Tapanendu Kundu

Bio: Tapanendu Kundu is an academic researcher from Indian Institute of Technology Bombay. The author has contributed to research in topics: Surface plasmon resonance & Optical fiber. The author has an hindex of 20, co-authored 51 publications receiving 997 citations. Previous affiliations of Tapanendu Kundu include Visva-Bharati University & Rutgers University.

Label-free fiber optic biosensor based on evanescent wave absorbance at 280 nm

Abstract: Several analytes of interest such as bacteria, virus and some of the clinically important proteins and marker molecules absorb light in the ultra violet region (UV). In this study, we have investigated the possibility to develop a label-free fiber optic biosensor based on evanescent wave absorbance (EWA) at 280 nm to detect the presence of such analytes. A light emitting diode (LED) in UV with peak emission at 280 nm and span of ±10 nm was chosen as a light source to limit the solarization of the fiber probes. Numerical simulations were performed to investigate the effect of fiber parameters and wavelength of operation on EWA and its sensitivity. Experimental verifications proved the validity of the simulations. The absorbance behavior of fiber sensor probes in the visible region was studied using FITC as absorbing molecule. Goat anti-human IgG (GaHIgG) was chosen as a model analyte. Human IgG immobilized fiber probes were subjected to goat anti-human IgG to test the absorbance response of the probes at 280 nm. These studies demonstrate that intrinsic absorbance properties of biomolecules may be utilized for development of absorbance based label-free biosensors. The sensitivity, which is a limiting factor, can be improved with better optics.

Effects of metal substitution on third-order optical non-linearity of porphyrin macrocycle

Abstract: The effects of axial ligands in Sn(IV)-substituted 5,10,15,20-tetrakis [4-(carboethoxymethyleneoxy)phenyl]porphyrin and divalent transition metal substitution in 5,10,15,20-tetraphenylporphyrin on the second molecular hyperpolarizability (γ) at 802 nm were studied using the Z-scan technique. A significant increase in γ for divalent metal ions is observed with decreasing d-shell occupancy. In the case of the tetravalent metal-substituted porphyrin a dramatic enhancement of γ is seen when a strongly electronegative axial ligand such as I2 is attached to the metal ion. A plausible explanation for the observed trend of γ has been sought in terms of metal-ligand interaction.

Synthesis, mixed valence aspects and non-linear optical properties of the triruthenium complexes [{(bpy)2RuII}3(L)]3+ and [{(phen)2RuII}3(L)]3+(bpy = 2,2′-bipyridine, phen = 1,10-phenanthroline and L3−= 1,3,5-triazine-2,4,6-trithiol)

Abstract: The triruthenium complexes [{(bpy)2RuII}3L]3+ [1]3+ and [{(phen)2RuII}3L]3+ [2]3+ have been synthesized via the reactions of [RuII(bpy)2(EtOH)2]2+ and [RuII(phen)2(EtOH)2]2+ with the trisodium salt of 1,3,5-triazine-2,4,6 trithiol (Na3L) respectively. In CH3CN, the complexes [1]3+ and [2]3+exhibit three reversible one-electron redox processes corresponding to successive Ru(II)/Ru(III) couples. The 190–250 mV separation in potential between the successive Ru(II)/Ru(III) couples is indicative of moderate intermetallic electronic coupling in the mixed valence states. The bipyridine and phenanthroline based reductions are observed at −1.58, −1.86 V and −1.77, −2.01, −2.43 V versus SCE respectively. The spectroelectrochemical study on the bipyridine derivative [1]n+ (n = 3–6) in acetonitrile medium at 243 K shows a broad and relatively weak intervalence charge-transfer transition (IVCT) near 1900 nm for both the mixed valence states RuIIRuIIRuIII [1]4+ and RuIIRuIIIRuIII [1]5+, characteristic of class II behaviour. The calculated coupling constant (Vab), 560 cm−1 is also supportive of class II mixed-valence states. The electrochemically generated one-electron oxidised species [1]4+ or [2]4+ exhibits an EPR spectrum characteristic of low-spin RuIII ion in a distorted octahedral environment (g1 = 2.246, g2 = 1.993 for [1]4+ and g1 = 2.469, g2 = 2.191 for [2]4+). The complexes are moderately strongly luminescent at 77 K. Both the complexes have also shown third order non-linear optical properties with γ = −4.5 × 10−29 esu for [1]3+ and −5.09 × 10−29 esu for [2]3+.

