Solid Host Materials Research Articles

Combining eutectic solvents and food-grade silica to recover and stabilize anthocyanins from grape pomace

Concentrated in the skins of red grapes are the anthocyanins, the primary colorants responsible for the fruits' reddish-purple color. These colorants are recognized for their significant antioxidant properties and potent nutraceutical and pharmaceutical ingredients. Nevertheless, their widespread use is compromised by the (i) need for more efficient yet sustainable downstream processes for their recovery and (ii) by the challenges imposed by their poor stability. In this work, these drawbacks were overcome by applying eutectic solvents and stabilizing agents. Besides, the anthocyanins were successfully loaded into a solid host material (approved in both food and pharmaceutical sectors) based on silicon dioxide (SiO2, loading capacity: 1extract:7silica m/m). Summing up, with the process developed, the extraction yield (21 mganthocyanins.gbiomass−1) and the stability (under 55, 75, and 95 °C) of the recovered anthocyanins were over three times better than with the conventional process. Finally, the raw materials and solvents were recycled, allowing an economical and environmentally friendly downstream process.

Ionic Liquid-Based Hybrid Materials: Ionogel Review

Ionic liquids (ILs) are gaining popularity due to their unique qualities, which include low vapor pressure, thermal stability, and non-flammability, as well as strong ionic conductivity and a wide electrochemical stability window. Ionogels (IGs) are solid electrolytes that are based on ionic liquid (IL). Incorporation/entrapment of ILs in any inorganic or organic solid host material results in the formation of IGs. Furthermore, to develop lithium-ion batteries (LIBs) with high capacity, high rate capability, and outstanding cycle stability, this paper focuses on clever methodologies for synthesizing organic, inorganic, and hybrid host-based IGs. In this review, ionogels are described as a novel type of hybrid material in which the characteristics of an IL are combined with those of another component, which can be organic (low molecular weight gelator, biopolymer, etc.) or inorganic (carbon nanotubes, silica, etc.) or a hybrid organic-inorganic (e.g., polymer and inorganic fillers.

Modification of the optical properties of molecular chains upon coupling to adatoms

Adsorbed atoms (adatoms) coupled to the matrix of solid state host materials as impurities can significantly modify their properties. Especially in low-dimensional materials, such as one-dimensional organic polymer chains or quasi-one-dimensional graphene nanoribbons, intriguing manipulation of the optical properties, such as the absorption cross section, is possible. The most widely used approach to couple quantum emitters to optical antennas is based on the Purcell effect. This formalism, however, does not comprise charge transfer from the emitter to the antenna, but only spontaneous emission of the quantum emitter into the tailored photonic environment, that is evoked by the antenna. To capture such effects, we present a tight-binding formalism to couple an adatom to a finite Su-Schrieffer-Heeger chain, where the former is treated as a two-level system and the latter acts as an optical antenna. We systematically analyze how the coupling strength and the position of the adatom influence the optical properties of the molecular chains in the model. We take into account charge transfer from the adatom to the antenna and vice versa via an inter-system hopping parameter, and also include Coulomb interaction within the antenna as well as between the adatom and the antenna. We show that coupling the adatom to one of the bulk atoms of the linear chain results in a substantial change in optical properties already for comparatively small coupling strengths. We also find that the position of the adatom crucially determines if and how the optical properties of the chains are altered. Therefore, we identify this adatom-chain hybrid system as a tunable platform for light-matter interaction at the nanoscale.

