption induced colloidal aggregation was not observed. These findings map out the extent of contaminant removal by colloids of different surface properties available in the aquatic environment. The methodology developed for the adsorption study also opens up the possibility for further investigations into colloidal-contaminant interactions.

Effects of Surface Functional Groups on the Adhesion of SiO2 Nanospheres to Bio-Based Materials.

The interactions between nanoparticles and materials must be considered when preparing functional materials. Although researchers have studied the interactions between nanoparticles and inorganic materials, little attention has been paid to those between nanoparticles and bio-based protein materials, like leather. In this study, organically modified silica nanospheres (SiO2 nanospheres) loaded with rose fragrance were prepared using (3-aminopropyl) triethoxysilane (APTES), (3-mercaptopropyl) triethoxysilane (MPTES), or 3-(2, 3-epoxypropyloxy) propyl triethoxysilane (GPTES) using the sol-gel method. To study the interactions between the modified SiO2 nanospheres and leather, a non-cross-linking adsorption experiment was conducted. According to the Dubinin–Radushkevich isotherm calculation, we found that the adsorption process of leather fiber and organically modified silica nanospheres is physical. The average adhesion energies of APTES-, MPTES-, and GPTES-modified SiO2 nanospheres on the leather are 1.34016, 0.97289, and 2.09326 kJ/mol, respectively. The weight gain, adsorption capacity, and average adhesion energy show that the modified SiO2 nanospheres can be adsorbed on leather in large quantities. The sensory evaluation confirmed that GPTES-modified SiO2 nanospheres endowed the leather with an obvious rose aroma.

Competitive Adsorption of Methanol-Acetone on Surface Functionalization (-COOH, -OH, -NH2, and -SO3H): Grand Canonical Monte Carlo and Density Functional Theory Simulations.

The capture and separation properties of surface-functionalized activated carbons (AC-Rs, R= -COOH, -OH, -NH2, and -SO3H) for the methanol-acetone mixture were investigated for the first time by grand canonical Monte Carlo simulation (GCMC)and density functional theory(DFT). The effects of surface functional groups and structural characteristics of AC-Rs on the adsorption and separation behaviors of methanol and acetone were clarified. The surface functional group with strong electron-donating or electron-accepting capacity (i.e., -NH2, -OH, and -SO3H) was a crucial factor for the methanol-acetone capture and separation performance at the lower pressure range, and the accessible surface area was found to be another determinative factor. AC-NH2 with the relatively large accessible surface area (4497 m2/g) exhibited an efficient capture performance for the single component (15.7 mol/kg for methanol and 6.7 mol/kg for acetone) and the highest methanol/acetone selectivity (∼23) at 0.02 kPa. At high pressures, the surface functionalization and available pore volume of AC-Rs played pivotal roles in the adsorptive separation process. This study provided mechanistic insights on how the surface functional groups affected the capture and separation properties of ACs, which would further provide a rational alternative strategy in the preparation and synthesis of ACs for the effective gas mixture separation.

Surface carboxyl groups enhance the capacities of carbonaceous oxygen electrodes for aprotic lithium−oxygen batteries: A direct observation on binder-free electrodes

In order to achieve the high capacities of carbonaceous oxygen diffusion electrodes for aprotic lithium–oxygen batteries (Li–O2 batteries), most efforts currently focus on the design of rational porous architectures. Only few works study the surface chemistry effect that might be a critical factor influencing the capacities of carbonaceous electrodes. In addition, the surface chemistry effect is very difficult to be studied in composite electrodes due to the influences of binders and additives. Herein, we propose chemically activated carbon cloth (CACC) as an ideal model to investigate the effect of surface functional groups on the discharge capacities of carbonaceous oxygen electrodes for Li–O2 batteries. The intrinsic surface chemistry effect on the performance of carbonaceous cathode is directly observed for the first time without the influences of binders and additives. Results indicate that the surface carboxyl groups introduced by the chemical treatment not only function as the appropriate nucleation sites for Li2O2 but also induce the formation of toroid-like Li2O2. Thus, the surface carboxyl modification enhances the discharge capacities from 0.48 mAh/cm2 of pristine carbon cloth to 1.23 mAh/cm2 of CACC. This work presents an effective way to further optimize the carbonaceous oxygen electrodes via surface functional group engineering

Synergistic effects and kinetics of rGO-modified TiO2 nanocomposite on adsorption and photocatalytic degradation of humic acid

