Hybrid Host Research Articles

Residents' journal review

Residents' journal review

Effect of acid or alkaline catalyst and of different capping agents on the optical properties of CdS nanoparticles incorporated within a diureasil hybrid matrix

CdS nanoparticles (NPs) were synthesized using colloidal methods and incorporated within a diureasil hybrid matrix. The surface capping of the CdS NPs by 3-mercaptopropyltrimethoxysilane (MPTMS) and 3-aminopropyltrimethoxysilane (APTMS) organic ligands during the incorporation of the NPs within the hybrid matrix has been investigated. The matrix is based on poly(ethylene oxide)/poly(propylene oxide) chains grafted to a siliceous skeleton through urea bonds and was produced by sol–gel process. Both alkaline and acidic catalysis of the sol–gel reaction were used to evaluate the effect of each organic ligand on the optical properties of the CdS NPs. The hybrid materials were characterized by absorption, steady-state and time-resolved photoluminescence spectroscopy and High Resolution Transmission Electron Microscopy (HR-TEM).The preservation of the optical properties of the CdS NPs within the diureasil hybrids was dependent on the experimental conditions used. Both organic ligands (APTMS and MPTMS) demonstrated to be crucial in avoiding the increase of size distribution and clustering of the NPs within the hybrid matrix. The use of organic ligands was also shown to influence the level of interaction between the hybrid host and the CdS NPs. The CdS NPs showed large Stokes shifts and long average lifetimes, both in colloidal solution and in the xerogels, due to the origin of the PL emission in surface states. The CdS NPs capped with MPTMS have lower PL lifetimes compared to the other xerogel samples but still larger than the CdS NPs in the original colloidal solution. An increase in PL lifetimes of the NPs after their incorporation within the hybrid matrix is related to interaction between the NPs and the hybrid host matrix.

Hollow Carbon Nanofibers Filled with MnO2 Nanosheets as Efficient Sulfur Hosts for Lithium–Sulfur Batteries

AbstractLithium–sulfur batteries have been investigated as promising electrochemical‐energy storage systems owing to their high theoretical energy density. Sulfur‐based cathodes must not only be highly conductive to enhance the utilization of sulfur, but also effectively confine polysulfides to mitigate their dissolution. A new physical and chemical entrapment strategy is based on a highly efficient sulfur host, namely hollow carbon nanofibers (HCFs) filled with MnO2 nanosheets. Benefiting from both the HCFs and birnessite‐type MnO2 nanosheets, the MnO2@HCF hybrid host not only facilitates electron and ion transfer during the redox reactions, but also efficiently prevents polysulfide dissolution. With a high sulfur content of 71 wt % in the composite and an areal sulfur mass loading of 3.5 mg cm−2 in the electrode, the MnO2@HCF/S electrode delivered a specific capacity of 1161 mAh g−1 (4.1 mAh cm−2) at 0.05 C and maintained a stable cycling performance at 0.5 C over 300 cycles.

Hollow Carbon Nanofibers Filled with MnO2 Nanosheets as Efficient Sulfur Hosts for Lithium-Sulfur Batteries.

Lithium-sulfur batteries have been investigated as promising electrochemical-energy storage systems owing to their high theoretical energy density. Sulfur-based cathodes must not only be highly conductive to enhance the utilization of sulfur, but also effectively confine polysulfides to mitigate their dissolution. A new physical and chemical entrapment strategy is based on a highly efficient sulfur host, namely hollow carbon nanofibers (HCFs) filled with MnO2 nanosheets. Benefiting from both the HCFs and birnessite-type MnO2 nanosheets, the MnO2 @HCF hybrid host not only facilitates electron and ion transfer during the redox reactions, but also efficiently prevents polysulfide dissolution. With a high sulfur content of 71 wt % in the composite and an areal sulfur mass loading of 3.5 mg cm(-2) in the electrode, the MnO2 @HCF/S electrode delivered a specific capacity of 1161 mAh g(-1) (4.1 mAh cm(-2) ) at 0.05 C and maintained a stable cycling performance at 0.5 C over 300 cycles.

