Preparation, characterization and application of ZnO sol containing quaternary ammonium salts

The zinc oxide sol containing quaternary ammonium salts (DMDAAC-ZnO) was synthesized by zinc acetate and dimethyldiallyl ammonium chloride via the sol–gel process. Effects of zinc acetate concentration, diethanolamine dosage and dimethyldiallyl ammonium chloride dosage on the absorbance-ratio and viscosity of the sol were investigated. Zinc oxide sols were characterized by XRD, TEM and FT-IR. DMDAAC-ZnO was applied to cotton samples and cotton samples treated were tested by antibacterial activity, UV resistance and breaking strength. The antibacterial activity and UV resistance of samples treated by zinc oxide sol containing quaternary ammonium salt were both better than sample treated by zinc oxide sol.     

Gelation Performance of Cationic Gemini Silica Sol with Inorganic Salts and Its Antibacterial Property Analysis

Cationic gemini silica sol (CGSS) was prepared via sol-gel method with tetraethoxysilane (TEOS) as a precursor and ethylene-bis (octadecyl dimethyl ammonium chloride) (EBODAC) as an additive. Inorganic salts, such as NaCl, KCl, MgCl₂, and CaCl₂ boost the gelation process while FeCl₃ delays this process. Antibacterial ratio of treated cotton achieves 90.6% under the baking condition of 160°C for 3 minutes and warp-wise strength, break elongation and whiteness are less impacted under this baking condition. The antibacterial rate of cotton treated by the sols with vinyl tris (β-methoxyethoxy) silane (VTMES) used as the coupling agent still reached up to 81.2% after washing 30 times.      

Effect of the alkyl chain of quaternary ammonium cationic surfactants on corrosion inhibition in hydrochloric acid solution

In this study, the effect of the alkyl chain of quaternary ammonium cationic surfactants on corrosion inhibition in hydrochloric acid (HCl) solution was investigated by using dodecyl trimethyl ammonium chloride (DTAC), tetradecyl trimethyl ammonium chloride (TTAC), cetyl trimethyl ammonium chloride (CTAC), and octadecyl trimethyl ammonium chloride (OTAC) as corrosion inhibitors to uncover their structure–efficiency relationships. The effect of the alkyl chain of quaternary ammonium cationic surfactants on corrosion inhibition in HCl solution was studied under different conditions, such as corrosion inhibitor concentration, temperature, and acidity, and this was done using the weightlessness method. The results obtained show that these inhibitors have high corrosion inhibition effect on A₃ steel, and the corrosion inhibition efficiency is dependent on the length of the alkyl chain. At the same concentration, the longer the alkyl chain, the weaker the corrosion inhibition effect. When the temperature was 50 °C and the concentration of corrosion inhibitor was 70 mg/L, the corrosion inhibition efficiency order of the four cationic surfactants was DTAC > TTAC > CTAC > OTAC. Besides, the experimental results obtained show that the adsorption of the inhibitor on the A₃ steel surface conforms to the Langmuir type isotherm, and then the corresponding adsorption thermodynamic parameters were obtained according to these parameters. It was observed that ΔH, ΔS, and E_a increased with increase in the length of the alkyl chain. The adsorption of the inhibitor on the steel surface is an exothermic, spontaneous, entropy process.     

Effects of diethanolamine on the evolution of silver/titanium dioxide sol–gel process

In order to clarify the effects of diethanolamine (DEA) in the silver (Ag)/titanium dioxide (TiO₂) sol–gel process, sols with and without DEA, and films derived from these sols were prepared. The samples were investigated by X-ray diffraction, transmission electron microscopy, electron diffraction and optical absorption spectra. The results showed that metallic Ag clusters were formed in the sol with DEA and was absent in the sol without DEA. This indicated that DEA worked not only as the stabilizer but also as the reduce agent in Ag/TiO₂ sol–gel process. After annealed, Ag metallic nanoparticles were generated in the films derived from both the sols with and without DEA. The particles in the films derived from the sol with DEA were smaller than those from the sol without DEA. This can be ascribed to the limitation of the growth of Ag cluster formed in the sol with DEA during heat treatment. Mechanisms for the formation of metallic Ag in the Ag/TiO₂ sols and films were discussed. The effects of DEA in the sols and films were studied in detail.     

