Nanofabrication of a Solid-State, Mesoporous Nanoparticle Composite for Efficient Photocatalytic Hydrogen Generation.

Room-temperature self-assembly was used to fabricate a periodic array of uniformly sized Al3+ -doped SiO2 nanoparticles (Al-SiO2 NPs, 20-30 nm). The uniform mesoporous structure was suitable for uniformly incorporating and distributing Pt nanoparticles (PtNPs), which were used as hydrogen-evolution catalysts in artificial photosynthetic systems, without agglomeration during the catalytic reaction. When the surfaces of the Al-SiO2 NPs were covered with an organic photocatalyst (2-phenyl-4-(1-naphthyl)quinolinium ion, QuPh+ -NA), each PtNP was surrounded by multiple QuPh+ -NA ions. The structure allowed the PtNP to receive multiple electrons from QuPh. -NA molecules, which were generated by reduction of the photoexcited state of QuPh+ -NA ions (QuPh. -NA. + ) with ß-dihydronicotinamide adenine dinucleotide (NADH), thereby resulting in efficient photocatalytic H2 evolution.

Fabricating Nanoporous Silica Structure on D-Fibres through Room Temperature Self-Assembly.

The room temperature deposition of self-assembling silica nanoparticles onto D-shaped optical fibres ("D-fibre"), drawn from milled preforms fabricated by modified chemical vapour deposition (MCVD), is studied. Vertical dip-and-withdraw produces tapered layers, with one end thicker (surface coverage >0.85) than the other, whilst horizontal dip-and-withdraw produces much more uniform layers over the core region. The propagation of induced fracturing over the core region during drying is overcome using a simple protrusion of the inner cladding. Thick coatings are discernible through thin film interference colouring, but thinner coatings require scanning electron microscopy (SEM) imaging. Here, we show that fluorescence imaging, using Rhodamine B, in this example, can provide some qualitative and speedy assessment of coverage.

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.

Room temperature self-assembly of mixed nanoparticles into photonic structures.

Manufacturing complex composites and structures using incompatible materials is central to next-generation technologies. In photonics, silica offers passivity, low loss and robustness, making it the ideal material platform for optical transport. However, these properties partly stem from the high-temperature processing conditions necessary for silica waveguide fabrication, restricting the functionalisation of waveguides to robust inorganic dopants. This means for many sensor and active device applications, large numbers of materials are excluded. These include many organic and carbon systems such as dyes and diamond. Here we propose using intermolecular forces to bind nanoparticles together at room temperature and demonstrate the room-temperature self-assembly of long microwires (length ~7 cm, width ~10 µm) with and without rhodamine B. Further we report on mixed self-assembly of silica and single-photon-emitting nitrogen-vacancy-containing diamond nanoparticles, opening up a new direction in material science.

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.

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.