Jyoti Tyagi; Lekha Sharma; Rita Kakkar
Abstract
Two different models, ovalene (C32H14) and circumcoronene (C54H18) and their respective doped models (C31XH14, C53XH18 where X = B, Al, N, P, Fe, Ni and Pt) have been considered for DFT calculations at the GGA-PBE/DNP level. The two models are compared on the basis of various calculated structural parameters ...
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Two different models, ovalene (C32H14) and circumcoronene (C54H18) and their respective doped models (C31XH14, C53XH18 where X = B, Al, N, P, Fe, Ni and Pt) have been considered for DFT calculations at the GGA-PBE/DNP level. The two models are compared on the basis of various calculated structural parameters and electronic properties. Electronic density of states (DOS) spectra are also plotted to see the changes in the electronic properties on increasing the size. No major changes are observed in the structural and electronic properties as one move from the smaller model to the higher one. It is found that doping maintains the planarity of the surface but induces comparatively large changes in the bond lengths around the doped atom, weakening the bonds. Copyright © VBRI Press.
Pragati Malik; Jyoti Singh; Rita Kakkar
Abstract
The primary aim of this review is to survey the literature on the ion sensing ability of quantum dots. Sensing of both cations and anions is important, since both play significant roles in various ecological and biological processes, which makes it important to ensure their concentration at balanced ...
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The primary aim of this review is to survey the literature on the ion sensing ability of quantum dots. Sensing of both cations and anions is important, since both play significant roles in various ecological and biological processes, which makes it important to ensure their concentration at balanced level. Contamination by heavy metal ions and various anions poses a serious threat to humans, aquatic organisms, and to the environment; therefore detection of these ions (in presence of other cations and anions), which are the major cause of environmental pollution is of immense significance at the present time. Owing to their enhanced fluorescence properties and photostability, QDs offer tremendous scope to be used for ion sensing. They offer several advantages over traditional chemical fluorophores. This review throws light on the mechanism adopted by CdSe QDs to act as flourophores. Owing to their enhanced photoluminescence properties, QDs offer selective and sensitive determination of various ions, which is a function of the capping on the surface of the QD nanosensor, i.e. it is possible to tune their sensing ability by changing the capping layer, which influences the QD's interaction with various analytes. Hence, these quantum dots may prove promising candidates in future for sensing approximately all types of analytes.
Pragati Malik; Sunita Gulia; Rita Kakkar
Abstract
The most widely researched and investigated disease, both medically and scientifically, in the current era is the formidable disease cancer. The chances of successful treatment and hence the curability increases if it is diagnosed at an early stage. This can be done only by increasing awareness amongst ...
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The most widely researched and investigated disease, both medically and scientifically, in the current era is the formidable disease cancer. The chances of successful treatment and hence the curability increases if it is diagnosed at an early stage. This can be done only by increasing awareness amongst people about its early diagnosis and screening tests. Cancer screening exams refers to the medical tests to identify people who have disease, often before symptoms of the illness occur. These tests help detecting cancer at its earliest stage when the chances for curing the disease are greatest. Advancements in nanotechnology have made the early screening of cancer possible. In this review, we have discussed the developments in nanotechnology that have encouraged the more recent innovative solutions for early diagnosis and treatment of cancer. Quantum dots, nanometer-sized semiconductors, are the new class of novel biosensors, now being exclusively employed as alternative fluorescent probes due to their unique properties, such as intense and stable fluorescence for a longer time, resistance to photobleaching, large molar extinction coefficients, and highly sensitive detection, due to their ability to absorb and emit light very efficiently. Their size approximates that of individual biomolecules, which offers unique possibilities for the ultrasensitive detection of cancer in persons’ serum, tissues, and other body fluids, when tagged with specific antibodies against specific tumor markers. In this review, we have account briefly the applications of semiconductor QDs employed for the early screening and diagnosis of cancer biomarkers between the years 2009-2012. We believe that this review will enable workers in the field to devise new applications of these materials for the early detection of cancer, and ultimate reduction in incidence of the disease.
Ritu Gaba; Mamta Bhandari; Rita Kakkar
Abstract
The present work deals with the adsorption of acetaldehyde, one of the most harmful volatile organic compounds (VOCs), on the TiO2 anatase nanosurface. The research was undertaken due to environmental concerns, as the TiO2 nanosurface serves as an excellent catalyst for the adsorption and decomposition ...
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The present work deals with the adsorption of acetaldehyde, one of the most harmful volatile organic compounds (VOCs), on the TiO2 anatase nanosurface. The research was undertaken due to environmental concerns, as the TiO2 nanosurface serves as an excellent catalyst for the adsorption and decomposition of VOCs. The chemistry of aldehydes on metal oxides is complex and elaborate, as it can result in a variety of reactions, such as selective oxidation, alcohols disproportionation, etherification and reductive coupling to higher olefins. The structural properties of the various nanosurfaces were first examined and finally adsorption studies were made on the (TiO2)17 cluster, as it shows least reconstruction and offers all kinds of coordination sites for the study. It is found that a myriad of different adsorption products are formed on the TiO2 nanosurface, depending upon the coordination site. The low coordination (3c) sites are highly reactive and form stronger bonds with the acetaldehyde molecule, whereas adsorption at the four coordination site leads to the reconstruction of the nanosurface. Acetaldehyde chemisorbs onto the surface producing zwitterionic four-membered rings, in which the carbonyl C=O bond is considerably weakened, or it adsorbs on the TiO2 surface in a H-bridge bonded form. The most feasible mode of adsorption on the TiO2 nanosurface is found to be methyl hydrogen migration resulting in the formation of [CH2-C(H)O] species, which may further undergo transformation by β-aldolization to yield crotonaldehyde and butane. Other products investigated in this work include oxidation to acetate and reduction to ethoxy species. The results obtained in this work can be of significant help in deciding the fate of reaction of acetaldehyde on the TiO2 nanosurface, and using it for decomposition of acetaldehyde to benign products.
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