Inorganic Host Materials Research Articles

Real-time observation of crystals growth under optical microscopy: A self-assembly process of organic-inorganic intercalation composites driven by electrostatic interaction

The utilization of self-assembly through non-covalent forces such as electrostatic interactions and hydrogen bonds offers an effective strategy for the construction of organic-inorganic intercalation composite materials. Although self-assembly strategies hold significant potential, the embedding of organic guest molecules within inorganic host materials through self-assembly processes remains unexplored. In this work, the real-time observation of the self-assembly process of organic-inorganic intercalation composite materials has been achieved using confocal microscopy. We found that methylene blue intercalated molybdenum oxide (MB-MoO3-x) can be synthesized using a mild solution-phase self-assembly reaction and proposed a potential crystal growth model. Our findings indicate that the intercalation of MB remarkably increases the interlayer spacing of MoO3, that causes a transition from an amorphous to a more ordered crystalline structure. Adjusting UV irradiation and N-Methyl-2-pyrrolidone (NMP) content, the particle size of MB-MoO3-x could be controlled, ranging from 400 nm to 500 μm. Characterization techniques such as XPS, FTIR and Raman spectroscopy revealed that the self-assembly of MB with MoO3 is driven by non-covalent electrostatic interactions. Our research provides significant insights into the self-assembly mechanism of organic-inorganic intercalation composite materials, aiding the development of materials that combine the stability and electronic utility of inorganic metal oxides with the chemical diversity and functionality of organic molecules.

Stability Enhancement of Naturally Occurring Dye by Incorporation into Several Inorganic Host Materials

Stability Enhancement of Naturally Occurring Dye by Incorporation into Several Inorganic Host Materials

Influence of Host Lattice Ions on the Dynamics of Transient Multiband Upconversion in Yb-Er Codoped NaLnF4 and LiLnF4 Microcrystals (Ln: Y, Lu, Gd).

Inorganic host matrices provide a tunable luminescence environment for lanthanide ions, allowing for the modulation of upconversion luminescence (UCL) properties. AREF4 (A = alkali metal, RE = rare earth) have a low phonon energy and a high optical damage threshold, making them widely used as the host matrix for UCL materials. However, the impact mechanism of alkali metal ions and lanthanide lattice ions on transient UCL dynamics in AREF4 remains unclear. This study utilized a high-power nanosecond-pulsed laser at 976 nm to excite Yb-Er codoped NaLnF4 and LiLnF4 (Ln: Y, Lu, and Gd) microcrystals (MCs). All samples exhibit multiband emission, and the transient UC dynamics are discussed in detail. Compared with LiLnF4, NaLnF4 has higher UC efficiency and red to green (R/G) ratio. Lanthanide ions (Y, Lu, and Gd) affect the energy transfer (ET) distance in Yb-Er codoped systems, thereby altering UC efficiency and the R/G ratio. The energy level coupling between Gd3+ and Er3+ prolongs the duration of the UC emission. Specifically, the red emission lifetime of NaGdF4 is five times longer than that of NaYF4. Our research contributes to exploring excellent alternative host matrices for NaYF4 in the fields of rapid-response optoelectronic devices, micro-nano lasers, and stimulated emission depletion (STED) microscopy.

Regulation of Electron Delocalization Region in 2D Heteroligand-Based Copper-Organic Framework to Enhance Charge Storage.

The rechargeable aqueous ammonium ion battery shows great potential in low-cost energy storage system because of its long life and environmental friendliness. However, most inorganic host materials used in ammonium ion batteries are still limited by slow diffusion kinetics. Herein, it is identified that a 2D heteroligand-based copper-organic framework featuring numerous ammonium ion adsorption site in the π-conjugated periodic skeleton supplies multiple accessible redox-active sites for high-performance ammonium storage. Benefitting from the effective regulation of electron delocalization by heteroligand and the inherent hydrogen bond cage mechanism between ammonium ions, the resultant full battery delivers a large specific energy density of 211.84Whkg-1, and it can be stably operated for 12000 cycles at 5Ag-1 for over 80 days. This explanatory understanding provides a new idea for the rational design of high-performance MOF-based ammonium ion battery cathode materials for efficient energy storage and conversion in the future.

