Improved light absorbance and quantum-dot loading by macroporous TiO₂ photoanode for PbS quantum-dot-sensitized solar cells

Basit, Muhammad Abdul,Abbas, Muhammad Awais,Jung, Eun Sun,Bang, Jin Ho,Park, Tae Joo Elsevier Sequoia S.A 2017 Materials chemistry and physics Vol.196 No.-

<P><B>Abstract</B></P> <P>Macroporous titanium dioxide (TiO<SUB>2</SUB>) layer was formed through selective etching of silica (SiO<SUB>2</SUB>) microspheres incorporated in TiO<SUB>2</SUB>/SiO<SUB>2</SUB> composite layer, resulting in a significant increase in the photovoltaic performance of PbS quantum-dot-sensitized solar cells (QDSSCs). Strategic incorporation of macroporous TiO<SUB>2</SUB> layer on top of a mesoporous layer improved the light absorption characteristics, which is concurrently attributed to light scattering behaviour of macropores and increased loading of quantum dots (QDs) <I>via</I> successive ionic layer adsorption and reaction process. Thereby, a direct increase in the photocurrent density of PbS-QDSSC was ensued. Open-circuit voltage decay analysis combined with in-depth electrochemical impedance spectroscopy revealed a significant improvement in the electron life time and recombination resistance of QDSSC which was credited to the barrier effect of more uniformly loaded PbS QDs inside macroporous TiO<SUB>2</SUB> photoanode.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Macroporous TiO<SUB>2</SUB> photoanode was developed using HF-etching of SiO<SUB>2</SUB> microspheres. </LI> <LI> Macroporous TiO<SUB>2</SUB> layer enhanced light scattering characteristics of photoanode. </LI> <LI> QD loading was enhanced due to better diffusion of ionic precursors in photoanode. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Numerical study of laminar flow and friction characteristics in narrow channels under rolling conditions using MPS method

Muhammad Abdul Basit,Wenxi Tian,Ronghua Chen,Suizheng Qiu,Guanghui Su 한국원자력학회 2019 Nuclear Engineering and Technology Vol.51 No.8

Modern small modular nuclear reactors can be built on a barge in ocean, therefore, their flow charac-teristics depend upon the ocean motions. In the present research, effect of rolling motion on flow and friction characteristics of laminar flow through vertical and horizontal narrow channels has been studied. A computer code has been developed using MPS method for two-dimensional Navier-Stokes equations with rolling motion force incorporated. Numerical results have been validated with the literature and have been found in good agreement. It has been found that the impact of rolling motions on flow characteristics weakens with increase in flow rate and fluid viscosity. For vertical narrow channels, the time averaged friction coefficient for vertical channels differed from steady friction coefficient. Furthermore, increasing the horizontal distance from rolling pivot enhanced the flow fluctuations but these stayed relatively unaffected by change in vertical distance of channel from the rolling axis. For horizontal narrow channels, the flow fluctuations were found to be sinusoidal in nature and their magnitude was found to be dependent mainly upon gravity fluctuations caused by rolling.

Enhanced PbS quantum dot loading on TiO₂ photoanode using atomic-layer-deposited ZnS interfacial layer for quantum dot-sensitized solar cells

Basit, Muhammad Abdul,Abbas, Muhammad Awais,Jung, Eun Sun,Ali, Ijaz,Kim, Dae Woong,Bang, Jin Ho,Joo Park, Tae Elsevier 2018 Materials chemistry and physics Vol.220 No.-

<P><B>Abstract</B></P> <P>Ultrathin and conformal ZnS film grown by atomic layer deposition was employed in quantum dot-sensitized solar cells (QDSSCs) as an interfacial layer (IL) between mesoporous TiO<SUB>2</SUB> photoanode and successive ionic layer adsorption and reaction (SILAR)-grown PbS QDs. ZnS IL provided more nucleation sites compared to a bare TiO<SUB>2</SUB> photoanode, which enhanced PbS QDs loading remarkably. As a result, the optical absorbance and thus photocurrent density considerably increased. The power conversion efficiency of QDSSCs increased from 3.4% to 4% by introducing the ZnS IL. However, the <I>β</I>-recombination model obtained from electrochemical impedance spectroscopy revealed the evolution of charge carrier recombination inside QDs as a consequence of enhanced QD loading, which partly dilutes this benefit.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Ultrathin and conformal ZnS interfacial layer (IL) was grown on mesoporous TiO<SUB>2</SUB> photoanode by atomic layer deposition. </LI> <LI> ZnS IL provided more nucleation sites for PbS QDs deposition using SILAR. </LI> <LI> Light absorbance, photocurrent density and power conversion efficiency of QDSSCs were increased by adoption of ZnS IL. </LI> </UL> </P>

