Fabrication of a Novel Electrochemical Sensor Based on Carbon Cloth Matrix Functionalized with MoO3 and 2D-MoS2 Layers for Riboflavin Determination.

The preparation and characterization of a hybrid composite, based on carbon cloth (CC) matrix functionalized with two-dimensional (2D) MoS2 flakes and MoO3, and its use for developing an electrochemical sensor for the determination of riboflavin (RF) is here reported. The 2D-MoS2-MoO3CC composite was prepared by depositing 2D-MoS2 nanosheets, obtained by liquid phase exfoliation (LPE), on the surface of a carbon cloth fiber network, previously functionalized with a layer of molybdenum oxide (α-MoO3) by radio-frequency magnetron reactive sputtering technique. The 2D-MoS2-MoO3CC composite was characterized by scanning electron microscopy and energy dispersive X-ray analysis (SEM-EDX), and Raman spectroscopy. An electrochemical sensor has been then fabricated by fixing a slice of the 2D-MoS2-MoO3CC composite on the working electrode of a screen-printed carbon electrode (SPCE). The 2D-MoS2-MoO3-CC/SPCE sensor display good electrochemical characteristics which have been exploited, for the first time, in the electroanalytical determination of riboflavin (RF). The sensitivity to RF, equal to 0.67 µA mM-1 in the linear range from 2 to 40 µM, and a limit of detection (LOD) of 1.5 µM at S/N = 3, demonstrate the promising characteristics of the proposed 2D-MoS2-MoO3-CC/SPCE electrochemical sensor for the determination of riboflavin.

Mo-Based Layered Nanostructures for the Electrochemical Sensing of Biomolecules.

Mo-based layered nanostructures are two-dimensional (2D) nanomaterials with outstanding characteristics and very promising electrochemical properties. These materials comprise nanosheets of molybdenum (Mo) oxides (MoO2 and MoO3), dichalcogenides (MoS2, MoSe2, MoTe2), and carbides (MoC2), which find application in electrochemical devices for energy storage and generation. In this feature paper, we present the most relevant characteristics of such Mo-based layered compounds and their use as electrode materials in electrochemical sensors. In particular, the aspects related to synthesis methods, structural and electronic characteristics, and the relevant electrochemical properties, together with applications in the specific field of electrochemical biomolecule sensing, are reviewed. The main features, along with the current status, trends, and potentialities for biomedical sensing applications, are described, highlighting the peculiar properties of Mo-based 2D-nanomaterials in this field.

Photochemical synthesis, characterization, and electrochemical sensing properties of CD-AuNP nanohybrids.

Among the existing nanosystems used in electrochemical sensing, gold nanoparticles (AuNPs) have attracted considerable attention owing to their intriguing chemical and physical properties such as good electrical conductivity, high electrocatalytic activity, and high surface-to-volume ratio. However, despite these useful characteristics, there are some issues due to their instability in solution that can give rise to aggregation phenomena and the use of hazardous chemicals in the most common synthetic procedures. With an aim to find a solution to these issues, recently, we prepared and characterized carbon dots (CDs), from olive solid wastes, and employed them as reducing and capping agents in photo-activated AuNP synthesis, thus creating CD-Au nanohybrids. These nanomaterials appear extremely stable in aqueous solutions at room temperature, are contemporary, and have been obtained using CDs, which are exclusively based on non-toxic elements, with an additional advantage of being generated from an otherwise waste material. In this paper, the synthesis and characterization of CD-Au nanohybrids are described, and the electrochemical experiments for hydroquinone detection are discussed. The results indicate that CD-Au acts as an efficient material for sensing hydroquinone, matching a wide range of interests in science from industrial processes to environmental pollution.

Electrochemical Detection of Dopamine and Riboflavine on a Screen-Printed Carbon Electrode Modified by AuNPs Derived from Rhanterium suaveolens Plant Extract.

A AuNP-modified screen-printed carbon electrode (AuNP/SPCE) for monitoring important biomolecules, such as dopamine (DA) and riboflavin (RF), having a high potential for personalized medicine and for continuous monitoring of human health is here proposed. AuNPs were synthesized using the extract of Rhanterium suaveolens as a reducing medium and were characterized by UV-vis spectroscopy, dynamic light scattering (DLS), and scanning and transmission electron microscopy (SEM and TEM). The synthesized AuNPs appear spherical and present a bimodal size distribution with a maximum centered at around 30-50 nm. Cyclic voltammetry (CV) experiments demonstrated that the modified AuNP/SPCE sensor exhibits superior electrochemical performances to the bare SPCE. Low limits of detection (LODs) of 0.2 and 0.07 µM at S/N = 3 and sensitivities of 550.4  and 2399 µA mM-1 cm-2 were registered for DA and RF detection, respectively. Results demonstrate the promising electrochemical characteristics of the synthesized AuNPs and developed AuNP/SPCE electrochemical sensor for the determination of these important biomolecules.

Synthesis of Silver and Gold Nanoparticles from Rumex roseus Plant Extract and Their Application in Electrochemical Sensors.

The room-temperature synthesis of silver (AgNPs) and gold (AuNPs) nanoparticles from aqueous solution of AgNO3 and HAuCl4 respectively, using Rumex roseus (RR) plant extract as a reducing agent, is reported here for the first time. The nanoparticles obtained were characterized by UV-Vis spectroscopy, transmission electron microscopy (TEM) and dynamic light scattering (DLS). The formation of nanoparticles with spherical-shaped morphology was verified by TEM and confirmed by UV-Vis spectroscopy through the analysis of Ag and Au plasmon resonance peak and DLS measurements. New electrochemical sensors have been developed by employing the synthesized Ag and Au nanoparticles as modifiers of glassy carbon electrode (GCE) and screen-printed carbon electrode (SPCE), respectively. The AgNPs-modified GCE was investigated for the electrochemical determination of hydrogen peroxide (H2O2). Further enhancement of electrochemical performances was obtained using a nanocomposite made of AgNPs and reduced graphene oxide (rGO)-modified GCE. The AuNPs-SPCE sensor was instead tested in the electrochemical sensing of riboflavin (RF). To our knowledge, this is the first paper reporting Rumex roseus plant extract as a source for the synthesis of metal nanoparticles and their use for developing simple, sensitive and reliable electrochemical sensors for H2O2 and RF.