Rare earth (Eu, Tb) centered composite gels Si-O-M (M = B, Ti) through hexafluoroacetyl-acetone building block: Sol-gel preparation, characterization and photoluminescence

This report focuses on the syntheses of a series of novel photoactive composite xerogels materials in which the functionalized hexafluoroacetylacetone (HFAASi) organic components are grafted into the different inorganic networks (SiO₂-B₂O₃ or SiO₂-TiO₂) via covalent bonds through a sol-gel process. Subsequently, the physical characterization and especially photoluminescent properties of the resulting xerogel materials are studied in detail. Except for composite xerogels linked to SiO₂-TiO₂ networks, all of these composite xerogels exhibit homogeneous microstructures and morphologies, suggesting that molecular-based materials are obtained with strong covalent bonds between the organic β-diketone ligand and inorganic matrices. In addition, the ternary rare earth composite gels present stronger luminescent intensities, longer lifetimes, and higher luminescent quantum efficiencies than the binary ones, indicating that the introduction of the second ligands (phen) can sensitize the luminescent emission of the rare earth ions in the ternary hybrid systems. It should be especially noted that these composite xerogels based on Si-O-B networks possess not only higher thermal stability but also stronger luminescent intensities than the other systems linked to different inorganic networks.     

A new luminescent molecular based terbium hybrid material containing both organic polymeric chains and inorganic silica networks

We have synthesized the ternary organic/inorganic/polymeric terbium hybrid material (ACAC-Si)-Tb-PVP [ACAC = acetylacetone; PVP = poly(4-vinylpyridine)]. Firstly, the ACAC was modified through the hydrogen transfer addition reaction with a cross-linking reagent 3-(triethoxysilyl)-propyl isocyanate (TEPIC) to obtain a functional molecular bridge ACAC-Si which subsequently coordinated with Tb³⁺ and thus formed the inorganic Si-O-Si networks with TEOS (tetraethoxysilane) through hydrolysis and polycondensation process, and PVP acted as organic polymeric chains was synthesized using 4-vinylpyridine as the monomer after coordination with Tb(III) in the presence of BPO (Benzoyl Peroxide). For comparison, the binary hybrid material Tb-(ACAC-Si) was also prepared. The properties of the two hybrid materials were characterized in detail. The results reveal that the terbium complex was embedded into the organic polymer matrix by covalent bond with uniform microstructure. Furthermore, the distinction of the excitation spectrum between the binary and ternary hybrid materials suggests that the introduction of the polymeric organic chain component changed the microenvironment around the coordination sphere of the terbium. The emission spectrum exhibit the strong characteristic fluorescence of Tb³⁺, which accounts for the efficient intro-molecular energy transfer taken place in the two hybrid materials.     

Covalently Interlayer-Confined Organic–Inorganic Heterostructures for Aqueous Potassium Ion Supercapacitors (Small 4/2023)

Artificial assembly of organic–inorganic heterostructures for electrochemical energy storage at the molecular level is promising, but remains a great challenge. Here, a covalently interlayer-confined organic (polyaniline [PANI])–inorganic (MoS₂) hybrid with a dual charge-storage mechanism is developed for boosting the reaction kinetics of supercapacitors. Systematic characterizations reveal that PANI induces a partial phase transition from the 2H to 1T phases of MoS₂, expands the interlayer spacing of MoS₂, and increases the hydrophilicity. More in-depth insights from the synchrotron radiation-based X-ray technique illustrate that the covalent grafting of PANI to MoS₂ induces the formation of Mo N bonds and unsaturated Mo sites, leading to increased active sites. Theoretical analysis reveals that the covalent assembly facilitates cross-layer electron transfer and decreases the diffusion barrier of K⁺ ions, which favors reaction kinetics. The resultant hybrid material exhibits high specific capacitance and good rate capability. This design provides an effective strategy to develop organic–inorganic heterostructures for superior K-ion storage. The K-ion storage mechanism concerning the reversible insertion/extraction upon charge/discharge is revealed through ex situ X-ray photoelectron spectroscopy.     

