Abstract: An alternative and effective route to prepare conducting polyaniline-grafted reduced graphene oxide (PANi-g-rGO) composite with highly enhanced properties is reported. In order to prepare PANi-g-rGO, amine-protected 4-aminophenol was initially grafted to graphite oxide (GO) via acyl chemistry where a concomitant partial reduction of GO occurred due to the refluxing and exposure of GO to thionyl chloride vapors and heating. Following the deprotection of amine groups, an in situ chemical oxidative grafting of aniline in the presence of an oxidizing agent was carried out to yield highly conducting PANi-g-rGO. Electron microscopic studies demonstrated that the resultant composite has fibrillar morphology with a room-temperature electrical conductivity as high as 8.66 S/cm and capacitance of 250 F/g with good cycling stability
Abstract: An efficient method for the preparation of a highly conducting hybrid material from graphene oxide nanosheets (GNS) and a novel conjugated polymer, poly(3,4-propylenedioxythiophene) is demonstrated. A functionalized monomer based on 3,4-propylenedioxythiophene, namely ProDOT-OH, was covalently functionalized with GNS, followed by oxidative polymerization to prepare GNS-f-PProDOT composites. The covalent functionalization process of GNS with the monomer ProDOT-OH was activated through the simple esterification reaction between the acyl chloride derivative on the nanosheets and the pendant hydroxyl group present in the monomer. Furthermore, the monomer functionalized GNS were co-polymerized with thiophene resulting in hybrid graphene nanostructures coated with highly conducting co-polymers with a room temperature electrical conductivity as high as 22.5 S cm-1. The resulting hybrid materials were characterized using a range of analytical techniques. The specific capacitance value of the composite and the co-polymer hybrids at a scan rate of 10 mV s-1 has been determined to be 158 and 201 F/g respectively and hence particularly promising for flexible supercapacitors.
Abstract: We report an effective route to prepare highly conducting and flexible few-walled carbon nanotube (FWNT) thin films. The free-standing thin films were fabricated by functionalizing FWNTs with 4-ethoxybenzoic acid (EBA) via a direct FriedelâCrafts acylation reaction in a nondestructive polyphosphoric acid/phosphorus pentoxide medium. The resulting ethoxybenzoyl-functionalized FWNT (EBA-f-FWNT) was readily dispersible in water. EBA-f-FWNT thin films were formed by a simple suction filtration of the dispersed solution. Electron microscopic studies were employed to characterize the morphologies of the resulting thin films. The obtained results indicate that the structure of FWNTs was not perturbed by the incorporation of EBA moieties, which were uniformly grafted onto FWNTs forming the FWNT networks. Room temperature electrical conductivity of the thin films was obtained using standard four-probe measurements, which revealed a value as high as 29â400 S mâ1, while the tensile strength and modulus of the film were found to be about 80 MPa and 15 GPa, respectively. Cyclic voltammograms revealed a rectangular shape, with superior capacitive behaviors nearing 133 F/g for the thin films, which is very attractive for capacitor applications.
Abstract: Manganese-doped ZnS nanocrystals with an amine capping layer have been synthesized and used to decorate MWNTs. FT-IR spectroscopy was employed to characterize the initial changes in surface functionalities. The MWNTs were then acylated with thionyl chloride, and further, the amine capped Mn-doped ZnS semiconductor nanocrystal quantum dots (QDs) were covalently immobilized on the acylated MWNTs. The resulting Mn-doped ZnS QDs and the hybrids with carbon nanotubes were characterized by UV-Vis spectrometer, phosphorescence measurements, and XRD. High resolution TEM and EDX studies were performed to confirm the immobilization of QDs onto the nanotubes.
Abstract: Porous, biodegradable and biocompatible chitosan, chitosan with natural hydroxyapatite derived from Thunnus Obesus bone (chitosan/HAp) and chitosan grafted with functionalized multiwalled carbon nanotube in addition to HAp (f-MWCNT-g-chitosan/HAp) scaffolds were prepared for the first time via freeze-drying method and physiochemically characterized as bone graft substitutes. The cross-linkages in the novel f-MWCNT-g-chitosan/HAp scaffold were observed by FT-IR spectroscopy. The water uptake, retention ability and degradation of composite scaffolds decreased whereas thermal stability increased with an addition of HAp and f-MWCNT. Uniform dispersion of HAp and f-MWCNT in chitosan matrix with interconnected porosity of 70â200 μm (chitosan/HAp) and 46â200 μm (f-MWCNT-g-chitosan/HAp) was observed by X-ray diffraction, scanning electron microscopy and optical microscopy. Cell proliferation in composite scaffolds was twice than in pure chitosan when checked in vitro using MG-63 cell line. These observations suggest that the novel chitosan/HAp and f-MWCNT-g-chitosan/HAp composite scaffolds are promising biomaterials for bone tissue engineering.
