Xun Fu

Formation of silver nanoshells on latex spheres

Silver nanoshells on styrene–acrylic acid copolymer latex spheres (PSA) were deposited by an in situ chemical reduction method, ageing a colloid solution at 85 °C containing PSA latex, AgNO3, urotropine, and poly-(vinylpyrrolidone). SEM and TEM observations showed that the silver nanoshells were made of closely packed silver nanoparticles of different sizes and morphologies. UV–visible absorption spectra were recorded to investigate their optical properties.

Hydrothermal synthesis of monodisperse Ag2Se nanoparticles in the presence of PVP and KI and their application as oligonucleotide labels

Monodispersed silver selenide (Ag2Se) nanoparticles have been prepared successfully by a hydrothermal reaction of AgNO3 with Na2SeSO3 in the presence of poly(vinyl pyrrolidone) (PVP) and KI at 180 °C for 20 h. TEM revealed that the nanoparticles are much like husked rice with lengths of about 60–80 nm and widths of about 30–40 nm. KI was dispersed in a PVP solution first, then an appropriate amount of AgNO3 solution was slowly added until the molar ratio of Ag+ to I− reached 1 : 1. The formed complex ions of [AgmIn](n−m)− and AgI in the procedure are more stable owing to the protection effect of PVP, or these could be considered as complexes of PVP–[AgmIn](n−m)− and PVP–AgI. These complexes functioned as the precursors; the formation rate of Ag2Se crystal cores in the hydrothermal reaction could be well controlled. The final shape and size of the product were affected by the amount of PVP and the molar ratio of I− to Ag+, and higher PVP content was beneficial to the formation of the husked rice-like shape. The Ag2Se nanoparticles can be used for the detection of DNA hybridization. A specific DNA sequence related to the PEP promoter gene in transgenic plants was determined with a detection range from 1.0 × 10−12 to 1.0 × 10−8 mol L−1 and a detection limit of 2.3 × 10−13 mol L−1 (3σ). The method had good selectivity and was successfully used to distinguish between a three-base mismatched ssDNA sequence, a non-complementary sequence and a complementary sequence.

Preparation of organic fluids with high loading concentration of Ag2S nanoparticles using the extractant Cyanex 301

Stable organic fluids containing Ag2S nanoparticles modified by Cyanex301 (di-(2,4,4-trimethylpentyl) dithiophosphinic acid) have been prepared directly in alkane via a solvent extraction synthesis method. The organic fluids are so stable that the nanoparticles do not precipitate at room temperature even after more than one year even when the content of Ag2S nanoparticles is as high as 42 g L−1. The Ag2S nanoparticles are characterized by XRD, TEM, IR, UV-vis and TG-DSC, showing that the particles are well modified by the extractant Cyanex301. The obtained nanoparticles can be well dispersed again in organic solvents and the new fluids are also very stable. The loading concentration of Ag2S nanoparticles prepared through the extraction synthesis method is much higher than that prepared via a two-step (preparation and dispersion) synthesis method and found to decrease with an increase of the solvent polarity. The tribological properties of the Ag2S nanoparticles modified by Cyanex301 in liquid paraffin (LP) for a steel–steel friction pair are evaluated on a four-ball machine, showing that such a fluid, LP+Ag2S, has a low friction coefficient.

Preparation of Organic Fluid Containing Ag Nanoparticles with Extractant Cyanex 301

Stable organic fluid containing silver nanoparticles modified by extractant Cyanex 301 (di‐(2, 4, 4‐trimethylpentyl) dithiophosphinic acid) has been prepared directly in alkane by the solvent extraction‐reduction method. Ag+ is extracted into alkane by Cyanex 301, then the obtained Ag+‐Cyanex 301 complex is reduced with solid sodium borohydride to obtain the organic fluids containing Ag nanoparticles. The organic fluids are so stable that the nanoparticles do not precipitate at room temperature for more than two months when the concentration of Ag nanoparticles is about 0.10 mol L−1. The nanoparticles are characterized by XRD, TEM, IR, UV‐Vis, and TG‐DTG, showing that Ag nanoparticles are well modified by the extractant. The obtained Ag nanoparticles can be dispersed well in organic solvent again, and the new fluids are very stable in air. The loading concentrations decrease with increase of solvent polarity.

Tribological properties of Cyanex 301‐modified MoS2 nano‐sized hollow spheres in liquid paraffin

Purpose – The purpose of this paper is to investigate the tribological properties of MoS2 nano‐sized hollow spheres in liquid paraffin (LP) and the corresponding action mechanism. Morever, its feasibity of industrial application as an oil additive in the industrial lubrication field is also explored.Design/methodology/approach – The tribological properties of MoS2 nano‐sized hollow spheres (NH‐MoS2) modified by Cyanex 301(di‐(2,4,4‐trimethylpentyl) dithiophosphinic acid) with size of 200 ∼ 300 nm in LP are studied and compared with those of the commercial colloidal MoS2 (CC‐MoS2) on a four‐ball tester and an Optimol SRV Oscillating friction and wear tester in a ball‐on disk configuration. The worn surfaces of the lower flat disc are examined with a scanning electron microscopy and an X‐ray photoelectron spectroscopy, respectively.Findings – Results show that NH‐MoS2 is a better extreme‐pressure additive and anti‐wear (AW) and friction‐reducing additive in LP than CC‐MoS2. Under the optimum concentration o...

