Superhydrophobic and ultraviolet-blocking cotton textiles

Cotton textile was coated with ZnO@SiO(2) nanorods in order to obtain superhydrophobic and ultraviolet (UV)-blocking properties. The coating process was conducted in mild conditions, which involved the low-temperature preparation of ZnO seeds, hydrothermal growth of ZnO nanorods, bioinspired layer-by-layer deposition of a SiO(2) shell on the surface of ZnO nanorods, and hydrophobic modification of ZnO@SiO(2) nanorods with octadecyltrimethoxysilane. Despite the highly curved morphology of cotton fibers, the ZnO@SiO(2) nanorods coated the textile densely and uniformly. The treated cotton textile was found to have a large UV protection factor (UPF = 101.51) together with UV-durable superhydrophobicity, as determined by contact-angle measurement under long-term UV irradiation. The good UV-blocking property can be ascribed to the high UV absorbance and scattering properties of ZnO nanorods, and the UV-durable superhydrophobicity is a result of suppression of the photoactivity of ZnO nanorods by a SiO(2) shell.     

Synthesis and characterization of ZnO/SiO2 core/shell nanocomposites and hollow SiO2 nanostructures

In this paper, we prepared the ZnO nanoparticles by a simple hydrothermal method and fabricated the ZnO/SiO₂ core/shell nanostructures through a sol-gel chemistry process successfully. The hollow SiO₂ nanostructures were obtained by selective removal of the ZnO cores. The structure, morphology and composition of the products were determined by the techniques of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS) and transmission electron microscopy (TEM). The results indicated that the ZnO nanoparticles were sphere-like shape with the average size of 60 nm and belonged to hexagonal wurtzite crystal structure. With the coating of SiO₂, the vibration modes of Si-O-Si and Si-OH were found. Furthermore, the measurement results of optical properties showed that spectra of bare ZnO nanoparticles and ZnO/SiO₂ core/shell nanocomposites exhibited similar emission features, including a blue emission peak and an orange emission band.     

AFM characterization of nonwoven material functionalized by ZnO sputter coating

Sputter coatings provide new approaches to the surface functionalization of textile materials. In this study, polyethylene terephthalate (PET) nonwoven material was used as a substrate for creating functional nanostructures on the fiber surfaces. A magnetron sputter coating was used to deposit functional zinc oxide (ZnO) nanostructures onto the nonwoven substrate. The evolution of the surface morphology of the fibers in the nonwoven web was examined using atomic force microscopy (AFM). The AFM observations revealed a significant difference in the morphology of the fibers before and after the sputter coating. The AFM images also indicated the effect of the sputtering conditions on the surface morphology of the fibers. The increase in the sputtering time led to the growth of the ZnO grains on the fiber surfaces. The higher pressure in the sputtering chamber could cause the formation of larger grains on the fiber surfaces. The higher power used also generated larger grains on the fiber surfaces.     

Nanoforests composed of ZnO/C core–shell hexagonal nanosheets: fabrication and growth in a sealed thermolysis reactor and optical properties

An efficient method was developed for fabricating a highly porous nanoforest structure composed of ZnO/C core–shell hexagonal nanosheets (HNSs). Compact thermolysis of zinc acetate dihydrate in a sealed bath reactor at 400 °C over 20 h yielded the nanoforest structures. A carbon shell layer coating was applied in situ during the growth of the ZnO nanosheet core. The structures, morphologies, growth processes, compositions, and binding characteristics of the ZnO/C core–shell HNS nanoforests were analyzed using multi-purpose high-performance X-ray diffraction (XRD), scanning electron microscopy, energy-dispersive X-ray spectroscopy, Raman spectroscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy (XPS) techniques. XRD and XPS results suggest the existence of oxygen vacancy defects in the core surface of ZnO/C core–shell. The ZnO/C core–shell HNS nanoforests exhibited strong absorption features from the visible to the near-IR region (400–1670 nm), and the nanoforest films showed high electrical conductivity.     

