High-resolution Field-emission Scanning Electron Microscopy Research Articles

Surfactant-free CuO mesocrystals with controllable dimensions: green ordered-aggregation-driven synthesis, formation mechanism and their photochemical performances

We have demonstrated the significant evidence on a green synthesis for the ordered-aggregation-driven growth from surfactant-free one-dimensional (1D) CuO nanosubunits into dimension-controlled mesostructures (three-dimensional (3D) mesospindles and two-dimensional (2D) mesoplates) by an additive-free complex–precursor solution route. Structural and morphological evolutions were investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and field-emission scanning electron microscopy (FESEM). The formation of CuO mesostructures here is essentially determined by the characteristic of [Cu(OH)4]2− precursors, and an oriented nanoparticle aggregation with tailoring shapes in different dimensions can be achieved in different concentration of reactants at higher reaction temperature. The 3D “layer-by-layer” growth of mesostructural CuO spindles is successfully synthesized in low concentrations of reagents, while the 2D “shoulder-by-shoulder” growth of mesostructural CuO plates is obtained in high concentrations of reagents. The study is of great importance in the bottom-up assembly of controllable ordering architectures, and offers a good opportunity to understand the fundamental significance for the investigation of the formation mechanism and growth process of surfactant-free CuO mesostructures with controllable aggregation-based behaviours. Additionally, we further demonstrated that such CuO mesocrystals could serve as a potential photocatalyst for the degradation of rhodamine B (RhB) under visible light irradiation in the presence of hydroxide water (H2O2). The results also suggest that these 3D mesostructural CuO spindles exhibit a higher adsorption and photocatalytic degradation of RhB than that of 2D mesostructural CuO plates.

Preparation and thermoelectric properties of multi-walled carbon nanotube/polyaniline hybrid nanocomposites

In this work, a facile strategy for the fabrication of PANI/multi-walled carbon nanotube (MWCNT) nanocomposites without the assistance of a dispersant is introduced. MWCNTs and polyaniline were homogeneously mixed by cryogenic grinding (CG) and then consolidated via Spark Plasma Sintering (SPS). X-ray power diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and field-emission scanning electron microscopy (FESEM) were employed to characterize the as-prepared composites. The XRD results showed that cryogenic grinding can refine the grain size of PANI and induce more dislocations. The FTIR spectra data showed that the peaks of the PANI/MWNT composites displayed a red shift. In the high resolution FESEM image, the layer-by-layer structure and smooth surface can be observed. The thermoelectric properties of the as-prepared nanocomposites were investigated as a function of MWCNT content. The results showed that the electrical conductivity increased remarkably with the increasing MWCNT content, and the maximum power factor was 10.73 × 10−8 W mK−2, higher than pure PANI. Additionally, as the MWNT content increased from 10% to 30%, the electrical conductivity of the PANI/MWNT composite increased from 3.51 S m−1 to 1.59 × 102 S m−1. This work demonstrates a simple and effective method for improving the dispersity of carbon nanotubes and the thermoelectric properties of conducting polymers.

Direct synthesis and characterization of highly ordered cobalt substituted KIT-5 with 3D nanocages for cyclohexene epoxidation

Highly ordered cobalt incorporated KIT-5 silica (Co-KIT-5) with different Co contents and a well-ordered three-dimensional cage type porous structure were prepared for the first time by using Pluronic F127 as structure directing agent at different molar water to hydrochloric acid (nH2O/nHCl) ratio. The amount of Co content in the silica framework of KIT-5 can be finely controlled with a simple adjustment of the nH2O/nHCl ratio as it controls the concentration of the H+ ions in the synthesis gel. It has been found that the nH2O/nHCl ratio of 463 is the best condition to obtain Co-KIT-5 with a high Co content. The obtained materials were characterized by various techniques such as powder X-ray diffraction (XRD), N2 adsorption studies, field emission high resolution scanning electron microscopy (FE-HRSEM), high resolution transmission electron microscopy (HRTEM), ultraviolet–visible diffused reflectance (UV–Vis DRS), electron spin resonance (ESR) and X-ray photoelectron spectroscopy (XPS). Characterization results revealed that Co atom can be introduced in the silica framework without affecting the structural order and the textural parameters of the samples. ESR, XPS and UV–Vis DR spectra confirmed that the Co atoms are indeed occupy the tetrahedral coordination with the silica framework of KIT-5. The catalytic performance of Co-KIT-5 with different Co contents in the cyclohexene epoxidation has been investigated using TBHP/H2O2 as oxidants and acetonitrile as a solvent. Co-KIT-5 exhibited a high catalytic performance with TBHP as oxidant and remained inactive when H2O2 was used. The effect of various reaction parameters such as reaction time, reaction temperature, and reactant feed ratio and oxidant, affecting the catalytic activity of Co-KIT-5 has also been studied. Among the catalysts studied, Co-KIT-5-0.90 was found to be the best catalyst, affording a high conversion of cyclohexene. In addition, the catalyst was found to be highly stable and can be reused several times without affecting its catalytic activity under the optimized reaction conditions.

