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Papers by Joseph Govan

Agronomy, Feb 7, 2024

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Journal of Industrial and Engineering Chemistry, Mar 1, 2018

Cu/Al and Cu/Cr layered double hydroxides (LDH) were synthesized using a simple co-precipitation ... more Cu/Al and Cu/Cr layered double hydroxides (LDH) were synthesized using a simple co-precipitation method at room temperature. These particles were further modified by Co +2 incorporation, and calcined at 500 C for synthesis of layered double oxides (LDO). The LDH crystallinity or these samples highly depended on the composition, with Cu/Al-LDH presenting much higher order than Cu/Cr-LDH. High values of methyl orange adsorption were measured especially after calcination. For instance, Cu/Al and Cu/Co/Al LDH exhibited maximum monolayer adsorption capacities of 313 and 240 mg/g, respectively, meanwhile the same particles transformed into LDO presented values of 780 and 583 mg/g.

Magnetochemistry, Oct 9, 2020

Water resources are of extreme importance for both human society and the environment. However, hu... more Water resources are of extreme importance for both human society and the environment. However, human activity has increasingly resulted in the contamination of these resources with a wide range of materials that can prevent their use. Nanomaterials provide a possible means to reduce this contamination, but their removal from water after use may be difficult. The addition of a magnetic character to nanomaterials makes their retrieval after use much easier. The following review comprises a short survey of the most recent reports in this field. It comprises five sections, an introduction into the theme, reports on single magnetic nanoparticles, magnetic nanocomposites containing two of more nanomaterials, magnetic nanocomposites containing material of a biologic origin and finally, observations about the reported research with a view to future developments. This review should provide a snapshot of developments in what is a vibrant and fast-moving area of research.

Journal of Soil Science and Plant Nutrition, Oct 6, 2020

The main aim of this study is to develop a mechanistic model of fertilization for recommending th... more The main aim of this study is to develop a mechanistic model of fertilization for recommending the application of zinc (Zn) fertiliser for maize based on the mass balance of Zn. The model would consider the critical Zn level for maize (Zn CL), Zn availability in the soil (Zn A) and Zn buffering capacity (Zn b). Soil samples were collected from 78 maize fields for chemical and physical characterization including measuring Zn A and Zn b. Additionally, a crop management survey was carried out in each field. The classification and regression trees method (CART) was used and relationships between Zn b and some soil properties were established, clay content being the most relevant to the model, besides soil reaction (pH) and silt content. The application of Zn fertilizer can be adequately calculated by a mechanistic model that considers Zn A , Zn b and Zn CL above that which maize crop yields do not increase. This work highlights the importance of Zn b evaluation by the incubation procedure and the extraction of available Zn by DTPA solution. As hypothesised and then demonstrated in this work, Zn b is closely related to soil pH and texture (clay and silt). Our results suggest that, in between 51 and 97% of fields examined, it would be necessary to apply Zn fertilisers to produce the maximum maize yield.

Scientific Reports, Apr 11, 2016

Proceedings of SPIE, Oct 9, 2015

The main goal of our research is to develop new types of technologically important optically acti... more The main goal of our research is to develop new types of technologically important optically active quantum dot (QD) based materials, study their properties and explore their biological applications. For the first time chiral II-VI QDs have been prepared by us using microwave induced heating with the racemic (Rac), D- and L-enantiomeric forms of penicillamine as stabilisers. Circular dichroism (CD) studies of these QDs have shown that D- and L-penicillamine stabilised particles produced mirror image CD spectra, while the particles prepared with a Rac mixture showed only a weak signal. It was also demonstrated that these QDs show very broad emission bands between 400 and 700 nm due to defects or trap states on the surfaces of the nanocrystals. These QDs have demonstrated highly specific chiral recognition of various biological species including aminoacids. The utilisation of chiral stabilisers also allowed the preparation of new water soluble white emitting CdS nano-tetrapods, which demonstrated circular dichroism in the band-edge region of the spectrum. Biological testing of chiral CdS nanotetrapods displayed a chiral bias for an uptake of the D- penicillamine stabilised nano-tetrapods by cancer cells. It is expected that this research will open new horizons in the chemistry of chiral nanomaterials and their application in nanobiotechnology, medicine and optical chemo- and bio-sensing.

Proceedings of SPIE, May 2, 2014

ABSTRACT Recently, the use of stereospecific chiral stabilising molecules has also opened another... more ABSTRACT Recently, the use of stereospecific chiral stabilising molecules has also opened another avenue of interest in the area of quantum dot (QD) research. The main goal of our research is to develop new types of technologically important quantum dot materials containing chiral defects, study their properties and explore their applications. The utilisation of chiral penicillamine stabilisers allowed the preparation of new water soluble white emitting CdS quantum nanostructures which demonstrated circular dichroism in the band-edge region of the spectrum. It was also demonstrated that all three types of QDs (D-, L-, and Rac penicillamine stabilised) show very broad emission bands between 400 and 700 nm due to defects or trap states on the surfaces of the nanocrystals. In this work the chiral CdS based quantum nanostructures have also been doped by copper metal ions and new chiral penicilamine stabilized CuS nanoparticles have been prepared and investigated. It was found that copper doping had a strong effect at low levels in the synthesis of chiral CdS nanostructures. We expect that this research will open new horizons in the chemistry of chiral nanomaterials and their application in biotechnology, sensing and asymmetric synthesis.

