Manoj Tripathi
@sussex.ac.uk
Research Fellow, Department of Physics and Astronomy
University of Sussex
RESEARCH INTERESTS
I am experimentalist and possess expertise in AFM (atomic force microscope) operations and Raman spectroscopy for carbon materials. My investigations allow me to explore graphene and other 2D materials over several surfaces that include metals, insulators and polymers like polystyrene and epoxy. Tribology, fracture mechanics, hybrid fillers and interfacial science are my area of research interest. Currently, I am fucussing the use of the 2D materials for flexible electronics and straintronics.
Scopus Publications
Scholar Citations
Scholar h-index
Scholar i10-index
Scopus Publications
Julia Fekete, Poppy Joshi, Thomas J. Barrett, Timothy Martin James, Robert Shah, Amruta Gadge, Shobita Bhumbra, William Evans, Manoj Tripathi, Matthew Large,et al.
American Chemical Society (ACS)
Electrically percolating nanowire networks are among the most promising candidates for next-generation transparent electrodes. Scientific interest in these materials stems from their intrinsic current distribution heterogeneity, leading to phenomena like percolating pathway rerouting and localized self-heating, which can cause irreversible damage. Without an experimental technique to resolve the current distribution and an underpinning nonlinear percolation model, one relies on empirical rules and safety factors to engineer materials. We introduce Bose–Einstein condensate microscopy to address the longstanding problem of imaging active current flow in 2D materials. We report on performance improvement of this technique whereby observation of dynamic redistribution of current pathways becomes feasible. We show how this, combined with existing thermal imaging methods, eliminates the need for assumptions between electrical and thermal properties. This will enable testing and modeling individual junction behavior and hot-spot formation. Investigating both reversible and irreversible mechanisms will contribute to improved performance and reliability of devices.
Abhijit Biswas, Gustavo A. Alvarez, Manoj Tripathi, Jonghoon Lee, Tymofii S. Pieshkov, Chenxi Li, Bin Gao, Anand B. Puthirath, Xiang Zhang, Tia Gray,et al.
Royal Society of Chemistry (RSC)
We used temperature-dependent spark plasma sintering to induce phase transformations of metastable 3D c-BN to mixed-phase 3D/2D c-BN/h-BN and ultimately to the stable 2D h-BN phase at high temperature, useful for extreme-temperature technology.
Najwa binti Hamzan, Min Kai Lee, Lieh-Jeng Chang, Keat Hoe Yeoh, Khian-Hooi Chew, Manoj Tripathi, Alan Dalton, and Boon Tong Goh
Elsevier BV
Ali Zein Khater, M.A.S.R. Saadi, Sohini Bhattacharyya, Alex Kutana, Manoj Tripathi, Mithil Kamble, Shaowei Song, Minghe Lou, Morgan Barnes, Matthew D. Meyer,et al.
Elsevier BV
Cencen Wei, Abhijit Roy, Manoj Tripathi, Adel K.A. Aljarid, Jonathan P. Salvage, S. Mark Roe, Raul Arenal, and Conor S. Boland
Wiley
AbstractSpectrally inactive, electrically insulating, and chemically inert are adjectives broadly used to describe phyllosilicate minerals like mica and chlorite. Here, the above is disproved by demonstrating aqueous suspensions of liquid exfoliated nanosheets from five bulk mica types and chlorite schist. Nanosheet quality is confirmed via transmission electron and X‐ray photoelectron spectroscopies, as well as electron diffraction. Through Raman spectroscopy, a previously unreported size‐ and layer‐dependent spectral fingerprint is observed. When analyzing the high‐yield suspensions (≈1 mg mL−1) through UV–vis spectroscopy, all phyllosilicates present bandgap (Eg) narrowing from ≈7 eV in the bulk to ≈4 eV for monolayers. Unusually, the bandgap is inversely proportional to the areal size (A) of the nanosheets, measured via atomic force microscopy. Due to an unrecorded quantum confinement effect, nanosheet electronic properties scale toward semiconducting behavior (bandgap ≈3 eV) as nanosheet area increases. Furthermore, modeling X‐ray diffraction spectra shows that the root cause of the initial bandgap narrowing is lattice relaxation. Finally, with their broad range of isomorphically substituted ions, phyllosilicate nanosheets show remarkable catalytic properties for hydrogen production.
