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DOE OSTI2018

Synthesis, Processing and Properties of Calcium- and Nickel-Doped Yttrium Chromates(III) Y{sub 0.8}Ca{sub 0.2}Cr{sub 1−x}Ni{sub x}O{sub 3} (x = 0-0.3) and Studies on Their Potential Application as Coatings for SOFC Interconnects

In the present study, a calcium- and nickel-doped yttrium chromates (YCCN)-based, conductive–protective layers for metallic interconnects used in the intermediate-temperature solid oxide fuel cells (IT-SOFCs) were investigated. Synthesis of Y{sub 0.8}Ca{sub 0.2}Cr{sub 1−x}Ni{sub x}O{sub 3} (x = 0; 0.15 and 0.3) powders was performed using a wet chemistry method with two different complexing agents: ethylenediaminetetraacetic acid and glycine. Based on the result of thermal analysis of obtained precursors, optimal conditions of the calcination process were determined. Powders were then milled, compacted and sintered at different temperatures using free sintering method, into series of dense, polycrystalline sinters. The use of glycine precursor allowed obtaining a single-phase material in all cases. Based on the electrical and sintering properties, the Y{sub 0.8}Ca{sub 0.2}Cr{sub 0.85}Ni{sub 0.15}O{sub 3} material was selected for further studies. It was deposited using cost-effective screen-printing method on the Crofer 22APU ferritic stainless steel. To investigate properties and suitability of the resulting layer/steel system for IT-SOFCs applications, the high-temperature, dual-atmosphere studies were carried out for the first time for ceramic/metallic system, in conditions as close as possible to actual working conditions of the fuel cell. The layer exhibited high stability and good protective properties. The area-specific resistance of the studied ceramic layer/metallic substrate composite was determined, with the obtained value of 0.0366 Ω cm{sup 2} being within the arbitrary limit set for these materials (0.1 Ω cm{sup 2}). The results show that the investigated materials are suitable for the projected application.

36 MATERIALS SCIENCE↗

DOE OSTI2026

Decoding α-MoC 1− x Nanoparticle Formation in Continuous Flow via Machine Learning

Molybdenum carbide nanoparticles (α-MoC 1−x NPs) are promising catalysts that offer noble-metal-like performance at lower cost. We report a mild continuous-flow synthesis of α-MoC 1−x NPs from Mo(CO) 6 , coupled with in-line spectroscopic monitoring and machine learning (ML)-based analysis to quantify precursor conversion and product formation in real time. A multilayer perceptron ML model was found to accurately deconvolute complex, nonlinear spectral patterns, enabling identification of a two-step reaction pathway, involving precursor conversion to an amorphous intermediate followed by intraparticle crystallization to α-MoC 1−x NPs, with the first step being rate limiting. Ex situ small angle X-ray scattering (SAXS) and X-ray diffraction (XRD) validation confirm the predicted concentration profiles and crystallization behavior. This integrated approach showcases how ML can empower insights into NP nucleation and growth, paving the way for self-driving, flow-based platforms for NP synthesis.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2018

The transcriptional factor Apt regulates neuroblast differentiation through activating CycE expression

Highlights: • Apt exclusively expresses in NB6-4T cells. • Apt controls NB6-4T differentiation. • Apt activates the expression of Cyc E in neuronal cells. • Gcm represses the expression of CycE through Apt in glial cells. In Drosophila, the thoracic neuroblast 6-4 (NB6-4T) divides asymmetrically into a glial precursor and a neuronal precursor, while the abdominal neuroblast 6-4 (NB6-4A) divides symmetrically to produce two glial cells. The underlying mechanism by which NB6-4T and NB6-4A undergo distinct differentiation is still elusive. Here, we find that the transcription factor Apontic (Apt) exclusively expresses in NB6-4T cells and is involved in regulating NB6-4T differentiation. Loss of Apt results in neuronal precursor loss. Epistasis analysis shows that Apt controls NB6-4T differentiation through activating CycE expression. On the other hand, Gcm suppresses Apt expression in the NB6-4A cell, thus inhibiting CycE expression. Taken together, our findings reveal a Gcm-Apt-CycE axis that regulates neuroblast and glia cell differentiation.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2024

A Microchannel Heat Exchanger Produced From a Metal Matrix Composite by Hybrid Laser Powder Bed Fusion and Inkjet Printing

