Deposition of silver nanoparticles on dendrimer functionalized multiwalled carbon nanotubes: synthesis, characterization and antimicrobial activity

The nanohybrids composed of silver nanoparticles and aromatic polyamide functionalized multiwalled carbon nanotubes (MWCNTs) is successfully synthesized and tested for their antibacterial activity against different pathogens. Prior to deposition of silver nanoparticles, acid treated MWCNTs (MWCNTs-COOH) were successively reacted with p-phenylenediamine and methylmethacrylate to form series of NH2-terminated aromatic polyamide dendrimers on the surface of MWCNTs through Michael addition and amidation. Existence of high abundance of amine groups on the surface of functionalized MWCNTs (f-MWCNTs) provided sites for formation of silver nanoparticles by the reduction of aqueous solution of AgNO3. The silver nanoparticles formed in the resulted f-MWCNTs-Ag nanohybrids were determined to be face centered cubic (fcc) symmetry. The structure and nature of f-MWCNTs and f-MWCNTs-Ag nanohybrids were characterized by UV-vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), powder X-ray diffraction analysis (XRD), Raman spectroscopy and thermogravimetric analysis (TGA). The dispersion state of f-MWCNTs and immobilization of silver nanoparticles on the surface of f-MWCNTs were investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Elemental composition of f-MWCNTs-Ag nanohybrids was determined by energy dispersive X-ray spectroscopy (EDS). The antimicrobial activity of f-MWCNTs-Ag nanohybrids were estimated against E. coli, P. aeruginosa and S. aureu and compared with MWCNTs-COOH and f-MWCNTs. The results indicate that functionalization of MWCNTs with aromatic polyamide dendrimers and successive deposition of Ag nanoparticles could play an important role in the enhancement of antimicrobial activity.     

The effect of the coupling agents KH550 and KH570 on the nanostructure and interfacial interaction of zinc oxide/chiral poly(amide–imide) nanocomposites containing l-leucine amino acid moieties

In this article, a series of optically active poly(amide–imide)/zinc oxide nanocomposites (PAI/ZnO NCs) with different ZnO contents were prepared by ultrasonic technique. For better dispersion of nanoparticles (NPs) in the PAI matrix, their surface was modified with two different silane coupling agents. Then, the effects of two linkers on dispersity of NPs, thermal stability and UV–Visible spectra of resulting NCs were investigated. The morphological structures, thermal, and UV properties of the prepared NCs with two different coupling agents were studied by X-ray diffraction, transmission electron micrograph, field emission scanning electron microscopy, thermogravimetric analysis, and UV–Visible analysis. These data demonstrated that the surface-modified ZnO NPs were homogeneously dispersed in the PAI matrix. However, in the case of KH570 the better dispersity is more pronounced.     

The use of novel biodegradable,optically active and nanostructured poly(amide-ester-imide) as a polymer matrix for preparation of modified ZnO based bionanocomposites

A novel biodegradable and nanostructured poly(amide-ester-imide) (PAEI) based on two different amino acids, was synthesized via direct polycondensation of biodegradable N,N′-bis[2-(methyl-3-(4-hydroxyphenyl)propanoate)]isophthaldiamide and N,N′-(pyromellitoyl)-bis-l-phenylalanine diacid. The resulting polymer was characterized by FT-IR, ¹H NMR, specific rotation, elemental analysis, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) analysis. The synthesized polymer showed good thermal stability with nano and sphere structure. Then PAEI/ZnO bionanocomposites (BNCs) were fabricated via interaction of pure PAEI and ZnO nanoparticles. The surface of ZnO was modified with two different silane coupling agents. PAEI/ZnO BNCs were studied and characterized by FT-IR, XRD, UV/vis, FE-SEM and TEM. The TEM and FE-SEM results indicated that the nanoparticles were dispersed homogeneously in PAEI matrix on nanoscale. Furthermore the effect of ZnO nanoparticle on the thermal stability of the polymer was investigated with TGA and DSC technique.     