Synthesis and electrocatalytic properties for p -nitrophenol deduction of nano-scaled M 3 O 4 (M=Fe, Co) products with different shapes

Spinel-structured M3O4 (M=Fe, Co) samples with different shapes were synthesised mainly via a hydrothermal procedure. All Fe3O4 samples were prepared using a one-step process; however, all Co3O4 samples were synthesised via two-step paths, namely their precursors were prepared first then the resultant oxide products were obtained by calcining their precursors at a certain temperature. The samples were characterised by thermogravimetric analysis, X-ray diffraction, transmission electron microscopy, high-resolution electron microscopy and field-emission scanning electron microscopy measurements, respectively. The results showed that plate-, particle- and sphere-like Fe3O4 and sheet-, particle- and tube-like Co3O4 samples were obtained successfully. The electrocatalytic properties of the samples modified on a glassy carbon electrode were investigated, and the results indicated that Fe3O4 and Co3O4 samples with different shapes exhibited different enhanced electrocatalytic activity for p-nitrophenol reduction, and Fe3O4 and Co3O4 nanoparticles all showed the highest elctrocatalytic activity.

Twins in polyhedral 26-facet Cu7S4 cages: Synthesis, characterization and their enhancing photochemical activities

Unusual polyhedral 26-facet Cu(7)S(4) cages wholly exposed with amazingly unique nanotwinned structures as building blocks were successfully synthesized via a facile ethanol-assisted sacrificial Cu(2)O templates approach. Furthermore, a solvent-controlled fabrication of polyhedral copper sulfides (Cu(7)S(4) and CuS) with different stoichiometries and microstructures can be artificially achieved, which is determined by the intrinsic difference of the surface states of Cu(2)O templates. Structural and morphological evolutions were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and field-emission scanning electron microscopy (FESEM). Stoichiometric-dependent characteristics were demonstrated in the UV-vis absorption investigations. The as-prepared Cu(7)S(4) microcages exhibit higher photocatalytic activity for enhancing degradation of methylene blue, which might be attributed to their special nanotwinned building blocks. This study is of great importance in "bottom-up" assembly of unusual ordering hollow copper sulfides superstructures, but also offers a good opportunity to understand the fundamental significance of nanotwinned structures for their potential applications.

Bottom-up assembly of hierarchical Cu2O nanospheres: controllable synthesis, formation mechanism and enhanced photochemical activities

A facile additive-assisted complex-precursor solution method is demonstrated for one-pot assembly of well-defined hierarchical Cu2O nanospheres with tunable sizes and shapes. Structural and morphological evolutions were investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and field-emission scanning electron microscopy (FESEM). The formation mechanism of these hierarchical nanostructures was rationally proposed, which can be attributed to the synergic effect of nanoparticle-aggregation and ripening with facet-selective adsorption. Significantly, it is believed that the additive-driven assembly of hierarchical architectures reported here would provide a facile way to design other exciting metal oxide nanostructures with controllable sizes. The photocatalytic superiority and stability for the methyl orange (MO) photodegradation by the hierarchical Cu2O nanospheres could be attributed to their exposed high active facets, which would be quite feasibly used for application in the fields of photocatalytic hazard pollutants.