Abstract This paper explores the production of an oxide dispersion strengthened (ODS) 304L stainless steel microchannel heat exchanger (HX) using a hybrid additive manufacturing process of laser powder bed fusion and inkjet printing. The study investigates the capabilities and economics of the hybrid inkjet-laser powder bed fusion (LPBF) process and evaluates the dimensional accuracy, functionality, and mechanical properties of the resulting ODS alloy. The effectiveness and pressure drop of the ODS heat exchangers produced by the hybrid LPBF tool are also determined. Results show that the inkjet-doped samples have a lower mean channel height with higher standard deviation than samples produced by LPBF alone. This is attributed to greater absorption of laser energy for the powder coated with the oxide precursor. The economic analysis shows that the hybrid process has a potential for reducing the unit cost of the heat exchanger based on cost modeling assumptions.

Engineering↗

DOE OSTI2021

Photoproduction of the b 1 (1235) Meson off the proton at E gamma = 6-12 GeV

The GlueX Experiment at Jefferson Lab directs a linearly polarized photon beam on a liquid hydrogen target surrounded by an almost hermetic detector. The experiment aims to study the meson spectrum in the light-quark sector and search for exotic spin-parity states predicted by lattice QCD calculations. The lightest exotic candidate is the π 1 meson, which is predicted to decay dominantly to b 1 π. In this thesis, we present efforts to characterize the ωπ 0 decay channel of the b 1 meson as precursor to an analysis of the sought-after π 1 exotic state. We present an introduction to the physics involved and an overview of the detector subsystems with a focus on the Barrel Calorimeter gain monitoring system, as part of the service work expected by the GlueX Collaboration. We discuss the data analysis method used and present two frameworks, for angular moments and partial waves analyses. Details of the simulation used to calculate the detector acceptance. A proof of concept partial wave analysis is presented along with experimental angular moments as first step to a full analysis of the angular distribution Our partial wave analysis indicates that both S- and D-waves are needed, in qualitative agreement with theoretical expectations. The cross-section of the omega π 0 channel is extracted to be of the scale of 1 μb in agreement with previous measurements. The differential cross-section indicates the presence of two production processes with p 1 = -5:24 ± 0:04 for 0:25 < -t < 0:95 GeV 2 ~c 2 and p 2 = -1:24 ± 0:05 for 0:95 < -t < 2:0 GeV 2 ~c 2 , which does not agree with results from previous experiments. The s-channel helicity conservation and helicity amplitudes of the b 1 meson are presented as additional experimental observables. Our results confirm that the b1 photoproduction process does not conserve s-channel helicity though they do not align with previous measurements. The helicity amplitude of the omega are extracted to be |F 1 | 2 = 0:3037 ± 0:0003 which does not agree with the expected value of a b 1 decay or results from a previous experiment. Future steps in all these analyses will be continued by a new graduate student in the group, culminating in a publication.

Foda, Ahmed↗

DOE OSTI2025

Autonomous Nanoparticle Synthesis Guided by In Situ Multiscale Structural Characterization

Autonomous synthesis platforms promise rapid exploration of vast parameter spaces; yet, integrating in situ structural characterization in closed-loop synthesis optimization remains challenging. We demonstrate a realization of such a closed-loop platform coupled with a droplet-flow microreactor, in situ X-ray scattering methods (SAXS/WAXS), and Gaussian process optimization to synthesize citrate-reduced Au nanoparticles with targeted characteristics. The system efficiently explored ∼19,000 synthesis recipes through 365 experiments, achieving precise control over size (4–60 nm) and polydispersity (σ < 0.11) across large citrate/gold ratios, exceeding traditional synthesis boundaries (1–10). Beyond confirming classical Turkevich–Frens trends, partial-dependence analysis revealed strong nonlinear coupling among precursor, citrate, and pH effects. Combining quantitative SAXS/WAXS analysis with electron microscopy characterization, we uncovered that crystallite size (d c ) and particle size (d) follow d c = 0.18d + β, where synthesis chemistry controls the intercept β while maintaining a universal slope. This parallel-band structure enables independent tuning of crystallite domain size at fixed particle diameter through a combination of chloride, gold precursor, citrate, and pH contributions (cross-validated Spearman ρ = 0.7 ± 0.1). High-resolution electron microscopy shows multiple lattice-fringe orientations within single particles, directly confirming polycrystalline domains and the ability to tune d c at the fixed d. The platform’s validation includes indistinguishable static versus flowing measurements, stable droplet transport at 100 °C, and <5% run-to-run variation, establishing a robust framework for mapping and controlling multiscale nanoparticle structure across expansive chemical spaces. In conclusion, the developed closed-loop platform can be applied to a borad range of nanosyntheis processes.

