Metallic nanosculptured thin films for biosensing applications using surface Plasmon resonance and enhanced spectroscopies

Metallic nanosculptured thin films are made of nanorods in different shapes prepared by means of the oblique angle deposition technique. Assessment of these films for biosensing and molecular detection has been investigated by our group recently using surface Plasmon resonance (SPR), surface enhanced fluorescence (SEF), and surface enhanced Raman scattering (SERS). Using columnar thin film (CTF) as the transducer layer in SPR sensors enhances both the angular and spectral sensitivity of the sensor. Sculptured thin films (STFs) made of different materials, shapes, sizes, orientations, porosities, and deposited on different substrates were examined as SEF and SERS detection platforms. The optimal features of STFs were examined to obtain the highest enhancement of SERS and SEF. The potential of these films for biosensing and bimolecular detection was demonstrated. Stability of the films was noticed over a period of one year without significant degradation

Microspot sensing based on surface-enhanced fluorescence from nanosculptured thin films

Nanosculptured thin films (STF) are prepared by the oblique angle deposition technique and take different forms of nano columnar structures. Varieties of STFs were investigated to find the optimum structure for biosensing based on the surface enhanced fluorescence. A comparative study was carried out with STFs containing the nanocolumnar structures that differ in their shape, height (h), and tilt angle with respect to the surface (α), thickness (d), and arrangement. The greatest enhancement of the fluorescent signal was found for Ag-based STFs on Si(100), giving an enhancement factor of ×71, where h=400  nm, d=75  nm, and α=23° relative to Ag closed film using fluorescent dye Rhodamine 123. We immobilized the fluorescent receptor to the thiol self-assembly monolayer on Ag-based STF and Ag dense film to demonstrate the applications of STFs for specific biosensing. Upon excitation of the fluorophore by an Hg light source, a CCD camera with controlled exposure time would detect the pattern of fluorescent receptor Anti-Rabbit IgG on the surfaces. A specially designed optical fiber housing attached to the microscope allowed quantitative measurement of the fluorescence spectrum on a microspot parallel to the image grab.Published versio

Detailed study of surface-enhanced Raman scattering from metallic nanosculptured thin films and their potential for biosensing

Surface-enhanced Raman scattering (SERS) from silver nanosculptured thin films (STF) was studied in detail for biosensing. The influences of the nanostructures’ sizes, topology, the substrate features, and the preparation conditions on the enhancement were examined. Enhancement factors on the order of 107 were obtained from silver nanorods deposited on bare silicon substrates with respect to their dense counterparts, using 4-aminotheophenol (4-ATP) for the Raman emission. The low detection limit that can be achieved with STFs is below 1 μg/lit of the probe molecule 4-ATP in Ethanol solution. Theoretical modeling based on a single small spheroidal nanoparticle helped in explaining the main properties of SERS from STFs. Stability of the films was noticed over a period of one year without significant degradation.Published versio

Fe–Cr–Al Containing Oxide Semiconductors as Potential Solar Water-Splitting Materials

A high-throughput thin film materials library for Fe–Cr–Al-O was obtained by reactive magnetron cosputtering and analyzed with automated EDX and XRD to elucidate compositional and structural properties. An automated optical scanning droplet cell was then used to perform photoelectrochemical measurements of 289 compositions on the library, including electrochemical stability, potentiodynamic photocurrents and photocurrent spectroscopy. The photocurrent onset and open circuit potentials of two semiconductor compositions (n-type semiconducting: Fe₅₁Cr₄₇Al₂Ox, p-type semiconducting Fe_36.5Cr_55.5Al₈O_<i>x</i>) are favorable for water splitting. Cathodic photocurrents are observed at 1.0 V vs RHE for the p-type material exhibiting an open circuit potential of 0.85 V vs RHE. The n-type material shows an onset of photocurrents at 0.75 V and an open circuit potential of 0.6 V. The p-type material showed a bandgap of 1.55 eV, while the n-type material showed a bandgap of 1.97 eV