Class Of Solid-state Materials Research Articles

Electron and Spin Delocalization in [Co6 Se8 (PEt3 )6 ]0/+1 Superatoms.

Molecular clusters can function as nanoscale atoms/superatoms, assembling into superatomic solids, a new class of solid-state materials with designable properties through modifications on superatoms. To explore possibilities on diversifying building blocks, here we thoroughly studied one representative superatom, Co6 Se8 (PEt3 )6 . We probed its structural, electronic, and magnetic properties and revealed its detailed electronic structure as valence electrons delocalize over inorganic [Co6 Se8 ] core while ligands function as an insulated shell. 59 Co SSNMR measurements on the core and 31 P, 13 C on the ligands show that the neutral Co6 Se8 (PEt3 )6 is diamagnetic and symmetric, with all ligands magnetically equivalent. Quantum computations cross-validate NMR results and reveal degenerate delocalized HOMO orbitals, indicating aromaticity. Ligand substitution keeps the inorganic core nearly intact. After losing one electron, the unpaired electron in [Co6 Se8 (PEt3 )6 ]+1 is delocalized, causing paramagnetism and a delocalized electron spin. Notably, this feature of electron/spin delocalization over a large cluster is attractive for special single-electron devices.

Influence of fluorescent dopants on the vat photopolymerization of acrylate-based plastic scintillators for application in neutron/gamma pulse shape discrimination.

Plastic scintillators, a class of solid-state materials used for radiation detection, were additively manufactured with vat photopolymerization. The photopolymer resins consisted of a primary dopant and a secondary dopant dissolved in a bisphenol A ethoxylate diacrylate-based matrix. The absorptive dopants significantly influence important print parameters, for example, secondary dopants decrease the light penetration depth by a factor > 12 ×. The primary dopant 2,5-diphenyloxazole had minimal impact on the printing process even when loaded at 25 % by mass of the resin. Working curve measurements, which relate energy dose to cure depth, were performed as a function of feature size to further assess the influence of dopants. Photopatterns smaller than 150 μm width had apparent increases in critical energy dose compared to larger photopatterns, while all resins maintained printed features in line gratings with 50 μm of separation. Printed scintillator monoliths were compared to scintillators cast by traditional molding, demonstrating that the layer-by-layer printing process does not decrease scintillation response. A maximum light output of 31 % of a benchmark plastic scintillator (EJ-200) and successful pulse shape discrimination were achieved with 20 % by mass 2,5-diphenyloxazole as the primary dopant and 0.1 % by mass 9,9-dimethyl-2,7-distyrylfluorene as the secondary dopant in printed scintillator samples.

Luminescence mechanisms in the 2V2O5–xLi2O–(98 − x)B2O3 glass matrices developed for creation of glass–ceramic materials

The oxide glass–ceramics is a promising class of solid state materials because they are using thermally stable and chemically inert glass oxide matrices. Development of such efficient glass matrices suitable for creation of glass–ceramic materials for several purposes is an important practical task. The xLi2O–yV2O5–(100 − x − y)B2O3 undoped glass and 47Li2O–2V2O5–50B2O3–1La0.3Eu0.7VO4 glass samples with crystalline nanoinclusions were synthesized and investigated using XRD, IR and UV–Vis spectroscopy and UV band-to-band excitation of luminescence. The synthesized glass samples are characterized by wide band photoluminescence emission with maximum at 570 nm and intensity increased with increase of Li2O concentration. The excitation spectra consist of three bands with maxima located at 270, 320 and 365 nm. The observed concentration dependencies of spectral distributions in the absorption and excitation spectra are explained by influence of the lithium ions on a ratio between triborate and tetraborate groups in the glass networks. The assumption is made that the observed wide band photoluminescence emission of the glass matrix can appear as a result of recombination processes between the defects in borate networks and the broken vanadate groups. The crystalline component in the doped glass samples is found to not affect the luminescence properties of the glass matrix. Intensity of narrow band photoluminescence emission of the crystalline component is up to 10 times more intense than that of the glass matrix wide band emission. The synthesized type of the glass matrices has promising characteristics for the use of developed materials in lighting devices, as it allows improving the spectral distribution of light emission towards the white light.