High density Si/ZnO core/shell nanowire arrays for photoelectrochemical water splitting

Si/ZnO core/shell nanowire (NW) arrays were fabricated using atomic layer deposition of ZnO shell on n-Si NW arrays prepared by metal assisted electroless etching method. Scanning electron microscopy, transmission electron microscopy and X-ray diffraction were utilized to characterize the core/shell structures. Water splitting performance of the core/shell structures was preliminarily studied. The Si/ZnO core/shell NW arrays yielded significantly higher photocurrent density than the planar Si/ZnO structure due to their low reflectance and high surface area. The photoelectrochemical efficiency was found to be 0.035 and 0.002 % for 10 μm-long Si/ZnO NW array and planar Si/ZnO sample, respectively. These results suggested that core/shell structure is superior to planar heterojunction for PEC electrode design. We demonstrated the dependence of photocurrent density on the length of the core/shell array, and analyzed the reasons why longer NW arrays could produce higher photocurrent density. The relationship between the thickness of ZnO shell and the photoconversion efficiency of Si/ZnO NW arrays was also discussed. By applying the core/shell structure in electrode design, one may be able to improve the photoelectrochemical efficiency and photovoltaic device performance.     

ZnO/SiO_2核壳结构热控涂层制备研究

ZnO表面包覆SiO2,可以提高ZnO热控涂层的空间环境适应性.采用液相沉淀法对ZnO颗粒进行SiO2包覆,并对包覆前后的ZnO表面形貌和组成进行了分析,研究了紫外辐照下ZnO/SiO2热控涂层太阳吸收率变化规律.研究表明：SiO2以无定型的形式通过化学键合方式,均匀地包覆到ZnO表面,形成了具有核壳结构的复合颗粒,进...     

Preparation and characterization of ZnO/ZnS core/shell nanocomposites through a simple chemical method

In this paper, we reported the preparation of ZnO/ZnS core/shell nanocomposites by sulfidation of ZnO nanostructures via a simple hydrothermal method. The precursors of bare ZnO nanoparticles and ZnO nanorods were synthesized by a surfactant-assisted hydrothermal growth. The structural, morphological, and element compositional analysis of bare ZnO nanostructures and ZnO/ZnS core/shell nanocomposites were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, and transmission electron microscopy techniques. The XRD results indicated that the phase of bare ZnO nanoparticles and ZnO nanorods was wurtzite structure, and the phase of coated ZnS nanoparticles on the surface of bare ZnO nanostructures was sphalerite structure with the size of about 8 nm. Photoluminescence measurement was carried out, and the PL spectra of ZnO/ZnS core/shell nanocomposites revealed an enhanced UV emission and a passivated orange emission compared to that of bare ZnO nanostructures. In addition, the growth mechanism of ZnO/ZnS core/shell nanostructures through hydrothermal method was preliminarily discussed.     

Fe3O4/SiO2/CMCH/CdTe荧光磁性微球的合成与表征

利用St ber法和交联法制备出具有荧光和磁性功能的Fe3O4/SiO2/CMCH/CdTe微球,并对其性能和应用效果进行了分析讨论.首先以正硅酸四乙酯为前躯体,Fe2＋和Fe3＋物质的量的比为1∶2,利用超临界干燥法制备出了Fe3O4/SiO2复合微球;并通过透射电镜对其进行观察,Fe3O4颗粒粒径为10 nm,SiO2层厚度为5 nm;其次羧甲基化的壳聚糖（CMCH）被嫁接在Fe3O4/SiO2表面上;然后利用水热法制备出CdTe荧光颗粒,通过壳聚糖与CdTe之间的静电吸引作用,CdTe被吸附在壳聚糖表面;最后利用戊二醛对壳聚糖的选择性交联作用制备出粒径在200 nm以内,饱和磁化强度为22.16 A.m2/kg,且具有良好荧光性能的Fe3O4/SiO2/CMCH/CdTe微球.荧光光谱分析表明最大发射波长从519 nm红移到528 nm,也证实了荧光颗粒CdTe成功吸附在Fe3O4/SiO2/CMCH表面.在动物实验中,该复合微球也显示出良好的荧光性、磁性及稳定性.     