Upconverting nanophosphors for various sensing applications

BackgroundUpconverting nanophosphors (UCNPs) are composed of certain nanosized inorganic host materials doped with specific rare earth ions. They exhibit the phenomenon of photon upconversion, whereby the sequential absorption of two or more low energy photons is followed by luminescent emission of multiple photons with higher energy. In addition, they have other attractive optical features such as NIR-absorption, sharp emission bands, exceptional photostability and high quantum yield. These properties make UCNPs lucrative probes for number of optical applications, such as imaging, sensing and theranostics. OverviewUCNPs have been used as specific and ultrasensitive probes for sensing of variety of analytes, such as gas molecules, metal ions, fine particles, pH and a number of molecules, biochemicals and macromolecules. Their absorption and emission in the NIR range facilitates the background free biosensing in situ, in vitro and in vivo. Their multicoloured emissions allow a suitable emission band to serve as a donor for energy transfer to another attached optical probe, while a separate emission band to serve as an internal reference in ratiometric sensing applications. This comprehensive review provides an in-depth exploration of the versatile applications of UCNPs in the optical sensing of various analytes based on energy transfer mechanisms, with emphasis on the recent developments. . The focus is on synthesizing UCNPs, surface functionalization, and their effective utilization especially in detecting gas molecules, pH changes, ions, free radicals, and disease biomarkers. Through a meticulous examination of the use of UCNPs, this review aims to contribute to a deeper understanding of their potential and pave the way for future advancements and challenges in optical sensing.

The Role of Anions in Rare-earth Activated Inorganic Host Materials for its Luminescence Characteristics.

This work is inspired from the comprehensive work done by our research team aimed at improving the efficiency of white light emitting diodes (LEDs) through improvements in the colour rendering index of the red light (CRI), one of the primary colours of white light. Such work is triggered through the incorporation of anions (BO33-, PO43-, SO42-), either individually or as an integral part of dopant activated inorganic phosphor host materials. Numerous host materials such as ZnO, Y2O3, Ca3(PO4)2, CaMoO4, ABPO4, ABSO4 (where A represents alkali metals and B alkaline earth metals) have been considered ideal hosts materials for studying luminescence properties of materials(including other phosphors). In addition, red emitting dopants such as Sm3+, Eu3+ and Ce3+ have been incorporated into these host materials to achieve a higher CRI of red colour, an essential component of white light. The role anions in various materials is multifaceted; firstly, it acts as sensitizer whereby it absorbs excitation energy and transfers it non-radiatively to the dopants, secondly, it acts as a charge compensator to dopants with a charge of + 3, thirdly, it creates crystal fields that affects the electronic transitions of the dopants and fourthly, it creates a stable crystal structure that allows for dopant embedding. By understanding the exact role of these anions and their interactions with the host lattice and dopant ions, we could further optimize the luminescent properties of these activated host materials, which leads to higher efficiencies and performances in white light-emitting diodes and other lighting technologies. This work is a comprehensive review of the work undertaken by our research team aimed at enhancing the luminescent properties of WLEDs.

Highly Connected Three-Dimensional Covalent Organic Framework with Flu Topology for High-Performance Li-S Batteries.

Lithium-sulfur batteries (LSBs) have been considered as a promising candidate for next-generation energy storage devices, which however still suffer from the shuttle effect of the intermediate lithium polysulfides (LiPSs). Covalent-organic frameworks (COFs) have exhibited great potential as sulfur hosts for LSBs to solve such a problem. Herein, a pentiptycene-based D2h symmetrical octatopic polyaldehyde, 6,13-dimethoxy-2,3,9,10,18,19,24,25-octa(4'-formylphenyl)pentiptycene (DMOPTP), was prepared and utilized as a building block toward preparing COFs. Condensation of DMOPTP with 4-connected tetrakis(4-aminophenyl)methane affords an expanded [8 + 4] connected network 3D-flu-COF, with a flu topology. The non-interpenetrated nature of the flu topology endows 3D-flu-COF with a high Brunauer-Emmett-Teller surface area of 2860 m2 g-1, large octahedral cavities, and cross-linked tunnels in the framework, enabling a high loading capacity of sulfur (∼70 wt %), strong LiPS adsorption capability, and facile ion diffusion. Remarkably, when used as a sulfur host for LSBs, 3D-flu-COF delivers a high capacity of 1249 mA h g-1 at 0.2 C (1.0 C = 1675 mA g-1), outstanding rate capability (764 mA h g-1 at 5.0 C), and excellent stability, representing one of the best results among the thus far reported COF-based sulfur host materials for LSBs and being competitive with the state-of-the-art inorganic host materials.