77 NANOSCIENCE AND NANOTECHNOLOGY↗

DOE OSTI2017

Monte Carlo/CFD Coupling for Accurate Modeling of the Delayed Neutron Precursors and Compressibility Effects in Molten Salt Reactors

Multiphysics reactor analysis has become one of the leading activities of most nuclear engineering research groups. Coupled neutronics and thermal/hydraulics (T/H) simulations have traditionally been performed by adopting deterministic transport tools and reactor system T/H codes. The main reason for avoiding higher fidelity numerical methods like continuous-energy Monte Carlo analysis has been the high computational cost of coupled, full-scale simulations. Nowadays, high fidelity multiphysics simulations represent a hot research topic, with several applications involving advanced nuclear systems. Liquid fuel Molten Salt Reactors (MSRs) feature peculiar physical phenomena that are not present in solid fuel reactors. Some of these phenomena are not correctly resolved by legacy reactor physics tools, and require specific treatments. This work focuses in particular on the analysis of the effect of the delayed neutron precursors drift and the impact of liquid fluid thermal expansion and compressibility in postulated criticality excursion transients in fast-spectrum MSRs. A new modeling tool based on a Monte Carlo approach for neutronics (Serpent code) coupled to a Computational Fluid Dynamic (CFD) analysis (OpenFOAM) was developed to obtain accurate modeling and simulation of these phenomena. The development of the Serpent Monte Carlo code [1] at VTT in the past few years has made this code particularly attractive for performing multiphysics studies. The availability of a flexible multiphysics interface, on-the-fly Doppler broadening and density-based collision rejection, and Delta-tracking, proved of paramount importance for the computationally efficient performance of coupled Monte Carlo/CFD calculations [2]. OpenFOAM is a C++ multiphysics toolkit featured by automatic matrix construction and solution capabilities for scalar and vector partial differential equations (PDEs), adopting several possible differencing and interpolation schemes, based on the Finite-Volume method. The ease of implementing the constitutive equations of different physical phenomena makes OpenFOAM particularly suitable for the modeling of complex coupled phenomena. In the past, several research activities proposed the adoption of both Serpent and OpenFOAM for the modeling and simulation of MSRs and the associated fuel cycles. In this work, these tools have been internally coupled for the steady-state and transient analysis of fast-spectrum systems, accounting for the effect of delayed neutron precursors transport and the salt thermal expansion and compressibility.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗

DOE OSTI2015

Electronic structure investigation of atomic layer deposition ruthenium(oxide) thin films using photoemission spectroscopy

Analyzing and manipulating the electronic band line-up of interfaces in novel micro- and nanoelectronic devices is important to achieve further advancement in this field. Such band alignment modifications can be achieved by introducing thin conformal interfacial dipole layers. Atomic layer deposition (ALD), enabling angstrom-precise control over thin film thickness, is an ideal technique for this challenge. Ruthenium (Ru{sup 0}) and its oxide (RuO{sub 2}) have gained interest in the past decade as interfacial dipole layers because of their favorable properties like metal-equivalent work functions, conductivity, etc. In this study, initial results of the electronic structure investigation of ALD Ru{sup 0} and RuO{sub 2} films via photoemission spectroscopy are presented. These experiments give insight into the band alignment, growth behavior, surface structure termination, and dipole formation. The experiments were performed in an integrated vacuum system attached to a home-built, stop-flow type ALD reactor without exposing the samples to the ambient in between deposition and analysis. Bis(ethylcyclopentadienyl)ruthenium(II) was used as precursor and oxygen as reactant. The analysis chamber was outfitted with X-ray photoemission spectroscopy (LIXPS, XPS). The determined growth modes are consistent with a strong growth inhibition situation with a maximum average growth rate of 0.21 Å/cycle for RuO{sub 2} and 0.04 Å/cycle for Ru.{sup 0} An interface dipole of up to −0.93 eV was observed, supporting the assumption of a strongly physisorbed interface. A separate experiment where the surface of a RuO film was sputtered suggests that the surface is terminated by an intermediate, stable, non-stoichiometric RuO{sub 2}/OH compound whose surface is saturated with hydroxyl groups.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2023

