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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Synthesis, structure, linear and nonlinear optical properties of noncentrosymmetric quaternary diamond-like semiconductors, Cu 2 ZnGeSe 4 (CZGSe) and the novel Cu 4 ZnGe 2 Se 7

In this work, two quaternary diamond-like semiconductors (DLSs) in the Cu-Zn-Ge-Se system, the known Cu 2 ZnGeSe 4 (also referred to as CZGSe) and the new Cu 4 ZnGe 2 Se 7 , are compared in terms of their crystal structures, electronic structures and physicochemical properties. Both compounds were prepared by high-temperature, solid-state synthesis at 800 degrees C. Single crystal X-ray diffraction was used to determine the structure of Cu 4 ZnGe 2 Se 7 . The structures of both Cu 2 ZnGeSe 4 and Cu 4 ZnGe 2 Se 7 can be considered as derivatives of cubic diamond. Cu 4 ZnGe 2 Se 7 , with a reduced symmetry due to the cation ordering pattern, adopts the Cu 4 NiSi 2 S 7 structure type, with space group C2. The corner-sharing tetrahedra in Cu 4 ZnGe 2 Se 7 are slightly distorted because the charge for some of the S 2 - anions is not compensated by the first-nearest-neighbor cations. Rietveld refinements using synchrotron X-ray powder diffraction data were used to assess the phase purity of the samples and confirm the bulk structural behavior. Diffuse reflectance UV/Vis/NIR spectroscopy shows that Cu 2 ZnGeSe 4 and Cu 4 ZnGe 2 Se 7 have direct optical bandgaps of 1.38 and 0.91 eV, respectively. Electronic structure calculations implementing density functional theory confirm the direct bandgap for Cu 4 ZnGe 2 Se 7 , with a calculated value of 0.62 eV. Both compounds are air stable, thermally stable up to relatively high temperatures, undergo phase transitions and have wide windows of optical clarity. The Kurtz-Perry powder technique was used to determine the second harmonic generation (SHG) responses using a commercial AgGaSe 2 standard. While Cu 4 ZnGe 2 Se 7 displays a weak SHG response, Cu 2 ZnGeSe 4 exhibits a response that is greater than several benchmark materials, with a large SHG coefficient, χ (2) , of 43 ± 6 pm/V at λ = 2900 nm.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Magnetic excitations from the hexagonal spin clusters in the 𝑆 = $\frac{1}{2}$ distorted honeycomb lattice antiferromagnet Cu 2 ⁢(pymca)⁢ 3 ⁢(ClO 4 )

Cu 2 ⁢(pymca) ⁢3 (ClO 4 ) (pymca: pyrimidine-2-carboxylate) consists of a slightly distorted honeycomb lattice of Cu 2+ spins, which shows no long-range magnetic order down to 0.6 K. A magnetization study revealed 1/3 and 2/3 plateau phases [A. Okutani et al., J. Phys. Soc. Jpn. 88, 013703 (2019)], which is not expected for regular honeycomb antiferromagnets. Inelastic neutron scattering experiments were performed using a powder sample to investigate the exchange interactions of this material. The spin excitations from the singlet ground state to the first three triplet states, predicted from the antiferromagnetic hexagonal spin cluster interacting with 3.9 meV, were observed. Using the exact diagonalization methods, the intercluster coupling was estimated from the excitation peak width to be about 20% of the intracluster interaction, which is consistent with the previously reported value. Finally, our exchange path model explains the anisotropic exchange interactions in the distorted honeycomb plane.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

Embedding Reverse Electron Transfer Between Stably Bare Cu Nanoparticles and Cation‐Vacancy CuWO 4

