Philani Mashazi - Academia.edu (original) (raw)

Papers by Philani Mashazi

ACS applied nano materials, Dec 28, 2022

Journal of Porphyrins and Phthalocyanines, 2019

This work describes the adsorption of synthesized cobalt mono (CoPc) and binuclear phthalocyanine... more This work describes the adsorption of synthesized cobalt mono (CoPc) and binuclear phthalocyanines (CoBiPc) with single walled carbon nanotubes (SWCNT) to form SWCNT-CoPc or SWCNT-CoBiPc as non-covalent conjugates onto glassy carbon electrodes (GCE). The cobalt complexes and their SWCNT-conjugate-modified electrodes were studied for their electrocatalytic oxidation towards 4-chlorophenol. All modified electrodes showed improved catalytic current and stability towards the detection of 4-chlorophenol. The best activity was observed for the SWCNT-CoBiPc2 system in terms of current response and the SWCNT-CoBiPc1 system in terms of resistance to electrode fouling.

for their great support, sharing their knowledge and guidance during my degree programme. I thank... more for their great support, sharing their knowledge and guidance during my degree programme. I thank you all a million times and I remain eternally grateful to your assistance, Thank you!!! I also wish to thank my family: mom, dad and everybody (too numerous to mention by names), for the support and encouragement throughout my academic years at Rhodes University. Ndaweni (mom) your prayers saw me through and I am grateful to be your son. Dad your wishes have stayed with me, I hope I have not disappointed you in anyway. My friends (too numerous to mention by names), I thank you guys for making Grahamstown and Ghent enjoyable. To the Chemistry Department staff (technical and academic) and postgraduate students, especially S22, thank you guys for the discussions we shared and for providing such a conducive environment and making Grahamstown a home away from home. I also wish to acknowledge all the helpful discussions, constructive criticism and concerns raised by referees of published work of this thesis, Thank you!!! Finally, I will remain eternally grateful to Project AuTEK (Mintek and Gold-Fields) for the M.Sc. Scholarship and the National Research Foundation (NRF) for financial assistance. I also would like to thank Ghent University (Belgium) for the support and a rewarding experience through bilateral research project funded by NRF (SA) and UGent-BOF (Belgium).

Journal of Materials Chemistry B, 2023

Nanozymes are nanomaterials that exhibit enzyme-like activity upon exposure to a substrate soluti... more Nanozymes are nanomaterials that exhibit enzyme-like activity upon exposure to a substrate solution. The use of noble and platinum group metals enhances enzyme-like catalytic activity. However, noble metals are obtained at a high cost; therefore, their recovery after use is of high importance. Herein, we report the fabrication of indium tin oxide-silica nanoparticles decorated with palladium nanoparticles (ITO-SiO 2-prS-PdNPs). The ITO-SiO 2-prS-PdNPs were evaluated for peroxidase-like activity toward the oxidation of 3,3 0 ,5,5 0-tetramethylbenzidine (TMB) in the presence of H 2 O 2. A colour change from clear or colourless TMB to blue colour (oxidized TMB products) was observed confirming the peroxidase-like activity. A typical Michaelis-Menten enzyme-like behaviour is observed with K m values of 0.68 mM for H 2 O 2 and 0.47 mM for TMB, which are better than the reported values for horseradish peroxidase (HRP) for the same substrate. The peroxidase-like activity of ITO-SiO 2-prS-PdNPs was found to proceed via the electron-transfer mechanism. The ITO-SiO 2-prS-PdNPs were cleaned successfully after each use by rinsing with water and ethanol solution thus making the surface simple and easy to recover and reuse. A reusable and highly selective colorimetric assay for glucose detection based on the peroxidaselike activity of ITO-SiO 2-prS-PdNPs gave excellent results. ITO-SiO 2-prS-PdNPs exhibited a good linear range of 5.0-30 mM, a low limit of detection (LOD) of 1.84 mM and a limit of quantification (LOQ) of 6.14 mM. Finally, the nanozyme (ITO-SiO 2-prS-PdNPs) was successfully used to detect glucose in a complex newborn calf serum (NCS), representing a real sample.