Study on the thiophosphinic extractants. II. Thermodynamic functions and structural parameters of the w/o microemulsion of the saponified acid systems

Abstract Purified sodium salt of Cyanex302, di (2,4,4-trimethylpentyl) monothiophosphinic sodium, NaDTMPTP, and that of Cyanex301, di (2,4,4-trimethylpentyl) dithiophosphinic sodium, NaDTMPDTP, are prepared from the corresponding extractant respectively. The thermodynamic function Δ G o→i 0 (standard Gibbs free energy change of transferring alcohol from oil phase to interface phase) and structural parameters of the sodium salt NaA (0.200 g)–alcohol–diluent–H 2 O microemulsion system are measured. The effects of substitution of oxygen by sulfur in the extractant molecule, the used diluent, alcohol, the temperature and water content V H 2 O on the thermodynamic function and structural parameters are discussed and compared with the corresponding sodium salt of phosphinic acid (purified Cyanex272) system, respectively. The replacement of oxygen atom(s) by sulfur in HA or NaA molecules makes their steric configurations and polarities changed.

Friction and Wear Properties of Cyanex 302-Modified MoS2 Micro-Sized Spheres as Additive in Liquid Paraffin

The friction and wear properties of MoS 2 micro-sized spheres (MS-MoS2) modified by Cyanex 302 (bis(2,4,4-trimethylpentyl) monothiophosphinic acid) as additive in liquid paraffin (LP) were studied and compared with those of commercial colloidal MoS 2 (CC-MoS 2 ) on a four-ball tester and an Optimol SRV oscillating friction and wear tester in a ball-on-disc contact configuration. The worn surfaces were examined with SEM and XPS, respectively. The results showed that the Cyanex 302-modified MS-MoS 2 was a better extreme-pressure and antiwear and friction-reducing additive in LP than CC-MoS 2 . The boundary lubrication mechanism could be deduced as the effective chemical adsorption film formed by the alkyl and active elements (S, O, and P) in Cyanex 302 and tribochemical reaction and deposition film containing MoS 2 , Fe 2 O 3 , and FePO 4 . Moreover, the coexistence of sliding and rolling frictions in the lubricant of MS-MoS 2 /LP also contributed to the enhanced tribological properties.

Surfactant‐Assisted Synthesis of Cube‐Shaped PbTe and PbSe Nanocrystals

Uniform cubic‐shaped PbTe and PbSe nanocrystals have been synthesized through the surfactant‐assisted hydrothermal reaction between Pb(NO3)2 and Te or Se powders with hydrazine hydrate as reducing reagent. The products were characterized by powder x‐ray diffraction (XRD) and transmission electron microscopy (TEM). It was found that the shapes of nanocubes are well controlled by using ethylenediaminetetraacetic acid as chelating reagent and in the presence of poly(vinyl‐pyrrolidone).

Solvothermal Synthesis and Characterization of Surfactant-Modified CdS Microspheres

CdS crystals with spherical morphology have been prepared by a solvothermal method using a self-made novel block-like imidazoline-gemini surfactant quaternary ammonium salt of di (2-undecyl-1-formyl aminoethyl thiourea imidazoline) hexanediamine (SUDEIHDI) as the shape-controlling agent. The obtained CdS products are characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), infrared ray spectroscopy (IR), UV-vis absorption spectroscopy, and x-ray diffraction (XRD), respectively. In addition, the formation mechanism for the CdS sphere was also discussed.

Investigation of the Tribological Properties of Surfactant-Modified MoS2 Microsized Spheres in Base Oil 500 SN

The tribological properties of MoS 2 microsized spheres (MS-MOS 2 ) with diameter of 0.5-3 μm modified by self-prepared surfactant quaternary ammonium salt of 2-undecyl-1-dithioureldo-ethyl-imidazoline (SUDEI) as an additive in base oil 500 SN were investigated and compared with those of commercial colloidal MOS 2 (CC-MOS 2 ) on a four-ball tester and an Optimol SRV oscillating friction and wear tester in a ball-on-disk contact configuration. The worn surfaces of the bottom flat disk were examined with scanning electron microscopy and X-ray photoelectron spectroscopy. It was found that the MoS 2 microsized spheres product was a much better extreme-pressure additive and antiwear and friction-reduction additive in 500 SN than commercial colloidal MOS 2 (CC-MoS 2 ). Under the appropriate concentration of 0.1% and 0.25% for MS-MOS 2 and CC-MoS 2 and the load of 400 N, the friction coefficient of MS-MOS 2 /oil and CC-MoS 2 /oil decreased about 25.0% and 12.5% and the wear volume loss decreased about 50.4% and 12.9% compared with the pure base stock. The boundary lubrication mechanism could be deduced as the effective chemical adsorption film formed by the long chain alkyl (C 11 H 23 ) and active elements (S and N) in the surfactant SUDEI and tribochemical reaction film composed of the tribochemical reaction products.