An evaluation of the distribution of metal ions in otherwise uniform titania sol-gel layers designed for optical sensing using laser ablation inductive coupled plasma mass spectroscopy

Free-base porphyrins are bound to titania sol-gel layers deposited on glass slides. The porphyrin-containing titania layers show the UV-VIS spectra of the porphyrin and are found to be uniformly and evenly distributed. By addition of a metal salt to the titania layer, it was possible to metallate the free-base porphyrin within and change the UV-VIS absorbance of the porphyrin. The metalloporphyrins based on Cu and Zn ions could be detected by laser ablation inductive coupled plasma mass spectroscopy (LA-ICP-MS). Aggregation of metals is observed indicating that metal ions are also attaching directly to the titania. In samples where already metalized porphyrins are used little or no aggregation is observed, indicating that the titania sol gel is non-uniform in its affinity for metal ions. © 2012 SPIE

Room temperature sol-gel fabrication and functionalization for sensor applications

The structure and physical properties of a thin titania sol-gel layer prepared on silicon and silica surfaces were examined. Spectroscopic (FTIR, UV-VIS spectroscopy), refractive index (ellipsometry) and microscopic (light microscopy and SEM/EDS) tools were used to examine both chemical uniformity and physical uniformity of the sol-gel glass layers. The conditions for the fabrication of uniform layers were established, and room temperature dopant incorporation was examined. The absorption bands of porphyrin-containing titania sol-gel layers were characterized. By addition of a metal salt to the titania layer, it was possible to metallate the free-base porphyrin within and change the UV-VIS absorbance of the porphyrin, the basis of metal detection using porphyrins. The metalloporphyrins were detected by localized laser ablation inductive coupled mass spectroscopy (LA-ICP-MS), indicating fairly uniform distribution of metals across the titania surface. © 2012 The Author(s)

Percolation diffusion into self-assembled mesoporous silica microfibres

© 2014 by the authors. Percolation diffusion into long (11.5 cm) self-assembled, ordered mesoporous microfibres is studied using optical transmission and laser ablation inductive coupled mass spectrometry (LA-ICP-MS). Optical transmission based diffusion studies reveal rapid penetration ( 80 μm2·s−1) of Rhodamine B with very little percolation of larger molecules such as zinc tetraphenylporphyrin (ZnTPP) observed under similar loading conditions. The failure of ZnTPP to enter the microfibre was confirmed, in higher resolution, using LA-ICP-MS. In the latter case, LA-ICP-MS was used to determine the diffusion of zinc acetate dihydrate, D~3 × 10−4 nm2·s−1. The large differences between the molecules are accounted for by proposing ordered solvent and structure assisted accelerated diffusion of the Rhodamine B based on its hydrophilicity relative to the zinc compounds. The broader implications and applications for filtration, molecular sieves and a range of devices and uses are described

Magnetic induction-induced resistive heating of optical fibers and gratings

Magnetic induction heating of optical fibers packaged with a steel plate is studied using a fiber Bragg grating. The dependence on the induced wavelength shift with magnetic field is obtained for a commercially available induction heater. More than a 300°C temperature rise is observed within seconds. The potential of magnetic induction as an efficient and rapid means of modulating devices and as a novel approach to potential optical based magnetic field and current sensing is proposed and discussed. The extension of the ideas into micro and nanophotonics is described. © 2013 Optical Society of America

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. © 2011 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE)

Characterisation and functionalisation of cold-processed titania sol-gel layers on silica and silicate surfaces

A thin titania sol-gel layer was prepared on thermal oxide silica-on-silicon and borosilicate surfaces with spin-coating techniques under cold (room temperature) processing conditions. The physical structure and chemical uniformity of these layers were examined by a series of spectroscopic (FTIR, UV-VIS spectroscopy and ellipsometry) and microscopic (light microscopy, SEM and EDS) techniques. Selective binding with hydroxy-containing (-OH) organic compounds is explored. © 2012 Optical Society of America

Processing waveguide photonic components into self-assembled organic films

A focused ion beam (FIB) is used to process 2-D self-assembled photonic porphyrin film flats to fabricate couplers in 2-D porphyrin slabs. These self-assembled structures have an initial root mean squared (rms) values for surface roughness < 0.5 nm as measured by atomic force microscopy. Under appropriate FIB processing and cutting conditions, the rms value for surface roughness falls to < 0.4 nm

Focused ion beam processing and engineering of devices in self-assembled supramolecular structures

Self-assembled supramolecular structures such as optical wires, films and 2D slabs offer a new generation of electronic and optical devices. In particular, self-assembled porphyrin devices, including those integrated onto silica and silicon platforms, open new opportunities in photonic applications spanning molecular biosensing, photovoltaics and telecommunications. All reports to date, however, largely highlight the potential but have not established a clear pathway to the actual implementation of more complex device prototypes. In this paper, we propose and demonstrate the use of a focused ion beam (FIB) to process and fabricate devices in porphyrin-based supramolecular structures. These self-assembled structures have an initial root mean squared (rms) values for surface roughness of <0.5 nm as measured by atomic force microscopy. Under appropriate FIB processing and cutting conditions, the rms value for surface roughness falls to <0.4 nm, comparable with some of the best optical flatnesses obtained within, for example, structured optical fibres and integrated optical waveguides. The milling rate of the porphyrin structures was estimated to be ∼70% of that of silica. The versatility of a FIB as a tool for rapid processing and fabricating 1D and 2D photonic waveguide structures within supramolecular self-assembled platforms is demonstrated by fabricating a 2D coupler, setting the groundwork for true optical device engineering and integration using these new organic systems

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. © 2011 Optical Society of America