Enhanced ionic mobility and increased efficiency of dye-sensitized solar cell by adding lithium chloride in poly(vinylidene fluoride) nanofiber as electrolyte medium

Sahito, I. A.,Ahmed, F.,Khatri, Z.,Sun, K. C.,Jeong, S. H. Springer Science + Business Media 2017 JOURNAL OF MATERIALS SCIENCE - Vol.52 No.24

Spindle Speed Optimization of a Ring Spinning Machine for Better Surface Irregularity and Hairiness of Yarn and Fabric

정성훈,Sahito, Iftikhar Ali,Arbab, Alvira Ayoub,Jeong, Sung Hoon 한국섬유공학회 2015 한국섬유공학회지 Vol.52 No.1

Producing yarn from natural fibers without creating irregularities in structure or having fibers protruding from the surface, remains the goal of spinners. This is a problem, as structural irregularities such as hairiness affect subsequent fabric manufacturing processes and the aesthetics of the final fabric. This work therefore focused on investigating the effects of varying the spindle speed of a ring spinning frame on the structure of yarn (i.e., its surface regularity and hairiness), its strength and the surface pilling of fabric made from such yarn with a view to optimizing the spindle speed. For this, yarns with counts of 20, 25, and 30 tex were produced at six different spindle speeds ranging from 11,000 to 21,000 rpm with an interval of 2,000 rpm. All other parameters were kept constant, including the draft for a particular count, the type and weight of the traveler, and the diameter of the ring. The results obtained revealed that as the spindle speed was increased to 17,000 rpm, the yarn structure became more regular and less hairy, thereby becoming stronger. Beyond 17,000 rpm, however, both the regularity and strength decreased, with the hairiness continuing to increase with increasing spindle speed. Consequently, the surface pilling of the fabric was found to be optimized when made from yarns produced at a spindle speed of 17,000 rpm.

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

Mengal, N.,Sahito, I.A.,Arbab, A.A.,Sun, K.C.,Qadir, M.B.,Memon, A.A.,Jeong, S.H. Applied Science Publishers ; Elsevier Science Ltd 2016 Carbohydrate polymers Vol.152 No.-

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<SUP>-1</SUP>, 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 efficient and durable dye-sensitized solar cells based on a wet-laid PET membrane electrolyte

Sun, Kyung Chul,Sahito, Iftikhar Ali,Noh, Jung Woo,Yeo, Sang Young,Im, Jung Nam,Yi, Sung Chul,Kim, Yeon Sang,Jeong, Sung Hoon The Royal Society of Chemistry 2016 Journal of Materials Chemistry A Vol.4 No.2

<▼1><P>Polyethylene terephthalate (PET), a commonly used textile fiber, was used in the form of a wet-laid non-woven fabric as a matrix for electrolytes in dye-sensitized solar cells (DSSCs).</P></▼1><▼2><P>Polyethylene terephthalate (PET), a commonly used textile fiber, was used in the form of a wet-laid non-woven fabric as a matrix for electrolytes in dye-sensitized solar cells (DSSCs). Also functioning as a separator between the photoanode and cathode of a DSSC, this non-woven membrane was prepared by a well-known wet-laid manufacturing process followed by calendaring to reduce the thickness and increase the uniformity of the structure. This membrane can better absorb the electrolyte turning into a quasi-solid, providing excellent interfacial contact between both electrodes of the DSSC and preventing a short circuit. An optimized membrane provides a better and more desirable structure for ionic conductivity, resulting in the improvement of the photovoltaic performance after calendaring. The quasi-solid-state DSSC assembled with an optimized membrane exhibited 10.248% power conversion efficiency (PCE) at 100 mW cm<SUP>−2</SUP>. With the aim of increasing the absorbance, the membrane was also plasma-treated with argon and oxygen separately, which resulted in retention of the electrolyte, avoiding its evaporation, and a 15% longer lifetime of the DSSC compared to liquid electrolytes. The morphology of the membrane was studied by field emission scanning electron microscopy, and the photovoltaic properties and impedance spectroscopy of the cells were studied using polarization curves and electrochemical impedance spectroscopy, respectively. The results suggest that this novel membrane can be used in high-efficiency solar cells, increasing their lifetime without compromising the photovoltaic properties.</P></▼2>

Shared molecular basis, diagnosis, and co-inheritance of alpha and beta thalassemia

Govinda Khatri,Abdul Moiz Sahito,Saboor Ahmed Ansari 대한혈액학회 2021 Blood Research Vol.56 No.4