Luminescent ion-doped transparent glass ceramics for mid-infrared light sources [invited

Glass ceramics (GCs), which consist essentially of a homogeneous solid state dispersion of nanocrystals (NCs) embedded in a chemically inert and mechanically robust glass matrix, appear to be an extremely promising class of solid state materials that can be easily tailored into arbitrary shapes, including a new generation of optical fibers, for efficient incoherent and coherent sources of mid-infrared (MIR) light emission. This unique capability not only stems from the fact that one can tailor the underlying glass matrix for optimal macroscopic physical properties and ultrahigh transparency at the wavelengths of interest (resulting in appropriate "transparent glass ceramics" or TGCs), but also stems from the fact that one can embed these matrices with size and structure-tailored NCs, which in turn can be doped with relatively high concentrations of MIR emitting rare-earth or transition metal ions. This potential is tantamount to the localization of these highly efficient MIR ionic emitters into carefully selected and highly favorable "process-engineered" custom crystalline host "nanocages," while insulating the ionic emitters from the emission-quenching glass host matrix, the latter being chosen largely because of its highly favorable macroscopic bulk properties, including its ductility and formability into near-arbitrary shapes (at appropriate temperatures). Such MIR TGCs appear to be very promising for numerous photonics applications, including compact and relatively efficient waveguide sensors, broadband incoherent MIR light sources, superluminescent light sources, advanced fiber-optic devices, and broadly wavelength-tunable and ultrashort pulse mode-locked fiber and bulk solid-state lasers. In this paper, we review past achievements in this field, starting with an overview of TGCs, followed by discussions of currently preferred methods of fabrication, characterization, and optimization of suitably doped oxyfluoride, tellurite, and chalcogenide TGCs and of our projections of anticipated future developments in this field at both the materials and device levels.

Emerging Trends in Coordination Polymers and Metal-Organic Frameworks: Perspectives, Synthesis, Properties and Applications

Coordination polymers including metal-organic frameworks, clathrates and cyanometallates have recently gained significance as an important class of solid state materials. In this critical review, the diversity, classification, synthesis, structure, properties, applications, geometrical and chemical factors that influence their formation have been carefully presented. The synthesis of these new classes of compounds from molecular building blocks and demonstration oftheir high surface area, adsorptive and trapping potentials of molecules, selectivity in separation and uptake of molecules, tunable and modifiable molecular structure, and photoluminescence, magnetic and antimicrobial responses holds the potential for innumerable applications based on these tailored properties.

Ultrafast helicity control of surface currents in topological insulators with near-unity fidelity.

In recent years, a class of solid-state materials, called three-dimensional topological insulators, has emerged. In the bulk, a topological insulator behaves like an ordinary insulator with a band gap. At the surface, conducting gapless states exist showing remarkable properties such as helical Dirac dispersion and suppression of backscattering of spin-polarized charge carriers. The characterization and control of the surface states via transport experiments is often hindered by residual bulk contributions. Here we show that surface currents in Bi2Se3 can be controlled by circularly polarized light on a picosecond timescale with a fidelity near unity even at room temperature. We reveal the temporal separation of such ultrafast helicity-dependent surface currents from photo-induced thermoelectric and drift currents in the bulk. Our results uncover the functionality of ultrafast optoelectronic devices based on surface currents in topological insulators.

Biomimetic Light Harvesting in Nanoporous Metal Organic Materials

Metal organic framework materials (MOFs) represent a class of solid state materials with a number of properties advantageous for numerous applications ranging from gas storage and separation, heterogeneous catalysis, and controlled drug release to name only a few. Of the plethora of unexplored applications of MOFs, frameworks that can facilitate biomimetic solar photochemistry are of significant interest. Solar photochemistry applications rely on the ability of the MOF material to undergo facile and directional photoinduced electron transfer, much like biological light harvesting systems. One strategy is to utilize the nanoscale cavities within the MOF to encapsulate photoactive guests that can participate in directional photo-induced electron transfer reminiscent of biological electron transport chains. Here we discuss two such light harvesting systems. First, photoexcitation of a Zn(II)-trimesic acid based metal organic framework containing co-encapsulated Ru(II)tris(2,2'-bipyridine) (RuBpy) and Co(II)tris(2,2'-bipyridine) (CoBpy) results in inter-molecular electron transfer (ET) between the excited state of RuBpy (3MLCT) and the ground state CoBpy The rate of inter-cavity ET, kET, is found to be 3.7x106 s−1. Using the semi-classical Marcus equation and the observed rate constant, it is determined that ET occurs between RuBpy and CoBpy complexes located in adjacent cavities (∼19.6 A). We have also previously demonstrated the ability to specifically encapsulate metall-porphyrins within the octahemioctahedral cavites of both Cu and Zn HKUST-1. Here the simultaneous encapsulation of both Zn(II) tetrakis(tetra 4-sulphonatophenyl)porphyrin (Zn4SP) and Fe(III)tetrakis (tetra 4-sulphonatophenyl)porphyrin (Fe4SP) into a Zn(II)-HKUST-1 metal organic framework is demonstrated. Photo-excitation of the Zn4SP results in inter-molecular electron transfer (ET) between the encapsulated 3Zn4SP and the Fe(III)4SP sites as evident by the reduction in 3Zn4SP lifetime from 370 μs (kobs 2.7x103 s−1) to 83 μs (kobs = 1.2x104 s−1) in the presence of Fe4SP giving a kET ∼ 9.xx103 s−1.

