Zinc oxide (ZnO) nanorods are highly valued for their exceptional optical, electrical, and mechanical properties, making them crucial for applications in electronics, optoelectronics, energy-harvesting, sensing, and biomedical fields. This study introduces a novel method for synthesizing ZnO nanorods using a controlled airflow furnace. Industrial-grade Zn dust was gradually heated in a 98

Core-shell absorbent granules are produced by coating commercial sand gravels with graphite oxide (few-layer oxidized graphene sheets). Graphite oxide (GO) is synthesized chemically from vein graphite, a rare form of high purity natural graphite. Repeated coatings of graphite oxide on sand followed by low temperature (1200 C) thermal pyrolysis produce core-shell granules with a hierarchical structure in which sand gravels are covered by graphite oxide layers. The intention of this study is to assessment of feasibility of the mitigation of Pb (II) form the water by sand/graphene oxide nano-composite and study the dynamic behavior of the adsorption mechanism using the mathematical modeling. Individual materials and the resulting nanocomposite are characterized using a range of spectroscopic (FTIR, XRD, XPS) and microscopic (SEM/EDXA) techniques to elucidate the process of transforming individual materials into nanocomposite and to assess its suitability for removing Pb (II) from water. Stable sand/graphite oxide nanocomposites were obtained upon five times coating of GO on the sand surface and characterization shows that functionalized and a porous coating developed on the sand. The Pb (II) removal efficiency increases from high-acidic to neutral pH and decreases after basic (pH-8). The adsorption process takes 150 minutes to reach the equilibrium. After 150 minutes, the Pb (II) ion adsorption rate was constant. The maximum dosage of the nanocomposite needed to reach the equilibrium was 0.06g. Under the optimum conditions, 96.3% of Pb (II) removal efficiency was recorded from simulated Pb (II) containing water. According to the mathematical modeling, adsorption follows the Langmuir isotherm and fits well with the pseudo 2nd order kinetics model, indicating a homogeneous adsorption process via a monolayer process and Pb adsorbed onto the surface of the sand/GO nanocomposite by chemisorption. Sand/GO nanocomposite is an excellent candidate for removing Pb (II) from contaminated water. Keywords: Adsorption, Graphene oxide, Sand, Water treatment

Even if granular media filtration effectively reduces the turbidity of water, its limited surface functionalities and physical properties may constrain its ability to effectively remove critical contaminants from water. In our research, we successfully synthesized a new type of porous material - multiple coated GO/sand (M-GO/S) by integrating ordinary river sand with graphite oxide (GO) for the adsorptive removal of calcium ions in terms of water softening. Prior investigations confirmed it could remove water turbidity and fluoride simultaneously. M-GO/S was characterized using microscopic and spectroscopic techniques. The results indicate the presence of an uneven coating of graphite oxide, and the nanocomposite contains oxygen containing functional groups. Under given conditions, the M-GO/S nanocomposite demonstrated remarkable efficacy in removing 75% of calcium ions (a higher removal percentage than commercial coal powdered activated carbon) from simulated hard water: pH 8, 5.0 g dosage, 50 mg/L calcium ions, and 20 min contact time. The isotherm and kinetic data revealed that the adsorption mechanism primarily comprises multilayer adsorption by means of a chemical sorption process. The mechanism of the proposed M-GO/S nanocomposite for removing calcium ions from hard water is elucidated using (IMPS) analysis. The presence of (-O-Ca-O-) chemical bonds on the surface of the nanocomposite after equilibration with calcium ions suggests the occurrence of chemical interactions between the calcium ions and oxygen-containing functional groups of the M-GO/S. Consequently, the synthesized M-GO/S nanocomposite can be identified as a promising candidate for hard water treatment.

