Alumni Dissertations

 

Alumni Dissertations

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  • MODIFICATION OF HYDROXYAPATITE (HAP) WITH 1-HYDROXYETHANE-1, 1-DIPHOSPHONIC ACID (HEDP) FOR THE SELECTIVE SORPTION OF METAL IONS FROM WATER

    Author:
    Yasmine Daniels
    Year of Dissertation:
    2013
    Program:
    Chemistry
    Advisor:
    Spiro Alexandratos
    Abstract:

    The United States Center for Disease Control and Prevention (CDC) has linked several diseases to water pollution. Metal ions such as lead, cadmium and copper are among the biggest contributors to water pollution and can leach into water from corroded plumbing, battery and paint discharges, glass and electronic production wastes and natural deposits. Toxic amounts of these metals have been shown to cause kidney failure, liver damage, developmental delay and several forms of cancer. The effect of groundwater pollution on disease has created a dire need to safely remove toxic metal ions from groundwater systems. The application of organophosphate-modified hydroxyapatite (mHAP) for water remediation is presented in this study. Hydroxyapatite (HAP) was modified with complexant 1-hydroxyethane 1, 1-diphosphonic acid (HEDP) and its effect on metal ion affinity and selectivity was determined. HAP was synthesized from calcium hydroxide and phosphoric acid, calcined at 700oC and modified by a post-functionalization method with HEDP. The influence of time and temperature on the extent of modification was investigated. An increasing concentration of HEDP (0.01 to 0.50 M) resulted in more modification. Both untreated and HEDP-treated HAP were characterized using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDS), ICP-OES and specific surface area (SSA) measurements. Ca/P ratios, acid capacities and phosphorus elemental analyses provide information about the effect of modification on mHAP composition, surface characteristics and interactions. A high reaction temperature during modification produced new, distinct phosphate bands (993cm-1, 1082cm-1, 1144cm-1) indicating the presence of HEDP. This was independent of reaction time. HAP modified at both high temperature and long reaction time had the highest HEDP loading and revealed the sharpest XRD peaks. The emergence of new HAP-HEDP strands was observed in SEM images for treated samples while EDS and ICP showed high phosphorus contents in these strands. HAP modified at high temperature for the long reaction also had a high acid capacity and more organic phosphorus than the controls, resulting from the presence of additional P-OH groups in HEDP. Selectivity for Pb(II) (90%) and Cd(II) (80%) over Zn(II) (25%), Ni(II) (18%) and Cu(II) (0%) from 10-4 N nitrate solutions was high for this sample compared to the metal ion sorption of unmodified HAP and HAP modified for the short reaction time at low temperature. The newly synthesized mHAP was not only selective for Pb(II) and Cd(II) but had unique chemical properties that were different from HAP-HEDP salts prepared by alternative pre-functionalization methods and different from Ca-HEDP salts.

  • Recruitment of the ribosomal 40S subunit to the 3'untranslated region of a viral mRNA, via the eIF4 complex, facilitates cap-independent translation.

    Author:
    Sohani Das Sharma
    Year of Dissertation:
    2014
    Program:
    Chemistry
    Advisor:
    Dixie Goss
    Abstract:

    Translation of uncapped plant viral RNAs can be facilitated by either an internal ribosomal entry site (IRES) in the 5' untranslated region (UTR) or a cap-independent translation element (CITE) in the 3' UTR. Barley yellow dwarf virus (BYDV) mRNA, which lacks both cap and poly(A) tail, has a translation element (3'BTE) in its 3' UTR that is essential for efficient translation initiation at the 5'-proximal AUG. This mechanism requires binding of the eukaryotic initiation factor 4G (eIF4G) subunit of the heterodimer eIF4F to the 3'BTE and base pairing between the 3'BTE and the 5' UTR. Here we investigate how this interaction recruits the ribosome to the 5' end of the mRNA. Using fluorescence anisotropy, SHAPE analysis and toe printing, we found that (i) 40S ribosomal subunits bind to the 3'BTE, (ii) the helicase complex eIF4F-eIF4A-eIF4B-ATP increases affinity of 40S subunit binding to the conserved SL-I of the 3' BTE by exposing more unpaired bases of the 3'BTE and (iii) long-distance base pairing transfers this complex to the 5' end of the mRNA where translation initiates. These results reveal an utterly novel mechanism of ribosome recruitment to an mRNA.

