Showing papers in "NANO in 2008"

Visible light photocatalysis by tailoring crystal defections in zinc oxide nanostructures

Abstract: The photocatalytic activity of zinc oxide (ZnO) nanoparticles, films and nanowires as a potential visible light photocatalyst is presented in this work. ZnO nanoparticles were synthesized in differ ...

A review of purification techniques for carbon nanotubes

Abstract: Purification of carbon nanotubes (CNTs) is a very actively discussed topic in contemporary CNT literature. To a large extent, impurities embedded in CNTs influence the physical and chemical characteristics of the CNTs. Different purification methods yield different CNT characteristics and may be suitable for the production of different types of CNTs. Developments in the purification methods of CNTs are reviewed, and the production methods are briefly discussed and summarized. This is followed by a detailed description of the three major purification methods, viz. chemical, physical, and multi-step purification.

Analytical and numerical modeling methods for impedance analysis of single cells on-chip

Abstract: Electrical impedance spectroscopy (EIS) is a noninvasive method for characterizing the dielectric properties of biological particles. The technique can differentiate between cell types and provide information on cell properties through measurement of the permittivity and conductivity of the cell membrane and cytoplasm. In terms of lab-on-a-chip (LOC) technology, cells pass sequentially through the microfluidic channel at high speed and are analyzed individually, rather than as traditionally done on a mixture of particles in suspension. This paper describes the analytical and numerical modeling methods for EIS of single cell analysis in a microfluidic cytometer. The presented modeling methods include Maxwell’s mixture theory, equivalent circuit model and finite element method. The difference and advantages of these methods have been discussed. The modeling work has covered the static case — an immobilized cell in suspension and the dynamic case — a moving cell in the channel.

Magnetism in Graphene Systems

Abstract: Graphene has attracted great interest in materials science, owing to its novel electronic structures. Recently, magnetism discovered in graphene-based systems has opened up the possibility of their spintronics application. This paper provides a comprehensive review of the magnetic behaviors and electronic structures of graphene systems, including two-dimensional graphene, one-dimensional graphene nanoribbons, and zero-dimensional graphene nanoclusters. Theoretical research suggests that such metal-free magnetism mainly comes from the localized states or edges states. By applying an external electric field, or by chemical modification, we can turn the zigzag nanoribbon systems into half metal, thus obtaining a perfect spin filter.

Carbon nanotube-graft-poly(citric acid) nanocomposites

Abstract: Novel biodegradable nanocomposites containing multi wall carbon nanotubes (MWCNT) and poly(citric acid) (PCA) were successfully synthesized. For preparation of nanocomposites, MWCNT was opened using a mixture of sulfuric and nitric acid and its derivative containing –COOH and –OH functional groups was obtained. Polycondensation of monohydrate citric acid in the presence of functionalized MWCNT in the melting state was lead to nanotube-graft-poly(citric acid) (CNT-g-PCA) nanocomposites. The degree of polymerization of grafted hyperbranched poly(citric acid) onto the CNTs was controlled using CNT/citric acid ratio. The CNT-g-PCA were soluble in water freely and stirring their water solution and silver nitrate at room temperature lead to the CNT-g-PCA containing encapsulated silver nanoparticles in their polymeric shell. The structure of nanocomposites was characterized by TEM, DLS and spectroscopy methods.

Purity measurement of single-walled carbon nanotubes by uv-vis-nir absorption spectroscopy and thermogravimetric analysis

Abstract: We measured the content of single-walled carbon nanotubes (SWCNTs) in SWCNT soot within 3.7% error using UV-VIS-NIR absorption spectroscopy. We also propose a better overall evaluation method by combining thermogravimetic analysis with UV-VIS-NIR absorption spectroscopy to analyze the purity of SWCNT providing the accurate assessment of the amounts of noncarbonaceous impurity, carbonaceous impurity, and SWCNT each with respect to a highly purified reference.

