Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2017
This study reports on the design of novel nanoconjugates of graphene quantum dots (GQDs) and tetr... more This study reports on the design of novel nanoconjugates of graphene quantum dots (GQDs) and tetra or octa-mercaptopyridine-substituted zinc and aluminium phthalocyanines (Pcs) deployed as fluorescence "turn ON" nanoprobes. The phthalocyanines were separately adsorbed onto the planar structure of graphene quantum dots (GQDs) via π-π stacking interaction to form GQDs-mercaptopyridine Pcs nanoconjugates. The quaternized Pc complexes could also interact with the GQDs through electrostatic attraction due to the positive charges on the Pcs ring substituents and the negative charges on the surface of GQDs. The fluorescence emission of the GQDs was quenched upon coordination to the respective Pcs. However, the fluorescence emission was "turned ON" in the presence of Hg(2+) employed as a test analyte. The mechanism of the "turn ON" of the GQDs emission in the nanoconjugates is ascribed to the strong affinity of Hg(2+) to bind with the bridging sulfur on the Pcs periphery thereby disrupting the π-π stacking interaction between the GQDs and the Pcs with a consequent "turn ON" of the coordinated GQDs' fluorescence.
A nanocomposite of (2,2,6,6-tetramethylpiperidin-1-yl)oxyl substituted zinc phthalocyanine and gr... more A nanocomposite of (2,2,6,6-tetramethylpiperidin-1-yl)oxyl substituted zinc phthalocyanine and graphene quantum dots is a selective fluorescence sensor for ascorbic acid.
Journal of Photochemistry and Photobiology A: Chemistry, 2016
Abstract Graphene quantum dots grafted with polyethyleneimine (GQDs-PEI) and Au@Ag core-shell nan... more Abstract Graphene quantum dots grafted with polyethyleneimine (GQDs-PEI) and Au@Ag core-shell nanoparticles blend was demonstrated to be a novel biosensing nanoprobe for the rapid and highly sensitive detection of biothiols such as cysteine (Cys), homocysteine (Hcys) and glutathione (GSH). The fluorescence emission of GQDs-PEI was quenched efficiently upon interaction with Au@Ag core-shell nanoparticles. The quenched fluorescence emission of the GQDs-PEI was restored in the presence of the biothiols. The fluorimetric sensing is based on the strong affinity between the mercapto (SH) groups of the biothiols and the Au@Ag core-shell nanoparticles by which the interaction between GQDs-PEI and Au@Ag core-shell nanoparticles was disrupted with a consequent modulation (‘turn-on’) of the quenched GQDs-PEI emission. Thus, a new, simple, rapid and highly sensitive fluorescence nanoprobe for detecting biothiols has been developed in this work.
Journal of Photochemistry and Photobiology A: Chemistry, 2016
Abstract Graphene quantum dots (GQDs) and zinc phthalocyanines interactions in different modes (c... more Abstract Graphene quantum dots (GQDs) and zinc phthalocyanines interactions in different modes (covalent and non-covalent) are reported in this study. GQDs were covalently attached to the following complexes: zinc tetraamino phthalocyanine (ZnTAPc) via amide coupling, zinc tetracarboxyphenoxy Pc (ZnTCPPc) (π–π interaction) and cationic zinc tetrapyridiloxy Pc (ZnTmPyPc) (ionic interaction). GQDs fluorescence was quenched in the presence of the ZnPc derivatives. The nanoensembles of GQDs–ZnPcs showed stimulated emissions of the ZnPcs. The suggested quenching mechanism is through Forster resonance energy transfer (FRET). These novel nanoensembles hold promise for various optical and luminescence based applications.
Novel fluorescent (FL) ag-oxCDs are derived from expired agar and oxalate. ag-oxCDs are selective... more Novel fluorescent (FL) ag-oxCDs are derived from expired agar and oxalate. ag-oxCDs are selective for Fe3+ ions detection (LOD ∼ 75 μM) via FL “turn ON” mechanism. FL nanosensor based on agar biomass with upscale potential is developed herein.
