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
George Kourmoulakis, Sotiris Psilodimitrakopoulos, George Miltos Maragkakis, Leonidas Mouchliadis, Antonios Michail, Joseph A. Christodoulides, Manoj Tripathi, Alan B. Dalton, John Parthenios, Konstantinos Papagelis,et al.
Springer Science and Business Media LLC
AbstractTwo-dimensional (2D) graphene and graphene-related materials (GRMs) show great promise for future electronic devices. GRMs exhibit distinct properties under the influence of the substrate that serves as support through uneven compression/ elongation of GRMs surface atoms. Strain in GRM monolayers is the most common feature that alters the interatomic distances and band structure, providing a new degree of freedom that allows regulation of their electronic properties and introducing the field of straintronics. Having an all-optical and minimally invasive detection tool that rapidly probes strain in large areas of GRM monolayers, would be of great importance in the research and development of novel 2D devices. Here, we use Polarization-resolved Second Harmonic Generation (P-SHG) optical imaging to identify strain distribution, induced in a single layer of WS2 placed on a pre-patterned Si/SiO2 substrate with cylindrical wells. By fitting the P-SHG data pixel-by-pixel, we produce spatially resolved images of the crystal armchair direction. In regions where the WS2 monolayer conforms to the pattern topography, a distinct cross-shaped pattern is evident in the armchair image owing to strain. The presence of strain in these regions is independently confirmed using a combination of atomic force microscopy and Raman mapping.
Andrés Seral-Ascaso, Ruth Lahoz, Manoj Tripathi, Katrín L. Elídóttir, Vicente L. Cebolla, Izabela Jurewicz, Alan B. Dalton, Rosa Garriga, and Edgar Muñoz
Elsevier BV
George Kourmoulakis, Antonios Michail, Dimitris Anestopoulos, Joseph A. Christodoulides, Manoj Tripathi, Alan Β. Dalton, John Parthenios, Konstantinos Papagelis, Emmanuel Stratakis, and George Kioseoglou
MDPI AG
Nanoscale-engineered surfaces induce regulated strain in atomic layers of 2D materials that could be useful for unprecedented photonics applications and for storing and processing quantum information. Nevertheless, these strained structures need to be investigated extensively. Here, we present texture-induced strain distribution in single-layer WS2 (1L-WS2) transferred over Si/SiO2 (285 nm) substrate. The detailed nanoscale landscapes and their optical detection are carried out through Atomic Force Microscopy, Scanning Electron Microscopy, and optical spectroscopy. Remarkable differences have been observed in the WS2 sheet localized in the confined well and at the periphery of the cylindrical geometry of the capped engineered surface. Raman spectroscopy independently maps the whole landscape of the samples, and temperature-dependent helicity-resolved photoluminescence (PL) experiments (off-resonance excitation) show that suspended areas sustain circular polarization from 150 K up to 300 K, in contrast to supported (on un-patterned area of Si/SiO2) and strained 1L-WS2. Our study highlights the impact of the dielectric environment on the optical properties of two-dimensional (2D) materials, providing valuable insights into the selection of appropriate substrates for implementing atomically thin materials in advanced optoelectronic devices.
Kristen Miller, Jessica M. Gayle, Soumyabrata Roy, Mohamed H. Abdellah, Rifan Hardian, Levente Cseri, Pedro G. Demingos, Hema Rajesh Nadella, Frank Lee, Manoj Tripathi,et al.
Wiley
AbstractStructural design of 2D conjugated porous organic polymer films (2D CPOPs), by tuning linkage chemistries and pore sizes, provides great adaptability for various applications, including membrane separation. Here, four free‐standing 2D CPOP films of imine‐ or hydrazone‐linked polymers (ILP/HLP) in combination with benzene (B‐ILP/HLP) and triphenylbenzene (TPB‐ILP/HLP) aromatic cores are synthesized. The anisotropic disordered films, composed of polymeric layered structures, can be exfoliated into ultrathin 2D‐nanosheets with layer‐dependent electrical properties. The bulk CPOP films exhibit structure‐dependent optical properties, triboelectric nanogenerator output, and robust mechanical properties, rivaling previously reported 2D polymers and porous materials. The exfoliation energies of the 2D CPOPs and their mechanical behavior at the molecular level are investigated using density function theory (DFT) and molecular dynamics (MD) simulations, respectively. Exploiting the structural tunability, the comparative organic solvent nanofiltration (OSN) performance of six membranes having different pore sizes and linkages to yield valuable trends in molecular weight selectivity is investigated. Interestingly, the OSN performances follow the predicted transport modeling values based on theoretical pore size calculations, signifying the existence of permanent porosity in these materials. The membranes exhibit excellent stability in organic solvents at high pressures devoid of any structural deformations, revealing their potential in practical OSN applications.
