Ex Situ Scanning Electrochemical Microscopy (SECM) Investigation of Bismuth- and Bismuth/Lead Alloy Film-Modified Gold Electrodes in Alkaline Medium

Scanning electrochemical microscopy (SECM) in feedback mode was employed to characterise the reactivity and microscopic peculiarities of bismuth and bismuth/lead alloys plated onto gold disk substrates in 0.1 molL(-1) NaOH solutions. Methyl viologen was used as redox mediator, while a platinum microelectrode was employed as the SECM tip. The metal films were electrodeposited ex situ from NaOH solutions containing either bismuth ions only or both bismuth and lead ions. Approach curves and SECM images indicated that the metal films were conductive and locally reactive with oxygen to provide Bi(3+) and Pb(2+) ions. The occurrence of the latter chemical reactions was verified by local anodic stripping voltammetry (ASV) at the substrate solution interface by using a mercury-coated platinum SECM tip. The latter types of measurements allowed also verifying that lead was not uniformly distributed onto the bismuth film electrode substrate. These findings were confirmed by scanning electron microscopy images. The surface heterogeneity produced during the metal deposition process, however, did not affect the analytical performance of the bismuth coated gold electrode in anodic stripping voltammetry for the determination of lead in alkaline media, even in aerated aqueous solutions. Under the latter conditions, stripping peak currents proportional to lead concentration with a satisfactory reproducibility (within 5% RSD) were obtained.

Use of copper and gold electrodes as sensitive elements for fabrication of an electronic tongue: Discrimination of wines and whiskies

A low-cost method is proposed to classify wine and whisky samples using a disposable voltammetric electronic tongue that was fabricated using gold and copper substrates and a pattern recognition technique (Principal Component Analysis). The proposed device was successfully used to discriminate between expensive and cheap whisky samples and to detect adulteration processes using only a copper electrode. For wines, the electronic tongue was composed of copper and gold working electrodes and was able to classify three different brands of wine and to make distinctions regarding the wine type, i.e., dry red, soft red, dry white and soft white brands. Crown Copyright (C) 2011 Published by Elsevier B.V. All rights reserved.

Surface-Enhanced Resonance Raman Scattering of Polyaniline on Silver and Gold Colloids

The interaction of emeraldine base (PANI-EB) with silver and gold colloids was probed by using Surface-Enhanced Resonance Raman Scattering (SERRS) at 3 different exciting radiations. Due to the great sensitivity of SERRS technique the detection limit of PANI-EB concentration was ca. 2 x 10(-7) mol L(-1) in Ag and Au colloidal suspensions. The UV-vis-NIR spectra of metal colloids in function of PANI-EB concentrations showed that gold colloids present a higher degree of aggregation than silver colloids. SERRS of PANI-EB on metal colloids allowed the study of the polymeric species formed primarily on the metallic surface. The polymer formed after the adsorption of PANI-EB on metallic nanoparticles is strongly dependent on the nature of the metal colloids. The oxidation of PANI-EB to pernigraniline occurred for silver colloids, while a doping process of PANI-EB on Au nanoparticles was evidenced through the observation of the characteristic SERRS spectrum of emeraldine salt at 1064nm.

Deposition of selenium thin layers on gold surfaces from sulphuric acid media: Studies using electrochemical quartz crystal microbalance, cyclic voltammetry and AFM

In this paper we report here new considerations about the relationship between the mass and charge variations (m/z relationship) in underpotential deposition (UPD), bulk deposition and also in the H(2)Se formation reaction. Nanogravimetric experiments were able to show the adsorption of H(2)SeO(3) on the AuO surface prior to the voltammetric sweep and that, after the AuO reduction, 0.40 monolayer of H(2)SeO(3) remains adsorbed on the newly reduced Au surface, which was enough to gives rise to the UPD layer. The UPD results indicate that the maximum coverage with Se(ads) on polycrystalline gold surface corresponds to approximately 0.40 monolayer, in good agreement with charge density results. The cyclic voltammetry experiments demonstrated that the amount of bulk Se obtained during the potential scan to approximately 2 Se monolayers, which was further confirmed by electrochemical quartz crystal microbalance (EQCM) measurements that pointed out a mass variation corresponding of 3 monolayers of Se. In addition, the Se thin films were obtained by chronoamperometric experiments, where the Au electrode was polarized at +0.10V during different times in 1.0 M H(2)SO(4) + 1.0 mM SeO(2). The topologic aspects of the electrodeposits were observed in Atomic Force Microscope (AFM) measurements. Finally, in highly negative potential polarizations, the H(2)Se formation was analyzed by voltammetric and nanogravimetric measurements. These finding brings a new light on the selenium electrodeposition and point up to a proposed electrochemical model for molecule controlled surface engineering. (c) 2009 Elsevier Ltd. All rights reserved.