We fabricated non-catalytic carbon spheres with controllable dimensions (diameter 0.3–1.5 µm) by chemical vapour deposition at 1273 K using C2H2 (carbon source) and N2 (dilutant) gas precursors. By varying the flow rates of precursor gases, spherical or pseudo-spherical morphologies with chain-like hierarchical structures are discerned. The X-ray diffraction data show hexagonally graphitized networks. The mechanism of carbon sphere formation is not yet fully resolved largely due to the ambiguity associated with the nucleation step, viz. pentagon or heptagon route. According to molecular dynamics calculations, the formation of carbon pentagons is energetically more favorable than heptagons. Pentagon structures seem to form by closing Fjord regions of the graphitized network as evidenced in IR bands at 635 cm−1 and 796 cm−1. The X-ray photon spectroscopic (XPS) measurements show adventitious oxygen on the carbon sphere’s surface sites with -COOH and -C-CO groups. The -COOH and -C-CO groups are polar; hence, the carbon spheres’ surface sites readily hydroxylate (where ≡GOHδ represents surface sites with a fractional charge). The carbon sphere synthesized under C2H2N2 = 56 gas flow ratio (viz., CS3) shows the highest fluoride removal capacity, viz., 0.095 ± 0.01 mmol.m2-. The comparable zeta potential values observed between the carbon spheres and fluoride laden carbon spheres point to an anion exchange of surface hydroxyl ions for F- sorption. In agreement with the XPS data, the broad IR band at 3440 cm−1 due to H-bonded surface hydroxyl stretching vibrations has resolved into three discrete bands, e.g., 3640, 3752, and 3738 cm−1, which evidenced fluoride adsorption. Compared to activated carbon, the retention of fluoride on carbon spheres is over 60 times higher, which shows its potential in water treatment in removing fluoride.

In drinking water treatment, sand filters are frequently used to remove turbidity. We enhanced the performance of the sand by a chemical modification using graphite oxide (GO). Repeated coating of sand granules with graphite oxide (GO) followed by low temperature (120 degrees C) pyrolysis yielded hierarchical core-shell structures. The sand granules can be coated with GO in a single (hereafter S-GO1) or multiple (presently five cycles, hereafter S-GO5) coating steps. The GO coated sand composites were characterized using spectroscopic, microscopic, and conventional techniques. When compared to S-GO1, the GO coatings on S-GO5 show enhanced stability in contact with water. The S-GO5 removes over 70% fluoride around pH 6.30 +/- 0.02 according to Hill adsorption model. We also used a simulated water sample to assess the efficacy of sand/GO composites to remove fluoride and turbidity. When S-GO5 is used, the solution turbidity has reduced by 87% (from 0.08 to 0.01 NTU). However, in the presence of S-GO1, the turbidity has increased by + 75% (from 0.08 to 0.14 NTU). The gradual dissolution of adhered GO on S-GO1 enhanced the turbidity of treated water. The S-GO5 can be used to regulate excess fluoride and turbidity in water, simultaneously.

Official journal of the Institute of Physics - Sri Lanka. Full text articles are available. The journal also has a website at http://www.ip-sl.org/sljp/The new email for the Editor is eic.ipsl@gmail.com.

Rubber sector is the third largest export earner in Sri Lanka thus; natural rubber has acquired the status of a globally significant industrial raw material. Hence, value addition to natural rubber has become increasingly important in developing rubber products with enhanced properties in order to meet the industrial demand. This study was conducted with the aim of improving the electrical conductivity of natural rubber latex through the incorporation of carbon nanotubes (CNT). Electrically conductive rubber materials are important to shield devices from electromagnetic radiation by discharging electrical charges which are accumulated when rubber is used in contact with electro sensitive material. Commercial applications of conductive rubber include; conductivetyres and gloves, stretchable conductors and antistatic coatings. In this study, CNT were synthesised using a chemical method and characterised using Raman spectrometer, UV visible spectrophotometer, XRD analysis, TEM and FT-IR spectrometry. Produced CNT were used as a conductive filler in preparing rubber nanocomposites. A series of rubber compounds were formed by varying the phr of CNT from 0-5. The electrical conductivity of these samples was determined using the Four- point probe conductivity meter and an increase in conductivity was observed compared with the control rubber sample. The electrical conductivity of pristine rubber was found to be 4.58×10-6 S/m. Addition of CNT showed a thousand fold improvement (2.49×10-3 S/m). Thisvalue lies in the antistatic range thereby proving its ability to neutralise the accumulated static charges. In addition to electrical conductivity, thermal conductivity and mechanical properties such as tensile strength, young’s modulus, elongation at break, hardness of CNT incorporated latex samples were measured and a significant improvement was observed in these properties. Results of this work give a promising insight towards the development of a novel rubber material with improved electrical and mechanical properties. Therefore, it can be concluded that the incorporation of CNT would be a value addition to natural rubber thus paving the way for the development of a highly profitable export material which will be beneficial for the local economy. Keywords: Natural rubber latex, Carbon nanotubes, Electrical conductivity

