A novel approach to prepare solvent-free cerium dioxide nanofluids

This paper develops a novel approach to prepare solvent-free cerium dioxide (CeO₂) nanofluids through N,N-didecyl-N-methyl-N-(3-trimethoxysilylpropyl) ammonium chloride covalently grafted on the surface of CeO₂ nanoparticles as core, and then poly(ethylene glycol) 4-nonylpheny 13-sulfopropyl ether sodium salt was grafted on the surface of CeO₂ nanoparticles through ion exchange reaction. It is obviously observed that CeO₂ nanofluids exhibited a solid state at room temperature, whereas they behave as liquid-like when being heated to above 45°C. To detect the properties of CeO₂ nanofluids, the morphology, thermal stability, dispersibility, and rheological behavior of CeO₂ nanofluids are mainly investigated. It is found that CeO₂ nanofluids can flow without solvent existence. Meantime, it shows good dispersion and stability in water and other organic solvents for weeks due to amphiphilic properties of the modifier molecules.     

A facile method to prepare PbS nanorods

PbS nanorods with an average diameter of about 30 nm have been successfully prepared through a simple polyglycol-assisted route for the first time. The obtained PbS nanorods have been characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), and selected area electronic diffraction (SAED). Experiments show that polyglycol plays an important role for the control of the morphology of PbS nanostructures. The preliminary result of the UV-vis absorption spectrum of the PbS nanorods is also presented.     

A facile approach to fabricate Ni inverse opals at controlled thickness

A vertical electrophoretic deposition method was employed to fabricate polystyrene (PS) colloidal crystals with negligible defects and considerable surface uniformity. Subsequently, the interstitial voids within the colloidal crystals were electroplated with Ni, followed by selective removal of the PS microspheres. With careful adjustment in the processing parameters, we were able to obtain Ni inverse opals at predetermined thickness in relatively short time. The inverse opals revealed superb structural stability and surface uniformity. Because the electrophoresis and electrodeposition were both carried out in a solution state, this fabrication scheme enables facile construction of inverse opals on conductive substrates over conventional approaches.     

A simple single-step approach towards synthesis of nanofluids containing cuboctahedral cuprous oxide particles using glucose reduction

Enhancement of thermal properties of conventional heat transfer fluids has become one of the important technical challenges. Since nanofluids offer a promising help in this regard, development of simpler and hassle free routes for their synthesis is of utmost importance. Synthesis of nanofluids using a hassle free route with greener chemicals has been reported. The single-step chemical approach reported here overcomes the drawbacks of the two-step procedures in the synthesis of nanofluids. The resulting Newtonian nanofluids prepared contained cuboctahedral particles of cuprous oxide and exhibited a thermal conductivity of 2.852 W·m^-1·K^-1. Polyvinylpyrrolidone (PVP) used during the synthesis acted as a stabilizing agent rendering the nanofluid a stability of 9 weeks.     

A facile approach to prepare regenerated cellulose/graphene nanoplatelets nanocomposite using room-temperature ionic liquid

This study presents the preparation of regenerated cellulose (RC)/graphene nanoplatelets (GNPs) nanocomposites via room temperature ionic liquid, 1-ethyl-3-methylimidazolium acetate (EMIMAc) using solution casting method. The thermal stability, gas permeability, water absorption and mechanical properties of the films were studied. The synthesized nanocomposite films were characterized by Fourier transform infrared (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The T20 decomposition temperature of regenerated cellulose improved with the addition of graphene nanoplatelets up to 5 wt%. The tensile strength and Young's modulus of RC films improved by 34 and 56%, respectively with the addition of 3 wt% GNPs. The nanocomposite films exhibited improved oxygen and carbon dioxide gas barrier properties and water absorption resistance compared to RC. XRD and SEM results showed good interaction between RC and GNPs and well dispersion of graphene nanoplatelets in regenerated cellulose. The FTIR spectra showed that the addition of GNPs in RC did not result in any noticeable change in its chemical structure.     

A facile method to prepare size-tunable silver nanoparticles and its antibacterial mechanism

The antibacterial effect of silver nanoparticles (denoted as Ag NPs) is closely related to size. This could partly explain why size controllable synthesis of Ag NPs for bactericidal application is drawing much attention. Thus, we establish a facile and mild route to prepare size-tunable Ag NPs with highly uniform morphologies and narrow size distributions. The as-prepared Ag NPs with averaged sizes of 2, 12 and 32?nm were characterized by transmission electron microscopy (TEM), ultraviolet–visible absorption spectroscopy (UV–vis), X-ray powder diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The antimicrobial effect of the as-prepared Ag NPs with different particles size was assessed by broth dilution and disk diffusion as well as measurement of optical density (OD₆₀₀). Moreover, their antibacterial mechanism was discussed in relation to morphology observation of microorganism by scanning electron microscopy (SEM) and to concentration detection of Ag⁺ by stripping voltammetry. It was found that the parameters such as reactant molar ratio, reaction time, dropping speed, and most of all, pH of the reactant solutions, have significant influences on size-regulation of Ag NPs. The as-prepared Ag NPs exhibit excellent antibacterial properties, and their antimicrobial activities increase with decreasing particles size. Besides, two kinds of mechanisms, i.e., contact action and release of Ag⁺, are responsible for the antimicrobial effect of Ag NPs.     

