Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Color”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,045 records · Page 58
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Quantum defects in carbon nanotubes as single-photon sources

Single-photon emitters are essential components of emerging quantum technologies, including secure communication and quantum computing. Single-walled carbon nanotubes (SWCNTs) have emerged as a promising platform for quantum light sources due to their quasi-one-dimensional excitonic host structure and compatibility with telecom photonic systems. Recent advances in deterministic defect engineering—most notably the development of organic color centers (OCCs)—have enabled stable, chemically controllable, and spectrally tunable single-photon emission. OCC-based emitters have demonstrated single-photon purity exceeding 99% and, more recently, room-temperature photon indistinguishability, placing them among the few solid-state systems with quantum-grade performance under ambient conditions. This review surveys progress in the field from three complementary perspectives: chemical synthesis and quantum defect engineering, computational studies of structure-property relationships and excitonic behavior, and experimental investigations of quantum optical properties. We also discuss alternative approaches, including air-suspended SWCNTs and hybrid van der Waals heterostructures, highlighting opportunities and open challenges for scalable integration into quantum photonic platforms.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Wildfire aerosol deposition likely amplified a summertime Arctic phytoplankton bloom

Summertime wildfire activity is increasing in boreal forest and tundra ecosystems in the Northern Hemisphere. However, the impact of long range transport and deposition of wildfire aerosols on biogeochemical cycles in the Arctic Ocean is unknown. Here, we use satellite-based ocean color data, atmospheric modeling and back trajectory analysis to investigate the transport and fate of aerosols emitted from Siberian wildfires in summer 2014 and their potential impact on phytoplankton dynamics in the Arctic Ocean. We detect large phytoplankton blooms near the North Pole (up to 82°N in the eastern Eurasian Basin). Our analysis indicates that these blooms were induced by the northward plume transport and deposition of nutrient-bearing wildfire aerosols. We estimate that these highly stratified surface waters received large amounts of wildfire-derived nitrogen, which alleviated nutrient stress in the phytoplankton community and triggered an unusually large bloom event. Our findings suggest that changes in wildfire activity may strongly influence summertime productivity in the Arctic Ocean.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2024

Increasing the presence of BIPOC researchers in computational science

Here, Nature Computational Science asked a group of scientists to discuss strategies for increasing the presence of Black, Indigenous, People of Color (BIPOC) researchers in computational science, as well as the various considerations to be made for improving education and methods design.

99 GENERAL AND MISCELLANEOUS↗
DOE OSTI2020

Robust fluorescent calcium coordination polymers as Cu 2+ sensors with high sensitivity and fast response

A three-dimensional (3D) and highly fluorescent calcium-based coordination polymer (Ca-CP) has been synthesized and structurally characterized. Furthermore, built on a strongly fluorescent (FL) chromophore ligand, [Ca(H 2 tcbpe)(H 2 O) 2 ] (1) (H 4 tcbpe = 4',4''',4''''',4'''''''-(ethene-1,1,2,2-tetrayl)tetrakis(([1,1'-biphenyl]-4-carboxylic acid))) is highly luminescent. Photoluminescence (PL) studies indicate that 1 undergoes a bathochromic shift in emission energy from blue to green color upon outgassing or under mechanic force. Notably, 1 exhibits selective FL sensing for Cu 2+ ions with a detection limit (LOD) of 0.064 ppm, far below the U.S. WHO and EPA standard for drinking water. Detailed investigation of the sensing mechanism reveals that uncoordinated COO– groups in 1 play a major role in recognizing Cu 2+ ions.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Eco-friendly, solution-processable and efficient low-energy lighting phosphors: copper halide based hybrid semiconductors Cu 4 X 6 (L) 2 (X = Br, I) composed of covalent, ionic and coordinate bonds

A series of copper halide based inorganic–organic hybrid semiconductors have been synthesized. Structural analysis confirms that all compounds are composed of one-dimensional Cu 4 X 6 2- anionic chains that coordinate to cationic ligands via Cu–N dative bonds. Different coordination affinities of the ligands lead to two types of ligand arrangements with various structural distortions. All compounds are highly resistant to heat and moisture as a result of the combination of coordinate and ionic bonds. Low energy emission with high efficiency is achieved for these compounds and the emission energy (~552–615 nm) and color (yellow-orange) can be tuned by varying the ligand and halogen element. The electronic structure and luminescence mechanism are examined by both experimental and theoretical methods. More importantly, all compounds demonstrate good solubility in polar aprotic solvents, a desired property that is absent in all other CuX hybrid families of extended structures, which is attributed primarily to the ionic nature of this material class. Furthermore, the good solution-processability, and cost effective and easily scalable synthesis coupled with high quantum efficiencies and framework stability make these hybrid materials promising phosphors for general lighting applications.

