Significant research outcome
A. Designing organic memory for ROM & RAM applications:
Recently we are working on design and characterization of Resistive Memory devices using organic materials. Such memory devices are expected to be a potential candidate to replace the existing memory based on silicon and will play vital role to realize Organic Electronics. Organic electronics is very promising due to the flexibility, modifiability as well as variety of the available organic molecules. We have already designed resistive memory using several organic molecules and demonstrated their use as both volatile (RAM) and non-volatile (ROM) memory. It has been observed that performance of these memory with respect to data retention, cyclibility, device yield, stability are very good and have every potential for commercial applications. Reference of few of our recent ongoing works are listed below:
RSC Advances 11 (2021) 10212–10223 (RSC, IF=3.070) download
Langmuir (American Chemical Society, IF=3.557) (Accepted) Download
Chemistry Select 4 (2019) 9065 – 9073 (Wiley, IF=1.716) Download
Organic Electronics 55 (2018) 50 – 62 (Elsevier, IF =3.399) Download
Scientific Reports 7, Article number: 13308 (2017) (A Nature Research Journal, IF = 4.259) Download
Langmuir 33 (34) (2017) 8383–8394 (American Chemical Society, IF=3.833) download link1 link2
A. Designing various sensors:
We are also working on designing various optical sensors. e.g. arsenic sensor and it was found that the sensor give good result while testing the arsenic contaminated water collected from different parts of Tripura. It was found that in Kamalpur there exist arsenic contamination. Our designed alcohol sensor is capable of identifying drunk person just by changing the colour very similar to litmus paper. We have also designed several other sensors like – DNA sensor, hard water sensor, pH sensor, cholesterol sensor, ion sensor etc. Reference of few of our recent ongoing works are listed below:
Cholesterol sensor: Sensors & Actuators: B. Chemical 255 (2018) 519-528 (Elsevier, IF = 6.393) Download
Arsenic sensor: Sensors & Actuators: B. Chemical 241 (2017) 1014-1023 (Elsevier, IF = 6.393) Download
Hard water sensor: Sensors & Actuators: B. Chemical 184 (2013) 268 – 273 (Elsevier; IF=6.393) download
Ion sensor: Sensors and Actuators B: Chemical 195 (2014) 382–388 (Elsevier;IF=6.393) download
Journal of Photochemistry & Photobiology A: Chemistry 252 (2013) 174– 182 (Elsevier; IF= 3.261) download
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 175 (2017) 110-116 (Elsevier; IF= 2.129) Download
Invertis Journal of Science and Technology, (ISSN : 0973-8940) 7( 2) (2014) 1-8 download
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 149 (2015) 143–149 (Elsevier; IF=2.129) Download
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 136 (2015) 1797–1802 (Elsevier; IF=2.129) Downlod
Sensors and Actuators B: Chemical 204 (2014) 746–753 (Elsevier; IF=6.393) download
J Biol Phys; 39(3) (2013) 387-394 (Springer, IF 1.152)
Alcohol sensor: Journal of Physics: Conference Series (IOP), (2019) 1330, 012012 Download
Mercury sensor: Int. J. Environmental Analytical Chemistry 100 (2020) 789-807 (Taylor and Francis, IF=1.372) Download
Sci. Lets. J. 2015, 4: 119 (Publisher – Cognizure: ISSN 2454 – 7239) Download
Ref: Journal of Physics and Chemistry of Solids 144 (2020) 109487 Click here
Organic Switching Devices:
Switching devices fabricated by using organic molecules are the promising candidates for the next generation of non-volatile memories due to their simple structure, low cost, excellent performance and great scale-down potential. By applying a suitable bias voltage a switching device can be switched between two states, a low conducting OFF state and a high conducting ON state. Depending on the ability to retain information, switching behaviour can be classified into two types – volatile and non-volatile (memory) switching. In case of memory switching it is possible to retained both ON and OFF state even after the removal of externally applied bias voltage, whereas in threshold switching only OFF state is stable at lower bias voltage. Suitable organic molecules for designing switching devices, which have found their potential application in logic and memory circuits are the subject of current interest.
Our ongoing works on switching devices:
Effect of Functional Group on Electrical Switching Behaviour of an Imidazole Derivative in Langmuir-Blodgett Film (Chemistry Select, 2019) click to download
Composition-dependent nanoelectronics of amido-phenazines: non-volatile RRAM and WORM memory devices (Scientific Reports 7, Article number: 13308 (2017)) click to download
Electrical switching behaviour of a metalloporphyrin in Langmuir-Blodgett film (Organic Electronics 55 (2018) 50) click to download
Nanoscale aggregates onto ultrathin films are gaining importance due to their potential applications towards opto-electronic device application.