Photofunctional terbium centered inorganic/organic hybrid material with the functionalized 5-dihydroxybenzoate linkage

In this study, silica-based organic-inorganic hybrids were prepared using sol-gel methods. A new kind of monomer (DHBA-TESPI) was derived by modifying the double hydroxyl groups of 3, 5-dihydroxybenzoic acid (DHBA) with 3-(triethoxysilyl)-propyl isocyanate (TESPI) through the addition reaction. Then, the obtained compound and tetraethoxysilane (TEOS) were used as the inorganic and organic counterparts respectively. Coordination reaction between Tb³⁺ and the carboxylic groups of the monomer happen simultaneously. IR, NMR, UV/Vis absorption, low-temperature phosphorescence spectroscopy and fluorescence spectroscopy were used to characterize the hybrids. The final materials exhibited strong green-colored fluorescence (Tb³⁺), which can be explained by the intramolecular energy transfer caused by coordination of the organic counterpart. The spectroscopic data also revealed that the triplet state energy of the organic ligand matches the emissive energy level of Tb³⁺.     

Raman intensity: An important tool to study the structure and phase transitions of amorphous/crystalline materials

The measurements of the Raman intensity are used mainly to determine quantitatively the amount, distribution and degree of crystallisation of different phases in a material, i.e. the Raman mapping. Our studies reveal that the analysis of relative and absolute Raman intensity is a very powerful tool, which allows to investigate and characterize the modifications of the structure in covalent bonded compounds, e.g. due to: (i) changes of BO₆ octahedra by the substitution of the B site by lanthanides or rare earth elements and the incorporation of protons in the case of high temperature protonic conductors, (ii) changes of the long range order correlations as the function of the nanoregion organization: continuous evolution of the local symmetry towards the long range cubic one in the case of PbMg_1/3Nb_2/3O₃–xPbTiO₃ (PMN–PT) relaxor ferroelectrics, (iii) changes of the Si–O network caused by the depolymerisation resulting from the substitution of the Si⁴⁺ ions (covalent bonds) by the M⁺ cations (ionic bonds) or by the incorporation of the metallic nanoprecipitates and (iv) changes caused by the lixiviation/protonation of the surface layers of the Cultural Heritage stained glasses as a function of their corrosion degree and age.     

Preparation and luminescent properties of lanthanide (Eu3+ and Tb3+) complexes grafted to 3-aminopropyltriethoxysilane by covalent bonds

A novel precursor PMA–Si was synthesized by modifying 1,2,4,5-benzene-tetracarboxylic acid (PMA) with 3-aminopropyltriethoxysilane (APTES). Then the hybrids were prepared by PMA–Si coordinating to lanthanide ions (Eu³⁺ and Tb³⁺) in sol–gel process. In order to improve luminescent efficiency, 1,10-Phenanthroline (Phen) was introduced to the system as the second ligand. As-prepared compounds in sol condition were coated on quartz plates to form a layer of thin film, which was different from other similar hybrids. The properties of the hybrids were characterized by FT-IR, fluorescence spectra, TG and SEM. The results showed that the obtained materials enhanced thermal stability, mechanical resistances, waterproofness as well as machining properties.     

聚己内酯/ 环氧树脂/ SiO2杂化材料的制备及性能

采用端硅氧烷基聚己内酯( PCL-TESi) 作为无机前躯物, 通过环氧树脂/ KB-2 的固化反应和PCL-TESi的溶胶2凝胶过程, 制备了聚己内酯/ 环氧树脂/ SiO₂ ( PCL/ EP/ SiO₂ ) 有机-无机杂化材料。利用红外光谱、透射电镜( TEM) 、热失重分析( TGA) 及在甲苯溶液中的溶胀试验对不同SiO₂ 含量的杂化材料进行分析。研究发现, 随着PCL-TESi 含量增大杂化体系交联密度降低; 此杂化体系中存在环氧和Si —O —Si 两种交联网络, 微观上形成纳米两相结构; Si —O —Si 交联网络的形成显著提高了材料的耐热性能, 使失重5 %时的热分解温度从120.5 ℃(纯环氧树脂/ KB-2 体系) 提高到277.6 ℃(SiO₂质量分数为3. 84 %的杂化体系) 。      

In situ X‐ray Measurements to Probe a New Solid‐State Polycondensation Mechanism for the Design of Supramolecular Organo‐Bridged Silsesquioxanes

A long‐range ordered organic/inorganic material is synthesized from a bis‐silane, (EtO)₃Si? (CH₂)₃? NHCONH? C₆H₄? NHCONH? (CH₂)₃? Si(OEt)₃. This crosslinked sol–gel solid exhibits a supramolecular organization via intermolecular hydrogen bonding interactions between urea groups (? NHCONH? ) and covalent siloxane bonding, ?Si? O? Si?. Time‐resolved in situ X‐ray measurements (coupling small‐ and wide‐angle X‐ray scattering techniques) are performed to follow the different steps involved in the synthetic process. A new mechanism based on the crystallization of the hydrolyzed species followed by their polycondensation in solid state is proposed.     