Control of airborne nanoparticles release during compounding of polymer nanocomposites

Abstract: Polymer nanocomposites, which contain nanoparticles dispersed in a polymer matrix, provide improved properties at low filler loadings. These materials are already produced commercially, with twin-screw extrusion being the preferred process for compounding the nanoparticles and polymer melts. Several recent studies have demonstrated that nanoparticles can enter the body through inhalation, but the risk assessments for nanoparticle exposures are incomplete. Recently, concerns had been expressed that airborne nanoparticles released during compounding might present significant exposure to extruder operators. To assess the impact of the nanoparticles during twin-screw compounding of nanocomposites, researchers with experience in occupational and environmental health and polymer manufacturing monitored the compounding process for a model nanoalumina-containing nanocomposite using a TSI Fast Mobility Particle Spectrometer (FMPS). FMPS measurements were taken at background locations, source locations, and operators' breathing zones. In parallel to the FMPS real time measurement, airborne nanoparticles were collected using polycarbonate filters fitted with filmed grids driven by a personal air sampling pump. Filter samples were analyzed for particle morphology and elemental composition, and the results were found to be in good agreement with particle measurements by FMPS. Engineering controls and administrative controls were applied to reduce particle release from the compounding process and other operations in the laboratory. The administrative controls dramatically eliminated nanoparticles in the laboratory air, reducing total concentration by as much as 53 000 particles/cm3. Engineering controls were investigated and significant reductions of particle release were attained. The primary solution to reduce exposure level of nanoalumina is to isolate the releasing source. Overall, the engineering controls and administrative controls were effective in reducing airborne nanoparticle release during compounding.

COMPARISON OF THE REACTIVITY OF NANOSIZED ZERO-VALENT IRON (nZVI) PARTICLES PRODUCED BY BOROHYDRIDE AND DITHIONITE REDUCTION OF IRON SALTS

Abstract: Dithionite can be used to reduce Fe(II) and produce nanoscale zero-valent iron (nZVI) under conditions of high pH and in the absence of oxygen. The nZVI is coprecipitated with a sulfite hydrate in a thin platelet. The nanoparticles formed are not pure iron but this feature does not appear to affect their degradation performance under air or N2 gas conditions. The efficiency of trichloroethylene (TCE) degradation, when one is employing nanoparticles manufactured using dithionite (nZVIS2O4), is similar to if not slightly better than that of the more conventional borohydride procedure (nZVIBH4). The other advantages of the dithionite method are that (i) it uses a less expensive and widely available reducing agent, and (ii) there is no production of potentially explosive hydrogen gas. Oxidation of benzoic acid using the nZVIS2O4 particles results in different byproducts than those produced when nZVIBH4 particles are used. The low oxidant yield based on hydroxybenzoic acid generation is offset by the production of higher concentrations of phenol. The high concentration of phenol compared to hydroxybenzoic acids suggests that OH• addition is not the primary oxidation pathway when one is using the nZVIS2O4 particles. It is proposed that sulfate radicals () are produced as a result of hydroxyl radical attack on the sulfite matrix surrounding the nZVIS2O4 particles, with these radicals oxidizing benzoic acid via electron transfer reactions rather than addition reactions.

Titantium Dioxide Nanoparticles Assembled by DNA Molecules Hybridization and Loading of DNA Interacting Proteins.

Abstract: This work demonstrates the assembly of TiO2 nanoparticles with attached DNA oligonucleotides into a 3D mesh structure by allowing base pairing between oligonucleotides. A change of the ratio of DNA oligonucleotide molecules and TiO2 nanoparticles regulates the size of the mesh as characterized by UV-visible light spectra, transmission electron microscopy (TEM) and atomic force microscopy (AFM) images. This type of 3D mesh, based on TiO2-DNA oligonucleotide nanoconjugates, can be used for studies of nanoparticle assemblies in materials science, energy science related to dye-sensitized solar cells, environmental science as well as characterization of DNA interacting proteins in the field of molecular biology. As an example of one such assembly, proliferating cell nuclear antigen protein (PCNA) was cloned, its activity was verified, and the protein was purified, loaded onto double strand DNA oligonucleotide-TiO2 nanoconjugates, and imaged by atomic force microscopy. This type of approach may be used to sample and perhaps quantify and/or extract specific cellular proteins from complex cellular protein mixtures based on their affinity for chosen DNA segments assembled into the 3D matrix.

