•Multi step reduction process of graphene oxide is proposed.•Low energy nitrogen ion beam implantation leads to enhancement in electrical conductivity and specific surface area.•Room temperature ...operated SO2 gas sensors have been fabricated using MSRGO samples.•MSRGO is found to be promising for SO2 detection with reasonably good response, selectivity and stability.
The proposed multistep reduction of graphene oxide includes two-step reduction process. The graphene oxide is reduced by hydrazine hydrate followed by further reduction with low energy nitrogen ion beam implantation technique. From the Raman spectra, reduction of graphene oxide samples has been estimated on the basis of Tuinstra and Koenig relation. FT-IR studies have shown the removal of oxygen functional groups such as epoxy, hydroxyl and carboxylic on reduction. Ion implantation has enhanced electrical conductivity and specific surface area of graphene oxide on reduction. Besides reduction, the second step has modified the surface morphology of the samples making them more appropriate for gas adsorption. The sample with higher implantation dose (1015ions/cm2) exhibits promising potential for room temperature chemiresistive SO2 gas sensor at ppm levels as low as 5ppm with reasonable response, selectivity and stability.
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ZnO-CuO nanocomposite thin films were prepared by carbothermal evaporation of ZnO and Cu, combined with annealing. The effects of 90 MeV Ni(7+) ion irradiation on the structural and optical ...properties of ZnO-CuO nanocomposites were studied by using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), UV-visible absorption spectroscopy and Raman spectroscopy. XRD studies showed the presence of ZnO and CuO nanostructures in the nanocomposites. FESEM images revealed the presence of nanosheets and nanorods in the nanocomposites. The photocatalytic activity of ZnO-CuO nanocomposites was evaluated on the basis of degradation of methylene blue (MB) and methyl orange (MO) dyes under sun light irradiation and it was observed that swift heavy ion irradiation results in significant enhancement in the photocatalytic efficiency of ZnO-CuO nanocomposites towards degradation of MB and MO dyes. The possible mechanism for the enhanced photocatalytic activity of ZnO-CuO nanocomposites is proposed. We attribute the observed enhanced photocatalytic activity of ZnO-CuO nanocomposites to the combined effects of improved sun light utilization and suppression of the recombination of photogenerated charge carriers in ZnO-CuO nanocomposites.
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•A Pd-Au alloy thin films are synthesized by co-sputtering process without post annealing. The alloy thin film formation is confirmed by Synchrotron XRD.•Low energy (500 keV) ion beam ...irradiation of the Pd-Au alloy thin film results in grain growth with significant enhancement in H2 sensing and reduction in response time.•The ion irradiated film show sensing response of 9.1% with a response time of 7 s and recovery time of 50 s in H2 sensing.
Present work reports a significant improvement in the hydrogen sensing characteristics of Pd-Au thin film by ion irradiation. The Pd-Au alloy thin film was synthesized by DC magnetron sputtering. The deposited film was irradiated by 500 keV Xe2+ ion at a fluence of 1 × 1016 ions/cm2. The characterizations of the pristine and irradiated samples were performed by XRD, AFM and TEM. The hydrogen sensing characteristics of the pristine and irradiated samples was carried out by electrical resistance measurements using 2% H2 concentration at 250 °C. The alloy film does not delaminate in hydrogen loading/deloading cycles. The improvement in sensing characteristics is attributed to ion irradiation induced defects which facilitate the rate of hydrogen absorption in the films.
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Graphene oxide consists of sp3 hybridization due to the presence of different oxygen containing functional groups on its edges and basal planes. However, its sp3/sp2 hybridization can be tuned by ...various methods. Ion beam irradiation can also be one of the methods to optimize sp2/sp3 hybridization for its desirable properties. In this work, graphene oxide films were irradiated with 100 keV Argon ions at different fluences varying from 1013 to 1016 ions/cm2. Synchrotron X-ray diffraction (XRD) measurements showed an increase in crystallinity at low fluence of 1013 ions/cm2. Raman spectroscopy qualitatively determines the defects induced by ion beam in graphene oxide. Also, identification of different groups and their removal at different ion fluences was done using Fourier transform infra-red spectroscopy technique.
•Graphene oxide films synthesized by drop casting technique.•Films irradiated by 100 keV Ar ion beam.•Characterization of irradiated films by Synchrotron XRD, Raman and FTIR technique.•Synchrotron XRD results showed an increase in crystallinity for the low fluence of 1 × 1013 ions/cm2.
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Ion beams have been used for decades to analyze materials. Now they can be used to modify materials in unprecedented ways. This book discusses the use of high-energy swift heavy ions for tailoring ...the properties of materials with nanoscale structures.
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FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The critical dimension of semiconductor devices is approaching the single-nm regime, and a variety of practical devices of this scale are targeted for production. Planar structures of nano-devices ...are still the center of fabrication techniques, which limit further integration of devices into a chip. Extension into 3D space is a promising strategy for future; however, the surface interaction in 3D nanospace make it hard to integrate nanostructures with ultrahigh aspect ratios. Here we report a unique technique using high-energy charged particles to produce free-standing 1D organic nanostructures with high aspect ratios over 100 and controlled number density. Along the straight trajectory of particles penetrating the films of various sublimable organic molecules, 1D nanowires were formed with approximately 10~15 nm thickness and controlled length. An all-dry process was developed to isolate the nanowires, and planar or coaxial heterojunction structures were built into the nanowires. Electrical and structural functions of the developed standing nanowire arrays were investigated, demonstrating the potential of the present ultrathin organic nanowire systems.