Journal of Photochemistry and Photobiology A-chemistry, Aug 1, 2020

Abstract Dye sensitized solar cells (DSSCs) were fabricated by using 2(3,5-biscarboxyphenoxy), 9(... more Abstract Dye sensitized solar cells (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 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) exhibit significant improvement on the performance of the DSSC compared to our previous work on symmetrical carboxylated phthalocyanines with ɳ = 3.19%.

Electrochimica Acta, 2020

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Talanta, Aug 1, 2022

In this work, the preparation of glucose encapsulating nanoliposomes was achieved using two diffe... more In this work, the preparation of glucose encapsulating nanoliposomes was achieved using two different lipid formulations, labelled as F1 and F2. Both formulations contained phosphatidylcholine (PC), oleylamido-4-butanoic acid (OABA) and in addition, F1 had cholesterol (CHO) while F2 contained cholesteroyl hemisussinate (CHEMS). These formulations were studied for their pH sensitivity and controlled release of encapsulated glucose for indirect detection of prostate-specific antigen (PSA) using sandwich immunoassay. As a signal generator, encapsulated glucose in nanoliposomes was quantified directly using the personal glucose meter (PGM) and colorimetrically using peroxidase property of horseradish peroxidase (HRP) enzyme and Pd|PdO as nanozymes. Controlled release of the encapsulated glucose was achieved using the pH effect or Triton-X 100 as a surfactant to destabilize the liposomal structure. The F2 formulation showed maximum controlled release at acidic phosphate buffer saline (PBS, pH 5.0). The concentration of encapsulated glucose was found to be high in F2 formulation and these were applied for the indirect detection of PSA. The limit of detection (LOD) values for PSA were found to be 53 fg mL-1, 64 fg mL-1 and 10 fg mL-1 when HRP, Pd|PdO and PGM were respectively used. The detection signal was linear over a wide concentration range for PSA including the clinical range of 4-10 ng mL-1. The HRP system showed low LOD value when compared with Pd|PdO nanozymes. PGM system gave lowest LOD values owing to the sensitivity of the system towards glucose. Pd|PdO nanozyme system showed good stability over a wide temperature up to 80 °C. PGM system required less reaction time (2 min), low reagents and results were readily generated in digital format.

Materials Today Chemistry, Dec 1, 2022

RSC Advances, 2021

The emergence of nanoscience and nanotechnology has revitalised research interest in using copper... more The emergence of nanoscience and nanotechnology has revitalised research interest in using copper and its derived nanostructures to find exciting and novel applications. In this work, mono-and bimetallic gold and palladium nanoparticles supported on copper oxide nanorods (CuONRs) were prepared and their catalytic performance towards the reduction of H 2 O 2 to form reactive oxygen radical species (ROS) was evaluated. The characterisation using microscopy and spectroscopic techniques confirms the successful synthesis of CuONRs, CuONRs@Au 6 NPs, CuONRs@Pd 6 NPs and CuONRs@Au 3 Pd 3 NPs. The efficient generation of ROS was confirmed using UV-vis spectroscopy and 1,3-diphenylisobenzofuran (DPBF) as a radical scavenger. The CuONRs possess excellent catalytic reduction activity for H 2 O 2 by generating ROS. However, CuONRs also have lattice oxygens which do not participate in the catalytic reduction step. The lattice oxygens however allowed for the adsorption of gold and palladium nanoparticles (Au 6 NPs, Pd 6 NPs and Au 3 Pd 3 NPs) and thus enhanced catalytic reduction of H 2 O 2 to produce ROS. The produced ROS was subsequently involved in the catalytic oxidation of a chromogenic substrate (TMB), resulting in blue coloured diimine (TMBDI) complex which was monitored using UV-vis and could also be observed using the naked eye. The catalyst dependence on pH, temperature, and H 2 O 2 concentration towards efficient ROS generation was investigated. The gold and palladium-supported CuONRs nanocatalysts were evaluated for their potential applications in the fabrication of colorimetric biosensors to detect glucose oxidation by glucose oxidase (GOx). Glucose was used as a model analyte. The enzymatic reaction between GOx and b-D-glucose produces H 2 O 2 as a by-product, which is then catalytically converted to ROS by the nanoparticles.

