Higher fullerenes such as C 84 present a rich variety of photophysical properties, due to their abundance of distinct geometric isomers. However, this multitude of isomers, along with their similar chromatographic properties, also creates difficulties in purifying and characterizing specific species of C 84 . In this paper, we present the application of an alternating-column HPLC technique to resolve C 84 isomers. We find that this technique presents markedly higher separation efficiency than the recycling HPLC method. Subsequent photophysical analysis of a previously uncharacterized isomer of C 84 , D 2d (I), shows its transient absorbance properties clearly differ from those of other C 84 isomers, in terms of both its spectral features (with maxima at 620 and 840 nm) and lifetime (ca. 45.6 μs). Singlet-oxygen quenching experiments demonstrate that the T 1 energy of D 2d (I) lies below 7880 cm -1 . Finally, the ground-state absorptivity of the D 2d (I) isomer has been characterized via quenching experiments with palladium octaethylporphyrin, showing an ε = 21,400 M -1 cm -1 at a local maximum of 590 nm.

Synthesis of gold nanoparticles (AuNPs) with controllable particle size and stable dispersion through green chemistry without using toxic regents is crucial for biomedical applications. In this study, spherical AuNPs with controllable particle size in the range of 8 to 18 run were synthesized by the reduction of HAuCl4 using only fruit juices/extract without adding any other chemicals. By controlling the chemical reaction steps and adjusting the pH of the solution at a later stage of the reaction, the sizes of the spherical AuNPs were fine tuned to 4.5 +/- 2.0 rum 5.9 +/- 2.5 rim, and 6.0 +/- 1.5 nm with fruit juices/extract of A. deliciosa, P. persica, and M.. domestica, respectively. For the first time, spherical ultrasmall AuNPs of 2.6 +/- 1.1 nm with uniform distribution were successfully achieved using M. Acuminate extract;at pH 10 and 11. The ultrasmall and small AuNPs were imaged again by transmission electron microscopy (TEM) after 4 months stored at the room temperature and 72 h incubation in 1 mM NaCl, which is typically found in biological media. No aggregation was observed in the above AuNP solutions after four months and incubation for 72 h in NaCl. These results indicate that highly stable AuNPs synthesized through green chemistry can be used in cells or embryos and hold great promise in biological applications.

Sunscreens are used to absorb or block harmful sunlight especially ultra violet (UV) radiation. An UV-vis spectrometer was employed to measure absorbance of sunscreen products. The same brand's sunscreens with sun protection factor (SPF) of 8, 15, 30, and 50 were tested under identical experimental conditions. The results show that the UV absorbance and the transmittance of the sunscreens are associated with the SPF value. The maximum absorbance of the sunscreens measured between 280 to 320 nm (UVB region) is linearly proportional to the SPF value with a correlation coefficient of 0.998 using the same brand's sunscreens. Thus, the absorbance can be used to evaluate the efficiency of a sunscreen that absorbs or blocks UVB radiation. Several commercial sunscreens of different brands but with the same SPF 30 were compared. The results confirmed that, although different brand sunscreens with the same SPF varied slightly in UV absorbance, they all offer adequate protection against UVB radiation. The utilization of UV-Vis spectroscopy is found to be particularly effective for determination of sunblock efficiency.

The physiological corrosion resistance of plasma nanocoated 316L stainless steel was studied in protein-containing electrolytes using electrochemical methods. Plasma nanocoatings with thicknesses of 20-30 nm were deposited onto 316L stainless steel coupons in a glow discharge of trimethylsilane (TMS) or its mixture with oxygen gas under various gas ratios. The surface chemistries of the plasma nanocoatings were characterized using Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Corrosion properties of the plasma nanocoated 316L stainless steel coupons were assessed using potentiodynamic polarization, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) in phosphate-buffered saline (PBS) electrolytes that contain bovine serum albumin (BSA) or lysozyme. It was found that BSA adsorption on the plasma nanocoated 316L coupons was heavily favored. BSA adsorption on the plasma nanocoating surfaces could block charge-transfer reactions between the electrolyte and 316L substrate, and thus stabilize the 316L substrates from further corrosion. In contrast, lysozyme adsorption on the plasma nanocoated specimens was not as pronounced and mildly influenced the corrosion properties of the plasma nanocoated 316L stainless steel.

A simple and green synthesis of gold nanoparticles (AuNPs) was achieved in tea solution and fruit juices with auric tetrachloride (HAuCl4) without the addition of any other chemicals. Natural antioxidants present in tea leaves and fruit juices were able to reduce Au3+ ions to form AuNPs spheres with an average diameter of 22.9 +/- 2.7nm in the tea solution and 12.8 +/- 2.4nm in the orange juice. A colorimetric determination of antioxidant activities based on the formation of citrate-capped AuNPs has been developed. It was found that the colorimetric response of AuNPs was dependent on the concentration of antioxidants tested. As compared with the standard reference assay, i.e., the Folin-Ciocalteu method, the colorimetric method reported in this study showed a very good correlation (R-2=0.9996). The results indicate that the AuNPs-based colorimetric method provides a simple, effective and reliable measurement of the antioxidant capacity in the tested fruit juices.

