| 1. |
- Albaqami, Munirah D., et al.
(författare)
-
The fast nucleation/growth of Co3O4 nanowires on cotton silk : the facile development of a potentiometric uric acid biosensor
- 2022
-
Ingår i: RSC Advances. - : Royal Society of Chemistry. - 2046-2069. ; 12:29, s. 18321-18332
-
Tidskriftsartikel (refereegranskat)abstract
- In this study, we have used cotton silk as a source of abundant hydroxyl groups for the fast nucleation/growth of cobalt oxide (Co3O4) nanowires via a hydrothermal method. The crystal planes of the Co3O4 nanowires well matched the cubic phase. The as-synthesized Co3O4 nanowires mainly contained cobalt and oxygen elements and were found to be highly sensitive towards uric acid in 0.01 M phosphate buffer solution at pH 7.4. Importantly, the Co3O4 nanowires exhibited a large surface area, which was heavily utilized during the immobilization of the enzyme uricase via a physical adsorption method. The potentiometric response of the uricase-immobilizing Co3O4 nanowires was measured in the presence of uric acid (UA) against a silver/silver chloride (Ag/AgCl) reference electrode. The newly fabricated uric acid biosensor possessed a low limit of detection of 1.0 +/- 0.2 nM with a wide linear range of 5 nM to 10 mM and sensitivity of 30.6 mV dec(-1). Additionally, several related parameters of the developed uric acid biosensor were investigated, such as the repeatability, reproducibility, storage stability, selectivity, and dynamic response time, and these were found to be satisfactory. The good performance of the Co3O4 nanowires was verified based on the fast charge-transfer kinetics, as confirmed via electrochemical impedance spectroscopy. The successful practical use of the uric acid biosensor was demonstrated based on the recovery method. The observed performance of the uricase-immobilizing Co3O4 nanowires revealed that they could be considered as a promising and alternative tool for the detection of uric acid under both in vitro and in vivo conditions. Also, the use of cotton silk as a source of abundant hydroxyl groups may be considered for the remarkably fast nucleation/growth of other metal-oxide nanostructures, thereby facilitating the fabrication of functional electrochemical devices, such as batteries, water-splitting devices, and supercapacitors.
|
|
| 2. |
- Ali Soomro, Razium, et al.
(författare)
-
Glycine-assisted preparation of Co3O4 nanoflakes with enhanced performance for non-enzymatic glucose sensing
- 2015
-
Ingår i: MATERIALS EXPRESS. - : AMER SCIENTIFIC PUBLISHERS. - 2158-5849. ; 5:5, s. 437-444
-
Tidskriftsartikel (refereegranskat)abstract
- In this study a simple, inexpensive and efficient route is proposed to synthesise attractive cobalt oxide (Co3O4) nanostructures using glycine as an effective growth controller and regulator. The as-synthesised Co3O4 nanostructures were observed to possess unique nanoflake shape morphological features with highly dense distribution. The formation of Co3O4 nanoflakes (Co3O4 NFKs) was elaborately explored using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Scanning electron microscopy (SEM) respectively. The unique Co3O4 nanoflakes were known to possess excellent electro-catalytic potential for the oxidation of glucose in alkaline medium. This potential property allowed successful development of highly sensitive (1180 mu A mM(-1) cm(-2)), selective and stable non-enzymatic glucose sensor. In addition, the developed sensor had a wide working range (0.1-5.0 mM), low limit of detection (0.7 mu M), and excellent reproducibility, besides the capability of analysing real blood glucose samples.
|
|
| 3. |
- Alshgari, Razan A., et al.