Design of new lanthanide pH switches based on a cross-linked poly(vinyl alcohol)/tetraethoxysilane hybrid matrix

The design and synthesis of cross-linked siloxane and polymeric matrices incorporated with terbium or europium complexes have been studied. The preparation of hybrid hosts demonstrated that poly(vinyl alcohol) in the presence of tetraethoxysilane with various concentrations gave different mechanical stabilities and water solubilities. The as-derived films exhibited excellent photophysical properties of lanthanides with large Stokes shifts, narrow emissions, and high color purity. It has been found that the luminescent materials were dramatically quenched over the assayed pH ranges (pH 7 to 1 and pH 7 to 14). These optical probes could be recycled for ten times by changing the aqueous media. The novel inorganic-organic responsive films that can be switched on or off based on pH values will find potential application in biological analysis.

Highly Efficient Chirality Transfer from Diamines Encapsulated within a Self-Assembled Calixarene-Salen Host.

A calix[4]arene host equipped with two bis-[Zn(salphen)] complexes self-assembles into a capsular complex in the presence of a chiral diamine guest with an unexpected 2:1 ratio between the host and the guest. Effective chirality transfer from the diamine to the calix-salen hybrid host is observed by circular dichroism (CD) spectroscopy, and a high stability constant K2,1 of 1.59×10(11) M(-2) for the assembled host-guest ensemble has been determined with a substantial cooperativity factor α of 6.4. Density functional calculations are used to investigate the origin of the stability of the host-guest system and the experimental CD spectrum compared with those calculated for both possible diastereoisomers showing that the M,M isomer is the one that is preferentially formed. The current system holds promise for the chirality determination of diamines, as evidenced by the investigated substrate scope and the linear relationship between the ee of the diamine and the amplitude of the observed Cotton effects.

Tuning the sensitivity of Ln3+-based luminescent molecular thermometers through ligand design

Luminescence thermometry is being addressed as one of the most promising techniques to non-contact measurement of temperature with sub-micrometric resolution, due to the possibility of design the thermometer performance by the smart combination of emitting centers, ligands and host matrix. Numerous applications in microelectronic circuits and photonic devices will benefit of improved spatial and temporal resolution in the temperature imaging. In this paper we report three Ln3+-based (Ln=Eu, Tb) molecular thermometers co-doping an organic–inorganic hybrid matrix with Eu3+/Tb3+ chelates that differ in the ligand used. We show that the sensitivity of such thermometers can be tuned from 0.042±0.002 to 3.0±0.4%•K−1, in the 295–330K range, through the wisest design of the ligand (and the ligand-hybrid host interactions). The maximum sensitivity value is one of the largest reported so far for luminescent ratiometric thermometers. Furthermore, we rationalize the increase on the performance of the molecular thermometers using a partial energy scheme involving the emitting levels of the Ln3+ ions and the singlet and triplet states of the ligands and the hybrid host.

An unprecedented porphyrin-pillar[5]arene hybrid ditopic receptor

A porphyrin-pillar[5]arene hybrid host compound with a ditopic receptor nature was synthesized for the first time, which combines a neutral 1,4-bis(imidazol-1-yl)butane guest by means of its two active centers to form a stable supramolecular complex.

A versatile efficient one-step approach for carbazole–pyridine hybrid molecules: highly efficient host materials for blue phosphorescent OLEDs

By using various fluoro-substituted pyridines and carbazole as starting materials, we have synthesized a series of carbazole-pyridine hybrid compounds through an efficient catalyst free C-N coupling reaction with high yields of 85-95%. The bi-, tri- and tetra-carbazole substituted pyridine derivatives exhibit increased thermal stabilities and comparatively high triplet energy levels of ∼3.0 eV. By using them as host materials for blue phosphorescent OLEDs, maximum current efficiencies are achieved ranging from 32-42 cd A(-1).

A novel tetraphenylsilane–phenanthroimidazole hybrid host material for highly efficient blue fluorescent, green and red phosphorescent OLEDs

A novel organosilane compound Si(PPI)2 with good carrier-transport ability has been used as an efficient host for high-performance fluorescent pure-blue and phosphorescent green/red OLEDs.

