Naveed Mengal

Fabrication of a flexible and conductive lyocell fabric decorated with graphene nanosheets as a stable electrode material

Textile electrodes are highly desirable for wearable electronics as they offer light-weight, flexibility, cost effectiveness and ease of fabrication. Here, we propose the use of lyocell fabric as a flexible textile electrode because of its inherently super hydrophilic characteristics and increased moisture uptake. A highly concentrated colloidal solution of graphene oxide nanosheets (GONs) was coated on to lyocell fabric and was then reduced in to graphene nanosheets (GNs) using facile chemical reduction method. The proposed textile electrode has a very high surface conductivity with a very low value of surface resistance of only 40Ωsq(-1), importantly without use of any binding or adhesive material in the processing step. Atomic force spectroscopy (AFM) and Transmission electron microscopy (TEM) were conducted to study the topographical properties and sheet exfoliation of prepared GONs. The surface morphology, structural characterization and thermal stability of the fabricated textile electrode were studied by field emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FT-IR), X ray photon spectroscopy (XPS), Raman spectroscopy, Wide angle X ray diffraction spectroscopy (WAXD) and Thermogravimetric analysis (TGA) respectively. These results suggest that the GONs is effectively adhered on to the lyocell fabric and the conversion of GONs in to GNs by chemical reduction has no adverse effect on the crystalline structure of textile substrate. The prepared graphene coated conductive lyocell fabric was found stable in water and electrolyte solution and it maintained nearly same surface electrical conductivity at various bending angles. The electrical resistance results suggest that this lyocell based textile electrode (L-GNs) is a promising candidate for flexible and wearable electronics and energy harvesting devices.

Highly Functional TNTs with Superb Photocatalytic, Optical, and Electronic Performance Achieving Record PV Efficiency of 10.1% for 1D-Based DSSCs

Different nanostructures of TiO2 play an important role in the photocatalytic and photoelectronic applications. TiO2 nanotubes (TNTs) have received increasing attention for these applications due to their unique physicochemical properties. Focusing on highly functional TNTs (HF-TNTs) for photocatalytic and photoelectronic applications, this study describes the facile hydrothermal synthesis of HF-TNTs by using commercial and cheaper materials for cost-effective manufacturing. To prove the functionality and applicability, these TNTs are used as scattering structure in dye-sensitized solar cells (DSSCs). Photocatalytic, optical, Brunauer-Emmett-Teller (BET), electrochemical impedance spectrum, incident-photon-to-current efficiency, and intensity-modulated photocurrent spectroscopy/intensity-modulated photovoltage spectroscopy characterizations are proving the functionality of HF-TNTs for DSSCs. HF-TNTs show 50% higher photocatalytic degradation rate and also 68% higher dye loading ability than conventional TNTs (C-TNTs). The DSSCs having HF-TNT and its composite-based multifunctional overlayer show effective light absorption, outstanding light scattering, lower interfacial resistance, longer electron lifetime, rapid electron transfer, and improved diffusion length, and consequently, J SC , quantum efficiency, and record photoconversion efficiency of 10.1% using commercial N-719 dye is achieved, for 1D-based DSSCs. These new and highly functional TNTs will be a concrete fundamental background toward the development of more functional applications in fuel cells, dye-sensitized solar cells, Li-ion batteries, photocatalysis process, ion-exchange/adsorption process, and photoelectrochemical devices.

Citric acid based durable and sustainable flame retardant treatment for lyocell fabric.

