Browsing by Subject "Click reaction"
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Item Open Access Covalent organic framework constructed by clicking azido porphyrin with perpropargyloxy-cucurbit[6]uril for electrocatalytic hydrogen generation from water splitting(American Chemical Society, 2021-04-26) Khaligh, Aisan; Sheidaei, Yasaman; Tuncel, DönüşIn the present study, we describe the synthesis and characterization of a new covalent organic framework (COF-TPP-CB[6]) which was assembled together by clicking perpropargyloxy cucurbit[6]uril (CB[6]) to the azido-functionalized tetraphenylporphyrin (TPP-4N3) through a copper-catalyzed azide–alkyne cycloaddition reaction (CuAAC). Perpropargyloxy CB[6] was synthesized through the direct oxidation of CB[6] to afford perhydroxy CB[6] followed by subsequent O-propargylation using NaH. We also demonstrated that the resulting framework (COF-TPP-CB[6]) can be employed as an efficient and stable electrocatalyst for hydrogen evolution reaction (HER) in alkaline medium upon loading it with a nickel cocatalyst. The effect of TiO2 and different loadings of Ni on the HER performance of TPP-CB[6] was also studied. Herein, 12%Ni@TPP-CB[6] as the optimum catalyst showed an impressive H2 production rate of 18.7 mmol h–1 g–1 with a low onset potential of −250 mV.Item Open Access Cyclodextrin-grafted electrospun cellulose acetate nanofibers via "Click" reaction for removal of phenanthrene(Elsevier, 2014-06-30) Çelebioğlu, A.; Demirci, S.; Uyar, T.Beta-cyclodextrin (p-CD) functionalized cellulose acetate (CA) nanofibers have been successfully prepared by combining electrospinning and "click" reaction. Initially, p-CD and electrospun CA nanofibers were modified so as to be azide-p-CD and propargyl-terminated CA nanofibers, respectively. Then, "click" reaction was performed between modified CD molecules and CA nanofibers to obtain permanent grafting of CDs onto nanofibers surface. It was observed from the SEM image that, while CA nanofibers have smooth surface, there were some irregularities and roughness at nanofibers morphology after the modification. Yet, the fibrous structure was still protected. ATR-FTIR and XPS revealed that, CD molecules were successfully grafted onto surface of CA nanofibers. The adsorption capacity of p-CD-functionalized CA (CA-CD) nanofibers was also determined by removing phenanthrene (polycyclic aromatic hydrocarbons, PAH) from its aqueous solution. Our results indicate that CA-CD nanofibers have potential to be used as molecular filters for the purpose of water purification and waste water treatment by integrating the high surface area of nanofibers with inclusion complexation property of CD molecules.Item Open Access Design and synthesis of monosaccharide functionalized conjugated polymers, polyrotaxanes and oligomers for biological applications(Bilkent University, 2015-09) Soner, Esra DenizIn this work, the design, synthesis and characterization of fluorescent, water-soluble, multivalent glycoconjugates for their potential applications in active-targetted cellular theranostics through receptor-mediated endocytosis are presented. Gluco-functionalized thiophene monomers are utilized for the pre-functionalized Suzuki coupling polymerization of glycopolythiophenes and glycopolythiophenerotaxanes. The pre-functionalized glycopolythiophenerotaxane synthesis route was designed to provide in situ complexation between boronic ester thiophene monomer and water-soluble macrocycle cucurbit[7]uril, for the Suzuki coupling with the glycothiophene monomer in water. Red emitting oligomers carrying azide groups were utilized for the synthesis of post-functionalized glycoconjugate oligomers. These functionalizations were carried through 1,3-dipolar cycloaddition (click reaction) between azide groups and alkyne-functionalized monosaccharides (mannose or glucose). Structural and photophysical properties of glycopolythiophenes were investigated through ¹H-NMR, UV-VIS, and Fluorescence Spectroscopy. Monomers in synthetic steps were analysed through ¹H-NMR, IR, and ¹³C-NMR. Structural, photophysical and morphological properties of red oligomers were investigated through ¹H-NMR, HRMS-TOF, DLS, SEM.Item Open Access Facile