Journal of Materials Chemistry Blog

A team from Oklahoma report the fabrication of non-leaching antibacterial surfaces using a single-step vapour crosslinking method.

Single-step fabrication of non-leaching antibacterial surfaces using vapor crosslinking
Yumin Ye, Qing Song and Yu Mao
J. Mater. Chem., 2010, Advance Article
DOI: 10.1039/C0JM02578J, Paper

Bactericidal surfaces are highly desirable to prevent bacteria-associated infections in hospital and health care facilities. Current surfaces are based on the release of antibacterial agents, however, leaching of antibiotics can contribute to the escalation of bacteria resistance. An alternative strategy is to create non-leaching antibacterial surfaces. The non-leaching surfaces kill bacteria on contact, which has been reported to reduce the probability of developing bacteria resistance.

Yu Mao and colleagues copolymerised vapours of dimethylaminomethylstyrene (DMAMS) and ethylene glycol diacrylate (EGDA) to produce crosslinked polymer coatings.  The tertiary amine groups in DMAMS units become partially protonated at neutral pH conditions, resulting in crosslinked coatings which have cationic charges distributed across the polymer network and kill bacteria through disruption of the bacteria membrane upon surface contact. Killing efficacy of more than 99.99% against both B. subtilis and E. coli was achieved and leaching tests indicated that the crosslinked coatings did not leach from the surface to kill bacteria and were stable after the durability tests.

Interested in knowing more?  Read the full article here.  Free until November 22nd!

Erin Murphy from the University of California reports the use of birefringence to assess damage and extent of repair in healable polymers based on the thermally reversible Diels–Alder reaction, in this ‘Hot Article’.

The return of photoelastic stress measurements: utilizing birefringence to monitor damage and repair in healable materials
Erin B. Murphy
J. Mater. Chem., 2011, Advance Article
DOI: 10.1039/C0JM02308F, Paper

Examining a transparent polymer under polarized light reveals the stress distribution throughout the sample due to the birefringence in the material arising from anisotropy, clearly indicating areas of high stress; by applying a photoelastic coating to metal and opaque composite structures, it is also possible to identify areas of stress in non-transparent materials and parts.

Herein, Erin Murphy demonstrates the application of birefringence and the principles of photoelastic stress measurements to monitor a healable polymer. By systematically monitoring the birefringence of the material under a controlled applied stress, her group have developed their own calibration curve for the analysis of isochromatic fringes in the polymers.

The birefringent property of these polymers affords the ability to analyze residual stress in a fabricated sample, in order to assess the sites most likely to fracture and to then re-design the specimen geometry and processing parameters to avoid such areas within the material.

Interested in knowing more?  Read the full article here.  Free until November 22nd!

Processable donor–acceptor type electrochromes switching between multicolored and highly transmissive states towards single component RGB-based display devices 
Abidin Balan, Derya Baran and Levent Toppare
J. Mater. Chem., 2010, Advance Article
DOI: 10.1039/C0JM01815E, Paper

Levant Toppare and his team reported last year in ChemComm on the synthesis of a polymer (PTBT) with the capability to switch between all RGB colours, black and transmissive states.  In this Journal of Materials Chemistry ‘Hot Article’ donor acceptor type PTBTs (PTBT-DAs) with alternating alkyl chain substitution were synthesized and characterized in terms of their electrochemical and optical properties.

The electrochemical and spectral results demonstrate that in the context of low cost flexible display device technology, requirements for polymers showing multicoloured and transmissive states can be fulfilled by PTBT-DAs.

Interested in reading more?  Read for free here until November 19th.