Efficacy of In₂S₃ interfacial recombination barrier layer in PbS quantum-dot-sensitized solar cells

Basit, Muhammad Abdul,Abbas, Muhammad Awais,Bang, Jin Ho,Park, Tae Joo Elsevier 2015 JOURNAL OF ALLOYS AND COMPOUNDS Vol.653 No.-

<P><B>Abstract</B></P> <P>In<SUB>2</SUB>S<SUB>3</SUB> interfacial recombination barrier layer (IBL) via successive ionic layer adsorption and reaction (SILAR) was successfully employed between PbS quantum dots and mesoporous TiO<SUB>2</SUB> in quantum-dot-sensitized solar cells (QDSSCs). In<SUB>2</SUB>S<SUB>3</SUB> IBL significantly increased the resistance against back electron transfer from TiO<SUB>2</SUB>, resulting an increment in the photocurrent density (<I>J</I> <SUB> <I>SC</I> </SUB>) for the cell with single SILAR cycle of In<SUB>2</SUB>S<SUB>3</SUB> IBL. Further increase in the number of SILAR cycles of In<SUB>2</SUB>S<SUB>3</SUB> IBL deteriorated the <I>J</I> <SUB> <I>SC</I> </SUB>, whereas open-circuit voltage sustained the increasing trend. Therefore, an optimal photo-conversion efficiency of ∼2.2% was obtained for the cell with 2 SILAR cycles of In<SUB>2</SUB>S<SUB>3</SUB> IBL, which strategically reached a value of ∼2.70% after annealing (increased by 40% compared to the control cell without IBL). In<SUB>2</SUB>S<SUB>3</SUB> IBL not only improved the recombination resistance and electron life time of the cells, but it also enhanced the photostability of the cells.</P> <P><B>Highlights</B></P> <P> <UL> <LI> In<SUB>2</SUB>S<SUB>3</SUB> interfacial recombination barrier layer was deposited on TiO<SUB>2</SUB> photoanode via SILAR process. </LI> <LI> Resistance against back electron transfer from TiO<SUB>2</SUB> (recombination) increased notably. </LI> <LI> Fabricated PbS-QDSSCs were characterized using IPCE, OCVD and EIS techniques. </LI> <LI> In<SUB>2</SUB>S<SUB>3</SUB> IBL improved chemical capacitance, electron life time and photostability of modified cells. </LI> <LI> 2In<SUB>2</SUB>S<SUB>3</SUB> IBL showed optimal performance, yielding 40% improvement in PCE after heat treatment. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Investigation of single bubble behavior under rolling motions using multiphase MPS method on GPU

Basit, Muhammad Abdul,Tian, Wenxi,Chen, Ronghua,Basit, Romana,Qiu, Suizheng,Su, Guanghui Korean Nuclear Society 2021 Nuclear Engineering and Technology Vol.53 No.6

Study of single bubble behavior under rolling motions can prove useful for fundamental understanding of flow field inside the modern small modular nuclear reactors. The objective of the present study is to simulate the influence of rolling conditions on single rising bubble in a liquid using multiphase Moving Particle Semi-implicit (MPS) method. Rolling force term was added to 2D Navier-Stokes equations and a computer program was written using C language employing OpenACC to port the code to GPU. Computational results obtained were found to be in good agreement with the results available in literature. The impact of rolling parameters on trajectory and velocity of the rising bubble has been studied. It has been found that bubble rise velocity increases with rolling amplitude due to modification of flow field around the bubble. It has also been concluded that the oscillations of free surface, caused by rolling, influence the bubble trajectory. Furthermore, it has been discovered that smaller vessel width reduces the impact of rolling motions on the rising bubble. The effect of liquid viscosity on bubble rising under rolling was also investigated and it was found that effects of rolling became more pronounced with the increase of liquid viscosity.