Synthetic Metals, Dec 1, 2018

Dye-sensitized solar cells (DSSC) were fabricated by incorporating graphene materials as catalyst... more 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 comparison 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 TiO 2 containing rGONS at the anode. The value 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. − /I − liquid electrolyte, and it tends to induce formation of polyiodides, strongly reducing the efficiency of DSSCs. The aforementioned problems have boosted efforts towards the replacement of Pt with cheaper and/or more stable materials [5]. In this work DSSCs were fabricated using ITO coated glass and graphene based materials as electrode material. In 2010, Roy-Mayhew et al. [15] discovered that functionalizing graphene contributes to the high catalytic activity of graphene towards I − /I 3 − redox reaction, showing comparable performance to the Pt catalyst. Hence doped (with nitrogen) graphene is employed in this work. Metallophthalocyanines (MPc) have been successfully employed as sensitizers for dye-sensitized solar cells [16-18], as a result of their light-harvesting properties in the red and near-infrared (near-IR) spectral regions. A successful phthalocyanine sensitizer for DSSCs should show stable adsorption to the semiconductor surface, preferably by covalent bonds. Such stable adsorption is typically realized by carboxylate or sulfonate anchoring groups or, in some cases, by ligation of surface metal atoms using metal-free phthalocyanines [16,19,20]. There are limited reports on the use of MPcs with graphene for construction of DSSCs. There is one report using an unsubstituted ZnPc-CdS/CdSe quantum dots and Au nanoparticles /graphene oxide composite in DSSCs [21]. The current work reports on the use of carboxylated phthalocyanines (Fig. 1). As stated above, carboxy groups on the Pcs allow for formation of covalent bonds to the hydroxide groups on the surface of the TiO 2. Reduced graphene oxide nanosheets (rGONS) and nitrogen doped graphene oxide (NrGONS) on ITO are used as counter electrodes for DSSC in this work. rGONS modified TiO 2 photoanodes were also used to fabricate DSSCs. Graphene improves suppression of charge recombination at the photoanode/dye/electrolyte interface and also enhances electron transport in the photoanode [22].

RSC Advances, 2021

The formation of solid solutions represents a robust strategy for modulating the electronic prope... more The formation of solid solutions represents a robust strategy for modulating the electronic properties and improving the electrochemical performance of spinel ferrites. However, solid solutions have been predominantly prepared via wet chemical routes, which involve the use of harmful and/or expensive chemicals. In the present study, a facile, inexpensive and environmentally benign solventless route is employed for the composition-controlled synthesis of nanoscopic Ni 1Àx Co x Fe 2 O 4 (0 # x # 1) solid solutions. The physicochemical characterization of the samples was performed by p-XRD, SEM, EDX, XPS, TEM, HRTEM and UV-Vis techniques. A systematic investigation was also carried out to elucidate the electrochemical performance of the prepared nanospinels towards energy generation and storage. Based on the results of CV, GCD, and stability tests, the Ni 0.4 Co 0.6 Fe 2 O 4 electrode showed the highest performance for the supercapacitor electrode exhibiting a specific capacitance of 237 F g À1 , superior energy density of 10.3 W h kg À1 and a high power density with a peak value of 4208 W kg À1 , and 100% of its charge storage capacity was retained after 4000 cycles with 97% coulombic efficiency. For HER, the Ni 0.6 Co 0.4 Fe 2 O 4 and CoFe 2 O 4 electrodes showed low overpotentials of 168 and 169 mV, respectively, indicating better catalytic activity. For OER, the Ni 0.8 Co 0.2 Fe 2 O 4 electrode exhibited a lower overpotential of 320 mV at a current density of 10 mA cm À2 , with a Tafel slope of 79 mV dec À1 , demonstrating a fast and efficient process. These results indicated that nanospinel ferrite solid solutions could be employed as promising electrode materials for supercapacitor and water splitting applications.