PPy/graphene nanosheets/rare earth ions: A new composite electrode material for supercapacitor

Highly conductive PPy/graphene nanosheets/rare earth ions (PPy/GNS/RE³⁺) composites were prepared via in situ polymerization with p-toluenesulfonic acid as a dopant and FeCl₃ as an oxidant. The effects of GNS and RE³⁺ on the electrical conductivity of the composites were investigated. The results showed that the GNS as a filler had effect on the conductivity of PPy/GNS/RE³⁺ composites, which played an important role in forming a conducting network in PPy matrix. The microstructures of GNS and PPy/GNS/RE³⁺ were characterized by the SEM and TEM examinations. It was found that GNS and PPy nanospheres formed a uniform composite with the PPy nanospheres absorbed on the GNS surface and/or filled between the GNS. Such uniform structure together with the observed high conductivities afforded high specific capacitance when used as supercapacitor electrodes. A specific capacitance of as high as 238 F/g at a current density of 1 A/g was achieved over the PPy/GNS/Eu³⁺ composite.     

Luminescence of novel terbium complex/inorganic/polymeric hybrid materials based on sol-gel technology

In this paper, a new terbium complex/inorganic/polymeric molecular hybrid material was prepared and its optical properties were studied. At first, 4-nitrobenzoic acid was modified by (3-aminopropyl) trimethoxysilane to form a precursor and coordinated with terbium ion. Then it was polymerized with inorganic host tetraethoxysilane or polymer host polyvinyl alcohol and formed hybrid material. ¹H NMR Fourier transform infrared (FT-IR), scanning electron microscope and TGA were applied to characterize the structure of the precursor. UV-vis spectrophotometer and fluorescence spectra were applied to characterize the photophysical properties of the obtained hybrid material. The strong luminescence of Tb³⁺ substantiates optimum energy couple and effective intramolecular energy transfer between the triplet state energy of modified ligand bridge and emissive energy level of Tb³⁺.     

Grafting the surface of carbon nanotubes and carbon black with the chemical properties of hyperbranched polyamines

Controlling the chemistry on the surface of new carbon materials is a key factor to widen the range of their applicability. In this paper we show a grafting methodology of polyalkylamines to the surface of carbon nanomaterials, in particular, carbon nanotubes and a carbon black. The aim of this work is to reach large degrees of covalent functionalization with hyperbranched polyethyleneimines (HBPEIs) and to efficiently preserve the strong chelating properties of the HBPEIs when they are fixed to the surface of these carbon materials. This functionalization opens new possibilities of using these carbon nanotubes-based hybrids. The results show that the HBPEIs are covalently attached to the carbon materials, forming hybrids. These hybrids emerge from the reaction of amine functions of the HBPEIs with carbonyls and carboxylic anhydrides of the carbon surface which become imine and imide bonds. Thus, due to the nature of these bonds, the pre-oxidized samples with relevant number of C=O groups showed an increase in the degree of functionalization with the HBPEIs. Furthermore, both the acid-base properties and the coordination capacity for metal ions of the hybrids are equivalent to that of the free HBPEIs in solution. This means that the chemical characteristics of the HBPEIs have been efficiently transferred to the hybrids. To reach this conclusion we have developed a novel procedure to assess the acid-base and the coordination properties of the hybrids (solids) by means of potentiometric titration. The good agreement of the values obtained for the hybrids and for the free HBPEIs in aqueous solution supports the reliability of the procedure. Moreover, the high capacity of the hybrids to capture Ni²⁺ by complexation opens new possibilities of using these hybrids to capture high-value metal ions such as Pd²⁺ and Pt²⁺.     

