Low-energy Ion Beam Implantation Research Articles

Ion implantation as an approach for tuning of electronic structure, optical, morphological and electrical transport properties of sputtered molybdenum disulfide thin films

Molybdenum disulfide (MoS2) thin films have acquired increasing consideration in the field of low-dimensional electronics as device-active layers and also in hydrogen evolution reaction (HER) as catalysts in distinct electrochemical processes. Thus, for distinct applications, extensive scalable fabrication techniques with tunable MoS2 properties are significant. To possess tunable efficiency of various device applications at nanoscale it is significant to acquire control over the density of defects, although attaining with direct growth techniques remains a significant issue. Here we illustrate a robust and effective approach to tailor the density of defects using Au ion implantation. In the present work, we illustrate the scalable technique i.e. magnetron sputtering for the fabrication of MoS2 thin films, subsequently, ion implantation with 80 keV Au ions at a distinct fluence of 1 × 1015 and 5 × 1015 ions/cm2 was carried out. Striking deviations were remarked in nanostructure and depth distributions of the resultant thin films of MoS2. Pristine and ion implanted thin films were characterized to comprehend the morphological, electrical transport and electronic structure properties. The surface micrographs’ results revealed noteworthy alterations in the thin films’ surface roughness. The modifications induced by low energy Au ion implantation in core-level electronic structure and atomic bonding was probed by XPS and Raman spectroscopy technique. The electrical properties of these films were studied to demonstrate the scattering and conduction mechanisms. The present work contributes to the significant passage of tailoring 2D MoS2 thin films’ electronic structure, optical and morphological properties through doping and defects formation by low energy ion beam implantation to extend their practical device applications.

Influence of low energy ion beam implantation on Cu nanowires synthesized using scaffold-based electrodeposition

Copper nanowires with 100 nm diameter were potentiostatically deposited in the pores of ion track etched polycarbonate membrane. Ion implantation in a colossally used technique to tailor properties of the materials. The nanowires were implanted with 1.5 MeV Ar6+ ions in the fluence range between 1012 to 1014 ions/cm2. XRD analysis confirmed the formation of Cu nanowires and EDS result established implantation of Ar into the nanowires. The crystallite size increased from 54 nm to 59 nm due to merging of grains caused during the implantation of Ar ions. XRD patterns show that nanowires exhibit a cubic fcc structure, with increase in preferred orientation along plane (311) with increase in implantation fluence. Rietveld analysis was performed to characterize the pristine and implanted samples. The relationship between the microstructural evolution and the variation of strengthening coefficient was examined in this study. The electrical conductivity of the nanowires was observed to increase from 5.21 × 106Ω−1m−1to 6.63 × 106Ω−1m−1. The increase in conductivity is due to ion implantation induced rise in charge carriers and local heating that resulted into coalescence of grain boundaries

离子束重组酵母菌Han0458基因组重复序列的分布特征

离子束重组酵母菌Han0458基因组重复序列的分布特征

Effect of various reduction methods of graphene oxide on electromagnetic shielding performance of reduced graphene oxide against electromagnetic pollution in X-band frequency

A comparative study based on the effect of various novel reduction techniques for the fabrication of devices for electromagnetic interference (EMI) shielding in X-band frequency is reported. Among various reduction methods, we have used hydrazine hydrate and thermal annealing, low energy ion beam implantation and swift heavy ion irradiation. The synthesis as well as reduction of the samples is confirmed by the Raman spectra and FT-IR studies. The room temperature dc electrical conductivity is correlated with the extent of reduction of graphene oxide samples. The sample reduced with hydrazine hydrate and swift heavy ion irradiation of Ag+8 at 100MeV has highest dc electrical conductivity value, which leads to higher EMI shielding effectiveness of 55.29dB and skin depth of 0.0188cm. It is also observed that the skin depth decreases with increase in electrical conductivity. This suggests a strong potential of these samples for high performance EMI shielding applications.

Doping of Graphene by Low-Energy Ion Beam Implantation: Structural, Electronic, and Transport Properties.

