Daniel R. Gamelin
VerifiedUniversity of Washington · Chemistry
Active 1994–2026
About
Daniel R. Gamelin is a professor at the University of Washington, holding the Nicole A. Boand Endowed Chair in Chemistry. His research focuses on areas within chemistry, and he is involved in advancing knowledge in this field through his academic and scientific activities. As a faculty member, he contributes to the department's mission of education and research, fostering developments in chemical sciences.
Research topics
- Materials science
- Nanotechnology
- Chemistry
- Engineering
- Optoelectronics
- Inorganic chemistry
- Computer Science
- Physics
- Optics
- Quantum mechanics
- Metallurgy
- Crystallography
- Psychology
- Electrical engineering
Selected publications
Synthesis and Magnetism of Silver Chromium Selenide Spinels
ChemRxiv · 2026-05-10
articleChalcogenide spinels exhibit electronic and magnetic properties that are tunable through lattice occupancy and composition. We report the first synthesis of spinel-phase Ag2Cr2Se4 and AgCr2Se4 and demonstrate an oxidation-induced ferro-to-ferrimagnetic transition associated with Ag+ site occupancy. The Ag spinels are synthesized through air-free cation exchange of CuCr2Se4 nanocrystals driven by excess AgNO3 to yield the ferromagnetic Ag2Cr2Se4 (a = 10.840(3) Å, TC = 151 K, 2 K saturation = 3.1 μB/Cr) with Ag+ occupying both Td 8a and Oh 16c sites. Upon air exposure, Ag2Cr2Se4 converts to ferrimagnetic AgCr2Se4 (a = 10.610(3) Å, TC > 400 K, 2 K saturation = 2.2 μB/Cr) through a loss of Oh-Ag+ alongside the formation of Ag2Se. We attribute the ferro-to-ferrimagnetic transition to the generation of holes in Ag–Se bands, which couple antiferromagnetically to Cr3+. This Ag–Cr–Se spinel system provides an excellent framework for further exploration of magnetic coupling as a function of oxidation and structure.
ACS Applied Materials & Interfaces · 2026-04-22
articleUnderstanding the interfacial energetics between low-dimensional semiconductors and metal electrodes is pivotal for optimizing charge injection and extraction in optoelectronic devices. In this work, we systematically investigate the energy-level alignment at the interface between the two-dimensional (2D) Ruddlesden–Popper perovskite (PEA)2CrCl4 and metal substrates with contrasting work functions (WFs), namely silver (Ag) and gold (Au). Kelvin probe force microscopy (KPFM) is performed to acquire surface potential maps of the perovskite between bulk and atomic thicknesses, revealing pronounced thickness-dependent modulation of interfacial energetics. These measurements also uncover a complex interplay between interfacial dipoles, defect states, and metal-induced gap states, leading to varied degrees of Fermi-level pinning (FLP). Temperature-dependent KPFM further reveals thermally induced shifts in the interfacial energetics. The Au interface exhibits strong FLP and stable electronic coupling, while the Ag interface manifests higher sensitivity to thermally activated interfacial dipoles and defect states. These findings underscore the sensitivity of 2D perovskite interfaces to metal WF and surface chemistry, offering important insights for tailoring contact properties in perovskite-based optoelectronic devices.
Chemistry of Materials · 2026-02-12
articleSenior authorCorrespondingColloidal fluoride nanocrystals containing luminescent rare-earth ions are powerful nanophosphors for bioimaging, optical sensing, and other photonic functions. The utility of luminescent fluoride nanocrystals could be broadened if a greater composition space could be accessed by the development of new synthetic capabilities. Here, we report a general solution-phase fluoride-salt synthesis method that allows preparation of colloidal fluoro-elpasolite and -cryolite nanocrystals, two phases that have received little attention at the nanoscale. We demonstrate that this synthetic method is compatible with various trivalent (e.g., Cr3+, Al3+, Ga3+) and monovalent (e.g., Cs+, Na+, NH4+) cations, providing access to a rich portfolio of ternary and quaternary fluoride nanocrystals. In particular, this method is used to prepare the Cr3+-based fluoro-elpasolite Cs2NaCrF6 on the nanoscale. Broadband near-infrared Cr3+ 4T2g → 4A2g emission is observed at room temperature from these nanocrystals. Under related conditions, analogous Cr3+-based cryolite nanocrystals (Na3CrF6) could also be prepared. With this method, Yb3+ was successfully doped into Cs2NaCrF6 nanocrystals at various concentrations. Cr3+ d–d transitions are found to sensitize the Yb3+ f–f luminescence at room temperature, and broad tunability of the relative photoluminescence intensities of Cr3+ and Yb3+ was achieved via composition control. The utility of this synthesis method for preparing these ternary and quaternary nanocrystals with complex and tunable compositions suggests opportunities for the development of other challenging fluoride lattices on the nanoscale using this approach.
