We report the determination of surface recombination velocity of electron-hole pairs for silicon ... more We report the determination of surface recombination velocity of electron-hole pairs for silicon samples passivated with organic monolayers by using the Kelvin probe. The recombination velocity was determined by monitoring the surface photovoltage as a function of the incident photon flux. By scanning of the Kelvin probe tip over the sample area, the change in surface recombination velocity can be measured allowing mapping of the recombination
Ionophore complexes of K(TCNQ˙−)(TCNQ0)n adopt a variety of stacking motifs such as wave-like inf... more Ionophore complexes of K(TCNQ˙−)(TCNQ0)n adopt a variety of stacking motifs such as wave-like infinite TCNQ columns separated by K+-cryptates (left) and K+-π-dimerised cation complexes separated by infinite slipped TCNQ stacks (right).
One of the current challenges in liquid crystal science is to understand the molecular factors le... more One of the current challenges in liquid crystal science is to understand the molecular factors leading to the formation of the intriguing twist-bend nematic phase (NTB) and determine its properties. During our earlier hunt for the NTB phase created on cooling directly from the isotropic phase and not the nematic phase, we had prepared 30 symmetric liquid crystal dimers. These had odd spacers and methylene links to the two mesogenic groups; desirable but clearly not essential features for the formation of the NTB. Here, we report the phases that the dimers exhibit and their transition temperatures as functions of both the lengths of the spacer and the terminal chains. In addition we describe the transitional entropies, their optical textures, the X-ray scattering patterns and the 2H NMR spectra employed in characterising the phases. All of which may lead to important properties of the twist-bend nematic phase. Graphical Abstract
Novel thermo-gelling polymers based on poly(2-alkyl-2-oxazoline)s grafted onto a polar carboxymet... more Novel thermo-gelling polymers based on poly(2-alkyl-2-oxazoline)s grafted onto a polar carboxymethylcellulose backbone gel are reported which have potential applications in areas such as drug delivery and tissue engineering.
Water molecules play a key structure-organising role in the crystallisation of 15-crown-5 complex... more Water molecules play a key structure-organising role in the crystallisation of 15-crown-5 complexes of lithium and sodium TCNQ in the presence of excess TCNQ0.
The intriguing twist-bend nematic phase (NTB) is formed, primarily, by liquid crystal dimers havi... more The intriguing twist-bend nematic phase (NTB) is formed, primarily, by liquid crystal dimers having odd spacers. Typically the phase is preceded by a nematic phase (N) via a weak first-order transition. Our aim is to obtain dimers where the NTB phase is formed directly from the isotropic phase via a strong first-order phase transition. The analogy between such behaviour and that of the smectic A (SmA)-N-I sequence suggests that this new dimer will require a short spacer. This expectation is consistent with the prediction of a molecular field theory since the decrease in the spacer length results in an increase in the molecular curvature. A vector of odd dimers based on benzoyloxybenzylidene mesogenic groups with terminal ethoxy groups has been synthesised with spacers composed of odd numbers of methylene groups. Spacers having 5, 7, 9, and 11 methylene groups are found to possess the conventional phase sequence NTB-N-I; surprisingly for the propane spacer the NTB phase is formed directly from the isotropic phase. The properties of these dimers have been studied with care to ensure that the identification of the NTB phase is reliable.