Cu nanoparticles (NPs) have attracted widespread attention in electronics, energy, and catalysis. However, conventionally synthesized Cu NPs face some challenges such as surface passivation and agglomeration in applications, which impairs their functionalities in the physicochemical properties. Here, the issues above by engineering an embedded interface of stably bare Cu NPs on the cation-vacancy CuWO 4 support is addressed, which induces the strong metal-support interactions and reverse electron transfer. Various atomic-scale analyses directly demonstrate the unique electronic structure of the embedded Cu NPs with negative charge and anion oxygen protective layer, which mitigates the typical degradation pathways such as oxidation in ambient air, high-temperature agglomeration, and CO poisoning adsorption. Kinetics and in situ spectroscopic studies unveil that the embedded electron-enriched Cu NPs follow the typical Eley-Rideal mechanism in CO oxidation, contrasting the Langmuir-Hinshelwood mechanism on the traditional Cu NPs. This mechanistic shift is driven by the Coulombic repulsion in anion oxygen layer, enabling its direct reaction with gaseous CO to form the easily desorbed monodentate carbonate.

Cu nanoparticles↗
DOE OSTI2025

Structural Diversity and Tunable Emission in Hybrid Organic–Inorganic Copper(I) Bromides

Recently, hybrid organic−inorganic copper(I) metal halides have attracted global attention due to their intriguing optical properties and low-cost solution processability. In this work, we report three hybrid organic−inorganic copper(I) bromides, [TMPA] 2 [Cu 2 Br 4 ], [TMPA] 4 [Cu 6 Br 10 ], and [TMPA] 2 [Cu 4 Br 6 ], synthesized through a slow evaporation method using trimethylphenylammonium (TMPA + ) as the organic cation. By precise control of the CuBr and TMPABr precursors, different copper halide [Cu 2 Br 4 ] 2− , [Cu 6 Br 10 ] 4− , and [Cu 4 Br 6 ] 2− structural units can be obtained. [TMPA] 2 [Cu 2 Br 4 ], [TMPA] 4 [Cu 6 Br 10 ], and [TMPA] 2 [Cu 4 Br 6 ] demonstrate distinct blue, orange, and greenish-yellow light emission, respectively. The first two compounds have zero-dimensional (0D) crystal structures in centrosymmetric triclinic space group P-1 and monoclinic space group P2 1 /n. In contrast, [TMPA] 2 [Cu 4 Br 6 ] features a unique one-dimensional (1D) structure and crystallizes in the centrosymmetric monoclinic space group P2 1 /c. Consequently, the observed greenish-yellow emission of [TMPA] 2 [Cu 4 Br 6 ] is also unique, in contrast to the typical orange-red emission of 0D [Cu 4 Br 6 ]-based compounds. This work provides insights into the design of copper halide light emitters and emphasizes the influence of structural dimensionality on photoluminescence. The tunable optical properties suggest the potential of these materials for multicolor photopatterning, information encryption, and anticounterfeiting applications.

Anions↗
DOE OSTI2020

Materials Data on Cu(CO)4 by Materials Project

Cu(CO)4 crystallizes in the monoclinic C2/c space group. The structure is one-dimensional and consists of two Cu(CO)4 ribbons oriented in the (0, 0, 1) direction. Cu2+ is bonded to six O2- atoms to form edge-sharing CuO6 octahedra. There are a spread of Cu–O bond distances ranging from 1.98–2.50 Å. There are two inequivalent C+1.50+ sites. In the first C+1.50+ site, C+1.50+ is bonded in a single-bond geometry to one O2- atom. The C–O bond length is 1.26 Å. In the second C+1.50+ site, C+1.50+ is bonded in a single-bond geometry to one O2- atom. The C–O bond length is 1.26 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to two equivalent Cu2+ and one C+1.50+ atom. In the second O2- site, O2- is bonded in a bent 120 degrees geometry to one Cu2+ and one C+1.50+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cu(TeO3)4 by Materials Project