Silicon carbide fiber manufacturing: Cost and technology

Significant advances have been made in the past decade concerning silicon carbide fiber manufacturing methods resulting in near-stoichiometric small-diameter fibers that meet the property requirements for most of the ceramic matrix composites (CMC) and nuclear applications. The manufacturing cost, however, remained prohibitively high, preventing the use of it in different applications requiring much lower cost. Silicon carbide (SiC) fiber reinforced CMC is dominated by the cost of SiC fiber which comprises more than 50 % of the finished part cost. Here, this article provides insight into the SiC fiber manufacturing costs and highlights the need for an alternative SiC fiber precursor and manufacturing method. Analysis of the existing polycarbosilane (PCS)-based SiC fiber manufacturing shows that the crosslinking (curing) and raw material preparation steps are high-cost steps that need lower cost options. Alternative SiC fiber precursor should be sought for lowering the cost of SiC fibers.

36 MATERIALS SCIENCE↗

DOE OSTI2017

Prediction of a Red Nova Outburst in KIC 9832227

We present the first identification of a candidate precursor for an imminent red nova. Our prediction is based on the example of the precursor to the red nova V1309 Sco, which was retrospectively found to be a contact binary with an exponentially decreasing period. We explore the use of this distinctive timing signature to identify precursors, developing the observational and analysis steps needed. We estimate that our Galaxy has roughly 1–10 observable precursors. Specifically, we lay out the observational case for KIC 9832227, which we identified as a tentative candidate two years ago (Molnar et al. 2015, AAS Meeting #225 Abstracts 415.05). Orbital timing over the past two years has followed the tentative exponential fit. As of late 2015, the period time derivative went beyond the range found in other systems ( P-dot <|1×10{sup −8}|), a necessary criterion for a serious candidate. We estimate time of merger is the year 2022.2 ± 0.7. Double absorption line spectra confirm directly the 0.458-day light-curve is the orbital period of a contact binary system and yield a mass ratio m{sub B}/m{sub A}=0.228±0.003. Closer analysis of the Kepler timing data shows evidence of a component C with orbital period P{sub C}=590±8 days and m{sub C}sini{sub C}=0.11 M{sub ⊙}. An alternative interpretation of the long-term timing trend, that is, a light travel-time delay due to the orbit around a distant component D, is ruled out by the spectroscopic data for any nondegenerate star. Additional measurements are needed to test further the merging hypothesis and to use fully this fortuitous opportunity.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2023

Verification of a Modeling Toolkit for the Design of Building Electrical Distribution Systems

DC electrical distribution systems offer many potential advantages over their AC counterparts. They can facilitate easier integration with distributed energy resources, improve system energy efficiency by eliminating AC/DC converters at end-use devices (e.g., laptop chargers), and reduce installation material, time, and cost. However, DC electrical distribution systems present additional design considerations, largely resulting from potentially greater magnitude and variation in cable losses. Modeling and simulation are rarely used to design such systems. However, the greater dependency of DC system energy efficiency on design choices such as distribution voltages, architecture, and integration of PV and BESS suggests that modeling and simulation may be required. Such system performance analysis is currently not a standard practice, in part due to limited availability and validation of capable software tools. This paper characterizes the accuracy of a Modelica-based Building Electrical Efficiency Analysis Model (BEEAM) toolkit, as a precursor for validating its use to perform system performance analysis and inform design decisions. The study builds upon previous verification research by characterizing complete systems comprised of commercially available equipment, and providing a more detailed analysis of simulation results. Five lighting systems with varying electrical distribution architectures were designed using market-available equipment, installed in a laboratory environment, modeled using BEEAM, and simulated using three Modelica integrated development environments (IDEs). Simulated and measured results were compared to characterize toolkit accuracy. Initial results revealed that simulated performance was mostly within ±5% of measured system-level and device-level performance. While simulation results were not found to be dependent on the IDE, some Modelica compiler interoperability issues were identified. Although the BEEAM toolkit showed promise for the targeted use case, further work is needed to determine whether the demonstrated 5% accuracy is sufficient for making real-world design decisions, and for BEEAM to advance from an interesting research tool to one that can impact real-world building projects.

