About

Pulak Dutta is a Professor of Physics and Astronomy at Northwestern University. He earned his Ph.D. in Condensed Matter Physics from the University of Chicago in 1980, his M.Sc. in Physics from the University of Delhi in 1973, and his B.Sc. in Physics from Presidency College, Kolkata, in 1971. His research focuses on nanoscale order in soft materials and at soft-hard interfaces, with particular interest in the structure of liquids near surfaces and interfaces. This work has relevance to industrial processes such as lubrication, wetting, spreading, tertiary oil recovery, and other applications, aiming to design new materials and systems to enhance these processes. Additionally, Dutta's group investigates how living organisms utilize soft surfaces to grow inorganic crystalline materials, like bones and shells, with the goal of developing biomimetic methods for creating hybrid materials in more energy-efficient ways. Much of his research is conducted using synchrotron radiation at facilities such as the Advanced Photon Source at Argonne National Laboratory and the National Synchrotron Light Source at Brookhaven National Laboratory.

Research topics

• Organic chemistry
• Chemistry
• Physical chemistry
• Chemical physics
• Materials science
• Nanotechnology
• Chemical engineering
• Crystallography
• Chromatography

Selected publications

• Direct Observations of Ion Densities at Functionalized Interfaces to Test Hypotheses Regarding the Origin of Specific Ion Effects

  The Journal of Physical Chemistry Letters · 2025-12-29

  articleSenior authorCorresponding

  Interactions of anions with protonatable groups were investigated using X-ray fluorescence near total reflection (XFNTR) on floating monolayers at the surface of water. The number of ions attracted to the interfacial region, which XFNTR measures directly, is ion-specific as well as monolayer-specific. Our observation of the distinctly different behaviors of ClO4– and ReO4–, two ions with the same tetrahedral structure and almost the same sizes and hydration enthalpies, challenges current theories of ion specificity. Our observations are inconsistent with not only the Gouy–Chapman model (as expected) but also size-modified Poisson–Boltzmann theory and the “law of matching water affinity”. We suggest that factors other than ion size and ion–water interactions, including possibly ion–ion interactions and lateral ordering at the interface, must be considered to account for specific ion effects.

  PublisherDOI

• Hydrothermal growth of vanadium pentoxide nanofibers on carbon nanofiber mat: An anodic material for solid-state asymmetric supercapacitors

  Solid State Sciences · 2024-12-09 · 5 citations

  articleCorresponding
  PublisherDOI

• Relationship of interface structure to the dynamics of selective lanthanide extraction

  Colloids and Surfaces A Physicochemical and Engineering Aspects · 2024-05-11 · 3 citations

  articleOpen accessSenior authorCorresponding
  PublisherOA PDFDOI

• Modifying Specific Ion Effects: Studies of Monovalent Ion Interactions with Amines

  The Journal of Physical Chemistry B · 2024-07-02 · 4 citations

  articleOpen accessSenior authorCorresponding

  Specific ion effects in the interactions of monovalent anions with amine groups─one of the hydrophilic moieties found in proteins─were investigated using octadecylamine monolayers floating at air-aqueous solution interfaces. We find that at solution pH 5.7, larger monovalent anions induce a nonzero pressure starting at higher areas/molecules, i.e., a wider "liquid expanded" region in the monolayer isotherms. Using X-ray fluorescence at near total reflection (XFNTR), an element- and surface-specific technique, ion adsorption to the amines at pH 5.7 is confirmed to be ion-specific and to follow the conventional Hofmeister series. However, at pH 4, this ion specificity is no longer observed. We propose that at the higher pH, the amine headgroups are only partially protonated, and large polarizable ions such as iodine are better able to boost amine protonation. At the lower pH, on the other hand, the monolayer is fully protonated, and electrostatic interactions dominate over ion specificity. These results demonstrate that ion specificity can be modified by changing the experimental conditions.

  PublisherOA PDFDOI

• Specific Ion Effects in Lanthanide–Amphiphile Structures at the Air–Water Interface and Their Implications for Selective Separation

  ACS Applied Materials & Interfaces · 2022 · 27 citations

  Senior authorCorresponding
  • Materials science
  • Crystallography
  • Physical chemistry

  M, bilayers form but only in the presence of the heavier lanthanide. Grazing incidence X-ray diffraction shows evidence of lateral ion-ion correlations in the bilayer structure but not in monolayers. Explicit solvent all-atom molecular dynamics simulations confirm the elevated ion-ion correlation in the bilayer system. This bilayer structure isolates heavier lanthanides but not lighter lanthanides from an aqueous solution and is therefore a potential mechanism for the selective separation of heavier lanthanides.

