M.S. Al-Assiri

Highly porous ZnO nanosheets self-assembled in rosette-like morphologies for dye-sensitized solar cell application

This paper reports a facile low temperature hydrothermal process to grow highly porous ZnO nanosheets, self-assembled in rosette-like morphology, over the transparent indium tin oxide (ITO) glass substrate for dye-sensitized solar cell application. The prepared porous nanosheets were examined in detail using several techniques to understand the morphological, structural, compositional, optical and photovoltaic properties. The detailed morphological investigations reveal that the prepared nanosheets are made by the accumulation of small ZnO nanoparticles with typical diameters of 28 ± 3 nm. A systematic growth process to prepare such ZnO nanosheets is also discussed in terms of chemical reactions involved. The prepared nanosheets possess the stoichiometric elemental ratios of Zn and oxygen and exhibiting good crystallinity and wurtzite hexagonal phase along with good optical properties. Furthermore, the prepared ZnO nanosheets on ITO substrates were directly utilized as a photo-anode to fabricate an efficient dye-sensitized solar cell (DSSC), which demonstrated a reasonable light-to-electricity conversion efficiency of ∼3.4% with high short circuit current (JSC) of 9.45 mA cm−2, open circuit voltage (VOC) of 0.654 and fill factor of 0.55. The obtained JSC and the performance of the fabricated DSSC are attributed to the high surface to volume ratio of porous ZnO nanosheets, which delivers the high light harvesting efficiency.

Two-dimensional ytterbium oxide nanodisks based biosensor for selective detection of urea

Herein, we demonstrate synthesis and application of two-dimensional (2D) rectangular ytterbium oxide (Yb2O3) nanodisks via a facile hydrothermal method. The structural, morphological, compositional, crystallinity, and phase properties of as-synthesized nanodisks were carried out using several analytical techniques that showed well defined 2D rectangular nanodisks/sheet like morphologies. The average thickness and edge length of the nanosheet structures were 20 ± 5nm and 600 ± 50nm, respectively. To develop urea biosensor, glassy carbon electrodes (GCE) were modified with Yb2O3 nanodisks, followed by urease immobilization and Nafion membrane covering (GCE/Yb2O3/Urease/Nafion). The fabricated biosensor showed sensitivity of 124.84μAmM-1cm-2, wide linear range of 0.05-19mM, detection limit down to ~ 2μM, and fast response time of ~ 3s. The developed biosensor was also used for the urea detection in water samples through spike-recovery experiments, which illustrates satisfactory recoveries. In addition, the obtained desirable selectivity towards specific interfering species, long-term stability, reproducibility, and repeatability further confirm the potency of as-fabricated urea biosensor.

A Highly-Sensitive Picric Acid Chemical Sensor Based on ZnO Nanopeanuts

Herein, we report a facile synthesis, characterization, and electrochemical sensing application of ZnO nanopeanuts synthesized by a simple aqueous solution process and characterized by various techniques in order to confirm the compositional, morphological, structural, crystalline phase, and optical properties of the synthesized material. The detailed characterizations revealed that the synthesized material possesses a peanut-shaped morphology, dense growth, and a wurtzite hexagonal phase along with good crystal and optical properties. Further, to ascertain the useful properties of the synthesized ZnO nanopeanut as an excellent electron mediator, electrochemical sensors were fabricated based on the form of a screen printed electrode (SPE). Electrochemical and current-voltage characteristics were studied for the determination of picric acid sensing characteristics. The electrochemical sensor fabricated based on the SPE technique exhibited a reproducible and reliable sensitivity of ~1.2 μA/mM (9.23 μA·mM−1·cm−2), a lower limit of detection at 7.8 µM, a regression coefficient (R2) of 0.94, and good linearity over the 0.0078 mM to 10.0 mM concentration range. In addition, the sensor response was also tested using simple I-V techniques, wherein a sensitivity of 493.64 μA·mM−1·cm−2, an experimental Limit of detection (LOD) of 0.125 mM, and a linear dynamic range (LDR) of 1.0 mM–5.0 mM were observed for the fabricated picric acid sensor.

Highly sensitive and selective non-enzymatic monosaccharide and disaccharide sugar sensing based on carbon paste electrodes modified with perforated NiO nanosheets

Herein, we report the fabrication and detailed characterization of a new electrochemical enzyme-free sensor for the direct sensing of monosaccharide and disaccharide sugars based on perforated NiO nanosheets (NSs). The NiO nanosheets were synthesized by a facile hydrothermal process followed by annealing and they were characterized in terms of their morphological, structural, compositional and optical properties. Detailed characterization confirmed the large-scale synthesis, good crystallinity and high purity of the synthesized perforated NiO nanosheets. To fabricate sugar sensors, sensor electrodes were prepared by modifying carbon paste with the perforated NiO nanosheets. Cyclic voltammetry and amperometry techniques were used to investigate the effect of the NiO nanosheets on the electrocatalytic oxidation of monosaccharide and disaccharide sugars. The electrodes exhibit a high sensitivity to glucose (724 μA mM−1 cm−2), with a low detection limit (10 μM), and respond over a wide linear range (from 50 μM to 3 mM). The analytical performance of the developed sensors, in addition to their ease of fabrication, qualifies them to be a good platform for enzyme-free sugar sensing.

Synthesis and characterisation of ZnO structures containing the nanoscale regime

Synthesis of ZnO nanorods assembled in flower-shaped spherical morphologies have been grown via solution process by using zinc nitrate hexahydrate (Zn(NO3)2. 6H2O) and sodium hydroxide (NaOH) at low-temperature of 100°C in eight hours. The grown ZnO structures were characterised in terms of their structural and optical properties. The detailed structural characterisations demonstrated that the synthesised products are single crystalline with the wurtzite hexagonal phase and grown along the [0001], c-axis direction. A strong absorption band at 480 cm−1 was observed in Fourier transform infra red (FTIR) spectrum which was related with the ZnO. The optical property of the grown ZnO structures was observed by using UV-visible studies. Only a sharp peak at 371 nm was observed in the UV-vis. spectrum which is a characteristic band for the wurtzite hexagonal pure ZnO. Moreover, systematic time-dependent reactions were also performed to know the detailed growth process for the synthesised ZnO nanostructures.