synthesis of cross-linked patchy fluorescent conjugated polymer nanoparticles by click reactions(2011) İbrahimova, V.; Ekiz, S.; Gezici, Ö.; Tuncel, D.Here, we report a novel method to synthesize multifunctional nanoparticles that can be used in biological studies, such as in cell imaging and as a carrier for biomolecules/drugs. The nanoparticles were prepared either via Cu-catalyzed or cucurbit[6]uril (CB6)-catalyzed click reactions between azide groups containing hydrophobic blue, green and yellow emitting fluorene-based conjugated polymers and a hydrophilic diaminodialkyne containing cross-linker. Through the click reaction, not only does the cross-linking confer stability, but it also introduces functional groups, such as triazoles and amines, to the nanoparticles. Moreover, CB6 not only acted as a catalyst to facilitate the copper-free click reaction, but it also allowed us to obtain nanoparticles containing rotaxanes in which the triazole units were encapsulated by CB6 units. TEM images of the nanoparticles also showed that they display very interesting morphologies. Incorporation of hydrophilic functional groups to the hydrophobic conjugated polymers resulted in a distinct phase separation, producing Janus-like or patchy particles.Item Open Access Synthesis and characterization of cucurbituril based photoactive multifunctional assemblies(Bilkent University, 2019-01) Koç, AhmetPreparation of cucurbituril based functional materials and their use in various applications ranging from biomedicine to optoelectronics have been studied intensely over the last decade. Supramolecular assemblies, networks and nanostructures constructed through noncovalent interactions of cucurbiturils with -conjugated, photoactive compounds have also been investigated and potential applications in the areas of theranostics, imaging, sensing and catalysis have been shown. In these cucurbituril based architectures, however, cucurbituril is disabled to act as a molecular receptor since they do not involve the covalent conjugation of cucurbituril directly to chromophore. The main motivation of this study is to synthesize multifunctional assemblies and nanostructures in which cucurbituril is covalently attached to various conjugated compounds including porphyrin, conjugated oligomers and polymers. A new multifunctional porphyrin-cucurbituril conjugate based on a photoactive mannosylated porphyrin and monoporpargyloxycucurbit[7]uril was synthesized. Azido-functionalized tetraphenylporphyrin (TPP) was used as a building block. TPP was first mannosylated by copper-catalyzed azide-alkyne cycloaddition (CuAAC), then a monoporpargyloxycucurbit[7]uril was covalently attached to the mannosylated TPP with a second CuAAC reaction. Singlet oxygen generation efficiency of the supramolecular assembly was measured and found to be significantly higher than that of unfunctionalized TPP. ¹H NMR experiments were performed using a suitable guest, bisimidazolium, to prove the availability of CB7 in the assembly as a host. Bisimidazolium guest was observed to form inclusion complex with CB7, which is a promising result for the potential use of this supramolecular assembly as a drug carrier in conjunction with photodynamic therapy. Conjugated oligomers and polymers were synthesized from suitably- functionalized monomers via Pd-catalyzed cross-coupling reactions and their characterizations were performed. Their assemblies and nanostructures with covalently attached functionalized cucurbiturils were investigated. Redox sensitive crosslinked conjugated oligomer nanoparticles (CONs) were synthesized from a conjugated oligomer, OFVBt-N3 and a disulfide bond- containing crosslinker via ultrasound-assisted copper-free click reaction in THF. These spherical and approximately 50 nm-sized CONs preserved their stability and size («60 nm) after dispersing them in water. The behavior of the CONs in the presence of glutathione (GSH) was studied in aqueous medium. It was observed that the CONs are rapidly disrupted by GSH, which is an effective SS bond cleaving biomolecule that is overexpressed in cancer cells. These results imply that when nanoparticles are loaded with an anticancer drug, targeted delivery of the drug