This paper presents our results on the successful fabrication of HCl‐doped polyaniline (PANI)/ZnO nanocomposites via an electrochemical synthesis route. Different weight percents of ZnO nanoparticles were uniformly dispersed in the PANI matrix. The interaction between the dispersed ZnO nanoparticle and PANI was studied using X‐ray diffraction, ultraviolet–visible absorption spectroscopy, photoluminescence (PL) spectroscopy, X‐ray photoelectron spectroscopy, atomic force microscopy, thermogravimetry, and transmission electron microscopy. It is shown that the doping state of the PANI/ZnO nanocomposite is highly improved as compared to that of PANI. The dispersed PANI/ZnO nanocomposites exhibit enhanced PL behavior and thermal stability. 相似文献
Fluorescent dyes are commonly conjugated to nanomaterials for imaging applications using stochastic synthesis conditions that result in a Poisson distribution of dye/particle ratios and therefore a broad range of photophysical and biodistribution properties. We report the isolation and characterization of generation 5 poly(amidoamine) (G5 PAMAM) dendrimer samples containing 1, 2, 3, and 4 fluorescein (FC) or 6‐carboxytetramethylrhodamine succinimidyl ester (TAMRA) dyes per polymer particle. For the fluorescein case, this was achieved by stochastically functionalizing dendrimer with a cyclooctyne “click” ligand, separation into sample containing precisely defined “click” ligand/particle ratios using reverse‐phase high performance liquid chromatography (RP‐HPLC), followed by reaction with excess azide‐functionalized fluorescein dye. For the TAMRA samples, stochastically functionalized dendrimer was directly separated into precise dye/particle ratios using RP‐HPLC. These materials were characterized using 1H and 19F NMR spectroscopy, RP‐HPLC, UV/Vis and fluorescence spectroscopy, lifetime measurements, and MALDI. 相似文献
Gold-dendrimer nanocomposites are prepared in aqueous solutions in the presence of poly(amidoamine)dendrimers (PAMAM) (generation 3 and 5) or poly(propyleneimine)dendrimers (PPI) (generation 3 and 4) by wet chemical NaBH(4) method. Thus prepared gold-dendrimer nanocomposites are irradiated by laser at 532 nm. UV-vis absorption spectroscopy and transmission electron microscopy reveal that the gold nanoparticles grow with the laser irradiation time as well as the fluence of the laser; in particular, the gold nanoparticles prepared at lower concentrations of PAMAM dendrimer as well as lower generations of PAMAM grow significantly. On the other hand, in the case of PPI dendrimers, the gold nanoparticles hardly grow by irradiation. In addition, dynamic light-scattering measurements show that the laser irradiation markedly promotes the association of the gold-PAMAM G3 dendrimer nanocomposites compared to that of the gold-PAMAM G5 dendrimer nanocomposites, while the sizes of association for the gold-PPI G3, G4 dendrimer nanocomposites hardly change by laser irradiation. 相似文献
The gamma irradiation method has provided a route for synthesis of highly water-soluble, good-quality luminescent CdS/dendrimer
nanocomposites with amino- or carboxyl-terminated PAMAM dendrimer. An attempt has been made to probe ascorbic acid with the
as-synthesized CdS/dendrimer nanocomposites (DNC). Ascorbic acid (AA) is an important biological antioxidant and marker for
different diseases in clinical chemistry as well as in quality control in the food industry. Micromolar concentrations of
AA significantly quenched the photoluminescence (PL) of both amino (–NH2) and carboxylic (–COOH) functionalized semiconductor nanocomposites. The quenching followed a linear Stern–Volmer equation
and time-resolved photoluminescence spectroscopy confirmed its static nature. A strong size dependence of the quenching pattern
was observed. The binding constants, and the corresponding thermodynamic parameters ΔGθ, ΔHθ, ΔSθ at different temperatures were calculated. CdS DNC showed selectivity towards ascorbic acid even in the presence of possible
interfering molecules, such as uric acid, tartaric acid and citric acid. Nanocomposites-based assay techniques could override
the complications involved in multitudes of assay procedures, providing a simple and fast new strategy for the quantification
of Ascorbic acid in the range of 16.6 to 100 μM (R = 0.998, n = 9). The proposed method was applied to the detection of ascorbic acid in Vitamin C tablets with satisfactory results. 相似文献
An Fe3O4/C nanocomposite was synthesized in a microwave‐assisted hydrothermal reaction. This green wet‐chemical approach is simple, low‐cost, and ideal for large‐scale production. The resulting composite material was characterized by transmission electron microscopy, powder X‐ray diffraction, energy‐dispersive X‐ray spectroscopy, Brunauer–Emmett–Teller analysis, X‐ray photoelectron spectroscopy, vibrating sample magnetometry, and UV/Vis spectroscopy. The product possesses porous structures and exhibits superparamagnetic behavior. Interestingly, its functional groups were inherited from the starting materials. This hydrophilic and biocompatible nanocomposite may find applications in catalysis, separation, adsorption, and bionanotechnology. 相似文献
Summary: A low‐density polyethylene (LDPE)/millable polyurethane (PU)/organoclay ternary nanocomposite was successfully prepared. The nanocomposites were characterized by X‐ray diffraction (XRD) and transmission electron microscopy (TEM). The nanocomposites, as evidenced by XRD, are intercalated. The heat shrinkable behavior of the nanocomposites, as well as their pristine counterparts, was studied. It was observed that heat shrinkability decreases with increased filler content. The tensile strength and the tensile modulus of the nanocomposites are higher than their pristine counterparts.
