Surface Protective Agent Research Articles

Synthesis and application of carbon substrate nano material from biomass for surface protection – Effect of variables, electrochemical and isotherm studies

Carbon based compounds have gained significant attention due to their environmental engineering applications with their favorable physical and chemical properties. Chitosan, a naturally available carbon based biopolymer, is identified as a potential surface protective agent and tested for its surface coverage properties to control the corrosion of mild steel. Chitosan nanoparticles (Ch-NP) were produced using a simple two-step synthesis to produce a corrosion protection agent for mild steel in 3.5% NaCl. The effect of immersion duration (4–24 h) was investigated using inhibitor extracts containing 400, 600, 800, and 1000 ppm at three temperatures, namely,305.15, 310.15, and 315.15 K. Inhibition efficiency increased with increase in the inhibitor dosage due to the development of protective surface film. An integrated electrochemical study was performed using electrochemical impedance spectroscopy, potentiodynamic polarization, and gravimetric measurement. Ch-NP has a mixed-type adsorption behavior for mild steel surface. The Langmuir isotherm was used to characterize the adsorption of Ch-NP molecules on the surface of mild steel. Tafel study confirmed the inhibitor examined as mixed type. Ch-NP demonstrated a high inhibitory effectiveness of 91% under the tested conditions and proved to be an effective alternative for industrial applications.

A comparative evaluation of resin- and varnish-based surface protective agents on glass ionomer cement – a spectrophotometric analysis

Objectives To evaluate and compare the effectiveness of resin- and varnish-based surface protective agents on Glass Ionomer Cement (GIC). The different surface protective agents used were: Vaseline®, GC Fuji VARNISH™ (varnish), G-Coat Plus™ (resin) and EQUIA® Coat (resin). Method Thirty-six identical specimens of GIC were made. Six specimens were used in preparation of standard solution and remaining thirty were divided into five groups with six specimens in each group. Each test specimen was coated with one of the surface protecting agent except for the control group. The specimens were immersed separately into 1 ml of 0.05% methylene blue solution for 24 h and then rinsed with deionised water and further immersed into tubes containing 1 ml of 65% nitric acid. Specimens, once completely dissolved in nitric acid solution, were filtered and centrifuged. The supernatant was used to determine the absorbance using a spectrophotometer. The effectiveness of the surface protecting agents for the GIC was recorded in micrograms of dye per specimen, where low values indicate good protection. Result Tukey HSD test revealed that GC Fuji VARNISH™ (varnish; mean = 21.25 µg/ml), G-Coat Plus™ (resin; mean = 30.39 µg/ml) and EQUIA® Coat (resin; mean = 9.32 µg/ml) were statistically not significantly different to each other and were effective in protecting the surface of GIC. Significance The study found that there was a statistically significant difference between control and GC Fuji VARNISH™, G-Coat Plus™ and EQUIA® Coat. The three agents were found to be equally effective in protecting the surface of GIC.

(Invited) Cyclic Voltammetry of Gold Nanoparticles: Comparative Analysis of Redox, Electronic and Optical Properties

It has been reported that cyclic voltammetry (CV) can be a useful tool for the electrosynthesis of gold nanoparticles (AuNPs) from AuCl4 - solutions in the presence of different protective (surfactant) agents. However, the use of this electrochemical analytical tools for the characterization of electroactive nanomaterials has been scarcely explored. In this work, cyclic voltammetry has been used to characterize the redox properties of AuNPs with controlled sizes and almost monodisperse, previously synthesized by chemical reduction of AuCl4 -in aqueous solutions, in the presence of two different surface protective agents (citric acid and tartaric acid). For the CV characterization, the as prepared AuNPs colloidal solution were used without addition of any supporting electrolyte. A typical three electrode system was used, with a glassy carbon electrode as a working electrode, a platinum wire as the counter electrode and a Ag/AgCl (KCl sat) electrode as reference. The potential window was scanned from +0.4 V to +0.95 V and ended at 0.25 V, at a scan rate of 1.0 Vs-1. Nanoparticles size distribution and zeta potential (ζ) were previously characterized by dynamic light scattering (DLS) in aqueous suspensions, while precise size and morphology analyses were performed using high-resolution scanning electron microscopy (HR-SEM) in a MAIA Tescan FESEM. The UV-VIS surface plasmon resonance spectrum of the AuNPs was obtained by UV-Vis spectroscopy in water. The nanoparticles chosen for this electrochemical analysis, which were nearly monodispersed, had average sizes of 15 and 40 nm and an almost spherical morphology. Their electrochemical behavior showed an irreversible oxidation peak at +0.7 V and it was observed that the generated current and potential was dependent of nanoparticle size: the 40 nm AuNPs showed a higher oxidation potential than those AuNPs with an average diameter of 15 nm. The current evolved during cycling the AuNPs solution. A comparative analysis of redox properties and other physical properties (plasmon energy, size distribution) will be discussed in this work.