This study assesses gas flaring and venting impacts in some oil producing areas in the Niger-Delt... more This study assesses gas flaring and venting impacts in some oil producing areas in the Niger-Delta of Nigeria. The research instrument adopted for this study was the questionnaire survey and laboratory analysis, both microbiological and physico-chemical. The analysis of the data was done using simple descriptive analysis of frequency distribution of the relevant statistical information, supplemented by Chi-Square (X2) statistical method. Soil samples obtained from selected flare sites were analyzed and they indicated a negative impact on the microbial content of the soil. Rain water samples collected from different locations at different times and analyzed revealed a significant level of acidity (4.5-6.9) which causes damage to property and affect crops yield. Nitrates produced by the gas flare which varied from 0.12 to 0.47 mg/L result in the production of dilute nitric acid which is also corrosive. A survey carried out in this study revealed that the majority of Nigerians believe ...
In this study, the synchronous removal of Pb and Cd ions from aqueous solutions by colloidal part... more In this study, the synchronous removal of Pb and Cd ions from aqueous solutions by colloidal particles made from rice husk ash (RHA) in aqueous sodium dodecyl sulfate (SDS) solution was investigated. The RHA derived from rice husk waste generated from the rice mills in Wukari, north-eastern Nigeria was combined with sodium dodecyl sulfate (SDS) for the metal ions adsorption. The adsorption studies under different experimental conditions were optimized and the removal of Pb and Cd ions was highly pH dependent. The results indicated that pH 8.0 was the optimum for the removal of the metal ions. Adsorption equilibration time was achieved in 2 hours with maximum removal efficiency of the metals ions attained at 71.8 and 88.9 % for Pb and Cd respectively. The equilibrium data were satisfactorily fitted to Langmuir and Freudlich isotherms. The Langmuir isotherm models gave a better representation of the data than the Freudlich isotherms. The RHA-SDS combination showed higher adsorption ca...
Heavy metal pollution is a major environmental problem, especially around highways with high traf... more Heavy metal pollution is a major environmental problem, especially around highways with high traffic density. This study investigates the levels of Pb, Cd, Zn and Cu in roadside soils of Wukari section of the Wukari-Jalingo highway, Taraba state, Nigeria. Samples were randomly collected and analyzed using standard methods. The mean concentrations (µg/g) of Pb, Cd, Zn and Cu from all sample sites ranged: 89.6-247.0, 0.15-5.3, 26.8-163.0 and 7.1-61.2 respectively. The extent of the heavy metals contamination was assessed, as analytical data were subjected to pollution calculation methods. The contamination factors (CF) reveal extreme contamination of the sites and an increasing trend in the heavy metals concentrations was observed in sites with more human activities. The pollution load index (PLI) showed that the sites are severely polluted as the PLI of the metals from each sample site exceeded the PLI of the background (control) sample (0.7). Spearman’s rank correlation analysis sho...
Thymine Zn phthalocyanine turned off the fluorescence of graphene quantum dots, which was subsequ... more Thymine Zn phthalocyanine turned off the fluorescence of graphene quantum dots, which was subsequently turned on by Hg2+ for its sensitive detection.
The global pandemic of COVID-19 is an example of how quickly a disease-causing virus can take roo... more The global pandemic of COVID-19 is an example of how quickly a disease-causing virus can take root and threaten our civilization. Nowadays, ultrasensitive and rapid detection of contagious pathogens is...
Ball-type zinc and gallium phthalocyanines were covalently linked to graphene and semiconductor q... more Ball-type zinc and gallium phthalocyanines were covalently linked to graphene and semiconductor quantum dots resulting in enhanced triplet parameters and nonlinear optical performance.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2017
This study reports on the design of novel nanoconjugates of graphene quantum dots (GQDs) and tetr... more This study reports on the design of novel nanoconjugates of graphene quantum dots (GQDs) and tetra or octa-mercaptopyridine-substituted zinc and aluminium phthalocyanines (Pcs) deployed as fluorescence "turn ON" nanoprobes. The phthalocyanines were separately adsorbed onto the planar structure of graphene quantum dots (GQDs) via π-π stacking interaction to form GQDs-mercaptopyridine Pcs nanoconjugates. The quaternized Pc complexes could also interact with the GQDs through electrostatic attraction due to the positive charges on the Pcs ring substituents and the negative charges on the surface of GQDs. The fluorescence emission of the GQDs was quenched upon coordination to the respective Pcs. However, the fluorescence emission was "turned ON" in the presence of Hg(2+) employed as a test analyte. The mechanism of the "turn ON" of the GQDs emission in the nanoconjugates is ascribed to the strong affinity of Hg(2+) to bind with the bridging sulfur on the Pcs periphery thereby disrupting the π-π stacking interaction between the GQDs and the Pcs with a consequent "turn ON" of the coordinated GQDs' fluorescence.
