Surface-modified ZnO Nanoparticles Research Articles

Image analysis of PDMS/ZnO nanocomposite surfaces for optimized superhydrophobic and self-cleaning surface design

Optimized superhydrophobic and self-cleaning nanocomposite surfaces were obtained by spraying surface modified ZnO nanoparticles (NPs) onto PDMS, using octadecylphosphonic acid and octadecanethiol as hydrophobic modifiers. In this study, it is the first time to our knowledge that surface parameters such as topography, morphology, superhydrophobicity, and self-cleaning are correlated to particle surface distribution and agglomeration parameters obtained by image analysis. The topography, morphology, and wettability of the surfaces were analyzed using atomic force microscopy, scanning electron microscopy, static contact angle (SCA), and contact angle hysteresis measurements. Image analysis was performed using the new enhanced graphical user interface of a previously self-developed Matlab® algorithm. Both hydrophobization methodologies increased the NPs’ surface coverage and the hierarchical rough structure formation on the substrates, resulting in more homogenous superhydrophobic self-cleaning surfaces. A higher coated fraction and lower degree of interconnected uncoated PDMS paths are correlated to an increase in SCA. The combination of a higher agglomerates fraction, lower agglomerate radius, and lower distance between agglomerates obtained for the surfaces with hydrophobized ZnO-NPs rendered self-cleaning surfaces. The observed correlations increase the understanding of the design and modelling of superhydrophobic self-cleaning PDMS/ZnO nanocomposite surfaces for use in high voltage outdoor insulators.

Surface functionalization of ZnO nanoparticles by Schiff base oriented tetrapodal ligands at room temperature and their photocatalytic applications: A comparative account on effect of structure directing agent on photocatalysis

Surface modification of ZnO nanoparticles at room temperature and their photocatalytic activity • Synthesis of surface modified ZnO NPs i.e. P-ZnO, Q-ZnO, R-ZnO and S-ZnO by ligands P , Q , R and S respectively at room temperature of different shape and size. • Photocatalytic efficiency of P-ZnO, Q-ZnO, R-ZnO and S-ZnO towards photocatalytic degradation of Rh B dye in 90 min is ∼92%, 80%, 89% and 79% respectively. • ZnO nanoparticles modified by tetrapodal ligands having urea linker moieties (P-ZnO and R-ZnO) have shown very high photocatalytic degradation (∼89-92%). ZnO is very popular and extremely sought after semiconductor material and more so as in the nanocrystalline form. It is biocompatible having a tunable band gap (3-3.7 eV) at room temperature and popular for several optical properties of interest in many fields. Nanoparticles have a lot of surface defects which affect their stability, properties and applications. We use structure directing agents to control the morphology of ZnO nanoparticles and also to control surface defects. We utilised four Schiff base oriented tetrapodal ligands (P, Q, R and S) as the structure directing agents for synthesis of surface modified ZnO nanoparticles i.e. P-ZnO [nanospheres (50-55 nm)], Q-ZnO [nanorods of length (∼1-2 µm) and breadth (∼130-170 nm)], R-ZnO [fibrous/entangled mesh] and S-ZnO [nanorods of length (30-40 nm) and breadth (5-20 nm)] at room temperature i.e. 30-40°C. The application of P-ZnO, Q-ZnO, R-ZnO and S-ZnO are further explored for photocatalytic degradation of Rhodamine B dye under UV lamp (90 min). The efficiency of P-ZnO, Q-ZnO, R-ZnO and S-ZnO towards photocatalytic degradation of Rhodamine B dye was ∼92%, ∼80%, ∼89% and ∼79% respectively.

Insights into the impact of photophysical processes and defect state evolution on the emission properties of surface-modified ZnO nanoplates for application in photocatalysis and hybrid LEDs.

