Efficient assembly of multi-walled carbon nanotube-CdSe/ZnS quantum dot hybrids with high biocompatibility and fluorescence property

CdSe/ZnS core-shell quantum dots (QDs) were efficiently tethered onto polyamidoamine dendrimer-modified multi-walled carbon nanotubes (MWCNTs) by covalent linkage and mercapto-mediated assembly. The obtained MWCNT-QD hybrids were both photophysically and morphologically characterized. The QDs are well-distributed on single nanotube surface in high density and the assembly of QDs onto MWCNTs does not change the fluorescence emission wavelength of QDs but significantly decreases the emission density. Cytotoxicity of MWCNT-QD hybrids to HeLa cells and their fluorescence property in living cell system were evaluated in detail. The hybrids show a little effect on cell viability even at very high concentration (100 μg mL(-1)). Moreover, they possess intense red fluorescence signal under optical fluorescence microscopy and good fluorescence stability over 72-h exposure in living cell system.     

Polymer-templated organosilicas with hexagonally ordered mesopores: the effect of organosilane addition at different synthesis stages

Two series of ordered mesoporous organosilica (OMO) SBA-15 materials with surface and bridging groups were fabricated by varying the organic precursor addition at different synthesis stages. The consequence of the delayed introduction of organic precursor on the structural and adsorption properties of the resulting OMOs was investigated. The OMOs studied were synthesized via co-condensation of tetraethyl orthosilicate (TEOS) and ureidopropyltrimethoxysilane (UPS) as well as TEOS and bis(triethoxysilylpropyl) disulfide (BTDS) in the presence of poly(ethylene oxide)-poly(propylene oxide)- poly(ethylene oxide) triblock copolymer Pluronic P123 (EO₂₀PO₇₀EO₂₀). The aforementioned OMOs were characterized by nitrogen adsorption-desorption isotherms at −196 °C and powder X-ray diffraction (XRD). Nitrogen adsorption isotherms were used to estimate the pore volume, mesopore diameter and the BET specific surface area, whereas the XRD data provided information about structural ordering and unit cell of the samples studied. Ryan Felix, undergraduate student from Oberlin College (Oberlin, OH, USA) participating in the NSF-REU program during Summer 2006.     

Preparation,characterization and biocompatibility of aspartic acid modified CdTe quantum dots

This study aims at preparing water soluble aspartic acid （ASP） modified CdTe quantum dots with tunable fluorescence emission controlled by reaction time. The size of the synthesized CdTe quantum dots was evaluated using transmission electron microscope （TEM） and also calculated based on their UV-vis spectra. The optical properties of TGA-CdTe quantum dots were characterized by UV-vis and fluorescence （FL） spectroscopy. The red-shift in the UV-vis absorption and FL emission with the increase of reaction time was observed. The biocompatibility examination indicated that the ASP modified CdTe QDs had low cytotoxicity.     

Nanocomposites of polystyrene-b-polyisoprene copolymer with layered silicates and carbon nanotubes

Nanocomposites of polystyrene-b-polyisoprene (PS-b-PI) copolymer with layered-smectite clays (organically modified montmorillonite) and nanostructured clay-carbon nanotube hybrids were prepared. The diblock copolymer was synthesized by anionic polymerization using high-vacuum techniques and was molecularly characterized by size exclusion chromatography. Carbon nanotubes were developed on clay-supported nickel nanoparticles by the CCVD method. Nanotubes attached on the clay platelets were then chemically modified to create ester groups on their surfaces. PS-b-PI nanocomposites at various polymer to reinforcement loadings were prepared by solution intercalation. The final nanocomposites were characterized by powder X-ray diffraction, FT-IR spectroscopy, thermal analysis, and scanning electron microscopy. The experiments complemented with viscometry measurements reveal the successful incorporation of the reinforcements in the polymer mass.     

Thermosensitive copolymer networks modify gold nanoparticles for nanocomposite entrapment

The core-shell gold nanoparticles and copolymer of N-isopropylacrylamide (NIPAM) and N,N'-methylenebisacrylamide (MBAA) hybrids (Au@copolymer) were fabricated through surface-initiated atom-transfer radical polymerization (ATRP) on the surface of gold nanoparticles in 2-propanol/water mixed solvents. The surface of citrate-stabilized gold nanoparticles was first modified by a disulfide initiator for ATRP. The slight cross-linking polymerization between NIPAM and MBAA occurred on the gold surface and resulted in the formation of core-shell Au@copolymer nanostructures that were characterized by TEM, and FTIR and UV-visible spectroscopy. Such synthesized Au@copolymer hybrids possess clearly thermosensitive properties and exhibit "inspire" and "expire" water behavior in response to temperature changes in aqueous solution. Because of this property, we enable to trap and encapsulate smaller nanoparticles by using the free space of the copolymer-network scaffold anchored at the gold surface.     