  PublisherOA PDFDOI

• Ionic Liquid Solutions Show Anomalous Crowding Behavior at an Electrode Surface

  Langmuir · 2022 · 14 citations

  Senior authorCorresponding
  • Chemical physics
  • Chemistry
  • Materials science

  was dissolved in either strongly polar propylene carbonate or weakly polar dimethyl carbonate. In the range of 19-100 vol % ionic liquid, between working electrode potentials +2 and +2.75 V, uniform 2-7 nm thick interfacial layers were observed. These layers are not pure anions but contain three to five times as many anions as cations and about the same percentage of solvent as the bulk solution. On the other side of the layer, the density is that of the bulk solution. These features are inconsistent with a picture of the crowded layer as a region of pure, close-packed counterions. Not only the layer thickness but also the charge density decrease with increasing dilution at any given applied voltage. This appears to indicate, counterintuitively, that a thinner layer with lower net charge density will screen an electric field as effectively as a thicker layer with higher charge density.

  PublisherDOI

• Interfacial Density Profiles of Polar and Nonpolar Liquids at Hydrophobic Surfaces

  Langmuir · 2020 · 8 citations

  Senior authorCorresponding
  • Chemical physics
  • Chemistry
  • Chemical engineering

  A density-depleted region ("gap") is known to exist between water and hydrophobic surfaces. Using X-ray reflectivity, we have observed similar gaps between hydrophobic self-assembled monolayers (SAMs) and four other polar liquids. For these liquids and for water, the observed electron density depletion is nonzero and is in most cases slightly greater than the depletion attributable to the layer of hydrogen atoms at the SAM surface. On the other hand, the observed X-ray reflectivity from the interfaces between SAMs and three nonpolar liquids studied can be explained either without gaps or with smaller gaps. Thus, polar liquids (including but not limited to water) stand away from even the terminal hydrogen atoms at hydrophobic surfaces, while nonpolar liquids interpenetrate the terminal region. There is no consistent correlation between the sizes of the gaps and the liquid-SAM contact angles, the relative polarities of the polar liquids, or their bulk densities.

  PublisherDOI

• Cation-specific effects on the attraction of anions to a hydrophobic surface

  APS March Meeting Abstracts · 2019-01-01

  articleSenior author
  Publisher

• Electrostatic Origin of Element Selectivity during Rare Earth Adsorption

  Physical Review Letters · 2019-02-08 · 42 citations

  articleOpen accessSenior author

  Rare earths, which are fundamental components of modern technologies, are often extracted from aqueous solutions using surfactants at oil-water interfaces. Heavier lanthanides are more easily extracted, even though all lanthanides are chemically very similar. Using x-ray fluorescence measurements and theoretical arguments, we show that there is a sharp bulk-concentration-dependent transition in the interfacial adsorption of cations from aqueous solutions containing Er^{3+} or Nd^{3+} in contact with a floating monolayer. The threshold bulk concentration of erbium (Z=68) is an order of magnitude lower than that of neodymium (Z=60), and erbium is preferentially adsorbed when the solution contains both ions. This implies that elemental selectivity during separation originates at the surfactant interface. Electrostatic effects arising from the interface dielectric mismatch, ionic correlations, and sizes of the ions explain the sharp adsorption curve and selectivity.

  PublisherOA PDFDOI

• What X-rays Tell Us About Langmuir Monolayers

  2018-05-04 · 1 citations

  book-chapter1st authorCorresponding

  This chapter describes the techniques used to scatter off the surface of water, and then discusses some recent experiments. It provides a few examples of the kinds of things that X-rays can tell people about Langmuir monolayers. The simplest X-ray scattering technique used to study surfaces is specular reflectivity. A simplified picture of reflection from a monolayer on a substrate is that X-rays are reflected both from the monolayer-air interface and the monolayer-substrate interface; interference between these two reflections gives rise to intensity maxima. Determining the symmetries of various phases is one of the very simplest things that can be done with X-ray diffraction. In any case X-ray diffraction is one of the core characterization tools for anyone working with three-dimensional materials, and there is no reason why it should not be so for monolayers as well.

  PublisherDOI

Recent grants

• Ions at aqueous interfaces: X-ray fluorescence and scattering studies

  NSF · $581k · 2020–2026

• Surface Order in Dielectric Liquids

  NSF · $345k · 2007–2011

• Surface/interface order in liquids with electrostatic correlations: X-ray scattering studies

  NSF · $390k · 2013–2017

• Interfacial ordering in aqueous solutions: X-ray scattering studies

  NSF · $499k · 2016–2021

• Liquid Surfaces and Interfaces: X-ray Studies

  NSF · $360k · 2010–2014

Frequent coauthors

• Guennadi Evmenenko

  Northwestern University

  136 shared

• Milko E. van der Boom

  Weizmann Institute of Science

  85 shared

• Tobin J. Marks

  Northwestern University

  82 shared

• A. G. Richter

  Valparaiso University

  48 shared

• J. B. Ketterson

  Northwestern University

  38 shared

• J. Kmeťko

  36 shared

• Antonio Facchetti

  Georgia Institute of Technology

  28 shared

• Luca Beverina

  University of Milano-Bicocca

  27 shared

Education

• Ph.D., Condensed Matter Physics

  University of Chicago

  1980

• M.S., Physics

  University of Delhi

  1973

• B.S., Physics

  Presidency College, Kolkata

  1971