Cu(TeO3)4 crystallizes in the triclinic P1 space group. The structure is three-dimensional. Cu2+ is bonded in a 3-coordinate geometry to six O2- atoms. There are a spread of Cu–O bond distances ranging from 1.96–2.54 Å. There are four inequivalent Te+5.50+ sites. In the first Te+5.50+ site, Te+5.50+ is bonded to six O2- atoms to form corner-sharing TeO6 octahedra. The corner-sharing octahedra tilt angles range from 32–40°. There are a spread of Te–O bond distances ranging from 1.95–2.05 Å. In the second Te+5.50+ site, Te+5.50+ is bonded to six O2- atoms to form corner-sharing TeO6 octahedra. The corner-sharing octahedra tilt angles range from 35–42°. There are a spread of Te–O bond distances ranging from 1.94–2.06 Å. In the third Te+5.50+ site, Te+5.50+ is bonded to six O2- atoms to form corner-sharing TeO6 octahedra. The corner-sharing octahedra tilt angles range from 32–42°. There are a spread of Te–O bond distances ranging from 1.96–2.03 Å. In the fourth Te+5.50+ site, Te+5.50+ is bonded to six O2- atoms to form corner-sharing TeO6 octahedra. The corner-sharing octahedra tilt angles range from 33–41°. There are a spread of Te–O bond distances ranging from 1.94–2.05 Å. There are twelve inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to one Cu2+ and two Te+5.50+ atoms. In the second O2- site, O2- is bonded in a bent 150 degrees geometry to two Te+5.50+ atoms. In the third O2- site, O2- is bonded in a bent 150 degrees geometry to two Te+5.50+ atoms. In the fourth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Cu2+ and two Te+5.50+ atoms. In the fifth O2- site, O2- is bonded in a bent 150 degrees geometry to two Te+5.50+ atoms. In the sixth O2- site, O2- is bonded in a bent 150 degrees geometry to two Te+5.50+ atoms. In the seventh O2- site, O2- is bonded in a distorted trigonal planar geometry to one Cu2+ and two Te+5.50+ atoms. In the eighth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Cu2+ and two Te+5.50+ atoms. In the ninth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Cu2+ and two Te+5.50+ atoms. In the tenth O2- site, O2- is bonded in a bent 150 degrees geometry to two Te+5.50+ atoms. In the eleventh O2- site, O2- is bonded in a distorted T-shaped geometry to one Cu2+ and two Te+5.50+ atoms. In the twelfth O2- site, O2- is bonded in a bent 150 degrees geometry to two Te+5.50+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cu(SnS2)4 by Materials Project

Cu(SnS2)4 is beta indium sulfide-derived structured and crystallizes in the cubic F-43m space group. The structure is three-dimensional. Cu2+ is bonded to four equivalent S2- atoms to form CuS4 tetrahedra that share corners with twelve equivalent SnS6 octahedra. The corner-sharing octahedral tilt angles are 57°. All Cu–S bond lengths are 2.33 Å. Sn+3.50+ is bonded to six S2- atoms to form SnS6 octahedra that share corners with three equivalent CuS4 tetrahedra and edges with six equivalent SnS6 octahedra. There are three shorter (2.60 Å) and three longer (2.67 Å) Sn–S bond lengths. There are two inequivalent S2- sites. In the first S2- site, S2- is bonded in a distorted rectangular see-saw-like geometry to one Cu2+ and three equivalent Sn+3.50+ atoms. In the second S2- site, S2- is bonded in a distorted T-shaped geometry to three equivalent Sn+3.50+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Formation Pathway of Wurtzite-like Cu 2 ZnSnSe 4 Nanocrystals

