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Over the last 3-4 decades, solid-state chemistry has emerged as the forefront of materials design and development. The field has revolutionized into a multidisciplinary subject and matured with a scope of new synthetic strategies, new challenges, and opportunities. Understanding the structure is very crucial in the design of appropriate materials for desired applications. Professor Mercouri G. Kanatzidis has encountered both challenges and opportunities during the course of the discovery of many novel materials. Throughout his scientific career, Mercouri and his group discovered several inorganic compounds and pioneered structure-property relationships. We, a few Ph.D. and postdoctoral students, celebrate his 60th birthday by providing a Viewpoint summarizing his contributions to inorganic solid-state chemistry. The topics discussed here are of significant interest to various scientific communities ranging from condensed matter to green energy production.

Sulfur cathodes in conversion reaction batteries offer high gravimetric capacity but suffer from parasitic polysulfide shuttling. We demonstrate here that transition metal chalcogels of approximate formula MoS3.4 achieve a high gravimetric capacity close to 600 mAh g–1 (close to 1000 mAh g–1 on a sulfur basis) as electrode materials for lithium-ion batteries. Transition metal chalcogels are amorphous and comprise polysulfide chains connected by inorganic linkers. The linkers appear to act as a “glue” in the electrode to prevent polysulfide shuttling. The Mo chalcogels function as electrodes in carbonate- and ether-based electrolytes, which further provides evidence of polysulfide solubility not being a limiting issue. We employ X-ray spectroscopy and operando pair distribution function techniques to elucidate the structural evolution of the electrode. Raman and X-ray photoelectron spectroscopy track the chemical moieties that arise during the anion-redox-driven processes. We find the redox state of Mo rem...

Chalcogels are a new class of aerogel materials with diverse properties relevant to catalysis, ion-exchange, and gas adsorption. We report the synthesis of high-surface-area antimony sulfide chalcogels through the sol–gel process followed by supercritical drying. Four different synthetic routes were employed: (1) hydrolysis of sodium thioantimonite (Na3SbS3); (2) ligand metathesis between Sb3+ metal linker and SbS33– anion; (3) reaction of Sb2S3 with Na2S·9H2O; and (4) reaction of Sb2S3 with KOH. All these reactions enable the formation of antimony sulfide gels. The aerogels derived after supercritical drying exhibit high porosity with Brunauer−Emmett−Teller (BET) surface areas up to 300 m2 g–1. The oxidation state of antimony in these chalcogels has been assigned by X-ray photoelectron spectroscopy (XPS) to be +3. Pair distribution function analysis suggests that the local environment around the Sb atoms is very similar to that of crystalline Sb2S3. All the antimony sulfide chalcogels possess the band ga...

Neurons in the middle temporal (MT) visual area are thought to represent the velocity (direction and speed) of motion. Previous studies suggest the importance of both excitation and suppression for creating velocity representation in MT; however, details of the organization of excitation and suppression at the MT stage are not understood fully. In this article, we examine how excitatory and suppressive inputs are pooled in individual MT neurons by measuring their receptive fields in a three-dimensional (3-D) spatiotemporal frequency domain. We recorded the activity of single MT neurons from anesthetized macaque monkeys. To achieve both quality and resolution of the receptive field estimations, we applied a subspace reverse correlation technique in which a stimulus sequence of superimposed multiple drifting gratings was cross-correlated with the spiking activity of neurons. Excitatory responses tended to be organized in a manner representing a specific velocity independent of the spatial pattern of the stimuli. Conversely, suppressive responses tended to be distributed broadly over the 3-D frequency domain, supporting a hypothesis of response normalization. Despite the nonspecific distributed profile, the total summed strength of suppression was comparable to that of excitation in many MT neurons. Furthermore, suppressive responses reduced the bandwidth of velocity tuning, indicating that suppression improves the reliability of velocity representation. Our results suggest that both well-organized excitatory inputs and broad suppressive inputs contribute significantly to the invariant and reliable representation of velocity in MT.

