Ashutosh Kumar
@universite-paris-saclay.fr
Postdoctoral Researcher
University of Paris Saclay France
EDUCATION
Ph.D. in Experimental Condensed Matter Physics
RESEARCH, TEACHING, or OTHER INTERESTS
Condensed Matter Physics, Materials Science, Electronic, Optical and Magnetic Materials, Ceramics and Composites
Scopus Publications
Scholar Citations
Scholar h-index
Scholar i10-index
Scopus Publications
Ashutosh Kumar, Preeti Bhumla, Duraisamy Sivaprahasam, Saswata Bhattacharya, and Nita Dragoe
American Physical Society (APS)
This study shows a method of enhancing the thermoelectric properties of GeTe-based materials by Ti and Bi co-doping on cation sites along with self-doping with Ge via simultaneous optimization of electronic (via crystal field engineering, and precise Fermi level optimization) and thermal (via point-defect scattering) transport properties. The pristine GeTe possesses high carrier concentration ($n$) due to intrinsic Ge vacancies, low Seebeck coefficient ($\\alpha$), and high thermal conductivity ($\\kappa$). The Ge vacancy optimization and crystal field engineering results in an enhanced $\\alpha$ via excess Ge and Ti doping, which is further improved by band structure engineering through Bi doping. As a result of improved $\\alpha$ and optimized Fermi level (carrier concentration), an enhanced power factor ($\\alpha^2\\sigma$) is obtained for Ti--Bi co-doped Ge$_{1.01}$Te. These experimental results are also evidenced by theoretical calculations of band structure, and thermoelectric parameters using density functional theory and Boltztrap calculations, respectively. A significant reduction in the phonon thermal conductivity ($\\kappa_{ph}$) from $\\sim$ 3.5 W.m$^{-1}$.K$^{-1}$ to $\\sim$ 1.06 W.m$^{-1}$.K$^{-1}$ at 300\\,K for Ti--Bi co-doping in GeTe, attributed to point-defect scattering due to mass and strain field fluctuation, in line with the Debye-Callaway model. The phonon dispersion calculations show a decreasing group velocity in Ti--Bi co-doped GeTe, supporting the obtained reduced $\\kappa_{ph}$. The strategies used in the present study can significantly increase the effective mass, optimize the carrier concentration, and decrease phonon thermal conductivity while achieving an impressive maximum zT value of 1.75 at 773\\,K and average zT (zT$_{av}$) of 1.03 for Ge$_{0.91}$Ti$_{0.02}$Bi$_{0.08}$Te over a temperature range of 300-773\\,K.
Ashutosh Kumar, David Bérardan, Diana Dragoe, Eric Riviere, Tomohiro Takayama, Hidenori Takagi, and Nita Dragoe
Elsevier BV
Ashutosh Kumar, Diana Dragoe, David Berardan, and Nita Dragoe
Elsevier BV
Ashutosh Kumar, Preeti Bhumla, Artur Kosonowski, Karol Wolski, Szczepan Zapotoczny, Saswata Bhattacharya, and Krzysztof T. Wojciechowski
American Chemical Society (ACS)
The preparation of composite materials is a promising methodology for concurrent optimization of electrical and thermal transport properties for improved thermoelectric (TE) performance. This study demonstrates how the acoustic impedance mismatch (AIM) and the work function of components decouple the TE parameters to achieve enhanced TE performance of the (1-z)Ge0.87Mn0.05Sb0.08Te-(z)WC composite. The simultaneous increase in the electrical conductivity (σ) and Seebeck coefficient (α) with WC (tungsten carbide) volume fraction (z) results in an enhanced power factor (α2σ) in the composite. The rise in σ is attributed to the creation of favorable current paths through the WC phase located between grains of Ge0.87Mn0.05Sb0.08Te, which leads to increased carrier mobility in the composite. Detailed analysis of the obtained electrical properties was performed via Kelvin probe force microscopy (work function measurement) and atomic force microscopy techniques (spatial current distribution map and current–voltage (I–V) characteristics), which are further supported by density functional theory (DFT) calculations. Furthermore, the difference in elastic properties (i.e., sound velocity) between Ge0.87Mn0.05Sb0.08Te and WC results in a high AIM, and hence, a large interface thermal resistance (Rint) between the phases is achieved. The correlation between Rint and the Kapitza radius depicts a reduced phonon thermal conductivity (κph) of the composite, which is explained using the Bruggeman asymmetrical model. Moreover, the decrease in κph is further validated by phonon dispersion calculations that indicate the decrease in phonon group velocity in the composite. The simultaneous effect of enhanced α2σ and reduced κph results in a maximum figure of merit (zT) of 1.93 at 773 K for (1-z)Ge0.87Mn0.05Sb0.08Te-(z)WC composite for z = 0.010. It results in an average thermoelectric figure of merit (zTav) of 1.02 for a temperature difference (ΔT) of 473 K. This study shows promise to achieve higher zTav across a wide range of composite materials.