Al Alloy Nanocomposite Reinforced with Physically Functionalized Carbon Nanotubes Synthesized via Spark Plasma Sintering

Nanocrystalline Al–11.5Si (in wt%) powders were prepared by high-energy ball milling of microcrystalline Al–Si powders, which were subsequently mixed with pristine and physically functionalized multiwalled carbon nanotubes (MWCNTs) separately and were consolidated by spark plasma sintering. Improvement in MWCNT dispersion was observed as a result of functionalization, which resulted in improved densification of the nanocomposites (NCs). Scanning electron microscopy was performed to understand the agglomeration and dispersion of CNTs. Distribution of MWCNTs, the dislocation activity, and the effect of primary Si particles in NC matrix were studied by carrying out transmission electron microscopy. Nanoindentation was performed to measure the elastic modulus and microhardness of the NCs which showed appreciable improvement for functionalized MWCNT reinforced NC.     

MWCNT reinforced Polyamide-6,6 films: preparation,characterization and properties

Composite films of Polyamide-6,6 (PA66) and multi-walled carbon nanotubes (MWCNTs) were prepared by a combination of solution casting followed by compression molding techniques. Both unfunctionalized (u-MWCNTs) and functionalized nanotubes (f-MWCNTs) were used in this study. The functionalization involved direct solvent-free amination of MWCNTs with hexamethylenediamine. Thermogravimetric analysis was used to observe the changes in the nanotubes upon functionalization and morphological features of the resulting composite films were studied using scanning electron microscopy, transmission electron microscopy, and atomic force microscopy. The crystallinity changes by incorporation of the u-MWCNTs and f-MWCNTs in the PA66 matrix were studied by wide angle X-ray scattering and differential scanning calorimetry. The f-MWCNT/PA66 film showed an improvement of ∼43% in maximum tensile stress (MTS) and ∼32% in Young’s modulus over pristine PA66 film, while at a similar loading of 0.5 wt%, the f-MWCNT/PA66 film showed ∼15% increase in MTS and ∼16% increase in modulus over the u-MWCNT/PA66 film. Dynamic mechanical analysis indicated significant difference in the small-strain mechanical properties between the MWCNT-filled and unfilled PA66 at the very low MWNT loadings that were tested and supported the tensile results. The water absorption trend of the composite films showed dramatic improvement over the neat film.     

Concise route to styryl-modified multi-walled carbon nanotubes for polystyrene matrix and enhanced mechanical properties and thermal stability of composite

Effective functionalization of multi-walled carbon nanotubes (MWCNTs) with styryl group was carried out via the esterification reaction of the carboxylate salt of carbon nanotubes and 4-vinylbenzyl chlorides in toluene. The functionalized MWCNTs were characterized through FTIR and Raman spectra to confirm the styryl groups covalently connected to the surface of MWCNTs. The weight loss of functionalized moieties determined by thermogravimetry-differential scanning calorimertry analysis is around 36%. Nanotube-reinforced polystyrene were fabricated by mixing functionalized MWCNTs and polystyrene. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images showed that the functionalized nanotubes had a better dispersion than the unfunctionalized MWCNTs in the matrix. Moreover, styryl-modified MWCNTs/PS nanocompsite presented obvious improvements in mechanical properties and thermal stability.     

Surface modification of nano-TiO2 with trimellitylimido-amino acid-based diacids for preventing aggregation of nanoparticles

Nanoparticles (NPs) are an essential material for science and technology, for instance in materials, medicals, and cosmetics. Controlling the dispersion of NPs is necessary to manage the properties of the final products. For this reason the surface modification of NPs is done by many techniques. In this work Nano-TiO₂ were modified using methanol as solvent and diacids based on natural amino acids as modifier at room temperature and using ultrasonic irradiation. Diacids were grafted onto the surface of TiO₂ NPs to improve the dispersion of the particles. The obtained modified TiO₂ were characterized by Fourier transform IR spectroscopy (FT-IR), X-ray diffraction (XRD), Field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and thermogravimetric analysis (TGA) techniques. These analyses proved this modification process at room temperature was possible. TEM and FE-SEM showed that fairly good dispersed TiO₂ NPs were obtained after surface modification. Since TiO₂ and diacids which were used in this work are biologically active, the modified powder would be environmentally friendly.     