The Transformation of Hybrid Silica Nanoparticles from Solid to Hollow or Yolk-Shell Nanostructures.

Here, a facile self-templating approach is presented for synthesis of hollow and yolk-shell mesoporous silica nanoparticles (HMSNs and YMSNs) through a selective etching of hybrid silica nanoparticles. The hybrid silica nanoparticles are from the co-condensation of tetraethylorthosilicate (TEOS) and N-[3-(trimethoxysilyl)propyl]ethylenediamine (TSD) by a simple one-step process. Two kinds of products including HMSNs and YMSNs can be easily prepared only by tuning the TSD amounts in the precursor. Significantly, the transformation of hollow structure does not use any sacrificial template and surface-protective agent. The etching mechanism and formation process are systematically investigated by SEM, TEM, TG, CHN elemental analysis and Si MAS NMR spectroscopy. The results reveal that the selective etching is mainly attributed to the discrepancy in density between the outer layer and inner area of hybrid silica, where its inner section is more readily dissolved while the outer shell is robust in hydrofluoric acid (HF) aqueous solution. Specifically, the new understanding is further extended to precisely prepare multi-shelled hollow/yolk-shell silica nanoparticles.

Influence of citric acid on the surface texture of glass ionomer restorative materials.

Aim:This study determined the effectiveness of G-coat plus surface protective agent over petroleum jelly on the surface texture of conventional Glass ionomer restorative materials.Materials and Methods:Three chemically cured conventional glass ionomer restorative materials type II, type IX and ketac molar were evaluated in this study. Sixty specimens were made for each restorative material. They were divided into two groups of thirty specimens each. Of the sixty specimens, thirty were coated with G-coat plus (a nano-filler coating) and the rest with petroleum jelly. Thirty samples of both protective coating agents were randomly divided into six groups of five specimens and conditioned in citric acid solutions of differing pH (pH 2, 3, 4, 5, 6 & 7). Each specimen was kept in citric acid for three hours a day, and the rest of time stored in salivary substitute. This procedure was repeated for 8 days. After conditioning, the surface roughness (Ra, μm) of each specimen was measured using a surface profilometer (Taylor & Habson, UK). Data was analyzed using one-way analysis of variance (ANOVA) and Tukey's HSD test at a significance level of 0.05.Results:The surface textures of all the tested glass ionomer restorative materials protected with G-coat plus were not significantly affected by acids at low pH. The surface textures of all the tested glass ionomer restorative materials protected with petroleum jelly coating were significantly affected by acids at low pH.Conclusion:The effects of pH on the surface texture of glass ionomer restoratives are material dependent. Among all the materials tested the surface texture of Type II GIC (Group I) revealed marked deterioration when conditioned in solutions of low pH and was statistically significant. Hence, a protective coating either with G-coat plus or with light polymerized low viscosity unfilled resin adhesives is mandatory for all the glass ionomer restorations to increase the wear resistance of the restorative materials.

Surface coatings on glass ionomer restorations in Pediatric dentistry-Worthy or not?

To know the effect of surface protective agents used in day-to-day practice on the fluoride release property of conventional glass ionomer cements (GIC) and discuss its pros and cons. Thirty disc-shaped specimens were fabricated from conventional GIC and block randomized into three groups (Group I, II, and III) of 10 each. Group I specimens were unprotected, group II coated with cavity varnish (Namuvar, Ratnagiri, India) and group III with petroleum jelly (Vaseline, Hindustan lever ltd). After polymerization, the disks were immersed in three individual sealable plastic bottles containing deionized distilled water which was changed every 24 hours for 15 days to measure the fluoride release. STATISTICS AND RESULTS: Statistical analysis was carried using software version Systat 10.0, and the data was subjected to one way ANOVA, using Duncan Multiple Range test (Variable LSD) with the level of significance set at 0.05 (P < 0.05). The greatest amount of fluoride was released from the uncoated group, followed in ranking by petroleum jelly and varnish coated and the difference among them was statistically significant (P < 0.05). Application of varnish over GIC can severely impede its fluoride release property. Similarly petroleum jelly also impedes the fluoride release, but to a very less extent. We suggest that in situations where the fluoride release property is more important than other properties it is better to coat the GIC with petroleum jelly or leave the restoration without any coating.

