Octa carboxy metal (II) phthalocyanine covalent films as pH sensitive electrochemical sensor for neurotransmitters
- Authors: Moyo, Iphithuli
- Date: 2023-10-13
- Subjects: Phthalocyanines , Thin films , Neurotransmitters , Carboxylic acids
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/424525 , vital:72161
- Description: Octa acyl chloride metallophthalocyanines of cobalt (CoOAClPc) and iron (FeOAClPc) were synthesized and characterized using spectroscopic and electrochemical techniques. The metallophthalocyanines were fabricated as thin films onto phenylethylamine (PEA) pre-grafted Au electrode following a covalent amide reaction. The spectroscopic and electrochemical characterization confirmed the modification of the bare Au with PEA monolayer thin film (Au-PEA) and the covalent immobilization of MOAClPc to yield Au-PEA-MOAClPc (where M is Co and Fe). The acyl chloride functional groups were hydrolyzed forming pH sensitive thin films of terminal carboxylic acid (-COOH) functional groups (Au-PEA-MOCAPc). The Au-PEA-MOCAPc electrode exhibited pH selectivity and sensitivity properties towards the negatively charged [Fe(CN)6]3-/4- and positively charged [Ru(NH3)6]2+/3+ redox probes. The Au-PEA-MOCAPc electrodes were studied for their electrocatalytic and electroanalytical properties towards the detection of catecholamine neurotransmitters; dopamine (DA), epinephrine (EP) and norepinephrine (NOR). The electrodes were further investigated in the screening of ascorbic and uric acids by means of pH sensitive functional groups. The modification process exhibited good reproducibility. Excellent electrocatalytic and electroanalytical properties were observed. The limits of detection (LOD) determined using 3σ/m was found to be 64 nM, 0.22 μM and 0.17 μM for DA, EP and NOR respectively using Au-PEA-CoOCAPc. For Au-PEA-FeOCAPc, the LOD was found to 0.24 μM, 0.45 μM and 0.34 μM for DA, EP and NOR respectively. The Au-PEA-MOCAPc electrodes screened off the strong interferents, ascorbic and uric acid. The Au-PEA-FeOCAPc electrode was evaluated for its potential application in real sample analysis using new born calf serum, and it showed excellent percentage recoveries. , Thesis (MSc) -- Faculty of Science, Chemistry, 2023
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- Date Issued: 2023-10-13
Design of Immunobiosensors for Detection of Tumor-Associated Anti-P53 Autoantibodies: Method Development
- Authors: Adeniyi, Omotayo Kayode
- Date: 2020
- Subjects: Uncatalogued
- Language: English
- Type: thesis , text , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/162988 , vital:41002 , 10.21504/10962/162988
- Description: Introduction -- Experimental -- Label-Free Impedimetric Sensing of Anti-P53ab... -- Fluorescent detection of Anti-P53ab -- Peroxidase-like activity of Fe3O4@SiNP-APTES-Au@Pd... -- Colorimetric detection of Anti-P53ab , Thesis (PhD)--Rhodes University, Science Faculty, Department of Chemistry, 2020. , Detection and profiling of circulating tumor-associated autoantibodies (TAAbs) are useful for screening and early-stage diagnosis of asymptomatic lung cancer. Immunobiosensor technologies aimed to accomplish the highly sensitive, rapid and low-cost detection of TAAbs can improve the early-stage detection of lung cancer. Immunobiosensors for the detection of anti-P53-tumour associated autoantibodies have been developed in this work. The design of sensing interfaces with immobilized P53 protein (P53ag) as a sensing element layer on a solid interface was investigated. Several methods of detecting anti-P53-antibodies (anti-P53ab) were investigated. These methods are label-free detection using electrochemical impedance spectroscopy (EIS) and two label techniques. The label-free electrochemical techniques utilize gold electrode pre-modified with a conducting layer of electrochemically grafted phenylethylamine for covalent immobilization of P53ag. The limit of anti-P53ab detection with the label-free EIS was 103.0 pg.ml-1. The labeled technique developed utilizes fluorescent, and peroxidase-like nanomaterial labeled antibody as a detection probe. For the fluorescence detection, fluorescent silica nanoparticles were synthesized by overloading FITC into the silica matrix and conjugated to detection antibody (anti-IgG). The detection of the anti-P53ab was based on the dissolution of the silica nanoparticles to release the loaded dye as a signal amplification strategy. The fluorescence detection was carried out on a microplate, and magnetic bead modified P53-antigen platforms and limit of detection (LoD) were 42.0 fg.ml-1 and 3.3 fg.ml-1 for anti-P53ab; respectively. Fe3O4@SiNP-APTES-Au@Pd hybrid nanoparticles were synthesized, and their peroxidase-like activity and colorimetric detection were evaluated. The Fe3O4@SiNP-APTES-Au@Pd exhibited comparable activity to HRP. The Fe3O4@SiNP-APTES-Au@Pd was conjugated to protein-G-anti-IgG for the detection of anti-P53ab on a microplate and cellulose paper platforms. The LoD was 20.0 fg.ml-1 and 63.0 fg.ml-1 for the microplate and cellulose paper platform; respectively. The potential application of the designed immunobiosensor was evaluated in simulated serum samples. The developed sensors showed higher detection sensitivity, stability and had a lower detection limit for anti-P53ab when compared with the ELISA based detection. The results have provided alternative and effective quantification approaches to ELISA and a promising future for multiplexed detection of tumor-associated autoantibodies. The developed methodologies in this thesis could be applied for the detection of other autoantibodies in other cancer types and auto-immune diseases.
