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The impact of lithium-ion implantation and postannealing processes on improving the electrical conductivity and field electron emission (FEE) characteristics of nitrogen-doped nanocrystalline diamond (nNCD) films was observed to be distinctly different from those of undoped NCD (uNCD) films. A high-dose Li-ion implantation induced the formation of electron trap centers inside the diamond grains and amorphous carbon (a-C) phases in grain boundaries for both types of NCD films. Postannealing at 1000 °C healed the defects, eliminated the electron trap centers, and converted the a-C into nanographitic phases. The abundant nanographitic phases in the grain boundaries of the nNCD films as compared to the uNCD films made an interconnected path for effectual electron transport and consequently enhanced the FEE characteristics of nNCD films., Competing Interests: The authors declare no competing financial interest.

Ion beam irradiation technique has been proposed, for efficient, fast and eco-friendly reduction of graphene oxide (GO), as an alternative to the conventional methods. 5 MeV, Au + ion beam has been used to reduce the free standing GO flake. Both electronic and nuclear energy loss mechanisms of the irradiation process play a major role in removal of oxygen moieties and recovery of graphene network. Atomic resolution scanning tunnelling microscopy analysis of the irradiated GO flake shows the characteristic honeycomb structure of graphene. X-ray absorption near edge structure analysis at C K-edge reveals that the features of the irradiated GO flake resemble the few layer graphene. Resonant Rutherford backscattering spectrometry analysis evidenced an enhanced C/O ratio of ∼23 in the irradiated GO. In situ sheet resistance measurements exhibit a sharp decrease of resistance (few 100 s of Ω) at a fluence of 6.5 × 10 14 ions cm -2 . Photoluminescence spectroscopic analysis of irradiated GO shows a sharp blue emission, while pristine GO exhibits a broad emission in the visible-near IR region. Region selective reduction, tunable electrical and optical properties by controlling C/O ratio makes ion irradiation as a versatile tool for the green reduction of GO for diverse applications.

The tunable electronic, electrical and optical properties of graphene oxide (GO) sheets were investigated using a controlled reduction by 500 keV Ar + -ion irradiation. The carbon to oxygen ratio of the GO sheets upon the ion beam reduction has been estimated using resonant Rutherford backscattering spectrometry analyses and its effect on the electrical and optical properties of GO sheets has been studied using sheet resistance measurements and photoluminescence (PL) measurements. The restoration of sp 2 -hybridized carbon atoms within the sp 3 matrix is found to be increases with increasing the Ar + -ion fluences as evident from Fourier transform infrared, and x-ray absorption near-edge structure measurements. The decrease in the number of disorder-induced local density of states (LDOSs) within the π-π* gap upon the reduction causes the shifting of PL emission from near infra-red to blue region and decreases the sheet resistance. The improved electrical and optical properties of GO sheets were correlated to the decrease in the number of LDOSs within the π-π* gap. Our experimental investigations suggest ion beam irradiation is one of an effective approaches to reduce GO to RGO and to tailor its electronic, electrical and optical properties.

The influence of carbon concentration on the electronic and magnetic properties of C-implanted ZnO thin films has been studied using synchrotron radiation based X-ray absorption spectroscopic techniques and vibrating sample magnetometer measurements. 20 keV carbon ions were implanted in ZnO films with different fluences (2 × 10 16 , 4 × 10 16 and 6 × 10 16 ions per cm 2 ). The pristine ZnO film shows diamagnetic behaviour while the C-implanted films exhibit room temperature ferromagnetism. Our first-principles calculations based on density functional theory show an appreciable magnetic moment only when the implanted C atom sits either in the O-site (2 μ B ) or in the interstitial position (1.88 μ B ), whereas the C atom in the Zn substitutional position does not possess any magnetic moment. X-ray absorption near edge structure analysis at the O K-edge reveals that the charge transfer from O-2p to the C-defect site causes the ferromagnetism in the C-implanted ZnO film at low fluence. However at high fluence, the implanted C replaces the lattice and produces more Zn vacancies, as evidenced by extended X-ray absorption fine structure studies at the Zn K-edge, which favors the ferromagnetism. The persistence of the implanted carbon and ferromagnetism of the C-implanted ZnO film has also been studied by isothermal annealing at 500 °C and discussed in detail.

