Wiley Online Library (wileyonlinelibrary.com).Nanopowders of pure nickel were directly synthesized for the first time by conventional solution combustion synthesis (SCS) method. In this article, a specific reaction pathway is suggested to describe the metallic phase formation during SCS. It is proposed that the exothermic reaction between NH 3 and HNO 3 species formed during the decomposition of glycine and nickel nitrate acts as the source of energy required to achieve the self-sustained reaction regime. A thermodynamic analysis of the combustion synthesis reaction indicates that increasing glycine concentration leads to establishing a hydrogen rich reducing environment in the combustion wave that in turn results in the formation of pure metals and metal alloys. TGA of reaction systems and XRD analysis of products in the quenched combustion wave show that the formation of oxide phases occurs in the reaction front, followed by gradual reduction of oxide to pure metallic phases in the postcombustion zone. A methodology for SCS of pure metals and metal alloys nanoparticles can be inferred from the results presented.

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Based on a general methodology for the preparation of metal-nanopowders by solution combustion synthesis (SCS), the reaction pathways for SCS of pure copper and copper-nickel alloy nanopowders are investigated. It is confirmed that the necessary condition for SCS of metals in a metal-nitrate oxidizer-glycine system is the property of the oxidizer to decompose with formation of HNO 3 species. In this case, for compositions with excess of glycine, a hydrogen reducing atmosphere develops in the reaction front, leading to the formation of reduced metals. The proposed reaction pathways are supported by X-ray diffraction analysis of the quenched samples and DTA-TGA studies of the Cu(NO 3 ) 2 Á6H 2 O-glycine and Ni(NO 3 ) 2 Á6H 2 O/Cu(NO 3 ) 2 Á6H 2 O-glycine systems. The results show that the formation of Cu 2 O and CuO oxide phases takes place at early stages in the reaction front followed by their reduction to pure Cu phase in the postcombustion zones. However, in a Cu-Ni alloy, a fraction of intermetallic Cu-Ni phase appeared directly in the combustion front, whereas the rest of the oxygen-free alloy formed through reduction of oxide phases. V

A paper based microfluidic device is fabricated that can rapidly detect very low concentrations of uric acid (UA) using 3,5,3',5'-tetramethyl benzidine (TMB), H2O2 and positively charged gold nanoparticles ((+)AuNPs). In the presence of (+)AuNPs, H2O2 reacts with TMB to produce a bluish-green colour which becomes colourless on reaction with UA. This colorimetric method can detect as low as 8.1 ppm of UA within <20 minutes on white filter paper. This technique provides an alternative way for UA detection.