Proton-exchange membranes (PEMs) consisting of sulfonated poly(ether sulfone) (SPES) with enhanced electrochemical properties have been successfully prepared by incorporating different amount of sulfonated graphene oxide (SGO). Composite membranes are tested for proton conductivity (30-90 °C) and methanol crossover resistance to expose their potential for direct methanol fuel cell (DMFC) application. Incorporation of SGO considerably increases the ion-exchange capacity (IEC), water retention and proton conductivity and reduces the methanol permeability. Membranes have been characterized by FTIR, XRD, DSC, SEM, TEM, and AFM techniques. Intermolecular interactions between the components in composite membranes are established by FTIR. The distribution of SGO throughout the membrane matrix has been examined using SEM and TEM and found to be uniform. The maximum proton conductivity has been found in 5% SGO composite with higher methanol crossover resistance.

No abstract

Ultrathin two-dimensional WSe2 has attracted huge attention due to its potential applications in future wearable electronics. Here, we demonstrate the flexible and high-performance photodetector using high-yield sonochemical exfoliation technique. An efficient and low cost fabrication strategy using Whatman filter paper is adopted for the first time for fabrication of a photodetector based on WSe2 nanodots (NDs). The WSe2 NDs have hexagonal lattice structure with P63/mmc and have indirect band gap of 1.63 eV. The exfoliation and number of layers in WSe2 NDs is confirmed by Raman, absorption, and photoluminescence spectroscopy. Subsequently, the photodetector based on WSe2 NDs is fabricated. The device shows excellent photoresponse with response time of 0.68 s and photoresponsivity of 17.78 mAW–1 and detectivity of 5.86 × 1010 Jones for 5 V. The device is analyzed for bias of 0 to 100 V and responsivity is enhanced up to 796.18 mA W–1 at 100 V bias. Furthermore, the paper-based detector exhibited great flexibility and air stability. The performance of the photodetector was also recorded in the spectral range 390 to 880 nm. Over all, the performance paper-based device advocates a novel pathway for flexible and intelligent electronics.

Titanium dioxide nanocrystals were prepared by the wet chemical method and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman scattering (RS) and photoluminescence techniques. The XRD pattern shows the formation of single phase anatase structure of average sizes ∼7 nm (sample A) and ∼15 nm (sample B) for two samples. Additionally, TEM and RS were used to confirm the anatase crystal structure for both samples. The PL spectra show that the intensity of the sample A is more than that of sample B, which has been attributed to defect(s) and particle size variation. A modified phonon confinement model incorporating particle size distribution function and averaged dispersion curves for two most dispersive phonon branch ( -X direction) have been used to interpret the size effect in Raman spectra. The obtained Raman peak shift and full width at half-maximum agree well with the experimental data. Our observations suggest that the phonon confinement effects are responsible for a significant shift and broadening for the Raman peaks.

Different membrane properties by inclusion of graphene oxide content.