Oxoiron(IV)-dominated Heterogeneous Fenton-like Mechanism of Fe-Doped MoS2.

Oxoiron(IV) species are a critical intermediate in the Fe-based Fenton-like process at circumneutral pH, and its oxidative reactivity is closely related to the ligands. An optional inorganic host material, MoS2 , is selected to construct a highly reactive sulfur ligand coordinated Fe species in this work. The Fe species doped in MoS2 is presented as the FeII centre and triggers the transformation of the 2H phase to the octahedral 1T phase MoS2 . The role of the interaction between doped Fe and the MoS2 host lattice on the formation of oxoiron(IV) is studied. A significant Fenton-like reactivity and a remarkable accumulation of oxoiron(IV) species were observed for Fe-MoS2 . The quenching experiment was implemented to disclose the predominant role of oxoiron(IV) species in the Fe-MoS2 /H2 O2 Fenton-like system. Furthermore, oxoiron(IV) species could transform into the ⋅O2 - and 1 O2 , which further expedites the Fenton-like reaction.

Effect of stabilizers on the stability enhancement of naturally occurring dye incorporated in clay interlayer

Naturally occurring dyes are expected as an environmentally- and eco-friendly colorant. The limitation of the usage by their low stability can partially be solved by the incorporation into inorganic host materials. However, the stability of the dye-inorganic host composites has still been insufficient. In this study, further stability enhancement of the dye composite is tried by adding several phenolic compounds as a radical scavenging stabilizer. The photostability and thermal stability of β-carotene incorporated in the organoclay interlayer is successfully improved especially when the stabilizer molecules can be efficiently intercalated together with the β-carotene. For rather slow rate of degradation, the phenolic compounds having hindered structure showed higher stabilization effect, whereas for the fast degradation, non-hindered phenols showed high efficiency. The difference in the effectiveness as a stabilizer can be explained both by the stability of the intermediate phenoxy radical species and by the steric hindrance. As a stabilizer of environmentally friendly dye composite materials, naturally occurring gallic acid and vanillic acid are the most preferrable compounds for the present composites.

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.

High-Capacity NH4+ Charge Storage in Covalent Organic Frameworks.

Ammonium ions (NH4+), as non-metallic charge carriers, have spurred great research interest in the realm of aqueous batteries. Unfortunately, most inorganic host materials used in these batteries are still limited by the sluggish diffusion kinetics. Here, we report a unique hydrogen bond chemistry to employ covalent organic frameworks (COFs) for NH4+ ion storage, which achieves a high capacity of 220.4 mAh g-1 at a current density of 0.5 A g-1. Combining the theoretical simulation and materials analysis, a universal mechanism for the reaction of nitrogen and oxygen bridged by hydrogen bonds is revealed. In addition, we explain the solvation behavior of NH4+, leading to a relationship between redox potential and desolvation energy barrier. This work provides a new insight into NH4+ ion storage in host materials based on hydrogen bond chemistry. This mechanism can be leveraged to design and develop COFs for electrochemical energy storage.

Polyoxotitanate Molecular Cage Featuring Four Types of Ethylenediamines: Formation Mechanism Insight from Host-Guest Interaction and Crystallographic Study.

Titanium-oxide or polyoxotitanate clusters are a new type of inorganic host materials that can encapsulate inorganic molecules or ions. We report herein a (NH4)4(enH2)[Ti18O27(PhCOO)24(en)9] molecular cage (Ti18) that encapsulates an entire organic ethylenediamine (en) ion. A thorough investigation has revealed the extraordinary versatility of en. Besides being a guest cation, it also functions as chelating and bridging ligand. It balances the charge of the negative Ti18 cage and facilitates the deprotonation of benzoic acid at the early stage of the reaction as well. DFT calculation and a derivative of Ti18 with open sites at its equatorial position shed further light on the formation mechanism. Ti18 strongly absorbs visible light as a result of en coordination, and it exhibits superior photocatalytic activity compared to anatase TiO2.

