Surface-enhanced Raman spectroscopy (SERS) is considered a highly promising technology for different analytical purposes. The applications of SERS are still quite limited due its relatively poor quantitative repeatability and the fact that SERS is very sensitive to oxidation, which is a challenge especially with silver based SERS substrates. Here, the link between these phenomena is investigated by exposing silver SERS substrates to ambient laboratory air. We show that SERS intensity decreases exponentially after the exposure, which consequently leads to an increasing standard deviation (σ) in intensity. Within a five-hour measurement window, the SERS intensity already drops by 60%, while σ triples from 7% to 21%. The SERS results are supplemented by elemental analysis, which shows that oxidation and atmospheric carbon contamination coincide with the rapid SERS intensity decrease. The results emphasize how sensitive SERS is towards atmospheric contamination and how it can also reduce the measurement repeatability – even if the substrates are exposed to air just for a very short period of time.

We describe the fabrication of roll-to-roll (R2R) printed organic photovoltaic (OPV) modules using gravure printing and rotary screen-printing processes. These two-dimensional printing techniques are differentiating factors from coated OPVs enabling the direct patterning of arbitrarily shaped and sized features into visual shapes and, increasing the freedom to connect the cells in modules. The inverted OPV structures comprise five layers that are either printed or patterned in an R2R printing process. We examined the rheological properties of the inks used and their relationship with the printability, the compatibility between the processed inks, and the morphology of the R2R-printed layers. We also evaluate the dimensional accuracy of the printed pattern, which is an important consideration in designing arbitrarily-shaped OPV structures. The photoactive layer and top electrode exhibited excellent cross-dimensional accuracy corresponding to the designed width. The transparent electron transport layer extended 300 µm beyond the designed values, whereas the hole transport layer shrank 100 µm. We also examined the repeatability of the R2R fabrication process when the active area of the module varied from 32.2 cm(2) to 96.5 cm(2). A thorough layer-by-layer optimization of the R2R printing processes resulted in realization of R2R-printed 96.5 cm(2) sized modules with a maximum power conversion efficiency of 2.1% (mean 1.8%) processed with high functionality.

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Solid state phase of V 7 O 16 with separate V 2 O 5 phase were fabricated by pulsed laser deposition. The crystal structure and symmetry of the deposited films were studied with X-ray diffraction and Raman spectroscopy, respectively. Rietveld analysis was performed to the X-ray diffraction measurement results. The surface potentials and morphologies of the films were studied with atomic force microscopy, and microstructure of the thin films was analyzed by transmission electron microscopy. Raman spectroscopy and Rietveld refinement results confirmed that the thin-film crystal structures varied between orthorombic V 2 O 5 phase and another phase, triclinic V 7 O 16 , previously found only in the walls of vanadium oxide nanotubes (VO x -NT), bound together with organic amine. We have earlier presented the first results of stable and pure metal-oxide solid-state phase of V 7 O 16 manufactured from ceramic V 2 O 5 target. Here we show more detailed study of these structures. The microstructure studies showed a variation on the porosity of the films according to crystal structures and also some fiber-like nanostructures were found in the films. The surface morphology depended strongly on the crystal structure and the surface potential studies showed ~ 50 meV difference in the work function values between the phases. Compounds were found to be extremely sensitive towards ammonia, NH 3 , down to ~ 40 ppb concentrations, and have shown to 2 have the stability and selectivity to control the Selective Catalytic Reduction process, where nitrogen oxides are reduced by ammonia in, e.g. diesel exhausts.