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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 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Water-Dispersible CsPbBr 3 Perovskite Nanocrystals with Ultra-Stability and its Application in Electrochemical CO 2 Reduction

Thanks to the excellent optoelectronic properties, lead halide perovskites (LHPs) have been widely employed in high-performance optoelectronic devices such as solar cells and light-emitting diodes. However, overcoming their poor stability against water has been one of the biggest challenges for most applications. Herein, we report a novel hot-injection method in a Pb-poor environment combined with a well-designed purification process to synthesize water-dispersible CsPbBr 3 nanocrystals (NCs). The as-prepared NCs sustain their superior photoluminescence (91% quantum yield in water) for more than 200 days in an aqueous environment, which is attributed to a passivation effect induced by excess CsBr salts. Thanks to the ultra-stability of these LHP NCs, for the first time, we report a new application of LHP NCs, in which they are applied to electrocatalysis of CO 2 reduction reaction. Noticeably, they show significant electrocatalytic activity (faradaic yield: 32% for CH 4 , 40% for CO) and operation stability (> 350 h).

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

Electrosynthesis of high purity ethylene using high-index facet Cu 2 O nanocrystals electrocatalyst

Electrochemical CO 2 reduction reaction (eCO2RR) to multi-carbon (C 2+ ) products with copper-based catalysts is often limited by poor selectivity. This challenge arises from the concurrent formation of various intermediates, dictated by the atomic arrangement and electronic properties of surface atoms. In this study, we found that copper (I) oxide (Cu 2 O) nanocrystals with 50 facets (50F-NC), predominantly featuring (211) facets that offers high density of under-coordinated sites, demonstrate superior ethylene (C 2 H 4 ) selectivity of 92% ± 2 with an overall current density of 212 mA/cm 2 at -650 mV vs RHE. Furthermore, after one month of storage in a 1 M KOH electrolyte, this catalyst demonstrated a C 2 H 4 Faradaic efficiency of 87% highlighting its stabile structure under strong alkaline environments. Here, operando electrochemical Raman spectroscopy revealed enhanced CO* intermediate coverage on the 50F-NC catalyst, correlating with improved C-C coupling. SEM, TEM, and XPS analyses, along with DFT calculations, suggested that Cu sites on the (211) facet of 50F-NC and those at the Cu/Cu 2 O interface formed in-situ due to the surface reconstruction during the reaction, are likely active sites for effective C-C coupling and sustained high-rate C 2 H 4 production.

Cu nano particle↗
DOE OSTI2022

On the surface passivating principle of functional thiol towards efficient and stable perovskite nanocrystal solar cells

Inorganic halide perovskite nanocrystals (PNCs) have demonstrated promising potential for solar cell applications. However, the lability of photoactive CsPbI3 phase under ambient conditions, coupled with considerable amounts of surface defects induced during solidification process, have impeded achieving high performances and longevities of the PNC-based solar cells. Post-treatment of the PNCs with organic ligands has been proposed as an efficient strategy for surface passivation, which, however, still relies on the binding actions of typical functional groups towards surface defects (especially, carboxylates onto iodine vacancies). Herein, we uncover that thiolate, a deprotonated form of thiol, renders distinctive binding feasibility towards iodine vacancies at the CsPbI3 PNC surface, compared with those of typical functional groups. By treating the PNC solid with deprotonated cysteine as a ligand, the surface defects are comprehensively passivated. The solar cells with the modified PNC films demonstrate an excellent PCE of 15.5 % and improved device longevity (77 % of initial PCE over 2 months) under ambient conditions. Our work not only elucidates the chemical principles of thiol on the binding with PNC surface, but also corroborates the power of thiolate as a promising strategy to develop high performances and improved longevity of solar cells.

