Deoxyribonucleic Acid Thin Films Research Articles

Fibres and films made from DNA and CTMA-modified DNA embedded with gold nanorods and organic light-emitting materials

The scaffolding of deoxyribonucleic acid (DNA) makes DNA molecules effective templates for hosting various types of nanomaterials. Recently, electrospun fibres formed by a variety of polymers have begun to see use in a number of applications, such as filtration in energy applications, insulation in thermodynamics and protein scaffolding in biomedicine. In this study, we constructed electrospun fibres and thin films made of DNA and cetyltrimethylammonium chloride (CTMA)-modified DNA (CDNA) embedded with dyes, organic light-emitting materials (OLEMs), and gold nanorods (GNRs). These materials provide significant advantages, including selectivity of dimensionality, solubility in organic and inorganic solvents, and functionality enhancement. In addition, coaxial fibres made of CDNA were constructed to demonstrate the feasibility of constructing relatively complex fibres with an electrospinner. To determine the basic physical characteristics of the fibres and thin films containing GNRs and OLEMs, we conducted current measurements, photoluminescence (PL) measurements, X-ray photoelectron spectroscopy (XPS), and ultraviolet–visible (UV–Vis) spectroscopy. The currents in DNA and CDNA were found to exhibit Ohmic behaviour, while the PL emission could be controlled by OLEMs. In addition, the XPS provided the chemical configuration of samples, and the UV–Vis spectra revealed the plasmon resonance of GNR. Due to their simple fabrication and enhanced functionality, these DNA and CDNA fibres and thin films could be used in various devices (e.g., filters or blocking layers) and sensors (e.g., gas detectors and bio sensors) in a number of industries.

Uracil-doped DNA thin solid films: a new way to control optical dispersion of DNA film using a RNA constituent.

Among five nucleobases, adenine (A), guanine (G), cytosine (C), thymine (T) and uracil (U), uracil is a key distinctive constituent existing only in ribonucleic acid (RNA). RNA shares the common A, G, and C with deoxyribonucleic acid (DNA) made of A-T, G-C hydrogen bonding. We explored a new attempt to combine uracil (U) with DNA, successfully realizing U-doped DNA thin solid films for the first time. Impacts of uracil on optical properties of the films were thoroughly investigated. The method was based on optimal spin-coating of an aqueous solution of DNA and uracil over silicon or silica substrates. Optical absorption of both aqueous solution and U-doped DNA thin solid films was characterized in a wide spectral range covering UV-visible-IR. Immobilization of uracil within DNA thin solid films was experimentally confirmed by FTIR spectroscopy studies. By using an ellipsometer, we measured the refractive indices of the films and discovered that U-doping was a very effective means to control optical dispersion DNA thin solid film. We further investigated thermo-optic behavior to find impacts of U-doping in DNA films. Detailed thin film processes and optical characterizations are discussed.

Optoelectrical and mechanical properties of multiwall carbon nanotube-integrated DNA thin films

Thin films made of deoxyribonucleic acid (DNA), dissolved in an aqueous solution, and cetyltrimethyl-ammonium-modified DNA (CDNA), dissolved in an organic solvent, utilising multiwall carbon nanotubes (MWCNTs) are not yet well-understood for use in optoelectronic device and sensor applications. In this study, we fabricate MWCNT-integrated DNA and CDNA thin films using the drop-casting method. We also characterise the optical properties (i.e. absorption spectra, Fourier-transform infrared spectra, Raman spectra, photoluminescence, and time-of-flight secondary ion mass spectrometry) to study spectral absorption, interaction, functional group, chirality, and compositional moiety and its distribution of MWCNTs in DNA and CDNA thin films. The electrical property for conductance and the mechanical characterisations of hardness, modulus and elasticity for stability are also discussed. Lastly, to show the feasibility of directional alignment of MWCNTs in DNA thin films, we perform an alignment experiment with MWCNTs in DNA via brushing and shearing methods, and we evaluate the results using polarised optical microscopy. Our simple methodology to align ingredients in DNA and CDNA thin films leveraging various optical, electrical and mechanical properties, provides great potential for the development of efficient devices and sensors.

DNA nanostructures doped with lanthanide ions for highly sensitive UV photodetectors.

