Optically hybrid lanthanide ions (Eu3+, Tb3+)‐centered materials with novel functional di‐urea linkages

The synthesis of 3‐(triethoxysilyl)‐propyl isocyanate (TEPIC) modified by (3‐aminopropyl)triethoxysilane (APS) and the preparation of the corresponding organic–inorganic molecular‐based hybrid material with the two components equipped with covalent bonds is described. The coupling agent moiety is a convolution of TEPIC and APS through ? NHC(?O)NH? groups, which is applied to coordinate to RE³⁺ and further formed Si? O backbones after hydrolysis and polycondensation processes. For comparison and luminescence efficiency purposes, we added 2,2‐bipyridyl to the above hybrids in order to increase the conjugating effects and sensitize rare earth ions emissions. Luminescence spectra were utilized to characterize the photophysical properties of the hybrid material obtained, and the above spectroscopic data reveal that the triplet energy of 2,2‐dipyridyl in this favorable hybrid system matches with the emissive energy level of RE³⁺. In this way, the intramolecular energy transfer process took place within these molecular‐based hybrids and strong green and red emissions of RE³⁺ have been achieved. Copyright © 2005 John Wiley & Sons, Ltd.     

Mesoporous hybrids containing Eu complexes covalently bonded to SBA-15 functionalized: Assembly, characterization and photoluminescence

A novel series of luminescent mesoporous organic-inorganic hybrid materials has been prepared by linking Eu³⁺ complexes to the functionalized ordered mesoporous SBA-15 which was synthesis by a co-condensation process of 1,3-diphenyl-1,3-propanepione (DBM) modified by the coupling agent 3-(triethoxysilyl)-propyl isocyanate (TEPIC), tetraethoxysilane (TEOS), Pluronic P123 surfactant as a template. It was demonstrated that the efficient intramolecular energy transfer in the mesoporous material Eu(DBMSi-SBA-15)₃phen mainly occurred between the modified DBM (named as DBM-Si) and the central Eu³⁺ ion. So the Eu(DBMSi-SBA-15)₃phen showed characteristic emission of Eu³⁺ ion under UV irradiation with higher luminescence quantum efficiency. Moreover, the mesoporous hybrid materials exhibited excellent thermal stability as the lanthanide complex was covalently bonded to the mesoporous matrix.     

Assembly, characterization, and photoluminescence of hybrids containing europium(III) complexes covalently bonded to inorganic Si-O networks/organic polymers by modified beta-diketone

1-(2-naphthoyl)-3,3,3-trifluoroacetonate (NTA) was grafted to the coupling agent 3-(triethoxysilyl)-propyl isocyanate (TEPIC) and used as the first kind of precursor, and other kinds of precursors (PVPD, PMAA, and PVPDMAA) were synthesized through the addition polymerization reactions of the monomer 4-vinylpyridine and methacrylic acid. Then, these precursors coordinated to rare earth ions, and the three kinds of hybrid polymeric materials were obtained after hydrolysis and copolycondensation with the tetraethoxysilane (TEOS) via a sol-gel process. FTIR, ultraviolet, ultraviolet-visible diffuse reflection and photoluminescent spectra, electronic microscopy diagraphs, room-temperature X-ray diffraction patterns, and TG plots were characterized, and the results reveal that the hybrid materials imbedded into the single polymer (PVPD and PMAA) showed more uniformity in the microstructure, more efficient intramolecular energy transfer between europium ions and the modified ligand NTA-Si and more excellent characteristic emission of europium ions under UV irradiation with higher (5)D(0) luminescence quantum efficiency and longer lifetime than the hybrid materials imbedded into the multipolymer (PVPDMAA).     