Pyrovatex CP New, is a commonly used organophosphorus based flame retardant (FR) reagent for cellulosic materials. However, it has a drawback of high formaldehyde release when used with methylated melamine (MM) based cross-linker, a known carcinogenous compound. In the present approach, a durable and sustainable flame retarding recipe formulation for lyocell fabrics is developed using citric acid (CA) as a cross-linker. The FR finish was applied by pad-dry-cure process. The treated fabrics were characterized for surface morphology, elemental analysis, TG analysis, char study and FT-IR spectroscopy. Furthermore, flame retardancy, washing durability, formaldehyde release and breaking strength were also assessed, and compared with the conventional MM based FR recipe. The fabric samples treated with 400gL(-1) of FR with either 40 or 80gL(-1) of CA demonstrate flame retardancy even after 10 washing cycles. Furthermore, a 75% reduction in formaldehyde release is achieved. Higher char yield and lower decomposition temperature are found compared to untreated and FR+ MM treated lyocell. Such an improved sustainable recipe formulation can be used for lyocell fabric without any health risk in apparel wear.

Large area growth of MoTe 2 films as high performance counter electrodes for dye-sensitized solar cells

A cost effective and efficient alternative counter electrode (CE) to replace commercially existing platinum (Pt)-based CEs for dye-sensitized solar cells (DSSCs) is necessary to make DSSCs competitive. Herein, we report the large-area growth of molybdenum telluride (MoTe2) thin films by sputtering-chemical vapor deposition (CVD) on conductive glass substrates for Pt-free CEs of DSSCs. Cyclic voltammetry (CV), Tafel curve analysis, and electrochemical impedance spectroscopy (EIS) results showed that the as-synthesized MoTe2 exhibited good electrocatalytic properties and a low charge transfer resistance at the electrolyte-electrode interface. The optimized MoTe2 CE revealed a high power conversion efficiency of 7.25% under a simulated solar illumination of 100 mW cm−2 (AM 1.5), which was comparable to the 8.15% observed for a DSSC with a Pt CE. The low cost and good electrocatalytic properties of MoTe2 thin films make them as an alternative CE for DSSCs.

Novel derivatives of 3D woven T-shaped composites with improved performance

Abstract Conventional 3D woven T-shaped preforms were modified for improving joint/ peel off strength of associated T-shaped polymeric composites. Preforms were modified at weaving level by preferred yarns orientations for better performance in associated composites. Major modifications studied are; the addition of supporting layer, single or double-crossing in joint layers and crossing along with supporting layer (in a single sample). Novel derivatives were compared with conventionally used (on-loom and off-loom) T-shaped 3D woven composites. Microscopic analysis was also carried out to analyze the orientation of yarns and analysis of samples from failure point after testing. By combined variation of crossing and supporting layers improvement of 47.37% in peel off strength and 70.37% in impact strength was observed. Modified T shapes can serve to be a good replacement for conventional T-shaped stiffener (used to avoid folding under loads) and in joints.

An evidence for an organic N-doped multiwall carbon nanotube heterostructure and its superior electrocatalytic properties for promising dye-sensitized solar cells

A novel organic heteroatom doping technique is proposed for the synthesis of N-doped multiwall carbon nanotube (MWCNT) heterostructures. The approach involves the effective doping of MWCNTs with nitrogen via a cationised bovine serum albumin (cBSA) protein complex. The cationization of BSA releases an exceptional number of activated nitrogen species present in localized amino groups, which are further embedded into the MWCNT framework. The amino groups present in BSA act as nitrogen donors and surface stabilizing agents to generate a highly conductive and functionalized carbon heterostructure. The doped nitrogen was present in the form of pyridinic and pyrrolic states, as evidenced by XPS analysis. Organic N-doped MWCNTs with predominant pyridinic N atoms displayed superior charge transfer (RCT = 0.06 Ω) owing to their superior electrocatalytic activity. A DSSC fabricated with organic N-doped MWCNT heterostructures exhibited a high conversion efficiency of 9.55%, which was similar to that of a Pt cathode, with an efficiency of 9.89%. The superior electrochemical performance of organic N-doped MWCNT heterostructures is due to the high charge polarization arising from the difference in electronegativity between nitrogen and carbon as well as the structural strain caused by the cationic BSA protein complex. Our proposed system provides new routes for the synthesis of organic heteroatom-doped nanomaterials for promising energy storage devices.