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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 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Ziram, a dithiocarbamate fungicide, exhibits pseudo-cytoprotective actions against oxidative stress in rat thymocytes: Possible environmental risks

Highlights: • Ziram exerted reciprocal actions on H{sub 2}O{sub 2}-induced cell death. • Ziram augmented H{sub 2}O{sub 2}-induced decrease in cellular glutathione levels. • Ziram enhanced H{sub 2}O{sub 2}-induced increase in intracellular Zn{sup 2+} levels. • Ziram attenuated H{sub 2}O{sub 2}-induced depolarization of mitochondrial membrane potential. • Ziram exhibited pseudo-cytoprotective actions against oxidative stress induced by H{sub 2}O{sub 2}. Ziram, a dithiocarbamate fungicide, protects various vegetables and fruits against infections by fungus. Recently, there have been increasing anxieties about the risks in the use of dithiocarbamate fungicides. Our previous studies showed that Zn{sup 2+} was a determinant of Ziram cytotoxicity. In addition, Zn{sup 2+} is linked to H{sub 2}O{sub 2} cytotoxicity. Therefore, in this study, we aimed to test the hypothesis that Ziram could augment the cytotoxicity of H{sub 2}O{sub 2} by examining the changes induced by Ziram in some cellular parameters in rat thymic lymphocytes subjected to H{sub 2}O{sub 2}-induced oxidative stress using flow-cytometric methods with fluorescent dyes. Ziram significantly attenuated H{sub 2}O{sub 2}-induced cell death at sublethal concentrations. However, in the cells under oxidative stress elicited by H{sub 2}O{sub 2}, Ziram promoted the changing over from intact cells to living cells with exposed phosphatidylserine (PS) on plasma membranes, whereas it inhibited the transition from PS-exposed living cells to dead cells. Ziram significantly augmented H{sub 2}O{sub 2} actions, including reduction of cellular glutathione levels and elevation of intracellular Zn{sup 2+} concentrations. Conversely, it attenuated H{sub 2}O{sub 2}-induced depolarization of mitochondrial membrane potential. Ziram at sublethal concentrations seems to exhibit promotive and suppressive actions on the process of cell death caused by H{sub 2}O{sub 2}. Ziram increased the number of living cells with exposed PS, a phenomenon characteristic of early stages of apoptosis. Thus, it is concluded that Ziram exhibits pseudo-cytoprotective actions against H{sub 2}O{sub 2}-induced oxidative stress. Ziram at sublethal concentrations exerts promotive and suppressive actions on the process of cell death caused by oxidative stress.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2016

Dithiocarbamate Self-Assembled Monolayers as Efficient Surface Modifiers for Low Work Function Noble Metals

Tuning the work function of the electrode is one of the crucial steps to improve charge extraction in organic electronic devices. Here, we show that N,N-dialkyl dithiocarbamates (DTC) can be effectively employed to produce low work function noble metal electrodes. Work functions between 3.1 and 3.5 eV are observed for all metals investigated (Cu, Ag, and Au). Ultraviolet photoemission spectroscopy (UPS) reveals a maximum decrease in work function by 2.1 eV as compared to the bare metal surface. Electronic structure calculations elucidate how the complex interplay between intrinsic dipoles and dipoles induced by bond formation generates such large work function shifts. Subsequently, we quantify the improvement in contact resistance of organic thin film transistor devices with DTC coated source and drain electrodes. These findings demonstrate that DTC molecules can be employed as universal surface modifiers to produce stable electrodes for electron injection in high performance hybrid organic optoelectronics.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Structure-activity relationships of novel dithiocarbamates containing α,β-unsaturated ketone fragment as potent anticancer agents

Based on the structure of novel lead compound 8 discovered by our group, systematic structural modification was carried out. A series of compound 8’s derivatives were synthesized and evaluated for their activities against human non-small cell lung cancer cell line H460. Among them, twelve compounds showed significant proliferation inhibition activities with IC{sub 50} values <1 μM and compound 12r was the most potent one. Further study on compound 12r revealed that it has significant inhibitory effect on the growth of eight kinds of cancer cell lines with IC{sub 50} values <1 μM. Especially for cell lines A375 and HCT116, the IC{sub 50} values of 12r achieved 63 nM and 66 nM, respectively. Meanwhile, our research results also revealed the following structure-activity relationships: (a) different substitutions on the benzene ring or heteroaromatic rings greatly effect on the activity; (b) the presence of α,β-unsaturated ketone fragment is favorable for the activity; (c) the receptor cavity binding with amine moiety might be a relatively small hydrophobic cavity. These results will be valuable for the further development of this novel kind of dithiocarbamates.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2020