Effect of dispersion method on the deterioration,interfacial interactions and re-agglomeration of carbon nanotubes in titanium metal matrix composites

The influence of various synthesis techniques on the dispersion and evolution of multi-walled carbon nanotubes (MWCNTs) in titanium (Ti) metal matrix composites (TMCs) prepared via powder metallurgy routes has been investigated. The synthesis techniques included sonication, high energy ball milling (HEBM), cold compaction, high temperature vacuum sintering and spark plasma sintering (SPS). Powder mixtures of Ti and MWCNTs (0.5 wt.%) were processed by HEBM in two batches: (i) ball milling of the mixtures (Batch 1) and (ii) ball milling of Ti powder alone, followed by a further ball milling with sonicated MWCNTs (Batch 2). Both batches of the powder mixtures were pressed at 40 MPa into green compacts and then sintered in vacuum. Batch 2 powder mixtures were also consolidated using SPS. The crystallinity and sp² carbon network of the MWCNTs were characterized through analyzing the characteristic Raman peak ratio (I_D/I_G) of each processed sample. X-ray diffraction (XRD) was used for phase identification. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to study the morphology of the MWCNTs in the powder mixtures. The evolution of MWCNTs during the fabrication process and mechanical properties of the sintered compacts were discussed in conjunction with the formation of nano-crystalline TiC.     

Study on novel poly (vinyl pyrrolidone) doped MWCNTs/polyrhodanine nanocomposites: Synthesis,characterization, and thermal performance

In this paper, poly (vinyl pyrrolidone) (PVP) doped multiwall carbon nanotubes (MWCNTs/polyrhodanine), were synthesized through one-step chemical oxidative polymerization of rhodanine monomers on the surface-modified carbon nanotubes. Characterization of MWCNTs/polyrhodanine was conducted by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transforms infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and EDX spectrum analyses in which the results confirmed the successful formation of MWCNTs/polyrhodanine. In addition, to investigate the thermal properties of samples, thermogravimetric analysis (TGA) was employed, and results exhibited significant improvement in the nanocomposite thermal stability due to the addition of MWCNTs with reinforcement effect in polymer matrix.     

Novel flame retardant zirconia-reinforced nanocomposites containing chlorinated poly(amide-imide): synthesis and morphology probe

In the present investigation, a thermally stable poly(amide-imide) (PAI) was synthesised from the polymerisation reaction of 4,4′-methylenebis(3-chloro-2,6-diethyl trimellitimidobenzene) as a chlorinated diacid with 4,4′-methylenebis(3-chloro-2,6-diethylaniline) using molten tetra-n-butylammonium bromide and triphenyl phosphite as a condensing agent and green media. This methodology offers enhancements for the synthesis of polymers with regard to yield of products, simplicity in operation, and green aspects by avoiding volatile solvents. From the chemical point of view, the chloride and ethylene groups impart to the polymer's chain increased solubility of obtained polymer in organic solvent. Then, the surface of zirconia nanoparticles (ZrO₂-NPs) was modified with 3-aminopropyltriethoxylsilane as a coupling agent. The obtained polymer and inorganic metal oxide NPs were used to prepare PAI/ZrO₂ nanocomposites through ultrasonic irradiation. The formation of PAI was confirmed by ¹H-NMR, FT-IR spectroscopy, and elemental analysis. The obtained polymer was synthesised with good yield (90%) and moderate inherent viscosity (0.48 dL/g). The resulting NP filled composites were also characterised by FT-IR, XRD, FE-SEM, TEM and TGA. The TEM and FE-SEM results indicated a high dispersion level of the nanoscale inorganic particles in the polymer matrix. In this article, ZrO₂-NPs are employed to improve flame retardancy of nanocomposites. TGA thermographs confirmed that the heat stability of the prepared NP-reinforced composites was improved in the presence of ZrO₂ nanocrystals.     

Novel fabrication of silica nanotubes using multi-walled carbon nanotubes as template

Silica nanotubes were synthesized using multi-walled carbon nanotubes (MWCNTs) as template. The as-obtained samples were characterized by infrared spectroscopy (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscope (FE-SEM) and photoluminescent (PL) spectroscopy. The results indicate that the thickness of the outer walls is about 10 nm and the inner diameter is completely dependent on the size of MWCNTs. The as-fabricated silica nanotubes emit a strong violet light under excitation of 250 nm.     

氨化碳纳米管接枝生物分子(蛋白质和DNA)

报告-种氨基功能化处理的多壁碳纳米管(f-MWCNTs)用于生物分子[如牛血浆蛋白素(BSA)蛋白质及脱氧核醣核酸(DNA)]的接枝处理高效方法.以苯-二茂铁喷入氩氛炉于～850 ℃裂解制得MWCNTs,,而后向纳米管表面导入羧基化合物,再以氨基基团对MWCNTs,进行功能化处理.该过程包括:乙二胺与羧基基团直接结合,经酰胺化引入胺基基团.对制得的MWCNTs、 f-MWCNTs以及由BSA蛋白质和DNA接枝的氨化f-MWCNTs等样品,采用SEM、TEM、FTIR进行表征.结果表明:生物分子(BSA蛋白质和DNA)接枝于氨化的f-MWCNTs.     

