Norazriena Yusoff

Graphene and its nanocomposite material based electrochemical sensor platform for dopamine

Dopamine (DA) is an important catecholamine neurotransmitter in the mammalian central nervous system that influences several physiological functions. The impact of DA levels within the human body significantly affects the body functions. Maintaining DA level is essential and the electrochemical detection methods are often used to detect the DA level to regulate the body function. In this review, graphene (functionalized graphene and N-doped graphene) and its composites (metal, metal oxide, polymer, carbonaceous materials, clay, zeolite, and metal–organic framework based graphene composites) modified electrodes with their improved sensing performance towards DA along with several interfering species are described. Further, recent developments on the fabrication of various graphene based composite modified electrodes are also presented. Some important strategies to improve the selectivity and sensitivity towards DA with graphene based composite modified electrodes are also described.

Gold nanoparticle based optical and electrochemical sensing of dopamine

AbstractThis review (with 110 refs.) gives an overview on the progress that has been made in the past few years on the use of gold nanoparticles (AuNPs) for use in sensors and analytical tools for the determination of dopamine (DA). Both AuNPs and their composites with other organic and inorganic materials including noble metals are treated. Following an overview on the clinical significance of DA, we discuss the various analytical methods that are (a) electrochemiluminescence (ECL); (b) surface enhanced Raman scattering (SERS); (c) colorimetric probing and visual detection; and (d) the large class of electrochemical sensors. Subsections cover sensors based on plain AuNPs, bimetallic NPs, AuNP-metal@metal oxide nanocomposites, AuNP nanocomposites with organic polymers, AuNP nanocomposites with carbon nanotubes or with graphene, and finally sensors based on ternary materials containing AuNPs. The review ends with a conclusion on current challenges of sensors for DA and an outlook on future trends. Graphical AbstractWe review the recent progress in sensing dopamine based on AuNPs and its nanocomposites including bimetallic nanoparticles, AuNPs-/metal oxide, AuNPs-polymer, AuNPs-carbon nanotubes, AuNPs-graphene and ternary materials using different types of sensing techniques such as electrochemiluminescence (ECL), colorimetric, surface enhanced Raman scattering (SERS) and electrochemical techniques.

Ternary nanohybrid of reduced graphene oxide-nafion@silver nanoparticles for boosting the sensor performance in non-enzymatic amperometric detection of hydrogen peroxide

A sensitive and novel electrochemical sensor was developed for the detection of hydrogen peroxide (H2O2) using a reduced graphene oxide-nafion@silver6 (rGO-Nf@Ag6) nanohybrid modified glassy carbon electrode (GC/rGO-Nf@Ag6). The GC/rGO-Nf@Ag6 electrode exhibited an excellent electrochemical sensing ability for determining H2O2 with high sensitivity and selectivity. The detection limit of the electrochemical sensor using the GC/rGO-Nf@Ag6 electrode for H2O2 determination was calculated to be 5.35×10-7M with sensitivity of 0.4508µAµM-1. The coupling between rGO-Nf with silver nanoparticles (AgNPs) significantly boosted the electroanalytical performance by providing more active area for analyte interaction, thereby allowing more rapid interfacial electron transfer process. The interfering effect on the current response of H2O2 was studied and the results revealed that the sensor electrode exhibited an excellent immunity from most common interferents. The proposed non-enzymatic electrochemical sensor was used for determining H2O2 in apple juice, and the sensor electrode provided satisfactory results with reliable recovery values. These studies revealed that the novel GC/rGO-Nf@Ag6 sensor electrode could be a potential candidate for the detection of H2O2.

Facile synthesis of nanosized graphene/Nafion hybrid materials and their application in electrochemical sensing of nitric oxide

This paper presents the preparation of nanosized graphene hybridized with Nafion using a simple two step, sonication and hydrothermal process which successfully produced a new nanosized graphene-Nafion hybrid (G-Nf) with lateral dimensions as small as 18 nm based on AFM results. The novel G-Nf hybrids were used to modify the glassy carbon electrode (GCE) for the fabrication of nitric oxide (NO) electrochemical sensors where the optimum sensing response was achieved with a G-Nf hybrid synthesized after 16 h of hydrothermal treatment. Under the optimized experimental conditions, the GC/G-Nf (16 h) electrode showed an oxidation peak at 0.85 V in the presence of NO. It also demonstrated an excellent performance toward the detection of NO, with a limit of detection of 11.61 μM (S/N = 3) in a linear range of 0.05–0.45 mM. Moreover, this GC/G-Nf (16 h) electrode exhibited a higher sensitivity of approximately 62 μA mM−1 and had a great selectivity toward NO in the presence of interferents such as dopamine and ascorbic acid. The combination of nanosized graphene and Nafion generates a synergic effect which facilitates excellent electron-transfer processes between the electrolyte and the GCE thus improving the sensing performance of the fabricated modified electrode.

Hydrothermally prepared graphene-titania nanocomposite for the solar photocatalytic degradation of methylene blue

Reduced graphene oxide–titania (rGO–TiO2) nanocomposites were prepared by hydrothermal method at different reaction temperatures and characterized by powder X-ray diffraction, transmission electron microscopy, micro-Raman spectroscopy, X-ray photoelectron spectroscopy, and photoluminescence spectroscopy techniques, respectively. The photocatalytic properties of the nanocomposites were investigated toward the degradation of methylene blue under natural sunlight. The rGO–TiO2 shows better photocatalytic activity due to the extended visible light absorption, excellent adsorptivity, and effective electron transfer process than the other controlled photocatalysts. In addition, rGO–TiO2 shows good sustainability after subjecting it to five consecutive cycles of photodegradation. This enhanced photocatalytic performance and good sustainability toward dye removal makes this rGO–TiO2 nanocomposite as a potential candidate for wastewater treatment in textile and dyeing industries.

Chitosan capped nickel oxide nanoparticles as a saturable absorber in a tunable passively Q-switched erbium doped fiber laser

Nickel oxide (NiO) nanoparticles successfully prepared from a nickel(II) chloride hexahydrate precursor are used to form a chitosan capped NiO nanoparticle thin film to serve as a saturable absorber (SA) for the generation of passively Q-switched pulses in an erbium doped fiber laser (EDFL). The NiO/chitosan SA based EDFL is able to generate stable pulsed outputs at a low threshold pump power of 104.90 mW with a central wavelength at 1562 nm. The highest pulse energy obtainable by the system is 15.30 nJ at a repetition rate of 42.66 kHz and a pulse duration of 2.02 μs. The laser has a spectral range of 58 nm from 1522 to 1580 nm, covering the C and L bands and even portions of the S band. This study experimentally demonstrates that the potential of the NiO/chitosan film as an SA material for Q-switching operations, combined with the biocompatibility, non-toxicity and high thermal resistance of Chitosan, holds great prospects for a broad range of applications.