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

Decoupling size and surface effects of intermetallic CuPd nanocrystals for electrocatalytic nitrate reduction to ammonia

Nitrate pollution poses a major environmental challenge, but its electrochemical conversion to ammonia offers a sustainable waste-to-value solution. Here, in this study, we synthesized monodisperse, size-tunable B2-phase CuPd intermetallic nanocrystals (6–46 nm) and studied their performance in the electrochemical nitrate reduction reaction (eNO 3 RR). By using bromide ions to modulate Pd reduction and applying mild annealing, we achieved phase-pure B2 structures across all sizes. Catalytic testing revealed a volcano-like trend in ammonia yield, peaking at 33 nm nanocubes with a rate of 6.97 mol h −1 g −1 at −0.6 V vs. reversible hydrogen electrode (RHE). This optimum reflects a balance between the increased surface area of smaller particles and the enhanced exposure of active (100) facets in larger ones. Theoretical calculations indicated that the B2-CuPd (100) facet is favorable for nitrate adsorption, thereby supporting the high activity of nanocubes. Our results highlight the critical role of tuning both nanoparticle size and surface structure to maximize eNO 3 RR efficiency.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Nanocrystal programmable assembly beyond hard spheres (or shapes) and other (simple) potentials

Ligands are the key to almost any strategy in the assembly of programmable nanocrystals (or nanoparticles) and must be accurately considered in any predictive model. Hard Spheres (or Shapes) provide the simplest and yet quite successful approach to assembly, with remarkable sophisticated predictions verified in experiments. There are, however, many situations where hard spheres/shapes predictions fail. This prompts three important questions: In what situations should hard spheres/shapes models be expected to work? and when they do not work, Is there a general model that successfully corrects hard sphere/shape predictions? and given other successful models where ligands are included explicitly, and of course, numerical simulations, can we unify hard sphere/shape models, explicit ligand models and all atom simulations? . Further, the Orbifold Topological Model (OTM) provides a positive answer to these three questions. In this paper, I give a detailed review of OTM, describing the concept of ligand vortices and how it leads to spontaneous valence and nanoparticle “eigenshapes” while providing a prediction of the lattice structure, without fitting parameters, which accounts for many body effects not captured by (two-body) potentials. I present a thorough survey of experiments and simulations and show that, to this date, they are in full agreement with the OTM predictions. I conclude with a discussion on whether NC superlattices are equilibrium structures and some significant challenges in structure prediction.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Probing the Self-Assembly dynamics of cellulose nanocrystals by X-ray photon correlation spectroscopy

Charge-stabilized colloidal cellulose nanocrystals (CNCs) can self-assemble into higher-ordered chiral nematic structures by varying the volume fraction. The assembly process exhibits distinct dynamics during the isotropic to liquid crystal phase transition, which can be elucidated using X-ray photon correlation spectroscopy (XPCS). Anionic CNCs were dispersed in propylene glycol (PG) and water spanning a range of volume fractions, encompassing several phase transitions. Coupled with traditional characterization techniques, XPCS was conducted to monitor the dynamic evolution of the different phases. Additionally, simulated XPCS results were obtained using colloidal rods and compared with the experimental data, offering additional insights into the dynamic behavior of the system. The results indicate that the particle dynamics of CNCs undergo a stepped decay in three stages during the self-assembly process in PG, coinciding with the observed phases. The phase transitions are associated with a total drop of Brownian diffusion rates by four orders of magnitude, a decrease of more than a thousand times slower than expected in an ideal system of repulsive Brownian rods. Given the similarity in the phase behaviors in CNCs dispersed in PG and in water, we hypothesize that these dynamic behaviors can be extrapolated to other polar solvent environments. Importantly, these findings represent the direct measurement of CNC dynamics using XPCS, underscoring the feasibility of directly assessing the dynamic behavior of other rod-like colloidal suspensions.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Colloidal synthesis and charge carrier dynamics of Cs 4 Cd 1-x Cu x Sb 2 Cl 12 (0 ≤ x ≤ 1) layered double perovskite nanocrystals

The toxicity and instability of lead-based metal halide perovskites are the two main obstacles that prevent perovskite materials from implementation in applications. Recently, layered double perovskites (LDPs) emerge as a new family of perovskite materials which provide a new route to solve these problems by lead-component replacement and reduction of crystal structure dimensionality. However, LDP nanocrystals (NCs) have been rarely studied, limiting the further property exploration and application realization. In this work, we report the colloidal synthesis of a series of Cs 4 Cd 1-x Cu x Sb 2 Cl 12 (0 ≤ x ≤ 1) LDP NCs by tuning the stoichiometry of metal precursors. The composition-structure-property relationships of the resulting LDP NCs are studied through materials characterizations, density functional theory calculations, and transient-absorption spectroscopy. In addition, we demonstrate that high-performance high-speed photodetectors can be fabricated using the colloidal LDP NCs through solution-processing. This work premises further expansion of such LDP-based materials for both fundamental studies and application integrations.