A nanocomposite of (2,2,6,6-tetramethylpiperidin-1-yl)oxyl substituted zinc phthalocyanine and gr... more A nanocomposite of (2,2,6,6-tetramethylpiperidin-1-yl)oxyl substituted zinc phthalocyanine and graphene quantum dots is a selective fluorescence sensor for ascorbic acid.
Journal of Photochemistry and Photobiology A: Chemistry, 2016
Abstract Graphene quantum dots grafted with polyethyleneimine (GQDs-PEI) and Au@Ag core-shell nan... more Abstract Graphene quantum dots grafted with polyethyleneimine (GQDs-PEI) and Au@Ag core-shell nanoparticles blend was demonstrated to be a novel biosensing nanoprobe for the rapid and highly sensitive detection of biothiols such as cysteine (Cys), homocysteine (Hcys) and glutathione (GSH). The fluorescence emission of GQDs-PEI was quenched efficiently upon interaction with Au@Ag core-shell nanoparticles. The quenched fluorescence emission of the GQDs-PEI was restored in the presence of the biothiols. The fluorimetric sensing is based on the strong affinity between the mercapto (SH) groups of the biothiols and the Au@Ag core-shell nanoparticles by which the interaction between GQDs-PEI and Au@Ag core-shell nanoparticles was disrupted with a consequent modulation (‘turn-on’) of the quenched GQDs-PEI emission. Thus, a new, simple, rapid and highly sensitive fluorescence nanoprobe for detecting biothiols has been developed in this work.
Journal of Photochemistry and Photobiology A: Chemistry, 2016
Abstract Graphene quantum dots (GQDs) and zinc phthalocyanines interactions in different modes (c... more Abstract Graphene quantum dots (GQDs) and zinc phthalocyanines interactions in different modes (covalent and non-covalent) are reported in this study. GQDs were covalently attached to the following complexes: zinc tetraamino phthalocyanine (ZnTAPc) via amide coupling, zinc tetracarboxyphenoxy Pc (ZnTCPPc) (π–π interaction) and cationic zinc tetrapyridiloxy Pc (ZnTmPyPc) (ionic interaction). GQDs fluorescence was quenched in the presence of the ZnPc derivatives. The nanoensembles of GQDs–ZnPcs showed stimulated emissions of the ZnPcs. The suggested quenching mechanism is through Forster resonance energy transfer (FRET). These novel nanoensembles hold promise for various optical and luminescence based applications.
Novel fluorescent (FL) ag-oxCDs are derived from expired agar and oxalate. ag-oxCDs are selective... more Novel fluorescent (FL) ag-oxCDs are derived from expired agar and oxalate. ag-oxCDs are selective for Fe3+ ions detection (LOD ∼ 75 μM) via FL “turn ON” mechanism. FL nanosensor based on agar biomass with upscale potential is developed herein.
This study assesses gas flaring and venting impacts in some oil producing areas in the Niger-Delt... more This study assesses gas flaring and venting impacts in some oil producing areas in the Niger-Delta of Nigeria. The research instrument adopted for this study was the questionnaire survey and laboratory analysis, both microbiological and physico-chemical. The analysis of the data was done using simple descriptive analysis of frequency distribution of the relevant statistical information, supplemented by Chi-Square (X2) statistical method. Soil samples obtained from selected flare sites were analyzed and they indicated a negative impact on the microbial content of the soil. Rain water samples collected from different locations at different times and analyzed revealed a significant level of acidity (4.5-6.9) which causes damage to property and affect crops yield. Nitrates produced by the gas flare which varied from 0.12 to 0.47 mg/L result in the production of dilute nitric acid which is also corrosive. A survey carried out in this study revealed that the majority of Nigerians believe ...
