Surface Modification Agent Research Articles

Interfacial strength and mechanical properties of biocomposites based on ramie fibers and poly(butylene succinate)

In this work, a single ramie fiber was firstly treated with various surface modification agents including alkali, silane, maleic anhydride and acetic anhydride. Then single fiber fragmentation was carried out to evaluate the interfacial interaction between the fiber and poly(butylene succinate) (PBS) matrix by means of interfacial shear strength (IFSS). The highest IFSS was found for the fiber treated with alkali. In this simple way, alkali was easily selected as a good surface modification agent for the preparation of PBS/ramie fibers biocomposites. In order to verify that the single fiber fragmentation is an effective method for the selection of a good surface modification agent, the interfacial interaction and mechanical properties of the prepared PBS/alkali treated ramie fibers composites were investigated. It was found that alkali treated ramie fibers could be well dispersed and had better interfacial adhesion with the matrix than untreated fibers, as indicated by scanning electron microscope (SEM) observation and dynamic mechanical analysis (DMA). The tensile strength and modulus of PBS were greatly increased by adding the alkali treated fibers, while only a slight increase of tensile strength and modulus was observed for those compounded with untreated fibers. These results indicate that alkali is indeed a good coupling agent for the improvement of the interfacial strength of the composites, which is well consistent with that obtained via the IFSS measurement. Therefore, single fiber fragmentation test can be used as an effective and simple method to evaluate the surface modification and interfacial enhancement as well.

Chemically conjugated sophorolipids on CdTe QDs: a biocompatible photoluminescence nanocomposite for theranostic applications

Functional nontoxic cadmium telluride (CdTe) quantum dots (QDs) have been synthesized using a natural functional glycolipid belonging to the family of sophorolipids (SL) as a surface-modifying agent. These SLs with open acidic form are highly suitable for QDs stabilization, are readily obtained by a fermentation process of the yeast Candida bombicola (polymorph Starmerella bombicola) in large amounts. In this work chemically stable, water soluble, and photoluminescent CdTe QDs were successfully conjugated to sophorolipids via a cross-linking reaction. The formation of SLs conjugated CdTe QDs was confirmed using different analytical techniques X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Transmission Electron Microscopy (TEM), Electron Diffraction (ED), Atomic Force Microscopy (AFM), Dynamic Light Scattering (DLS), and Photoluminescence (PL). It was shown that after being conjugated with SL the SL-CdTe QDs becomes biocompatible, still maintaining its water solubility and photoluminescence properties. The final SL coated photoluminescent CdTe QDs represent interesting biocompatible materials potentially useful for biomedical applications.

Facile deposition of continuous gold shells on Tween-20 modified Fe3O4 superparticles.

A facile method to deposit continuous Au shells on Fe3O4 colloidal superparticles was developed by introducing Tween-20 as a surface modification agent to maintain the colloidal stability of the Fe3O4 superparticles and provide nucleation and growth sites for the Au shells. The Fe3O4-Au core-shell particles showed excellent chemical stability, superparamagnetic properties and efficient photothermal conversion performance under laser irradiation at 808 nm, and were expected to be a useful material for biodetection and cancer therapy.

Highly‐Tunable Nickel Cobalt Oxide as a Low‐Temperature P‐Type Contact in Organic Photovoltaic Devices

AbstractWe report on the investigation of nickel cobalt oxide (NixCo3−xO4) thin films grown by pulsed laser deposition as hole‐transport interlayers (HTL) in organic photovoltaic (OPV) devices. Films of 7 nm thickness were grown under various oxygen deposition pressures (pO2) in the range of 2–200 mTorr. We explore both bulk and surface properties of these thin films. The workfunction (ϕ) for each of the films was statistically similar (∼4.7 eV), regardless of pO2. There was not a strong dependence of the power conversion efficiency (η) on the conductivities of the HTLs varying between 0.009 ‐ 10 S/cm. The observed differences in OPV efficiencies (ranging from 1.16 to 2.46%) were correlated to the near surface chemical composition of the NixCo3−xO4 HTL, as observed by differences in the relative surface hydroxyl concentration. The critical role of the near‐surface composition of the HTL at the HTL/organic interface was further explored by modifying the hydroxyl concentration using an oxygen plasma treatment. This treatment mitigated the impact of surface hydroxyl coverage, demonstrating either identical or increased values for ϕ and η, regardless of initial pO2 in the creation of the NixCo3−xO4 HTL. To further explore this we also employed a phosphonic acid surface modification agent on the HTL, increasing ϕ to 5.2 eV producing the best η value of 3.4%, equivalent to the PEDOT:PSS control devices. These results indicate that nickel cobalt oxide is a promising p‐type oxide for carrier‐selective interlayers in organic solar cells; however, for this to be fully realized the specific surface chemistry at the oxide/polymer interface must be controlled to increase ϕ and optimize device performance.