Effect of Annealing on the Formation of p-Type Conductivity in Nano-Zn0.92Mn0.08O:N Films

P-type conductive Mn-N co-doped ZnO films were prepared by annealing N(+)-implanted Zn0.92Mn0.08O films in a N2 ambient. Effect of the annealing on the structural, surface morphological, electrical and local chemical states of the films were investigated by X-ray diffraction (XRD), high-resolution field-emission scanning electron microscopy (FE-SEM), Hall-effect and X-ray photoelectron spectroscopy (XPS) measurements, respectively. The results indicate that all the samples were single phase and well oriented along the c-axis. The as-implanted samples were n-type semiconductors, while after thermal annealing at 650 degrees C ranging from 10 to 30 minutes, they were converted to p-type conductivity with the hole concentration of 10(16)-10(17) cm(-3). But with further increasing the annealing time or the temperature, it was observed that the p-type conductivity decreased and ultimately reverted to n-type conductivity again. The change of conductive type may be ascribed to the local chemical states evolution of nitrogen in the process of thermal annealing.

Growth of branched rutile TiO 2 nanorod arrays on F-doped tin oxide substrate

Branched rutile TiO 2 nanorod arrays were directly synthesized on the F-doped tin oxide (FTO) substrate through a two-step hydrothermal treatment by a seeding method with TiO 2-nanorods as seeds. The samples were characterized respectively by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and field-emission scanning electron microscopy (FESEM). Results showed that TiO 2 nanorods with nanobranches (TiO 2-NB) grew vertically on the FTO substrate. XRD and HRTEM results confirmed that the TiO 2-NB arrays were single-crystalline rutile. The optical properties of the samples were studied with a UV–vis spectrometer. The photocatalytic activity of the TiO 2-NB film is better than that of P25 particulate film. Direct electrical pathway and improved light-harvesting efficiency were crucial for the superior photocatalytic activity of the TiO 2-NB arrays.

Low-temperature formation of nanocrystalline SiC particles and composite from three-layer Si/C/Si film for the novel enhanced white photoluminescence

In this article, nanocrystalline silicon carbide (nc-SiC) and composite have been synthesized at an annealing temperature as low as 750 °C through the thermal reaction of Si/C/Si multilayers deposited on the Si(100) substrate by ultra-high-vacuum ion beam sputtering (UHV IBS) compared with the conventional thermal formation of crystalline SiC (c-SiC) nanostructures above 1,000 °C. The evolution of microstructure and reaction between C and Si was examined by Raman spectroscopy, Fourier transform infrared spectrometer (FTIR), high-resolution field emission scanning electron microscope (HR-FESEM), and high-resolution transmission electron microscopy. The c-SiC nanoparticles (np-SiC) of around 20–120 nm in diameter appeared on the top and bottom of the three-layer film with a particle density of around 2.63 × 1010 cm−2 after 750 °C annealing. The composite of nc-SiC and Si nanocrystals (nc-Si) size below 5 nm embedded in an amorphous SiC (a-SiC) matrix appeared at the interface between the Si and C layers. Efficient thermal energy is the driving force for the formation of nc-SiC and composite through interdiffusion between C and Si. The broad visible photoluminescence (PL) spectrum of 350–750 nm can be obtained from the annealed composite Si/C/Si multilayer and deconvoluted into four bands of blue (~430 nm), green (~500 nm), green–yellow (~550 nm), and orange (~640 nm) emission, corresponding to the emission origins from nc-SiC, sp2 carbon clusters, np-SiC, and nc-Si, respectively.

Insight into Copper‐Based Catalysts: Microwave‐Assisted Morphosynthesis, In Situ Reduction Studies, and Dehydrogenation of Ethanol