25 ENERGY STORAGE↗
DOE OSTI2022

Widespread opportunities for materials engineering of nanocrystals: Synthetically tailorable effects and methodologies

Since their initial development, semiconductor nanocrystals (NCs) and metal nanoparticles (NPs) have become widely utilized in a variety of applications, including solar energy harvesting, lighting, catalysis, biomedical imaging, and targeted cancer treatments. Because of their reduced dimensionality, NCs and NPs have vastly different optical and electronic properties than their bulk counterparts, and the properties often depend heavily on the NC or NP surface. Surface defects and ligands alter the optoelectronic properties of NCs and NPs and affect their interaction with the environment, allowing tailoring of their properties without changing the overall chemical composition. In this review, we discuss research progress focusing on optoelectronic properties of NPs and NCs and their respective applications. We highlight how different surface treatments and ligand functionalization of nanomaterials can influence these applications.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Pre-steady-state kinetics of nanocrystal:molybdenum nitrogenase biohybrids reveals hole-scavenging efficiency is critical to N 2 reduction

Molybdenum (Mo) nitrogenase is a two-component enzyme complex that catalyzes the reduction of dinitrogen to ammonia and protons to hydrogen gas. We have shown that electrons for dinitrogen reduction can be delivered photochemically to the catalytic MoFe protein component by cadmium sulfide (CdS) nanocrystals. In this study, we used electron paramagnetic resonance spectroscopy to measure the transient populations of catalytic intermediates. We fit the populations with a pre-steady-state kinetic model, which allowed us to distinguish between productive and non-productive reaction pathways and extract the rate constants for the reaction. Our results demonstrated that the rate of catalytic electron delivery into MoFe protein increased with the concentration of the sacrificial electron donor. This enabled electron delivery to exceed the rate of hydride protonation, a relaxation pathway that competes with N 2 binding. Thus, managing the balance between electron transfer and hole transfer reactions is required to achieve a kinetic regime that favors N 2 reduction.

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

Mechanistic Insights into Dinitrogen Reduction to Ammonia in Light-Controlled Nanocrystal:Nitrogenase Complexes