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

Pressure-induced excimer formation and fluorescence enhancement of an anthracene derivative

Excimer materials have been widely studied and have generated significant interest for their applications in many optoelectronic devices. However, a thorough investigation of the entire process involved in excimer formation, enhancement, and annihilation in solid materials is still lacking. Here we designed a crystal based on an anthracene derivative with dissociative, molecular-ordered dimer assembly, and studied the formation and evolution of an anthracene excimer as a function of pressure. During the initial stage of pressurization, the fluorescence intensity arising from anthracene monomers gradually decreases. Therefore, with continued compression, the two anthracene units become increasingly closer allowing strong intermolecular π–π interactions to develop that lead to excimer formation at 3.5 GPa, accompanied with a phase transition. The fluorescence intensity then keeps increasing with pressure and reaches its maximum at 5.6 GPa due to the strengthening of the excimer and the increased structural defects. Meanwhile the fluorescence color shows a continuous redshift, which initially results from conformation planarization and then excimer evolution. After releasing pressure back to ambient conditions, the structural changes in the sample are reversible, while the fluorescence signal preserves some high-pressure features due to the partial retention of the π–π interactions between the anthracene dimers. This study reveals the evolution of an excimer and its intrinsic photophysical properties, and provides guidance for future research on pressure-sensitive fluorescent devices.

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

Tailoring capping-layer composition for improved stability of mixed-halide perovskites

Incorporating a low dimensional (LD) perovskite capping layer on top of a perovskite absorber, improves the stability of perovskite solar cells (PSCs). However, in the case of mixed-halide perovskites, which can undergo halide segregation into single-halide perovskites, a systematic study of the capping layer's effect on mixed-halide perovskite absorber is still lacking. This study bridges this gap by investigating how the 1D perovskite capping layers on top of MAPb(I x Br 1–x ) 3 (x = 0, 0.25, 0.5, 0.75, 1) absorbers affect the films' stability. We utilize a new method, dissimilarity matrix, to investigate the image-based stability performance of capping-absorber pair compositions across time. This method overcomes the challenge of analyzing various film colors due to bandgap difference in mixed-halide perovskites. We also discover that the intrinsic absorber stability plays an important role in the overall stability outcome, despite the capping layer's support. Within the 55 unique capping-absorber pairs, we observe a notable 1D perovskite material, 1-methoxynaphthalene-2-ethylammonium chloride (2MeO–NEA–Cl or 9-Cl), that improves the stability of MAPbI 3 and MAPb(I 0.5 Br 0.5 ) 3 by at least 8 and 1.5 times, respectively, compared to bare films under elevated humidity and temperature. Surface photovoltage results also show that the accumulation of electrostatic charges on the film surface depends on the capping layer type, which could contribute to the acceleration/deceleration of degradation.

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

Triphenylamine/benzothiadiazole-based compounds for non-doped orange and red fluorescent OLEDs with high efficiencies and low efficiency roll-off

Long-wavelength materials are key for development of pure-color and white organic light-emitting devices (OLEDs). An organic molecule, combining hybridized local electron and charge-transfer (HLCT) states and aggregation-induced emission (AIE), not only breaks the 5% external quantum efficiency (EQE) limit but also overcomes emission quenching. Herein, we designed and synthesized four novel donor–acceptor compounds of TBAN, TBT, TBAT, and TABAT using triphenylamine (TPA) as the donor, benzothiadiazole (BT) as the acceptor, and anthracene (AN) as a bridge. We found that the emission peaks of TBAN, TBT, TBAT and TABAT are located at 596, 615, 580 and 546 nm, respectively. We successfully applied them to non-doped OLEDs, and the resulting devices exhibited excellent performance. For example, the optimal TBAN-based OLEDs showed a maximum luminance of 74 820 cd m –2 , a current efficiency of 12.1 cd A –1 and a maximum EQE of 5.7% with low roll-off. Additionally, the device with TBAN as both the emitter and hole-transport material also exhibited high efficiency that is comparable to that of an NPB-based device. Furthermore, this work demonstrates that it is feasible to obtain excellent orange and red emitters by employing BT- and TPA-based D–A architectures.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Optical sensing of aqueous nitrate anion by a platinum( II ) triimine salt based solid state material

Selective and quantitative measurement of aqueous nitrate (NO 3 – ) anion is achieved using solid [Pt(Cl-4-tpy)Cl]ClO 4 salt (Cl-4-tpy = 4-chloro-2,2':6'2''-terpyridine), and as the salt supported on controlled porous glass. This detection method relies on the color change of the Pt(II) complex from yellow to red and intense luminescence response upon ClO 4 – exchange with NO 3 – due to concomitant enhancement of Pt∙∙∙Pt interactions. Finally, the spectroscopic response is highly selective for NO 3 – over a large range of halides and oxoanions.

