About

Sarah H. Tolbert is a distinguished professor in the Department of Chemistry and Biochemistry at UCLA, with a research focus on self-organized nanoscale materials. Her group investigates both organic templated inorganic phases and colloidal materials, aiming to understand and control structure and periodicity in complex nanostructured composite materials. Her work explores the exploitation of nanoscale architecture to produce new physical properties, including optical, magnetic, electrical, and structural behaviors, by intrinsically tying these properties to nanoscale structure. Her research employs methods such as colloidal assembly and inorganic/organic co-assembly to create nanoperiodic structures. Colloidal assembly allows for the formation of periodic structures across various length scales, suitable for photonic materials, while inorganic/organic co-assembly involves amphiphilic surfactants or block co-polymers with inorganic oligomers to produce periodic inorganic/organic composites or nanoporous inorganics. Her contributions include examining nanoscale phase transitions, designing electro-active composite materials, and advancing understanding of heat dissipation, phase behavior, and reaction networks in nanostructured systems. Her work has significant implications for energy storage, electronic, and optical applications.

Research topics

• Materials science
• Chemistry
• Organic chemistry
• Nanotechnology
• Composite material
• Chemical engineering
• Physical chemistry
• Inorganic chemistry
• Metallurgy
• Chemical physics
• Optoelectronics

Selected publications

• Resistance to Overdoping Allows Over 2000 S cm ⁻¹ Conductivity in P(g ₃ BTTT) With Anion‐Exchange Doping

  Advanced Materials · 2026-04-04

  articleOpen access

  ABSTRACT Chemical doping of conjugated polymers significantly enhances their conductivity, making them attractive for a large range of applications. Recently, anion‐exchange doping, where the dopant counterion is replaced by inorganic anions by exposure of a p‐doped film to an electrolyte, has been demonstrated as an effective way to overcome the limitations of molecular dopants in terms of bulkiness, stability and energetics. Here, we demonstrate anion‐exchange doping for polymers bearing oligoether side chains and report over 2000 S cm −1 electrical conductivity for the P(g 3 BTTT) polymer. We investigate several thiophene and thienothiophene‐based polymers in the high‐doping regime to understand this high conductivity. We show that transport involves delocalized charges, that all generated charges participate to the transport, and that the mobility is resilient over nanometer to micrometer length scales. However, the high‐doping regime also shows a trade‐off between high charge density and high mobility, limiting the conductivity at excess concentrations of doubly charged species. Surprisingly, P(g 3 BTTT) is resistant to this ‘overdoping’ effect and sustains particularly high levels of doubly charged species without drop in mobility. The exceptional conductivity of doped P(g 3 BTTT) can thus be related to the high doping level that is achieved thanks to the oligoether side chains, without significant trade‐off on the concomitantly high mobility.

  PublisherDOI

• Resistance to Overdoping Allows Over 2000 S cm-1 Conductivity in P(g3BTTT) With Anion-Exchange Doping.

  Open Access CRIS of the University of Bern · 2026-04-04

  articleOpen access

  Chemical doping of conjugated polymers significantly enhances their conductivity, making them attractive for a large range of applications. Recently, anion-exchange doping, where the dopant counterion is replaced by inorganic anions by exposure of a p-doped film to an electrolyte, has been demonstrated as an effective way to overcome the limitations of molecular dopants in terms of bulkiness, stability and energetics. Here, we demonstrate anion-exchange doping for polymers bearing oligoether side chains and report over 2000 S cm-1 electrical conductivity for the P(g3BTTT) polymer. We investigate several thiophene and thienothiophene-based polymers in the high-doping regime to understand this high conductivity. We show that transport involves delocalized charges, that all generated charges participate to the transport, and that the mobility is resilient over nanometer to micrometer length scales. However, the high-doping regime also shows a trade-off between high charge density and high mobility, limiting the conductivity at excess concentrations of doubly charged species. Surprisingly, P(g3BTTT) is resistant to this 'overdoping' effect and sustains particularly high levels of doubly charged species without drop in mobility. The exceptional conductivity of doped P(g3BTTT) can thus be related to the high doping level that is achieved thanks to the oligoether side chains, without significant trade-off on the concomitantly high mobility.

