An International Peer Reviewed Research Journal



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Vol 29, Nos 3 & 4, March-April, 2020


Journal of Physics


Volume 29                                                             Nos 3 & 4                                                         March-April 2020


A Special Issue Dedicated
Prof P K Gupta

Guest Edited By : Anindya Dutta

Anita Publications
FF-43, 1st Floor, Mangal Bazar, Laxmi Nagar, Delhi-110 092, India

Prof P K Gupta

Prof P K Gupta is an eminent scientist in the field of laser physics, with special emphasis on biomedical application of lasers. Having obtained M Sc in Physics from Lucknow University, Prof. Gupta joined BARC training school in 1973. He obtained Ph D from Heriot Watt University, Edinburgh, UK, in 1981, with support from a Commonwealth Scholarship. While in BARC, he worked extensively on generation of coherent -infrared radiation using non-linear optical mixing and optically pumped molecular gas lasers and received the N S Satyamurthy memorial award of Indian Physics Association for this work. The watershed moment in his career came when he decided to relocate to the newly formed Center for Advanced Technology in Indore, India and took up the challenge of treading into the unfamiliar territory of biomedical applications of lasers in general and development of laser based methods for diagnosis and cure of cancer, in particular, in 1990. The lab nucleated and nurtured by him for these activities grew into Biomedical Applications Section and Instrumentation Division (LBAID). Apart from LBAID Dr Gupta also headed the Laser Materials and Devices Division and retired as a Distinguished Scientist and Acting Director of Raja Ramanna Center for Advanced Technology, RRCAT, as the institute is now called. Under Prof Gupta’s leadership, Laser induced fluorescence and Raman spectroscopy-based instruments for early detection of cancer have been fabricated and tested in real clinical setup. Prof Gupta’s group has also worked in diverse areas of Optical Coherence Tomography, optical tweezers, time resolved fluorescence, SNOM, photodynamic therapy, optics of turbid media etc. With him at the helm, RRCAT has evolved into a most prominent center for research and development in biomedical applications of lasers. More than 350 publications have come in the process. Prof Gupta’s contribution has been recognized in the form of fellowship of National Academy of Sciences India (NASI), Indian Academy of Science (IAS), Optical Society of America (OSA), Homi Bhabha Science and Technology Award and Group Achievement Awards of the Department of Atomic Energy (DAE) and many more accolades. After retirement from RRCAT, Prof Gupta has been actively involved in teaching, first in IISER Bhopal and then in IIT Delhi.

Anindya Dutta
Guest Editor
Oct 1, 2019

About Guest Editor

Prof Anindya Datta

Prof Anindya Datta obtained his Ph D in 1994 from Jadavpur University, Kolkata, under the guidance of Prof Kankan Bhattacharyya in Indian Association for the Cultivation of Science. He was a Postdoctoral Fellow in Iowa State University and Visiting Scientist in Raja Ramanna Center of Advanced Technology, Indore, before joining Department of Chemistry, IIT Bombay, as an Assistant Professor in 2002. Presently, he is Professor and Head of the Department, Chemistry, IIT Bombay. His research interest in ultrafast dynamics in chemical systems, fluorescence correlation spectroscopy and fluorescence lifetime imaging microscopy. He has received Bronze Medal from Chemical Research Society of India and is a Fellow of National Academy of Sciences, India.

N Ghosh
Vinod Rastogi
Oct 2, 2019


“LIFE” WITH PHOTONS: Universal Health Care.