Structure and associated properties of concentrated SiO2 sols in dilute salt solutions

Using the Verwey-Overbeek potential (VO) function the various liquid-state properties of SiO₂ sols in dilute salt solutions have been evaluated under the mean spherical model approximation (MSMA). The structure factors of these SiO₂ sols predicted by this model are compared with results obtained from small-angle neutron scattering experiments by Ramsay et al. Fourier transformation of these structure factors have been performed to obtain the radial distribution functions (RDF), and from these RDF's we computed coordination numbers of the sol particles. The interparticle distanced _c of sol particles has been obtained from the peak position in structure factorS(k) by using the Bragg's equation. The surface potential _s of the oxide sols has been determined from the amplitude (A) of the VO potential. The present calculations clearly indicate some sort of ordering in the sols system. It is gratifying to note that the present theoretical calculations could reproduce the available observed results very satisfactorily with respect to structure factor and other data.     

Development of mullite and mullite/Al2O3 precursor sols for electrophoretic deposition of oxidation protection coatings

Mullite and mullite/Al₂O₃ precursor sols have been developed for the deposition of oxidation barrier coatings on carbon fibre reinforced composites using a combination of sol–gel synthesis and electrophoresis.The sols were synthesised by controlled hydrolysis and condensation of TEOS (tetraethoxysilane) and Al(OBu^s)₃ (aluminium tri-sec-butylate). The main objective was the definition of synthesis conditions which yield sols suitable for the electrophoretic deposition (EPD). Measurements of the Electrokinetic Sonic Amplitude were used to investigate the electrokinetic properties of the sols in the as-prepared state and depending on the later addition of H₂O. ²⁹Si CP/MAS NMR spectra of dried precursor samples were recorded to study the homogeneity of Al/Si mixture. The progress of crystallisation with increasing temperature of heat treatment was examined by XRD. Oxidation protection coatings on C/C–SiC composites were prepared by EPD.Whereas a low H₂O to TEOS ratio during the sol synthesis was advantageous for a low mullite formation temperature, a high H₂O to TEOS ratio was necessary to enable the EPD. The synthesis of a sol with a low H₂O to TEOS ratio in the first step and the later modification of this sol by the addition of water was a successful method to combine the required electrokinetic properties and mullitisation temperatures below 1200 °C.     

Effect of precursor sol pH on microstructural, optical and photocatalytic properties of vacuum annealed zinc tin oxide thin films on glass

Dip coated vacuum annealed zinc tin oxide thin films on soda lime silica glass have been deposited from the precursor sols containing zinc acetate dihydrate and tin (IV) chloride pentahydrate (Zn:Sn = 67:33, atomic ratio in percentage) in 2-methoxy ethanol by varying sol pH (0.85–5.5). Crystallinity, morphology, optical and photocatalytic properties of the films strongly depend on sol pH. Measurement of grazing incidence X-ray diffraction confirms the presence of hexagonal nano ZnO in the films derived from the sols of pH < 5.5. Film crystallinity deteriorates on increasing sol pH and the film deposited from the sol of pH 5.5 shows XRD amorphous but the selected area diffraction pattern and HRTEM image evidence the presence of nano Zn₂SnO₄ (size, 5–6 nm). Direct band gap energy of films increases on increasing sol pH. To visualize the film surface microstructure, FESEM study has been done and a rod-like surface feature is revealed in the film deposited from the sol of pH 2.85. A dependence of precursor sol pH on the photocatalytic activity of films towards degradation of Rhodamine 6G dye under UV (254 nm) irradiation is found and the highest decomposition rate constant, ‘k’ value is obtained from the film prepared from the sol of pH 5.5. The presence of zinc deficient nano Zn₂SnO₄ in the film may consider for generating the highest ‘k’ value. We also measure gelling time, viscosity of sols as well as UV and FTIR studies on the films and propose chemical reactions.     

Antibacterial glass films prepared on metal surfaces by sol–gel method

This paper describes the preparation and characterization of glass films consisting of SiO₂, Li₂O, Na₂O, K₂O or MgO in varying compositions on stainless steel and aluminum substrates by sol–gel method. Silver phosphate or silver incorporated zeolite was also introduced into the sols for obtaining antibacterial effect. The SiO₂/Li₂O/Na₂O system having the composition of 85:5:10 wt% was found as the optimum for obtaining a stable sol and film formation. The films were investigated by scanning electron microscopy (SEM) and electron dispersive analysis by X-ray (EDX), Fourier transformed infrared (FTIR) spectroscopy, thermo-gravimetric analysis (TGA) and differential thermal analysis (DTA). Homogenous films having 300 ± 20 nm thicknesses were formed by spin coating and then by curing at 500 °C for 1 h. Obtained films had high adherence to the metal substrates and they were also durable in acidic, basic or NaCl environments. They also presented a powerful antibacterial effect against E. coli.     

