Surface-enhanced Raman spectroscopy (SERS) of living cells has rapidly become a powerful trend in biomedical diagnostics. It is a common belief that highly ordered, artificially engineered substrates are the best future decision in this field. This paper, however, describes an alternative successful solution, a new effortless chemical approach to the design of nanostructured silver and heterometallic continuous coatings with a stochastic ''coffee ring'' morphology. The coatings are formed from an ultrasonic mist of aqueous diamminesilver hydroxide, free of reducing agents and nonvolatile pollutants, under mild conditions, at about 200-270 C in air. They consist of 30-100 micrometer wide and 100-400 nm high silver rings composed, in turn, of a porous silver matrix with 10-50 nm silver grains decorating the sponge. This hierarchic structure originates from ultrasonic droplet evaporation, contact-line motion, silver(I) oxide decomposition and evolution of a growing ensemble of silver rings. The fabricated substrates are a remarkable example of a new scalable and low cost material suitable for SERS analyses of living cells. They evoke no hemolysis and reduce erythrocyte lateral mobility due to suitable ''coffee ring'' sizes and a tight contact with the silver nanostructure. A high SERS enhancement, characteristic of pure silver rings, made it possible to record Raman scattering spectra from submembrane hemoglobin in its natural cellular environment inside single living erythrocytes, thus making the substrates promising for various biosensor chips.
Ultrasonic-hydrothermal and hydrothermal treatment was used for synthesis of nanocrystalline zirconia, titania, nickel and nickel-zinc ferrites powders from precipitated amorphous zirconyl, titanyl, binary nickel-iron and ternary nickel-zinc-iron hydroxides, respectively. Resulted nanopowders were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), nitrogen adsorption (BET), and magnetic susceptibility measurements. It was established that ultrasonically assisted hydrothermal treatment of amorphous zirconyl and titanyl gels results in significant rise of the rate of ZrO2 and TiO2 crystallization and promotes formation of thermodynamically stable monoclinic zirconia, but does not affect the microstructure and mean particles size of resulting nanopowders. Ultrasonic-hydrothermal processing of co-precipitated amorphous nickel, zinc and iron hydroxides favours formation of nanocrystalline ferrite powders with narrower particle size distribution.
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