5% smaller than the theoretical values regardless of the composition. Subjected to heating to 250°C, the NP deposits can be regarded as bulk PF-6463922 price metals judged by their lattice constants. Figure 5 Variation in the coalescence temperature with respect to particle composition. Figure 6 Lattice constant as a find more function of heating temperature and size states. (a) Variation in the estimated lattice constant as a function of heating temperature, and (b) Lattice constants at nano and heat-treated states (designated as NP and HT, respectively) compared with the theoretical values (REF). Using Equation 1, the
variations in the estimated particle sizes of all the NP deposits after being coalesced as a function of heating temperature are given in Figure 7. It should be noted that the Scherrer equation assumes the fine particles are strain free. Non-uniform strain causes additional line broadening and gives rise to underestimated crystallite size . This also explains the underestimated diameter for Au NPs prior to coalescence as indicated in Figure 4. Figure 7 illustrates that all the NPs exhibited a particle diameter of about 10 nm at their coalescence temperature. With a higher temperature, the particle sizes of most the NPs increased and reached 20 ~ 30 nm at high temperatures. Remarkably, the Ag NP deposits possessed a greater grain growth rate and the estimated CFTRinh-172 particle diameter after heating to 250°C reached
40 nm, obviously larger than the others. The surface morphologies of the NP deposits after being heated to a specific
temperature (Figure 8) verify the extraordinarily large grains of the heat-treated Ag deposits. This should be prevented because discontinuity and even rupture of NP deposits due to abnormal growth have been witnessed . Figure 7 Variations in the estimated particle size. Figure 8 The SEM images of the heat-treated NP deposits. Figure 9a,b,c illustrates the S2p region of the XPS spectra of the Au, AuAg, and Ag deposits under non-heat-treated (Non-HT) and heat-treated (HT) states, respectively. The binding energy values of XPS peaks are also marked. For all the non-heat treated samples, there is a broad through peak at 161 ~ 163 eV. This probably consists of two components, the 2p3/2 and 2p1/2, separated by approximately 1 eV . After heating to 250°C, this broad peak disappeared for the Au and AuAg deposits, but its intensity remained strong for the Ag samples. The other broad peak located at 168 eV was found in the heat-treated Ag and AuAg deposits. It corresponds to S bonded three O atoms and has been observed in previous reports indicating thiols experienced photo-oxidation [34, 35]. Accordingly, it can be inferred that the interactions between S and Ag were more complicated and stronger than those between S and Au, which resulted in late desorption of thiols from the surface atoms of Ag. S still bonded with the surface atoms of the pure Ag deposits after heating.