The effects of surface modification on the defect state densities, optical properties, and photocatalytic and quantum efficiencies of zinc oxide (ZnO) nanoplates were studied in this work. The aim of this study is to identify the photophysical processes that dictate the quenching of emission from defect states upon surface modification and the role of different defects such as zinc interstitials (Zni) or oxygen vacancies (VO) beside the photophysical processes in determining the photocatalytic efficiency of plate-like ZnO nanostructures. For controlling the intrinsic defect state densities of ZnO nanoplates, which is difficult to achieve, their surface was modified using different polymers such as PMMA and PVA. X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL) emission spectroscopy were employed to identify and quantify the defect states. The analysis of relative defect state densities of Zni or VO showed that Zni significantly impacts the photocatalytic activity (PCA) besides VO, but it has a lower influence than VO because of the difference in the accessibility and intrinsic nature of these two defects. Synchronous quenching of emission from different defect states with different formation energies and its correlation with the photocatalytic activity led us to conclude that photophysical processes such as concentration-dependent Förster resonance energy transfer (FRET), charge transfer (CT) and Zni defects play a significant role behind PCA, which has been previously reported to be influenced by VO only. FRET and CT also play a critical role behind emission quenching upon surface modification. Upon the surface modification of nanoplates, a drop in the quantum efficiency from 12.14% to 4.44% was observed with the fine-tuning of emission colour from bluish-white to blue. Besides the defect states, FRET and CT phenomena are dominant in reducing the quantum efficiency of hybrid light-emitting diodes (HyLEDs) and photocatalytic efficiency. Therefore, the work outlines the reason behind the suppression of luminescence and photocatalytic efficiency of ZnO nanoparticles after surface modification and how to optimise them for their applications as an emissive layer in HyLEDs and efficient photocatalysts.

Preparation and characterization of polyacrylate composite and its application in superhydrophobic coating based on silicone-modified ZnO

In this paper, a kind of silicone containing double bond and hydrogen bond has been synthesized via telomerization. In order to disperse and incorporate ZnO into the polymer matrix, ZnO was modified with silicone. Finally, ZnO/polyacrylate and silicone/polyacrylate composites were prepared using modified ZnO and silicone. The present study reports synthesis and characterization of ZnO/polyacrylate and silicone/polyacrylate nanocomposites by in situ emulsion polymerization. The effects of ZnO and silicone on the morphological structure and thermal properties of composites were systematically studied. The composites were characterized using FTIR, XRD, SEM, TEM, TGA, particle size analysis, UV, and WCA. It could be seen that the thermal degradation temperature of the composites increased significantly with the addition of ZnO and silicone. SEM analysis showed that the films were evenly distributed with the surface-modified ZnO nanoparticles. Then, the modified ZnO/polyacrylate superhydrophobic composite coating was prepared using modified ZnO and silicone/polyacrylate emulsion. The coating has excellent self-cleaning and oil–water separation properties.

Enhanced photocatalytic decolorization of Congo red dye with surface-modified zinc oxide using copper(II)–amino acid complex

Photocatalytic decolorization of Congo red dye has been investigated using surface-modified ZnO nanoparticles by adsorbing copper(glycinato) complex on the surface of nanosized ZnO. The complex-adsorbed photocatalyst is shown to exhibit enhanced photodecolorization of the dye compared to the pure ZnO nanoparticles. Effect of catalyst dose, initial dye concentration, and role of H2O2 as oxidizing agent has been studied in order to optimize the condition for efficient decolorization. The nanosized ZnO was prepared by precipitation method onto which the amino acid complex was adsorbed. The synthesized catalysts were characterized by XRD, UV, FTIR, SEM, and EDAX. Comparative evaluation of photodecolorization of the dye was investigated for both the nanosized ZnO and the complex-adsorbed ZnO nanoparticles under optimized conditions.