Organic Light-Emitting Materials and Devices IX, 2005
ABSTRACT We presented detailed spectroscopic data obtained from Nd3+ pyridine-2,6-dicarboxylic ac... more ABSTRACT We presented detailed spectroscopic data obtained from Nd3+ pyridine-2,6-dicarboxylic acid based complexes in which the 4-position of the pyridine ring has been substituted with OH and Cl. In each case the ligands formed stable complexes with the Nd3+ ion without the requirement for any additional 'neutral' ligand to satisfy the 8-9 coordination requirement of the lanthanide ion. Photoluminescence is observed from both the ligand (centered ~700 nm) and the Nd3+ ion (at ~900 nm, 1064 nm, and 1320 nm due to the 4F3/2 --> 4I9/2, 4F3/2 --> 4I11/2, and 4F13/2 --> 4I9/2 transitions respectively) following excitation in the low energy tail of the ligand pi --> pi* absorption. The intensity of the ligand emission and sensitized Nd3+ emission was found to be dependent on the substituted 4-position of the pyridine ring. The origin of the observed phenomena are discussed in relation to the energy transfer process from ligand to Nd3+ ion and the nonradiative relaxation of the sensitized Nd3+ ion. These results suggest that further modification of the ligand through complete halogenation and/or addition of other functional groups may provide an attractive route to obtaining an efficient near-infrared emitting organolanthanide complex.
Electronic Laboratory Notebooks (ELNs) are progressively replacing traditional paper books in bot... more Electronic Laboratory Notebooks (ELNs) are progressively replacing traditional paper books in both commercial research establishments and academic institutions. University researchers require specific features from ELNs, given the need to promote cross-institutional collaborative working, to enable the sharing of procedures and results, and to facilitate publication. The LabTrove ELN, which we use as our exemplar, was designed to be researcher-centric (i.e., not only aimed at the individual researcher's basic needs rather than to a specific institutional or subject or disciplinary agenda, but also able to be tailored because it is open source). LabTrove is being used in a heterogeneous set of academic laboratories, for a range of purposes, including analytical chemistry, X-ray studies, drug discovery and a biomaterials project. Researchers use the ELN for recording experiments, preserving data collected, and for project coordination. This perspective article describes the experiences of those researchers from several viewpoints, demonstrating how a web-based open source electronic notebook can meet the diverse needs of academic researchers.
A photolabile azido derivative of the kaurene oxidase inhibitor 1-(4chlorophenyl)4,4-dimethyl-2-(... more A photolabile azido derivative of the kaurene oxidase inhibitor 1-(4chlorophenyl)4,4-dimethyl-2-(1,2,4-triazol-1-yl) pentan-3-ol (paclobutrazol) has been synthesized for use as a photoaffinity labeling agent. The compound was tested as an inhibitor of the oxidation of ent-kaurene catalyzed by cell-free preparations from endosperm of Cucurbita maxima. The I5 of the azido derivative was 9.5 nanomolar, which compares well with that of paclobutrazol (6.3 nanomolar in our measurements). The azido compound bound to Cytochrome P450 in microsomes from Cucurbita maxima, and induced a Type II spectral change, with an apparent binding constant of 0.24 ± 0.04 micromolar. seeds of Marah macrocarpus (16), Cucurbita maxima (7), and Pisum sativum (1), as well as in germinating barley (Hordeum distichon) seeds (15). Similar activity has also been demonstrated in the fungus Gibberellafujikuroi (4).
We report an inelastic neutron scattering investigation of the quantum dynamics of hydrogen molec... more We report an inelastic neutron scattering investigation of the quantum dynamics of hydrogen molecules trapped inside anisotropic fullerene cages. Transitions among the manifold of quantized rotational and translational states are directly observed. The spectra recorded as a function of energy and momentum transfer are interpreted in terms of the rotational potential and the cage dimensions. The thermodynamics of orthohydrogen and parahydrogen are investigated through temperature dependence measurements.
We present an overview of solid-state NMR studies of endohedral H 2-fullerene complexes, includin... more We present an overview of solid-state NMR studies of endohedral H 2-fullerene complexes, including 1 H and 13 C NMR spectra, 1 H and 13 C spin relaxation studies, and the results of 1 H dipole-dipole recoupling experiments. The available data involves three different endohedral H 2-fullerene complexes, studied over a wide range of temperatures and applied magnetic fields. The symmetry of the cage influences strongly the motionally-averaged nuclear spin interactions of the endohedral H 2 species, as well as its spin relaxation behaviour. In addition, the non-bonding interactions between fullerene cages are influenced by the presence of endohedral hydrogen molecules. The review also presents several pieces of experimental data which are not yet understood, one example being the structured 1 H NMR lineshapes of endohedral H 2 molecules trapped in highly symmetric cages at cryogenic temperatures. This review demonstrates the richness of NMR phenomena displayed by H 2-fullerene complexes, especially in the cryogenic regime.