As of March 2020, the estimated world population stands at >7.775 billion [1]. Of this, the 35 OECD (Organization of Economic Development and Cooperation) “developed” countries all together have a total ~1.291 billion (16.6 % of total), more than 80% of which live in urban areas, with only about 6% of the remaining, in remote areas [2]. The rest of more than 6.4 billion people in the world are mostly in the developing countries. Of these, India alone accounts for 1.38 billion (17.7%), only ~32% of them in urban areas, 68% in rural areas [1].
An idea of the humongous disparity in human development between the two groups- OECD and the Rest of the world- can be seen in the “Human Development Index-HDI-” [3]. All the OECD countries belong to the “Very High HDI” group (HDI > 0.8, except Mexico & Turkey 0.77 & 0.79, respectively) while the “Developing and Underdeveloped” countries (including India) all have medium or low HDI (< 0.7). India, 129th in a list of 189, has an HDI = 0.65 only. One of the important parameters, perhaps the most important, defining HDI is “Access to quality health” [3]. The difference at birth, in life expectancy between low and very high human development countries, is 19 years; more than a quarter of a lifespan! Lost just because of your place of birth, a choice not made by you! Article 25 of the Universal Declaration of Human Rights states: “Everyone has the right to a standard of living adequate for the health and well-being of himself and of his family--” (
One of the great anomalies in health-care services in countries like India is the fact that, the small fraction of urban population consisting mostly of employees of Public and Private Sector enterprises, are given complete, almost free, health care by their employers, the Government and Industries. In other words, the health-care financial burden on the country at present is mostly due to health care given to the few million Public and Private Sector regular employees who can afford it even otherwise, while people at the lower end of economic and social status, without any regular employment, who need it most and who cannot afford it, are very poorly served. This highly biased distribution of health-care services, combined with the huge disparity in income between urban and rural populations, have led to a situation in which routine health care has become almost unavailable and unaffordable for the bulk of the country’s population.
Though a host of illnesses contribute to the health-care burden, it is well recognized that a major part of it is due to the “killer” diseases which may require prolonged therapies (because they are detected at advanced stages), and costly medicines, and which also cause considerable loss of man-power, even before detection, because of physical and mental incapacities inflicted on the victims by the diseases even under dormant/indolent conditions. It is also well-known that the “Killer” diseases, both non-communicable (Cardiovascular diseases, various types of cancer, diabetes, child malnutrition), and communicable (TB, Malaria, Diarrhoea), are all amenable to successful therapy if detected in earlier stages. Cost-effective methods for screening and early detection of these diseases or their causative factors, which can be made easily available for universal applications, can obviously contribute to a considerable extent to reduction of the health-care burden.
For the 70% of the rural population in developing countries like India, regular screening facilities, available only at multi-speciality hospitals in big towns and cities, are almost always unavailable and un-affordable, not only because of their high cost, but also because of the difficulties for the subjects to leave their home/work-place, for repeated screening. In addition to this, most of the rural poor are unaware of the need for regular screening. Even those who are aware, are highly reluctant to undergo the current personally invasive screening programs, like mammography, Trans-Vaginal Sonography, colposcopy, sigmoidoscopy etc., for screening and early detection of diseases like cancers of breast, ovarian, cervical, and colo-rectal, which constitute some of the major killers. Similar situations arise in screening for coronary diseases, since methods like cardiac CT, Coronary CT Angiography (CTA), Myocardial Perfusion Imaging (MPI), etc., are not easily accessible for the rural population. For diagnosis of pre-diabetic and diabetic conditions, currently a few markers like HbA1c and glucose are available, but not affordable for regular screening for the rural poor.
The outcome of such deficiencies is a humongous indirect health-care burden on the country in terms of manpower, economy, societal well-being, and human welfare index. In an analysis of global burden of disease study [4], out of 188 countries worldwide, India was ranked as 143rd in health-related sustainable development goals Index.
Since the urban/upper class is readily available for regular screening, even if we can minimize their requirement through advanced technology, we can then divert some of the corresponding financial gains to the rural population of self- or poorly- employed daily wagers, farmers,etc., providing better universal health care.
In general, life expectancy has increased almost two-fold even in the under-developed countries [1,5] and in many of the diseases mentioned above this has lead to serious concerns about health-care. The best method to reduce the health-care burden is “Early Diagnosis”; that is, detect, locate, evaluate, and understand the disease process down to the cellular/molecular level.
The solution for the problem is thus, provide Nation-wide access, on a Point-of-Care (POC)/Location basis through small hospitals, health-care centers, and other public avenues, cost-effective, non- or minimally- invasive screening technology,. That is, accessibility and affordability has to be ensured, awareness has to be created and reluctance for regular screening has to be eliminated.
In many disease conditions, especially in the killer diseases mentioned above, the progression of the disease from the early stage of “Induction” to the final stages of catastrophic conditions is controlled by several bio-molecular processes, which in turn change the bio-molecular scenario in the living systems, including changes in usually present molecular species, production of entire arrays of new bio-molecular species not usually observed in normal state etc. It is to be emphasized that the structures and functions of such “Marker” molecules will also vary during the successive stages of induction, progression, regression or recurrence of the disease, allowing staging of the disease and resultant better therapy modes, if detected.
It follows that the best method for Screening, Early detection, Staging, Therapy- Planning etc. is thus detection of the bio-molecular markers as early as possible, that is, as soon as they start appearing. The markers include, Transcription factors, DNA Re-modelling Enzymes, RNA Binding Proteins, Cellular Receptors and Associated Proteins, Enzymes etc. These markers can be detected not only at the origin of their production( Cells, Tissue sites, and various organs) where the disease starts, but also in other samples since they will enter the blood as soon as they are produced, and will be transported around. The blood (similarly other body fluids like saliva and urine) also thus provides a convenient detection medium since it can be sampled in a minimally invasive way and can be handled and transported easily, by standard procedures. Many of the new molecular marker species will also be transported through blood, from the different locations where they are produced, to the lungs finally. The volatile species among them, called Volatile Organic Compounds-VOCs- thus end up in exhaled breath. Detection of these BREATH markers, Breath Analysis, also provides a powerful, totally non-invasive tool for screening and early detection of diseases like various cancers (which remain clinically silent over long periods), TB, and even viral diseases, and conditions like malnutrition, neurological disorders etc., which usually remain unobserved for long periods until overt symptoms appear.