Developing systems that can efficiently capture photon energy and convert this energy into fuels and chemicals requires understanding how to assemble molecular components with diverse functions into complete systems possessing selectivity and efficiency in directing charge carriers to catalytic reactions. There are many challenges to achieving this goal. One promising approach is the development of hybrid systems that combine semiconductor nanocrystals (NCs) for light capture and enzymes as efficient catalysts. Such biohybrid systems capitalize on the tunable electronic and optical properties of NCs while leveraging the unmatched specificity and efficiency of enzymes in catalyzing chemical reactions, thereby offering opportunities to surpass the limitations of each component alone. Here, we focus on recent progress in developing a biohybrid system that combines CdS NCs for photon capture with the enzyme nitrogenase to accomplish light-driven dinitrogen (N 2 ) reduction to ammonia (NH 3 ). Integrating light-harvesting materials with biological catalysts requires a deep understanding of NC properties, protein stability, and electron transfer (ET), making it an inherently multidisciplinary problem. The reduction of N 2 to NH 3 is a challenging reaction, with a high demand in both agriculture and industrial chemical production. This reaction is intrinsically energy intensive, due to the need to activate the N≡N triple bond. The current standard industrial approach to N 2 reduction, the Haber−Bosch reaction, obtains the necessary energy input from fossil fuels, whereas biological systems capable of N 2 reduction utilize the hydrolysis of ATP as their energy source. Replacing these costly, energy-intensive inputs with renewable light energy represents a critical step toward sustainable NH 3 production. Recent progress has demonstrated that semiconductor CdS NCs can be coupled to the catalytic component of nitrogenase, the MoFe protein, to form a biohybrid CdS NC:MoFe protein complex, enabling light-driven N 2 reduction rather than energy input from fossil fuels or ATP. This illustrates how inorganic NCs can functionally replace the natural Fe protein partner, yielding a biohybrid catalyst that enables controlled electron delivery and provides not only light-driven NH 3 production but also new approaches for probing enzyme catalytic function. The CdS NC:MoFe protein biohybrid system enables light-initiated electron delivery at ambient temperature, as well as temperatures below freezing, allowing for stabilization and spectroscopic characterization of key reaction intermediates. These findings highlight how photochemical biohybrids can serve as both functional catalysts and mechanistic probes. Beyond studies of the nitrogenase mechanism, studies of the CdS NC:MoFe system reveal how variables such as NC size, electrostatic binding interactions, and sacrificial electron donors (SEDs) govern complex stability, charge transfer efficiency, and catalytic performance. In addition, studies of nitrogenase and the high activation barrier for N 2 reduction are enabling investigations of new and interesting questions regarding the properties and limitations of NC biocatalysis. In this Account, we describe the key features of CdS NC:MoFe protein biohybrids and the parameters for optimal light-driven N 2 reduction, and how controlling ET with light illuminates the path to new insights into the nitrogenase mechanism.

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

Beyond Strain: Controlling the Surface Chemistry of CsPbI 3 Nanocrystal Films for Improved Stability against Ambient Reactive Oxygen Species

Colloidal halide perovskite nanocrystals (NCs) have the possibility of easy scale-up due to their batch synthesis and have demonstrated excellent optoelectronic properties. In particular, perovskite NCs have remarkably high photoluminescence quantum yields in solution and as thin films and impressive open circuit voltages in photovoltaic devices. Despite these promising results, little work has been done to understand the stability of CsPbI 3 NCs for optoelectronic device applications. It has been previously shown that the ligands impart tensile surface strain, which stabilizes the black three-dimensional (3D) perovskite phase against phase degradation, making CsPbI 3 NCs some of the most structurally robust inorganic halide perovskites to date. However, understanding exactly how CsPbI 3 NCs degrade under ambient conditions is critical. Additionally, we demonstrate that the degradation mechanism of NCs is unique from, and 2 orders of magnitude slower than, their polycrystalline thin-film counterparts. Under specific conditions, CsPbI 3 NC films show a compositional instability instead of the phase instability seen in large grain CsPbI 3 . This is mediated through reactions with superoxide and other reactive oxygen species, which are initiated from surface defect states, O 2 and light. We then use this mechanistic insight to identify multiple strategies to prolong the lifetimes of CsPbI 3 NC films, by going beyond surface strain to mitigate key surface chemistries. We demonstrate that (1) minimizing the number of surface defects (2) using an alkylammonium bromide ligand surface treatment and (3) encapsulation with an oxygen scavenging layer all increase NC film lifetimes by inhibiting various steps in the photo-oxidation degradation reaction.

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

PbI 2 Nanocrystal Growth by Atomic Layer Deposition from Pb(tmhd) 2 and HI

Atomic layer deposition (ALD) allows for fine control over the thickness, stoichiometry, and structural defects of materials. ALD provides a suitable route to deposit lead halides, which can further be converted to perovskites for photovoltaics, photoemission, and photodetection, among other applications. Deposition of lead halides by ALD has already begun to be explored; however, the precursors used in published processes are highly hazardous, require expensive fabrication processes, or contain impurities that can jeopardize the optoelectronic properties of metal halide perovskites after conversion. In this work, we deposited lead iodide (PbI 2 ) by a facile ALD process involving only two readily accessible and low-cost precursors. PbI 2 nanocrystals were grown on soda-lime glass (SLG), silicon dioxide support grids, and silicon wafer substrates and provided the groundwork for further investigation into developing lead halide perovskite processes by ALD. Further, the ALD-grown PbI 2 was characterized by annular dark-field scanning transmission electron microscopy (ADF-STEM), atomic force microscopy (AFM), high resolution transmission electron microscopy (HRTEM), X-ray fluorescence (XRF), and X-ray photoemission spectroscopy (XPS), among other methods. This work presents the first step to synthesize lead halide perovskites with atomic control for applications such as interfacial layers in photovoltaics and for deposition in microcavities for lasing.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Variable Surface Termination and Ligand Passivation of Lead Sulfide Nanocrystals Synthesized with Excess Lead Chloride