Graphene oxide was prepared using the modified Hummers method and reduced graphene oxide (rGO) - titanium dioxide (TiO2) nanocomposite was synthesised using the one-step hydrothermal treatment. The synergistic effects on adsorption and photocatalytic properties of the rGO-TiO2 nanocomposite for the humic acid removal were systematically investigated. The results of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Raman and infrared (IR) spectroscopy indicate that GO was partially reduced to reduced graphene oxide (rGO) in the hydrothermal synthesis process and anatase TiO2 nanoparticles uniformly grew on the surface of rGO. The photoelectron and photohole generated under visible light irradiation were effectively separated on the surface of rGO-TiO2. The rGO-TiO2 nanocomposite exhibited higher photocatalytic activity as a result of the synergistic effects of surface functional groups for adsorption and the excellent conductivity for photocatalytic reaction. The effect of rGO-TiO2 nanocomposite dosage, light intensity and system temperature on the removal of humic acid solution was investigated. The results show that the removal efficiency of humic acid increased with system temperature and light intensity. When the dosage of rGO-TiO2 nanocomposite was 1.2 g/L, the temperature, the light intensity and the pH of this system was 303 K, 4.37 Wm−2 and 7, respectively, the removal efficiency of humic acid reached 88.7% under visible light irradiation.

Perfluorocarbon-Based 19 F MRI Nanoprobes for In Vivo Multicolor Imaging.

In vivo multicolor imaging is important for monitoring multiple biomolecular or cellular processes in biology. 19F magnetic resonance imaging (MRI) is an emerging in vivo imaging technique because it can non‐invasively visualize 19F nuclei without endogenous background signals. Therefore, 19F MRI probes capable of multicolor imaging are in high demand. Herein, we report five types of perfluorocarbon‐encapsulated silica nanoparticles that show 19F NMR peaks with different chemical shifts. Three of the nanoprobes, which show spectrally distinct 19F NMR peaks with sufficient sensitivity, were selected for in vivo multicolor 19F MRI. The nanoprobes exhibited 19F MRI signals with three colors in a living mouse. Our in vivo multicolor system could be utilized for evaluating the effect of surface functional groups on the hepatic uptake in a mouse. This novel multicolor imaging technology will be a practical tool for elucidating in vivo biomolecular networks by 19F MRI.

Perfluorocarbon‐Based 19F MRI Nanoprobes for In Vivo Multicolor Imaging

AbstractIn vivo multicolor imaging is important for monitoring multiple biomolecular or cellular processes in biology. 19F magnetic resonance imaging (MRI) is an emerging in vivo imaging technique because it can non‐invasively visualize 19F nuclei without endogenous background signals. Therefore, 19F MRI probes capable of multicolor imaging are in high demand. Herein, we report five types of perfluorocarbon‐encapsulated silica nanoparticles that show 19F NMR peaks with different chemical shifts. Three of the nanoprobes, which show spectrally distinct 19F NMR peaks with sufficient sensitivity, were selected for in vivo multicolor 19F MRI. The nanoprobes exhibited 19F MRI signals with three colors in a living mouse. Our in vivo multicolor system could be utilized for evaluating the effect of surface functional groups on the hepatic uptake in a mouse. This novel multicolor imaging technology will be a practical tool for elucidating in vivo biomolecular networks by 19F MRI.

The effect of surface functional groups on the performance of graphite powders used as electrodes

The use of commercial graphite powders (different sources and particle sizes), as electrode materials, was evaluated in an electrochemical cavity cell. The graphite powders were characterized by electron microscopy, XRD, vibrational spectroscopy, porosimetry, contact angle, Boehm titration and cyclic voltammetry. Despite similarities, the graphite powders differed significantly in terms of surface functional groups (SFGs), hydrophobicity and particle size. The surface chemistry of both graphites was modified by HCl treatment, followed by 200 °C heating, prior to electrode fabrication, which was found to play an important role on the electrode performance. Cyclic voltammetries were carried out for the two different graphites in acid medium and absence of reagent, and the results were correlated to Boehm titration, showing evidences of the presence of acidic and basic SFGs. After HCl + heat treatment, it was observed the diminishing of the SFGs for both commercial graphite powders tested. The electro-reduction of benzyl bromide was used as standard reaction, yielding 1,2-diphenylethane and toluene as products. A 23 factorial design was used to optimize some electrode parameters. The compaction of the graphite electrodes showed to be fundamental for obtaining good results. HCl + heat treatment favored the 1-electron process, giving 1,2‑diphenylethane as major product on both electrodes (GF, 61% and GA, 52%). The absence of graphite powder treatment favored the 2-electron process, furnishing toluene as major product (GF, 55% and GA, 43%).

