Nanofluids are promising in many fields, including engineering and medicine. Stability deterioration may be a critical constraint for potential applications of nanofluids. Proper ultrasonication can improve the stability, and possibility of the safe use of nanofluids in different applications. In this study, stability properties of TiO2–H2O nanofluid for varying ultrasonication durations were tested. The nanofluids were prepared through two-step method; and electron microscopies, with particle size distribution and zeta potential analyses were conducted for the evaluation of their stability. Results showed the positive impact of ultrasonication on nanofluid dispersion properties up to some extent. Ultrasonication longer than 150 min resulted in re-agglomeration of nanoparticles. Therefore, ultrasonication for 150 min was the optimum period yielding highest stability. A regression analysis was also done in order to relate the average cluster size and ultrasonication time to zeta potential. It can be concluded that performing analytical imaging and colloidal property evaluation during and after the sample preparation leads to reliable insights. 相似文献
The aim of this study was to determine the reference value of pH in healthy women and men using the phosphorus magnetic resonance spectroscopy technique. The brains of 65 young volunteers were examined. The intracellular pH was calculated in the group of women and the group of men. In both groups, the average pH was slightly alkaline (respectively 7.10?±?0.08 and 7.08?±?0.12). No statistically significant sex difference in brain pH was found. Thus, in case if this method is used to estimate possible brain pathology in the young population, it is not needed to take the gender factor into consideration. 相似文献
Summary : Viscosity, asymmetric flow field-flow fractionation (AFFFF) methods, and dynamic light scattering (DLS) experiments were used to characterize the effect of pH on the behavior of dilute and semidilute aqueous buffered solutions of hyaluronic acid (HA). It is shown that degradation of HA occurs at pH < 4 and pH > 11, and in the domain 4 < pH < 11 virtually no disruption of the HA chains occurs. The pH-induced scission of HA is attributed to the cleavage of glycosidic bonds. In dilute solutions, intramolecular rupture of HA chains occurs and in the semidilute concentration regime network-fragmentation is observed at low and high pH values. The degree of degradation of HA is most marked at high pH. From the molecular weight and radius of gyration obtained from AFFFF at different pH values, it is clear that the degradation of HA starts at early times after preparation of the solution, and continues for a couple of days. The kinetics of degradation of HA is fastest at high pH. 相似文献
A highly pH sensitive water‐soluble polyfluorene derivative (PFP‐aa) has been designed and synthesized by Suzuki coupling reaction. The PFP‐aa contains two amino and four carboxylic acid groups in each repeat unit (RU). The protonation and deprotonation of both the carboxylate and amine are controlled by medium pH values. The polymer charge is anticipated to control electrostatic repulsion between polymer chains and lead to different levels of aggregation behaviors. Different fluorescent responses of the PFP‐aa are demonstrated as the environmental pH is changed from 3 to 12. Different sugars can bind to boronic acid to form boronic esters with different binding constants following proton release, thus generating diverse changes in pH. It is demonstrated that PFP‐aa can be used as a pH sensor to detect D ‐fructose.