Amphiphilic Anionic Pt(II) Complexes: from spectroscopic to morphological changes

A new class of amphiphilic anionic platinum(II) bzimpy complexes has been demonstrated to show aggregation in water through PtfflfflfflPt and π–π stacking interactions. An interesting aggregation–partial deaggregation–aggregation process and a morphological transformation from vesicles to nanofibers have been demonstrated. These changes can be systematically controlled by the variation of solvent composition and could readily be probed by UV-vis absorption, emission, NMR, transmission electron microscopy and even with our naked eyes ...postprin

NIR-emissive Alkynylplatinum(II) Terpyridyl Complex as a turn-on selective probe for heparin quantification by induced helical self-assembly behaviour

The extent of self-assembly viametal–metal and π-π stacking interactions, induced by the polyanionic biopolymers, enables the class of alkynylplatinum(II) terpyridyl complexes to be applicable for the sensing of important biomacromolecules through the monitoring of spectral changes. Strong demand arises for the design of selective and practical detection techniques for the quantification of heparin, a highly negative-charged polysaccharidethat can function as anticoagulant, due to the prevention of hemorrhagic complications upon overdose usage.Aconvenient sensing protocol for the detection of UFH and LMWH, two common forms of heparins in clinical use, in buffer and biological medium has been demonstrated with the spectral changes associated with the induced self-assembly of a NIR-emissive platinum(II) complex. The detection range has been demonstrated to cover clinical dosage levels and the structurally similar analogues can be effectively differentiated based on their anionic charge density and the formation of supramolecular helical assembly of the platinum(II) complex with them ...postprin

Induced self-assembly and Förster Resonance Energy Transfer Studies of Alkynylplatinum(II) Terpyridine Complex through interaction with water-soluble Poly(phenylene ethynylene sulfonate) and the proof-of-principle demonstration of this two-component ensemble for selective label-free detection of Human Serum Albumin (HSA)

The interaction of conjugated polyelectrolyte, PPE-SO3−, with platinum(II) complexes, [Pt(tpy)(C≡CC6H4CH2NMe3-4)](OTf)2 (1) and [Pt(tpy)(C≡C–CH2NMe3)](OTf)2 (2), has been studied by UV–vis, and steady-state and time-resolved emission spectroscopy. A unique FRET from PPE-SO3−to the aggregated complex 1on the polymer chain with PtfflfflfflPt interactionhas been demonstrated, resulting in the growth of triplet metal-metal-to-ligand charge transfer (3MMLCT) emission ...postprin

CO2 selective carbon tubular membrane: the effect of stabilization temperature on BTDA-TDI/MDI P84 co-polyimide

Membranes offer remarkable attributes such as possessing small equipment footprints, having high efficiency and are environmentally friendly, with carbon membranes progressively investigated for gas separation applications. In this study, carbon tubular membranes for CO2 separation are prepared via dip-coating method with P84 co-polyimide as carbon precursor. The prepared membranes were characterized using Thermogravimetric Analysis (TGA), pore structure analysis Brunauer-Emmett-Teller (BET), Fourier Transform Infrared Spectroscopy (FTIR) and pure gas permeation system. The permeation properties of the carbon membranes are measured and analyzed using CO2, CH4 and N2 gases. The P84-based carbon tubular membrane stabilized at 300°C and featured excellent permeation properties with permeance range of 2.97±2.18, 3.12±4.32 and 206.09±3.24 GPU for CH4, N2 and CO2 gases, respectively. This membrane exhibited the highest CO2/CH4 and CO2/N2 selectivity of 69.48±1.83 and 65.97±2.87, respectively

Zeolitic imidazolate frameworks blended polysulfone hollow fiber membranes for natural gas purification

