# Rapid Synthesis of Silver Nanowires in the Polyol Process with Conventional and Microwave Heating
## 3 Results and Discussion  
Figure 2 presents typical XRD spectra for products manufactured with 1,3-propanediol and 1,3-butanediol as reductants in syntheses accompanied by conventional and dielectric heating. Diffraction peaks occurring for 2\(\Theta\) = 38.12, 44.31, 64.45, 77.41, 81.56, 97.90, 110.5 and 114.9\({}^{\circ}\) correspond with peaks which describe silver (ICSD sheet No. 01-071-6549). They correspond with crystallographic planes (111), (200), (220), (311), (222), (400), (331) and (420) of face-centred cubic Ag crystals. Low-intensity reflexes may be attributed to AgCl residues. A high-ratio value of intensities of reflexes (111) to (200) amounts, respectively, to 3.4 and 3.1 (Figure 2a,b) for conventional heating and 3.0 (Figure 2c,d) for microwave-assisted syntheses, so it exceeds the theoretical value of 2.2 (ICSD sheet No. 01-071-6549). It implies a considerable quantity of the [111] crystal planes in the samples examined and a preferential direction of growth of one-dimensional silver nanostructures [41]. The crystallite grain size was determined using the Williamson-Hall equation (\(\beta\)\(cos(\Theta)\) = \(K\lambda/d_{g}\) +\(\epsilon sin(\Theta)\)) [42], whereby: \(d_{g}\) is the average value of crystal grain size, \(\lambda\) is the wavelength of the X-rays, \(\beta\) is the total broadening of reflection due to crystallite size effect and lattice strain, \(\Theta\) is the diffraction angle of a particular reflection, \(\epsilon\) is the lattice strain due to crystal imperfection and the K constant equals 0.90. After linearisation of the Williamson-Hall equation in the \(\beta cos(\Theta)\) vs. \(sin(\Theta)\) coordinates system (Figures 3 and 4), the average crystallite size and lattice strain were determined based on the knowledge of the intersection point of the straight and its slope found from the least squares method. The average crystallite sizes for silver nanowires synthesised in a batch process using 1,3-butanediol and 1,3-propanediol as reductants are 25 and 38 nm, respectively (Figure 3). The crystallite sizes shown above are smaller than those determined for the products synthesised using the same polyols in a microwave-assisted process. In the latter case, the crystallite sizes are 53 and 65 nm (Figure 4). In both analysed cases the results correspond with values obtained for silver nanoparticles [42; 43]. The observed trend in crystallite size changes for both heating methods corresponds to that reported herein for average nanowire diameters. The experimentally determined lattice strains for all cases range from \(1.3\times 10^{-3}\) to \(1.7\times 10^{-3}\) and they are consistent with the values reported in the literature [43]. The lattice constant, defined according to the XRD diffraction pattern, amounts to 0.4086 nm and corresponds well with the value specified for silver (ICSD card No. 01-071-6549). Figure 5a presents a selected area electron diffraction (SAED) image recorded for silver nanowires obtained in the microwave-assisted process, in which 1,3-propanediol was used as a reducing agent. The SAED pattern contains more than two sets of diffraction spots that correspond with the multiply twinned crystal structures in the synthesis product. The EDS analysis for the same sample, shown in Figure 5b, proves that its main ingredient is silver. The EDS also contains a peak typical of chlorine presence whose source may be the mediating agent used in the synthesis. Figure 2: XRD patterns of the silver structures prepared in the conventional heating process, reductant (**a**) 1,3-butanediol or (**b**) 1,3-propanediol, and a microwave-assisted process, reductant (**c**) 1,3-butanediol or (**d**) 1,3-propanediol. Figure 4: Williamson–Hall plot for AgNWs synthesised using different reductants in a microwave-assisted process. Figure 3: Williamson–Hall plot for AgNWs synthesised using different reductants under conventional heating conditions.