A5088125083- Crystallization and Solubility Studies
- X-ray Diffraction in Crystallography
- Rare-earth and actinide compounds
- Perovskite Materials and Applications
- Crystallography and molecular interactions
- Iron-based superconductors research
- Organic Light-Emitting Diodes Research
- Organic Electronics and Photovoltaics
- Solid-state spectroscopy and crystallography
- Advanced Condensed Matter Physics
- Physics of Superconductivity and Magnetism
- Magnetic and transport properties of perovskites and related materials
- Luminescence and Fluorescent Materials
- Conducting polymers and applications
- Cannabis and Cannabinoid Research
- Topological Materials and Phenomena
- Crystal Structures and Properties
- Organic and Molecular Conductors Research
- Shape Memory Alloy Transformations
- Inorganic Chemistry and Materials
- Luminescence Properties of Advanced Materials
- Thermal Expansion and Ionic Conductivity
- Biochemical Analysis and Sensing Techniques
- GABA and Rice Research
- 2D Materials and Applications
Colorado State University
2018-2023
The University of Texas at Dallas
2014-2019
University of North Texas
2011-2019
Rice University
2015
Czech Academy of Sciences
2003
In this work, we present our discovery and characterization of a new kagome prototype structure, ${\mathrm{KV}}_{3}{\mathrm{Sb}}_{5}$. We also the isostructural compounds ${\mathrm{RbV}}_{3}{\mathrm{Sb}}_{5}$ ${\mathrm{CsV}}_{3}{\mathrm{Sb}}_{5}$. All materials exhibit structurally perfect two-dimensional net vanadium. Density-functional theory calculations indicate that are metallic, with Fermi level in close proximity to several Dirac points. Powder single-crystal syntheses presented,...
Two-dimensional perovskites have emerged as more intrinsically stable materials for solar cells. Chemical tuning of spacer organic cations has attracted great interest due to their additional functionalities. However, how the chemical nature affects properties two-dimensional and devices is rarely reported. Here we demonstrate that selection (i.e., selective fluorination phenethylammonium) film perovskites, leading different device performance perovskite cells (average n = 4). Structural...
The demonstrated square-planar Pt(II)-complex has reduced triplet-triplet quenching and therefore a near unity quantum yield in the neat thin film. A non-doped phosphorescent organic light-emitting diode (PhOLED) based on this emitter achieves (31.1 ± 0.1)% external efficiency without any out-coupling, which shows that PhOLED can be comparable to best doped devices with very complicated device structures.
Water cluster formation and methane adsorption within a hydrophobic porous metal organic framework is studied by in situ vibrational spectroscopy, isotherms, first-principle DFT calculations (using vdW-DF). Specifically, the stability of H2O clusters cavities fluorinated metal–organic (FMOF-1) examined. Although isotherms water show no measurable uptake (see Yang et al. J. Am. Chem. Soc. 2011, 133, 18094), large dipole internal modes makes it possible to detect low concentrations using IR...
By means of alloying appropriate amounts MnNiSi and MnFeGe, materials are found that undergo a paramagnetic to ferromagnetic transition close room temperature, accompanied by huge volume change. Thanks this change, application moderate pressures leads remarkable enhancement the magnetocaloric response. Work like may open new opportunities in development solid-state magnetic refrigeration devices.
We report the crystal growth of well-faceted single crystals methylammonium lead iodide, CH3NH3PbI3, and detailed neutron diffraction structural studies aimed at elucidating orientation (CH3NH3+) cation in tetragonal cubic phases hybrid inorganic–organic perovskite. Room temperature experiments reveal a structure where protonated amine substituent (−NH3+) is disordered four positions, each preferentially located near neighboring iodine [PbI6] octahedra, while methyl (−CH3) eight positions...
