Browsing by Author "Siddique, A.B."

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Cost effective synthesis of sulfur and nitrogen co-doped graphene aerogel and application in binder free supercapacitor
(American Institute of Physics, 2024) Muhiuddin, M.; Khan, A.Z.; Devi, N.A.; Bharadishettar, N.; Meti, S.; Siddique, A.B.; Bhat K, U.; Akhtar, W.; Rahman, M.R.
Incorporating heteroatoms into graphene lattice results in enhanced electrical conductivity and electrochemically active sites and has significant importance in developing high-performance supercapacitors. In this study, sulfur and nitrogen co-doped graphene aerogel is synthesized via hydrothermal technique followed by a simple but effective freeze-thawing and ambient pressure drying process (referred to as SN-GA). The process requires low-cost raw materials and cost-effective equipment without the utilization of any special instrument that operates at ultra-low temperatures, under high pressure, or vacuum environment. Ammonium sulfate [(NH4)2SO4] and ethylenediamine are used as a source of sulfur and nitrogen and as a reducing agent. (NH4)2SO4 with different molarities (0, 12, 24, and 36 mM) are used to synthesize four different aerogel samples marked as GA, SN-GA1, SN-GA2, and SN-GA3. The electrode is prepared using an SN-GA2 sample, exhibiting an outstanding specific capacitance of 244 F g−1 at an applied current density of 1 A g−1 with almost 98.5% Coulomb efficiency. Furthermore, based on the SN-GA2 sample, the symmetrical supercapacitor is fabricated, displaying an energy density of 18.14 Wh kg−1 at a power density of 498.4 W kg−1. Hence, SN-GA2 renders a promising material for supercapacitor applications. © 2024 Author(s).
Efficiency enhancement in dye-sensitized solar cells through neodymium-doped graphene quantum dot-modified TiO? photoanodes
(Elsevier B.V., 2025) Senadeera, G.K.R.; Weerasekara, W.M.S.K.; Jaseetharan, T.; Sandunika, P.U.; Kumari, J.M.K.W.; Dissanayake, M.A.K.L.; Muhiuddin, M.; Rahman, M.R.; Bhat K, U.; Akhtar, M.W.; Udayakumar, U.; Siddique, A.B.; Ekanayake, P.
This study explored the effects of Neodymium-doped graphene quantum dots (NdGQDs) on improving the performance efficiency of TiO2 based dye-sensitized solar cells (DSSCs). By employing in-situ physical assisted mixing, DSSCs with optimized NdGQDs in TiO2 photoanodes showed a power conversion efficiency of 8.76 %, a significant improvement compared to the 6.01 % efficiency of pristine TiO2-based DSSCs under 100 mW cm?2 illumination (AM 1.5). Notably, the short-circuit current density increased by 74 %. HRTEM analysis revealed that the NdGQDs have a size range of approximately 7–9 nm. UV–visible spectroscopy and Mott-Schottky analysis revealed a positive shift in the Fermi level, promoting better electron transfer and increased photocurrent density at the expenses of the open circuit voltage. Electrochemical impedance spectroscopy characterization of DSSCs incorporating NdGQD-modified photoanodes revealed a reduction in electron transfer resistance at the photoanode|dye|electrolyte interface, accompanied by an increase in recombination resistance within the device suppressing the electron recombination rate. © 2024 Elsevier B.V.
Facile and rapid method to synthesis sulfur and nitrogen co-doped graphene quantum dots as an electrode material with excellent specific capacitance for supercapacitors application
(Elsevier Ltd, 2024) Muhiuddin, M.; Devi, N.A.; Bharadishettar, N.; Meti, S.; Siddique, A.B.; Satyanarayan, M.N.; Udaya, B.K.; Akhtar, W.; Rahman, M.R.
The current invention pertains to the expeditious simple synthesis of electrode materials that improve the storage capacity of supercapacitors (SCs). Sulfur and nitrogen co-doped graphene quantum dots (SN-GQDs) are synthesized using a microwave-assisted hydrothermal (MAH) process at low pressure and with a short reaction time. The utilization of SN-GQDs in conjunction with Polyaniline (PANI) has the potential to enhance the supercapacitor's energy and power density, owing to their notable specific capacitance. Implementing SN-GQDs material as an SCs electrode, exhibiting an outstanding specific capacitance of 1040 F/g at an applied current density of 0.5 A g−1. Furthermore, a composite of SN-GQDs/PANI is synthesized and the electrochemical performance is compared with the as-synthesized PANI. The symmetrical SCs are fabricated using SN-GQDs/PANI composite, and PANI. At a current density of 0.5 A g−1 SN-GQDs/PANI composite-based SC displays a superior energy density of 44.25 Wh/kg at a power density of 1.227 kW/kg. This is high in comparison to PANI-based SC which shows an energy density of 18.71 Wh/kg at 0.8 kW/kg power density at the same current density. The SC created using SN-GQDs/PANI composite exhibits superior properties and is a promising material for SC applications. © 2024 Elsevier B.V.
Neodymium doped graphene quantum dots/PANI composite for supercapacitor application
(Elsevier Ltd, 2025) Muhiuddin, M.; Bharadishettar, N.; Devi, N.A.; Gautam, A.; Chauhan, S.S.; Siddique, A.B.; Ahmad, M.I.; Satyanarayan, M.N.; K, U.B.; Akhtar, W.; Rahman, M.R.