Tin sulfide (Sn2S3) chalcogels are one of the most effective nonoxide aerogels evaluated to date for iodine gas capture. This is attributed to the fact that the Sn within the gel network has a strong affinity for chemisorption of iodine to form SnI4. This study demonstrates an approach for consolidating the raw and iodine-sorbed Sn2S3 chalcogels into a chalcogenide glass using GeS2 as a glass-forming additive. Adding GeS2 to iodine-sorbed or iodine-free Sn2S3 chalcogels provides better glass formation than Sn–S or Sn–S–I alone, and the quantity of iodine measured in the bulk glass of the consolidated iodine-sorbed Sn2S3 chalcogel was at ∼45 mass%. Additional experiments were conducted using microwave sintering and hot isostatic pressing with iodine-sorbed Sn2S3 xerogels to evaluate alternative consolidation techniques.

Iodine (129I and 131I) is one of the radionuclides released in nuclear fuel reprocessing and poses a risk to public safety due to its involvement in human metabolic processes. In order to prevent the release of hazardous radioactive iodine into the environment, its effective capture and sequestration is pivotal. In the context of finding a suitable matrix for capturing radioactive iodine, several sulfidic chalcogels were explored as iodine sorbents including NiMoS4, CoMoS4, Sb4Sn3S12, Zn2Sn2S6, and K0.16CoSx (x = 4–5). All of the chalcogels showed high uptake, reaching up to 225 mass % (2.25 g/g) of the final mass owing to strong chemical and physical iodine–sulfide interactions. Analysis of the iodine-loaded specimens revealed that the iodine chemically reacted with Sb4Sn3S12, Zn2Sn2S6, and K0.16CoSx to form the metal complexes SbI3, SnI4, and, KI, respectively. The NiMoS4 and CoMoS4 chalcogels did not appear to undergo a chemical reaction with iodine since iodide complexes were not observed with these s...

The self-assembly of uniform nanocrystals into large porous architectures is currently of immense interest for nanochemistry and nanotechnology. These materials combine the respective advantages of discrete nanoparticles and mesoporous structures. In this article, we demonstrate a facile nanoparticle templating process to synthesize a three-dimensional mesoporous BiFeO3 material. This approach involves the polymer-assisted aggregating assembly of 3-aminopropanoic acid-stabilized bismuth ferrite (BiFeO3) nanocrystals followed by thermal decomposition of the surfactant. The resulting material consists of a network of tightly connected BiFeO3 nanoparticles (∼6–7 nm in diameter) and has a moderately high surface area (62 m2 g−1) and uniform pores (ca. 6.3 nm). As a result of the unique mesostructure, the porous assemblies of BiFeO3 nanoparticles show an excellent catalytic activity and chemical stability for the reduction of p-nitrophenol to p-aminophenol with NaBH4.

We report the sonochemical synthesis of a hybrid nanoarchitecture composed of vertically aligned arrays of ZnO nanorods (diameter ∼80 nm and length ∼1 μm) and a few atomic layers of arc discharge prepared graphene. High resolution FESEM images demonstrated that graphene layers have successfully been embedded in between the ZnO nanorod arrays (NRAs). Raman spectra of the hybrid nanomaterial exhibited D, G and 2D Raman fingerprints of graphene and ZnO (E2) modes at 437 cm−1 which confirmed the formation of a ZnO–graphene hybrid nanomaterial. The ZnO–graphene hybrid nanomaterial exhibits intense broad room temperature photoluminescence. Using graphene as a nanofiller considerably enhanced the electrical conductivity of the ZnO NRAs and the hybrid material exhibits a semi-metallic behaviour. Photoconductivity of the hybrid nanosystem has also been investigated which strengthens its candidature as a potential hybrid nanomaterial with optoelectronic synergy between its components.

High-surface-area molybdenum sulfide (MoSx) and antimony sulfide (SbSx) chalcogels were studied for Xe/Kr gas separation. The intrinsic soft Lewis basic character of the chalcogel framework is a unique property among the large family of porous materials and lends itself to a potential new approach toward the selective separation of Xe over Kr. Among these chalcogels, MoSx shows the highest Xe and Kr uptake, reaching 0.69 mmol g–1 (1.05 mmol cm–3) and 0.28 mmol g–1 (0.42 mmol cm–3) respectively, at 273 K and 1 bar. The corresponding isosteric heat of adsorption at zero coverage (Qst0) is 22.8 and 18.6 kJ mol–1 and both are the highest among the selected chalcogels. The IAST (10:90) Xe/Kr selectivity at 273 K for MoSx is 6.0, whereas for SbSx chalcogels, it varies in the range 2.0–2.8. The higher formal charge of molybdenum, Mo4+, in MoSx versus that of antimony, Sb3+, in SbSx coupled with its larger atomic size could induce higher polarizability in the MoSx framework and therefore higher Xe/Kr selectivity.