We investigate the structural, electronic, and transport properties of substitutional defects in SiC-graphene by means of scanning tunneling microscopy and magnetotransport experiments. Using ion incorporation via ultralow energy ion implantation, the influence of different ion species (boron, nitrogen, and carbon) can directly be compared. While boron and nitrogen atoms lead to an effective doping of the graphene sheet and can reduce or raise the position of the Fermi level, respectively, (12)C(+) carbon ions are used to study possible defect creation by the bombardment. For low-temperature transport, the implantation leads to an increase in resistance and a decrease in mobility in contrast to undoped samples. For undoped samples, we observe in high magnetic fields a positive magnetoresistance that changes to negative for the doped samples, especially for (11)B(+)- and (12)C(+)-ions. We conclude that the conductivity of the graphene sheet is lowered by impurity atoms and especially by lattice defects, because they result in weak localization effects at low temperatures.

Analysis of ROP signaling in the leaf epidermis of mutant tomato with low-energy ion beam.

The importance of the ROP small GTPase signaling pathway in the regulation of cellular polarity growth in eukaryotes has been thoroughly studied. In this study, we examined the LeROP small GTPase (related to Arabidopsis thaliana genome LeROP GTPase in tomato) signaling of cell polarity growth in the mutant (M-1) tomato. Interestingly, we detected expansive growth of epidermis cells in M-1, in which the leaves appeared slightly lobed shaped. However, we observed jigsaw puzzle shaped and deeply lobed shaped leaves in wild-type leaf epidermis cells. The t-test showed significant difference (P < 0.05). Based on previous studies of the AtROP gene in Arabidopsis leaf epidermis cells, we hypothesized that the growth of mutant M-1 tomato leaf epidermis cell is related to AtROP gene signal transmission. The results of reverse transcription-polymerase chain reaction showed the expression of LeROP2, LeROP4, and LeROP7 in M-1 mutants were stronger than in wild-type cells. At the flowering stage, LeROP2 GTPase showed no expression in wild-type cells, but was expressed in mutant cells. This study revealed a link between the low-energy ion beam and the ROP GTPase signaling pathway in tomato. In addition, the ROP gene changes analyzed suggest a new mechanism for mutations following low-energy ion beam implantation.

Simple General Purpose Ion Beam Deceleration System Using a Single Electrode Lens

Ion beam deceleration properties of a newly developed low-energy ion beam implantation system were studied. The objective of this system was to produce general purpose low-energy (5 to 15 keV) implantations with high current beam of hundreds of μA level, providing the most wide implantation area possible and allowing continuously magnetic scanning of the beam over the sample(s). This paper describes the developed system installed in the high-current ion implanter at the Laboratory of Accelerators and Radiation Technologies of the Nuclear and Technological Cam-pus, Sacavem, Portugal (CTN).

Enhanced Production of Vitamin K2 from Bacillus subtilis (natto)by Mutation and Optimization of the Fermentation Medium

The aim of this study was to enhance the production of vitamin K2 by using N-methyl-N-nitro-N-nitroso-guanidine (NTG) and low energy ion beam implantation and optimizing the fermentation medium. Mutation resulted in 1.66-fold higher production of vitamin K2 than that of the parentl strain. The production by the mutant BN-P15-11-1was increased 55% and reached 3.593±0.107 mg/L by using the Plackett-Burman and Box-Behnken designs to optimize the fermentation medium. The optimal fermentation culture medium was composed of (g/L) glycerol 69.6, sucrose 34.5, K2HPO4 4.0, peptone 20, yeast extract 25 and fermented at 37 °C and 150 rpm for 72 h. The results showed that the NTG and low energy ion beam implantation mutations and optimizing fermentation medium were effective methods to enhance vitamin K2 production.

Enhanced Production of Vitamin K2 from Bacillus subtilis (natto) by Mutation and Optimization of the Fermentation Medium

The aim of this study was to enhance the production of vitamin K2 by using N-methyl-N-nitro-N-nitroso-guanidine (NTG) and low energy ion beam implantation and optimizing the fermentation medium. Mutation resulted in 1.66-fold higher production of vitamin K2 than that of the parentl strain. The production by the mutant BN-P15-11-1was increased 55% and reached 3.593±0.107 mg/L by using the Plackett-Burman and Box-Behnken designs to optimize the fermentation medium. The optimal fermentation culture medium was composed of (g/L) glycerol 69.6, sucrose 34.5, K2HPO4 4.0, peptone 20, yeast extract 25 and fermented at 37 °C and 150 rpm for 72 h. The results showed that the NTG and low energy ion beam implantation mutations and optimizing fermentation medium were effective methods to enhance vitamin K2production.

