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Oxidation of the Ag nanoparticle surface is shown to have an impact on the adsorption, orientation, and SERS detection limit of nitroaromatic molecules in aqueous solution. Ultrasensitive SERS detection of p-nitrophenol is achieved when oxidation of surface-immobilized Ag nanoparticles is inhibited by replacing the oxygen dissolved in water with argon gas.

Foetal ovarian cysts are the most frequently encountered intra-abdominal cystic masses diagnosed prenatally. The aetiology of foetal ovarian cysts is still unknown, but hormonal stimulation is generally considered to be responsible for the disease. The diagnosis is made by the exclusion of other cystic lesions confined to the foetal abdomen. In this article we report antenatally-detected foetal ovarian cyst with a review of the available literature. Antenatal ultrasonography (USG) re vealed an abdominal cystic mass 41x33 mm in diameter in a 33-week gestation female foetus. The normal anatomy of other foetal abdominal organs suggested that an ovarian cyst was the most likely diagnosis. In the antenatal follow-up period, the cyst diameter increased with time. After delivery, USG scan confirmed the antenatal findings. Due to abdominal distension and respiratory distress, ovarian cystectomy was performed on the second postnatal day. The histopathological evaluation of the surgical material reported a serous cystadenoma of the ovary with non-malignant properties. [ABSTRACT FROM AUTHOR]

The recycling of fly ash obtained from the combustion of coal in thermal power plant has been studied. Coal fly ash was vitrified by melting at 1773 K for 5 hours without any additives. The properties of glasses produced from coal fly ash were investigated by means of Differential Thermal Analysis (DTA), X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) techniques. DTA study indicated that there was only one endothermic peak at 1003 K corresponding to the glass transition temperature. XRD analysis showed the amorphous state of the glass sample produced from coal fly ash. SEM investigations revealed that the coal fly ash based glass sample had smooth surface. The mechanical, physical and chemical properties of the glass sample were also determined. Recycling of coal fly ash by using vitrification technique resulted to a glass material that had good mechanical, physical and chemical properties. Toxicity characteristic leaching procedure (TCLP) results showed that the heavy metals of Pb, Cr, Zn and Mn were successfully immobilized into the glass. It can be said that glass sample obtained by the recycling of coal fly ash can be taken as a non-hazardous material. Overall, results indicated that the vitrification technique is an effective way for the stabilization and recycling of coal fly ash. [ABSTRACT FROM AUTHOR]

A grazing incidence X-ray diffraction technique was developed to characterize the effectiveness of the coating of the solid particles by the binder in energetic formulations and was used in conjunction with scanning electron microscopy, traditional wide-angle X-ray diffraction, and specific gravity measurements to probe the microstructure of PAX-12 granules. The grazing incidence X-ray technique was applied to granules formed upon slurry coating and indicated different X-ray scattering characteristics for high- and low-sensitivity granules, suggesting significant differences in the distribution of the binder at the surface of the granules. The granules were made by slurry-coating crystals of epsilon CL-20 with cellulose acetate butyrate, a binder, and bis-(2,2 dinitropropyl acetal/formal), a plasticizer. Granules with high sensitivity to impact and friction were shown to have an interior that was relatively porous and that consisted of uncoated CL-20 crystals. Their surface had regions with a thick layer of coating material and other regions of uncoated crystals. Granules that showed a low sensitivity to impact and friction had coated CL-20 crystals throughout their interior and on the surface. [ABSTRACT FROM AUTHOR]

