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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 451 records · Page 25
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Red-Colored Circularly Polarized Luminescence from a Benzo-Fused BODIPY-BINOL Complex

Red emission with sharp bandwidth and high quantum yield are desired characteristics for organic chromophores in optoelectronic, spintronic, and biomedical applications. Here, we observe circularly polarized luminescence (CPL) with these characteristics from a benzo-fused BODIPY-BINOL complex (1). Using time-resolved optical spectroscopy, electrochemistry, and density functional theory calculations, we showed that the emissive excited state of 1 does not have a charge-transfer character, unlike the regular BODIPY counterpart (2). In conclusion, the rigidity and the lack of charge-transfer character make this class of molecules an appealing platform for CPL-active molecules in the red spectral region with ample room for improvement in the dissymmetry factor and brightness.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Toward Metal-free Photocatalysis: Photochemical Regeneration of Organic Hydride Donors Using Phenazine-Based Photosensitizers

Earth-abundant chromophores and catalysts are important molecular building blocks for artificial photosynthesis applications. Our team previously reported that metal-free hydride donors, such as biomimetic benzoimidazole-based motifs, can reduce CO 2 selectively to the formate ion and that they can be electrochemically regenerated using the proton-coupled mechanism. To enable direct utilization of solar energy, we report here the photochemical regeneration of a benzoimidazole-based hydride donor using a phenazine-based metal-free chromophore. The photochemical regeneration was investigated under different experimental conditions involving varying sacrificial donors, proton donors, solvents, and component concentrations. The best hydride regeneration yield of 50% was obtained with phenol as a proton source and thiophenolate as a sacrificial electron donor. The mechanism of photochemical regeneration was studied using steady-state and time-resolved UV/Vis spectroscopies. Based on the results of these studies, we hypothesize that the initial photoinduced electron transfer from photoexcited phenazine chromophores involves the benzoimidazole cation and that this process is likely coupled with proton transfer to generate protonated benzoimidazole-based radical cation. The second photoinduced electron transfer is hypothesized to generate the hydride form. Furthermore, our findings provide the requisite information for the future development of reductive photocatalysts for solar energy and light-harvesting applications utilizing earth-abundant metal-free materials.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Conical Intersection Passages of Molecules Probed by X-ray Diffraction and Stimulated Raman Spectroscopy

Conical intersections (CoIns) play an important role in ultrafast relaxation channels. Their monitoring remains a formidable experimental challenge. We theoretically compare the probing of the S 2 → S 1 CoIn passage in 4-thiouracil by monitoring its vibronic coherences, using off-resonant X-ray-stimulated Raman spectroscopy (TRUECARS) and time resolved X-ray diffraction (TRXD). The quantum nuclear wavepacket (WP) dynamics provides an accurate picture of the photoinduced dynamics. Upon photoexcitation, the WP oscillates among the Franck–Condon point, the S2 minimum, and the CoIn with a 70 fs period. A vibronic coherence first emerges at 20 fs and can be observed until the S 2 state is fully depopulated. The distribution of the vibronic frequencies involved in the coherence is recorded by the TRUECARS spectrogram. Here, the TRXD signal provides spatial images of electron densities associated with the CoIn. In combination, the two signals provide a complementary picture of the nonadiabatic passage, which helps in the study of the underlying photophysics in thiobases.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Effect of Water Concentration in LiPF 6 -Based Electrolytes on the Formation, Evolution, and Properties of the Solid Electrolyte Interphase on Si Anodes