In this study, a composite of nanomagnesium oxide (MgO) and granular activated carbon (GAC) was synthesized and analyzed for itsH(2)S adsorption capacity. The synthesis of composite involved a spray technique, which incorporates nano MgO even into micropores of GAC. The nanocomposite was characterized structurally and chemically, using scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), N-2-BET adsorption studies, ultra-violet photoelectron spectroscopy (UPS) and near edge X-ray absorption fine structure spectroscopy (NEXAFS) and inductively coupled plasma optical emission spectroscopy (ICP-OES). The composite described herein showedmore than five times higher H2S adsorption capacity than the virgin GAC. The high adsorption capacity shown by the MgO-GAC composite could be attributed to the fact that the composite structure exploits both physical and chemical adsorption processes simultaneously. The physical adsorption was occured at themacro and mesoporous structure of GAC whereas as the chemical adsorption was at the nano-MgO site. The differential thermogravimetric (DTG) analysis evidenced that the main mode of chemical adsorption was the oxidation of H2S, whereas a secondary metal supported addition mechanism was also shown to exist. (C) 2017 Elsevier Ltd. All rights reserved.

While slow release of chemicals has been widely applied for drug delivery, little work has been done on using this general nanotechnology-based principle for delivering nutrients to crops. In developing countries, the cost of fertilizers can be significant and is often the limiting factor for food supply. Thus, it is important to develop technologies that minimize the cost of fertilizers through efficient and targeted delivery. Urea is a rich source of nitrogen and therefore a commonly used fertilizer. We focus our work on the synthesis of environmentally benign nanoparticles carrying urea as the crop nutrient that can be released in a programmed manner for use as a nanofertilizer. In this study, the high solubility of urea molecules has been reduced by incorporating it into a matrix of hydroxyapatite nanoparticles. Hydroxyapatite nanoparticles have been selected due to their excellent biocompatibility while acting as a rich phosphorus source. In addition, the high surface area offered by nanoparticles allows binding of a large amount of urea molecules. The method reported here is simple and scalable, allowing the synthesis of a urea-modified hydroxyapatite nanohybrid as fertilizer having a ratio of urea to hydroxyapatite of 6:1 by weight. Specifically, a nanohybrid suspension was synthesized by in situ coating of hydroxyapatite with urea at the nanoscale. In addition to the stabilization imparted due to the high surface area to volume ratio of the nanoparticles, supplementary stabilization leading to high loading of urea was provided by flash drying the suspension to obtain a solid nanohybrid. This nanohybrid with a nitrogen weight of 40% provides a platform for its slow release. Its potential application in agriculture to maintain yield and reduce the amount of urea used is demonstrated.

Oil contaminated wastewater comes from variety of sources such as crude oil production, oil refinery, petrochemical industry, metal processing, lubricants, cooling agents, car washing, and restaurants, etc. Oil is a highly visible pollutant and it reduces the levels of dissolved oxygen in water and increases the level of toxic hydrocarbons. Therefor it affects the aquatic life and water environment. Water and oil cannot be easily separated from oil-water mixtures, as oil exists in droplets in the oil-water mixture. Oil droplets which are greater than or equal to 150 microns is classified as free oil while oil droplets with size ranging between 20 and 150 microns are classified as dispersed oil mixture. Emulsified oil mixtures are oil-water mixtures with droplets smaller than 20 microns and oil-water mixture with droplet sizes smaller than 5 microns are classified as soluble oil mixtures. High purity vein graphite available in Sri Lanka is well renowned for electrical conductivity and lubricity. Beside it also has higher adsorption capacity. In this study, vein graphite of different particle sizes (<65, 65-125, 125-150 and 150-500μm) with two purity grades (99+% and 95%) were used to treat oil-water mixtures (motor engine oil with distilled water) similar to service station waste water of different concentrations of oil. Minimum amount of graphite (weight) required to completely separate oil from water was measured in each treatment. Most effective particle size of graphite for this treatment was found to be in the range of 125-150 μm. Oil separation capacity of high purity graphite (99+ %) and less pure (95%) graphite was found to be similar to each other. Maximum concentration of oil that can be treated with this method was found to be 400%. Final oil concentrations of all samples treated with graphite were measured and the efficiency of the treatment was found to be 99.98%. Keywords: Natural vein graphite, Absorption capacity, Waste water, Hydrocarbon

Carbon nanotubes (CNT) are produced from a rare variety of natural vein graphite (VG) distinctive to Sri Lanka using electric arc discharge. Electric arc-discharge produces both single walled and multi walled nanotubes. The products are characterized using high resolution electron microscopy and Raman spectroscopy for verification and validation.

