Effect of graphene quantum dots on photoluminescence property of polyvinyl butyral nanocomposite

Design and development of new photoluminescence system are much in demand for various engineering and technological applications. The present investigation focused on the influence of graphene quantum dots (GQDs) dispersion in the polyvinyl butyral (PVB) matrix. The structural and chemical interaction of GQD‐dispersed PVB composites was confirmed by X‐ray diffraction (XRD), Fourier transform infrared (FTIR), micro‐Raman spectroscopy, ultraviolet and visible (UV‐Vis), and photoluminescence (PL) techniques. Chemical interaction between the functional groups leads to PL quenching at 455 nm. Changes on crystallite size and interplanar spacing hinders on the structural properties of the nanocomposite. Raman spectroscopy reveals the decrease in D/G intensity ratio influenced by GQD loading wt% in the polymer system. The dispersion and occupied network of GQD in the PVB matrix was confirmed by optical polarizing microscopy (OPM), atomic force microscopy (AFM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Effect of electrical conductivity of composites as a function of temperature has been verified. Decrease in direct bandgap as a function of GQD loading confirms the promising PL properties of the prepared composite system. Thus GQD‐derived composites may further be developed as a membrane for improved PL property.     

A Surface Coordination Network Based on Copper Adatom Trimers

Surface coordination networks formed by co‐adsorption of metal atoms and organic ligands have interesting properties, for example regarding catalysis and data storage. Surface coordination networks studied to date have typically been based on single metal atom centers. The formation of a novel surface coordination network is now demonstrated that is based on network nodes in the form of clusters consisting of three Cu adatoms. The network forms by deposition of tetrahydroxybenzene (THB) on Cu(111) under UHV conditions. As shown from a combination of scanning tunneling microscopy, X‐ray photoelectron spectroscopy, and density functional theory calculations, all four hydroxy groups of THB dehydrogenate upon thermal activation at 440 K. This highly reactive ligand binds to Cu adatom trimers, which are resolved by high‐resolution STM. The network creates an ordered array of mono‐dispersed metal clusters constituting a two‐dimensional analogue of metal–organic frameworks.     

Imidazolium‐modified clay‐based ABS nanocomposites: a comparison between melt‐blending and solution‐sonication processes

Acrylonitrile–butadiene–styrene (ABS) nanocomposites containing imidazolium‐modified montmorillonite have been prepared by melt‐blending (MB) and solution‐sonication in order to study the effects of processing on the morphology and properties of the polymer/clay composites. The structure‐property relationships of the prepared composites have been studied by means of X‐ray diffraction (XRD), transmission electron microscopy (TEM), mechanical testing, dynamic‐mechanical analyses (DMA), thermal gravimetrical analyses (TGA), fluorescence probe confocal microscopy, and fluorescence spectroscopy (FS). X‐Ray and TEM show that both nanocomposites have a mixed intercalated/exfoliated structure. Fluorescence probe confocal microscopy reveals that the sonicated sample has a more homogeneous dispersion: this result is confirmed by the values of elongation at break and flexural elastic modulus measured for the composites. Fluorescence spectroscopy has also been used to investigate the distribution of clay in the composites and results indicate that clay layers in ABS are preferentially located in the styrene‐acrylonitrile (SAN) phase, independent of the dispersion process used. Published in 2008 by John Wiley & Sons, Ltd.     

Synthesis and Characterization of SnO2 One-dimensional Nanostructures

Single-crystalline SnO2 nanowires have been successfully prepared in large scale on Au-coated silicon substrate by heating the mixture of self-made high-purity SnO2 powders and graphite powders at 900℃. Besides the line type nanowires some more features were observed. The products were characterized by means of X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED) and Raman spectrum techniques. The results indicate that the tin dioxide nanowires have a rutile structure with diameters ranging from 30 to 120 nm and lengths up to several tens of micrometers. The possible mechanism of the growth and reaction for the nanowires was also discussed.     