Herein, we report results of three distinct controlled CuO morphologies, urchin-like (CuO-UC), fiber-like (CuO-FB) and nanorods (CuO-NR), prepared by MWA method. These well-designed structures were then dispersed in silica (SiO2) and reduced in a H2 flow that produced the following catalysts: CuO1� xUC, CuO1� xFB, and CuO1� xNR (x = 0, 1, and/or 2); their subsequent activity for the dehydrogenation of ethanol is also discussed herein. The activity and selectivity of these catalysts depend on the physical and chemical structure of the active components, which are largely influenced by the catalyst preparation method. [13] In particular, the use of small-sized CuO crystals produced a highly active and selective catalyst for the dehydrogenation of ethanol into acetaldehydes with high turnover frequencies (TOF). The structural characterization of catalysts was carried out by using several ex situ techniques; highresolution field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), conventional temperature-programmed reduction under H2 (TPR-H2), X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET) method for surface area determination, and in situ time-resolved X-ray absorption near-edge structure (XANES) spectroscopy at the Cu K-edge during TPR under H2 experiments (XANES–TPR-H2). Complete experimental details are provided in the Supporting Information. In addition, the Cu metal surface after the reduction treatment of the samples was subjected to TPR measurements with N2O oxidation. [14] FESEM images of CuO assemblies with different morphologies obtained by efficient MWA synthesis are shown in Figure 1 . Our results show that both the solvent and the base influence the final shape of crystals. By using copper(II) chloride dihydrate in deionized water and ammonium hydroxide as the base, CuO-UC structures were obtained with an average size of 3 mm in diameter and nanostructured spines (10 nm of

Fabrication and characterization of dense zirconia and zirconia-silica ceramic nanofibers.

The objective of this study was to prepare dense zirconia-yttria (ZY), zirconia-silica (ZS) and zirconia-yttria-silica (ZYS) nanofibers as reinforcing elements for dental composites. Zirconium (IV) propoxide, yttrium nitrate hexahydrate, and tetraethyl orthosilicate (TEOS) were used as precursors for the preparation of zirconia, yttria, and silica sols. A small amount (1-1.5 wt%) of polyethylene oxide (PEO) was used as a carry polymer. The sols were preheated at 70 degrees C before electrospinning and their viscosity was measured with a viscometer at different heating time. The gel point was determined by viscosity-time (eta-t) curve. The ZY, ZS and ZYS gel nanofibers were prepared using a special reactive electrospinning device under the conditions near the gel point. The as-prepared gel nanofibers had diameters between 200 and 400 nm. Dense (nonporous) ceramic nanofibers of zirconia-yttria (96/4), zirconia-silica (80/20) and zirconia-yttria-silica (76.8/3.2/20) with diameter of 100-300 nm were obtained by subsequent calcinations at different temperatures. The gel and ceramic nanofibers obtained were characterized by scanning electron microscope (SEM), high-resolution field-emission scanning electron microscope (FE-SEM), thermogravimetric analyzer (TGA), differential scanning calorimeter (DSC), Fourier transform infrared spectrometer (FT-IR), and X-ray diffraction (XRD). SEM micrograph revealed that ceramic ZY nanofibers had grained structure, while ceramic ZS and ZYS nanofibers had smooth surfaces, both showing no visible porosity under FE-SEM. Complete removal of the polymer PEO was confirmed by TGA/DSC and FT-IR. The formation of tetragonal phase of zirconia and amorphous silica was proved by XRD. In conclusion, dense zirconia-based ceramic nanofibers can be fabricated using the new reactive sol-gel electrospinning technology with minimum organic polymer additives.

Energy dispersive analysis in the TEM

Large area silicon drift detectors have been very successful as an analytical tool when used in conjunction with the scanning electron microscope (SEM). Sensors with detectors of up to 80mm2 have been employed for such tasks as fast area mapping, linescans, fast quantitative analysis and analysis of nanoparticles in SEMs at low accelerating voltages. Thin samples may also be analysed in scanning transmission (STEM) mode in high resolution field emission SEMs. In this case the large sensor area improves the collection efficiency improving the X-ray count rate significantly. The use of these detectors for analysis in the analytical transmission electron microscope (TEM) offers certain advantages over traditional liquid nitrogen cooled Si(Li) detectors while also increasing solid angle for improved signal acquisition.

