J. Kelly - Academia.edu (original) (raw)
Papers by J. Kelly
![Research paper thumbnail of The photophysics of fac-[Re(CO)3(dppz)(py)]+ in CH3CN: a comparative picosecond flash photolysis, transient infrared, transient resonance Raman and density functional theoretical studyDedicated to the memory of Nobel Laureate, Lord George Porter FRSC FRS OM](https://attachments.academia-assets.com/43580854/thumbnails/1.jpg)
](Photochemical & Photobiological Sciences, 2003
The microwave (MW)-assisted formation of ZnO micro-javelins from zinc nitrate and urea in aqueous... more The microwave (MW)-assisted formation of ZnO micro-javelins from zinc nitrate and urea in
aqueous solution is described. The particles (named as ‘micro-javelins’ because of their high aspect ratio
and needle-like tips) grow hexagonally with well-defined facets in the h0110i direction and pointed
tips in (0001) direction. Powder X-ray diffraction patterns show the appearance of a strikingly
dominant (1000) orientation. Scanning electron microscopy (SEM) and transmission electron
microscopy (TEM) investigations reveal the morphological evolution of these hexagonal ZnO particles
with time. The effect of precursor concentrations, counterion type andMWirradiation power and their
consequent influence on pH and Zn2+ ion concentration are investigated. A mechanism for the
formation of the micro-javelins is postulated. The microwave induced supersaturation of Zn(OH)+
species under the weakly basic pH condition and the initial growth through the (0001) direction
(oxygen-rich face) are proposed to be the key factors that dictate the formation of these ZnO
micro-javelins. The present one-step microwave process is a straightforward and a reproducible method
for the bulk synthesis of defect-free ZnO micro-javelins, which would find potential applications in
microelectronic devices (e.g. lasers, cantilevers in surface probing equipment, etc.).
Nanoparticles of ZnO were prepared by the reaction of ethanolic solutions of zinc acetate and oxa... more Nanoparticles of ZnO were prepared by the reaction of ethanolic solutions of zinc acetate and oxalic acid
followed by drying (80 uC) and calcination (500 uC). Subsequently varistor materials were fabricated from this
nanoparticular ZnO via two separate routes:- a) from a ‘‘core shell’’ material using metal salts as additives; b)
by using a conventional solid state mixing of metal oxides. Sintering (1050 uC) and subsequent electrical studies
were carried out for each of these samples and they were compared with commercial varistor samples prepared
under similar conditions. ‘‘Core shell’’ type varistor material showed considerably higher breakdown voltage
(Vc ~ 850 ¡ 30 V mm21) as compared to a sample prepared by mixing with metal oxides (Vc ~ 683 ¡
30 V mm21) or commercial varistor discs (Vc ~ 507 ¡ 30 V mm21). The high breakdown voltage obtained is
attributed to the formation of more varistor-active grain boundaries per unit area.
![Research paper thumbnail of Excited state dependent electron transfer of a rhenium-dipyridophenazine complex intercalated between the base pairs of DNA: a time-resolved UV-visible and IR absorption investigation into the photophysics of fac-[Re(CO)3(F2dppz)(py)]+ bound to either [poly(dA-dT)]2 or [poly(dG-dC)]2](https://attachments.academia-assets.com/43580853/thumbnails/1.jpg)
](Photochemical & Photobiological Sciences, 2011
ZnO varistor materials were prepared by a sol gel route with subsequent drying and calcination. V... more ZnO varistor materials were prepared by a sol gel route with subsequent drying and calcination.
Varistor discs fabricated from these materials were subjected to a two step sintering schedule.
Therefore in a typical experiment, the samples were heated to 1000uC, then allowed to cool for over
30 min to 900uC and held there for 6 h. The results were compared with commercial varistor samples
sintered in a similar way. Considerably higher breakdown voltages were obtained for the varistorsmade
from nanosample (1192¡30 V mm21) compared with the commercial samples (723 ¡30 V mm21)
sintered under the same experimental conditions. The sintered materials were characterised by X-ray
diffraction (XRD), field emission scanning electron microscopy (FESEM) and density measurements
Hydrolysis of the new metallorganic precursor Fe(OBut)2- (THF)2 followed by ultrasound and therma... more Hydrolysis of the new metallorganic precursor Fe(OBut)2-
(THF)2 followed by ultrasound and thermal treatment
yielded either nanoparticles of c-Fe2O3 or Fe3O4, depending
on the process conditions. The samples have been
characterised by X-ray powder diffraction, TEM, SEM,
Mo¨ ssbauer spectroscopy and magnetization measurements.
The maghemite nanoparticles (9¡2 nm) are superparamagnetic
and form unique needle-like assemblies of
nanoparticle arrays. The nanoparticles of Fe3O4 (19¡
2 nm) form plate-like aggregates about 10 mm thick.
