A5022595225- Inorganic Chemistry and Materials
- Crystallization and Solubility Studies
- X-ray Diffraction in Crystallography
- MXene and MAX Phase Materials
- Luminescence Properties of Advanced Materials
- Crystal Structures and Properties
- Chemical Synthesis and Characterization
- Advanced ceramic materials synthesis
- Boron and Carbon Nanomaterials Research
- Synthesis and characterization of novel inorganic/organometallic compounds
- Inorganic Fluorides and Related Compounds
- Metal-Organic Frameworks: Synthesis and Applications
- Organometallic Compounds Synthesis and Characterization
- Metal and Thin Film Mechanics
- Perovskite Materials and Applications
- Crystallography and molecular interactions
- Organometallic Complex Synthesis and Catalysis
- Electronic and Structural Properties of Oxides
- Ammonia Synthesis and Nitrogen Reduction
- Crystal structures of chemical compounds
- Coordination Chemistry and Organometallics
- Rare-earth and actinide compounds
- Magnetism in coordination complexes
- Advanced Photocatalysis Techniques
- Machine Learning in Materials Science
Ludwig-Maximilians-Universität München
2016-2025
Center for NanoScience
2011-2023
Walter de Gruyter (Germany)
2021
Technical University of Munich
2014-2021
Technische Universität Braunschweig
1993-2021
Clausthal University of Technology
2021
Translational Research Platform for Veterinary Biologicals (India)
2021
University of Konstanz
2021
University of Münster
2021
Laboratoire de Chimie Moléculaire et Thioorganique
2016-2020
Single-phase melem (2,5,8-triamino-tri-s-triazine) C6N7(NH2)3 was obtained as a crystalline powder by thermal treatment of different less condensed C−N−H compounds (e.g., melamine C3N3(NH2)3, dicyandiamide H4C2N4, ammonium dicyanamide NH4[N(CN)2], or cyanamide H2CN2, respectively) at temperatures up to 450 °C in sealed glass ampules. The crystal structure determined ab initio X-ray diffractometry (Cu Kα1: P21/c (No. 14), = 739.92(1) pm, b 865.28(3) c 1338.16(4) β 99.912(2)°, and Z 4). In the...
Abstract Poly(aminoimino)heptazine, otherwise known as Liebig's melon, whose composition and structure has been subject to multitudinous speculations, was synthesized from melamine at 630 °C under the pressure of ammonia. Electron diffraction, solid‐state NMR spectroscopy, theoretical calculations revealed that nanocrystalline material exhibits domains well‐ordered in two dimensions, thereby allowing solution projection by electron diffraction. Melon ([C 6 N 7 (NH 2 )(NH)] n , plane group p...
Color point tuning is an important challenge for improving white light LEDs. In this paper, the possibilities of color with efficient LED phosphor Sr1−x−y−zCaxBaySi2O2N2:Euz2+ (0 ≤ x, y 1; 0.005 z 0.16) are investigated. The emission can be tuned in two ways: by changing Eu2+ concentration and substitution host lattice cation Sr2+ either Ca2+ or Ba2+. variation shows a red shift upon increasing Eu above 2%. explained energy migration transfer to ions emitting at longer wavelengths. Along...
Abstract The development and demonstration of a highly efficient warm‐white all‐nitride phosphor‐converted light emitting diode (pc‐LED) is presented utilizing GaN based quantum well blue LED two novel nitrogen containing luminescent materials, both which are doped with Eu 2+ . For color conversion the primary nitridosilicates M 2 Si 5 N 8 (orange‐red) MSi O (yellow‐green), = alkaline earth, were employed, thus achieving high luminous efficiency (25 lumen/W at 1 W input), excellent quality...
Fluorescence emission was investigated in a series of Ba2−xEuxSi5N8 compounds. Two maxima corresponding to the two crystallographic Eu2+ sites are observed. Excitation with intense laser light at 1.047 μm reveals strong fluorescence ∼600 nm due two-photon-excitation. In Ba1.89Eu0.11Si5N8 long lasting luminescence studied. The peaking about 590 has been observed dark naked eye even 15 min after removal activating lamp. This effect is recombination holes and traps consisting nitrogen vacancies...
A new dimension: The doping of amorphous poly(triazine imide) (PTI) through ionothermal copolymerization dicyandiamide with 4-amino-2,6-dihydroxypyrimidine (4AP) results in triazine-based carbon nitrides increased photoactivity for water splitting compared to crystalline (PTI/Li(+)Cl(-), see picture) and melon-type nitrides. This family nitride semiconductors has potential as low-cost, environmentally clean photocatalysts solar fuel production.