Effect of modified ZnO on electrical properties of PP/SEBS nanocomposites for HVDC cables

Polypropylene (PP) has the potential to be used as insulation for high voltage direct current cables due to its high melting point, excellent recyclability and electrical insulation properties. The PP/SEBS composites filled with surface-modified ZnO (m-ZnO) nanoparticles were fabricated through melt blending. Scanning electron microscopy (SEM) showed that the m-ZnO nanoparticles were well dispersed in the PP/SEBS matrix. With doping of 0.5 wt% m-ZnO, the DC breakdown strength, space charge suppression and mechanical properties of the PP/SEBS were remarkably improved, and their DC conductivity was found to be lowered. Moreover, the incorporation of m-ZnO has little effect on the melting and crystallization process as well as dielectric properties of the PP/SEBS. Thus, the PP/SEBS/m-ZnO composites have shown promise to be used as insulation for recyclable HVDC cables.

Performance analysis of the solidification of acrylic esters photo-initiated by systematically modified ZnO nanoparticles

Photo-induced polymerization by nanomaterials and their analyses are challenging topics with combines multiple fields of research. The first one, the preparation/characterization of surface modified ZnO nanoparticles is by far the most obvious one. Photosensitive semiconductors can lead to a replacement of migrating initiators by non-migrating nanoscaled photo-initiators (NanoPI) for radical polymerization. The class of NanoPI is especially promising to be applicable in printing/coating applications to result in organic inorganic hybrid materials and to reduce health risks by reducing/preventing contamination of the surroundings by gas-phase transfer, by diffusion of reacted/remaining compounds (migration) and so on. The polymer related area of the research (analysis of the kinetic) is the main part of the discussion within this contribution. The reactivity of the particles to initiate free-radical polymerization of bulk printable resin mixtures (the performance of the curing) is proven for LED@365 nm and simulated LED illumination. Finally, the novel kinetic analysis method, the transmission UV-vis solidification is explained in detail within the present manuscript.

The effects of poly(amide-imide) coating on the thermal, combustion and mechanical properties of polyvinyl chloride ZnO nanocomposites

The surface of new polyvinyl chloride (PVC)/ZnO nanocomposite films was coated using semi-aromatic synthesized poly(amide-imide) (PAI) by dip-coating process. ZnO nanoparticles were organo-modified with imide functionalized polyethyleneimine (PEI) and were used for preparation of PVC nanocomposite films by solution casting method. The effect of PAI coating along with PEI surface modified ZnO nanoparticles (PSZN) on the morphology, thermal stability, combustion and mechanical properties of PVC were investigated. The uniform dispersion of ZnO nanoparticles and PAI coating manner on surface of the PVC films were confirmed by ATR-FTIR spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray and elemental mapping. From thermal gravimetry analysis (TGA) results, the 10 mass% loss temperature (T10) increased from 229 °C to 244 °C in PVC-coated with PAI containing 2 mass% of PSZN and also char residue of PVC increase from 10.5 to 28.9% in PVC-coated contaning 5 mass% of PSZN. According to microscale combustion calorimetry (MCC) and tensile test results, the peak of heat release rate decreased from 129.8 W/g to 81.2 W/g and the tensile strength increased from 28.7 to 43.6 MPa for PVC-coated containing 5 mass% of PSZN compared to the neat PVC.

Design and synthesis of imine linked ZnO nanoparticles functionalized with Al(III), candidate for application in light emitting diodes

Zinc oxide nanoparticles 1.ZnO decorated with dipodal organic receptor 1 bearing imine linkage were synthesized using wet chemical precipitation technique. The imine linked receptor 1 used as capping agent was synthesized using condensation reaction. 1.ZnO nanoparticles were characterized through FTIR, SEM, TEM, DLS and fluorescence spectroscopy. The emission spectra of surface modified ZnO nanoparticles authenticated the passivation of surface defects and dangling bonds which otherwise are available on the surface of uncapped ZnO nanoparticles. 1.ZnO nanoparticles demonstrated blue emission at 461 nm. The binding affinity of 1.ZnO nanoparticles was also checked in presence of metal ions through changes observed in the emission spectra. An enhancement up to threefold in the fluorescence intensity was achieved from 1.ZnO nanoparticles upon coordination with Al3+ metal ion. The results demonstrated that our design strategy resulted in pure and narrow emission with FWHM 70 nm. This effective way of achieving the selectivity factor and enhanced quantum yield can be utilized in electronic device like light emitting diodes.

