Undergraduate Research:
During my undergraduate studies, I was always interested in theoretical modeling of interesting physics problem, learning new topics in physics related to quantum mechanics, computational physics, and quantum field theory. I learned the beauty of Einstein notation in field theory, writing equation from Feynman diagram and so on. Even though i was extremely interested in understanding fundamental science through theoretical physics, but my vision of research has already inspired by some of my undergraduate teacher who has significant contribution in the field of optics and photonics. Therefore, to conduct my MS thesis, i had decided to join in “Non-linear Optics and Laser Spectroscopy Laboratory (NOLSL)” at center of excellence, University of Dhaka, which is also one of the biggest research and laser facility of the country. During my research experience at NOLSL, we have designed a non-gated Laser Induced breakdown Spectroscopy (LIBS) system which has broad application in the identification of elements in solids and minerals. My thesis project was entitled “Study of River Bed Soil of Buriganga, Coral and Beach Sand Samples of Bangladesh by Laser Induced Breakdown Spectroscopy”.
During my undergraduate studies, I was always interested in theoretical modeling of interesting physics problem, learning new topics in physics related to quantum mechanics, computational physics, and quantum field theory. I learned the beauty of Einstein notation in field theory, writing equation from Feynman diagram and so on. Even though i was extremely interested in understanding fundamental science through theoretical physics, but my vision of research has already inspired by some of my undergraduate teacher who has significant contribution in the field of optics and photonics. Therefore, to conduct my MS thesis, i had decided to join in “Non-linear Optics and Laser Spectroscopy Laboratory (NOLSL)” at center of excellence, University of Dhaka, which is also one of the biggest research and laser facility of the country. During my research experience at NOLSL, we have designed a non-gated Laser Induced breakdown Spectroscopy (LIBS) system which has broad application in the identification of elements in solids and minerals. My thesis project was entitled “Study of River Bed Soil of Buriganga, Coral and Beach Sand Samples of Bangladesh by Laser Induced Breakdown Spectroscopy”.
![Picture](/uploads/5/6/2/2/56227457/7466580.jpg?250)
Laser Induced Breakdown Spectroscopy:
LIBS is an extremely powerful and flexible elemental analysis technique that utilizes the energy in a short, intense laser pulse to vaporize or “ablate” a small volume of sample material. The ablated target material absorbs enough energy to ionize the constituent atoms, creating a small cloud of plasma that expands rapidly. As the cloud expands and cools, a significant fraction of the ions recombine to form excited atoms, which eventually decay via spontaneous emission to the atomic ground state. The photons given off during spontaneous emission can be collected and spectrally analyzed which provides a “spectral fingerprint” of all the constituent elements of the target and the plasma. Since each element has a unique spectral fingerprint, relative and absolute elemental concentrations within the target material can be determined.
In my thesis, I claimed that for measurements in remote or harsh environments, portable LIBS set up is extremely convenient. And I showed three possible aspects for remote detection using LIBS based sensors. One, LIBS sensors could be placed on robotic platform (Land, Air or Sea-based) for deployment in hostile areas or environments. Two, fiber optic LIBS can be used for remote detection in hostile environments. Three, because LIBS is laser based sensor, stand-off LIBS could be utilized with the proper telescope focusing and collection optics. Later on, I was fascinated to see that stand off LIBS technique has been utilized by NASA for Mars exploration.
LIBS is an extremely powerful and flexible elemental analysis technique that utilizes the energy in a short, intense laser pulse to vaporize or “ablate” a small volume of sample material. The ablated target material absorbs enough energy to ionize the constituent atoms, creating a small cloud of plasma that expands rapidly. As the cloud expands and cools, a significant fraction of the ions recombine to form excited atoms, which eventually decay via spontaneous emission to the atomic ground state. The photons given off during spontaneous emission can be collected and spectrally analyzed which provides a “spectral fingerprint” of all the constituent elements of the target and the plasma. Since each element has a unique spectral fingerprint, relative and absolute elemental concentrations within the target material can be determined.
In my thesis, I claimed that for measurements in remote or harsh environments, portable LIBS set up is extremely convenient. And I showed three possible aspects for remote detection using LIBS based sensors. One, LIBS sensors could be placed on robotic platform (Land, Air or Sea-based) for deployment in hostile areas or environments. Two, fiber optic LIBS can be used for remote detection in hostile environments. Three, because LIBS is laser based sensor, stand-off LIBS could be utilized with the proper telescope focusing and collection optics. Later on, I was fascinated to see that stand off LIBS technique has been utilized by NASA for Mars exploration.
Graduate Research:
My current research, under Professor David B. Mast and Donglu Shi, focuses on understanding and tailoring the magnetic, electronic transport and optical properties of superparamagnetic Fe3O4 nanoparticles. Based on my studies, I was able to successfully develop a model for hyperthermia heating of nanomaterial systems with which new phenomena of nanomaterials can be understood in terms of dipole interactions and relaxation. The relaxation dynamics, anisotropic properties of some unique Fe3O4 nanoparticle was studied over audio-radio-microwave frequency range (10Hz-6GHz). In doing so, I became familiar with, S-parameter measurements by a vector network analyzer, complex impedance measurement by an Impedance analyzer, coaxial transmission line technique and high frequency complex dielectric measurements. I also have the potential to look at the physics problem from all angles, one such example is finding the photoluminescence (PL) or semiconductor behavior in magnetic Fe3O4 nanoparticles.