Preparation of Polymer-Functionalized Iron Oxide Nanoparticles and Their Biomedical Properties

Superparamagnetic iron oxide nanoparticles with narrow size distributions were successfully prepared in large scale by a facile one‐pot synthetic method in the presence of hydrophilic polymers, such as polyethylene glycol diacid (HOOC‐PEG‐COOH) and poly(acrylic acid) (PAA). The as‐prepared products were investigated in detail by powder X‐ray diffraction (XRD), thermogravimetric analyses (TGA), transmission electron microscopy (TEM), high‐resolution transmission electron microscopy (HRTEM), dynamic light scattering (DLS), and vibrating sample magnetometer (VSM). The interaction between polymers and iron oxide nanoparticles was investigated using Fourier transform infrared spectrometry (FT‐IR). The results show that polymers can be attached onto the surface of iron oxide nanoparticle by bridging coordination and monodentate fashion, respectively. The interaction affects iron oxide nanoparticle properties significantly, such as XRD diffraction intensity, hydrodynamic diameter, isoelectric point, and saturation magnetization. Furthermore, the results of in vitro experiments indicated that iron oxide‐PEG‐COOH nanoparticle is more cytotoxic than iron oxide‐PAA nanoparticle due to different coordinating modes.     

The Role of Multiwall Carbon Nanotubes in Cu‐BTC Metal‐Organic Frameworks for CO2 Adsorption

The discovery of natural gas fields with a high content of CO₂ in world gas reservoirs poses new challenges for CO₂ capture. This work investigates the use of the metal‐organic framework (MOF) Cu‐BTC and hybrid MWCNTs@Cu‐BTC for CO₂ adsorption. Cu‐BTC and hybrid MWCNTs@Cu‐BTC were synthesized by the solvothermal method. The results of imaging of intact MOF pores in Cu‐BTC and hybrid MWCNTs@Cu‐BTC nanocrystals by high‐resolution transmission electron microscopy (HRTEM) under liquid nitrogen conditions are presented. Physical characterizations of the solid adsorbents were made by using a selection of different techniques, including field‐emission scanning electron microscopy (FESEM), X‐ray powder diffraction (XRD), Fourier transform infrared (FT‐IR) spectroscopy, thermogravimetric analysis (TGA), Brunauer–Emmet–Teller (BET) surface area, and CO₂ adsorption and physisorption measurements. HRTEM and FESEM confirmed that Cu‐BTC has an octahedral shape and that the surface morphology of Cu‐BTC changes by the intercalation of MWCTNs. The results show that the modified Cu‐BTC improved the CO₂ adsorption compared to pure Cu‐BTC. The increase in the CO₂ uptake capabilities of hybrid MWCNTs@Cu‐BTC was ascribed to the intercalation of MWCNTs with Cu‐BTC crystals. The CO₂ sorption capacities of Cu‐BTC and hybrid MWCNTs@Cu‐BTC were found to increase from 1.91701 to 3.25642 mmol/g at ambient conditions.     

A new cellular carbon support for catalysts: preparation and study of structure

Cellular carbon has been prepared by pyrolysis of a propane—butane mixture in a flow reactor at 700–1250 K. Its structural characteristics were studied by scanning electron microscopy, high resolution transmission electron microscopy, X-ray diffraction and adsorption methods. It was shown that cell-type carbon possesses a unique structure in contrast to carbon composite “Sibunnit” and filamentous carbons and it may be a promising support for catalyst preparation.     

Effects of Halogen Bonding in Chemical Activity of Lead(II) Electron Pair: Sonochemical Synthesis,Structural Studies,and Thermal Analysis of Novel Lead(II) Nano Coordination Polymer

The nanoflower lead(II) coordination compound {[Pb(phen)(μ‐CH₃COO)][PF₆]}_n ( 1 ) (phen = 1,10‐phenanthroline) was synthesized by a sonochemical method. The nanostructure was characterized by using scanning electron microscopy (SEM), X‐ray powder diffraction, elemental analysis, and thermal analysis. The single‐crystal X‐ray structure shows that the overall structure of 1 is a 1D coordination polymer. Complex 1 has a bridging acetate pathway. Three halogen bonds observed in the structure and the strong halogen bonding of F–Pb causes chemical activity of the lead electron pair. This is further extended into a 3D supramolecular structure by weak π–π intermolecular interactions. The coordination number of the lead(II) ions is six, resulting in PbN₂O₄. PbO nanoparticles were obtained by the thermolysis of 1 at 180 °C with oleic acid as a surfactant. The morphology and size of the prepared PbO nanoparticles were further observed using scanning electron (SEM) and transmission electron microscopy (TEM), and were analyzed by X‐ray photoelectron spectroscopy (XPS).     