Electrochimica Acta, Nov 1, 2020

This article describes an improved data acquisition system from a previous system dedicated to on... more This article describes an improved data acquisition system from a previous system dedicated to one-sensor site studies, aimed at recording ambient vibrations (microtremors). A multi-channel and/or remote triggering system is proposed. The system was conceived by IRD-Leas, France, and used at ISTerre, France, for research activities. The size, weight of this high quality system and its autonomy (no need to be connected to a laptop) make it a real portable device. The system acquires data with 24-bit delta-sigma ADCs in the 10-1000 sps range at 10-20 bit resolution on up to 18 channels in the multi-channel version. The input stage dynamics is available at ±2.5V or ±5V. The dynamic range varies, for example, from 108 dB at 100 sps to 90 dB at 250 sps. Gain is selectable from 1 (0 dB) to 8192 (78 dB) by powers of two (6 dB). Its very low level of internal noise allows recording of very low tension signals without missing code. Continuous recording and GPS may also be implemented in the system, and continuous recording is available. While primarily dedicated to ambient vibration recordings, this system can be connected to any type of instrument delivering an output tension in the ±5V range.

ACS Applied Materials & Interfaces, Dec 17, 2019

Nanomagnets-silica shell (Fe3O4@SiO2) decorated with Au@Pd nanoparticles (NPs) were synthesised s... more Nanomagnets-silica shell (Fe3O4@SiO2) decorated with Au@Pd nanoparticles (NPs) were synthesised successfully. The characterization of Fe3O4@SiO2-NH2-Au@PdNPs was achieved using several spectroscopic and microscopic techniques. The quantitative surface analysis was confirmed using X-ray photoelectron spectroscopy (XPS).

Journal of Photochemistry and Photobiology A-chemistry, Jun 1, 2021

Molecular Catalysis, Aug 1, 2022

Microchemical Journal, Sep 1, 2022

Microchemical Journal, Jul 1, 2022

Analytical Methods

Cardiovascular diseases (CVDs) affect the heart and blood vessels. CVDs are fatal when their diag... more Cardiovascular diseases (CVDs) affect the heart and blood vessels. CVDs are fatal when their diagnosis is delayed. C-reactive protein (CRP) is expressed in high concentrations during a cardiac event, thus quantitative monitoring of CRP necessary.

ACS applied nano materials, Dec 28, 2022

Journal of Porphyrins and Phthalocyanines, 2019

This work describes the adsorption of synthesized cobalt mono (CoPc) and binuclear phthalocyanine... more This work describes the adsorption of synthesized cobalt mono (CoPc) and binuclear phthalocyanines (CoBiPc) with single walled carbon nanotubes (SWCNT) to form SWCNT-CoPc or SWCNT-CoBiPc as non-covalent conjugates onto glassy carbon electrodes (GCE). The cobalt complexes and their SWCNT-conjugate-modified electrodes were studied for their electrocatalytic oxidation towards 4-chlorophenol. All modified electrodes showed improved catalytic current and stability towards the detection of 4-chlorophenol. The best activity was observed for the SWCNT-CoBiPc2 system in terms of current response and the SWCNT-CoBiPc1 system in terms of resistance to electrode fouling.

for their great support, sharing their knowledge and guidance during my degree programme. I thank... more for their great support, sharing their knowledge and guidance during my degree programme. I thank you all a million times and I remain eternally grateful to your assistance, Thank you!!! I also wish to thank my family: mom, dad and everybody (too numerous to mention by names), for the support and encouragement throughout my academic years at Rhodes University. Ndaweni (mom) your prayers saw me through and I am grateful to be your son. Dad your wishes have stayed with me, I hope I have not disappointed you in anyway. My friends (too numerous to mention by names), I thank you guys for making Grahamstown and Ghent enjoyable. To the Chemistry Department staff (technical and academic) and postgraduate students, especially S22, thank you guys for the discussions we shared and for providing such a conducive environment and making Grahamstown a home away from home. I also wish to acknowledge all the helpful discussions, constructive criticism and concerns raised by referees of published work of this thesis, Thank you!!! Finally, I will remain eternally grateful to Project AuTEK (Mintek and Gold-Fields) for the M.Sc. Scholarship and the National Research Foundation (NRF) for financial assistance. I also would like to thank Ghent University (Belgium) for the support and a rewarding experience through bilateral research project funded by NRF (SA) and UGent-BOF (Belgium).

