# Induced Effect of Gold Nanoparticles (AuNPs) and Halide Ions on Pyridoxine Molecule Stability
## 3 Results and Discussion
### The Influence of Fluoride Ions on Electrochemical Behavior of Pyridoxine
A comparison of the UV-Vis molecular absorption spectra of freshly prepared solutions, as well as after the recording of cyclic voltammograms, is presented in Figure 2.  
The UV-Vis spectra corresponding to the support electrolyte solution (NaF) show a great similarity before (b) and after (a) the performance of cyclic voltammetry. This means that the supporting electrolyte influences the electrode processes only to a very small extent, for example through its high polarizability. The UV-Visible spectrophotometer provides qualitative and quantitative information about the participation of AuNPs in electrode processes and implicitly about the modification of their properties. The presence of AuNPs in the electrolyte solution is confirmed by the absorption maximum recorded at the wavelength of 570 nm [37]. As can be seen in Figure 2 (NaF_AuNP spectra), during the recording of the cyclic voltammogram, the gold nanoparticles undergo both chemical and physicochemical changes. Thus, the spectrum recorded after the CV is located at slightly lower values of the absorbance, being the proof of their consumption in the electrode processes. The spectral properties of the pyridoxine molecule are highlighted by three absorption maxima, in the UV range, corresponding to the wavelengths Amax = 326, 256 and 221 nm [1]. Cyclic voltammetry is a \"short-time\" method, and therefore the processes of electrochemical degradation of pyridoxine cannot ensure a total consumption of pyridoxine molecules from the electrolyte solution. However, the UV-Vis spectrum of pyridoxine recorded after CV (NaF_B6, -a) is below the initial spectrum (NaF_B6, -b), the electrocatalytic properties of the gold electrode being effective for the electrochemical degradation of this vitamin. The UV-Vis spectrum of the electrolyte solution for the ternary system (NaF_B6_AuNPs) corroborates the results obtained both by cyclic voltammetry and by spectrophotometer  
Figure 2: UV–Vis absorption spectra of electrolyte solution containing NaF/B6/AuNP systems; b—before and a—after performing cyclic voltammetry. ric analysis. Thus, this spectrum highlights both strong chemical interactions between ionic and molecular species present in the electrolyte solution and their electrochemical degradation. The electrochemical behavior of pyridoxine over time has been studied in order to identify the electrochemical stability of the vitamin and how its stability is influenced by gold nanoparticles (Figure 3). Figure 3 shows the UV-Vis spectra during the electrode processes (current density = 50 mA \(\times\) cm\({}^{-2}\)) for pyridoxine and gold nanoparticles, individually (NaF_B\({}_{6}\) and NaF_AuNPs) as well as together (NaF_B\({}_{6}\)AuNPs). The UV-Vis spectrum NaF_B\({}_{6}\) indicates a gradual decrease in absorbance over time. In this electrolyte solution, vitamin molecules participate in redox processes, but there is only a minor decrease in absorbance corresponding to pyridoxine. An important indication is also given by the fact that no new absorption maxima are recorded. This indicates an electrochemical degradation of the pyridoxine to the final products that are not active in the analyzed spectrophotometric range (200-800 nm); pyridoxine molecules are most likely degraded to final products such as carbon dioxide, nitrogen oxides and water. During electrolysis at a constant current density, the gold nanoparticles are also oxidized in the NaF support electrolyte solution. Under an electrical impulse, the UV-Vis spectra (NaF_AuNPs) recorded every 10 min show a total degradation at the end of the electrolysis of 60 min. The NaF_B\({}_{6}\)_AuNP ternary system has two important features of evolution over time: (i) the absorbance values decrease over time, both those corresponding to pyridoxine and those corresponding to nanoparticles, and (ii) the absorption maxima show a slight shift towards longer wavelengths (bathochromic effect), both those corresponding to pyridoxine and those corresponding to nanoparticles.