(författare)
-
Manipulation of CuO morphology for efficient potentiometric detection of urea via slow nucleation/growth kinetics exerted by mixed solvents
- 2022
-
Ingår i: Journal of materials science. Materials in electronics. - : SPRINGER. - 0957-4522 .- 1573-482X. ; 33, s. 25250-25262
-
Tidskriftsartikel (refereegranskat)abstract
- Controlling the reaction kinetics during the nucleation/growth of cupric oxide (CuO) nanostructures is very critical in order to achieve a specific and well-defined morphology. For this purpose, we have slowed down the reaction speed using a mixed solvent concept and successfully obtained a chain-like morphology of CuO nanostructures using hydrothermal method. The CuO chain-like morphology was synthesized using a 1:1 (v/v) ratio of ethylene glycol and water. The morphology and crystalline features of CuO were studied by scanning electron microscopy (SEM) and powder X-ray diffraction techniques. The high resolution transmission electron microscopy revealed 5 nm crystallite size for the CuO material prepared in the mixed solvents. The obtained results have shown that the prepared CuO chains had a monocline phase, containing only Cu and O as main elements as confirmed by energy dispersive spectroscopy. This unique morphology obtained from mixed solvent process has provided a better surface for the loading of urease enzyme, thus it enabled the development of sensitive and selective urea biosensor in phosphate buffer solution of pH 7.4. The physical adsorption method was used to immobilize urease enzyme onto the nano surface of CuO. The fabricated biosensor based on urease/CuO chains has shown a dynamic linear range from 0.0005 to15 mM with a low limit of detection 0.0001 mM. Additionally, a fast response time aroudn1s, h high selectivity, stability, repeatability, storage time, and reproducibility were observed. The effect of pH and temperature on the potentiometric signal of the developed biosensor was also examined. Importantly, the practical aspects of the fabricated urea biosensor were probed and the obtained percent recovery results revealed an outstanding performance. The strategy of using mixed solvent with equal volume ratio would be useful for the preparation of other metal oxides with improved catalytic properties for a wide range of clinical, biomedical and other related applications.
|
|
| 4. |
- Chang, Abdul Sattar, et al.
(författare)
-
Pd-Co3O4-based nanostructures for the development of enzyme-free glucose sensor
- 2022
-
Ingår i: Bulletin of Materials Science. - : INDIAN ACAD SCIENCES. - 0250-4707 .- 0973-7669. ; 45:2
-
Tidskriftsartikel (refereegranskat)abstract
- In this study, we report enzyme-free glucose sensors based on palladium (Pd) nanoparticles deposited onto Co3O4 nanostructures. A simple, low-temperature aqueous method was used for the fabrication of Co3O4 nanostructures. Then, Pd nanoparticles were decorated onto Co3O4 nanostructures using the ultraviolet reduction method. Morphology, elemental composition and crystalline features of the proposed composite nanostructures were investigated by powder X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy techniques. Cyclic voltammetry and linear sweep voltammetry were used to investigate the electrochemical behaviour of Pd-Co3O4 nanostructures during glucose sensing. The proposed nanostructures showed excellent electrochemical activity for the quantitative detection of glucose at a potential of 0.6 V vs. Ag/AgCl. Importantly, the fabricated enzyme-free glucose sensor shows a linear response over the range of 1-6.0 mM glucose, with a limit of detection of 0.01 mM. The interference study was also carried out to probe the selectivity of Pd-Co3O4 nanostructures towards glucose detection in the presence of different interfering substances. The combined results attest that the as-synthesized Pd-Co3O4 nanostructures are highly stable and selective for the detection of glucose, suggesting their great potential for the quantitative determination of glucose in different biological fluids.
|
|
| 5. |
- Ujan, Zaheer Ahmed, et al.