Microstructure and Dielectric Properties of PZS-PLZT Ceramics System

Piezoelectric ceramics are an important class of solid-state materials as they exhibit a wide range of applications. This article investigates the sintering temperature effect on microstructure and dielectric properties of a new ceramics material Pb (Zn, Sb) O3-PbLa (Zr, Ti) O3 (PZS-PLZT), which was prepared by a solid mixed-oxide solution method. Scanning electron micrograph (SEM) and X-ray diffraction (XRD) techniques was employed to examine the crystallization of the ceramics. The results of XRD show that the phase structure of the samples is tetragonal. The lattice parameters and the density increased with increase of the sintering temperature. The dielectric constant and the dielectric loss of the investigated samples decreased with increase in the frequency.

Micro- and mesoporous solids: From science to application

The concept of a porous solid might sound like a term of contradiction as solids are typically regarded as a dense and compact state of matter. Of course this is obviously not so, and zeolites are probably the most prominent representatives of such solids, known for already more than 250 years, and have been used in technical applications for more than 50 years in industry. 200 different structural types of zeolites have already been listed, with this number increasing each year. However, the pore sizes of zeolites are restricted to well below 1 nm (for faujasite), which in turn restricts the scope of the chemistry that is possible inside the pores, typically to the molecular level. However, in the last two decades especially, mesoporous materials having pore dimensions between 2 and approximately 50 nm have emerged, and this group has established itself as an important class of solid-state materials with a huge and still constantly growing number of new congeners with pores on the nano- to mesoscale. These can be broadly classified into inorganic, organic and metal–organic types. Nevertheless, hybrids of these compositions have even been realized, extending the diversity in the chemical composition of such mesoporous solids further still. Besides their different chemical composition, the pore morphology, geometry and pore dimensions make these materials outstanding with respect to, e.g., catalytic reaction processes, in the area of sensorics, photonics and gas storage (Fig. 1). In the realm of gas storage, mesoporous metal–organic frameworks (MOFs) appeared on the scene a couple of years ago and have quickly emerged as most-promising highly meso- and macroporous materials exhibiting enormous pore volumes with inner surface areas comparable with bare nanoparticles and thus coming close to the ultimate adsorption limit for solid materials. Consequently they have paved the way for the design of new materials, e.g., for the storage of fuel molecules, such as H2 and CH4 as well as other technologically and environmentally important small molecules. Besides the prospective applications of mesoporous materials in these and other areas, one of the other main focus points of research into these solids is to achieve a basic understanding of what happens inside the porous framework of such a solid on the molecular, and nano- and mesocopic level, in a hierarchical order, during adsorption, desorption and chemical reactions. Alongside the development of experimental methods to unravel the details of the adsorption sites and dynamics, a theoretical understanding, e.g., employing state of the art theoretical modeling techniques, is certainly necessary. The development of synthetic concepts for the formation of two-dimensional, layered, porous structures, e.g., by swelling and delamination followed by film-formation techniques, is another avenue of basic research into exciting mesoporous materials, and the application of such mesoporous layered materials to adsorption and catalysis can certainly be envisaged in the near future. Figure 1 Artificially colorized view of a hexagonally ordered cell structure of mesoporous alumina. The pores are shown in yellow and are ca. 40 nm in diameter. The red color grading represents the typically different densities of the alumina cells surrounding ... In this Thematic Series the interested reader will find a compilation of recent experimental findings relating to mesoporous inorganic solids, covering aspects of synthesis as well as the functional properties of such materials in catalysis and sensing. Jorg J. Schneider Darmstadt, November 2011

ChemInform Abstract: Mechanical Properties of Hybrid Inorganic—Organic Framework Materials: Establishing Fundamental Structure—Property Relationships

AbstractReview: 137 refs.

