Solvation shell water around gold nanoparticles of varying sizes studied by raman and infrared spectroscopy Taritra Mukherjee and Martin Rabe Max-Planck-Institut für Eisenforschung GmbH, Germany Reactions catalysed by gold nanoparticles (Au NPs) in water are influenced by the sizes of the Au NPs 1 and by the structural reorganisation induced in the water molecules at the interface between the NP and the bulk water, i.e., in the solvation shell. 2 Also, the extent of reorganisation of interfacial water is predicted to depend on the size of solutes. 3 So, structural reorganisation of solvation shell water might depend on Au NP size which could possibly be one of the factors dictating different catalytic activities shown by Au NPs of different sizes. The correlation between Au NP size and reorganisation of interfacial water warrants an experimental investigation, which is lacking in literature. In this work, a Raman and infrared solvation shell spectroscopic 4,5 study of water around different sizes of high- purity pulsed laser ablated Au NPs will be presented. These NPs are considered to present an adsorbate-free interface and are stabilised by charge effects. The weak spectral response from the solvation shell water (buried under a strong spectral response from the bulk solvent) was recovered by multivariate curve resolution methods. The recovered vibrational solvation shell spectra demonstrate a greater disruption in the H-bonding network of water in the solvation shell, where the amount of fully H-bonded H 2 O molecules is reduced compared to the bulk. This effect is magnified for water in solvation shell around larger Au NPs for which the spectral contribution from fully H-bonded water is suppressed to an even greater extent. The results show, the extent of structural reorganisation of interfacial water is influenced by Au NP size. Insights gained from this work are expected to improve the understanding of the role Au NPs play in affecting reactions in aqueous medium.
Raman (A) and IR (B) solvation shell spectra for water around Au NPs of different sizes References 1. Wang, L.; Tang, Z.; Yan, W.; Yang, H.; Wang, Q.; Chen, S. ACS Appl. Mater. Interfaces 2016 , 8 , 20635. 2. Gilles,M.; Brun,E.; Sicard-Roselli, C. J. Colloid Interface Sci. 2018 , 525 , 31. 3. Chandler, D. Nature 2005 , 437 , 640.
4. Ben-Amotz, D. J. Am. Chem. Soc. 2019 , 141 , 10569. 5. Sun, Y.; Petersen, P.B. J. Phys. Chem. Lett. 2017 , 8 , 611.
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