The heat shrinkability of the unfilled LDPE/millable PU blend is highest and it decreases with increased nanofiller content. 相似文献
Summary: Poly(propylene)/monoalkylimidazolium‐modified montmorillonite (PP/IMMT) nanocomposites were prepared by in situ intercalative polymerization of propylene with TiCl4/MgCl2/MMT catalyst. The PP synthesized possessed high isotacticity and molecular weight. Both wide‐angle X‐ray diffraction (XRD) and transmission electron microscopy (TEM) examinations evidenced the nanocomposite formation with exfoliated MMT homogeneously distributed in the PP matrix. A thermal stability study revealed that the nanocomposites possess good thermal stability.
X‐ray diffraction patterns of PP/IMMT (MMT = 2.2 wt.‐%) nanocomposite before and after processing. 相似文献
In this work, we have employed a suite of complementary analytical techniques to shed light on the nanocomposite structures formed during gold nanoparticles (AuNPs) synthesis in the presence of poly(amidoamine) (PAMAM) dendrimers. Nanocomposites of AuNPs and either fourth or eighth generation amine-terminated PAMAM dendrimers (G4 or G8) were prepared. The size distributions of AuNPs and the nanocomposites were determined by transmission electron microscopy. Atomic force microscopy phase imaging and neutral impact collision ion scattering spectroscopy (NICISS) were utilized for the first time to investigate and compare nanocomposite structures formed from G4 and G8. Our results suggest that G4 stabilized the AuNP by capping the AuNP particle surface but that a certain fraction of the gold surface was still barely covered. In contrast, the metal nanoparticle surface was completely covered by G8. In addition, NICISS results provided evidence that nanocomposites deformed when being deposited directly onto a substrate. 相似文献
Interactions between poly(amidoamine) dendrimer (PAMAM)-gold nanocomposites and alkanethiols and between the former nanocomposites and thiol-modified poly(amidoamine) dendrons in ethyl acetate were investigated by adding alkanethiols, such as 1-propanethiol and 1,3-propanedithiol, and thiol-modified poly(amidoamine) dendrons, generations 0.5 and 2.5 (G0.5-SH and G2.5-SH). The PAMAM dendrimers with surface methyl ester groups used were generations 1.5 and 5.5 (G1.5 and G5.5). The mean particle sizes of PAMAM-gold nanocomposites were about 2.1 for G1.5 and 2.4 nm for G5.5. In both nanocomposite systems where 1-propanethiol and 1,3-propanedithiol were added, the mean particle size was about 4 nm, twice that of the systems where these thiols were not added. Increasing the addition of 1,3-propanedithiol made the average particle size smaller for both nanocomposites systems. To compare with alkanethiol, thiol-modified poly(amidoamine) dendron with a highly branched structure on one side was synthesized. Using G2.5-SH as a protective agent, dendron-gold nanocomposites with mean diameters of 3 to 4 nm were obtained. The difference in particle size was seen only when the combination of PAMAM-gold nanocomposites and thiol-modified dendron was less sterically dense, modified dendron (G0.5-SH). The mechanisms for morphology changes in the dendrimer-gold nanocomposites by the addition of these thiols are discussed. 相似文献
In this article, a detailed electrochemical study of a novel 6‐ferrocenylhexanethiol (HS(CH2)6Fc) self‐assembled multiwalled carbon nanotubes‐Au nanoparticles (MWNTs/Au NPs) composite film was demonstrated. MWNTs/Au NPs were prepared by one‐step in situ synthesis using linear polyethyleneimine (PEI) as bifunctionalizing agent. HS(CH2)6Fc, which acted as the redox mediator, was self‐assembled to MWNTs/Au NPs via Au‐S bond. Transmission electron microscopy (TEM), energy‐dispersive X‐ray analysis (EDX), Fourier transformed infrared absorption spectroscopy (FT‐IR), UV‐visible absorption spectroscopy, and cyclic voltammetry were used to characterize the properties of the MWNTs/Au NPs/HS(CH2)6Fc nanocomposite. The preparation of the nanocomposite was very simple and effectively prevented the leakage of the HS(CH2)6Fc mediator during measurements. The electrooxidation of AA could be catalyzed by Fc/Fc+ couple as a mediator and had a higher electrochemical response due to the unique performance of MWNTs/Au NPs. The nanocomposite modified electrode exhibited excellent catalytic efficiency, high sensitivity, good stability, fast response (within 3 s) and low detection limit toward the oxidation of AA at a lower potential. 相似文献