An insight into effect of surface functional groups on reactivity of Sphalerite (110) surface with Xanthate collector: a DFT study

The reactivity of the protonated and hydroxylated sphalerite (1 1 0) surface with xanthate was simulated using the density functional theory (DFT). The difference between the energy of the lowest unoccupied molecular orbital of the sphalerite surface and the energy of the highest occupied molecular orbital of xanthate ( was used to compare the reaction capability of xanthate with fresh and functionalized surfaces. The Mulliken atomic charge analysis was used to provide an in-depth insight into the effects of –H+ and –OH- groups on the reactivity of Zn atoms at the sphalerite surface. The values for different systems showed that the protonated surfaces exposed a higher reactivity with xanthate than the fresh and hydroxylated surfaces. The results of the Mulliken atomic charge analysis demonstrated that after the formation of –H+ and –OH- contained groups on the sphalerite surface, the surface atoms found a new charge due to the reduction and oxidation mechanism. In addition, the results obtained revealed that the electrophilicity of Zn atoms after the ion adsorption could be considered as a key factor in the reactivity of the sphalerite surface with xanthate. The DFT-based calculations also showed that different alkyl groups of xanthate had no significant influence on the reactivity of their head groups. The findings of this research work provided insights into the reactions of the sphalerite surface with xanthate.

Effect of graphene oxide nanosheets on visible light-assisted antibacterial activity of vertically-aligned copper oxide nanowire arrays

In the present work, the effect of graphene oxide (GO) nanosheets on the antibacterial activity of CuO nanowire arrays under visible light irradiation is shown. A combined thermal oxidation/electrophoretic deposition technique was employed to prepare three-dimensional networks of graphene oxide nanosheets hybridized with vertically aligned CuO nanowires. With the help of standard antibacterial assays and X-ray photoelectron spectroscopy, it is shown that the light-activated antibacterial response of the hybrid material against gram-negative Escherichia coli is significantly improved as the oxide functional groups of the GO nanosheets are reduced. In order to explore the physicochemical mechanism behind this behavior, ab-initio simulations based on density functional theory were performed and the effect of surface functional groups and hybridization were elucidated. Supported by the experiments, a three-step photo-antibacterial based mechanism is suggested: (i) injection of an electron from CuO into rGO, (ii) localization of the excess electron on rGO functional groups, and (iii) release of reactive oxygen species lethal to bacteria. Activation of new photoactive and physical mechanisms in the hybrid system makes rGO-modified CuO nanowire coatings as promising nanostructure devices for antimicrobial applications in particular for dry environments.

Suitability of pyrolusite as additive to activated coke for low‐temperature NO removal

AbstractBACKGROUNDPyrolusite was used as additive to prepare coal‐based activated coke (AC) for low‐temperature NO removal. The pyrolusite modified AC was prepared by a blending method, and the denitrification performance was evaluated in a lab‐scale simulated fixed‐bed reactor.RESULTSThe blending of pyrolusite promoted the specific surface area and pore structure of AC, even though the MnO2 and Fe2O3 showed inhibitory effects when blended separately. Both the basic and acid sites of AC‐Mn(x) increased owing to the participation of the blended MnO2 during the activation, while the blending of Fe2O3 showed an inhibited effect. AC‐P10 showed the highest NO removal efficiency at 74.2%, which was 32.8%, 27.0% and 24.2% higher than that of AC, AC‐Mn4 and AC‐Fe6. The operating temperature adaptability and stability of catalysis activity of AC‐P10 are good. Manganese is the main catalyst of AC‐P(x), and Fe is an accelerant to stimulate the catalytic activity of Mn. The extremely high NO removal activity of AC‐P(x) was due to the synergistic effect of surface functional groups and metals, but the catalysis of metals played a more important role.CONCLUSIONPyrolusite is suitable to prepare the AC‐based denitrification catalyst (AC‐P(x)) for SCR NO removal because the Mn and Fe contained in the pyrolusite showed a synergistic effect. © 2017 Society of Chemical Industry

Understanding the Effect of Functional Groups on the Seeded Growth of Copper on Carbon Nanotubes for Optimizing Electrical Transmission.