Ashutosh Kumar and Krzysztof T. Wojciechowski
Elsevier BV
Mohammad Mehdi Ghanbarnezhad, Mohammad Bagher Shahsavani, Pramod S. Mali, Mansi Upadhyay, Ashutosh Kumar, Rawayh Muslim Albaghlani, Ali Niazi, and Reza Yousefi
Elsevier BV
Artur Kosonowski, Ashutosh Kumar, Karol Wolski, Szczepan Zapotoczny, and Krzysztof T. Wojciechowski
Elsevier BV
Samaneh Ahmadi, Mohammad Bagher Shahsavani, Zohreh Tavaf, Rawayh Muslim Albaghlany, Ashutosh Kumar, Ali Akbar Moosavi-Movahedi, and Reza Yousefi
Public Library of Science (PLoS)
Nowadays, a small number of incretin mimics are used to treat type 2 diabetes mellitus (T2DM) due to their longer half-life. The present study aimed to introduce a novel method for producing the liraglutide precursor peptide (LPP) and developing a potentially new incretin mimic. Here, human αB-crystallin (αB-Cry) was ligated to the LPP at the gene level, and the gene construct was expressed in Escherichia coli with a relatively good efficiency. The hybrid protein (αB-lir) was then purified by a precipitation method followed by anion exchange chromatography. After that, the peptide was released from the carrier protein by a chemical cleavage method yielding about 70%. The LPP was then purified by gel filtration chromatography, and HPLC estimated its purity to be about 98%. Also, the molecular mass of the purified peptide was finally confirmed by mass spectroscopy analysis. Assessment of the secondary structures suggested a dominant α-helical structure for the LPP and a β-sheet rich structure for the hybrid protein. The subcutaneous injection of the LPP and the αB-lir hybrid protein significantly reduced the blood sugar levels in healthy and diabetic mice and stimulated insulin secretion. Also, the hybrid protein exerts its bioactivities more effectively than the LPP over a relatively longer period of time. The results of this study suggested a novel method for the easy and cost-effective production of the LPP and introduced a new long-acting incretin mimic that can be potentially used for the treatment of T2DM patients.
Fatemeh Khosravi, Mansi Upadhyay, Ashutosh Kumar, Mohammad Bagher Shahsavani, Mohsen Akbarian, Haniyeh Najafi, Ali Mohammad Tamaddon, and Reza Yousefi
Elsevier BV
Brahmeshwar Mishra, Mansi Upadhyay, and Ashutosh Kumar
Elsevier
Ashutosh Kumar, D. Sivaprahasam, and Ajay D. Thakur
Elsevier BV
Karuna Kumari, Ashutosh Kumar, Ajay D Thakur, and S.J. Ray
Elsevier BV
Ashutosh Kumar, Preeti Bhumla, Taras Parashchuk, Stanislaw Baran, Saswata Bhattacharya, and Krzysztof T. Wojciechowski
American Chemical Society (ACS)
GeTe, as a p-type semiconductor, has been intensively studied in recent years as a promising lead-free mid-temperature-range thermoelectric (TE) material. Herein, we report an improved energy conve...
Narayanaperumal Pravin, Rakesh Kumar, Shalini Tripathi, Pardeep Kumar, Ganesh M Mohite, Ambuja Navalkar, Rajlaxmi Panigrahi, Namrata Singh, Laxmikant G. Gadhe, Shaffi Manchanda,et al.
