1542 nm). The absorption spectra were measured by a Jasco V-570 UV–vis-NIR spectrophotometer (Jasco Analytical CAL-101 supplier Instruments, Eaton, MD, USA). The NIR photothermal conversion property of Cs0.33WO3 nanoparticles was investigated
in deionized water at different concentrations. The aqueous dispersion of Cs0.33WO3 nanoparticles was added to a 2-mL polystyrene cell, and then the dispersion was exposed to SBI-0206965 ic50 an 808-nm diode laser (HPM (LD1202) X26, Power Technology Inc., Little Rock, AR, USA) with an irradiation area of 0.3 cm2 and an intensity of 820 mW (i.e., 2.73 W/cm2). The temperature of aqueous dispersion was detected with a thermocouple. Photothermal conversion efficiency was calculated using the method reported by Chen et al. . For the study on the photothermal stability of Cs0.33WO3 nanoparticles under NIR irradiation, the aqueous dispersion of Cs0.33WO3 nanoparticles (0.08 wt.%, obtained after grinding for 3 h) was continuously re-exposed to an 808-nm diode laser (2.73 W/cm2) for 5 cycles. For each cycle, the aqueous dispersion selleck chemicals was irradiated for 10 min and then cooled to the initial temperature. Using a thermocouple, the variation of temperature with time was monitored. Results and discussion In this work, the bead milling of Cs0.33WO3 coarse powder was performed in aqueous solution in the absence of extra stabilizers. The
resulting Cs0.33WO3 nanoparticles were stabilized in aqueous solution via electrostatic repulsion mechanism, owing to their electric double layer. Since the electrostatic repulsion was strongly influenced by the surface charge of particles, the effect of pH on the zeta potential of Cs0.33WO3 nanoparticles was investigated to determine the appropriate
solution pH. As indicated in Figure 1, the preliminary study revealed that Cs0.33WO3 nanoparticles had an isoelectric point of about pH 1.8. With increasing pH, their zeta potential decreased and then approached a constant of about −35 mV when pH was above 8. Thus, the aqueous solution Sitaxentan for the bead milling of Cs0.33WO3 coarse powder was fixed at pH 8 by adding potassium hydroxide in deionized water. Figure 1 Effect of pH on the zeta potential of Cs 0.33 WO 3 nanoparticles in aqueous solutions. Figure 2 shows the variation of mean hydrodynamic diameter of Cs0.33WO3 powder with grinding time. It was obvious that the mean hydrodynamic diameter of Cs0.33WO3 powder decreased quickly from about 1,310 nm to about 50 nm within 3 h, revealing that the size of Cs0.33WO3 powder could be reduced to nanoscale efficiently by the bead milling process. Inset a in Figure 2 indicates the hydrodynamic diameter distributions of Cs0.33WO3 powder after grinding for 1, 2, and 3 h. It revealed that increasing the grinding time not only led to the decrease of hydrodynamic diameters, but also made the hydrodynamic diameter distribution become narrower.