A trace amount of water in an electrolyte is one of the factors detrimental to the electrochemical performance of silicon (Si)-based lithium-ion batteries that adversely affect the formation and evolution of the solid electrolyte interphase (SEI) on Si-based anodes and change its properties. Thus far, a lack of fundamental and mechanistic understanding of SEI formation, evolution, and properties in the presence of water has inhibited efforts to stabilize the SEI for improved electrochemical performance. As such, we investigated the SEI formed in a Gen2 electrolyte (1.2 M LiPF6 in ethylene carbonate/ethyl methyl carbonate, 3:7 wt %, water content: <10 ppm) with and without additional water (50 ppm) at varying potentials (1.0, 0.5, 0.2, and 0.01 V vs Li/Li + ). The impact of additional water on the morphological, (electro)chemical, and structural properties of SEI was studied using microscopic (atomic force microscopy and scanning spreading resistance microscopy) and spectroscopic (X-ray photoelectron spectroscopy, attenuated total reflection Fourier-transform infrared spectroscopy, and time-of-flight secondary ion mass spectrometry) techniques. The SEI exhibits both potential- and water concentration-dependent trends in its morphology and chemical composition. The presence of additional water in the electrolyte causes parasitic reactions, which onset at ~1.0 V, resulting in a reduction of electrolyte components and result in the formation of an insulating, fluorophosphate-rich SEI. In addition, hydrolysis of LiPF 6 creates hydrofluoric acid, which reacts with the surface oxide layer on the Si electrode, leading to a pitted and inhomogeneous SEI structure.

36 MATERIALS SCIENCE↗
DOE OSTI2026

“Antenna-like” Light-Harvesting in Partially Metalated Porphyrin Hydrogen-Bonded Organic Frameworks

Arrays of light harvesting molecules with long-range order hold promise as materials capable of efficient collection of photons as well as rapid transport of captured solar energy to chemical catalysts. Hydrogen-bonded organic frameworks (HOFs) could be promising artificial light-harvesting platforms, due to their crystalline nature and their comparative ease of synthesis. In this work, mixed-linkers of either zinc-metallated or free base tetrakis(4-carboxyphenyl)porphyrin HOFs were examined and found to demonstrate ‘antenna-like’ light harvesting behavior. Using time-resolved emission spectroscopy, Förster resonance energy transfer from zinc porphyrin to free-base porphyrin was assessed. Based on changes in the emission peak profile as the ratio of zinc porphyrin to free-base porphyrin is varied, we find that, in the limit of 100% zinc porphyrin, a photogenerated exciton can sample ~48 chromophores. These findings suggest that stacked linkers within HOFs can act as light harvesting ‘antennae’ and with encapsulation of suitable catalysts, may offer prospective application as photochemical energy conversion systems.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Large Polaron Screening Delays Mobility Roll-Off in Halide Perovskites under High Injection

The interplay between carrier density regimes and the various scattering processes is fundamental for understanding charge transport efficiency in high-performance semiconductors. Combining ultrafast time-resolved terahertz spectroscopy (TRTS) and transient microwave photoconductivity (TRMC), we measure carrier mobilities over 7 orders of magnitude (10 13 –10 20 carriers cm –3 ), reaching a regime where carrier–carrier scattering dominates and mobility begins to roll off. We find the Caughey–Thomas model can be effectively employed for transport modeling in 3D metal halide perovskites (MHPs), and the mobility roll-off near ∼10 19 cm –3 can be tuned by MHP composition. Carrier lifetime in MHPs starts decreasing at much lower carrier densities due to interband multi-carrier recombination, while intraband carrier mobility remains unchanged as carrier–carrier scattering is screened by the presence of polarons. The validated Caughey–Thomas model provides a practical input for device simulations, prevents overestimation of diffusion length under high injection, and suggests that MHPs are excellent candidates for unipolar device applications under high carrier densities.

14 SOLAR ENERGY↗
DOE OSTI2022

Thickness- and Twist-Angle-Dependent Interlayer Excitons in Metal Monochalcogenide Heterostructures

Interlayer excitons, or bound electron-hole pairs whose constituent quasiparticles are located in distinct stacked semiconducting layers, are being intensively studied in heterobilayers of two dimensional semiconductors. They owe their existence to an intrinsic type-II band alignment between both layers that convert these into p-n junctions. Here, we unveil a pronounced interlayer exciton (IX) in heterobilayers of metal monochalcogenides, namely gamma-InSe on epsilon-GaSe, whose pronounced emission is adjustable just by varying their thicknesses given their number of layers dependent direct bandgaps. Time-dependent photoluminescense spectroscopy unveils considerably longer interlayer exciton lifetimes with respect to intralayer ones, thus confirming their nature. The linear Stark effect yields a bound electron-hole pair whose separation d is just (3.6 ± 0.1) Å with d being very close to d Se = 3.4 Å which is the calculated interfacial Se separation. The envelope of IX is twist angle dependent and describable by superimposed emissions that are nearly equally spaced in energy, as if quantized due to localization induced by the small moiré periodicity. Furthermore, these heterostacks are characterized by extremely flat interfacial valence bands making them prime candidates for the observation of magnetism or other correlated electronic phases upon carrier doping.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Transport of Delocalized Excitons through DNA-Based Molecular Photonic Wires