Journal of Materials Chemistry B, 2023

Nanozymes are nanomaterials that exhibit enzyme-like activity upon exposure to a substrate soluti... more Nanozymes are nanomaterials that exhibit enzyme-like activity upon exposure to a substrate solution. The use of noble and platinum group metals enhances enzyme-like catalytic activity. However, noble metals are obtained at a high cost; therefore, their recovery after use is of high importance. Herein, we report the fabrication of indium tin oxide-silica nanoparticles decorated with palladium nanoparticles (ITO-SiO 2-prS-PdNPs). The ITO-SiO 2-prS-PdNPs were evaluated for peroxidase-like activity toward the oxidation of 3,3 0 ,5,5 0-tetramethylbenzidine (TMB) in the presence of H 2 O 2. A colour change from clear or colourless TMB to blue colour (oxidized TMB products) was observed confirming the peroxidase-like activity. A typical Michaelis-Menten enzyme-like behaviour is observed with K m values of 0.68 mM for H 2 O 2 and 0.47 mM for TMB, which are better than the reported values for horseradish peroxidase (HRP) for the same substrate. The peroxidase-like activity of ITO-SiO 2-prS-PdNPs was found to proceed via the electron-transfer mechanism. The ITO-SiO 2-prS-PdNPs were cleaned successfully after each use by rinsing with water and ethanol solution thus making the surface simple and easy to recover and reuse. A reusable and highly selective colorimetric assay for glucose detection based on the peroxidaselike activity of ITO-SiO 2-prS-PdNPs gave excellent results. ITO-SiO 2-prS-PdNPs exhibited a good linear range of 5.0-30 mM, a low limit of detection (LOD) of 1.84 mM and a limit of quantification (LOQ) of 6.14 mM. Finally, the nanozyme (ITO-SiO 2-prS-PdNPs) was successfully used to detect glucose in a complex newborn calf serum (NCS), representing a real sample.

Journal of Photochemistry and Photobiology A-chemistry, Aug 1, 2020

Abstract Dye sensitized solar cells (DSSCs) were fabricated by using 2(3,5-biscarboxyphenoxy), 9(... more Abstract Dye sensitized solar cells (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 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) exhibit significant improvement on the performance of the DSSC compared to our previous work on symmetrical carboxylated phthalocyanines with ɳ = 3.19%.

Electrochimica Acta, 2020

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Talanta, Aug 1, 2022

In this work, the preparation of glucose encapsulating nanoliposomes was achieved using two diffe... more In this work, the preparation of glucose encapsulating nanoliposomes was achieved using two different lipid formulations, labelled as F1 and F2. Both formulations contained phosphatidylcholine (PC), oleylamido-4-butanoic acid (OABA) and in addition, F1 had cholesterol (CHO) while F2 contained cholesteroyl hemisussinate (CHEMS). These formulations were studied for their pH sensitivity and controlled release of encapsulated glucose for indirect detection of prostate-specific antigen (PSA) using sandwich immunoassay. As a signal generator, encapsulated glucose in nanoliposomes was quantified directly using the personal glucose meter (PGM) and colorimetrically using peroxidase property of horseradish peroxidase (HRP) enzyme and Pd|PdO as nanozymes. Controlled release of the encapsulated glucose was achieved using the pH effect or Triton-X 100 as a surfactant to destabilize the liposomal structure. The F2 formulation showed maximum controlled release at acidic phosphate buffer saline (PBS, pH 5.0). The concentration of encapsulated glucose was found to be high in F2 formulation and these were applied for the indirect detection of PSA. The limit of detection (LOD) values for PSA were found to be 53 fg mL-1, 64 fg mL-1 and 10 fg mL-1 when HRP, Pd|PdO and PGM were respectively used. The detection signal was linear over a wide concentration range for PSA including the clinical range of 4-10 ng mL-1. The HRP system showed low LOD value when compared with Pd|PdO nanozymes. PGM system gave lowest LOD values owing to the sensitivity of the system towards glucose. Pd|PdO nanozyme system showed good stability over a wide temperature up to 80 °C. PGM system required less reaction time (2 min), low reagents and results were readily generated in digital format.