The publication presents a streamlined and economical technique for fabricating advanced electrode materials to enhance the energy storage capabilities of supercapacitors (SCs). The focus is on synthesizing neodymium-doped graphene quantum dots (Nd-GQDs) via a microwave-assisted hydrothermal (MAH) process. This method uses microwave irradiation's rapid heating and efficient energy transfer under low pressure and minimal reaction time. The resulting Nd-GQDs exhibit enhanced electrochemical properties, including increased capacitance and improved charge storage, making this approach practical and effective for advancing supercapacitor technology. An exceptional specific capacitance of 618 F g?1 at a 5 mV s?1 scan rate is demonstrated using Nd-GQDs as the SC electrode material. Due to their high specific capacitance, Nd-GQDs, when combined with polyaniline (PANI), improve the energy and power density of SCs. Nd-GQDs/PANI composites with varying amounts of Nd-GQDs in symmetric SCs are fabricated to demonstrate their promising properties for SC applications. SCs fabricated with 20 mL of Nd-GQDs in the PANI matrix showed a superior specific capacitance of 354 F g?1 at a current density of 1 A g?1, while the energy density and power density were 49.15 Wh kg?1 and 2000 W kg?1, respectively. © 2025 Elsevier B.V.
Replacement of heat sink fan by nanocoolants for enhancement of CPU efficiency
(2013) Siddique, A.B.; Prabhu, K.N.
The highest temperature under which a CPU can operate without interruption is 90�C. Heat sink fans generally provided for removal of heat produced by the processor are proved to be inadequate when CPU usage is 100%. The objective of this work is to exploit the enhanced thermal properties of nanofluid for dissipation of heat from the Intel (R) Core (TM) i5- 2310 CPU @ 2.9GHz quad-core processor for cooling it to a suitable operating temperature. Nanocoolants were prepared with two types of nanoparticles, titania and copper. The volume percentage of nanoparticles in nanocoolants were 0.01 and 0.1. It was observed that nanofluids are more efficient coolants than the base fluid and found to be significantly better than the traditional heat sink fan, as indicated by the CPU temperature, under the same loading condition. The average CPU temperatures were 90�C, 58�C, 56.6�C and 54.5�C with heat sink fan, deionized water, 0.1 vol% TiO2 and 0.1 vol% Cu nanofluids respectively at the flow rate of 700ml/min and CPU usage of 100%. The lowest CPU operating temperature (54.5�C) was obtained with 0.1 vol% Cu at the flow rate of 700ml/min. The cooling of CPU was also affected by the flow rate and the volume fraction of nanoparticles in the nanocoolant.
Replacement of heat sink fan by nanocoolants for enhancement of CPU efficiency
(Institution of Engineering and Technology journals@theiet.org, 2013) Siddique, A.B.; Prabhu, K.N.
The highest temperature under which a CPU can operate without interruption is 90Â°C. Heat sink fans generally provided for removal of heat produced by the processor are proved to be inadequate when CPU usage is 100%. The objective of this work is to exploit the enhanced thermal properties of nanofluid for dissipation of heat from the Intel (R) Core (TM) i5- 2310 CPU @ 2.9GHz quad-core processor for cooling it to a suitable operating temperature. Nanocoolants were prepared with two types of nanoparticles, titania and copper. The volume percentage of nanoparticles in nanocoolants were 0.01 and 0.1. It was observed that nanofluids are more efficient coolants than the base fluid and found to be significantly better than the traditional heat sink fan, as indicated by the CPU temperature, under the same loading condition. The average CPU temperatures were 90Â°C, 58Â°C, 56.6Â°C and 54.5Â°C with heat sink fan, deionized water, 0.1 vol% TiO2 and 0.1 vol% Cu nanofluids respectively at the flow rate of 700ml/min and CPU usage of 100%. The lowest CPU operating temperature (54.5Â°C) was obtained with 0.1 vol% Cu at the flow rate of 700ml/min. The cooling of CPU was also affected by the flow rate and the volume fraction of nanoparticles in the nanocoolant.
Tunable dual color emission from the opposite faces of silicon nanoparticle embedded gel-glass
(Elsevier B.V., 2023) Das, B.; Hossain, S.M.; Mohanraj, G.T.; Chowdhury, S.R.; Siddique, A.B.; Rahman, M.R.; Ray, M.
A luminescent silicon nanoparticle embedded gel-glass, prepared by room temperature hydrolysis and reduction of aminosilane, exhibits intriguing dual photoluminescence (PL) from opposite faces of the glass. The face, which is excited with UV, exhibits excitation energy dependent blue-green emission. As the excitation energy is varied from 350 nm to 450 nm the PL peaks shift from 435 nm to 506 nm. The opposite surface, on the other hand emits nearly excitation independent green light – the PL peak shifts by ∼17 nm as the excitation energy is varied from 350 nm to 450 nm. The luminescent properties provide interesting insights into the light emission mechanism from nanostructured silicon. Spectral filtering by reabsorption and photon reabsorption-reemission in a size distributed nanoparticle system having different optical gaps play a combined role in the observed dual emission. We show that the dual emission can be tuned by simply varying the thickness of the glass. Such dual emission renders the luminescent glass amenable for several applications as a novel solid state display material. © 2023 Elsevier B.V.