(författare)
-
The Crystal Disorder into ZnO with Addition of Bromine and Its Outperform Role in the Photodegradation of Methylene Blue
- 2022
-
Ingår i: Journal of cluster science. - : SPRINGER/PLENUM PUBLISHERS. - 1040-7278 .- 1572-8862. ; 33:1, s. 281-291
-
Tidskriftsartikel (refereegranskat)abstract
- In this research work, bromine (Br) is successfully doped into ZnO nanostructures using solvothermal method. The morphology, crystalline features, and composition of Br doped ZnO nanostructures were studied by scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive X ray spectroscopy (EDX) respectively. These newly prepared nanostructured materials were tested as photocatalysts for the photodegradation of methylene blue (MB) in aqueous solution under UV light. The kinetic rate constants were observed in the order (20% Br/ZnO > 15% Br/ZnO > 10% Br/ZnO > 5% Br/ZnO >pristine ZnO), thus they are indicating that the increasing Br dopant level has linear effect on the photodegradation of MB. The photocatalytic degradation efficiency of 60% was achieved for the pristine ZnO during the irradiation of UV light for 5 h, however 20% Br doped ZnO nanostructures has shown enhanced degradation efficiency of 97.63% during the irradiation of UV light for short interval of time of 2.2 h. The 20% Br/ZnO describes the highest rate constant value of (24.13 x 10(-3) min(-1)), for time period of 2.2 h and this values is about 8 and 4 times higher than the pristine ZnO (3.72 x 10(-3) min(-1)) and 5% Br/ZnO (6.13 x 10(-3) min(-1)), respectively. The obtained results of 20% Br doped ZnO sample are superior or equal in performance than the recently reported works. The catalytic mechanism is also proposed and it indicates the role of electrons coming from the bromine ion might act as radical for the degradation of MB. The present approach is simpler, environment friendly, scalable and could be of great consideration for the diverse energy and environment related applications. Graphic
|
|
| 6. |
- Abbasi, Mazhar Ali, et al.
(författare)
-
Decoration of ZnO nanorods with coral reefs like NiO nanostructures by the hydrothermal growth method and their luminescence study
- 2014
-
Ingår i: Materials. - : MDPI. - 1996-1944. ; 7:1, s. 430-440
-
Tidskriftsartikel (refereegranskat)abstract
- Composite nanostructures of coral reefs like p-type NiO on n-type ZnO nanorods have been decorate on fluorine-doped tin oxide glass substrates by the hydrothermal growth. Structural characterization was performed by field emission scanning electron microscopy, high-resolution transmission electron microscopy and X-ray diffraction techniques. This investigation has shown that the adopted synthesis has led to high crystalline quality nanostructures. Morphological study shows that the coral reefs like nanostructures are densely packed on the ZnO nanorods. Cathodoluminescence (CL) spectra for the synthesized composite nanostructures were dominated by a near band gap emission at 380 nm and by a broad interstitial defect related luminescence centered at ~630 nm. Spatially resolved CL images reveal that the luminescence originates mainly from the ZnO nanorods.
|
|
| 7. |
- Abbasi, Mazhar Ali, et al.
(författare)
-
Potentiometric Zinc Ion Sensor Based on Honeycomb-Like NiO Nanostructures
- 2012
-
Ingår i: Sensors. - : MDPI. - 1424-8220. ; 12:11, s. 15424-15437
-
Tidskriftsartikel (refereegranskat)abstract
- In this study honeycomb-like NiO nanostructures were grown on nickel foam by a simple hydrothermal growth method. The NiO nanostructures were characterized by field emission electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) techniques. The characterized NiO nanostructures were uniform, dense and polycrystalline in the crystal phase. In addition to this, the NiO nanostructures were used in the development of a zinc ion sensor electrode by functionalization with the highly selective zinc ion ionophore 12-crown-4. The developed zinc ion sensor electrode has shown a good linear potentiometric response for a wide range of zinc ion concentrations, ranging from 0.001 mM to 100 mM, with sensitivity of 36 mV/decade. The detection limit of the present zinc ion sensor was found to be 0.0005 mM and it also displays a fast response time of less than 10 s. The proposed zinc ion sensor electrode has also shown good reproducibility, repeatability, storage stability and selectivity. The zinc ion sensor based on the functionalized NiO nanostructures was also used as indicator electrode in potentiometric titrations and it has demonstrated an acceptable stoichiometric relationship for the determination of zinc ion in unknown samples. The NiO nanostructures-based zinc ion sensor has potential for analysing zinc ion in various industrial, clinical and other real samples.
|
|
| 8. |
- Abbasi, Mazhar Ali, et al.