The emission of white light from a single material is atypical and interest for solid-state lighting applications. Broadband has been observed in some layered perovskite derivatives, A2PbBr4 (A = R-NH3+), correlates with static structural distortions corresponding to out-of-plane tilting the lead bromide octahedra. While materials different organic cations can yield distinct tilts, underlying origin octahedral remains poorly understood. Using high energy resolution (e.g., quasi-elastic)...
Abstract By introducing a neat Pt(II)‐based phosphor with remarkably short decay lifetime, simplified doping‐free phosphorescent organic light‐emitting diode (OLED) forward viewing external quantum efficiency (EQE) and power of 20.3 ± 0.5% 63.0 0.4 lm W −1 , respectively, is demonstrated. A quantitative analysis how triplet‐triplet annihilation (TTA) triplet‐polaron (TPA) affect the device EQE roll‐off at high current densities performed. The contributions from loss charge balance associated...
Two-dimensional (2D) organic–inorganic hybrid perovskites (OIHPs) have showed impressive stability, compared to their three-dimensional (3D) counterparts. However, tuning the chemical structure of organic cations simultaneously improve device performance and stability 2D OIHP solar cells is rarely reported. Here, we demonstrate that by introducing a classic noncovalent aryl-perfluoroaryl interaction, with 1:1 mixed phenethylammonium (PEA) perfluorophenethylammonium (F5-PEA) can achieve an...
Today's state‐of‐the‐art phosphorescent organic light‐emitting diodes (PhOLEDs) must rely on the host‐guest doping technique to decrease triplet quenching and increase device efficiency. However, is a sophisticated fabrication process. Here, Pt(II)‐based complex with near unity photoluminescence quantum yield excellent electron transporting properties in form of neat film reported. Simplified doping‐free white PhOLED yellow‐orange based this emitter achieve rather low operating voltages...
CO<sub>2</sub> isotherms for FMOF-1 reveal 11.0 mol L<sup>−1</sup> max uptake and suggest framework expansion, substantiated by <italic>in situ</italic> neutron diffraction GCMC simulations.
The isostructural alloying of two compounds with different magnetic and thermo-structural properties has resulted in a new system, (MnNiSi)1−x(FeCoGe)x, that exhibits large magnetocaloric effects acute sensitivity to both compositional variation applied hydrostatic pressure. maximum isothermal entropy change reaches value −ΔSmax = 143.7 J/kg K for field ΔB 5 T at atmospheric first-order magnetostructural transition responsible the shifts lower temperature pressure (∼−10 K/kbar) but maintains −ΔSmax.
Honeycomb iridates are thought to have strongly spin-anisotropic exchange interactions that could lead an extraordinary state of matter known as the Kitaev quantum spin liquid. The realization this requires almost perfectly frustrated between magnetic Ir$^{4+}$ ions, but small imbalances in energy make other ordered states more favorable. Indeed, closeness these is itself a signature intrinsic frustration system. In work, we illustrate fields can be employed drive magnet...
Hybrid metal halides yield highly desirable optoelectronic properties and offer significant opportunity due to their solution processability. This contribution reports a new series of hybrid semiconductors, (C7H7)MX4 (M = Bi3+, Sb3+; X Cl-, Br-, I-), that are composed edge-sharing MX6 chains separated in space by π-stacked tropylium (C7H7+) cations; the inorganic resemble connectivity BiI3. The Bi3+ compounds have blue-shifted optical absorptions relative Sb3+ span visible near-IR region....
Orienting light-emitting molecules relative to the substrate is an effective method enhance optical outcoupling of organic devices. Platinum(II) phosphorescent complexes enable facile control molecular alignment due their planar structures. Here, orientation Pt(II) during growth emissive layers controlled by two different methods: modifying structure and using structural templating. Molecules whose structures are modified adjusting diketonate ligand Pt complex, dibenzo-(f,h)quinoxaline...
Cannabis sativa L. produces over 200 known secondary metabolites that contribute to its distinctive aroma. Studies on compounds traditionally associated with the scent of this plant have focused those within terpenoid class. These isoprene-derived are ubiquitous in nature and major source many odors. Nonetheless, there is little evidence they provide characteristic "skunk-like" aroma cannabis. To uncover chemical origins scent, we measured aromatic properties cannabis flowers concentrated...
