skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.


Title: BaWO 2 F 4 : a mixed anion X-ray scintillator with excellent photoluminescence quantum efficiency
A new self-activated X-ray scintillator, BaWO 2 F 4 , with an excellent photoluminescence quantum efficiency is reported. Hydrothermally grown single crystals, space group P 2/ n , exhibit a 3D framework structure containing isolated WO 2 F 4 octahedra. BaWO 2 F 4 exhibits green emission under UV light with a high quantum yield of 53% and scintillates when exposed to X-rays(Cu).  more » « less
Award ID(s):
1806279
PAR ID:
10221559
Author(s) / Creator(s):
; ; ; ; ; ; ;
Date Published:
Journal Name:
Dalton Transactions
Volume:
49
Issue:
31
ISSN:
1477-9226
Page Range / eLocation ID:
10734 to 10739
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. Abstract A unique approach is used to relate the HOMO‐LUMO energy difference to the difference between the ionization potential (IP) and electron affinity (EA) to assist in deducing not only the colors, but also chromophores in elemental nonmetals. Our analysis focuses on compounds with lone pair electrons and σ electrons, namely X2(X = F, Cl, Br, I), S8and P4. For the dihalogens, the [IP – EA] energies are found to be: F2(12.58 eV), Cl2(8.98 eV), Br2(7.90 eV), I2(6.78 eV). We suggest that theinterahalogen X–X bond itself is the chromophore for these dihalogens, in which the light absorbed by the F2, Cl2, Br2, I2leads to longer wavelengths in the visible by a π → σ* transition. Trace impurities are a likely case of cyclic S8which contains amounts of selenium leading to a yellow color, where the [IP – EA] energy of S8is found to be 7.02 eV. Elemental P4with an [IP – EA] energy of 9.09 eV contains a tetrahedral and σ aromatic structure. In future work, refinement of the analysis will be required for compounds with π electrons and σ electrons, such as polycyclic aromatic hydrocarbons (PAHs). 
    more » « less
  2. For some intermetallic compounds containing lanthanides, structural transitions can result in intermediate electronic states between trivalency and tetravalency; however, this is rarely observed for praseodymium compounds. The dominant trivalency of praseodymium limits potential discoveries of emergent quantum states in itinerant 4f1systems accessible using Pr4+-based compounds. Here, we use in situ powder x-ray diffraction and in situ electron energy-loss spectroscopy (EELS) to identify an intermetallic example of a dominantly Pr4+state in the polymorphic system Pr2Co3Ge5. The structure-valence transition from a nearly full Pr4+electronic state to a typical Pr3+state shows the potential of Pr-based intermetallic compounds to host valence-unstable states and provides an opportunity to discover previously unknown quantum phenomena. In addition, this work emphasizes the need for complementary techniques like EELS when evaluating the magnetic and electronic properties of Pr intermetallic systems to reveal details easily overlooked when relying on bulk magnetic measurements alone. 
    more » « less
  3. null (Ed.)
    Lead-free perovskites and their analogues have been extensively studied as a class of next-generation luminescent and optoelectronic materials. Herein, we report the synthesis of new colloidal Cs 4 M( ii )Bi 2 Cl 12 (M( ii ) = Cd, Mn) nanocrystals (NCs) with unique luminescence properties. The obtained Cs 4 M( ii )Bi 2 Cl 12 NCs show a layered double perovskite (LDP) crystal structure with good particle stability. Density functional theory calculations show that both samples exhibit a wide, direct bandgap feature. Remarkably, the strong Mn–Mn coupling effect of the Cs 4 M( ii )Bi 2 Cl 12 NCs results in an ultra-short Mn photoluminescence (PL) decay lifetime of around 10 μs, around two orders of magnitude faster than commonly observed Mn 2+ dopant emission in NCs. Diluting the Mn 2+ ion concentration through forming Cs 4 (Cd 1−x Mn x )Bi 2 Cl 12 (0 < x < 1) alloyed LDP NCs leads to prolonged PL lifetimes and enhanced PL quantum yields. Our study provides the first synthetic example of Bi-based LDP colloidal NCs with potential for serving as a new category of stable lead-free perovskite-type materials for various applications. 
    more » « less
  4. null (Ed.)
    Coincidence ion pair production (cipp) spectra of F 2 were recorded on the DELICIOUS III coincidence spectrometer in the one-photon excitation region of 125 975–126 210 cm −1 . The F + + F − signal shows a rotational band head structure, corresponding to F 2 Rydberg states crossing over to the ion pair production surface. Spectral simulation and quantum defect analysis allowed the characterization of five new molecular Rydberg states (F 2 **): one Π and four Σ states. The lowest-energy Rydberg state spectrum observed ( T 0 = 125 999 cm −1 ) lacked some of the predicted rotational structure, which allowed an accurate determination of the ion pair production threshold of 15.6229 4 ± 0.0004 3 eV. Using the well-known atomic fluorine ionization energy and electron affinity, this number leads to a ground state F–F dissociation energy of 1.6012 9 ± 0.0004 4 eV. Photoelectron photoion coincidence (PEPICO) experiments were also carried out on F 2 and the dissociative photoionization threshold to F + + F was determined as 19.0242 ± 0.0006 eV. Using the atomic fluorine ionization energy, this can be converted to an F 2 dissociation energy of 1.6013 2 ± 0.0006 2 eV, further confirming the cipp-derived value above. Because the two experiments were independently energy-calibrated, they can be averaged to 1.6013 0 ± 0.0003 6 eV and this value can be used to derive the fluorine atom's 0 K heat of formation as 77.25 1 ± 0.01 7 kJ mol −1 . This latter is in excellent agreement with the latest Active Thermochemical Table (ATcT) value but improves its accuracy by almost a factor of three. 
    more » « less
  5. Abstract Herein, a new family of hybrid metal halides, (DMAP)2MBr4(M = Cu, Zn), featuring zero‐dimensional (0D), pseudo‐layered crystal structures containing isolated molecular 4‐dimethylaminopyridinium (DMAP, C7H11N2+) cations and MBr42−tetrahedral anions are reported. (DMAP)2MBr4show remarkable long‐term stability, with no signs of degradation after one year of ambient air exposure. The reported solution synthesis affords large crystals measuring up to 1 cm, which showed significant response to soft 8 keV X‐ray photons when implemented into X‐ray detectors. Furthermore, (DMAP)2ZnBr4demonstrates tunable color light emission properties, which is attributed to the organic molecular units based on our combined experimental and computational results. The measured photoluminescence quantum yield (PLQY) for (DMAP)2ZnBr4is 7.35 %, a remarkable enhancement of emission efficiency as compared to a weak emission from the organic precursor. The inexpensive and earth‐abundant chemical compositions and ease of preparation of the new hybrid metal halides make them promising candidates for optical and electronic applications. 
    more » « less