Synthesis of imidazolium‐functionalized ionic polyurethane and formation of CdTe quantum dot–polyurethane nanocomposites

A series of positively charged imidazolium‐functionalized ionic polyurethanes (IPUs) were prepared in one‐step polymerization process by polymerization of presynthesized short‐chain imidazolium‐based ionic diol, polyethylene glycols with different molecular weights as long‐chain diols, and toluylene‐2,4‐diisocyanate. The structures of IPUs are confirmed by ¹H NMR analysis, and the thermogravimetric analysis measurement indicates that the IPUs have high degradation temperature. Fluorescent nanocrystal–polymer composites CdTe–IPU can be prepared conveniently, by the electrostatic interaction between positively charged IPUs and the negatively charged aqueous CdTe quantum dots (QDs). UV–vis absorption and photoluminescence spectra indicate the photochemical stability and strong fluorescent emission of CdTe–IPU composites. The quantum yields (QYs) of the composites are high and basically restore the QYs of the pure QDs. In addition, the transmission electron microscopy photographs show that the QDs in composites are uniform (about 3 nm in diameter) and monodisperse. The obtained nanocomposites are powder or elastomers with good film building. The casted CdTe–IPU films are transparent under visible light, and the colors of the composites and their films are vivid under a UV lamp. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Facile Self‐Assembly Synthesis of PdPt Bimetallic Nanotubes with Good Performance for Ethanol Oxidation in an Alkaline Medium

PdPt bimetallic nanotubes were prepared by the self‐assembly of Pt and Pd on Te nanowires at room temperature. The morphologies of the as‐prepared PdPt nanotubes were investigated by scanning electron microscopy and transmission electron microscopy, and the results display a large amount of PdPt bimetallic nanotubes with a diameter of 10–20 nm and a length of several micrometers. The composition and structure of the nanotubes were characterized by X‐ray diffraction, high‐resolution transmission electron microscopy, scanning transmission electron microscopy, and energy spectrum analysis, and the results display uniform compositional distributions of both elements (Pd and Pt). The mechanism of the formation of the nanotube structure was supposed. The electrocatalytic performance of PdPt nanotubes were studied by cyclic voltammetry and chronoamperometry. Electrochemical results show that the as‐prepared PdPt nanotube catalysts have not only high activity but also good stability for ethanol oxidation in alkaline medium.     

Cross‐sectional structural characterization of the surface of exfoliated HOPG using HRTEM‐EELS

We analyzed the surface atomic structure of highly oriented pyrolytic graphite (HOPG) substrate exfoliated with adhesive tape, using high‐resolution transmission electron microscopy and scanning transmission electron microscopy‐electron energy‐loss spectroscopy (STEM‐EELS). The surface step height of the exfoliated HOPG substrate was determined using high‐angle annular dark‐field‐scanning transmission electron microscopy (HAADF‐STEM) images and the depth profiles of the EELS spectra of a cross‐sectioned thin foil specimen prepared via focused ion beam milling. The exfoliated surface of the HOPG substrate presented disordered and curved graphene layers. The STEM‐EELS measurements indicated that upon exfoliation, the surface of the HOPG substrate reacted with atmospheric water and oxygen molecules.     

Highly Luminescent Cesium Lead Halide Perovskite Nanocrystals with Tunable Composition and Thickness by Ultrasonication

We describe the simple, scalable, single‐step, and polar‐solvent‐free synthesis of high‐quality colloidal CsPbX₃ (X=Cl, Br, and I) perovskite nanocrystals (NCs) with tunable halide ion composition and thickness by direct ultrasonication of the corresponding precursor solutions in the presence of organic capping molecules. High angle annular dark field scanning transmission electron microscopy (HAADF‐STEM) revealed the cubic crystal structure and surface termination of the NCs with atomic resolution. The NCs exhibit high photoluminescence quantum yields, narrow emission line widths, and considerable air stability. Furthermore, we investigated the quantum size effects in CsPbBr₃ and CsPbI₃ nanoplatelets by tuning their thickness down to only three to six monolayers. The high quality of the prepared NCs (CsPbBr₃) was confirmed by amplified spontaneous emission with low thresholds. The versatility of this synthesis approach was demonstrated by synthesizing different perovskite NCs.     