The surface termination and ligand passivation of semiconducting nanocrystals (NCs) impact the stability, optical properties, and self-assembly of NCs. In this work, we definitively characterize the surface of lead sulfide (PbS) NCs synthesized from excess PbCl 2 . With a combination of small-angle neutron scattering (SANS), photoluminescence, and 1D and 2D NMR experiments, we show that the surface termination of PbS NCs depends on the presence of PbCl 2 during ligand exchange. When excess PbCl 2 is removed prior to ligand exchange, PbS[RNH 3 + Cl – ] NCs are obtained, which are terminated by a monolayer of PbCl x on the {100} PbS facet and passivated by oleylammonium chloride ligands. On the other hand, when excess PbCl 2 remains in solution during ligand exchange, lead oleate forms and attaches to the {111} PbS facets of PbS[RNH 3 + Cl – ] NCs, creating PbS@PbCl x NCs. PbS@PbCl x NCs are coated in an epitaxial layer of PbCl x on both the {100} PbS and {111} PbS facets, making them 0.3–0.4 nm larger on average than PbS[RNH 3 + Cl – ] NCs with identical absorption wavelengths. Additionally, PbS@PbCl x NCs have a consistently higher photoluminescence quantum yield and longer photoluminescence lifetimes than PbS[RNH 3 + Cl – ] NCs. This study clarifies the surface structure of PbS NCs synthesized from excess PbCl 2 , highlighting ligand exchange strategies and reconciling observations from across the literature.

Anions↗
DOE OSTI2023

Plasmon-Induced Hot-Carrier Excited-State Dynamics in Plasmonic Semiconductor Nanocrystals

The variance of carrier relaxation pathways for WO 3–x plasmonic semiconductor nanocrystals (PSNCs) is monitored by transient absorption spectroscopy following excitation of the localized surface plasmon resonance (LSPR) versus the optical band gap (E g,opt ). Excitation of the LSPR leads to efficient hot carrier population above the Fermi level in WO 3–x via Landau damping, in analogy to noble metal LSPR relaxation mechanisms. Hot carrier depopulation occurs on the femtosecond timescale, observed as the concomitant recovery of an LSPR bleach with the appearance of discrete interband and intraband photoinduced absorption features. Further, by comparison, the direct excitation of E g,opt results in trion recombination at donor–acceptor sites within the WO 3–x NC, consistent with exciton decay dynamics observed for typical wide-band-gap semiconductor NCs. From the analysis of pump power dependency data, a hot-carrier electron–phonon coupling constant of 1.47 × 10 11 J K –1 s –1 cm –3 is extracted. The direct comparison of the decay dynamics following E g,opt versus LSPR excitation confirms that the observed plasmon in trioctylphosphine oxide passivated, spherical WO 3–x is a resonance state in which hot carriers are generated only from excitation on resonance with the LSPR frequency. This study on WO 3–x PSNCs provides a toolset that can be used to evaluate the role of hot carriers following LSPR excitation of n-type, plasmonic transparent conducting oxide NCs, where enhancement of photocatalysis, photovoltaic performance, and optical enhancement has been reported.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Intraband Cooling and Auger Recombination in Weakly to Strongly Quantum-Confined CsPbBr 3 Perovskite Nanocrystals

