Nano

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 MoS_1.9 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.

Gamma radiation and ozone sensing properties of mixed oxides in the form of thermally evaporated thin films are explored. External effects, such as radiation and ozone cause defects in the materials they interact with, cause changes in the material properties. An Edwards E306A thermal coating system was used for the mixed oxides thin films deposition. Cu electrodes were manufactured on the substrate via thermal evaporation, photoresist was spin-coated over it and was exposed to UV light via acetate containing the desired inter-digitated electrode patterns. After the exposure, the substrate was placed in a developer solution and then rinsed in water and placed in the etching solution to reveal the electrode pattern. The optical properties of the films were explored using CARY 1E UV-Visible Spectrophotometer. The influence of gamma radiation on the electrical properties of the films was traced via the measurements of conductance versus radiation dose, which were recorded in real-time using HP 4277A LCZ impedance analyzer at a frequency of 1 kHz. The fact that the explored thin films were sensitive to both gamma radiation and ozone exposure enables the development of cost-effective real-time monitoring system for personnel protection and environmental monitoring. This novel approach would allow the manufacture of the sensor system with multiple sensor heads during one technological process, whereas various shielding materials or pattern recognition could be employed to differentiate between the effects of ozone and gamma radiation on the mixed oxide thin film sensors.

Ozone sensing properties of mixed oxides of In₂O₃, ZnO, and SnO₂ in the form of thin films are explored. Exposure to ozone causes defects in the materials, and subsequently causes changes in the materials properties. In this work, a cost-effective, room temperature, real-time ozone monitoring device has been developed. The fabricated sensors are capable of detecting threshold ozone safety levels proposed by the World Health Organization (WHO) while operating at room temperature. Room temperature operation offers many advantages over high temperature operation, such as reduced power consumption, reduced fabrication costs, and ease of implementation into portable devices, such as laptops and mobile phones. The fabrication of these sensors was carried out by means of an Edwards E306A Coating System. Various mixtures of In₂O₃, ZnO, and snO₂ were deposited in a rectangular pattern on top of copper interdigitated electrodes. X-ray Photo Spectroscopy (XPS) analysis showed that there were levels of impurities in the sensor samples, which were dependant on the fabrication process and parameters. XPS analysis also gave a detailed account of the shifts in binding energies of the thin oxide layers. The results presented show that the highest response to environmentally relevant ozone concentrations is achieved with a very thin sensing layer and a high deposition rate. The performance of the sensors has been investigated and compared.

In this work, nanocrystalline hexagonal tungsten oxide was prepared by acidic precipitation from sodium tungstate solution. TEM studies of nanopowders showed that the average size of the hexagonal nanoparticles is 30–50 nm. Novel nanocomposites were prepared by embedding a low amount of gold-decorated carbon nanotubes into the hex-WO₃ matrix. The addition of MWCNTs lowered the temperature range of sensitivity of hex-WO₃ nanocomposites to NO₂ hazardous gas. The sensitivity of hex-WO₃ with Au-decorated MWCNTs to NO₂ is at the temperature range between 25°C and 250°C.

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.

Organophosphate compounds (OPs) are common in pesticides and can be highly toxic. Negative environmental impacts resulting from the release of OPs can be reduced with rapid detection, which relies on sensitive sampling techniques. In this work, nanosized silica and silica/alumina were tested for their ability and behavior in adsorbing gas-phase dimethyl methylphosphonate (DMMP). Surface interactions were probed using Fourier transform infrared (FT-IR) spectroscopy with attenuated total reflectance (ATR) to establish correlations between surface properties and adsorption behavior. Adsorption characteristics were also investigated by gas chromatography (GC) equipped with a flame ionization detector (FID). Silica and silica/alumina adsorbents were exposed to DMMP in a flow system. FT-IR spectroscopy revealed that physical interactions between the adsorbents and DMMP were attributed to the presence of surface silanol. GC-FID results showed that adsorption onto both silica and silica/alumina followed Langmuir isotherm behavior. Silica demonstrated superior adsorption behavior as compared to silica/alumina. The following Langmuir isotherm constants are representative of the data: 0.88 for silica and 0.82 for silica/alumina.

The simultaneous catalytic removal of NO_x and soot over the rare earth element (REE) oxide-based mixture oxides loaded with potassium and transition nanosized metal oxide (designated as M/K/REE oxide) was investigated by using temperature-programmed reaction (TPR). The influence of the type of REE oxides together with the type and amount of transitional metal oxides on the catalytic removal activity was discussed. K/Nd₂O₃ was found to be the most active oxide among the REE oxides to simultaneous remove the NO_x and soot under lean conditions. Chromium oxide was more active than the other transition metal oxides on enhancing the activity of soot oxidation of Nd₂O₃ loaded with potassium. The optimum loading level of chromium was about 10 wt%, with ignition temperature at about 237°C and the conversion ratio NO → N₂ about 24.1%. The Mn-loading on K/Nd₂O₃ resulted in the biggest conversion efficiency of NO to N₂ at about 30.2%. The increasing catalytic reaction of NO_x–soot activities is attributed to the formation of complex crystalline phase in the catalyst together with the improving contacting between catalysts and soot.

In relation to potential health risks, there is little available information on exposure to aerosols containing nanometer-size particles in work environments in factories producing engineered nanomaterials. We measured the concentrations and size distributions of particles of nanometer-sized to coarse-sized particles in an engineered carbon nanomaterial factory and a titanium dioxide factory. In addition, particles were collected with a quartz fiber filter in the engineered carbon nanomaterial factory, and their morphology was examined by scanning electron microscopy and their carbon composition was examined with a carbon analyzer. In the carbon nanomaterial factory, the particle number increased to more than 10⁵ cm^-3 when a vacuum cleaner was used to clean the inside of the producing device, and the particle number increased for particles with a diameter of about 100 nm compared with the background. This is the only case an increase in particle numbers is observed during this measurement. The emitted particles appear to consist of agglomerates of carbon nanomaterial particles smaller than 100 nm. The major fraction was the EC3 fraction (EC: elemental carbon; combustion at 800°C in a 98:2 He/O₂ atmosphere), which is a minor fraction in diesel engine particulate matter. This suggests that the combustion temperature can be used to differentiate atmospheric particulate matter from engineered carbon material. Personal sampling conducted in addition to stationary measurements in the titanium dioxide factory indicated that stationary measurements can be used to generate representative data on the basis of the particle number but not the particle mass.

This paper provides an overview of current knowledge regarding the aquatic effects of nanomaterials. Aquatic receptors can potentially be exposed to nanoparticles through ingestion, movement across gills, passive transport, and cellular absorption. Our review indicates that the toxicological research on nanomaterials is still relatively narrow. The present research has been targeted primarily at understanding potential effects to humans, and relatively few ecotoxicity studies have been conducted; however, new research is evolving rapidly. The studies that are currently available focus on metal oxide particles, carbon nanotubes, and fullerenes. Aquatic tests have examined the uptake of these nanoparticles by fish and filter feeders, and have provided evidence of toxicity or behavioral changes. Some of these studies conclude that nanoparticles can be taken up by or produce effects in biota, and that dose-response relationships and patterns of relative toxicity among types of particles are emerging. Caution should be used in designing and interpreting studies on nanoparticles, because factors such as the particle medium preparation method, the presence of other chemicals, and particle behavior such as agglomeration can influence exposure and aquatic toxicity. Ultimately, the objectives of this review are to expand our knowledge of the effects of nanomaterials on ecological processes and aquatic receptor populations, as well as help guide future research.

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 Å 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 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.

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.

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.

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 (Cr^VI). 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.

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.

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.

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.