Hybridization of gold nanoparticles in the ultrananocrystalline diamond materials improves the electrical conductivity of the materials to a high level of 230 (Ω cm)(-1) with a sheet carrier concentration of 8.9 × 10(20) cm(-2). These hybrid materials show enhanced electron field emission (EFE) properties, viz. a low turn-on field of 2.1 V μm(-1) with a high EFE current density of 5.3 mA cm(-2) (at an applied field of 4.9 V μm(-1)) and the life-time stability up to a period of 372 min. The fabrication of these hybrid materials with high conductivity and superior EFE behaviors is a direct and simple process which opens new prospects in flat panel displays and high brightness electron sources.

The effects of Cu and Au ion implantation on the structural and electron field emission (EFE) properties of ultrananocrystalline diamond (UNCD) films were investigated. High electrical conductivity of 186 (Ω•cm)(-1) and enhanced EFE properties with low turn-on field of 4.5 V/μm and high EFE current density of 6.70 mA/cm(2) have been detected for Au-ion implanted UNCD (Au-UNCD) films that are superior to those of Cu-ion implanted UNCD (Cu-UNCD) ones. Transmission electron microscopic investigations revealed that Au-ion implantation induced a larger proportion of nanographitic phases at the grain boundaries for the Au-UNCD films in addition to the formation of uniformly distributed spherically shaped Au nanoparticles. In contrast, for Cu-UNCD films, plate-like Cu nanoparticles arranged in the row-like pattern were formed, and only a smaller proportion of nanographite phases along the grain boundaries was induced. From current imaging tunneling spectroscopy and local current-voltage curves of scanning tunneling spectroscopic measurements, it is observed that the electrons are dominantly emitted from the grain boundaries. Consequently, the presence of nanosized Au particles and the induction of abundant nanographitic phases in the grain boundaries of Au-UNCD films are believed to be the authentic factors, ensuing in high electrical conductivity and outstanding EFE properties of the films.

Single-site CeAlPO-5 with Al/Ce ratios 25, 50, 75, 100 and 125 were synthesized hydrothermally in fluoride medium. The XRD patterns of CeAlPO-5 exhibited characteristic reflections of AlPO-5. 27Al MAS-NMR of CeAIPO-5(25) showed two unusual peaks at -20.78 and -71.35 ppm due to delocalization of cerium unpaired electron. However, 31P MAS-NMR exhibited the usual characteristic peak similar to that of AlPO-5. Vapour phase oxidation of toluene in air over CeAlPO-5 yielded benzaldehyde with high toluene conversion. The time on stream study established the stability of the catalyst. This catalyst can also be used for the selective oxidation of other alkyl aromatics.

Photosensitization of TiO2 with other transition metal oxides can extend its light absorption property in the visible region. Such materials could emerge as excellent catalysts for solar photocatalytic degradation. In the present study mesoporous Fe2O3/TiO2 (10, 30, 50, 70 and 90 wt% Fe2O3) photocatalysts were synthesized by sol-gel process and characterized using different techniques. The XRD patterns exhibited the presence of mesoporous structure and isomorphic substitution of Fe(3+) in TiO2 at low Fe(3+) loading and Ti(4+) in Fe2O3 at high Fe(3+) loading. The XPS results revealed the presence of Ti(4+) and Fe(3+) in Fe2O3/TiO2 materials. The DRS UV-vis spectra showed a shift in the band gap excitation of TiO2 to longer wavelength, thus illustrating incorporation of Fe(3+) in TiO2. In addition, free TiO2 and Fe2O3 particles were also present. Their photocatalytic activity was tested for the degradation of 4-chlorophenol in aqueous medium using sunlight. The activity of the catalysts followed the order: meso-30 wt% Fe2O3/TiO2>meso-10 wt% Fe2O3/TiO2>meso-50 wt% Fe2O3/TiO2>meso-70 Fe2O3/TiO2>meso-90 wt% Fe2O3/TiO2>meso-Fe2O3>meso-TiO2. This order concluded that mesoporous Fe2O3/TiO2 could be an active catalyst for pollutant degradation, as TiO2 with framework Fe(3+) and photosensitization with free Fe2O3 were involved in the activity., (Copyright © 2013 Elsevier B.V. All rights reserved.)