Anomalous Eu layer doping in Eu, Si co-doped aluminium nitride based phosphor and its direct observation
Takashi Takeda, Naoto Hirosaki, Rong-Jun Xie, Koji Kimoto and Mitsuhiro Saito
J. Mater. Chem., 2010, Advance Article
DOI: 10.1039/C0JM02096F, Paper

Takeshi Takeda and colleagues in Japan have provided insight into the luminescent properties of Eu, Si co-doped AlN.  This material shows blue luminescence by UV and electron excitation. However, it is not clear how Eu is located in the wurtzite AlN lattice as there is not enough space for a large Eu cation.  In the present study, the team from The National Institute of Materials Science and Tohoku University set out to elucidate the luminescent Eu centre’s location and the role of co-dopant Si.

Their findings show that Si co-doping is essential for Eu incorporation into AlN and that Eu forms a single layer structure with the Si condensation between the AlN wurtzite blocks.  Their work indicates that layer type doping can be used to design new phosphors.

Interested in reading more?  Read for free here until November 19th.

An improved synthesis of Mn-doped ZnSe quantum dots offers tailored fluorescent labels for biomedical imaging.

Mn:ZnSe quantum dots have many interesting properties including tuneable photoluminescence, high colour purity and biocompatibility. To improve the properties Hongzhi Wang, Yaogang Li, and colleagues at Donghua University, Shanghai, China, have developed a new synthesis. The simple aqueous phase method allows control over the size of the quantum dots and the photoluminescence can be tuned across a broader range by changing the reaction conditions. The quantum dots created by this method also have a higher quantum yield compared to previous synthetic routes which should improve the performance of any biomedical imaging agents based on this material.

Mn:ZnSe quantum produced by this method are more stable than CdTe to UV irradiation and chemical oxidation. Mn:ZnSe quantum dots don’t contain Cd (a common component in quantum dots) eliminating the risk of Cd leaching from the material and poisoning patients. The stability and lack of Cd makes these quantum dots promising candidates for biomedical applications.

Read the full article here: Pengtao Shao, Qinghong Zhang, Yaogang Li and Hongzhi Wang, J. Mater. Chem., 2010, DOI: 10.1039/C0JM01878C

Nanogel-based sensors with dual temperature and mercury ion detection capabilities is reported in this ‘Hot Article’ from Changhua Li and Shiyong Liu from the University of Science and Technology of China in Hefei.  This is the first report of successful integration of stimuli-responsive nanogels with well-developed small molecule reaction-based selective metal ion sensing moieties.

Mercury is one of the most harmful heavy metal ions to humans, therefore sensitive detection and imaging in organisms and tissue is crucial.  To achieve this, current efforts have focused on the invention of ratiometric, water-soluble, and cell-permeable Hg²⁺-sensing ensembles. 

In this study, Li and Liu synthesise a 1,8-naphthalimide-based polarity-sensitive and Hg²⁺-reactive monomer (NPTUA) and copolymerise this with N-isopropylacrylamide (NIPAM) to produce NUPTA labelled PNIPAM nanogels. The nanogel-based chemosensors possess a high selectivity and sensitivity for Hg²⁺ at room temperature, achieving a detection limit at the nanomolar level on a ratiometric basis.  Furthermore, thermo-induced nanogel collapse can considerably enhance the detection sensitivity.

Interested in knowing more?  Read the full article here… FREE until November 16th.

Responsive nanogel-based dual fluorescent sensors for temperature and Hg²⁺ ions with enhanced detection sensitivity
Changhua Li and Shiyong Liu
J. Mater. Chem., 2010, Advance Article
DOI: 10.1039/C0JM01828G, Paper

L. Muccioli and colleagues from the University of Bologna have investigated, using atomistic molecular dynamics simulations, the high temperature molecular organization of the linear oligothiophene α-sexithienyl (T6), well known for its organic electronics applications. The team found that the torsional flexibility of sexithiophene allows for a temperature dependence of the aspect ratio, which drives the formation of nematic and smectic liquid crystalline phases.

Liquid crystalline oligothiphenes are of interest as they may provide the best morphology to maximise overlap between neighbouring molecules, thus conferring the greatest charge (hole) mobility between molecular units. Due to the difficulty of performing experimental measurements at ~600K this theoretical study was performed to investigate the potential of liquid crystal oligothiophenes.  The authors hope that their findings will stimulate future experimental determinations.

