Muhammad Bilal Qadir

Integrating high electrical conductivity and photocatalytic activity in cotton fabric by cationizing for enriched coating of negatively charged graphene oxide.

Electroconductive textiles have attended tremendous focus recently and researchers are making efforts to increase conductivity of e-textiles, in order to increase the use of such flexible and low cost textile materials. In this study, surface conductivity and photo catalytic activity of standard cotton fabric (SCF) was enhanced by modifying its surface charge, from negative to positive, using Bovine Serum Albumin (BSA) as a cationic agent, to convert it into cationised cotton fabric (CCF). Then, both types of fabrics were dip coated with a simple dip and dry technique for the adsorption of negatively charged graphene oxide (GO) sheets onto its surface. This resulted in 67.74% higher loading amount of GO on the CCF making self-assembly. Finally, this coating was chemically converted by vapor reduction using hydrazine hydrate to reduced graphene oxide (rGO) for restoration of a high electrical conductivity at the fabric surface. Our results revealed that with such high loading of GO, the surface resistance of CCF was only 40Ω/sq as compared to 510Ω/sq of the SCF and a 66% higher photo catalytic activity was also achieved through cationization for improved GO coating. Graphene coated SCF and CCF were characterized using FE-SEM, FTIR, Raman, UV-vis, WAXD, EDX and XPS spectroscopy to ascertain successful reduction of GO to rGO. The effect of BSA treatment on adsorption of cotton fabric was studied using drop shape analyzer to measure contact angle and for thermal and mechanical resistance, the fabric was tested for TGA and tensile strength, respectively. rGO coated fabric also showed slightly improved thermal stability yet a minor loss of strength was observed. The high flexibility, photocatalytic activity and excellent conductivity of this fabric suggests that it can be used as an electrode material for various applications.

Hydrothermal synthesis of TiO2 nanotubes and their application as an over-layer for dye-sensitized solar cells

Different nanostructures of TiO2 play an important role in the kinetics of dye sensitized solar cells (DSSC) and affect the overall light harvesting efficiency of the cells. This article describes that the one dimensional nanostructure of TiO2 (nanotubes) can increase the light scattering effect, light harvesting effect and electron transport in the DSSC to improve its performance. Pure anatase TiO2 nanotubes were synthesized by a hydrothermal method using commercial material (P25) due to which the manufacturing cost of the DSSC was enormously reduced. To enhance the power conversion efficiency of the DSSC, a new type of double layered photoanode was prepared and optimized by using TiO2 nanoparticles as the main layer and TiO2 nanotubes (TNT) as the over-layer. These prepared cells were analysed by optical, photovoltaic and electrochemical measurement systems. The cells having the TNT over-layer showed longer electron life time, higher BET surface area and pore volume and 40% improved light harvesting efficiency. This new and optimized structure will be concrete fundamental background towards the development of the applications of next generation dye-sensitized solar cells.

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.

A PVdF-based electrolyte membrane for a carbon counter electrode in dye-sensitized solar cells

This research demonstrates the design and operation of a dye-sensitized solar cell (DSSC) with a multi-walled carbon nanotube counter electrode (CE) and a pore-filled membrane consisting of polyvinylidene fluoride-co-hexafluoropropylene (PVdF-co-HFP) as an electrolyte. In this cell, the internal resistance was substantially reduced and the efficiency was found to be as high as 6.04% under 1 sun. For this purpose, a sequence of experiments was carried out to demonstrate that the PVdF-co-HFP membrane possessed superior porosity to absorbed electrolytes and is more compatible with MWCNT CE as compared to the commonly used liquid electrolyte. For a comparison of results, different types of DSSC assemblies composed of MWCNT CEs were fabricated with liquid-, gel- and electrolyte-filled PVdF-co-HFP membranes. Morphological studies showed that the PVdF-co-HFP membrane is a regular and highly porous nano-web which provides optimized interfacial contact with defect-rich MWCNT CE. Detachment of the carbon particles from the CE causes short circuits and lower efficiency of the DSSCs. The proposed DSSC design not only lowers the interfacial charge transfer resistance (RCT = 2.98 Ω) but also reduces the risk of short circuits in the cell. This sustainable and highly efficient DSSC structure provides a new method for the simple fabrication of flexible solar cells and electronic devices.

Effect of elastane linear density and draft ratio on the physical and mechanical properties of core-spun cotton yarns

The aim of this study was to investigate the effect of elastane linear density and draft ratio on the physical and mechanical properties of core-spun yarns. Twenty yarn samples were prepared on industrial scale in a spinning mill with two different yarn linear densities, each with different two elastane deniers and five draft ratios. It was found that core-spun yarn’s tenacity, elongation and hairiness are affected not only by the overall yarn linear density but also by the elastane linear density and the draft ratio. However, the effect of elastane linear density and draft ratio was not found to be statistically significant on the yarn mass variations and total imperfections, which are only affected by the overall yarn liner density. A statistically significant interaction for yarn elongation at break was found between the yarn liner density and the elastane linear density concluding that elastane linear density used in the core must be compatible with the overall yarn liner density for attaining the best yarn elongation.

Statistical analysis of yarn to metal frictional coefficient of cotton spun yarn using Taguchi design of experiment

Yarn’s surface to metal friction is an important consideration in the subsequent process of knitting and weaving as it influences mainly the ends down rate, fly generation, process efficiency, wear and tear of machine parts, and production rate of the process. These frictional properties are measured in terms of the coefficient of friction of yarn. The effect of cotton type, yarn twist, yarn linear density, process type, and finishing treatment was studied on the surface to the metal friction coefficient of cotton spun yarn using Taguchi experimental design. The experiments were conducted with Pakistani and Indian cotton using combed and carded ring spinning processes. Using Taguchi design of experiment, a total of 36 samples of cotton ring-spun yarns were produced. The coefficient of friction between the yarn’s surface and metal’s surface is measured in compliance with ASTM D3108. The outcome of the Taguchi model to predict the coefficient of friction of yarns with a predefined combination of constituting parameters was further confirmed with nine yarn samples. The frictional characteristics of yarns are found to be influenced by all factors. In addition to the application of wax, the longer fiber length, lower trash count, lower short fiber index, and the optimum level of twist are found advantageous to reduce the yarn coefficient of friction.

Response Surface Modeling of Physical and Mechanical Properties of Cotton Slub Yarns

Abstract The objective of this study was to model the physical and mechanical properties of 100% cotton slub yarns commonly used in denim and other casual wear. Statistical models were developed using central composite experimental design of the response surface methodology. Yarn’s linear density, slub thickness, slub length and pause length were used as the key input variables while yarn strength, elongation, coefficient of mass variation, imperfections and hairiness were used as response/output variables. It was concluded that yarn strength and elongation increased with increase in linear density and pause length, and decreased with increase in slub thickness and slub length. Yarn mass variation and total imperfections increased with increase in slub thickness and pause length, whereas yarn imperfections and hairiness decreased with increase in slub length. It was further concluded that due to statistically significant square and interaction effects of some of the input variables, only the quadratic model instead of the linear models can adequately represent the relationship between the input and the output variables. These statistical models will be of great importance for the industrial personnel to improve their productivity and reduce sampling.