The photo-switching study of guest 2-(phenylazo)pyridine (PAP) embedded in solid host material MOF-5

Herein, a photo-responsive molecule, 2-phenylazopyridine (PAP) was incorporated as a guest into a porous crystalline metal-organic framework (MOF), MOF-5. Detail experimental studies like elemental analysis, PXRD measurements, IR spectroscopy have been performed to confirm the successful embedment of PAP into the host framework. Thermogravimetric and elemental analysis revealed that two PAP molecules per unit of the host were present in the host-guest composite, MOF-5⊃PAP. Photo-switching study of the composite MOF-5⊃PAP was performed and investigated by details IR spectroscopy and UV-Vis spectroscopy. The percentage of photo-induced trans to cis isomerization of the guest molecule, PAP in the hybrid host-guest compound (MOF-5⊃PAP) was less compared to the azobenzene embedded in MOF-5 i.e. AZB@MOF-5. There is no structural transformation of the host MOF-5 after loading PAP or prolong UV irradiation, exhibiting the non-responsive nature of the framework retaining its cubic lattice structure. This was also reflected in N2 adsorption isotherm as no change in the isotherm was observed even after prolong photo-irradiation in the hybrid MOF-5⊃PAP composite.

Tunable 4f/5f Bimodal Emission in Europium-Incorporated Uranyl Coordination Polymers.

There have been numerous studies on emission-color regulation by the adjustment of molar amounts of multiple trivalent lanthanide cations, such as Eu3+, Tb3+, Dy3+, and others, in many types of solid host materials. Although uranyl emission originating from charge-transfer transitions has been well-recognized and investigated for many decades, as of now there is no report on tunable 4f/5f bimodal emission based on heterobimetallic lanthanide(III) and uranyl(VI) compounds. In most cases, complete energy transfer between uranyl(VI) and lanthanide(III) centers was observed. In this work, a series of isotypic-europium-incorporated uranyl coordination polymers, Eu@UO2L(DMF) (L2- = 3,5-pyridinedicarboxylate, denoted as 1-10, which represent the different Eu contents in UO2L(DMF); DMF = N,N-dimethylformamide), has been synthesized by solvothermal reactions. Crystallographic evidence of this series unveiled one-dimensional chains of UO22+ as pentagonal-bipyramidal units bridged by pyridinedicarboxylate with no defined, crystallographically unique site containing Eu, even for the products with high concentrations of Eu in this series. However, emission bands characteristic of Eu3+ were clearly observed in every product along with the characteristic uranyl-emission feature when observed with UV-vis fluorescence spectroscopy. Laser-ablation inductively coupled plasma mass spectrometry indicated that europium was concomitant with uranium, corroborating the incorporation of europium into crystals of UO2L(DMF). Systematic control of the solvent ratio (VH2O/VDMF) in each reaction gives rise to an enrichment of Eu3+ in the interior of UO2L(DMF). In addition, the color of emission of these compounds changed significantly from bright red to bright green with decreasing Eu content. This phenomenon occurs from the highly efficient energy transfer between the UO22+ and Eu3+ centers within each sample, providing the first case of a tunable 4f/5f bimodal emission in a mixed 4f/5f-elements-bearing metal-organic-hybrid material.

Digital design of cellular solids for noise and vibration mitigation

Cellular solids are of large interest in structural vibration due to their high strength-to-weight ratio and ability for high energy absorption. This presentation describes concepts for digitally designing cellular solids and demonstrates the ability of this design method for tuning effective material properties for noise and vibration mitigation applications. The designs can be created by defining a complete topology mathematically or by specifying section cut-outs from a solid host material. The digital designs are then analyzed with finite element software to determine effective material properties. This approach is advantageous because it allows for an automated computer procedure for designing and characterizing materials. In addition, resulting designs can be fabricated through either 3D printing processes or CNC milling. In this presentation, the relationship between geometrical/physical properties and effective static material properties (such as Young's modulus and Poisson ratio) of cellular solids will be discussed for the digital designs, with reference to existing theory.

Electrochemical Techniques for Intercalation Electrode Materials in Rechargeable Batteries.