Effects of aging time on V2O5 sol-gel coatings

Vanadium pentoxide (V₂O₅) sols have been used in conductive coatings and related applications [1, 2, 3]; however, the changes which may occur in the properties of these coatings with sols of different ages have not been carefully shown. Properties which may be dependent on the age of the sol (sol viscosity, film morphology and conductance) were measured in this work. The coating sols were prepared by ion-exchange of sodium metavanadate solutions.It was found that the coating thickness, sol viscosity, and surface morphology of the coatings were directly related to the age of the sol used. The dried coating thickness increased from 3 microns to 20 microns over a 30 day period. The sol viscosity increased from 1 centipoise to near 2 centipoise. The surface morphology of the coatings changed from that of a featureless surface at day 1 to a continual coverage of micron-sized fibers as the coating sols aged. The conductivity of the coatings, though, was unaffected by the age of the sol. The coating properties were correlated to the amount of polymerization of dissolved precursors in solution.     

Preparation and Antibacterial Function of Quaternary Ammonium Salts Grafted Cellulose Fiber Initiated by Fe2 +-H2O2 Redox

The surface contact disinfecting technique is a newly developed method for water sterilization. In this paper, the grafted quaternary ammonium salts (QAS) antibacterial fibers were prepared and designed to apply for the surface contact disinfecting process in water treatment. The antibacterial fibers were directly prepared by grafting methacryloxylethyl benzyl dimethyl ammonium chloride (DMAE-BC) onto cellulose fiber using thiocarbonate-H₂O₂ redox system. All kinds of factors in the grafting reactions, such as reaction time, reaction temperature, monomer concentration, initiator concentration, which influence the percentage of grafting, were studied and optimized. The modified cellulose fibers were characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscope(SEM). The effects of the percentage of grafting of the grafted cellulose fibers on bactericidal activity were also studied. The spread plate method was used to characterize the bactericidal activity. The disinfection process was further investigated by directly observing the morphology of the bacterial cells adsorbed on the antibacterial fibers with SEM and measuring extracelluar total protein concentration in suspension. The poly(DMAE-BC)-grafted cellulose ?ber was found to exhibit particularly high activity against E.coli.     

Synthesis,Surface Properties,and Antibacterial Activity of Quaternary Ammonium Salts Containing Epoxide Group

Epoxypropyl dodecyl dimethyl ammonium chloride (EPDDMAC) was synthesized with N,N-dimethyl dodecyl amine (DMDA) and epichlorohydrin (EPIC). Diethyl-2,3-epoxypropyl-[3-methyldimethoxyl)] silpropyl ammonium chloride (DEEPSAC) was synthesized with N,N-diethyl-aminopropyl-methyldimethoxysilane (DEAPMDES) and epichlorohydrin (EPIC). The products were characterized by infrared and elemental analysis and ¹H NMR spectroscopy. The surface tension, conductivity, and antibacterial activities of EPDDMAC and DEEPSAC were studied.     

SbxZn1-xO1+x/2及其壳聚糖复配物的制备和抗菌性能

采用溶胶-凝胶法制备了SbxZn1-xO1+x/2及其壳聚糖的复配物,通过X-射线衍射仪(XRD)、傅里叶变换红外光谱仪(FTIR)、扫描电子显微镜(SEM)和透射电子显微镜(TEM)等表征了样品的物相结构、组成和微观形貌。以大肠杆菌、白色念珠菌和金黄色葡萄球菌为测试菌种,研究了样品的抗菌性能。结果表明,SbxZn1-xO1+x/2的抗菌活性优于纯ZnO,其中x=0.05的样品活性最好;复配物的抗菌活性明显优于单一组分,当Sb0.05Zn0.95O1.025和壳聚糖质量比mSZ/mCS=2时,样品抗菌性能最佳。     

Preparation of highly stable TiO<Subscript>2</Subscript> sols and nanocrystalline TiO<Subscript>2</Subscript> films via a low temperature sol–gel route

Highly stable TiO₂ sols were prepared by adjusting the water-to-titanium molar ratio to ~4 in the process of hydrolysis and condensation of titanium isopropoxide in ethanol with HNO₃. Particularly, long-term stable TiO₂ sols were prepared without adding any chemical additives. Anatase TiO₂ nanocrystallites with sizes of 3–5 nm in diameter were uniformly dispersed in the stable sol. Crystallized TiO₂ films were successfully deposited on Si (100) using the stable sol via a dip-coating process with low temperature curing at as low as 100 °C. The synthesized TiO₂ sols and films are promising for use in flexible or dye-sensitized solar cells.     

