Atul Kulkarni

Highly Air‐Stable Phosphorus‐Doped n‐Type Graphene Field‐Effect Transistors

Phosphorus-doped double-layered graphene field-effect transistors (PDGFETs) show much stronger air-stable n-type behavior than nitrogen-doped double-layered graphene FETs (NDGFETs), even under an oxygen atmosphere, due to strong nucleophilicity, which may lead to real applications for air-stable n-type graphene channels.

Highly Sensitive and Selective Gas Sensor Using Hydrophilic and Hydrophobic Graphenes

New hydrophilic 2D graphene oxide (GO) nanosheets with various oxygen functional groups were employed to maintain high sensitivity in highly unfavorable environments (extremely high humidity, strong acidic or basic). Novel one-headed polymer optical fiber sensor arrays using hydrophilic GO and hydrophobic reduced graphene oxide (rGO) were carefully designed, leading to the selective sensing of volatile organic gases for the first time. The two physically different surfaces of GO and rGO could provide the sensing ability to distinguish between tetrahydrofuran (THF) and dichloromethane (MC), respectively, which is the most challenging issue in the area of gas sensors. The eco-friendly physical properties of GO allowed for faster sensing and higher sensitivity when compared to previous results for rGO even under extreme environments of over 90% humidity, making it the best choice for an environmentally friendly gas sensor.

A novel nanometric DNA thin film as a sensor for alpha radiation

The unexpected nuclear accidents have provided a challenge for scientists and engineers to develop sensitive detectors, especially for alpha radiation. Due to the high linear energy transfer value, sensors designed to detect such radiation require placement in close proximity to the radiation source. Here we report the morphological changes and optical responses of artificially designed DNA thin films in response to exposure to alpha radiation as observed by an atomic force microscope, a Raman and a reflectance spectroscopes. In addition, we discuss the feasibility of a DNA thin film as a radiation sensing material. The effect of alpha radiation exposure on the DNA thin film was evaluated as a function of distance from an 241Am source and exposure time. Significant reflected intensity changes of the exposed DNA thin film suggest that a thin film made of biomolecules can be one of promising candidates for the development of online radiation sensors.

The label free DNA sensor using a silicon nanowire array

Biosensors based on silicon nanowire (Si-NW) promise highly sensitive dynamic label free electrical detection of various biological molecules. Here we report Si-NW array electronic devices that function as sensitive and selective detectors of as synthesized 2D DNA lattices with biotins. The Si-NW array was fabricated using top-down approach consists of 250 nanowires of 20 μm in length, equally spaced with an interval of 3.2 μm. Measurements of photoresistivity of the Si-NW array device with streptavidin (SA) attached on biotinylated DNA lattices at different concentration were observed and analyzed.. The conductivity in the DNA lattices with protein SA shows significant change in the photoresistivity of Si-NW array device. This Si-NW based DNA sensor would be one of very efficient devices for direct, label free DNA detection and could provide a pathway to immunological assays, DNA forensics and toxin detection in modern biotechnology.

A novel approach to use of elastomer for monitoring of pressure using plastic optical fiber

Elastomer has become a material of much interest for use as a deformation element in pressure and force monitoring devices. In the present work, we fabricated and characterized a pressure sensor that uses the polydimethylsiloxane (PDMS) elastomer and the plastic optical fiber (POF). The POF is used to guide light through the 10 mm thick PDMS block and collect the transmitted light and deliver it to the detector. In the force sensor, an applied pressure deforms the PDMS block, increasing the transmissivity of the device. The fabricated pressure sensor shows satisfactory response up to 478 kPa with excellent sensitivity and repeatability. The present pressure sensor is simple to fabricate and can be used for a wide range industrial and automobile applications.

