## 3 Results and Discussion
### Effect of Process Conditions on Particle Size Distribution  
Figure 7 presents how the particle mean diameter changes depending on the process conditions. The PSD results revealed that the process conditions strongly influence the precipitation process in the impinging jet reactor. With increasing initial molybdenum concentration, the particle mean size also increases (Figure 7a). The specific sizes were determined on the basis of the entire PSD, including agglomerates and aggregates. The higher Mo concentration resulted in a greater precipitation rate, thus a higher concentration of the MoS\({}_{2}\) primary particles, which promotes the formation of agglomerates and aggregates. For nanoparticle production, arithmetic mean L\({}_{10}\) is the most important. The best results were obtained for Mo concentration equal to 0.2 M, which is the minimum concentration for the proper course of the reaction [25].  
The velocity of the inlet streams does not have as much of an effect on the PSD as the concentration (Figure 7b). The smallest particles are obtained for higher speeds. This is due to the greater turbulence dissipation rate in the mixing area. However, one of the synthesis products is hydrogen sulfide. Due to the rapid release of this dangerous gas, 20 mL/min was considered the best flow velocity. The effect of the temperature is presented in Figure 7c.  
The smallest particle sizes are obtained at 20 \({}^{\circ}\)C. As the temperature increases, the viscosity of the liquids decreases, and thus there is greater mobility of the particles. Therefore, as the temperature drops, the specific particle size increases slightly. However, at 25 \({}^{\circ}\)C, an insignificant increase in the mean size of the particles was observed. This can be explained as this temperature is close to the flash point of AS, which is 32 \({}^{\circ}\)C. Therefore, ammonium sulfide vapor pressure is higher, and less sulfur precursor is in the reacting solution, promoting particle growth over the nucleation and formation of Mo-oxides. Thus, the temperature of 20 \({}^{\circ}\)C was considered the best. Tables 3-5 present specific sizes for all cases. The L\({}_{10}\) dimension shows that the particles obtained for an initial concentration of 0.2 M with a reagent flow of 20 mL/min at 20 \({}^{\circ}\)C are in the size range of 0.190-0.226 \(\upmu\)m.  
\begin{table}
\begin{tabular}{c c c c} \  
\begin{table}
\begin{tabular}{c c c c} \hline \hline  & \multicolumn{3}{c}{**Mean Sizes**} \\ \hline
**[mL/min]** & **L\({}_{10}\) [\(\mu\)m]** & **L\({}_{32}\) [\(\mu\)m]** & **L\({}_{43}\) [\(\mu\)m]** \\ \hline
10 & 0.254 \(\pm\) 0.030 & 0.645 \(\pm\) 0.073 & 1.007 \(\pm\) 0.101 \\
20 & 0.225 \(\pm\) 0.004 & 0.475 \(\pm\) 0.019 & 0.759 \(\pm\) 0.024 \\
40 & 0.223 \(\pm\) 0.001 & 0.446 \(\pm\) 0.014 & 0.720 \(\pm\) 0.097 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Mean sizes depending on the substrate flow velocity.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline  & \multicolumn{3}{c}{**Mean Sizes**} \\ \hline
**T** & **L\({}_{10}\) [\(\mu\)m]** & **L\({}_{32}\) [\(\mu\)m]** & **L\({}_{43}\) [\(\mu\)m]** \\ \hline
10 & 0.268 \(\pm\) 0.056 & 0.802 \(\pm\) 0.219 & 1.180 \(\pm\) 0.208 \\
15 & 0.225 \(\pm\) 0.001 & 0.563 \(\pm\) 0.021 & 0.893 \(\pm\) 0.036 \\
20 & 0.225 \(\pm\) 0.004 & 0.475 \(\pm\) 0.019 & 0.759 \(\pm\) 0.024 \\
25 & 0.239 \(\pm\) 0.001 & 0.579 \(\pm\) 0.031 & 0.934 \(\pm\) 0.096 \\ \hline \hline \end{tabular}
\end{table}
Table 5: Mean sizes depending on the process temperature.  
Figure 7: Effect of the process conditions on particle mean size. (**a**) Initial molybdenum concentration at 20 \({}^{\circ}\)C and with flow velocity of 20 mL/min, (**b**) reagent flow velocity at 20 \({}^{\circ}\)C and with Mo concentration of 0.2 mol/m\({}^{3}\), (**c**) reaction temperature with flow velocity of 20 mL/min and with Mo concentration of 0.2 mol/m\({}^{3}\).