Designing a family of luminescent hybrid materials by 3-(triethoxysilyl)-propyl isocyanate grafted 2-hydroxynicotinic acid bridge molecules

The study concentrates on the syntheses of modified 2-hydroxynicotinic acid by 3-(triethoxysilyl)-propyl isocyanate (TESPIC) and the preparation of their corresponding organic-inorganic molecular-based hybrid material with the two components equipped with covalent bonds. The bridging unit is a derivative of 2-hydroxynicotinic acid which is utilized to coordinate to Tb³⁺, Eu³⁺ or Zn²⁺ and further occurred hydrolysis and polycondensation processes by functional triethoxysilyl groups. Ultraviolet absorption, phosphorescence spectra, and luminescence spectra were applied to characterize the photophysical properties of the obtained hybrid material and the above spectroscopic data present that the triplet energy of modified 2-hydroxynicotinic acid efficiently initiates the antenna effect and matches with the emissive energy level of metal ions. As a result, the intramolecular energy transfer process completed within these molecular-based hybrids and strong green or red emissions of Ln³⁺ have been obtained.     

Luminescent lanthanide molecular‐based hybrid materials bridged through novel urethane linkages

Novel organosilicates with covalently linked functional modified aromatic acid have been synthesized from 3‐aminopropyl triethoxysilane (APS) grafted 4‐ethoxy benzoic acid (EB‐Si) and terbium ions via a simple low‐temperature route. The existence of covalent bonds between EB‐Si and silica matrices was shown by the hydrolysis and polycondensation processes of ethoxysilyl groups. Luminescence spectra were used to characterize the photophysical properties of the obtained hybrid material and the above spectroscopic data reveal that the triplet energy of modified para ethoxy benzoic acid in this favorable hybrid system matches the emissive energy level of RE³⁺. Copyright © 2006 John Wiley & Sons, Ltd.     

Covalently assembly and photophysical properties of novel lanthanide centered hybrid materials by functionalized thioacylureas bridge

A novel molecular precursor (abbreviated as TAM-Si) derives from thioacetaminde (TAM) modified by 3-(triethoxysilyl)-propyl isocyanate (TEPIC) though the hydrogen transfer addition reaction. Then TAM-Si behaves as functional molecular bridge which coordinates to RE³ (Eu³⁺, Tb³⁺) as well as form SiO network with inorganic precursor (TEOS) after a sol–gel process (cohydrolysis and copolycondensation reaction), resulting in the covalently bonded hybrid materials (RE–TAM-Si). On the other hand, the hybrid material of TAM-Si without introduction of RE³⁺ as well has been obtained. SEM pictures indicate that the TAM-Si show the sphere micromorphology with particle size of micrometer dimension while RE–TAM-Si hybrids present different nanometer particle, which suggests that lanthanide ions has influence on the microstructure of hybrid systems through its coordinated effect. The blue emission for TAM-Si hybrids and the narrow-width green and red emissions were achieved for Tb³⁺ and Eu³⁺ ions, respectively, indicating that the intramolecular energy transfer process take place from photoactive group to Tb³⁺ and Eu³⁺ ions in these hybrid microsphere systems. Especially the lifetime and quantum efficiency for europium hybrids have been determined.     

Molecular design of luminescent organic-inorganic hybrid materials activated by europium (III) ions

Luminescent hybrid materials consisting in rare-earth (Eu³⁺, Gd³⁺) organic complexes covalently attached to a silica-based network have been obtained by a sol–gel process. Four dicarboxylic acids with different aromatic subunits (dipicolinic acid, 4-phenyl-2,6-pyridinedicarboxylic acid, 4-(phenylethynyl)-2,6-pyridinedicarboxylic acid and 2,6-Bis(3-carboxy-1-pyrazolyl)pyridine) have been chosen as ligands for Ln³⁺ ions. They were grafted to 3-aminopropyltriethoxysilane (APTES) to give organically modified alkoxysilanes that were used as molecular precursors for the preparation of hybrid materials. Ln³⁺ first coordination sphere, composition of the siloxane matrix and connection between the organic and inorganic parts have been characterized by infrared spectroscopy, by ¹³C²⁹Si solid-state NMR as well as by elemental analyses. UV excitation in the organic component resulted in strong emission from Eu³⁺ ions due to an efficient ligand-to-metal energy transfer. As compared to reference organic molecules, hybrid samples exhibited similar emission properties under UV excitation in addition to mainly unchanged excited states lifetimes. However, by direct excitation of the Eu³⁺-⁵D₀ energy level, the presence of two different site distributions were evidenced in the four hybrid compounds. Emission features related to each of these site distributions and their respective attribution were investigated. Variations in the relative emission intensities were observed according to the nature of the organic chromophore. These variations were discussed in relation to the ATE (Absorption-Transfer-Emission) mechanism and to the relative energy positions of the ligand and the rare-earth ions respectively.     

