Optical dispersion control in surfactant-free DNA thin films by vitamin B2 doping

A new route to systematically control the optical dispersion properties of surfactant-free deoxyribonucleic acid (DNA) thin solid films was developed by doping them with vitamin B2, also known as riboflavin. Surfactant-free DNA solid films of high optical quality were successfully deposited on various types of substrates by spin coating of aqueous solutions without additional chemical processes, with thicknesses ranging from 18 to 100 nm. Optical properties of the DNA films were investigated by measuring UV-visible-NIR transmission, and their refractive indices were measured using variable-angle spectroscopic ellipsometry. By doping DNA solid films with riboflavin, the refractive index was consistently increased with an index difference Δn ≥ 0.015 in the spectral range from 500 to 900 nm, which is sufficiently large to make an all-DNA optical waveguide. Detailed correlation between the optical dispersion and riboflavin concentration was experimentally investigated and thermo-optic coefficients of the DNA-riboflavin thin solid films were also experimentally measured in the temperature range from 20 to 85 °C, opening the potential to new bio-thermal sensing applications

RF-DNA Raw Data

Figure 2(b)_Absorbance-Wavenumber Figure 3_Current-Voltage Figure 4_Absorbance-Wavelength Figure 5_PL dat

Data from: Topological, chemical, and electro-optical characteristics of riboflavin-doped artificial and natural DNA thin films

DNA is considered as a useful building bio-material, and it serves as an efficient template to align functionalized nanomaterials. Riboflavin (RF)-doped synthetic double-crossover DNA (DX-DNA) lattices and natural salmon DNA (SDNA) thin films are constructed using substrate assisted growth and drop-casting methods, respectively, and their topological, chemical, and electro-optical characteristics were evaluated. The critical doping concentration of RF ([RF]C, ~5 mM) at given concentrations of DX-DNA and SDNA were obtained by observing the phase transition (from crystalline to amorphous structures) of DX-DNA and precipitation of SDNA in solution above [RF]C. [RF]C are verified by analyzing the atomic force microscopy images for DX-DNA and current, absorbance, and photoluminescence for SDNA. We study the physical characteristics of RF-embedded SDNA thin films, which are the Fourier transform infrared (FTIR) spectrum to understand the interaction between the RF and DNA molecules, current to evaluate the conductance, absorption to understand the RF binding to the DNA, and photoluminescence (PL) to analyze the energy transfer between the RF and DNA. The current and UV absorbance band of SDNA thin films decrease up to [RF]C followed by an increase above [RF]C. In contrast, the PL intensity illustrates the reverse trend, as compared to the current and UV absorbance behavior as a function of the varying [RF]. Due to the intense PL characteristic of RF, the DNA lattices and thin films with RF might offer immense potential to develop efficient bio-sensors and useful bio-photonic devices

Optoelectronic properties of DNA thin films implanted with titania nanoparticle-coated multiwalled carbon nanotubes

Rendering the unique features of individual nanoscale constituents into macroscopic thin films remains technologically challenging; the engineering of these constituents habitually compromises their inherent properties. Efficient, environmentally benign, and biodegradable DNA and cetyltrimethyl-ammonium chloride-modified DNA (DNA-CT) thin films (TFs) implanted with titania nanoparticle-coated multiwalled carbon nanotubes (MCNT-TiO2) are prepared by a drop-casting technique. The energy dispersive X-ray spectroscopy studies of DNA and DNA-CT TFs with MCNT-TiO2 identifies various elements (C, O, N, P, Na, and Ti) via quantitative microanalysis. The X-ray photoelectron, Raman, Fourier-transform infrared (FTIR), and UV-visible absorption spectra show changes in the chemical compositions and functional groups associated with binding energies, enhancement of characteristic MCNT-TiO2 Raman bands, and intensity changes and peak shifts of the FTIR and UV-Vis-NIR absorption bands, respectively. The PL spectra indicate an energy transfer in the measured samples, and the quenching of PL indicates a decrease in the recombination efficiency. Lastly, we measure the conductivity, which increased with an increasing concentration of MCNT-TiO2 in the DNA and DNA-CT TFs due to the better connectivity of MCNT-TiO2. By using these materials, the optoelectronic properties of DNA and DNA-CT TFs implanted with MCNT-TiO2 are easily tunable, enabling several engineering and multidisciplinary science applications, such as photonics, electronics, energy harvesting, and sensors

Growth of single-crystalline cubic structured tin(II) sulfide (SnS) nanowires by chemical vapor deposition

Single crystalline tin(ii) sulfide (SnS) nanowires are synthesized using a chemical vapor deposition (CVD) method with the support of gold as catalyst. Field emission electron microscopy studies show that SnS nanostructures grown at temperatures between 600 and 700 °C have wire-like morphology. These nanowires have an average diameter between 12 and 15 nm with lengths up to several microns. These NWs consist of uniform and smooth surfaces, and exhibit nearly stoichiometric chemical composition (Sn/S = 1.13). Transmission electron microscopy analysis reveals that the NWs consist of single crystalline cubic crystal structure with a preferential growth direction of 〈100〉. Field-effect transistor devices fabricated with SnS nanowires show that the nanowires consist of p-type conductivity along with carrier density of 6 × 1018 cm-3. © 2017 The Royal Society of Chemistry.1

Morphological and Optoelectronic Characteristics of Double and Triple Lanthanide Ion-Doped DNA Thin Films

Double and triple lanthanide ion (Ln³⁺)-doped synthetic double crossover (DX) DNA lattices and natural salmon DNA (SDNA) thin films are fabricated by the substrate assisted growth and drop-casting methods on given substrates. We employed three combinations of double Ln³⁺-dopant pairs (Tb³⁺–Tm³⁺, Tb³⁺–Eu³⁺, and Tm³⁺–Eu³⁺) and a triple Ln³⁺-dopant pair (Tb³⁺–Tm³⁺–Eu³⁺) with different types of Ln³⁺, (i.e., Tb³⁺ chosen for green emission, Tm³⁺ for blue, and Eu³⁺ for red), as well as various concentrations of Ln³⁺ for enhancement of specific functionalities. We estimate the optimum concentration of Ln³⁺ ([Ln³⁺]_O) wherein the phase transition of Ln³⁺-doped DX DNA lattices occurs from crystalline to amorphous. The phase change of DX DNA lattices at [Ln³⁺]_O and a phase diagram controlled by combinations of [Ln³⁺] were verified by atomic force microscope measurement. We also developed a theoretical method to obtain a phase diagram by identifying a simple relationship between [Ln³⁺] and [Ln³⁺]_O that in practice was found to be in agreement with experimental results. Finally, we address significance of physical characteristicscurrent for evaluating [Ln³⁺]_O, absorption for understanding the modes of Ln³⁺ binding, and photoluminescence for studying energy transfer mechanismsof double and triple Ln³⁺-doped SDNA thin films. Current and photoluminescence in the visible region increased as the varying [Ln³⁺] increased up to a certain [Ln³⁺]_O, then decreased with further increases in [Ln³⁺]. In contrast, the absorbance peak intensity at 260 nm showed the opposite trend, as compared with current and photoluminescence behaviors as a function of varying [Ln³⁺]. A DNA thin film with varying combinations of [Ln³⁺] might provide immense potential for the development of efficient devices or sensors with increasingly complex functionality