Surface-modified ZnO Nanoparticles Research Articles

Immobilized silver on surface-modified ZnO nanoparticles: As an efficient catalyst for synthesis of propargylamines in water

Silver nanoparticles were immobilized on ionic liquid modified zinc oxide nanoparticles leading to a ZnO-IL/Ag NPs catalyst, which exhibits high catalytic performance in the synthesis of propargylamines through one-pot three-component condensation reaction of aldehydes, amines, and alkynes in water. The as-prepared catalyst was characterized by ICP-AES, FT-IR, XRD, SEM, and TEM. The catalyst was easily recycled and reused at least five times without significant loss of its catalytic 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.

Surface modified ZnO nanoparticles: structure, photophysics, and its optoelectronic application

Nanostructured ZnO has been synthesized by wet chemical route. Poly(vinylpyrrolidone) is used for stabilization and surface passivation of synthesized nanoparticles, thus tailoring the growth of ZnO at nanoscale. Structural characterization using X-ray diffraction, scanning electron microscopy, high-resolution transmission electron micoroscopy and Fourier transformed infrared spectroscopy of the synthesized nanoparticles confirm the evolution of nanocrystalline ZnO prevailing in hexagonal wurtzite phase. UV–Vis and photoluminescence spectroscopy studies show blue shift phenomenon in the synthesized nanoparticle in contrast to the bulk ZnO furnishing evidence in support of quantum size effect. The nanocomposites of ZnO and poly [9,9-dioctylfluorenyl-2,7-diyl] are prepared and characterized to investigate its luminescent and spectral emission effects. The nanocomposites are then incorporated in light-emitting diodes, and influence of ZnO on the device performance has been explored via electroluminescence, current density evaluation, and corresponding CIE coordinates calculation.

Manufacture of zinc oxide/chiral poly(amide-imide)-functionalized amino acid and thiazole bionanocomposites

In this work, novel optically active poly(amide-imide)/zinc oxide bionanocomposites (PAI/ZnO BNCs) containing l-valine moiety in the main chain were prepared via a simple and inexpensive ultrasonic irradiation process. Chiral PAI was synthesized by direct polycondensation reaction of N,N′-(pyromellitoyl)-bis-valine with 3,5-diamino- N-(thiazol-2-yl)benzamide in the tetrabutyl ammonium bromide/triphenylphosphite as a green solvent system. Due to the high surface energy and the tendency for agglomeration, the surface of ZnO nanoparticles (NPs) was modified with γ-aminopropyltriethoxysilane. PAI/ZnO BNCs containing 4, 8, and 12% of NPs were successfully fabricated through ultrasonic irradiation technique. The obtained BNCs were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis (TGA), x-ray diffraction, ultraviolet–visible spectroscopy, field emission scanning electron microscopy, and transmission electron microscopy (TEM) techniques. TGA data indicated an increase in thermal stability of the BNCs when compared with the pure polymer. From the TEM image of PAI/ZnO BNCs, it can be found that the surface-modified ZnO NPs, with a diametric size of less than 35 nm, are uniformly dispersed in the PAI matrix.

Research on the Lipophilic Degree of Surface Modified ZnO Nanocrystals with Different Morphologies

ZnO nanorods and nanoparticles were successfully modified by NDZ-311w titanate coupling agent. The result of lipophilic degree showed that both ZnO nanocrystals with different morphologies were well lipophilic. Although both values of lipophilic degree firstly became larger and then smaller with the increase of modifier dosage, the different maximal lipophilic degree of ZnO nanorods and nanoparticles could be 68.8% and 77.9%, respectively. By comparing the two curves of lipophilic degree of surface modified ZnO nanocrystals with different morphologies, it could be demonstrated that the optimal dosage of NDZ-311w titanate coupling agent is inversely proportional to the grain size. TEM and XRD results showed that the grain size of ZnO nanoparticles were much smaller than that of ZnO nanorods, which can be the evidence for the equation. Otherwise, the surface modified ZnO nanoparticles displayed better dispersion than unmodified ones.