Molecular photonic wires conduct electronic energy via their rapid transport properties. In photosynthesis, nature achieves efficient transport across large distances using delocalized excitons, generated by strong excitonic coupling between chromophores. How, or even whether, delocalization facilitates long-distance energy transport in synthetic systems has been challenging to experimentally test and optimize. Thus, far, studies have been limited to strongly coupled, heterogeneous chromophore aggregates or weakly coupled chromophore monomers. Here, in this work, we employed DNA nanostructures to engineer molecular photonic wires constructed from a series of excitonically coupled indocarbocyanine chromophores─achieving the intermediate and strong coupling regimes. Using time-resolved fluorescence spectroscopy and complementary simulations, we demonstrated that an intermediate intermolecular electronic coupling (∼ k B T ) enables up to 40% faster exciton transport as compared to strongly coupled chromophores. The delocalized excitons generated in the intermediate coupling regime exhibited properties conducive to rapid diffusivity, similar to their monomeric counterparts. Thus, intermediate excitonic coupling, analogous to natural systems, achieves long-distance exciton transport with the high chromophore density required for energy capture.

DNA origami↗
DOE OSTI2025

Dynamic Behavior of Bound Interlayer Excitons in Interlayer-Doped Cs 3 Bi 2 Br 9 Vacancy-Ordered Perovskite

Interlayer doping of the vacancy-ordered 2D perovskite Cs 3 Bi 2 Br 9 (CBB) enables the formation of bound interlayer excitons (BIEs), a unique charge-transfer excited state within the layered solid. BIEs previously reported with silver (Ag + ) as an interlayer dopant exhibited bright broadband photoluminescence (PL) with prolonged lifetime at room temperature, offering potential applications in efficient white light emission, photocatalysis, and optoelectronics. However, the dynamic behavior of radiation and excited carriers remains poorly understood due to the limitations of ensemble spectroscopic measurements. Here, we investigate the temperature-dependent dynamics of Ag-doped Cs 3 Bi 2 Br 9 (Ag-CBB) using single-particle time-resolved PL spectroscopy and ultrafast transient absorption imaging. Single-particle PL measurements reveal three distinct emission regimes across temperature: (i) BIE-dominant emission at high temperatures, (ii) a mixture of radiation from BIEs and self-trapped excitons (STEs) at intermediate temperatures, and (iii) STE-dominant emission below 100 K. Rapid transient absorption mapping using Parallel Rapid Imaging with Spectroscopic Mapping (PRISM) reveals subpicosecond STE formation in pristine CBB and long-lived photoinduced absorption by BIEs, consistent with electron–hole separation and suppressed STE transfer. The spatial uniformity of these signals confirms homogeneous Ag doping across single crystals. These findings highlight the role of Ag interlayer dopants in governing the BIE dynamics.