Abstract: A mechanism is proposed that accounts for all the known examples of A-frame inversion... more Abstract: A mechanism is proposed that accounts for all the known examples of A-frame inversion for complexes of the general types [Pt2 (p-dppm),(pY) X, 1+(dppm= bis (diphenylphosphino) methane, n= 0 or 1). The key step in this process involves an ...
Abstract An X-ray diffraction study of the title compound has revealed a centrosymmetric molecule... more Abstract An X-ray diffraction study of the title compound has revealed a centrosymmetric molecule with a large cryptand cavity (radius ca. 1.65 A), in agreement with ion-extraction experiments.
Supplementary Information Experimental The 1 H NMR and 13 C NMR spectra of compounds dissolved in... more Supplementary Information Experimental The 1 H NMR and 13 C NMR spectra of compounds dissolved in deuteriated chloroform were recorded by the School of Chemistry NMR Service using a Bruker DPX 400 or Bruker 300 spectrometer. Melting points were measured on an electrothermal melting point apparatus. Electron-impact mass spectra (EIMS) were recorded by the School of Chemistry Mass Spectrometry Service. Thin Layer Chromatography (TLC) was carried out on aluminium-backed Merck Si 60/F 254 sheets. All the chemicals used were reagent grade and were supplied the by Aldrich Chemical Company. 1,7-bis-(4-fluorophenyl-1-yloxy)heptane, FC7 4-Fluorophenol (13.4x10-3 mol, 1.50g) was dissolved in DMF (60ml) and potassium carbonate (7.4g) and sodium iodide (6.69x 10-4 mol, 0.10g) were added. The mixture was then stirred at ~100°C under N 2 for 2 h. This was then followed by the dropwise addition of 1,7-dibromoheptane (1.72g, 1.14ml, 6.69x10-3 mol). The mixture was again stirred under nitrogen for seven days at room temperature. TLC at this stage showed the reaction to be complete (50% DCM in petroleum ether 40/60 eluent). Water (2 x 50ml) was added to the reaction mixture, which was then shaken vigorously, and a solid was recovered by filtration at the pump. The solid was recrystallised from the minimum quantity of hot ethanol (~5ml) to afford white crystals (1.53g, yield 71%, mp = 55.5°C).
Journal of Biomedical Materials Research Part A, 2012
Age‐related macular degeneration (AMD) is the most common cause of blindness in the developed wor... more Age‐related macular degeneration (AMD) is the most common cause of blindness in the developed world. There is currently no treatment for the cellular loss, which is characteristic of AMD. Transplantation of retinal pigment epithelium (RPE) cells represents a potential therapy. Because of AMD‐related pathology in the native support, Bruch's membrane, transplanted RPE cells require a scaffold to reside on. We present here the development of an electrospun fibrous scaffold derived from methyl methacrylate and poly(ethylene glycol) (PEG) methacrylate for novel application as an RPE scaffold. Scaffolds were chemically modified to improve cell adhesion by functionalization not previously reported for this type of copolymer system. A human RPE cell line was used to investigate cell‐scaffold interactions for up to two weeks in vitro. Scanning electron microscopy was used to characterize the fibrous scaffolds and confirm cell attachment. By day 15, cell area was significantly (p < 0.0...
RSC Publishing Logo View PDF VersionView Previous ArticleView Next Article DOI:10.1039/ B617051J ... more RSC Publishing Logo View PDF VersionView Previous ArticleView Next Article DOI:10.1039/ B617051J (Communication) CrystEngComm, 2007, 9, 207-210. Solid-state assemblies from pyridine-2,6-dicarboxylates: “changing the instruction set through hydration”†. ...
