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FLUORESCENCE STUDY OF CdSe QUANTUM DOTS SUSPENDED IN LIQUID PARAFFIN
S. C. DEY,R. DAS,S. S. NATH,R. BHATTACHERJEE 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2010 NANO Vol.5 No.6
Here we report a safer, easier, and quicker chemical route for synthesis of CdSe quantum dots (QDs), followed by their characterizations by UV/vis Spectroscopy (UV/vis), X-ray diffraction study (XRD), High Resolution Transmission Electron Microscopy (HRTEM) and fluorescence (FL) spectroscopy. The average size of the quantum dots is 7.5 nm. Fluorescence study reveals that CdSe quantum dots emit green light when excited by optical source of wavelength of 550 nm or less.
Dey, S.K. The Korean Institute of Electrical and Electronic 2003 전기전자재료 Vol.16 No.9
A 4 nm layer of ZrOx (targeted x-2) was deposited on an interfacial layer(IL) of native oxide (SiO, t∼1.2 nm) surface on 200 mm Si wafers by a manufacturable atomic layer chemical vapor deposition technique at 30$0^{\circ}C$. Some as-deposited layers were subjected to a post-deposition, rapid thermal annealing at $700^{\circ}C$ for 5 min in flowing oxygen at atmospheric pressure. The experimental x-ray diffraction, x-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, and high-resolution parallel electron energy loss spectroscopy results showed that a multiphase and heterogeneous structure evolved, which we call the Zr-O/IL/Si stack. The as-deposited Zr-O layer was amorphous $ZrO_2$-rich Zr silicate containing about 15% by volume of embedded $ZrO_2$ nanocrystals, which transformed to a glass nanoceramic (with over 90% by volume of predominantly tetragonal-$ZrO_2$(t-$ZrO_2$) and monoclinic-$ZrO_2$(m-$ZrO_2$) nanocrystals) upon annealing. The formation of disordered amorphous regions within some of the nanocrystals, as well as crystalline regions with defects, probably gave rise to lattice strains and deformations. The interfacial layer (IL) was partitioned into an upper Si $o_2$-rich Zr silicate and the lower $SiO_{x}$. The latter was sub-toichiometric and the average oxidation state increased from Si0.86$^{+}$ in $SiO_{0.43}$ (as-deposited) to Si1.32$^{+}$ in $SiO_{0.66}$ (annealed). This high oxygen deficiency in $SiO_{x}$ indicative of the low mobility of oxidizing specie in the Zr-O layer. The stacks were characterized for their dielectric properties in the Pt/{Zr-O/IL}/Si metal oxide-semiconductor capacitor(MOSCAP) configuration. The measured equivalent oxide thickness (EOT) was not consistent with the calculated EOT using a bilayer model of $ZrO_2$ and $SiO_2$, and the capacitance in accumulation (and therefore, EOT and kZr-O) was frequency dispersive, trends well documented in literature. This behavior is qualitatively explained in terms of the multi-layer nanostructure and nanochemistry that evolves.ves.ves.
Room-temperature ferroelectricity in supramolecular networks of charge-transfer complexes
Tayi, Alok S.,Shveyd, Alexander K.,Sue, Andrew C.-H.,Szarko, Jodi M.,Rolczynski, Brian S.,Cao, Dennis,Kennedy, T. Jackson,Sarjeant, Amy A.,Stern, Charlotte L.,Paxton, Walter F.,Wu, Wei,Dey, Sanjeev K. Nature Publishing Group, a division of Macmillan P 2012 Nature Vol.488 No.7412
Materials exhibiting a spontaneous electrical polarization that can be switched easily between antiparallel orientations are of potential value for sensors, photonics and energy-efficient memories. In this context, organic ferroelectrics are of particular interest because they promise to be lightweight, inexpensive and easily processed into devices. A recently identified family of organic ferroelectric structures is based on intermolecular charge transfer, where donor and acceptor molecules co-crystallize in an alternating fashion known as a mixed stack: in the crystalline lattice, a collective transfer of electrons from donor to acceptor molecules results in the formation of dipoles that can be realigned by an external field as molecules switch partners in the mixed stack. Although mixed stacks have been investigated extensively, only three systems are known to show ferroelectric switching, all below 71 kelvin. Here we describe supramolecular charge-transfer networks that undergo ferroelectric polarization switching with a ferroelectric Curie temperature above room temperature. These polar and switchable systems utilize a structural synergy between a hydrogen-bonded network and charge-transfer complexation of donor and acceptor molecules in a mixed stack. This supramolecular motif could help guide the development of other functional organic systems that can switch polarization under the influence of electric fields at ambient temperatures.
