Hydrothermal synthesis and characterisation of Cu2ZnSnS4 light absorbers for solar cells

This project has extended the knowledge in the hydrothermal synthesis of copper zinc tin sulphide (CZTS) semiconductor material which is regarded as one of the most promising light absorbing material for PV technologies. The investigation of various reaction parameters on the controlled synthesis of CZTS compound has provided important insight into the formation mechanism as well as the crystal growth behaviour of the material. CZTS nanocrystals with different crystal structure and particle size were synthesised throughout this project. The growth mechanism of CZTS crystals through a high temperature annealing treatment was also explored.

Polymer-mediated synthesis of γ-Fe2O3 nano-particles

Nano-particles of γ-Fe2O3 were synthesized by reacting polyethylene oxide–FeCl3 complex with NH4OH. These were characterized by X-ray diffraction (XRD), scanning electron miscroscopy (SEM), selected area electron diffraction (SAED) and transmision electron microscopy (TEM). The average particle size was found to be 10 nm, as determined from the line broadening of the main XRD peak. The crystalline phase was a spinel-type tetragonal structure, which was confirmed from the electron diffraction pattern. The zero field cooled magnetization of samples with varying γ-Fe2O3 content as a function of temperature was measured using a vibrating sample magnetometer. The magnetization curves show a peak at low temperature (15 K) corresponding to the blocking temperature TB. The value of TB was found to decrease with decreasing particle size. The magnetization measurements with respect to field at 5 and 170 K confirmed the transition from superparamagnetic to spin-glass state at TB, as evidenced from the remanence and hysteresis. These results can be explained on the basis of Néel's theory of superparamagnetism as applied to nano-particles.

Pyrene based conjugated materials: synthesis, characterization and electroluminescent properties

In this work, three novel pyrene cored small conjugated molecules, namely 1,3,6,8-tetrakis(6-(octyloxy)naphthalene-2-yl)pyrene (PY-1), 1,3,6,8-tetrakis((E)-2-(6-(n-octyloxy)naphthalene-2-yl)vinyl)pyrene (PY-2) and 1,3,6,8-tetrakis((6-(n-octyloxy)naphthalene-2-yl)ethynyl)pyrene (PY-3) have been synthesized by Suzuki, heck and Sonogashira organometallic coupling reactions, respectively. The effects of single, double and triple bonds on their optical, electrochemical, and thermal properties are studied in detail. These are all materials fluorescent and they have been used in organic light-emitting diodes (OLEDs) and their electroluminescent properties have been studied.

Synthesis of heterocyclic nitroxides with an improved yield by investigating the tetraalkylation of N-benzylphthalimide

The synthesis of a novel class of antioxidants, namely pyridine annulated heterocyclic nitroxides has been investigated. Two analogues were developed that differed in the structure around the free radical nitroxide. The isolation and characterisation of several side products formed in the reactions gave insight into the reaction mechanism. These findings were exploited in order to improve the overall synthetic yield of the reaction.

Graphene-type sheets of Nb1-xWxS2 : synthesis and in situ functionalization

Enlightened by the discovery of graphenes, a variety of inorganic analogues have been synthesized and characterized in recent years. Solvated Nb1-xWxS2 analogues of graphene-type sheets were prepared by lithiation and exfoliation of multistacked Nb1-xWxS2 coin roll nanowires (CRNWs), followed by in situ functionalization with gold nanoparticles to synthesize gold-loaded Nb1-xWxS2/Au nanocomposites. The Nb1-xWxS2 nanosheets and the corresponding Nb1-xWxS2/Au nanocomposites were characterized by high resolution electron microscopy (HRTEM), energy-dispersive X-ray spectroscopy (EDX), scanning transmission electron microscopy (STEM), dynamic light scattering (DLS) and scanning force microscopy (AFM). The graphene-type sheets are stable in water and other solvents and can be functionalized similarly as chalcogen-terminated surfaces (e.g. with Au nanoparticles).