Efficient visible-light active mesoporous Ce incorporated TiO2 nanoparticles have been prepared by sol-gel method using Pluranic P123 as the structure directing agent. Low angle XRD and BET analysis revealed the mesoporous nature of the nanoparticles. The incorporation of Ce4+ into TiO2 and Ti4+ into CeO2 is evident from the slight shift in their respective XRD patterns. XPS results exhibited +4 oxidation state for Ce and Ti ions. UV-DRS analysis of Ce incorporated TiO2 demonstrated red shift in the absorbance spectrum of TiO2, which is mainly due to the formation of Ce impurity states below the conduction band edge of TiO2. The photocatalytic activity of mesoporous Ce incorporated TiO2 nanoparticles has been evaluated in the degradation of 4-chlorophenol in aqueous solution under solar light illumination. Pure mesoporous TiO2 showed poor visible-light activity due to its small absorption of sun light. Mesoporous Ce incorporated TiO2 photocatalysts exhibited the highest photocatalytic activity compared to pristine mesoporous TiO2 and CeO2. The incorporation of Ce4+ in TiO2 played a major role in the enhancement of photocatalytic activity under sun light.

PrAlPO-5 with (Al + P)/Pr ratios of 25, 50, 75 and 100 molecular sieves were successfully synthesized by hydrothermal method. These molecular sieves were characterised using XPS, TPD-NH3, ex-situ pyridine adsorbed IR, TPR, TGA, 27Al and 31P MAS-NMR and ESR studies. The incorporation of praseodymium in the framework of AlPO-5 was confirmed by XRD, DRS UV-vis and 27Al and 31P MAS-NMR analysis. ESR spectrum showed the presence of adsorbed oxygen. The nature and strength of acid sites were identified by ex-situ pyridine adsorbed IR and TPD-NH3. The BET surface area was found to be in the range of 238-272 m2 g(-1). The catalytic activity of the molecular sieves was tested for the liquid phase aerobic oxidation of ethylbenzene. Acetophenone was found to be the major product with more than 90% ethylbenzene conversion. ICP-OES analysis revealed the presence of praseodymium intact in the framework of AlPO-5 up to five cycles.

A novel magnetic Fe3O4 core-shell nanorods (MCSNs) were synthesized by crosslinking amine functionalized Fe3O4@SiO2 core-shell nanoparticles with 1,2-bromochloroethane. These nanorods were then protonated with dilute HCl. The MCSNs nanorods were characterized using FT-IR, N2 adsorption, VSM, SEM and TEM. The surface area of MCSNs nanorods was found to be 335 m2/g, which is higher than bare iron oxide and amine functionalized Fe3O4@SiO2. These nanorods were used simultaneously as ion-exchanger and adsorbent for the removal of arsenic from aqueous solution. It exhibited high adsorption capacity for arsenic. The kinetic study revealed that adsorption equilibrium attained within five min. The adsorbed arsenic on the nanorods were removed by magnetic separation and regenerated by acid treatment. The percentage removal of arsenic was more than 99%. Such nanorods can be used to remove not only arsenic but also other anions from potable water.

SBA-15 supported Co3O4 with different weight percentage have been prepared by wet impregnation method. The prepared catalysts were characterised by XRD, DRUV-vis, FT-IR, N2 adsorption-desorption, TPR, XPS, SEM and TEM. The TPR profile revealed good dispersion of active sites and interaction of Co3O4 on SBA-15 support. The catalytic activity of SBA-15 supported Co3O4 was evolved in liquid phase benzylic oxidation under mild condition using H2O2 as the oxidant. The benzylic oxidation was ascribed by hydrogen abstraction of the C-H bond. The various reaction parameters such as Co3O4 loading, solvent, temperature and reaction time on the catalytic activity were also investigated. The 5 wt% of Co3O4/SBA-15 catalyst was found to exhibit high conversion (-75%) with product selectivity of -87%.

