In this work, a binary metal sulfide composite (CoS2-MoS2) was obtained by a hydrothermal method. To further improve the electrochemical activity of CoS2-MoS2, an activated N-doped lignocellulose was composited with CoS2-MoS2. The resulting composite was denoted as N-LC/CoS2-MoS2, which was modified onto glassy carbon electrode (GCE) and used as a simple and non-enzymatic electrochemical biosensor. Nyquist plots of electrochemical impedance spectra showed that the N-LC/CoS2-MoS2 modified GCE had better electrocatalytic activity than bare, MoS2 and CoS2-MoS2 modified GCE. Cyclic Voltammetry (CV) results displayed the N-LC/CoS2-MoS2 had excellent electrocatalytic activity toward ascorbic acid (AA), dopamine (DA) and nitrite. The amperometric response results indicated the N-LC/CoS2-MoS2 modified GCE could be used to determine AA, DA and nitrite concentration in wide linear ranges of 9.9–6582, 0.99–261.7 and 0.5–5160 μM, respectively. And the sensitivities of the N-LC/CoS2-MoS2 modified GCE for AA (516–6582 μM), DA and nitrite (179–5160 μM) are 4941.8, 73.3 and 5732.9 μA μM− 1 cm− 2, respectively. The corresponding detection limits were 3.0, 0.25 and 0.20 μM, respectively. The proposed sensors had good anti-interference properties and stabilities.Download high-res image (136KB)Download full-size image

•A Fe3O4/MoS2 nanostructure was obtained by a facile hydrothermal method.•HRTEM results show the Fe3O4 nanospheres disperse well on the MoS2 nanoflake.•The Fe3O4/MoS2 has excellent electrocatalytic performance.•The Fe3O4/MoS2/GCE can be used to determine nitrite and Cr(VI)concentration.A Fe3O4/MoS2 nanostructure was obtained by a facile hydrothermal method. High-resolution transmission electron microscopy (HRTEM) results show the Fe3O4 nanospheres disperse well on the MoS2 nanoflake. The presence of characteristic of Fe–O and Mo–O vibrations in the Fe3O4/MoS2 FT-IR spectra indicate the Fe3O4 has been composited with MoS2 successfully. High resolution of O 1s spectrum shows the presence of three types of oxygen including lattice oxygen, hydroxyl groups and S–OH. As expected, the Fe3O4/MoS2 nanostructure modified glassy carbon electrode (GCE) has the best electrochemical activity when compared with bare, Fe3O4 or MoS2 modified GCE. The Fe3O4/MoS2 displays excellent electrocatalytic performance on nitrite and Cr(VI) in different electrolytes, respectively. The amperometric response result indicates the Fe3O4/MoS2 modified GCE can be used to determine nitrite concentration in a wide linear range of 1.0–2630 μM (R2 = 0.998) with a detection limit of 0.5 μM. The Fe3O4/MoS2 is also an effective material for Cr(VI) detection, which is superior to the Cr(VI) sensors reported previously.

•Modified and functionalized nanocelluloses have great potential in environmental remediation.•TEMPO oxidized straw cellulose/molybdenum sulfide (TOSC-MoS2) has been fabricated by a one-step hydrothermal method.•The TOSC-MoS2 composites were modified on the GCE to develop an electrochemical sensor.•The sensor can be used to determine nitrite concentration in a wide linear range with a low detection limit.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 3140–4200 µM with a detection limit of 2.0 µM. The proposed sensor has good anti-interference property. Real sample analysis and the electrocatalytic mechanism have also been presented.

A novel yttrium-doped graphene oxide (GOY) composite was prepared by a hydrothermal method. The morphology results showed that graphene oxide (GO) can successfully form a composite with yttrium and that the as-prepared GOY had a nanoflake structure. From the photoelectrochemical analysis and photoluminescence (PL) spectra, the primary role of GO in Y2O3 was confirmed as an electron conductor, which enhanced the photocurrent density. As expected, the as-obtained GOY composites had better photocatalytic performance for the decomposition of methylene blue molecules than bare GO and Y2O3. The 5 GOY (10 mg) could degrade MB (25 ppm) thoroughly (∼100%) within 10 min, which was quite comparable with the commercial TiO2 P25 under UV irradiation. In addition, a possible mechanism of photocatalysis is presented.