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난카이 해구 지진해일이 한반도 연안에 미치는 영향

김샛별(SatByul Kim),Tatsuhiko Sahito,Eiichi Fukuyama,강태섭(Tae-Seob Kang) 대한지질학회 2017 대한지질학회 학술대회 Vol.2017 No.10

Self-assembled nitrogen-doped graphene quantum dots (N-GQDs) over graphene sheets for superb electro-photocatalytic activity

Riaz, Rabia,Ali, Mumtaz,Sahito, Iftikhar Ali,Arbab, Alvira Ayoub,Maiyalagan, T.,Anjum, Aima Sameen,Ko, Min Jae,Jeong, Sung Hoon Elsevier BV * North-Holland 2019 Applied Surface Science Vol.480 No.-

<P><B>Abstract</B></P> <P>Nitrogen-doped graphene quantum dots (N-GQDs) are emerging electroactive and visible light active organic photocatalysts, known for their high stability, catalytic activity and biocompatibility. The edge surfaces of N-GQDs are highly active, however, when N-GQDs make the film the edges are not fully exposed for catalysis. To avoid this issue, the N-GQDs are shaped to branched leaf shape, with an extended network of voids, offering highly active surfaces (edge) exposed for electrocatalytic and photocatalytic activity. The nitrogen doping causes a decrease in the bandgap of N-GQDs, thus enabling them to be superb visible light photocatalyst, for degradation of Methylene blue dye from water. Photoluminescence results confirmed that by a synergistic combination of the highly conductive substrate; Carbon fabric coated graphene sheets (CF-rGO) the recombination of photogenerated excitons is significantly suppressed, hence enabling their efficient utilization for catalysis. Comparatively, uniformly coated N-GQDs showed 49.3% lower photocatalytic activity, owing to their hidden active sites. The degradation was further boosted by 30% by combining the electrocatalytic activity, i.e. electro-photocatalysis of the proposed electrode. The proposed electrode material was analyzed using TEM, FE-SEM, FTIR, AFM, and WA-XRD, whereas the stability of electrode was confirmed by TGA, tensile test, bending test, and in harsh chemical environments. The proposed photo-electrocatalyst electrode is binder-free, stable, flexible and highly conductive, which makes the electrode quite suitable for flexible catalytic devices like flexible solar cells and wearable supercapacitors.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A flexible electrode is fabricated using self-assembled overlayer of Nitrogen doped Graphene Quantum Dots (N-GQDs). </LI> <LI> Self-assembeled highly porous leaflets structure has maximum exposed edge surfaces to accelarate the catalytic reaction. </LI> <LI> The proposed electrode is metal free and is stable at high temperature, harsh chemical environments, and mechanical stresses. </LI> <LI> The surface resistance of the all carbon electrode is only 2.5 Ω sq.<SUP>−1</SUP>. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Nitrogen doped graphene quantum dots (N-GQDs) were self-assembled (with high porosity) on reduced graphene oxide coated carbon fabric to fabricate a highly stable visible light photocatlytically and electrocatalytically active flexible electrode for water treatment.</P> <P>[DISPLAY OMISSION]</P>

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

Arbab, Alvira Ayoub,Memon, Anam Ali,Sahito, Iftikhar Ali,Mengal, Naveed,Sun, Kyung Chul,Ali, Mumtaz,Jeong, Sung Hoon The Royal Society of Chemistry 2018 Journal of materials chemistry. A, Materials for e Vol.6 No.18

<P>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 <I>via</I> 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 (<I>R</I>CT = 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.</P>

An electrocatalytic active lyocell fabric cathode based on cationically functionalized and charcoal decorated graphite composite for quasi-solid state dye sensitized solar cell

Mengal, Naveed,Arbab, Alvira Ayoub,Sahito, Iftikhar Ali,Memon, Anam Ali,Sun, Kyung Chul,Jeong, Sung Hoon Elsevier 2017 SOLAR ENERGY -PHOENIX ARIZONA THEN NEW YORK- Vol.155 No.-

