Ren Ying; Wang Renjie; Cheng Qiaohuan; Chen Qianqian; Xu Zhigao
Abstract
Diamond-like carbon (DLC) coatings, due to excellent tribological and biological properties, were used wildly to improve the wear resistance and corrosion resistance of the metal-based artificial joints. In this work, DLC coatings were deposited by a vacuum arc using the anode-cathode diameter ratio ...
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Diamond-like carbon (DLC) coatings, due to excellent tribological and biological properties, were used wildly to improve the wear resistance and corrosion resistance of the metal-based artificial joints. In this work, DLC coatings were deposited by a vacuum arc using the anode-cathode diameter ratio of da/dc=3/1 with the negative bias applied to the P2000 steel substrate. The relation between the substrate bias and properties of DLC coatings was investigated. The study showed that DLC coating had lower ratio of sp < sup > 2 /sp < sup > 3 and lower friction coefficient at higher bias of – 750 V. With increasing bias, the wear particle size of DCL coatings tended to move towards the distribution of smaller particles. Comparing with the uncoated P2000, P2000 coated with DLC deposited at – 750 V had better biocompatibility. It was revealed that DLC coating deposited by a vacuum arc technique in conjunction with high substrate DC biasing can improve the tribological property and biocompatibility of P2000.
Lori Rastogi;J. Arunachalam
Abstract
A green synthetic approach for the highly stable, size controlled synthesis of gold nanoparticles is being described. The study explores the use of aqueous extract of garlic cloves as reducing/stabilizing agent for the synthesis of gold nanoparticles. The synthesis is achieved by heating the mixture ...
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A green synthetic approach for the highly stable, size controlled synthesis of gold nanoparticles is being described. The study explores the use of aqueous extract of garlic cloves as reducing/stabilizing agent for the synthesis of gold nanoparticles. The synthesis is achieved by heating the mixture of aqueous garlic extract and HAuCl4 at 95ºC in water bath at pH-10 for 2 hrs. The formation of gold nanoparticles was confirmed from the appearance of pink color and an absorption maximum at 530 nm. Further, extract concentration and type of alkali (NH4OH/NaOH) has been varied to tune the size of nanoparticles. The size of the synthesized gold nanoparticles was found to decrease (56.5 ± 13.6 to 24.7 ± 8.2) with increasing extract concentration (0.5%-1.0%) in the presence of NH4OH. In the presence of NaOH, the synthesis time was reduced to 20 min, with an average particle size of 5.5 ± 2.7. Transmission electron microscopy analysis indicated that non-aggregated gold nanoparticles of various sizes could be synthesized by simple change in reaction conditions. The synthesized gold nanoparticles were found to be pure face centered cubic crystals as suggested by selected area electron diffraction and X-ray diffraction patterns. Fourier transform infrared spectroscopy revealed possible role of S-allyl-cysteine as the major component responsible for reduction of Au 3+ to Au 0 and protein/amino acids as stabilizing agents. The gold nanoparticles were found to have remarkable in vitro stability: showed no sign of aggregation at room temperature storage for a long time (more than 6 months), could resist aggregation in aqueous media with high concentrations of NaCl, in various buffers including: cysteine, histidine, bovine serum albumin and at host of pH ranges. Further, cytotoxicity evaluations on S. cerevisiae have shown non-toxic nature of the synthesized gold nanoparticles up to 100 µM of concentration as assessed by well diffusion and inhibition of colony forming efficiency assay. Ease in size control, high stability and biocompatible nature of garlic extract reduced, stabilized gold nanoparticles suggests that they could be potential candidates for drug delivery applications.