Jinhua Lu

Nitrogen-doped carbon nanotubes synthesized by pyrolysis of nitrogen-rich metal phthalocyanine derivatives for oxygen reduction

Two kinds of N-doped multiwalled carbon nanotubes (N-MWCNTs) S1 and S2 are prepared by pyrolysis of nitrogen-rich metal phthalocyanine derivatives, i.e. a mixture of metal tetrapyridinoporphyrazines (MTAPs, M = Fe2+, Ni2+) and tetrapyrazinoporphyrazines (MPTpzs) in a chemical vapour deposition furnace. The N-MWCNTs S1 and S2 have a straight structure and a high N/C atomic ratio. The ratios of N/C in S1 and S2 are 20.01% and 18.50%, respectively. The N atoms in S1 exhibit a uniform distribution, and the majority of N atoms are present in a pyridine type environment, while the N atoms in S2 are concentrated in certain areas, and are mainly in a graphite type environment. The electrocatalytic activities of the N-MWCNTs obtained are measured by the rotating disk electrode technique and cyclic voltammetry in an oxygen-saturated 0.1 M KOH solution. The results show that S1 exhibits a one-step, four-electron pathway for the reduction of oxygen (ORR), whereas S2 exhibits a two-step, two-electron process for ORR, S1 has much higher catalytic activity than S2.

3D CuO nanosheet wrapped nanofilm grown on Cu foil for high-performance non-enzymatic glucose biosensor electrode

3D binder-free CuO nanosheets wrapped nanofilms has been in situ synthesized on Cu substrate by a simple and facile procedure, with an aim of fabricating high-performance glucose sensor. The complex morphology that the nanosheet grown on Cu subtract evolved into nanofilms and eventually converged to nanowires, is benefit for the mass transport and electro-catalysis. Compared the ECSA of the CuO modified electrode to that of the bare Cu electrode, the effective surface area during the electro-catalysis of the CuO/Cu electrode is much larger. The glucose sensor based on CuO products exhibited high sensitivity (4201μAcm-2mM-1), low detection limit (0.5μmol/L) and quick response time (0.7s). And the stability and selectivity is also fantastic. According to the serum sample analysis, it transpires that the CuO/Cu sensor displayed excellent recovery compared to the concentration values measured by medial method. So this material shows great potential applications in glucose sensors.

Dipotassium hydrogen phosphate as reducing agent for the efficient reduction of graphene oxide nanosheets

By using dipotassium hydrogen phosphate (K2HPO4·3H2O), an efficient and environmentally friendly route for the reduction of the exfoliated graphene oxide nanosheets (GO) is reported in this work. The chemically reduced graphene oxide nanosheets (RGO) have been analyzed by X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectra, X-ray photoelectron spectroscopy, Field emission transmission electron microscopy, Atomic force microscopy, and Thermogravimetric analysis. Considering the analysis results, dipotassium hydrogen phosphate plays a key role in the efficient removal of the oxygen-containing groups in GO, which avoids the use of high toxic and hazardous reducing agents commonly used to obtain RGO in chemical reduction of GO. Dipotassium hydrogen phosphate itself and prepared graphene are environmentally friendly and inexpensive, which may open new opportunities for mass production of graphene by reducing GO.

MG63 OSTEOBLAST-LIKE CELLS RESPONSE OF SiC COATING FOR CARBON/CARBON COMPOSITES

A SiC coating for carbon/carbon (C/C) composites was produced by pack cementation to use as a bonding and buffer layer between C/C composites and bioactive ceramic for application in orthopaedic implants. The microstructure and MG63 osteoblast-like cell responses of the coating were investigated. The results confirmed that the SiC coating displayed a dense and uniform microstructure. MG63 cells attached and spread favorably on SiC coating, and cell proliferation was better on SiC coating than on uncoated C/C composites surface. The SiC coated C/C composites have the potential to be used in artificial implants.

N-doped graphene analogue synthesized by pyrolysis of metal tetrapyridinoporphyrazine with high and stable catalytic activity for oxygen reduction

We fabricated N-doped graphene analogue by pyrolysis of metal tetrapyridinoporphyrazine (MTAP), a kind of N rich metal phthalocyanine derivative with four pyridine substituents. The combination results of elemental analysis, X-ray photoelectron spectroscopy and electron-energy-loss spectrometry mapping show that the obtained N-doped graphene analogue is nitrogen-rich and has uniform distribution of C and N atoms. The atomic ratio of N/C in the obtained graphene is about 20.5%. The majority of N atoms are present in a pyridine type environment. Theoretical analysis based on DFT calculations has been performed for a deep understanding of the role of MTAP in the synthesis of the N-doped graphene analogue. Electrochemistry results show the N-doped graphene analogue exhibits a one-step, four-electron pathway for oxygen reduction reaction, and shows almost identical voltammetric responses before and after about 100 000 cycles, indicating that it has high and stable electrocatalytic activity for oxygen reduction.

In vitro mineralization of MC3T3‐E1 osteoblast‐like cells on collagen/nano‐hydroxyapatite scaffolds coated carbon/carbon composites

Collagen/nano-hydroxyapatite (collagen/nHA) scaffolds were successfully prepared on carbon/carbon composites as bioactive films using the layer-by-layer coating method. Surface characterizations of collagen/nHA scaffolds were detected by scanning electron microscope (SEM), X-ray diffraction (XRD), and Fourier transform infrared (FTIR) spectroscopy. Compressive strengths of the scaffolds were evaluated by a universal test machine. In vitro biological performances were determined using scaffolds seeded with MC3T3-E1 osteoblasts-like cells and cultured in mineralization medium for up to 21 days. In addition, cellular morphologies and several related gene expressions of MC3T3-E1 cells in the scaffolds were also evaluated. Chemical and morphological analysis showed that the scaffolds had uniform pore sizes and unified phase composition. Mechanical testing indicated that the collagen/nHA scaffolds had the highest compressive strength in 50% of strain condition when the proportion of collagen and nano-hydroxyapatite was 1:3. Cellular morphology observations and cytology tests indicated that MC3T3-E1 cells were adhered on these scaffolds and proliferated. SEM photographs and gene expressions showed that mineralized MC3T3-E1 cells and newly formed extra cellular matrix (ECM) filled up the pores of the scaffolds after the 3-week mineralization inducement. Nano-sized apatite particles were secreted from MC3T3-E1 cells and combined with the reconstructed ECM. Collectively, collagen/nHA scaffolds provided C/C composites with a biomimetic surface for cell adhesion, proliferation and mineralized extra cellular matrices formation.