Controlled synthesis of Ag nanoparticles with different morphologies and their antibacterial properties

In this paper, Ag triangle nanoplates and nanospheres were synthesized by liquid chemical reduction method in the presence of seeds, with l-ascorbic acid as the reductant and polyvinyl pyrrolidone (PVP) as the surface modification agent, respectively. Characterizations of the particles were conducted by various techniques such as X-ray powder diffraction, transmission electron microscopy, ultraviolet–visible absorption spectroscopy, Fourier transformation infrared spectrometry, and thermal analysis. The antibacterial properties of Ag nanoparticles against Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa were investigated by disk diffusion and broth dilution methods. The results indicate that Ag nanospheres exhibit better antibacterial properties than that of triangle nanoplates.

Preparation of dispersed aluminum hydroxide nanoparticles via non-aqueous route and surface modification

A novel non-aqueous route for the preparation of aluminum hydroxide nanoparticles, from aluminum nitrate nonahydrate and anhydrous sodium acetate in ethylene glycol (EG), has been developed. Aluminum hydroxide nanoparticles modified with ethyl acetoacetate (EAA) as surface modification agent were prepared by chemical surface-modification method. The surface-modified wet aluminum hydroxide nanoparticles can be well dispersed in n-hexane when using the appropriate ligand concentration. EAA is chemically attached to the surface of the aluminum hydroxide nanoparticles. The mass percentage of the chemisorbed EAA on the modified aluminum hydroxide nanoparticles is 2.4%. The phase transformation temperature of the surface-modified aluminum hydroxide nanoparticles to the stable α-alumina rises about 50 °C compared with that of the as-prepared aluminum hydroxide nanoparticles without surface modification. The EAA-surface modified aluminum hydroxide nanoparticles lead to fine and weak-agglomerated alumina nanoparticles after calcination.

Use of silane coupling agent for surface modification of zinc oxide as inorganic filler and preparation of poly(amide-imide)/zinc oxide nanocomposite containing phenylalanine moieties

A series of novel poly(amide–imide)/ZnO nanocomposites with modified ZnO nanoparticles contents was prepared by ultrasonic irradiation. For this purpose, surface of ZnO nanoparticle was modified with $\boldsymbol\gamma$ -aminopropyltriethoxysilane as a coupling agent. Then the effect of surface modification on dispersion of nanoparticles, thermal stability and UV absorption property of the obtained nanocomposites were investigated. The resulting novel nanocomposites were characterized by several techniques. Field emission scanning electron microscopy and transmission electron microscopy analyses of the nanocomposites were performed in order to study the dispersion of nanofillers in the polymer matrix. According to thermogravimetry analysis results, the addition of ZnO nanoparticles improved thermal stability of the obtained nanocomposites. Since the resulting nanocomposites contain phenylalanine amino acid and ZnO, they are expected to be biocompatible as well as biodegradable.

