Joseph C. Bear

Superhydrophobic Photocatalytic Surfaces through Direct Incorporation of Titania Nanoparticles into a Polymer Matrix by Aerosol Assisted Chemical Vapor Deposition

A new class of superhydrophobic photocatalytic surfaces that are self-cleaning through light-induced photodegradation and the Lotus effect are presented. The films are formed in a single-step aerosol-assisted chemical vapor deposition (AACVD) process. The films are durable and show no degradation on continuous exposure to UV-C radiation.

Laser-generated ultrasound with optical fibres using functionalised carbon nanotube composite coatings

Optical ultrasound transducers were created by coating optical fibres with a composite of carbon nanotubes (CNTs) and polydimethylsiloxane (PDMS). Dissolution of CNTs in PDMS to create the composite was facilitated by functionalisation with oleylamine. Composite surfaces were applied to optical fibres using dip coating. Under pulsed laser excitation, ultrasound pressures of 3.6 MPa and 4.5 MPa at the coated end faces were achieved with optical fibre core diameters of 105 and 200 μm, respectively. The results indicate that CNT-PDMS composite coatings on optical fibres could be viable alternatives to electrical ultrasound transducers in miniature ultrasound imaging probes.

Copper-Doped CdSe/ZnS Quantum Dots: Controllable Photoactivated Copper(I) Cation Storage and Release Vectors for Catalysis†

The first photoactivated doped quantum dot vector for metal-ion release has been developed. A facile method for doping copper(I) cations within ZnS quantum dot shells was achieved through the use of metal-dithiocarbamates, with Cu+ ions elucidated by X-ray photoelectron spectroscopy. Photoexcitation of the quantum dots has been shown to release Cu+ ions, which was employed as an effective catalyst for the Huisgen [3+2] cycloaddition reaction. The relationship between the extent of doping, catalytic activity, and the fluorescence quenching was also explored.

A general method for the incorporation of nanoparticles into superhydrophobic films by aerosol assisted chemical vapour deposition

A general method for the synthesis of a novel class of superhydrophobic polymer thin films with embedded nanoparticles is presented. These materials combine the superhydrophobic nature of silicone polymer matrices and the properties of the nanoparticles for photocatalysis, magnetic applications, or high surface area catalysis. The films themselves are deposited using a one-pot aerosol assisted chemical vapour deposition (AACVD) process, and are characterised using electron microscopy, X-ray dispersive spectroscopy, water contact angle and bouncing measurements and elemental mapping. We show that these materials demonstrate multifunctional behaviour through magnetic, catalytic and superhydrophobic measurements.

Nanoparticle–sulphur “inverse vulcanisation” polymer composites

Composites of sulphur polymers with nanoparticles such as PbS, with tunable optical properties are reported. A hydrothermal route incorporating pre-formed nanoparticles was used, and their physical and chemical properties evaluated by transmission and scanning electron microscopy, thermogravimetric and elemental analyses. These polymers are easily synthesised from an industrial waste material, elemental sulphur, can be cast into virtually any form and as such represent a new class of materials designed for a responsible energy future.

Synthesis and characterization of carbon nanotubes covalently functionalized with amphiphilic polymer coated superparamagnetic nanocrystals

Herein, we report the synthesis of three covalently linked superparamagnetic nanocrystal-multi-walled carbon nanotube (MWCNT) composites. A generic strategy for amphiphilic polymer coating of nanocrystals and further functionalization for amide bond formation with the MWCNTs is discussed. This approach can in principle allow attachment of any colloidal nanocrystal to the MWCNTs. The materials were characterized at each stage of the syntheses using DLS, zeta-potential measurements, FT-IR, TEM, and XPS techniques. The practicality of this linkage is demonstrated by the reversible magnetic immobilization of these materials on an electrode during non-aqueous electrochemistry.

A thin silica-polymer shell for functionalizing colloidal inorganic nanoparticles.