Semiconductor nanocrystals (NCs) with size-tuned energy gaps present unique and desirable properties for optoelectronic applications. Recent synthetic advancements offer routes to spheroidal CsPbBr 3 perovskite NCs in the strong quantum confinement regime with narrow size dispersion. Further, using tunable femtosecond laser pulses, we examine intraband carrier relaxation using transient absorption spectroscopy and show that, across the transition from weak to strong confinement, hot carrier lifetime increases compared to larger bulk-like particles. However, further increases of confinement subsequently lead to a reduction of the hot carrier lifetime and increase of the non-radiative Auger recombination rate. Finally, we show that hot carrier lifetimes increase as a function of excess energy above the band gap less sensitively under high confinement in comparison to the bulk. Understanding such unique trends is important for maximizing hot carrier lifetimes for use in next-generation hot carrier devices as well as evaluating the transition from weak to strong confinement.

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

Mechanistic Insights into Superlattice Transformation at a Single Nanocrystal Level Using Nanobeam Electron Diffraction

Understanding the mechanism and ultimately directing nanocrystal (NC) superlattice assembly and attachment have important implications on future advances in this emerging field. Here, we use 4D-STEM to investigate a monolayer of PbS NCs at various stages of the transformation from a hexatic assembly to a nonconnected square-like superlattice over large fields of view. Maps of nanobeam electron diffraction patterns acquired with an electron microscope pixel array detector (EMPAD) offer unprecedented detail into the 3D crystallographic alignment of the polyhedral NCs. Our analysis reveals that superlattice transformation is dominated by translation of prealigned NCs strongly coupled along the <11n>AL direction and occurs stochastically and gradually throughout single grains. We validate the generality of the proposed mechanism by examining the structure of analogous PbSe NC assemblies using conventional transmission electron microscopy and selected area electron diffraction. Here, the experimental results presented here provide new mechanistic insights into NC self-assembly and oriented attachment.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Kinetically Controlled Self-Assembly of Binary Polymer-Grafted Nanocrystals into Ordered Superstructures via Solvent Vapor Annealing

Polymer-inorganic nanocomposites based on polymer-grafted nanocrystals (PGNCs) are enabling technologically relevant applications owing to their unique physical, chemical, and mechanical properties. While diverse PGNC superstructures have been realized through evaporation-driven self-assembly, this approach presents multifaceted challenges in experimentally probing and controlling assembly kinetics. Here, we report a kinetically controlled assembly of binary superstructures from a homogeneous disordered PGNC mixture utilizing solvent vapor annealing (SVA). Using a NaZn 13 -type superstructure as a model system, we demonstrate that varying the solvent vapor pressure during SVA allows for exquisite control of the rate and extent of PGNC assembly, providing access to nearly complete kinetic pathways of binary PGNC crystallization. Characterization of kinetically arrested intermediates reveals that assembly follows a multistep crystallization pathway involving spinodal-like preordering of PGNCs prior to NaZn 13 nucleation. Our work opens up new avenues for the synthesis of multicomponent PGNC superstructures exhibiting multifunctionalities and emergent properties through a thorough understanding of kinetic pathways.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2021

Optical and Magneto-Optical Properties of Donor-Bound Excitons in Vacancy-Engineered Colloidal Nanocrystals

Controlled insertion of electronic states within the band gap of semiconductor nanocrystals (NCs) is a powerful tool for tuning their physical properties. One compelling example is II–VI NCs incorporating heterovalent coinage metals in which hole capture produces acceptor-bound excitons. To date, the opposite donor-bound exciton scheme has not been realized because of the unavailability of suitable donor dopants. Here, we produce a model system for donor-bound excitons in CdSeS NCs engineered with sulfur vacancies (V S ) that introduce a donor state below the conduction band (CB), resulting in long-lived intragap luminescence. V S -localized electrons are almost unaffected by trapping, and suppression of thermal quenching boosts the emission efficiency to 85%. Magneto-optical measurements indicate that the V S are not magnetically coupled to the NC bands and that the polarization properties are determined by the spin of the valence-band photohole, whose spin flip is massively slowed down due to suppressed exchange interaction with the donor-localized electron.

77 NANOSCIENCE AND NANOTECHNOLOGY↗