Synthesis and characterisation of cellulose/silica hybrids obtained by heteropoly acid catalysed sol–gel process

Cellulose/silica hybrids (CSHs) were synthesized by a sol–gel method using eucalyptus bleached kraft pulp as cellulose source and tetraethyl orthosilicate (TEOS) as the silica precursor in the presence of heteropoly acids (HPAs) as catalysts. HPAs, and especially tungstophosphoric acid H₃PW₁₂O₄₀, showed better catalytic efficiency than conventional mineral acids. Silica was deposited on fibres in the form of a thin film or mesoparticles as revealed by SEM/EDS and AFM analyses. Roughly 40–60% of silica was incorporated into cellulosic material considerably diminishing its hydrophilicity and improving thermal stability. CSHs were structurally characterised by FTIR, ¹³C and ²⁹Si solid state NMR. It was suggested that proportions of Q², Q³ and Q⁴ structures in silica counterpart depended on the synthesis conditions (H₂O/TEOS molar ratio and catalyst concentration among others). A clear relationship between the thermal stability of CSH and the degree of silica crosslinking in hybrids has been observed.     

The fabrication of rare earth covalent luminescent hybrid materials with potential molecular bridge by in situ sol–gel process

1,2,4-Benzenetricar boxylic acid (abbreviated as TMA) was modified to achieve a functional molecular bridge (TMA-APMES) with double reactivity by the reaction with a cross-linking molecule (3-aminopropyl-methyl-diethoxylsiliane, APMES). The modified functional ligand further behaves as a bridge both coordinates to Ln³⁺ through oxygen atom and occurs in situ sol–gel process with matrix precursor (tetraethoxysilane, TEOS) through co-hydrolysis and co-polycondensation reaction. Then a novel molecular hybrid material (named as hybrid Ln³⁺) with double chemical bond (TbO coordination bond and SiO covalent bond) resulted. 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 couple and effective intramolecular energy transfer between the triplet state energy of modified ligand bridge and emissive energy level of Tb³⁺.     

Pilot study of organic and inorganic nanocomposite optical fibre materials

The nanocomposite method was used to introduce Pr³⁺ into copolymer of methyl methacrylate (MMA) and methacrylic acid (MAA), and thus the nanocomposite glass was produced. The size of inorganic Pr³⁺–Al³⁺ codeposition particles was tested by transmission electron microscopy (TEM) and the components of codeposits were analysed by X-ray diffractometry (XRD). Atom force microscope (AFM) was used to examine the size of the particles encapsulated by copolymer in the surface of nanocompisite glass. In UV wavelength we studied the fluorescence of the glass and preliminarily investigated the feasibility of the method to synthesize organic and inorganic nanocomposite optical fibre.     

One-step synthesis of mesoporous silica–graphene composites by simultaneous hydrothermal coupling and reduction of graphene oxide

Silica–graphene oxide composites were synthesized by hydrothermal method with simultaneous functionalization and reduction of graphene oxide (GO) in the presence of mesoporous silica. Two types of silica were used in the study, mesoporous synthetic silica (MSU-F) synthesized by sol-gel method and mesoporous mineral silica (meso-celite) from pseudomorphic synthesis. The infrared spectra of the composites showed the disappearance of the carboxyl peak at 1735 cm^-1 which could be due to the reduction of the –COOH group. The enhancement of the band at 1385 cm^–1 is attributed to the vibration of the Si–O–C=O moiety formed by reaction of the –COOH group of GO and the silanol (Si–OH) of silica. The Raman spectra of the composites show a diminished intensity ratio of D to G band indicating that GO was reduced to graphene sheets. The TEM images demonstrate the coupling of silica to GO surface revealing dense loading of silica on GO in planar structure.     

Decoration of surface-carboxylated graphene oxide with luminescent Sm3+-complexes

A Sm³⁺ complex, tris-(2-thenoyltrifluoroacetone) mono-1,10-phenanthroline-Sm³⁺ [Sm(TTA)₃(Phen)], can be easily integrated in situ via covalent functionalization to surface-carboxylated graphene oxide (GO-COOH) from a ethanol solution. The Sm³⁺ containing material has been comprehensively characterized via Fourier transform infrared spectra, X-ray photoelectron spectroscopy, UV–Vis absorption spectra, luminescence spectra, transmission electron microscopy, powder X-ray diffraction, thermogravimetric analysis (TG and DTG). The integration of rare earth complexes (RE) onto GO-COOH, as well as the individual nature of the hybrids, is confirmed. The GO-COOH with high load capacity can integrate more RE than GO. The brilliant optical properties of the GO-COOH-RE complex hybrids make them promising candidates applying in many practical fields, such as biomedical applications.     