24 POWER TRANSMISSION AND DISTRIBUTION↗

DOE OSTI2018

Immunogenetic and structural analysis of a class of HCV broadly neutralizing antibodies and their precursors

Elicitation of broadly neutralizing antibodies (bnAbs) is a leading strategy in rational vaccine design against antigenically diverse pathogens. Here, we studied a panel of monoclonal antibodies (mAbs) from mice immunized with the hepatitis C virus (HCV) envelope glycoproteins E1E2. Six of the mAbs recognize the conserved E2 antigenic site 412–423 (AS412) and cross-neutralize diverse HCV genotypes. Immunogenetic and structural analysis revealed that the antibodies originated from two different germline (GL) precursors and bind AS412 in a β-hairpin conformation. Intriguingly, the anti-HCV activity of one antibody lineage is associated with maturation of the light chain (LC), whereas the other lineage is dependent on heavy-chain (HC) maturation. Crystal structures of GL precursors of the LC-dependent lineage in complex with AS412 offer critical insights into the maturation process of bnAbs to HCV, thus providing a scientific foundation for utilizing the mouse model to study AS412-targeting vaccine candidates.

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2017

A Model of the Pulsating Extremely Low-mass White Dwarf Precursor WASP 0247–25B

We present an analysis of the evolutionary and pulsation properties of the extremely low-mass white dwarf precursor (B) component of the double-lined eclipsing system WASP 0247−25. Given that the fundamental parameters of that star have been obtained previously at a unique level of precision, WASP 0247−25B represents the ideal case for testing evolutionary models of this newly found category of pulsators. Taking into account the known constraints on the mass, orbital period, effective temperature, surface gravity, and atmospheric composition, we present a model that is compatible with these constraints and show pulsation modes that have periods very close to the observed values. Importantly, these modes are predicted to be excited. Although the overall consistency remains perfectible, the observable properties of WASP 0247−25B are closely reproduced. A key ingredient of our binary evolutionary models is represented by rotational mixing as the main competitor against gravitational settling. Depending on assumptions made about the values of the degree index ℓ for the observed pulsation modes, we found three possible seismic solutions. We discuss two tests, rotational splitting and multicolor photometry, that should readily identify the modes and discriminate between these solutions. However, this will require improved temporal resolution and higher S/N observations, which are currently unavailable.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2025

Influence of Alkyne Precursor Structure on Carbon Nanotube Chiral Distribution: Data-Dense Analysis Across Multiple Catalyst Types

Carbon nanotubes (CNTs) are a desirable material in the field of optoelectronics and semiconductors due to electronic properties (e.g., bandgap) that are dependent upon their chirality, defined by their diameter and lattice angle. Unfortunately, industrial-scale syntheses have yet to realize growth of a single desired chirality and instead rely on postsynthetic separation techniques to refine a chiral mixture, which increases process complexity and cost. Here, we studied the influence of precursor structure on chiral distribution, using a series of terminal alkyne precursors (acetylene, methylacetylene, vinylacetylene, 1-butyne, two enantiomers of 3-butyn-2-ol and a racemic mixture thereof) to grow CNTs across five transition-metal catalysts (Fe, FeMo, and three proportions of CoMo). Multiwavelength Raman spectroscopy on 5,145 spots (5 catalysts, 7 precursors, 3 lasers, and 49 distinct substrate locations on each) determined that acetylene grew the smallest diameter CNTs, while vinylacetylene produced fewer subnanometer CNTs. Though precursor structure did not dictate a uniform chiral shift, it was shown to broaden or narrow chiral distribution, while catalyst structure played a dominant role. In conclusion, this is consistent with metal-precursor binding occurring through unsaturated bonds in the hydrocarbons via the alkyne polymerization mechanism.