Abstract: The synthesis of biocompatible magnetic nanoparticles is one of the important topics in nanoscience because such materials have potential biomedical applications. Herein, we report a facile approach for surface functionalization of magnetic nanoparticles (MNPs) with boronic acid and their use for the covalent immobilization of adenosine. The iron nanoparticles were firstly coated by layer of gold using the inverse micelle method to form coreâshell structure. Then, the surface functionalization of MNPs was carried out using 4-mercaptophenylboronic acid through the well-developed AuâS chemistry. The covalent immobilization of functionalized MNPs with adenosine was obtained via the strong covalent interactions of boroester linkages, which were formed between free hydroxyl groups of adenosine and boronic acid. X-ray diffraction (XRD) and high resolution transmission electron microscopy (HR-TEM) were used to confirm the successful preparation of coreâshell magnetic nanoparticles. Fourier transformed infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), UVâvisible absorption spectroscopy (UVâvis), X-ray photoelectron spectroscopy (XPS), superconducting quantum interference device magnetometer (SQUID) was employed to characterize the change of surface functionalities and to study the magnetic properties. The digital image provided a vivid observation on the separation of adenosine-immobilized MNPs under an external magnetic field.
Abstract: A new and effective route to synthesize conducting polyaniline-multiwalled carbon nanotube (PANI -f-MWNT) nanocomposites (where f denotes that the MWNTs have been functionalized) starting with amine-protected 4-aminophenol is reported. Aminophenol-functionalized MWNTs were initially synthesized by functionalizing acyl chloride-terminated nanotubes with N-(tert-butoxycarbonyl)-4-aminophenol followed by the in situ chemical oxidative grafting of aniline in the presence of ammonium persulfate as an oxidizing agent. Control of the morphology and thickness of the polymer-MWNT nanocomposites was achieved by varying the weight ratios of aniline monomers and MWNTs in the polymerization process. Fourier transform infrared spectroscopy was employed to characterize the initial changes in surface functionalities which also confirmed that PANI was covalently grafted to the MWNTs. Electron microscopy and UV-visible absorption spectroscopy were employed to characterize the morphology and chemical structure of the resulting hybrids. The results obtained indicate that the structure of the MWNTs was not perturbed by the incorporation of PANI. The content of the polymer in the nanocomposites was determined thermogravimetrically, while the electrical conductivity was obtained using four-probe measurements. The PANI -f-MWNT nanocomposites were adopted as templates for further decoration with gold nanoparticles in solution, thus opening new possibilities for their prospective technological applications.
Abstract: An efficient strategy for the preparation of water-dispersible hybrid material containing graphene oxide and polyglycerol for the first time is demonstrated. Pristine graphite was firstly oxidized to obtain graphene oxide with hydroxyl functional groups. Then, the covalent grafting of polyglycerol onto the surface of graphene oxide was carried out based on in situ ring-opening polymerization of glycidol. For the construction of novel hybrid nanostructure, Fe-core/Au-shell nanoparticles were prepared and further functionalized using 4-mercaptophenylboronic acid through the well-developed AuâS chemistry. Subsequently, magnetic nanoparticles were anchored on the surface of polyglycerol-grafted graphene nanosheets via boroester bonds. The resulting hybrid materials were characterized using a range of analytical techniques. Fourier transform infrared spectroscopy (FT-IR) was employed to investigate the initial changes in surface functionalities. While X-ray diffraction (XRD) was used to confirm the structure of graphene oxide nanosheets, high resolution transmission electron microscopy (HR-TEM), and field emission scanning electronic microscopy (FE-SEM) equipped with an energy dispersive X-ray (EDX) spectrometer were used to study the morphologies and distribution of magnetic nanoparticles onto the surface of polyglycerol-grafted graphene. Thermogravimetric analysis (TGA) was used to study the weight loss of the samples on heating. Superconducting quantum interference device magnetometer (SQUID) was employed to the magnetic property of magnetic nanoparticles. The digital images provided a vivid observation on the high dispersion stability of the prepared novel hybrid materials in distilled water.