Chemically bonded assembly and photophysical properties of luminescent hybrid polymeric materials embedded into silicon–oxygen network and carbon unit

Through the reaction between the hydroxyl groups of 2-hydroxyl-3-methylbenzoic acid (HMBA), the glycol (G), the diglycol (DG) or the polyethylene glycol (PEG) and the isocyanate groups of 3-(triethoxysilyl)-propyl isocyanate (TEPIC), the hybrid precursors HMBA-Si, G-Si, DG-Si and PEG-Si were obtained. And then the precursors HMBA-Si and G-Si (DG-Si, PEG-Si) have coordinated to the rare earth ions with the carbonyl group of G-Si (DG-Si, PEG-Si) and the carboxyl group of HMBA-Si to form the hybrid materials HMBA-G-RE-Si (HMBA-DG-RE-Si, HMBA-PEG-RE-Si) through hydrolysis and copolycondensation with the tetraethoxysilane (TEOS) via sol–gel process. Subsequently, the NMR, FT-IR and ultraviolet absorption spectra have indicated that the effective precursors have been obtained successfully and the obtained materials possess the characteristic fluorescent properties, thermal stabilities and regular trunk with hole-like microstructures.     

Lanthanide/zinc centered photoactive hybrids with functional sulfonamide linkage: Coordination bonding assembly,characterization and photophysical properties

In this paper, two novel kinds of organic–inorganic monomer, SUA-APEMS and SUA-APS, have been achieved by modifying 5-sulfosalicylic acid (SUA) with 3-aminopropyl-methyl-diethoxylsilane (APEMS) and 3-aminopropyl trimethoxysilane (APS). These two organic–inorganic monomers were used as multi-functional bridged components, which can coordinate to metal ions (Tb³⁺/Eu³⁺/Zn²⁺) with carbonyl groups, strongly absorb ultraviolet and effectively transfer energy to metal ions through their triplet excited state, as well as involve in the sol–gel process with inorganic host precursor tetraethoxysilane (TEOS), resulting two series of molecular hybrid materials (named as SUA-APEMS/APS-RE) with double chemical bond (RE(Zn)–O coordination bond and Si–O covalent bond). The effective intra-molecular energy transfer process gives rise to the characteristic emission of metal ions and the chemical bond make the hybrid materials owning better properties.     

Rare-earth/inorganic/organic polymeric hybrid materials: molecular assembly, regular microstructure and photoluminescence