Environment-Controlled Tethering by Aggregation and Growth of Phosphonic Acid Monolayers on Silicon Oxide

Phosphonic acid monolayers are being considered as versatile surface modification agents due to their unique ability to attach to surfaces in different configurations, including mono-, bi-, or even tridentate arrangements. Tethering by aggregation and growth (T-BAG) of octadecylphosphonic acid (ODPA) on silicon oxide surfaces has proven to be a robust method to establish a strong chemical bond. However, it requires a long processing time (> 48 h) that is a substantial drawback for industrial applications. We demonstrate here that the humidity level during processing is the most important parameter controlling the reaction. Using in situ Fourier Transform Infrared Spectroscopy (FTIR), we first show that the initially physisorbed layer obtained upon immersion in ODPA is composed of well-ordered bilayers and only reacts with the SiO(2) surface at 140 °C. Importantly, we show that the presence of water at the interface (determined by the humidity level) greatly influences the reaction time and completion. In humid environments (relative humidity, RH > 40%), there is no reaction, while in dry environments (RH < 16%), the reaction is essentially instantaneous at 140 °C. Ab initio calculations and modeling confirm that the degree of chemical reaction with the surface OH groups depends on the chemical potential (i.e., concentration) of interfacial water molecules. These findings provide a workable modification of the traditional T-BAG method consistent with many industrial applications.

Mediatorless amperometric glucose biosensing using 3-aminopropyltriethoxysilane-functionalized graphene

A mediatorless glucose biosensor was developed by the immobilization of glucose oxidase (GOx) to graphene-functionalized glassy carbon electrode (GCE). The surface of GCE was functionalized with graphene by incubating it with graphene dispersed in 3-aminopropyltriethoxysilane (APTES), which acted both as a dispersion agent for graphene and as an amine surface modification agent for GCE and graphene. This was followed by the covalent binding of GOx to graphene-functionalized GCE using 1-ethyl-3-[3-dimethylaminopropyl]carbodiimide hydrochloride (EDC) based crosslinking. Graphene provided signal enhancement by providing greater surface area for GOx binding, while APTES-functionalization led to a higher GOx immobilization density by providing free amino groups for crosslinking. The developed biosensor used a redox potential of −0.45V (vs. Ag/AgCl) for detecting glucose in the diabetic pathophysiological range 0.5–32mM. There was no interference from endogenous electroactive substances and drug metabolites. The developed biosensor was further validated for detecting blood glucose in commercial artificial blood glucose linearity standards in the range 1.4–27.9mM. Therefore, it is ideal for diabetic blood glucose monitoring. The developed bioanalytical procedure for preparation of GOx-bound graphene-functionalized GCEs had high production reproducibility and high storage stability, which is appropriate for the commercial mass production of enzyme-bound electrodes.

A Novel Liposome Surface Modification Agent that Prolongs Blood Circulation and Retains Surface Ligand Reactivity

Liposomes are recognized as potentially useful drug carriers but many problems preclude practical medical application. Liposomes bind with serum proteins (opsonization) and are captured by the reticuloendothelial system cells in the liver and spleen, which limits their ability to deliver drugs to other target sites. Modification of lipids with flexible, hydrophilic polymers such as poly(ethylene glycol) (PEG) to yield sterically stabilized liposomes is one approach to improve liposome blood circulation and tissue distribution properties. In this study, we examined liposomes prepared using lipids modified with a new branched oligoglycerol (BGL) moiety for steric stabilization. This novel BGL comprised 14 glycerol units (termed BGL014) connected with flexible ether linkages, resulting in a branched cascade-like structure that is highly expanded in aqueous solution. BGL014 was coupled to 1,2-distearoylphosphatidylethanolamine to yield BGL014-modified lipids. Incorporation of BGL014 into liposomes (BGL014L) resulted in long blood circulation times, despite a much thinner fixed aqueous layer thickness compared to PEG formulations. BGL014 produced a liposome surface coating that appears to function through steric inhibition of non-specific protein binding without strong interference of specific protein-binding reactions. Liposome structure and functionality was maintained following BGL014-modification, as the incorporation ratio of drug remained high. These results suggest that the BGL014 modification of liposomes is a promising approach to produce stable and long circulating drug carriers capable of selective binding to specific proteins.