Microwave irradiation of solutions of Zn(NO3)2 and urea provides a straightforward route to a-axi... more Microwave irradiation of solutions of Zn(NO3)2 and urea
provides a straightforward route to a-axis oriented crystals of
needle-like morphology
ZnO based varistors are widely used for overvoltage protection in many electrical and electronic ... more ZnO based varistors are widely used for overvoltage protection in many electrical and electronic circuits, at
voltages ranging from a few to over a million volts. By careful control of the microstructure, through nanostructuring
by chemical routes, it should be possible to produce varistors with high breakdown voltage (Vc),
as this is proportional to the number of active grain boundaries in the sintered body. This property is
particularly important for the production of the small-sized varistors needed for modern electronic
instruments such as tablet computers and mobile phones. The current review will outline the recent
advances in the chemical processing (e.g. sol–gel, combustion synthesis plasma pyrolysis, micro-emulsion
synthesis and precipitation routes) of varistors from ZnO nanomaterials and the properties of these
materials. Uncontrolled grain growth at higher temperature is highlighted as a major challenge for
obtaining desirable electrical properties for nano-varistors. Various novel sintering techniques such as
step-sintering, spark plasma and microwave sintering methods are expected to deliver a varistor with
controlled grain growth and optimum electrical characteristics.
Linear arrays of ZnO nanoparticles have been successfully prepared by a simple sol–gel condensati... more Linear arrays of ZnO nanoparticles have been successfully prepared by a simple sol–gel condensation reaction
involving chemical modifiers, followed by drying (80 uC) and calcination (500 uC). The calcined material (nanoarray
ZnO) is composed of approximately spherical nanoparticles of average diameter 21 ¡ 3 nm, selfassembled
to form arrays extending in length to 2–4 mm. The morphology of the ZnO is found to depend
sensitively on the amounts of chemical modifiers present. In their absence the ZnO produced (nano-ZnO) is an
unstructured agglomerate of nanoparticles. The mechanism for formation of these linear arrays has been
investigated by examining the intermediates formed at 80 uC and 250 uC using XRD and TEM and by
following the decomposition reactions using TGA and DSC. Varistors prepared from the nano-array ZnO by
sintering (1050 uC) with appropriate mixtures of metal oxides showed a breakdown voltage of 786 ¡ 30 V mm21,
which is substantially higher than that of samples prepared under similar conditions from either micron-sized
commercial ZnO (507 ¡ 30 V mm21) or from nano-ZnO (683 ¡ 30 V mm21).
Section 1 by J. Kelly
Chemical Communications, 2005
In this paper we demonstrate the use of picosecond time-resolved infrared spectroscopy (ps-TRIR) ... more In this paper we demonstrate the use of picosecond time-resolved infrared spectroscopy (ps-TRIR) to monitor the early structural dynamics of DNA bases and polydeoxynucleotides following UV excitation in solution.
Photochemical & Photobiological Sciences, 2003
The microwave (MW)-assisted formation of ZnO micro-javelins from zinc nitrate and urea in aqueous... more The microwave (MW)-assisted formation of ZnO micro-javelins from zinc nitrate and urea in
aqueous solution is described. The particles (named as ‘micro-javelins’ because of their high aspect ratio
and needle-like tips) grow hexagonally with well-defined facets in the h0110i direction and pointed
tips in (0001) direction. Powder X-ray diffraction patterns show the appearance of a strikingly
dominant (1000) orientation. Scanning electron microscopy (SEM) and transmission electron
microscopy (TEM) investigations reveal the morphological evolution of these hexagonal ZnO particles
with time. The effect of precursor concentrations, counterion type andMWirradiation power and their
consequent influence on pH and Zn2+ ion concentration are investigated. A mechanism for the
formation of the micro-javelins is postulated. The microwave induced supersaturation of Zn(OH)+
species under the weakly basic pH condition and the initial growth through the (0001) direction
(oxygen-rich face) are proposed to be the key factors that dictate the formation of these ZnO
micro-javelins. The present one-step microwave process is a straightforward and a reproducible method
for the bulk synthesis of defect-free ZnO micro-javelins, which would find potential applications in
microelectronic devices (e.g. lasers, cantilevers in surface probing equipment, etc.).
Nanoparticles of ZnO were prepared by the reaction of ethanolic solutions of zinc acetate and oxa... more Nanoparticles of ZnO were prepared by the reaction of ethanolic solutions of zinc acetate and oxalic acid
followed by drying (80 uC) and calcination (500 uC). Subsequently varistor materials were fabricated from this
nanoparticular ZnO via two separate routes:- a) from a ‘‘core shell’’ material using metal salts as additives; b)
by using a conventional solid state mixing of metal oxides. Sintering (1050 uC) and subsequent electrical studies
were carried out for each of these samples and they were compared with commercial varistor samples prepared
under similar conditions. ‘‘Core shell’’ type varistor material showed considerably higher breakdown voltage
(Vc ~ 850 ¡ 30 V mm21) as compared to a sample prepared by mixing with metal oxides (Vc ~ 683 ¡
30 V mm21) or commercial varistor discs (Vc ~ 507 ¡ 30 V mm21). The high breakdown voltage obtained is
attributed to the formation of more varistor-active grain boundaries per unit area.