Understanding of the thermodynamic and kinetic properties of electrode materials is of great importance to develop new materials for high performance rechargeable batteries. Compared with computational understanding of physical and chemical properties of electrode materials, experimental methods provide direct and convenient evaluation of these properties. Often, the information gained from experimental work can not only offer feedback for the computational methods but also provide useful insights for improving the performance of materials. However, accurate experimental quantification of some properties can still be challenging. Among them, chemical diffusion coefficient is one representative example. It is one of the most crucial parameters determining the kinetics of intercalation compounds, which are by far the dominant electrode type used in rechargeable batteries. Therefore, it is of significance to quantitatively evaluate this parameter. For this purpose, various electrochemical techniques have been invented, for example, galvanostatic intermittent titration technique (GITT), potentiostatic intermittent titration technique (PITT), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV). One salient advantage of these electrochemical techniques over other characterization techniques is that some implicit thermodynamic and kinetic quantities can be linked with the readily measurable electrical signals, current, and voltage, with very high precision. Nevertheless, proper application of these techniques requires not just an understanding of the structure and chemistry of the studied materials but sufficient knowledge of the physical model for ion transport within solid host materials and the analysis method to solve for chemical diffusion coefficient. Our group has been focusing on using various electrochemical techniques to investigate battery materials, as well as developing models for studying some emerging materials. In this Account, the principles of the aforementioned four electrochemical techniques and the corresponding analytical equations for calculating the chemical diffusion coefficients are first briefly summarized, followed by a discussion of the hidden assumptions for deriving these analytical equations and the resulting limitations in their implementation. To address these limitations, various corrections have been made in the literature. Nevertheless, the phase transition behavior, which is the typical feature for many intercalation materials, is barely considered. Here we retrospect our previous work on developing a two-phase model for describing the phase transition behavior of some intercalation compounds and discuss how to obtain the chemical diffusion coefficients based on the model, using LiFePO4 as an example material. After that, we have a discussion on the methodology for using electrochemical techniques to investigate new material features. It is our hope that this Account can serve as a call for more endeavors into the development of novel electrochemical tools for battery research.

Interfaces Promoted Conversion-Type Reactions for Energy Storage

Conversion-type reactions based battery chemistry presents a great promise for next-generation energy storage. It is based on using the chemical reaction (also called chemical transformation) of the working ion to store energy, different than intercalation-type reactions as used in today’s Li-ion batteries. Good examples include Li-S, Li-O2, and broadly speaking metal electrodes (Li, Mg, Zn, etc.). Interfaces generally play a more crucial role in these battery chemistry systems because of the complexity of this type of reaction even though each of the systems has its unique characteristics. This not only includes electrode/electrolyte interfaces, but also the interfaces within the electrode materials. Here, we use two examples of battery chemistry to demonstrate how the manipulation of interfaces can promote the conversion-type reactions for energy storage: Mg chemistry and Li-S chemistry. In Mg battery chemistry, due to the divalent nature of Mg2+, the ion transport kinetics in solid host materials is limited. Therefore, the development of Mg battery has been limited by poor performance of electrode materials. We have developed two conversion-type electrode materials with improved Mg2+ storage performance: SnSb alloys for anode1 , 2 and V2O5 nanoclusters for cathode.3 More importantly, our experimental and theoretical modeling reveal that the interfaces between the multicomponent phases generated during repeated magnesiation–demagnesiation is responsible for the improved performance of SnSb; a surface-controlled reaction of Mg2+ and V2O5, denoted as a molecular energy storage mechanism, improves the reaction kinetics which increases the rates and capability. In Li-S battery chemistry, control of solution chemistry and nucleation of polysulfides (on cathode host surface) is crucial for improved capacity and cycling stability. We have demonstrated that, through tuning the solubility of polysulfides in electrolytes, an improved cycling stability is achieved. The controlled nucleation of polysulfides on carbon nanofiber surface leads to the formation of a unique porous microsphere structure of Li2S. This unique porous Li2S microsphere enables a close to 100% utilization of S (specific capacity >1600mAh/gS); it also decreases the passivation of cathode. This opens up a new avenue for Li-S R&D of using low surface area carbon host materials, thus a great potential for high pack density and low electrolyte/sulfur ratio in Li-S cells. In this talk, we will present our understanding on these interface-related conversion-type reactions and recent progress of material innovation that improves device performance. New electrode architecture engineering will also be discussed. 1. Y. W. Cheng, Y. Y. Shao, L. R. Parent, M. L. Sushko, G. S. Li, P. V. Sushko, N. D. Browning, C. M. Wang and J. Liu, Adv. Mater., 2015, 27, 6598-6505. 2. L. R. Parent, Y. W. Cheng, P. V. Sushko, Y. Y. Shao, J. Liu, C. M. Wang and N. D. Browning, Nano Lett., 2015, 15, 1177-1182. 3. Y. W. Cheng, Y. Y. Shao, V. Raju, X. L. Ji, B. L. Mehdi, K. S. Han, M. H. Engelhard, G. S. Li, N. D. Browning, K. T. Mueller and J. Liu, Advanced Functional Materials, 10.1002/adfm.201505501, 2016.