Mixed matrix membranes (MMMs) have received world-wide attention for natural gas purification due to their superior performance in terms of permeability and selectivity. In this study, zeolitic imidazole framework (ZIF) based polysulfone (PSf) hollow fiber membranes were fabricated for natural gas purification. A new micron-sized leaf-like ZIF (ZIF-L) and hexagonal nano-sized ZIF-8 were synthesized in an aqueous basic solution at room temperature with the same molar ratio of reagents (Zn+2/Hmim = 8). Furthermore, various moles of triethylamine (TEA)/total moles ratio of reactants ranging from 0–0.006 were used. Both ZIF powders were characterized by field emission scanning electron microscopy, X-ray diffraction, CO2 temperature programmed desorption, Fourier transform infrared spectroscopy, thermogravimetric analysis, transmission electron microscopy, and surface area and pores textural properties using nitrogen adsorption-desorption analysis. ZIF- 8 particles have shown improved thermal stability, textural properties, basic sites and CO2 adsorption capacity compared to ZIF-L. The neat PSf membrane and mixed matrix hollow fiber membranes incorporated with the various loading of ZIF-8 ranging from 0–1.25% were fabricated at bore fluid rate of 1.5 and 1.8 ml/min. The prepared membranes were further investigated with respect to their structural morphology, thermal stability, functional groups, surface roughness and finally gas separation performance. The gas permeation results at room temperature showed that fabricated MMM at 1.8 ml/min of bore fluid and loaded with 0.5 wt% of ZIF-8 showed 28% higher CO2/CH4 selectivity at 6 bar (g) feed pressure compared to neat PSf membrane. High loading of ZIF-8 =0.75 wt% deteriorated the separation performances. However, CO2/CH4 selectivity decreased at elevated pressure (8 and 10 bar) due to CO2-induced plasticization. The amine modification of ZIF-8 particles with 25 ml ammonium hydroxide solution at room temperature was found to significantly improve textural properties, basic sites strength and CO2 desorption capacity. MMM prepared at 1.8 ml/min of bore fluid rate and loaded with 0.25 wt% of amine modified ZIF-8 showed 18% increase in CO2/CH4 selectivity compared to unmodified ZIF-8 based membrane. The amine modification was proven to be a membrane’s anti-plasticization agent with superior gas separation performance at elevated pressure. In comparison to the neat PSf membrane, amine modified MMM prepared at the bore fluid rate of 1.8 ml/min has shown 50, 72 and 69% higher selectivity at 6, 8 and 10 bar (g) feed pressure respectively. Also, the selectivity of A-M0.25 was 18% higher than unmodified ZIF-8 based MMM at 6 bar (g) feed pressure. The permeance of both gases decreased at an acceptable level with an increase of selectivity at elevated pressure. Hence, the promising results obtained in this study has demonstrated the potential of amine modified ZIF-8 based MMMs for natural gas purification

Physical and antimicrobial characterization of bacterial cellulose obtained by green tea fermentation

Kombucha je osvježavajući napitak koji se dobiva fermentacijom zaslađenog čaja ili voćnih napitaka zahvaljujući snažnom simbiotičkom djelovanju bakterija octene kiseline i kvasaca. U radu je proučavano nastajanje octene i glukonske kiseline, etanola i bakterijske celuloze biotransformacijom kombuche u zelenom čaju zaslađenim saharozom (60, 80 i 100 g/L). Promjene pH vrijednosti posljedica su simbiotičke metaboličke aktivnosti osmofilnih kvasaca i bakterija octene kiseline i smanjivale su se s nastajanjem organskih kiselina. Analiziranjem uzoraka pomoću FT-IR spektroskopije, XRD analize i SEM pretraživanja, otkriveno je da su svi uzorci imali veći postotak amorfne strukture, a ne kristalične, kako je očekivano. Debljina i prinos bakterijske celuloze povećavali su se tijekom vremena fermentacije. Najveći prinos bakterijske celuloze bio je pri 100 g/L saharoze (143.66 %). Dobiveni rezultati ovog istraživanja ukazuju da maksimalni prinos bakterijske celuloze ovisi o mnogo čimbenika koje još treba dodatno optimizirati.Kombucha is a traditional refreshing beverage obtained by the fermentation of sweetened tea with a powerful symbiosis of acetic bacteria and yeasts. The production of acetic and gluconic acids, ethanol and bacterial cellulose by biotransformation of kombucha, in green tea sweetened with sucrose (60, 80 and 100 g/L) was studied. Changes in pH were related to the symbiotic metabolic activities of yeasts and acetic acid bacteria, and it is decreased by the formation of organic acids. Analysing samples by FT-IR spectroscopy, XRD analysis and scanning electron microscopy, it was detected that all the samples had higher precentage of amorphous regions, than crystalline regions, as it was expected. The thickness and yield of bacterial cellulose in creased with fermentation time. The highest yield of bacterial cellulose obtained was 120,27% (100 g/L). Findings from this study suggest that the yield of cellulose depends on many factors that need to be optimized to achieve maximum yield

Development of polyether block amide (PEBAX) nanocomposite membranes using nanoadsorbent from agricultural wastes as fillers for gas separation