to cancer cells can be achieved by cooperative action of enhanced permeability and retention (EPR) effect and S-S bond cleavage by GSH.Item Open Access Synthesis and characterizations of conjugated oligomers and nanoparticles for optoelectronic and biological applications(Bilkent University, 2016-08) Köken, EmreThis project firstly aims to develop water dispersible conjugated nanoparticles by reprecipitation method for FRET based white light emission. Preliminary NPs study with only OFT Pgy and only OFVBt N3 were done in order to determine size and distribution of NPs. Overlapping optical properties of donor (OFT Pgy) and acceptor (OFVBt N3) give possibility to FRET applications. By click reaction in water, terminal sites of oligomers are connected and white emission is sealed by keeping D-A pair close. FRET based white light is widely used in optoelectronic applications such as OLEDs or more specifically WOLEDs. Since the white light covers all visible spectrum, different color emissions are obtainable depending on excitation wavelength. Various biosensor and bioimaging applications are also possible with white light emitting NPs, since they are readily and stably dispersed in water. In second part of the project, OFVBt N3 oligomer is cross-linked with di-sulfide containing crosslinker via copper catalyzed click reaction. NPs were synthesized in THF to obtain high click efficiency and redispersed in water, since the biological applications are targeted. OFVBt N3 oligomer is advantageous for bioimaging with its red emission close to IR region, since lower frequency emission overcomes the background auto-fluorescence and penetrates deeper in the body. Di-sulfide crosslinker, in addition to connecting the oligomer molecules and stabilizing NPs, provides possibility of drug delivery application. Since GSH (glutathione) or Trx (thioredoxin) like thiol bearing bio-molecules subsist in higher concentrations in tumorous tissues, di-sulfide bond can be cleaved, releasing the loaded drug from NPs. Thus, crosslinked OFVBt N3 NPs is a theranostic agent with an advantageous emission color for bio-imaging and a cleavable di-sulfide bond for drug delivery & controlled release. In last part of the study, white light emitting bi-oligomer nanoparticles were designed and obtained by using OFB Pgy and Porph N3. A quality white emission requires to cover all visible spectrum and overlapping optical properties of OFB Pgy (D) and Porph N3 (A) is used to white light emission by FRET. The purpose of clicking the oligomer pair is to stabilize the FRET efficiency. Moreover, using THF as the solvent is not only facilitated a better click chemistry, but also provided ease of applicability for solid state white light applications. Since THF evaporates easily, white light emitting NPs can form film on various surfaces. Thus, these NPs requires no host layer and can be applied directly to electrode surface when optoelectronic applications e.g. OLEDs or WOLEDs are considered.Item Open Access Synthesis of novel photoactive nanoparticles towards phototherapy(Bilkent University, 2021-09) Duah, Ishmeal KwakuNanomaterial-based compounds are attracting a lot of interest because many functionalities such as photoactive units, drugs and targeting groups can be combined on one platform to fight against infectious diseases and cancer. Recently, conjugated polymer-based nanomaterials have proven to be effective photosensitizers for antibacterial and photodynamic cancer therapies owing to their unique electronic and optical properties, including high singlet oxygen generation capacity, strong light-harvesting ability and its tunable optical spectrum. In this study, novel cross-linked conjugated polymer nanoparticles-based photosensitizers namely conjugated polymer-porphyrin nanoparticles (CPPN) and cross-linked conjugated polymer nanoparticles (PCP) were synthesized. The nanoparticles were prepared via nanoprecipitation using cucurbit[6]uril-(CB6)-catalyzed azide-alkyne cycloaddition (CB6-AAC) reaction. Conjugated polymer-porphyrin nanoparticles (CPPN) are advantageous than micelles incorporating porphyrin systems. For micelles containing porphyrin systems, the phototherapy effect of the porphyrin can