Growth rate measurement of c60 fullerene nanowhiskers

Abstract: The growth rate of C60 fullerene nanowhiskers (C60NWs) prepared by the liquid–liquid interfacial precipitation method is measured and the growth mechanism is discussed. The growth of C60NWs is investigated from the data obtained at the growth temperatures of 5, 10, 15 and 20°C. It is found that the convection of the solution scarcely influences the growth rate, suggesting that a surface reaction of C60 molecules dominates the growth process. The activation energy of C60NWs' growth is estimated at about 52.8 kJ/mol from their initial stage of growth. This activation energy is much greater than that of C60 diffusion in solutions found in the literature. This result suggests that the desolvation process of C60 on the whisker surface governs the growth of C60NWs.

Highly reproducible single polyaniline nanowire using electrophoresis method

Abstract: Site-specific single polyaniline nanowires were fabricated through electrophoresis growth with acetone wetting. After growing the nanowires, the post-process of acetone wetting of the nanowires improved morphology, topology, and electrical conductivity with coagulation and substitution in polyaniline. They showed resistance changes of 39.57 ± 11.57% and presented 2.38 × 10-4 ± 3 × 10-5 Ω · cm, 133.77 ± 13.82 nm thickness, and 133.17 ± 13.01 nm width in 1 μm to 5.5 μm length. The new combined growth process of electrophoresis and acetone wetting significantly improved reproducibility, reliability, and controllability in the fabrication of single polymer nanowires.

Few walled carbon nanotube production in large-scale by nano-agglomerate fluidized-bed process

Abstract: Few walled carbon nanotubes (FWCNTs) have been successfully synthesized using a nano-agglomerate fluidized-bed process. FWCNTs can be obtained by fluidization of Fe(Co/Ni)/Mo/MgO catalysts at a high temperature with methane cracking in a nano-agglomerate fluidized-bed reactor. The products were mainly 2 to 5 walled CNTs with an outer diameter of 1–7 nm in high purity, as revealed by Raman spectrometry, SEM, and HRTEM analysis. Two keys were crucial for this process. The first key was to get the small size of activity catalyst particles which was realized by Mo addition in catalyst. The graphitization of FWCNTs strongly depended on the composition of catalyst. Fe/Mo/MgO catalyst showed the highest activity and the FWCNT product with the best graphitization. Another key for this process was that the particles must be kept in fluidized state during FWCNT formation. Detailed process information was reported in this article, which showed a potential way for the large scale production of FWCNTs, thereby the urgent need for FWCNTs in high performance will be overcome.

Label-free biomolecular detection using carbon nanotube field effect transistors

Abstract: Carbon nanotube field effect transistor (FET) type biosensors have been widely investigated as one of the promising platforms for highly sensitive personalized disease-monitoring electronic devices Combined with high level cutting edge information technology (IT) infra systems, carbon nanotube transistor biosensors afford a great opportunity to contribute to human disease care by providing early diagnostic capability Several key prerequisites that should be clarified for the real application include sensitivity, reliability, reproducibility, and expandability to multiplex detection systems In this brief review, we introduce the types, fabrication, and detection methods of single-walled carbon nanotube FET (SWNT-FET) devices As surface functionalization of the devices by which nonspecific bindings (NSBs) are efficiently prohibited is also another important issue regarding reliable biosensors, we discuss several key strategies about surface passivation along with examples of various biomolecules such as proteins, DNA, small molecules, aptamers, viruses, and cancer and neurodegenerative disease markers which have been successfully sensed by SWNT-FET devices Finally, we discuss proposed detection mechanisms, according to which strategies for fabricating sensor devices having high sensitivity are determined Two main mechanisms — charge transfer (or electrostatic gate effect) and Schottky barrier effect, depending on the place where biomolecules are adsorbed — will be covered

Excimer laser crystallization and nanostructuring of amorphous silicon for photovoltaic applications

Abstract: Excimer laser crystallization of amorphous silicon has been extensively studied for electronic applications. Most of the early works has been on thin film transistor fabrication from laser crystallized silicon. However, in parallel, the applicability of the technique for photovoltaics has also been pursued. Direct crystallization of the absorber layer of a thin film amorphous silicon cell has proven unsuitable, due to poor device performance. The surface nanostructuring capability of the laser process, as a result of the crystallization appears to be of more scientific significance, and a number of applications have been reported. This review covers the established physics of excimer laser crystallization in the context of photovoltaics. It also expands on more recent applications of excimer laser nanostructuring of amorphous silicon, especially for photovoltaic applications. The outlook of the technique for photovoltaics is discussed with the use of reported successes, briefly discussing the fundamental improvements.