The multilayer graphene oxide membranes (MGOMs) are fabricated using graphite oxide synthesized using a rare form of high purity natural vein graphite (NVG) and are characterized using FE-SEM, AFM and C 1s and O 1s core level photoemission (ESCA) for their properties. It is observed that NVG based MGOM can be thermally reduced energy efficiently to obtain graphene-like membranes.

The electronic structure and magnetism of nanocrystalline graphite prepared by ball milling of graphite in an inert atmosphere have been investigated using valence band spectroscopy (VB), core level near-edge X-ray absorption fine structure (NEXAFS) spectroscopy and magnetic measurements as a function of the milling time. The NEXAFS spectroscopy of graphite milled for 30 hours shows simultaneous evolution of new states at ~284.0 eV and at ~290.5 eV superimposed upon the characteristic transitions at 285.4 eV and 291.6 eV, respectively. The modulation of the density of states is explained by evolution of discontinuities within the sheets and along the fracture lines in the milled graphite. The magnetic measurements in the temperature interval 2-300-2 K at constant magnetic field strength show a correlation between magnetic properties and evolution of the new electronic states. With the reduction of the crystallite sizes of the graphite fragments, the milled material progressively changes its magnetic properties from diamagnetic to paramagnetic with contributions from both Pauli and Curie paramagnetism due to the evolution of new states at ~284 and ~290.5 eV, respectively. These results indicate that the magnetic behaviour of ball-milled graphite can be manipulated by changing the milling conditions.

The time-resolved change in the surface potential upon photoexcitation has been measured in two n-type photovoltaics, Si (111) 7×7 and ZnO (101[over ¯]0), using two different laser pump-synchrotron x-ray probe methodologies. Taken together, these experiments allow the dynamics of the surface photovoltage (SPV) to be monitored over timescales of subnanoseconds to milliseconds. The timescales for the photoinduced change in the SPV are dramatically different in the two samples, with measured SPV decay time constants of 6.6 μs for Si and up to 1.2 ms (dependent on surface oxygen concentration) for ZnO. The carrier dynamics at the Si (111) 7×7 surface are well modeled by a self-decelerating relaxation model involving the recombination of carriers by thermionic emission across the surface depletion layer on nanosecond timescales. In the case of ZnO (101[over ¯]0), a persistent photoconductivity (PPC) is observed, which is influenced by oxygen annealing conditions during sample preparation. Persistent photoconductivity is also observed when the surface is illuminated with subband-gap (405 nm) radiation, revealing that defect states approximately 340 meV above the valence band edge are directly associated with the PPC. We demonstrate that, under the conditions of our experiment, PPC mediated by these defects dominates over the oxygen photodesorption mechanism. These observations are consistent with the hypothesis that ionized oxygen vacancy states are responsible for PPC in ZnO. Time-resolved surface photovoltage measurements at n-type photovoltaic surfaces: Si(111) and ZnO(101[over ¯]0) - ResearchGate. Available from: http://www.researchgate.net/publication/258782678_Time-resolved_surface_photovoltage_measurements_at_n-type_photovoltaic_surfaces_Si(111)_and_ZnO(101over_0).