Optically Active Yb3+ Spin Defects in Cerium Oxide Nanocrystals
ChemRxiv · 2026-03-09
articleOpen accessNanocrystalline CeO 2 is a chemically tunable wide-bandgap host lattice of interest for quantum information technologies due to its ability to accommodate optically-and spin-active defects. Here, we investigate CeO 2 nanocrystals as hosts for near-infrared-compatible Yb 3+ ions as optically active spin quantum bits (qubits). We characterize the as-synthesized Yb 3+ -doped CeO 2 nanocrystals (0.01-10% Yb) by photoluminescence, which reveals short photoluminescence lifetimes dominated by non-radiative decay arising from surface and Ce 3+ -related defects. Thermal annealing at 700 °C increases crystalline domain sizes (from ~7 nm to ~20 nm) and reduces the concentration of Ce 3+ defects, yielding an enhancement in excited-state lifetimes. Low-temperature optical spectroscopy reveals at least two distinct Yb 3+ lattice sites with cubic and trigonal symmetries, and a ~5-fold difference in photoluminescence lifetimes between the two sites. Continuous-wave EPR measurements support these site assignments, while pulse EPR measurements further show that annealing the nanocrystals nearly doubles the spin-lattice relaxation time ( T 1 ) from 33.9 to 62.7 µs at 0.08% Yb. Phase memory times, however, remain relatively constant, indicating that coherence is limited by dephasing mechanisms (e.g., slowly fluctuating local fields or spectral diffusion) rather than by spin-lattice relaxation. Collectively, these results establish defect mitigation, rather than dopant identity alone, as a bottleneck in realizing nanocrystalline CeO 2 as a viable quantum host. This work provides quantitative benchmarks for optical and spin coherence in CeO 2 :Yb 3+ nanocrystals and highlights defect engineering as a critical pathway toward scalable rare-earth-based qubits.
Inorganic Chemistry · 2026-03-05
articleSenior authorCorrespondingWe report the synthesis of a library of colloidal Zr4+-, Ti4+-, and Si4+-based A2BF6 (A = Na+, Cs+, NH4+, and N(CH3)4+) nanocrystals. These lattices are synthesized without the use of aqueous HF but instead are prepared using safer fluoride salt precursors dissolved in nonpolar solutions. We show that nanocrystal morphologies, including shape anisotropy, are altered when various synthetic parameters are adjusted, including reaction temperature, time, and solvent polarity. Nucleation and growth pathways of A2ZrF6 compositions are compared. An in situ A-site cation exchange requiring internal anion sublattice reorganization is described that allows for conversion of anisotropic (NH4)2ZrF6 nanorods into Cs2ZrF6 nanorods that could not be prepared directly. The development of colloidal nanocrystals as a new form factor for A2BF6 lattices addresses fundamental synthesis challenges in inorganic nanoscience and lays the groundwork for future work into doping such nanocrystals for solution-phase photonic applications, processing, or printing.
Physical Review Materials · 2026-05-01
articleSenior authorThe Journal of Physical Chemistry C · 2026-02-02
articleSenior authorJournal of the American Chemical Society · 2026-03-30
articleSenior authorCorrespondingThe rich magnetic properties of rare-earth orthochromites (RCrO3) have been studied for decades, but luminescence from their rare-earth ions has not been reported. We report the photoluminescence (PL) of faceted microcrystals of the G-type antiferromagnetic orthochromites YCrO3, Yb3+-doped YCrO3, and YbCrO3 (i.e., Y1-xYbxCrO3, 0 ≤ x ≤ 1), prepared via a molten-salt synthesis. The 4 K PL of the Yb3+-containing samples is dominated by narrow multiline f–f emission from Yb3+, with most intensity concentrated into two pronounced lines associated with the 2F5/2(0′) → 2F7/2(0) crystal-field transition that are split by ∼13 cm–1 at 4 K. This splitting is attributed to Cr3+-Yb3+ magnetic exchange coupling, which spontaneously lifts Yb3+ Kramers degeneracies upon ordering of the Cr3+ spin sublattice. The splitting energy decreases with increasing temperature, and the two peaks eventually coalesce at the orthochromite’s magnetic-ordering temperature of TN = 118 – 140 K (depending on composition). All compositions show pronounced Cr3+-Yb3+ simultaneous pair excitation (SPE) bands at 407 nm in their Yb3+ PL excitation (PLE) spectra, with this SPE feature dominating the PLE spectra at room temperature. Variable-temperature PL and PLE measurements reveal that Yb3+ PL sensitization via Cr3+ d–d excitation is ineffective due to efficient nonradiative deactivation of the 2Eg state, whereas simultaneous pair excitation circumvents the need for intervening energy-transfer steps. The ability to monitor lattice spin correlation using Yb3+ PL up to relatively high temperatures suggests exploration of such microstructures as local spin probes, microscale spin-photonic transducers, or magnetically tunable emitters.