Najwa Hamzan, Mehran Sookhakian, Mohd Arif Mohd Sarjidan, Manoj Tripathi, Alan B. Dalton, Boon Tong Goh, and Yatimah Alias
American Chemical Society (ACS)
Enrico Gnecco, Arkadiusz Janas, Benedykt R. Jany, Antony George, Andrey Turchanin, Grzegorz Cempura, Adam Kruk, Manoj Tripathi, Frank Lee, A.B. Dalton,et al.
Elsevier BV
Peter J. Lynch, Manoj Tripathi, Aline Amorim Graf, Sean P. Ogilvie, Matthew J. Large, Jonathan Salvage, and Alan B. Dalton
American Chemical Society (ACS)
Tuneable infrared properties, such as transparency and emissivity, are highly desirable for a range of applications, including thermal windows and emissive cooling. Here, we demonstrate the use of carbon nanotube networks spray-deposited onto an ionic liquid-infused membrane to fabricate devices with electrochromic modulation in the mid-infrared spectrum, facilitating control of emissivity and apparent temperature. Such modulation is enabled by intraband transitions in unsorted single-walled carbon nanotube networks, allowing the use of scalable nanotube inks for printed devices. These devices are optimized by varying film thickness and sheet resistance, demonstrating the emissivity modulation (from ∼0.5 to ∼0.2). These devices and the understanding thereof open the door to selection criteria for infrared electrochromic materials based on the relationship between band structure, electrochemistry, and optothermal properties to enable the development of solution-processable large-area coatings for widespread thermal management applications.
Abhijit Biswas, Qiyuan Ruan, Frank Lee, Chenxi Li, Sathvik Ajay Iyengar, Anand B. Puthirath, Xiang Zhang, Harikishan Kannan, Tia Gray, A. Glen Birdwell,et al.
Elsevier BV
Jamil Islam, Parthiba Karthikeyan Obulisamy, Venkata K.K. Upadhyayula, Alan B. Dalton, Pulickel M. Ajayan, Muhammad M. Rahman, Manoj Tripathi, Rajesh Kumar Sani, and Venkataramana Gadhamshetty
American Chemical Society (ACS)
Md Hasan-Ur Rahman, Vidya Bommanapally, Dilanga Abeyrathna, Md Ashaduzzman, Manoj Tripathi, Mahzuzah Zahan, Mahadevan Subramaniam, and Venkataramana Gadhamshetty
IEEE
Biofilms are ubiquitous in aqueous environments, exerting significant influence on diverse surfaces, including metals prone to microbiologically influenced corrosion (MIC). This multifaceted phenomenon demands interdisciplinary collaborations to combat its far-reaching implications. In this context, our research delves into the intricate characterization of twodimensional (2D) materials, particularly hexagonal boron nitride (hBN), which is crucial for advancing corrosion prevention coatings. The nanoscale dimensions of 2D materials pose challenges in microstructural analysis and defect identification, necessitating labor-intensive traditional techniques. To address these complexities, we utilized two unsupervised machine learning models, namely, (a) K-means clustering, and (b) Gaussian Mixture Model (GMM), which enabled clear differentiation between multilayer hBN (MLhBN) and cracks. Our approach will streamline the characterization process and facilitate the extraction of thin layers with enhanced accuracy.
Frank Lee, Manoj Tripathi, Roque Sanchez Salas, Sean P. Ogilvie, Aline Amorim Graf, Izabela Jurewicz, and Alan B. Dalton
Royal Society of Chemistry (RSC)
There is a growing interest in 2D materials-based devices as the replacement for established materials, such as silicon and metal oxides in microelectronics and sensing, respectively.
Abhijit Biswas, Rishi Maiti, Frank Lee, Cecilia Y. Chen, Tao Li, Anand B. Puthirath, Sathvik Ajay Iyengar, Chenxi Li, Xiang Zhang, Harikishan Kannan,et al.
Royal Society of Chemistry (RSC)
Hexagonal boron nitride (h-BN) nanosheets are grown at room temperature by pulsed laser deposition that exhibits remarkable functional properties, creating a scenario for “h-BN on demand” under a frugal thermal budget, essential for nanotechnology.