2-Hydroxynicotinic acid (HNA) was grafted by 3-(triethoxysilyl)propyl isocyanate (TEPIC) to achieve the molecular precursor HNA-Si through the hydrogen-transfer nucleophilic addition reaction between the hydroxyl group of HNA and the isocyanate group of TEPIC. Then, a chemically bonded rare-earth/inorganic polymeric hybrid material (A) was constructed using HNA-Si as a bridge molecule that can both coordinate to rare-earth ions (HNA-Si-RE) and form an inorganic Si-O network with tetraethoxysilane (TEOS) after cohydrolysis and copolycondensation processes. Further, three types of novel rare-earth/inorganic/organic polymeric hybrids (B-D) were assembled by the introduction of three different organic polymeric chains into the above system. First, methacrylic acid (MAA) [or methacrylic acid and acrylamide (ALM) in the molar ratio of 1:1] was mixed to polymerize (or copolymerize) with benzoyl peroxide (BPO) as the initiator to form poly(methacrylic acid) (PMAA) [or poly(methacrylic and acrylamide) (PMAALM)], and then PMAA or PMAALM was added to the precursor HNA-Si before the assembly of HNA-Si-RE, resulting in the hybrid materials HNA-Si-RE-PMAA (B) and HNA-Si-RE-PMAALM (C). Second, poly(vinylpyrrolidone) (PVP) was added to coordinate to the rare-earth ions by the carbonyl group in the complex HNA-Si-RE, to achieve the hybrid HNA-Si-RE-PVP (D). All of these hybrid materials exhibit homogeneous, regular, and ordered microstructures and morphologies, suggesting the occurrence of self-assembly of the inorganic network and organic chain. Measurements of the photoluminescent properties of these materials show that the ternary rare-earth/inorganic/organic polymeric hybrids present stronger luminescent intensities, longer lifetimes, and higher luminescent quantum efficiencies than the binary rare-earth/inorganic polymeric hybrids, indicating that the introduction of the organic polymer chain is a benefit for the luminescence of the overall hybrid system.     

High-Voltage Rechargeable Alkali–Acid Zn–PbO2 Hybrid Battery

Aqueous rechargeable batteries have attracted attention owning to their advantages of safety, low cost, and sustainability, while the limited electrochemical stability window (1.23 V) of water leads to their failure in competition with organic-based lithium-ion batteries. Herein, we report an alkali–acid Zn–PbO₂ hybrid aqueous battery obtained by coupling an alkaline Zn anode with an acidic PbO₂ cathode. It shows the capability to deliver an impressively high open-circuit voltage (V_oc) of 3.09 V and an operate voltage of 2.95 V at 5 mA cm⁻², thanks to the contribution of expanding the voltage window and the electrochemical neutralization energy from the alkali–acid asymmetric-electrolyte hybrid cell. The hybrid battery can potentially deliver a large area capacity over 2 mAh cm⁻² or a high energy density of 252.39 Wh kg⁻¹ and shows almost no fading in area capacity over 250 charge–discharge cycles.     

Interactions of pyridinecarboxylic acid chelators with brain metal ions: Cu(II), Zn(II), and Al(III)

Abstract  

The interactions of Cu(II), Zn(II), and Al(III) with 1,6-dimethyl-4-hydroxy-3-pyridinecarboxylic acid (DQ716) and 2,6-dimethyl-3-hydroxy-4-pyridinecarboxylic acid (DT726), possible chelating agents in Alzheimer’s disease, were investigated in aqueous solution. The proton dissociation constants of the ligands, the stability constants, and the coordination modes of the metal complexes formed were determined by pH-potentiometric, UV–vis spectrophotometric, and ¹H NMR methods. The nitrogen of the pyridine ring changes the proton affinity of the carboxylate and phenolate moieties and these pyridine derivatives form stronger complexes with Cu(II), Zn(II), and Al(III) than salicylic acid. Interactions of the ligands with human serum albumin as their potential transporter in blood were investigated at physiological pH through ultrafiltration by UV–vis and fluorescence spectroscopy.     

A novel path to luminescent hybrid molecular materials: modifying the hydroxyl group of 6‐hydroxynicotinic acid by grafting to a silica network

In this paper, a novel path was put forward to modify the hydroxyl group of 6‐hydroxynicotinic acid by 3‐(triethoxysilyl)‐propyl isocyanate and prepare the corresponding organic–inorganic molecular‐based hybrid material with the two components connected by covalent bonds. The bridging unit is a derivative of 6‐hydroxynicotinic acid that is utilized to coordinate to Tb³⁺ via hydrolysis and polycondensation processes with functional triethoxysilyl groups. Ultraviolet absorption, phosphorescence spectra and luminescence spectra were applied to characterize the photophysical properties of the hybrid material obtained and the spectroscopic data show that the triplet energy of modified 6‐hydroxynicotinic acid efficiently initiates the antenna effect and matches the emissive energy level of the metal ions. As a result, the intramolecular energy transfer process is completed within these molecular‐based hybrids. Copyright © 2005 John Wiley & Sons, Ltd.     