(författare)
-
The fabrication of white light-emitting diodes using the n-ZnO/NiO/p-GaN heterojunction with enhanced luminescence
- 2013
-
Ingår i: Nanoscale Research Letters. - 1931-7573 .- 1556-276X. ; 8:320
-
Tidskriftsartikel (refereegranskat)abstract
- Cheap and efficient white light-emitting diodes (LEDs) are of great interest due to the energy crisis all over the world. Herein, we have developed heterojunction LEDs based on the well-aligned ZnO nanorods and nanotubes on the p-type GaN with the insertion of the NiO buffer layer that showed enhancement in the light emission. Scanning electron microscopy have well demonstrated the arrays of the ZnO nanorods and the proper etching into the nanotubes. X-ray diffraction study describes the wurtzite crystal structure array of ZnO nanorods with the involvement of GaN at the (002) peak. The cathodoluminescence spectra represent strong and broad visible emission peaks compared to the UV emission and a weak peak at 425 nm which is originated from GaN. Electroluminescence study has shown highly improved luminescence response for the LEDs fabricated with NiO buffer layer compared to that without NiO layer. Introducing a sandwich-thin layer of NiO between the n-type ZnO and the p-type GaN will possibly block the injection of electrons from the ZnO to the GaN. Moreover, the presence of NiO buffer layer might create the confinement effect.
|
|
| 9. |
- Ali Soomro, Razium, et al.
(författare)
-
A highly selective and sensitive electrochemical determination of melamine based on succinic acid functionalized copper oxide nanostructures
- 2015
-
Ingår i: RSC Advances. - : ROYAL SOC CHEMISTRY. - 2046-2069. ; 5:127, s. 105090-105097
-
Tidskriftsartikel (refereegranskat)abstract
- This study presents the development of a highly selective and sensitive electrochemical sensor for the determination of melamine from aqueous environments. The sensor system is based on functionalised marigold-like CuO nanostructures fabricated using a controlled hydrothermal process, where the utilised succinic acid is considered to play a dual role as a functionalising and growth controlling agent (modifier). The fabricated nanostructures exhibit sharp and well-ordered structural features with dimensions (thickness) in the range of 10-50 nm. The sensor system exhibits strong linearity within the concentration range of 0.1 x 10(-9) to 5.6 x 10(-9) M and demonstrates an excellent limit of detection up to 0.1 x 10(-10) M. The extreme selectivity and sensing capability of the developed sensor is attributed to the synergy of selective interaction between succinic acid and melamine moieties, and the high surface area of marigold-like CuO nanostructures. In addition to this, the developed sensor was also utilised for the determination of melamine from real milk samples collected from different regions of Hyderabad, Pakistan. The obtained excellent recoveries proved the feasibility of the sensor for real life applications. The sensor system offers an operative measure for detecting extremely low melamine content with high selectivity in food contents.
|
|
| 10. |
- Ali Soomro, Razium, et al.
(författare)
-
Amino acid assisted growth of CuO nanostructures and their potential application in electrochemical sensing of organophosphate pesticide
- 2016
-
Ingår i: Electrochimica Acta. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0013-4686 .- 1873-3859. ; 190, s. 972-979
-
Tidskriftsartikel (refereegranskat)abstract
- This work reports a highly sensitive electrochemical sensor for organophosphate pesticide (malathion) based on unique and attractive CuO nanostructures. The discussed nanostructures were synthesized using low temperature hydrothermal growth method utilizing green amino acids such as glycine, serine, threonine and histidine as effective bio-compatible templates. The morphological evaluation demonstrated formation of unique and attractive 1-D nanostructures reflecting the effective growth controlling and directing capabilities of the utilized amino acids. The as-synthesized CuO nanostructures were noted to possess high affinity towards malathion which enabled their application as electrode material for the development of affinity based electrochemical sensor. Although, the as-synthesized morphologies were all sensitive towards malathion but the glycine directed triangular flake-like nanostructures exhibited greater sensitivity compared to other competitors. The electrochemical behaviour of the modified electrodes was studied using cyclic voltammetry (CV) whereas, differential pulse voltammetry (DPV) was utilized for the analytical evaluation of the sensor. The developed sensor demonstrated high reproducibility, stability, wide detection window (1-12 nM), and sensitivity to detect malathion up to 0.1 nM based on suppressive signal measurement. In addition, the sensor system exhibited high anti-interference capability in the presence of common co-existing pesticides like lindane, carbendazim, and trichlorfon. The developed sensor provides an effective measure for detecting extremely low concentration of malathion with wide applicability in various fields. (C) 2015 Elsevier Ltd. All rights reserved.
|
|
