Characterization and analysis of hybrid electronic materials for molecular based devices

The goal of this work is to characterize and to analyze hybrid electronic materials (HEMs) using fluorescence (FL) spectroscopy and conductive probe-atomic force microscopy (CP-AFM) in order to investigate the electrical and optical properties of these materials. Currently, research efforts to characterize novel organic materials for the determination of molecular level transport properties are of great interest.[6] One of the most interesting organic materials is the porphyrin molecule, which exhibits behavior useful for memory applications.[4] Colloidal CdS quantum dots (Q-CdS) capped with dioctyl sulfosuccinate (AOT) and thiol functionalized porphyrin molecules are explored for their potential application to next-generation hybrid electronic systems. Q-CdS capped with AOT self-assembled on various substrates are used to study the effect of electron transport in colloidal quantum dots using FL spectroscopy. In turn, porphyrin molecules chemisorbed onto gold surfaces are used to study the phonon-electron interaction in these molecules due to their metal cations. Maximum fluorescence intensities are obtained at specific angles of incidence, such as 80 and 45 degree with respect to the sample, for Q-CdS and porphyrin molecules, respectively. Emission spectra of Q-CdS absorbed onto different substrates such as gold, GaAs, and mica show a slight but systematic redshift of peak characteristics of spatially confined phonon interactions. The effects of relative quantum dot size, different substrates, and light intensity are discussed in this thesis. As the relative sizes of the quantum dots decrease, the excitonic peaks are slightly blue shifted. In order to study the electron transport mechanism of a single or a few molecules in metal-molecule-metal heterostructures, the electronic characteristics of self-assembled monolayers (SAMs) of n-alkanethiols such as hexanethiol and octanethiol are investigated using CP-AFM. SAMs of alkanethiols on gold surfaces have been shown to form stable surface structures.[21] Studies have shown that thiolated porphyrins readily self-assemble on gold surfaces.[73] The I-V characteristics of self-assembled monothiolated porphyrin molecules on gold substrates are measured under ambient conditions. I-V traces of porphyrin molecules behave sigmoidally according to the Simmons Equation for square barrier tunneling and illustrate that the electron transport mechanism through porphyrin is direct tunneling for the applied bias levels in this study

Fluorescence spectroscopy characterization of cadmium sulfide quantum dots on metal, insulator, and semiconductor substrates

Colliodal cadmium sulfide quantum dots (Q-CdS), ranging in size from 1 to 5 nm and capped with dioctyl sulfosuccinate (AOT), were synthesized and deposited upon substrates of gold (Au), mica, and gallium arsenide (GaAs). Fluorescence spectroscopy is used to identify the range and maxima of excitation and emission spectra of each structure. A red shift in emission spectra from the Au to mica to GaAs substrate based samples is observed for the smallest-sized quantum dots. The midrange and largest-sized dots display the longest emission wavelengths when physisorbed to the Au substrates with a shift to shorter and then longer emission wavelengths for the mica and GaAs-based samples, respectively. The display of emission spectra throughout the visible range for the Q-CdS deposited on all three types of substrates bodes well for future optical device applications using hybrid (organic-inorganic) electronic materials. © 2011 Wiley Periodicals, Inc

Characterization of AOT capped cadmium sulfide quantum dots using fluorescence spectroscopy

Colloidal cadmium sulfide quantum dots (Q-CdS) capped with dioctyl sulfosuccinate (AOT) were synthesized and characterized. Fluorescence spectroscopy is used to verify quantized dot formation, size, and emission wavelength. Optical characterization of this form is necessary for fundamental investigation of hybrid electronic materials and their potential use in next-generation devices. © 2010 Wiley Periodicals, Inc

ORGINAL PAPER<br>Modulation of the tissue defense system by squalene in cyclophosphamide induced toxicity in rats

Introduction: Antineoplastic drug, Cyclophosphamide (CP), is a widely used drug that causes toxicity through its metabolites, phosphoramide mustard and acrolein. Squalene (SQ), an intermediate in the cholesterol metabolism has antioxidant and membrane stabilizing property. In the present study, the protective role of SQ towards the tissue defense system of the liver and kidney in the toxicity induced by CP was assessed. Material and methods: Normal Wistar albino rats were administered CP in a dose of 150 mg/kg b.wt., i.p., twice, for 2 consecutive days to induce toxicity. SQ, in a dose of 0.4 ml/day/rat p.o. was used to treat the toxicity induced by CP. Results: Significantly decreased activities of enzymic antioxidants [superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione-s-transferase (GST) and glutathione reductase (GR)], decreased levels of reduced glutathione and increased levels of thiobarbutric acid reactive substance (TBARS) were observed. These pathological alterations were significantly normalized during the treatment of SQ. Conclusions: CP toxicity increased the free radical levels in the tissues and affected the activities of the enzymic antioxidants. Increased levels of TBARS [a measure of lipid peroxidation (LPO)] and decreased levels of GSH (due to utilization for detoxification process) evidenced the damage to these tissues. Protection exerted by SQ could be due to free radical quenching, providing additional alkylation site to CP metabolites and by inducing enzymic antioxidant production in these tissues. In conclusions improved antioxidant defense system in the liver and kidney of the experimental rats confirms the protective role of SQ against CP induced toxicities

Emerging Trends of Nanotechnology and Genetic Engineering in Cyanobacteria to Optimize Production for Future Applications

Nanotechnology has the potential to revolutionize various fields of research and development. Multiple nanoparticles employed in a nanotechnology process are the magic elixir that provides unique features that are not present in the component&rsquo;s natural form. In the framework of contemporary research, it is inappropriate to synthesize microparticles employing procedures that include noxious elements. For this reason, scientists are investigating safer ways to produce genetically improved Cyanobacteria, which has many novel features and acts as a potential candidate for nanoparticle synthesis. In recent decades, cyanobacteria have garnered significant interest due to their prospective nanotechnological uses. This review will outline the applications of genetically engineered cyanobacteria in the field of nanotechnology and discuss its challenges and future potential. The evolution of cyanobacterial strains by genetic engineering is subsequently outlined. Furthermore, the recombination approaches that may be used to increase the industrial potential of cyanobacteria are discussed. This review provides an overview of the research undertaken to increase the commercial avenues of cyanobacteria and attempts to explain prospective topics for future research