Here, we report, for the first time, on the first-order Raman spectra of the layered Mo-based ternaries: MoAlB, Mo2Ga2C and Mo2GaC. Polycrystalline samples were fabricated, and well-defined Raman spectra were recorded. When the experimental peak positions were compared with those predicted from density functional theory, good agreement was obtained, indirectly validating both. Furthermore, all modes in the three compounds were symmetry assigned. Copyright (c) 2017 John Wiley amp; Sons, Ltd. Funding Agencies|Swedish Research Council [621-2011-4420, 621-2014-4890]; Swedish FUNCASE (Foundation for Strategic Research through the Synergy Grant Functional Carbides for Advanced Surface Engineering); Knut and Alice-Wallenberg Foundation [2015.0043]

We report detailed studies showing that the novel layered polysulfide compounds Sx-LDH (Sx2–, polysulfides, x = 2, 4, 5; LDH, Mg–Al layered double hydroxides) can capture efficiently large quantities of mercury (Hg0) vapor. During the adsorption process, the interlayer polysulfides [Sx]2– react with Hg0 through their S–S bond to produce HgS. The structure of Sx-LDH before and after Hg-adsorption was characterized with X-ray diffraction, vibration spectroscopy, and scanning electron microscopy. The presence of adsorbed Hg was verified by weight gain, inductively coupled plasma atomic emission spectroscopy and X-ray photoelectron spectroscopy. Despite their relatively low surface areas, the S2-LDH, S4-LDH, and S5-LDH samples show excellent Hg capture capacities of 4.9 × 105, 7.4 × 105, and 1.0 × 106 μg/g, respectively, corresponding to 50–100% adsorption rates by weight, highlighting the potential of these materials in natural gas purification. The Hg-capture efficiency and mechanism in Sx-LDH are supported...

New molybdenum thiochlorides, α-MoSCl3 and β-MoSCl3, have been synthesized by chemical vapor transport. A selenium analog, MoSeCl3, could also be prepared in the same way. The crystal structures consist of infinite chains stabilized by weak van der Waals forces. For the α-phase an infinite chain of ∞1[Mo2(S2)Cl4Cl4/2] runs along the crystallographic c axis, while for the β-phase ∞1[Mo2(S2)Cl3Cl6/2] chain passes through the b-axis. MoSeCl3 is isostructural to α-MoSCl3. The formal charge on molybdenum in these thiochlorides have been assigned by X-ray photoelectron spectroscopy (XPS) to be +IV. β-MoSCl3 and already known Mo3S7Cl4 and MoS2Cl3 are weakly paramagnetic. Thermal decomposition of molybdenum thiochlorides leads to MoS2. Red MoS2Cl3 and Mo3S7Cl4 exhibit band gaps of ∼2.07 and ∼2.11 eV, while black α-MoSCl3, β-MoSCl3, and MoSeCl3 exhibit band gaps of ∼1.2, 1.24, and 1.18 eV, respectively. The new thiochlorides can serve as precursors in the synthesis of molybdenum–sulfide gels and aerogels. The MoSx...

A series of 2-substituted-4-([1,2,4]triazolo[1,5-a]pyridin-6-yl)-5-(6-methylpyridin-2-yl)imidazoles was synthesized and evaluated to optimize a prototype inhibitor of TGF-β type I receptor kinase (ALK5), 6. Combination of replacement of a quinoxalin-6-yl moiety of 6 with a [1,2,4]triazolo[1,5-a]pyridin-6-yl moiety, insertion of a methyleneamino linker, and a o-F substituent in the phenyl ring markedly increased ALK5 inhibitory activity, kinase selectivity, and oral bioavailability. The 12b (EW-7197) inhibited ALK5 with IC50 value of 0.013 μM in a kinase assay and with IC50 values of 0.0165 and 0.0121 μM in HaCaT (3TP-luc) stable cells and 4T1 (3TP-luc) stable cells, respectively, in a luciferase assay. Selectivity profiling of 12b using a panel of 320 protein kinases revealed that it is a highly selective ALK5/ALK4 inhibitor. Pharmacokinetic study with 12b·HCl in rats showed an oral bioavailability of 51% with high systemic exposure (AUC) of 1426 ng × h/mL and maximum plasma concentration (Cmax) of 1620 ng/mL. Rational optimization of 6 has led to the identification of a highly potent, selective, and orally bioavailable ALK5 inhibitor 12b.

