TY - JOUR
T1 - Specific Ion Effects at the Vapor-Formamide Interface
T2 - A Reverse Hofmeister Series in Ion Concentration Depth Profiles
AU - Kumar, Anand
AU - Craig, Vincent S.J.
AU - Robertson, Hayden
AU - Page, Alister J.
AU - Webber, Grant B.
AU - Wanless, Erica J.
AU - Mitchell, Valerie D.
AU - Andersson, Gunther G.
PY - 2023/9/12
Y1 - 2023/9/12
N2 - Employing neutral impact collision ion scattering spectroscopy (NICISS), we have directly measured the concentration depth profiles (CDPs) of various monovalent ions at the vapor-formamide interface. NICISS provides CDPs of individual ions by measuring the energy loss of neutral helium atoms backscattered from the solution interface. CDPs at the vapor-formamide interface of Cl-, Br-, I-, Na+, K+, and Cs+ are measured and compared to elucidate the interfacial specific ion trends. We report a reverse Hofmeister series in the presence of inorganic ions (anion and cation) at the vapor-formamide interface relative to the water-vapor interface, and the CDPs are found to be independent of the counterion for most ions studied. Thus, ions at the surface of formamide follow a "Hofmeister paradigm" where the counterion does not impact the ion series. These specific ion trends are complemented with surface tension and X-ray absorption near-edge structure (XANES) measurements on formamide electrolyte solutions.
AB - Employing neutral impact collision ion scattering spectroscopy (NICISS), we have directly measured the concentration depth profiles (CDPs) of various monovalent ions at the vapor-formamide interface. NICISS provides CDPs of individual ions by measuring the energy loss of neutral helium atoms backscattered from the solution interface. CDPs at the vapor-formamide interface of Cl-, Br-, I-, Na+, K+, and Cs+ are measured and compared to elucidate the interfacial specific ion trends. We report a reverse Hofmeister series in the presence of inorganic ions (anion and cation) at the vapor-formamide interface relative to the water-vapor interface, and the CDPs are found to be independent of the counterion for most ions studied. Thus, ions at the surface of formamide follow a "Hofmeister paradigm" where the counterion does not impact the ion series. These specific ion trends are complemented with surface tension and X-ray absorption near-edge structure (XANES) measurements on formamide electrolyte solutions.
KW - Anions
KW - Cations
KW - Interfaces
KW - Ions
KW - Solvents
UR - http://www.scopus.com/inward/record.url?scp=85170717241&partnerID=8YFLogxK
UR - http://purl.org/au-research/grants/ARC/DP190100788
U2 - 10.1021/acs.langmuir.3c01286
DO - 10.1021/acs.langmuir.3c01286
M3 - Article
C2 - 37642667
AN - SCOPUS:85170717241
SN - 0743-7463
VL - 39
SP - 12618
EP - 12626
JO - Langmuir
JF - Langmuir
IS - 36
ER -