New in situ solid-state NMR strategies for exploring materials formation and adsorption processes: prospects in heterogenous catalysis

Solid-state NMR spectroscopy is a powerful technique for studying structural and dynamic properties of solids and has considerable potential to be exploited for in situ studies of chemical processes. However, adapting solid-state NMR techniques and instrumentation for in situ applications are often associated with technical challenges, and for this reason, the opportunities remain underexploited. This paper highlights two experimental strategies that we have developed in recent years for in situ solid-state NMR investigations of solid-state processes. One technique is focused on probing details of the time evolution of materials formation processes, and the other technique is focused on understanding the time evolution of adsorption processes in microporous and mesoporous solid host materials. Each of these in situ solid-state NMR techniques has significant prospects for applications in areas relating to heterogeneous catalysis.

Electron Transfer from Excited [Ir(2‐phenylpyridyl)3] through a Coexisting Electron Relay in Zeolite

AbstractPhotoinduced electron transfer was investigated between an ortho‐metalated IrIII complex encapsulated in the supercage of faujasite zeolite dispersed in solution and viologen derivatives dissolved in the solution. The electron‐transfer rate across the zeolite solution interface was 310 times slower than that between the free molecules in solution. To facilitate electron transfer, 1,1′‐ethylene‐2,2′‐bipyridyldiylium (diquat = 2DQ2+) was introduced as an electron relay into the zeolite by ion exchange. When triethanolamine (TEOA) was added as a sacrificial electron donor into the dispersion solution, the 2DQ2+ in the supercages was reduced to 2DQ·+ radical cation under light irradiation, which can be explained as the electron transfer from the excited state of the IrIII complex to 2DQ2+, and the regeneration of the complex through the reduction of the resulting oxidized complex by the electron donor TEOA in the solution through the zeolite solution interface. An electron is transferred through the zeolite framework from the 2DQ·+ radical cation formed in the supercage to propyl viologen sulfonate in the solution. This system demonstrates controllability of the electron transfer by solid host materials such as zeolites.

ChemInform Abstract: Photoprocesses of Coordination Compounds and Dyes in Solution and Nanoporous Materials: Evolution from Milliseconds to Femtoseconds

AbstractReview: 95 refs.

Ambient rutile VO2(R) hollow hierarchitectures with rich grain boundaries from new-state nsutite-type VO2, displaying enhanced hydrogen adsorption behavior