Cu 2 ZnSnSe 4 is a direct band gap semiconductor composed of Earth-abundant elements, making it an attractive material for thin film photovoltaic technologies. Cu 2 ZnSnSe 4 crystallizes in the kesterite structure type as a bulk material, but it can also crystallize in a metastable wurtzite-like crystal structure when synthesized on the nanoscale. The wurtzite-like polymorph introduces unique and useful properties to Cu 2 ZnSnSe 4 materials, including widely tunable band gaps and superior composi-tional flexibility as compared to kesterite Cu 2 ZnSnSe 4 . Here, we investigate the formation pathway of colloidally prepared wurtzite-like Cu 2 ZnSnSe 4 nanocrystals. We show that this quaternary material forms through a chain of reactions, starting with binary Cu 3 Se 2 nanocrystals that, due to both kinetic and thermodynamic reasons, preferentially react with tin to yield hexagonal copper tin selenide intermediates. Furthermore, these ternary intermediates then react with zinc to form the resulting wurtzite-like Cu 2 ZnSnSe 4 nanocrystals. Based on this formation pathway, we suggest synthetic methods that may prevent the for-mation of unwanted impurity phases that are known to hamper the efficiency of Cu 2 ZnSnSe 4 -based optoelectronic devices.

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

Materials Data on Cu(IN)4 by Materials Project

Cu(N2I)2(I)2 crystallizes in the monoclinic C2/m space group. The structure is two-dimensional and consists of two iodine molecules and one Cu(N2I)2 sheet oriented in the (0, 0, 1) direction. In the Cu(N2I)2 sheet, Cu2+ is bonded in a distorted square co-planar geometry to four equivalent N+0.50+ atoms. All Cu–N bond lengths are 1.90 Å. N+0.50+ is bonded in a 3-coordinate geometry to one Cu2+ and two equivalent I1- atoms. There are one shorter (2.04 Å) and one longer (2.21 Å) N–I bond lengths. I1- is bonded in a 4-coordinate geometry to four equivalent N+0.50+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cu(CO2)4 by Materials Project

Cu(C2O4)2 crystallizes in the monoclinic P2_1/c space group. The structure is two-dimensional and consists of one Cu(C2O4)2 sheet oriented in the (1, 0, 0) direction. Cu2+ is bonded in an octahedral geometry to six O2- atoms. There are a spread of Cu–O bond distances ranging from 2.07–2.54 Å. There are two inequivalent C+3.50+ sites. In the first C+3.50+ site, C+3.50+ is bonded in a bent 150 degrees geometry to two O2- atoms. Both C–O bond lengths are 1.22 Å. In the second C+3.50+ site, C+3.50+ is bonded in a linear geometry to two O2- atoms. Both C–O bond lengths are 1.18 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Cu2+ and one C+3.50+ atom. In the second O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Cu2+ and one C+3.50+ atom. In the third O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Cu2+ and one C+3.50+ atom. In the fourth O2- site, O2- is bonded in a single-bond geometry to one C+3.50+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Atomic Dynamics of Multi‐Interfacial Migration and Transformations

Redox-induced interconversions of metal oxidation states typically result in multiple phase boundaries that separate chemically and structurally distinct oxides and suboxides. Directly probing such multi-interfacial reactions is challenging because of the difficulty in simultaneously resolving the multiple reaction fronts at the atomic scale. Using the example of CuO reduction in H 2 gas, a reaction pathway of CuO → monoclinic m-Cu 4 O 3 → Cu 2 O is demonstrated and identifies interfacial reaction fronts at the atomic scale, where the Cu 2 O/m-Cu 4 O 3 interface shows a diffuse-type interfacial transformation; while the lateral flow of interfacial ledges appears to control the m-Cu 4 O 3 /CuO transformation. Together with atomistic modeling, it is shown that such a multi-interface transformation results from the surface-reaction-induced formation of oxygen vacancies that diffuse into deeper atomic layers, thereby resulting in the formation of the lower oxides of Cu 2 O and m-Cu 4 O 3 , and activate the interfacial transformations. In conclusion, these results demonstrate the lively dynamics at the reaction fronts of the multiple interfaces and have substantial implications for controlling the microstructure and interphase boundaries by coupling the interplay between the surface reaction dynamics and the resulting mass transport and phase evolution in the subsurface and bulk.