Recently we have developed a series of aggregates (J aggregate/H aggregate/excimer etc) onto thin films via LB/LbL techniques. See list of publications: click here
Fluorescence Resonance Energy Transfer (FRET):
FRET is a physical dipole–dipole coupling between the excited state of a donor fluorophore and an acceptor chromophore that causes relaxation of the donor to a non-fluorescent ground state, which excites fluorescence in the acceptor. In the process of FRET, initially a donor fluorophore (D) absorbs the energy due to the excitation of incident radiation and transfers the excitation energy to a nearby chromophore, the acceptor (A). The process can be expressed as follows:
FRET is a highly distance dependent phenomenon – 1 to 10 nm distance between donor and acceptor flurophore is crucial for the process to occur. There are few criteria that must be satisfied in order for FRET to occur.
(a) the fluorescence spectrum of the donor molecule must overlap with the absorption or excitation spectrum of the acceptor chromophore. The degree of overlap is referred to as spectral overlap integral.
(b) The two fluorophores (donor and acceptor) must be in the close proximity to one another (typically 1 to 10 nanometer).
(c) The transition dipole orientations of the donor and acceptor must be approximately parallel to each other.
(d) The fluorescence lifetime of the donor molecule must be of sufficient duration to allow the FRET to occur.
FRET has wide applications in biomedical, protein folding, RNA/DNA identification, sensors, investigating molecular level interactions etc.
Recently we have developed several FRET based sensors – Hard water sensor (link 1), Ion sensor (link 1), pH sensor (link 1, link 2), DNA sensor (link 1 link 2 link 3), Cholesterol sensor, Arsenic sensor etc. See the publication list. click here.
Click here to see some of our recent works
Download review paper written by me:
1. Fluorescence Resonance Energy Transfer (FRET) sensor (Invited Review article) download pdf
2. Nano Dimensional Hybrid Organo-clay Langmuir-Blodgett Films (Invited review article) download pdf
3. Langmuir-Blodgett Films and Molecular Electronics (Brief Review) download pdf
Introduction to Molecular Engineering:
Molecular materials are currently used in many different applications, from plastics for new building materials to light emitting diodes.
My current research activities include the preparation and characterizations thin films of some interesting organic, inorganic, metallorganic, dyes and biomolecules and organo-clay hybrid films. Also to explore the organization and molecular mechanism involves in such systems.
In order to fabricate a thin film of the material under investigations are deposited onto solid substrate. This can be accomplished in a variety of ways, however we use mainly spincoating, Layer-by-Layer (LbL) self assembly, and Langmuir-Blodgett (LB) deposition technique. Although we are particularly interested in the Langmuir-Blodgett technique, which allows organic structures to be assembled sequentially, one molecular monolayer at a time. The resultant film thickness can therefore be precisely controlled. In addition, the orientation of the molecules within the films can be arranged so that the multilayered structure possesses specific functional characteristics.
The aim of these work is to identify structure-property relationships within such thin films and investigate the mechanisms through which certain physical or chemical processes occur.
Langmuir-Blodgett films have long formed the core of our research activity; however, we rarely delve into the area of ideal LB compatible materials in which classically amphiphilic molecules ensure highly ordered molecular arrangement. Instead, we prefer to push the LB technique to new limits, investigating a much broader range of material types. For instance our current work involves investigations of non-amphiphilic molecules, water soluble materials, organo-clay hybrid materials and biomolecules (DNA, lipid, RNA) into the restricted geometry indicating that our approach to research is based on being diverse rather than too narrow.
Clay particles are natural nanoparticles with cation exchange capacities and have layered structure. Due to strong cation exchange capacity (CEC) or intercalation properties of clay the organic molecules are either adsorbed on to the clay surface or enter in to the inter laminar space of clay surface resulting the formation of organo-clay hybrid system. It is possible to prepare ultrathin films of organo-clay hybrids by LB or LbL technique. In this hybrid system the organic part gives the flexibility whereas the inorganic part imparts the stability. Interesting new properties are observed in such systems energy transfer, nonlinear optics, nano-aggregates, J-dimer etc.
What is Langmuir-Blodgett Films?
References: Click here to read my publication