Polyelectrolyte brushes as efficient platform for synthesis of Cu and Pt bimetallic nanocrystals onto TiO2 nanowires

A Cu–Pt nanoparticle catalyst supported on TiO₂ nanowires (NWs) was prepared through regenerative counterion exchange–reduction using polyelectrolyte brush as template. Cationic polydimethyl aminoethyl methacrylate brushes were grafted onto TiO₂ NWs. Cu–Pt nanocrystals were produced by anionic counterions CuCl₄^2? and PtCl₆^2? bound with the polymer brush through in situ reduction with NaBH₄ of high density and low polydispersity. The as‐prepared TiO₂ NWs/polymer brush/Cu–Pt was characterized by Fourier transform infrared spectroscopy (FT‐IR spectrometry), X‐ray photoelectron spectroscopy, transmission electron microscopy, and UV–Vis adsorption spectrometry analyses. Results showed that the highly dispersed Cu and Pt nanoparticles were present on the surface of the TiO₂ NWs/polymer brush. The resultant TiO₂ NWs/polymer brush/Cu–Pt exhibited extremely high catalytic activity and reduced p‐nitrophenol at room temperature. Copyright © 2017 John Wiley & Sons, Ltd.     

新型可见光响应的 InVO4-Cu2O-TiO2三元纳米异质结：制备及其光催化性能

由于日益严重的环境和能源危机,可见光催化剂的开发已成为当今最具挑战和紧迫的任务之一.将 TiO2和其它窄禁带半导体复合,已被证明是一种有效的可提高其可见光光催化性能的策略. Cu2O是一种禁带宽度为2.0 eV的 p型窄禁带半导体, InVO4则是一种禁带宽度为2.0 eV的 n型半导体,因它们可用于可见光光解水产氢和有机污染物的可见光降解而在过去的数年中引起了人们广泛的关注.但是纯的 Cu2O和 InVO4由于光生电子空穴对在其内部快速地复合,光催化活性通常都比较低.基于能带工程的策略本文设计了一种新型的可见光响应的 InVO4-Cu2O-TiO2三元纳米异质结,并通过普通的湿化学法进行制备：先通过水热法制备 InVO4,再通过溶胶-凝胶法制备 InVO4-TiO2二元复合物,最后通过沉淀和还原过程制备得到 InVO4-Cu2O-TiO2三元纳米异质结.
　　在10%InVO4-40%Cu2O-50%TiO2三元纳米异质结的 X-射线衍射谱中没有观察到明显的杂质峰;通过透射电子显微技术和高分辨透射电子显微技术观察到了它们之间异质结的形成,纳米颗粒的尺寸范围在5?20 nm;经紫外可见漫反射光谱估算得到10%InVO4-40%Cu2O-50%TiO2的禁带宽度为2.78 eV,在可见光区域具有较强的吸收.以普通的9 W节能灯作为可见光光源光照甲基橙5 h后,纯的 InVO4, TiO2和 Cu2O几乎没有光催化活性;10%InVO4-90%TiO2的光催化活性也很低,甲基橙降解率为8%;70%Cu2O-30%TiO2对甲基橙降解率达84%,但初始活性较低;10%InVO4-40%Cu2O-50%TiO2对甲基橙降解率接近90%,并且循环使用6次后,其光催化活性的保持率还维持在90%以上,而50%Cu2O-50%TiO2光催化活性的保持率只有74%.
　　经对使用过的10%InVO4-40%Cu2O-50%TiO2进行 X射线光电子能谱表征发现,存在一弱小的 Cu(II)震动卫星峰,表明在 InVO4-Cu2O-TiO2的光催化过程中 Cu2O的光蚀并不严重.从能带工程的角度分析, InVO4-Cu2O-TiO2三元纳米异质结具有优异的可见光催化性能的主要原因为： InVO4的导带电极电位约为?0.5 eV(vs. SHE,下同),价带电位约为+1.5 eV, Cu2O的分别约为?1.6和+0.4 eV,与 TiO2(导带和价带电极电位分别约为?0.23和+2.97 eV)相比,它们的导带位置更负,将它们组装成三元复合结构,可见光激发的导带电子就可能从 InVO4和 Cu2O的导带迁移到 TiO2的导带上去.同时, n型的 TiO2和 InVO4都与 p型的 Cu2O形成 p-n异质结, n型的 TiO2和 InVO4之间形成 n-n异质结,由于 p-n异质结中内电场的存在以及不同能级相互耦合,可进一步促进可见光激发的导带电子从 InVO4和 Cu2O的导带迁移到 TiO2的导带上去,以及可见光激发的价带空穴从 InVO4的价带迁移到 Cu2O的价带上去,从而实现光生载流子空间上的有效分离.本文有望为新型可见光响应的半导体复合催化剂的设计和制备提供新的思路.     