Stability synthesis of power hardware-in-the-loop (PHIL) simulation

A virtual power system can be interfaced with a physical system to form a power hardware-in-the-loop (PHIL) simulation. In this scheme, the virtual system can be simulated in a fast parallel processor to provide near real-time outputs, which then can be interfaced to a physical hardware that is called the hardware under test (HuT). Stable operation of the entire system, while maintaining acceptable accuracy, is the main challenge of a PHIL simulation. In this paper, after an extended stability analysis for voltage and current type interfaces, some guidelines are provided to have a stable PHIL simulation. The presented analysis have been evaluated by performing several experimental tests using a Real Time Digital Simulator (RTDS™) and a voltage source converter (VSC). The practical test results are consistent with the proposed analysis.

Synthesis of imines from amines in aliphatic alcohols on Pd/ZrO2 catalyst under ambient conditions

Synthesis of imines from amines and aliphatic alcohols (C1–C6) in the presence of base on supported palladium nanoparticles has been achieved for the first time. The catalytic system shows high activity and selectivity in open air at room temperature. As an example of the isostructural Ln3Sb3Co2O14 (Ln: La, Pr, Nd, Sm—Ho) series with an ordered pyrochlore structure, the La variant is prepared by a citrate complex method employing stoichiometric amounts of La(NO3)3, Co(NO3)2, and Sb tartrate together with citric acid with a metal/citrate molar ratio of 1:2

Pt(II) bipyridyl complexes bearing substituted fluorenyl motif on the bipyridyl and acetylide ligands : synthesis, photophysics, and reverse saturable absorption

A series of Pt(II) diimine complexes bearing benzothiazolylfluorenyl (BTZ-F8), diphenylaminofluorenyl (NPh2- F8), or naphthalimidylfluorenyl (NI-F8) motifs on the bipyridyl or acetylide ligands (Pt-4−Pt-8), (i.e., {4,4′-bis[7-R1-F8-(≡)n-]bpy}Pt(7- R2-F8- ≡ -)2, where F8 = 9,9′-di(2-ethylhexyl)fluorene, bpy = 2,2′- bipyridine, Pt-4: R1 = R2 = BTZ, n = 0; Pt-5: R1 = BTZ, R2 = NI, n = 0; Pt-6: R1 = R2 = BTZ, n = 1; Pt-7: R1 = BTZ, R2 = NPh2, n = 1; Pt- 8: R1 = NPh2, R2 = BTZ, n = 1) were synthesized. Their ground-state and excited-state properties and reverse saturable absorption performances were systematically investigated. The influence of these motifs on the photophysics of the complexes was investigated by spectroscopic methods and simulated by time-dependent density functional theory (TDDFT). The intense absorption bands below 410 nm for these complexes is assigned to predominantly 1π,π* transitions localized on either the bipyridine or the acetylide ligands; while the broad low-energy absorption bands between 420 and 575 nm are attributed to essentially 1MLCT (metal-to-ligand charge transfer)/ 1LLCT (ligand-to-ligand charge transfer) transitions, likely mixed with some 1ILCT (intraligand charge transfer) transition for Pt-4−Pt-7, and predominantly 1ILCT transition admixing with minor 1MLCT/1LLCT characters for Pt-8. The different substituents on the acetylide and bipyridyl ligands, and the degrees of π-conjugation in the bipyridyl ligand influence both the 1π,π* and charge transfer transitions pronouncedly. All complexes are emissive at room temperature. Upon excitation at their respective absorption band maxima, Pt-4, Pt-6, and Pt-8 exhibit acetylide ligand localized 1π,π* fluorescence and 3MLCT/3LLCT phosphorescence in CH2Cl2, while Pt-5 manifests 1ILCT fluorescence and 3ILCT phosphorescence. However, only 1LLCT fluorescence was observed for Pt-7 at room temperature. The nanosecond transient absorption study was carried out for Pt-4−Pt-8 in CH3CN. Except for Pt-7 that contains NPh2 at the acetylide ligands, Pt-4−Pt-6 and Pt-8 all exhibit weak to moderate excited-state absorption in the visible spectral region. Reverse saturable absorption (RSA) of these complexes was demonstrated at 532 nm using 4.1 ns laser pulses in a 2 mm cuvette. The strength of RSA follows this trend: Pt-4 > Pt-5 > Pt-7 > Pt-6 > Pt-8. Incorporation of electron-donating substituent NPh2 on the bipyridyl ligand significantly decreases the RSA, while shorter π-conjugation in the bipyridyl ligand increases the RSA. Therefore, the substituent at either the acetylide ligands or the bipyridyl ligand could affect the singlet and triplet excited-state characteristics significantly, which strongly influences the RSA efficiency.