Green synthesis of polysaccharide stabilized gold nanoparticles: chemo catalytic and room temperature operable vapor sensing application

A facile, one pot, completely green, and cheap route for the synthesis of gold nanoparticles (AuNPs) has been developed by using locust bean gum (LBG), both as a reducing and a stabilizing agent. Synthesized AuNPs were characterized by UV-vis spectroscopy, TEM, XRD, dynamic light scattering analysis (DLS) and EDAX. A characteristic surface plasmon peak at 537 nm confirmed the formation of AuNPs. Synthesized AuNPs were found to be an efficient catalyst for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). The reaction follows pseudo-first order kinetics with a rate constant of 14.46 × 10−2 min−1. Furthermore, the catalytic efficiency of AuNPs for ethanol vapor sensing was investigated by doping AuNPs in a tin oxide (SnO2) matrix synthesized by a single step thermal decomposition method. The AuNPs doped SnO2 sensor showed a fast response (∼5 seconds) and excellent ethanol sensing behavior in the range of 10 to 120 ppm at room temperature. A two fold increase in ethanol vapor sensing response was observed with AuNPs doped SnO2 as compared with the pure SnO2 sensor.

A sensitive hydrogen peroxide optical sensor based on polysaccharide stabilized silver nanoparticles

The paper reports a rapid and single pot synthesis of polysaccharide stabilized silver nanoparticles (Ag NPs). The ability of Ag NPs to catalyze the reduction of hydrogen peroxide (H2O2) is successfully explored for the development of an optical fiber H2O2 sensor in the concentration range of 10−2 to 10−6 M.

Development of optical monitor of alpha radiations based on CR-39.

Fukushima accident has highlighted the need to intensify efforts to develop sensitive detectors to monitor the release of alpha emitting radionuclides in the environment caused by the meltdown of the discharged spent fuel. Conventionally, proportional counting, scintillation counting and alpha spectrometry are employed to assay the alpha emitting radionuclides but these techniques are difficult to be configured for online operations. Solid State Nuclear Track Detectors (SSNTDs) offer an alternative off line sensitive technique to measure alpha emitters as well as fissile radionuclides at ultra-trace level in the environment. Recently, our group has reported the first ever attempt to use reflectance based fiber optic sensor (FOS) to quantify the alpha radiations emitted from (232)Th. In the present work, an effort has been made to develop an online FOS to monitor alpha radiations emitted from (241)Am source employing CR-39 as detector. Here, we report the optical response of CR-39 (on exposure to alpha radiations) employing techniques such as Atomic Force Microscopy (AFM) and Reflectance Spectroscopy. In the present work GEANT4 simulation of transport of alpha particles in the detector has also been carried out. Simulation includes validation test wherein the projected ranges of alpha particles in the air, polystyrene and CR-39 were calculated and were found to agree with the literature values. An attempt has been further made to compute the fluence as a function of the incidence angle and incidence energy of alphas. There was an excellent correlation in experimentally observed track density with the simulated fluence. The present work offers a novel approach to design an online CR-39 based fiber optic sensor (CRFOS) to measure the release of nanogram quantity of (241)Am in the environment.

An optical fiber weighing sensor based on bending

The bending of plastic optical fiber (POF) is used to develop a weighing sensor by fully gluing POF onto a strip of spring steel used as a clamped beam for sensing, keeping the glued fiber either on the top or bottom side of the beam. Force, in the form of weight, is applied to the beam in two ways: by attaching a pan (i) at one of the ends of the beam or (ii) at the center of the beam, with proper clamping. The known weight is added in the pan for calibration purposes. The output light intensity of the fiber, measured as voltage, changes practically linearly with increasing weight up to a certain limit due to the macrobending of POF. It is found that though elongative bending decreases the output intensity, compressive bending gives a reverse effect. The response time for sensing is found to be approximately 5–7 s with larger recovery time (≤1 min). No noticeable hysteresis is observed. The thickness and length of the beam are varied and optimized. The sensor specifications can be tailored by this to some extent. A minimum weight of 5 g and a maximum of ~1900 g could be measured in a linear range for the beam-length used.

Size‐Controllable DNA Rings with Copper‐Ion Modification

by simple molecular modi-fication, it makes DNA nanostructures one of the most viable biomaterials for use with current techniques. Although many developments took advantage of these characteristics, what has been lacking in DNA nanotechnology is sufficient investi-gation into specific interactions between DNA nanostructures and metal ions. Due to DNA’s poor conductivity,