The fabrication of flexible multilayer graphene oxide (GO) membrane and carbon nanotubes (CNTs) using a rare form of high-purity natural graphite, vein graphite, is reported for the first time. Graphite oxide is synthesized using vein graphite following Hummer's method. By facilitating functionalized graphene sheets in graphite oxide to self-assemble, a multilayer GO membrane is fabricated. Electric arc discharge is used to synthesis CNTs from vein graphite. Both multilayer GO membrane and CNTs are investigated using microscopy and spectroscopy experiments, i.e., scanning electron microscopy (SEM), atomic force microscopy (AFM), high-resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), core level photoelectron spectroscopy, and C K-edge X-ray absorption spectroscopy (NEXAFS), to characterize their structural and topographical properties. Characterization of vein graphite using different techniques reveals that it has a large number of crystallites, hence the large number of graphene sheets per crystallite, preferentially oriented along the (002) plane. NEXAFS and core level spectra confirm that vein graphite is highly crystalline and pure. Fourier transform infrared (FT-IR) and C 1s core level spectra show that oxygen functionalities (-C-OH, -C=O,-C- O-C-) are introduced into the basal plane of graphite following chemical oxidation. Carbon nanotubes are produced from vein graphite through arc discharge without the use of any catalyst. HRTEM confirm that multiwalled carbon nanotube (MWNTs) are produced with the presence of some structure in the central pipe. A small percentage of single-walled nanotubes (SWNTs) are also produced simultaneously with MWNTs. Spectroscopic and microscopic data are further discussed here with a view to using vein graphite as the source material for the synthesis of carbon nanomaterials.

The time-resolved change in the surface potential upon photoexcitation has been measured in two n-type photovoltaics, Si (111) 7x7 and ZnO (10 (1) over bar0), using two different laser pump-synchrotron x-ray probe methodologies. Taken together, these experiments allow the dynamics of the surface photovoltage (SPV) to be monitored over timescales of subnanoseconds to milliseconds. The timescales for the photoinduced change in the SPV are dramatically different in the two samples, with measured SPV decay time constants of 6.6 mu s for Si and up to 1.2 ms (dependent on surface oxygen concentration) for ZnO. The carrier dynamics at the Si (111) 7x7 surface are well modeled by a self-decelerating relaxation model involving the recombination of carriers by thermionic emission across the surface depletion layer on nanosecond timescales. In the case of ZnO (10 (1) over bar0), a persistent photoconductivity (PPC) is observed, which is influenced by oxygen annealing conditions during sample preparation. Persistent photoconductivity is also observed when the surface is illuminated with subband-gap (405 nm) radiation, revealing that defect states approximately 340 meV above the valence band edge are directly associated with the PPC. We demonstrate that, under the conditions of our experiment, PPC mediated by these defects dominates over the oxygen photodesorption mechanism. These observations are consistent with the hypothesis that ionized oxygen vacancy states are responsible for PPC in ZnO.

Studies using synchrotron radiation (SR) to probe the electronic structure, bonding and carrier dynamics at photovoltaic surfaces and interfaces are described. This includes a study of the growth of the p-type inorganic semiconductor CuI on n-type TiO2 nanoparticulate and single-crystal anatase surface using SR photoemission spectroscopy. This is complemented by NEXAFS (near-edge X-ray absorption fine structure) studies of the adsorption of model sensitising dyes at this interface. The data show that the interface between p-CuI and single crystal and nanocrystalline anatase-phase n-TiO2 is a type II heterojunction interface, with significant band-bending, contrasting with the 'flat-band' energy level line-up normally assumed for such cells. NEXAFS is used to derive a canted, roughly upright geometry for BINA (bi-isonicotinic acid, a part of the dye molecule structure) adsorbed at the anatase surface.

A comparison of the electronic structure of rutile (110), anatase (101), and anatase (001) single-crystal surfaces has been made using resonant photoemission and x-ray absorption spectroscopy. Under identical preparative conditions, the anatase (101) surface shows the lowest Ti 3d and 4sp hybridization in the states close to the valence-band maximum of the three surfaces. It also shows the highest concentration of surface-oxygen vacancies. The effect on the electronic structure of modifying the surface preparative route and thus the concentration of surface-oxygen vacancies is examined. The sigma-antibonding Ti 3d e(g)/O 2p hybridization (probed by XAS) is reduced by the removal of surface-oxygen. Photoemission shows that as the number of surface-defects is increased, the O 2p-Ti 3d t(2g) pi-bonding interaction is disrupted. For the anatase (101) surface it is found that as the number of surface-oxygen vacancies is increased, the Ti 3d and 4sp contributions at the valence-band maximum are reduced. We discuss the correlation between electronic structure and photocatalytic activity of the different polymorphs of TiO2.