We report the determination of surface recombination velocity of electron-hole pairs for silicon ... more We report the determination of surface recombination velocity of electron-hole pairs for silicon samples passivated with organic monolayers by using the Kelvin probe. The recombination velocity was determined by monitoring the surface photovoltage as a function of the incident photon flux. By scanning of the Kelvin probe tip over the sample area, the change in surface recombination velocity can be measured allowing mapping of the recombination
Ionophore complexes of K(TCNQ˙−)(TCNQ0)n adopt a variety of stacking motifs such as wave-like inf... more Ionophore complexes of K(TCNQ˙−)(TCNQ0)n adopt a variety of stacking motifs such as wave-like infinite TCNQ columns separated by K+-cryptates (left) and K+-π-dimerised cation complexes separated by infinite slipped TCNQ stacks (right).
One of the current challenges in liquid crystal science is to understand the molecular factors le... more One of the current challenges in liquid crystal science is to understand the molecular factors leading to the formation of the intriguing twist-bend nematic phase (NTB) and determine its properties. During our earlier hunt for the NTB phase created on cooling directly from the isotropic phase and not the nematic phase, we had prepared 30 symmetric liquid crystal dimers. These had odd spacers and methylene links to the two mesogenic groups; desirable but clearly not essential features for the formation of the NTB. Here, we report the phases that the dimers exhibit and their transition temperatures as functions of both the lengths of the spacer and the terminal chains. In addition we describe the transitional entropies, their optical textures, the X-ray scattering patterns and the 2H NMR spectra employed in characterising the phases. All of which may lead to important properties of the twist-bend nematic phase. Graphical Abstract
Novel thermo-gelling polymers based on poly(2-alkyl-2-oxazoline)s grafted onto a polar carboxymet... more Novel thermo-gelling polymers based on poly(2-alkyl-2-oxazoline)s grafted onto a polar carboxymethylcellulose backbone gel are reported which have potential applications in areas such as drug delivery and tissue engineering.
Water molecules play a key structure-organising role in the crystallisation of 15-crown-5 complex... more Water molecules play a key structure-organising role in the crystallisation of 15-crown-5 complexes of lithium and sodium TCNQ in the presence of excess TCNQ0.
The intriguing twist-bend nematic phase (NTB) is formed, primarily, by liquid crystal dimers havi... more The intriguing twist-bend nematic phase (NTB) is formed, primarily, by liquid crystal dimers having odd spacers. Typically the phase is preceded by a nematic phase (N) via a weak first-order transition. Our aim is to obtain dimers where the NTB phase is formed directly from the isotropic phase via a strong first-order phase transition. The analogy between such behaviour and that of the smectic A (SmA)-N-I sequence suggests that this new dimer will require a short spacer. This expectation is consistent with the prediction of a molecular field theory since the decrease in the spacer length results in an increase in the molecular curvature. A vector of odd dimers based on benzoyloxybenzylidene mesogenic groups with terminal ethoxy groups has been synthesised with spacers composed of odd numbers of methylene groups. Spacers having 5, 7, 9, and 11 methylene groups are found to possess the conventional phase sequence NTB-N-I; surprisingly for the propane spacer the NTB phase is formed directly from the isotropic phase. The properties of these dimers have been studied with care to ensure that the identification of the NTB phase is reliable.
Organic Light-Emitting Materials and Devices IX, 2005
ABSTRACT We presented detailed spectroscopic data obtained from Nd3+ pyridine-2,6-dicarboxylic ac... more ABSTRACT We presented detailed spectroscopic data obtained from Nd3+ pyridine-2,6-dicarboxylic acid based complexes in which the 4-position of the pyridine ring has been substituted with OH and Cl. In each case the ligands formed stable complexes with the Nd3+ ion without the requirement for any additional &#39;neutral&#39; ligand to satisfy the 8-9 coordination requirement of the lanthanide ion. Photoluminescence is observed from both the ligand (centered ~700 nm) and the Nd3+ ion (at ~900 nm, 1064 nm, and 1320 nm due to the 4F3/2 --&gt; 4I9/2, 4F3/2 --&gt; 4I11/2, and 4F13/2 --&gt; 4I9/2 transitions respectively) following excitation in the low energy tail of the ligand pi --&gt; pi* absorption. The intensity of the ligand emission and sensitized Nd3+ emission was found to be dependent on the substituted 4-position of the pyridine ring. The origin of the observed phenomena are discussed in relation to the energy transfer process from ligand to Nd3+ ion and the nonradiative relaxation of the sensitized Nd3+ ion. These results suggest that further modification of the ligand through complete halogenation and/or addition of other functional groups may provide an attractive route to obtaining an efficient near-infrared emitting organolanthanide complex.