Universally applicable, thin, and reproducible coatings for colloidal nanoparticles are a prerequisite for almost any of the wide-ranging applications of these exciting materials. Many techniques developed for coating and functionalization of nanoparticles have restrictions toward future applications with regard to key properties, such as solubility, size, and colloidal stability. The greatest weakness of current methods, such as ligand exchange, silica shells of various thicknesses, and organic shells, 7] is the strong dependence of the chemistry on the inorganic core surface. Herein, InP/ ZnS and Fe3O4 colloidal inorganic nanoparticles that have different surface properties are coated with a thin, cross-linked and functionalized shell containing organic and inorganic layers. Although not shown in this report, the method has also been applied to other colloidal particles, such as Au, CuInS2 (CIS), CdSe/ZnS, and InP. This work expands nanoparticle coating techniques to develop a completely new type of hybrid coating technique. Using silicon as a marker, we conclusively prove that the underlying amphiphilic polymer foundation is arranged on the particle surface as predicted in past reports. The synthesis of the hybrid surface layer takes advantage of the adsorption of amphiphilic polymers to the hydrophobic stabilizing ligands on the colloidal nanoparticle surfaces. Commercial poly(styrene-co-maleic anhydride) (PSMA) was adsorbed as described by Mulvaney and coworkers (Scheme 1, step A). The silica precursor, 3-aminopropyltriethoxysilane (TEAPS), was then reacted, resulting in a silane being tethered to the polymer (Scheme 1, step B). Generally, other methods for thin silica layers 4,13] use trimethoxysilanes as silica precursors. In an effort to separate the nucleophilic attack of the silica precursor to the polymer foundation and the polymerization to form silica the triethoxysilane equivalent was used, thus attempting to resolve steps B and C in Scheme 1. The temperature of the reaction mixture was also lowered to further aid this process. The polymerization of the tethered silica precursors occurs (Scheme 1, step C) resulting in particles that are soluble in dimethyl sulfoxide (DMSO), dimethylformamide (DMF), and 0.05m NaOH (aq). High-resolution transmission electron microscopy (HRTEM) and dynamic light scattering (DLS) measurements (Figure 1) both show that the particles were well-dispersed in solution. The DLS results show an increase in the hydrodynamic radius of the particles during the synthesis indicating that a layer has formed on the surface of the particles. The HRTEM image of a single hybrid-layer-coated particle (Figure 1b) showed no indication of a layer. This is unsurprising because the layer is amorphous and consists of elements that scatter electrons weakly. Once transferred to 0.05m NaOH (aq) the zeta potential of the colloid was 37.1 mV indicating a good stability. Retention of nanoparticle properties when coated with a hybrid layer is fundamental for their application. To investigate the retention of nanoparticle properties, the luminescence of InP/ZnS quantum dots was monitored during the formation of the layer. The luminescence decreased by approximately 33% between polymer coating and growth of the silica component of the layer. Once transferred to DMF the luminescence was still present although approximately Scheme 1. Formation of the thin layer around the nanoparticle. A) The amphiphilic polymer, PSMA, wraps around the particle. B) The silica precursor, TEAPS, opens the anhydride ring on the polymer and attaches the silane to the polymer. C) Polymerization between the bound and free TEAPS to form a thin silica layer. The solvent used at each stage is noted above each structure.

A SPION-eicosane protective coating for water soluble capsules:Evidence for on-demand drug release triggered by magnetic hyperthermia

An orally-administered system for targeted, on-demand drug delivery to the gastrointestinal (GI) tract is highly desirable due to the high instances of diseases of that organ system and harsh mechanical and physical conditions any such system has to endure. To that end, we present an iron oxide nanoparticle/wax composite capsule coating using magnetic hyperthermia as a release trigger. The coating is synthesised using a simple dip-coating process from pharmaceutically approved materials using a gelatin drug capsule as a template. We show that the coating is impervious to chemical conditions within the GI tract and is completely melted within two minutes when exposed to an RF magnetic field under biologically-relevant conditions. The overall simplicity of action, durability and non-toxic and inexpensive nature of our system demonstrated herein are key for successful drug delivery systems.

SWCNT photocathodes sensitised with InP/ZnS core-shell nanocrystals

Increasing the light harvesting efficiency of photocathodes is an integral part of optimising the future efficiencies of solar technologies. In contrast to the more extensively studied photoanode systems, current state-of-the-art photocathodes are less efficient and are commonly replaced with rare and expensive materials such as platinum group metals. The significance of photocathodes is in the development of tandem electrodes, enhancing the performance of existing devices. Carbon nanotubes are promising candidates for photocathodes, which, in addition to their p-type conductivity and catalytic properties, possess a suite of unique optical and electrical attributes. This work describes the fabrication of single walled carbon nanotube (SWCNT) photocathodes sensitised with indium phosphide/zinc sulfide (InP/ZnS) core–shell nanocrystals (NCs). Under air mass (AM) 1.5 conditions, the sensitisation of SWCNT photocathodes with InP/ZnS NCs increased the photocurrent density by 350% of the unsensitised output. This significant enhancement of current density demonstrates the potential of InP/ZnS NCs as effective sensitisers to improve the performance of carbon-based photocathode thin films.

Active removal of waste dye pollutants using Ta3N5/W18O49 nanocomposite fibres

A scalable solvothermal technique is reported for the synthesis of a photocatalytic composite material consisting of orthorhombic Ta3N5 nanoparticles and WOx≤3 nanowires. Through X-ray diffraction and X-ray photoelectron spectroscopy, the as-grown tungsten(VI) sub-oxide was identified as monoclinic W18O49. The composite material catalysed the degradation of Rhodamine B at over double the rate of the Ta3N5 nanoparticles alone under illumination by white light, and continued to exhibit superior catalytic properties following recycling of the catalysts. Moreover, strong molecular adsorption of the dye to the W18O49 component of the composite resulted in near-complete decolourisation of the solution prior to light exposure. The radical species involved within the photocatalytic mechanisms were also explored through use of scavenger reagents. Our research demonstrates the exciting potential of this novel photocatalyst for the degradation of organic contaminants, and to the authors’ knowledge the material has not been investigated previously. In addition, the simplicity of the synthesis process indicates that the material is a viable candidate for the scale-up and removal of dye pollutants on a wider scale.