Surface Modification Agent Research Articles

Photocatalytic removal of gaseous nitrogen oxides using WO3/TiO2 particles under visible light irradiation: Effect of surface modification

Photocatalytic nanoparticles have been receiving considerable attention for their potential use in many environmental management applications, including urban air quality control. This paper investigates the performance of surface modified WO3/TiO2 composite particles in removing gaseous nitrogen oxides (NOx) under visible light irradiation. The WO3/TiO2 composite particles were synthesized using a modified wet chemical method with different concentrations of NaOH solution used as a surface modification agent for the host TiO2 particles. The NOx removal efficiency of the WO3/TiO2 particles was evaluated using a lab–scale continuous gas flow photo-reactor with a gas contact time of 1 min. Results showed that surface modification using NaOH can enhance the photocatalytic activity of the WO3/TiO2 particles. The NOx removal efficiency of the surface modified WO3/TiO2 was greater than 90%, while that of WO3/TiO2 particles prepared by the conventional wet chemical method was ∼75%. The enhanced removal efficiency might be attributed to the formation of oxygen vacancies on the TiO2 surface, providing sites for WO3 particles to effectively bind with TiO2. However, excess amount of NaOH >3 M deteriorated the photocatalytic performance due to the increased agglomeration of the host TiO2 particles.

TiO2/Silane Coupling Agent Composed Two Layers Structure: A Novel Stability Super-hydrophilic Self-cleaning Coating Applied in PV Panels

Abstract In order to improve the properties of anti-dust and self-cleaning for PV panels, self-cleaning has been proposed. But traditional self-cleaning coatings are unstable in nature environment, so it limited the application in the PV panels. Based on the above discussions, this study aims to design a novel super-hydrophilic coating with high stability and corrosion resistance which would be very advantageous for applying in the PV panels. The super-hydrophilic self-cleaning coating is composed by 3-triethoxysilylpropylamine (KH550) and TiO2. KH550 is a kind of surface modification agent which creates more active group on surface of glass. Due to the water as the solvent, the coating is environmental friendly and the material coast is low. This coating can be applied with spraying technology and roller coating by changing the coating's viscosity. The composition was measured by Fourier transform infrared spectroscopy (FTIR), particle size distribution and the surface structure was characterized by Scanning Electron Microscope (SEM). The water contact angle (WCA) was measured by contact angle instrument. It was found that the static water contact angle on the surface of super-hydrophobic coating was as lower than 5, which show an excellent super-hydrophilic property.

Effect of type and loading of surface-modifying agent on mechanical properties of modified geothermal scale powder/stereolithography polymer composite

This study investigated the effect of stearic acid (SA), glycerol monostearate (GMS) and 3-trimethoxysilylpropyl methacrylate (TSPM) at varied loadings on the hardness and flexural properties of modified geothermal scale powder (GSP)/stereolithography (SLA) polymer composite. TSPM-modified GSP/SLA composite has the highest value of hardness due to increased filler dispersion and crystallinity. Hardness of GSP/SLA composite increases with loading of surface-modifying agent due to increase filler dispersion. Pronounced effect of surface modification to flexural modulus is observed. While low loading of SA and GMS leads to reduction of flexural modulus, increasing loading enhances the said property. Further increase of SA deteriorates the property. TSPM-modified GSP enhances the modulus due to increased crystalline phase of the system owing to TSPM copolymerization. Likewise, addition of SA and GMS increases flexural strength due to efficient reduction of filler agglomerates. However, unreacted TSPM produces weak interfaces and poor adhesion between GSP and SLA matrix.