Mesoporous Silica Hollow Spheres with Ordered Radial Mesochannels by a Spontaneous Self-Transformation Approach

We demonstrate a self-transformation approach for the synthesis of ordered mesoporous silica hollow spheres with radially oriented mesochannels. The method is simple and facile, in which mesostructured silica spheres synthesized in a Stober solution can spontaneously transform to hollow structure when they are incubated with water. The formation of the hollow structure does not require any sacrificial templates, emulsion droplets, or surface protective agents. The obtained mesoporous silica hollow spheres possess controllable diameter, tunable shell thickness, high specific surface area, and uniform mesopore. Transmission electron microscopy (TEM) observations show that the formation of the hollow spheres undergoes a selective etching process in the inner section. 29Si NMR spectra and detailed reactions demonstrate that the solid-to-hollow transformation of the Stober silica spheres in water is attributed to the difference in the degree of condensation of silica between their outer layer and inner section...

Forming double layer-encapsulated quantum dots for bio-imaging and cell targeting

We report a simple and effective approach for the preparation of double layer-encapsulated quantum dots (DL-Qdots) composed of alkyl-capping ligands to interdigitate with hydrophobic, protective agents on the surface of AgInS(2)/ZnS quantum dots (Qdots), which allow phase transfer of hydrophobic Qdots from the organic phase into the aqueous phase. The alkyl-capping ligands consist of a hydrophobic, aliphatic chain and different functional terminal groups (e.g., carboxyl, amine, hydroxyl, and thiol groups) that can serve as reactive sites to chemically couple with other materials. The resulting DL-Qdots bearing various functional groups retain good fluorescence properties and show excellent solubility as well as stability over a range of pH in the aqueous phase. Cytotoxicity studies of DL-Qdots bearing carboxyl groups (DL-Qdots-COOH) were carried out against human cervical (HeLa) cancer cells to elicit no apparent toxicity even at high concentrations of 300 μg mL(-1) and 24 h of incubation. To demonstrate their potential biomedical application, DL-Qdots-COOH were further conjugated with folate for staining in HeLa, human liver carcinoma (HepG2), and human breast (MCF-7) cancer cells. Confocal imaging characterization revealed that folate-conjugated DL-Qdots could target most specifically and effectively HeLa cells via folate receptor-mediated targeted delivery compared to HepG2 and MCF-7 cells. The generality and simplicity of this newly developed strategy can possibly be extended to a large variety of hydrophobic Qdots and nanocrystals whose surface protective agents have a long aliphatic chain.

Effects of the Ratio of Surface Protective Agent on the Preparation of Nano-Silver

It has many advantages with liquid phase reduction method to prepare the nano-silver, such as experimental conditions are simple, low cost, energy-saving, etc.. At the same time, the nano silver powder prepared by this method has high surface activity, catalytic property and wide usage. In this paper, nano-silver powder was prepared by changing the amount of protective agents with chemical liquid phase reduction method. This paper focuses on the impact of the amount of protective agent on the nano-silver. In addition, we also analyzed the reaction temperature, PH value of solution, viscosity and electrical conductivity on the preparation of nano-silver. Finally, test results from the TEM shows that the nano-silver was prepared with smaller size, uniform size and good dispersion.

Effects of Different Reducing Agents and Protective Agents on the Preparation of Nano-Silver Powder

Solution chemical reduction method is a means which used reducing agent in aqueous or organic systems to deoxidize silver ions. Its essence is an integrated process of the electrochemistry, thermodynamics, kinetics and fluid dynamics and so on. The process determines the physical and chemical properties such as the size distribution of powder, purity and reunion situations, etc. Nano-silver powder has high surface activity and catalytic properties, and is widely used to a lot of fields. So it has very important realistic significance to study the preparation method. In this paper, nano-silver powder was prepared with industrial AgNO3 as raw materials, sodium borohydride or hydrazine hydrate as reducing agent, polyvinyl alcohol, SDBS or polyvinylpyrrolidone(PVP) as the surface protective agent by solution chemical reduction method. The influences of different reducing agents and protective agents on the preparation of nano-silver were analyzed. The results from the XRD diffraction analysis and TEM show that it can be obtained high purity flake nano-silver in the reaction temperature range of 50-60°C.