Compression of curium pyrrolidine-dithiocarbamate enhances covalency

Curium is unique in the actinide series because its half-filled 5f 7 shell has lower energy than other 5f n configurations, rendering it both redox-inactive and resistant to forming chemical bonds that engage the 5f shell. This is even more pronounced in gadolinium, curium’s lanthanide analogue, owing to the contraction of the 4f orbitals with respect to the 5f orbitals. However, at high pressures metallic curium undergoes a transition from localized to itinerant 5f electrons. This transition is accompanied by a crystal structure dictated by the magnetic interactions between curium atoms. Therefore, the question arises of whether the frontier metal orbitals in curium(III)–ligand interactions can also be modified by applying pressure, and thus be induced to form metal–ligand bonds with a degree of covalency. Here we report experimental and computational evidence for changes in the relative roles of the 5f/6d orbitals in curium–sulfur bonds in [Cm(pydtc) 4 ] – (pydtc, pyrrolidinedithiocarbamate) at high pressures (up to 11 gigapascals). We compare these results to the spectra of [Nd(pydtc) 4 ] – and of a Cm(III) mellitate that possesses only curium–oxygen bonds. Compared with the changes observed in the [Cm(pydtc) 4 ] – spectra, we observe smaller changes in the f–f transitions in the [Nd(pydtc) 4 ] – absorption spectrum and in the f–f emission spectrum of the Cm(III) mellitate upon pressurization, which are related to the smaller perturbation of the nature of their bonds. These results reveal that the metal orbital contributions to the curium–sulfur bonds are considerably enhanced at high pressures and that the 5f orbital involvement doubles between 0 and 11 gigapascal. Furthermore, our work implies that covalency in actinides is complex even when dealing with the same ion, but it could guide the selection of ligands to study the effect of pressure on actinide compounds.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

A series of dithiocarbamates for americium, curium, and californium

Characterizing how actinide properties change across the f-element series is critical for improving predictive capabilities and solving many nuclear problems facing our society. Unfortunately, it is difficult to make direct comparisons across the 5f-element series because so little is known about trans-plutonium elements. Results described in this paper help to address this issue through isolation of An(S 2 CNEt 2 ) 3 (N 2 C 12 H 8 ) (Am, Cm, and Cf). These findings included the first single crystal X-ray diffraction measurements of Cm–S (mean of 2.86 ± 0.04 Å) and Cf–S (mean of 2.84 ± 0.04 Å) bond distances. Furthermore, they highlight the potential of An(S 2 CNEt 2 ) 3 (N 2 C 12 H 8 ) for providing a test bed for comparative analyses of actinide versus lanthanide bonding interactions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Design of a Hole Trapping Ligand

A new ligand that covalently attaches to the surface of colloidal CdSe/ CdS nanorods and can simultaneously chelate a molecular metal center is described. The dithiocarbamate$-$bipyridine ligand system facilitates hole transfer through energetic overlap at the inorganic$-$organic interface and conjugation through the organic ligand to a chelated metal center. Density functional theory calculations show that the coordination of the free ligand to a CdS surface causes the formation of two hybridized molecular states that lie in the band gap of CdS. The further chelation of Fe(II) to the bipyridine moiety causes the presence of seven midgap states. Hole transfer from the CdS valence band to the midgap states is dipole allowed and occurs at a faster rate than what is experimentally known for the CdSe/CdS band-edge radiative recombination. In the case of the ligand bound with iron, a two-step process emerges that places the hole on the iron, again at rates much faster than band gap recombination. The system was experimentally assembled and characterized via UV$-$vis absorbance spectroscopy, fluorescence spectroscopy, time-resolved photoluminescence spectroscopy, and energy dispersive X-ray spectroscopy. Lastly, theoretically predicted red shifts in absorbance were observed experimentally, as well as the expected quench in photoluminescence and lifetimes in time-resolved photoluminescence