A copper trimesate selenite compound is reported which shows a robust 3-D porous structure with unprecedented structural characteristics and represents a unique example of a metal inorganic–organic framework with considerable permanent microporosity and selective CO2 sorption properties.

Interaction of graphene, graphene oxide, and related nanocarbons with radiation gives rise to many novel properties and phenomena. Irradiation of graphene oxide in solid state or in solution by sunlight, UV radiation, or excimer laser radiation reduces it to graphene with negligible oxygen functionalities on the surface. This transformation can be exploited for nanopatterning and for large scale production of reduced graphene oxide (RGO). Laser-induced dehydrogenation of hydrogenated graphene can also be used for this purpose. All such laser-induced transformations are associated with thermal effects. RGO emits blue light on UV excitation, a feature that can be used to generate white light in combination with a yellow emitter. RGO as well as graphene nanoribbons are excellent detectors of infra-red radiation while RGO is a good UV detector.

Few-layer graphene can be chlorinated up to 56 wt.% by irradiation with UV light in a liquid chlorine medium. The chlorinated sample decomposes on heating or on laser irradiation releasing all the chlorine. Similar results have been obtained with the bromination of few-layer graphene.

High-temperature ferromagnetism in graphene and other graphite-derived materials reported by several workers has attracted considerable interest. Magnetism in graphene and graphene nanoribbons is ascribed to defects and edge states, the latter being an essential feature of these materials. Room-temperature ferromagnetism in graphene is affected by the adsorption of molecules, especially hydrogen. Inorganic graphene analogues formed by layered materials such as BN and MoS2 also show such ferromagnetic behaviour. Magnetoresistance observed in graphene and graphene nanoribbons is of significance because of the potential applications.

Graphenes with varying number of layers can be synthesized by different strategies. Thus, single-layer graphene is obtained by the reduction of single layer graphene oxide, CVD and other methods besides micromechanical cleavage. Few-layer graphenes are prepared by the conversion of nanodiamond, arcdischarge of graphite and other means. We briefly present the various methods of synthesis and the nature of graphenes obtained. We then discuss the various properties of graphenes. The remarkable property of graphene of quenching fluorescence of aromatic molecules is shown to be associated with photo-induced electron transfer, on the basis of fluorescence decay and time-resolved transient absorption spectroscopic measurements. The interaction of electron donor and acceptor molecules with few-layer graphene samples has been discussed. Decoration of metal nano-particles on graphene sheets and the resulting changes in electronic structure are examined. Few-layer graphenes exhibit ferromagnetic features along with antiferromagnetic properties, independent of the method of preparation. Graphene-like MoS 2 and WS 2 have been prepared by chemical methods, and the materials are characterized by electron microscopy, atomic force microscopy (AFM) and other methods. Boron nitride analogues of graphene have been obtained by a simple chemical procedure starting with boric acid and urea and have been characterized by various techniques.

Effect of irradiation on graphene oxide by sunlight, UV light and KrF excimer laser has been investigated in detail. Both sunlight and ultraviolet light reduce graphene oxide well after prolonged irradiation, but laser irradiation produces graphene with negligible oxygen functionalities within a short time. Laser irradiation is also useful for one-step synthesis of metal particle decorated graphene. Laser irradiation of graphene oxide appears to be an efficient procedure for large-scale synthesis of graphene., Comment: 23 pages, 12 figures

Investigations on the fluorescence quenching of graphene have been carried out with two organic donor molecules, pyrene butanaoic acid succinimidyl ester (PyBS, I) and oligo(p-phenylenevinylene) methyl ester (OPV-ester, II). Absorption and photoluminescence spectra of I and II recorded in mixture with increasing the concentrations of graphene showed no change in the former, but remarkable quenching of fluorescence. The property of graphene to quench fluorescence of these aromatic molecules is shown to be associated with photo-induced electron transfer, on the basis of fluorescence decay and time-resolved transient absorption spectroscopic measurements.

