Hydrophilic silica (SiO2) nanoparticles were dispersed in solutions of poly(methyl methacrylate) (PMMA) and in solutions of a commercial poly(alkyl siloxane) (Rhodorsil 224), and the suspensions were sprayed on glass surfaces. The effect of the particle concentration on the hydrophobic character of PMMA-SiO2 and Rhodorsil-SiO2 films was investigated and showed the following: (i) Static contact angles (theta s), measured on surfaces that were prepared from dilute dispersions (particle concentration <1% w/v), increase rapidly with particle concentration and reach maximum values (154 and 164 degrees for PMMA-SiO2 and siloxane-SiO2, respectively). Further increases in particle concentration do not have any effect on theta s. (ii) The effect of particle concentration on the contact angle hysteresis (thetaAlpha - thetaR) is more complicated: as the particle concentration increases, we first notice an increase in hysteresis, which then decreases and finally becomes constant at elevated particle concentrations. The lowest thetaAlpha - thetaR values were 5 degrees for PMMA-SiO2 and 3 degrees for siloxane-SiO2, respectively. (iii) SEM and AFM images show that a two-length-scale hierarchical structure is formed on the surface of the superhydrophobic films. It is demonstrated that superhydrophobicity can be achieved using various hydrophilic nanoparticles (alumina and tin oxide nanoparticles were successfully tested) and that the substrate has almost no effect on the hydrophobic character of the applied coatings, which were produced on silicon, concrete, aluminum, silk, wood, marble, and of course glass. The results are discussed in light of Wenzel and Cassie-Baxter models.

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Different methods for the extraction of Dactylopius coccus Costa, Rubia tinctorum L., Isatis tinctoria L., Reseda luteola L., Curcuma longa L. and Cotinus coggygria Scop. from wool fibres are investigated using high-performance liquid chromatography with diode array detector (HPLC-DAD). The efficiencies of five extraction methods which include the use of HCl (widely used extraction method), citric acid, oxalic acid, TFA and a combination of HCOOH and EDTA are compared on the basis of the (a) number, (b) relative quantities, measured as HPLC peak areas and (c) signal-to-noise ratios (S/N) of the compounds extracted from the wool substrates. Flavonoid glycosides and curcuminoids contained in R. luteola L. and C. longa L., respectively, according to liquid chromatography with mass spectrometry (LC-MS) identifications, are not detected after treating the fibres with HCl. All the other milder methods are successful in extracting these compounds. Experiments are performed using HPLC-DAD to compare the HPLC peak areas and the S/N of the following extracted compounds: indigotin, indirubin, curcumin, demethoxycurcumin, bisdemethoxycurcumin, fisetin, sulfuretin, luteolin, luteolin-7-O-glucoside, apigenin, carminic acid, alizarin, puruprin and rubiadin. It is shown that the TFA method provides overall the best results as it gives elevated extraction yields except for fisetin, luteolin, apigenin and luteolin-7-O-glucoside and highest S/N except for fisetin and luteolin-7-O-glucoside. It is noteworthy that treatment of the fibres with the typical HCl extraction method results overall in very low S/N. The TFA method is selected for further studies, as follows. First, it is applied on silk dyed samples and compared with the HCl method. The same relative differences of the TFA and HCl methods observed for the wool dyed samples are reported for the silk dyed samples too, except for rubiadin, luteolin and apigenin. Thus, in most cases, the nature of the substrate (wool or silk) appears to have negligible effects on the relative difference of the two extraction methods. Second, the selected TFA method is applied to treat wool and silk historical samples extracted from textiles of the Mamluk period, resulting in the identification of several colouring compounds. In all extraction methods mentioned above, DMSO is used to dissolve the dyes, after acid treatment.

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