Preparation and characterization of mesoporous lithium borosilicate material via the sol–gel process

The lithium borosilicate gels were prepared from the cohydrolysis of the tetraehtylorthosilicate (Si(C₂H₅O)₄) and triethylborate (B(C₂H₅O)₃) by using an ethanolic solution of tetradecyltrimethylammonium bromide (TTAB) as surfactant. The Li⁺ ions were introduced from an acidic solution of lithium carbonate (Li₂CO₃). Depending on the B/Si, Li/Si and TTAB/Si molar ratios at pH equal to 1 and at room temperature, monolithic and transparent colourless gels were obtained. The structure of the gel was investigated by infrared spectroscopy (IR), ²⁹Si, ¹¹B and ⁷Li solid-state magnetic resonance (MAS NMR) and by thermal analysis (DTA–TG). The results show the possibility of obtaining a borosilicate network via B–O–Si bonds in which Li⁺ ions were dispersed. The adsorption–desorption isotherms of the xerogel were characteristic of mesoporous materials. These materials may provide a greater free volume through which conducting ions can move.     

Preparation and characterization of antibacterial graphene oxide functionalized with polymeric <Emphasis Type="Italic">N</Emphasis>-halamine

Organic–inorganic composites have also gained much attention owing to their excellent combined properties. For the enhancement of the bacteria-inactivation ability of graphene oxide (GO), poly[5,5-dimethyl-3-(3′-triethoxysilylpropyl)hydantoin] (PSPH) was synthesized and attached onto GO through covalent bond. The synthesized inorganic–organic composites (GO-PSPH) were characterized by FT-IR, XPS, XRD, AFM, SEM, etc. After chlorination treatment by sodium hypochlorite, biocidal efficacies of the chlorinated GO-PSPH (GO-PSPH-Cl) against S. aureus (ATCC 6538) and E. coli O157:H7 (ATCC 43895) were tested. The antibacterial testing results showed that the GO-PSPH-Cl has great antibacterial activity and could completely inactivate 5.5 × 10⁶ CFU/mL of S. aureus and 1.2 × 10⁸ CFU/mL of E. coli O157:H7 within 30 and 10 min of contact time, respectively.     

Synthesis and characterization of an antibacterial powder based on the covalent bonding of aminosilane-stabilized silver nanoparticles to a colloidal silica

Stable dispersions of silver nanoparticles (Ag NPs) were synthesized employing glycerol as both a solvent and reducing agent, and 3-aminopropyl trimethoxysilane (APTMS) as a stabilizer. Average sizes varied between 13 and 55 nm, depending on the molar ratio of APTMS/Ag. Terminal alkoxysilanes reacted with OH groups of glycerol leading to the covalent bonding of glycerol moieties to the chain ends of the stabilizer. This produced extremely stable colloidal dispersions from which NPs could not be extracted with solvents immiscible with glycerol (as THF). Ag NPs were covalently bonded to the surface of a colloidal silica by hydrolysis/condensation of terminal Si–O–C bonds of the stabilizer with superficial SiOH bonds of silica. TEM images revealed the presence of individual NPs and small clusters of NPs attached to the silica surface. These clusters were presumably generated by intermolecular reactions among chain ends of the stabilizer producing Si–O–Si bonds. The antibacterial properties of the resulting powder were confirmed by conventional tests employing a culture of Escherichia Coli.     

Highly water-resistant and organic miscible inorganic/polymer composite luminescent material

A novel highly water-resistant and organic miscible luminescent phosphor has been synthesized by grafting a polymer onto the surface of SrAl₂O₄:Eu²⁺, Dy³⁺ (SAO–ED). A bifunctional ligand, 3-allyl-2, 4-pentanedione (APD) was used as a bridge to introduce the polymer onto the surface of SAO–ED. The coordination of APD with SAO–ED was confirmed by FT–IR spectra. The luminescence property of SAO–ED/polymer composite material was analyzed by spectrometer LS-100. The water resistance and miscibility with organics of the product were also investigated. Compared with traditional inorganic SAO–ED, this novel polymer-grafted SAO–ED has higher brightness, much better water resistance and good miscibility with organic solvents and polymers.