Graphenes with varying number of layers can be synthesized by different strategies. Thus, single-layer graphene is obtained by the reduction of single layer graphene oxide, CVD and other methods besides micromechanical cleavage. Few-layer graphenes are prepared by the conversion of nanodiamond, arc-discharge of graphite and other means. We briefly present the various methods of synthesis and the nature of graphenes obtained. We then discuss the various properties of graphenes. The remarkable property of graphene of quenching fluorescence of aromatic molecules is shown to be associated with photo-induced electron transfer, on the basis of fluorescence decay and time-resolved transient absorption spectroscopic measurements. The interaction of electron donor and acceptor molecules with few-layer graphene samples has been discussed. Decoration of metal nano-particles on graphene sheets and the resulting changes in electronic structure are examined. Few-layer graphenes exhibit ferromagnetic features along with antiferromagnetic properties, independent of the method of preparation. Graphene-like MoS 2 and WS 2 have been prepared by chemical methods, and the materials are characterized by electron microscopy, atomic force microscopy (AFM) and other methods. Boron nitride analogues of graphene have been obtained by a simple chemical procedure starting with boric acid and urea and have been characterized by various techniques.

It has been demonstrated that acid-treated graphene samples as well as reduced graphene oxide show fairly intense blue emission centered around 440 nm. Reduction of graphene oxide can be carried out either chemically or by using different types of radiations. Blue emission from graphene-based materials can be combined with the yellow emission from materials like ZnO to produce white light sources.

Interaction of nanoparticles of metals such as Ag, Au, Pt and Pd with graphene has been examined by employing Raman spectroscopy and first-principles calculations. There is a significant shift of the G-band as well as of the other bands, in addition to variation in the relative intensities of D- and 2D-bands when the metal nanoparticles are deposited on graphene. The shifts in the G- and D-bands show meaningful trends with the ionization energies of the metals as well as the charge-transfer energies. Results from the calculations underscore the importance of charge-transfer between the metal particles and graphene.

Manganese-enhanced MRI (MEMRI) is a newly developed noninvasive imaging technique of brain activities. The signal intensity of MEMRI reflects cumulative activities of the neurons. To validate the use of MEMRI technique to investigate the neural mechanisms of learning and memory, we tried to map brain areas involved in the retrieval of conditioned taste aversion (CTA) memory. CTAs were established to saccharin (conditioned stimulus: CS) by pairing its ingestion with an i.p. injection of LiCl (unconditioned stimulus: US). LiCl solutions (as a robust aversion chemical) of 0.15 M were injected i.p. 15 min after drinking the saccharine solution (CS). After the two times conditionings, these rats showed a robust aversion to the saccharine solution (CS). Rats of the control group were injected saline i.p. instead of LiCl solutions. The MRI signal intensities at the gustatory cortex (GC), the core subregion of the nucleus accumbens (NAcC), the shell subregion of the nucleus accumbens (NAcSh), the ventral pallidum (VP), the central nucleus of amygdala (CeA), the lateral hypothalamus (LH), and the basolateral nucleus of amygdala (BLA) of the conditioned group were higher than those of the control group. There were no significant differences between the conditioned and the control groups in the intensities for other regions, such as the striatum area, motor cortex, cingulate cortex, interstitial nucleus of the posterior limb of the anterior commissure and hippocampus. These indicate that the GC, NAcC, NAcSh, VP, CeA, LH and BLA have important roles in the memory retrieval of CTA.

Field-effect transistor characteristics of few-layer graphenes prepared by several methods have been investigated in comparison with those of single-layer graphene prepared by the in situ reduction of single-layer graphene oxide. Ambipolar features have been observed with single-layer graphene and n-type behaviour with all the few-layer graphenes, the best characteristics being found with the graphene possessing 2-3 layers prepared by arc-discharge of graphite in hydrogen. FETs based on boron and nitrogen doped graphene show n-type and p-type behaviour respectively. (C) 2010 Elsevier Ltd. All rights reserved.