Proceedings of SPIE, Apr 23, 2010

ABSTRACT Quantum dots (QDs) are fluorescent semiconductor (e.g. II-VI) nanocrystals, which have a... more ABSTRACT Quantum dots (QDs) are fluorescent semiconductor (e.g. II-VI) nanocrystals, which have a strong characteristic spectral emission. This emission is tunable to a desired energy by selecting variable particle size, size distribution and composition of the nanocrystals. QDs have recently attracted enormous interest due to their unique photophysical properties and range of potential applications in photonics and biochemistry. The main aim of our work is develop new chiral quantum dots (QDs) and establish fundamental principles influencing their structure, properties and biosensing behaviour. Here we present the synthesis and characterisation of chiral CdSe semiconductor nanoparticles and their utilisation as new chiral biosensors. Penicillamine stabilised CdSe nanoparticles have shown both very strong and very broad luminescence spectra. Circular dichroism (CD) spectroscopy studies have revealed that the D- and Lpenicillamine stabilised CdSe QDs demonstrate circular dichroism and possess almost identical mirror images of CD signals. Studies of photoluminescence and CD spectra have shown that there is a clear relationship between defect emission and CD activity. We have also demonstrated that these new QDs can serve as fluorescent nanosensors for various chiral biomolecules including nucleic acids. These novel nanosensors can be potentially utilized for detection of various chiral biological and chemical species with the broad range of potential applications.

Encyclopedia of Inorganic and Bioinorganic Chemistry, Jun 15, 2016

Nanoscience, 2016

Chirality plays an important role in the fields of chemistry, pharmacology, biology and medicine.... more Chirality plays an important role in the fields of chemistry, pharmacology, biology and medicine. Recently, chirality has also been envisaged to play an important role in nano-biotechnology. This review presents some recent years’ advances in the production and potential applications of various chiral nanostructured inorganic materials, including metallic (plasmonic), semiconducting, metal oxide and silica based chiral nanomaterials as well as chiral hybrid nanostructures. Chiral plasmonic nanostructures have deserved major attention due to their ability to enhance chiral signals and their consequent development as highly sensitive chiral plasmonic sensors. Also, significant advancements were made in the synthesis of chiral quantum dots (QDs) and development of their applications including sensing of various chiral organic drug molecules and catalysis of asymmetric aldol condensation reactions. The preparation of chiral metal oxide based nanomaterials such as chiral TiO2 nanofibres, chiral ZrO2 nanotubes and chiral mesoporous silica can lead to important applications in catalysts and separation of enantiomeric compounds. Finally, recently fabricated novel types of chiral hybrid nanostructures containing combinations of plasmonic and other nanomaterials in one system may find many potential applications ranging from chiral sensing to asymmetric catalysis.

Nanomaterials, Apr 2, 2014

Magnetic nanoparticles are a highly valuable substrate for the attachment of homogeneous inorgani... more Magnetic nanoparticles are a highly valuable substrate for the attachment of homogeneous inorganic and organic containing catalysts. This review deals with the very recent main advances in the development of various nanocatalytic systems by the immobilisation of homogeneous catalysts onto magnetic nanoparticles. We discuss magnetic core shell nanostructures (e.g., silica or polymer coated magnetic nanoparticles) as substrates for catalyst immobilisation. Then we consider magnetic nanoparticles bound to inorganic catalytic mesoporous structures as well as metal organic frameworks. Binding of catalytically active small organic molecules and polymers are also reviewed. After that we briefly deliberate on the binding of enzymes to magnetic nanocomposites and the corresponding enzymatic catalysis. Finally, we draw conclusions and present a future outlook for the further development of new catalytic systems which are immobilised onto magnetic nanoparticles.

Chemical Communications, Sep 7, 2010

The utilisation of chiral penicillamine stabilisers allowed the preparation of new water soluble ... more The utilisation of chiral penicillamine stabilisers allowed the preparation of new water soluble white emitting CdS nano-tetrapods, which demonstrated circular dichroism in the band-edge region of the spectrum.

Nanoscale horizons, 2016

Please note that technical editing may introduce minor changes to the text and/or graphics, which... more Please note that technical editing may introduce minor changes to the text and/or graphics, which may alter content. The journal's standard Terms & Conditions and the Ethical guidelines still apply. In no event shall the Royal Society of Chemistry be held responsible for any errors or omissions in this Accepted Manuscript or any consequences arising from the use of any information it contains.