Atomic hydrogen-driven size control of catalytic nanoparticles for single-walled carbon nanotube growth

Abstract: The effects of an atomic hydrogen (Hat ) pretreatment of the catalyst layer on the low tem- perature growth of single-walled carbon nanotubes (SWCNTs) have been investigated using a modified catalytic chemical vapor deposition system. Well-defined and isolated individual Fe nanoparticles as a catalyst are successfully formed on the defects with high trapping energy which are created on the Al2O3 surface by Hat pretreatment, yielding highly dense SWCNTs. The pretreatment mechanism of Hat , compared to H2 , is also discussed. It was also found that the quality of SWCNTs can be enhanced when Hat is flowed with CH4 during nanotubes growth at low temperature. In this case, the undesired carbon products and defects on catalyst seeds and nanotube walls can be selectively removed by Hat . Therefore it is essential to use Hat in the pretreatment stage for increasing catalytic activity and to keep the size of nanoparticles in the nm range. Hat can also be employed in growth stage for enhancing SWCNTs quality and density at low temperature.

THRESHOLD AND SATURATION VOLTAGES MODELING OF CARBON NANOTUBE FIELD EFFECT TRANSISTORS (CNT-FETs)

Abstract: We present analytical model equations for threshold voltage (Vth) and saturation voltage (Vds,sat) characterizing CNT-FETs. These model equations have been obtained from the charge and potential distributions between the gate and substrate in a CNT-FET. It is shown that both Vth and Vds,sat are strongly dependent on chiral vectors of CNTs. The results show close agreement between theoretical and graphical modeling techniques. It is also shown that the calculated Vth of a CNT-FET with chiral vector (3, 1) is in close agreement with the corresponding published work.

Application of nanoscale zero-valent iron for groundwater remediation: laboratory and pilot experiments

Abstract: It is known that the reductive effects of zero-valent iron (Fe0) and the sorptive capability of iron and its oxides can be used for both the dehalogenation of chlorinated hydrocarbons (CHC), especially of chlorinated ethenes (PCE → TCE → DCE → VC → ethene, ethane), and the removing of heavy metals from groundwater by turning them into a less-soluble form through changes of their oxidation state, or by adsorption. These consequences are being exploited in the construction of iron filling permeable reactive barriers for a longer time.1 The advantages of nanoscale zero-valent iron (nanoFe0) over the macroscopic one consist not only in the better reactivity implicit in their greater specific surface area but also in their mobility in rock environment.2,3 Numerous laboratory experiments, especially the batch-agitated experiments, with samples from seven various contaminated localities in Europe have been carried out with the aim to discover the measurement of the reductive effect of the nanoFe0 on selected contaminants. It was found that the nanoFe0 can be reliably usable as a reductive reactant for in-situ chemical decontamination of sites polluted by chlorinated ethenes (CEs), or hexa-valent chromium (CrVI). The rate of reductive reaction and the optimal concentrations for the real remediation action were determined. On the basis of these laboratory experiments, the methods for pilot application of nanoFe0 have been specified. Subsequently the pilot experiments were accomplished in surveyed localities.

Nanotechnology in medicine and health sciences

Abstract: The present investigation is aimed at the biomedical aspects of nanomaterials in medicine and health sciences. Synthesis of nanomaterials can be categorized into three main sections based on their system designation, viz. nanocolloidal systems, surface modification of the biomaterials at molecular level, and nanodevices. An overview of functionalized nanomaterials, devices, and systems in drug and gene delivery, controlled release systems, molecular imaging and diagnostics, cardiac therapy, dental care, orthopedics, and targeted cancer therapy is presented. We further present some preliminary results of our investigation of biodegradable polymeric nanospheres and nanofibers with significant applications in health and medicine.

Synthesis of single-walled carbon nanotubes from liquefied petroleum gas

Abstract: Hydrocarbons such as methane, ethylene, and CO with high purity (> 99.9%) have been widely used to synthesize single-walled carbon nanotubes (SWCNTs). Here, liquefied petroleum gas (LPG) was used to synthesize SWCNTs by catalytic chemical vapor deposition. The LPG converted into CNTs and other stable hydrocarbons. The BET specific surface area of SWCNT was about 583 m2/g. The as-grown SWCNT showed good graphitization. The graphitization can be further modulated by the growth temperature. Certain amount of sulfur in LPG was a promoter for SWCNT growth. Compared SWCNTs obtained from methane, more semiconductive SWCNTs were synthesized from LPG as carbon source. The LPG is in low price, thus, a methodology to lower the production cost of SWCNTs with hydrocarbon mixtures is realized.

