Electrocatalytic determination of nitrite based on straw cellulose/molybdenum sulfide nanocomposite.

Cellulose is the most abundant, renewable, biodegradable natural polymer resource on earth, which can be a good substrate for catalysis. In this work, straw cellulose has been oxidized through 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-mediated oxidation, and then a TEMPO oxidized straw cellulose/molybdenum sulfide (TOSC-MoS2) composite has been synthesized via a hydrothermal method. Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) analysis confirm that TOSC and MoS2 have successfully composited. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images show the TOSC as a carbon nanotube-like structure and edged MoS2 grows on the TOSC substrate. The TOSC-MoS2 modified glassy carbon electrode (GCE) is used as a simple and non-enzymatic electrochemical sensor. Cyclic Voltammetry (CV) result shows TOSC-MoS2 has excellent electrocatalytic activity for the oxidation of nitrite. The amperometric response result indicates the TOSC-MoS2 modified GCE can be used to determine nitrite concentration in wide linear ranges of 6.0-3140 and 3140-4200µM with a detection limit of 2.0µM. The proposed sensor has good anti-interference property. Real sample analysis and the electrocatalytic mechanism have also been presented.

Wang H ，Wen F ，Chen Y ，Sun T ，Meng Y ，Zhang Y ... -  《-》

Glassy carbon electrodes modified with reduced graphene oxide-MoS(2)-poly (3, 4-ethylene dioxythiophene) nanocomposites for the non-enzymatic detection of nitrite in water and milk.

The detrimental effect of (NO2-) on environment, a sensitive and selective detection of nitrite (NO2-) ions with point-to-care device is need to be fabricated. Herein, we report the non-enzymatic nitrite sensor using a novel reduced graphene oxide/molybdenum disulfide/poly (3, 4-ethylene dioxythiophene) (rGO/MoS2/PEDOT) nanocomposite electrode. The rGO/MoS2/PEDOT nanocomposite was synthesized using facile and cost-effective hydrothermal and polymerization approaches. The characteristics of rGO-MoS2-PEDOT nanocomposite was investigated by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Raman, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Brunauer-Emmett-Teller (BET) analyses. The rGO-MoS2-PEDOT nanocomposite modified glassy carbon electrode (GCE) was directly used for electrocatalytic detection of nitrite ions present in the solution. TEM images show the PEDOT nanoparticles with an average size of 100-120 nm are uniformly covered on the outer face of rGO-MoS2 nanosheets. The interaction between the PEDOT and rGO-MoS2 is evidenced in the FTIR, XRD and XPS studies, and they produced synergistic effect, resulting enhanced electrocatalytic performance activity towards oxidation of nitrite. Under optimized conditions, the fabricated electrode exhibited remarkably good sensitivity (874.19 μA μM-1 cm-2), low detection limit (LOD) (0.059 μM, S/N = 3), wide linear range (0.001-1 mM) of nitrite with desirable selectivity, long-term stability and reproducibility. Furthermore, the practical feasibility of the fabricated sensor is validated by the successful detection of nitrite ion in some water and milk samples with excellent correlation. Thus, feasible easier synthesis method was adopted first time to fabricate rGO-MoS2-PEDOT nanocomposite nitrite sensor in the milk and water samples with enhanced selectivity, sensitivity and LOD.

Madhuvilakku R ，Alagar S ，Mariappan R ，Piraman S ... -  《-》

A novel electrochemical sensor based on silver/halloysite nanotube/molybdenum disulfide nanocomposite for efficient nitrite sensing.

In the present study, the silver/halloysite nanotube/molybdenum disulfide (Ag/HNT/MoS2) nanocomposite was successfully synthesized. For this purpose, the lumen of HNTs was firstly modified by silver to generate Ag nanorods via chemical process and then the MoS2 layers deposited on the Ag/HNT nanocomposite by hydrothermal method. The characterization of Ag/HNT/MoS2 nanocomposite were investigated by field emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FT-IR) spectroscopy, transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) analyses. The nanocomposite modified carbon paste electrode (CPE) was applied for the electrocatalytic detection of nitrite in aqueous solutions. It was demonstrated that the treatment of HNTs with Ag and MoS2 materials enhanced the catalytic performance of modified CPE. At optimal experimental conditions, the designed sensor displayed remarkable sensing ability toward nitrite oxidation, offering a good linearity from 2 to 425 µM. The limit of detection (LOD) of the proposed strategy was estimated to be 0.7 µM based S/N = 3. The good reproducibility, acceptable stability, fast response time and anti-interference performance of the proposed assay suggests that the modified CPE has great potential working as a nitrite electrochemical sensor for environmental applications.

Ghanei-Motlagh M ，Taher MA 《-》

Investigations of an electrochemical platform based on the layered MoS2-graphene and horseradish peroxidase nanocomposite for direct electrochemistry and electrocatalysis.

The self-assembly of layered molybdenum disulfide-graphene (MoS2-Gr) and horseradish peroxidase (HRP) by electrostatic attraction into a novel hybrid nanomaterial (HRP-MoS2-Gr) is reported. The properties of the MoS2-Gr were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (TEM), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). UV-vis and Fourier transform infrared spectroscopy (FT-IR) indicate that the native structure of the HRP is maintained after the assembly, implying good biocompatibility of MoS2-Gr nanocomposite. Furthermore, the HRP-MoS2-Gr composite is utilized as a biosensor, which displays electrocatalytic activity to hydrogen peroxide (H2O2) with high sensitivity (679.7 μA mM(-1)cm(-2)), wide linear range (0.2 μM-1.103 mM), low detection limit (0.049 μM), and fast amperometric response. In addition, the biosensor also exhibits strong anti-interference ability, satisfactory stability and reproducibility. These desirable electrochemical properties are attributed to the good biocompatibility and electron transport efficiency of the MoS2-Gr composite, as well as the high loading of HRP. Therefore, this biosensor is potentially suitable for H2O2 analysis in environmental, pharmaceutical, food or industrial applications.

Song H ，Ni Y ，Kokot S 《-》

Electrochemical and bio-sensing platform based on a novel 3D Cu nano-flowers/layered MoS₂ composite.

A novel 3D nano-flower-like Cu/multi-layer molybdenum disulfide composite (CuNFs/MoS2) modified glassy carbon electrode (GCE) has been successfully constructed. It was a highly sensitive and selective non-enzymatic hydrogen peroxide (H2O2) and glucose biosensor. The morphology of the obtained CuNFs-MoS2 nano-particles was investigated with the use of a scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDS). The physicochemical properties of the modified electrode were characterized at each of the construction stages with the use of an electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) techniques. The new sensor combined the advantages of MoS2 and CuNFs, and exhibited high electro-catalytic activity toward H2O2 and glucose. Quantitative analysis of H2O2 and glucose was carried out with the use of the amperometric i-t method. Linear ranges were obtained between 0.04-1.88 μM and 1.88-35.6 μM for H2O2 and 1-20 μM and 20-70 μM for glucose, and their corresponding limits of detection (LOD) were 0.021 μM and 0.32 μM. This novel sensor was successfully applied for the quantitative analysis of H2O2 in tap water and glucose in human serum samples.

Lin X ，Ni Y ，Kokot S 《-》