Ultrafast Vibrational Dynamics of Water at a Solid Charged Interface Eric Borguet, Temple University, Philadelphia PA, 19122
Ultrafast Time resolved Sum Frequency Generation (tr‐SFG) probes the vibrational relaxation of water at the charged and neutral silica surface. 2.0
0.0 M
Edc
1.8
0.0001 M
30 nm
0.001 M
10 nm
0.01 M
3 nm
1.4
16
0.05 M
1.2
600
0.1 M
1.0
0.5 M
0.8
0
2 4 time delay (ps)
Debye Length (nm) 8 4 2 1
1 nm
T1(fs)
Normalized SFG
1.6
Interfacial water vibrational dynamics is significantly different compared to the bulk and appears to depend on surface charge. However, this is a consequence of SFG sampling of near interface water that has a bulk like solvation environment. For pure H2O, the vibrational lifetime at the charged surface is similar to the bulk value (~250 fs) at low ionic strength an approaches that of the neutral surface (~570 fs) at 10‐2 M NaCl and greater
400 200
0.5 nm
6
PPP SSP
- - - - - - -
0 0.0001
0.001 0.01 0.1 NaCl Concentration (M)
0.5
