Melissa R. Dewi

A TiO2 Nanofiber-Carbon Nanotube-Composite Photoanode for Improved Efficiency in Dye-Sensitized Solar Cells.

A light-scattering layer fabricated from electrospun titanium dioxide nanofibers (TiO2 -NFs) and single-walled carbon nanotubes (SWCNTs) formed a fiber-based photoanode. The nanocomposite scattering layer had a lawn-like structure and integration of carbon nanotubes into the NF photoanodes increased the power conversion efficiency from 2.9 % to 4.8 % under 1 Sun illumination. Under reduced light intensity (0.25 Sun), TiO2 -NF and TiO2 -NF/SWCNT-based DSSCs reached PCE values of up to 3.7 % and 6.6 %, respectively.

CuInS2/ZnS nanocrystals as sensitisers for NiO photocathodes

Nickel oxide (NiO) is the most universally studied photocathode to date, however, its poor fill factor (FF) makes its efficiency much lower than its counterpart, n-type photoanodes. Its significance in photovoltaics is based on the potential to fabricate tandem photoelectrodes in order to enhance the overall efficiency of the existing devices. Furthermore, limited work on the sensitisation of NiO with semiconducting nanocrystals (NCs) exists. For the first time, we have fabricated NiO photocathodes sensitised with aqueous CuInS2/ZnS NCs. The NCs were chemically bound to the NiO films with the aid of carboxyl and thiol groups. This was achieved without modifying the bulk surface properties of NiO. Binding of the NCs was investigated using TEM, SEM, XPS, XANES, EXAFS modelling and ToF-SIMS. NiO films were assembled into CuInS2/ZnS NC sensitised photocathodes and their photovoltaic properties were compared to those of unsensitised and dye-sensitised NiO solar cells. We demonstrate that non-toxic NCs can be used to sensitise NiO photocathodes to achieve an (almost) all-inorganic system.

A highly efficient ligand exchange reaction on gold nanoparticles: preserving their size, shape and colloidal stability

This study presents a new ligand exchange method for cetyl trimethylammonium bromide/chloride (CTAB/C) stabilised gold nanoparticles. It has been shown that the resulting thiol-coated nanoparticles remained colloidally stable in aqueous dispersion and that particle size and morphology was not affected. Furthermore, we were able to achieve nearly complete ligand exchange.

Cation exchange of aqueous CuInS2 quantum dots

Chalcopyrite copper indium disulfide (CIS) QDs have been of recent interest due to their non-toxicity. Although publications on CIS QDs are becoming more common, the majority of synthesis involves long chained insulating ligands, which are only soluble in non-polar solvents. Recent works have explored the tunable properties of CIS QDs by means of cation exchange with ZnS. Despite this, their tunable properties have been limited to use in organic solvents. This may be due to the cation exchange not being completely understood. For the first time, we present a controllable cation exchange for water soluble, tunable CIS QDs. We also show the partial exchange of indium for zinc, which is shown to provide these QDs with unique optical properties.

Synthesis and Phase Transfer of Monodisperse Iron Oxide (Fe3O4) Nanocubes

Cube-shaped magnetic iron oxide nanoparticles were synthesised and studied with the aim to achieve superior magnetic properties. This study describes a straightforward and simple synthesis method for preparing monodisperse 11–14-nm superparamagnetic iron oxide nanocubes via an ‘effective monomer’ growth mechanism. The as-synthesised nanoparticles are insoluble in water. However, substitution of the non-polar ligands of the particles using a new method that involved an ionic compound generated colloidally stable and water dispersible cube-shaped particles with a very small hydrodynamic diameter. The cubes displayed superior magnetic properties over spherical particles.

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.

Selective assembly of Au-Fe3O4 nanoparticle hetero-dimers

AbstractHetero-dimeric magnetic nanoparticles of the type Au-Fe3O4 have been synthesised from separately prepared, differently shaped (spheres and cubes), monodisperse nanoparticles. This synthesis was achieved by the following steps: (a) Mono-functionalising each type of nanoparticles with aldehyde functional groups through a solid support approach, where nanoparticle decorated silica nanoparticles were fabricated as an intermediate step; (b) Derivatising the functional faces with complementary functionalities (e.g. amines and carboxylic acids); (c) Dimerising the two types of particles via amide bond formation. The resulting hetero-dimers were characterised by high-resolution TEM, Fourier transform IR spectroscopy and other appropriate methods. Graphical AbstractNano-LEGO: Assembling two types of separately prepared nanoparticles into a hetero-dimer is the first step towards complex nano-architectures. This study shows a solid support approach to combine a gold and a magnetite nanocrystal.

The power of heterogeneity: Parameter relationships from distributions

Complex scientific data is becoming the norm, many disciplines are growing immensely data-rich, and higher-dimensional measurements are performed to resolve complex relationships between parameters. Inherently multi-dimensional measurements can directly provide information on both the distributions of individual parameters and the relationships between them, such as in nuclear magnetic resonance and optical spectroscopy. However, when data originates from different measurements and comes in different forms, resolving parameter relationships is a matter of data analysis rather than experiment. We present a method for resolving relationships between parameters that are distributed individually and also correlated. In two case studies, we model the relationships between diameter and luminescence properties of quantum dots and the relationship between molecular weight and diffusion coefficient for polymers. Although it is expected that resolving complicated correlated relationships require inherently multi-dimensional measurements, our method constitutes a useful contribution to the modelling of quantitative relationships between correlated parameters and measurements. We emphasise the general applicability of the method in fields where heterogeneity and complex distributions of parameters are obstacles to scientific insight.

Disperse-and-Collect Approach for the Type-Selective Detection of Matrix Metalloproteinases in Porous Silicon Resonant Microcavities

We report on the design and testing of photonic biosensors for the type-selective detection of different types of matrix metalloproteinases (MMPs). The ability to detect a panel of different MMP types has important implications for prognosis of wound healing. We combine the immunocapture of MMPs on dispersed magnetic nanoparticles modified with antibodies specific for target MMPs (immuno-magNPs) with subsequent MMP detection upon fluorogenic peptide cleavage in porous silicon resonant microcavity (pSiRM) architectures. We report fast, sensitive, and type-selective detection of MMPs directly in wound fluid. This study sets the scene for downstream developments of multiparametric biosensors as point-of-care (POC) prognostic tools that may step-change chronic wound management.

Rapid microwave assisted synthesis of nearly monodisperse aqueous CuInS2/ZnS nanocrystals

A rapid microwave-assisted synthesis for nearly monodisperse CuInS2/ZnS nanocrystals (NCs) has been developed. CuInS2/ZnS NCs have been prepared in water using thioglycolic acid as a stabilising ligand. The proposed synthesis results in stable and monodisperse NCs after only 5 minutes. In addition, the NCs were tested as potential sensitisers for photoanodes.