Surface modification of luminescent lanthanide phosphate nanorods with cationic "Quat-primer" polymers

"Quat-primer" polymers bearing cationic groups were investigated as a surface modifier for Tb-doped cerium phosphate green-emitting fluorescent nanorods (NRs). The NRs were synthesized by a microwave process without using any complex agents or ligands and were characterized with different analytical tools such as X-ray diffraction, transmission electron microscopy, and fluorescence spectroscopy. Poly(ethyleneimine) partially quarternized with glycidyltrimethylammonium chloride was synthesized separately and characterized in detail. (1)H and (13)C NMR spectroscopic studies revealed that the quaternary ammonium group was covalently attached to the polymer. UV-vis spectroscopy was used to examine the stability of the colloidal dispersions of the bare NRs as well as the modified NRs. ζ potential, thermogravimetric analysis, and atomic force microscopy studies were carried out to confirm that the positively charged Quat-primer polymer is adsorbed on the negatively charged surface of the NRs, which results in high dispersion stability. Emission spectra of the modified NRs indicated that there was no interference of the Quat-primer polymer with the fluorescence behavior.     

Complexation of zearalenone and zearalenols with native and modified β-cyclodextrins

The complexation of the oestrogenic mycotoxin zearalenone (ZEN) and its metabolites α- and β-zearalenol (ZOLs) with native β-cyclodextrins (β-CD) and modified hydroxypropyl-β-CD and dimethyl-β-CD was studied by fluorescence spectroscopy, nuclear magnetic resonance spectroscopy and electrospray-mass spectrometry. The formation of the inclusion complex was confirmed by NMR studies of zearalenone:β-CD solution. NMR, ESI-MS and fluorescence data are in agreement with the formation of a 1:1 complex between zearalenone and β-CD, characterized by the deep insertion of the phenolic moiety inside the cavity of the CD from its secondary side. The complexes formed between the guests and native β-CD are characterized by high stability constants (>10⁴), as measured by fluorescence titrations.     

Peptide separation through a CB[8]-mediated supramolecular trap-and-release process

We demonstrate a supramolecular peptide separation approach by the selective immobilization of peptides bearing an N-terminal tryptophan onto a CB[8]-modified gold substrate, followed by electrochemical release. The CB[8]-stabilized heteroternary complexes were characterized by (1)H NMR, ESI-MS, UV/vis, and fluorescence spectroscopy and cyclic voltammetry. Micropatterned CB[8]-modified gold substrates were found to trap only the recognizable N-tryptophan-containing peptides from a peptide mixture that could be visualized as green peptide arrays under fluorescence microscopy. Subsequently, the bound peptides were released from the modified substrates by the controlled single-electron reduction of viologen. The fully reversible trap-and-release process was repeated for 13 cycles, and the cumulative release profile of the dye-peptide conjugate was monitored by fluorescence spectroscopy, indicating that no degradation occurred.     

DNA‐Mediated Copper Nanoparticle Formation on Dispersed Single‐Walled Carbon Nanotubes

A new and facile method for the preparation of single‐walled carbon nanotubes (SWCNTs) decorated with Cu nanoparticles (CuNPs) formed on a double‐stranded DNA template in aqueous solution has been developed. A specially designed synthetic DNA sequence, containing a single‐stranded domain for the dispersion of carbon nanotubes and double‐stranded domains for the selective growth of CuNPs, was utilized. The final SWCNT/CuNP hybrids were characterized using fluorescence spectroscopy and transmission electron microscopy. The analyses clearly demonstrated the selective formation of uniform CuNPs on the carbon nanotube scaffold.     

New synthesis strategies for effective functionalization of kaolinite and saponite with silylating agents

Functionalization of Brazilian São Simão kaolinite and Spanish Yunclillos saponite with the alkoxysilanes 3-aminopropyltriethoxysilane and 3-mercaptopropyltrimethoxysilane is reported. The resulting hybrids were characterized by X-ray diffraction, thermal analysis, infrared absorption spectroscopy, and scanning electron microscopy, which demonstrated the effectiveness of the interlamellar grafting process. The X-ray diffractograms revealed incorporation of the alkoxide molecules into the interlayer space of the clays. The displacement of the stretching bands of interlayer hydroxyls in the infrared spectra of the modified kaolinites and the increased intensity of the Mg–OH vibrations in the spectra of the modified saponites confirmed the functionalization of the clays. The thermal behavior of the organoclays confirmed the stability of the hybrids, which was dependent on the clay used for preparation of the materials.     

