# Rapid Synthesis of Silver Nanowires in the Polyol Process with Conventional and Microwave Heating
## 3 Results and Discussion
Figures 6 and 7 portray SEM images, UV-Vis spectra, conversion coefficients, average diameter, length and the diameter distribution of the product synthesised with conventional and dielectric heating. The presented results have been ordered in line with the increasing viscosity and decreasing dielectric constant value of polyols applied. Histograms of the product diameter distribution show the presence of a prominent fraction of nanowires with diameters between 40 and 200 nm and fractions of silver wires with diameters up to 320 nm. Nanowires with diameters above 100 nm are considered to have excellent mechanical stability at room temperature, which allows them to be easily machined to obtain a variety of electrically conductive circuits [44]. In addition, nanowires with diameters in this range are the preferred material for fabricating the active layer of a photovoltaic cell due to their effect on increasing optical haze. This effect increases light scattering and trapping inside the layer [45]. Figure 5: Silver nanowires synthesised in the microwave-assisted process, 1,3-propanediol reducer: (a) SAED pattern of AgNPs, (b) EDS spectrum for AgNPs. Figure 6: A summary of the properties of AgNPsWs produced with the application of the different reductants in a batch process under conventional heating conditions: (**a**) 1,2-ethanediol, (**b**) 1,3-propanediol, (**c**) 1,3-butanediol, (**d**) 1,4-butanediol, (**e**) 1,5-pentenediol. _d,_ _l_--average diameter, length, respectively; _s_—standard deviation, _a_—conversion; scale bar 10 μm. Figure 7: A summary of the properties of AgNPsWs produced with the application of the different reductants in a batch, microwave-assisted process: (**a**) 1,2-ethanediol, (**b**) 1,3-propanediol, (**c**) 1,3-butanediol, (**d**) 1,4-butanediol, (**e**) 1,5-pentenediol. _d,_ _l_—average diameter, length, respectively; _s_—standard deviation; _a_—conversion; scale bar 10 μm. The observed lengths of the produced nanowires lie in the 2 to 26 \(\upmu\)m range, while the average values for the analysed nanomaterial range from 3.3 to 10 \(\upmu\)m. When comparing the corresponding values (Figures 6 and 7), no significant effect of the heating method on the average length can be observed. This leads to the conclusion that the determining factor for the length of the nanowires may lie in the capping agent used, i.e., polyvinylpyrrolidone. The influence of the molecular weight of PVP on the length of AgNPs has been noted by other authors [31]. As SEM images show, the morphology and average diameter of the final product considerably depends upon the type of polyol, which may be attributed to the simultaneous influence of viscosity and polarity of the solvent upon the nucleation process and the growth of nanowires. It is also worth noting that for the respective polyol, the final product has similar characteristics for the synthesis with conventional and dielectric heating. Significant differences in the diameter of the product prepared with 1,2-ethanediol and 1,3-propanediol, respectively equal to 166 and 158 nm, can be discerned while analysing the obtained results. In the latter case, the product is silver nanowires. In contrast, when 1,2-ethanediol is used, the product consists of structures with various shapes, confirmed by UV-Vis spectra with multiple maximums (Figures 6a and 7a). It is worth stressing that at the temperature at which the syntheses were carried out, the viscosity of the solvents is similar (Figure S1, Supplementary Materials). A plausible explanation for the differences observed in the final product characteristics may be some dissimilarities in the dielectric constant values of the polyols applied (Table S1, Supplementary Materials). It is believed that solvents having higher dielectric constant values can guarantee better stability of ions present in the solution [34]. This observation is corroborated by a rather low degree of conversion reached for both conventional (64%) and dielectric (72%) heating.