In our previous work we demonstrated a 3X increase in the nonlinearity, or electro-optic (EO) coefficient of the nonlinear optic (NLO) polymer disperse red 1:Polymethylmethacrylate (DR1: PMMA) by introducing a thin guanine nucleobase interfacial buffer layer, deposited between the NLO polymer and the cathode and a thin bathocuproine (BCP) interfacial buffer layer, deposited between the NLO polymer and the anode, being poled at 100 V/μm. In addition, we observed a 40% increase in EO coefficient by depositing either a thin sol-gel derived titanium dioxide layer or a thin guanine layer on either the anode or cathode side of the structure, poling at 100 V/μm. This paper addresses our analysis of these differences and is based on surface resistance.
After the invention of DNA-surfactant films and the proposal of dye doping into them by Ogata, many applications were demonstrated. Among them tunable thin film laser is one of the most attractive functional devices. Development and progress in DNA based lasers after the first observation of amplified spontaneous emission (ASE) by us has been reviewed in a former paper published in 2011.1 In this proceeding, progresses in the subsequent half a decade are described.
Recent experimental Dynamic Light Scattering (DLS) studies of the coil sizes of DNA-CTMA:Rh solutions have lead to numerical discrepancies with theoretical predictions amounting to one-two orders of magnitude.1 In this paper, which has partially character of a tutorial, we present the basic theoretical concepts underlying an analysis of the polymer coil sizes from DLS experiments. In particular, we discuss the limitations of those methods. We present a wormlike model of a polymer chain which is a promising candidate for inferring information about the spatial structure of the DNA chain from experimental data.
In this study, we demonstrated the use of DNA-CTMA (DC) in combination with Nickel Nanostrands (NiNs) for application in Electromagnetic Interference (EMI) shielding. The addition of NiNs fillers to DC led to films with higher shielding effectiveness (SE) than when Silver nanoparticles were used. An enhanced EMI shielding effectiveness (SE) was also achieved by the fabrication of the DC-NiNs shielding film structure in a layered architecture. Very thin layer of Guanine (∼60 nm) were inserted between layers of DNA-NiNs (∼ 100um each) to total a thickness of 500um of the shielding film. An increase of the SE by 6-8 dB for the layered structure as compared to the bulk thick film with NiNs loadings up to 10 wt%. At higher loadings (>10 wt. %), a significant physical degradation of the films was observed for all films regardless of the thickness or the process of fabrication.
Fluorescence yields of many organic dyes are enhanced via incorporation into DNA-surfactant complex which also extends the lifetime of the dyes. We have developed wavelength tunable lasers with hemicyanine dyes embedded in DNAcetyltrimethylammonium (DNA-CTMA). A couple of methods were applied to the dye doping, leading to different modes of interaction with DNA or its complex. Even though optical properties depended on the material structure reflecting preparation method, dyes showed good performance as laser media in various cases. Therefore, it is important to study the details of their interaction mechanism and the effects on their lasing performance. In order to investigate the interaction mode, three types of dyes were employed, that is, 4-[4-(dimethylamino)stylyl]-1-methylpyridinium iodide (DMASMPI or p-Hemi1), 2-[4-(dimethylamino)styryl]-1-methylpyridinium iodide (o-Hemi1), and 2-(4- dimethylaminostyryl)-1-ethylquinolinium iodide (Quinaldine Red). Strong fluorescence enhancement and spectral shift of the dyes interacting with DNA in water suggested the importance of direct binding to DNA, while the dyes showed strongest fluorescence emission without significant spectral shift when interacting with DNA-CTMA in ethanol. The facts implied that multiple origins of fluorescence enhancement could be applicable to build up lasers. DNA-CTMA thin films incorporating the dyes were fabricated with several different methods aiming to control the interaction modes of the dye. p-Hemi1 doped thin films with 'immersion method' gave light amplification and laser oscillations in the range 590-620nm under optical pumping. The films operated more than 1 hour before the output stimulated emission diminished, showing strong durability of the dye in the complex.