Modulating the interaction between small gas molecules and solid host materials is becoming increasingly important for the future society due to the alternative energy resources especially for the hydrogen energy. As is known, two catalogues of materials such as two-dimensional (2D) lamellar cavity structures and three-dimensional (3D) infinite tunnel structures have received intensive considerations during the past decades. Herein, we put forward a new alternative that the solid materials with synergic effects of grain-boundary-rich (GBR) structure and 3D hierarchical hollow structure would also be a promising candidate for modulating the gas molecules in solid adsorbents. As expected, our constructed novel 3D hollow hierarchitectures with GBR shells standing on the hollow spherical cavity indeed resulted in the enhanced hydrogen adsorption behavior. The as-prepared 3D hollow hierarchitectures were very uniform in large scale, and the very simple reaction process offers high convenience, short reaction time, and no need for any complex manipulations or equipments. The hollow outlook of the rutile VO(2)(R) 3D hierarchitectures is the reminiscence of the hollow cavity of nsutite-type VO(2), while the formation of the VO(2)(R) GBR structure is attributed to volume shrink from a unique intergrowth structure of nsutite-type VO(2). The novel gas modulation model with the synergic effect of GBR structure and hierarchical hollow structure may pave a new way for developing materials in energy and environmental fields in the near future.

Photoprocesses of coordination compounds and dyes in solution and nanoporous materials: Evolution from milliseconds to femtoseconds#

The photoredox reactions of cobalt(III), nickel(II) complexes and organic dyes are reviewed with particular emphasis on using flash photolysis methods to identify the transients in the time scale from milliseconds to subpicoseconds. The excitation flash radiation initially was limited to flash lamps with a time resolution to study the decay of the excited states and the fast reactions of photo produced transients in milliseconds and microseconds. Some of the photolysis reactions investigated provide details in real time including the thermal reactions of molecular oxygen with cobalt(II) amine systems and the cobalt (III) alkyl complex formation on photolysis of cobalt(III) aminoacid complexes. Photoredox reactions of thiazine and safranine dyes are investigated using time resolved absorption and emission techniques in solution and on encapsulation in micro and mesoporous host materials. Picosecond and femtosecond diffuse reflectance fluorescence investigations in the porous solid host materials show intramolecular proton transfer reactions of the dyes and deprotonation of the dyes in the excited states. Photosensitization of nanoparticles of semiconductors, anatase TiO2 and ZnO by the excited states of dyes in meso and microporous silicate hosts is investigated using pico and femtosecond fluorescence and transient absorptions techniques and the results are reviewed. The photophysics and photochemistry of dyes and metal complexes have been investigated in solution and in nanoporous hosts. The various pathways of the excited molecules have been studied by different techniques.

Enzymatic hydrolysis of biomass with recyclable use of cellobiase enzyme immobilized in sol–gel routed mesoporous silica

In this work, a new immobilized cellobiase enzyme system was used in the enzymatic hydrolysis of biomass for the generation of cellulosic ethanol. The application of the immobilized cellobiase enzyme enabled easy post-hydrolysis separation of the enzyme from the reaction mixture. The cellobiase enzyme was immobilized in porous solid silica host material via acid catalyzed non-surfactant templated sol–gel reaction of tetraethyl orthosilicate (TEOS). The pore size and porosity of the host material were controlled by varying the template (d-fructose) content. The immobilized cellobiase enzyme samples when used in the hydrolysis of pre-treated biomass yielded hydrolysis efficiency up to 74% (with FeCl3 pre-treated biomass) and 81% (with oxalic acid pre-treated biomass) when compared to hydrolysis with free cellobiase enzyme. The solid immobilized enzyme samples could be easily recycled from the reaction mixture after the hydrolysis reaction. When re-used in multiple batches, the immobilized samples retained their enzymatic activity in biomass hydrolysis. The re-usability of the immobilized cellobiase with retained activity would actively bring down the enzyme cost. Thus, our immobilized cellobiase enzyme opens up great potential in the enzymatic hydrolysis of biomass for generating cellulosic ethanol, as it leads to overall process cost reduction.

Local field effect of the host matrix on the decay time of doped emitters

Experimental results for variations in the lifetime of excited states of Sm3+ ions incorporated in a glassy system with a ‘refractive index’ have been reported. Increasing content of barium carbonate in the solid host matrix results in a fairly large variation in its refractive index, which provides a way to determine the local field effects for ions doped in the solid host material. Measurements are observed to be in disagreement with the virtual cavity model, while they show a reasonable agreement with the real cavity model.