Metabolic engineering of Penicillium chrysogenum morphology

Filamentous fungi are widely used in the field of industrial fermentation, and their morphological diversity and complex regulation during fermentation have attracted serious attention from researchers. Penicillium chrysogenum morphology, intervention and regulation, as well as the relationship between morphology and yield, were researched in this study. We have established an effective image processing method to measure several hyphal morphological parameters. These parameters were applied to quantitative analysis of morphology and the metabolic status of the product under different culture conditions. Simultaneously, morphological dynamics equations were also established. Low energy ion beam implantation and low temperature air plasma techniques were used in this work to mutate P. chrysogenum . To reveal the relationship between hyphal morphology and the production of secondary metabolites, quantitative analysis of hyphal morphological variations in the fermentation process was also carried out with mutant strains and the original strain. We constructed an RNAi vector to silence the class III chitin synthase gene chs4 to construct morphological mutants. All transformants except PcRNAi1-15 exhibited enhanced penicillin yields, especially PcRNAi1-17 and PcRNAi2-1, whose yields were 27% and 41% higher than the original strain. Our results provide a theoretical basis for understanding the regulatory mechanisms of penicillin production.

Acetone, butanol, and ethanol production from cane molasses using Clostridium beijerinckii mutant obtained by combined low-energy ion beam implantation and N-methyl-N-nitro-N-nitrosoguanidine induction

In order to obtain mutant strains showing higher solvent tolerance and butanol production than those of wild-type strains, the butanol-producing strain Clostridium beijerinckii L175 was subjected to mutagenesis using a combined method of low-energy ion beam implantation and N-methyl-N-nitro-N-nitrosoguanidine induction. With this effort, mutant strain MUT3 was isolated. When it was used for butanol fermentation in P2 medium, the production of butanol was 15.8±0.7 g/L 46% higher than the wild-type strain. Furthermore, after optimization of butanol production from cane molasses with MUT3, the maximum butanol production of 14.9±0.5 g/L were obtained in crew-capped bottles. When ABE production by MUT3 was carried out in a bioreactor, the production of butanol and total solvent were 15.1±0.8 g/L and 22.1±0.9 g/L, respectively. The remarkable butanol production and solvent tolerance of MUT3 make it promising for butanol production from cane molasses.

Ion Beam Mutagenesis in Arthrobotrys oligospora Enhances Nematode-Trapping Ability

The nematode-trapping fungus Arthrobotrys oligospora is able to produce extracellular protease that degrades the body walls of parasitic nematode larvae found in livestock and immobilizes the nematodes. Our aim was to obtain a strain of A. oligospora with a strong ability to trap nematodes by production of high levels of extracellular protease. A wild type strain of A. oligospora was subjected to mutagenic treatments involving low-energy ion beam implantation to generate mutants. Among these mutants, A. oligospora N showed high efficiency in trapping nematodes and was also able to secrete more extracellular protease, helping it to penetrate and digest the body walls of larvae. This work represents the first application of low-energy ion beams to generate mutations in a nematode-trapping fungus, and provides a new method of obtaining a fungus with high potential application.

Improvement of nitrilase production from a newly isolated Alcaligenes faecalis mutant for biotransformation of iminodiacetonitrile to iminodiacetic acid

The nitrilase activity of a newly isolate strain, Alcaligenes faecalis WBX11, which is capable of catalyzing the direct hydrolysis of iminodiacetonitrile to its corresponding dicarboxylic acid iminodiacetic acid, was significantly enhanced by low-energy ion beam implantation, a novel microbial breeding way. After ion implantation, nitrilase activity and the total biomass of the mutant were significantly improved by 45% and 75%, respectively, compared with the wild strain. The temperature and pH optimum of the variant nitrilase were 35°C and pH 7.5, respectively, basically consistent with those of the wild strain. The nitrilase was mesophilic because of the quick deactivation in temperature higher than 45°C. Nitrilase showed a broad substrate spectrum, especially on arylacetonitrile and aliphatic nitrile. Study on reaction kinetics showed that no obvious substrate inhibition was observed even though the concentration of the substrate was up to 250mM. All results indicate that the low-energy ion implantation is an effective way for microbial breeding and the resulting mutant may be suitable for industrial applications.