Drug Discovery Today

Abstract: In recent years, tools for the development of new drugs have been dramatically improved. These include genomic and proteomic research, numerous biophysical methods, combinatorial chemistry and screening technologies. In addition, early ADMET studies are employed in order to significantly reduce the failure rate in the development of drug candidates. As a consequence, the lead finding, lead optimization and development process has gained marked enhancement in speed and efficiency. In parallel to this development, major pharma companies are increasingly outsourcing many components of drug discovery research to biotech companies. All these measures are designed to address the need for a faster time to market. New screening methodologies have contributed significantly to the efficiency of the drug discovery process. The conventional screening of single compounds or compound libraries has been dramatically accelerated by high throughput screening methods. In addition, in silico screening methods allow the evaluation of virtual compounds. A wide range of new lead finding and lead optimization opportunities result from novel screening methods by NMR, which are the topic of this review article.

Nonlinear Optical Properties of Porphyrins

Abstract: Porphyrins and phthalocyanines have outstanding chemical and thermal stability. The macrocyclic structure and chemical reactivity of tetrapyrroles offers architectural flexibility and facilitates the tailoring of chemical, physical and optoelectronic parameters. The specific optical properties of the tetrapyrrole macrocycle combined with the synthetic methodologies now available and the already available theoretical and spectroscopic knowledge on their optical behavior make porphyrins a target of choice for this area. They are versatile organic nanomaterials with a rich photochemistry and their excited state properties are easily modulated through conformational design, molecular symmetry, metal complexation, orientation and strength of the molecular dipole moment, size and degree of conjugation of the π-systems, and appropriate donor-acceptor substituents. Here we review the structural chemistry and optical properties of recently synthesized porphyrin derivatives that offer potential for nonlinear optical (NLO) applications and complement existing studies on phthalocyanines. Classes of interest include the classic A4 symmetric tetrapyrroles, while optimized systems include push-pull porphyrins, oligomeric and supramolecular self-assembled systems, films and nanoparticle systems, and highly conjugated porphyrin arrays.

Gold nanorod-based localized surface plasmon resonance biosensors: A review

Abstract: Noble metal nanoparticle-based localized surface plasmon resonance (LSPR) is an advanced and powerful label-free biosensing technique which is well-known for its high sensitivity to the surrounding refractive index change in the local environment caused by the biomolecular interactions around the sensing area. The characteristics of the LSPR effect in such sensors are highly dependent on the size, shape and nature of the material properties of the metallic nanoparticles considered. Among the various types of metallic nanoparticles used in studies employing the LSPR technique, the use of gold nanorods (GNRs) has attracted particular attention for the development of sensitive LSPR biosensors, this arising from the unique and intriguing optical properties of the material. This paper provides a detailed review of the key underpinning science for such systems and of recent progress in the development of a number of LSPR-based biosensors which use GNR as the active element, including an overview of the sensing principle, the synthesis of GNRs, the fabrication of a number of biosensors, techniques for surface modification of GNRs and finally their performance in several biosensing applications. The review ends with a consideration of key advances in GNR-based LSPR sensing and prospects for future research and advances for the development of the GNR-based LSPR biosensors.

Review of plasmonic fiber optic biochemical sensors: improving the limit of detection.

Abstract: This paper presents a brief overview of the technologies used to implement surface plasmon resonance (SPR) effects into fiber-optic sensors for chemical and biochemical applications and a survey of results reported over the last ten years. The performance indicators that are relevant for such systems, such as refractometric sensitivity, operating wavelength, and figure of merit (FOM), are discussed and listed in table form. A list of experimental results with reported limits of detection (LOD) for proteins, toxins, viruses, DNA, bacteria, glucose, and various chemicals is also provided for the same time period. Configurations discussed include fiber-optic analogues of the Kretschmann–Raether prism SPR platforms, made from geometry-modified multimode and single-mode optical fibers (unclad, side-polished, tapered, and U-shaped), long period fiber gratings (LPFG), tilted fiber Bragg gratings (TFBG), and specialty fibers (plastic or polymer, microstructured, and photonic crystal fibers). Configurations involving the excitation of surface plasmon polaritons (SPP) on continuous thin metal layers as well as those involving localized SPR (LSPR) phenomena in nanoparticle metal coatings of gold, silver, and other metals at visible and near-infrared wavelengths are described and compared quantitatively.