Firas Awaja, Roberto Guarino, Manoj Tripathi, Mariangela Fedel, Giorgio Speranza, Alan B. Dalton, Nicola M. Pugno, and Michael Nogler
Elsevier BV
Manoj Tripathi, Rosa Garriga, Frank Lee, Sean P Ogilvie, Aline Amorim Graf, Matthew J Large, Peter J Lynch, Konstantinos Papagelis, John Parthenios, Vicente L Cebolla,et al.
IOP Publishing
Abstract Heterostructures of two-dimensional (2D) materials using graphene and MoS2 have enabled both pivotal fundamental studies and unprecedented sensing properties. These heterosystems are intriguing when graphene and MoS2 are interfaced with 2D sheets that emulate biomolecules, such as amino-terminated oligoglycine self-assemblies (known as tectomers). The adsorption of tectomer sheets over graphene and MoS2 modulates the physicochemical properties through electronic charge migration and mechanical stress transfer. Here, we present a systematic study by Raman spectroscopy and tectomer-functionalised scanning probe microscopy to understand mechanical strain, charge transfer and binding affinity in tectomer/graphene and tectomer/MoS2 hybrid structures. Raman mapping reveals distinctive thickness dependence of tectomer-induced charge transfer to MoS2, showing p-doping on monolayer MoS2 and n-doping on multilayer MoS2. By contrast, graphene is n-doped by tectomer independently of layer number, as confirmed by x-ray photoelectron spectroscopy. The interfacial adhesion between the amino groups and 2D materials are further explored using tectomer-functionalised probe microscopy. It is demonstrated here that these probes have potential for chemically sensitive imaging of 2D materials, which will be useful for mapping chemically distinct domains of surfaces and the number of layers. The facile tectomer-coating approach described here is an attractive soft-chemistry strategy for high-density amine-functionalisation of atomic force microscopy probes, therefore opening promising avenues for sensor applications.
Geetanjali Deokar, Abdeldjalil Reguig, Manoj Tripathi, Ulrich Buttner, Alberto Fina, Alan B. Dalton, and Pedro M. F. J. Costa
American Chemical Society (ACS)
Graphite sheets are known to exhibit remarkable performance in applications such as heating panels and critical elements of thermal management systems. Industrial-scale production of graphite films relies on high-temperature treatment of polymers or calendering of graphite flakes; however, these methods are limited to obtaining micrometer-scale thicknesses. Herein, we report the fabrication of a flexible and power-efficient cm2-scaled heater based on a polycrystalline nanoscale-thick graphite film (NGF, ∼100 nm thick) grown by chemical vapor deposition. The stability of these NGF heaters (operational in air over the range 30-300 °C) is demonstrated by a 12-day continuous heating test, at 215 °C. The NGF exhibits a fast switching response and attains a steady peak temperature of 300 °C at a driving bias of 7.8 V (power density of 1.1 W/cm2). This excellent heating performance is attributed to the structural characteristics of the NGF, which contains well-distributed wrinkles and micrometer-wide few-layer graphene domains (characterized using conductive imaging and finite element methods, respectively). The efficiency and flexibility of the NGF device are exemplified by externally heating a 2000 μm-thick Pyrex glass vial and bringing 5 mL of water to a temperature of 96 °C (at 2.4 W/cm2). Overall, the NGF could become an excellent active material for ultrathin, flexible, and sustainable heating panels that operate at low power.
Christina D. Polyzou, Ondřej Malina, Michaela Polaskova, Manoj Tripathi, Alan B. Dalton, John Parthenios, and Vassilis Tangoulis
Royal Society of Chemistry (RSC)
The extreme downsizing effect on 2D SCO nanoparticles resulted in a two-step hysteretic behavior and stability in aqueous dispersions.
Andrea Mescola, Guido Paolicelli, Sean P. Ogilvie, Roberto Guarino, James G. McHugh, Alberto Rota, Erica Iacob, Enrico Gnecco, Sergio Valeri, Nicola M. Pugno,et al.
Wiley
Friction-induced energy dissipation impedes the performance of nanomechanical devices. Nevertheless, the application of graphene is known to modulate frictional dissipation by inducing local strain. This work reports on the nanomechanics of graphene conformed on different textured silicon surfaces that mimic the cogs of a nanoscale gear. The variation in the pitch lengths regulates the strain induced in capped graphene revealed by scanning probe techniques, Raman spectroscopy, and molecular dynamics simulation. The atomistic visualization elucidates asymmetric straining of CC bonds over the corrugated architecture resulting in distinct friction dissipation with respect to the groove axis. Experimental results are reported for strain-dependent solid lubrication which can be regulated by the corrugation and leads to ultralow frictional forces. The results are applicable for graphene covered corrugated structures with movable components such as nanoelectromechanical systems, nanoscale gears, and robotics.
