About

Matthew D. Law is a Professor at the UCI Department of Chemistry. His research interests include Inorganic and Organometallic Physical Chemistry and Chemical Physics, as well as Polymer, Materials, Nanoscience. He is affiliated with the UC Irvine School of Physical Sciences and is involved in advancing knowledge in these scientific areas through his academic and research activities.

Research topics

• Nanotechnology
• Optoelectronics
• Materials science
• Chemistry
• Chemical engineering
• Electrical engineering
• Molecular physics
• Chemical physics
• Engineering
• Physics

Selected publications

• (<i>Invited</i>) Multilayered Nanoporous Photoanodes of Mixed-Metal Oxides for Solar Water Splitting

  ECS Meeting Abstracts · 2025-07-11 · 1 citations

  article1st authorCorresponding

  The lack of efficient, stable, and low-cost materials for water oxidation is a major barrier to the development of a photoelectrochemical (PEC) water splitting technology that can meet the U.S. Hydrogen Shot goal of producing green hydrogen at a cost of less than $1/kg H 2 within the nextseven years. Many new materials for PEC water oxidation have been identified by calculations or high-throughput combinatorial discovery campaigns, yet detailed fundamental studies of these materials are needed to understand and control the factors that govern their water oxidationperformance (efficiency and stability) and develop suitable photoanode architectures for practical PEC water splitting. Our lab is combining studies of high-quality bulk single crystals and nanostructured films to understand the properties and photoelectrochemical behavior of several promising metal oxide semiconductors for solar-driven water oxidation and to test new concepts and strategies to enhance solar-to-hydrogen efficiency and durability. In this talk, I will describe a novel class of nanoporous metal oxide films that have a suitable architecture for high-performance, practical water oxidation. The nanoporous film morphology orthogonalizes the directions of light absorption in the semiconductor and hole delivery to the electrolyte to enable efficient light absorption and charge carrier utilization. These films are made by a general and scalable solution-phase method that offers independent control of nanocrystal composition and size, film porosity, and film thickness, providing a versatile experimental platform for developing solar fuels electrodes. Film materials made to date span a wide variety of binary and mixed-metal oxides, including BiVO 4 , Mn 2 V 2 O 7 , BiFeO 3 , FeWO 4 , WO 3 , Fe 2 O 3 , and TiO 2 . Some of these phases are intended for use as the core material of core-shell nanoporous films that feature a distributed n - n heterojunction between the core and shell materials with a type-II (staggered) band offset to force photogenerated electrons into the core and holes into the shell, greatly reducing recombination and improving OER efficiency. Ongoing studies of the performance of core-shell nanoporous film photoanodes for the oxygen evolution reaction will be discussed.

  PublisherDOI

• A General Solution Route to Nanoporous Metal Oxide Films

  Chemistry of Materials · 2025-07-25

  articleSenior authorCorresponding

  Metal oxide semiconductors are of interest as efficient, stable, and low-cost photoanode materials for photoelectrochemical water splitting, but their characteristically poor charge transport properties remain a fundamental challenge to practical use. Nanoporous metal oxide films that feature open bicontinuous networks of nanocrystals and nanopores can overcome such inefficient charge transport to enable high-performance photoanodes. This paper describes a general method to make high-quality nanoporous films of metal oxides by spin coating and calcining molecular inks that contain a porosity-generating block copolymer. Phase-pure nanoporous films of BiFeO3, FeWO4, WO3, Fe2O3, and TiO2 serve to demonstrate the versatility of the approach. It is demonstrated that the crystallite size, film porosity, and film thickness can be independently tuned by adjusting the ink composition and film processing conditions. The method is extended to fabricate core–shell nanoporous films consisting of a nanoporous film coated in a thin shell of a second metal oxide, using WO3–BiVO4 and BiFeO3–BiVO4 as examples. Given its simplicity and flexibility, this solution-phase route should prove useful for making nanoporous films of many different materials for a variety of applications, including energy conversion and storage, catalysis, and chemical sensing.

  PublisherDOI

• Synthesis and Characterization of Epitaxially-Fused Quantum Dot Superlattices at the Single Grain Limit