Poly(triazine imide) with intercalation of lithium and chloride ions (PTI/Li(+)Cl(-)) was synthesized by temperature-induced condensation dicyandiamide in a eutectic mixture potassium as solvent. By using this ionothermal approach the well-known problem insufficient crystallinity carbon nitride (CN) products could be overcome. The structural characterization PTI/Li(+)Cl(-) resulted from complementary spectroscopic methods well different diffraction techniques. Due to high structure solution...
Abstract Silicates are one of the most important classes compounds on this planet, and more than 1000 silicates have been identified in mineral kingdom. Additionally, several hundreds artificial synthesized. The substitution oxygen by nitrogen leads to structurally diverse manifold class nitridosilicates. Silicon nitride, non‐oxidic ceramic materials, is binary parent compound nitridosilicates, it symbolizes inherent material properties these refractory compounds. However, prior last...
The isotypic compounds M[Mg3SiN4] (M = Ca,Sr,Eu) have been synthesized by solid-state reactions in sealed tantalum ampules or a radio-frequency furnace. nitridomagnesosilicates crystallize space group I41/a (No. 88). Crystal structures were solved and refined from single-crystal X-ray diffraction data (Z 16, Ca[Mg3SiN4]:Ce3+, 11.424(2), c 13.445(3) Å, R1 0.040, wR2 0.106; Sr[Mg3SiN4]:Eu2+, 11.495(2), 13.512(3) 0.036, 0.102; Eu[Mg3SiN4], 11.511(4), 13.552(4) 0.016, 0.039). are to Na[Li3SiO4],...
Ca[LiAl3N4]:Eu2+ is an intriguing new narrow-band red-emitting phosphor material with potential for application in high-power phosphor-converted light-emitting diodes (pc-LEDs). With excitation by blue InGaN-based LEDs, the compound exhibits emission maximum at 668 nm a full width half of only 1333 cm–1 (∼60 nm). was synthesized from Ca, LiAlH4, LiN3, AlF3, and EuF3 weld-shut Ta ampules, structure solved refined on basis single-crystal X-ray diffraction data. After isotypical crystallization...
Abstract Sr 2 Si 5 N 8 und Ba werden phasenrein durch Umsetzung von Siliciumdiimid mit den jeweiligen Metallen Strontium bzw. Barium unter Stickstoffatmosphäre in einem speziellen Hochfrequenzofen bei 1 550 bis 650°C synthetisiert. (Pmn2 , a = 571,0(2), b 682,2(2), c 934,1(2) pm, Z 2, R 0,037, wR 0,021) 578,3(2), 695,9(2), 939,1(2) 0,022, 0,018) kristallisieren isotyp sind aus M 2+ ‐Ionen (M Ba) sowie einer kovalenten dreidimensionalen Raumnetzstruktur eckenverknüpfter SiN 4 ‐Tetraeder...
We report on the existence and formation of carbon nitride precursor melam (H(2)N)(2)(C(3)N(3))NH(C(3)N(3))(NH(2))(2), thereby clarifying one last unresolved issues posed by complex thermal condensation melamine C(3)N(3)(NH(2))(3). Experimental proof is put forward that a direct product melamine, but can be detected only in small amounts under special reaction conditions owing to its rapid transformation into melem. The coexistence melem during yields two adduct phases with distinct...
The first non-metal tricyanomelaminates have been synthesized via metathesis reactions and characterized by means of single-crystal X-ray diffraction vibrational solid-state NMR spectroscopy. crystal structures [NH4]2[C6N9H] (1) (P21/c, a = 1060.8(2) pm, b 1146.2(2) c 913.32(18) β 112.36(3)°, V 1027.0(4) × 106 pm3), [C(NH2)3]3[C6N9]·2 H2O (2) (P212121, 762.12(15) 1333.6(3) 1856.6(4) 1887.0(7) pm3) [C3N6H7]2[C6N9H]·2.5 (3) (P1̄, 1029.5(2) 1120.3(2) 1120.7(2) α 104.22(3)°, 112.74(3)°, γ...
Abstract Among the nonmetal nitrides, polymeric binary compounds BN and Si 3 N 4 are of particular interest for development materials high‐performance applications. The outstanding features both substances their thermal, mechanical, chemical stability, coupled with low density. Because extremely reactivity, boron silicon nitride hardly ever used as starting preparation ternary but primarily in manufacture crucibles or other vessels insulation materials. chemistry higher nitrides that contain...
