The shrunk surface area contributes to the decrease in absorbance especially for the Au NP C59 deposits. This reveals a faster coalescence kinetics compared with the other two NP deposits containing silver. Figure 10 also demonstrates the sheet resistance shows a consistent tendency with the shift

of SPR band, suggesting that the elimination of the interparticle point contact and also the intraparticle grain boundaries reduced electrical resistance [21]. The measured electrical resistivities of the NP deposits for the as-prepared and annealed states are listed in Table 1. It can be found that the resistivity was hugely reduced when subjected to heating due to the

removal of the ligand shell on the particle surface and thus particle coalescing. Worthy of notice is that the Ag NP deposits exhibit an inferior electrical resistivity twice as higher as those of Au and AuAg3 NPDs. In combintaiton with the above XPS observations, it can be deduced that residual sulfur had a negative influence on electrical conductance. Table 1 Electrical resistivity of the NP deposits NPs Electrical resistivity(μΩ-cm) As-prepared As-annealed Au 1.75 × 103 7.88 AuAg3 2.5 × 103 8.32 Ag 3.75 × 103 18.45 Factors affecting the coalesence of the thiol-protected AuAg nanoparticles Particle size has significant influences on the melting and the coalescence Selleckchem PD173074 of nano-sized particles

[19, 38–41]. As reported, nanoparticles are characterized by low melting points, low coalescence temperature, and short sintering time as a result of the atom thermal vibration amplitude increase in the surface layer. Although this study focuses on most the composition effects, the size-dependent effect on particle coalescence can still be found when two batches of Ag NPs with different diameters are compared. Smaller Ag NPs exhibit relatively reduced coalescence temperature. As for Au NPs with the average LXH254 in vivo diameter of 3.6 nm used in this study, if they have similar size with the other samples (6.5 ~ 10 nm), a higher coalescence temperature is predictable. As mentioned above, the coalescence temperatures of the thiol-capped binary gold-silver alloy nanoparticle deposits followed a convex relation with the silver content as illustrated in Figure 11a, i.e., the average coalescence temperature decreased from 160°C to 120°C at the low silver side, and at the high silver side, it ascended to 150°C for pure Ag NPs. To explain this phenomenon, a rivalry between thermodynamic factors and surface chemistry should be considered. Figure 11 Transition temperatures of gold-silver alloys and free energy states.