Electronic Laboratory Notebooks (ELNs) are progressively replacing traditional paper books in bot... more Electronic Laboratory Notebooks (ELNs) are progressively replacing traditional paper books in both commercial research establishments and academic institutions. University researchers require specific features from ELNs, given the need to promote cross-institutional collaborative working, to enable the sharing of procedures and results, and to facilitate publication. The LabTrove ELN, which we use as our exemplar, was designed to be researcher-centric (i.e., not only aimed at the individual researcher's basic needs rather than to a specific institutional or subject or disciplinary agenda, but also able to be tailored because it is open source). LabTrove is being used in a heterogeneous set of academic laboratories, for a range of purposes, including analytical chemistry, X-ray studies, drug discovery and a biomaterials project. Researchers use the ELN for recording experiments, preserving data collected, and for project coordination. This perspective article describes the experiences of those researchers from several viewpoints, demonstrating how a web-based open source electronic notebook can meet the diverse needs of academic researchers.
A photolabile azido derivative of the kaurene oxidase inhibitor 1-(4chlorophenyl)4,4-dimethyl-2-(... more A photolabile azido derivative of the kaurene oxidase inhibitor 1-(4chlorophenyl)4,4-dimethyl-2-(1,2,4-triazol-1-yl) pentan-3-ol (paclobutrazol) has been synthesized for use as a photoaffinity labeling agent. The compound was tested as an inhibitor of the oxidation of ent-kaurene catalyzed by cell-free preparations from endosperm of Cucurbita maxima. The I5 of the azido derivative was 9.5 nanomolar, which compares well with that of paclobutrazol (6.3 nanomolar in our measurements). The azido compound bound to Cytochrome P450 in microsomes from Cucurbita maxima, and induced a Type II spectral change, with an apparent binding constant of 0.24 ± 0.04 micromolar. seeds of Marah macrocarpus (16), Cucurbita maxima (7), and Pisum sativum (1), as well as in germinating barley (Hordeum distichon) seeds (15). Similar activity has also been demonstrated in the fungus Gibberellafujikuroi (4).
We report an inelastic neutron scattering investigation of the quantum dynamics of hydrogen molec... more We report an inelastic neutron scattering investigation of the quantum dynamics of hydrogen molecules trapped inside anisotropic fullerene cages. Transitions among the manifold of quantized rotational and translational states are directly observed. The spectra recorded as a function of energy and momentum transfer are interpreted in terms of the rotational potential and the cage dimensions. The thermodynamics of orthohydrogen and parahydrogen are investigated through temperature dependence measurements.
We present an overview of solid-state NMR studies of endohedral H 2-fullerene complexes, includin... more We present an overview of solid-state NMR studies of endohedral H 2-fullerene complexes, including 1 H and 13 C NMR spectra, 1 H and 13 C spin relaxation studies, and the results of 1 H dipole-dipole recoupling experiments. The available data involves three different endohedral H 2-fullerene complexes, studied over a wide range of temperatures and applied magnetic fields. The symmetry of the cage influences strongly the motionally-averaged nuclear spin interactions of the endohedral H 2 species, as well as its spin relaxation behaviour. In addition, the non-bonding interactions between fullerene cages are influenced by the presence of endohedral hydrogen molecules. The review also presents several pieces of experimental data which are not yet understood, one example being the structured 1 H NMR lineshapes of endohedral H 2 molecules trapped in highly symmetric cages at cryogenic temperatures. This review demonstrates the richness of NMR phenomena displayed by H 2-fullerene complexes, especially in the cryogenic regime.