Synthesis of Bioactive and Porous Organic-Inorganic Hybrids for Biomedical Applications

Bioactivity has been exhibited by a limited range of ceramics since the invention of Bioglass®. Recently, some bioactive polymeric organic-inorganic hybrids were introduced, including not only organically modified silicates (Ormosils) synthesized from polydimethylsiloxane (PDMS) and tetraethoxysilane but also those with gelatin and 3-glycidoxypropyl-tremethoxysilane. Preparation of the bulk and porous hybrids and their polymeric structures analyzed by Si NMR spectroscopy were presented. In vitro bioactivity or apatite deposition in a simulated body fluid of the Kokubo recipe were also described for those hybrids. Freeze-drying techniques introduced porosity (up to 90%) and pores extending in a preferred direction.     

Langmuir-Blodgett thin films of quantum dots: synthesis, surface modification, and fluorescence resonance energy transfer (FRET) studies

We describe herein studies on as-prepared hydrophobic ZnS-CdSe quantum dots (QDs) at the air-water interface. Surface pressure-area (pi-A) isotherms have been used to study the monolayer behavior. Uniform, lamellar multilayer thin films of QDs were deposited by the Langmuir-Blodgett (LB) technique. The role of two different surfactant systems commonly employed in the synthesis of these QDs (trioctylphosphine oxide-octadecylamine (TOPO-ODA) system and trioctylphosphine oxide-tetradecylphosphonic acid (TOPO-TDPA) system) on the monolayer behavior and the quality of thin films produced has been investigated. The thin films were characterized by quartz crystal microgravimetry (QCM), contact angle measurements, fluorescence spectroscopy, and transmission electron microscopy (TEM). These QD films were further modified by an amphiphilic polymer, poly(maleic anhydride-alt-1-tetradecene) (PMA). The hydrophobic interaction between the polymers and the surfactants attached to the QDs drove the self-assembly process. The carboxylic acid functional groups in the polymer were also used to immobilize avidin. We have demonstrated a proof of concept for the biosensing strategy wherein the avidin-coated QD films attracted biotinylated gold nanoparticles, resulting in fluorescence resonance energy transfer (FRET) quenching of the thin films.     

A comparative catalytic study using different metal ions by incorporating functionalized metallosalen into the lacunary position of Keggin polyoxometalate

A series of new hybrids, POM (M-Salen@POM) were synthesized by successfully inserting metallosalen compounds (where M ​= ​Co, Cu, Fe and Ru) into the lacunary position of Keggin type polyoxometalate, K₈SiW₁₁O₃₉ (POM). The hybrids were characterized by FT-IR, powder XRD, diffuse reflectance UV–Vis, energy dispersive X-Ray and inductively coupled plasma atomic emission spectroscopy (ICP) techniques. The hybrids with different metal centers were comparatively studied for their catalytic activity in the oxidation of cycloalkanes, cycloalcohols and alkyl aromatic using a green oxidant, hydrogen peroxide. The products obtained during catalysis were estimated by gas chromatography(GC) and mass spectroscopy(MS). Catalytically synthesized products are of high industrial importance.     

Light-activated covalent formation of gold nanoparticle-graphene and gold nanoparticle-glass composites

Monolayer protected gold nanoparticles (AuNPs) modified with a 3-aryl-3-(trifluoromethyl)diazirine functionality at its terminus (Diaz-AuNPs, 3.9 nm) were prepared and irradiated in the presence of two very different substrates, reduced graphene and glass. Upon irradiation, the terminal diazirine group loses nitrogen to generate a reactive carbene at the interface of the AuNPs that can then undergo addition or insertion reactions with functional groups on the graphene or glass surfaces, leading to the formation of graphene-AuNP and glass-AuNP hybrids, respectively. The AuNP hybrids were characterized using TEM, XRD, XPS, AFM, and UV-vis spectroscopy. Control experiments done in the absence of irradiation demonstrate that carbene activation is required for incorporation of significant AuNP onto the materials. The AuNP hybrids are robust and stable to excessive washing and centrifugation supporting the covalent nature of the interaction between the AuNP and the graphene or silicate glass substrates. Because the formation of the composite is light activated, it lends itself to photopatterning; this application is demonstrated for making the glass-AuNP composites.     

对称排列的咔唑基树状分子的合成及其光物理性能和电化学性能(英文)

采用乌尔曼缩合反应合成了新型的咔唑基树状分子;利用核磁共振谱仪(1HNMR,13CNMR)和飞行时间质谱仪(MALDI-TOF-Mass)对其进行了表征;并评价了树状分子的荧光性能和电化学性能.结果表明,所合成的咔唑基树状化合物在394nm处发蓝光,同时具有低的HOMO能级.     