  • CORRELATION BETWEEN EXCITED STATE ORBITAL PARENTAGE AND EXCITED STATE ACID-BASE BEHAVIOR IN TRANSITION METAL COMPLEXES

    Author:
    Jim Dimitrakopoulos
    Year of Dissertation:
    2013
    Program:
    Chemistry
    Advisor:
    Harry Gafney
    Abstract:

    Chromium (III) polypyridyl and rhodium (III) polypyridyl complexes have been the subjects of considerable interest because of their extraordinary rich photophysical and photochemical properties. The following complexes were synthesized and studied: bis(2,2'-bipyridine) (2,3-bis (pyridyl)pyrazine) chromium(III) Hexafluorophosphate, tris(2,2'-bipyridine) chromium(III) Hexafluorophosphate, bis(1,10-phenanthroline) (2,3-bis(pyridyl)pyrazine) chromium(III) Hexafluorophosphate, bis(2,2'-bipyridine)(2,3-bis(pyridyl)pyrazine) rhodium(III) Nitrate, tris(2,2'-bipyridine) rhodium(III) Nitrate, and bis(2,2'-bipyridine)bis chloride rhodium(III)Hexafluorophosphate. All chromium polypyridyl complexes studied exhibit only metal-centered emissions (d-d); they display a fluorescence signal at approximately 695 nm (4A2g © 4T2g) and a phosphorescence signal at approximately 730 nm (4A2g© 2Eg). Quenching of both emissions occurs at high pH, while emission is enhanced at low pH. The [Rh(bpy)2dpp]3+ complex is found to display both metal-centered and ligand-centered emissions. The metal-centered emission (d-d) is the dominant luminescence feature at 77 K in ethanol-methanol glasses (4:1 v/v), but the ligand-centered (&pi ¨ &pi*) emission is enhanced relative to the metal-centered luminescence in fluid acetonitrile solutions. The bis complex, [Rh(bpy)2C12]+, displays a dominant metal centered emission under all conditions that were studied. The [Rh(bpy)3]3+ complex emits only from ligand-centered excited states at 77K. From this thesis, it became clear that the excited-state properties of a complex are related to the energy ordering of its low-energy excited states and, particularly, to the orbital nature of its lowest excited state. The energy positions of the MC, MLCT, and LC excited states depend on the ligand field strength, the redox properties of metal and ligands, and intrinsic properties of the ligands, respectively. Thus, in a series of complexes of the same metal ion, the energy ordering of the various excited states, and particularly the orbital nature of the lowest excited state, can be controlled by the choice of suitable ligands. It is therefore possible to design complexes having, at least to a certain degree, desired properties.

  • Synthesis of Drug/Dye Incorporated Copolymer-Protein Hybrids and Novel Curcumin Derivatives for Imaging and Therapeutic Applications.

    Author:
    Sukanta Dolai
    Year of Dissertation:
    2010
    Program:
    Chemistry
    Advisor:
    Krishnaswami Raja
    Abstract:

    This thesis describes novel synthetic methodologies towards: (a) novel polymer-protein hybrids with a significantly increased number of functional units attached per protein and (b) the synthesis of curcumin derivatives with increased solubility and amplified bioactivity. Azide terminated poly(tert-butyl acrylate) was synthesized via atom transfer radical polymerization [ATRP]. Subsequent deprotection was performed to yield poly(acrylic acid) (PAA) possessing a reactive chain-end. A one pot sequential amidation of the PAA with the amine derivatives of a near infrared fluorescent dye (ADS832WS) and glucose produced NIRF dye incorporated water soluble copolymers. End-group modifications were performed to produce alkyne/biotin terminated copolymers which were further employed to generate dye incorporated polymer-protein hybrids via the biotin-avidin interaction with avidin or "click" bioconjugation with azide modified bovine serum albumen or apoferritin. We have overcome two fundamental limitations in the synthesis of bioconjugates: (a) the basic restriction in the diversity of copolymers which can be synthesized for producing bioconjugates, (b) the limitation in the number of dyes/drug molecules that can be attached per protein molecule. The copolymers possessed enhanced optical properties compared to the dye due to increased solubility in water. Potential utility of these copolymers and conjugates in multiwell plate based assays, cell surface imaging and in vivo animal imaging were explored. In order to overcome the difficulties associated with the low water/plasma solubility of the potent anti-oxidant, anti-inflammatory, anti-carcinogenic, anti-Alzheimer's active curcumin we have successfully synthesized several mono-functional derivatives via one-two step covalent modification methods. Freely water soluble derivatives or adducts of curcumin e.g. curcumin sugar conjugate, dendrimer-curcumin conjugate were synthesized. Antibody-curcumin adduct was produced to develop an intelligent drug delivery system. The curcumin mono-carboxylic acid was able to stain and dissolute amyloid-beta plaques at a much lower concentrations compared to curcumin. A curcumin sugar conjugate which was able to modulate Aβ aggregation in nM concentrations was synthesized compared to curcumin which is effective in μM concentrations, the sugar conjugate is ~1000 times more potent. The curcumin sugar conjugate was found to be neuro-protective as well. The curcumin dimer which have the same numbers of free phenolic-OH as curcumin, was able to selectively destroy human neurotumor cells. The dendrimer-curcumin conjugate displays curcumin in a polyvalent architecture, it was freely soluble in water and was effective against BT459 mammalian cancer cells at much lower concentrations than curcumin. Towards the synthesis of targeted drug delivery module for curcumin, the synthesis of Antibody-curcumin adduct showed a great promise in destroying GL261 glioblastoma cells as well as B16F10 melanoma cells in nM concentrations compared to curcumin which is effective in μM concentrations. The in vivo studies in both glioblastoma and melanoma models for brain tumors indicated that mice treated with antibody-curcumin conjugate resulted in significant decrease in tumor size and a significant increase in survival life span.

  • 2D & 3D NANOMATERIAL FABRICATION WITH BIOLOGICAL MOLECULAR FRAMEWORKS

    Author:
    Kristina Fabijanic
    Year of Dissertation:
    2014
    Program:
    Chemistry
    Advisor:
    HIROSHI MATSUI
    Abstract:

    Recently, there has been a heightened amount of work done in the field of biomineralization. By taking inspiration from natures' phenomenonal individualities as a means to develop new and interesting nanostructures of varying sizes and dimensions, there is a newly developed design, namely Biomimetic Crystallization Nanolithography (BCN). With this method, the simultaneous nano-patterning and crystallization has been achieved using urease as the nucleation point and the hydrolysis of urea to obtain patterns of oxide semiconductor material, namely zinc oxide, at room temperature and aqueous solvent. The new and interesting characteristic of BCN involves the construction of amorphous inks of ZnO through the use of an enzyme, its hydrolyzing abilities, and Zn-precursors. These inks are nano-patterned with the tip of an atomic force microscope, which has found to induce the crystallization of the amorphous inks into crystalline patterns. Also, a micro-contact printing process was developed and utilized as a means to directly pattern enzymes in a single step without the loss of enzyme activity after printing. By modifying the substrate to display aldehyde groups, the direct stamping of urease enables the simultaneous patterning and covalent cross-linking of urease under the reducing agent NaCNBH4, which does not degrade the enzyme activity. The exposed urease particles on the substrate, free from the cross-linker, were still catalytically active and utilized to grow crystalline ZnO nanoparticles on the enzyme patterns in ambient conditions and in aqueous solution. Recently, there has been a growing demand to have the ability of fabricating nanosized structures that are 3D in orientation, produced in large quantities and yield uniform shapes and sizes. Biomimetic assembly has been given attention in that it relies on the use of bio-inspired materials that are characteristically organized from the macroscale all the way to the nanoscale. Peptides are one of nature's building blocks that have the ability to take an active role in self-assembly and that can further be integrated to consequently yield the self-organization of structures with interesting properties in high quantities. In this study, first, micron-sized assembly of streptavidin-functionalized Au nanoparticles and biotinylated collagen peptides into cubic structures was demonstrated as assembled peptide frameworks incorporate nanoparticles in the exact position of unit cell, and then other fluorescent molecules or nanoparticles with biotin moieties were co-assembled to generate complex 3D nanoparticle assemblies. Energy transfer (FRET) and excitonic lifetime change of between QDs (donors) and AuNPs (acceptors) in these assemblies were investigated. As the interparticle distance was changed, the FRET efficiency also changed, shown by emission lifetime measurements. The energy transfer efficiency was also affected by the number of acceptor nanoparticles around the donor QDs. This type of robust large-scale 3D material assembly technique with precise positioning could be beneficial for future bottom-up device assembly such as solar cells, batteries, and metamaterials.