My current research, under Professor David B. Mast and Donglu Shi, focuses on understanding and tailoring the magnetic, electronic transport and optical properties of superparamagnetic Fe3O4 nanoparticles. Based on my studies, I was able to successfully develop a model for hyperthermia heating of nanomaterial systems with which new phenomena of nanomaterials can be understood in terms of dipole interactions and relaxation. The relaxation dynamics, anisotropic properties of some unique Fe3O4 nanoparticle was studied over audio-radio-microwave frequency range (10Hz-6GHz). In doing so, I became familiar with, S-parameter measurements by a vector network analyzer, complex impedance measurement by an Impedance analyzer, coaxial transmission line technique and high frequency complex dielectric measurements. I also have the potential to look at the physics problem from all angles, one such example is finding the photoluminescence (PL) or semiconductor behavior in magnetic Fe3O4 nanoparticles.
![Picture](/uploads/5/6/2/2/56227457/4660235.jpg?301)
1. Effect of Spatial Confinement on Magnetic Hyperthermia via Dipolar Interactions in Fe3O4 Nanoparticles for Biomedical Applications:
We investigated hyperthermia behaviors of two distinct Fe3O4 nanoparticle systems.
Publication: Materials Science and Engineering C 42 (2014) 52–63
We investigated hyperthermia behaviors of two distinct Fe3O4 nanoparticle systems.
- These systems were differed by their spatial confinements.
- Unconfined–Fe3O4 nanoparticle system generates more heat than the confined one.
- The dipole interaction is responsible for the reduced heating rate in confined one.
Publication: Materials Science and Engineering C 42 (2014) 52–63
![Picture](/uploads/5/6/2/2/56227457/1052802.gif?383)
2. Photoluminescence and photothermal effect of Fe3O4 nanoparticles for medical imaging and therapy:
Photoluminescence (PL) of Fe3O4 nanoparticle was observed from the visible to near-infrared(NIR) range by laser irradiation at 407 nm. PL spectra of ∼10 nm diameter Fe3O4 nanoparticlesorganized in different spatial configuration, showed characteristic emissions with a major peak near 560 nm, and two weak peaks near 690 nm and 840 nm. Different band gap energies were determined for these Fe3O4 nanoparticle samples corresponding to, respectively, the electronband structures of the octahedral site (2.2 eV) and the tetrahedral site (0.9 eV). Photothermal effect of Fe3O4 nanoparticles was found to be associated with the photoluminescenceemissions in the NIR range. Also discussed is the mechanism responsible for the photothermal effect of Fe3O4 nanoparticles in medical therapy.
Publication: Appl. Phys. Lett. 105, 091903 (2014)
Photoluminescence (PL) of Fe3O4 nanoparticle was observed from the visible to near-infrared(NIR) range by laser irradiation at 407 nm. PL spectra of ∼10 nm diameter Fe3O4 nanoparticlesorganized in different spatial configuration, showed characteristic emissions with a major peak near 560 nm, and two weak peaks near 690 nm and 840 nm. Different band gap energies were determined for these Fe3O4 nanoparticle samples corresponding to, respectively, the electronband structures of the octahedral site (2.2 eV) and the tetrahedral site (0.9 eV). Photothermal effect of Fe3O4 nanoparticles was found to be associated with the photoluminescenceemissions in the NIR range. Also discussed is the mechanism responsible for the photothermal effect of Fe3O4 nanoparticles in medical therapy.
Publication: Appl. Phys. Lett. 105, 091903 (2014)
![Picture](/uploads/5/6/2/2/56227457/1866976.jpg?335)
3. Influence of interparticle interactions on the blocking temperature and high frequency permeability of Fe3O4 nanoparticle systems:
In Neel’s model of superparamagnetism, magnetization and relaxation dynamics depend on the magnetic anisotropy constant of the non-interacting, individual nanoparticles (NPs). However, in real systems, interactions in NPs affect the anisotropy and magnetic properties that related to the anisotropy should also change. To investigate the influence of magnetic interactions on NP anisotropy, we compare the results from measurements of the blocking temperature of Fe3O4 NP systems with very different average interparticle separations, one with uniformly dispersed NPs and the other with the NPs tightly confined in a polystyrene matrix. The blocking temperature for the confined NPs (263K) was substantially higher than for the uniformly dispersed NPs (166K), which we attribute to stronger dipolar interactions. The relaxation times are determined from peaks in the imaginary part of the complex permeability versus frequency from 10 MHz - 3 GHz. For uniformly dispersed Fe3O4 NP (in hydrocarbon carrier), the Neel relaxation and the gyromagnetic resonance were observed at 41 MHz and 1.2 GHz, respectively, which corresponds to an anisotropy constant of ~15 KJ/m3 compared to 12 kJ/m3 predicted by Neel’s relaxation model for 10 nm diameter Fe3O4 NPs.
Abstract: http://meetings.aps.org/link/BAPS.2015.MAR.M30.11
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4. Design and development of an AC susceptometer system for magnetic characterization of nanoparticles:
Low temperature, Alternating Current (AC) Susceptometers have become a convenient and powerful tool for measuring magnetic ordering and dynamical behavior in a wide variety of materials from thin film superconductors to superparamagnetic nanoparticles. This susceptometer will be capable of measuring the complex AC susceptibility (magnetization and loss) as a function of magnetic field, temperature and frequency in order to give information about phase transitions, resonance phenomena and relaxation mechanisms of different magnetic materials. In particular, this AC susceptometer will be used to characterize the magnetic behavior of superparamagnetic iron and novel mixed oxide nanoparticles for potential use in cancer therapies. Superparamagnetic particles are unique in that they exhibit single domain ferromagnetic behavior below a certain temperature (referred to as the blocking temperature, TB) and superparamagnetic behavior above that temperature. An AC susceptometer can also be used to probe the various relaxation times (τ’s) of the superparamagnetic particles by varying measurement frequency (100 Hz- 10 KHz for our system).