bound interlayer exciton↗
DOE OSTI2022

Charge Delocalization and Vibronic Couplings in Quadrupolar Squaraine Dyes

Squaraines are prototypical quadrupolar charge-transfer chromophores that have recently attracted much attention as building blocks for solution-processed photovoltaics, fluorescent probes with large two-photon absorption cross sections, and aggregates with large circular dichroism. Their optical properties are often rationalized in terms of phenomenological essential state models, considering the coupling of two zwitterionic excited states to a neutral ground state. As a result, optical transitions to the lowest S 1 excited state are one-photon allowed, whereas the next higher S 2 state can only be accessed by two-photon transitions. A further implication of these models is a substantial reduction of vibronic coupling to the ubiquitous high-frequency vinyl-stretching modes of organic materials. Here, in this study, we combine time-resolved vibrational spectroscopy, two-dimensional electronic spectroscopy, and quantum-chemical simulations to test and rationalize these predictions for nonaggregated molecules. We find small Huang–Rhys factors below 0.01 for the high-frequency, 1500 cm –1 modes in particular, as well as a noticeable reduction for those of lower frequency modes in general for the electronic S 0 → S 1 transition. The two-photon allowed state S 2 is well separated energetically from S 1 and has weak vibronic signatures as well. Thus, the resulting pronounced concentration of the oscillator strength in a narrow region relevant to the lowest electronic transition makes squaraines and their aggregates exceptionally interesting for strong and ultrastrong coupling of excitons to localized light modes in external resonators with chiral properties that can largely be controlled by the molecular architecture.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Oxidation Chemistry of Bicarbonate and Peroxybicarbonate: Implications for Carbonate Management in Energy Storage

Carbonate formation presents a major challenge to energy storage applications based on low-temperature CO 2 electrolysis and recyclable metal–air batteries. While direct electrochemical oxidation of (bi)carbonate represents a straightforward route for carbonate management, knowledge of the feasibility and mechanisms of direct oxidation is presently lacking. Herein, we report the isolation and characterization of the bis(triphenylphosphine)iminium salts of bicarbonate and peroxybicarbonate, thus enabling the examination of their oxidation chemistry. Infrared spectroelectrochemistry combined with time-resolved infrared spectroscopy reveals that the photoinduced oxidation of HCO 3 – by an Ir(III) photoreagent results in the generation of the short-lived bicarbonate radical in less than 50 ns. The highly acidic bicarbonate radical undergoes proton transfer with HCO 3 – to furnish the carbonate radical anion and H 2 CO 3 , leading to the eventual release of CO 2 and H 2 O, thus accounting for the appearance of H 2 O and CO 2 in both electrochemical and photochemical oxidation experiments. Here, the back reaction of the carbonate radical subsequently oxidizes the Ir(II) photoreagent, leading to carbonate. In the absence of this back reaction, dimerization of the carbonate radical provides entry into peroxybicarbonate, which we show undergoes facile oxidation to O 2 and CO 2 . Together, the results reported identify tangible pathways for the design of catalysts for the management of carbonate in energy storage applications.

25 ENERGY STORAGE↗
DOE OSTI2023

Direct Evidence for Excited Ligand Field State-based Oxidative Photoredox Chemistry of a Cobalt(III) Polypyridyl Photosensitizer

Increasing interest in sustainable chemistry coupled with the quest to explore new reactivity has spurred research on first-row transition metal complexes for potential applications in a variety of settings. One of the more active areas of research is photoredox catalysis, where the synthetically tunable nature of their electronic structures provides a rich palette of options for tailoring their reactivity to a desired chemical transformation. Understanding the mechanism of excited-state reactivity is critical for the informed development of next-generation catalysts, which in turn requires information concerning the propensity of their electronic excited states to engage in the desired electron or energy transfer processes. Herein we provide direct evidence of the highly oxidizing nature of the lowest-energy ligand-field (LF) excited state of a first-row d 6 -low-spin Co(III) photosensitizer [Co(4,4'-Br 2 bpy) 3 ] 3+ (where 4,4'-Br 2 bpy is 4,4'-dibromo-2,2'-bipyridine). The redox potential associated with the LF excited state of the Co(III) complex was bracketed by performing bimolecular quenching studies by using a series of simple organic electron donors. Time-resolved absorption spectroscopy confirmed a dynamic quenching process attributed to reductive quenching of the lowest-energy ligand-field excited state of the Co(III) chromophore. Analysis of the Stern–Volmer plots for each chromophore-quencher pair revealed a limiting value of E red * ~ 1.25 V vs Fc/Fc + for the metal-centered excited state, which is significantly stronger than that of more commonly employed transition metal-based photoredox agents such as [Ru(bpy) 3 ] 2+ (E red * = 0.32 V vs Fc/Fc + ) and [Ir(ppy) 2 (bpy)] + (E red * = 0.27 V vs Fc/Fc + ). Finally, these results suggest that this class of chromophores could find utility in applications requiring the activation of oxidatively resistant organic substrates for photoredox catalysis.

