Huaqiang Shi

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.

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...

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.

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.

Facile Synthesis of Molybdenum Disulfide Micro-Spheres and the Tribological Properties in Liquid Paraffin

Well-dispersed MoS2 micro-spheres with the diameters of 0.5∼1.5 µm have been successfully synthesized via the extraction-solvothermal method. The ions were extracted into hexane by the extractant Cyanex 302 (di-(2,4,4-trimethylpentyl) monothiophosphinic acid) firstly, then the extracted solution was given solvothermal treatment to synthesize MoS2 at 150 °C for 24 hours. The obtained samples was characterized by XRD, EDS, SEM, TEM, and HRTEM technologies, respectively. Results indicated that Cyanex 302 acted as phase transferring agent, reductant, sulfur source and morphology-controlling agent in the whole procedure. Moreover, the tribological properties of liquid paraffin (LP) containing the as-prepared MoS2 micro-spheres were also evaluated on a four-ball machine and the chemical states of some typical elements on the worn surfaces were examined with XPS, showing that the MoS2 product was an excellent oil additive in LP with good anti-wear and friction-reducing properties.

Study on the Synthesis of Cyanex 301-Modified Fe2O3 Nanoparticles

Surface modified Fe2O3 nanoparticles were successfully synthesized via different thermal treatment of the Fe(OH)3 precursor, which was obtained by the extraction-precipitation system. The Fe3+ ions were extracted into hexane by the extractant first, then the extracted solution containing Fe(III) complex was precipitated with NaOH solution. The obtained Fe(OH)3 precursor was given different thermal treatment, such as solvothermal reaction, an intense refluxing boiling tetralin and calcine at air, respectively. The obtained Fe2O3 nanoparticles were characterized by XRD, TEM, SEM, IR, UV-vis, and TG-DTG, respectively. The results showed that Fe2O3 products were well modified by extractant, which could be well dispersed into organic solvents to form the stable fluids.

Synthesis of Sulfides Nanomaterials at Aqueous-Organic Interfaces

CdS, CuS and MoS2 semiconductors were successfully synthesized at the aqueous-organic interfaces via the chemical synthesis method. The Cd2+, Cu2+, and ions were extracted into organic phase by the extractant di- (2,4,4-trimethylpentyl) monothiophosphinic acid firstly, then the obtained Cyanex 302-Cd2+ (Cu2+ or ) complexes in organic phase reacted with S2− in the aqueous phase at the aqueous-organic interfaces to synthesize sulfide nanomaterials, respectively. The obtained nanomaterials were characterized by x-ray powder diffraction, transmission electron microscopy and electron diffraction, respectively. It could be seen that the extractant played several functions in the whole procedure: the phase transferring agent, the morphology controlling agent and surface-modifying agent.

Biomolecule-Assisted Hydrothermal Synthesis ZnSe Nanocrystallites and Its Application as Oligonucleotides Label

A simple biomolecule-assisted hydrothermal approach was developed to synthesize ZnSe nanoparticles in this article. As-prepared zinc selenide was characterized by XRD, TEM, FTIR and UV-vis technologies. During the whole procedure, L-glutamic acid acted not only as complexing and capping agent, but a bridging agent between DNA molecule and zinc selenide nanospheres. The ZnSe nanoshperes could be used for the detection of the DNA hybridization. DNA specific-sequence related to PAT gene in the transgenic plants was determined with a detection range from 1.0 × 10−11 to 1.0 × 10−7 mol L−1 and a detection limit of 4.7 × 10−12 mol L−1 (3σ).