Modeling Course

Education

Ph.D., University of Ljubljana, Slovenia
Senior Fulbright Scholar: SUNY at Stony Brook, N.Y.

Research interests

Our research in solution theories focuses on colloidal, biopolymeric and electrolyte systems relevant to biophysics and chemical engineering. We have been developing and applying analytic methods and computational techniques based on principles of statistical mechanics. These include molecular and mesoscopic simulations, integral equation theory of liquids, and field-theoretic approaches to soft matter and disordered materials. The goal is to explain microscopic mechanisms behind observed macroscopic behaviors, predict new designs, and identify conditions optimizing biological function or pragmatic performance of the material.

Our work is often synergistic with experimental groups in respective fields. Systems of interest include dispersions of nanoparticles, synthetic and biological polyelectrolytes, surfactant self-assemblies, liquid and quenched ionic media and aggregating protein solutions. This research has helped elucidate several crucial aspects of solution electrostatics and solvation phenomena that affect the structure and phase behavior of colloidal solutions, including the important role of ion-ion correlations in intercolloidal attraction.

In recent years, we have been concerned with modeling of interfacial liquids under the influence of confining surfaces, neutral and ionic co-solutes, and applied external field. These efforts advance our understanding of solvation forces, and the ability to tune materials’ surface thermodynamics for new applications.

Specific salt effects, crucial to solution properties of biomolecules, are analyzed by a combination of molecular simulations and integral equation approaches. We are extending these studies to solutions of nanoparticles with ionic ingredients. In view of close relation with physics of ionic colloids, our studies also impact several topics in colloidal theory, including hydration and confinement effects, ion-recognition, and multipolar electrostatic interactions.

VCU publications

D. Bratko, Reversible surface energy storage in molecular-scale porous materials, Special Issue on Wettability Control Materials: Synthesis, Characterization, Properties and Applications, Molecules 29, 664 (2024)

N. Mulpuri, D. Bratko, Polarity-dependence of the nonlinear dielectric response in interfacial water, J. Chem. Phys. 158, 134716 (2023)

D. Vanzo, A. Luzar, D. Bratko, Pressure-sensitive conversions between Cassie and Wenzel states on a nanocorrugated surface, Theme Series on Materials by Design Under Pressure: Experiments and Theory, Appl. Phys. A 128, 323 (2022)

D. Vanzo, A. Luzar, D. Bratko, Reversible electrowetting transitions on superhydrophobic surfaces, Phys. Chem. Chem. Phys. 23, 27005 (2021)

S. G. Zamfir, F. Moucka, D. Bratko, High Pressure Infiltration/Expulsion of Aqueous NaCl in Planar Hydrophopic Nanopores, J. Phys. Chem. C 124, 23433 (2020) 

N. Ojaghlou, D. Bratko, M. Salanne, M. Shafiei, A. Luzar, Solvent-Solvent Correlations across Graphene: The Effect of Image Charges, ACS Nano 14, 7987 (2020)

M. Shafiei, N. Ojaghlou, S. Zamfir, D. Bratko, A. Luzar, Modulation of Structure and Dynamics of Water Under Alternating Electric Field and the Role of Hydrogen Bonding, Mol. Phys. 117, 3282 (2019)

C. D. Daub, N. M. Cann, D. Bratko, Alenka Luzar, Electrokinetic Flow of an Aqueous Electrolyte in Amorphous Silica Nanotubes, Phys. Chem. Chem. Phys. 20, 27838 (2018)

N. Ojaghlou, H. V. Tafreshi, D. Bratko, A. Luzar, Dynamical Insights into the Mechanism of a Droplet Detachment from a Fiber, Soft Matter 14, 8924 (2018).

B. S. Jabes, D. Bratko, A. Luzar, Curvature Dependence of the Effect of Ionic Functionalization on the Attraction among Nanoparticles in Dispersion, J. Chem. Phys. 148, 222815 (2018).

B. S. Jabes, D. Bratko, A. Luzar, Extent of Surface Force Additivity on Chemically Heterogeneous Substrates at Varied Orientations, J. Phys. Chem. B 122, 3596 (2018).

B. S. Jabes, J. Driskill, D. Vanzo, D. Bratko, A. Luzar, Metastable Vapor in a Janus Nanoconfinement, J. Phys. Chem. C 121, 13144 (2017).

J.R. Choudhuri, D.Vanzo, P. A. Madden, M. Salanne, D. Bratko, A. Luzar,Dynamic Response in Nanoelectrowetting on a Dielectric, ACS Nano 10, 8536 (2016).

B.S. Jabes, D. Bratko, A. Luzar, Universal Repulsive Contribution to the Solvent- Induced Interaction Between Sizable, Curved Hydrophobes, J. Phys. Chem. Lett. 7, 3158 (2016).

F. Moucka, D. Bratko, A. Luzar, Salt and Water Uptake in Nanoconfinement under Applied Electric Field: An Open Ensemble Monte Carlo Study, J. Phys. Chem. C 119, 20416 (2015).

D. Vanzo, D. Bratko, A. Luzar, Dynamic Control of Nanopore Wetting in Water and Saline Solutions under an Electric Field, J. Phys. Chem. B, 115, 8890 (2015).

F. Moucka, D. Bratko, A. Luzar, Electrolyte Pore/Solution Partitioning by Expanded Grand Canonical Ensemble Monte Carlo Simulation, J. Chem. Phys. 142, 124705 (2015).

J. Driskill, D. Vanzo, D. Bratko, A. Luzar, Wetting transparency of graphene in water, J. Chem. Phys. 141, 18C517 (2014).