Diluted magnetic semiconductor nanowires

Abstract: An idea for simultaneously manipulating spin and charge in a single semiconductor medium has resulted in the development of diluted magnetic semiconductors (DMSs), which exhibits surprisingly room temperature ferromagnetic signatures despite having controversial ferromagnetic origin. However, achievement of truly room temperature ferromagnetism by carrier mediation is still the subject of intense research to develop the practical spin-based devices. Nanowires with one-dimensional nanostructure, which offers thermodynamically stable features and typically single crystalline and defect free, have a number of advantages over thin films with respect to studying ferromagnetism in DMSs. This review focuses primarily on our works on GaN-based DMS nanowires, i.e., Mn-doped GaN, Mn-doped AlGaN and Cu-doped GaN nanowires. These DMS nanowires have room temperature ferromagnetism by the local magnetic moment of doping elements that are in a divalent state and in tetrahedral coordination, thus substituting Ga in the wurtzite-type network structure of host materials. Importantly, our evidences indicate that the magnetism is originated from the ferromagnetic interaction driven by the carrier. These outcomes suggest that nanowires are ideal building blocks to address the magnetism in DMS due to their thermodynamic stability, single crystallinity, free of defects and free standing nature from substrate. Nanowires themselves are ideal building blocks for nanodevices and, thus, it would also be helpful in developing DMS-based spin devices.

Biological effect of intranasally instilled titanium dioxide nanoparticles on female mice

Abstract: The toxicological effect of TiO2 nanoparticles with different crystal structure (80 nm for rutile and 155 nm for anatase) on female mice was investigated through intranasal instillation. After exposure for 30 days at the dose of 50 mg/kg body weight, no abnormal activity and mortality were observed with the normally increasing body weight of mice. The coefficients of tissues to body weight also show no obvious difference from the control except the increased coefficient of kidneys in mice exposed to 80 nm TiO2 nanoparticles. Titanium contents and histopathology examination indicate the no pathological response in the lung was induced by the increased TiO2 deposition, and the liver, heart, and spleen were not influenced. The severe pathology changes in kidneys suggest that TiO2 nanoparticles may be excreted out by kidneys via system circulation. However, the serum biochemical parameters were not changed compared with the control, which means no obvious functional impairment induced by the nasal exposure for 30 days. In addition, the higher titanium contents in the brain tissues imply that the translocation and deposition of nanoparticles through intranasal instilling pathway is different from the other routes such as intratracheal inhalation or intratracheal instillation. The influence of deposited nanoparticles on central nervous system needs further investigation and is underway.

Decontamination of nitrates and nitrites in wastewater by zero-valent iron nanoparticles

Abstract: The chemical reduction of nitrate or nitrite species by zero-valent iron nanoparticle (ZVIN) in aqueous solution and related reaction kinetics or mechanisms using fine structure characterization were investigated. Experimentally, ZVIN of this study was prepared by borohydride reduction method at room temperature. The morphology of as-synthesized ZVIN shows that the nearly ball and ultrafine particles ranged of 20–50 nm were observed with FE-SEM analysis. The kinetic model of nitrites or nitrates reductive reaction by ZVIN is proposed as a pseudo-first-order kinetic equation. The nitrite and nitrate removal efficiencies using ZVIN were found 65–83% and 51–68%, respectively, based on three different initial concentrations. By using XRD patterns, the quantitative relationship between nitrite and Fe(III) or Fe(II) becomes similar to the one between nitrate and Fe(III) in the ZVIN study. The possible reason is linked with a faster nitrite reduction by ZVIN. In fact, the occurrence of the relative faster nitrite reductive reaction suggested that the passivation of the ZVIN have a significant contribution to iron corrosion. The XANES spectra show that the nitrites or nitrates reduce to N2 while oxidizing the ZVIN to Fe2O3 or Fe3O4 electrochemically. It is also very clear that decontamination of nitrate or nitrite species in groundwater via the in-situ remediation with a ZVIN permeable reactive barrier would be environmentally attractive.

