Silver nanoparticles prepared by gamma irradiation across metal-organic framework templates

In this study, we demonstrate for the first time the successful fabrication of well-dispersed ultrafine silver nanoparticles inside metal-organic frameworks through a single step gamma irradiation at room temperature. HKUST-1 crystals are soaked in silver nitrate aqueous solution and irradiated with a Cobalt 60 source across a range of irradiation doses to synthesize highly uniformly distributed silver nano-particles. The average size of the silver nanoparticles across the Ag@HKUST-1 materials is found to vary between 1.4 and 3 nm for dose exposures between 1 and 200 kGy, respectively. The Ag@HKUST-1 hybrid crystals exhibit strong surface plasmon resonance and are highly durable and efficient catalytic materials for the reduction of 4-nitrophenol to 4-aminophenol (up to 14.46 × 10-3 s-1 for 1 kGy Ag@HKUST-1). The crystals can be easily recycled for at least five successive cycles of reaction with a conversion efficiency higher than 99.9%. The gamma irradiation is demonstrated to be an effective and environmental friendly process for the synthesis of nano-particles across confined metal-organic frameworks at room temperature with potential applications in environmental science.

Tuning the grade of graphene: Gamma ray irradiation of free-standing graphene oxide films in gaseous phase

A direct approach to functionalize and reduce pre-shaped graphene oxide 3D architectures is demonstrated by gamma ray irradiation in gaseous phase under analytical grade air, N2 or H2. The formation of radicals upon gamma ray irradiation is shown to lead to surface functionalization of the graphene oxide sheets. The reduction degree of graphene oxide, which can be controlled through varying the γ-ray total dose irradiation, leads to the synthesis of highly crystalline and near defect-free graphene based materials. The crystalline structure of the graphene oxide and γ-ray reduced graphene oxide was investigated by x-ray diffraction and Raman spectroscopy. The results reveal no noticeable changes in the size of sp2 graphitic structures for the range of tested gases and total exposure doses suggesting that the irradiation in gaseous phase does not damage the graphene crystalline domains. As confirmed by X-ray photoemission spectroscopy, the C/O ratio of γ-ray reduced graphene oxide is increasing from 2.37 for graphene oxide to 6.25 upon irradiation in hydrogen gas. The removal of oxygen atoms with this reduction process in hydrogen results in a sharp 400 times increase of the electrical conductivity of γ-ray reduced graphene oxide from 0.05 S cm-1 to as high as 23 S cm-1. A significant increase of the contact angle of the γ-ray reduced graphene oxide bucky-papers and weakened oxygen rich groups characteristic peaks across the Fourier transform infrared spectra further illustrate the efficacy of the γ-ray reduction process. A mechanism correlating the interaction between hydrogen radicals formed upon γ-ray irradiation of hydrogen gas and the oxygen rich groups on the surface of the graphene oxide bucky-papers is proposed, in order to contribute to the synthesis of reduced graphene materials through solution-free chemistry routes.

Single step preparation of meso-porous and reduced graphene oxide by gamma-ray irradiation in gaseous phase

A facile and highly efficient route to produce simultaneously porous and reduced graphene oxide by gamma ray irradiation in hydrogen is here demonstrated. Narrowly distributed nano-scale pores (average size of ∼3 nm and surface density >44,900 pore μm-2) were generated across 10 μm thick graphene oxide bucky-papers at a total irradiation dose of 500 kGy. The graphene oxide sheet reduction was confirmed to occur homogeneously across the structures by Fourier transform infrared spectroscopy and Raman analysis. This one-step, catalyst-free, high penetration and through-put technique, offers great promises potential for the mass production of reduced graphene oxide from cheap graphene oxide. © 2013 Elsevier Ltd. All rights reserved.

Evaluating irradiation dose for sterility induction and quality control of mass-produced fruit fly Bactrocera tryoni (Diptera : Tephritidae)

The sterile insect technique has been routinely used to eradicate fruit fly Bactrocera tryoni (Froggatt) incursions. This study considers whether fly quality in a mass-rearing facility can be improved by reducing irradiation doses, without sacrificing reproductive sterility. Pupae were exposed to one of five target irradiation dose ranges: 0, 40-45, 50-55, 60-65, and 70-75 Gy. Pupae were then assessed using routine quality control measures: flight ability, sex ratio, longevity under nutritional stress, emergence, and reproductive sterility. Irradiation did not have a significant effect on flight ability or sex ratio tests. Longevity under nutritional stress was significantly increased at 70-75 Gy, but no other doses differed from 0 Gy. Emergence was slightly reduced in the 50-55, 60-65, and 70-75 Gy treatments, but 40-45 Gy treatments did not differ from 0 Gy, though confounding temporal factors complicate interpretation. Reproductive sterility remained acceptable (> 99.5%) for all doses--40-45 Gy (99.78%), 50-55 Gy (100%), 60-65 Gy (100%), and 70-75 Gy (99.99%). We recommend that B. tryoni used in sterile insect technique releases be irradiated at a target dose of 50-55 Gy, providing improved quality and undiminished sterility in comparison with the current 70-75 Gy standard while also providing a substantial buffer against risk of under dosing.