Impact of feed spacer and membrane modification by hydrophilic, bactericidal and biocidal coating on biofouling control

The influence of polydopamine- and polydopamine-graft-poly(ethylene glycol)-coated feed spacers and membranes, copper-coated feed spacers, and commercially-available biostatic feed spacers on biofouling has been studied in membrane fouling simulators. Feed spacers and membranes applied in practical membrane filtration systems were used; biofouling development was monitored by feed channel pressure drop increase and biomass accumulation. Polydopamine and polydopamine-g-PEG are hydrophilic surface modification agents expected to resist protein and bacterial adhesion, while copper feed spacer coatings and biocides infused in feed spacers are expected to restrict biological growth. Our studies showed that polydopamine and polydopamine-g-PEG coatings on feed spacers and membranes, copper coatings on feed spacers, and a commercial biostatic feed spacer did not have a significant impact on feed channel pressure drop increase and biofilm accumulation as measured by ATP and TOC content. The studied spacer and membrane modifications were not effective for biofouling control; it is doubtful that feed spacer and membrane modification, in general, may be effective for biofouling control regardless of the type of applied coating.

One-Step Multipurpose Surface Functionalization by Adhesive Catecholamine.

Surface modification is one of the most important techniques in modern science and engineering. The facile introduction of a wide variety of desired properties onto virtually any material surface is an ultimate goal in surface chemistry. To achieve this goal, the incorporation of structurally diverse molecules onto any material surface is an essential capability for ideal surface modification. Here, we present a general strategy of surface modification, in which many diverse surfaces can be functionalized by immobilizing a wide variety of molecules. This strategy functionalizes surfaces by a one-step immersion of substrates in a one-pot mixture of a molecule and a catecholamine surface modification agent. This one-step procedure for surface modification represents a standard protocol to control interfacial properties.

An efficient method for clay modification and its application for phenol removal from wastewater

A new type of modified clay was produced from a Ca-bentonite treated with hydrochloric acid as a surface modifier agent and then with hexadecyltrimethylammonium bromide (HDTMA) as a surfactant to produce an organophilic adsorbent. The specific surface area of the modified clays was 40% higher than the specific surface area of bentonite treated only with HDTMA. A series of kinetic and equilibrium tests was carried out to study the effectiveness of the modification method to improve the bentonite ability to remove phenol from aqueous solutions. The adsorption capacity of modified bentonite was 10 times greater than the natural bentonite. Phenol adsorption was fast and reached equilibrium in 30min. Adsorption was physical and exothermic and was described with Henry and Freundlich isotherms.

Influence of thermal process on microstructural and physical properties of ambient pressure dried hydrophobic silica aerogel monoliths

The experimental results of thermal process on the microstructural and physical properties of ambient pressure dried hydrophobic silica aerogel monoliths are reported and discussed. With sodium silicate as precursor, ethanol/hexamethyldisiloxane/hydrochloric acid as surface modification agent, the crack-free and high hydrophobic silica aerogel monoliths was obtained possessing the properties as low density (0.096 g/cm3), high surface area (651 m2/g), high hydrophobicity (~147°) and low thermal conductivity (0.0217 Wm/K). Silica aerogels maintained hydrophobic behavior up to 430 °C. After a thermal process changing from room temperature to 300 °C, the hydrophobicity remained unchanged (~128°), of which the porosity was 95.69% and specific density about 0.094 g/cm3. After high temperature treatment (300–500 °C), the density of final product decreased from 0.094 to 0.089 g/cm3 and porosity increased to 96.33%. With surface area of 466 m2/g, porosity of 91.21% and density about 0.113 g/cm3, silica aerogels were at a good state at 800 °C. Thermal conductivities at desired temperatures were analyzed by the transient plane heat source method. Thermal conductivity coefficients of silica aerogel monoliths changed from 0.0217 to 0.0981 Wm/K as temperature increased to 800 °C, revealed an excellent heat insulation effect during thermal process.

Bostrycin, a novel coupling agent for protein immobilization and prevention of biomaterial-centered infection produced by Nigrospora sp. No. 407

Bostrycin, a red antibacterial agent with tetrahydroanthraquinone structure, has been isolated from Nigrospora sp. No. 407. This study investigated the potential antibacterial and multifunctional properties of matrixes through immobilization of bostrycin on their surface for immobilization of protein and prevention of bacterial growth. Bostrycin was immobilized on nonwoven polypropylene (PP) fabric by a technique using glutaraldehyde and polyethyleneimine for the activation of the surface. Glucose oxidase immobilized on bostrycin-treated nonwoven PP fabric showed high activity. The immobilization process improved thermal stability of the enzymes. During repeated assay for 30 cycles, the enzyme activity dropped to only 70% of the initial activity. Both bostrycin-treated nonwoven PP fabric sample and subsequently immobilized glucose oxidase sample on the surface also still exhibited a bacteriostatic effect. This is the first study to show that bostrycin is a promising coupling agent for surface modification on matrix and its potential applications in protein immobilization and biomaterial-centered infection.