TiO2/silane coupling agent composed of two layers structure: A super-hydrophilic self-cleaning coating applied in PV panels

To improve the properties of anti-dust for PV modules, the concept of self-cleaning has been proposed for many years. However, the traditional self-cleaning coating is unstable in nature environment, which limited its application in the PV panels. Therefore, this study aims to design a novel super-hydrophilic coating with high stability and corrosion resistance, which would be very advantageous to apply in the PV panels. The super-hydrophilic self-cleaning coating is composed of 3-triethoxysilylpropylamine (KH550) and TiO2. KH550 is a kind of surface modification agent, which creates more active groups on the surface of glasses. TiO2 is prepared by a hydrothermal reaction with titanium ethoxide, and the influence of pH is investigated as an important factor during the application in PV panels. The composition was measured by UV/VIS/NIR spectrophotometer, and the particle size distribution and the surface structure were characterized by Scanning Electron Microscope (SEM). The TiO2 nanocrystal was investigated by X-Ray Diffraction (XRD) and Transmission Electron Microscope (TEM). The water contact angle (WCA) was measured by contact angle instrument. It was found that the static water contact angle on the surface of super-hydrophobic coating was as lower than 5°, which show an excellent super-hydrophilic property. Abstract should state the principal results and conclusions briefly, and the significance of this study.

Atmospheric pressure plasma-assisted green synthesis of amphiphilic SiO2 Janus particles

A facile green approach for the synthesis of amphiphilic SiO2 Janus particles using low temperature atmospheric pressure plasma is reported in this study. Monodispersed SiO2 particles were masked by embedding half of their surface inside a polystyrene film. The exposed surfaces of the SiO2 particles were readily modified using He/CF3CFH2 low-temperature atmospheric pressure plasma to obtain amphiphilic Janus particles. Their amphiphilic nature was confirmed using fluorescent microscopy by tagging their hydrophilic part with a fluorescent dye. The present method can be used to generate amphiphilic Janus particles with a variety of functionalities, which may find applications as surfactants and surface modifying agents.

Synthesis of phosphorus-containing silane coupling agent for surface modification of glass fibers: Effective reinforcement and flame retardancy in poly(1,4-butylene terephthalate)

In this study, a novel silane coupling agent containing phosphorus element with a low oxidation state, N-diphenylphosphoryl-3-aminopropyltriethoxysilane (P-APTES), was synthesized through the nucleophilic-substitution reaction between 3-aminopropyltriethoxysilane (APTES) and diphenylphosphinic chloride. The nuclear magnetic resonance and Fourier transform infrared spectra results showed that P-APTES was successfully synthesized. The commercial glass fibers (GF) were calcined to remove the surface modifier, and then respectively modified by APTES and P-APTES. APTES modified GF (A-m-GF) and P-APTES modified GF (P-m-GF) were respectively added into poly(1,4-butylene terephthalate) (PBT) to prepare fire retarded composites containing aluminium phosphinate (AlP). In comparison with A-m-GF, the introduction of P-m-GF into PBT and PBT/AlP resulted in the improved tensile properties owing to the better interfacial compatibility between P-m-GF and PBT matrix. Thermogravimetric analysis demonstrated that the modifier P-APTES on the surface of glass fibers could improve the residue yields and reduce the mass loss rate of PBT more significantly. The flammability testing results showed that the fire retardant properties of PBT composites were significantly enhanced through a synergistic effect between P-m-GF and AlP. Residue analysis indicated that more compact and continuous char residues were wrapped on GF surface in PBT/P-m-GF and PBT/P-m-GF/AlP composites, which could reduce the interface energy to the suppress the interfacial flame. Overall, the PBT/P-m-GF/AlP composites were found to be a viable option as a reinforced flame retarded polymer material with encouraging mechanical properties and outstanding fire safety performances.

Efficient and Stable Perovskite Solar Cells Prepared in Ambient Air Based on Surface-Modified Perovskite Layer

Among many photovoltaic conversion technologies, perovskite solar cells have received significant research interests as effective photovoltaic materials owing to their high solar conversion efficiencies and low cost. However, the performance of perovskite solar cells is limited by the instability of CH3NH3PbI3 to water and ambient moisture. To address this issue, in this study, we introduced a new fundamental approach that utilizes 4-tert-butylpyridine (tBP) as the surface modification agent to enhance the performance and stability of CH3NH3PbI3-based perovskite solar cells fabricated in ambient air. The tertiary butyl group in tBP is highly hydrophobic, leading to the formation a hydrophobic layer on the surface of CH3NH3PbI3, thus increasing the moisture stability of perovskite solar cells. With this strategy, the performance of perovskite solar cells prepared at even >50% RH in ambient air was tremendously enhanced by as much as 200% compared to that without tBP additive. Besides, the stability of pero...