Bioinspired nanoencapsulation of purple membranes.

Embedding biological compounds, e.g. enzymes or whole cells, in solid host material seems to be a promising approach to widen their field of application far beyond the limits of natural conditions. In fields such as medicine and biotechnology, there is great interest in new methods to produce these types of composite materials in the form of micro- or nanosized particles. Such methods should be applicable to large amounts of substance. Inspired by one of nature's remarkable features-its ability to combine (bio)organic and inorganic components at the nanoscale-we developed a generic silica encapsulation method for biomolecules based on the concepts of polyelectrolyte layer adsorption followed by templated silica mineralization similar to biomineralization in diatoms. Application of this method to the model substance purple membrane (PM) resulted in a defined hybrid material with a nanoscale protective encapsulating silica shell providing a high barrier for the diffusion of low molecular weight molecules.

Scalable solid-state quantum processor using subradiant two-atom states.

We propose a realization of a scalable, high-performance quantum processor whose qubits are represented by the ground and subradiant states of effective dimers formed by pairs of two-level systems coupled by resonant dipole-dipole interaction. The dimers are implanted in low-temperature solid host material at controllable nanoscale separations. The two-qubit entanglement either relies on the coherent excitation exchange between the dimers or is mediated by external laser fields.

The temperature dependence of energy transfer between the Tm 3F 4 and Ho 5I 7 manifolds of Tm-sensitized Ho luminescence in YAG and YLF

The temperature dependence of the energy transfer process between the Tm 3F 4 and Ho 5I 7 manifolds in Tm : Ho doped laser materials is investigated. Decay data of luminescence in Tm : Ho : YAG and Tm : Ho : YLF in the temperature range 243–323 K are analyzed to extract energy transfer rates and elucidate the theoretical description of the energy distribution between Tm and Ho ions in solid host materials.

Conformational properties of monosubstituted cyclohexane guest molecules constrained within zeolitic host materials. A solid-state NMR investigation

The conformational properties of monosubstituted cyclohexane guest molecules (C6H11X with X = CH3, OH, Cl, Br and I) included within microporous solid host materials (silicalite-I, H-ZSM-5, NH4-mordenite and zeolite NH4-Y) have been elucidated via high-resolution solid-state 13C NMR spectroscopy. For all of the inclusion compounds investigated, the fraction of monosubstituted cyclohexane molecules in the equatorial conformation is similar to that in solution, suggesting that these host materials do not impose any significant constraints upon the conformational properties of the monosubstituted cyclohexane guest molecules. For the monohalogenocyclohexane guest molecules (C6H11X with X = Cl, Br and I), this result is in marked contrast to the situation for the same guest molecules in the thiourea host structure, for which the conformational properties of the guest molecules are substantially different from those of the same molecules in solution. For cyclohexanol (C6H11OH) in H-ZSM-5, some amount of dicyclohexyl ether (C6H11OC6H11) is observed, and is analogous to the proposed production of dimethyl ether in the first stage of methanol-to-gasoline conversion on this zeolite. The comparatively low temperature (ambient temperature) at which this conversion from cyclohexanol to dicyclohexyl ether occurs is noteworthy. In addition to our high-resolution solid-state 13C NMR studies of these materials, 1H MAS and 27AI MAS NMR spectra have also been recorded, and are discussed.

Theoretical calculation of distribution coefficients of impurities in germanium and silicon, heats of solid solution

The distribution coefficients of Groups III, IV and V impurities in germanium and silicon were calculated, and very satisfactory agreement with experimental values was obtained. The method of calculation consisted in estimating the change in energy involved in transferring the impurity atoms from a crystalline reservoir to the solid and molten host material respectively. The binding energy of an impurity in the host lattice and the strain energy which it introduces were estimated. The change in vibrational entropy is believed to be negligible.