A Novel Electrochemical Sensor Based on Silsesquioxane/Nickel (II) Phthalocyanine for the Determination of Sulfanilamide in Clinical and Drug Samples

This paper describes the immobilization of nickel (II) phthalocyanine‐tetrasulfonic acid tetrasodium salt (NiTsPc) in 3‐n‐propyl(3‐methylpyridinium) silsesquioxane chloride (Si3Pic⁺Cl^?). This hybrid material was synthetized and characterized by ²⁹Si NMR CP‐MAS, FTIR and DRS. The modified material, designated as Si3Pic⁺Cl^?/NiTsPc, was used to build carbon paste electrodes to determine sulfanilamide (SFL) by differential pulse voltammetry. The modified electrode showed a higher current response when compared to the bare carbon paste electrode. The evaluation of SFL was possible in the presence of salicylic acid, commonly used in solid ointment compositions in a high concentration. Theoretical calculations using density functional theory were done aiming to shed light at dimerization process at SFL. The oxidation peak increased with increasing concentrations of SFL in the range of 35–301 μmol L^?1. The LOD and LOQ values obtained were 12 and 35 μmol L^?1 of SFL, respectively. The novel electrochemical sensor was successfully applied for the determination of SFL in pet drug samples, urine and serum through the standard addition method. Validation was performed through a comparison with values obtained by the molecular absorption spectrometry method and there were no significant differences in the results, as confirmed by the statistical paired t‐test. This demonstrates the promise of a new approach for analytical application in clinical and drug samples of sulfonamide compounds.     

Electrocatalytic oxidation of phytohormone salicylic acid at copper nanoparticles-modified gold electrode and its detection in oilseed rape infected with fungal pathogen Sclerotinia sclerotiorum

Salicylic acid (SA) is a biological substance that acts as a phytohormone and plays an important role in signal transduction in plants. It is important to accurately and sensitively detect SA levels. A gold electrode modified with copper nanoparticles was used to assay the electrocatalytic oxidation of salicylic acid. It was found that the electrochemical behavior of salicylic acid was greatly improved at copper nanoparticles, indicating that anodic oxidation could be catalyzed at copper nanoparticles. And the pH had remarkable effect on the electrochemical process, a very well-defined oxidation peak appeared at pH 13.3 (0.2 M NaOH). The kinetics parameters of this process were calculated and the heterogeneous electron transfer rate constant (k) was determined to be 1.34 × 10⁻³ cm s⁻¹, and (1 − α)n_α was 1.22. The gold electrode modified with copper nanoparticles could detect SA at a higher sensitivity than common electrodes. The electrode was used to detect the SA levels in oilseed rape infected with the fungal pathogen Sclerotinia sclerotiorum. The results showed that the SA concentration reached a maximum during the 10th-25th hours after infection. This result was very similar to that determined by HPLC, indicating that the gold electrodes modified with copper nanoparticles could be used as salicylic acid sensors.     

New Multifunctional Porous Materials Based on Inorganic–Organic Hybrid Single‐Walled Carbon Nanotubes: Gas Storage and High‐Sensitive Detection of Pesticides