In this study, the synchronous removal of Pb and Cd ions from aqueous solutions by colloidal part... more In this study, the synchronous removal of Pb and Cd ions from aqueous solutions by colloidal particles made from rice husk ash (RHA) in aqueous sodium dodecyl sulfate (SDS) solution was investigated. The RHA derived from rice husk waste generated from the rice mills in Wukari, north-eastern Nigeria was combined with sodium dodecyl sulfate (SDS) for the metal ions adsorption. The adsorption studies under different experimental conditions were optimized and the removal of Pb and Cd ions was highly pH dependent. The results indicated that pH 8.0 was the optimum for the removal of the metal ions. Adsorption equilibration time was achieved in 2 hours with maximum removal efficiency of the metals ions attained at 71.8 and 88.9 % for Pb and Cd respectively. The equilibrium data were satisfactorily fitted to Langmuir and Freudlich isotherms. The Langmuir isotherm models gave a better representation of the data than the Freudlich isotherms. The RHA-SDS combination showed higher adsorption ca...
Heavy metal pollution is a major environmental problem, especially around highways with high traf... more Heavy metal pollution is a major environmental problem, especially around highways with high traffic density. This study investigates the levels of Pb, Cd, Zn and Cu in roadside soils of Wukari section of the Wukari-Jalingo highway, Taraba state, Nigeria. Samples were randomly collected and analyzed using standard methods. The mean concentrations (µg/g) of Pb, Cd, Zn and Cu from all sample sites ranged: 89.6-247.0, 0.15-5.3, 26.8-163.0 and 7.1-61.2 respectively. The extent of the heavy metals contamination was assessed, as analytical data were subjected to pollution calculation methods. The contamination factors (CF) reveal extreme contamination of the sites and an increasing trend in the heavy metals concentrations was observed in sites with more human activities. The pollution load index (PLI) showed that the sites are severely polluted as the PLI of the metals from each sample site exceeded the PLI of the background (control) sample (0.7). Spearman’s rank correlation analysis sho...
Thymine Zn phthalocyanine turned off the fluorescence of graphene quantum dots, which was subsequ... more Thymine Zn phthalocyanine turned off the fluorescence of graphene quantum dots, which was subsequently turned on by Hg2+ for its sensitive detection.
The global pandemic of COVID-19 is an example of how quickly a disease-causing virus can take roo... more The global pandemic of COVID-19 is an example of how quickly a disease-causing virus can take root and threaten our civilization. Nowadays, ultrasensitive and rapid detection of contagious pathogens is...
Ball-type zinc and gallium phthalocyanines were covalently linked to graphene and semiconductor q... more Ball-type zinc and gallium phthalocyanines were covalently linked to graphene and semiconductor quantum dots resulting in enhanced triplet parameters and nonlinear optical performance.
Graphene quantum dots (GQDs) have emerged as novel tools for the fabrication and design of nanose... more Graphene quantum dots (GQDs) have emerged as novel tools for the fabrication and design of nanosensors and biosensors. GQDs exhibit excellent photoluminescence properties which make them effective alternatives (in terms of non-toxicity and aqueous dispersibility) to colloidal metal quantum dots (QDs) that have attracted much attention for decades [1]. The supramolecular assembles of GQDs and macrocycles with extended π-conjugated systems such as phthalocyanines (Pcs) could considerably extend GQDs-based nanosensors fabrication due to the excellent optical properties of phthalocyanines [2]. Mercaptopyridine-substituted zinc and aluminum phthalocyanines and 2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) derivatized zinc phthalocyanine were coordinated to GQDs via π-π interaction to form GQDs-Pcs nanoconjugates. The GQDs fluorescence emission was substantially quenched in the GQDs-Pcs nanoconjugates which was ascribed to energy transfer (FRET) process between GQDs and the respective Pcs. However, for the GQDs-mercaptopyridine-Pcs nanoconjugates, the emission of the GQDs was “switched ON” in the presence of Hg2+ as a test analyte. On the other hand,, the GQDs-TEMPO-ZnPc nanoconjugates were deployed for ascorbic acid (AA) detection. The GQDs emission was switched to the “ON” mode in the presence of AA following the fluorescence principle of “off-on” mechanism. The novel nanoprobes were highly sensitive and selective towards Hg2+ and AA, respectively. The limits of detection were in the nanomolar range. These novel nanoprobes function on the basis of fluorescence “turn ON” process which is more reliable than the widely reported “turn OFF” process.
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Papers by Ojodomo Achadu, PhD