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2020

Isolation and Structural Elucidation of 15–Nuclear Copper Dihydride Clusters: An Intermediate in the Formation of a Two–Electron Copper Superatom

Highly reactive copper-dihydride clusters, [Cu 15 (H) 2 (S 2 CNR 2 ) 6 (C 2 Ph) 6 ](PF 6 ) {R = n Bu (1 H ), n Pr (2 H ), i Bu (3 H )}, are isolated during the reaction of [Cu 28 H 15 {S 2 CN n Bu 2 } 12 ](PF 6 ) with ten equivalents of phenylacetylene. They are found to be intermediates in the formation of the earlier reported two-electron superatom [Cu 13 (S 2 CNR 2 ) 6 (C 2 Ph) 4 ] + . Better yields are obtained by reacting dithiocarbamate sodium salts, [Cu(CH 3 CN) 4 ](PF 6 ), BH 4 – and phenylacetylene. The presence of two hydrides in the isolated clusters is confirmed by the synthesis and characterization of its deuteride analogue [Cu 15 (D) 2 (S 2 CNR 2 ) 6 (C 2 Ph) 6 ] + , and a single-crystal neutron structure of 2 H . Structural characterization of 1 H reveals a new bicapped icosahedral copper(I) cage encapsulating a linear copper dihydride (CuH 2 ) – unit. In conclusion, reaction of 3 H with Au(I) salts yields a highly luminescent [AuCu 12 (S 2 CNiBu 2 ) 6 (C 2 Ph) 4 ] + cluster.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2018

Klotho prevents DEX-induced apoptosis in MC3T3-E1 osteoblasts through the NF-κB signaling pathway

Highlights: • Klotho can inhibit DEX-induced apoptosis of MC3T3-E1 osteoblasts by inhibiting the expression of caspase-3. • NF-κB inhibitor PDTC reduced the number of DEX-induced apoptotic cells and attenuated the activity of caspase-3. • Klotho can inhibit IκB degradation, NF-κB nuclear translocation, and p65 phosphorylation in DEX-induced MC3T3-E1 apoptosis. Dexamethasone (DEX) is a commonly used anti-inflammatory drug and an immunosuppressive drug used in clinical practice to treat a variety of diseases. Glucocorticoid-induced osteoporosis (GIOP) is a consequence of high dose, or a long-term low dose use of glucocorticoids (GCs). These treatment regimens can cause a variety of bone-related adverse effects, leading to increased osteoblast and bone cell apoptosis. Evidence suggests that klotho (KL) can inhibit GIOP. It is unknown whether KL attenuates DEX-induced apoptosis in MC3T3-E1 cells or the underlying mechanisms involved. In the present study, we found that MC3T3-E1 cells pretreated with DEX led to the up-regulation of cleaved-caspase-3, and down-regulation of caspase-3, which were inhibited by KL transfection. Furthermore, flow cytometry and western blot analysis revealed that the NFκB inhibitor pyrrolidine dithiocarbamate (PDTC) could restore the DEX-induced caspase-3 decrease and inhibit the DEX-induced cleaved caspase-3 increase. We observed that DEX stimulated the degradation of IκBα(NFκB inhibitor α) and the translocation of NFκB, which were suppressed by KL transfection. These findings therefore, indicate a protective role for KL against osteoblastic cell apoptosis induced by DEX, via the NF-κB signaling pathway.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2025

Small-Molecule Models of Hydrogen-Evolving MX 2 (M = Mo, W; X = S, Se) Bulk Solids: Composition–Activity Relationships