The new nitridoalumosilicate phosphor SrAlSi4N7:Eu2+ has been synthesized under nitrogen atmosphere at temperatures up to 1630 °C in a radio-frequency furnace starting from Sr metal, α-Si3N4, AlN, and additional Eu metal. crystal structure of the host compound SrAlSi4N7 solved refined on basis single-crystal powder X-ray diffraction data. In solid, there is network corner-sharing SiN4 tetrahedra incorporating infinite chains all edge-sharing AlN4 running along [001] (SrAlSi4N7: Pna21 (No....
The highly efficient nitridosilicate phosphors M2Si5N8 (M = Sr, Ba, Eu) for phosphor-converted pc-LEDs were synthesized at low temperatures using a novel precursor route involving metal amides M(NH2)2. These precursors have been by dissolution of the respective metals in supercritical ammonia 150 °C and 300 bar. thermal behavior decomposition process investigated with temperature programmed powder X-ray diffractometry thermoanalytical measurements (DTA/TG). investigations rendered as...
Recently, molecular fluorophores were shown to be formed in the bottom-up chemical synthesis, contributing emission of carbon dots (CDs), derived from a citric acid precursor. We applied an ammonothermal synthesis toward CDs, employing two reactants and supercritical ammonia functioning as both solvent The resulting nanoparticles are identified amorphous aggregates based on citrazinic derivatives, which resemble many features typically reported characteristic for CDs. absorb emit at short...
Highly efficient red-emitting nitridosilicate phosphors Sr2Si5N8:Eu2+ and Ba1.5Sr0.5Si5N8:Eu2+ (doping level 1 %) applicable to phosphor converted pc-LEDs were synthesized in nanocrystalline form at low temperatures employing a novel single-source precursor approach. Synthesis starts from silicon uses mixed metal amides M(NH2)2 with M = Sr, Ba, Eu as reactive intermediates. In second approach, mixture obtained one-pot reaction of the corresponding elements (Sr/Ba, Eu, Si) was supercritical...
The isotypic nitridomagnesoaluminates M[Mg2Al2N4] (M = Ca,Sr, Ba,Eu) as well a novel nitridomagnesogallate Ba[Mg2Ga2N4] have been synthesized by high-temperature reactions in arc-welded tantalum ampules. crystal structures were solved and refined using single-crystal X-ray diffraction or powder data, respectively. All compounds crystallize the UCr4C4-structure type (space group I4/m (no. 87), Z 2, Ca[Mg2Al2N4]: 8.0655(11), c 3.2857(7) Å, wR2 0.085 Sr[Mg2Al2N4]: 8.1008(11), 3.3269(7) 0.084;...
Eu2+- as well Ce3+-doped Ba[Li2(Al2Si2)N6] and its related Mg-substituted compounds Ba[(Mg2–xLix) (Al4–xSix)N6]:Eu2+ (x = 0–2) with x 1.6, 1.8 have been synthesized by metathesis reactions in tantalum ampules. Crystal structures were solved refined from single-crystal X-ray diffraction data. All three crystallize tetragonal space group P4/ncc (no. 130) (Z 4, Ba[Li2(Al2Si2)N6]:Eu2+: a 7.8282(4), c 9.9557(5) Å, R1 0.0144, wR2 0.0366). Their crystal structures, exhibiting the novel framework...
Abstract Highly efficient phosphor‐converted light‐emitting diodes (pc‐LEDs) are popular in lighting and high‐tech electronics applications. The main goals of present LED research increasing light quality, preserving color point stability reducing energy consumption. For those purposes excellent phosphors all spectral regions required. Here, we report on ultra‐narrow band blue emitting oxoberyllates AELi 2 [Be 4 O 6 ]:Eu 2+ (AE=Sr,Ba) exhibiting a rigid covalent network isotypic to the...
The nitridomagnesosilicates Li2Ca2[Mg2Si2N6]:Eu2+ and Li2(Ca1.88Sr0.12)[Mg2Si2N6]:Eu2+ show narrow-band red emission at 638 634 nm, respectively, with an bandwidth of 62 nm (∼1513 cm–1) after excitation in the blue spectral region. Ce3+-doped samples luminescence green range (λem = 540 nm). compounds were synthesized via solid-state metathesis reaction Li melts. Refinement single-crystal X-ray diffraction data revealed that Li2(Ca1.88Sr0.12)[Mg2Si2N6] crystallizes isomorphic to...