Prof. Rajratan Basu
Department of Physics, The United States Naval Academy, Annapolis, MD 21402, USA
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Academic Career Length
19Years (2008-Present)
(Calculated once Scilit publication data is synced: current year − year of first publication + 1)
Representative Publications
View All Publications22 July 2009 in Physical Review E
Journal Article
Rajratan BasuGIGermano Iannacchione
Germano IannacchioneAssembling quantum dots (QDs) into nanoscale configurations over macroscopic dimensions is an important goal to realizing their electro-optical potential. In this Rapid Communication, we present a detailed study of a pentylcyanobiphenyl liquid crystal (LC) and a CdS QD colloidal dispersion by probing the dielectric property and relaxation as a function of an applied ac electric field . In principle, dispersing QDs in a nematic LC medium can direct the dots to align in nearly one-dimensional chainlike structures along the nematic director and these assemblies of QDs can be directed by external electric fields. In a uniform planar aligned cell, the Fréedericksz switching of the appears as a two-step process with the same initial switching field as the bulk but with the final value larger than that for an aligned bulk LC. The relaxation of immediately following the removal of follows a single-exponential decay to its original value that is slower than the bulk but becomes progressively faster with increasing , eventually saturating. These results suggest that the arrangement of the QDs is mediated by the LC.
3 November 2008 in Applied Physics Letters
Journal Article
Rajratan BasuGIGermano Iannacchione
Germano IannacchioneElectric field induced director orientation of a nematic liquid crystal nanotube (CNT) system reveals insights on switching behavior for this anisotropic composite. Once the field goes off, the system relaxes back to the original orientation through a mechanical rotation, revealing the intrinsic dynamics. LC molecules and CNTs cooperatively form local pseudonematic domains in the isotropic phase due to strong LC-CNT interactions. These field-responsive anisotropic domains do not relax back to the original orientation on switching of the field off, which could find potential applications in memory devices.
11 May 2010 in Physical Review E
Journal Article
Rajratan BasuGIGermano Iannacchione
Germano IannacchioneWe present a detailed study of a dilute suspension of carbon nanotubes (CNTs) in a pentylcyanobiphenyl (5CB) liquid crystal (LC) by probing the dielectric properties as a function of applied ac voltage and frequency. In principle, to minimize the elastic distortion in the nematic matrix, the monodispersed CNTs follow the nematic director without disturbing the director field significantly. A strong anchoring energy due to $\pi${}-$\pi${} electron stacking between LC-CNT molecules results in an increase in the dielectric anisotropy for the hybrid system, indicating a significant enhancement in the orientational order parameter. The frequency-dependent dielectric anisotropy for the composite system reveals the intrinsic frequency response of the LC-CNT anchoring mechanism. As a matter of consequence, the extracted value of splay elastic constant suggests that LC-CNT anchoring has an impact on the structural modification of the hybrid LC+CNT system. This strong anchoring energy stabilizes local pseudonematic domains, giving rise to a nonzero dielectric anisotropy in the isotropic phase that also shows an intrinsic frequency response.
13 October 2014 in Applied Physics Letters
Journal Article
Rajratan BasuAGAlfred Garvey
Alfred Garvey
A small quantity of BaTiO3 ferroelectric nanoparticles (FNPs) of 50 nm diameter was doped in a nematic liquid crystal (LC), and the free ion concentration was found to be significantly reduced in the LC + FNP hybrid compared to that of the pure LC. The strong electric fields, due to the permanent dipole moment of the FNPs, trapped some mobile ions, reducing the free ion concentration in the LC media. The reduction of free ions was found to have coherent impacts on the LC's conductivity, rotational viscosity, and electric field-induced nematic switching.
18 February 2014 in Physical Review E
Journal Article
Rajratan BasuA small quantity of ${\text{BaTiO}}_{3}$ ferroelectric nanoparticles (FNP) was doped in a liquid crystal (LC), and the LC + FNP hybrid was found to exhibit a nonvolatile electromechanical memory effect in the isotropic phase. The permanent dipole moment of the FNPs causes the LC molecule to form short-range pseudonematic domains surrounding the FNPs. The FNP-induced short-range orders become more prominent in the isotropic phase when the global nematic order is absent. These short-range domains, being anisotropic in nature, interact with an external electric field, exhibiting a Fr\'eedericksz-type transition. When the field is turned off, these domains stay oriented, showing a hysteresis effect due to the absence of any long-range order and restoring forces in the isotropic phase. The hysteresis graph for this memory effect shows a significant pretransitional behavior on approaching the nematic phase from the isotropic phase.
26 October 2009 in Applied Physics Letters
Journal Article
Rajratan BasuGIGermano Iannacchione
Germano IannacchioneA dilute suspension of carbon nanotubes (CNTs) in a nematic liquid crystal (LC) does not disturb the LC director. Due to a strong LC-CNT anchoring energy and structural symmetry matching, CNT long axis follows the director field, possessing enhanced dielectric anisotropy of the LC media. This strong anchoring energy stabilizes local pseudonematic domains, resulting in nonzero dielectric anisotropy in the isotropic phase. These anisotropic domains respond to external electric fields and show intrinsic frequency response. The presence of these domains makes the isotropic phase electric field-responsive, giving rise to a large dielectric hysteresis effect.
About Me
Dr. Rajratan Basu is currently serving as a Professor of Physics at the United States Naval Academy (USNA) in Annapolis, MD. His academic journey began with a bachelor's degree in physics from the University of Calcutta, followed by a master's degree in physics from the Indian Institute of Technology (IIT), Kharagpur, India. He holds a Ph.D. in Physics from the Worcester Polytechnic Institute, Massachusetts, where he specialized in liquid crystals and soft matter physics. His extensive research experience includes postdoctoral work at Case Western Reserve University in Cleveland, Ohio. At USNA, Professor Basu's research interests encompass the alignment of liquid crystals at nanostructured surfaces, the directed self-assembly of nanomaterials, and the development of liquid crystal-based nano-electromechanical systems (NEMS) and electro-optic devices. His work has significantly contributed to the understanding of order–disorder phenomena in soft-matter systems and the interactions between liquid crystals and nanomaterials. Professor Basu holds seven U.S. patents and has authored 43 peer-reviewed publications. His contributions to the field have been recognized with numerous awards, including the prestigious Navy Meritorious Civilian Service Award and the USNA Faculty Excellence in Research Award.