Novel polymer synthesis methodologies using combination of thermally and photochemically-induced nitroxide mediated polymerisation

The combination of thermally- and photochemically-induced polymerization using light sensitive alkoxyamines was investigated. The thermally driven polymerizations were performed via the cleavage of the alkoxyamine functionality, whereas the photochemically-induced polymerizations were carried out either by nitroxide mediated photo-polymerization (NMP2) or by a classical type II mechanism, depending on the structure of the light-sensitive alkoxyamine employed. Once the potential of the various structures as initiators of thermally- and photo-induced polymerizations was established, their use in combination for block copolymer syntheses was investigated. With each alkoxyamine investigated, block copolymers were successfully obtained and the system was applied to the post-modification of polymer coatings for application in patterning and photografting.

Synthesis of biodegradable polymer-mesoporous silica composite microspheres for DNA prime-protein boost vaccination

DNA vaccines or proteins are capable of inducing specific immunity; however, the translation to the clinic has generally been problematic, primarily due to the reduced magnitude of immune response and poor pharmacokinetics. Herein we demonstrate a composite microsphere formulation, composed of mesoporous silica spheres (MPS) and poly(d,l-lactide-co-glycolide) (PLGA), enables the controlled delivery of a prime-boost vaccine via the encapsulation of plasmid DNA (pDNA) and protein in different compartments. Method with modified dual-concentric-feeding needles attached to a 40 kHz ultrasonic atomizer was studied. These needles focus the flow of two different solutions, which passed through the ultrasonic atomizer. The process synthesis parameters, which are important to the scale-up of composite microspheres, were also studied. These parameters include polymer concentration, feed flowrate, and volumetric ratio of polymer and pDNA-PEI/MPS-BSA. This fabrication technique produced composite microspheres with mean D[4,3] ranging from 6 to 34 μm, depending upon the microsphere preparation. The resultant physical morphology of composite microspheres was largely influenced by the volumetric ratio of pDNA-PEI/MPS-BSA to polymer, and this was due to the precipitation of MPS at the surface of the microspheres. The encapsulation efficiencies were predominantly in the range of 93-98% for pDNA and 46-68% for MPS. In the in vitro studies, the pDNA and protein showed different release kinetics in a 40 day time frame. The dual-concentric-feeding in ultrasonic atomization was shown to have excellent reproducibility. It was concluded that this fabrication technique is an effective method to prepare formulations containing a heterologous prime-boost vaccine in a single delivery system.

Large-volume methacrylate monolith for plasmid purification : process engineering approach to synthesis and application

The extent of exothermicity associated with the construction of large-volume methacrylate monolithic columns has somewhat obstructed the realisation of large-scale rapid biomolecule purification especially for plasmid-based products which have proven to herald future trends in biotechnology. A novel synthesis technique via a heat expulsion mechanism was employed to prepare a 40 mL methacrylate monolith with a homogeneous radial pore structure along its thickness. Radial temperature gradient was recorded to be only 1.8 °C. Maximum radial temperature recorded at the centre of the monolith was 62.3 °C, which was only 2.3 °C higher than the actual polymerisation temperature. Pore characterisation of the monolithic polymer showed unimodal pore size distributions at different radial positions with an identical modal pore size of 400 nm. Chromatographic characterisation of the polymer after functionalisation with amino groups displayed a persistent dynamic binding capacity of 15.5 mg of plasmid DNA/mL. The maximum pressure drop recorded was only 0.12 MPa at a flow rate of 10 mL/min. The polymer demonstrated rapid separation ability by fractionating Escherichia coli DH5α-pUC19 clarified lysate in only 3 min after loading. The plasmid sample collected after the fast purification process was tested to be a homogeneous supercoiled plasmid with DNA electrophoresis and restriction analysis.