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

Conversion of plastic waste into high-value lubricants: techno-economic analysis and life cycle assessment

Given the low recycling rate of plastic waste in the United States due to low economic incentives, it is of great interest to develop a technology to upgrade plastic waste with favorable economics. Plastic upcycling to valuable chemicals could ensure a circular economy for plastics and reduce the environmental burden caused by their end use cycle and disposal. A conceptual facility to convert 250 metric ton (MT) per day of plastic waste was modeled; the main product was a high-quality liquid (HQL) with a similar performance to polyalphaolefin (PAO) lubricants. The modeled process had a lubricant yield of up to 90% based on the experimental results at the laboratory scale. Techno-economic analysis (TEA) and life cycle assessment (LCA) were also performed to evaluate the process economics and its environmental impact. By using a mixture of colored and natural high-density polyethylene (HDPE), the production cost was in the range of 0.6–1.98 dollars per kg of lubricant, depending on the operating conditions. The life cycle emissions were in the range of 0.48–1.2 kg CO 2e kg Lub -1 showing, for the best case scenario, a 52% reduction relative to the emissions for petroleum lubricants, and a 74% reduction relative to the emissions for PAO lubricants. Finally, the impacts of the lubricant yield, the catalyst amount, and reaction time were evaluated, and their effect on the final production cost was discussed.

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

Reliably obtaining white light from layered halide perovskites at room temperature

The recent observation of broadband white-light emission from the inorganic sheets of certain layered lead-bromide perovskites has instigated a multitude of studies on this unusual phenomenon. However, the vast majority of layered bromide perovskites have flat (001) inorganic sheets and display a narrow photoluminescence at room temperature. A handful of heavily distorted (001) perovskites display broad emission, but to date, there is no method of predicting which perovskites will produce white light at room temperature prior to screening different organic molecules that can template 2D perovskites and crystallizing and analyzing the material. By studying ten Pb–Cl perovskites, we find that they all exhibit a broad yellow emission, which is strikingly invariant despite different distortions in the inorganic framework seen across the series. We postulate that this broad emission is intrinsic to all layered Pb–Cl perovskites. Although broad, the emission is not white. By adding Br to the Pb–Cl perovskites we obtain both the narrow emission and the broad emission such that the combined emission color smoothly varies from yellow to warm white to cold white as a function of the halide ratio. Thus, alloying Br to Pb–Cl perovskites appears to be a simple and general strategy for reliably obtaining white light at room temperature from (001) perovskites, regardless of the templating effects of the organic molecules, which should greatly expand the number of white-light-emitting layered perovskites.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Highly soluble copper(ι) iodide-based hybrid luminescent semiconductors containing molecular and one-dimensional coordinated anionic inorganic motifs

Copper(I) iodide-based inorganic–organic hybrid semiconductors are considered promising materials for various optoelectronic applications. Here, using imidazolium bridged benzotriazoles as multidentate ligands, we designed and synthesized a series of all-in-one (AIO)-type CuI hybrid materials that hold both ionic and coordinate bonds at the interface of organic and inorganic modules. Their structures range from 0D clusters to 2D extended networks built on various molecular (0D) and chain-like (1D) anionic inorganic motifs that are interconnected through cationic ligands via multiple Cu–N bonds. Benefiting from their unique bonding nature, these compounds exhibit high stability towards heat and moisture and can be well dissolved in polar aprotic solvents. They emit low-energy light spanning from yellow to red color (550–625 nm). Finally, the electronic structure, emission mechanism, and effect of different coordination modes on their photophysical properties were studied using both experimental and theoretical methods, which has provided insight into the structure–property relationship of these inorganic–organic semiconductors.

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

Review of low-cost self-driving laboratories in chemistry and materials science: the “frugal twin” concept

This review proposes the concept of a “frugal twin,” similar to a digital twin, but for physical experiments. Frugal twins range from simple toy examples to low-cost surrogates of high-cost research systems. For example, a color-mixing self-driving laboratory (SDL) can serve as a low-cost version of a costly multi-step chemical discovery SDL. Frugal twins already provide hands-on experience for SDLs with low costs and low risks. They can also offer as test beds for software prototyping (e.g., optimization, data infrastructure), and a low barrier to entry for democratizing SDLs. However, there is room for improvement. The true value of frugal twins can be realized in three core areas. Firstly, hardware and software modularity; secondly, purpose-built design (human-inspired vs. hardware-centric vs. human-in-the-loop); and thirdly state-of-the-art (SOTA) software (e.g., multi-fidelity optimization). We also describe the ethical benefits and risks that come with the democratization of science through frugal twins. For future work, we suggest ideas for new frugal twins, SDL educational course outcomes, and a classification scheme for autonomy levels.