Nanostructured particles and layers for sensing contaminants in air and water

Abstract: Chemical sensor layers for environmental applications require optimal selectivity, sensitivity, and long term stability, which can be achieved in artificial matrices. For detecting thiols in air, reversible affinity interactions can be optimized by varying the stoichiometry of molybdenum disulphide nanoparticles to achieve sulphur deficiencies. Generating MoS1.9 increases the quartz crystal microbalance (QCM) sensor responses towards butane thiol by a factor of three. Artificial recognition sites are accessible by molecular imprinting: acrylate copolymers can be tuned in polarity to interact selectively with atrazine in water leading to detection limits below one ppb with QCM sensors. Finally, sensor arrays coated with six different molecularly imprinted polymers (MIP) correctly reproduce the ethyl acetate concentration of a composter over a period of two weeks validated by GC-MS measurements.

Nonlinear optical transmission of surface-modified nickel sulfide nanoparticles: saturation of absorption and optical limiting

Abstract: Saturable absorbers and optical limiters have contrary optical transmission properties. We report observations of simultaneous occurrence of both these effects in a nickel sulfide nanoparticle (average diameter ~5 nm) solution and a simultaneous quantitative measurement of both. Intensity-dependent nonlinear transmission studies carried out using a 7 ns Nd:YAG laser at 532 nm by the Z-scan method, revealed efficient optical limiting in nickel sulfide nanoparticle suspensions. Induced nonlinear optical scattering was identified to be the mechanism of optical limiting, and absorption at 532 nm was found to saturate. A modification of the conventional Z-scan implementation led to the retrieval of the saturation intensity, which is otherwise overshadowed by very strong nonlinear scattering.

Electrochemical dna sensor technology for monitoring of drug-dna interactions

Abstract: The objective of this investigation is to understand the nature and dynamics of binding small molecules to bio-macromolecules using electrochemical methods. The investigation pertaining to the design of site- and conformation-specific reagents provides a rationale for new studies of drug delivery design. Some anticancer drugs and DNA interactions have been undertaken by using a variety of techniques. Determination of interaction between DNA and DNA-targeted molecules would be valuable in the design of molecule-specific electrochemical biosensors for applications in diagnostics, development of drugs for chemotherapy, and as a biotechnological tool for DNA-based point-of-care diagnosis.

Integrating nanoscale zero-valent iron and titanium dioxide for nutrient removal in stormwater systems

Abstract: Nutrients, such as nitrate, nitrite, and phosphorus, are common contaminants in many aquatic systems in the United States Ammonia and nitrate are both regulated by the drinking water standards in the US primarily because excess levels of nitrate might cause methemoglobinemia Phosphorus might become sources of the eutrophication problems associated with toxic algae in the freshwater bodies Toxic algal blooms can cause severe acute and chronic public health problems Chemical reduction of nitrate by using zero-valent iron started as early as 1964, and considerable research reports relating to this technology to nanomaterial were extensively reported in 1990s making the use of nanoscale zero-valent iron (NZVI) particles for nitrate removal become one of the most popular technologies in this field The purpose of the present study was to examine the potential of integrating green sorption media, such as sawdust, limestone, tire crumb, and sand/silt, with two types of nanoparticles, including NZVI and Titanium Dioxide (TiO2), for nitrate removal in an engineering process The study consists of running packed bed column tests followed by the addition of NZVI and TiO2 to improve nitrate and phosphorus removal efficiency Preliminary results in this paper show that the potential and advanced study may support the creation of design criteria of stormwater and groundwater treatment systems for water reuse in the future