Synthesis,Characterization, and Photocatalytic Activity of N‐Doped TiO2 Nanotubes

N‐doped TiO₂ nanotubes with high photocatalytic activity were prepared by the combination of sol‐gel process with hydrothermal treatment. The prepared materials are characterized with transmission electron microscopy (TEM), high‐resolution transmission electron microscopy (HRTEM), x‐ray diffraction (XRD), x‐ray photoelectron spectra (XPS), and UV‐vis spectra. Photocatalytic performance of the N‐doped TiO₂ nanotubes is studied by testing the degradation rate of methyl orange under UV irradiation. Obtained results indicate that N‐doped TiO₂ nanotubes have high catalytic activity for photocatalytic oxidation.     

Recyclable Porous Polymer‐Supported Copper Catalysts for Glaser and Huisgen 1,3‐Diolar Cycloaddition Reactions

A family of polymer‐attached phenanthrolines was prepared from solvothermal copolymerization of divinylbenzene with N‐(1,10‐phenanthroline‐5‐yl)acrylamide in different ratios. The polymer‐supported copper catalysts were obtained through typical impregnation with copper(II) salts. The polymers and supported copper catalysts have been characterized by N₂ adsortion, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and thermogravimetric analysis (TG); they exhibit a high surface area, hierarchical porosity, large pore volume, and high thermal and chemical stabilities. The copper catalyst has proved to be highly active for Glaser homocoupling of alkynes and Huisgen 1,3‐diolar cycloaddition of alkynes with benzyl azide under mild conditions at low catalyst loading. The heterogeneous copper catalyst is more active than commonly used homogeneous and nonporous polystyrene‐supported copper catalysts. In particular, the catalyst is easily recovered and can be recycled at least ten times without any obvious loss in catalytic activity. Metal leaching was prevented due to the strong binding ability of phenanthroline and products were not contaminated with copper, as determined by ICP analysis.     

Solution route to inorganic nanobelt‐conducting organic polymer core‐shell nanocomposites

A facile and versatile solution‐based approach was developed to prepare semiconductor metal oxide nanobelt‐conducting organic polymer core‐shell nanocomposites. Well‐defined nanobelts of several types of oxide nanobelts were combined with conducting polymer [polypyrrole (PPy) and polyaniline (PANi)] via in situ polymerization in aqueous solution to obtain a new type of inorganic–organic composite nanostructure. Samples were characterized by using X‐ray diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared, electron energy loss spectra, high‐resolution transmission electron microscopy, and ultraviolet–visible techniques. Electron energy loss spectra revealed the existence of C?C and C? N bonds in coating layers to prove the encapsulation of PPy or PANi. The red‐shift of absorption band at high‐energy was observed for PPy‐encapsulated composites via ultraviolet–visible spectroscopy, and significant absorption band shifts were also encountered to PANi‐encapsulated composites, which suggest possibilities of band‐gap tuning of such metal oxide‐conducting polymer composites to be applied especially in solar cell devices. However, the sacrifice of nanobelts‐core led to hollow structures of PPy and PANi, which expands the synthetic strategies to prepare conducting polymer nanotubes. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2892–2900, 2005     