Mechanical performance tailoring of tough ultra-high porosity foams prepared from cellulose I nanofiber suspensions

Low-density structures of mechanical function in plants, arthropods and other organisms, are often based on high-strength cellulose or chitin nanofibers and show an interesting combination of flexibility and toughness. Here, a series of plant-inspired tough and mechanically very robust cellular biopolymer foams with porosities as high as 99.5% (porosity range 93.1–99.5%) were therefore prepared by solvent-free freeze-drying from cellulose I wood nanofiber water suspensions. A wide range of mechanical properties was obtained by controlling density and nanofiber interaction in the foams, and density–property relationships were modeled and compared with those for inorganic aerogels. Inspired by cellulose–xyloglucan (XG) interaction in plant cell walls, XG was added during preparation of the toughest foams. For the cellulose–XG nanocomposite foams in particular, the mechanical properties at comparable densities were superior to those reported in the literature for clay aerogel/cellulose whisker nanocomposites, epoxy/clay aerogels, polymer/clay/nanotube aerogels, and polymer/silica aerogels. The foam structure was characterized by high-resolution field-emission scanning electron microscopy and the specific surface area was measured by nitrogen physisorption. Dynamic mechanical thermal analysis and uniaxial compression tests were performed. The foam was thermally stable up to 275 °C where cellulose started to degrade.

Reconstruction of atomic force microscopy image by using nanofabricated tip characterizer toward the actual sample surface topography

The atomic force microscopy (AFM) image is a dilation of the sample surface topography due to the finite-sized AFM tip. We accurately estimated the tip apex shape with a nanofabricated Si tip characterizer and applied the estimated tip shape function to a dilation-erosion algorithm for image reconstruction. The reconstructed images from the original AFM images attained with different AFM tips show consistent surface features and closely match the high-resolution field-emission scanning electron microscope image. The results demonstrate the reliability of our method and suggest the importance of AFM image reconstruction for a variety of technologies requiring new strategies of measuring, interpreting, manipulating, and positioning in the submicrometer and nanometer range.

Analyzing indirect secondary electron contrast of unstained bacteriophage T4 based on SEM images and Monte Carlo simulations

The indirect secondary electron contrast (ISEC) condition of the scanning electron microscopy (SEM) produces high contrast detection with minimal damage of unstained biological samples mounted under a thin carbon film. The high contrast image is created by a secondary electron signal produced under the carbon film by a low acceleration voltage. Here, we show that ISEC condition is clearly able to detect unstained bacteriophage T4 under a thin carbon film (10–15 nm) by using high-resolution field emission (FE) SEM. The results show that FE-SEM provides higher resolution than thermionic emission SEM. Furthermore, we investigated the scattered electron area within the carbon film under ISEC conditions using Monte Carlo simulation. The simulations indicated that the image resolution difference is related to the scattering width in the carbon film and the electron beam spot size. Using ISEC conditions on unstained virus samples would produce low electronic damage, because the electron beam does not directly irradiate the sample. In addition to the routine analysis, this method can be utilized for structural analysis of various biological samples like viruses, bacteria, and protein complexes.

Synthesis and functionalization of magnetic nanoparticles with covalently bound electroactive compound doxorubicin

We report here on covalent functionalization of magnetic nanoparticle colloidal suspension (ferrofluid) with doxorubicin. Since doxorubicin (adriamycin) is a potent anti-cancer drug, such particles can be guided with external magnetic field to a target tissue, a carrier process that may overcome the non-specificity and efficiency of adriamycin as a drug. The nanoferrite functionalization was effected by means of acid chloride chemistry leading to the formation of covalent bond between the hydroxyl groups at the nanoparticle surface and acid chloride molecules. This procedure can be easily tailored to provide the nanoferrites with various functionalities capable of further modifications with, e.g., drug molecules. Thus, we used such modified nanoferrites to covalently attach molecules of anti-tumor drug—doxorubicin. The attachment was verified by means of FTIR and cyclic voltammetry. Mean size of nanoferrites was evaluated by powder X-ray diffraction (PXRD) technique and high-resolution field emission scanning electron microscope (HR-FESEM). The amount of doxorubicin attached to nanoparticles was assessed by means of quartz crystal microbalance combined with cyclic voltammetry.

3D Tomographic EBSD Measurements of Heavily Deformed Ultra Fine Grained Cu-0.17wt%Zr Obtained from ECAP

Obtaining knowledge on the grain boundary topology in three dimensions is of great importance as it controls the mechanical properties of polycrystalline materials. In this study, the three dimensional texture and grain topology of as-deformed ultra fine grained Cu-0.17wt%Zr have been investigated using three-dimensional orientation microscopy (3D electron backscattering diffraction, EBSD) measurements in ultra fine grained Cu-0.17wt%Zr. Equal channel angular pressing was used to produce the ultra fine grained structure. The experiments were conducted using a dual-beam system for 3D-EBSD. The approach is realized by a combination of a focused ion beam (FIB) unit for serial sectioning with high-resolution field emission scanning electron microscopy equipped with EBSD. The work demonstrates that the new 3D EBSD-FIB technique provides a new level of microstructure information that cannot be achieved by conventional 2D-EBSD analysis.

