A rapid heating and high magnetic field thermal analysis technique

Journal of Thermal Analysis and Calorimetry - A new thermal analysis technique is described that allows measurements to be performed on bulk samples at extreme heating and cooling rates and in high...     

Development of a Carbon Paste Electrode for Lactate Detection Based on Meldola’s Blue Adsorbed on Silica Gel Modified with Niobium Oxide and Lactate Oxidase

A reagentless amperometric biosensor sensitive to lactate was developed. The sensor employs a carbon paste electrode modified with lactate oxidase (LOx) and Meldola’s Blue (MB) adsorbed on silica gel coated with niobium oxide. The dependence on the biosensor response was investigated in terms of pH, supporting electrolyte, ionic strength, lactate oxidase (LOx) amounts and applied potential. The biosensor showed an excellent operational stability (96 % of the activity was maintained after 150 determinations) and storage stability (allowing measurements for more than 1.5 months, when stored in a refrigerator). The proposed biosensor also presented good sensitivity allowing lactate quantification at levels down to 6.5×10^?7 mol L^?1. Moreover, the biosensor showed a good linear response range (from 0.1 to 5.0 mmol L^?1 for lactate). Lactate analysis in biological samples such as blood was also performed. The precision of the data obtained by the proposed biosensor showed reliable results for real complex matrices.     

The role of oxidative etching in the synthesis of ultrathin single-crystalline Au nanowires

The fabrication of ultrathin single-crystal Au nanowires with high aspect ratio and that are stable in air is challenging. Recently, a simple wet-chemical approach using oleylamine has been reported for the synthesis of Au nanowires with micrometer length and 2 nm in diameter. Despite efforts to understand the mechanism of the reaction, an ultimate question about the role of oxygen (O(2)) during the synthesis remained unclear. Here we report that the synthesis of ultrathin Au nanowires employing oleylamine is strongly affected by the amount of O(2) absorbed in the reaction solution. Saturating the solution with O(2) leads to both a high-yield production of nanowires and an increase in their length. Nanowires with diameters of about 2 nm and lengths of 8 μm, which corresponds to an aspect ratio of approximately 4000, were produced. The role of oxygen is attributed to the enhanced oxidation of twin defects on Au nanoparticles formed in the first stage of the reaction. Understanding the role of oxidative etching is crucial to significantly increasing the yield and the length of ultrathin Au nanowires.     

Submicrometer-MOS capacitor with ultra high capacitance biased by Au nanoelectrodes

The ultimate limits of size of the current metal-oxide-semiconductor capacitors can be overcome by preparation of three-dimensional devices that can vertically be biased using one-dimensional metal nanostructures. Here, we present a general and efficient approach to the assembly and integration of Au nanocrystals into functional nanoelectrodes of three-dimensional submicrometer-MOS (0.35 μm²) capacitors, presenting an ultra high capacitance (24±1 pF). The Au nanocrystals were directly produced into a nanoporous template of anodized aluminum oxide that was evaluated, and the electrical characterization of this device corroborates the formation of the MOS capacitor. Flat band voltage is independent of sweep voltage range, and negligible hysteresis of capacitance-voltage curves is observed when sweep voltage ranges from positive to negative and turned again to positive bias. In addition, experimental results match theoretical analysis and indicate the presence of free surface charges stored in the Au nanostructures. The demonstrated ability to control the assembling of the nanocrystals and the results of electrical characterization indicate that the embedded Au nanoelectrodes have a high potential for memory applications based on three-dimensional devices.