The most generally spread neurotransmitter acetylcholine (Ach) is used as a chemical messenger assisting in conveying signals transversely through the nerve synapse. Herein, two enzymes ...acetylcholinesterase and choline oxidase were covalently immobilized over the gold nanoparticles (AuNPs) embedded graphene oxide (GO; 2D carbon material) nanocomposite modified ITO coated glass plate. The synergetic and unique properties of AuNPs and GO present in nanocomposite are used to detect the ultra-small concentration of analyte, Ach. The prepared nanocomposites were characterized using different techniques i.e. TEM, XRD, SEM, FTIR, UV–Vis and Raman Spectroscopy. All the electrochemical measurements were performed using 3 electrodes integrated electrochemical system by introducing Ach through varying its concentration from 100 pM to 1000 nM. Cyclic voltammetry curves for different concentrations of Ach indicate the facile charge transfer process over the working electrode. Square wave voltammetry curves indicate the good sensing measurements of the modified electrode at the fixed potential. The limit of detection was found to be as low as 100 pM. In addition to these, selectivity of the electrode towards Ach molecule was confirmed by measuring the response towards other interfering agents. Besides this, the present nano interface is capable of detecting Ach in biological fluid such as serum.
•Gold nanoparticles (AuNPs) embedded graphene oxide (GO) nanocomposite modified ITO electrode was fabricated.•Acetylcholine esterase (AChE) and choline oxidase (ChO) were co-immobilized onto modified ITO electrode.•Fabricated electrochemical biosensor showed excellent detection limit and storage stability.•The present biosensor is also tested for the real sample analysis.
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•Samples retain structural integrity even after irradiation dose of 1 × 1013ions/cm2.•Increase of irradiation dose reduces degree of inversion, and affects spin canting.•Irradiation induced ...modification of cation migration affects magnetic properties.•Irradiation changes magnetic dead layer thickness, and affects magnetic properties.•Antistructural modeling for MgFe2O4gives information on active surface centers.
Effect of swift heavy ion irradiation on MgFe2O4 (annealed at 450 °C/3 h) sample prepared by a sol–gel auto-combustion procedure has been studied. Single phase samples were irradiated with 120 MeV 28Si9+ with ion fluence: 1 × 1011, 1 × 1012, and 1 × 1013 ions/cm2 to monitor its effect on the structure, cation distribution, and magnetic properties. Electronic energy loss induced modifications of cation distribution, structural, magnetic properties were examined by XRD, VSM, FE-SEM, and EDS. XRD measurements show the formation of single phase nanocrystalline mixed cubic spinel structure (grain size 31–35 nm). Observed slight changes of experimental lattice parameter with increasing irradiation dose is ascribable to the migration of Mg2+ ions (ionic radius: 0.071 nm) from B to A site with simultaneous migration of Fe3+ ions (ionic radius: 0.063 nm) from A to B site. Sample irradiated at a lower fluence (1 × 1011 ions/cm2) has higher specific surface area (S), is more suitable for catalytic activity. Irradiation leads formation of dead layer, thus affects magnetic properties, via spin canting at surface. Therefore, irradiation can be used to control both structural, magnetic properties. SEM images display agglomerated nano-particles, while EDS pattern confirms the presence of Mg, Fe and O elements in the sample. First time the antistructural modeling for magnesium ferrite is reported to get information on active surface centers.
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The Cu (3 to 15 at%) is incorporated into ZnO thin film by atomic beam co-sputtering has been investigated for enhancement in room temperature ferromagnetism and green photo-luminance. These Cu-ZnO ...thin films examined with Raman spectroscopy, X-Ray Diffraction (XRD), UV-Visible spectroscopy, Hall measurement, magnetic force microscopy (MFM) and magnetic hysteresis. Raman spectroscopy, XRD confirms wurtzite structure and improvement in the crystallinity of ZnO upto 7% Cu. Further increase in Cu concentration results in growth in Cu nanoparticles. On increasing Cu concentration, there is decrement in transparency and increase in band gap with increase in n-type carrier concentration as confirmed from UV-Visible and Hall measurement studies. Magnetic measurement exhibited unique feature of room temperature ferromagnetic ordering in undoped and doped sample upto 3% Cu. The enhancement in magnetic moment as well as green emission in photoluminescence response with increase in Cu doping indicates that generation of large defects in ZnO by Cu doping, which can be attributed to combined effect of the presence of oxygen vacancies and/or structural inhomogeneity as well as formation of bound magnetic polarons. Importantly, synthesised Cu doped ZnO thin films can be used as spin LEDs and switchable spin-laser diodes.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Ion beam irradiation is one of the methods to tune the properties of graphene oxide (GO) by modifying the ratio of sp2 and sp3 hybridization. However, the inherent defects present in GO during its ...synthesis deteriorate its properties (e.g., reduction efficiency) and are difficult to remove. We have earlier demonstrated the annealing of defects in carbon nanostructures (fullerene, carbon nanotube, and graphene) at a lower fluence of swift heavy ion (SHI) irradiation. In the present work, we have studied the irradiation of the GO film with 120 MeV Au ions at fluences ranging from 1010 to 1013 ions/cm2. In situ X-ray diffraction measurements showed an increase in the crystallinity of the GO film at low fluence. The irradiated samples showed an increase in the intensity of aromatic carbon bonds by Fourier transform infrared spectroscopy which indicates the maximization of graphitic regions for lower fluences up to 3 × 1011 ions/cm2. Higher fluences of ion beam irradiation indicated the loss in crystallinity and presence of carbyne in Raman measurements. Thermal spike simulations were performed to understand the physical processes involved during ion beam irradiation by estimating the radii of core and halo of the tracks formed by SHI.
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