Modeling calculations were carried out on the surface plasmon resonance interferometry (SPRI) technique the experimental studies of which were previously described. This effort was carried out with the goal to clarify the dependencies of the sensing function on the many parameters and variables that impact the performance of this technique. In particular, the calculations focused on the comparison of the sensing function between SPR with interferometry and SPR-only at fixed angles. MATLAB was used in these calculations because it provided detailed control of the modeling efforts.
The surfaces of Portobello mushroom spores (PMS) have been used to produce Au and Ag nanoparticles, which are held thereon. They have then been overcoated with TiOx. These adsorbed more methyl orange (MO) pollutant from water than commercial P25 TiO2. After calcination they form biomimetic TiO2 (PMS) and removal of the biotemplate, they catalyse faster rates of MO from water (molecules/mg/s) than P25 anataserutile. Other biotemplates are now anticipated that will yield biomimetic photocatalysts with higher turnover number (s-1) removal of endocrine disrupters from water.
Thin films of DNA biopolymer thin film are fabricated by a drop casting process on glass and silicon substrates, as well as freestanding. The refractive index is measured by elliposmetry and in bulk DNA film the refractive index is shown to be increased in the 600 to 900 nm DNA transparency window by doping with riboflavin. Further analysis with FT-IR, Raman, and XRD are used to determine whether binding between riboflavin and DNA occurs.
Complexes formed of deoxyribose nucleic acid (DNA) and trivalent lanthanide ions (Ln3+) promise a combination of high optical gain and low optical loss in an organic polymer host matrix. However, there has been some dispute about the binding mechanism between the DNA helix and the positively-charged lanthanide ions. Here we introduce an attempt to resolve the mechanism for binding through Judd-Ofelt analysis on DNA-Eu3+, DNA-Tb3+, and DNA-Sm3+ to first order. From initial Judd-Ofelt parameters extrapolations can be made to the line strengths, Einstein coefficients, and fluorescence lifetimes.
In the last decades, nanotechnology has converged various fields such physical, chemical and biological sciences to bring significant technological advancement. The potential of nanotechnology can be envisaged based on the fact that in the last two decades this technology has touched and revolutionized the research in the fields of electronics, computers, communications, defense, energy and medicine. Nanoparticles, in particular, are a class of nanomaterials which has drawn tremendous interest and advancement in its synthesis (chemical, physical or biological). In this work, a Pulsed laser ablation approach has been developed for the synthesis of ligand-free nanoparticles. Characterization techniques such as optical spectroscopy and Transmission Electron Microscopy (TEM) were combined with Dynamic Light Scattering (DLS) measurements. To further understand this synthesis technique, nanoparticle generation was studied as a function of height of liquid above ablation target. Additionally, systematic investigation was performed to study the effect of irradiation time on nanoparticle yield.
Photothermal therapy (PT) provides a strong potential in treatment of tumors, selective cell death, through the ability of gold nanoparticles to target destructive heat preferentially to tumor regions. And yet, clinical application of the thermal therapies has not accomplished due to insufficient processes of the heating methods and temperature measuring techniques leading to low reproducibility of such treatment. In this study, we created a 3 dimensional tissue platform to characterize the heating method and to control the generated heat in the tissue used for a superficial cancer model using gold nanorods (GNRs) and near-infrared (NIR, 808 nm) laser. The 3D tissue platform involved a 2 mm wide hemisphere to confine the GNRs covered with20 μm thick polymer film designed to mimic localized nanoparticles in tumor. Moreover, this platform provides an easy way to measure heat distribution and temperature created in tumor cross section. To investigate the photothermal effect of GNRs on heat generation, the amount of GNRs and laser power density were controlled. The GNRs were shown to be the large absorption cross sections generating localized photothermal effects and hyperthermic effects on destructive consequences in the cell dynamics causing a partial tumor regression.