Substrate bias effects during diamond like carbon film deposition by microwave ECR plasma CVD
R.M. Dey,S.B. Singh,A. Biswas,R.B. Tokas,N. Chand,S. Venkateshwaran,D. Bhattacharya,N.K. Sahoo,S.W. Gosavi,S.K. Kulkarni,D.S. Patil 한국물리학회 2008 Current Applied Physics Vol.8 No.1
Diamond like carbon (DLC) coatings were deposited on silicon(11) substrates by microwave electron cyclotron resonance (ECR)plasma CVD process using a plasma of Ar and CH4 gases under the inuence of DC self bias generated on the substrates by applicationof RF (13.56 MHz) power. DLC coatings were deposited under the varying inuence of DC bias (. 60 V to. 150 V) on the Si substrates.atomic force microscopy (AFM), Hardness and elastic modulus determination technique, Raman spectroscopy, scanning electronmicroscopy (SEM) and contact angle measurement. The results indicate that the lm grown at. 100 V bias has optimised propertieslike high sp3/sp2 ratio of carbon bonding, high refractive index (2.262.17) over wide spectral range 4001200 nm, low roughness of0.8 nm, high contact angle (80.) compared to the lms deposited at other bias voltages (. 60 V and . with each other and nd august explanation under the subplantation model for DLC growth.
Anthelmintic activity of Clerodendrum viscosum
Jayanta Kumar Das,S. Choudhury,S. Adhikary,B. Das,S. Samanta,S. C. Mandal,S. P. Dey 경희대학교 융합한의과학연구소 2011 Oriental Pharmacy and Experimental Medicine Vol.11 No.2
The juice of the fresh leaves of Clerodendrum viscosum is widely used in the treatment of helminthiasis in folklore medicine. In this present study we have investigated the folklore claim methodically and scientifically. The ethanolic and aqueous extracts of leaves and roots of the plant are tested against Pheretima posthuma & Ascardia galli to ascertain their anthelmintic potential. All the extracts showed significant anthelmintic activity in dose dependent manner; the ethanolic extract of root at a dose of 200 mg/ml exhibited better anthelmintic activity than the reference drug,Piperazine citrate (10 mg/ml) against both type of worms.
Sharmin Akter,A S M Bazlul Karim,Md Wahiduzzaman Mazumder,Md Rukunuzzaman,Khan Lamia Nahid,Bishnu Pada Dey,Maimuna Sayeed,A Z M Raihanur Rahman,Kaniz Fathema,Mukesh Khadga 대한소아소화기영양학회 2022 Pediatric gastroenterology, hepatology & nutrition Vol.25 No.5
Purpose: Perinatal cytomegalovirus (CMV) infection can lead to biliary atresia (BA) in different entities. This study aimed to compare the clinical, hematological, biochemical, and histological features of infants with BA based on their CMV immunoglobulin M (IgM) status at presentation. Methods: This cross-sectional descriptive study was carried out between January 2019 and June 2020 at the Department of Pediatric Gastroenterology and Nutrition at the Bangabandhu Sheikh Mujib Medical University (BSMMU) in Dhaka. Forty-three patients with BA were selected purposively and categorized into either the CMV IgM-positive or CMV IgM-negative BA group. Categorical variables were compared using Fisher’s exact test and chi-square tests, while the Student’s t-test and Mann–Whitney U-test were used to compare continuous variables. For all statistical tests, a p-value <0.05 was considered statistically significant. Results: Thirty-three (76.7%) of the cases were between 2 and 3 months of age on admission. The clinical, hematological, and biochemical parameters did not differ significantly between the CMV IgM-positive and CMV IgM-negative BA groups. Most (50.0%) of the CMV IgM-positive cases had fibrosis stage F2, while 43.5% of the CMV IgM-negative cases had fibrosis stage F3, with no significant difference between the groups (p=0.391). Conclusion: Our data shows no significant distinction between CMV IgM-positive and CMV IgM-negative BA, suggesting that CMV does not contribute to BA pathogenesis.