D. Vanzo, D. Bratko, A. Luzar, Nanoconfined water under electric field at constant chemical potential undergoes electrostriction, J. Chem. Phys. 140, 074710 (2014).

M. von Domaros, D. Bratko, B. Kirchner, A. Luzar, Dynamics at a Janus Interface, J. Phys. Chem. C 117, 4561 (2013).

D. Vanzo, D. Bratko, A. Luzar, Tunable wetting of surfaces with ionic functionalities, J. Phys. Chem. C 116, 15467 (2012).

C. D. Daub, D. Bratko, A. Luzar, Nanoscale Wetting Under Electric Field from Molecular Simulations, Top. Curr. Chem. 307, 155 (2012).

D. Vanzo, D. Bratko, A. Luzar, Wettability of pristine and alkyl-functionalized graphane, J. Chem. Phys. 137, 034707 (2012).

J. A. Ritchie, J. Seyed Yazdi, D. Bratko, and A. Luzar, Metastable sessile nanodroplets on nanopatterned surfaces, J. Phys. Chem. C 116, 8634 (2012).

J. H. Wang, D. Bratko, A. Luzar, Length-Scale Dependence of Hydration Free Energy: Effect of Solute Charge, J. Stat. Phys. 145, 253 (2011).

C. D. Daub, D. Bratko, A. Luzar, Length-Scale Dependence of Hydration Free Energy: Effect of Solute Charge, J. Stat. Phys. 145, 253 (2011).

J. H. Wang, S. Kudesia, D. Bratko and A. Luzar, Computational probe of cavitation events in protein systems, Phys. Chem. Chem. Phys. 13, 19902 (2011).

C. D. Daub, D. Bratko, A. Luzar, Electric Control of Wetting by Salty Nanodrops: Molecular Dynamics Simulations, J. Phys. Chem. C 115, 22393 (2011).

J. Wang, D. Bratko, A. Luzar, Probing surface tension additivity on chemically heterogeneous surfaces: A molecular approach, Proc. Natl. Acad. Sci. 108, 6374 (2011).

C. D. Daub, J. Wang, S. Kudesia, D. Bratko, A. Luzar,The influence of molecular-scale roughness on the surface spreading of an aqueous nanodrop, Faraday Discuss. 146, 67 (2010), featured on issue cover.

C. D. Daub, D. Bratko, T. Ali, A. Luzar, Microscopic dynamics of the orientation of a hydrated nanoparticle in an electric field, Phys. Rev. Letters 103, 207801 (2009).

D. Bratko, C. D. Daub, A. Luzar, Water-mediated ordering of nanoparticles in an electric field, Faraday Discuss. 141, 55 (2009).

V. Deniz, M. Bostrom, D. Bratko, F. W. Tavares, B. W. Ninham, Specific ion effects: Interaction between nanoparticles in electrolyte solutions. Colloids Surf. A 319, 98 (2008).

D. Bratko, C. D. Daub, A. Luzar, Field-exposed water in a nanopore: liquid or vapour? Phys. Chem. Chem. Phys. 10, 6807 (2008).

D. Bratko, A. Luzar, Attractive surface force in the presence of dissolved gas: A molecular approach. Langmuir  24, 1247 (2008).

T. Cellmer, D. Bratko, J. M. Prausnitz, H. W. Blanch, Protein aggregation in silico. Trends Biotechnol. 25, 254 (2007), featured on issue cover.

C. D. Daub, D. Bratko, K. Leung, A. Luzar, Electrowetting at the nanoscale. J. Phys. Chem. C 111, 505 (2007).

D. Bratko, T. Cellmer, J. M. Prausnitz, H. W. Blanch, Molecular simulation of protein aggregation. Biotechnol.Bioeng. 96, 1 (2007), featured on issue cover.

D. Bratko, C. D. Daub, K. Leung, A. Luzar, Effect of field direction on electrowetting in a nanopore. J. Am. Chem. Soc. 129, 2504 (2007).

M. Bostroem, F. W. Tavares, D. Bratko, B. W. Ninham, Ion-Specific Interactions between Pairs of Nanometer Sized Particles in Aqueous Solutions, Prog. Coll. Polym. Sci. 133, 74 (2006).

D. Bratko, T. Cellmer, J. M. Prausnitz, H. W. Blanch, Effect of single-point sequence alterations on the aggregation propensity of a model protein. J. Am. Chem. Soc. 128, 1683 (2006).

M. Bostroem, F. W. Tavares, D. Bratko, B. W. Ninham, Specific ion effects in solutions of globular proteins: Comparison between analytical models and simulation. J. Phys. Chem. B 109, 24489 (2005).

T. Cellmer, D. Bratko, J. M. Prausnitz, H. W. Blanch, Protein-folding landscapes in multichain systems. Proc. Natl. Acad. Sci. 102, 11692 (2005).

A. Luzar, D. Bratko, Gas solubility in hydrophobic confinement. J. Phys. Chem. B 109, 22545 (2005).

T. Cellmer, D. Bratko, J. M. Prausnitz, H. W. Blanch, Thermodynamics of folding and association of lattice-model proteins. J. Chem. Phys. 122, 174908 (2005).

T. Cellmer, D. Bratko, J. M. Prausnitz, H. Blanch, The competition between protein folding and aggregation: Off-Lattice Minimalist Model Studies, Biotechnol. Bioeng. 89, 78 (2005).

F. W. Tavares, D. Bratko, J. M. Prausnitz, The Role of Salt-Macroion van der Waals Interactions in the Colloid-Colloid Potential of Mean Force, Curr. Opinion Coll. Interface Sci. 9, 81 (2004).