Titanium Dioxide Nanomaterials: Synthesis, Properties, Modifications, and Applications

The major strategies for designing surfaces that prevent fouling due to proteins, bacteria, and marine organisms are reviewed. Biofouling is of great concern in numerous applications ranging from biosensors to biomedical implants and devices, and from food packaging to industrial and marine equipment. The two major approaches to combat surface fouling are based on either preventing biofoulants from attaching or degrading them. One of the key strategies for imparting adhesion resistance involves the functionalization of surfaces with poly(ethylene glycol) (PEG) or oligo(ethylene glycol). Several alternatives to PEG-based coatings have also been designed over the past decade. While protein-resistant coatings may also resist bacterial attachment and subsequent biofilm formation, in order to overcome the fouling-mediated risk of bacterial infection it is highly desirable to design coatings that are bactericidal. Traditional techniques involve the design of coatings that release biocidal agents, including antibiotics, quaternary ammonium salts (QAS), and silver, into the surrounding aqueous environment. However, the emergence of antibiotic- and silver-resistant pathogenic strains has necessitated the development of alternative strategies. Therefore, other techniques based on the use of polycations, enzymes, nanomaterials, and photoactive agents are being investigated. With regard to marine antifouling coatings, restrictions on the use of biocide-releasing coatings have made the generation of nontoxic antifouling surfaces more important. While considerable progress has been made in the design of antifouling coatings, ongoing research in this area should result in the development of even better antifouling materials in the future.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/adma.201001215

Antifouling coatings: recent developments in the design of surfaces that prevent fouling by proteins, bacteria, and marine organisms.

The photocatalytic properties of titanium dioxide are well known and have many applications including the removal of organic contaminants and production of self-cleaning glass. There is an increasing interest in the application of the photocatalytic properties of TiO2 for disinfection of surfaces, air and water. Reviews of the applications of photocatalysis in disinfection (Gamage and Zhang 2010; Chong et al., Wat Res 44(10):2997–3027, 2010) and of modelling of TiO2 action have recently been published (Dalrymple et al. , Appl Catal B 98(1–2):27–38, 2010). In this review, we give an overview of the effects of photoactivated TiO2 on microorganisms. The activity has been shown to be capable of killing a wide range of Gram-negative and Gram-positive bacteria, filamentous and unicellular fungi, algae, protozoa, mammalian viruses and bacteriophage. Resting stages, particularly bacterial endospores, fungal spores and protozoan cysts, are generally more resistant than the vegetative forms, possibly due to the increased cell wall thickness. The killing mechanism involves degradation of the cell wall and cytoplasmic membrane due to the production of reactive oxygen species such as hydroxyl radicals and hydrogen peroxide. This initially leads to leakage of cellular contents then cell lysis and may be followed by complete mineralisation of the organism. Killing is most efficient when there is close contact between the organisms and the TiO2 catalyst. The killing activity is enhanced by the presence of other antimicrobial agents such as Cu and Ag.

/pdf/photocatalytic-disinfection-using-titanium-dioxide-spectrum-jxvf67pgc7.pdf

Photocatalytic disinfection using titanium dioxide: spectrum and mechanism of antimicrobial activity

The diversity of (potential) applications using shape memory alloys (SMA), apart from the medical field, becomes quite large. Classic categories such as free recovery, actuators, constrained recovery, pseudo-elasticity or damping require further specifications. For example, micro-actuators, smart materials or active damping, can be all classified as actuator applications, but each of those items demands specific functional performance, dimensions and processing. Furthermore, success for applications can only be realised in so far those materials offer also a price-competitive advantage relative to other functional materials or mechanical designs. This competition requires perfect control of the material performance. It is known that especially Ni–Ti alloys can be tuned relatively easy to some specific requirements of the envisaged application: hysteresis, transformation temperatures, damping capacity. At the other side little is known on recovery stresses, wear resistance, fracture mechanics, fatigue … In this paper we would like to stress the need for further exploration of the 4P-relation: principles–properties–processing–products as well in companies as in universities or other research laboratories. This will be illustrated by describing some actual applications indicating why they are successful, other applications why they failed and still others that can only be realised if some further, probably possible, material improvement can be realised.