Conducting diamond nanowires (DNWs) films have been synthesized by N₂-based microwave plasma enhanced chemical vapor deposition. The incorporation of nitrogen into DNWs films is examined by C 1s X-ray photoemission spectroscopy and morphology of DNWs is discerned using field-emission scanning electron microscopy and transmission electron microscopy (TEM). The electron diffraction pattern, the visible-Raman spectroscopy, and the near-edge X-ray absorption fine structure spectroscopy display the coexistence of sp³ diamond and sp² graphitic phases in DNWs films. In addition, the microstructure investigation, carried out by high-resolution TEM with Fourier transformed pattern, indicates diamond grains and graphitic grain boundaries on surface of DNWs. The same result is confirmed by scanning tunneling microscopy and scanning tunneling spectroscopy (STS). Furthermore, the STS spectra of current-voltage curves discover a high tunneling current at the position near the graphitic grain boundaries. These highly conducting regimes of grain boundaries form effective electron paths and its transport mechanism is explained by the three-dimensional (3D) Mott's variable range hopping in a wide temperature from 300 to 20 K. Interestingly, this specific feature of high conducting grain boundaries of DNWs demonstrates a high efficiency in field emission and pave a way to the next generation of high-definition flat panel displays or plasma devices.

Enhanced electron field emission (EFE) properties have been observed for ultrananocrystalline diamond (UNCD) films grown on Au-coated Si (UNCD/Au-Si) substrates. The EFE properties of UNCD/Au-Si could be turned on at a low field of 8.9 V/μm, attaining EFE current density of 4.5 mA/cm(2) at an applied field of 10.5 V/μm, which is superior to that of UNCD films grown on Si (UNCD/Si) substrates with the same chemical vapor deposition process. Moreover, a significant difference in current-voltage curves from scanning tunneling spectroscopic measurements at the grain and the grain boundary has been observed. From the variation of normalized conductance (dI/dV)/(I/V) versus V, bandgap of UNCD/Au-Si is measured to be 2.8 eV at the grain and nearly metallic at the grain boundary. Current imaging tunneling spectroscopy measurements show that the grain boundaries have higher electron field emission capacity than the grains. The diffusion of Au into the interface layer that results in the induction of graphite and converts the metal-to-Si interface from Schottky to Ohmic contact is believed to be the authentic factors, resulting in marvelous EFE properties of UNCD/Au-Si.

We report a direct observation of dramatic mass transport due to 1.5 MeV Au(2+) ion impact on isolated Au nanostructures of average size ≈7.6 nm and height ≈6.9 nm that are deposited on Si(111) substrate under high flux (3.2 × 10(10)-6.3 × 10(12) ions cm(-2) s(-1)) conditions. The mass transport from nanostructures was found to extend up to a distance of about 60 nm into the substrate, much beyond their size. This forward mass transport is compared with the recoil implantation profiles using SRIM simulation. The observed anomalies with theory and simulations are discussed. At a given energy, the incident flux plays a major role in mass transport and its redistribution. The mass transport is explained on the basis of thermal effects and the creation of rapid diffusion paths in the nanoscale regime during the course of ion irradiation. The unusual mass transport is found to be associated with the formation of gold silicide nano-alloys at subsurfaces. The complexity of the ion-nanostructure interaction process is discussed with a direct observation of melting (in the form of spherical fragments on the surface) phenomena. Transmission electron microscopy, scanning transmission electron microscopy, and Rutherford backscattering spectroscopy methods have been used.

The high-energy and heavy-ion induced sputtered particles from nanostructures under various conditions can result in variety of size distributions. 1.5 MeV Au2+ ions induced sputtering from isolated gold nanostructures deposited on silicon substrate have been studied as a function of incident ion flux (dose rate) and the sputter particle catcher at low temperature. At higher fluxes, a bimodal distribution of the sputtered particles has been observed. Cross-sectional transmission electron microscopy and Rutherford backscattering spectrometry measurements showed that the sputter particle size distribution depends on morphology at surface and interfaces. The results for the size distribution from a catcher at low temperature showed the less agglomeration of ejected clusters on the catcher grids, resulting in the lower-disperse size distribution.