Wiley
Protein aggregation into amyloid fibrils is a key feature of a multitude of neurodegenerative diseases such as Alzheimer's, Parkinson's, and Prion disease. To detect amyloid fibrils, fluorophores with high sensitivity and better efficiency coupled with the low toxicity are in high demand even to date. In this pursuit, we have unveiled two benzimidazole‐based fluorescence sensors ([C15H15N3] (C1) and [C16H16N3O2] (C2), which possess exceptional affinity toward different amyloid fibrils in its submicromolar concentration (8 × 10–9 M), whereas under a similar concentration, the gold standard Thioflavin‐T (ThT) fails to bind with amyloid fibrils. These fluorescent markers bind to α‐Syn amyloid fibrils as well as amyloid fibrils forming other proteins/peptides including Aβ42 amyloid fibrils. The 1H‐15N heteronuclear quantum correlation spectroscopy nuclear magnetic resonance data collected on wild‐type α‐Syn monomer with and without the fluorophores (C1 and C2) reveal that there is weak or no interactions between C1 or C2 with residues in α‐Syn monomer, which indirectly reflects the specific binding ability of C1 and C2 to the α‐Syn amyloid fibrils. Detailed studies further suggest that C1 and C2 can detect/bind with the α‐Syn amyloid fibril as low as 100 × 10–9 M. Extremely low or no cytotoxicity is observed for C1 and C2 and they do not interfere with α‐Syn fibrillation kinetics, unlike ThT. Both C1/C2 not only shows selective binding with amyloid fibrils forming various proteins/peptides but also displays excellent affinity and selectivity toward α‐Syn amyloid aggregates in SH‐SY5Y cells and Aβ42 amyloid plaques in animal brain tissues. Overall, our data show that the developed dyes could be used for the detection of amyloid fibrils including α‐Syn and Aβ42 amyloids with higher sensitivity as compared to currently used ThT.
Ashutosh Kumar, D. Sivaprahasam, and Ajay D. Thakur
Elsevier BV
Artur Kosonowski, Ashutosh Kumar, Taras Parashchuk, Raul Cardoso-Gil, and Krzysztof T. Wojciechowski
Royal Society of Chemistry (RSC)
The influence of grain size and interface thermal resistance on thermal conductivity of PbTe–CoSb3 polycrystalline composite.
Ashutosh Kumar, Artur Kosonowski, Piotr Wyzga, and Krzysztof T. Wojciechowski
Elsevier BV
Ashutosh Kumar, Ravi Kumar, and Dillip K. Satapathy
Elsevier BV
Soumik Ray, Nitu Singh, Rakesh Kumar, Komal Patel, Satyaprakash Pandey, Debalina Datta, Jaladhar Mahato, Rajlaxmi Panigrahi, Ambuja Navalkar, Surabhi Mehra,et al.
Springer Science and Business Media LLC
Ashutosh Kumar, Karuna Kumari, S. J. Ray, and Ajay D. Thakur
AIP Publishing
Multifunctional materials are of utmost importance owing to the combination of several functionalities into a single device. We present the multifunctional properties, namely, thermoelectric (TE) for energy harvesting and resistive switching (RS) for memory storage in the LaCoO 3 (LCO)–graphene nanocomposite system. The existence of individual phases of LCO and graphene is confirmed from x-ray diffraction and electron microscopy techniques. The x-ray photoelectron spectroscopy measurement reveals the formation of oxygen vacancies in the nanocomposite with the addition of graphene. The bipolar resistive switching behavior observed in a LCO–graphene nanocomposite is explained using space charge limited conduction mechanism and is found to evolve from a trap-limited to a trap-free region with an increase in the graphene volume fraction, which eventually ascribed to the ordering of oxygen vacancies in the nanocomposite system. The endurance plot of the nanocomposite shows a stable RS behavior for consecutive 1000 cycles. On the other hand, the creation of oxygen vacancies in the nanocomposite leads to change in the configurational entropy of charge states of cobalt, which tunes the Seebeck coefficient ( α). The decrease in α leads to an increase in the hopping hole concentration ( n h) estimated using the classical Heikes formula and is consistent with the increase in the electrical conductivity. The increase in oxygen vacancies leads to point-defect scattering, which further reduces the thermal conductivity of the nanocomposite. The optimized TE parameters show a figure-of-merit of 0.004 ± 0.000 48 at 300 K. The simultaneous observation of RS and TE properties in LCO–graphene nanocomposite provides new directions for multifunctional materials.
Karuna Kumari, Ashutosh Kumar, Ajay D. Thakur, and S. J. Ray
AIP Publishing
Ashutosh Kumar, Karuna Kumari, D. Sivaprahasam, and Ajay D. Thakur
AIP Publishing
Ashutosh Kumar, Karuna Kumari, C. V. Tomy, and Ajay D. Thakur
AIP Publishing
Karuna Kumari, Ashutosh Kumar, Dinesh K. Kotnees, Jayakumar Balakrishnan, Ajay D. Thakur, and S.J. Ray
Elsevier BV
D. Sivaprahasam, S.B. Chandrasekhar, S. Kashyap, Ashutosh Kumar, and R. Gopalan
Elsevier BV