Synthesis and Characterization of Titania Nanotubes for Dye Wastewater Treatment

Abstract: This paper starts with the preparation of anatase titania nanotube (TN) in large quantities by hydrothermal routes with different calcination temperatures, and then delves into a thorough investigation for the characterization of fine structures or formation mechanism of TN. Experimentally, anatase TiO2 nanoparticle was used as a precursor for TN synthesis. The results showed that the length and diameter of TN range are 50–100 nm and 10–15 nm, respectively. The XRD patterns and BET isotherms indicated that TN owns anatase-typed structures with a surface area of 292m2/g. By extended X-ray absorption fine structure (EXAFS) spectra, the valency and framework of TN are Ti(IV) with octahedral structures. The EXAFS data also revealed that TN has a first shell of Ti–O bonding with bond distances of 1.95 A and coordination numbers were 2. The results revealed that the TiO2 anatase nanoparticles can be solved into layer under strong alkaline. The layer of TN further curling itself to reduce the energetics was postulated and found. For calcination temperature larger than 400°C, the microstructure of TN might transform from nanotube into nanoparticles accompanying with the sharp increase for the nanoparticle crystalline phase. With the understanding of pore structure variation on the basic dye (Basic Green 5 (BG5)), the adsorption ability, mechanisms, and kinetics of (Basic Green 5 (BG5)) dye onto TN were examined as well.

The potential intrinsic and extrinsic toxicity of silica nanoparticles and its impact on marine organisms

Abstract: The intrinsic and extrinsic toxicity of SiO2 nanoparticles (Aerosil OX50, ϕ ~ 40 nm) are investigated with a comparison to the particles in micron size (SiO2 gel, ϕ ~ 1.5 μ m). Nanoparticles potentially functioned as a carrier of harmful substances transfer was assessed by examining the surface adsorption behavior of the nanoparticles towards γ-picoline (4-methylpyridine), recognized as one type of the marine pollutants, as well as the penetration behavior of the nanoparticles towards a typical marine macro-organism (Caulerpa taxifolia). Silica nanoparticle surface can take up to 2.6 molecules/nm2 of γ-picoline in an aqueous solution comparable to the marine environment. These nanoparticles can further travel onto the surface and into the bulk of the algae (Caulerpa taxifolia) with a depth of ~ 1 μm while carrying toxic γ-picoline. The integrated intrinsic and extrinsic toxicity of SiO2 nanoparticles has a significant effect on the growth of the algae. The large surface area of the silica nanoparticles results in a high adsorption capability and allows the particles to participate in possible toxic carrier activities in water medium towards marine organisms.

PHOTOCATALYTIC DEGRADATION OF PYRENE IN POROUS Pt/TiO2-SiO2 PHOTOCATALYST SUSPENSION UNDER UV IRRADIATION

Abstract: Pyrene is a high molecular weight polycyclic aromatic hydrocarbon (PAH) that is found in water systems worldwide. It is harmful to living organisms, even when taken in very small amounts. The photocatalytic degradation of pyrene in porous Pt/TiO2–SiO2 photocatalyst (PPtPC) suspension under UV irradiation was investigated in this study. PPtPC was prepared by a simple heat treatment of the compacted powder mixtures of anatase TiO2 and amorphous SiO2 with camphor as a pore directing template, followed by coating platinum by the dip-coating method. X-ray diffraction (XRD), scanning electron microscopy (SEM) with an integrated energy-dispersive analysis of the X-ray (EDX) system, and Brunauer–Emmett–Teller (BET) were used to characterize PPtPC. The degradation kinetics of pyrene in different experimental conditions, such as initial concentration of pyrene, oxygen concentrations, pH, and temperature, were investigated. The durability of PPtPC was also tested. The results indicate that the structure of TiO2 in PPtPC is anatase. The aggregated size of PPtPC is in the range of 10–100 μm, the mean pore diameter is 3 nm, and the BET surface area is 109 m2 g-1. The photocatalytic degradation process of pyrene follows pseudo-first-order kinetics. The rate constants increase as the initial concentration of pyrene and pH decrease. Higher temperature slightly enhances the rate constant. The dissolved oxygen in the photocatalytic degradation process is not as important as in the photolysis process. The recovered PPtPC still shows high photoactivity. This work suggests that PPtPC offers a promising method for high molecular weight PAH removal.

Fe-DECORATED FULLERENE (C60) NANOWHISKERS FOR ENVIRONMENTAL APPLICATION

Abstract: Fe-decorated fullerene nanowhiskers were prepared by using the liquid–liquid interfacial precipitation method. The prepared nanowhiskers were characterized using scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM), X-ray diffraction (XRD) and Raman spectroscopy. Formation of both tubular and nontubular nanowhiskers was observed with fine dispersion of Fe ions. The XRD and Raman-spectroscopic studies showed the fcc crystalline nature and polymerization of the nanowhiskers, respectively. The results were compared with Ce- and Ni-incorporated fullerene nanowhiskers.