Influence of quantum confinement on the ferromagnetism of (Ga,Mn)As diluted magnetic semiconductor

We investigate the effect of quantum confinement on the ferromagnetism of diluted magnetic semiconductor Ga$_{1-x}$Mn$_x$As using a combination of tight-binding and density functional methods. We observe strong majority-spin Mn $d$-As $p$ hybridization, as well as half metallic behavior, down to sizes as small as 20 \AA in diameter. Below this critical size, the doped holes are self-trapped by the Mn-sites, signalling both valence and electronic transitions. Our results imply that magnetically doped III-V nanoparticles will provide a medium for manipulating the electronic structure of dilute magnetic semiconductors while conserving the ferromagnetic properties and even enhancing it in certain size regime.Comment: 4 pages, 3 figure

Simultaneous control of nanocrystal size and nanocrystal-nanocrystal separation in CdS nanocrystal assembly

We report an easy, one pot synthesis to prepare ordered CdS nanocrystals with varying inter-particle separation and characterize the particle separation using x-ray diffraction at low and wide angles

NOVEL RP-HPLC METHOD DEVELOPMENT AND VALIDATION FOR THE SIMULTANEOUS ESTIMATION OF SAXAGLIPTIN AND GLIMEPIRIDE

Objective: The objective of the present study was to develop, and validate a novel reverse phase high performance liquid chromatographic (RP-HPLC) method, for simultaneous determination of saxagliptin (SAXA) and glimepiride (GLIM), in bulk mixtures, and in tablets.Methods: Determination of the drugs, SAXA and GLIM, was carried out employing ODS C18 column (250 mm X 4.6 mm i. d, 5 µm particle size), with diode array detector at λmax of 230 nm. The mobile phase employed for the current study, composed of two solvents, i.e., A (acetonitrile), and B (0.1 % w/v sodium di-hydrogen orthophosphate buffer, pH 3.8 adjusted with orthophosphoric acid). The mobile phase was pumped at a flow rate of 0.75 ml/min in the gradient mode. The validation study with respect to specificity, linearity, precision, accuracy, robustness, limit of detection (LOD), and limit of quantification (LOQ), was carried out employing the ICH Guidelines.Results: The developed method was selective and linear for both the drugs, i.e., between 15.63 µg/ml and 250.00 µg/ml for SAXA, and 7.81 µg/ml and 125.00 µg/ml for GLIM, with a correlation coefficient (R2) 0.9977 and 0.9982, for SAXA, and GLIM, respectively. The % recovery obtained was 102.98±0.14% for SAXA, and 101.84±1.96% for GLIM. The LOD and LOQ values for SAXA were obtained to be 1.30 µg/ml, and 3.94 µg/ml, respectively, while for GLIM, LOD was 0.82 µg/ml and LOQ was 2.48 µg/ml. The method also exhibits good robustness for different chromatographic conditions like wavelength, flow rate, mobile phase and injection volume.Conclusion: The method was successfully employed, for the quantification of SAXA and GLIM, in the quality control of in-house developed tablets, and can be applied for the industrial use

CONSUMER INITIATED HIGH-VALUE PAYMENTS

The present disclosure relates to a method and a system for facilitating a consumer to initiate a secure, high-value payment transfer. The present disclosure suggests sending, by a payment initiator, an inquiry about a payment receiver account along with the payment receiver’s details to a payment network via an originating financial institution. Thereafter, the payment network validates the payment receiver details and provides a validation code using the payment data to uniquely identify the transaction. Subsequently, the payment network confirms the validity of the payment receiver details to the payment initiator via the originating financial institution and requests confirmation from the payment initiator to continue with a money transfer. Based on the confirmation, the money transfer request, including the validation code and a Transaction ID (Tran ID), is sent from the payment initiator via the originating financial institution to the payment network. The payment network re-validates both the validation code as well as the Tran ID before sending the money transfer request to a receiving financial institution. Upon receiving the money transfer request, the receiving financial institution completes the request and sends the response back to the originating financial institution. Subsequently, the payment recipient receives the fund from the recipient financial institution. As a result, the payment initiator may transfer an adequate amount of money to the payment receiver account without having to physically visit a bank branch

Luminescence in Mn-doped CDS nanocrystals

We have synthesized Mn-doped CdS nanocrystals (NCs) with size ranging from 1.8-3 nm. Photoluminescence (PL) spectra of the doped NCs differ from that of the undoped NCs with an additional peak due to Mn d-d transitions. Electron paramagnetic resonance spectra along with X-ray absorption spectroscopy and PL spectra confirm the incorporation of Mn in the CdS lattice. The fact that emissions from surface states and the Mn d levels occur at two different energies, allowed us to study the PL lifetime decay behaviour of both kinds of emissions