Quasi-anhydrous proton conducting di-ureasil hybrid electrolytes incorporating a protic ionic liquid

A wide range of concentrations of the [EIm][TfO] proton ionic liquid (PIL) were for the first time incorporated into a poly(oxyethyelene) (POE)/siloxane hybrid host matrix (d-U(2000)) belonging to the di-ureasil family. The synthesis procedure adopted, involving the lowest amount of water possible, resulted in the formation of essentially anhydrous electrolytes at certain PIL levels. The optimized sample d-U(2000)/[EIm][TfO]50 (where 50 represents the ratio in % of the mass of [EIm][TfO] per mass of POE precursor) is amorphous, thermally stable up to 200°C, displays good mechanical properties and exhibits an ionic conductivity of 3.2×10-4 and 4.3×10-3Scm-1 at 20 and 186°C, respectively. These features have persisted for more than three years. These new electrolytes appear quite attractive for applications in fuel cells operating under non-humidified conditions.

Origin of improved stability in green phosphorescent organic light-emitting diodes based on a dibenzofuran/spirobifluorene hybrid host

A highly efficient and stable green phosphorescent organic light-emitting diode (PHOLED) was fabricated by using a new dibenzofuran/spirobifluorene hybrid material (named as DBFSF2) as the host material. The DBFSF2-based PHOLEDs exhibited slightly better electroluminescence efficiency than that in the conventional host material 4,4′-bis(carbazol-9-yl)biphenyl (CBP)-based ones. Moreover, further studies demonstrated that the DBFSF2-based PHOLEDs had a better stability with about 1.5 times improvement in half lifetime compared with that of CBP-based ones. To investigate the mechanism behind the enhanced stability in the DBFSF2-based PHOLEDs, the evaluations of dark spots growth, film crystallization properties and carrier recombination zone were carried out.

ChemInform Abstract: Small Molecule Host Materials for Solution Processed Phosphorescent Organic Light‐Emitting Diodes.

AbstractReview: 86 refs.

Performance of a Hybrid Fungal Pathogen on Pure-Species and Hybrid Host Plants

Premise of research. Recent hybridization events in fungi have produced emerging pathogens characterized by novel host specificities, increased infectivity, and/or elevated severity. We investigated the potential for host shifts and increased infectivity following hybridization of fungal pathogens in the genus Microbotryum, which causes anther-smut disease on caryophyllaceous hosts. Hybrids of the closely related species Microbotryum lychnidis-dioicae (MvSl) and Microbotryum silenes-dioicae (MvSd) are viable and fertile. Although historical genetic exchange between MvSl and MvSd is rare, there is evidence of recent hybridization of these fungal species, as well as of their plant hosts, Silene latifolia and Silene dioica. Methodology. We examined the fitness of hybrid pathogens and hosts by using F1 hybrids of MvSl × MvSd to inoculate S. latifolia × S. dioica hybrids. Experimental inoculations of S. latifolia and hybrid hosts with pure-species and hybrid pathogens allowed assessment of the likelihood of hybrid emergence on a novel host (the hybrid plant) and of increased infectiousness of the hybrid pathogen on the pure-species host. Pivotal results. We found no evidence for pathogen hybrid inferiority, arguing against interspecific incompatibilities at small genetic distances. Instead, we found that hybrid pathogens are more infectious on pure-species hosts, while pure-species pathogens are more infectious on hybrid hosts, indicating an interaction of host and parasite genotypes. Conclusions. This finding argues against emergence of hybrid pathogens on a novel hybrid host. However, our study suggests that hybridization of pathogens and hosts in natural populations may lead to elevated disease prevalence overall, thus furthering the impact of anther-smut disease in these Silene species.

Small molecule host materials for solution processed phosphorescent organic light-emitting diodes.