Influence of different parameters and their coupled effects on the stability of alumina nanofluids by a fractional factorial design approach

Nanofluids have been introduced as new-generation fluids able to improve energy efficiency in heat exchangers. However, stability problems related to both agglomeration and sedimentation of nanoparticles have limited industrial-level scaling. A fractional factorial experimental 2^k?1 design was applied in order to evaluate the effects of nanoparticle concentration, surfactant type and concentration, ultrasonic amplitude as well as ultrasonic time on the stability of alumina (Al₂O₃) nanofluids. Commercial alumina nanoparticles (particle diameter <50 nm) were dispersed in deionized water using ultrasonic probe dispersion equipment. Sodium dodecylbenzenesulfonate (SDBS) and cetyltrimethylammonium bromide (CTAB) were used as surfactants. The stability of the nanofluids in static mode was monitored by visual inspection and UV visible spectroscopy. The results of the experimental design showed that the coupled effects between surfactant type and surfactant concentration and between ultrasonication tip amplitude and ultrasonication time had the most pronounced effects on nanofluid stability. The experimental conditions providing the best stability were 0.5 wt% of Al₂O₃, CTAB, critical micelle surfactant concentration, 30% ultrasonic amplitude and 30 min of ultrasonication.     

制备HDI及IPTS的新方法

采用毒性较小的固体光气(BTC)代替光气与己二胺和γ-氨基丙基三乙氧基硅烷反应合成了1,6-己二异氰酸酯(HDI)以及γ-异氰酸酯丙基三乙氧基硅烷(IPTS),研究了原料配比、加料温度、反应温度以及反应时间等对实验产物的影响.实验表明,-NH-和固体光气的比例为3:1,加料温度为-20℃,反应温度为60℃,反应时间为3h时能够得到目标产物.用红外光谱和质谱对产物进行了表征,结果显示合成产物具有异氰酸酯的显著特征,纯度较高.因此采用BTC代替光气合成HDI和IPTS是一条切实可行的路线.     

A facile method to prepare layered manganese oxides with large interplanar spacing

Layered manganese oxides with basal spacings up to 38.1 Å have been synthesized by a facile novel method in which cationic surfactant CTAB directly reacts with MnSO₄·H₂O and NaOH. The as-synthesized samples have expanded birnessite-type layered structures characterized by powder XRD and TEM. Synthetic parameters that are important to the formation and the basal spacing of the layered mesostructures are investigated, including the surfactant concentration, OH⁻/Mn²⁺ ratio, CTAB/Mn²⁺ ratio and aging time. Mechanisms based on self-assembling are discussed.     

A green and facile route to synthesize calcium silicate nanowires

Large-scale single crystalline calcium silicate nanowires have been synthesized via a simple and facile hydrothermal route using nanoscale SiO₂ and CaO powders as the starting materials. Xonotlite [Ca₆(Si₆O₁₇)(OH)₂] nanowires were first achieved after hydrothermal treatment at 220 °C for 12 h. After being calcinated at 800 °C for 1 h, the Ca₆(Si₆O₁₇)(OH)₂ nanowires are completely transformed into β-CaSiO₃ nanowires. The β-CaSiO₃ nanowires have a diameter of 30–150 nm and a length of tens of micrometers. The hydrothermal conditions and the size of the raw materials play important roles on the size of the nanowires. A possible growth mechanism of the nanowires is also proposed.     

A facile and green route to silver nanoparticles in water

Stable water-dispersible silver nanoparticles with a narrow size distribution are obtained by light-assisted spontaneous reduction of silver nitrate with gelatin, which acts as both the reducing and the stabilizing agents, in water. The formation mechanism of the silver nanoparticles involves an in-situ conversion of Ag(+)-gelatin aggregates to gelatin-stabilized silver nanoparticles via a Ag(+)-mediated oxidation of primary amine groups of the gelatin to carboxylic acid groups. The resultant silver nanoparticles are well within the quantum size domain (10 nm). In addition, the nanoparticles are stable in aqueous solutions and can be separated easily by simple pH adjustment.     

A facile route to prepare PdPt alloys for ethanol electro-oxidation in alkaline electrolyte

We adopted a displacement reaction in acidic solution that enabled the spontaneous reduction of Pd and Pt cations in conjunction with corrosive dissolution of Ni. The composition for the PdPt was adjusted by varying the concentration of Pd and Pt cations. From SEM images and XRD patterns, the PdPt formed an fcc alloy uniformly deposited on the Ni substrate. Electro-oxidation of ethanol was conducted in alkaline electrolyte for samples of Pd, Pt, and PdPt alloys. In cyclic voltammetric profiles, the Pd₇₇Pt₂₃ revealed the highest electrocatalytic ability in both apparent current and mass activity, followed by Pd₈₇Pt₁₃, Pd, and Pt. Similar behaviors were observed in life time measurements in which stable performances for ethanol electro-oxidation were obtained.     