Materials Today Chemistry, Dec 1, 2022

RSC Advances, 2021

The emergence of nanoscience and nanotechnology has revitalised research interest in using copper... more The emergence of nanoscience and nanotechnology has revitalised research interest in using copper and its derived nanostructures to find exciting and novel applications. In this work, mono-and bimetallic gold and palladium nanoparticles supported on copper oxide nanorods (CuONRs) were prepared and their catalytic performance towards the reduction of H 2 O 2 to form reactive oxygen radical species (ROS) was evaluated. The characterisation using microscopy and spectroscopic techniques confirms the successful synthesis of CuONRs, CuONRs@Au 6 NPs, CuONRs@Pd 6 NPs and CuONRs@Au 3 Pd 3 NPs. The efficient generation of ROS was confirmed using UV-vis spectroscopy and 1,3-diphenylisobenzofuran (DPBF) as a radical scavenger. The CuONRs possess excellent catalytic reduction activity for H 2 O 2 by generating ROS. However, CuONRs also have lattice oxygens which do not participate in the catalytic reduction step. The lattice oxygens however allowed for the adsorption of gold and palladium nanoparticles (Au 6 NPs, Pd 6 NPs and Au 3 Pd 3 NPs) and thus enhanced catalytic reduction of H 2 O 2 to produce ROS. The produced ROS was subsequently involved in the catalytic oxidation of a chromogenic substrate (TMB), resulting in blue coloured diimine (TMBDI) complex which was monitored using UV-vis and could also be observed using the naked eye. The catalyst dependence on pH, temperature, and H 2 O 2 concentration towards efficient ROS generation was investigated. The gold and palladium-supported CuONRs nanocatalysts were evaluated for their potential applications in the fabrication of colorimetric biosensors to detect glucose oxidation by glucose oxidase (GOx). Glucose was used as a model analyte. The enzymatic reaction between GOx and b-D-glucose produces H 2 O 2 as a by-product, which is then catalytically converted to ROS by the nanoparticles.

Synthetic Metals, Dec 1, 2018

Dye-sensitized solar cells (DSSC) were fabricated by incorporating graphene materials as catalyst... more 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 comparison 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 TiO 2 containing rGONS at the anode. The value 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. − /I − liquid electrolyte, and it tends to induce formation of polyiodides, strongly reducing the efficiency of DSSCs. The aforementioned problems have boosted efforts towards the replacement of Pt with cheaper and/or more stable materials [5]. In this work DSSCs were fabricated using ITO coated glass and graphene based materials as electrode material. In 2010, Roy-Mayhew et al. [15] discovered that functionalizing graphene contributes to the high catalytic activity of graphene towards I − /I 3 − redox reaction, showing comparable performance to the Pt catalyst. Hence doped (with nitrogen) graphene is employed in this work. Metallophthalocyanines (MPc) have been successfully employed as sensitizers for dye-sensitized solar cells [16-18], as a result of their light-harvesting properties in the red and near-infrared (near-IR) spectral regions. A successful phthalocyanine sensitizer for DSSCs should show stable adsorption to the semiconductor surface, preferably by covalent bonds. Such stable adsorption is typically realized by carboxylate or sulfonate anchoring groups or, in some cases, by ligation of surface metal atoms using metal-free phthalocyanines [16,19,20]. There are limited reports on the use of MPcs with graphene for construction of DSSCs. There is one report using an unsubstituted ZnPc-CdS/CdSe quantum dots and Au nanoparticles /graphene oxide composite in DSSCs [21]. The current work reports on the use of carboxylated phthalocyanines (Fig. 1). As stated above, carboxy groups on the Pcs allow for formation of covalent bonds to the hydroxide groups on the surface of the TiO 2. Reduced graphene oxide nanosheets (rGONS) and nitrogen doped graphene oxide (NrGONS) on ITO are used as counter electrodes for DSSC in this work. rGONS modified TiO 2 photoanodes were also used to fabricate DSSCs. Graphene improves suppression of charge recombination at the photoanode/dye/electrolyte interface and also enhances electron transport in the photoanode [22].