Band gap engineering and photoluminescence studies of imine linked ZnO nanoparticles synthesized by direct precipitation route

An imine linked dipodal organic receptor 1 is synthesized using condensation reaction between 2-aminothiophenol and 4-diethylaminosalicylaldehyde which is used as a capping agent over ZnO resulting in surface modified ZnO nanoparticles 1.ZnO. The conjugate 1.ZnO shows emission at 420 nm. The emission spectra obtained from surface modified ZnO nanoparticles is pure and sharp with full width half maximum (FWHM) 60 nm in comparison to emission spectra of pure ZnO which shows emission at 434 nm, 456 nm and 520 nm. It is demonstrated that organic receptor 1 acted as a capping monolayer over ZnO semiconductor as the surface defects that otherwise resulted in electronic transitions has not shown emission at various wavelengths in visible range. Thus the capping agent has successfully passivated the ZnO nanoparticles. The synthesized 1.ZnO nanoparticles can be used in active layer of light emitting diode providing blue emission at 420 nm.

Suppression of elevated temperature space charge accumulation in polypropylene/elastomer blends by deep traps induced by surface-modified ZnO nanoparticles

Space charge accumulation is a critical issue for the deterioration of the elevated temperature insulating property of polymeric materials. We present the influence of surface-modified ZnO nanoparticles on the space charge distribution and direct current (DC) resistivity of polypropylene (PP)/elastomer blends under elevated temperature. Octyltrimethoxysilane, a silane coupling agent, was used for the surface modification of nanoparticles. Morphology characterization results indicated that the elastomer and coated ZnO were well dispersed in the PP matrix. It was observed that the coated ZnO can significantly improve the insulating properties, including a minimized electric field distortion (4.0%) and increased DC volume resistivity (1.41 × 1018 Ω m) under an electric field of 40 kV/mm and 70 °C. The DC resistivity of 2 phr PP/elastomer/ZnO ternary composites was improved by 13.4 times compared with that of pure PP/elastomer blends. The suppression of space charges may originate from deep traps existing in spherulite boundaries and interfacial zones between polypropylene and ZnO. This work provides an effective method to endow a recyclable insulating material with outstanding elevated temperature insulating performances.

Optical, thermal and combustion properties of self-colored polyamide nanocomposites reinforced with azo dye surface modified ZnO nanoparticles

New self-colored aromatic-polyamide (PA) nanocomposites containing azo and naphthalene chromophores were prepared with azo-dye surface-modified ZnO nanoparticles (SMZnO) using solution method in dimethylformamide. The X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) results showed the uniform distribution for ZnO nanoparticles in the PA matrix. The UV–vis spectra of PA/ZnO nanocomposites (PANC) showed a blue shift as well as reduction in absorbance intensities and the photoluminescence studies revealed that the increasing intensities of the violet emission in SMZnO loading. From thermo gravimetric analysis (TGA), the temperature at 10% mass loss (T10) increased from 291.8°C to 387.6°C for PANC containing 8 mass% of SMZnO, as well as the char yield enhanced significantly, which was about 23.5% higher than the neat PA. The peak heat release rate resulted from microscale combustion calorimeter (MCC), by 8 mass% loading of SMZnO, decreased about 56.9% lower than the neat PA.