An electrochemical reduced graphene oxide/poly(aniline-co-o-aminophenol)/palladium (ERGO–PANOA–Pd) nanocomposite modified glassy carbon (GC) electrode was fabricated by electrochemical reduction of GO, electrochemical polymerization of PANOA and electrochemical deposition of Pd nanoparticles, respectively. TEM and SEM display a well-defined nanofiber with diameters of 60–70 nm of PANOA synthesized on ERGO. After deposition of Pd nanoparticles, the ERGO–PANOA–Pd shows a caterpillar-like nanofiber structure. The ERGO–PANOA–Pd modified GC electrode exhibits excellent electrochemical activity in a 0.2 M H2SO4 compared to the ERGO and ERGO–PANOA modified GC electrode. CV results also show the as-prepared electrode has good electrocatalytic behavior to bromate in a pH 4.0 PBS. Under the optimal conditions, the ERGO–PANOA–Pd modified GC electrode can be used to determine bromate concentration in a wide linear range of 4 and 840 μM with a detection limit of 1 μM. The sensitivity of the electrode was 33.2 nA μM−1. The proposed sensor has good anti-interference property.

An electrochemical reduced graphene oxide/palladium (ERGO-Pd) nanocomposite modified glassy carbon (GC) electrode was fabricated by electrochemical reduction of GO and electrochemical deposition of Pd nanoparticles, respectively. Raman spectra indicate the GO can be successfully reduced to ERGO. SEM displays a high density of Pd nanoparticles loading on the surface of ERGO with a diameter of 50–100 nm. The electrode exhibits enhanced electrocatalytic behavior to the oxidation of nitrite compared to the GO and ERGO modified GC electrode. The effects of solution pH and amount of Pd deposition onto the ERGO-Pd modified GC electrode were investigated and discussed. Under the optimal conditions, the ERGO-Pd modified GC electrode can be used to determine nitrite concentration in a wide linear range of 0.04 and 108 μM and a limit of detection of 15.64 nM. The sensitivity of the electrode was 7.672 μA μM−1 cm−2. It also shows good storage stability.

•A MoS2-MWCNTs-Au nanostructure is obtained in this work.•SEM results show the MoS2 works as the substrate for MWCNTs.•The MoS2-MWCNTs-Au modified GCE exhibits good electrochemical activity.•The MoS2-MWCNTs-Au/GCE can be used to determine nitrite concentration.A molybdenum sulfide/multi-walled carbon nanotubes/gold nanocomposite (MoS2-MWCNTs-Au) modified glassy carbon electrode (GCE) was developed via a hydrothermal synthesis followed by an electrochemical deposition of gold nanoparticles onto the surface of GCE. Scanning electron microscopy (SEM) and transmission electron microscope (TEM) images indicated the MoS2 worked as the substrate for MWCNTs and the gold nanoparticles were grown on the MoS2-MWCNTs. Cyclic voltammetry (CV) results showed the MoS2-MWCNTs-Au modified GCE exhibited the best electrochemical activity in a 0.1 M phosphate buffered saline (PBS) compared to the MoS2 and MoS2-MWCNTs modified GCE. Both CV and differential pulse voltammetry (DPV) results indicated the MoS2-MWCNTs-Au had excellent electrocatalytic ability to oxide nitrite in a pH 5.0 PBS. Quantitative analysis of nitrite was carried out using amperometric i–t method. The amperometric response displayed the MoS2-MWCNTs-Au modified GCE could be used to determine nitrite concentration in a wide linear range of 12 and 6500 μM with a detection limit of 4.0 μM. The proposed sensor also showed good anti-interference and real sample analysis properties.

A novel yttrium-doped graphene oxide (GOY) composite was prepared by a hydrothermal method. The morphology results showed that graphene oxide (GO) can successfully form a composite with yttrium and that the as-prepared GOY had a nanoflake structure. From the photoelectrochemical analysis and photoluminescence (PL) spectra, the primary role of GO in Y2O3 was confirmed as an electron conductor, which enhanced the photocurrent density. As expected, the as-obtained GOY composites had better photocatalytic performance for the decomposition of methylene blue molecules than bare GO and Y2O3. The 5 GOY (10 mg) could degrade MB (25 ppm) thoroughly (∼100%) within 10 min, which was quite comparable with the commercial TiO2 P25 under UV irradiation. In addition, a possible mechanism of photocatalysis is presented.