A facile method to prepare stable noncovalent functionalized graphene solution by using thionine

A novel noncovalent functionalization approach was presented here to exfoliate and stabilize the chemical converted graphene and the low-temperature exfoliated graphene in aqueous solution by using thionine. It was found that the thionine exhibited the π-π stacking force with the graphene sheets, and the attachment of thionine molecules onto the graphenes’ surfaces could obviously improve their solubility in water. The AFM observation further verified that the graphene sheets with single-layer to double-layer were existed in the dispersions. The electronic test indicated that the modified graphene sheets possessed excellent electronic properties.     

A highly effective and facile way to prepare cellular labelling quantum dots with cetyltrimethylammonium bromide

We report a facile and effective way to prepare cell labelling quantum dots (QDs) using cetyltrimethylammonium bromide (CTAB) and to enhance biocompatibility of the QD labels. There are several reports on the use of this ligand to encapsulate nanoparticles including QDs. However, due to its high cellular toxicity, CTAB has still not been employed to prepare QDs for cellular labelling. After removing the free ligand by dialysis, we could successfully use CdSe/CdS/ZnS (core/shell/shell) QDs for cellular labelling. In addition, we found that the simple introduction of a sonication step to cause the emulsion of the QDs in the aqueous surfactant solution could lead to a five-times higher encapsulation of the QDs as compared to other methods. Fluorescent microscopy images of HeLa cells revealed that the QDs were evenly dispersed inside them. Furthermore, fluorescent morphological images of the QD labelled cells were more distinct than bright field images.     

A facile single-source approach to urchin-like NiS nanostructures

Highly regular urchin-like NiS architectures were synthesized on a large scale by solvothermal treatment of a single-source molecular precursor of nickel diethyldithiocarbamate [Ni(DDTC)₂] at 180 °C. The urchin-like architectures, with an average diameter of ∼16 μm, were composed of single-crystalline NiS nanoneedles with a diameter of ∼100 nm and a length of up to 8 μm. It was revealed that the solvent medium can strongly affect the composition and crystal phases of the products, and a surfactant is crucial to form urchin-like patterns. Based on the experimental observations, a probable three-step growth mechanism is proposed to explain the formation of the urchin-like nanostructures. The optical properties were investigated by ultraviolet-visible (UV-vis) absorption spectroscopy. This simple and mild single-source solvothermal route may be expected to extend to fabricating other inorganic nano-/micro-superstructures with novel morphologies and complex architectures.     

Ag-catalyzed synthesis of ultrafine nickel nanoparticles: A facile way to size control

We report here a facile strategy, Ag-catalyzed reduction of Ni²⁺ ions, for the synthesis of metallic nickel nanoparticles. The phase structure and morphology of particles were analyzed by means of X-ray diffraction and scanning electron microscopy. It was found that the resultant Ni nanoparticles had narrow size distribution, and the control of particle size could be easily achieved through manipulation of the molar ratio between nickel salts and silver seeds. XRD analysis of the final particles showed the crystalline nickel structure and the presence of metallic Ag, which was influenced by the Ni/Ag molar ratio. The effects of reduction temperature on the final particle size were also investigated.     

A facile method to prepare noble metal nanoparticles modified Self-Assembly (SAM) electrode

Noble metal nanoparticles (NPs) modified electrodes have shown promising applications in the areas of catalysis, (electro)chemical analysis and biosensing due to their unique characters. In this paper, we introduced a so-called ligand exchange method to prepare self-assembly (SAM) electrode modified with noble metal nanoparticles. The noble metal nanoparticles protected by weakly adsorbed tetraoctylammonium bromide (TOAB) were synthesized firstly, then self-assembly (SAM) dithiol-modified Au electrode (Au-SH_SAM) was immersed into the solutions containing TOAB-protected nanoparticles. Due to the strong interaction between the dithiol groups on the electrode and noble metal nanoparticles, the weakly adsorbed TOAB on the surface of noble metal NPs were replaced by dithiol groups. As a result, the TOAB protected NPs were anchored on the Au-SH_SAM template electrode surface by ligand exchange, obtaining noble metal NPs modified electrode with high quality and stability. By adjusting the soaking time, the coverage of nanoparticles on the Au-SH_SAM electrode surface could be controlled. The morphology and distribution of noble metal NPs on Au-SH_SAM surface was analysis by scanning tunneling microscope (STM), and their electrochemical property was studied by cyclic voltammetry (CV) in H₂SO₄ solution. The approach is proved as a universal way to prepare noble metal NPs modified SAM electrode.     

AlN/EG纳米流体的制备及稳定性研究

通过两步法制备了氮化铝/乙二醇(Al N/EG)纳米流体,研究了超声分散时间、p H值、分散剂种类及添加量3种因素对其稳定性的影响。结果表明,超声分散时间太长或太短都不利于流体的稳定性,实验中取30 min最好;酸溶液的加入使Al N/EG纳米流体稳定性急剧恶化;碱溶液的加入也使Al N/EG纳米流体稳定性恶化,但速度较酸的加入慢。适量分散剂PVP的加入能够改善Al N/EG纳米流体的稳定性。