Studies of Lead Zirconate Titanate Sol Ageing Part I: Factors Affecting Particle Growth

The formation and growth of polymeric particles during the hydrolysis and condensation of PbZr_0.3Ti_0.7O₃ (PZT 30/70) precursor solutions have been studied as functions of time by using photon correlation spectroscopy (PCS). Particle shape was deduced by measuring the rheological properties of the sols and was found to remain chain-like during sol ageing. Various factors that affect the ageing of PZT sols have been investigated. Ethylene glycol (EG) was found to greatly accelerate the hydrolysis and condensation of the acid-modified Pb-free Zr/Ti solutions but had little effect on the particle growth for the Pb-containing PZT sols. Temperature and H₂O concentration were found to have major effects on the ageing behaviors. The higher the temperature and H₂O concentration, the higher the particle growth rates and the faster the sol gels.     

Preparation and characterization of TiO2 sols and their UV-cured hybrid thin films on plastic substrates

In this research, TiO₂ sols were synthesized via a sol?Cgel reaction at room temperature followed by heating under reflux. Hybrid thin films were prepared using the TiO₂ sols and dipentaerythritol hexacrylate on poly(methyl methacrylate) substrates via spin coating followed by UV-curing. The images of transmission electron microscopy (TEM) and results of dynamic light scattering (DSL) showed that some originally synthesized TiO₂ nanoparticles aggregated while many small-sized (~5?nm) TiO₂ nanoparticles still existed after reflux heating. The synthesized TiO₂ sols showed poor photocatalytic ability, which might avoid degradation of organic moieties in the hybrids. The refractive indices of the hybrid thin films were increased from 1.66 to 1.82 while the water contact angles on the thin films were increased from 70.2° to 87.7° with the increment of TiO₂ content. Increasing the heating time of the TiO₂ sol resulted in an increase in the refractive index and contact angle.     

Ultra-low expansion glass from gels

Pyrolysis of mixed titanium and silicon metal halides produces a commercial glass (7.4% TiO₂) with ultra-low thermal expansion that is essentially zero over the temperature range of 0 to 300°C. A colloidal particulate gel process involving potassium silicate, titania sol and formamide gel reagent was found to produce glass compositions with similar low expansion behavior. Due to the strongly basic nature of the precursor solutions, special titania sols had to be prepared that were stable in these alkali silicate solutions. The preferred TiO₂ sols were those containing quaternary ammonium stabilizing counter-ions. These sols served not only as the source of homogeneously distributed titania, but they may also serve as nucleating species that contribute to particle growth and pore size control of the gel network. The large pore (0.3 µm) TiO₂/SiO₂ gel structures were easily dealkalized, dried and sintered to uncracked glass shapes. Plates up to 9.5 cm×6.6 cm× 0.5 cm thick and some intricate cast shapes were produced and their glass properties evaluated.     

Antibacterial membranes based on chitosan and quaternary ammonium salts modified nanocrystalline cellulose

Etherification of nanocrystalline cellulose (NCC) with three kinds of quaternary ammonium salts epoxypropyltrimethylammonium chloride, N,N‐dimethyl‐N‐dodecyl‐N‐(1,2‐epoxypropyl) ammonium chloride (DMDEPAC), and N,N‐dimethyl‐N‐octadecyl‐N‐(1,2‐epoxypropyl) ammonium chloride (DMOEPAC) was successfully performed via a nucleophilic addition reaction. The synthesized DMDEPAC and DMOEPAC were characterized by nuclear magnetic resonance. The modified NCC particles, NCC epoxypropyltrimethylammonium chloride, NCC‐DMDEPAC, and NCC‐DMOEPAC, were characterized by energy dispersive spectrometer. Nanocomposite films based on chitosan (CS) containing quaternary ammonium salts modified NCC were prepared with nanoparticle loadings of 5.0, 7.5, and 10.0%, respectively. The effect of nanoparticle content on the tensile strength of composite films was studied. The results indicated that the films with 5.0% nanoparticle loading exhibited the biggest increase in tensile strength. Surface morphology, smoothness, and antibacterial properties of composite films containing 5% modified NCC were also studied. CS/NCC‐DMDEPAC‐5.0 and CS/NCC‐DMOEPAC‐5.0 displayed excellent biocidal abilities against both Gram‐positive Staphylococcus aureus (ATCC 6538) and Gram‐negative Escherichia coli O157:H7 (ATCC 43895). The bio‐based nanocomposite films with increased mechanical strength and excellent antibacterial properties show great potential as food packaging materials. Copyright © 2017 John Wiley & Sons, Ltd.     