Single‐walled carbon nanotubes (SWNTs) that are covalently functionalized with benzoic acid (SWNT‐PhCOOH) can be integrated with transition‐metal ions to form 3D porous inorganic–organic hybrid frameworks (SWNT‐Zn). In particular, N₂‐adsorption analysis shows that the BET surface area increases notably from 645.3 to 1209.9 m² g^?1 for SWNTs and SWNT‐Zn, respectively. This remarkable enhancement in the surface area of SWNT‐Zn is presumably due to the microporous motifs from benzoates coordinated to intercalated zinc ions between the functionalized SWNTs; this assignment was also corroborated by NLDFT pore‐size distributions. In addition, the excess‐H₂‐uptake maximum of SWNT‐Zn reaches about 3.1 wt. % (12 bar, 77 K), which is almost three times that of the original SWNTs (1.2 wt. % at 12 bar, 77 K). Owing to its inherent conductivity and pore structure, as well as good dispersibility, SWNT‐Zn is an effective candidate as a sensitive electrochemical stripping voltammetric sensor for organophosphate pesticides (OPs): By using solid‐phase extraction (SPE) with SWNT‐Zn‐modified glassy carbon electrode, the detection limit of methyl parathion (MP) is 2.3 ng mL^?1.     

Selective Electrochemical Determination of Salicylic Acid in Wheat Using Molecular Imprinted Polymers

Salicylic acid is a phytohormone, playing crucial roles in signal transduction, crop growth, and development, and defense to environmental challenges. In this study, a highly selective electrochemical sensor was designed and used to determine salicylic acid using molecularly imprinted polymers for recognition. The electrochemical sensor was fabricated via stepwise modification of gold nanoparticle–graphene–chitosan and molecularly imprinted polymers on a glassy carbon electrode. With electrochemical deposition, a gold nanoparticle–graphene–chitosan film was deposited on the glassy carbon electrode and enhanced the sensitivity. Molecularly imprinted polymers with adsorbed template salicylic acid were added to the surface of the modified electrode. Cyclic voltammetry and electrochemical impedance spectroscopy were used to characterize the modified electrodes. Salicylic acid in wheat was quantified by the sensor using the molecularly imprinted polymer/gold nanoparticle–graphene–chitosan/glassy carbon electrode. Concentrations of salicylic acid from 5?×?10^?10 to 5?×?10^?5?mol?L^?1 were determined showing that the developed sensor was suitable for the analysis of food.     

Design of a Novel Sort of Luminescent Terbium(III) Hybrid Materials with Potential Molecular Bridge

Summary. A kind of precursor molecule (abbreviated as EPDA–APMS) was synthesized by means of the amidation reaction of 5-ethylpyridine-2,3-dicarboxylic acid (EPDA) with a crosslinking molecule (3-aminopropyl)trimethoxysilane (APMS). Then the hybrid materials were obtained by reaction of this kind of monomer (EPDA–APMS), tetraethoxysilane (TEOS) and Tb(NO₃)₃·6H₂O by an in-situ sol-gel process, resulting in a novel molecular hybrid material (named as Tb–EPDA–APMS) with double chemical bonds (Tb–O coordination bond and Si–O covalent bond). Ultraviolet absorption, phosphorescence, and fluorescence spectra were applied to characterize the photophysical properties of the obtained hybrid material. The strong luminescence of Tb³⁺ substantiates optimum energy match and effective intramolecular energy transfer between the triplet state energy of modified ligand bridge and emissive energy level of Tb³⁺.     

Hybrid materials of MCM-41 functionalized by lanthanide (Tb, Eu) complexes of modified meta-methylbenzoic acid: Covalently bonded assembly and photoluminescence

Novel organic-inorganic mesoporous hybrid materials were synthesized by linking lanthanide (Tb³⁺, Eu³⁺) complexes to the mesoporous MCM-41 through the modified meta-methylbenzoic acid (MMBA-Si) using co-condensation method in the presence of the cetyltrimethylammonium bromide (CTAB) surfactant as template. The luminescence properties of these resulting materials (denoted as Ln-MMBA-MCM-41, Ln=Tb, Eu) were characterized in detail, and the results reveal that luminescent mesoporous materials have high surface area, uniformity in the ordered mesoporous structure. Moreover, the mesoporous material covalently bonded Tb³⁺ complex (Tb-MMBA-MCM-41) exhibits the stronger characteristic emission of Tb³⁺ and longer lifetime than Eu-MMBA-MCM-41 due to the triplet state energy of organic legend MMBA-Si matches with the emissive energy level of Tb³⁺ very well.