Interested in knowing more?  Read the full article here.  FREE until November 15th.

An atomistic simulation of the liquid-crystalline phases of sexithiophene 
A. Pizzirusso, M. Savini, L. Muccioli and C. Zannoni
J. Mater. Chem., 2011, Advance Article
DOI: 10.1039/C0JM01284J, Paper

Growth and replication of ordered ZnO nanowire arrays on general flexible substrates
Su Zhang, Yue Shen, Hao Fang, Sheng Xu, Jinhui Song and Zhong Lin Wang
J. Mater. Chem., 2010, Advance Article
DOI: 10.1039/C0JM02915G, Communication  

During the past several years, there has been a growing interest in one-dimensional ZnO nanostructures for their potential applications in fabricating electronic, optoelectronic, electromechanical and electrochemical devices. Current synthesis techniques require single crystallinity of the substrate and high growth temperatures, seriously limiting the compatibility of these methods with organic substrates for applications in flexible electronics. Hydrothermal synthesis is an attractive alternative because it could be carried out at a relatively low temperature around 70–90 °C, and could allow for multiple crystalline and even amorphous substrates.  Zhong Lin Wang and colleagues have developed a new technique of synthesizing patterned ZnO nanowire arrays on multiple flexible organic substrates using a novel chemical approach and a new transferring method.  

To find out more read the full article here.  Free until November 12^th!  

Self-assembled anodic TiO₂ nanotube arrays: electrolyte properties and their effect on resulting morphologies
Sorachon Yoriya and Craig A. Grimes
J. Mater. Chem., 2011, Advance Article
DOI: 10.1039/C0JM02421J, Paper

A team from The Pennsylvania State University have, for the first time, revealed the parameters, during synthesis, which affect the morphology of TiO₂ nanotube arrays.  

Self-assembled TiO₂ nanotube arrays fabricated by electrochemical anodization of titanium are of great interest having been successfully used in many applications including gas sensing, water photoelectrolysis, drug delivery and photovoltaics.  In the synthesis of TiO₂ nanotube array films it is important to achieve specific nanotube array morphological features, including pore size, length, wall thickness, and tube-to-tube spacing for enhanced device performance, however, the key parameters controlling self-organization of the nanotubes have remained unclear. This study, by Sorachon Yoriya and Craig Grimes elucidates the dependence of the electrolyte conductivity on the titanium concentration, and electrolyte effect on the morphological features of the resulting nanotubes.  

To find out more read the full article here.  Free until November 12^th!

Polymers that can capture harmful bacteria as they pass through the gut have been developed by UK scientists. This could reduce incidence of salmonella poisoning and improve shelf-life of meat products, they claim. 

Salmonella, a major food-borne pathogen is a serious problem in the food industry, as well as of clinical and veterinary importance. The ‘use-by date’ marked on foods reflects the date by which such bacteria will have multiplied to their maximum safe level for consumption. 

‘If the pathogen level can be lowered at the point of food production, then the shelf-life may become longer and the food safer,’ says Mark Bradley at Edinburgh University. In collaboration with Maurice Gallagher, also at Edinburgh University, Bradley’s team have identified polymers that bind strongly to a particular strain of salmonella while having minimal effect on the beneficial ‘good’ bacteria. These polymers could be added to commercial feedstuff for animals, such as chickens.

This article has featured in Highlights in Chemical Science and has been selected as a ‘Hot Article’ for Journal of Materials Chemistry.  It will be free to read until the 9^th November. 

To view Erica Wise’s full Highlights in Chemical Science article, please click here: Banishing bad bacteria 

To read the full article please click here: Colonising new frontiers—microarrays reveal biofilm modulating polymers
Salvatore Pernagallo, Mei Wu, Maurice P. Gallagher and Mark Bradley
J. Mater. Chem., 2011, Advance Article
DOI: 10.1039/C0JM01987A, Paper