Kamran Akbar

A highly sensitive enzymeless glucose sensor based on 3D graphene–Cu hybrid electrodes

We report a facile route to prepare the hybrid structure of 3 dimensional (3D) graphene and Cu and its uses for ultrahigh performance in enzymeless glucose detection. The graphene film was synthesized onto a 3D porous Ni foam substrate by chemical vapor deposition and a thin Cu layer was evaporated onto the 3D graphene/Ni foam by thermal evaporation. The structural and morphological properties of the Cu/3D graphene structure were characterized by X-ray diffraction, Raman spectroscopy, SEM and TEM. The developed sensor exhibited high selectivity towards glucose. We herein demonstrate that the Cu/3D graphene hybrid-based electrode has capability to deliver excellent cycling stability and it can detect glucose with an ultrahigh sensitivity of 7.88 mA mM−1 cm−2 and a detection limit of 18 nM (S/N = 8.6). The sensitivity value of our Cu/3D graphene hybrid is greater than any reported values of the materials. The superior long cycling stability and high sensitivity make the Cu/3D graphene hybrid promising for applications in the direct sensing of glucose.

Cu/MoS2/ITO based hybrid structure for catalysis of hydrazine oxidation

We have successfully demonstrated large-area and continuous MoS2 films grown on indium tin oxide (ITO) substrates by RF sputtering followed by a post-annealing process. Thin Cu layers were prepared on MoS2/ITO films by thermal evaporation to enhance electron-transfer rates as well as the catalytic activity of hydrazine oxidation. High electrocatalytic activity towards hydrazine oxidation was observed in a Cu/MoS2/ITO hybrid structure. A large residual current was also observed in the Cu/MoS2/ITO hybrid due to the combination of MoS2 and Cu film. The electrocatalytic activity was enhanced with the increase of the MoS2 film thickness. The observed results showed that the Cu/MoS2/ITO catalyst is indeed a valuable material for future applications in hydrazine fuel cells.

Enhanced photoresponse of ZnO quantum dot-decorated MoS2 thin films

Transition metal dichalcogenides (TMDs) have been attracting attention because of their applications in optoelectronics and photo-detection. A widely used TMD semiconductor is molybdenum disulfide (MoS2), which has tremendous applications because of its tunable bandgap and high luminescence quantum efficiency. This paper reports on high photo responsivity (Rλ ∼ 1913 A W−1) of MoS2 photodetector by decorating a thin layer of zinc oxide (ZnO) quantum dots (ZnO-QDs) on MoS2. Results show that Rλ increases dramatically to 2267 A W−1 at Vbg = 30 V. The high response of ZnO-QDs/MoS2 heterostructures is attributed to a number of factors, such as effective charge transfer between ZnO-QDs and MoS2 surface and re-absorption of light photon resulting in production of electron–hole pairs.

Synthesis of MoS2(1−x)Se2x and WS2(1−x)Se2x alloys for enhanced hydrogen evolution reaction performance

Herein, we demonstrate the synthesis of molybdenum disulphoselenide (MoS2(1−x)Se2x) and tungsten disulphoselenide (WS2(1−x)Se2x) alloys onto FTO substrates, to obtain a higher hydrogen evolution reaction (HER) activity compared to pristine MoS2 and WS2. By incorporating selenium (Se) into MoS2 and WS2 matrices, an excellent HER catalytic activity was ensured in an acidic electrolyte with overpotentials of 141 mV and 167 mV @ 10 mA cm−2 with Tafel slopes of 67 and 107 mV per decade for MoS2(1−x)Se2x and WS2(1−x)Se2x, respectively. Moreover, MoS2(1−x)Se2x and WS2(1−x)Se2x alloys showed robust durability over 20 h of continuous HER operation in acidic solutions. Our investigation provides the synthesis of tunable metal dichalcogenide hybrid structures with better electrochemical performance.

Facile Synthesis of Molybdenum Diselenide Layers for High-Performance Hydrogen Evolution Electrocatalysts

A cost-effective solution-based synthesis route to grow MoSe2 thin films with vertically aligned atomic layers, thereby maximally exposing the edge sites on the film surface as well as enhancing charge transport to the electrode, is demonstrated for hydrogen evolution reaction. The surface morphologies of thin films are investigated by scanning electron microscopy and atomic force microscopy, and transmission electron microscopy analyses confirm the formation of the vertically aligned layered structure of MoSe2 in those films, with supporting evidences obtained by Raman. Additionally, their optical and compositional properties are investigated by photoluminescence and X-ray photoelectron spectroscopy, and their electrical properties are evaluated using bottom-gate field-effect transistors. The resultant pristine MoSe2 thin film exhibited low overpotential of 88 mV (at 10 mA·cm–2) and a noticeably high exchange current density of 0.845 mA·cm–2 with excellent stability, which is superior to most of other reported MoS2 or MoSe2-based catalysts, even without any other strategies such as doping, phase transformation, and integration with other materials.

Correction: A highly sensitive enzymeless glucose sensor based on 3D graphene–Cu hybrid electrodes

Correction for ‘A highly sensitive enzymeless glucose sensor based on 3D graphene–Cu hybrid electrodes’ by Sajjad Hussain et al., New J. Chem., 2015, 39, 7481–7487.

Induced superaerophobicity onto a non-superaerophobic catalytic surface for enhanced hydrogen evolution reaction

Despite tremendous progress in the development of novel electrocatalysts for hydrogen evolution reaction (HER), the accumulation of hydrogen gas bubbles produced on the catalyst surface has been rather poorly addressed. The bubbles block the surface of the electrode, thus resulting in poor performance even when excellent electrocatalysts are used. In this study, we show that vertically grown graphene nanohills (VGNHs) possess an excellent capability to quickly disengage the produced hydrogen gas bubbles from the electrode surface, and thus exhibit superaerophobic properties. To compensate for the poor electrolytic properties of graphene toward HER, the graphene surface was modified with WS2 nanoparticles to accelerate the water-splitting process by using this hybrid catalyst (VGNHs-WS2). For comparison purposes, WS2 nanoparticles were also deposited on the flat graphene (FG) surface. Because of its superior superaerophobic properties, VGNHs-WS2 outperformed FG-WS2 in terms of both catalytic activity toward the HER and superaerophobicity. Furthermore, VGNHs-WS2 exhibited a low onset potential (36 mV compared to 288 mV for FG-WS2) and long-term stability in the HER over an extended period of 20 h. This study provides an efficient way to utilize highly conductive and superaerophobic VGNHs as support materials for intrinsic semiconductors, such as WS2, to simultaneously achieve superaerophobicity and high catalytic activity.