Synthesis and magnetic properties of FePt nanoparticles with hard nonmagnetic shells

Chemically synthesized FePt nanoparticles were coated with nonmagnetic SiO2 and MnO shells by sol-gel and polyol processes. TEM images show that the FePt/SiO2 nanoparticles exhibit a thick spherical shell. The size and morphology of the MnO shell can be controlled by changing the reaction temperature, the molar ratio of surfactants/Mn(acac)2, and/or the concentration of precursor. The morphology of the MnO shell can be either spherical-like or cubic-like, depending on whether the molar ratio of surfactants/Mn(acac)2 is less than or larger than 2. From XRD measurements, the spherical core/shell nanoparticles exhibit 3D random crystallographic orientation, while the cubic core/shell nanoparticles prefer (200) texture. The magnetic moment of FePt particles can be enhanced by coating with SiO2 and MnO shells. Furthermore, the agglomeration of FePt particles upon the thermal annealing can be significantly inhibited with SiO2 and MnO shells.     

分散聚合法制备SiO2/PAM核壳复合微球

采用分散聚合法制备出以SiO2为核、PAM为壳的核壳复合微球。根据Stber法制备了单分散SiO2微球,粒径随着TEOS、氨水浓度的增加而增大。采用硅烷偶联剂对SiO2微球进行表面处理,TEM显示处理后的微球继续保持单分散性,粒径有所增加。以SiO2微球或处理后的SiO2微球为核,采用分散聚合法在其上包覆AM,借助TEM、IR对其进行表征;研究发现,以处理后的Si O2微球为核能得到核壳结构,这种SiO2/PAM核壳微球的粒径大约为163 nm,包覆层30 nm左右。     

Characterization of SiO2/Ag composite particles synthesized by in situ reduction and its application in electrically conductive adhesives

In the study, SiO₂/Ag composite particles with silver coating onto the surface of silica have been successfully prepared via a novel and facile approach (Oxidation–Reduction Method). In this approach, the SiO₂ particles were first modified with 3-ammoniatriethoxysilane (APTES) and glyoxalic acid (GA) through two-step reaction, the aldehyde group (CHO) were anchored onto the surfaces of silica spheres via electrostatic attraction, these [Ag(TEA)₂]⁺ ions in the solution were then reduced by the CHO and coated onto the surface of silica to obtain SiO₂/Ag composite particles. The effects of the reaction conditions on silver content and synthetic mechanism had also been discussed. The structure, morphology and optical properties of the SiO₂/Ag composite particles were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV–vis spectroscopy. The results showed the surface of SiO₂ was surrounded by pure silver nanoparticles, and the silver nanoparticles had face-centered-cubic structure, the SiO₂/Ag composite particles with core–shell morphology and special optical properties. And the small content SiO₂/Ag composite particles applied in electrically conductive adhesives (ECAs) improved the electrical bulk resistivity and tensile shear strength.     

Fast synthesis,formation mechanism,and control of shell thickness of CuS–polystyrene core–shell microspheres

The silanol-modified polystyrene microspheres were prepared through dispersion polymerization. Then copper sulfide particles were grown on silanol-modified polystyrene through sonochemical deposition in an aqueous bath containing copper acetate and sulfide, released through the hydrolysis of thioacetamide. The resulting particles were continuous and uniform as characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Fourier transform infrared, thermogravimetric analysis and UV–vis absorption spectroscopy were used to characterize the structure and properties of core–shell particles. The results showed the coating thickness of CuS shell can be controlled by the amount of silanol and the UV–vis absorption intensity of PSt/CuS composite also changed with the coating thickness of CuS.     