Visible light-emitting and temperature-sensitive copolymer gel/ZnO nanocomposites loaded with surface-modified ZnO nanoparticles having polyethylene glycol chains

New visible light-emitting and temperature-sensitive poly(VCL-co-SA)/ZnO gel nanocompsites (GNs) 4 loaded with surface-modified ZnO nanoparticles NPs 3 with polyethylene glycol (PEG) chains were successfully prepared by the cross-linking of N-vinylcaprolactam (VCL), sodium acrylate (SA) and tetraethylene glycol dimethacrylate (TEGDM) in the presence of NPs 3. The NPs 3 having nanostructured size were prepared from ZnO NPs 2 with 2-bromo-2-methylpropionyl linkages on the surface, and sodium alcoholate of polyethylene glycol monomethyl ether (PEGME). The NPs 3 and the GNs 4 were characterized by FTIR, UV–vis absorption and photoluminescent (PL) spectroscopies, X-ray analysis measurements, TEM and SEM observations and dynamic light scattering (DLS) measurements. The measurements indicated that the GNs 4 with wurtzite crystal structures based on the ZnO NPs show absorptions and yellow light-emitting properties arising from the NPs 3, except for the GNs 4 containing a high weight % of NPs 3. The size of the GNs 4 drastically decreased with increasing temperature in the range of 20–35°C, probably because of the induction of steric hindrance and enhancement of hydrophilic PEG chain concentrations inside the GN networks 4.

Preparation and characterization of UV-cured polyurethane acrylate/ZnO nanocomposite films based on surface modified ZnO

A series of polyurethane acrylate (PUA)/ZnO nanocomposite films with different ZnO contents were prepared via a UV-curing system. To ensure good dispersion in the PUA matrix, ZnO nanoparticles were modified with a silane coupling agent and confirmed by FT-IR analysis. The morphological structures, thermal properties, mechanical properties and water transfer properties of the prepared films were investigated as a function of their ZnO concentration. WAXD and SEM analyses showed that the surface-modified ZnO nanoparticles were homogeneously dispersed in the PUA matrix and the molecular ordering increased with increasing ZnO content. Compared with neat PUA, the hardness and elastic modulus in films increased from 0.03 to 0.056GPa and from 2.75 to 3.55GPa, respectively. Additionally, the water uptake and WVTR in the PUA/ZnO nanocomposite films decreased as the ZnO content nanoparticles increased, which may come from enhanced molecular ordering and hydrophobicity in films. UV light below approximately 450nm can be efficiently absorbed by incorporating ZnO nanoparticles into a PUA matrix, indicating that these composite films exhibit good weather ability and UV-shielding effects. The enhanced physical properties achieved by incorporating modified ZnO nanoparticles can be advantageous in various applications, whereas the thermal stability of the composite films should be increased.

Cytotoxicity of surface-modified ZnO nanoparticles in human lung epithelial cells: modified nanoparticles alter biological responses from cell death toward inflammation

Cytotoxicity of surface-modified ZnO nanoparticles in human lung epithelial cells: modified nanoparticles alter biological responses from cell death toward inflammation

New surface-modified zinc oxide nanoparticles with aminotriethylene oxide chains linked by 1,2,3-triazole ring: Preparation, and visible light-emitting and noncytotoxic properties

Novel surface-modified, visible light-emitting and noncytotoxic ZnO nanoparticles (NPs) (ZPAZ) having aminotriethylene oxide chains linked by 1,4- and/or 1,5-disubstituted 1,2,3-triazole rings were prepared from ZnO NPs (ZPA) with ethynyl groups on the surfaces and an azide derivative of triethylene oxide chain linking terminal amino group (ATA) via 1,3-dipolar azide/alkyne click reaction by heating without Cu(I) catalyst. FTIR spectroscopy, elemental analysis, XRD analysis and TEM observation suggested that the resulting ZPA and ZPAZ NPs have the particle sizes below 10nm in diameters, triethylene oxide chains linking the terminal amino groups and wurtzite crystal structure. UV–vis absorption spectrum of the ZPAZ NPs in methanol showed maximum absorption band at 346.5nm, supporting the TEM observation. PL spectra depicted that the ZPA and ZPAZ NPs display broad light green and lightly greenish yellow visible light emitting bands in methanol. Zeta potentials measured in distilled water suggested that the ZPAZ NPs have a low tendency to aggregate and possess better stability than the ZPA NPs. Cytotoxicity assay revealed that the ZPAZ NPs, having water-dispersion properties, are noncytotoxic at low concentrations and almost all RAW264.7 cells are alive after 24h of treatment.