Carbon nanotubes↗

DOE OSTI2020

Multi-device study of temporal characteristics of magnetohydrodynamic modes initiating disruptions

Disruptions in tokamaks are often preceded by magnetohydrodynamic (MHD) instabilities that can rotate or become locked to the wall. Measurements from magnetic diagnostics in the presence of MHD mode precursors to disruptions can yield potentially valuable input to the plasma control system, with a view to disruption avoidance, prediction and mitigation. This report presents an exploratory analysis of the growth of MHD modes and corresponding time scales on the basis of magnetic measurements in multiple tokamaks. To this end, a database was compiled using disruptive discharges from COMPASS, ASDEX Upgrade, DIII-D and JET, manually classified according to disruption root cause, and characterized by a great diversity of operational conditions and mode dynamics. The typical time during which a mode can be detected using saddle coils and the duration of the locked mode phase in the database both extend over several orders of magnitude, but generally the time scales increase with plasma size. Several additional factors are discussed that can influence these durations, including the disruption root cause. A scaling law for the locked phase duration was estimated, yielding predictions toward ITER of the order of hundreds of milliseconds or even seconds. In addition, a scaling law for the mode amplitude at the disruption onset, proposed earlier by de Vries et al. (2016), is applied to the database, and its predictive capabilities are assessed. Despite significant uncertainty on the predictions from both scaling laws, encouraging trends are observed of the fraction of disruptions that may be detected with sufficient warning time to allow mitigation or even avoidance, based solely on observations of MHD mode dynamics. When combined with similar analysis of measurements from diagnostics that are sensitive to other disruption precursors, our analysis methods and results may contribute to the reliability, robustness and generalization of disruption warning schemes for ITER.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2018

Quantitative atomic-scale structure characterization of ordered mesoporous carbon materials by solid state NMR

In this study, solid-state (SS)NMR techniques were applied to characterize the atomic-scale structures of ordered mesoporous carbon (OMC) materials prepared using Pluronic F127 as template with resorcinol and formaldehyde as polymerizing precursors. A rigorous quantitative analysis was developed using a combination of 13 C SSNMR spectra acquired with direct polarization and cross polarization on natural abundant and selectively 13 C-enriched series of samples pyrolyzed at various temperatures. These experiments identified and counted the key functional groups present in the OMCs at various stages of preparation and thermal treatment. Lastly, the chemical evolution of molecular networks, the average sizes of aromatic clusters and the extended molecular structures of OMCs were then inferred by coupling this information with the elemental analysis results.

36 MATERIALS SCIENCE↗

DOE OSTI2019

Pore-Templated Growth of Catalytically Active Gold Nanoparticles within a Metal–Organic Framework

Obtaining persistently well-dispersed gold nano-particles (AuNPs) on solid support with optimum particle size for heterogeneous catalysis can be challenging. Here, we report on the channel-templated growth of AuNPs within a stable zirconium-based metal–organic framework, NU-1000, via channel-anchored monometallic precursors. Pair distribution function analysis of total X-ray scattering by the incorporated face-centered-cubic nanopar-ticles reveals a bimodal size distribution, with ca. 98% of the en-shrouded nanoparticles having a diameter that closely reflects the ~10 Å width of triangular pores and with ca. 2% closely reflecting the ~31 Å width of hexagonal pores of NU-1000. The resulting ma-terial is catalytically active (and recyclable) for condensed-phase hydrogenation of 4-nitrophenol to 4-aminophenol.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2026

Vapor-Phase Heteroatom Incorporation into Semiconductive Molecular-Scale Magic-Size Clusters

Magic-size metal chalcogenide clusters of molecular size exhibit well-defined structure and unique properties that might be further expanded with the incorporation or substitution of a second metal. Here, we report the postmodification of magic-size clusters synthesized in polymer thin films via exposure to volatile metal organic precursors commonly utilized for atomic layer deposition. Exposure of In 6 S 6 (CH 3 ) 6 clusters to dimethylcadmium results in exposure-dependent incorporation of Cd 2+ , which extends the optical absorbance of the clusters into the visible spectrum. The mechanism for Cd 2+ incorporation is consistent with Cd 2+ replacement of In 3+ that includes methyl ligand removal to maintain charge neutrality. Even for clusters embedded in a polymer matrix, ligand loss leads to sintering and transformation into larger nanoscale aggregates with zinc blende-type structure. The extent of Cd incorporation can be modulated by varying the process temperature and volatile metal organic exposure as well as the choice of volatile metal organic precursor. A computational thermodynamic analysis of heteroatom incorporation for several metals and chemistries reveals that both the stability of the substituted cluster and the favorability of reaction byproducts jointly determine the favorability of cation incorporation.

atomic layer deposition↗