(Terpyridine)copper(II)-carbon nanohorns: metallo-nanocomplexes for photoinduced charge separation

New metallo-nanostructured materials of carbon nanohorns (CNHs), within the family of elongated carbon nanotubes, have been prepared by the coordination of copper(II)-2,2':6',2' '-terpyridine (Cu(II)tpy) with oxidized carbon nanohorns (CNHs-COOH). The resulted CNHs-COO-Cu(II)tpy metallo-nanocomplexes have been characterized by diverse analytical spectroscopic tools and cyclic and differential pulse voltammetry. Scanning transmission electron microscopy (STEM), dynamic light scattering (DLS), and energy dispersive X-ray spectroscopy (EDX) measurements have been employed to probe the morphological characteristics and particle-size distribution of CNHs-COO-Cu(II)tpy as well as to investigate the elemental composition of the metallo-nanocomplex. Steady-state and time-resolved fluorescence emission studies have shown efficient fluorescence quenching, suggesting that electron transfer occurs from the singlet excited state of Cu(II)tpy to CNHs. Photoexcitation of Cu(II)tpy resulted in the one-electron reduction of nanohorns with a simultaneous one-electron oxidation of the Cu(II)tpy unit (CNHs(*-)-COO-(Cu(II)tpy)*+) as revealed by transient absorption measurements. The charge-separated state of CNHs(*-)-COO-(Cu(II)tpy)*+ has been confirmed with the aid of an electron mediator, such as hexyl-viologen dication (HV2+) and an electron-hole shifter in polar solvents.     

High-yield Synthesis of Branched Gold Nanocrystals by a Sodium Diphenylamine-4-Sulfonate Reduction Process in Polyethylene Glycol Aqueous Solution

For developing new excellent electrocatalysts toward methanol and oxygen, branched Au nanocrystals have been prepared in high yield by the reaction of HAuCl₄ and sodium diphenylamine‐4‐sulfonate in the presence of PEG (polyethylene glycol) at room temperature. When the amount of PEG was in the range of 1–3 mL, branched Au nanocrystals were all obtained, and the amounts of sodium diphenylamine‐4‐sulfonate and HAuCl₄ had no obvious effect on the morphology of gold nanocrystals. PEG molecules play an important role in the formation of branched gold nanocrystals. The nanocrystals were characterized by transmission electron microscopy (TEM), selected area electron diffraction, high‐resolution transmission electron microscopy (HRTEM) and UV‐Vis absorption spectrum. HRTEM research suggests that the tips of gold nanocrystals grow selectively in the [111] directions. The UV‐Vis absorption spectrum displays two‐separated surface plasmon resonance peaks.     

Synthesis and characterization of pyrene bearing amphiphilic miktoarm star polymer and its noncovalent interactions with multiwalled carbon nanotubes

A novel amphiphilic miktoarm star polymer, polystyrene‐poly(ethylene glycol)‐poly(methyl methacrylate), bearing a pyrene group at the end of PS arm (Pyrene‐PS‐PEG‐PMMA) was successfully synthesized via combination of atom transfer radical polymerization and click chemistry. The structure and composition of the amphiphilic miktoarm star polymer were characterized by gel permeation chromatography and ¹H NMR. The functionalization of multiwalled carbon nanotubes (MWCNTs) via “π–π” stacking interactions with pyrene‐PS‐PEG‐PMMA miktoarm star polymer was accomplished and the resulting polymer‐MWCNTs hybrid was analyzed by using ¹H NMR, UV–vis, fluorescence spectroscopy, and thermal gravimetric analysis. The high‐resolution transmission electron microscopy and analytical techniques aforementioned confirmed that the noncovalent functionalization of MWCNT's with the amphiphilic miktoarm star polymer was successfully achieved. The MWCNT/pyrene‐PS‐PEG‐PMMA exhibited significant dispersion stability in common organic solvents such as dimethyl formamide, chloroform, and tetrahydrofuran. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012