only be seen after the porphyrin is released by conditions such as a change in pH, which is not the case for conjugated polymer-porphyrin nanoparticles (CPPN). The nanoparticles demonstrated high reactive oxygen species (ROS) generation efficiency which is evident in the antibacterial and anticancer photodynamic therapy (PDT) experiments. From the antibacterial photodynamic therapy experiment, when Gram-negative (Escherichia coli, E. coli) and Gram-positive (Bacillus subtilis, B. Subtilis and Staphylococcus aureus, S. aureus) bacteria were incubated with CPPN (20 µg/mL) and irradiated with white light (22 mW/cm2) for 10 min, more than 3.5-log reduction in colony-forming units (CFUs) was recorded for CPPN. Furthermore, when E. coli and B. subtilis were treated with PCP (24 µg/mL) and illuminated with light, about 3-log killing efficiency was recorded. However, in the dark, the nanoparticles demonstrated minimal dark cytotoxicity against the model bacteria. In addition, the anticancer photodynamic effect of CPPN and PCP on MCF-7 breast cancer cells was investigated. When MCF-7 breast cancer cells were treated with PCP in the dark and under light irradiation, almost all cells were alive for both cases. It may be that PCP could not generate enough reactive oxygen species to kill the cells. When MCF-7 breast cancer cells were treated with CPPN in the dark, the cell viability was 96% and upon irradiation with light for 20 minutes, the cell viability decreased to about 4%. Moreover, conjugated polymer-porphyrin-gold nanoparticles (CPPN-Au) and cross-linked conjugated polymer-gold nanoparticles (PCP-Au) nanoparticles were prepared, but due to the instability of the nanoparticles, they could not be used in phototherapy.Item Open Access White-emitting conjugated polymer nanoparticles: tuning emission via förster resonance energy transfer in nanostructures assembled through click reactions(Bilkent University, 2014-06) Keita, HamidouIn this work, we present the design, synthesis and characterization of water-dispersible conjugated polymer nanoparticles with tunable emission wavelengths for their potential applications in the areas of white organic light emitting diodes and cellular imaging. Blue, green and red emitting polymers carrying azide or alkyne groups are utilized and assembled together through 1,3-dipolar cycloaddition (click reaction) to obtain stable, shape-persistent white-emitting nanoparticles. The emission properties can both be tuned by varying polymer concentration and nanostructure design as a result of intimate interactions between the polymers within the nanostructure, which facilitate a highly efficient Förster Resonance Energy Transfer (FRET). For this purpose, four different nanostructured architectures were designed and investigated. In the first method, NPs of donor and acceptor are prepared separately and then mixed physically at certain ratios. The second method involves the formation of homogenous solution of both donor and acceptor polymers in THF followed by formation of NPs from the resulting solution. And in the third and fourth methods, sequentially formed NPs were designed. In the former, donor NPs were core and coated with solution of the acceptor polymer as the outer shell, while the latter is quite the reverse where acceptor NPs form the core surrounded by the donor as the outer shell. Polymers used in this study are namely, poly[(9,9-bis{3-azidopropyl}fluorenyl-2,7-diyl)-cobenzene] (PFBN3) which is a blue emitter that serves as a donor, while poly[(9,9-bis(3- (prop-2 ynyloxy)propyl)fluorenyl-2,7-diyl)-co-(1,4-benzo-{2,1,3}-thiadiazole)] (PFBT-Pgy) is a green emitting polymer whose absorbance strongly overlaps with the emission of the donor serves as the acceptor. Moreover, red emitting polymers such as poly[(2-azidoethyl)-2- (5-(thiophen-2-yl)thiophen-2-yl)thiophene (PTN3 ) and Poly[(4-(2-(prop-2- ynyloxy)ethyl)thiophen-2-yl)-co-(1.4-benzo{1,2,5}thiadiazole)] (PBTTH-Pgy) were incorporated into multi-shell nanoparticle design to form white emitting tandem nanoparticles. The morphology and photophysical properties were investigated by DLS, SEM, TEM and UV-VIS, Steady-State Fluorescence, Time-resolved Fluorescence Spectroscopy respectively.