Deoxyribonucleic acid (DNA) and lanthanide ions (Ln3+) exhibit exceptional optical properties that are applicable to the development of nanoscale devices and sensors. Although DNA nanostructures and Ln3+ ions have been investigated for use in the current state of technology for more than a few decades, researchers have yet to develop DNA and Ln3+ based ultra-violet (UV) photodetectors. Here, we fabricate Ln3+ (such as holmium (Ho3+), praseodymium (Pr3+), and ytterbium (Yb3+))‒doped double crossover (DX)‒DNA lattices through substrate-assisted growth and salmon DNA (SDNA) thin films via a simple drop-casting method on oxygen (O2) plasma-treated substrates for high performance UV photodetectors. Topological (AFM), optical (UV-vis absorption and FTIR), spectroscopic (XPS), and electrical (I‒V and photovoltage) measurements of the DX‒DNA and SDNA thin films doped with various concentrations of Ln3+ ([Ln3+]) are explored. From the AFM analysis, the optimum concentrations of various Ln3+ ([Ln3+]O) are estimated (where the phase transition of Ln3+‒doped DX‒DNA lattices takes place from crystalline to amorphous) as 1.2 mM for Ho3+, 1.5 mM for Pr3+, and 1.5 mM for Yb3+. The binding modes and chemical states are evaluated through optical and spectroscopic analysis. From UV-vis absorption studies, we found that as the [Ln3+] was increased, the absorption intensity decreased up to [Ln3+]O, and increased above [Ln3+]O. The variation in FTIR peak intensities in the nucleobase and phosphate regions, and the changes in XPS peak intensities and peak positions detected in the N 1 s and P 2p core spectra of Ln3+‒doped SDNA thin films clearly indicate that the Ln3+ ions are properly bound between the bases (through chemical intercalation) and to the phosphate backbone (through electrostatic interactions) of the DNA molecules. Finally, the I‒V characteristics and time-dependent photovoltage of Ln3+‒doped SDNA thin films are measured both in the dark and under UV LED illuminations (λLED = 382 nm) at various illumination powers. The photocurrent and photovoltage of Ln3+‒doped SDNA thin films are enhanced up to the [Ln3+]O compared to pristine SDNA due to the charge carriers generated from both SDNA and Ln3+ ions upon the absorption of light. From our observations, the photovoltages as function of illumination power suggest higher responsivities, and the photovoltages as function of time are almost constant which indicates the stability and retention characteristics of the Ln3+‒doped SDNA thin films. Hence, our method which provides an efficient doping of Ln3+ into the SDNA with a simple fabrication process might be useful in the development of high-performance optoelectronic devices and sensors.

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.

Ultrafast nonlinear optical properties of thin-solid DNA film and their application as a saturable absorber in femtosecond mode-locked fiber laser

A new extraordinary application of deoxyribonucleic acid (DNA) thin-solid-film was experimentally explored in the field of ultrafast nonlinear photonics. Optical transmission was investigated in both linear and nonlinear regimes for two types of DNA thin-solid-films made from DNA in aqueous solution and DNA-cetyltrimethylammonium chloride (CTMA) in an organic solvent. Z-scan measurements revealed a high third-order nonlinearity with n2 exceeding 10−9 at a wavelength of 1570 nm, for a nonlinarity about five orders of magnitude larger than that of silica. We also demonstrated ultrafast saturable absorption (SA) with a modulation depth of 0.43%. DNA thin solid films were successfully deposited on a side-polished optical fiber, providing an efficient evanescent wave interaction. We built an organic-inorganic hybrid all-fiber ring laser using DNA film as an ultrafast SA and using Erbium-doped fiber as an efficient optical gain medium. Stable transform-limited femtosecond soliton pulses were generated with full width half maxima of 417 fs for DNA and 323 fs for DNA-CTMA thin-solid-film SAs. The average output power was 4.20 mW for DNA and 5.46 mW for DNA-CTMA. Detailed conditions for DNA solid film preparation, dispersion control in the laser cavity and subsequent characteristics of soliton pulses are discussed, to confirm unique nonlinear optical applications of DNA thin-solid-film.

DNA damage induced by carbon ions (C3+) beam accessed by independent component analysis of infrared spectra

Purpose: To understand the degradation processes and role of secondary species on deoxyribonucleic acid (DNA)-damaged fragments as a result of irradiation with energetic ions.Materials and methods: Damage caused to DNA thin films as a result of exposure to 4 keV carbon ions beam was accessed by analyzing the infrared spectra, obtained in situ for different irradiation times, with both bi-dimensional (2D) correlation spectroscopy and independent component analysis (ICA).Results: Results indicated that deoxyribose, phosphate and base groups of the DNA molecule were being damaged and new reaction products as oxime and furfural groups are being formed.Conclusions: Damage on DNA bases is consistent with the formation of oxime products which react with DNA deoxyribose products forming furfural groups and confirming that DNA damage is caused by direct and indirect processes.

Excitation Energy Migration of Acridine Orange Intercalated into Deoxyribonucleic Acid Thin Films

The excitation energy migration of acridine orange (AO) immobilized in deoxyribonucleic acid (DNA) thin film was investigated by time-resolved fluorescence and fluorescence anisotropy decay measurements. Polyvinylalcohol (PVA) was used as a reference matrix. The absorption and fluorescence spectra indicated that the molecular aggregation was depressed in DNA thin films rather than in PVA thin films. Time-resolved fluorescence spectra of AO in DNA films suggested effcient energy transfer from monomer to trap sites, dimers, or aggregates. Fluorescence lifetime of AO in DNA films was decreased with increasing fractions of AO, which suggested efficient energy migration between intercalated AOs. The fluorescence anisotropy measurements directly supported the efficient energy migration between intercalated AOs. These findings indicate that the double-helix DNA contributes to the efficient energy migration between intercalated dyes.