Positively charged silver nanoparticles, Ag [+], obtained by UV-assisted reduction of silver nitrate using branched poly(ethyleneimine) (BPEI) and 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) solutions as reducing agents, were immobilized on glass surfaces to produce substrates active in surface-enhanced Raman scattering (SERS). Negatively charged silver nanoparticles, Ag [-], synthesized via a modified citrate reduction method, were also investigated for comparison. At a sparse surface coverage of 30 nanoparticles/microm(2), substrates with immobilized Ag [+] showed increasing SERS sensitivity to a variety of anions in water in the order SO(4)(2-) < CN(-) < SCN(-) approximately ClO(4)(-), with corresponding binding constants of 10(5), 3.3 x 10(5), and 10(7) (for both SCN- and ClO(4)(-)) M(-1), respectively. This order followed the Hofmeister series of anion binding in water. Significantly, substrates with Ag [+] allowed limit of detection values of 8.0 x 10(-8) M (8 ppb) and 2.7 x 10(-7) M (7 ppb) for environmentally relevant perchlorate (ClO(4)(-)) and cyanide (CN(-)) anions, respectively. In contrast, substrates with immobilized Ag [-], even upon subsequent modification by a monolayer of BPEI for positive surface charge of the nanoparticles, showed a drastically lower sensitivity to these anions. The high sensitivity of substrates with Ag [+] for anion detection can be attributed to the presence of two types of functional groups, amino and amide, on the nanoparticle surface resulting from UV-assisted fragmentation of BPEI chains. Both amino and amide provide strong binding of anions with Ag [+] nanoparticles due to the synergistic effect through a combination of electrostatic, hydrogen bonding, and dispersive interactions.

Branched polyethyleneimine (BPEI) and 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) were used collaboratively to reduce silver nitrate under UV irradiation for the synthesis of positively charged silver nanoparticles. The effects of molar ratio of the ingredients and the molecular weight of BPEI on the particle size and distribution were investigated. The mechanism for the reduction of Ag+ ions in the BPEI/HEPES mixtures entails oxidative cleavage of BPEI chains that results in the formation of positively charged BPEI fragments enriched with amide groups as well as in the production of formaldehyde, which serves as a reducing agent for Ag+ ions. The resultant silver nanoparticles are positively charged due to protonation of surface amino groups. Importantly, these positively charged Ag nanoparticles demonstrate superior SERS activity over negatively charged citrate reduced Ag nanoparticles for the detection of thiocyanate and perchlorate ions; therefore, they are promising candidates for sensing and detection of a variety of negatively charged analytes in aqueous solutions using surface-enhanced Raman spectroscopy (SERS).

This study concerns the design of protein-resistant polymer adsorbed layers for the control of surface binding of biospecific recognition entities. Polymer surface layers were prepared using the adsorption of poly(allylamine hydrochloride) (PAH), poly(l-lysine) (PL), and branched and linear polyethyleneimine (PEI) and further modified by the covalent attachment of biotin for specific avidin attachment. The adsorption of PAH, PL, and PEI on silicon substrates was studied as a function of pH and ionic strength using ellipsometry. Average dry layer thicknesses of approximately 10, approximately 5, approximately 9, and approximately 3 A (+/-1 A) were obtained when polymer adsorption occurred from solutions at pH 9.5 that contained 0.5 M NaCl for PAH, PL, branched PEI, and linear PEI, respectively. These polymers showed significant differences in their efficiency to suppress nonspecific avidin adsorption. At low ionic strength, avidin adsorption occurred on all polymer-coated surfaces at basic pH values, despite the same positive electrostatic charge for protein globules and the surface. Though the net electrostatic repulsion between avidin molecules and branched PEI was efficiently screened in a protein solution of pH 7 and 0.15 M NaCl, branched-PEI coatings of high molecular weight were unique in their ability to provide avidin-resistant surfaces as a result of steric hindrance from the branched architecture of adsorbed polymer chains. All polymers studied were effective in suppressing avidin adsorption at pH 3 as a result of protonation of the avidin surface functional groups at this pH. Branched-PEI-coated surfaces were also effective for the suppression of smaller positively charged proteins such as lysozyme and ribonuclease A at pH 7 and 0.15 M NaCl. They were also resistant to the adsorption of negatively charged proteins such as BSA and fibrinogen at pH 7 and 0.75 M NaCl. Furthermore, by using PEI-modified protein-repellent surfaces, selective binding of avidin was achieved to surface-bound silver nanoparticles, which should provide a promising application for the label-free detection of biological species using surface-enhanced Raman scattering (SERS).