Ingemar Petermann

Measurement of Fluorescence in a Rhodamine-123 Doped Self-Assembled “Giant” Mesostructured Silica Sphere Using a Smartphone as Optical Hardware

The blue OLED emission from a mobile phone was characterised, revealing a sharp emission band centred at λ = 445 nm with a 3dB bandwidth Δλ ∼ 20 nm. It was used to excite Rhodamine 123 doped within a “giant” mesostructured silica sphere during fabrication through evaporative self-assembly of silica nanoparticles. Fluorescence was able to be detected using a standard optical microscope fitted with a green transmission pass filter and cooled CCD and with 1 ms exposure time demonstrating the potential of mobile platforms as the basis for portable diagnostics in the field.

Surface treatment of silicate based glass: base Piranha treatment versus 193nm laser processing

Contact angle measurements of water on pathology grade borosilicate glass microscope slides before and after base piranha treatment are compared to treatment with 193nm laser irradiation. 193nm irradiation in the presence of hydrogen was also explored. Within experimental resolution, the observed changes in contact angle as a result of treatment either with base Piranha solution or with laser processing are identical. The contact angle, a, in both cases is reduced from a = (27 ± 6)º to a = (8 ± 3)º with treatment. However, for the piranha base method, there is an observed reversal over time either fully recovering or partially recovering within hours. By contrast, with laser processed, the increased surface wettability is retained with no change for more than 15 hours. In all cases, surface functionalisation, as measured by contact angle, with (3-mercaptopropyl)trimethoxysilane (MPTS) is found to be largely independent of any processing. We conclude that the method of contact angle as a means for qualitatively asserting improvements in attachment is unjustified.

Porphyrin-doped solgel-lined structured optical fibers for local and remote sensing

We constructed a type of sensor by depositing a solgel layer within the interior holes of a silica-structured fiber and, subsequently, coating this with an acid-responsive porphyrin. Protonation of the porphyrin by an acidic gas (HCl in this case), is detected by a large change in the visible spectrum. Compared to previous work on a liquid-core sensor in a structured optical fiber, the signal-to-noise ratio of this gas sensor shows a reduced signal strength, but the detection rate is increased about fortyfold.

Sol-gel surface functionalisation by cold-processing for optical sensor applications

The structure and physical properties of a thin titania sol-gel layer, prepared on silicon and silica surfaces by cold processing and spin-coating techniques, were examined. A series of spectroscopic (FTIR, UV-VIS spectroscopy and ellipsometry) and microscopic (light microscopy, SEM and EDS) techniques were used to examine the chemical and physical uniformities of the sol-gel layers. Conditions were established to generate uniform layers reproducibly. The high refractive index, selective binding to organic functional groups and the light and gas transmission properties of the titania layers can be successfully made use of for new optical sensor applications.

“Giant” self-assembled mesostructured silica sphere characterised using a doped fluorophore and an AMOLED mobile screen as the excitation source

Using the emission for the blue OLED component of a HTC Android Phone, a Rhodamine 123 doped silica mesostructured shell, fabricated by evaporative self-assembly on a super hydrophobic surface, is excited with blue light and the fluorescence image taken. The results demonstrate the potential of smart mobile platforms as optical hardware for portable and intelligent diagnostics as well as illustrating the fabrication of large mesostructured spheres.

Fabrication of gold-based fractal surfaces

A novel method for fabrication of complex gold nanostructures is presented. Fractal aggregations of ethylenediaminetetraacetic acid (EDTA) chelates formed in seconds during solvent evaporation are used as masks for gold plating. SEM analysis shows evidence of general features on several scales from 100 μm down to considerably less than 100 nm with complete metal coverage.