Surface Modification by Electrostatic Self‐Assembly Followed by Covalent Fixation

Sticks and bonds: Surface-modifying agents can be functionalized with ionic groups that enable high exhaustion from a processing bath through electrostatic self-assembly. Using cyclic oniums as the ionic functional groups, thermally induced ring-opening converts the ionic bonds to covalent bonds, thus lending permanency to the modification of the surface.

Starch/SBR Biocomposites Prepared by Solid Blend Method: Effect of Surface Modification and Coupling Agent

Starch/Styrene Butadiene Rubber (SBR) biocomposites were prepared by directly blending of starch and SBR on a two-roll miller. Two types of starch: pure starch and modified starch (M-starch) were used as rubber fillers. M-starch were synthesized by grafting of methyl methacrylate (MMA) monomer onto starch backbone using ceric ammonium nitrate-initiated radical polymerization. Coupling agent styrene-g-(maleic anhydride) (SMA) was used to further improve the interfacial interaction between the filler and rubber matrix. The morphology and mechanical properties of unmodified starch/SBR and M-starch/SBR biocomposites with SMA content of 0, 1, 3, and 5 phr were investigated. SEM observations showed the particle size of M-starch decreased and their dispersion in the SBR matrix significantly improved than unmodified starch. Mechanical properties of M-starch/SBR biocomposites were superior than those of unmodified starch/SBR biocomposites.

Multiphoton Reactive Surfaces Using Ruthenium(II) Photocleavable Cages

Photoreactive surfaces derived from a new photocleavable surface modification agent and with photosensitivity in the Vis and IR region are described. A ruthenium(II) caged aminosilane, [Ru(bpy)(2)(PMe(3))(APTS)](PF(6))(2), was synthesized and attached to silica surfaces. Light irradiation removed the cage and generated surface patterns with reactive amine groups. The photosensitivity of this compound under single (460 nm) and two-photon (900) excitation is demonstrated. Functional patterns with site-selective attachment of other molecular species are described.

Production of a robust nanobiocatalyst for municipal wastewater treatment

Immobilization is a fundamental method to improve both enzyme activity and stability. In the present work, the process previously described for immobilizing laccase – an enzyme oxidizing phenolic compounds – onto fumed silica was optimized, in order to efficiently produce industrially relevant amounts of a nanobiocatalyst for biological micropollutant elimination, whilst saving 80% of surface modification agent (3-aminopropyl triethoxy silane) and 90% of cross-linker (glutaraldehyde). Minimized losses during preparation and favorable effects of immobilization yielded conjugates with drastically increased enzymatic activity (164% of invested activity). Long-term stability and activity regarding bisphenol A (2,2-bis(4-hydroxyphenyl)propane) removal of the synthesized biocatalyst were assessed under application-relevant conditions. With 81.1±0.4% residual activity after 7days, stability of conjugates was drastically higher than of free laccase, which showed virtually no activity after 1.5days.These results illustrate the huge potential of fumed silica nanoparticles/laccase-composites for innovative biological wastewater treatment.

Bio-inspired strategy for on-surface synthesis of silver nanoparticles for metal/organichybrid nanomaterials and LDI-MS substrates

A strategy for the on-surface synthesis of silver nanoparticles (AgNPs) on a variety oftwo- to three-dimensional material surfaces, utilizing polydopamine, an emerging surfacemodifying agent, is reported in this paper. This material-independent platform for AgNPsynthesis is useful for fabricating organic/inorganic hybrid nanomaterials and for preparingsubstrates for laser desorption–ionization time-of-flight mass spectrometry (LDI-ToF MS).