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- Date Issued: 2020
Design of immunosensor for the detection of C-reactive protein using oriented antibody immobilization
- Authors: Adesina, Abiola Olanike
- Date: 2020
- Subjects: Uncatalogued
- Language: English
- Type: thesis , text , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/163080 , vital:41010 , https://dx.doi.org/10.21504/10962/163080
- Description: Thesis (PhD)--Rhodes University, Science Faculty, Department of Chemistry, 2020.
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- Date Issued: 2020
Development of graphene materials and phthalocyanines for application in dye-sensitized solar cells
- Authors: Chindeka, Francis
- Date: 2020
- Subjects: Dye-sensitized solar cells , Graphene , Phthalocyanines , Molecular orbitals , Impedance spectroscopy
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/166092 , vital:41328
- Description: Two sets of dye-sensitized solar cells (DSSCs) were fabricated. In the first set, dye-sensitized solar cells (DSSC) were fabricated by incorporating graphene materials as catalysts at the counter electrode. Platinum was also used as a catalyst for comparative purposes. Different phthalocyanines: hydroxyl indium tetracarboxyphenoxy phthalocyanine (1), chloro indium octacarboxy phthalocyanine (2) and dibenzoic acid silicon phthalocyanine (3) were used as dyes. Complex 3 gave the highest power conversion efficiency (η) of 3.19% when using nitrogen doped reduced graphene oxide nanosheets (NrGONS) as a catalyst at the counter electrode, and TiO2 containing rGONS at the anode. The value obtained is close to 3.8% obtained when using Pt catalyst instead of NrGONS at the cathode, thus confirming that NrGONS is a promising candidate to replace the more expensive Pt. The study also shows that placing rGONS on both the anode and cathode improves efficiency. In the second set, DSSCs were fabricated by using 2(3,5-biscarboxyphenoxy), 9(10), 16(17), 23(24)-tri(tertbutyl) phthalocyaninato Cu (4) and Zn (5) complexes as dyes on the ITO-TiO2 photoanodes containing reduced graphene oxide nanosheets (rGONS) or nitrogen-doped rGONS (NrGONS). The evaluation of the assembled DSSCs revealed that using ITO-TiO2-NrGONS-CuPc (4) photoanode had the highest fill factor (FF) and power conversion efficiency (ɳ) of 69 % and 4.36 % respectively. These results show that the asymmetrical phthalocyanine complexes (4) and (5) showed significant improvement on the performance of the DSSC compared to previous work on symmetrical carboxylated phthalocyanines with ɳ = 3.19%.
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- Date Issued: 2020
Evaluating the potential of monometallic and bimetallic nanomaterials as horseradish peroxidase mimetics
- Authors: Mvango, Sindisiwe
- Date: 2017
- Subjects: Uncatalogued
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/65134 , vital:28694
- Description: This study presents the synthesis of citrate-capped gold nanoparticles (cit-AuNPs), copper oxide nanoparticles (CuONPs), glutathione-capped gold nanoparticles (GSH-AuNPs), 4- aminothiophenol-capped gold nanoparticles (4-ATP-AuNPs), 4-mercapto benzoic acid- capped gold nanoparticles (4-MBA-AuNPs) and copper oxide gold nanoalloys (CuO-Au nanoalloys). Microscopy and spectroscopy techniques were used to confirm the successful synthesis of these nanoparticles. The synthesized nanoparticles were studied their potential applications as horseradish peroxidase (HPR) enzyme mimetics and for the detection of glucose. The cit-AuNPs and GSH-AuNPs exhibited peroxidase-like activity towards hydrogen peroxide (H2O2) with high Michaelis-Menten (Km) values of 61.5 mM and 30.8 mM, respectively. The other nanoparticles, that is, 4-ATP-AuNPs, CuONPs and CuO-Au nanoalloys gave lower Km values of 4.74 mM, 1.92 mM and 4.05 mM, respectively. The obtained Km values were comparable to those of HRP enzymes which ranged from 0.214 - 3.70 mM with 4-ATP-AuNPs and CuO-Au nanoalloys slightly higher. These values were within the reasonable experimental values of the HRP enzyme. The studies showed that the gold nanoparticles had low adsorptive efficiency towards H2O2 compared to the copper-based nanoparticles (CuONPs and CuO-Au nanoalloys). The CuO-Au nanoalloys also showed the synergistic effect between the gold