The Journal of Physical Chemistry C · 2025-06-10 · 1 citations
articleSenior authorCorrespondingExcitons in two-dimensional (2D) magnetic van der Waals (vdW) materials offer unique windows into the properties of strongly correlated electrons. Their generation can be used to drive magnetic phase transitions, manipulate spins coherently, or access novel nonequilibrium regimes. Despite extensive investigation into the spin physics of CrI3, exciton dynamics in this archetypal magnetic 2D material remain underexplored. Here, we report the use of Yb3+ impurity point defects as exciton annihilators to probe exciton diffusion in CrI3. Variable-temperature photoluminescence (PL) measurements for a series of x% Yb3+:CrI3 samples reveal thermally activated Dexter-type site-to-site hopping of excitons, with low exciton diffusivity associated with strong electron–nuclear coupling. Using Monte Carlo modeling calibrated by the experimental data, diffusivities are found to be orders of magnitude lower than in 2D vdW semiconductors. Exciton diffusion lengths (LD) are below ∼3 nm at all temperatures, and thus well below the optical diffraction limit. These results have basic implications for the use of excitons to probe and manipulate their surroundings in this and related magnetic CrX3 materials.
ChemRxiv · 2025-10-14
articleSenior authorColloidal fluoride nanocrystals containing luminescent rare-earth ions are powerful nanophosphors for bio-imaging, optical sensing, and other photonic functions. The utility of luminescent fluoride nanocrystals could be broadened if a greater composition space could be accessed by development of new synthetic capabilities. Here, we report a general solution-phase fluoride-salt synthesis method that allows preparation of high-quality colloidal fluoro-elpasolite and -cryolite nanocrystals, two phases that have received little attention at the nanoscale. We demonstrate that this synthetic method is compatible with various trivalent (e.g., Cr3+, Al3+, Ga3+) and monovalent (e.g., Cs+, Na+, NH4+) cations, providing access to a rich portfolio of ternary and quaternary fluoride nanocrystals. In particular, this method is used to prepare the Cr3+-based fluoro-elpasolite Cs2NaCrF6 for the first time on the nanoscale. Broadband near-infrared Cr3+ 4T2g → 4A2g emission is observed at room temperature from these nanocrystals. Under related conditions, analogous Cr3+-based cryolite nanocrystals (Na3CrF6) could also be prepared. With this method, Yb3+ was successfully doped into the Cs2NaCrF6 nanocrystals at various concentrations. Cr3+ d-d transitions are found to sensitize the Yb3+ f-f luminescence at room temperature, and broad tunability of the relative photoluminescence intensities of Cr3+ and Yb3+ was achieved via composition control. The utility of this synthesis method for preparing these ternary and quaternary nanocrystals with complex and tunable compositions suggests opportunities for development of other challenging fluoride lattices on the nanoscale using this approach.
Recent grants
Reduced colloidal metal-oxide nanocrystals as novel redox reagents
NSF · $553k · 2012–2016
NSF · $553k · 2003–2008
CRC: Electronically Active Defects in Magnetic ZnO Films and Nanocrystalline Aggregates
NSF · $2.5M · 2006–2012
New Photophysical Processes in Impurity Doped Quantum Dots
NSF · $457k · 2015–2018
MRSEC: UW Molecular Engineering Materials Center
NSF · $16.0M · 2017–2023
Frequent coauthors
- 59 shared
Edward I. Solomon
SLAC National Accelerator Laboratory
- 30 shared
Kevin R. Kittilstved
University of Massachusetts Amherst
- 26 shared
Stefan T. Ochsenbein
ETH Zurich
- 26 shared
Paul Archer
University of Manchester
- 23 shared
Rémi Beaulac
Michigan State University
- 22 shared
Christine K. Luscombe
Okinawa Institute of Science and Technology Graduate University
- 22 shared
Dana A. Schwartz
University of Washington
- 22 shared
Xiaosong Li
Awards & honors
- Paul B. Hopkins Endowed Faculty Award, 2023
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