Md Hasan-Ur Rahman, Rabbi Sikder, Manoj Tripathi, Mahzuzah Zahan, Tao Ye, Etienne Gnimpieba Z., Bharat K. Jasthi, Alan B. Dalton, and Venkataramana Gadhamshetty
MDPI AG
Detecting pathogenic bacteria and their phenotypes including microbial resistance is crucial for preventing infection, ensuring food safety, and promoting environmental protection. Raman spectroscopy offers rapid, seamless, and label-free identification, rendering it superior to gold-standard detection techniques such as culture-based assays and polymerase chain reactions. However, its practical adoption is hindered by issues related to weak signals, complex spectra, limited datasets, and a lack of adaptability for detection and characterization of bacterial pathogens. This review focuses on addressing these issues with recent Raman spectroscopy breakthroughs enabled by machine learning (ML), particularly deep learning methods. Given the regulatory requirements, consumer demand for safe food products, and growing awareness of risks with environmental pathogens, this study emphasizes addressing pathogen detection in clinical, food safety, and environmental settings. Here, we highlight the use of convolutional neural networks for analyzing complex clinical data and surface enhanced Raman spectroscopy for sensitizing early and rapid detection of pathogens and analyzing food safety and potential environmental risks. Deep learning methods can tackle issues with the lack of adequate Raman datasets and adaptability across diverse bacterial samples. We highlight pending issues and future research directions needed for accelerating real-world impacts of ML-enabled Raman diagnostics for rapid and accurate diagnosis and surveillance of pathogens across critical fields.
Surbhi Slathia, Cencen Wei, Manoj Tripathi, Raphael Tromer, Solomon Demiss Negedu, Conor S Boland, Suman Sarkar, Douglas S Galvao, Alan Dalton, and Chandra Sekhar Tiwary
IOP Publishing
Abstract Two-dimensional (2D) layered transition-metal based tellurides (chalcogens) are known to harness their surface atoms’ characteristics to enhance topographical activities for energy conversion, storage, and magnetic applications. The gradual stacking of each sheet alters the surface atoms’ subtle features such as lattice expansion, leading to several phenomena and rendering tunable properties. Here, we have evaluated thickness-dependent mechanical properties (nanoscale mechanics, tribology, potential surface distributions, interfacial interaction) of 2D CoTe2 sheets and magnetic behavior using surface probe techniques. The experimental observations are further supported and explained with theoretical investigations: density functional theory and molecular dynamics. The variation in properties observed in theoretical investigations unleashes the crucial role of crystal planes of the CoTe2. The presented results are beneficial in expanding the use of the 2D telluride family in flexible electronics, piezo sensors, tribo-generators, and next-generation memory devices.
Surbhi Slathia, Manoj Tripathi, Raphael Tromer, Chinmayee Chowde Gowda, Prafull Pandey, Douglas S. Galvao, Alan Dalton, and Chandra Sekhar Tiwary
Elsevier BV
M. Tripathi, G. Deokar, J. Casanova-Chafer, J. Jin, A. Sierra-Castillo, S. P. Ogilvie, F. Lee, S. A. Iyengar, A. Biswas, E. Haye,et al.
Royal Society of Chemistry (RSC)
2D materials, given their form-factor, high surface-to-volume ratio, and chemical functionality have immense use in sensor design.
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.
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.
Anne Sehnal, Sean P. Ogilvie, Keiran Clifford, Hannah J. Wood, Aline Amorim Graf, Frank Lee, Manoj Tripathi, Peter J. Lynch, Matthew J. Large, Shayan Seyedin,et al.
American Chemical Society (ACS)
Solution-processed nanomaterials can be assembled by a range of interfacial techniques, including as stabilizers in Pickering emulsions. Two-dimensional (2D) materials present a promising route toward nanosheet-stabilized emulsions for functional segregated networks, while also facilitating surface energy studies. Here, we demonstrate emulsions stabilized by the 2D materials including the transition metal carbide MXene, titanium carbide (Ti3C2Tx), and develop an approach for in situ measurement of nanosheet surface energy based on emulsion inversion. This approach is applied to determine the influence of pH and nanosheet size on surface energy for MXene, graphene oxide, pristine graphene, and molybdenum disulfide. The surface energy values of hydrophilic Ti3C2Tx and graphene oxide decrease significantly upon protonation of usually dissociated functional groups, facilitating emulsion stabilization. Similarly, pristine graphene and molybdenum disulfide increase in surface energy when their surface functional groups are deprotonated under basic conditions. In addition, the surface energies of these pristine materials are correlated with nanosheet size, which allows for the calculation of the basal plane and edge surface energies of pristine nanosheets. This understanding of surface energies and control of emulsion inversion will allow design of emulsion-templated structures and surface energy studies of a wide range of solution-processable nanomaterials.
Manoj Tripathi, Sathvik Ajay Iyengar, Md. Hasan-ur Rahman, Venkataramana Gadhamshetty, Pulickel Madhava Ajayan, and Alan B. Dalton
Springer International Publishing
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
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.
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, 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.
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.
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.