Enhancement of Sophorolipid Production of Wickerhamiella domercqiae var. sophorolipid CGMCC 1576 by Low-Energy Ion Beam Implantation

To meet the increasing demands of sophorolipids as biosurfactants and bioactive compounds, it is necessary to obtain higher and more specific sophorolipid-producing strains. One sophorolipid-producing strain, Wickerhamiella domercqiae var. sophorolipid CGMCC 1576 (Y(2A)), was mutated by low-energy nitrogen ion beam implantation. Eighteen mutants produced 20 % more sophorolipids than the wild strain, and one mutant, N3-18, produced the highest yield of sophorolipids, 104 g/l, in a shaking flask, which increased by 84.71 % than the wild strain, and further elevated to 135 g/l in a 5-l bioreactor. High performance liquid chromatography analysis showed that the composition of every sophorolipid mixture from different strains was similar, while the contents of most components from mutants were higher than that from the wild strain. Two mutants, N1-32 and N3-18, produced more acidic sophorolipid components; three lactonic sophorolipid molecules with good anticancer activities were greatly enhanced in several mutants, especially monoacetylated lactonic sophorolipid with a C18 monounsaturated fatty acid, which were enhanced by 153 and 211 % in strains N1-32 and N3-18. Low-energy nitrogen ion beam implantation was efficient for obtaining a variety of high and specific sophorolipid-producing mutants to be applied in food, cosmetic, environmental, and pharmaceutical sectors.

Implantation with low-energy N+ Beam Changes the Transcriptional Activation of the Expression Sequence Tags (ESTs) from the Transposable Elements in Rice

Transposable elements (TEs) have played important roles in the evolution of the genes and genomes. As a new resource of mutagens, low-energy ion beam implantation is characterized as slightly physiological damages, wide mutation spectrum, and high mutation frequency comparing with other mutagenicity methods. In order to shed light on the expression profiles of the functional genes from the transposons responding to the stress of the ion-beam radiation, we have investigated the transcriptome features of rice implanted with the nitrogen-ion-beam implantation, using the Agilent Rice Oligo Microarray (4×44K) Genome Array including more 40,000 encoding expression sequence tags (ESTs), involving 177 ESTs from TEs. The results show that there are 982 differentially expressed genes (fold changei¼ž2 and P valuei¼œ0.05) in rice seedlings underlying the implantation of the nitrogen ion beam, including 429 up-regulated transcripts and 553 down-regulated transcripts, underlying the implantation of the lower-energy nitrogen beam. The gene ontology enrichment analysis shows that the up-regulated genes are statistically significant (P valuei¼œ0.05) clusterred into five molecular functions GO terms, three cellular component GO terms and one metabolic process GO terms. The down-regulated genes are statistically significant (P valuei¼œ0.05) clusterred into ten molecular functions GO terms, nineteen metabolic process GO terms, but no cellular component GO terms. The results showed that 42 ESTs, including the functional transposase, intergrase, conserveddeoxyribonucleic acid deoxyribonucleic acid (DNA) transposon protein, retrotransposon pol and viral coat and capsid protein, are expressed differentially, comprising 24% the total transposable elements ESTs in the genechip expression data. Most of these differential expression ESTs are up-regulated or re-activated, which provide more transposable potentiality to the TEs. These results imply that the increased potentiality of the transposition of the TEs is contributed to the biological effects of the low-energy-ion-beam implantation. These results provide the profiles of the differentially expressed genes and the fundamental relation between the TEs in plants and the implantation of the ion beam. Key words: Implantation of the ion beam, transposable elements, transcriptional activation, rice.

Genome shuffling of Trichoderma viride for enhanced cellulase production

Genome shuffling is an efficient approach for the rapid engineering of microbial strains with desirable industrial phenotypes. In this study, we used genome shuffling in an attempt to improve the cellulase production of the wild-type strain Trichoderma viride TL-124. The initial mutant populations were generated by ultraviolet (UV) irradiation, low-energy ion beam implantation and atmospheric pressure non-equilibrium discharge plasma (APNEDP). The mutants were subjected to recursive protoplast fusion. The cellulase activities of shuffled strains were assayed after solid-state fermentation using wheat straw, an economical raw material, as substrate. The shuffled strain T. viride F161, which was selected from among about 2,000 shuffled strains after two rounds of genome shuffling, exhibited a total cellulase activity of 4.17 U g-1 dry weight, which was 1.97-fold higher that of wild-type strain T. viride TL-124 (2.12 U g-1 dry weight). Analysis by random amplification of polymorphic DNA revealed genetic differences between the shuffled strains and the wild-type strain.