The leaching of Rhodamine B, Naphthol Blue Black, Metanil Yellow and Bismarck Brown R from silica deposits on polyester and viscose textiles

Rhodamine B (RB), Naphthol Blue Black (NBB), Metanil Yellow (MTY) and Bismarck Brown R (BHR) immobilized within a modified silica sol were used for the surface dyeing of textiles, namely polyester and viscose fabrics. Silica sols were characterized by FTIR and dynamic light-scattering measurements. The sol was dip-coated onto the fabrics and deposits were formed. Three similar procedures for the formation of silica deposits, using tetraethoxysilane (TEOS) and (3-glycidoxypropyl)trimethoxysilane (GPTMS) as precursors in acidified ethanol, were tested. Interactions between dyes and silica precursors were investigated by FTIR measurements. Leaching was detected and quantified by UV–Vis measurements on the composition of washing solutions. Incorporation of GPTMS into silica sols reduces dye leaching from the silica deposits.     

Hydrophobic Silica Sol Coatings on Textiles—the Influence of Solvent and Sol Concentration

Hydrophobic silica sol coatings on textiles were investigated with respect to the influence of the solvents and the concentration of the sol. For this purpose, two silica sols, prepared with the hydrophobic additives octyltriethoxysilane and perfluoroctyltriethoxysilane were diluted by different solvents: water, ethanol and aceton.In case of using pure water for dilution, the hydrophobicity of coated textiles decreases drastically with increasing dilution of the applied sol. For coatings on polyester fabrics or mixed fabrics made from polyester and cotton, the use of the organic solvents ethanol or aceton leads to significant hydrophobicity even in case of strong dilution down to a sol concentration < 1%. The hydrophobic effect of coated polyamide textile is less. The reason for different hydrophobicity of coated textiles resulting from the use of water instead of organic solvents is explained by different surface morphologies of the coatings deposited on the textile fibres, as observed by REM. In case of using organic solvents the coatings contain a more flat morphology which covers the fibres completely. In contrast, sols with higher water content lead to less adhesive coatings with crack formation.The use of a combination of water with less inflammable organic solvents such as di(propylene glycol) n-propyl ether (Dowanol^TM DPnP) in hydrophobic silica sols yields textile coatings with good hydrophobicity, even in case of low sol concentration. For practical application of textile coatings, especially silica sols with high water content are of interest, due to less risk of inflammation and lower ecological impact. Therefore, the use of water diluted hydrophobic silica sols with small amounts of DPnP offers a chance for textile refinement by the sol–gel technique.     

Sol hydrolysis and condensation reaction time influence the sensitivity of class II xerogel-based sensing materials

Simplicity of preparation, a wide variety of precursors, and numerous processing variables (e.g., pH, time, temperature) are often described as attractive aspects of sol–gel derived materials. In the current work we create a series of O₂-responsive xerogel-based sensor films by simultaneously co-hydrolyzing and co-condensing tetramethylorthosilane and n-octyltriethoxysilane. Tris(4,7′-diphenyl-1,10′-phenanthroline) ruthenium(II) ([Ru(dpp)₃]²⁺) is used as the O₂-responsive luminophore. We determine the effects of [Ru(dpp)₃]²⁺ addition time to the sol and the sol hydrolysis and condensation reaction time (H&C) on the xerogel film O₂ sensitivity. [Ru(dpp)₃]²⁺ addition time has no significant effect on the O₂ sensitivity; H&C effects the O₂ sensitivity. The highest O₂ sensitivity is seen at early H&C (0.5 h). This behavior arises because TMOS and C8-TMOS react at different rates to form sols. At early H&C the co-hydrolysis and co-condensation reactions are not complete and the so formed sols are rich in C8-TMOS in comparison to their composition at longer H&C. At longer H&C, the TMOS and C8-TMOS co-hydrolyze and co-condense more completely. SEM images show that xerogel films formed at early H&C is more porous in comparison to those formed a longer H&C. The results of these experiments: (a) highlight the importance of documenting how sols are processed and xerogels formed and (b) demonstrate the use of a single sol formulation and H&C to create suites of sensor materials with different responses.