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

Ligand Control of Structural Diversity in Luminescent Hybrid Copper(I) Iodides

Copper(I) iodide hybrids are of interest for next-generation lighting technologies because of their efficient luminescence in the absence of rare-earth elements. Here, we report 10 structurally diverse hybrid copper(I) iodides that emit in the green–red region with quantum yields reaching 67%. The compounds display a diversity of structures including ones with one-dimensional (1D) Cu–1 chains, Cu 2 I 2 rhomboid dimers, and structures with two different arrangements of Cu 4 I 4 tetramers. The compounds with Cu 2 I 2 rhomboid dimers or Cu 4 I 4 cubane tetramers have higher photoluminescence quantum yields than those with Cu–I 1D chains and octahedral Cu 4 I 4 tetramers, owing to the optimal degree of condensation of the inorganic motifs, which suppresses nonradiative processes. Electronic structure calculations on these compounds point out the critical influence of the inorganic motif and organic ligand on the nature of the band gaps and thus the excitation characteristics. Temperature-dependent photoluminescence spectra are presented to better understand the nature of luminescence in compounds with different inorganic motifs. Here. the emerging understanding of composition–structure–property correlations in this family provides inspiration for the rational design of hybrid phosphors for general lighting applications.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Mixed‐Valence Cu I /Cu III Metal–Organic Frameworks with Non‐innocent Ligand for Multielectron Transfer

Abstract We report two novel three‐dimensional copper‐benzoquinoid metal–organic frameworks (MOFs), [Cu 4 L 3 ] n and [Cu 4 L 3 ⋅ Cu(iq) 3 ] n (LH 4 =1,4‐dicyano‐2,3,5,6‐tetrahydroxybenzene, iq=isoquinoline). Spectroscopic techniques and computational studies reveal the unprecedented mixed valency in MOFs, formal Cu(I)/Cu(III). This is the first time that formally Cu(III) species are witnessed in metal–organic extended solids. The coordination between the mixed‐valence metal and redox‐non‐innocent ligand L, which promotes through‐bond charge transfer between Cu metal sites, allows better metal‐ligand orbital overlap of the d‐π conjugation, leading to strong long‐range delocalization and semiconducting behavior. Our findings highlight the significance of the unique mixed valency between formal Cu(I) and highly‐covalent Cu(III), non‐innocent ligand, and pore environments of these bench stable Cu(III)‐containing frameworks on multielectron transfer and electrochemical properties.

Fu, Shang‐Yuan↗
DOE OSTI2023

Mixed‐Valence Cu I /Cu III Metal–Organic Frameworks with Non‐innocent Ligand for Multielectron Transfer

Abstract We report two novel three‐dimensional copper‐benzoquinoid metal–organic frameworks (MOFs), [Cu 4 L 3 ] n and [Cu 4 L 3 ⋅ Cu(iq) 3 ] n (LH 4 =1,4‐dicyano‐2,3,5,6‐tetrahydroxybenzene, iq=isoquinoline). Spectroscopic techniques and computational studies reveal the unprecedented mixed valency in MOFs, formal Cu(I)/Cu(III). This is the first time that formally Cu(III) species are witnessed in metal–organic extended solids. The coordination between the mixed‐valence metal and redox‐non‐innocent ligand L, which promotes through‐bond charge transfer between Cu metal sites, allows better metal‐ligand orbital overlap of the d‐π conjugation, leading to strong long‐range delocalization and semiconducting behavior. Our findings highlight the significance of the unique mixed valency between formal Cu(I) and highly‐covalent Cu(III), non‐innocent ligand, and pore environments of these bench stable Cu(III)‐containing frameworks on multielectron transfer and electrochemical properties.

