Enhanced intrinsic fluorescence from carboxidized nano-sculptured thin films of silver and their application for label free dual detection of glycated hemoglobin.

Enhanced intrinsic fluorescence (~x103) from novel carboxidized nanosculptured thin films (CO-nSTFs) of silver is reported. The sources of intrinsic fluorescence, confirmed by X-ray photoelectron spectroscopy, are Ag2O grains and residual carbon formed on the outer layer of silver nSTFs when exposed to air, while the localized surface plasmons on silver nSTFs enhance this intrinsic fluorescence. The CO-nSTFs are optimized with respect to porosity for the maximum enhancement. A sensor developed by using the self-assembled monolayer technique on optimized CO-nSTF is used for the label free detection of glycated hemoglobin, performed by simultaneously using fluorescence imaging and spectroscopy. The specificity of the sensor is established from control experiments on hemoglobin. These novel nanorod like intrinsically fluorescent CO-nSTFs pose huge potential in label free biosensing, light sources, imaging and many more applications.

Correlation of Interface Impurities and Chemical Gradients with High Magnetoelectric Coupling Strength in Multiferroic BiFeO3-BaTiO3 Superlattices.

The detailed understanding of magnetoelectric (ME) coupling in multiferroic oxide heterostructures is still a challenge. In particular, very little is known to date concerning the impact of the chemical interface structure and unwanted impurities that may be buried within short-period multiferroic BiFeO3-BaTiO3 superlattices during growth. Here, we demonstrate how trace impurities and elemental concentration gradients contribute to high ME voltage coefficients in thin-film superlattices, which are built from 15 double layers of BiFeO3-BaTiO3. Surprisingly, the highest ME voltage coefficient of 55 V cm-1 Oe-1 at 300 K was measured for a superlattice with a few atomic percent of Ba and Ti that diffused into the nominally 5 nm thin BiFeO3 layers, according to analytical transmission electron microscopy. In addition, highly sensitive enhancements of the cation signals were observed in depth profiles by secondary ion mass spectrometry at the interfaces of BaTiO3 and BiFeO3. As these interface features correlate with the ME performance of the samples, they point to the importance of charge effects at the interfaces, that is, to a possible charge mediation of ME coupling in oxide superlattices. The challenge is to provide cleaner materials and processes, as well as a well-defined control of the chemical interface structure, to push forward the application of oxide superlattices in multiferroic ME devices.