Synthesis and investigation of photonic properties of surface modified ZnO nanoparticles with imine linked receptor as coupling agent- for application in LEDs

Wet chemical precipitation route is developed for the synthesis of ZnO nanoparticles using a dipodal receptor as capping agent to control the size and shape of ZnO nanoparticles and also to passivate the surface defects. The capping of ZnO nanoparticles with dipodal receptor is characterized with NMR and IR spectroscopy. EDX analyses also confirmed the presence of organic receptors together with ZnO nanoparticles. The morphology and size of surface modified ZnO nanoparticles is checked by SEM, TEM and DLS spectroscopic techniques. The surface decorated ZnO nanoparticles demonstrate emission peak at 333 nm. The emission peak at 333 nm in case of surface capped ZnO demonstrate fewer surface defects present in comparison to their bulk counterpart, where blue, red, green, yellowish green emission peaks are present. The photophysical studies of ZnO nanoparticles are further carried in presence of metal ions where it is observed that the binding with Mn(II) result in increase in fluorescence intensity. The three fold increase in fluorescence intensity of ZnO nanoparticles in presence of Mn(II) can be utilized in case of lighting devices, where high quantum yield is desirable. To the best of our knowledge, this manuscript represents the first surface decorated ZnO nanoparticles for their application in lighting devices.

Effect of Particle Concentration on Tribological Properties of ZnO Nanofluids

ABSTRACTIn this research, oleic acid surface-modified ZnO nanoparticles were successfully dispersed into 60SN base oil. The distribution of ZnO nanoparticles in the lubricant was tested by transmission electron microscopy. The friction and wear properties of nanofluids were evaluated with a four-ball tester, and the morphologies of wear scars were measured by a scanning electron microscope (SEM) and a surface profiler. Results show that oleic acid can improve the stability of ZnO nanoparticles in the lubricant; oil-based nanofluids with ZnO nanoparticles could remarkably reduce friction and wear. When the amount of oleic acid added was 8 wt% and ZnO nanoparticles was 0.5 wt%, the coefficient of friction and average diameter of the wear scars were minimum and the fluid exhibited better friction-reducing and antiwear properties.

Biopolymers nanocomposite for material protection: Enhancement of corrosion protection using waterborne polyurethane nanocomposite coatings

Abstract Low volatile organic content based, cost effective and simple procedural nanocomposite coatings were prepared by solution blending technique. Waterborne polyurethane dispersion containing nanoparticles of ZnO, modified with biopolymers were successfully prepared and the resulting nanocomposites were coated on mild steel. The coatings with different loading levels of nano ZnO, which was modified with biopolymers of sodium alginate and lignosulfonate were prepared via ultrasonication method. Surface morphology of these nanomaterials were characterized by scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM); crystallinity by X-ray Diffraction (XRD) analysis. The effect of incorporating surface modified ZnO nanoparticles on the corrosion resistance of waterborne polyurethane coated steel was investigated by potentiodynamic polarization and electrochemical impedance spectroscopy. Also the surface wettability of the composite coating, studied through contact angle suggested that increase in dosages of nanomaterials does not affect the surface wettability of the coating. The results revealed that the increasing percentage of surface modified ZnO in waterborne polyurethane not only promotes the dispersion of the particles but also improves the corrosion performance of nanocomposite coatings. Corrosion results from Tafel plot and impedance analysis showed that the 0.3 wt% loading of ZnO surface modified with lignosulfonate gives better protection than sodium alginate.

Fabrication of Langmuir-Blodgett Film of Surface-Modified ZnO Nanoparticles Prepared by Solution Process

Fabrication of Langmuir-Blodgett Film of Surface-Modified ZnO Nanoparticles Prepared by Solution Process

Surface plasmon enhanced near-UV emission in monodispersed ZnO:Ag core–shell type nanoparticles synthesized by a wet chemical method