四苯基卟啉在改性磷酸锆层间的插入及荧光增强

近年来,出于节约一次性能源的考虑,人们已经加大对太阳能等天然资源的利用,致力于模拟天然光合作用的研究[1￣3],而光合作用中的捕光复合物又称为光子天线。光子天线中往往存在一种或几种猝灭剂,猝灭剂吸收光子后产生激发态的能量可以在不同分子或者同一分子的不同生色团之间转移,转移出能量的一方为能量给体,另一方为能量受体。     

Self-assembly and optical properties of water-soluble porphyrin alternating CdSe nanoparticulate films

A new type of self-assembled film was prepared by alternating deposition of oppositely charged meso-tetra-(4-trimethylaminophenyl) porphyrin nickel iodide (NiTAPPI) and citrate-stabilized CdSe nanoparticles. The stepwise deposition process was monitored by means of UV–vis spectroscopy. The interaction between the porphyrin and CdSe nanoparticles was characterized with UV–vis and fluorescence spectra. The SEM images showed the formation of densely packed two-dimensional array and the conversion of disorder-to-order of CdSe nanoparticles on the quartz substrate modified by PDDA when depositing positively charged NiTAPPI. The self-assembled film placed in ambient air exhibited significant enhancement of fluorescence intensity. The effects of heat treatment and UV-light irradiating on fluorescence properties of the composite films were investigated in details.     

金属卟啉有机共价和非共价修饰多壁碳纳米管

合成了5-(4-羟基苯基)-10,15,20-三苯基卟啉锌配合物, 与活化的多壁碳纳米管(MWNT)发生酯化反应, 从而得到金属卟啉有机共价化学修饰的多壁碳纳米管复合物; 利用金属卟啉环上的π电子与多壁碳纳米管管壁上的π电子通过π-π堆积效应, 得到金属卟啉有机非共价修饰的多壁碳纳米管复合物. 通过透射电镜(TEM)考察了金属卟啉-多壁碳纳米管复合物的形貌特征; 通过红外光谱对产物的化学结构进行了表征; 通过紫外光谱、荧光光谱和热失重分析(TGA)对比分析了两类复合物, 发现非共价修饰的金属卟啉-碳纳米管复合物的荧光淬灭率更高, 非共价修饰的金属卟啉-碳纳米管复合物中卟啉的含量比较高.     

甲基三乙氧基硅烷修饰的Ti3+/SiO2复合薄膜的发光性能

采用溶胶-凝胶(Sol-Gel)法, 以正硅酸乙酯(TEOS)和甲基三乙氧基硅烷(MTES)为先驱物, 盐酸为催化剂, 用二步水解法制备了Ti3+/SiO2薄膜和甲基三乙氧基硅烷修饰的Ti3+/SiO2复合薄膜. 采用红外光谱仪、X射线衍射仪、椭偏仪、荧光光谱仪等对膜层性质进行了分析. 结果表明, 掺杂Ti3+的SiO2薄膜分别在250 nm附近有一弱的激发峰, 294 nm附近有一强的激发峰, 在393 nm附近出现一强的发射峰. IR光谱发现, MTES修饰的Ti3+/SiO2复合薄膜的Si—OH的吸收峰强度比Ti3+/SiO2薄膜的略减小, Si—O—Si的吸收峰明显增强, 表明复合薄膜硅氧网络结构更规则, 有利于Ti3+的均匀分散. Ti3+/SiO2薄膜与复合薄膜的孔隙率分别为13.64%和6.66%, 表明MTES的加入使薄膜更致密. 在空气中陈放30 d后, Ti3+/SiO2薄膜已经检测不到荧光发射峰, 而MTES修饰的Ti3+/SiO2复合薄膜荧光强度只下降了18%. 在氮气中陈放30 d后, 普通薄膜与复合薄膜的荧光强度均仅下降了10%. 表明Ti3+的荧光猝灭的主要原因是由于Ti3+被氧化造成的. 溶胶中加入MTES后, 薄膜表面结构得到改善, 有效地防止了Ti3+的氧化, 荧光强度更稳定.     

Spectral characterization,antimicrobial and antibiofilm activity of poly(propylene imine) metallodendrimers in solution and applied onto cotton fabric

Abstract

Poly(propylene imine) dendrimers from first and third generation modified with 1,8-naphthalimide units and their Cu(II) complexes have been characterized by fluorescence and EPR spectroscopy. Cotton fabric has been modified with these dendrimers and their color characteristics were determined. The antimicrobial activity of dendrimer ligands and their Cu(II) complexes in solution and after their deposition on a cotton fabric was investigated. Good antibacterial effect of dendrimer ligands has been obtained, which is enhanced at their Cu(II) complexes. After their deposition on cotton fabric metallodendrimers exhibit good antibiofilm activity.