Mutation breeding of nuclease p1 production in Penicillium citrinum by low-energy ion beam implantation

The mutant strain designated as N409 was obtained with a high yield of nuclease p1. The activity of nuclease p1 was 421 U/mL from the mutant strain N409, which was increased by 86% compared with the control. The fermentation kinetics of nuclease p1 by the mutant strain N409 was studied in a 30 L external airlifting bioreactor. A model was proposed using the logistic equation for microbial growth, the Luedeking-Piret equation for product formation and a Luedeking-Piret-like equation for substrate uptake. The results predicted from the model were in good agreement with the experimental observations.

Strain improvement for enhanced production of cellulase in Trichoderma viride

The filamentous fungi Trichoderma species produce extracellular cellulase. The current study was carried out to obtain an industrial strain with hyperproduction of cellulase. The wild-type strain, Trichoderma viride TL-124, was subjected to successive mutagenic treatments with UV irradiation, low-energy ion beam implantation, atmospheric pressure non-equilibrium discharge plasma (APNEDP), and N-methyl-N'-nitro-N-nitrosoguanidine to generate about 3000 mutants. Among these mutants, T. viride N879 strain exhibited the greatest relevant activity: 2.38-fold filter paper activity and 2.61-fold carboxymethyl cellulase, 2.18-fold beta-glucosidase, and 2.27-fold cellobiohydrolase activities, compared with the respective wild-type activities, under solid-state fermentation using the inexpensive raw material wheat straw as a substrate. This work represents the first application of APNEDP in eukaryotic microorganisms.

Strain improvement and metabolic flux modeling of wild-type and mutant Alcaligenes sp. NX-3 for synthesis of exopolysaccharide welan gum

Low-energy nitrogen ion beam implantation technique was used for the strain improvement of Alcaligenes sp. NX-3 for the production of exopolysaccharide welan gum. A high welan gum producing mutant, Alcaligenes sp. NX-3-1, was obtained through 20 keV N+ ion beam irradiation. Starting at a concentration of 50 g/L of glucose, mutant NX-3-1 produced 25.0 g/L of welan gum after 66 h of cultivation in a 7.5 L bioreactor, which was 34.4% higher than that produced by the wild-type strain. The results of metabolic flux analysis showed that the glucose-6-phosphate and acetyl coenzyme A nodes were the principle and flexible nodes, respectively. At the glucose-6-phosphate node, the fraction of carbon measured from glucose-6-phosphate to glucose-1-phosphate was enhanced after mutagenesis, which indicated that more flux was used to synthesize welan gum in the mutant. By analyzing the activities of related enzymes in the biosynthetic pathway of sugar nucleotides essential for welan gum production, we found that the specific activities of phosphoglucomutase, UDP-glucose pyrophosphorylase, UDP-glucose dehydrogenase, and dTDP-glucose pyrophosphorylase in the mutant strain were higher than those in the wild-type strain. These improvements in enzyme activities could be due to the affected of ion beam implantation.

Proteome Changes in Maize Embryo (Zea mays L) Induced by Ion Beam Implantation Treatment

Low energy ion beam implantation was applied to the maize (Zea mays L) embryo proteome using two-dimensional gel electrophoresis. Protein profile analysis detected more than 1100 protein spots, 72 of which were determined to be expressed differently in the treated and control (not exposed to ion beam implantation) embryos. Of the 72 protein spots, 53 were up-regulated in the control and 19 were more abundantly expressed in the ion beam-treated embryos. The spots of up- or down-regulated proteins were identified by matrix assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF-MS). Among the identified proteins, 11 were up-regulated in the treated embryos. Four of these up-regulated proteins were antioxidant molecules, three were related to stress response, two to sugar metabolism and two were associated with heat shock response. Of the five proteins up-regulated in the control embryos, three were functionally related to carbohydrate metabolism; the functions of the remaining two proteins were unknown. The data collected during this study indicate that treatment of maize embryos with low energy ion beam implantation induces changes in stress tolerance enzymes/proteins, possibly as a result of alterations in metabolism.