Abstract: Multiwalled carbon nanotubes (MWNTs) were functionalized with poly(3,4-propylenedioxythiophene) (PProDOT) using a simple âchemical graftingâ approach. After the conventional acid oxidation (AO) process, the MWNT-COOH was converted to the acyl chloride functionalized MWNTs (MWNT-COCl) by treating them with thionyl chloride. The MWNT-COCl were further reacted with a functionalized monomer based on 3,4-propylenedioxythiophene (ProDOT-OH), followed by oxidative polymerization to prepare the MWNT-g-PProDOT hybrid. The monomer-functionalized MWNTs was further copolymerized with thiophene to prepare conducting copolymers on carbon nanotubes (CNTs). Fourier-transformed infrared spectrophotometry was employed to characterize the change in surface functionalities, which revealed that the PProDOT was covalently grafted to the MWNTs, while TGA was used to study the weight gain due to the functionalization. UVâVis absorption spectra revealed the functionalization of the conjugated polymer by showing the typical absorption band. The morphology micrographs of the grafted PProDOT on MWNTs as evidenced by field emission scanning electron microscopy and transmission electron microscopy showed apparent effect on the structure and appearance of the MWNTs by growing thicker as expected from surface modification. Using the facile route developed in this study, CNTs can be easily fabricated with other types of polymers for several applications.
Abstract: A well-reproducible and completely green route towards highly water dispersible multi-walled carbon nanotubes (MWNT) is achieved by a non-invasive, polymer wrapping technique, where the polymer is adsorbed on the MWNT's surface. Simply mixing an amino-acid-based polymer derivative, namely poly methacryloyl beta-alanine (PMBA) with purified MWNTs in distilled water resulted in the formation of PMBA-MWNT nanocomposite hybrids. Gold nanoparticles (AuNPs) were further anchored on the polymer-wrapped MWNTs, which were previously sonicated in distilled water, via the hydrogen bonding interaction between the carboxylic acid functional groups present in the polymer-modified MWNTs and the citrate-capped AuNPs. The surface morphologies and chemistries of the hybrids decorated with nanoparticles were characterized by transmission electron microscopy (TEM) and UV-visible absorption spectroscopy. Additionally, the composites were also prepared by the in situ free radical polymerization of the monomer, methacryloyl beta-alanine (MBA), with MWNTs. Thus functionalized MWNTs were studied by thermogravimetric analysis (TGA), field emission scanning electron microscopy (FE-SEM) and TEM. Both methods were effective in the nanotube functionalization and ensured good dispersion and high stability in water over three months. Due to the presence of the high densities of carboxylic acid functionalities on the surface of CNTs, various colloidal nanocrystals can be attached to MWNTs.
Abstract: A generic approach for immobilizing gold nanoparticles (GNPs) and the construction of multilayered gold structures are reported. The process involves the use of UV cross-linked poly(4-vinylpyridine) (P4VP) thin films for the immobilization and construction of multilayered GNP architectures. P4VP thin films were prepared by spin-coating of the polymer solution onto silicon wafer substrates which was then cross-linked via UV exposure. GNPs, about 70 nm were immobilized via electrostatic adsorption onto the P4VP films. Further, these monolayer surfaces containing GNPs were capped with a bifunctional cross-linker, 1,6-hexanedithiol (HDT). To the additional end termini of HDT, a second layer of GNPs (approximately 20 nm) was assembled. The self-assembly of 1,6-hexanedithiol on the immobilized GNPs and the bilayered architectures were investigated by atomic force microscopy (AFM), filed emission scanning electron microscopy (FE-SEM), and UV-Vis absorption spectroscopy.
Abstract: Combining hybrid nanostructures of metal nanoparticles (NPs) and carbon nanotubes could afford a novel strategy to prepare promising nanomaterials for the highly sensitive sensors and imaging science applications. Conventional acid oxidation process was used to obtain carboxylic acid bound multi-walled carbon nanotubes (MWNTs) which was further acylated with thionyl chloride to give acyl chloride functionalized MWNTs. Thiol functionalized MWNTs were synthesized by amidation reaction of the acylated MWNTs with cysteamine. Further, gold nanoparticles (GNPs) were successfully fabricated on the tube walls to yield the CNT/Au hybrid. Fourier transform infrared spectroscopy and energy dispersive X-ray studies were used to characterize the surface chemical functionalities and composition of MWNTs, respectively. Evidence for the attachment of GNPs to thiol functionalized MWNTs was obtained from ultravioletâvisible absorption spectra. In addition, TEM images provided a vivid image of uniform decoration of GNPs on the nanotube sidewalls.
