Direct observation of anisotropic growth of water films on minerals driven by defects and surface tension

Abstract

Knowledge of the occurrences of water films on minerals is critical for global biogeochemical and atmospheric processes, including element cycling and ice nucleation. The underlying mechanisms controlling water film growth are, however, misunderstood. Using infrared nanospectroscopy, amplitude-modulated atomic force microscopy, and molecular simulations, we show how water films grow from water vapor on hydrophilic mineral nanoparticles. We imaged films with up to four water layers that grow anisotropically over a single face. Growth usually begins from the near edges of a face where defects preferentially capture water vapor. Thicker films produced by condensation cooling completely engulf nanoparticles and form thicker menisci over defects. The high surface tension of water smooths film surfaces and produces films of inhomogeneous thickness. Nanoscale topography and film surface energy thereby control anisotropic distributions and thicknesses of water films on hydrophilic mineral nanoparticles.

Electric field stimulates production of highly conductive microbial OmcZ nanowires

“…As described previously 18 , we used IR radiation from a wavelength-tunable quantum cascade laser (Daylight Solutions MIRcat Amide QCL tunable from 1450–1700 cm −1 with a bandwidth < 1 cm −1 and spectral resolution of 0.25 cm −1 ) to illuminate a conductive AFM tip with < 20 nm spatial resolution ( Extended Data Fig. 5a , b ).…”

“…All IR s -SNOM analyses and statistics were performed using Gwyddion software ( Figures 2 , 5 and Extended Data Figures 5 – 6 ). To extract near-field phase (absorption) properties of proteins, we used a two-phase homodyne detection technique by changing the reference arm between two orthogonal known phase components such as Φ 1 = Φ 2 +π/2 and extracted near-field phase signal using following relations 18 , 19 : where I is the intensity and A is a constant. Nanoscale infrared spectroscopy studies have demonstrated sensitivity to detect beta sheets in a wide range of proteins such as insulin 12 , tobacco mosaic virus 12 , silk 54 , β 2 -microglobulin 55 , diphenylalanine 56 , Josephin domain of ataxin-3 amyloid 57 and Huntingtin protein 58 .…”

“…6c ). Previously, we used IR s -SNOM-based nanoscopic chemical imaging to directly visualize water molecules as they bind to individual minerals[ 18 ]. Here, to evaluate the reliability and accuracy of our imaging platform for protein structure determination, we first performed IR s -SNOM imaging and spectroscopy of two proteins with well-known structures: bacteriorhodopsin[ 12 19 ] and lysozyme[ 17 ] as well as on individual OmcS nanowires at pH 10.5 (conditions used to solve their atomic structure[ 4 ], Extended Data Figs.…”

Torsional and lateral eigenmode oscillations for atomic resolution imaging of HOPG in air under ambient conditions

“…2 m–q). The growing corrugation amplitude (measured vertical distance between atomic and hollow side) is assumed to originate from an increase in the mean cantilever deflection 16 , 29 , 30 . Strikingly, the height image at a z -sensor position of 3.7 nm (Fig.…”

Torsional And Lateral Eigenmode Oscillations For Atomic Resolution Imaging Of HOPG In Air Under Ambient Conditions

“…Lowering the second flexural-eigenmode-amplitude setpoint, atomic contrast becomes more and more apparent in the height images (Figure 2m-q). The growing corrugation amplitude (measured vertical distance between atomic and hollow side) is assumed to originate from an increase in the mean cantilever deflection 13,25,26 . Strikingly, the height image at a z-sensor position of 3.7 nm (Fig.…”