Foreword_Vol29 Nos 3&4 by V Bhaskaran Kartha.pdf
V Bhaskaran Kartha


Valery V Tuchin

Valery V Tuchin

I met Professor P K Gupta for the first time personally not so long ago at an international meeting in Asia, but I was well acquainted with his brilliant research for much longer time. Prof Gupta is well known for his pioneering research in many relevant areas of biophotonics, including in vivo Raman spectroscopy of tissue neoplasia, polarization fluorescence spectroscopy of normal and malignant tissues, real-time in vivo OCT imaging of brain, depolarization of light in tissues, manipulating cells with optical tweezers, etc. I enjoyed collaborating with Professor Gupta when writing the book “Optical Flow Cytometry: Methods and Diagnosis of Diseases” (WILEY, 2011), where he has an excellent chapter “Optical Tweezers and Cytometry”. I often discuss his outstanding research findings and innovative ideas in my review papers and books.

I hope this special issue of AJP that is dedicated to a creative and productive scientist and great mentor – P K Gupta, will be useful and memorable for the international community of biophotonics.

I also take the opportunity to congratulate Prof Vinod Rastogi my old friend to bring out this special issue to honour Prof Pradeep Gupta, a great scientist of great country. Two months ago, I had an opportunity to visit India for the first time on the invitation of Prof Vinod Rastogi to deliver a Plenary Lecture at VIII ICOPVS2020, Feb 24-29, 2020 at JNCASR, Bangalore, India. I have many pleasant memories of my meeting with many great Indian Scientists like Chandrabhas Narayana, Nirmalya Ghosh, Santhosh Chidangil, and Beer Pal Singh, and many students especially at Physics Department, CCS University, Meerut.

Valery V Tuchin

Tree plantation by Prof Tuchin and others on March 2, 2020

Tree plantation by Prof Tuchin and others on March 2, 2020

Asian Journal of Physics                                                                                                    Vol. 29 Nos 3 & 4, 2020, 203-226

Development and application of Monte Carlo model to study light transport in tissue phantoms

Vipul M Patela, Atul Srivastavaa* and Suneet Singhb
aDepartment of Mechanical Engineering, IITB, Mumbai- 400 076, India
bDepartment of Energy Science and Engineering, IITB, Mumbai-400 076, India

This article is dedicated to Prof Pradeep K Gupta for his contributions to optics and photonics with biomedical applications

In the present work, Monte Carlo ray tracing based statistical model is developed to simulate the radiation transport in biological tissue mimicking phantom. Both Snell’s law and Fresnel’s reflection are used to incorporate the optical interface treatment at the common interface of refractive index discontinuity. The effects of (i) nature of scattering, (ii) absorption and scattering coefficients, (iii) tissue layer thickness (iv) refractive index and (v) laser source on quantities such as reflectance, transmittance and fluence rate distribution are investigated. The anisotropic scattering, considered in the present work, is modelled using the Henyey-Greenstein function and linear anisotropic function. The developed model is further extended to investigate the transient radiation transport in one-dimensional homogeneous participating medium subjected to short-pulse laser irradiation, a phenomenon which holds its importance in the context of photothermal therapy. In order to calculate temporal evolution of temperature in two dimensional biological tissue, the transient Monte Carlo ray tracing model is integrated with the Fourier based heat conduction model. The Monte Carlo based statistical model, developed in the present work, captures reflection and refraction of radiation at the interface where discontinuity in the refractive index exists. The radiation dose distribution is observed to be enhanced with (i) forward-directed nature of the scattering (ii) high absorption coefficient of the tissue (iii) High refractive index of the tissue, and (iv) collimated laser beam source. The radiation dose distribution in multilayered tissue phantom shows peaks in the blood vessels. The time resolved Monte Carlo model, developed in the present work, successfully mimics the effect of various parameters on transient transmittance and reflectance behaviour. The thermal analysis of the two-dimensional tissue phantom, carried out in the present work agrees well with the discrete ordinate method based numerical model. © Anita Publications. All rights reserved.
Keywords: Photo-thermal Therapy, Bio-heat Transfer; Monte-Carlo, Radiation Heat Transfer.