Nur Afira binti Anuar, Nurul Hidayah Mohamad Nor, Rozidawati binti Awang, Hideki Nakajima, Sarayut Tunmee, Manoj Tripathi, Alan Dalton, and Boon Tong Goh
Elsevier BV
Manoj Tripathi, Frank Lee, Antonios Michail, Dimitris Anestopoulos, James G. McHugh, Sean P. Ogilvie, Matthew J. Large, Aline Amorim Graf, Peter J. Lynch, John Parthenios,et al.
American Chemical Society (ACS)
Two-dimensional materials such as graphene and molybdenum disulfide are often subject to out-of-plane deformation, but its influence on electronic and nanomechanical properties remains poorly understood. These physical distortions modulate important properties which can be studied by atomic force microscopy and Raman spectroscopic mapping. Herein, we have identified and investigated different geometries of line defects in graphene and molybdenum disulfide such as standing collapsed wrinkles, folded wrinkles, and grain boundaries that exhibit distinct strain and doping. In addition, we apply nanomechanical atomic force microscopy to determine the influence of these defects on local stiffness. For wrinkles of similar height, the stiffness of graphene was found to be higher than that of molybdenum disulfide by 10-15% due to stronger in-plane covalent bonding. Interestingly, deflated graphene nanobubbles exhibited entirely different characteristics from wrinkles and exhibit the lowest stiffness of all graphene defects. Density functional theory reveals alteration of the bandstructures of graphene and MoS2 due to the wrinkled structure; such modulation is higher in MoS2 compared to graphene. Using this approach, we can ascertain that wrinkles are subject to significant strain but minimal doping, while edges show significant doping and minimal strain. Furthermore, defects in graphene predominantly show compressive strain and increased carrier density. Defects in molybdenum disulfide predominantly show tensile strain and reduced carrier density, with increasing tensile strain minimizing doping across all defects in both materials. The present work provides critical fundamental insights into the electronic and nanomechanical influence of intrinsic structural defects at the nanoscale, which will be valuable in straintronic device engineering.
Govind Chilkoor, Namita Shrestha, Alex Kutana, Manoj Tripathi, Francisco C. Robles Hernández, Boris I. Yakobson, Meyya Meyyappan, Alan B. Dalton, Pulickel M. Ajayan, Muhammad M. Rahman,et al.
American Chemical Society (ACS)
Graphene is a promising material for many biointerface applications in engineering, medical, and life-science domains. Here, we explore the protection ability of graphene atomic layers to metals exposed to aggressive sulfate-reducing bacteria implicated in corrosion. Although the graphene layers on copper (Cu) surfaces did not prevent the bacterial attachment and biofilm growth, they effectively restricted the biogenic sulfide attack. Interestingly, single-layered graphene (SLG) worsened the biogenic sulfide attack by 5-fold compared to bare Cu. In contrast, multilayered graphene (MLG) on Cu restricted the attack by 10-fold and 1.4-fold compared to SLG-Cu and bare Cu, respectively. We combined experimental and computational studies to discern the anomalous behavior of SLG-Cu compared to MLG-Cu. We also report that MLG on Ni offers superior protection ability compared to SLG. Finally, we demonstrate the effect of defects, including double vacancy defects and grain boundaries on the protection ability of atomic graphene layers.
Najwa binti Hamzan, Calvin Yi Bin Ng, Rad Sadri, Min Kai Lee, Lieh-Jeng Chang, Manoj Tripathi, Alan Dalton, and Boon Tong Goh
Elsevier BV
Abstract In this study, manganese silicide (Mn5Si3) nanorods grown on c-Si/SiO2 substrate by chemical vapor deposition were investigated in detail, where the reaction temperature was varied from 750 to 1, 000 °C. The Mn5Si3 nanorods were successfully grown at reaction temperatures above 750 °C. The growth of these Mn5Si3 nanorods was followed by a direct vapor transport process, which strongly dependent on the vapor pressure of the Mn precursor. Manganese silicide particles were used as the templates to initiate the growth of these nanorods. The results showed that increasing the reaction temperature increased the delivery of Mn vapor to the substrate surface. The magnetic properties of the Mn5Si3 nanorods were also investigated. The properties of the nanorods were influenced by the formation of Mn-rich silicide phase at higher reaction temperatures. The magnetic result indicated that the nanorods were mainly in ferromagnetic characteristic. The saturation magnetization values at 4 and 300 K were found to be higher at a reaction temperature of 950 °C, with a value of 0.70 and 0.03 emu/g, respectively. The maximum coercivity was obtained for the nanorods prepared at reaction temperature of 950 °C, with a value of 100 Oe.