Synthesis and characterization of copolyimides containing fluorine and silicon surface-modifying agents

Understanding the effects that monomer chemistries have on material properties allows for fine tuning of polymer synthesis for current and future applications. In order to develop polymeric-based coatings that have minimal surface adhesion characteristics when exposed to a variety of contaminants, a more thorough understanding of fundamental structure–property relationships is needed. In the aeronautics field, one concept to improve fuel efficiency of future aircraft is to modify the wing design to enable laminar flow. There is a concern that contaminants such as insect residue and other debris will adhere to airflow surfaces and have sufficient height to disrupt laminar flow thereby increasing drag with concomitant loss of fuel efficiency. One potential solution would be a polymer surface or coating that prevents or minimizes adhesion of such contaminants. As part of a structure–property relationship study involving modification of surface properties, a series of copolyimides containing both fluorine and silicon surface-modifying agents (SMAs) were prepared and characterized. Based on knowledge of structure–property relationships with polyimides containing either type of SMA, it was hypothesized that the combination of two different SMAs may lead to unique surface properties as the two SMAs competed for surface area at the polymer–air interface. Copolyimides for this study were prepared through a multistep synthesis using an aromatic dianhydride with equimolar amounts of diamino functionalities comprised of an aromatic diamine along with two SMAs. Films were cast from copoly(amide acid) solutions that were subsequently thermally imidized under a nitrogen atmosphere. Polyimide films and coatings were characterized using differential scanning calorimetry, Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy, contact angle goniometry, scanning electron microscopy, and energy-dispersive X-ray spectroscopy to determine chemical, thermal, and surface properties. Select samples were subject to high velocity insect impacts in a small-scale wind tunnel and the resulting residues were characterized for height and surface area and compared to those of a control surface.

Enhanced dielectric performance of poly(vinylidene fluoride)-based composites filled with hexadecylphosphonic acid functionalized nanometals

Zero-dimensional nickel nanosphere (0-D NiNS), one-dimensional silver nanowire (1-D AgNW) and two-dimensional silver nanoplate (2-D AgNP) were prepared and studied as conductive nanofiller within flexible dielectric poly(vinylidene fluoride) (PVDF) matrix. Hexadecylphosphonic acid (HDPA) modifiers were functionalized onto the surface of those nanometals. X-ray photoelectron spectroscopy (XPS) verified the functionalization of organophosphonic acid surface modification agent. X-ray diffraction characterization (XRD) suggested the surface functionalization did not change the crystal structure of nanometals. The organic dielectric surface modified layer not only acted as interparticle barriers to prevent nanometals from direct connection but also produced excellent compatibility between the fillers and the polymer matrix and ensures the dispersion of fillers in the polymer matrix. Fourier transform infrared spectroscopy (FT-IR) spectra information indicated the increase of electro-active β-phase of PVDF composites after doping of nanometals and surface functionalization of filler. Among all the PVDF composites, dielectric materials with HDPA functionalized AgNP as fillers have the best dielectric performance. The good dielectric performance could be triggered by relatively smaller size effect, parallel micro-capacitor microstructure, particular morphology and large-small nanosize co-doping way.

PERFORMANCE COMPARISON OF VARIOUS SURFACE MODIFYING AGENTS ON PROPERTIES OF SILICA-FILLED CHLOROPRENE RUBBER

ABSTRACTInfluence of the surface modifying agents (SMAs) polyethylene glycol (PEG), 3-aminopropyl triethoxysilane (APTES), and bis-(3-triethoxysilylpropyl)tetrasulfide (TESPT) on properties of silica-filled chloroprene rubber (CR) was investigated. Results reveal that the presence of SMAs greatly improves mechanical and dynamic properties of the silica-filled CR because of the reduced filler–filler interaction and improved rubber–filler interaction as evidenced by the Payne effect and bound rubber content results, respectively. When compared at the same SMA dosage, TESPT gives the best overall vulcanizate properties. This effect is attributed to high coupling efficiency of TESPT and its ability to donate sulfur atoms during vulcanization, leading to the improved filler dispersion, rubber–filler interaction, and cross-link density. APTES gives high coupling efficiency, but because of the lack of sulfur atoms, its performance is slightly inferior to that of TESPT. In contrast, PEG can only reduce filler–filler interaction, with no significant impact on rubber–filler interaction and cross-link density; therefore, PEG provides lower property improvement.