  ECS Meeting Abstracts · 2024-08-09

  articleSenior author

  Epitaxially-fused superlattices of colloidal quantum dots (QD epi-SLs) may exhibit electronic minibands and high-mobility charge transport, but doing so requires epi-SLs with extremely high degrees of spatial and chemical (compositional) uniformity. In this talk, I will discuss both our efforts to understand and improve the epi-SL formation process, as well as recent charge transport studies on single epi-SL grains. Epi-SLs are synthesized from a parent SL structure, typically composed of QDs with long insulating ligands. Over the past several years, we have developed insight into the physical and chemical mechanisms by which this parent SL structure is converted into an epi-SL. I will present detailed, multi-model structural characterization of the SL structures, which unveils the astonishing choreographic process by which millions of QDs rotate and translate, in concert, to form the epi-SL. This structural transformation is initiated by chemical changes to the QD ligand layer, usually through manual introduction of liquids into the SL film. Mechanistic studies into this ligand-exchange process reveal a multi-step chemical sequence that initiates with a simple acid-base reaction. We exploit this insight to fabricate epi-SLs by means of photochemical triggering (using ultraviolet illumination) rather than alternative “hands-on” techniques which suffer from poor experimental control and pronounced chemical inhomogeneity and structural damage in the films. The use of light to trigger the SL conversion process enables much finer control in both the temporal and spatial domains, opening the door to much larger-area SL films and direct photopatterning of epi-SLs. In the latter portion of the talk, I will present recent work charge transport studies in individual, highly-ordered PbSe QD epi-SL grains. One technical challenge in making these devices is the inherent mismatch in using traditional microfabrication techniques to make single-grained devices of air-sensitive materials. Here, we demonstrate the air-free fabrication of microscale field-effect transistors (μ-FETs) with channels consisting of single PbSe QD epi-SL grains (~ 1 -10 µm grain sizes) and analyze charge transport phenomena in these samples. The devices exhibit p -channel or ambipolar transport with a hole mobility as high as 3.5 cm 2 V –1 s –1 at 290 K and 6.5 cm 2 V –1 s –1 at 170–220 K, one order of magnitude larger than that of previous QD solids.

  PublisherDOI

• Atomic Lattice Resolved Electron Tomography of a 3D Self‐Assembled Mesocrystal

  Advanced Functional Materials · 2023-03-10 · 2 citations

  article

  Abstract Complex 3D architectures of nanoscale building blocks can be created by self‐assembly, but characterization of the atomic to mesoscale structure of such materials is limited by the difficulty of visualizing atoms across multiple length scales. Here, scanning transmission electron microscopy (STEM) and full‐tilt tomographic reconstruction are used to image a single‐crystalline region of a 3D epitaxially‐fused PbSe quantum dot (QD) superlattice containing 633 QDs at a spatial resolution of 2.16 Å. The combined real‐space and reciprocal‐space analysis enables 3D mesoscale correlations of atomic lattice and superlattice order across hundreds of nanocrystals in 3D for the first time. Inhomogeneity in QD positional and orientational order reveals that the QD surface layers template the superlattice and that orientational entropy is higher in the interior layers than the surface layers. The measurement and analysis techniques presented here are applicable to a broad range of 3D nanostructured materials.

  PublisherDOI

• Method to fabricate quantum dot field-effect transistors without bias-stress effect

  OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information) · 2023-01-23

  articleOpen access1st authorCorresponding

  Disclosed herein are embodiments of a method to form quantum dot field-effect transistors (QD FETs) having little to no bias-stress effect. Bias-stress effect can be reduced or eliminated through, as an example, the use of a gas or liquid to remove ligands and/or reduce charge trapping on the QD FETs, followed by deposition of an inorganic or organic matrix around the QDs in the FET.

  PublisherOA PDF

• Structural and Temperature Dependence of Emergent Electronic States in PbSe Quantum Dot Superlattices

  Microscopy and Microanalysis · 2023-07-22

  article

  Journal Article Structural and Temperature Dependence of Emergent Electronic States in PbSe Quantum Dot Superlattices Get access Eric R Hoglund, Eric R Hoglund Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN, United States Search for other works by this author on: Oxford Academic Google Scholar Geemin Kim, Geemin Kim Department of Materials Science and Engineering, University of California, Irvine, CA, United States Search for other works by this author on: Oxford Academic Google Scholar Mahmut S Kavrik, Mahmut S Kavrik Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, United States Search for other works by this author on: Oxford Academic Google Scholar Matt Law, Matt Law Department of Materials Science and Engineering, University of California, Irvine, CA, United StatesDepartment of Chemical and Biomolecular Engineering, University of California, Irvine, CA, United StatesDepartment of Chemistry, University of California, Irvine, CA, United States Search for other works by this author on: Oxford Academic Google Scholar Jordan A Hachtel Jordan A Hachtel Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN, United States Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 29, Issue Supplement_1, 1 August 2023, Page 361, https://doi.org/10.1093/micmic/ozad067.168 Published: 22 July 2023

  PublisherDOI

• Elimination of the bias-stress effect in ligand-free quantum dot field-effect transistors