Solution processed phosphorescent organic light-emitting diodes (OLEDs) have been actively developed due to merits of high quantum efficiency of phosphorescent materials and simple fabrication processes of solution processed OLEDs. The device performances of the solution processed phosphorescent OLEDs have been greatly improved in the last 10 years and the progress of the device performances was made by the development of small molecule host materials for solution processes. A hybrid host of polymer and small molecules, a single small molecule host and a mixed host of small molecule hosts have effectively enhanced the quantum efficiency of the solution processed phosphorescent OLEDs. Therefore, this paper reviews recent developments in small molecule host materials for solution processed phosphorescent OLEDs and provides future directions for the development of the small molecule host materials.

Corymbia phloem phenolics, tannins and terpenoids: interactions with a cerambycid borer

Plant secondary chemistry mediates the ability of herbivores to locate, accept and survive on potential host plants. We examined the relationship between attack by the cerambycid beetle Phoracantha solida and the chemistry of the secondary phloem (inner bark) of two differentially attacked plantation forestry taxa, Corymbia variegata and its hybrid with C. torelliana. We hypothesised that this differential rate of attack may have to do with differences in secondary chemistry between the taxa. We found differences in the bark chemistry of the taxa, both with respect to phenolic compounds and terpenoids. We could detect no difference between bored and non-bored C. variegata trees (the less preferred, but co-evolved host). Hybrid trees were not different in levels of total polyphenols, flavanols or terpenes according to attack status, but acetone extracts were significantly different between bored and non-bored trees. We propose that variations in the bark chemistry explain the differential attack rate between C. variegata and the hybrid hosts.

Synthesis of the Aluminophosphate ICP-1 by Self-Assembly of 1,3-Diphenylguanidine: Insights into Supramolecular Aggregation

1,3-Diphenylguanidine (DPG) has distinguishable polar and apolar groups, aromatic rings that can self-assemble through π–π type interactions, and high conformational flexibility. These features make it a potential self-assembling structure-directing agent in the synthesis of hybrid host–guest aluminophosphates. Computational simulations show that the molecule has a strong tendency to self-assemble in aqueous solution. Large supramolecular organic aggregates are produced, with the hydrophobic aromatic rings located in the center of the aggregates, stabilized by π–π type interactions, and the hydrophilic guanidine groups on the external surface in close contact with water molecules. With this organic molecule, a new 1-D AlPO framework material (ICP-1) was formed. Its structure, characterized by a combination of single-crystal and powder diffraction techniques, consists of AlP2O8H chains connected to the polar groups of the organic DPG molecules through a complex H-bonding network. This material has an extremely high organic content, close to that of typical mesoporous materials. However, DPG molecules are part of the ICP-1 network, rather than guest molecules in the pores, so removal of DPG results in a collapse of the structure, limiting its potential applications. Nevertheless, this work demonstrates the potential of using self-assembling organic molecules for producing very open-framework materials.

Organic–inorganic hybrid: a novel template for synthesis of nanostructured Ag

We herein demonstrate that the amino acid arginine (Arg) can interact with phosphotungstate (Keggin) anions generating an excellent template for the synthesis of nanostructured silver wherein the Arg–PTA hybrid host plays the role of a UV-switchable reducing agent. The binding strength of the complex between arginine and phosphotungstate (PW12O40)3− i.e. the Keggin ions in aqueous medium has been assessed by the isothermal titration calorimetric technique. It is shown that the Arg–PTA complex may be used as a new class of organic–inorganic scaffolds in the synthesis of nanostructured silver. The crystalline Arg–PTA host can be photochemically reduced, resulting in electron transfer to the entrapped silver ions to form nanoparticle assemblies on the underlying colloidal template.

Highly efficient single-layer organic light-emitting devices based on a bipolar pyrazine/carbazole hybrid host material

High efficiency blue (F), green (P), orange (P) and F–P hybrid warm white single-layer OLEDs are fabricated through a simple manufacturing process.

Correction to “Achilles Heels of Phosphine Oxide Materials for OLEDs: Chemical Stability and Degradation Mechanism of a Bipolar Phosphine Oxide/Carbazole Hybrid Host Material”

Correction to “Achilles Heels of Phosphine Oxide Materials for OLEDs: Chemical Stability and Degradation Mechanism of a Bipolar Phosphine Oxide/Carbazole Hybrid Host Material”