Fu, Shang‐Yuan↗
DOE OSTI2021

Quasi-one-dimensional magnetism in the spin-12 antiferromagnet BaNa 2 Cu(VO 4 ) 2

Here, we report synthesis and magnetic properties of quasi-one-dimensional spin- 1 2 Heisenberg antiferromagnetic chain compound BaNa 2 Cu ( VO 4 ) 2 . This orthovanadate has a centrosymmetric crystal structure, C 2 / c , where the magnetic Cu 2 + ions form spin chains. These chains are arranged in layers, with the chain direction changing by 62 ° between the two successive layers. Alternatively, the spin lattice can be viewed as anisotropic triangular layers upon taking the interchain interactions into consideration. Despite this potential structural complexity, temperature-dependent magnetic susceptibility, heat capacity, electron spin resonance intensity, and nuclear magnetic resonance (NMR) shift agree well with the uniform spin- 1 / 2 Heisenberg chain model with an intrachain coupling of J / k B ≃ 5.6 K. The saturation field obtained from the magnetic isotherm measurement consistently reproduces the value of J / k B . Further, the V 51 NMR spin-lattice relaxation rate mimics the one-dimensional character in the intermediate temperature range, whereas magnetic long-range order sets in below T N ≃ 0.25 K. The effective interchain coupling is estimated to be J ⊥ / k B ≃ 0.1 K. The theoretical estimation of exchange couplings using band-structure calculations reciprocate our experimental findings and unambiguously establish the one-dimensional character of the compound. Finally, the spin lattice of BaNa 2 Cu ( VO 4 ) 2 is compared with the chemically similar but not isostructural compound BaAg 2 Cu ( VO 4 ) 2 .

36 MATERIALS SCIENCE↗
DOE OSTI2020

Structural Rearrangements of Subnanometer Cu Oxide Clusters Govern Catalytic Oxidation

Sub-nanometer metal oxide clusters are very important materials that are widely used, for example, in catalysis or electronic devices such as sensors. Hence, it is critical to understand the atomic structures and properties of sub-nanometer metal oxide clusters under a reactive gas environment, such as O 2 . We consider here experimentally accessible precise-size Cu clusters (Cu 4 ) supported on partially hydroxylated amorphous alumina and show that such clusters can access, in catalytic conditions at high temperature under a pressure of O 2 , a large ensemble of oxidized structures, representing a large variety of oxygen content, of geometries in link with the support, and of catalytic activities for oxidation reactions, as seen from their reducibilities. A grand canonical basin hopping method based on first-principles energy reveals an ensemble of 24 configurations for the Cu 4 O x cluster of low free energy, less than 0.8 eV above the global minimum. The low free energy ensemble consists of clusters of different stoichiometries, which are mainly Cu 4 O 3 and Cu 4 O 4 in the temperature range of 200–400 °C and under a pressure of 0.5 bar of O 2 . The presence of several competitive isomers at each composition implies that cluster fluxionality impacts the phase diagram, which should be ensemble-averaged. In terms of catalytic oxidation activity, Cu 4 O 3 isomers present highly variable O abstraction energy: the most stable isomers are inactive for alkane oxidative dehydrogenation, but isomerization to metastable isomers, that proceed with low barrier, enable to create active configurations with low O abstraction energy. O atoms with the lowest anionic character, and thus of more electrophilic nature, present the best oxidation capability. In contrast, all Cu 4 O 4 isomers show a low O abstraction energy and a high potential catalytic activity. Here, this manuscript demonstrates the unique structural and electronic properties of sub-nano Cu oxide clusters and illustrates the critical roles of configuration ensembles and rearrangement to highly reactive metastable cluster isomers in nanocatalysis.

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

Rigidochromism of tetranuclear Cu( I )–pyrazolate macrocycles: steric crowding with trifluoromethyl groups

Macrocyclic Cu(I)–pyrazolate tetramers (Cu 4 pz 4 ) can fold into compact structures with luminescent Cu 4 cores whose emission wavelengths are sensitive to steric effects along the periphery of the macrocycle. Introducing CF 3 at the C 4 position of 3,5-di- t Bu-pyrazolate increases steric crowding that modifies the conformational behavior of the Cu 4 pz 4 complex, highlighted by a low-temperature martensitic transition. Variable-temperature analysis of solid-state luminescence reveal an unexpected blueshifting of emission with rising temperature.

Rajagopal, Shinaj K.↗