Pyrolytic deposition of nanostructured titanium carbide coatings on the surface of multiwalled carbon nanotubes

Nanostructured titanium carbide coatings have been deposited on the surface of multiwalled carbon nanotubes (MWCNTs) by the MOCVD method with bis(cyclopentadienyl)titanium dichloride precursor. The obtained TiC/MWCNT hybrid materials were characterized by X-ray diffraction, scanning electron microscopy, and high-resolution transmission electron microscopy. It is established that a TiC coating deposits onto the MWCNT surface with the formation of a core–shell (MWSNT–TiC) type structure.     

Improvement of anti-oxidation properties of carbon fibers by SiC/SiO2 ceramic coating

To improve the anti-oxidation properties of carbon fibers (CFs), the sol-gel method followed by pyrolysis was used to coat CFs with SiC/SiO2 ceramic coatings. The SiO2 sol-gel coating was performed by dip coating a PAN(polyacrylonitrile)-based stabilized fiber (PSF) in a silica sol prepared by the polycondensation of tetraethylorthosilicate (TEOS) in the presence of an acidic catalyst. The PSF coated with SiO2 sol then underwent heat treatments at high temperatures in an inert atmosphere to deposit the SiC/SiO2 and carbonize the deposited fibers. The surface morphology of the CFs deposited with SiC/SiO2 was characterized using a scanning electron microscope (SEM). The relative oxidation resistance of the SiC/SiO2 layer deposited on the CFs was determined by the weight loss due to the use of a thermogravimetric analyzer (TGA) under flowing air, and the data were used to calculate the activation energies through an Arrhenius plot.     

ZnO nanorod/CdS nanocrystal core/shell-type heterostructures for solar cell applications

ZnO/CdS core/shell nanorod arrays were fabricated by a two-step method. Single-crystalline ZnO nanorod arrays were first electrochemically grown on SnO(2):F (FTO) glass substrates. Then, CdS nanocrystals were deposited onto the ZnO nanorods, using the successive ion layer adsorption and reaction (SILAR) technique, to form core/shell nanocable architectures. Structural, morphological and optical properties of the nanorod heterojunctions were investigated. The results indicate that CdS single-crystalline domains with a mean diameter of about 7 nm are uniformly and conformally covered on the surface of the single-crystalline ZnO nanorods. ZnO absorption with a bandgap energy value of 3.30 ± 0.02 eV is present in all optical transmittance spectra. Another absorption edge close to 500 nm corresponding to CdS with bandgap energy values between 2.43 and 2.59 eV is observed. The dispersion in this value may originate in quantum confinement inside the nanocrystalline material. The appearance of both edges corresponds with the separation of ZnO and CdS phases and reveals the absorption increase due to CdS sensitizer. The photovoltaic performance of the resulting ZnO/CdS core/shell nanorod arrays has been investigated as solar cell photoanodes in a photoelectrochemical cell under white illumination. In comparison with bare ZnO nanorod arrays, a 13-fold enhancement in photoactivity was observed using the ZnO/CdS coaxial heterostructures.     

Preparation,characterization and application of Fe3O4/ZnO core/shell magnetic nanoparticles

Fe₃O₄ magnetic nanoparticles (MNPs) were synthesized by a co-precipitation method. The phase purity was confirmed by X-ray powder diffraction (XRD) analysis. The crystal size was found to be 10 nm from transmission electron microscopy (TEM). It is evidenced that the surface of Fe₃O₄ MNPs was modified by sodium citrate. The Fe₃O₄/ZnO core/shell MNPs were obtained by coating the MNPs with direct precipitation using zinc acetate and ammonium carbonate. The precursor was firstly dried and then calcined at 350 °C. The antioxidation tests indicated that the core/shell MNPs give better antioxidation than that of the Fe₃O₄ MNPs. The photocatalytic degradation of methyl orange revealed that the core/shell MNPs have higher photocatalytic activity than that of the ZnO nanoparticles. Separation of the core/shell MNPs from the aqueous suspension using a magnet provides an easy way to recycle the core/shell MNPs. After four-time recycling, the photocatalytic degradation percentage of the core/shell MNPs is about 70%.     

