Detection of water and its derivatives on individual nanoparticles using vibrational electron energy-loss spectroscopy

• High spatial resolution spectroscopic detection of water related species in nanoparticles.
• Detection of OH stretch modes with vibrational EELS.
• Differentiation between hydrate and hydroxide species on or on nanoparticles.
• Detection of hydrate on a single 60 nm oxide nanoparticle of MgO.
• Use of aloof beam EELS to minimize radiation damage.

Understanding the role of water, hydrate and hydroxyl species on nanoparticle surfaces and interfaces is very important in both physical and life sciences. Detecting the presence of oxygen-hydrogen species with nanometer resolution is extremely challenging at present. Here we show that the recently developed vibrational electron energy-loss spectroscopy using subnanometer focused electron beams can be employed to spectroscopically identify the local presence and variation of OH species on nanoscale surfaces. The hydrogen-oxygen fingerprint can be correlated with highly localized structural and morphological information obtained from electron imaging. Moreover, the current approach exploits the aloof beam mode of spectral acquisition which does not require direct electron irradiation of the sample thus greatly reducing beam damage to the OH bond. These findings open the door for using electron microscopy to probe local hydroxyl and hydrate species on nanoscale organic and inorganic structures.