Quantitative Surface Acoustic Wave Detection Based on Colloidal Gold Nanoparticles and Their Bioconjugates

The immobilization scheme of monodispersed gold nanoparticles (10-nm diameter) on piezoelectric substrate surfaces using organosilane molecules as cross-linkers has been developed for lithium niobate (LiNbO3) and silicon oxide (SiO2)/gold-covered lithium tantalate (LiTaO3) of Rayleigh and guided shear horizontal- (guided SH) surface acoustic wave (SAW) sensors. In this study, comparative measurements of gold nanoparticle adsorption kinetics using high-resolution field-emission scanning electron microscopy and SAW sensors allow the frequency responses of SAW sensors to be quantitatively correlated with surface densities of adsorbed nanoparticles. Using this approach, gold nanoparticles are used as the "nanosized mass standards" to scale the mass loading in a wide dynamical range. Rayleigh-SAW and guided SH-SAW sensors are employed here to monitor the surface mass changes on the device surfaces in gas and liquid phases, respectively. The mass sensitivity ( approximately 20 Hz.cm2/ng) of Rayleigh-SAW device (fundamental oscillation frequency of 113.3 MHz in air) is more than 2 orders of magnitude higher than that of conventional 9-MHz quartz crystal microbalance sensors. Furthermore, in situ (aqueous solutions), real-time measurements of adsorption kinetics for both citrate-stabilized gold nanoparticles and DNA-gold nanoparticle conjugates are also demonstrated by guided SH-SAW (fundamental oscillation frequency of 121.3 MHz). By comparing frequency shifts between the adsorption cases of gold nanoparticles and DNA-gold nanoparticle conjugates, the average number of bound oligonucleotides per gold nanoparticle can also be determined. The high mass sensitivity ( approximately 6 Hz.cm2/ng) of guided SH-SAW sensors and successful detection of DNA-gold nanoparticle conjugates paves the way for real-time biosensing in liquids using nanoparticle-enhanced SAW devices.

Practical Applications of High-Resolution Field Emission Scanning Electron Microscopy (HR-FESEM) for Magnetic Recording Heads and Disks and Related Materials

Practical Applications of High-Resolution Field Emission Scanning Electron Microscopy (HR-FESEM) for Magnetic Recording Heads and Disks and Related Materials

Preparation of multi-walled carbon nanotubes grafted with synthetic poly(l-lysine) through surface-initiated ring-opening polymerization

A surface-initiated ring-opening polymerization approach was used to functionalize multi-walled carbon nanotubes (MWNTs) with linear poly(l-lysine) (PLL). The oxidized MWNTs, which resulted from the treatment of MWNTs with mixed concentrated sulfuric acid and nitric acid, were converted into amino-functionalized MWNTs (MWNT-NH2) by the amidation of carboxylic group on MWNT surface with excess 1,6-diaminohexane. Surface-initiated ring-opening polymerization of ɛ-(benzyloxycarbonyl)-l-lysine N-carboxyanhydride with MWNT-NH2 as the initiator resulted in MWNTs grafted with poly(ɛ-(benzyloxycarbonyl)-l-lysine) (MWNT-g-PLys(Z)). After the acidolysis of benzylcarbamate group of the grafting poly(ɛ-(benzyloxycarbonyl)-l-lysine) chain, water-soluble MWNTs grafted with PLL (MWNT-g-PLL) were obtained. The successful grafting was confirmed by Fourier transform infrared spectroscopy, thermal gravimetric analysis, X-ray photoelectron spectroscopy, elemental analyses, high-resolution transmission electron microscopy (HRTEM) and field-emission scanning electron microscopy. HRTEM indicates that MWNTs were enveloped by PLL layer. The as-prepared MWNT-g-PLys(Z) and MWNT-g-PLL exhibited excellent ability to disperse homogeneously in THF and water, respectively.