Fluorescence of D-Glucose-Derived Carbon Dots: Effect of Process Parameters.

The aim of this study was to synthesize highly fluorescent carbon dots (CDs) from glucose using a microwave hydrothermal method. It explored the impact of glucose concentration, process time, molar ratio of KH2PO4 to glucose, and homogenization time on the resulting CDs, employing a fractional plan 3(k-1) with four independent parameters for twenty-seven synthesis. Results showed that longer process times at 200°C increased the fluorescence intensity of the CDs. The molar ratio of KH2PO4 to glucose, glucose concentration, and process time significantly influenced fluorescence. Homogenization was crucial for obtaining small particles, though an anti-aggregation agent might still be needed. UV-vis spectroscopy, spectrofluorimetry, and DLS were used to analyze the synthesized CDs. The UV-vis absorption maxima were observed around 230 nm and 282 nm, with peak shifts at different excitation wavelengths. Out of the twenty-seven samples, six CDs samples were identified to be below 10 nm and a total of twelve below 50 nm. Analyzing the results, the study concluded that the CDs possess strong fluorescence and are suitable for diverse applications. For enhanced fluorescence, longer process times at 200°C and the use of KH2PO4 were recommended, while shorter processes were preferred for obtaining smaller particles. Hierarchical clustering, the k-means method, Pareto charts, and profiles for predicted values and desirability were used to analyze the results. It was confirmed that higher fluorescence is favored by longer process time at 200°C and the use of KH2PO4. In order to obtain smaller particles, shorter processes should be used.

Impact Fracture Surfaces as the Indicators of Structural Steel Post-Fire Susceptibility to Brittle Cracking.

The results of experimental research on forecasting post-fire resistance to brittle failure of selected steel grades used in construction are presented and discussed in this paper. The conclusions are based on detailed analysis of fracture surfaces obtained in instrumented Charpy tests. It has been shown that the relationships formulated based on these tests agree well with conclusions drawn based on precise analysis of appropriate F-s curves. Furthermore, other relationships between lateral expansion LE and energy Wt required to break the sample constitute an additional verification in both qualitative and quantitative terms. These relationships are accompanied here by values of the SFA(n) parameter, which are different, depending on the character of the fracture. Steel grades differing in microstructure have been selected for the detailed analysis, including: S355J2+N-representative for materials of ferritic-pearlitic structure, and also stainless steels such as X20Cr13-of martensitic structure, X6CrNiTi18-10-of austenitic structure and X2CrNiMoN22-5-3 duplex steel-of austenitic-ferritic structure.

Statistical Analysis of Optimal Ultrasound Emulsification Parameters in Thistle-Oil Nanoemulsions.

Thistle oil (INCI: Silybum marianum seed oil) is known as an anti-oxidant, moisturizing and skin regenerating cosmetic raw material. Nanoemulsions are a new form of cosmetic product showing very good user properties (ease of spreading over the skin with no greasy feeling). Moreover, due to their structure, they can also transport both hydrophilic and hydrophobic active substances to the skin. The aim of this work was the preparation and characterization of nanoemulsions, based on thistle oil. The non-ionic surfactants polysorbate 80 (PEG-20 sorbitan monooleate), decyl glucoside, and a polyglyceryl-4 ester blend were applied to stabilize the nanosystems. All formulations were obtained by a high energy method, using an ultrasonic device (Labsonic U, an ultrasound homogenizer). Variations in the emulsification parameters were tested, including surfactants concentration, pre-emulsification time, ultrasound power and sonication time. On the basis of statistical analysis (experimental design, cluster analysis, classification and regression trees) the best emulsification process parameters were determined. In order to verify the results of statistical analysis, once more an experimental study was conducted. The results obtained confirmed that statistical analysis can be a useful method in determining the conditions for obtaining stable nanoemulsions with desired properties. Formulations obtained with the use of Silybum marianum seed oil were characterized by long-term stability, a low polydispersity index, low viscosity and an average droplet size less than 200 nm.

Studies on the formation of O/W nano-emulsions, by low-energy emulsification method, suitable for cosmeceutical applications.

The formation of oil/water (O/W) nano-emulsions suitable for cosmeceutical application was studied. Nano-emulsions were prepared by using phase inversion composition (PIC) method, one of the low-energy emulsification methods. The process consist of stepwise water addition to oil/surfactant mixture, at T = 25°C. Caprylic/capric triglycerides (GTCC), propylene glycol dicaprylate/dicaprate (PC) and oleic acid (OA) were applied as an oil phase. Polysorbate 80 was used as the surfactant. Kinetic stability of the nano-emulsions was analyzed by measuring droplet size as a function of time for different oil/surfactant ratio. The particles size distribution was analyzed by means DLS measurement technique (Dynamic Light Scattering), using Zetasizer Nano ZS (Malvern Instruments, UK). One of triterpenoic acid, practically non-water soluble substance was selected as an active and incorporated into the stable formulation. The obtained results proved that the nanoemulsion NE-T80-GTCC-20:80 based on caprylic/capric triglycerides with the oil/surfactant ratio O/S = 2 0:80 and the droplet size r = 25 nm was the most stable one and additionally showed the highest solubilisation capacity for the triterpene.