Effects of crystallinity and surface modification of calcium phosphate nanoparticles on the loading and release of tetracycline hydro-chloride

The influences of crystallinity and surface modification of calcium phosphate nanoparticles (nCaP) on their drug loading capacity and drug release profile were studied in the present investigation. The CaP nanoparticles with different crystallinity were prepared by precipitation method under different temperatures. CaP nanoparticles with lower crystallinity exhibited higher drug loading capacity. The samples were characterized by XRD, FT-IR, SEM, TEM and BET surface area analyzer respectively. The drug loading capacity of nCaP was evaluated to tetracycline hydro-chloride (TCH). The internalization of TCH loaded nCaP in cancer cell was observed by florescence microscope. nCaP could be stabilized and dispersed in aqueous solution by poly(acrylic acid) surface modification agent, leading to enhanced drug loading capacity. The drug release was conducted in different pH environment and the experimental data proved that nCaP were pH sensitive drug carrier, suggesting that nCaP could achieve the controlled drug release in intracellular acidic environment. Furthermore, nCaP with higher crystallinity showed lower drug release rate than that of lower crystallinity, indicating that the drug release profile could be adjusted by crystallinity of nCaP. nCaP with adjustable drug loading and release properties are promising candidate as drug carrier for disease treatment.

Effect of Surface Modification on the In vitro Protein Adsorption and Cell Cytotoxicity of Vinorelbine Nanoparticles.

Context:Nanocarriers possessing long-circulating abilities could take advantage of the pathophysiology of tumor vasculature to achieve spatial placement. To attain such qualities, the drug carriers should possess suitable physicochemical properties such as size and surface hydrophilicity.Aim:The aim of this study was to prepare poly(ε-caprolactone) nanoparticles (NPs) loaded with vinorelbine bitartrate (VB) and to modify its steric properties using polyethylene glycol and poloxamer. Furthermore, the influence of surface modification of NPs on their physicochemical and cell interactive properties was evaluated.Materials and Methods:NPs were prepared by double emulsion solvent extraction–evaporation technique. The prepared NPs were evaluated for their physicochemical properties, in vitro protein adsorption and cell cytotoxicity.Results and Discussion:The NPs were <250 nm with an entrapment efficiency ranging between 40% and 52%. The zeta potential of the NPs varied from −7.52 mV to −1.27 mV depending on the surface modification. The in vitro release studies exhibited a biphasic pattern with an initial burst release followed by controlled release of the drug over 72 h. The protein adsorption studies revealed that the ability to resist protein adsorption was influenced by the concentration of surface-modifying agents and the amount of proteins available for interaction. The surface-modified NPs produced cell cytotoxicity comparable to free VB at higher concentrations owing to sustained release of the drug into the cellular environment.Conclusion:The results emphasize that surface modification of nanocarriers is an essential and effective tool to dodge opsonization and phagocytosis in the physiological milieu.

Improved Cycling Performance of a Si Nanoparticle Anode Utilizing Citric Acid as a Surface-Modifying Agent.

Citric acid and its analogues have been investigated as surface-modifying agents for Si nanoparticle anodes using electrochemical cycling, attenuated total reflectance infrared (ATR IR), and X-ray photoelectron spectroscopy (XPS). A Si nanoparticle anode prepared with citric acid (CA) has better capacity retention than one containing 1,2,3,4-butanetetracarboxylic acid (BA), but both electrodes outperform Si-PVDF. The Si-CA anode has an initial specific capacity of 3530 mA h/g and a first cycle efficiency of 82%. Surprisingly, the Si-CA electrode maintains a high specific capacity of ∼2200 mA h/g after 250 cycles, corresponding to 64% capacity retention, which is similar to the Si prepared with long-chain poly(acrylic acid) (PAA). On the contrary, the silicon electrode prepared with PVDF has a fast capacity fade and retains only 980 mA h/g after 50 cycles. The IR and XPS data show that the Si-CA electrode has an SEI composed primarily of lithium citrate during the first 50 cycles, resulting from the electrochemical reduction of citric acid. Only low concentrations of electrolyte reduction products are observed. The lithium citrate layer derived from CA stabilizes the silicon surface and suppresses electrolyte reduction, which likely contributes to the enhanced cycling performance of the Si nanoparticle anode.