We present a study of the seeded growth of copper on the surface of two classes of single-walled carbon nanotubes (SWNTs) in order to compare the effects of surface functional groups. Pyridine-functionalized HiPco SWNTs and ultrashort SWNTs (US-SWNTs) were synthesized (py-SWNTs and py-US-SWNTs, respectively), and the functionality was used as seed sites for copper, via an aqueous electroless deposition reaction, as a comparison to the carboxylic acid functionality present on piranha-etched SWNTs and the native US-SWNTs. UV-vis spectroscopy demonstrated the take-up of Cu(II) ions by the functionalized SWNTs. TEM showed that the SWNTs with pyridine functionality more rapidly produced a more even distribution of copper seeds with a narrower size distribution (3-12 nm for py-US-SWNTs) than those SWNTs with oxygen functional groups (ca. 30 nm), showing the adventitious role of the pyridine functional group in the seeding process. Seed composition was confirmed as Cu(0) by XPS and SAED. Copper growth rate and morphology were shown to be affected by degree of pyridine functionality, the length of the SWNT, and the electroless reaction solvent used.

Influence of physico-chemical properties of soil clay fractions on the retention of dissolved organic carbon.

This study investigated the effects of surface functional groups, cation exchange capacity (CEC), surface charge, sesquioxides and specific surface area (SSA) of three soil clay fractions (SCFs) (kaolinite-illite, smectite and allophane) on the retention of dissolved organic carbon (DOC) in soils. Physico-chemical properties of the SCFs before and after removing native carbon and/or sesquioxides were characterised, and the DOC adsorption-desorption tests were conducted by a batch method. Native organic carbon (OC)/sesquioxide removal treatments led to a small change in the CEC values of kaolinite-illite, but significant changes in those of smectite and allophane. The net negative surface charge increased in all samples with an increase in pH indicating their variable charge characteristics. The removal of native OC resulted in a slight increase in the net positive charge on soil clay surfaces, while sesquioxide removal increased the negative charge. Changes in the functional groups on the SCF surfaces contributed to the changes in CEC and zeta potential values. There was a strong relationship (R 2=0.93, p<0.05) between the Langmuir maximum DOC adsorption capacity (Q max) and SSA. The Q max value also showed a moderately strong relationship (R 2=0.55, p<0.05) with zeta potential (at pH 7). Q max was only poorly correlated with CEC and native OC content. Therefore, along with SSA, the surface charge and functional groups of SCFs played the key role in determining the adsorption affinity and hence retention of DOC in soils.

Simple anodization of home-made screen-printed carbon electrodes makes significant activity enhancement for hydrogen evolution: the synergistic effect of surface functional groups, defect sites, and hydrophilicity

Undoubtedly, electrocatalyzing the hydrogen evolution reaction (HER) is now becoming the subject of extensive studies due to its crucial role in harvesting clean energy. In general, bare screen-printed carbon electrodes (SPCEs) have negligible ability to catalyze the HER due to the lack of effective sites. Here we find that: 1) a facile anodization treatment can improve the electrocatalytic activity of home-made SPCEs with apparently reduced overpotential and increased current density for the HER; 2) the activity enhancement of SPCEs is highly dependent on anodization conditions including electrolyte, treatment time, and anodization potential; 3) the introduction of negatively charged oxygen-containing functional groups during anodization, together with the increased defect sites and hydrophilicity on electrode surface, leads to the promoted activity of anodized SPCEs synergistically. Similar phenomena are also found in other carbon-based electrodes including glassy carbon electrode and carbon nanotube-modified electrode. These findings reported in this work are expected to guide the future design of advanced electrode systems for efficient hydrogen evolution.

Effect of surface functional groups on hydrogen adsorption properties of Pd dispersed reduced graphene oxide

Pd/reduced graphene oxide (Pd-RGO) composites were successfully prepared from graphite and PdCl2 precursors using wet impregnation and reverse micro emulsion methods. From hydrogen adsorption studies it is confirmed that spillover of hydrogen from Pd to graphene layers occurs at room temperature. However, at low temperatures there is negligible spillover effect and this is explained based on lower kinetic energy available with hydrogen atoms to overcome the activation barrier involved in diffusion. Detailed 13C MAS NMR and Raman spectroscopic studies confirmed that small amounts of structural units (functional groups) like carboxylate and polyacetylenic linkages are retained in Pd-RGO samples prepared by wet impregnation and reverse micro-emulsion methods, respectively. Such structural moieties facilitate the atomic scale mixing of Pd with the graphene layers thereby improving the spillover efficiency.