Nature Protocols, Mar 5, 2015

chiral quantum dots (QDs) are expected to have a range of potential applications in photocatalysi... more chiral quantum dots (QDs) are expected to have a range of potential applications in photocatalysis, as specific antibacterial and cytotoxic drug-delivery agents, in assays, as sensors in asymmetric synthesis and enantioseparation, and as fluorescent chiral nanoprobes in biomedical and analytical technologies. In this protocol, we present procedures for the synthesis of chiral optically active QD nanostructures and their quality control using spectroscopic studies and transmission electron microscopy imaging. We closely examine various synthetic routes for the preparation of chiral cds, cdse, cdte and doped Zns QDs, as well as of chiral cds nanotetrapods. Most of these nanomaterials can be produced by a very fast (70 s) microwave-induced heating of the corresponding precursors in the presence of d-or l-chiral stabilizing coating ligands (stabilizers), which are crucial to generating optically active chiral QDs. alternatively, chiral QDs can also be produced via the conventional hot injection technique, followed by a phase transfer in the presence of an appropriate chiral stabilizer. We demonstrate that the properties, structure and behavior of chiral QD nanostructures, as determined by various spectroscopic techniques, strongly depend on chiral stabilizers and that the chiral effects induced by them can be controlled via synthetic procedures.

Chemical Science, 2017

On-demand initiation of chemical reactions is becoming increasingly popular in many areas. The us... more On-demand initiation of chemical reactions is becoming increasingly popular in many areas. The use of a magnetic field to trigger reactions is an intriguing concept, with vast potential in both research and industrial settings, though it remains a challenge as yet unsolved. Here we report the first example of on-demand magnetic activation of a polymerisation process using an anaerobic adhesive formulation as an example of this new approach toward triggering polymerisation reactions using an external magnetic field. Our strategy involves the use of a colloidal system comprising functional methacrylate ester monomers, peroxide and Cu II-salt as polymerisation initiators and magnetic nanoparticles coated with an oxidising shell. This unique combination prevents reduction of the reactive transition metal (Cu II) ion by the metal substrates (steel or aluminium) to be joinedhence inhibiting the redox radical initiated cationic polymerisation reaction and efficiently preventing adhesion. The polymerisation and corresponding adhesion process can be triggered by removal of the functional magnetic particles using a permanent external magnet either prior to formulation application or at the joint to be adhered, enabling the polymerisation to proceed through Cu II-mediated reduction. This new approach enables on-demand magnetically-triggered reaction initiation and holds potential for a range of useful applications in chemistry, materials science and relevant industrial manufacturing.

Nanomaterials, Apr 23, 2014

In this work, CoFe2O4@SiO2@TiO2 core-shell magnetic nanostructures have been prepared by coating ... more In this work, CoFe2O4@SiO2@TiO2 core-shell magnetic nanostructures have been prepared by coating of cobalt ferrite nanoparticles with the double SiO2/TiO2 layer using metallorganic precursors. The Transmission Electron Microscopy (TEM), Energy Dispersive X-Ray Analysis (EDX), Vibrational Sample Magnetometer (VSM) measurements and Raman spectroscopy results confirm the presence both of the silica and very thin TiO2 layers. The core-shell nanoparticles have been sintered at 600 °C and used as a catalyst in photo-oxidation reactions of methylene blue under UV light. Despite the additional non-magnetic coatings result in a lower value of the magnetic moment, the particles can still easily be retrieved from reaction mixtures by magnetic separation. This retention of magnetism was of particular importance allowing magnetic recovery and re-use of the catalyst.

Nano Letters, Apr 27, 2015

A new class of chiral nanoparticles is of great interest not only for nanotechnology, but also fo... more A new class of chiral nanoparticles is of great interest not only for nanotechnology, but also for many other fields of scientific endeavor. Normally the chirality in semiconductor nanocrystals is induced by the initial presence of chiral ligands/stabilizer molecules. Here we report intrinsic chirality of ZnS coated CdSe quantum dots (QDs) and quantum rods (QRs) stabilized by achiral ligands. As-prepared ensembles of these nanocrystals have been found to be a racemic mixture of D-and L-nanocrystals which also includes a portion of nonchiral nanocrystals and so in total the solution does not show a circular dichroism (CD) signal. We have developed a new enantioselective phase transfer technique to separate chiral nanocrystals using an appropriate chiral ligand and obtain optically active ensembles of CdSe/ZnS QDs and QRs. After enantioselective phase transfer, the nanocrystals isolated in organic phase, still capped with achiral ligands, now display circular dichroism (CD). We propose that the intrinsic chirality of CdSe/ZnS nanocrystals is caused by the presence of naturally occurring chiral defects.