Application of Achillea millefolium extract as a reducing agent for synthesis of silver nanoparticles (AgNPs) on the cotton: antibacterial, antioxidant and dyeing studies.

The phyto-synthesis of silver nanoparticles and cotton dyeing with natural colorants can reduce the environmental impact of the process considerably. In this study, the extraction of natural colorants from Achillea millefolium petals was optimized by ultrasound technique. The AMP extract was applied for synthesis of silver nanoparticles (Ag NPs) on the cotton fabrics. The dyeing, antibacterial and antioxidant characteristics of cotton samples were investigated to optimize the process and evaluate its efficiency. The AMP extract had good substantivity towards cotton fabrics and the presence of tannic acid, as an environmentally-friendly mordant, further improved the absorption of AMP dye. The antibacterial and antioxidant activities of the dyed samples with AMP extract of were 50%and 60%, respectively. The addition of TA and Ag enhanced the antibacterial and antioxidant activities on the cotton samples to over 99%.

Effect of nano-oxides on the color stability of maxillofacial silicone elastomers.

STATEMENT OF PROBLEM: A significant challenge of craniofacial prostheses is their limited service life because of degradation and color instability. In spite of improvements in the materials and techniques used for the fabrication of silicone maxillofacial prostheses, undesirable color change over time remains a challenge. Zn and Ti nano-oxides (nano-TiO2) have been reported to impart an ultraviolet- (UV) shielding property to silicone elastomers. However, studies examining the effects of nanopigments on the color stability of craniofacial prostheses are sparse. PURPOSE: The purpose of this in vitro study was to evaluate the color stability of a room-temperature vulcanizing (RTV) silicone elastomer with the addition of iron oxide and titanium dioxide nanopigments under accelerated artificial aging. MATERIAL AND METHODS: Sixty disks (Ø15×2 mm) were fabricated from RTV silicone 4408 Q. The specimens were divided into 5 groups containing iron oxide nanopigment, iron oxide nanopigment and rutile nano-TiO2 (as an opacifier), burnt sienna pigment, burnt sienna and nano-TiO2, and silicone without pigment or opacifier. The specimens were subjected to accelerated aging in a Xenotest chamber for 1000 hours. CIELab color coordinates and the total color difference (ΔE∗) values were determined before and after aging. ΔE∗ values were compared between the groups by using 1-way ANOVA and Tamhane multiple comparisons (α=.05), and a standard deviation of 1.09 was considered. RESULTS: ANOVA showed that the values of ΔE∗ differed among all groups (P<.05). The minimum amount of a color change perceived (ΔE∗ approximately =1.1) by the visual system as the threshold was observed in the specimens treated with burnt sienna and nano TiO2. The greatest color change occurred in the specimens treated with iron oxide nanopigment. As per the acceptable clinical threshold, the color change was satisfactory in all groups. CONCLUSIONS: Nano-TiO2 with burnt sienna groups had a lower color change than the other groups. The color change in all groups was within a clinically acceptable range.

Analysis of color and fluorescence of different dentin ceramics and natural human dentin's to enhance shade matching.

OBJECTIVES: This study aimed to compare the color and fluorescence of five dentin ceramic systems with human dentin to enhance shade matching. MATERIALS AND METHODS: Five dentin ceramic systems, including Vita, GC, Creation, Noritake, and Ivoclar in 16 shades, and 12 human dentins, were prepared. The fluorescence and color coordinates were measured at 380-780 nm. A light source including a visible and a ultraviolet (UV) complemented with a geometry 45° illumination and 0° observer was used. The mean minimum difference in color coordinates and fluorescence efficiency was statistically analyzed before and after UV excitation by one-way ANOVA (p < 0.05). Post-hoc multiple comparisons were performed using the LSD test (p < 0.05). RESULTS: While the fluorescence efficiency of Noritake and Ivoclar ceramics displayed no significant difference with natural dentin, Vita, GC, and Creation ceramics presented a lower fluorescence compared to the natural dentin (p < 0.05). Noritake and Ivoclar had a better color match with human dentin than the other ceramics. Studying the color differences under UV showed that just Creation offers statistically worse performance than the other ceramic. CONCLUSIONS: The color and fluorescence of the used different brands of dentin ceramic are not the same as the human dentin. However, Noritake and Ivoclar presented the most similarity. CLINICAL SIGNIFICANCE: Knowledge of ceramic and natural teeth fluorescence is essential for acceptable reproduction of optical properties in esthetic restorations.

LED primary selection algorithms for simulation of CIE standard illuminants.