14 SOLAR ENERGY↗
DOE OSTI2025

Efficient Self-Sensitized Photochemical CO 2 Reduction Using [Re(bpy 2+ )(CO) 3 (I)] 2+ and [Re(bpy 2+ )(CO) 3 (CH 3 CN)] 3+ Photocatalysts with Pendent Ammonium Cations

Rhenium(I) tricarbonyl complexes fac-[Re(bpy)(CO) 3 (L)]n + are the classical examples of self-sensitized photocatalysts capable of the dual roles of light absorption and catalysis. Here, in this work, a series of dicationic halido or tricationic solvento complexes fac-[Re(bpy 2+ )(CO) 3 X] n+ (PF 6 ) n (where X = Cl - or I - (n = 2), or CH 3 CN (n = 3) and bpy 2+ is bipyridine modified by two -CH 2 -(NMe3) + tetra-alkylammonium cations) have been investigated as self-sensitized and sensitized CO 2 reduction photocatalysts. Four structural isomers differing in the cation position have been tested in N,Nʹ-dimethylacetamide solvent (DMA) using 1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzimidazole (BIH) as the electron donor, and the position of the cationic pendants has a significant impact on the catalyst turnover number and quantum efficiency (ϕ). Up to 455 self-sensitized turnovers of CO and a high photon efficiency (ϕ CO ) of 22% have been achieved. Time-resolved infrared spectroscopy and theoretical calculations were used to characterize the catalytic cycle including the ligand exchange between one-electron reduced (OER) halido and solvento species as well as the binding of CO 2 to the putative two-electron reduced (TER) species. The CO 2 -reactive TER catalyst was formed by disproportionation or intramolecular electron transfer between two forms of the OER catalyst as indicated by the formation of the fully oxidized catalyst concurrent with CO 2 binding. When [Ru(bpy) 3 ] 2+ was used as a sensitizer, catalyst durability improved, and the selectivity toward formate increased as high as 3.3:1 over CO (total TON = 1370) due to acidification of the reaction, which promotes formation of the hydride intermediate, as BIH was consumed and deprotonated.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Quantitative Determination of Electronic Effects in Free Radicals through Open-Shell Hammett Substituent Constants

Hammett substituent constants (σ), which quantify the electronic effects of functional groups, are widely used for predicting the properties of organic compounds and investigating reaction mechanisms. While these values have been obtained for a wide range of closed-shell substituents, measurements of analogous values for open-shell substituents are rare due to challenges associated with their short lifetimes. Here, in this report, we developed a combined experimental and computational approach for quantifying the electronic properties of open-shell substituents based on changes in nitrile vibrational frequencies (ν(C≡N)). By coupling pulse radiolysis and time-resolved infrared spectroscopy (PR-TRIR), we measured ν(C≡N) IR bands of 30 para - and meta -substituted benzonitriles bearing C-, N-, and S-centered radicals. A linear scaling relationship was obtained between these experimental values and values obtained from DFT calculations. Using these computed values, two different Hammett constants, σ m , and σ p + , were determined for a series of C-, N-, O-, S-, Si-, and B-centered radicals. The differences between σm and σp+ values enable the separate evaluation of inductive and resonance effects in these open-shell substituents. The results suggest that there are three classes of radicals: one is electron withdrawing (σ m , σ p + > 0), one is electron donating (σm, σp+ < 0), and one is inductively withdrawing but resonance donating (σ m > 0, σ p + < 0). Our study represents a general approach to the analysis of the electronic properties of open-shell species and has potential applications in a wide range of molecular processes involving free radical intermediates.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Enhanced Menshutkin S N 2 Reactivity in Mesoporous Silica: The Influence of Surface Catalysis and Confinement

