A Method of Evaluation Efficacy of Cosmetics Exfoliator and Its Application

Measuring the tanning skin can provide a scientific method to evaluate the efficacy of cosmetics exfoliator.Dihydroxyacetone(DHA,5.0%(w/w))was used to stain the inner forearms cuticle of subjects.The skin surface L*and b*were determined,then ITA and its recovery rate were calculated to evaluate the exfoliating efficacy of cosmetics.The results showed that no significant(P≥0.05)differences were observed for L*,b*and ITA on different skin surface of unstained subjects.After staining with DHA,no adverse reaction was found in the stained areas,and the changes of L*,b*and ITA on different skin surface were consistent(P≥0.05).Two different cosmetics were used continuously to exfoliate the skin in different areas.After treatment for 7 days,the corresponding areas of skin L*,b*and ITA had significant(P<0.05)improvement in comparison with negative control area.But there were differences in the evaluation results of the exfoliation efficacy using these three parameters.The recovery rate of ITA of two samples improved significantly(P<0.05)than the negative control area.The work indicated that using 5.0%DHA for skin browning and measuring the skin surface color change by ITA recovery rate can accurately and sensitively assess the skin cuticle renewal rate difference.This method can be used as one of the effective way to evaluate the efficacy of cosmetics exfoliation.

Base-free aerobic oxidation of glycerol on TiO_2-supported bimetallic Au–Pt catalysts

The aerobic oxidation of glycerol provides an economically viable route to glyceraldehyde, dihydroxyacetone and glyceric acid with versatile applications, for which monometallic Pt, Au and Pd and bimetallic Au-Pt, Au- Pd and Pt-Pd catalysts on TiO2 were examined under base-free conditions. Pt exhibited a superior activity relative to Pd, and Au-Pd and Pt-Pd while Au was essentially inactive. The presence of Au on the Au-Pt/TiO2 catalysts led to their higher activities （normalized per Pt atom） in a wide range of Au/Pt atomic ratios （i.e. 1/3-7/1 ）, and the one with the Au/Pt ratio of 3/1 exhibited the highest activity. Such promoting effect is ascribed to the increased electron density on Pt via the electron transfer from Au to Pt, as characterized by the temperature-programmed desorption of CO and infra-red spectroscopy for CO adsorption. Meanwhile, the presence of Au on Au-Pt/TiO2, most like due to the observed electron transfer, changed the product selectivity, and facilitated the oxidation of the secondary hydroxyl groups in glycerol, leading to the favorable formation of dihydroxyacetone over glyceraldehyde and glyceric acid that were derived from the oxidation of the primary hydroxyl groups. The synergetic effect between Au and Pt demonstrates the feasibility in the efficient oxidation of glycerol to the targeted products, for example, by rational tuning of the electronic properties of metal catalysts.