Although mixture of LEDs is being considered as a simulator of the CIE daylight series, the performance of the simulations is highly dependent on the SPD of the selected LEDs. An algorithm for selection of the best LEDs for simulation of the CIE daylight series is helpful in this regard. To address this problem, using 200 imaginary light primaries and 40 real LEDs, three algorithms based on concepts of equally spacing of wavelength range ("Equal"), Gram Schmidt orthogonalization in LEDs/light primaries spectral subspace ("Gram") and the generalization of Gram Schmidt orthogonalization in the LEDs/light primaries projections onto the illuminants subspace ("Ortho") were proposed and studied. Algorithms, in simulation and reality, were implemented for the CIE standard illuminants of D50, D55, D65 and D75, C and A. The results showed that the performance of the proposed algorithms generally increase with the higher number of selected LEDs/light primaries, while for the LEDs "Gram" and "Ortho" methods showed superior performance, simulations on the imaginary light primaries showed "Ortho" could be considered as the best algorithm.

Cross-cultural variation of memory colors of familiar objects.

The effect of cross-regional or cross-cultural differences on color appearance ratings and memory colors of familiar objects was investigated in seven different countries/regions - Belgium, Hungary, Brazil, Colombia, Taiwan, China and Iran. In each region the familiar objects were presented on a calibrated monitor in over 100 different colors to a test panel of observers that were asked to rate the similarity of the presented object color with respect to what they thought the object looks like in reality (memory color). For each object and region the mean observer ratings were modeled by a bivariate Gaussian function. A statistical analysis showed significant (p < 0.001) differences between the region average observers and the global average observer obtained by pooling the data from all regions. However, the effect size of geographical region or culture was found to be small. In fact, the differences between the region average observers and the global average observer were found to of the same magnitude or smaller than the typical within region inter-observer variability. Thus, although statistical differences in color appearance ratings and memory between regions were found, regional impact is not likely to be of practical importance.

Estimation of dye concentration by using Kubelka-Munk and Allen-Goldfinger reflective models: comparing the performance.

If the relationship between the reflectance function (K/S) and dye concentration (C) is known, the color of the dyed textile (R∞) and C could be predicted from each other. In the present work, the concentration value estimated from the reflectance data using two reflective models, i.e. the Kubelka-Munk and the Allen-Goldfinger is compared. First, the Allen-Goldfinger model was run by using the absorption coefficient of dyes in fiber, i.e. the unit k/s values instead of that in the solution. The results showed that the replacement of the unit k/s for the Beer-Lambert absorption coefficient in the Allen-Goldfinger model causes lower error in the prediction of the spectral reflectance factor as well as the dye concentration. However, this model did not lead to better results. Then, an inverse form was used to estimate the concentration of dyes from the corresponding spectral reflectance. Consequently, it was observed that the Kubelka-Munk model is still a more reliable method while benefiting from more simplicity than the Allen-Goldfinger model. The analysis of errors showed that the results deeply depend on different factors such as the applied concentration range as well as the dye spectral adsorption behavior.

Eco-Friendly Procedure for Rendering the Antibacterial and Antioxidant of Cotton Fabrics via Phyto-Synthesized AgNPs With Malva sylvestris (MS) Natural Colorant.

There is a growing interest for producing multifunctional cellulose fabrics using green and sustainable technology. In this study, we explored an eco-friendly procedure for dyeing cotton fabrics with Malva sylvestris (MS) as a natural colorant and rendering antibacterial cotton fabric by the silver nanoparticles. MS colorants were extracted from dried petals in water using the ultrasound technique, cotton fabrics were dyed with the extracted MS colorant at 100°C for 90 min. The colorimetric data and colorfastness properties were investigated in the absence and presence of tannic acid (TA) as a bio-mordant. Results indicated that MS dye had a high potential for reducing the silver nitrate, so that the silver particle size distribution on cotton fabric was obtained 50-80 nm, and TA had a positive effect on the MS extract and reduced Ag on the cotton. Furthermore, the reduction of bacterial growth of the dyed cotton considerably (up to 99%) improved by AgNPs. The wash-, and light-fastness properties of samples dyed with MS were enhanced from moderate to good-very good by mordanting.

Heat insulation effect in solar radiation of polyurethane powder coating nanocomposite.

This study aims to improve polyurethane-based coating by modified zirconium oxide and aluminum oxide nanoparticles for preparing thin polymeric heat insulation coatings. In the first step, the nanoparticles were chemically modified with the silane coupling agent. Then, three different weight percent of modified nanoparticles (1, 3, and 5% w/w) were mixed with polyurethane, to prepare the nanocomposites, which were coated on metallic plate samples. Then, these plates are used to measure the radiation heat transfer coefficients, absorption coefficient in a region of short wavelengths (UV/VIS/NIR), the emissivity coefficient, and thermography of the samples in a region of long wavelengths (IR). Results showed that by adding the modified nanoparticles to the polyurethane matrix, absorption was decreased and the emissivity coefficient was increased. According to the thermography results, it was observed that the surface temperature of both samples with 3% w/w of nanoparticles had the minimum temperature compare to others. Minimum heat surface observed for 3% w/w of modified nano zirconium oxide.