Qingren Zhu

Synthesis and characterization of water-soluble multiwalled carbon nanotubes grafted by a thermoresponsive polymer

Water-soluble multiwalled carbon nanotubes (MWNTs) with temperature-responsive shells were successfully prepared by grafting poly (N-isopropylacrylamide) (PNIPAM) from the sidewalls of MWNTs, via surface reversible addition-fragmentation chain transfer (RAFT) polymerization using RAFT agent functionalized MWNTs as the chain transfer agent. Thermogravimetric analysis (TGA) measurements showed that the weight composition of the as-grown PNIPAM polymers on the MWNTs can be well controlled by the feed ratio (in weight) of NIPAM to RAFT agent functionalized MWNTs (MWNT-SC(S)Ph). The MWNT-g-PNIPAM has good solubility in water, chloroform, and tetrahydrofuran (THF). Transmission electron microscope (TEM) and scanning electron microscope (SEM) images also showed that the MWNT-g-PNIPAM was dispersed individually and eventually bonded with the polymer layer by surface RAFT polymerization. The PNIPAM shell is very sensitive to a change of temperature. This method could find potential applications by grafting other functional polymer chains onto MWNTs.

Fabrication of silver/cross-linked poly(vinyl alcohol) cable-like nanostructures under γ-ray irradiation

Ag/cross-linked poly(vinyl alcohol) (PVA) cable-like nanostructures were synthesized with control in an aqueous solution of a hydrolysable amphiphilic block polymer, poly(vinyl acetone) (PVKA) (ketalization degree DH = 0.533) under γ-ray irradiation, via one-step in situ reduction of Ag+ and cross-linking of alcohol units. In the present approach, we try to control the speed of the cross-linking reaction of PVA chains (alcohol units), which are yielded from the hydrolysed PVKA, utilizing the low hydrolysis rate of the PVKA in dilute acidic solution.

One-step functionalization of multi-walled carbon nanotubes with Ag/polymer under γ-ray irradiation.

We reported an easy strategy of using γ-ray irradiation to functionalize multi-walled carbon nanotubes (MWCNTs) without the use of aggressive acid treatment, all in a single processing step. In this paper, we tried to decorate MWCNTs with Ag nanoparticles relying on covalently bonded polymers, via one-step covalent grafting of the polymer to the surface of MWCNTs, and simultaneous reducing of Ag(+) ions to Ag which are then efficiently anchored onto the MWCNTs. Herein, the polymer involved was the commercially available polymer poly(vinyl alcohol) (PVA) and two of its derivatives, polyvinylacetone with ketalization degree D(H) = 0.22 and 0.53. It is envisioned that this simple but efficient method could be extended to fabricate other CNT-based hybrids for both theoretical study and applications in biological and technological fields.

Functionalized carbon nanotubes with polystyrene-block-poly (N -isopropylacrylamide) by in situ RAFT polymerization

A fascinating nano-object, amphiphilic polymer brushes with a hard core of multiwalled carbon nanotubes (MWNTs) and a relatively soft shell of polystyrene-block-poly (N-isopropylacrylamide) (PS-b-PNIPAM), was easily constructed by in situ surface reversible addition–fragmentation chain transfer (RAFT) polymerization of styrene followed by N-isopropylacrylamide on the modified convex surfaces of MWNTs (MWNT-PS). The structure and morphology of the as-prepared hybrid nanomaterials were characterized and confirmed by Fourier-transform infrared (FTIR) spectrometry, nuclear magnetic resonance (NMR) spectrometry, thermogravimetric analysis (TGA) and Raman spectroscopic analysis. The MWNT-PS-b-PNIPAM that was produced has a PNIPAM block, which is very sensitive to temperature. Such a complex nano-object could open a door to the fabrication of novel functional carbon nanotube-based nanomaterials or nanodevices with designable structures and tailor-made properties.

In situ formation of Ag flowerlike and dendritic nanostructures in aqueous solution and hydrolysis of an amphiphilic block copolymer

Silver flowerlike and dendritic nanostructures were synthesized in an aqueous solution of a hydrolysable amphiphilic block copolymer polyvinylacetone (PVKA) via in situ reduction of Ag(+) and hydrolysis of PVKA at room temperature. Compared with a previous result, the complete hydrolysis time of PVKA is greatly shortened in this process.