Monodispersed core–shell type ZnO:Ag nanoparticles were synthesized by a wet chemical method and their salient properties were reported. The synthesis technique explores a facile route following a chemical reaction between aqueous solutions of poly-vinyl alcohol (PVA), sucrose and Zn2+ salt. The Zn2+-PVA-sucrose polymer precursor powders so obtained after the reaction was further explored for the synthesis of ZnO:Ag nanoparticles. The key part of the process lies in the use of polymer encapsulated ZnO nanoparticles as templates to obtain the ZnO core-Ag shell type nanostructures. Structural, morphological and optical properties of the derived ZnO:Ag core–shell nanoparticles were evaluated with X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), high resolution transmission electron microscope (HRTEM), Raman spectroscopy, UV–visible diffuse reflectance spectroscopy, and photoluminescence (PL) spectroscopy. Microstructural analysis revealed monodispersed platelet shaped ZnO nanoparticles with a thin layer of Ag coating on the surface. The surface modified ZnO nanoparticles show colossal enhancement in their near-UV emission characteristics, primarily due to the efficient excitation of surface plasmons and excellent semiconductor-metal interfacing in the ZnO:Ag nanoparticles.

Investigation of optical properties of mixed ligand directed ZnO luminescent nanoparticles for application in light emitting diodes

Developing the heavy metal free QD-LEDs is required to curtail the risks to human beings and environment. Nanoparticles that are ecofriendly, chemically stable, easy to synthesize, nontoxic, biocompatible too are the preferred one. ZnO are biocompatible and low cost semiconductor nanoparticles with tunable band gap and large excitonic binding energy, which make them suitable for LED applications. To achieve the same purpose, this research work is focused on the synthesis of surface modified ZnO nanoparticles for their application in light emitting diodes. The condensation reaction is used to synthesize the ligand and wet chemical precipitation method is used to synthesize surface modified ZnO nanoparticles. The optical properties are evaluated using UV–Vis absorption and fluorescence studies. The optical properties are also investigated in the presence of metal ions and an increased band gap is achieved when Fe3+ ion is added to organic receptor coated ZnO nanoparticles. The stability of ZnO coupled receptor is confirmed theoretically using density functional theory.

Highly dispersive waterborne polyurethane/ZnO nanocomposites for corrosion protection

The interfacial interactions between surface-modified zinc oxide with oleic acid (OA-ZnO) and polymer matrix have important effects on the properties of nanocomposites. This zinc oxide nanoparticle was synthesized and characterized by various techniques such as field emission scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. The water contact angle of waterborne polyurethane (WPU) nanocomposites is found to be increased with the addition of OA-ZnO compared with pure WPU. The corrosion protection of the polyurethane nanocomposites coatings on mild steel was assessed by potentiodynamic polarization and electrochemical impedance spectroscopy techniques. Coating with OA-ZnO in the WPU matrix showed the enhancement of resistance of mild steel to corrosion. This can be related to the surface modification by oleic acid which enhances the dispersion of nano-ZnO and improves the corrosion resistance of the WPU coating. Compared with unmodified ZnO nanoparticles, there were noticeable improvements in the hydrophobicity, corrosion protection, and uniform dispersion without agglomeration, and also improvement in the antisettling behavior when surface-modified ZnO nanoparticles with oleic acid (OA-ZnO) were used.

Surface modification of ZnO nano-particles with Trimetoxyvinyl Silane and Oleic Acid and studying their dispersion in organic media

Zinc oxide nano-particles with the average diameter of about 25 nm were modified with different mole ratios of trimetoxyvinyl silane (TMVS) and oleic acid, as coupling agents, in order to modify their surface properties and render them more hydrophobic. Then, dispersibility of the surface modified nano-particles was examined in some monomers with different levels of hydrophobicity, including methyl methacrylate (MMA), butylacrylate (BuA), and styrene with low, medium and high hydrophobicity, respectively. The modified ZnO nanoparticles were characterized using elemental analysis (EA), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) and scanning electron microscopy (SEM). Findings revealed that the surface modified ZnO nano-particles were more dispersible in the examined organic media indicating better compatibility. TMVS behaved more efficient than Oleic acid, as coupling agent, to make compatibility with MMA; Whereas, ZnO modified with oleic acid exerted more compatibility with styrene. The mixed coupling agent (50/50 Wt% TMVS/oleic acid) showed better compatibility with BuA.