Manipulation of small particles at solid liquid interface: light driven diffusioosmosis.

The strong adhesion of sub-micron sized particles to surfaces is a nuisance, both for removing contaminating colloids from surfaces and for conscious manipulation of particles to create and test novel micro/nano-scale assemblies. The obvious idea of using detergents to ease these processes suffers from a lack of control: the action of any conventional surface-modifying agent is immediate and global. With photosensitive azobenzene containing surfactants we overcome these limitations. Such photo-soaps contain optical switches (azobenzene molecules), which upon illumination with light of appropriate wavelength undergo reversible trans-cis photo-isomerization resulting in a subsequent change of the physico-chemical molecular properties. In this work we show that when a spatial gradient in the composition of trans- and cis- isomers is created near a solid-liquid interface, a substantial hydrodynamic flow can be initiated, the spatial extent of which can be set, e.g., by the shape of a laser spot. We propose the concept of light induced diffusioosmosis driving the flow, which can remove, gather or pattern a particle assembly at a solid-liquid interface. In other words, in addition to providing a soap we implement selectivity: particles are mobilized and moved at the time of illumination, and only across the illuminated area.

From solvent-free microspheres to bioactive gradient scaffolds

A solvent-free microsphere sintering technique was developed to fabricate scaffolds with pore size gradient for tissue engineering applications. Poly(D,L-Lactide) microspheres were fabricated through an emulsification method where TiO2 nanoparticles were employed both as particulate emulsifier in the preparation procedure and as surface modification agent to improve bioactivity of the scaffolds. A fine-tunable pore size gradient was achieved with a pore volume of 30±2.6%. SEM, EDX, XRD and FTIR analyses all confirmed the formation of bone-like apatite at the 14th day of immersion in Simulated Body Fluid (SBF) implying the ability of our scaffolds to bond to living bone tissue. In vitro examination of the scaffolds showed progressive activity of the osteoblasts on the scaffold with evidence of increase in its mineral content. The bioactive scaffold developed in this study has the potential to be used as a suitable biomaterial for bone tissue engineering and hard tissue regeneration.

Equilibrium isotherm and kinetic studies for the simultaneous removal of phenol and cyanide by use of S. odorifera (MTCC 5700) immobilized on coconut shell activated carbon

In this study, simultaneous removal of phenol and cyanide by a microorganism S. odorifera (MTCC 5700) immobilized onto coconut shell activated carbon surface (CSAC) was studied in batch reactor from mono and binary component aqueous solution. Activated carbon was derived from coconut shell by chemical activation method. Ferric chloride (Fecl3), used as surface modification agents was applied to biomass. Optimum biosorption conditions were obtained as a function of biosorbent dosage, pH, temperature, contact time and initial phenol and cyanide concentration. To define the equilibrium isotherms, experimental data were analyzed by five mono component isotherm and six binary component isotherm models. The higher uptake capacity of phenol and cyanide onto CSAC biosorbent surface was 450.02 and 2.58 mg/g, respectively. Nonlinear regression analysis was used for determining the best fit model on the basis of error functions and also for calculating the parameters involved in kinetic and isotherm models. The kinetic study results revealed that Fractal-like mixed first second order model and Brouser–Weron–Sototlongo models for phenol and cyanide were capable to offer accurate explanation of biosorption kinetic. According to the experimental data results, CSAC with immobilization of bacterium S. odorifera (MTCC 5700) seems to be an alternative and effective biosorbent for the elimination of phenol and cyanide from binary component aqueous solution.