Non-medical applications of shape memory alloys

Electrochromics for smart windows: Oxide-based thin films and devices

Titanium dioxide (TiO2) has been developed and applied extensively in the form of coatings, in particular for its unique properties such as non-toxicity, high photocatalytic activity, and strong self-cleaning ability. These coatings, which can be prepared via various processes, have not yet been proved to be antimicrobial. This research involves an arc ion plating method to produce TiO2 film on medical grade AISI 304 stainless steel. Antimicrobial efficacy of the deposits is expected due to the photocatalysis action of the anatase phase presented in the deposit. The performance of the coating is evaluated by a JIS Z2801:2000 industrial standard. Experimental results show that TiO2 film mainly consisting of anatase structure can be prepared with a high growth rate of 5 microm/h. Antimicrobial activity (R) of the deposited TiO2 film against Staphylococcus aureus and Escherichia coli was 3.0 and 2.5, respectively, far beyond the value designated in JIS standard. This provides an effective antimicrobial surface coating method for medical implements thereby reducing the risk of hospital-acquired infections.

An antimicrobial TiO2 coating for reducing hospital-acquired infection.

http://mehdymotamedi.persiangig.com/document/nano/The%20cavitation%20erosion%20behavior%20of%20electroless%20Ni%E2%80%93P%E2%80%93SiC%20comp.pdf

The cavitation erosion behavior of electroless Ni–P–SiC composite coating

The wear characteristics of TiNi shape memory alloys against Cr-steel have been studied. Experimental results indicate that the Ti49Ni51 alloy can exhibit a better wear resistance than Ti50Ni50 alloy due to their higher hardness and pseudoelastic behaviors. Four main mechanisms, adhesion, abrasion, surface fatigue, and brinelling, are found to have important contributions to the wear characteristics of TiNi alloys. The weight loss increases with increasing wear load and sliding distance but decreases with increasing sliding speed. The contact area during sliding wear will be increased due to the variant accommodation and/or pseudoelasticity and, hence, will reduce the average compressive stress and wear damage. Variant accommodation and/or pseudoelasticity can also stabilize the crack tips and hinder crack propagation, hence improving the wear characteristics of TiNi alloys.

Wear characteristics of TiNi shape memory alloys

Antibacterial silver coatings on textiles, formed by various coating processes, have attracted substantial attention. However, the durability of these coatings in practice is poor, limiting their usage. The goal of this study is to prepare antibacterial silver films on poly(ethylene terephthalate) (PET) fabrics by high-power impulse magnetron sputtering (HIPIMS), which is known to provide a high plasma density, so as to form a strongly adhered film at a relatively low substrate temperature. These silver-coated textiles are expected to exhibit antibacterial efficacy and durability. The experimental results herein reveal that the silver coating can be successfully deposited on PET fabric by HIPIMS with a crystal structure presenting (111) preferred orientation and that the fibers are uniformly covered. Pre-treatment with oxygen plasma for a single minute can effectively enhance film adhesion in dry and wet rubbing tests, such that the color fastness can be ranked Grade 5 and Grade 4, respectively. The coated fabric retains the mechanical properties of its original bare fabric and the coating procedure does not induce damage to PET fabric. Antimicrobial performance testing indicates that a silver film that is deposited for more than 1 min provides strong bacteriostatic (> 2.0) and bactericidal (> 0) effects, based on the JIS Standard. Additionally, the coated fabrics retain their antimicrobial capability after 20 cycles of washing, demonstrating their long-term durability.

Ju-Liang He

Papers

An antimicrobial TiO2 coating for reducing hospital-acquired infection.

The cavitation erosion behavior of electroless Ni–P–SiC composite coating

Wear characteristics of TiNi shape memory alloys

Antibacterial silver coating on poly(ethylene terephthalate) fabric by using high power impulse magnetron sputtering

Cavitation erosion and corrosion behavior of Ni–Al intermetallic coatings