## 3 Results and Discussion
### Final Particle Characteristics of Samples Obtained by SpraySyn1 and SpraySyn2
#### 3.1.4 TGA-DSC-MS
In the absence of oxygen, the decomposition of these species is hindered, leading to a splitting of thermal events (pyrolysis). As a result, the CO\({}_{2}\) and H\({}_{2}\)O signals separate into an increased number of events at \(\sim\)270, \(\sim\)360, \(\sim\)385, and \(\sim\)680 \({}^{\circ}\)C.  
Despite the above-mentioned thermal events being qualitatively identical among all samples, the respective mass losses differ crucially depending on the sample type, and the TGA-DSC-MS data can be quantitatively compared in two distinct ways:  
1. Since \(\gamma\)-Fe\({}_{2}\)O\({}_{3}\) represents the dominant particle phase, each sample's total \(\gamma\)-Fe\({}_{2}\)O\({}_{3}\) content is given by the final steady-state TGA value in air, and all four contents of \(\gamma\)-Fe\({}_{2}\)O\({}_{3}\) are presented in Table 3. As shown, the materials exhibit considerable mass losses (\(\sim\)17-21 wt.%) since by-products are present. The fact that solely four-fifths of the overall material mass belonging to \(\gamma\)-Fe\({}_{2}\)O\({}_{3}\) is of particular relevance for weight-related particle applications, e.g., the vibrational magnetometry conducted earlier. To demonstrate this issue, Figure 8 depicts the materials as-measured  
Figure 7: Exemplary TGA-DSC-MS data for \(\gamma\)-Fe\({}_{2}\)O\({}_{3}\) particles prepared by SpraySyn1 by processing 0.1 M INN in EtOH + EHA. Synthetic air (**a**) and argon (**b**) are applied at atmosphere. values vs. \(M_{\rm S}\) values normalized to each sample's respective \(\gamma\)-Fe\({}_{2}\)O\({}_{3}\) content. These normalized values represent the \(M_{\rm S}\) values one would achieve if particle surfaces were entirely pure. This could be accomplished by applying post-synthesis treatments (e.g., thermal annealing or wet-chemistry procedures [2; 15; 57]). Since water, carbonates, and carboxylates are diamagnetic, they do not contribute to magnetic responses in VSM measurements, making the normalization procedure mentioned above plausible for the \(M_{\rm S}\) data. 2. Moreover, the individual mass fractions of water and carbonates/carboxylates can be determined by differentiating the TGA mass losses according to their respective TGA temperature ranges (below 150 \({}^{\circ}\)C for water desorption and above for thermal decomposition of organic species). This temperature threshold can be chosen because it represents a balanced compromise between the water desorption process and the organic species oxidation process (cf. Figure 7). Examining the TGA data this way reveals that the materials exhibit a weight loss of \(\sim\)14-18 wt.% due to the oxidation of carbonates/carboxylates and of \(\sim\)2-3 wt.% caused by water desorption (Table 3). Given the fact that these species are located on the particle surface, one can subsequently normalize their relative mass fractions to the samples' respective \(SSA\), yielding values for the particle surface loading (\(PSL\), unit: mg m\({}^{-2}\)). This normalization procedure yields \(PSL\) values for water and organics, and corresponding values are shown in Table 3. As presented there, organic \(PSLs\) are independent of the precursor concentration. However, they depend on the burner type applied: SpraySyn1 samples exhibit organic \(PSLs\) at \(\sim\)0.87 mg m\({}^{-2}\), while SpraySyn2 samples attain slightly lower organic \(PSLs\) in the range of \(\sim\)0.69-0.73 mg m\({}^{-2}\). On the one hand, this indicates that SpraySyn2 yields particles with fewer carboxylates on the surface. On the other hand, this also indicates that surface-bond carboxylates could have lower average molar masses for SpraySyn2 samples. Both possibilities could coincide with a slightly more complete combustion for this burner type, likely attributable to differences in the burners' flame activity profile: Recently, the study of [PERSON] et al. indicated in experiments on a single SFS burner type that more transient combustion conditions can cause higher carboxylate and carbonate contents, which aligns well with the findings here [18].