Low density and hydrophobic silica aerogels dried under ambient pressure using a new co-precursor method

Hydrophobic silica aerogels were prepared by a fast co-precursor method based on sol-gel process under ambient pressure drying. Organic tetraethoxysilane (TEOS) and inorganic aqueous alkaline silica sol were simultaneously used as starting materials, while trimethylchlorosilane (TMCS) was chosen as surface modification agent. Alkaline silica sol plays a double role of increasing pH value for condensation reactions and as co-precursor. The porosity and hydrophobicity of silica aerogels were in close correlation with the synthesis parameters. The monolithic and crack-free sample with a low density of 0.130g∙cm−3 and high water contact angle of 142.8° was obtained by optimized the synthesis conditions (silica sol/TEOS molar ratio, ethanol/silica sol molar ratio, H2O/silica sol molar ratio and TMCS/n-Hexane volume ratio were 0.58, 1.32, 5.34 and 1:7, respectively).

One-step fabrication of transparent hydrophobic silica aerogels via in situ surface modification in drying process

We developed a novel method to facilely prepare transparent hydrophobic silica aerogels via in situ surface modification in drying process in one-step. The as-prepared silica aerogels were characterized by means of scanning electron microscope, transmittance electron microscope, nitrogen adsorption, and contact angle/interface system. In the process, methyltrimethoxysilane was used as the surface modification agent to modify wet gels simultaneously in the supercritical drying process without any solvent exchange. This was beneficial for the sufficient surface hydrophobic modification and time-effective as well as maintaining transparent pore structure of silica aerogels. We reported to rationally design and facilely fabricate transparent hydrophobic silica aerogels via in situ surface modification in drying process in one-step. In the process, the methyltrimethoxysilane (MTMS) molecule was used as the surface modification agent to modify wet gels simultaneously in the supercritical drying process. Thus, the in situ surface modification in drying process illustrated simplification of the surface hydrophobization for silica aerogels. Meanwhile, due to the inertial property of methyl groups in the MTMS molecule, it had been found that when the MTMS ratio was 3, the silica aerogel had the lowest volume shrinkage. Furthermore, all the modified silica aerogels maintained the typical three-dimensional pore structure and showed highly transparent (~80 % at λ = 550 nm) and hydrophobic property (higher than 140°). In a word, owing to its sufficient surface modification and time-effective, the method via in situ surface modification in drying process in one-step would be widely used to facilely fabricate transparent hydrophobic silica aerogels with stable microstructure in future.

Influence of concentration of hydroxyapatite surface modifier agent on bioactive composite characteristics

The characterization of chitosan – hydroxyapatite (CH – HAp) composite sponges prepared via freeze-drying methodology is reported in this study. Stearic acid (SA), added as a surface modifier of the HAp nanoparticles, induced changes in the TG/DTG results, particle size distribution and particle morphology. Composite sponges prepared with SA coated HAp demonstrated enhanced biocompatibility and structural properties, as compared to the composites prepared with uncoated HAp. SA coating modified the morphology of the composite, promoting a better dispersion of HAp particles within the composite sponges, and better homogeneity of the polymeric cover with HAp particles. The viability of the composites for cell culture applications was analyzed, and the results suggest that the sponges are biocompatible. Therefore, SA proved to be a good candidate for surface coating of HAp nanoparticles prevent agglomerations, and could be used effectively in the preparation of biocompatible composite sponges with chitosan.

A facile and cheap coating method to prepare SiO2/melamine-formaldehyde and SiO2/urea-formaldehyde composite microspheres

A facile and cheap coating route has been explored to prepare SiO2/melamine formaldehyde hybrid particles. In this process, SiO2 microspheres act as seeds, and a polycondensation reaction occurs on the surface of melamine-formaldehyde pre-polymers. Formaldehyde is essential in this coating process because it acts as a novel and cheap surface modification agent instead of a traditional silane coupling agent. Ultrasonic method is used in the synthesis to avoid aggregation of nano- and micro-particles. Most of the traditional methods preparing composite microspheres were implemented under difficult conditions and at high costs. The improved coating method is much more able to provide a convenient path for researchers and engineers to more easily and economically perform experiments and engage in manufacturing. To verify this convenient method, SiO2/urea-formaldehyde composite microspheres were also prepared. SEM images show that the surfaces of all the products are smooth and well-shaped.