Structural distortion induced enhancement in UV-C emitting properties of Pr3+-activated La-substituted yttrium phosphates (Y1-xLaxPO4:Pr3+)

The UV-C emission with a spectral range of 200–280 nm is of paramount importance in the germicidal and medical applications for disinfection, sterilization, and deactivation of microorganisms such as bacteria and virus considering current global pandemic crisis of coronavirus (COVID-19). Such intense UV-C radiation (4.4–6.2 eV) can be often generated using Pr3+ activators (as a result of their electronic transition [Xe]4f15d1→[Xe]4f2) doped in crystalline inorganic host matrices. In this regard, Pr3+-activated rare earth phosphates have been intensively studied as a model system of UV-C emitters thus far. Here, we have prepared three different representative crystalline UV-C phosphors of YPO4:Pr3+ (tetragonal), LaPO4:Pr3+ (monoclinic), and La-substituted YPO4:Pr3+ (tetragonal), respectively, and further investigated the effect of La substitution in YPO4 crystal structures on UV-C emitting properties. The structural lattice distortion in the local environment of activator Pr3+ cations induced by La substitution indeed impacts on the UV-C emitting properties. Small amount of substitutional doping of La3+ (ca. 5 mol.%) in Y site of YPO4 enhances the UV-C emission intensity by a two-fold of magnitude recorded under 225 nm excitation (photoluminescence) and cathode ray (cathodeluminescence). This finding can provide a fundamental designing principle of inorganic phosphor materials to enhance the emitting properties of activators, directly influenced by local environment and symmetry of the crystal structures.

Facile Synthesis of a Color-Tunable Microcrystal Phosphor for Anti-Counterfeit Applications.

Developing luminescent materials with tunable emission colors provides exciting opportunities for application in the display, anti-counterfeiting, and optical sensors. Here, we report a convenient, versatile approach to synthesize color-tunable, up/down-conversion luminescence in an inorganic host material. The emission color can be tuned by varying the excitation wavelength, allowing dynamic color tuning in the visible spectrum. We demonstrate that an unprecedented luminescence tunability from these phosphors can be achieved by tailoring the intensity ratio of different emission peaks. These findings provide valuable insights into controlling multiple emission color processes while offering the possibility for dynamic anti-counterfeiting and visual sensing of ultraviolet light in the range from 250 to 320 nm. These results open the opportunity for developing next-generation stimuli-responsive luminescent materials and smart devices.

Nanocrystalline TiO2 and Li4Ti5O12 as Novel Inorganic Host Materials for Li-S Batteries

Composites of sulfur with nanocrystalline TiO2, Li4Ti5O12, and carbon were prepared by melting diffusion and characterized by X-ray diffraction, Raman spectroscopy, and cyclic voltammetry. XRD analysis was hindered by overlap of the majority of diagnostic peaks of TiO2 with diffraction peaks of sulfur. Raman spectroscopy indicates strong attenuation of sulfur-related modes, if S is encapsulated in porous carbonaceous material or coated with conductive carbonaceous additive in thin film electrode. In turn, this effect proves perfect accommodation of S inside pores of the carbonaceous skeleton. The best electrochemical performance of a composite of nanocrystalline TiO2 with sulfur was ascribed to large surface area of the host enabling even coverage of its surface by adsorbed sulfur. TiCl4 post treatment had negative effect on electrochemical performance of modified electrodes.

Polycyclic Quinone and Its Dithiin Derivative As Cathode Materials for Sustainable Aqueous Zn-Organic Secondary Batteries

Aqueous Zinc-ion (Zn-ion) batteries are considered as attractive energy storage devices for large scale applications owing to their intrinsic safety, low cost and robustness1. However, their implementation is held back by sluggish diffusion kinetics of Zn2+ into inorganic host materials. Therefore, the focus is on redox active organic materials particularly quinone derivatives. These materials show moderate coulombic repulsions to the Zn2+ diffusion by having big tunnels in the crystal lattice2. Yet, very few organic materials have been reported for aqueous Zn-ion batteries. In the contextual importance of exploring new organic materials that can reversibly host Zn2+. Herein, we have explored highly conjugated pentacene-5,7,12,14-tetraone (PT) as cathode material for aqueous ZIBs for the first time. The versatile features such as strong π-stacking, high theoretical capacity (i.e. 317 mAh g-1 for 4e- transfer), structural diversity, inherent insolubility and non-defamation upon electrochemical process unlike simple quinones make PT a promising candidate to study. Moreover, we used filter paper as a separator instead of nafion membrane and ZnSO4 as supporting electrolyte salt which makes this battery more environmentally friendly and cost effective. In order to improve the rate capability and cycling stability, PT was incorporated in the mesoporous nanonetwork of CMK-3 carbon. In addition, the discharge voltage of the cell was enhanced by introducing sulfur atoms in the PT skeleton. Figure 1

Zein-layered hydroxide biohybrids: strategies of synthesis and characterization.