36 MATERIALS SCIENCE↗
DOE OSTI2025

UV-Vis spectrophotometric determination of rare earth elements (REE) speciation at near-neutral to alkaline pH. Part II: hydrolysis of Er from 25 to 75 °C

Aqueous speciation of rare earth elements (REE) controls their mobilization, fractionation, and enrichment in the natural waters. Geochemical modeling of their speciation is key to improve our understanding of the formation of economic mineral deposits, for developing mineral separation and mine tailing recovery technologies, and for characterizing the geochemistry of thermal water. However, our ability to predict the fate of REE in a wide pH and temperature range is limited by the scarcity of thermodynamic data for the REE hydroxyl complexes. In part I of this study (H. J. Han and A. P. Gysi, Dalton Trans., 2024, 53, 13129–13141), the optical properties of m-cresol purple (mCP) were determined using UV-Vis spectrophotometry between 25 and 75 °C in order to develop a method for deriving the hydrolysis constants of erbium (Er). Here, UV-Vis spectrophotometry experiments were conducted as a function of temperature between 35 and 75 °C to determine the hydrolysis of Er in near-neutral to alkaline solutions using mCP as an in situ pH color indicator. Here, the experiments were conducted with Er concentrations from 0 to ~0.253 mmol kg –1 in low ionic strength solutions (≤0.001 mol kg –1 ).

58 GEOSCIENCES↗
DOE OSTI2025

Trinuclear gold chains and octanuclear copper gyrobifastigia stabilized using a fluorinated pyridyl ligand

The fluorinated pyridyl ligand [6-(CF 3 )-2-Py] − with gold( I ) affords trinuclear Au 3 assemblies that further organize into a supramolecular helical column through aurophilic interactions. Its chemistry with copper( I ) is even more remarkable, leading to an unprecedented octanuclear copper–pyridyl cluster complex featuring a central Cu 8 core with an approximate gyrobifastigium geometry. Solid powders of compounds {(6-(CF 3 )-2-Py)Au} 3 and {(6-(CF 3 )-2-Py)Cu} 8 exhibit intense photoluminescence at room temperature, displaying green and yellow colors to the naked eye, respectively. Here, the octanuclear copper complex is also an effective catalyst for azide–alkyne cycloaddition, producing triazoles. Detailed computational analyses confirm the preference for experimental geometries and provide insights into the observed luminescence.

Phan, Vo Quang Huy [University of Texas at Arlingt↗
DOE OSTI2025

Influence of functional additives, fillers, and pigments on thermal and catalytic pyrolysis of polyethylene for waste plastic upcycling

Pyrolysis offers a relatively green and economical method to convert waste plastics into valuable chemicals and fuels without the need for harmful solvents, toxic chemicals, or costly high-pressure reactors. Despite its popularity among chemical upcycling technologies, industrial adoption suffers from feedstock heterogeneity, low-quality products, and catalyst deactivation. Most plastics in our daily lives are formulated with functional additives, fillers, and colorants. These additives remaining in end-of-life waste streams increase feedstock heterogeneity, creating a challenging issue in recycling plastics. Still, the potential impacts of additives on the chemical upcycling of plastics have been poorly understood. In this study, polyethylene compounded with a range of widely used additives (antioxidants, stabilizers, pigments, fillers, slip agents, and flame retardants) was subjected to both thermal pyrolysis and catalytic pyrolysis in different catalyst-to-feedstock contact modes. It showed that many inorganic additives, such as talc, kaolin, CaCO 3 , TiO 2 , carbon black, and zinc stearate, facilitated polymer decomposition during pyrolysis, increasing light hydrocarbons while also promoting aromatic and carbon residue formation. Conversely, antioxidants and stabilizers inhibited depolymerization, favoring heavier hydrocarbons. During catalytic pyrolysis with HZSM-5 zeolite, additives strongly enhanced aromatic and catalytic coke formation, especially when there was direct contact between plastics and catalysts. Although certain additives seem beneficial in the short term by promoting polymer cracking and improving the selectivity of aromatics, the transport of the additives and their degradation products and increased carbon coking can contaminate products, deactivate or modify catalysts, and foul reactors. These findings address a critical knowledge gap in effectively converting waste plastics via a greener route.

42 ENGINEERING↗