RSC Advances, 2021

The formation of solid solutions represents a robust strategy for modulating the electronic prope... more The formation of solid solutions represents a robust strategy for modulating the electronic properties and improving the electrochemical performance of spinel ferrites. However, solid solutions have been predominantly prepared via wet chemical routes, which involve the use of harmful and/or expensive chemicals. In the present study, a facile, inexpensive and environmentally benign solventless route is employed for the composition-controlled synthesis of nanoscopic Ni 1Àx Co x Fe 2 O 4 (0 # x # 1) solid solutions. The physicochemical characterization of the samples was performed by p-XRD, SEM, EDX, XPS, TEM, HRTEM and UV-Vis techniques. A systematic investigation was also carried out to elucidate the electrochemical performance of the prepared nanospinels towards energy generation and storage. Based on the results of CV, GCD, and stability tests, the Ni 0.4 Co 0.6 Fe 2 O 4 electrode showed the highest performance for the supercapacitor electrode exhibiting a specific capacitance of 237 F g À1 , superior energy density of 10.3 W h kg À1 and a high power density with a peak value of 4208 W kg À1 , and 100% of its charge storage capacity was retained after 4000 cycles with 97% coulombic efficiency. For HER, the Ni 0.6 Co 0.4 Fe 2 O 4 and CoFe 2 O 4 electrodes showed low overpotentials of 168 and 169 mV, respectively, indicating better catalytic activity. For OER, the Ni 0.8 Co 0.2 Fe 2 O 4 electrode exhibited a lower overpotential of 320 mV at a current density of 10 mA cm À2 , with a Tafel slope of 79 mV dec À1 , demonstrating a fast and efficient process. These results indicated that nanospinel ferrite solid solutions could be employed as promising electrode materials for supercapacitor and water splitting applications.

Electrochimica Acta, Nov 1, 2020

This article describes an improved data acquisition system from a previous system dedicated to on... more This article describes an improved data acquisition system from a previous system dedicated to one-sensor site studies, aimed at recording ambient vibrations (microtremors). A multi-channel and/or remote triggering system is proposed. The system was conceived by IRD-Leas, France, and used at ISTerre, France, for research activities. The size, weight of this high quality system and its autonomy (no need to be connected to a laptop) make it a real portable device. The system acquires data with 24-bit delta-sigma ADCs in the 10-1000 sps range at 10-20 bit resolution on up to 18 channels in the multi-channel version. The input stage dynamics is available at ±2.5V or ±5V. The dynamic range varies, for example, from 108 dB at 100 sps to 90 dB at 250 sps. Gain is selectable from 1 (0 dB) to 8192 (78 dB) by powers of two (6 dB). Its very low level of internal noise allows recording of very low tension signals without missing code. Continuous recording and GPS may also be implemented in the system, and continuous recording is available. While primarily dedicated to ambient vibration recordings, this system can be connected to any type of instrument delivering an output tension in the ±5V range.

ACS Applied Materials & Interfaces, Dec 17, 2019

Nanomagnets-silica shell (Fe3O4@SiO2) decorated with Au@Pd nanoparticles (NPs) were synthesised s... more Nanomagnets-silica shell (Fe3O4@SiO2) decorated with Au@Pd nanoparticles (NPs) were synthesised successfully. The characterization of Fe3O4@SiO2-NH2-Au@PdNPs was achieved using several spectroscopic and microscopic techniques. The quantitative surface analysis was confirmed using X-ray photoelectron spectroscopy (XPS).

Journal of Photochemistry and Photobiology A-chemistry, Jun 1, 2021

Molecular Catalysis, Aug 1, 2022

Microchemical Journal, Sep 1, 2022

Microchemical Journal, Jul 1, 2022

Analytical Methods

Cardiovascular diseases (CVDs) affect the heart and blood vessels. CVDs are fatal when their diag... more Cardiovascular diseases (CVDs) affect the heart and blood vessels. CVDs are fatal when their diagnosis is delayed. C-reactive protein (CRP) is expressed in high concentrations during a cardiac event, thus quantitative monitoring of CRP necessary.