Quantum dot-sensitized solar cells: A review on interfacial engineering strategies for boosting efficiency

Muhammad Abdul Basit,Muhammad Aanish Ali,Zunair Masroor,Zeeshan Tariq,방진호 한국공업화학회 2023 Journal of Industrial and Engineering Chemistry Vol.120 No.-

Quantum dot-sensitized solar cells (QDSSCs) have become important in dealing with the energyeconomy-environment dilemma of today’s world. QDSSCs offer a unique set of characteristics includingmultiple exciton generation and higher extinction coefficients associated with quantum dots (QDs),avowing its potential for high photoconversion efficiency (PCE), which is evident from its augmentedincrease of the PCE to 15 % within the past decade. To make full use of the photoelectrochemical competenceof QDSSCs, researchers have strategically dealt with various detrimental events taking placewithin QDs and on interfacial positions in photoanodes. Back transfer of photogenerated electrons, electron/hole recombination via surface defects, and photocorrosion of QDs seriously deteriorate the performanceof QDSSCs and are thus considered a bottleneck for their further improvements. Deposition ofinterfacial layers (ILs) has proven beneficial in this regard and hence, it requires a comprehensive overview. Based on their positions inside the photoanode of QDSSCs, ILs offer single or multiple roles inimproving the PCE: improvement of surface passivation (passivation ILs), deposition of QDs (seedingILs), and/or control of the back transfer of electrons to the electrolyte (blocking ILs). This review coversthe multifunctional diversity of ILs inside QDSSCs, apposite characterization techniques for ILs, and prospectsregarding their role.

Design and Analysis of a Compact GSM/GPS Dual-Band Bandpass Filter Using a T-Shaped Resonator

Basit Abdul,Khattak Muhammad Irfan,Al-Hasan Mauth,Nebhen Jamel,Jan Atif 한국전자파학회 2022 Journal of Electromagnetic Engineering and Science Vol.22 No.2

This study presents an ultracompact dual-band bandpass filter with controllable transmission zeros based on quarter-wave dual-mode resonator for GSM (global system for mobile communications) and GPS (global positioning system) wireless applications. The filter is made up of two quarter-wave resonators, which help to independently control the passbands. A direct feed resonator creates the first operating band, which serves as a feeding source for the interior resonator and operates at a higher frequency band. Therefore, a pair of transmission zeros can be energized between the two passbands, and high roll-off skirts are obtained. To reduce the size of the entire filter, the two resonators are bent and connected together through a hole in a metal base. The structure is symmetrical in nature, so both frequency bands can be obtained using the even-odd mode analysis method. For GSM applications, the center frequency of the first working band is 850 MHz, while for GPS wireless applications, the center frequency of the second working band is 1.57 GHz. Although there is a feed line (λg is based on a waveguide length of 850 MHz), the filter has been simulated and fabricated for verification, with an ultra-compact size of 0.10 λg × 0.09 λg (0.0095 λg 2). The simulation results and measured results match well, and the theory of the design concept is recognized.

Compact Tri-band Bandpass Filter Based on Asymmetric Step Impedance Resonators for WiMAX and RFID Systems

Abdul Basit,Muhammad Irfan Khattak,Ayman Althuwayb,Jamel Nebhen 한국전자파학회JEES 2021 Journal of Electromagnetic Engineering and Science Vol.21 No.4

In this article, a simple method is developed to design a highly miniaturized tri-band bandpass filter (BPF) utilizing two asymmetric coupled resonators with one step discontinuity and one uniform impedance resonator (UIR) for worldwide interoperability for microwave access (WiMAX) and radio frequency identification (RFID) applications. The first and second passbands located at 3.7 GHz and 6.6 GHz are achieved through two asymmetric coupled step impedance resonators (SIRs), while the third passband, centered at 9 GHz, is achieved using a half-wavelength UIR, respectively. The fundamental frequencies of this BPF are implemented by tuning the physical length ratio (α) and impedance ratio (R) of the asymmetric SIRs. The proposed filter is designed and fabricated with a circuit dimension of 13.69 mm × 25 mm (0.02 λg × 0.03 λg), where λg represents the guided wavelength at the first passband. The experimental and measured results are provided with good matching.