Electrochemical reduction of nalidixic acid at glassy carbon electrode modified with multi-walled carbon nanotubes

The aqueous phase electrochemical degradation of nalidixic acid (NAL) is studied in this work, using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) as instrumental techniques. The promotional effect of multi-walled carbon nanotubes (MWCNT) on the performance of glassy carbon electrodes is demonstrated, being observed that these materials catalyze the NAL reduction. The effect of surface functional groups on MWCNT −MWCNT-COOH and MWCNT-NH2–was also studied. The modification of glassy carbon electrode (GCE) with MWCNT leads to an improved performance for NAL reduction following the order of MWCNT>MWCNT-NH2>MWCNT-COOH. The best behavior at MWCNT-GCE is mainly due to both the increased electrode active area and the enhanced MWCNT adsorption properties.The NAL degradation was carried out under optimal conditions (pH=5.0, deposition time=20s and volume of MWCNT=10μL) using MWCNT-GCE obtaining an irreversible reduction of NAL to less toxic products. Paramaters as the number of DPV cycles and the volume/area (V/A) ratio were optimized for maximize pollutant degradation. It was observed that after 15 DPV scans and V/A=8, a complete reduction was obtained, obtaining two sub-products identified by liquid chromatography-mass spectrometry (LC–MS).

The effect of PAMAM dendrimer concentration, generation size and surface functional group on the aqueous solubility of candesartan cilexetil

This article investigates the aqueous solubility of the poorly soluble drug candesartan cilexetil (CC) in the presence of poly(amidoamine) (PAMAM) dendrimers. The effect of variables such as concentration, generation size (G2–G4), and surface groups (NH2, COOH and TRIS) of PAMAMs on the aqueous solubility of CC was studied. A two-factor factorial (3 × 3) ANOVA design was used to study the effect of generation size and surface functional group of the PAMAMs. The results showed that the aqueous solubility of CC in the presence of carboxyl and TRIS-terminated PAMAMs was higher than those of amine-terminated PAMAMs, and the effect of surface functional group of the PAMAMs on the aqueous solubility of CC was dependent on the generation size (p < 0.05). The sequence of the observed solubility fold enhancement due to PAMAMs was G4.COOH (8378)>G3.COOH (3456)>G4.TRIS (2362)>G2.COOH (1013)>G3.TRIS (749)>G2.TRIS (293)>G4.NH2 (91)>G3.NH2 (50)>G2.NH2 (37). The CC-PAMAM dendrimer inclusion complexes were characterized by UV–Vis, attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and differential thermal analysis (DTA) techniques. Regarding the results of these techniques, improvement in the solubility of CC is expected primarily through the intermolecular hydrogen bonding between the drug and internal tertiary and surface functional groups of the studied PAMAMs.

Effects of surface functional groups on proliferation and biofunction of Schwann cells.

Scaffolds in tissue engineering should be rationally designed to become an adhesion substrate friendly to cells. Schwann cells play an important role in nerve regeneration and repair. Previous studies have suggested that surface chemical groups have effect on many types of cells. However, there have hitherto been few reports on Schwann cells. In this study, we investigated cell adhesion, survival, proliferation, and neurotrophic actions of Schwann cells cultured on glass coverslips modified with different chemical groups, including methyl, carboxyl, amino, hydroxyl, mercapto, and sulfonic groups. Schwann cells on amino and carboxyl surfaces had higher attachment rate, presenting good morphology, high proliferation, and strong neurotrophic functions, while on methyl surfaces, few cells can survive, cells shrunk into round shape, exhibiting poor proliferation and weak neurotrophic functions. Growth of cells on other groups was between methyl and amino, carboxyl, and had little difference among them. Our data indicated that chemical groups can regulate behavior of Schwann cells, indicating a way to design new scaffolds for peripheral nerve regeneration.

The importance of wetting in carbon paper electrodes for vanadium redox reactions

As demand for renewable energy storage increases, flow batteries such as those based on the resilient vanadium redox reactants and inexpensive carbon electrode materials have become more widespread. Thus far, however, there are many conflicting results in the literature regarding the reaction kinetics of the V2+/V3+ and VO2+/VO2+ redox couples and various methods to enhance these reactions. The present work demonstrates how the misinterpretation of cyclic voltammetry for porous carbon materials may account for many of these inconsistencies. Several oxidation treatments investigated here are observed to have a significant effect on the cyclic voltammogram of the V2+/V3+ redox couple reactions. Using electrochemical impedance spectroscopy and a recently developed analytical flow cell technique, these changes are shown to be due almost entirely to the effective wetting of the porous carbon paper rather than any electroactivation effect of surface functional groups on the intrinsic kinetics of the V2+/V3+ reaction. A similar methodology is recommended for any future assessment of electrode treatments.