Self-assembly and characterization of novel amorphous SiOx (x = 2.1) nanospheres

We report the self-assembly and characterization of amorphous SiOx nanospheres with diameters 210–240 nm. The preparation method was based on hydrolysation-induced self-assembly with Na2SiO3 as the silica precursor and polyacrylamide gels as the template. Ultraviolet and blue–green photoluminescence were observed at room temperature from amorphous SiOx nanospheres. The photoluminescence spectrum has peaks at 400 and 530 nm. From the x-ray photoelectron spectroscopy and energy disperse x-ray spectroscopy we found that the atomic ratio of Si to O is about 1:2.1. From the infrared spectrum and x-ray photoelectron spectroscopy, we suggest that the origin of the stable emission is Si–OH complexes located on the surface of the nanospheres. The silica nanospheres may have potential applications in future integrated optical devices.

Preparation of nanoporous SiOx materials via interpenetrating polymer network method

Abstract In this letter, polyacrylamide gels with SiO 3 2− and Na + ions in the porous were prepared by using free-radical aqueous polymerization method. Nanoporous SiO x materials were prepared by heating the polyacrylamide gels with colloid of silicic acid in porous to 600 °C and held at this temperature for 24 h. The porous size of nanoporous SiO x materials in the obtained samples was investigated by scanning electron microscopy (SEM) and the average porous size is 50 nm in diameter. From SEM image, we can see the porous size distribution is narrow, but the porous array is irregular. Nanoporous SiO x materials were investigated from the X-ray photoelectron spectra (XPS) spectra and infrared spectrum of the obtained samples. The chemical mechanism for the formation of nanoporous SiO x materials is discussed.

Synthesis of various size CdS nanocrystals in pore of polyacrylamide gels at room temperature

Abstract In this letter, polyacrylamide gels were prepared by using free-radical aqueous polymerization method and varying the concentration of the N , N ′-methylene-bis-acrylamide from 0.1% to 0.3%, which act as crosslinker. CdS nanocrystals were formed in pore of the polyacrylamide by immersing the gels in 0.1 mol l −1 CdCl 2 and 0.1 mol l −1 Na 2 S aqueous solution at room temperature. The effect of pore size of polyacrylamide gels on the size of CdS nanocrystals in the samples was investigated by X-ray powder diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). The CdS crystallite structure was investigated from the XRD spectra of the samples and the CdS crystallite average sizes in the pore of polyacrylamide gels were 4.1, 3.4 and 2.2 nm in diameter, respectively. From HRTEM, we can see the size distribution is narrow. The chemical mechanism for the formation of CdS nanocrystals is discussed.

Controlled synthesis of novel 3D dendritic Bi2S3 /cross-linked poly(vinyl alcohol) nanocomposites

Novel spherical three-dimensional (3D) dendritic Bi2S3 /cross-linked poly(vinyl alcohol) (PVA) nanocomposites were successfully synthesized in aqueous solution of amphiphilic polyvinylacetone (PVKA) (ketalization degree DH = 0.549), via one-step in situ decomposition of the complex [Bi(Tu)x]3+ under γ-ray irradiation, utilizing the controllable hydrolysis property of PVKA in acidic solution. Herein, PVA chains are obtained from the hydrolysed PVKA. These uniform 3D spherical nanocomposites have a structure similar to that found in the natural lotus leaf, where every microscale papilla on the leaf surface is covered by nanoscale papillae.

Novel dendritic nanostructures: self-assemblies of nanoparticles of poly(vinyl alcohol) coated Ag and/or Cu2O

Novel dendritic nanostructures, which are actually self-assemblies of nanoparticles of poly(vinyl alcohol) (PVA) coated Ag and/or Cu2O, were controllably synthesized in an aqueous solution of amphiphilic polyvinylacetone (PVKA) (DH = 0.549), via a one-step in situ reduction of Ag+ and Cu2+ under γ-ray irradiation, using the low hydrolysis rate of the PVKA in the dilute acidic solution. Subsequently, the hydrolysis of PVKA yields PVA chains.