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Vo K.D.N.,CNRS Institute of Molecular Chemistry - Reims | Kowandy C.,CNRS Institute of Molecular Chemistry - Reims | Dupont L.,CNRS Institute of Molecular Chemistry - Reims | Coqueret X.,CNRS Institute of Molecular Chemistry - Reims | Hien N.Q.,Vietnam Atomic Energy Institute
Radiation Physics and Chemistry | Year: 2014

Gold nanoparticles were synthesized via radiolytic reduction of Au(III) salts induced by e- beam or γ-irradiation, using chitosan as a stabilizer. The effect of irradiation dose, chitosan concentration and the conditioning of HAuCl4-chitosan solutions were studied. UV-visible absorption measurements reveal that the size of Au clusters formed immediately after irradiation is correlated with the extent of chitosan scission chain of chitosan and fall with the increase of dose absorbed. This effect is more pronounced with solution conditioned under Argon (Ar). Au clusters coalesce to form stable nanoparticles after two weeks. © 2013 Elsevier Ltd.

Hien P.D.,Vietnam Atomic Energy Institute | Hangartner M.,ETH Zurich | Fabian S.,Swisscontact | Tan P.M.,Hanois Center for Environmental Monitoring and Analysis
Atmospheric Environment | Year: 2014

The concentrations of NO2, SO2, and benzene were measured by passive diffusion samplers at 96 sites across Hanoi consisting of 80 sites in the inner city background, 6 traffic hot spots, 5 industry hot spots, and 5 rural sites. Two sampling campaigns were conducted in the winter and summer seasons of 2007, and the average concentration of the two campaigns was used as a proxy for the annual mean. The annual means of NO2, SO2, and benzene in the inner city background ranged from 17.9 to 65.9μgm-3, 11.7-47.4μgm-3, and 3.5 to 15.4μgm-3, respectively. The NO2/benzene and SO2 concentrations were higher at the traffic and industry hot spots, respectively. The background concentrations of NO2 and benzene tended to increase with the population density and were highest in crowded Hanoi downtown areas. These areas are facing high risks of violating the national legislation threshold for NO2 (40μg-3). The SO2 background concentrations were generally below the legislation threshold (50μg-3). Motorbikes, which dominate the Hanoi vehicle fleet, are the main polluters of NO2 and benzene, whereas SO2 comes mainly from diesel buses and trucks, except in some areas that are directly affected by industrial coal burning. Stringently regulating the exhaust emissions of vehicles, especially for motorbikes, and reducing the sulfur and benzene contents in fuels could be implemented to improve Hanoi's air quality. © 2014 Elsevier Ltd.

Hanh T.T.,Vietnam Atomic Energy Institute | Huy H.T.,Vietnam National University, Ho Chi Minh City | Hien N.Q.,Vietnam Atomic Energy Institute
Radiation Physics and Chemistry | Year: 2015

Radiation-induced grafting is an effective technique for preparation of novel materials. In this study, partially deacetylated chitin with deacetylation degree (DDA) of about 40% was graft-copolymerized with acrylonitrile (AN) by a γ-ray pre-irradiation method. The maximal grafting degree of AN onto pre-irradiated chitin at 25±1.2kGy was 114% for AN concentration in dimethylformamide of 40% (v/v) at 70°C for 8h. The mixture ratio of 0.1N NH2OH·HCl to 0.1N NaOH was selected to be 7:3 (v/v) for amidoxime conversion of cyano-groups on grafted chitin (Chi-g-AN). The characteristics of modified chitin were depicted by the FT-IR spectra, BET area and SEM images. Adsorption equilibrium of As(III) onto Chi-g-AN converted amidoxime (Chi-g-AN-C) fits with the Langmuir model and the maximal adsorption capacity was 19.724mg/g. The break-through times of As(III) on Chi-g-AN-C in column adsorption experiments increased with the increase in bed depths. © 2014.