Mechanical properties of hybrid inorganic–organic framework materials: establishing fundamental structure–property relationships

The mechanical properties of hybrid framework materials, including both nanoporous metal-organic frameworks (MOFs) and dense inorganic-organic frameworks, are discussed in this critical review. Although there are relatively few studies of this kind in the literature, major recent advances in this area are beginning to shed light on the fundamental structure-mechanical property relationships. Indeed research into the mechanical behavior of this important new class of solid-state materials is central to the design and optimal performance of a multitude of technological applications envisaged. In this review, we examine the elasticity of hybrid frameworks by considering their Young's modulus, Poisson's ratio, bulk modulus and shear modulus. This is followed by discussions of their hardness, plasticity, yield strength and fracture behavior. Our focus is on both experimental and computational approaches. Experimental work on single crystals and amorphized monoliths involved primarily the application of nanoindentation and atomic force microscopy to determine the elastic moduli and hardness properties. The compressibility and bulk moduli of single crystals and polycrystalline powders were studied by high-pressure X-ray crystallography in the diamond anvil cell, while in one instance spectroscopic ellipsometry has also been used to estimate the elastic moduli of MOF nanoparticles and deposited films. Theoretical studies, on the other hand, encompassed the application of first principles density-functional calculations and finite-temperature molecular dynamics simulations. Finally, by virtue of the diverse mechanical properties achievable in hybrid framework materials, we propose that a new domain be established in the materials selection map to define this emerging class of materials (137 references).

Anisotropic mechanical properties of polymorphic hybrid inorganic–organic framework materials with different dimensionalities

Hybrid inorganic–organic framework materials have recently developed into an important new class of solid-state materials. Their mechanical properties are as yet unexplored, although they could be of great utility in view of their enormous structural and chemical diversity. The anisotropic mechanical properties of two new copper phosphonoacetate polymorphs, one a three-dimensional coordination polymer and the other a layered material with inter-layer hydrogen bonding, have been studied by nanoindentation with single crystals. The elastic and plastic anisotropy, the onset of plasticity and the fracture toughness anisotropy have been investigated along the main crystallographic directions. The anisotropy of the mechanical properties can be correlated directly with the underlying crystalline structures. For example, the elastic modulus is largest (up to ∼90 GPa) along directions that are dominated by inorganic chains or sheets and smallest (∼35 GPa) along directions where the organic ligands provide the primary linkages. This study also highlights the capabilities and limitations of nanoindentation for studying the anisotropic mechanical properties of hybrid framework materials.

Structural diversity and chemical trends in hybrid inorganic–organic framework materials

Hybrid framework compounds, including both metal-organic coordination polymers and systems that contain extended inorganic connectivity (extended inorganic hybrids), have recently developed into an important new class of solid-state materials. We examine the diversity of this complex class of materials, propose a simple but systematic classification, and explore the chemical and geometrical factors that influence their formation. We also discuss the growing evidence that many hybrid frameworks tend to form under thermodynamic rather than kinetic control when the synthesis is carried out under hydrothermal conditions. Finally, we explore the potential applications of hybrid frameworks in areas such as gas separations and storage, heterogeneous catalysis, and photoluminescence.

Hydrothermal Synthesis of the Deep-UV NLO Material Sr2Be2B2O7

ABSTRACTThe synthesis of non-linear optical (NLO) materials that are transparent into the deep-UV (<200 nm) region is an important component in the development of advanced optical technology. Such materials are sought after for their potential applications in the fields of high resolution photolithography, micro-machining, and laser spectroscopy. Borates are one class of solid-state materials that have received consideration for these applications because of their favorable physical and optical properties. One such compound, Sr2Be2B2O7(SBBO) has been reported to be transparent below 200 nm, and exhibits a large second harmonic generation (SHG) coefficient. Significant difficulties in the flux growth of large, high quality crystals have prevented this material from further development. We have successfully grown large crystals of SBBO by a hydrothermal synthetic method for the first time, and have characterized their physical properties. The synthesis and structure of a new material encountered during the synthesis of SBBO, LiBeSr2B3O8, is also reported here.

Solid‐State Coordination Chemistry: Hydrothermal Synthesis of Layered Vanadium Oxides with Interlayer Metal Coordination Complexes

A new class of solid-state materials are the hydrothermally synthesized compounds (L2M)y[VOx] (L = bidentate amine, M = Cu or Zn), which combine mixed-valence vanadium oxide layers with interlamellar coordination complexes. A section of the crystal structure of one example of these compounds with M = Cu and L = ethylenediamine is shown on the right.