  • Probing Reaction Dynamics in Complex Gas-Phase Systems Using Guided-Ion-Beam Scattering and Computational Methods

    Author:
    Yigang Fang
    Year of Dissertation:
    2013
    Program:
    Chemistry
    Advisor:
    Jianbo Liu
    Abstract:

    An electrospray ionization (ESI) guided-ion-beam tandem mass spectrometer was developed in our research lab, including vacuum systems, electronics and instrument control and data acquisition (DAQ) systems using LabVIEW programming. Capitalizing on this instrument, two experimental projects have been accomplished as described below. In project 1, formation and characterization of multiply positively and negatively charged sodium bis(2-ethylhexyl)sulfosuccinate (NaAOT) aggregates were studied in the gas phase. Mass spectra show the compositions of [(NaAOT)nNaz]z+ for positively charged aggregates and [Nan-zAOTn]z- for negatively charged aggregates, with various aggregation numbers (n) and charges (z). Collision-induced dissociation (CID) of mass-selected micellar ions with Xe was performed to probe structures of gas-phase micellar assemblies, identify effects of charge states, solute-surfactant interactions, and determine preferential incorporation sites of different amino acids. Gas-phase NaAOT surfactants are able to assemble into a reverse micelle-like structure in positive ion mode and a direct micelle-like structure in negative ion mode, respectively. Both direct and reverse micelles are able to incorporate amino acids. Driving forces for amino acid solubilization in gas-phase micelles come from hydrophobic and/or electrostatic interactions, which strongly depend on amino acid hydrophobicity and charge states. In project 2, the reaction of deprotonated cysteine ([Cys-H]-) with singlet molecular oxygen (O2[a1?g]) has been studied, including the measurement of effects of collision energy (Ecol) on reaction cross sections. [Cys-H]- has a carboxylate anionic structure (HSCH2CH(NH2)CO2-) in the gas phase. Density functional theory (DFT) calculations were employed to examine the properties of various complexes, transition states and products. Three product channels were observed, corresponding to the formation of NH2CH2CO2- with remaining neutral products, OSCH2CH(NH2)CO2- via elimination of OH from an intermediate complex, and HSCH2C(NH)CO2- + H2O2 via abstraction of two hydrogen atoms from HSCH2CH(NH2)CO2- by 1O2, respectively. Quasi-classical direct dynamics trajectory simulations were carried out at Ecol = 0.2 eV using B3LYP/4-31G(d) level of theory. Trajectory results were used to guide the construction of the reaction coordinate, discriminate between different mechanisms, and provide additional mechanistic insights. Analysis of trajectories highlights the importance of complex mediation at the early stage of all reactions, and suggests a partially concerted mechanism for the H2O2 elimination reaction.

  • Heterolytic Activation of Hydrogen Promoted by Ruthenium Nanoparticles immobilized on Basic Supports and Hydrogenation of Aromatic Compounds

    Author:
    Minfeng Fang
    Year of Dissertation:
    2013
    Program:
    Chemistry
    Advisor:
    Roberto Sánchez-Delgado
    Abstract:

    Despite the aggressive development and deployment of new renewable and nuclear technologies, petroleum-derived transportation fuels--gasoline, diesel and jet fuels-- will continue to dominate the markets for decades. Environmental legislation imposes severe limits on the tolerable proportion of aromatics, sulfur and nitrogen contents in transportation fuels, which is difficult to achieve with current refining technologies. Catalytic hydrogenation plays an important role in the production of cleaner fuels, both as a direct means to reduce the aromatics and as a key step in the hydrodenitrogenation (HDN) and hydrodesulfurization (HDS) processes. However, conventional catalysts require drastic conditions and/or are easily poisoned by S or N aromatics. Therefore, there is still a need for new efficient catalysts for hydrogenation reactions relevant to the production of cleaner fossil fuels. Our catalyst design involves metallic nanoparticles intimately associated with a basic support, with the aim of creating a nanostructure capable of promoting the heterolytic activation of hydrogen and ionic hydrogenation mechanisms, as a strategy to avoid catalyst poisoning and enhance catalytic activity. We have designed and prepared a new nanostructured catalytic material composed of RuNPs immobilized on the basic polymer P4VPy. We have demonstrated that the Ru/P4VPy catalyst can promote heterolytic hydrogen activation and a unique surface ionic hydrogenation mechanism for the efficient hydrogenation of N-aromatics. This is the first time these ionic hydrogenation pathways have been demonstrated on solid surfaces. For the RuNPs surfaces without basic sites in close proximity, the conventional homolytic H2 splitting is otherwise involved. Using the mechanistic concepts from Ru/P4VPy, we have designed and prepared the Ru/MgO catalyst, with the aim to improve the catalytic efficiency for the hydrogenation of heteroatom aromatics operating by the ionic hydrogenation mechanism. The Ru/MgO catalyst significantly improves the catalytic efficiency for hydrogenation of a variety of N-/S-heteroaromatics and mono-/polycyclic aromatic hydrocarbons representative of components of petroleum-derived fuels. The catalyst is superior to the few other known supported noble metal catalysts for these reactions. Mechanistic studies also point to the ionic hydrogenation mechanism on the Ru/MgO surfaces. In addition, the Ru/MgO catalyst is highly recyclable and long-lived.

  • SYNTHESIS, CRYSTAL GROWTH AND CHARACTERIZATION OF PHOSPHIDES, SELENIDES, SULFIDES AND OXIDES

    Author:
    Chun-Min Feng
    Year of Dissertation:
    2010
    Program:
    Chemistry
    Advisor:
    Glen Kowach
    Abstract:

    The desire to build smaller, faster, inexpensive electronics has prompted researchers to exploit electron "spin" in transistors. Spin in semiconductors offers a pathway towards integration of storage and processing in a single material. These "spintronic" transistors could be highly energy-efficient and perform more computations than traditional transistors in a smaller space. In addition, in optoelectronic applications, lasers and lightemitting diodes that take advantage of electron spin could increase the data-carrying capacity of light. But one of the key hurdles in this emerging field is that the magnetic and semiconducting materials needed to make a spintronic device are notoriously incompatible. We have focused on different oxides, phosphides and sulfides to study crystal growth and properties of spintronics. We have reported the synthesis of pure ZnO and Mn substituted ZnO crystals from sodium hydroxide and potassium hydroxide flux for the first time. Various oxides, including boron oxide (B2O3), vanadium oxide (V2O5), tungsten oxide (WO3) and vmolybdenum oxide (MoO3), were also used for crystal growth. A non-uniform distribution of Mn substitution was found in ZnO single crystals, and 3 at.% Mn concentration was identified. In addition, polycrystalline Mn-substituted ZnO powder samples exhibited solubility of Mn in the ZnO lattice. SQUID magnetic propertiesinvestigation of Mn-substituted polycrystalline samples indicated paramagnetism down to 5 K. We have also investigated phosphides, selenides, and sulfides for spintronic applications, based on the well-studied spintronic material, gallium arsenide (GaAs), with a Curie temperature of 110 . GaAs has the zincblende structure with Ga in tetrahedral coordination. ZnSiP2, CdSiP2, KGaS2 and KGaSe2 have metal atoms in tetrahedral coordination with no localized spin. Localized spin will be present if transition metals are substituted in. The synthesis of single phase ZnSiP2 and CdSiP2 were grown from two different heat treatments. Also, potassium gallium selenide (KGaSe2) and potassium gallium sulfide (KGaS2) were reported. Temperature dependence susceptibility data revealed a ferromagnetic transition near 300 K followed by an antiferromagnetic transition near 50 K. Hysteresis loops at room temperature were present in all Mn substituted samples. Magnetic properties of Mn substituted samples are comparable with the crystalline MnP sample; they remain unidentified in X-ray diffraction data.