Electric field effects on CNTs/vinyl ester suspensions and the resulting electrical and thermal composite properties

In this study, electrical conductivity of a vinyl ester based composite containing low content (0.05, 0.1 and 0.3 wt.%) of double and multi-walled carbon nanotubes with and without amine functional groups (DWCNTs, MWCNTs, DWCNT-NH₂ and MWCNT-NH₂) was investigated. The composite with pristine MWCNTs was found to exhibit the highest electrical conductivity. Experiments aimed to induce an aligned conductive network with application of an alternating current (AC) electric field during cure were carried out on the resin suspensions with MWCNTs. Formation of electric anisotropy within the composite was verified. Light microscopy (LM), scanning electron (SEM) and transmission electron microscopy (TEM) were conducted to visualize dispersion state and the extent of alignment of MWCNTs within the polymer cured with and without application of the electric field. To gain a better understanding of electric field induced effects, glass transition temperature (T_g) of the composites was measured via Differential Scanning Calorimetry (DSC). It was determined that at 0.05 wt.% loading rate of MWCNTs, the composites, cured with application of the AC electric field, possessed a higher T_g than the composites cured without application of the AC electric field.     

Ultrasound-aided formation of gold nanoparticles on multi-walled carbon nanotubes functionalized with mercaptobenzene moieties

A hybrid of multi-walled carbon nanotube (MWCNT) and gold nanoparticle (Au NP) was prepared under ultrasound irradiation. The approach starts with the functionalization of the walls of MWCNTs with mercaptobenzene moieties for the subsequent immobilization of Au NPs. From the Raman spectra, mercaptobenzene was proven to exist on the MWCNTs. Gold ions were added to the aqueous dispersion of functionalized MWCNTs (f-MWCNTs), and were reduced with the aid of ultrasound and ammonium hydroxide. The reduced gold nanoparticles were examined from the TEM images. Au NPs adhered specifically on the thiol groups of mercaptobenzene to be deposited uniformly on the outer walls of the f-MWCNTs. The application of ultrasound led to a high yield of MWCNT-Au nanocomposites and to the dense distribution of the Au NPs. Moreover, the synthesis reaction rate of the hybrid was considerably enhanced relative to synthesis with mechanical agitation. Through an adsorption test using gold-binding-peptide-(GBP)-modified biomolecules, the hybrid's potential for biological diagnosis was verified.     

Anionic clay intercalated by multi-walled carbon nanotubes as an efficient 3D nanofiller for the preparation of high-performance l-alanine amino acid containing poly(amide-imide) nanocomposites

In this study, three-dimensional (3D) nanohybrids with excellent properties were prepared by the simple combination of 1D carbon nanotubes (CNTs) and 2D MgAl-layered double hydroxides (LDHs). An optically active amino acid containing poly(amide-imide) was prepared by direct polycondensation reaction of N-trimellitylimido-l-alanine and 4,4′-diaminodiphenyl methane under green condition in molten tetra-n-butylammonium bromide. PAI/LDH-CNT nanocomposites containing 2, 4, and 8 wt% LDH-CNT were prepared via a simple and an effective ultrasonic method. The presence of CNT in the interlayer space of LDH was confirmed by thermogravimetry analysis, Fourier transformed infrared spectroscopy, and X-ray diffraction techniques. The homogeneous dispersion of nanofillers in the PAI matrix was observed by field emission scanning electron microscopy and transmission electron microscopy. The obtained results revealed the coexistence of exfoliated and intercalated modified LDH-CNT in the polymer matrix.     