  The Journal of Chemical Physics · 2023-07-28 · 4 citations

  articleOpen accessSenior author

  Field-effect transistors (FETs) made from colloidal quantum dot (QD) solids commonly suffer from current-voltage hysteresis caused by the bias-stress effect (BSE), which complicates fundamental studies of charge transport in QD solids and the use of QD FETs in electronics. Here, we show that the BSE can be eliminated in n-channel PbSe QD FETs by first removing the QD ligands with a dose of H2S gas and then infilling the QD films with alumina by atomic layer deposition (ALD). The H2S-treated, alumina-infilled FETs have stable, hysteresis-free device characteristics (total short-term stability), indefinite air stability (total long-term stability), and a high electron mobility of up to 14 cm2 V-1 s-1, making them attractive for QD circuitry and optoelectronic devices. The BSE-free devices are utilized to conclusively establish the dependence of the electron mobility on temperature and QD diameter. We demonstrate that the BSE in these devices is caused by both electron trapping at the QD surface and proton drift within the film. The H2S/alumina chemistry produces ligand-free PbSe/PbS/Al2O3 interfaces that lack the traps that cause the electronic part of the BSE, while full alumina infilling stops the proton motion responsible for the ionic part of the BSE. Our matrix engineering approach should aid efforts to eliminate the BSE, boost carrier mobilities, and improve charge transport in other types of nanocrystal solids.

  PublisherOA PDFDOI

• Photobase-Triggered Formation of 3D Epitaxially Fused Quantum Dot Superlattices with High Uniformity and Low Bulk Defect Densities

  ACS Nano · 2022-01-26 · 11 citations

  articleSenior authorCorresponding

  Highly ordered epitaxially fused colloidal quantum dot (QD) superlattices (epi-SLs) promise to combine the size-tunable photophysics of QDs with the efficient charge transport of bulk semiconductors. However, current epi-SL fabrication methods are crude and result in structurally and chemically inhomogeneous samples with high concentrations of extended defects that localize carriers and prevent the emergence of electronic mini-bands. Needed fabrication improvements are hampered by inadequate understanding of the ligand chemistry that causes epi-SL conversion from the unfused parent SL. Here we show that epi-SL formation by the conventional method of amine injection into an ethylene glycol subphase under a floating QD film occurs by deprotonation of glycol by the amine and subsequent exchange of oleate by glycoxide on the QD surface. By replacing the amine with hydroxide ion, we demonstrate that any Brønsted-Lowry base that creates a sufficient dose of glycoxide can produce the epi-SL. We then introduce an epi-SL fabrication method that replaces point injection of a base with contactless and uniform illumination of a dissolved photobase. Quantitative mapping of multilayer (3D) films shows that our photobase-made epi-SLs are chemically and structurally uniform and have much lower concentrations of bulk defects compared to the highly inhomogeneous and defect-rich epi-SLs produced by amine point injection. The structural-chemical uniformity and structural perfection of photobase-made epi-SLs make them leading candidates for achieving emergent mini-band charge transport in a self-assembled mesoscale solid.

  PublisherDOI

• Emergence of distinct electronic states in epitaxially-fused PbSe quantum dot superlattices

  Nature Communications · 2022-11-10 · 17 citations

  articleOpen accessSenior author

  Quantum coupling in arrayed nanostructures can produce novel mesoscale properties such as electronic minibands to improve the performance of optoelectronic devices, including ultra-efficient solar cells and infrared photodetectors. Colloidal PbSe quantum dots (QDs) that self-assemble into epitaxially-fused superlattices (epi-SLs) are predicted to exhibit such collective phenomena. Here, we show the emergence of distinct local electronic states induced by crystalline necks that connect individual PbSe QDs and modulate the bandgap energy across the epi-SL. Multi-probe scanning tunneling spectroscopy shows bandgap modulation from 0.7 eV in the QDs to 1.1 eV at their necks. Complementary monochromated electron energy-loss spectroscopy demonstrates bandgap modulation in spectral mapping, confirming the presence of these distinct energy states from necking. The results show the modification of the electronic structure of a precision-made nanoscale superlattice, which may be leveraged in new optoelectronic applications.

  PublisherOA PDFDOI

• 2022 Coolloidal Semiconductor Nanocrystals GRC &amp; GRS

  2022-07-02

  articleOpen accessSenior author

  July 2-8, 2022.The meeting covered a variety of scientific topics and the content presented was

  PublisherOA PDFDOI

Recent grants

• An FTIR Spectrometer for the Development of Nanostructured Solar Cells and Novel Fuel Cell Materials

  NSF · $71k · 2010–2011

• SOLAR: Phase-Field Crystal Modeling and Analytical Surface Analysis of Iron Pyrite (FeS2) for Thin-Film Photovoltaics

  NSF · $1.6M · 2010–2014

Frequent coauthors

• Peidong Yang

  University of California, Berkeley

  94 shared

• Justin C. Johnson

  University of Michigan–Ann Arbor

  58 shared

• Richard J. Saykally

  52 shared

• Lori E. Greene

  University of California, Berkeley

  45 shared

• Arthur J. Nozik

  Northwestern University

  42 shared

• Matthew C. Beard

  National Renewable Energy Laboratory

  39 shared

• Joseph M. Luther

  National Renewable Energy Laboratory

  37 shared

• Donald J. Sirbuly

  University of California, San Diego

  36 shared