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Asian Journal of Physics                                                                                                    Vol. 29 Nos 3 & 4, 2020, 229-248

Excited state relaxation dynamics of trans-4-[4-(dimethylamino)–styryl]-1-methylpyridinium iodide (DASPI):

Dimethylanilino or methylpyridinium twist?        

Chandralekha Singh1, Brindaban Modak2,  Rajib Ghosh1 and Dipak K Palit1, 3

1Radiation & Photochemistry Division, Bhabha Atomic Research Center, Mumbai-400 085, India.

2Theoretical Chemistry Section, Bhabha Atomic Research Center, Mumbai-400 085, India.

3UM-DAE Centre for Excellence in Basic Sciences, Mumbai University, Kalina Campus, Santacruz (E), Mumbai-400 098, India

This article is dedicated to Prof Pradeep K Gupta for his contributions to optics and photonics with biomedical applications


Excited state dynamics of trans-[4-(dimethylamino)-styryl]-1-methylpyridinium iodide (DASPI) hasbeen studied using femtosecond transient absorption spectroscopic technique and quantum chemical calculations using DFT and TDDFT methods. Time evolution of the transient absorption and fluorescence spectra and temporal dynamics recorded in a wide spectral range and in wide varieties of solvents suggest that relaxation of the excited singlet (S1) state is associated with a conformational relaxation process prior to undergoing intersystem crossing to the triplet (T1) state (in nonpolar or less polar solvents) or internal conversion to the ground (S0) state (in polar solvents). TDDFT calculations reveal that the single bond twisting process involving the N,N-dimethylaniline group is barrierless (barrier height is 0.015 ev), but that involving the N-methylpyridinium group is associated with a moderate barrier (0.12 eV), whereas twisting of the N,N-dimethylamine group or the olefinic double bond needs to overcome a large barrier (0.6 and 1.93 eV, respectively). Based on these results, the ultrafast relaxation of the local excited (LE) state has been assigned to the intramolecular charge transfer (ICT) process associated with the barrierless twisting of the N, N-dimethylaniline (donor) group, leading to formation of the TICT state, which is nonfluorescent. In low and moderate polarity solvents, small barrier along the torsional coordinates govern the twisting dynamics leading to LE to TICT relaxation, which is slower than solvation. On the other hand, in polar aprotic solvents, CT relaxation is barrierless and  controlled by solvent relaxation dynamics. © Anita Publications. All rights reserved.

Keywords: Excited state dynamics, Transient absorption and fluorescence spectroscopy, DFT and TDDFT methods


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Asian Journal of Physics                                                                                                    Vol. 29 Nos 3 & 4, 2020, 255-259

Impulsive Stimulated Raman Spectroscopy (ISRS) of nile blue

Shaina Dhamija, Garima Bhutani and Arijit K De*
Department of Chemical Sciences, Indian Institute of Science Education and Research Mohali,
Knowledge City, Sector 81, SAS Nagar, Punjab-140 306, India

This article is dedicated to Prof Pradeep K Gupta for his contributions to optics and photonics with biomedical applications

We present a method for recording coherent vibrational wavepacket dynamics using Impulsive Stimulated Raman Spectroscopy (ISRS). We use this technique to record Raman spectrum for a dye, nile blue, in methanol under resonant excitation. We show how this method can be used to suppress the background signals to get Raman active modes. © Anita Publications. All rights reserved.
Keywords: Impulsive excitation, Vibrational wavepacket, Fourier transform, Raman spectrum, Resonance enhancement.

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Impulsive Stimulated Raman Spectroscopy (ISRS) of nile blue.pdf
Shaina Dhamija, Garima Bhutani and Arijit K De


Asian Journal of Physics                                                                                                    Vol. 29 Nos 3 & 4, 2020, 273-278

Origin of photoluminescence in carbon “Dots”

Avinash Kumar Singh† and Anindya Datta*
Department of Chemistry, Indian Institute of Technology Bombay, Mumbai, India 400 076. 

This article is dedicated to Prof Pradeep K Gupta for his contributions to optics and photonics with biomedical applications 


Using the method of dialysis a differentiation has been made between the photophysical properties of carbon dots and the photoluminescent impurities that are inherently associated with them owing to the various synthetic methodologies developed for the easy and inexpensive synthesis of these comparatively newer class of organic nanoparticles. © Anita Publications. All rights reserved.
Keywords: Dialysis, Photoluminescence, Photoluminescence lifetime, Carbon dots

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Origin of photoluminescence in carbon “Dots”.pdf
Avinash Kumar Singh and Anindya Datta



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