Abstract: We report a simple method for the functionalization of multi-walled carbon nanotubes (MWNTs) with a biomedically important polymer, poly(2-hydroxyethyl methacrylate) (poly(HEMA)), by chemical grafting of HEMA monomer followed by free radical polymerization. The nanotubes were first oxidized with a mixture of conc. nitric acid and sulfuric acid (1:3), in order to obtain carboxylic acid functionalized MWNTs. Then the grafting of HEMA on to the surface of MWNTs was carried by chemical functionalization of HEMA with acid chloride-bound nanotubes by esterification reaction. FT-IR was used to identify functionalization of âCOOH and HEMA groups attached to the surface of the nanotubes. The presence of poly(HEMA) on the nanotubes were confirmed by FESEM, TEM, and TGA analyses. Additionally, the dispersibility of the polymer functionalized nanotubes in methanol was also demonstrated. Considering the biomedical importance of poly(HEMA) and the recent successful in vivo studies on CNTs, in future, these materials are expected to be useful in the pharmaceutical industry as novel biomaterials composites with potential applications in drug delivery.
Abstract: Cluster like network structures of single-walled carbon nanotubes (SWNTs) were synthesized by chemical grafting poly 2-hydroxyethyl methacrylate (poly HEMA) to the sidewalls of SWNTs. Acid chloride-functionalized tubes were coupled with commercially available HEMA monomer, which was in turn polymerized using a radical initiator. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy were used to identify the surface changes on the nanocomposites. Microscopic observations of the nanotube complexes by field emission scanning electron microscopy (FE-SEM) shows that the tubes were dispersed and forming cluster like network, branched structures with less bundling, thus, strongly suggesting a firm coating of the polymer on nanotube walls. The coating was further confirmed by transmission electron microscopy. The thermal properties of the nanotube complex as studied by thermal gravimetric analysis (TGA) revealed that coating enhanced stability of the complex, when compared to that of bulk polyHEMA and pristine SWNTs. The nanotube complexes showed excellent suspension stability when dispersed in organic solvent.
Abstract: The raise in clinical significance of multidrug-resistant bacterial pathogens has directed us to synthesize 2,6-diarylpiperidin-4-one and Delta(3)-tetrahydropyridin-4-ol based benzimidazole and O-arylsulfonyl derivatives. X-ray crystal structure of tetrahydropyridinol (23) confirmed a change in conformation and orientation of substituents upon amide formation. Antibacterial activities evaluated against a wide number of bacterial pathogens (both sensitive and multidrug-resistant) revealed that 19, 27 against Staphylococcus aureus, 27 against Enterococcus faecalis, and 19, 21, 23, and 27 against Enterococcus faecium are significantly good at lowest MIC(90) (16 microg/mL). Inhibitory power noticed by 23 against Vancomycin-Linezolid-resistant E. faecalis and 27 against Vancomycin-resistant E. faecium are onefold better than the standard Linezolid and Trovafloxacin drugs, respectively. Moreover, antitubercular activity for the selected compounds against Mycobacterium tuberculosis H37Rv revealed that compounds 23, 24, and 27 expressed onefold improved potency compared to the standard Rifampicin drug.
Abstract: In the title compound, C21H25NO3, the piperidinone ring adopts a chair conformation with an equatorial orientation of all substituents; the 3-methoxyphenyl groups make a dihedral angle of 60.26 (15)°. The carbonyl group O atom is disordered over two positions in a 0.643 (3):0.357 (3) ratio. The crystal structure is stabilized by N-HO and C-HO hydrogen bonding.
Abstract: Abstract
We report a novel method for the immobilization of Tris-(8-hydroxyquinoline) aluminum (Alq3) onto poly(4-vinylpyridine) (P4VP) thin polymer films by UV irradiation cross-linking. The polymer films were prepared by spin-coating of P4VP onto cleaned silicon wafer surface followed by UV irradiation. The thicknesses of the polymer thin films were measured by ellipsometry with different irradiation times. The immobilization of Alq3, orientation and the surface activity were followed using photoluminescence and UVâvisible spectroscopy. The surface morphology was investigated by using field emission scanning electron microscopy and atomic force microscopy. Patterning of Alq3 on P4VP film was obtained using photolithography technique. Our experimental results show that the cross-linked P4VP thin film is a universal surface modifier.