Triangular metal chalcogenide clusters of the form [M 3 Q 7 L 3 ]An (M = Mo or W; Q = S or Se; L = i Bu 2 NCS 2 – , (CF 3 CH 2 ) 2 NCS 2 – , i Bu 2 NCSe 2 – , or i Bu 2 PS 2 – ; An = Cl – or I – ) have been investigated as molecular analogues of layered metal dichalcogenide (MX 2 ) H 2 -evolution catalysts. These clusters have been evaluated for their relative H 2 -evolving ability under a common photolysis protocol implementing [Ru(bpy) 3 ] 2+ as chromophore and Et 3 N as sacrificial electron donor. With M constant as Mo and with constant supporting ligand, clusters with an all-sulfide core enable greater H 2 -TON than clusters with an all-selenide core. A more active catalyst is produced by [Mo 3 S 7 (S 2 CN i Bu 2 ) 3 ] + I – than its W 3 analogue with the same core sulfide composition and supporting dithiocarbamate ligands. Dichalcogenocarbamate ligands provide more active catalysts than dialkyldithiophosphate ligated clusters, and within the dichalcogenocarbamate set, greater H 2 -turnovers correlate with more-electron-donating ligands (i.e., i Bu 2 NCS 2 – > (CF 3 CH 2 ) 2 NCS 2 – > i Bu 2 NCSe 2 – ). Cluster cations with Cl – as counteranion are very similar in activity H 2 -evolving levels to identical clusters with I – , ruling out any significant interfering effect by I – upon the electron transfer relay between Et 3 N and catalyst. In the aggregate, observations are consistent with a mechanism for H 2 evolution that involves reductive extrusion of H 2 from a metal hydride intermediate.

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

Ultralow Boundary Lubrication Friction by Three-Way Synergistic Interactions among Ionic Liquid, Friction Modifier, and Dispersant

Interactions among antiwear additives (AWs), friction modifiers (FMs), and dispersant in a lubricating oil are critical for tribological performance. This study investigates compatibilities of three oil-soluble ionic liquids (ILs, candidate AWs) with an FM, molybdenum dithiocarbamate (MoDTC), and a dispersant, polyisobutene succinimide (PIBSI) under boundary lubrication. Either synergistic or antagonistic effects were observed depending on the IL’s chemistry. Adding an aprotic phosphonium–alkylphosphate or phosphonium–alkylphosphinate IL into the oil containing MoDTC and PIBSI had detrimental impact on the friction and wear behavior. PIBSI was found to preferably interact/react with the aprotic IL to lose its ability of suspending MoDTC and to partially consume or even deplete the IL. In contrast, a protic ammonium–alkylphosphate IL seemed to be able to coexist with PIBSI and work synergistically with MoDTC, yielding a sustainable, ultralow boundary friction. A three-stage tribochemical process is proposed to explain how this IL + MoDTC pair interacts with the contact surface to form a chemically reacted, wear-protective tribofilm supporting a physically adsorbed, friction-reducing film on top. We report this study provides fundamental insights of the compatibilities among three common lubricant components, antiwear, friction modifier, and dispersant, which can be used to guide future lubricant development.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Block Copolymer Sequence Inversion through Photoiniferter Polymerization

Block copolymers prepared by reversible addition–fragmentation chain transfer (RAFT) polymerization are often restricted to a specific comonomer blocking sequence that is dictated by intermediate radical stability and relative radical leaving group abilities. Techniques that provide alternative pathways for reinitiation of thiocarbonylthio-terminated polymers could allow access to block copolymer sequences currently unobtainable through the RAFT process. In this paper, we report a method for preparing “inverted” block copolymers, whereby the traditional order of monomer addition has been reversed through the use of photoiniferter-mediated radical polymerization. Specifically, thiocarbonylthio photolysis of xanthate- and dithiocarbamate-functional macromolecular chain transfer agents (macro-CTAs) led to the direct formation of leaving group macroradicals otherwise unaffordable by an addition–fragmentation mechanism. We believe this method could provide a route to synthesize multiblock copolymers of synthetically challenging comonomer sequences.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Cooperative adsorption of carbon disulfide in diamine-appended metal–organic frameworks

