Dipankar Saha


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Tuning the Chemical and Mechanical Properties of Conductive MoS<sub>2</sub> Thin Films by Surface Modification with Aryl Diazonium Salts
Dipankar Saha, Shayan Angizi, Maryam Darestani-Farahani, Johnson Dalmieda, P. Ravi Selvaganapathy, Peter Kruse
Langmuir, Volume 38, Issue 12

Molybdenum disulfide (MoS2) is a promising material for applications in sensors, energy storage, energy conversion devices, solar cells, and fuel cells. Because many of those applications require conductive materials, we recently developed a method for preparing a conductive form of MoS2 (c-MoS2) using dilute aqueous hydrogen peroxide in a simple and safe way. Here, we investigate modulating the chemical and mechanical surface properties of c-MoS2 thin films using diazonium chemistry. In addition to a direct passivation strategy of c-MoS2 with diazonium salts for electron-withdrawing groups, we also propose a novel in situ synthetic pathway for modification with electron-donating groups. The obtained results are examined by Raman spectroscopy and X-ray photoelectron spectroscopy. The degree of surface passivation of pristine and functionalized c-MoS2 films was tested by exposing them to aqueous solutions of different metal cations (Fe2+, Zn2+, Cu2+, and Co2+) and detecting the chemiresistive response. While pristine films were found to interact with several of the cations, modified films did not. We propose that a surface charge transfer mechanism is responsible for the chemiresistive response of the pristine films, while both modification routes succeeded at complete surface passivation. Functionalization was also found to lower the coefficient of friction for semiconducting 2H-MoS2, while all conductive materials (modified or not) also had lower coefficients of friction. This opens up a pathway to a palette of dry lubricant materials with improved chemical stability and tunable conductivity. Thus, both in situ and direct diazonium chemistries are powerful tools for tuning chemical and mechanical properties of conductive MoS2 for new devices and lubricants based on conductive MoS2.

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Facile fabrication of conductive MoS<sub>2</sub> thin films by sonication in hot water and evaluation of their electrocatalytic performance in the hydrogen evolution reaction
Dipankar Saha, Vinay Patel, P. Ravi Selvaganapathy, Peter Kruse
Nanoscale Advances, Volume 4, Issue 1

Molybdenum disulfide (MoS 2 ) has long been used in catalysis and is a promising material for energy conversion devices.

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Reagent-Free Hydrogen Peroxide Sensing Using Carbon Nanotube Chemiresistors with Electropolymerized Crystal Violet
Vinay Patel, Dipankar Saha, Peter Kruse, P. Ravi Selvaganapathy
ACS Applied Nano Materials, Volume 5, Issue 3

Hydrogen peroxide (H2O2) is an intermediate molecule generated in numerous peroxidase assays used to measure concentrations of biomolecules such as glucose, galactose, and lactate. Here, we develop a solid-state reagent-free chemiresistive H2O2 sensor, which can measure H2O2 over a wide measuring range of 0.5–1000 ppm (0.015–29.4 mM). The sensor was fabricated using a network of functionalized single-walled carbon nanotubes (SWCNTs) as a sensitive layer and a xurographically patterned gold leaf as a contact electrode. The SWCNTs were functionalized with crystal violet to impart selective detection of H2O2. The crystal violet was self-assembled on the SWCNT film and subsequently polymerized via cyclic voltammetry to improve its retention on the sensing layer. The functionalized sensor exhibited good selectivity against common interferents such as uric acid, urea, glucose, and galactose. In addition, the sensor was used to measure in situ H2O2 generated during peroxidase assays performed using enzymes like glucose oxidase. The sensor was tested in standard buffer solutions for both enzymes. The glucose oxidase assay was also demonstrated in spiked pooled human plasma samples. The glucose oxidase-coated sensor exhibited a glucose detection range of 2–20 mM in standard buffer and blood plasma solutions, with a good recovery rate (∼95–107%) for glucose measurements in blood plasma.


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Editors’ Choice—Review—Conductive Forms of MoS<sub>2</sub> and Their Applications in Energy Storage and Conversion
Dipankar Saha, Peter Kruse
Journal of The Electrochemical Society, Volume 167, Issue 12

Conductive forms of MoS 2 are important emerging 2D materials due to their unique combination of properties such as high electrical conductivity, availability of active sites in edge and basal planes for catalytic activity and expanded interlayer distances. Consequently, there has been a drive to find synthetic routes toward conductive forms of MoS 2 . Naturally occurring or synthetically grown semiconducting 2H-MoS 2 can either be converted into metallic 1T-MoS 2 , or various dopants may be introduced to modulate the electronic band gap of the 2H-MoS 2 phase and increase its conductivity. Chemical and electrochemical intercalation methods, hydrothermal and solvothermal processes, and chemical vapor deposition have all been developed to synthesize conductive MoS 2 . Conductive MoS 2 finds applications in energy storage devices, electrocatalytic reactions, and sensors. Here, we summarize a detailed understanding of the atomic structure and electronic properties of conductive MoS 2 which is crucial for its applications. We also discuss various fabrication methods that have been previously reported along with their advantages and disadvantages. Finally, we will give an overview of current trends in different applications in energy storage and electrocatalytic reactions in order to help researchers to further explore the applications of conductive MoS 2 .

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Peroxide-Induced Tuning of the Conductivity of Nanometer-Thick MoS<sub>2</sub> Films for Solid-State Sensors
Dipankar Saha, P. Ravi Selvaganapathy, Peter Kruse
ACS Applied Nano Materials, Volume 3, Issue 11

Applications of molybdenum disulfide (MoS2) in energy storage devices, solar cells, electrocatalysts, and sensors require good electrical conductivity. However, neither of the current ways to prepa...