Tue Anh N.,Vietnam Atomic Energy Institute | Van Phu D.,Vietnam Atomic Energy Institute | Ngoc Duy N.,Vietnam Atomic Energy Institute | Duy Du B.,Institute of Applied Material Science | Quoc Hien N.,Vietnam Atomic Energy Institute
Radiation Physics and Chemistry | Year: 2010

Gold nanoparticles with pre-selected size in the range 5-40 nm were synthesized by γ-irradiation of Au3+ solution containing natural polysaccharide alginate as a stabilizer. The gold nanoparticles with controllable size were prepared by two approaches: (i) varying the concentration of Au3+ from 0.25 to 1 mM and alginate from 0.25% to 1% (w/v) and (ii) enlargement of seed particles with double size from 20 to 40 nm at [Au3+]/[Au0]=6. The obtained gold nanoparticles were characterized by UV-vis spectroscopy and transmission electron microscopy. The results indicated that γ-irradiation method is suitable for production of gold nanoparticles with controllable size and high purity. © 2009 Elsevier Ltd. All rights reserved.

Hien N.Q.,Vietnam Atomic Energy Institute | Phu D.V.,Vietnam Atomic Energy Institute | Duy N.N.,Vietnam Atomic Energy Institute | Lan N.T.K.,Vietnam Atomic Energy Institute
Carbohydrate Polymers | Year: 2012

Chitosan from squid pens with deacetylation degree (DD) of 70% and average molecular weight (M w0) 90.5 × 10 3 in dilute lactic acid solution containing H 2O 2 (1%) was effectively degraded by irradiation with gamma 60Co radiation (1.33 kGy/h) at doses in the range 4-16 kGy. Based on the results of M w measured by gel permeation chromatography (GPC), it was concluded that there was particularly strong synergy between H 2O 2 and radiation for degradation at the lower radiation doses studied. Radiation scission yields (Gs) were found out to be 2.2 μmol/J and 0.2 μmol/J for 5% chitosan with and without 1% H 2O 2, respectively. The DD of degraded chitosan measured from IR spectra was almost unchanged by the treatment. © 2011 Elsevier Ltd. All Rights Reserved.

Hien N.Q.,Vietnam Atomic Energy Institute | Van Phu D.,Vietnam Atomic Energy Institute | Duy N.N.,Vietnam Atomic Energy Institute | Quoc L.A.,Vietnam Atomic Energy Institute
Carbohydrate Polymers | Year: 2012

Gold nanoparticles (AuNPs) with diameter from 4 to 10 nm, capping by hyaluronan (HA) were synthesized using a γ-irradiation method. The maximum absorption wavelengths at 517-525 nm of colloidal AuNPs/HA solutions were measured by UV-vis spectroscopy. The size and size distribution of AuNPs were determined from TEM images. The influence of various factors on the size of AuNPs particularly the concentration of Au 3+ and HA, and dose rate were also investigated. Results indicated that higher dose rate and HA concentration favor smaller sizes of AuNPs whereas the size increases with Au 3+ concentration. The colloidal AuNPs/HA solution was fairly stable more than 6 months under storage at ambient condition. The AuNPs stabilized by biocompatible HA with the size less than 10 nm as prepared can potentially be applied in biomedicines and cosmetics. © 2012 Elsevier Ltd. All rights reserved.

Phu D.V.,Vietnam Atomic Energy Institute | Quoc L.A.,Vietnam Atomic Energy Institute | Duy N.N.,Vietnam Atomic Energy Institute | Hien N.Q.,Vietnam Atomic Energy Institute
Radiation Physics and Chemistry | Year: 2013

Polyethylene nonwoven (PE) fabric was grafted with acrylic acid (PE-g-PAAc) by the γ-ray pre-irradiation process. The effect of dose and acrylic acid concentration on the grafting degree was investigated. The dose of about 20-30. kGy, acrylic acid concentration of 20-30%, and the reaction time of about 2. h at ~90. °C were selected as suitable parameters for grafting. The PE-g-PAAc fabric was then impregnated in colloidal silver nanoparticles (AgNPs) solution for incorporating AgNPs. The resultant PE-g-PAAc/AgNPs fabric containing ~10,000. ppm AgNPs exhibits high antimicrobial activity (η>99%) against Escherichia coli in water. The release of silver into water filtrate determined by ICP-MS was less than 0.1. mg/L. The PE-g-PAAc/AgNPs fabric can be potentially applied for water and/or air treatment as an antimicrobial membrane filter. © 2013 Elsevier Ltd.