Over one million tons of CS 2 are produced annually, and emissions of this volatile and toxic liquid, known to generate acid rain, remain poorly controlled. As such, materials capable of reversibly capturing this commodity chemical in an energy-efficient manner are of interest. Recently, we detailed diamine-appended metal–organic frameworks capable of selectively capturing CO 2 through a cooperative insertion mechanism that promotes efficient adsorption–desorption cycling. We therefore sought to explore the ability of these materials to capture CS 2 through a similar mechanism. Employing crystallography, spectroscopy, and gas adsorption analysis, we demonstrate that CS 2 is indeed cooperatively adsorbed in N,N-dimethylethylenediamine-appended M 2 (dobpdc) (M = Mg, Mn, Zn; dobpdc 4- = 4,4'-dioxidobiphenyl-3,3'-dicarboxylate), via the formation of electrostatically paired ammonium dithiocarbamate chains. In the weakly thiophilic Mg congener, chemisorption is cleanly reversible with mild thermal input. Finally, this work demonstrates that the cooperative insertion mechanism can be generalized to other high-impact target molecules.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Ground electronic state description of thiourea coordination in homoleptic Zn 2+ , Ni 2+ and Co 2+ complexes using sulfur K -edge X-ray absorption spectroscopy

Sulfur K-edge X-ray absorption spectroscopy (XAS) was employed to experimentally characterize the coordinative bond between the thiourea (TU) or thiocarbamide ligand and transition metal (TM) ions Zn 2+ , Co 2+ and Ni 2+ in distorted tetrahedral and octahedral homoleptic coordination environments. Comparisons of XAS spectra of the free TU ligand and [Zn(TU) 4 ] 2+ , [Co(TU) 4 ] 2+ and [Ni(TU) 6 ] 2+ complexes clearly identify spectral features unique to TM 2+ –S(TU) bonding. Quantitative analysis of pre-edge intensities describes the covalency of Ni 2+ —S(TU) and Co 2+ —S(TU) bonding to be at most 21% and 9% as expressed by the S 3p contributions per TM 3d electron hole. Using relevant Ni 2+ complexes with dithiocarbamate and thioether ligands, we evaluated the empirical S 1s → 3p transition dipole integrals developed for S-donor ligands and their dependence on heteroatom substitutions. With the aid of density functional theory-based ground electronic state calculations, we found evidence for the need of using a transition dipole that is dependent on the presence of conjugated heteroatom (N) substitution in these S-donor ligands.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2025

Apple Bitter Rot: Biology, Ecology, Omics, Virulence Factors, and Management of Causal Colletotrichum Species

ABSTRACT Apple bitter rot is caused by various Colletotrichum spp. that threaten apple production globally resulting in millions of dollars in damage annually. The fungus causes a decline in fruit quality and yield, eventually rotting the fruit and rendering it inedible. The pathogen is difficult to keep out of orchards because of its broad host range and transmissibility by rain splash and insects. Once the disease manifests, pathogen identification is difficult due to evolving taxonomy and similar morphology between species. Current management strategies are threatened by an increase in fungicide resistance and regulations on many multisite fungicides, leading to a pressing need for new management options for control. This review aims to summarise the most current knowledge regarding the biology, virulence factors, ecology, omics and emerging management strategies for Colletotrichum species that cause apple bitter rot. Taxonomy Colletotrichum species—Domain Eukaryota, Kingdom Fungi, Phylum Ascomycota, Class Sordariomycetes, Order Glomerellales, Family Glomerellaceae, Genus Colletotrichum . Biology Hemibiotrophic pathogen with a wide host range that establishes a biotrophic interaction where it penetrates host plants using appressoria followed by a switch to necrotrophy causing rot symptoms. Toxins Cercosporin, colletotrichins, colletotric acid, ferricrocin. Host Range The host range varies by species but largely occurs on dicotyledonous plants and is less prevalent on monocots as well as gymnosperms, ferns, mosses and animals (e.g., insects). Disease Symptoms Symptoms often manifest as flat to sunken necrotic areas on fruit. Lesions on leaves and fruit can have concentric rings with abundant pathogen sporulation. Disease Control Colletotrichum spp. are primarily managed by single‐site quinone outside inhibitor (Qol), methyl benzimidazole carbamate (MBC), demethylation inhibitor (DMI) fungicides, and multisite dithiocarbamate and phthalimide fungicides. Susceptibility may vary with species, strain specificity, or geographic region. Other management options include clean stock production, cultural practices, resistance breeding, and biological control through the introduction of protective or competing microorganisms.

Boeckman, Nathanial J. [Plant Pathology Laboratory↗