Cannabidiol (CBD) is a non-intoxicating phytocannabinoid with increasing popularity due to its purported therapeutic efficacy for numerous off-label conditions including anxiety and autism spectrum disorder (ASD). Those ASD are commonly deficient in endogenous cannabinoid signaling GABAergic tone. CBD has complex pharmacodynamic profile that includes enhancing GABA endocannabinoid signaling. Thus, there mechanistic justification investigating CBD's potential improve social interaction...
Two-dimensional (2D) Ruddlesden–Popper hybrid perovskites are a homologous series of compounds with the formula A′2An–1BnX3n+1 (A′ = bulky organic cation; A small B Pb2+ or Sn2+, X Cl–, Br–, I–; n is an integer) composed inorganic octahedral layers separated by spacer cations. The layer thickness modified stoichiometry A-site cation, but limited methods exist for controlled and discriminating synthesis all compositions. We report general method its principles that yield phase-pure 2D...
Recent reports have linked severe lung injuries and deaths to the use of e-cigarettes vaping products. Nevertheless, causal relationship between exposure emissions observed health outcomes remains be elucidated. Through chemical toxicological characterization emission products, this study demonstrates that during processes, changes in composition several commonly used vape juice diluents (also known as cutting agents) lead formation toxic byproducts, including quinones, carbonyls, esters,...
Single crystals of Lu3T4Ge13–x (T = Co, Rh, Os) and Y3T4Ge13–x Ir, have been grown using the self-flux method found to adopt Yb3Rh4Sn13–x structure type. Magnetization specific heat measurements confirm that all compounds are bulk superconductors, some with reduced superconducting gaps determined from suggesting multiband superconductivity. However, an unusual increase electrical resistivity a decrease charge carrier density on cooling in normal state observed for six even though functional...
Compounds adopting the Yb3Rh4Sn13 structure type have drawn attention because of revelation exotic states such as heavy fermion behavior, superconductivity, charge density wave, and quantum critical behavior. The prototypical has historically been modeled with a primitive cubic space group, Pmn; however, structural studies led to realization disordered atomic sites, requiring lower symmetry models. We will review low models required describe distortions in related type. In addition, we...
Single crystals of ${\mathrm{Yb}}_{3}(\mathrm{Rh}{}_{1\ensuremath{-}x}{T}_{x}){}_{4}{\mathrm{Ge}}_{13}$ $(T\phantom{\rule{0.5em}{0ex}}=\phantom{\rule{0.5em}{0ex}}\mathrm{Co},\phantom{\rule{0.16em}{0ex}}\mathrm{Ir})$ have been grown using the self-flux method. Powder x-ray diffraction data on these compounds are consistent with cubic structure space group $Pm\overline{3}n$. Intermediate-valence behavior is observed in upon $T$ = Co doping, while Ir doping drives system into a heavy-fermion...
The ZrSiS family of compounds has garnered interest as Dirac nodal-line semimetals and offers an approach to study structural motifs coupled with electronic features, such crossings. CeSbTe, the ZrSiS/PbFCl structure type, is due its magnetically tunable topological states. crystal consists rare earth capped square nets separating magnetic Ce–Te layers. In this work, we report single growth, properties, structures LnSb1−xBixTe (Ln = La, Ce, Pr; x ∼ 0.2) CeBiTe, adopting CeSbTe structure,...
The layered Ruddlesden–Popper derivatives of CH3NH3PbI3 have recently emerged as high-performing materials for photovoltaics with improved stability. inclusion organic molecules within the inorganic framework provides additional dynamic degrees freedom that influence optoelectronic properties. rotational dynamics CH3NH3+ dielectric behavior and electronic excited-state in CH3NH3PbI3; however, cation on properties has not yet been determined. We employ quasi-elastic neutron scattering to...