Binh D.,Vietnam Atomic Energy Institute | Duoc N.T.,Vietnam Atomic Energy Institute | Hong P.T.T.,Vietnam Atomic Energy Institute
Nuclear Science and Techniques | Year: 2013

Carboxymethyl starch (CMS) can be cross-linked by electron beam radiation to form a biocompatible and environment-friendly hydrogel at a high absorbed dose and a condensed CMS concentration. Acrylic acid (AAc) can be used as a sensitizer in order to reduce the absorbed doses to an acceptable certain level. At an absorbed dose of 3-4 kGy, the gel content of crosslinked CMS can be obtained about 50% with 5% (w/w) AAc concentration used. The compressive strength of CMS samples increased with increasing their cross-linked densities due to raising absorbed doses. The swelling ratio of cross-linked CMS was also attainable at a maximum of 50 times in the distilled water. The enzymatic degradation of cross-linked CMS was carried out in acetate buffer pH 4.6 with 0.1% α-amylase enzymatic solution incubated at 40°C for 6 h. The crosslinked CMS samples were degraded slower than uncrosslinked CMS ones. The results indicated that the highly cross-linked CMS was almost fully degradable when the enzymatic hydrolysis was performed during 6 h. The FT IR spectra of cross-linked CMS in the presence of AAc were examined to observe the carboxyl group of AAc in the structure of cross-linked CMS. The hydrophilic of cross-linked CMS surface was determined by a contact-angle analysis. © 2013, Science Press. All rights reserved.

Khang P.D.,Vietnam Atomic Energy Institute | Hai N.X.,Vietnam Atomic Energy Institute | Tan V.H.,Vietnam Atomic Energy Institute | Dien N.N.,Vietnam Atomic Energy Institute
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment | Year: 2011

The gammagamma coincidence spectrometer has been setup at the tangential neutron beam port of the Dalat Nuclear Research Reactor (DNRR) for neutron activation analysis and nuclear structure studies. The selected parameters were chosen by new method, and the quality of parameters was evaluated with peak area ratios of spectra which have been measured by two detectors in eventevent coincidence mode. The experimental setup, its performance and analysis method using 60Co source and 35Cl(n,2γ)36Cl reaction are presented in this paper. © 2011 Elsevier B.V. All rights reserved.

Duy N.N.,Vietnam Atomic Energy Institute | Phu D.V.,Vietnam Atomic Energy Institute | Anh N.T.,Vietnam Atomic Energy Institute | Hien N.Q.,Vietnam Atomic Energy Institute
Radiation Physics and Chemistry | Year: 2011

Synergistic degradation of chitosan by γ-irradiation of chitosan solution (3%) in the presence of hydrogen peroxide (0.25%, 0.5% and 1%) was investigated. The efficiency of the degradation process was demonstrated by gel permeation chromatography (GPC) analysis of the average molecular weight of degraded chitosan (oligochitosan). Structures of resultant oligochitosan were characterized by Fourier-transform infrared spectra (FT-IR) and X-ray diffraction (XRD). Results showed that oligochitosan with Mw from 5000 to 10,000 could be efficiently prepared by γ-irradiation of chitosan solution containing a small amount of hydrogen peroxide at low dose less than 10kGy. There was almost no significant change in the main chain structure of oligochitosan; however, the obtained oligochitosans lost about 10% of amino groups and the formation of carboxyl groups could not be specified by FT-IR spectra. The morphology state of oligochitosan was essentially amorphous, which differs from that of original chitosan. The combined γ ray/H2O2 method is significantly efficient for scale-up manufacture of oligochitosan. © 2011 Elsevier Ltd.

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