Applications of novel dithienothiophene- and 2,7-carbazole-based conjugated polymers with surface-modified ZnO nanoparticles for organic photovoltaic cells

Two kinds of novel conjugated polymers containing 2,7-carbazole, thiophene, and fused-dithienothiophene rings as backbones bearing acid-protected and benzoic acid pendants ( PC1 and PC2, respectively) were utilized for organic solar cell applications. The absorption spectra of these polymers (in both solutions and solid films) showed an absorption range at 300–580 nm. Furthermore, ZnO nanoparticles were synthesized and surface-modified with pyridyl surfactants ( ZnOpy) to be ca. 3–4 nm. The pyridyl surfactants of ZnOpy nanoparticles (as electron acceptors to partially replace expensive electron acceptor PCBM) not only induce supramolecular interactions with benzoic acid pendants of polymer PC2 via H-bonds, but also enhance the homogeneous dispersions of ZnOpy nanoparticles in polymer PC2. Thus, the ternary systems of PC1–PC2/ ZnOpy/PCBM in weight ratios of 1:0.05:1 and 1:0.1:1 were investigated in bulk heterojunction polymer solar cells (PSCs). Under the standard illumination of AM 1.5, 100 mW/cm 2, the best power conversion efficiency (PCE) of the PSC cell containing a polymer blend of PC2/ ZnOpy/PCBM = 1:0.05:1 reached PCE = 0.55%, with J sc = 2.11 mA/cm 2, V oc = 0.88 V, and FF = 29.4%.

Highly Stabilized Monodispersed Citric Acid Capped $\hbox{ZnO:Cu}^{2+}$ Nanoparticles: Synthesis and Characterization for Their Applications in White Light Generation From UV LEDs

Nanophosphors of ZnO:Cu <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> were synthesized by a chemical technique based on coprecipitation method. The synthesized nanophosphors were annealed at different temperatures (100-400°C) in steps of 100°C for 4 h. A reduction in photoluminescence intensity was observed with increase in the annealing temperature. Further, these nanophosphors were capped with citric acid, which results in enhancement in the luminescence intensity. These surface-modified ZnO nanoparticles were found to be remarkably stable. The reduction in luminescence with annealing temperature occurred due to removal of surface defects and intrinsic impurities, while the citric acid reduced the unsaturated bond density and passivated the surface, resulting in reduction in the number of surface trap sites for nonradiative recombination processes to occur, enhancing the luminescence intensity. Currently, LEDs giving UV emission have been combined with broadband visible green phosphors to make white-light LEDs. Thus, green luminescent ZnO:Cu <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> nanoparticles can be seen as necessary and critical constituent for white light generation from UV LEDs, underlying the findings and importance of current investigations. Besides this citric acid capped ZnO:Cu <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> nanophosphors can also be used in biological (drug delivery system, bioimaging, etc.) and biosensors.

Bionanocomposites Preparation and Characterization: Dispersion of Surface-Modified ZnO Nanoparticles in Optically Active Poly(Amide-Imide) Derived from 3,5-Diamino-N-(4-Hydroxyphenyl)Benzamide and Amino Acid

Bionanocomposites (BNCs) containing 4, 8 and 12% (w/w) modified ZnO nanoparticles (NPs) were successfully prepared by homogenous dispersion of these NPs in an optically active poly(amide-imide) (PAI) matrix through an ultrasonic process. PAI was synthesized via solution polycondensation of 3,5-diamino-N-(4-hydroxyphenyl) benzamide and N,N-(pyromellitoyl)-bis-L-phenylalanine diacid chloride at low temperature. The ZnO NPs were treated with γ-aminopropyltriethoxysilane (KH550) as a coupling agent to change the surface property of NPs from hydrophilic to hydrophobic nature for better dispersion in PAI matrix. The obtained BNCs were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray powder diffraction, atomic force microscopy (AFM), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and thermogravimetry analysis. AFM studies of the BNCs suggest that the ZnO NPs of 20–50 nm in diameter were dispersed in polymer matrices. FE-SEM and TEM results also confirmed the formation of well-dispersed nano ZnO in the PAI matrix.

Effects of surface modification on the fluorescence properties of conjugated polymer/ZnO nanocomposites

We report the effects of surface modification on the fluorescence properties of conjugated polymer/zinc oxide nanocomposites. Zinc oxide nanoparticle surface was partially capped by poly(vinylpyrolidone) (PVP) during hydrolysis of zinc acetate dihydrate in methanol in ambient condition. The ZnO-capped nanoparticles were characterized by XRD and TEM. The fluorescence properties of poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV)/ZnO nanocomposites with different mass ratios were studied by steady-state and time-resolved spectroscopy. The results indicate that the surface-modified ZnO nanoparticles are more effective to quench the emission of MEH-PPV by charge transfer process than the non-capped ZnO. The more effective charge transfer in MEH-PPV/ZnO-capped is attributed to the better dispersion of the nanoparticles in MEH-PPV matrix and THF solvent.