Preparation, structure and photoluminescence properties of SiO2/ZnO nanocables via electrospinning and vapor transport deposition

SiO₂/ZnO nanocables were prepared by the combination of electrospinning technology and vapor transport deposition procedure. X-ray diffraction patterns indicated that ZnO with wurtzite structure was deposited on SiO₂ nanofibers templates successfully. Field emission scanning electron microscopy and transmission electron microscopy showed that the products were core/shell nanocables with a narrow distribution of the core/shell diameters. The nanocables showed a strong near band edge emission in ultraviolet region and a weak deep level emission at room temperature in their photoluminescence (PL) spectra. The anomalous temperature characteristic of integrated PL intensity in temperature-dependent PL spectra was discussed by considering carrier injection across the interface of SiO₂/ZnO nanocables.     

Rapid synthesis, characterization and optical properties of TiO2 coated ZnO nanocomposite particles by a novel microwave irradiation method

A novel and rapid microwave method was used to prepare TiO₂ coated ZnO nanocomposite particles. The resulted particles were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HR-TEM) and X-ray photoelectron spectroscopy (XPS). Results show that ZnO nanoparticles were coated with 6-10 nm amorphous TiO₂ layers. In addition, zeta potential analysis demonstrated the presence of TiO₂ layer on the surface of ZnO nanoparticles. Photoluminescence (PL) spectroscopy and UV-visible spectroscopy were used to investigate the optical properties of the nanoparticles. Compared to uncoated ZnO nanoparticles, the TiO₂ coated ZnO nanoparticles showed enhanced UV emission. The UV-visible diffuse reflectance study revealed the significant UV shielding characteristics of the nanocomposite particles. Moreover, amorphous TiO₂ coating effectively reduced the photocatalytic activity of ZnO nanoparticles as evidenced by the photodegradation of Orange G with uncoated and TiO₂ coated ZnO nanoparticles under UV radiation.     

Tribological and Repairing Properties of Combined Nanoparticle SiO2/ZnO

A type of additive-SiO2/ZnO combined nanoparticle were obtained by chemical method. The tribologica land repairing properties as lube additives have been studied by four-ball tester and ring-on-block tribotesters. The morphographies of the worn surfaces were analyzed by means of scanning electron microscopy(SEM). The results show that the additive possesses excellent extreme-pressure( EP), anti-wear(AW) , friction reducion and self-repairing properties. The lubrication and repairing mechanism is inferred that SiO2/ZnO combined nanoparticle is sedimented on the surface of steel, the lower surface film is formed under the high temperature and high pressure. The film possess excellent anti-wear , friction-reducing and repairing properties.     

Fabrication of SiO2@ZrO2@Y2O3:Eu3+ core-multi-shell structured phosphor

ZrO2 interface was designed to block the reaction between SiO2 and Y2O3 in SiO2@Y2O3:Eu coreshell structure phosphor. SiO2@ZrO2@Y2O3:Eu core-multi-shell phosphors were successfully synthesized by combing an LBL method with a Sol-gel process. Based on electron microscopy, X-ray diffraction, and spectroscopy experiments, compelling evidence for the formation of the Y2O3:Eu outer shell on ZrO2 were presented. The presence of ZrO2 layer on SiO2 core can block the reaction of SiO2 core and Y2O3 shell effectively. By this kind of structure, the reaction temperature of the SiO2 core and Y2O3 shell in the SiO2@Y2O3:Eu core-shell structure phosphor can be increased about 200-300 degrees C and the luminescent intensity of this structure phosphor can be improved obviously. Under the excitation of ultraviolet (254 nm), the Eu3+ ion mainly shows its characteristic red (611 nm, 5D0-7F2) emissions in the core-multi-shell particles from Y2O3:Eu3+ shells. The emission intensity of Eu3+ ions can be tuned by the annealing temperatures, the number of coating times, and the thickness of ZrO2 interface, respectively.