Dicarboxylic acids analysed by x-ray photoelectron spectroscopy, Part I - propanedioic acid anhydrous

Abstract

SECTION A -OverviewA-3. Abstract: X-ray photoelectron spectroscopy (XPS) was carried out to analyse a commercially available propanedioic acid (malonic acid) powder . XPS spectra were obtained using incident monochromatic Al Ka radiation at 1486.6 eV. A survey spectrum together with O 1s and C 1s core level spectra are presented. The presence of characteristic carbon and oxygen photoelectrons peaks allows the use these results as a reference for dicarboxylic acids.A-3a. Introduction: Propanedioic acid (malonic acid) is used as a chemical building block to produce a number of compounds; its main use being as a polymer precursor [1,2]. It is employed in chemical processes for the manufacture of special materials in a variety of industrial segments, with examples including special solvents, alkyd resins, nutritional, fragrances, electronics and pharmaceutical industries and also the production of surgical adhesives [3][4][5]. More recently, with the development of the biotechnology industry and the need to replace petrochemical compounds, propanedioic acid has been listed by the US Department of Energy as one of the top 30 chemicals produced from biomass [6].Research addressing the potential of propanedioic acid for the corosion protection of metal substrates can be dated back to the late 1950s. Its use as an electrolyte in the anodisation of aluminium suggests that the acid would be suitable for producing anodic coatings with a wide variety of structures and properties. Propanedioic acid has also been employed as a corrosion inhibitor on various metal substrates such as a carbon steel, copper and zinc [7][8][9][10][11].In order to understand the interaction between dicarboxylic acids and metallic substrates, characterisation of the pure compounds is required. This work presents X-ray photoelectron spectroscopy results of a propanedioic acid standard powder. It is the first part in a series of three papers containing results for dicarboxylic acids with varying chain lengths: propanedioic, butanedioic and pentanedioic.Dicarboxylic acids and their respective salts are rather unstable and known to undergo damage when exposed to X-rays, hence there was always a compromise between quality of spectra and level of damage, as reported for calcium oxalate by Salvi et. al [12]. The use of a 50 eV pass energy required a lower acquisition time to achieve a reasonable signal-to-noise ratio. For the same reason, the channel width was chosen to be 0.2 eV rather than the typical value of 0.1 eV. The acquisition time was 101 s. In addition to the spectra recorded under standard acquisition conditions, 'snapshot' spectra (acquisition time 1 s) of the C 1s and O 1s peaks are also presented to give an indication of a spectrum expected from an undamaged surface. The molecular structure of propanedioic acid (Figure 1) contains two carboxyl group carbons and one aliphatic carbon, and thus is expected to yield two C 1s photoelectron peaks at binding energies around 289 eV (-COOH) and 285 eV (C-C/C-H) [13] with an intensity ratio of 2:1. T...

Pre-deliquescent water uptake in deposited nanoparticles observed with in situ ambient pressure X-ray photoelectron spectroscopy

“…For UHV conditions, the best fit was acquired with a splitting of approximately 1.0 eV between the C=O and C-OH peaks (at 532.0 and 533.0 eV, respectively). This splitting is smaller than the previously reported values of 1.1 and 1.3 eV by Ferreira Jr. et al (2017b). For our measurements with water vapor, the best fits were obtained with a splitting of 1.2 eV between the C=O and C-OH oxygen peaks (at 531.6 and 532.8 eV at 3.2% RH, respectively), now in good agreement with the work of Ferreira Jr. et al (2017b).…”

“…The best fit was acquired with the feature at 286.8 eV and 286.2 eV for 0.6% and 3.2% RH, respectively. This is 1.4 eV higher than the C-C carbon peak of malonic acid in both cases, in good agreement with the position of the DP1 peak of Ferreira Jr. et al (2017b). https://doi.org/10.5194/acp-2020-330 Preprint.…”

“…This splitting is smaller than the previously reported values of 1.1 and 1.3 eV by Ferreira Jr. et al (2017b). For our measurements with water vapor, the best fits were obtained with a splitting of 1.2 eV between the C=O and C-OH oxygen peaks (at 531.6 and 532.8 eV at 3.2% RH, respectively), now in good agreement with the work of Ferreira Jr. et al (2017b). The peak at highest binding energy in the spectra recorded at humid conditions is the O 1s peak from water vapor.…”

“…This can give rise to additional peaks in the XPS spectra arising from malonic acid molecules damaged by the X-ray beam (Ferreira Jr. et al, 2017a, b). These peaks, denoted DP1 and DP2, following the notation of Ferreira Jr. et al (2017b) were also included in the fit for 0% RH (UHV), where a good fit could not be produced without their inclusion. They were fixed to be at 1.5 eV (DP1) and 1.2 eV (DP2) higher binding energies than the malonic acid C-C and COOH carbon peaks, respectively.…”

Response to reviewer comments

“…"The decomposition peaks DP1 and DP2 observed by Ferreira Jr. et al (2017) were included in the fit for 0% RH (UHV), where a good fit could not be produced without their inclusion. "…”