Abstract: A mechanism is proposed that accounts for all the known examples of A-frame inversion... more Abstract: A mechanism is proposed that accounts for all the known examples of A-frame inversion for complexes of the general types [Pt2 (p-dppm),(pY) X, 1+(dppm= bis (diphenylphosphino) methane, n= 0 or 1). The key step in this process involves an ...
Abstract An X-ray diffraction study of the title compound has revealed a centrosymmetric molecule... more Abstract An X-ray diffraction study of the title compound has revealed a centrosymmetric molecule with a large cryptand cavity (radius ca. 1.65 A), in agreement with ion-extraction experiments.
Supplementary Information Experimental The 1 H NMR and 13 C NMR spectra of compounds dissolved in... more Supplementary Information Experimental The 1 H NMR and 13 C NMR spectra of compounds dissolved in deuteriated chloroform were recorded by the School of Chemistry NMR Service using a Bruker DPX 400 or Bruker 300 spectrometer. Melting points were measured on an electrothermal melting point apparatus. Electron-impact mass spectra (EIMS) were recorded by the School of Chemistry Mass Spectrometry Service. Thin Layer Chromatography (TLC) was carried out on aluminium-backed Merck Si 60/F 254 sheets. All the chemicals used were reagent grade and were supplied the by Aldrich Chemical Company. 1,7-bis-(4-fluorophenyl-1-yloxy)heptane, FC7 4-Fluorophenol (13.4x10-3 mol, 1.50g) was dissolved in DMF (60ml) and potassium carbonate (7.4g) and sodium iodide (6.69x 10-4 mol, 0.10g) were added. The mixture was then stirred at ~100°C under N 2 for 2 h. This was then followed by the dropwise addition of 1,7-dibromoheptane (1.72g, 1.14ml, 6.69x10-3 mol). The mixture was again stirred under nitrogen for seven days at room temperature. TLC at this stage showed the reaction to be complete (50% DCM in petroleum ether 40/60 eluent). Water (2 x 50ml) was added to the reaction mixture, which was then shaken vigorously, and a solid was recovered by filtration at the pump. The solid was recrystallised from the minimum quantity of hot ethanol (~5ml) to afford white crystals (1.53g, yield 71%, mp = 55.5°C).
Journal of Biomedical Materials Research Part A, 2012
Age‐related macular degeneration (AMD) is the most common cause of blindness in the developed wor... more Age‐related macular degeneration (AMD) is the most common cause of blindness in the developed world. There is currently no treatment for the cellular loss, which is characteristic of AMD. Transplantation of retinal pigment epithelium (RPE) cells represents a potential therapy. Because of AMD‐related pathology in the native support, Bruch's membrane, transplanted RPE cells require a scaffold to reside on. We present here the development of an electrospun fibrous scaffold derived from methyl methacrylate and poly(ethylene glycol) (PEG) methacrylate for novel application as an RPE scaffold. Scaffolds were chemically modified to improve cell adhesion by functionalization not previously reported for this type of copolymer system. A human RPE cell line was used to investigate cell‐scaffold interactions for up to two weeks in vitro. Scanning electron microscopy was used to characterize the fibrous scaffolds and confirm cell attachment. By day 15, cell area was significantly (p < 0.0...
RSC Publishing Logo View PDF VersionView Previous ArticleView Next Article DOI:10.1039/ B617051J ... more RSC Publishing Logo View PDF VersionView Previous ArticleView Next Article DOI:10.1039/ B617051J (Communication) CrystEngComm, 2007, 9, 207-210. Solid-state assemblies from pyridine-2,6-dicarboxylates: “changing the instruction set through hydration”†. ...
Uploads
Papers by Martin Grossel