Debdutta Ray

Bio: Debdutta Ray is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Pentacene & Charge carrier. The author has an hindex of 4, co-authored 10 publications receiving 37 citations. Previous affiliations of Debdutta Ray include Indian Institutes of Technology.

Enhancing the sensitivity of point-of-use electrochemical microfluidic sensors by ion concentration polarisation – A case study on arsenic

Abstract: Point of use (POU) sensors are extremely relevant, being capable of providing fast and reliable analysis in remote and resource-limited settings. Of all the diverse techniques utilised for POU sensors, a combination of electrochemistry and microfluidics may have the greatest potential towards quantitative assessment of heavy metal ions. The major challenge in combining these for sensing applications lies in the complexity of fabricating integrated devices and the insufficient quantity of analytes in the sample volume. To address these issues, we have developed a radial microfluidic device capable of electrokinetic preconcentration by ion concentration polarization (ICP) and integrated it with electroactive surfaces. The proposed sensor is the first demonstration of concentration of heavy metal ions by ICP and its quantitative assessment by voltammetry. Utilising the integrated sensor, we have shown the sensing of As3+ down to 1 ppb by linear sweep voltammetry with ∼40 μL of sample. The sensor was also tested successfully for sensing As3+ in a field sample from an arsenic affected region of India. The sensor was also tested for the detection of other metal ions too. This work would facilitate the development of highly sensitive POU hand-held sensors for water quality monitoring in resource-limited areas.

Dual Probe Sensors Using Atomically Precise Noble Metal Clusters

Abstract: This article adds a new direction to the functional capability of protein-protected atomically precise gold clusters as sensors. Counting on the extensively researched intense luminescence of these clusters and considering the electron donating nature of select amino acids, we introduce a dual probe sensor capable of sensing changes in luminescence and conductivity, utilizing bovine serum albumin-protected atomically precise gold clusters hosted on nanofibers. To this end, we have also developed a hybrid nanofiber with a conducting core with a porous dielectric shell. We show that clusters in combination with nanofibers offer a highly selective and sensitive platform for the detection of trace quantities of trinitrotoluene, both in solution and in the vapor phase. In the solution phase, trinitrotoluene (TNT) can be detected down to 1 ppt at room temperature, whereas in vapor phase, 4.8 × 109 molecules of TNT can be sensed using a 1 mm fiber. Although the development in electrospinning techniques for fabri...

Study of exciton-polaron interaction in pentacene field effect transistors using high sensitive photocurrent measurements

Abstract: Luminescence quenching in the presence of polarons is one of the major challenges in organic light emitting devices. In this work, exciton quenching in the presence of polarons is studied using phase sensitive photocurrent measurements on pentacene field effect transistors. The enhancement of conduction in the organic field effect transistors on light illumination is studied using photocurrent spectral response measurements and corresponding optical simulations. The photocurrent is shown to be governed by the polaron mobility and the exciton quenching efficiency, both of which depend on the polaron density in the channel. Two models are proposed on the exciton dynamics in the presence of gate induced polarons in the transistor channel. The first model simulates the steady-state exciton concentration profile in the presence of exciton-polaron interaction. The second one is a three-dimensional steady state exciton-polaron interaction model, which supports the findings from the first model. It is shown that the excitons quench by transferring its energy to polarons, thereby promoting the latter to high energy states in the density of states manifold. The polarons move in the higher energy states with greater microscopic mobility before thermalizing, thereby leading to an enhancement of conduction. It is observed that for the present system, where charge carrier transport is by hopping, all polarons interact with excitons. This implies that for low mobility systems, the interaction is not limited to deep trapped polarons.

Programmable Metal Nanoclusters with Atomic Precision.

Abstract: With the recent establishment of atomically precise nanochemistry, capabilities toward programmable control over the nanoparticle size and structure are being developed. Advances in the synthesis of atomically precise nanoclusters (NCs, 1-3 nm) have been made in recent years, and more importantly, their total structures (core plus ligands) have been mapped out by X-ray crystallography. These ultrasmall Au nanoparticles exhibit strong quantum-confinement effect, manifested in their optical absorption properties. With the advantage of atomic precision, gold-thiolate nanoclusters (Aun (SR)m ) are revealed to contain an inner kernel, Au-S interface (motifs), and surface ligand (-R) shell. Programming the atomic packing into various crystallographic structures of the metal kernel can be achieved, which plays a significant role in determining the optical properties and the energy gap (Eg ) of NCs. When the size increases, a general trend is observed for NCs with fcc or decahedral kernels, whereas those NCs with icosahedral kernels deviate from the general trend by showing comparably smaller Eg . Comparisons are also made to further demonstrate the more decisive role of the kernel structure over surface motifs based on isomeric Au NCs and NC series with evolving kernel or motif structures. Finally, future perspectives are discussed.

Indication of current-injection lasing from an organic semiconductor

Abstract: In this study, we investigate the lasing properties of 4,4'-bis[(N-carbazole)styryl]biphenyl thin films under electrical pumping. The electroluminescent devices incorporate a mixed-order distributed feedback SiO2 grating into an organic light-emitting diode structure and emit blue lasing. The results provide an indication of lasing by direct injection of current into an organic thin film through selection of a high-gain organic semiconductor showing clear separation of the lasing wavelength from significant triplet and polaron absorption and design of a proper feedback structure with low losses at high current densities. This study represents an important advance toward a future organic laser diode technology.