Rehabilitation of reinforced concrete frames with non-seismic details using eccentric steel braces

Abdul Basit,Muhammad S. Khan,Naveed Ahmad 국제구조공학회 2021 Structural Engineering and Mechanics, An Int'l Jou Vol.80 No.4

This paper presents quasi-static cyclic loading tests of reduced scale reinforced concrete Eccentrically Steel Brace (ESB) retrofitted and bare portal frames. A hollow square steel brace was attached to the beam diagonally at a distance of LBeam/8 from the beam ends for enhancing the seismic performance of deficient frames. Results indicated promising behavior of ESB retrofitted frame opposed to the bare frames and shifted the damage mechanism from severe shear cracking and column flexural hinging to beam flexural cracking. ESB retrofitted frame also increased lateral force-displacement capacity, stiffness and hysteretic damping compared to the bare frames. The test results were also used to calibrate a nonlinear modeling technique proposed using a finite element based program. Additionally, a nonlinear dynamic acceleration time history analysis were carried out for two-story ESB retrofitted and bare frames and inter-story drift limits were identified for each structure. The study also confirms the importance of joint detailing’s and its beneficial role in improving the seismic performance of frames under earthquake ground motions.

Outcomes of Large Volume Paracentesis in Cirrhotic Patients with Spontaneous Bacterial Peritonitis

( Hafiz Abdul Basit Siddiqui ),( Muhammad Tahir Khan ),( Hasnain Ali Shah ),( Rabeea Azmat ),( Saad Bin Zafar ) 대한간학회 2017 춘·추계 학술대회 (KASL) Vol.2017 No.1

Aims & Background: Bacterial infections are one of the most frequent complication in cirrhosis, particularly in patients with decompensated cirrhosis and accounts for significant mortality. Ascites is one of the most common complications of hepatic cirrhosis (1). In a country like Pakistan where the prevalence of Hepatitis C is on the rise, end stage liver disease is becoming a common scenario (2-4). Spontaneous bacterial peritonitis (SBP) occurs in 10-30% of such patients and is associated with high mortality rate among hospitalized patients (1, 5-7). The diagnosis of SBP through paracentesis is crucial in the management of SBP. SBP should be diagnosed early as for successful treatment of patients. Diagnostic paracentesis facilitates rapid initiation of antimicrobial therapy and permits optimal coverage in case a causative organism identified. However, more recently, the role of paracentesis in management of SBP is also explored through large volume removal of ascitic fluid. Despite the proposed risk of renal failure, Large Volume Paracentesis (LVP) among SBP patients has shown promising results indicated by lesser morbidity and mortality (8). Rationale of the study: Spontaneous bacterial peritonitis is a serious infectious condition with grave outcome in cirrhotic patients. Large volume paracentesis decreases the burden of infective fluid causing further deterioration of condition. Outcomes of LVP in SBP patients are not clearly addressed in previous studies. Furthermore, to date, no study from the country has reported the effect of large volume paracentesis on the management of SBP in hospitalized patients. This study will assess the outcomes of LVP in patients with SBP, both in terms of length of stay, in hospital 6 week mortality. Objectives: To compare the treatment outcomes among patients with and without large volume paracentesis diagnosed with Spontaneous Bacterial Peritonitis Methods: Study design: Analytical Cross-sectional Study Setting: Gastroenterology Unit, The Aga Khan University Hospital, Karachi Study Duration: 2 Years Study population: Patients admitted with Spontaneous Bacterial Peritonitis to Gastroenterology Unit, the Aga Khan University Hospital Sample Size: Using OpenEpi.com online sample size calculator and using the differences in hospital stay among patients with and without delayed paracentesis as 36.84% and 21.48% (8) the sample size was calculated to be 200 at 95% confidence level (100 in each group). Sampling Technique: Consecutive Sampling Inclusion Criteria: Patients admitted with ascites found to have spontaneous bacterial peritonitis on diagnostic paracentesis. 1) Patients with complete records 2) Above 18 and below 75 years of age Exclusion criteria: 1) Incomplete records 2) Secondary peritonitis Data Collection: The data will be extracted from the records and information analyzed will be patient age, gender, whether the patients receive large volume paracentesis or not, the length of hospital stay, and length of ICU stay. No patient will be enrolled for the study and retrospective data analysis will be carried out. Conclusions: Extracted data till now favours that LVP in patients with SBP translates into significantly positive outcomes in terms of length of hospital stay, spcecial care unit stay, need for terlipressin infusions, in hosptial mortality and 6 weeks mortality post large volume paracentesis. Hence LVP shoiuld be performed in patients suffering from SBP.