Intensified photocatalytic degradation of nitrobenzene by Pickering emulsion of ZnO nanoparticles

In this paper, zinc oxide nanoparticles were first prepared and surface-modified. A Pickering emulsion was then prepared, consisting of nitrobenzene (oil phase), water (water phase) and the modified zinc oxide nanoparticles located on the water–oil interface. The effects of different emulsions on the removal rate of nitrobenzene by photocatalytic degradation were studied. The results proved that use of a Pickering emulsion stabilized by surface-modified ZnO nanoparticles provides an effective and novel way to intensify the photocatalytic degradation of the organic contaminant.

Optical Properties of Composites of PMMA and Surface-Modified Zincite Nanoparticles

Composites that show visible light transmittance, UV absorption, and moderately high refractive index, based on poly(methyl methacrylate) (PMMA) and zinc oxide (zincite, ZnO) nanoparticles, were prepared in two steps. First, surface-modified ZnO nanoparticles with 22 nm average diameter were nucleated by controlled precipitation via acid-catalyzed esterification of zinc acetate dihydrate with pentan-1-ol. The surface of growing crystalline particles was modified with tert-butylphosphonic acid (tBuPO3H2) in situ by monolayer coverage. Particle size and graft density of −PO3H2 on the particle surface were controlled by the amount of surfactant applied to the reaction solution. Second, the surface-modified particles were incorporated into PMMA by in-situ bulk polymerization. Free radical polymerization was carried out in the presence of these particles using AIBN as initiator. Volume fraction (φ) of the particles was varied from 0.10 to 7.76% (0.5 to 30 wt %). Although the particles are homogeneously dispers...

Synthesis and surface modification of ZnO nanoparticles

ZnO precursor was prepared by direct precipitation from zinc acetate and ammonium carbonate. ZnO nanoparticles were synthesized by calcination of the precursor at 450 degrees C for 3 h and the calcination after the heterogeneous azeotropic distillation of the precursor, respectively. The synthesized ZnO nanoparticles were characterized by FT-IR, XRD and TEM. It is concluded that the heterogeneous azeotropic distillation of the precursor effectively reduced the formation of hard agglomerates. The surface modification of synthesized ZnO nanoparticles was conducted by capping with oleic acid, and the existence of organic layer can be confirmed by the FT-IR spectra. The lipophilic degree of surface modified ZnO nanoparticles was measured. The ZnO nanoparticle surface was also modified by SiO2, coating. The FT-IR spectrum and XPS clearly showed the formation of an interfacial chemical bond between ZnO and SiO2. In addition, photocatalytic degradation of methyl orange in aqueous solution was performed using ZnO nanoparticles or ZnO/SiO2 nanoparticles as photocatalyst, respectively. The results showed that the ZnO/SiO2 nanoparticles have reduced catalytic activity than that of ZnO nanoparticles. (c) 2006 Elsevier B.V. All rights reserved.

Random Lasers Based on Organic-Inorganic Hybrids

AbstractLaser action is demonstrated in organic/inorganic nanocomposites consisting of pristine and surface-modified ZnO nanoparticles dispersed in an optically inert polymer matrix. The semiconductor particles feature simultaneously gain behavior and strong scattering ability, whereas the polymer matrix provides better processability and mechanical robustness. When excited by a laser pulse of appropriately short duration (pico- to nanoseconds), the composites give off fluorescence emission, which is strongly amplified as a result of light trapping due to multiple scattering. This laser action is manifested as a dramatic increase in the emitted light intensity accompanied by a significant spectral and temporal narrowing above a threshold value of the pumping laser intensity. Applications may include brighter flat-panel displays, inexpensive lasers for communications, military countermeasures, and lasers for search and rescue operations.

Highly monodisperse polymer-capped ZnO nanoparticles: Preparation and optical properties

We report the preparation of highly monodisperse ZnO nanoparticles using poly(vinyl pyrrolidone) (PVP) as the capping molecules. The surface-modified ZnO nanoparticles were found to be remarkably stable. The optical absorption shows distinct excitonic features. Markedly enhanced near-band-edge ultraviolet photoluminescence and significantly reduced defect-related green emission were also observed. We attribute this observation to the nearly perfect surface passivation of the ZnO nanoparticles by the PVP molecules. The third-order nonlinear optical response of these PVP-capped ZnO nanoparticles in a dilute solution was found to be significantly larger (by at least two orders of magnitude) than that of the bulk ZnO.