R. DELL'ANNA, E. IACOB, M. TRIPATHI, A. DALTON, R. BÖTTGER, and G. PEPPONI
Wiley
Nanoscale structures were produced on silicon surfaces by low‐energy oxygen ion irradiation: periodic rippled or terraced patterns formed spontaneously, depending on the chosen combination of beam incidence angle and ion fluence. Atomic force microscopy image processing and analysis accurately described the obtained nanotopographies. Graphene monolayers grown by chemical vapour deposition were transferred onto the nanostructured silicon surfaces. The interfacial interaction between the textured surface and the deposited graphene governs the conformation of the thin carbon layer; the resulting different degree of regularity and conformality of the substrate‐induced graphene corrugations was studied and it was related to the distinctive topographical features of the silicon nanostructures. Raman spectroscopy revealed specific features of the strain caused by the alternating suspension and contact with the underlying nanostructures and the consequent modulation of the silicon–graphene interaction.
Govind Chilkoor, Kalimuthu Jawaharraj, Bhuvan Vemuri, Alex Kutana, Manoj Tripathi, Divya Kota, Taib Arif, Tobin Filleter, Alan B. Dalton, Boris I. Yakobson,et al.
American Chemical Society (ACS)
Corrosion by sulfur compounds is a long-standing challenge in many engineering applications. Specifically, designing a coating that protects metals from both abiotic and biotic forms of sulfur corrosion remains an elusive goal. Here we report that atomically thin layers (∼4) of hexagonal boron nitride (hBN) act as a protective coating to inhibit corrosion of the underlying copper (Cu) surfaces (∼6-7-fold lower corrosion than bare Cu) in abiotic (sulfuric acid and sodium sulfide) and biotic (sulfate-reducing bacteria medium) environments. The corrosion resistance of hBN is attributed to its outstanding barrier properties to the corrosive species in diverse environments of sulfur compounds. Increasing the number of atomic layers did not necessarily improve the corrosion protection mechanisms. Instead, multilayers of hBN were found to upregulate the adhesion genes in Desulfovibrio alaskensis G20 cells, promote cell adhesion and biofilm growth, and lower the protection against biogenic sulfide attack when compared to the few layers of hBN. Our findings confirm hBN as the thinnest coating to resist diverse forms of sulfur corrosion.
Manoj Tripathi, Luca Valentini, Yuanyang Rong, Silvia Bittolo Bon, Maria F. Pantano, Giorgio Speranza, Roberto Guarino, David Novel, Erica Iacob, Wei Liu,et al.
MDPI AG
Hybrid nanomaterials fabricated by the heterogeneous integration of 1D (carbon nanotubes) and 2D (graphene oxide) nanomaterials showed synergy in electrical and mechanical properties. Here, we reported the infiltration of carboxylic functionalized single-walled carbon nanotubes (C-SWNT) into free-standing graphene oxide (GO) paper for better electrical and mechanical properties than native GO. The stacking arrangement of GO sheets and its alteration in the presence of C-SWNT were comprehensively explored through scanning electron microscopy, X-ray photoelectron spectroscopy (XPS) and X-ray diffraction. The C-SWNTs bridges between different GO sheets produce a pathway for the flow of electrical charges and provide a tougher hybrid system. The nanoscopic surface potential map reveals a higher work function of the individual functionalised SWNTs than surrounded GO sheets showing efficient charge exchange. We observed the enhanced conductivity up to 50 times and capacitance up to 3.5 times of the hybrid structure than the GO-paper. The laminate of polystyrene composites provided higher elastic modulus and mechanical strength when hybrid paper is used, thus paving the way for the exploitation of hybrid filler formulation in designing polymer composites.