<P><B>Abstract</B></P> <P>The state of the art of conductive functional textile woven fabrics have given rise to a demand for textile integrated electrodes. Herein, we report a highly conductive and flexible woven fabric electrode using highly absorbent lyocell fabric as the substrate and cationically functionalized and activated charcoal decorated graphite composite (AC-GC) as the coating film. This (AC-GC) coated lyocell fabric is used as a cathode for quasi-solid state dye sensitized solar cell (Q-DSSCs). Our suggested fabric based cathode shows sufficiently high conductivity and electrocatalytic activity (ECA) compared to platinum (Pt) based reference counter electrode (CE). This efficient CE demonstrates extremely low charge transfer resistance (R<SUB>CT</SUB>) of 1.56Ωcm<SUP>2</SUP> with polyethylene oxide based quasi-solid electrolyte. The cationic charged enriched charcoal decorated graphite planner structure provide more availability of active sites for the reduction of negatively charged tri-iodide ( I 3 - ) ions present in polymeric gel electrolyte. The formation of porous charcoal voids and conductive graphite channels entrap large amounts of gel electrolyte and provide fast diffusion of iodide/tri-iodide ( <SUP> I - </SUP> / I 3 - ) ions. Our organic system of AC-GC coated lyocell fabric based DSSCs assembly demonstrated 7.09% power conversion efficiency (PCE) when fabricated with quasi-solid electrolyte. This AC-GC coated fabric CE is also highly stable in water and electrolyte solution. The adequate electrocatalytic activity and cyclic stability demonstrate that this AC-GC coated fabric can be used to replace expensive Pt CE and can be used in flexible solar cells in future.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Various composites of activated charcoal and enzyme functionalized graphite (AC-GC) were prepared by a facile route. </LI> <LI> Highly porous and electrocatalytic AC-GC coatings were applied on lyocell fabric for preparation of flexible electrode. </LI> <LI> The flexible electrodes showed high stability in water and lithium iodide based electrolyte. </LI> <LI> DSSC based on optimized flexible electrode demonstrated maximum power conversion efficiency of 7.09%. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Cationic functionalized and activated charcoal decorated graphite coated lyocell fabric cathode is Q-DSSCs, displayed 7.1% efficiency.</P> <P>[DISPLAY OMISSION]</P>

Synthesis of highly photo-catalytic and electro-catalytic active textile structured carbon electrode and its application in DSSCs

Memon, Anam Ali,Arbab, Alvira Ayoub,Sahito, Iftikhar Ali,Sun, Kyung Chul,Mengal, Naveed,Jeong, Sung Hoon Elsevier 2017 SOLAR ENERGY -PHOENIX ARIZONA THEN NEW YORK- Vol.150 No.-

<P><B>Abstract</B></P> <P>Due to the growing need of portable smart devices, textile based solar cells have gained widespread attention in the field of wearable electronics. Here, we have demonstrated facile fabrication of metal free DSSCs by printing cotton, polyester and linen fabric counter electrodes with highly photo catalytic and electro catalytic active mesoporous carbon composite composed of highly conductive acid functionalized multi-walled carbon nanotubes decorated with mesoporous activated charcoal. Different mesoporous carbon structures were formulated by varying the concentration of activated charcoal intercalated in the acid functionalized MWCNT matrix. The mesoporous carbon composite with high level of porosity and oxygen rich surface exhibits low charge transfer resistance and excellent electro-catalytic activity for the reduction of tri-iodide ions. The mesoporous carbon composite exhibited 52% higher photo catalytic activity than the acid modified MWCNT. Besides that, in-depth comparison was carried out in between different kinds of textile fabrics coated with the carbon composite. The slight variation in the microporous structures and surface characteristics of cotton, polyester and linen fabrics led to marginal difference in the electrochemical and photovoltaic performance of DSSCs. High mobility of gel electrolyte within the porous structure of mesoporous carbon and textile fabrics assembly demonstrated low R<SUB>CT</SUB> of 0.82Ω, 0.77Ω and 1.37Ω for cotton, polyester and linen respectively. The obtained photovoltaic conversion efficiency of cotton, polyester and linen based DSSCs using gel electrolyte were 6.06%, 6.26% and 5.80% respectively. The suggested TCO and Pt free DSSC assemblies paved a way to the facile fabrication of textile based DSSC.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Photocatalytic and conductive textile counter electrodes (CEs) were synthesized. </LI> <LI> Cotton, Polyester and Linen fabrics were used as CEs substrate. </LI> <LI> CEs were coated with mesoporous Activated Charcoal intercalated carbon composites. </LI> <LI> Flexible CEs showed a very low charge transfer resistance of 0.77Ω. </LI> <LI> Flexible CEs exhibited a highest conversion efficiency of 6.26%. </LI> </UL> </P>