Study of a gold electrode modified by trans-[Ru(NH(3))(4)(Ist)SO(4)](+) to produce an electrochemical sensor for nitric oxide

The modification of a gold electrode surface by electropolymerization of trans-[Ru(NH(3))(4)(Ist)SO(4)](+) to produce an electrochemical sensor for nitric oxide was investigated. The influence of dopamine, serotonin and nitrite as interferents for NO detection was also examined using square-wave voltammetry (SWV). The characterization of the modified electrode was carried out by cyclic voltammetry, electrochemical quartz crystal microbalance (EQCM) and SERS techniques. The gold electrode was successfully modified by the trans-[Ru(NH(3))(4)(Ist)SO(4)](+) complex ion using cyclic voltammetry. The experiments show that a monolayer of the film is achieved after ten voltammetric cycles, that NO in solution can coordinate to the metal present in the layer, that dopamine, serotonin and nitrite are interferents for the detection of NO, and that the response for the nitrite is much less significant than the responses for dopamine and serotonin. The proposed modified electrode has the potential to be applied as a sensor for NO. (C) 2011 Elsevier Ltd. All rights reserved.

The origin of the molecular interaction between amino acids and gold nanoparticles: A theoretical and experimental investigation

This study describes the synthesis of novel biological hybrid materials, where 3D structures were obtained using gold nanoparticles (AuNps) and methionine (Met) in a one-step procedure in aqueous media. The type of nanostructure can be controlled by tuning the intermolecular interactions between Met and AuNp, which strongly depends on the pH used for the synthesis. Computational simulation using the density-functional theory (DFT) showed that the AuNp - Met 3D structures are formed upon reorientation of Met molecules so that the backbone amine groups interact via H-bonds. These findings were experimentally confirmed using FTIR and UV-vis spectroscopy. Crown Copyright (C) 2008 Published by Elsevier B. V. All rights reserved.

Nat Gold, Sheet Metal Graduate from the New York Trade School

Nat Gold graduated from the Sheet Metal program at the New York Trade School in 1942. He is represented here in the sheet metal shop he owns. Notice the blueprints for the White Plains Senior High School hanging on the wall behind him. Original caption reads, "Shop Owner, Brook Sheet Metal Inc. Nat Gold - Sheet Metal 1942, represents one of many Sheet Metal graduates who became owners of their own business." Black and white photograph.

Evelyn Levine Gold Scrapbook

Evelyn Mae Levine was born April 11, 1907 and died on February 6, 1957. She was one of the children born to William and Sarah Levine. The scrapbook includes photographs, family memories, negative copies of grade sheets from Coburn Classical Instituteand Emerson College.

Winning the Accreditation Game: The Library as Key Player and Hidden Gold Mine

Libraries are a central hub of information resources supporting college and university curricula. Several library strategies, cross-campus collaborations, and philosophical considerations of electronic and print offerings led to successful accreditations in business and engineering programs.

Interests prices and the Barosky - Summers resolution of the Gibson paradox under the gold standard

This paper presents a structural monetary úamework featunng a demand function for non-monetary uses of gold, such as the one drawn by Barsky and Summers in their 1988 analy8ÚI of the Gibson Paradox as a natural concomitant of the gold standard period. That structural model predicts that the laws of behavior of nominal prices and interest rates are functions of the rules set by the government to command the money supply. !ta fiduciary vemon obtaina Fisherian relationships &8 particular cases. !ta gold atandard 801ution yields a modelsimilar to the Barsky and Summers model, in which interest rates are exogeneous and subject to shocb. This paper integrates governnment bonds into the analysis, treats interest rates endogenously, and ahifts the responsibility for the shocb to the government budgetary financing policies. The Gibson paradox appears as "practically" the only cl&18 of behavioral pattern open for interest rates and price movements under apure gold standard economy. Fisherian-like relationshipe are utterly ruled out.