  • GROUND- AND EXCITED-STATE CHEMISTRY OF [BIS(2,2'-BIPYRIDINE)(2-(2-PYRIDYL)PYRAZINE) RUTHENIUM(II)]: PROTONATION AND COORDINATION

    Author:
    Elena Ferloni
    Year of Dissertation:
    2012
    Program:
    Chemistry
    Advisor:
    Harry Gafney
    Abstract:

    Ruthenium(II) diimines have been extensively studied for their notable photo physical properties. Of particular interest are compounds with ligands with peripheral base sites, where the metal-to-ligand charge transfer shifts electron density onto the ligand yielding an emissive state of increased in basicity. One well known example of such complexes, (bis(2,2'-bipyridine) (2-3-bis(2-pyridyl) pyrazine) ruthenium(II), [Ru(bpy)2dpp]2+, has been studied extensively, yet questions remained regarding the sequence of protonation steps at the two peripheral dpp nitrogens in the ground and excited states and the magnitude of the photo-induced change in acid-base properties at each site. In order to reach a deeper understanding of the kinetic and thermodynamic steps involved in its protonation and coordination, a similar complex was synthesized and studied, (bis(2,2'-bipyridine) (2-(2-pyridyl) pyrazine) ruthenium(II), [(bpy)2Ru(pypz)]2+. The alternative ligand is identical in almost every respect to dpp except for the absence of the free pyridyl ring and the fact that it has only one possible protonation site instead of two. The pypz ligand, thus, represents an ideal candidate to elucidate how the pyrazinyl nitrogen on the coordinated dpp would behave if the additional pyridyl ring on dpp was not present. The differences and similarities in the properties of [(bpy)2Ru(pypz)]2+ and [Ru(bpy)2dpp]2+ in the same environment are highlighted here, describing the peculiar behavior of the acid-base sites of each complex upon excitation and their role in protonation reactions and coordination reactions to d10 metals, namely zinc.

  • Synthesis and Evaluation of Sensitizer Drug Photorelease Chemistry: Micro-Optic Method Applied to Singlet Oxygen Generation and Drug Delivery

    Author:
    Goutam Ghosh
    Year of Dissertation:
    2014
    Program:
    Chemistry
    Advisor:
    Alexander Greer
    Abstract:

    This thesis summarizes a new micro-optic method for singlet oxygen generation and sensitizer drug delivery, which include i) synthesis and evaluation of a first generation device for drug delivery from native and fluorinated silica probe tips, ii) synthesis of PEG conjugated sensitizers to study phototoxicity in ovarian cancer cells, and iii) synthesis and evaluation of tris-PEGylated chlorin conjugated fluorinated silica for its future integration into the device to use as a 2nd generation device. A first generation micro-optic device was developed that works by sparging O2 gas and light generating cytotoxic singlet oxygen that cleaves the covalently attached drug (sensitizer) from the probe tip at the distal end of the fiber. The aim is to develop a 1st and 2nd generation device for site specific delivery of photosensitizer and singlet oxygen to overcome the challenges involved in systemic administration of the sensitizer. Synthesis and evaluation of drug (pheophorbide-a) delivery applying micro-optic method from native and fluorinated silica probe tip was achieved. The amount of sensitizer photocleavage depends on the loading level of sensitizer onto the probe tips. We also found that photorelease efficiency depends on the nature of the solvents where sensitizer is photocleaved. For example, no photorelease was observed in an aqueous solvent where sensitizer remained adsorbed to the native silica probe-tip. But, 90% photocleavage was obtained in octanol. A significant amount of photosensitizer (formate ester of pyropheophorbide-a) diffused into the liposome when photocleavage study was carried out in liposome. Substantial increase of photorelease was observed in organic solvent when pyropheophorbide-a (PPa) sensitizer was attached to the partially fluorinated porous Vycor glass. We also explored sensitizer photorelease from the fluorinated silica surface at various temperatures and we found that autocatalytic photorelease happened at room temperature and above. No photorelease was observed at low temperature. Chlorin e6 and its one, two and three short chain methoxy triethylene glycol (PEG) conjugated derivatives were synthesized. A comparative study of photocytotoxicity and cellular uptake between each showed that 173,152,131- chlorin e6 methoxy triethylene glycol triester has the highest photocytotoxic activity and uptake by ovarian OVCAR-5 cancer cells. Therefore, we decided to load three short chain PEG conjugated chlorin e6 onto the silica surface through spacer alkene for delivery via a fiber-optic probe tip. In order to load chlorin e6-triPEG ester conjugate, in chapter 4, we explored different synthetic strategies. We have been successful in synthesizing spacer alkene succinate linker conjugated chlorin e6-tri PEG ester, which was attached to the fiber-optic probe tip. Reactions were carried out in mild conditions to avoid detachment of the PEG ester from the carboxylic acid sites of chlorin. Photocleavage of the triPEG modified fluorinated probe tip system was studied in n-butanol.