A significant enhancement in the Menshutkin S N 2 reaction between 1-methylimidazole (MeIm) and methyl thiocyanate (MeSCN) is observed when the reaction is confined in the nanoscale silica pores of MCM41 and SBA15. The experiments in the silica pores are conducted without surrounding bulk reaction mixture. The influences of temperature, pore radius, and surface chemistry on the kinetics of the confined reaction are analyzed with time-dependent infrared spectroscopy, molecular dynamics simulations, and ab initio calculations. The rate constant of the pseudo-first order reaction increases with decreasing pore size, and the activation energy is found to decrease by 5.6 kJ/mol in the smallest pore studied (2.8 nm) relative to the bulk reaction. The rate constant dependence on pore size is accurately described by a two-state model in which molecules within the 4.6 Å interfacial layer experience a 2.4-fold rate constant increase relative to those reacting at the bulk rate further away from the interface. The removal of polar silanol groups from the silica surface via passivation with trimethylsilyl chloride results in bulk-like kinetics despite a reduction in the pore diameter, demonstrating the role of silanols as catalytic sites. Here, electronic structure calculations of the energy profile on a model silica surface confirm that silanol groups, particularly those of the vicinal type, can reduce the activation energy and reaction endothermicity through the donation of hydrogen bonds to the reactant, transition state, and product complexes.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Indistinguishable photons from an artificial atom in silicon photonics

Silicon is the ideal material for building electronic and photonic circuits at scale. Integrated photonic quantum technologies in silicon offer a promising path to scaling by leveraging advanced semiconductor manufacturing and integration capabilities. However, the lack of deterministic quantum light sources and strong photon-photon interactions in silicon poses a challenge to scalability. In this work, we demonstrate an indistinguishable photon source in silicon photonics based on an artificial atom. We show that a G center in a silicon waveguide can generate high-purity telecom-band single photons. We perform high-resolution spectroscopy and time-delayed two-photon interference to demonstrate the indistinguishability of single photons emitted from a G center in a silicon waveguide. Our results show that artificial atoms in silicon photonics can source single photons suitable for photonic quantum networks and processors.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2024

Molecular catalyst coordinatively bonded to organic semiconductors for selective light-driven CO 2 reduction in water

The selective photoreduction of CO 2 in aqueous media based on earth-abundant elements only, is today a challenging topic. Here we present the anchoring of discrete molecular catalysts on organic polymeric semiconductors via covalent bonding, generating molecular hybrid materials with well-defined active sites for CO 2 photoreduction, exclusively to CO in purely aqueous media. The molecular catalysts are based on aryl substituted Co phthalocyanines that can be coordinated by dangling pyridyl attached to a polymeric covalent triazine framework that acts as a light absorber. This generates a molecular hybrid material that efficiently and selectively achieves the photoreduction of CO 2 to CO in KHCO 3 aqueous buffer, giving high yields in the range of 22 mmol g -1 (458 μmol g -1 h -1 ) and turnover numbers above 550 in 48 h, with no deactivation and no detectable H 2 . The electron transfer mechanism for the activation of the catalyst is proposed based on the combined results from time-resolved fluorescence spectroscopy, in situ spectroscopies and quantum chemical calculations.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Time-resolved chemically-selective spectroscopic investigation of the redox reaction between hematite and aluminium

Thermite reactions –highly energetic redox processes between a metal and an oxide—are used in welding, propulsion, and the fabrication of advanced materials. When reduced to the nanoscale, these reactions exhibit enhanced energetic performance, but their ultrafast dynamics remain poorly understood. Gaining insight into charge transfer during these processes is essential for advancing applications in energy conversion and materials design. Here we show that the reaction between aluminium and hematite, a common iron oxide, can be tracked with femtosecond resolution using extreme ultraviolet (EUV) time-resolved absorption spectroscopy at the Fe M 2,3 and Al L 2,3 edges. By exciting the system with an ultrashort optical pulse and probing element-specific absorption changes, we observe an early spectral shift that reveals the formation of localized charge carriers (polarons). Comparing samples with different supporting substrates highlights ultrafast electron transfer from aluminium to hematite. These results demonstrate an approach to investigating charge flow in energetic materials and provide a basis for studying fast chemical reactions with chemical specificity.

Electron transfer↗