  PublisherDOI

• Exploring the Chemical Doping of a Water-Soluble Cylindrical Micelle-Forming Conjugated Polyelectrolyte

  ACS Applied Materials & Interfaces · 2026-02-09

  articleSenior authorCorresponding

  The chemical doping of water-soluble conjugated polyelectrolytes (CPEs) offers a promising pathway for the direct printing of semiconducting polymer films by using environmentally friendly solvents. In this study, we explored the chemical doping of the cationic cylindrical micelle-forming CPE poly(cyclopentadithiophene-alt-thiophene) (PCT-NBr) in aqueous solution using two Fe(III)-halide dopants, FeCl3 and FeBr3. Treatment with nonoxidizing salts (KCl and KBr) showed that polymer micelles preferentially interact with Br– ions over Cl– ions, resulting in a more rigid micelle and spectroscopic evidence of Br– ion accumulation around the polymer. Doping with both FeCl3 and FeBr3 was followed using UV-visible-near IR absorption spectroscopy, which indicated that the polymer micelles could be stably doped with both iron compounds. FeCl3 was shown to be a stronger dopant due to differences in the lability of Cl– and Br– ligands in water. Compared at similar concentrations, FeCl3 induces higher doping levels, while FeBr3 generates more delocalized charge carriers, as evidenced by spectral shifts in the polaronic bands, likely due to weaker counterion Coulombic trapping. Small-angle X-ray scattering was used to confirm that a micellar structure was preserved at all doping levels of PCT-NBr, but the data also indicate increased structural disorder in doped polymer micelles, likely due to partial loss of the polymer’s amphiphilic character and ion–polymer interactions. Films spin-cast directly from FeBr3-doped polymer solutions exhibited a stable conductivity of 1.0 S/cm, demonstrating the viability of using doped micellar CPE solutions as a route to single-step deposition of conductive polymer films.

  PublisherDOI

• How the Carrier Mobility and Seebeck Coefficient of Doped Semiconducting Polymers Are Controlled by Counterion Interactions and Mesoscale Order

  Advanced Functional Materials · 2026-04-24

  articleOpen accessCorresponding

  ABSTRACT Charge transport/structure relationships in chemically‐doped poly(3‐hexylthiophene‐2,5‐diyl) (P3HT) films are explored using four different dopants: the classic 2,3,5,6‐tetrafluoro‐7,7,8,8‐tetracyanoquinodimethane (F 4 TCNQ) as well as two large dodecaborane (DDB) cluster‐based dopants that minimize counterion Coulomb interactions with carriers on the polymer backbone. Anion‐exchange doping with F 4 TCNQ and lithium bis(trifluoromethane)sulfonimide (LiTFSI) was also used to put TFSI − counterions into the doped polymer. The Seebeck coefficient ( S ) and conductivity ( σ ) were measured as a function of doping level, along with temperature‐dependent conductivity, wide‐ and small‐angle x‐ray scattering, optical spectroscopy, and Hall effect mobility. The results indicate that large DDB‐based counterions produce lower carrier transport activation energies and thus more favorable S ‐ σ relationships than F 4 TCNQ. Anion‐exchange doping leads to higher activation energies but still produces a favorable S ‐ σ relationship. Analysis using the semi‐localized transport (SLoT) model indicates that anion‐exchange doping produces films with the highest intrinsic conductivities, which results from doping‐induced crystallization of originally amorphous regions of the film. Such crystallization leads to increased mesoscale domain sizes, as observed by small‐angle X‐ray scattering. Together, the results indicate that transport in doped conjugated polymers can be equivalently improved either by reducing the Coulomb interaction of carriers with counterions or by structurally improving mesoscale conductivity pathways.

  PublisherDOI

• Morphological Impact on Sodium-Ion Storage in TiO ₂ (B) Nanostructures

  Chemistry of Materials · 2025-12-30

  article

  Among the various anodes considered for sodium ion batteries, titania polymorphs have often been regarded as one of the more appealing candidates given its theoretical specific capacity of 335 mAh·g–1. TiO2(B), in particular, has received considerable attention owing to its open framework structure that is believed to allow sodium insertion. However, the existing literature does not provide adequate evidence to draw conclusions on either the sodium capacity of TiO2(B) or the nature of the redox mechanism occurring upon sodiation. In this study, we systematically compare 0D, 1D, and 2D nanostructures of TiO2(B) to determine the extent of sodium insertion in relation to preferentially exposed crystal facets and lattice strain. We demonstrate experimentally that a clear insertion of Na+ at 1.2 V vs Na/Na+ can only be achieved when introducing lattice expansion via nanostructuring, which extends to a thermodynamic limit of 0.25 Na+ mol per Ti4+ center. Our results consist of electrochemical measurements in combination with high-resolution synchrotron techniques and are supported by computational calculations. A major outcome of this study is that despite Na+ insertion being thermodynamically favorable, its diffusion in practical time frames can only be made possible via strain generation aimed at expanding the crystal lattice.

