The TiO2/CdS system has attracted great attention in solar water-splitting applications owing to its desirable electronic and optical properties. With the aim of enhancing its photoelectrochemical water splitting efficiency, an efficient strategy is proposed via nanostructuring and linking it in a p–n junction configuration with NiOx. The deposition of TiO2 nanorods (NRs) and CdS was achieved using a hydrothermal synthesis route in the sequence, after which NiOx was deposited via RF magnetron sputtering. Characterisation revealed the uniform deposition of CdS onto the TiO2 NRs, forming a core-shell morphology, and the deposition of NiOx on top of the TiO2-NR/CdS resulted in a nanostructured p–n junction. X-ray photoelectron spectroscopy was used to resolve the valence band edge, and impedance studies confirmed the formation of a p–n junction; accordingly, the probable band edge positions of the photoelectrode were identified. The optimised TiO2-NR/CdS-NiOx p–n junction electrode exhibited a remarkable photocurrent of ˜30 mA cm−2 (at 1 V vs. Ag/AgCl) under AM 1.5 G simulated sunlight and an incident photon-to-current efficiency of ˜97% at 500 nm. Furthermore, during illumination, the production of H2 gas occurred with a faradaic efficiency of 95%. The results of the study demonstrate the advantage of utilizing the TiO2-NR/CdS-NiOx system in a p-n junction configuration to greatly enhancethe charge generation, separation and suppression of the charge recombination, which boosts its photoelectrochemical water-splitting performance.

A nanoscale p-n junction photoelectrode consisting of an NiOx layer on a TiO2/CdS nanorod core-shell structure for highly efficient solar water splitting

A biomaterial can be defined as a material intended to interface with biological systems to evaluate, treat, augment or replace any tissue, organ or function of the body. Major problems associated with biomaterials are their properties and biocompatibility, which need to be tackled and resolved before promoting a particular biomaterial to the market or implanting it into a biological system. To enhance the biocompatibility of the biomaterials, several surface modification strategies, such as physico-chemical, mechanical and biological modifications, have been explored. In this review, some recent applications of physico-chemical modification technologies, such as alteration in the structure of a molecule by chemical modification, surface grafting, abrasive blasting and acid etching, surface coatings, heat and steam treatment for medical materials such as polymers, metals, ceramics and nanocomposites are discussed. This article will promote physico-chemical modification as a versatile technology in surface engineering to improve the properties and biocompatibility of medical materials. Furthermore, it will instigate the growth of the biomaterial market with various high quality biomaterials.

Review: physico-chemical modification as a versatile strategy for the biocompatibility enhancement of biomaterials

Herein, we report a new Na-insertion electrode material, Na2Ti9O19, as a potential candidate for Na-ion hybrid capacitors. We study the structural properties of nanostructured Na2Ti9O19, synthesized by a hydrothermal technique, upon electrochemical cycling vs Na. Average and local structures of Na2Ti9O19 are elucidated from neutron Rietveld refinement and pair distribution function (PDF), respectively, to investigate the initial discharge and charge events. Rietveld refinement reveals electrochemical cycling of Na2Ti9O19 is driven by single-phase solid solution reaction during (de)sodiation without any major structural deterioration, keeping the average structure intact. Unit cell volume and lattice evolution on discharge process is inherently related to TiO6 distortion and Na ion perturbations, while the PDF reveals the deviation in the local structure after sodiation. Raman spectroscopy and X-ray photoelectron spectroscopy studies further corroborate the average and local structural behavior derived fro...

Nanostructured Na2Ti9O19 for Hybrid Sodium-Ion Capacitors with Excellent Rate Capability.

Agnes Aruna John, Saravana Kumar Jaganathan*, Eko Supriyanto and A. Manikandan Faculty of Biosciences and Medical Engineering, Universiti Teknologi Malaysia, Johor Bahru 81310, Malaysia Department for Management of Science and Technology Development, Ton Duc Thang University, Ho Chi Minh City 70000, Vietnam Faculty of Applied Sciences, Ton Duc Thang University, Ho Chi Minh City 70000, Vietnam IJN-UTM Cardiovascular Engineering Centre, Faculty of Biosciences and Medical Engineering, Universiti Teknologi Malaysia, Johor Bahru 81310, Malaysia Department of Chemistry, Bharath Institute of Higher Education and Research, Bharath University, Chennai 600 073, India

http://www.currentscience.ac.in/Volumes/111/06/1003.pdf

Surface modification of titanium and its alloys for the enhancement of osseointegration in orthopaedics

To improve the biocompatibility of medical implants, a chemical composition of bone-like material (e.g., hydroxyapatite) can be deposited on the surface of various substrates. When hydroxyapatite is deposited on surfaces of orthopedic implants, several parameters must be addressed including the need of rapid bone ingrowth, high mechanical stability, corrosion resistance, biocompatibility, and osseointegration induction. However, the deposition process can fail due to poor adhesion of the hydroxyapatite coating to the metallic substrate. Increasing adhesion by enhancing chemical bonding and minimizing biocoating degradation can be achieved through surface activation and pretreatment techniques. Surface activation can increase the adhesion of the biocoating to implants, providing protection in the biological environment and restricting the leaching of metal ions in vivo. This review covers the main surface activation and pretreatment techniques for substrates such as titanium and its alloys, stainless steel, magnesium alloys, and CoCrMo alloys. Alkaline, acidic, and anodizing techniques and their effects on bioapatite deposition are discussed for each of the substrates. Other chemical treatment and combination techniques are covered when used for certain materials. For titanium, the surface pretreatments improve the thickness of the TiO2 passive layer, improving adhesion and bonding of the hydroxyapatite coating. To reduce corrosion and wear rates on the surface of stainless steel, different surface modifications enhance the bonding between the bioapatite coatings and the substrate. The use of surface modifications also improves the morphology of hydroxyapatite coatings on magnesium surfaces and limits the concentration of magnesium ions released into the body. Surface treatment of CoCrMo alloys also decreased the concentration of harmful ions released in vivo. The literature covered in this review is for pretreated surfaces which then undergo deposition of hydroxyapatite using electrodeposition or other wet deposition techniques and mainly limited to the years 2000-2019.

/pdf/surface-activation-and-pretreatments-for-biocompatible-xhc1w66icq.pdf

Surface Activation and Pretreatments for Biocompatible Metals and Alloys Used in Biomedical Applications.

The results of XPS measurements of commercially pure titanium cp-Ti) before and after chemical treatment are presented. We have measured XPS spectra of core levels (Ti 2p, O 1s, C 1s, F 1s) and valence bands of coarse-grained cp-Ti before and after standard acid treatment accepted in dentistry (in 1% HF and 40% HF for 1 min). It is found, that acid treatment of cp-Ti reduces the content of hydrocarbons increasing the surface energy and bio-compatibility of Ti-implants. On the other hand, it is fixed that oxygen concentration on the surface of the acid treated cp-Ti is much higher than for the untreated sample, because the acid treatment removes the contaminated surface layers, increases their reactivity, provides a better passivation and formation of thick protecting TiO2 layer.

https://file.scirp.org/pdf/JBNB20120100013_70606286.pdf

Stefan Bartkowski

Papers

Surface Characterization of Titanium Implants Treated in Hydrofluoric Acid