Characterization and photoactivity of TiO 2 sols prepared with triethylamine

Using triethylamine as a surface protective agent, a transparent and pale yellowish TiO 2 sol had been prepared at 90 °C. This method was very different from the traditional methods, which produced titanium dioxide nanoparticles with anatase crystalline structure either at high acid condition or high temperature. X-ray diffraction (XRD) and transmission electron spectroscopy (TEM) demonstrated that the as-prepared TiO 2 sol nanoparticles with anatase crystalline structure were uniformly distributed, and the average size was 3 nm. X-ray photoelectron spectroscopy (XPS) and UV–vis absorption spectra showed that triethylamine was adsorbed on TiO 2 sol particles surface. FTIR spectroscopy noted that TiO 2 sol particles had the similar spectra with Degussa P25. Photoactivity of the as-prepared TiO 2 sol was studied by investigating the photodegradation of methyl violet in hydrosol reaction system under visible light irradiation.

Sucralfate interactions with gastric mucus

Sucralfate protects the stomach against a number of experimental damaging agents and is efficacious in the treatment of peptic ulcer disease. It binds with acidity to the base of an ulcer to form a protective barrier. Sucralfate also enchances prostaglandin synthesis and release in the mucosa. In this study, the rat stomach was examined to determine sucralfate's interaction with gastric mucus. Mucus in the rat stomach forms a distinct and continuous blanket. In snap-frozen samples, pretreatment with phosphate-buffered saline as a control shows a layer of mucus of homogeneous structure thinner than the homogeneous layer after pretreatment with antibodies developed against rat gastric mucus. Pretreatment with the surface protective agent sucralfate shows some increase in the thickness of mucus with a thin dense sublayer adjacent to the epithelium and a less dense-appearing outer zone of variable thickness. Analysis of x-rays generated by the electron beam on windows of mucus and epithelium showed the expected gradients of sodium, potassium, chloride, and sulfur. The percentage of aluminum and sulfur in the mucus was higher in sucralfate-treated samples than in controls. Interaction between sucralfate and gastric mucus needs further investigation.

The influence of high- and low-molecular-weight inhibitors on dissolution kinetics of hydroxyapatite and human enamel in lactate buffers: a constant composition study.

The kinetics of dissolution of hydroxyapatite (HAP) and human enamel (HE) powders in lactate buffers was investigated by means of a Constant Composition technique. The rates were interpreted in terms of a surface-controlled dissolution mechanism. It was shown that the overall dissolution of both HAP and HE crystallites in lactate buffers resulted from an interplay of the calcium chelating action of lactate ion, its interaction with surface calcium sites, and the retardation effects of both ionized (L-) and un-ionized (HL) lactic acid due to adsorption at phosphate surface sites. The presence of lactate in demineralizing solutions also influenced the "acquired crystallite resistance" for dissolution, and the rates decreased as the reaction proceeded. The influence of surface protective agents [methanehydroxydiphosphonate (MHDP) and polyacrylic acid (PAA)] on HAP and HE dissolution rates was also extensively studied in partially saturated lactate buffer (0.05 mol L-1). Although the overall kinetic effects of both additives appeared to be similar, there were considerable mechanistic differences. MHDP might interact with lactate by competition for surface calcium sites. In contrast, PAA appeared to act independently of lactate under the experimental condition used. This would tend to support the recommendation of White (1987), that PAA was more suitable as a surface protective agent for artificial caries lesion preparation.

Use of synthetic polymer gels for artificial carious lesion preparation.

Synthetic polymer gels have been examined as decalcifying media for the preparation of artificial carious lesions in tooth enamel. Enamel specimens were demineralized in lactic acid/calcium phosphate buffers containing 0.1–0.5% (w/w) polyacrylic acid (Carbopol C907, MW = 450,000 daltons) to act as a surface-protective agent. The rate, histology and physical characteristics of lesions were characterized by surface microhardness, polarized light, and microradiographic analyses. Following demineralization, selected lesions were remineralized in solutions supersaturated with respect to fluoroapatite. The results show that polyacrylic acid is extremely useful and effective as a surface-protective agent for artificial carious lesion preparation. The histology of lesions formed in C907 gels can be carefully controlled by adjusting the undersaturation of the demineralization medium with respect to tooth mineral salts. Lesions formed in C907 gels are extremely reactive towards remineralization and the rate and histology of mineral repair are not noticeably influenced by the resin content in solution. The use of synthetic polymer gels is recommended for the systematic reproducible preparation of artificial carious lesions in dental enamel.