Improved Surface Wettability of Water by Applying SiC/Ti6Al4V Coatings on Carbon/Carbon Composites

SiC/Ti6Al4V coatings were applied on carbon/carbon composites to improve the surface wettability of water. SiC interlayers were preprepared by pack cementation to bond both the carbon/carbon composites and the Ti6Al4V, and then the Ti6Al4V coatings were applied by magnetron sputtering technique. The morphology and crystalline of the SiC/Ti6Al4V coatings were analyzed by scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction. The surface wettability of the coatings was tested by video-based contact angle measuring device. The results showed that SiC can serve as an interlayer between the carbon/carbon composites and Ti6Al4V. The SiC/Ti6Al4V coatings covered the carbon/carbon composites uniformly with spherical morphology. The coatings improved the surface wettability of carbon/carbon composites with the contact angle of water decreasing from 85.7 ± 4.1° to 26.5 ± 0.1°.

Unique cytological behavior of MC3T3-E1 osteoblasts on H2O2-modified C/C composites in vitro

MC3T3-E1 osteoblasts were cultured on H2O2-modified and unmodified carbon/carbon (H-C/C and C/C) composites for one week in order to evaluate differences in cell adhesion, spreading, and proliferation. The results indicated a certain degree of enhancement in the cell adhesion capability of osteoblasts cultured on H-C/C samples. Cellular morphologies after cell adhesion were observed via scanning electron microscopy (SEM), which showed that the cells adhered more closely and spread more widely on the H-C/C sample surface. However, no cell appeared in several multiple and continuous types of minor pores on both the C/C and H-C/C surfaces. In addition, two unique situations were observed on the H-C/C samples: an outline change of the osteoblasts was observed when the cells spread across some minor pores, and the cells entered and adhered well in some larger pores.摘要本文评估了MC3T3-E1成骨细胞在碳/碳复合材料和H2O2改性的碳/碳复合材料表面的细胞黏附、增殖和细胞铺展的细节差异. 结果表明, 成骨细胞的黏附率在改性的碳/碳复合材料表面有一定的提高. 通过对细胞形貌的扫描电子显微镜(SEM)观察和对比, 两个特殊的细胞形貌使我们意外发现细胞的黏附与碳/碳复合材料表面固有的孔隙有着密切关系. 一个是没有细胞在碳/碳复合材料表面可见的孔隙处,另一个是成骨细胞在跨越孔隙时出现轮廓的变化. 最后我们还发现, 成骨细胞可以黏附到改性碳/碳复合材料的内部.

Surface characterisation and in vitro behaviour of carbon/carbon composites with various surface modifications

Abstract The success of implants is determined by the cell response to biomaterials and the integration into the tissue. The surface characteristic of the biomaterial is considered as a key factor to influence the cell response and integration. The aim of this work is to determine the effect of various surface modifications for carbon/carbon (C/C) composites on the MG63 cell responses. Surface modified C/C composites including rough shaped C/C composites (RCC), post-deposition treated C/C composites (PCC) and diamond-like carbon coated C/C composites (DCC) were prepared. The surface characterisation was performed on three kinds of surface modified C/C composites using scanning electron microscopy, Raman spectroscopy, laser confocal scanning microscope and video based contact angle measuring device. Evaluation of the human osteoblast-like MG63 cell responses to the three kinds of surface modified C/C composites was carried out. The RCC had a rough surface with some grooves. The PCC and DCC showed spherical morphologies with different grain sizes. The surface roughnesses for RCC, PCC and DCC were Ra = 1·60±0·10, 0·69±0·10 and 0·76±0·10 μm respectively. The RCC, PCC and DCC had similar water contact angles of 85·7±4·1, 83·6±0·4 and 92·7±2·3° respectively. The cell responses showed that both PCC and DCC had better cell spreading than RCC. The cell proliferation behaviour of the three kinds of surface modified C/C composites was in the following order: DCC>PCC>RCC. The DCC shows favourable cell compatibility and further has the potential to be used in orthopaedic applications.

Electrodeposition of nanostructured calcium phosphate coating under magnetic field

Abstract To obtain nanostructured calcium phosphate (CaP) and improve the adhesion of CaP coating to carbon/carbon (C/C) composites, the CaP coating was deposited on the substrate through electrodeposition under magnetic field. The effect of magnetic fields with different orientations on the morphology, phase and adhesion strength between the coating and C/C composites was investigated. The octacalcium phosphate coating was deposited on C/C composites under magnetic fields with different orientations. The morphology of the coating could be altered by superimposed magnetic field. Fishbone-like particles composed of nanofibred CaP were formed on the C/C when the magnetic field was oriented parallel to the current density. A homogeneous coating with a flower-like structure was formed when the magnetic field was applied perpendicularly to the electric field. The flower-like structure was composed of nanosized and plate-like crystals. The adhesion of the coating to the C/C substrate was improved by applying magnetic field, especially magnetic field perpendicular to the electric field.