Electronic structure of and Quantum size effect in III-V and II-VI semiconducting nanocrystals using a realistic tight binding approach

We analyze the electronic structure of group III-V semiconductors obtained within full potential linearized augmented plane wave (FP-LAPW) method and arrive at a realistic and minimal tight-binding model, parameterized to provide an accurate description of both valence and conduction bands. It is shown that cation sp3 - anion sp3d5 basis along with the next nearest neighbor model for hopping interactions is sufficient to describe the electronic structure of these systems over a wide energy range, obviating the use of any fictitious s* orbital, employed previously. Similar analyses were also performed for the II-VI semiconductors, using the more accurate FP-LAPW method compared to previous approaches, in order to enhance reliability of the parameter values. Using these parameters, we calculate the electronic structure of III-V and II-VI nanocrystals in real space with sizes ranging upto about 7 nm in diameter, establishing a quantitatively accurate description of the band-gap variation with sizes for the various nanocrystals by comparing with available experimental results from the literature.Comment: 28 pages, 8 figures, Accepted for publication in Phys. Rev.

Cellular interaction of folic acid conjugated superparamagnetic iron oxide nanoparticles and its use as contrast agent for targeted magnetic imaging of tumor cells

The purpose of the study was to develop tumor specific, water dispersible superparamagnetic iron oxide nanoparticles (SPIONs) and evaluate their efficacy as a contrast agent in magnetic resonance imaging (MRI). We have developed SPIONs capped with citric acid/2-bromo-2-methylpropionic acid which are compact, water dispersible, biocompatible having narrow range of size dispersity (8–10 nm), and relatively high T2 relaxivity (R2 = 222L · mmol−1 · sec−l). The targeting efficacy of unconjugated and folic acid-conjugated SPIONs (FA-SPIONS) was evaluated in a folic acid receptor overexpressing and negative tumor cell lines. Folic acid receptor-positive cells incubated with FA-SPIONs showed much higher intracellular iron content without any cytotoxicity. Ultrastructurally, SPIONs were seen as clustered inside the various stages of endocytic pathways without damaging cellular organelles and possible mechanism for their entry is via receptor mediated endocytosis. In vitro MRI studies on tumor cells showed better T2-weighted images in FA-SPIONs. These findings indicate that FA-SPIONs possess high colloidal stability with excellent sensitivity of imaging and can be a useful MRI contrast agent for the detection of cancer

Realistic Tight Binding Model for the Electronic Structure of II-VI Semiconductors

We analyze the electronic structure of group II-VI semiconductors obtained within LMTO approach in order to arrive at a realistic and minimal tight binding model, parameterized to provide an accurate description of both valence and conduction bands. It is shown that a nearest-neighbor $sp^3d^5$ model is fairly sufficient to describe to a large extent the electronic structure of these systems over a wide energy range, obviating the use of any fictitious $s^*$ orbital. The obtained hopping parameters obey the universal scaling law proposed by Harrison, ensuring transferability to other systems. Furthermore, we show that certain subtle features in the bonding of these compounds require the inclusion of anion-anion interactions in addition to the nearest-neighbor cation-anion interactions.Comment: 9 pages, 9 figure

Evolution of the electronic structure with size in II-VI semiconductor nanocrystals

In order to provide a quantitatively accurate description of the band gap variation with sizes in various II-VI semiconductor nanocrystals, we make use of the recently reported tight-binding parametrization of the corresponding bulk systems. Using the same tight-binding scheme and parameters, we calculate the electronic structure of II-VI nanocrystals in real space with sizes ranging between 5 and 80 {\AA} in diameter. A comparison with available experimental results from the literature shows an excellent agreement over the entire range of sizes.Comment: 17 pages, 4 figures, accepted in Phys. Rev.

An accurate description of quantum size effects in InP nanocrystallites over a wide range of sizes

We obtain an effective parametrization of the bulk electronic structure of InP within the Tight Binding scheme. Using these parameters, we calculate the electronic structure of InP clusters with the size ranging upto 7.5 nm. The calculated variations in the electronic structure as a function of the cluster size is found to be in excellent agreement with experimental results over the entire range of sizes, establishing the effectiveness and transferability of the obtained parameter strengths.Comment: 9 pages, 3 figures, pdf file available at http://sscu.iisc.ernet.in/~sampan/publications.htm