PEGylated polyethyleneimine-entrapped gold nanoparticles for enhanced and targeted gene delivery applications

Gene therapy, which involves the transfer of nucleic acid into target cells in patients, has become one of the most important and widely explored strategies to treat a variety of diseases, such as cancer, infectious diseases and genetic disorders. Relative to viral vectors that have high immunogenicity, toxicity and oncogenicity, non-viral vectors have gained a lot of interest in recent years. This is largely due to their ability to mimic viral vector features including the capacity to overcome extra- and intra-cellular barriers and to enhance transfection efficiency. Polyethyleneimine (PEI) has been extensively investigated as a non-viral vector. This cationic polymer, which is able to compact nucleic acid through electrostatic interactions and to transport it across the negatively charged cell membranes, has been shown to effectively transfect nucleic acid into different cell lines. Moreover, entrapment of gold nanoparticles (Au NPs) into such an amine-terminated polymer template has been shown to significantly enhance gene transfection efficiency. In this work, a novel non-viral nucleic acid vector system for enhanced and targeted nucleic acid delivery applications was developed. The system was based on the functionalization of PEI with folic acid (FA; for targeted delivery to cancer cells overexpressing FA receptors on their surface) using polyethylene glycol (PEG) as a linker molecule. This was followed by the preparation of PEI-entrapped Au NPs (Au PENPs; for enhancement of transfection efficiency). In the synthesis process, the primary amines of PEI were first partially modified with fluorescein isothiocyanate (FI) using a molar ratio of 1:7. The formed PEI-FI conjugate was then further modified with either PEG or PEGylated FA using a molar ratio of 1:1. This process was finally followed by entrapment of Au NPs into the modified polymers. The resulting conjugates and Au PENPs were characterized by several techniques, namely Nuclear Magnetic Resonance, Dynamic Light Scattering and Ultraviolet-Visible Spectroscopy, to assess their physicochemical properties. In the cell biology studies, the synthesized conjugates and their respective Au PENPs were shown to be non-toxic towards A2780 human ovarian carcinoma cells. The role of these materials as gene delivery agents was lastly evaluated. In the gene delivery studies, the A2780 cells were successfully transfected with plasmid DNA using the different vector systems. However, FA-modification and Au NPs entrapment were not determinant factors for improved transfection efficiency. In the gene silencing studies, on the other hand, the Au PENPs were shown to effectively deliver small interfering RNA, thereby reducing the expression of the B-cell lymphoma 2 protein. Based on these results, we can say that the systems synthesized in this work show potential for enhanced and targeted gene therapy applications.

6-Mercaptopurine complexes with silver and gold ions: Anti-tuberculosis and anti-cancer activities

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Accuracy of six minute walk test, stair test and spirometry using maximal oxygen uptake as gold standard

OBJETIVO: Determinar a acurácia das variáveis: tempo de escada (tTE), potência de escada (PTE), teste de caminhada (TC6) e volume expiratório forçado (VEF1) utilizando o consumo máximo de oxigênio (VO2máx) como padrão-ouro. MÉTODOS: Os testes foram realizados em 51 pacientes. O VEF1 foi obtido através da espirometria. O TC6 foi realizado em corredor plano de 120m. O TE foi realizado em escada de 6 lances obtendo-se tTE e PTE. O VO2máx foi obtido por ergoespirometria, utilizando o protocolo de Balke. Foram calculados a correlação linear de Pearson (r) e os valores de p, entre VO2máx e variáveis. Para o cálculo da acurácia, foram obtidos os pontos de corte, através da curva característica operacional (ROC). A estatística Kappa (k) foi utilizada para cálculo da concordância. RESULTADOS: Obteve-se as acurácias: tTE - 86%, TC6 - 80%, PTE - 71%, VEF1(L) - 67%, VEF1% - 63%. Para o tTE e TC6 combinados em paralelo, obteve-se sensibilidade de 93,5% e em série, especificidade de 96,4%. CONCLUSÃO: O tTE foi a variável que apresentou a melhor acurácia. Quando combinados o tTE e TC6 podem ter especificidade e sensibilidade próxima de 100%. Estes testes deveriam ser mais usados rotineiramente, especialmente quando a ergoespirometria para a medida de VO2máx não é disponível.