  PublisherDOI

• <i>(Invited)</i> Using Surface Coatings to Control Deposition in Aqueous Batteries

  ECS Meeting Abstracts · 2025-11-24

  article1st authorCorresponding

  Plating and stripping chemistries have the potential to produce low-cost, high-capacity, non-flammable batteries for large-scale energy storage. Although these chemistries form the basis of some of our oldest battery technologies, they were rapidly replaced by lithium-ion secondary batteries in the rechargeable battery market because of the challenges with creating highly reversible reactions: uncontrolled plating morphology can lead to active material loss and poor Coulombic efficiency. In this talk, we explore ways to control deposition of both metals and metal oxides in low cost carbon scaffolds as a way to control the morphology of plated materials. Carbon papers and cloths provide readily-available, high-porosity, conductive electrode scaffolds that can support the deposition of large volumes of metals or metal oxides. Here, we specifically focus on ways to control deposition within carbon scaffolds using surface coatings. We consider ways to lower plating overpotentials, improve homogeneity, and to control the distribution of plated material within the porous carbon network.

  PublisherDOI

• Modeling Finite Deformations in Alloying Electrodes -- A Closer Look at Cracks and Pores During Phase Transformation

  ArXiv.org · 2025-06-24

  preprintOpen access

  Nanostructured electrodes with voids or interconnected pores accommodate large volume changes, shorten ion diffusion pathways, and enhance the structural reversibility of alloying electrodes. While these nanoporous features improve the performance of architected electrodes over bulk electrodes, they also act as geometric irregularities that localize and concentrate internal stresses. In this work, we investigate the hierarchical interplay between phase boundaries and nanoporous features at the microstructural scale and their collective role in mitigating chemo-mechanical failure at the engineering scale. Using Sb$\to$Li$_2$Sb$\to$Li$_3$Sb as a model system, we develop a continuum framework coupling lithium diffusion and reaction kinetics with the finite deformation of alloying electrodes. We analytically show that large volume changes in the Sb$\rightarrow$Li$_2$Sb transformation induce fracture, which nanoporous geometries can mitigate. Building on this, we develop a micromechanical model using a hyper-elastic neo-Hookean material law to predict the deformations accompanying the Li$_2$Sb$\to$Li$_3$Sb transformation. Our results reveal how diffusion and reaction kinetics shape phase boundary morphology, identify crack geometries likely to propagate, and show how carefully architected electrodes relieve stresses. These findings highlight critical design principles to optimize electrode lifespan and demonstrate a potential application of our continuum model as an electrode design tool.

  PublisherOA PDFDOI

• Ballistic transport from propagating vibrational modes in amorphous silicon dioxide: Thermal experiments and atomistic-machine learning modeling

  Materials Today Physics · 2025-01-24 · 1 citations

  articleOpen access

  Understanding thermal transport in amorphous materials is critical for a wide range of applications, including buildings, vehicles, aerospace, and acoustic technologies. Despite its importance, the fundamental behavior of heat carriers in amorphous structures remains poorly understood and is often attributed to localized vibrational modes with mean free paths of about 1 nm, posing significant challenges for engineering their thermal functionalities. In this study, we present experimental measurements on mesoporous silica and atomistic analyses using Monte Carlo simulations and machine learning models to quantify the relationship between nanoarchitecture and effective thermal conductivity. Through rational chemical synthesis and ultrafast spectroscopy measurements, a strong size dependence within the sub-10 nm regime is observed, where the classical Fourier heat conduction theory fails to account for the effects of porosity and pore size. This deviation from diffusive transport is attributed to the significant contribution of propagating vibrational modes, in addition to non-propagating modes, revealing unexpectedly long mean free paths and ballistic thermal transport for heat carriers in amorphous silica. The fundamental vibrational modes in amorphous silica are further investigated using spectral-dependent Boltzmann transport equation simulations and molecular dynamics with machine learning potentials, showing good agreement with experimental results. This study provides valuable insights into nanoscale-modulated thermal transport properties in mesoporous silica and opens new opportunities for the rational design of thermally insulating materials.