This study for the first time reports a quantitative analysis of phthalates and spatial distribution of phthalates in Lake Pontchartrain, Louisiana, USA using solid phase micro-extraction (SPME) coupled with gas chromatography mass spectroscopy (GC-MS). During 2008-2009, di-n-butylphthalate (DnBP) along with its congener (DiBP) and di(2-ethylhexyl) phthalate (DEHP) were detected in Lake Pontchartrain. Concentrations of these phthalates in the lake were monitored in different areas before and after the opening of the Bonnet Carré Spillway that occurred from April to May in 2008. The concentration of sigma3PAEs (DnBP, DiBP and DEHP) ranged from 0 to 20 microg/L in the surface water of the lake from March 2008 to June 2009. The distribution of the three phthalates varied with locations in the lake. An increase trend of sigma3PAEs was observed after the opening of the Bonnet Carré Spillway in the central lake area. The observed increase of the phthalates could be correlated to the opening of the spillway. The SPME followed by GC-MS employed in this study has been proved to be a rapid, sensitive and practical method to quantitatively analyse and evaluate phthalate concentrations in salt lake waters.

A geographical information system (GIS) has the capability to store, manipulate, analyze, and display a large amount of spatial and tabular data. This study carried out a regional metal contaminati...

A geographical information system (GIS) has the capability to store, manipulate, analyze, and display a large amount of spatial and tabular data. This study carried out a regional metal contamination assessment for the New Orleans area using a GIS. Heavy metal contamination in and around the New Orleans area during two disasters, Hurricanes Rita and Katrina, has hindered the rebuilding of both businesses and homes. This study presented the merging of maps, spatial and tabular data bases, and object-oriented programming so that levels of arsenic and lead can be easily seen and understood by New Orleans officials. This can help them make decisions regarding rebuilding so as to comply with the EPA guidelines that were set up after Hurricane Katrina.

The aim of this study was the multi-elemental detection of toxic metals such as lead (Pb) in non-crushed oyster shells by using a portable X-ray fluorescence (XRF) spectrometer. A rapid, simultaneous multi-element analytical methodology for non-crushed oyster shells has been developed using a portable XRF which provides a quick, quantitative, non-destructive, and cost-effective mean for assessment of oyster shell contamination from Pb. Pb contamination in oyster shells was further confirmed by scanning electron microscopy with energy dispersive spectroscopy (SEM–EDS). The results indicated that Pb is distributed in-homogeneously in contaminated shells. Oyster shells have a lamellar structure that could contribute to the high accumulation of Pb on oyster shells.

This paper reports environmental assessment and identification of environmental contaminants caused by exposure to toxic metals such as Pb and As after Hurricane Katrina using an onsite analysis method. Concentrations of lead (Pb) and arsenic (As) detected in many soil samples after Hurricane Katrina were reported to exceed EPA allowable value. Toxic metals mentioned above were measured by a portable X-ray fluorescence analyzer (XRF) in the greater New Orleans area. The portable XRF analyzer provides rapid data collection in the field. Distribution of Pb in New Orleans is displayed in a regional map using geographic information system (GIS). The map provides an updated image of environmental exposure to Pb contamination in the greater New Orleans area after Hurricane Katrina and also shows Pb contaminated areas where Pb concentrations exceed the EPA allowable level. The portable XRF provides a rapid analysis method for toxic metals and can be used for the field screening of soils at any place and for identifying contamination areas rapidly.

An electrochemical sensor for the detection of dopamine (DA) was designed using a modified Nafion membrane on a glassy carbon electrode. The electrochemical signals from dopamine were enhanced more than 10-fold on a Nafion membrane coated electrode relative to a bare electrode. The hypothesis that the origin of the signal enhancement was due to the accumulation of cationic dopamine in the Nafion was tested using Pd ions as an analog which undergo a two electron reduction similar to dopamine. Electroless deposition of palladium was used to deposit palladium on a highly oriented pyrolytic graphite surface with and without the Nafion membrane. Using scanning electron microscopy (SEM) significantly greater deposits of metallic Pd were observed on the Nafion coated surfaces than in the absence of Nafion and energy dispersive X-ray spectroscopy (EDS) confirmed quantitatively greater Pd deposition on the Nafion coated surfaces.

We deposit Pt particles electrochemically on an electrode covered with a Nafion membrane. Platinum ions travel through the hydrophilic channels of the membrane, and platinum deposits are formed at the place where the channels make contact with the planar electrode. This procedure deposits the catalyst only at the end of the hydrophilic channels that cross the membrane; no catalyst is placed under the hydrophobic domains, where it would not be in contact with the electrolyte. By performing a series of cyclic voltammograrns with this system, we show that deposition of the platinum through the membrane achieves better platinum utilization than deposition of platinum oil the naked electrode followed by the placement of the membrane on top.

Nafion membranes are used as semisolid electrolytes in methanol and hydrogen fuel cells. The ion conduction takes place through those hydrophilic channels in the Nafion that can provide continuous pathways through the membrane. There is as yet limited information about the density, the size, and the shape of these channels. We have developed two electrochemical methods of visualizing the pore structure which involve the creation of metal lithographs using the membrane pores as templates. In the experiments, the membrane is supported on a flat solid surface on one side, and is in contact with an electrolyte on the other side. Using hydrogen-terminated n-doped Si(111), we deposited gold from an electrolyte containing a gold salt. The Au ions traverse the membrane through the pores, reach the silicon surface, and are spontaneously reduced. A metallic Au deposit is formed on the silicon surface, at the base of the hydrophilic channel. The Au deposits are imaged after the membrane is dissolved. Another method involves supporting the membrane on a Pt surface and depositing silver wires through the hydrophilic channels of the membrane. The scanning electron microscope pictures of these wires provide an image of the size and the shape of the hydrophilic channels.