Off-line two-dimensional liquid chromatography for metabolomics: an example using Agaricus bisporus mushrooms exposed to UV irradiation

It has previously been shown that irradiation with UV light increases the vitamin D content of certain mushroom species, but the effect on other nutrients is unknown, and is difficult to assess due to the complexity of the sample matrix. Here, an offline reversed phase × reversed phase two-dimensional liquid chromatography methodology was developed and applied to Agaricus bisporus mushrooms in order to demonstrate the potential of the technique and assess the effect of UV irradiation on the mushroom’s metabolic profile. The method allowed the detection of 158 peaks in a single analytical run. A total of 51 compounds including sugars, amino acids, organic and fatty acids and phenolic compounds were identified using certified reference standards. After irradiation of the mushrooms with UV for 30 s the number of peaks detected decreased from 158 to 150; 47 compounds increased in concentration while 72 substances decreased. This is the first time that two-dimensional liquid chromatography has been carried out for the metabolomic analysis of mushrooms. The data provide an overview of the gain/loss of nutritional value of the mushrooms following UV irradiation and demonstrate that the increased peak capacity and separation space of two-dimensional liquid chromatography has great potential in metabolomics.

Aortic intima-media thickness measured by trans-abdominal ultrasound as an early life marker of subclinical atherosclerosis

Atherosclerosis is a chronic inflammatory process that begins in early life. Improved identification of markers of early atherosclerosis via neonatal aortic intima-media thickness (aIMT) measurement may allow the development of interventions to prevent or reduce later cardiovascular disease.

Real-time ultrasound measures of lumbar erector spinae and multifidus: reliability and comparison to magnetic resonance imaging

In this work we examine the reliability and validity (in comparison to magnetic resonance imaging; MRI) of real-time ultrasound measures of lumbar erector spinae thickness. We also consider the between-day reliability of the lumbar multifidus muscle area as measured via ultrasound. 23 male subjects aged 21-45 years were measured three times over the course of nine days by one operator. The first (L1) through to the fifth (L5) lumbar vertebral levels were measured on the left and right sides. MRI was performed on the same day as first ultrasound scanning. For between-day intra-rater reliability, intra-class correlation co-efficients (ICCs), standard error of the measurement, minimal detectable difference and co-efficients of variation (CVs) were calculated along with their 95% confidence intervals and Bland-Altman analysis was performed. On Bland-Altman analysis, erector spinae thickness and multifidus area ultrasound measures 'agreed' with equivalent MR measures, though the correlation between MR and ultrasound measures was typically poor to moderate. For both ultrasound measures, the ICCs ranged from 'moderate' to 'excellent' at individual vertebral levels, although multifidus area (CV ranged from 8 to 15%) was less reliable than erector spinae thickness (CV ranged from 6 to 10%). 'Agreement' on Bland-Altmann analysis was present between days for all ultrasound measures. Averaging between sides and between vertebral levels improved reliability. Average erector spinae thickness showed a CV of 5.5% (ICC 0.77) and average multifidus area 6.2% (ICC 0.80).

Rapid surface functionalization of carbon fibres using microwave irradiation in an ionic liquid

The modification of carbon fibre surfaces has been achieved using a novel combination of low power microwave irradiation (20 W) in both an ionic liquid (1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide) and an organic solvent (1,2-dichlorobenzene). The use of the ionic liquid was superior to the organic solvent in this application, resulting in a higher density of surface grafted material. As a consequence, carbon fibres treated in the ionic liquid displayed improved interfacial adhesion in the composite material (+28% relative to untreated fibres) compared to those treated in organic solvent (+18%). The methodology presented herein can be easily scaled up to industrially relevant quantities and represent a drastic reduction in both reaction time (30 min from 24 h) and energy consumption, compared to previously reported procedures. This work opens the door to potential energy and time saving strategies which can be applied to carbon fibre manufacture for high performance carbon fibre reinforced composites.