  PublisherDOI

• Formation of LiF₄TCNQ Complexes During High Concentration Anion-Exchange Doping of Semiconducting Polymers

  The Journal of Physical Chemistry C · 2025-08-21 · 1 citations

  article

  Anion-exchange doping, in which a semiconducting polymer is exposed to a solution containing both a dopant and an electrolyte, has become a popular method to create polarons on conjugated polymers to increase their electrical conductivity. Although many different initiator dopants can be used, a common dopant/salt combination for anion-exchange p-doping is 2,3,5,6-tetrafluoro-tetracyanoquinodimethane (F4TCNQ) and lithium bis(trifluoromethane) sulfonimide (LiTFSI). Depending on the concentration of initiator dopant, it is usually presumed that all the F4TCNQ– ions that remain after doping are exchanged out by mass action for the salt anion, TFSI–. When both LiTFSI and F4TCNQ are present in excess, however, we find that two new peaks appear in the UV–visible absorption spectrum of anion-exchange-doped conjugated polymers that are not seen when conventionally doping without the addition of salt. We further see that these peaks appear in the same spectral regions, ∼1.95 and ∼3.65 eV, independent of the conjugated polymer being doped by F4TCNQ/TFSI anion exchange, and that they do not appear when initiator dopants other than F4TCNQ are used. With the aid of Resonance Raman spectroscopy and quantum chemistry calculations, we assign these peaks to a LiF4TCNQ complex that forms during the exchange process of anion-exchange doping and remains in the doped polymer film. We estimate that roughly ∼25% of the F4TCNQ– ions present during the anion exchange doping process are converted into LiF4TCNQ complexes, and show that the complex can be dissociated back into F4TCNQ– by washing with an appropriate solvent.

  PublisherDOI

• Ultrafast Transient Absorption Studies of the Dynamics of Free and Coulombically Trapped Polarons in Doped Conjugated Polymers

  Advanced Functional Materials · 2025-07-01 · 3 citations

  articleOpen accessCorresponding

  Abstract The relaxation of photoexcited polarons in doped conjugated polymers is studied with ultrafast transient absorption (TA) spectroscopy to examine the effect of polymer morphology and counterion size on polaron mobility. Processing conditions are first used to create F 4 TCNQ‐doped (2,3,5,6‐tetrafluoro‐tetracyanoquinodimethane) poly(3‐hexylthiophene‐2,5‐diyl) (P3HT) films with different morphologies and thus free and trapped polarons in different ratios. We find that less crystalline films have a higher fraction of trapped polarons, but, remarkably, that free and trapped polarons have the same relaxation times in all films. Films doped with a large dodecaborane (DDB) cluster‐based dopant are then used to show that trapping is based on Coulomb interactions between polarons and counterions; no trapped polarons are observed in TA due to the reduced Coulomb interaction between the polarons and the DDB counterion. Indeed, the relaxation of polarons in these films is an order of magnitude faster than that in F 4 TCNQ‐doped films, consistent with reduced trapping. Finally, the results are used to argue that counterion size has a greater effect on polaron mobility than polymer morphology and crystallinity. All of the experiments show that pump/probe spectroscopy provides a straightforward way to determine the local mobilities and degree of carrier trapping in doped conjugated polymer films.

  PublisherOA PDFDOI

Recent grants

• Building Electron Transfer Cascades into Amphiphlic Donor-Acceptor Assemblies

  NSF · $700k · 2016–2020

• Using Self-Organization to Control Nanometer-Scale Architecture in Semiconducting Polymer-Based Solar Cells

  NSF · $916k · 2011–2016

• Using Amphiphilic Semiconducting Polymers to Control Structure and Exited State Dynamic in Conjugated Organic Assemblies

  NSF · $600k · 2020–2024

• Understanding Carrier Delocalization and Transport in Micelle Forming Amphiphilic Conjugated Polymers

  NSF · $800k · 2023–2026

• Geometric and Size Control of Mechanical Properties in Surfactant Templated Silicas and Periodic Nanoporous Oxides

  NSF · $500k · 2003–2007

Frequent coauthors

• Bruce Dunn

  133 shared

• Benjamin J. Schwartz

  University of California, Los Angeles

  113 shared

• Richard B. Kaner

  University of California, Los Angeles

  110 shared

• Laurent Pilon

  82 shared

• Galen D. Stucky

  University of California, Santa Barbara

  55 shared

• Yves Rubin

  52 shared

• Christopher C. Landry

  University of Vermont

  45 shared

• Alain Monnier

  Institut Agro Rennes-Angers

  45 shared

Awards & honors

• Tolman Medal (2023)
• Center for Strain Optimization for Renewable Energy (2023)
• ACS Henry H. Storch Award in Energy Chemistry (2023)
• UCLA Academic Senate Community Service and Praxis Diversity,…
• US DOE SCALAR Center Grant (2018)