Over the past decade, membrane processes for gas separation are gaining a larger acceptance in the industry and the markets are competing with consolidated operations such as pressure swing absorption and cryogenic distillation. There have been intensive efforts in the development of better and more robust membrane material called nanocomposite membranes which involved the incorporation of nanoadsorbents such as zeolite and silica in the polymer matrix. Recently, interest has been given to nanoadsorbents derived from agricultural wastes due to their abundance, promising features, and reasonable adsorption performances compared to the conventional nanoadsorbents. Therefore, the purpose of this study is to develop, characterise, evaluate and optimise the nanocomposite membranes comprised of the coated polyether block amide (Pebax) filled with two different types of nanoadsorbent (pineapple peel and oil palm frond) on the commercial polyvinylidene fluoride (PVDF) support membrane. A 24 full factorial design (FFD) was utilized in this study to minimize the influenced factors during nanocomposite membrane preparation. A total of four factors were chose to run simultaneously and the responses were based on permeability (CO2, CH4, N2) and ideal selectivity (CO2/CH4, CO2/N2). For the preparation of flat sheet membrane, the factors include Pebax concentration (3 and 6 wt%), types of nanoadsorbent (pineapple peel and OPF), nanoadsorbent concentration (0.5 and 5 wt% based on Pebax weight) and sonication time (15 and 30 min). Two most influenced factors towards the final separation efficiency were further study for optimisation using central composite design (CCD). The surface morphologies of the newly synthesized nanocomposite membranes were analysed using Field Emission Scanning Electron Microscope (FESEM), functional groups using Fourier Transform Infrared Spectroscopy (FTIR), force measurement and imaging using Atomic force microscopy (AFM), and crystallinity using X-Ray Diffraction instrument (XRD). The findings from the screening suggested that the most influential factors that affect the permeability and selectivity are Pebax concentration and types of nanoadsorbent. The best condition was known to maximize the permeability and selectivity. The identified conditions were Pebax concentration at 5.5 wt% using 4.5 wt% nano-pineapple peel activated carbon and sonication time of 15 min which gave CO2 permeability, CO2/CH4 selectivity and CO2/N2 selectivity of 1537.08 Barrer, 40.21 and 41.39, respectively. The outcome of this study indicates that FFD was suitable to minimize and eliminate factors by considering the interaction among the factors involves in membrane film synthesis for excellent gas separation performance. Besides, the incorporation of this nanoadsorbents were reported to alter the polymer membrane structure and chemical properties which led to an improvement of the membrane’s performance that lie significantly near and above the Robeson upper bound limit, which satisfies both high selectivity as well as high permeability

Establishment Of in vitro Plantlets Of Artemisia annua L. For The Analysis Of Artemisinin Biosynthetic Gene (CYP71AV1) And Trichome Initiation Gene (GL3)

Artemisia annua L. is an herb known for its secondary metabolite, artemisinin. Artemisinin is used as antimalarial drug but its availability is limited by low yield in plantation. To produce artemisinin using in vitro technique, a high yielding in vitro cultivar must first be selected. Artemisia annua L. ialah sejenis tumbuhan herba yang terkenal untuk metabolit sekundernya iaitu, artemisinin. Artemisinin digunakan sebagai ubat antimalaria tetapi pengunaannya terhad disebabkan oleh hasil artemisinin yang rendah di ladang. Untuk menghasilkan artemisinin menggunakan teknik in vitro, kultivar in vitro yang menghasilkan artemisinin tinggi perlu dipilih terlebih dahul

Doctor of Philosophy

dissertationDrug-free macromolecular therapeutics are a new paradigm in polymer-based nanomedicines. Instead of carrying cytotoxic small molecular weight drugs, drug-free macromolecular therapeutics crosslink proteins in the cell membrane through hybridization of oligonucleotides to initiate apoptosis signaling. However, the mechanism of the nanomedicines was not fully understood. To study the mechanism and to better understand the interactions between the therapeutics and the cell membrane, super-resolution optical microscopy was used. Super-resolution imaging was performed on Raji B cells treated with the drug-free conjugates. The clustering of CD20 and lipid rafts was quantified. Lipid raft cluster size increased after treatment with drug-free conjugates. Drug-free conjugates induced apoptosis in a lipid raft-dependent mechanism where stable lipid rafts are needed for proper initiation of apoptosis. Direct stochastic optical reconstruction microscopy revealed nanoscale differences in membrane distribution of CD20 and lipid rafts. Pair-correlation analysis of super-resolution images showed lipid raft sizes of ~200 nm in cells treated with drug-free conjugates. General applicability of direct stochastic optical reconstruction microscopy to studying drug-delivery systems was also demonstrated. Two conceptually different polymer-based therapeutics were labeled with 4 different synthetic fluorophores, and three-dimensional (3D) direct stochastic optical reconstruction microscopy was conducted at different time points to track localization of the therapeutic components. An internalized polymer conjugate was localized in clusters at 4 h, but after 24 h, the polymer released into the cytosol a fluorophore attached via an enzymatically degradable peptide. Pair-correlation functions of the dye attached to the polymer and the released dye showed changes in their decay lengths between 4 h and 24 h. The pair-correlation function of the released dye showed random distribution after 24 h. Using reversible addition?fragmentation chain-transfer (RAFT) polymerization, branched and star polymers were synthesized to study the effect of architecture on apoptosis induction in Raji B cells. A new chain transfer monomer was synthesized in order to produce controlled branched polymers in RAFT polymerization. A degradable tetra-functional chain transfer agent was also synthesized. The star chain transfer agent produced degradable star polymers of high molecular weight (~170 kDa). Drug-free conjugates were synthesized to produce linear, branched, and star polymer-MORF2 conjugates. Apoptosis in Raji B cells was measured but the three different architectures induced the same levels of apoptosis as measure by annexin V and caspase 3