Photochemical & Photobiological Sciences, 2011
ZnO varistor materials were prepared by a sol gel route with subsequent drying and calcination. V... more ZnO varistor materials were prepared by a sol gel route with subsequent drying and calcination.
Varistor discs fabricated from these materials were subjected to a two step sintering schedule.
Therefore in a typical experiment, the samples were heated to 1000uC, then allowed to cool for over
30 min to 900uC and held there for 6 h. The results were compared with commercial varistor samples
sintered in a similar way. Considerably higher breakdown voltages were obtained for the varistorsmade
from nanosample (1192¡30 V mm21) compared with the commercial samples (723 ¡30 V mm21)
sintered under the same experimental conditions. The sintered materials were characterised by X-ray
diffraction (XRD), field emission scanning electron microscopy (FESEM) and density measurements
Hydrolysis of the new metallorganic precursor Fe(OBut)2- (THF)2 followed by ultrasound and therma... more Hydrolysis of the new metallorganic precursor Fe(OBut)2-
(THF)2 followed by ultrasound and thermal treatment
yielded either nanoparticles of c-Fe2O3 or Fe3O4, depending
on the process conditions. The samples have been
characterised by X-ray powder diffraction, TEM, SEM,
Mo¨ ssbauer spectroscopy and magnetization measurements.
The maghemite nanoparticles (9¡2 nm) are superparamagnetic
and form unique needle-like assemblies of
nanoparticle arrays. The nanoparticles of Fe3O4 (19¡
2 nm) form plate-like aggregates about 10 mm thick.
Microwave irradiation of solutions of Zn(NO3)2 and urea provides a straightforward route to a-axi... more Microwave irradiation of solutions of Zn(NO3)2 and urea
provides a straightforward route to a-axis oriented crystals of
needle-like morphology
ZnO based varistors are widely used for overvoltage protection in many electrical and electronic ... more ZnO based varistors are widely used for overvoltage protection in many electrical and electronic circuits, at
voltages ranging from a few to over a million volts. By careful control of the microstructure, through nanostructuring
by chemical routes, it should be possible to produce varistors with high breakdown voltage (Vc),
as this is proportional to the number of active grain boundaries in the sintered body. This property is
particularly important for the production of the small-sized varistors needed for modern electronic
instruments such as tablet computers and mobile phones. The current review will outline the recent
advances in the chemical processing (e.g. sol–gel, combustion synthesis plasma pyrolysis, micro-emulsion
synthesis and precipitation routes) of varistors from ZnO nanomaterials and the properties of these
materials. Uncontrolled grain growth at higher temperature is highlighted as a major challenge for
obtaining desirable electrical properties for nano-varistors. Various novel sintering techniques such as
step-sintering, spark plasma and microwave sintering methods are expected to deliver a varistor with
controlled grain growth and optimum electrical characteristics.
Linear arrays of ZnO nanoparticles have been successfully prepared by a simple sol–gel condensati... more Linear arrays of ZnO nanoparticles have been successfully prepared by a simple sol–gel condensation reaction
involving chemical modifiers, followed by drying (80 uC) and calcination (500 uC). The calcined material (nanoarray
ZnO) is composed of approximately spherical nanoparticles of average diameter 21 ¡ 3 nm, selfassembled
to form arrays extending in length to 2–4 mm. The morphology of the ZnO is found to depend
sensitively on the amounts of chemical modifiers present. In their absence the ZnO produced (nano-ZnO) is an
unstructured agglomerate of nanoparticles. The mechanism for formation of these linear arrays has been
investigated by examining the intermediates formed at 80 uC and 250 uC using XRD and TEM and by
following the decomposition reactions using TGA and DSC. Varistors prepared from the nano-array ZnO by
sintering (1050 uC) with appropriate mixtures of metal oxides showed a breakdown voltage of 786 ¡ 30 V mm21,
which is substantially higher than that of samples prepared under similar conditions from either micron-sized
commercial ZnO (507 ¡ 30 V mm21) or from nano-ZnO (683 ¡ 30 V mm21).
Chemical Communications, 2005
In this paper we demonstrate the use of picosecond time-resolved infrared spectroscopy (ps-TRIR) ... more In this paper we demonstrate the use of picosecond time-resolved infrared spectroscopy (ps-TRIR) to monitor the early structural dynamics of DNA bases and polydeoxynucleotides following UV excitation in solution.