Optical Sensors

Sensing chemical warfare like 2,4-dinitrotoluene (DNT) and 2,4,6-trinitrotoluene (TNT) are of significant interest for civilian and military applications as well as for environmental reason. The nitroaromatics in the form of plastic explosives, nerve gas, and toxic spills pose significant threat to civilian and military safety. The threat has grown especially during the last two decades due to the enhanced globalization and mobility of the society at large. In addition, TNT and other nitroaromatics in groundwater and seawater have been classified as potential environmental hazards. Therefore, it is of utmost importance to develop sensor which can detect them with high sensitivity and selectivity. 

FRET based sensor for nitroaromatics detection:

We have developed a Fluorescence Resonance Energy Transfer (FRET) based sensor system for highly sensitive detection of nitro-aromatic compounds. The sensor system is composed of polymer, small molecule and nanoparticles as donor and acceptor molecule respectively. Primarily, the fluorescence of the donor material is quenched by non-radiative energy transfer to acceptor which occurs when the two molecules are within FRET distance scale. The efficiency of this FRET process is calculated. We have observed a noticeable decrease in the FRET signal when nitroaromatics viz. 2,4-dinitrotoluene (DNT) and 2,4,6-trinitrotoluene (TNT) is gradually introduced into the sensor system. Fluorescence lifetime was measured to validate the efficacy of the energy transfer process in sensor system. The mechanistic details of molecular interactions was established by infrared spectroscopy and UV-vis absorption spectroscopy. Finally, a prototype sensor was fabricated for field use.

FRET System for the Detection of Heavy Metal Pollutants in Aqueous System:

Heavy metal ions including mercury (Hg2+) and lead (Pb2+) pollution poses severe health and environmental and health hazards. A highly sensitive and environment friendly multimodal nanosensor encompassing magnetic and fluorescent functionality is designed for the simultaneous detection and removal of mercury ion in water. A significant fluorescence quenching is observed with the increasing concentration of Hg2+ with low limit of detection. The detected analyte is successfully removed with the help of a bar magnet leaving no residual secondary pollution. The details mechanism of sensing is investigated. The simple and elegant material chemistry provide a facile route towards field based mercury sensor development in the future.

Optical Sensing with Terahertz Spectroscopy:

The identification of gases is of great interest in many fields. e.g. the analysis of human breath has a large medical potential because it contains hundreds of volatile organic compounds (VOCs) that can be attributed to certain physiological processes and pulmonary as well as non-pulmonary diseases (e.g. chronic obstructive pulmonary disease (COPD) and diabetes, respectively). Further interests arise from the detection of toxic industrial chemicals (TICs) or security-relevant gases (e.g. explosives).

With Terahertz/millimeter wave spectroscopy, gases are identified with high sensitivity, high specificity and high selectivity due to strong rotational transitions of the molecules that exhibit distinct spectral fingerprints. Our research involves the development of a breath gas sensor based on a terahertz/millimeter wave gas spectrometer around 250 GHz which requires high sensitivity detection with gas concentration levels below 1 part per million.

List your best Papers in the Optical Sensing Research Area:

[1] “Multimodal Fluorescent Polymer Sensor for Highly Sensitive Detection of Nitroaromatics”, Vishal Kumar, Binoy Maity, Mrinmoy K Chini, Priyodarshi De, Soumitra Satapathi, Nature Scientific Reports, 9(1), 7269, 2019. [Featured in DST, PTI, Economic Times]

[2] Mrinmoy K Chini, Vishal Kumar, Ariba Javed, Soumitra Satapathi, Graphene quantum dots and carbon nano dots for the FRET based detection of heavy metal ions, Nano-Structures & Nano-Objects, 19,100347, 2019.

[3] “Design of a novel FRET based fluorescent chemosensor and their application for highly sensitive detection of nitroaromatics”, Payal Taya, Binoy Maiti, V Kumar, Priyodarshi De, Soumitra Satapathi, Sensors and Actuators B: Chemical, 255, 3, 2628-2634, 2018.

[4] “Highly sensitive detection and removal of mercury ion using a multimodal nanosensor”, Soumitra Satapathi, Vishal Kumar, Mrinmoy Kumar Chini, Rajesh Bera, Krishna Kanta Halder, Amitava Patra,  Nano-Structures & Nano-Objects, 120-126,16, 2018.