This work constitutes a basic study about the first exploration on the preparation of biohybrids based on the corn protein zein and layered metal hydroxides, such as layered double hydroxides (LDH) and layered single hydroxides (LSHs). For this purpose, MgAl layered double hydroxide and the Co2(OH)3 layered single hydroxide were selected as hosts, and various synthetic approaches were explored to achieve the formation of the zein-layered hydroxide biohybrids, profiting from the presence of negatively charged groups in zein in basic medium. Zein-based layered hydroxide biohybrids were characterized by diverse physicochemical techniques such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis/differential thermal analysis (TG/DTA), solid state 13C cross-polarization magical angle spinning nuclear magnetic resonance (CP-MAS NMR), field emission-scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), etc., which suggest that the different synthesis procedures employed and the anion located in the interlayer region of the inorganic host material seem to have a strong influence on the final features of the biohybrids, resulting in mixed, single intercalated, or highly exfoliated intercalated phases. Thus, the resulting biohybrids based on zein and layered hydroxides could have interest in applications in biomedicine, biosensing, materials for electronic devices, catalysis, and photocatalysis.

Continuous Mesoporous Aluminum Oxide Film with Perpendicularly Oriented Mesopore Channels.

Mesoporous aluminum oxide (MAO) films with perpendicularly oriented cylindrical mesopores (pore diameter: ca. 10 nm) were successfully deposited on a glass substrate by a surfactant-templating approach using aluminum nitrate as an aluminum source. The perpendicular orientation of mesopores was confirmed by grazing-incidence small-angle X-ray scattering and neutron reflection experiments. The thickness of the MAO film was around 100 nm, with a surface roughness of less than 6 nm. Since the inner surface of MAO pores was positively charged, negatively charged glucose oxidase molecules could be densely loaded into the cylindrical mesopores without significant loss of enzymatic activity. The present MAO film is potentially useful as an inorganic host material for an enzyme toward the development of a biocatalytic system.

Critical Power Density: A Metric To Compare the Excitation Power Density Dependence of Photon Upconversion in Different Inorganic Host Materials

In photon upconversion (UC) based on triplet-triplet annihilation, the upconversion photoluminescent quantum yield (UC-PLQY) depends on the excitation power density in a way that can be described by a single figure of merit. This figure of merit, the threshold value, allows the excitation power density required for efficient UC-PLQY to be compared between different triplet-triplet annihilation systems. Here, we investigate the excitation power density dependence of two-photon UC processes in a series of four lanthanide-doped inorganic host materials (oxides, fluorides, and chlorides) all doped with 18 mol % Yb3+ sensitizer ions and 2 mol % Er3+ activator ions. We demonstrate that an analogous figure of merit, which we call the critical power density (CPD), accurately describes the UC power dependence of these samples. Better CPD values are obtained when the lifetime of the intermediate states is long. The UC-PLQY at the CPD is linked to the saturation UC-PLQY. Thus, a measurement of the UC-PLQY at this low power density can be used to estimate the theoretical saturation UC-PLQY in the absence of deleterious effects such as laser-induced heating. This is compared to another method to estimate the saturation based on the CPD model, namely, taking half of the level's PLQY under direct excitation. Our careful analysis of the upconversion spectra as a function of excitation power density gives several insights into the differing upconversion pathways in the hosts and proves to be a useful tool for their comparison.

Recent Advances in Rare Earth‐Doped Hydrides

The optical properties of rare earth ions in different inorganic host materials, for instance oxides, silicates, borates, or nitrides, have been used in applications for many years, from color TV to fluorescent tubes, lasers, or pc‐LEDs. However, rare earth metal ion‐doped hydrides have not really been considered as host lattices and up to now only been studied in a relatively small number of investigations. Yet, for certain metal hydrides these studies, e.g., allowed the determination of the crystal field strength and nephelauxetic effect of the hydride anion using the Eu2+ 5d excited state. In air‐sensitive hydrides, the use may be restricted to fundamental studies and local probes. But recently more and more air‐stable mixed anionic hydrides have been discovered, which may serve as hosts. This short review summarizes the synthesis and characterization of rare earth metal ion‐doped hydrides reported so far.