Alle paar Jahre werden neue Stoffklassen mit einzigartigen und faszinierenden Eigenschaften entdeckt. Beispiele aus der jungeren Vergangenheit sind Hochtemperatur-Supraleiter und Nanorohren aus Kohlenstoff. Die jungste dieser spektakularen Entdeckungen ist Graphen. Graphen weist ungewohnliche Eigenschaften wie einen halbzahligen Quanten-Hall-Effekt und eine ballistische Elektronenbewegung auf. Graphen ist ein zweidimensionaler Stoff und die Stammverbindung aller graphitischen Kohlenstoff-Formen. Graphen besteht in Reinform nur aus Monoschichten, es gibt aber auch betrachtliches Interesse an Graphen-Doppel- und -Mehrfachschichten. Die Synthese und Charakterisierung von Graphenen ist schwierig, in jungster Zeit sind hier aber grose Fortschritte erzielt worden. Wir berichten hier uber den aktuellen Stand der Graphenforschung einschlieslich Synthese, Charakterisierung, Struktur und Eigenschaften.

Investigations of the magnetic properties of graphenes prepared by different methods reveal that dominant ferromagnetic interactions coexist along with antiferromagnetic interactions in all of the samples, somewhat like in frustrated or phase-separated systems. All of the graphene samples exhibit room-temperature magnetic hysteresis. The magnetic properties of the graphene samples depend on the number of layers and the sample area, small values of both favoring larger magnetization. Molecular charge-transfer affects the magnetic properties of graphene, interaction with a donor molecule such as tetrathiafulvalene having greater effect than with an electron-withdrawing molecule such as tetracyanoethylene.

Graphene samples prepared by the exfoliation of graphitic oxide and conversion of nanodiamond exhibit good hydrogen uptake at 1 atm, 77 K, the uptake going up to 1.7 wt %. The hydrogen uptake varies linearly with the surface area, and the extrapolated value of hydrogen uptake by single-layer graphene works out to be just above 3 wt %. The H2 uptake at 100 atm and 298 K is found to be 3 wt % or more, suggesting thereby the single-layer graphene would exhibit much higher uptakes. Equally interestingly, the graphene samples prepared by us show high uptake of CO2, the value reaching up to 35 wt % at 1 atm and 195 K. The first-principles calculations show that hydrogen molecules sit alternately in parallel and perpendicular orientation on the six-membered rings of the graphene. Up to 7.7 wt % of hydrogen can be accommodated on single-layered graphene. CO2 molecules sit alternatively in a parallel fashion on the rings, giving use to a maximum uptake of 37.93 wt % in single-layer graphene. The presence of more t...

Graphenes prepared by three different methods have been investigated as electrode materials in electrochemical supercapacitors. The samples prepared by exfoliation of graphitic oxide and by the transformation of nanodiamond exhibit high specific capacitance in aq. H2SO4, the value reaching up to 117 F/g. By using an ionic liquid, the operating voltage has been extended to 3·5 V (instead of 1 V in the case of aq. H2SO4), the specific capacitance and energy density being 75 F/g and 31·9 Wh kg−1 respectively. This value of the energy density is one of the highest values reported to date. The performance characteristics of the graphenes which are directly related to the quality, in terms of the number of layers and the surface area, are superior to that of single-walled and multi-walled carbon nanotubes.

Altered sensory experience in early life often leads to remarkable adaptations so that humans and animals can make the best use of the available information in a particular environment. By restricting visual input to a limited range of orientations in young animals, this investigation shows that stimulus selectivity, e.g., the sharpness of tuning of single neurons in the primary visual cortex, is modified to match a particular environment. Specifically, neurons tuned to an experienced orientation in orientation-restricted animals show sharper orientation tuning than neurons in normal animals, whereas the opposite was true for neurons tuned to non-experienced orientations. This sharpened tuning appears to be due to elongated receptive fields. Our results demonstrate that restricted sensory experiences can sculpt the supranormal functions of single neurons tailored for a particular environment. The above findings, in addition to the minimal population response to orientations close to the experienced one, agree with the predictions of a sparse coding hypothesis in which information is represented efficiently by a small number of activated neurons. This suggests that early brain areas adopt an efficient strategy for coding information even when animals are raised in a severely limited visual environment where sensory inputs have an unnatural statistical structure.