and copper nanoparticles with extended linear concentration range for the quantification of H2O2. The mechanism of catalysis was confirmed using UV-vis spectroscopy and electron paramagnetic resonance (EPR) in that the generation of reactive oxygen species was observed. The use of 1,3-diphenylisobenzofuran (DPBF) as radical quencher and 5,5- dimethyl-1-pyrroline N-oxide (DMPO) as a radical scavenger confirmed the production of reductive reactive oxygen species using UV-vis and EPR studies. The rate of production of reactive oxygen species in the gold-based nanoparticles was small compared to the copper-based nanoparticles, that is CuONPs and CuO-Au (bimetallic) nanoalloys. The synthesized nanoparticles were further studied their potential use in the colorimetric detection of glucose. The copper-based nanomaterials, CuONPs and CuO-Au nanoalloys, were excellent towards detection of glucose, with a limit of detection (LoD) of 9.34 pM for CuONPs and 6.75 pM for CuO-Au nanoalloys. The linear concentration (LCR) range of CuONPs was 0 to 70 pM and for CuO-Au nanoalloys the LCR was 0.0 - 30 pM. , Thesis (MSc) -- Faculty of Science, Chemistry, 2017
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- Date Issued: 2017
Tetra 4-(propargyloxy)phenoxy phthalocyanines: synthesis, spectroscopic, nonlinear optical and electrocatalytic properties
- Authors: Mwanza, Daniel
- Date: 2017
- Subjects: Phthalocyanines , Nonlinear optics , Electrocatalysis , Spectrum analysis , Thermogravimetry , Phthalocyanines Spectra
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/65144 , vital:28695
- Description: This study presents the synthesis, spectroscopic, photophysical and theoretical characterisation of metal-free (H2TPrOPhOPc), cobalt (CoTPrOPhOPc) and manganese (MnTPrOPhOPc) tetra 4-(4-propargyloxy) phenoxy phthalocyanines. Thermal analysis using thermogravimetric analysis (TGA) confirmed the excellent thermal stability of synthesized tetra 4-(4- propargyloxy) phenoxy phthalocyanines. The metal complexes, CoTPrOPhOPc and MnTPrOPhOPc, exhibited better thermal stability when compared to H2TPrOPhOPc. The residual percentage weight remaining was approximately 70% for CoTPrOPhOPc and MnTPrOPhOPc and 45% for H2TPrOPhOPc after 600°C, clearly confirming the stability of the metal complexes. The MTPrOPhOPcs (where M = H2, Co and Mn) complexes exhibited excellent nonlinear optical properties with strong reverse saturable absorption (RSA), especially when 560 nm excitation laser was used. Their nonlinear optical properties followed this trend: H2TPrOPhOPc > CoTPrOPhOPc > MnTPrOPhOPc. According to the trend observed, the H2TPrOPhOPc was an excellent nonlinear optical limiter when compared to the CoTPrOPhOPc and MnTPrOPhOPc. All the investigated complexes exhibited optical limiting properties comparable to the phthalocyanine complexes reported in the literature. The MTPrOPhOPc complexes were further studied for their electrocatalytic and electroanalytical properties towards the detection of hydrogen peroxide. For the electrocatalytic studies, the synthesized complexes were immobilized onto gold electrode surfaces pre-functionalized with phenylazide (Au-PAz) monolayer. Copper (I) catalyzed alkynyl-azide cycloaddition reaction was used to covalently immobilize the MTPrOPhOPcs onto the gold electrode surfaces to form Au-PAz-MTPrOPhOPc. The MTPrOPhOPcs modified gold surfaces (Au-PAz-MTPrOPhOPc) exhibited good reproducibility and stability in various electrolyte conditions. Electrochemical and surface characterisation of the functionalised gold electrode surfaces confirmed the presence of the MTPrOPhOPcs and their electroanalysis was excellent towards electrocatalytic reduction of H2O2, with the limit of detection (LoD) and limit of quantification (LoQ) in the ^M range. The electrocatalytic reduction peaks for H2O2 were observed at -0.37 V for Au-PAz-MnTPrOPhOPc and -0.31 V for Au-PAz-CoTPrOPhOPc when Ag|AgCl pseudo-reference electrode was used. The Au-PAz-MnTPrOPhOPc and Au- PAz-CoTPrOPhOPc gold electrode surfaces showed good sensitivity and reproducibility towards the electrocatalytic reduction of hydrogen peroxide in pH 7.4 phosphate buffer solution. , Thesis (MSc) -- Faculty of Science, Chemistry, 2017
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- Date Issued: 2017