Highly ordered mesoporous molecular sieves AlMCM‐41 and a new NiO/AlMCM‐41 nanocomposite were synthesized using a sol–gel method. Fourier transform infrared (FT‐IR) spectroscopy, X‐ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X‐ray spectroscopy (EDX), and N2 adsorption desorption analyses were used to examine the structure, morphology, size and phase composition of the synthesized NiO/AlMCM‐41 nanocomposites. AlMCM‐41 embedded with NiO nanoparticles was subsequently prepared using different nickel loadings in a direct synthetic route. The results show the successful deposition of NiO nanoparticles onto the framework of AlMCM‐41. AlMCM‐41 provides enormous benefits such as environmentally safe, economic viability and porosity when used as support for NiO nanoparticles. The excellent catalytic activities of AlMCM‐41 and NiO/AlMCM‐41 were investigated for the reduction of nitrophenols (4‐NP, 2‐NP) to aminophenols (4‐AP, 2‐AP) in water at ambient temperature. The best observed performance of reduction of NP with 100% conversion into analogous amino derivatives occurred within 6 min with an estimated rate constant of 0.46 min?1. The efficiency of reduction was observed to increase as a function of NiO enrichment. The NiO/AlMCM‐41 nanocomposite could be recycled and reused up to five times without noticeable change in its structure and activity. These properties make NiO/AlMCM‐41 nanocomposite an ideal platform to study various heterogeneous catalytic processes which can have application in purification, catalysis, sensing devices, and green chemistry. 相似文献
Protein-resistant films derived from the fifth-generation poly(amidoamine) dendrimers (PAMAM G5) functionalized with oligo(ethylene glycol) (OEG) derivatives consisting of various ethylene glycol units (EG(n), n = 3, 4, and 6) were prepared on the self-assembled monolayers (SAMs) of 11-mercaptoundecanoic acid (MUA) on gold substrates. The resulting films were characterized by ellipsometry, contact angle goniometry, and X-ray photoelectron spectroscopy (XPS). About 35% of the peripheral amines of the dendrimers were reacted with N-hydroxysuccinimide-terminated EG(n) derivatives (NHS-EG(n)). The dendrimer films showed improved stability over octadecanethiolate SAMs on gold in hot solvents, attributed to the formation of multiple amide bonds per PAMAM unit with underlying NHS-activated MUA monolayer. The EG(n)-attached PAMAM surfaces with n = 3 reduced the adsorption of fibrinogen to approximately 20% monolayer, whereas 2-3% for n = 4 or 6. The dendrimer films with various densities of EG(n) molecules on PAMAM surfaces were prepared by immersion of the NHS-terminated MUA-functionalized gold substrates in ethanolic solutions containing PAMAM and NHS-EG(n) of various mole ratios. The density (r) of the EG(n) molecules on the PAMAM surfaces is consistent with the mole ratio (r') of NHS-EG(n)/free amine of PAMAM in solutions. The resistance to protein adsorption of the resulting surfaces is correlated with the surface density and the length of the EG chains. At their respective r, the EG(n)-modified dendrimer films resisted approximately 95% adsorption of fibrinogen on gold surfaces. Finally, the specific binding of avidin to the approximately 5% and approximately 40% biotinylated EG3 dendrimers (surface density of biotin with respect to the total number of terminal amino groups on PAMAM G5) gave rise to about 50% and 100% surface coverage by avidin, respectively. 相似文献
Sulfur doped ZnO/TiO2 nanocomposite photocatalysts were synthesized by a facile sol‐gel method. The structure and properties of catalysts were characterized by X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), UV‐vis diffusive reflectance spectroscopy (DRS) and N2 desorption‐adsorption isotherm. The XRD study showed that TiO2 was anatase phase and there was no obvious difference in crystal composition of various S‐ZnO/TiO2. The XPS study showed that the Zn element exists as ZnO and S atoms form SO2?4. The prepared samples had mesoporosity revealed by N2 desorption‐adsorption isotherm result. The degradation of Rhodamine B dye under visible light irradiation was chosen as probe reaction to evaluate the photocatalytic activity of the ZnO/TiO2 nanocomposite. The commercial TiO2 photocatalyst (Degussa P25) was taken as standard photocatalyst to contrast the prepared different photocatalyst in current work. The improvement of the photocatalytic activity of S‐ZnO/TiO2 composite photocatalyst can be attributed to the suitable energetic positions between ZnO and TiO2, the acidity site caused by sulfur doping and the enlargement of the specific area. S‐3.0ZnO/TiO2 exhibited the highest photocatalytic activity under visible light irradiation after Zn amount was optimized, which was 2.6 times higher than P25. 相似文献