Growth, structure and luminescence properties of multilayer Si/β-FeSi2NCs/Si/…/Si nanoheterostructures

Multilayer structures (up to 15 layers) with β-FeSi₂ nanocrystallites (NCs) buried in silicon crystalline lattice were grown by successive repetition of reactive deposition epitaxy (RDE) or solid phase epitaxy (SPE) of thin iron film on Si(100) or Si(111) substrates and silicon molecular beam epitaxy (MBE) (100-200 nm). Cross-section high resolution transmission electron microscopy (HR TEM) images and ex situ optical and Raman spectroscopy data prove that NCs formed in silicon matrix have the structure and optical properties of β-FeSi₂. The growth conditions provide no dislocations in silicon lattice were found in the course of TEM analysis. Two types of NCs depth distribution were observed: (i) layered that corresponds to iron RDE and (ii) uniform that occurs in the case of iron SPE. The uniform NCs distribution points out the fact that during a growth process NCs moves up to the surface. In spite of small nanocrystallites size (5-50 nm) and their distribution in silicon cap layers the significant photoluminescence (PL) signal at 0.8 eV was observed for all grown samples.     

Thermoplastic elastomers with multi-walled carbon nanotubes: Influence of dispersion methods on morphology

PBT-block-PTMO thermoplastic elastomers derived from dimethyl terephthalate (DMT), 1,4-butanediol(BD) and poly(tetramethylene glycol) (PTMG) were synthesized in the presence of oxidized multi-walled carbon nanotubes (MWCNTs) by a two-stage process involving transesterification and in situ polycondensation. Two procedures were applied to nanotubes in the polymer matrices were used. In procedure 1, nanotubes were dispersed in DMT + BD before the transesterification, while in procedure 2 nanotubes were dispersed in PTMG after transesterification. The mole ratio of the starting components was selected to produce copolymers with a constant hard to soft segment weight ratio of 45:55. Characterization of the new nanocomposites was performed by transmission electron microscopy (TEM), scanning electron microscopy (SEM), small- and wide-angle X-ray scattering (SAXS/WAXS). A better nanotube dispersion can be achieved when oxidized MWCNTs are added to the DMT + BD monomers before transesterification (procedure 1). Oxidized MWCNTs exhibit strong interfacial adhesion to the polymer matrix for both procedures.     

Modeling and mechanical performance of carbon nanotube/epoxy resin composites

The effect of multi-walled carbon nanotube (MWCNT) addition on mechanical properties of epoxy resin was investigated to obtain the tensile strength, compressive strength and Young’s modulus from load versus displacement graphs. The result shows that the tensile strength, compressive strength and Young’s modulus of epoxy resin were increased with the addition of MWCNT fillers. The significant improvements in tensile strength, compressive strength and Young’s modulus were obtained due to the excellent dispersion of MWCNT fillers in the epoxy resin. The dispersion of MWCNT fillers in epoxy resin was observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analysis.Also, Halpin–Tsai model was modified by considering the average diameter of internal/external of multi-walled nanotube and orientation factor (α) to calculate the Young’s modulus of multi-walled carbon nanotubes (MWCNTs)/epoxy resin composite. There was a good correlation between the experimentally obtained Young’s modulus and modified Halpin–Tsai model.     

Sonochemical synthesis of luminescent CeCO3OH one-dimensional quadrangular prisms

Orthorhombic single-crystalline cerium carbonate hydroxide (CeCO₃OH) with one-dimensional (1D) microstructures has been successfully synthesized by a facile sonochemical reaction between cerous nitrate and urea. These 1D microstructures were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), field-emission scanning electron microscopy (FE-SEM). The as-synthesized CeCO₃OH has uniform lengths and good dispersion. Synthetic parameters, such as the concentration of reagents, were found to have close relationship with the morphologies and sizes of the final products. The ultrasound-induced oriented attachment growth mechanism has been proposed for the possible formation mechanism of sample. Room-temperature photoluminescence of CeCO₃OH samples with different morphologies has also been investigated.     

Structure and photoluminescent properties of microstructural YBO3 : Eu3+ nanocrystals

YBO3 : Eu3+ nanocrystals (NCs) were prepared by a hydrothermal method and characterized by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and Fourier-transform infrared (FTIR) spectroscopy. The results demonstrate that morphology and structure of the NCs varied strongly with hydrothermal temperature. Their luminescent properties were investigated in comparison to the bulk. A large number of NO3- groups were adsorbed at the surface of hydrothermal products, which acted as luminescent killers; Two symmetry sites of Eu3+ ions in NCs, the interior and the surface sites, were identified by the site-selective excitation and time-resolved emission experiments; The intensity ratio of 5D0-7F2 to 5D0-7F, of EU3+ at the surface site increased greatly than that at the interior site; as a result, the chromaticity was improved; The total radiative transition rate of 5D0-sigmaJ7FJ for Eu3+ at the surface site was 3-5 times larger than that at the interior.