Bio-Organic Optoelectronic Devices Using DNA

Bio-Organic Optoelectronic Devices Using DNA

(Parte 1 de 5)

Adv Polym Sci DOI:10.1007/12 2009 6 c© Springer-Verlag Berlin Heidelberg 2009

Bio-Organic Optoelectronic Devices Using DNA Thokchom Birendra Singh, Niyazi Serdar Sariciftci, and James G. Grote

Abstract Biomolecular DNA, as a marine waste product from salmon processing, has been exploited as biodegradable polymeric material for photonics and electronics. For preparing high optical quality thin films of DNA, a method using DNA with cationic surfactants such as DNA–cetyltrimethylammonium,CTMA has been applied. This process enhances solubility and processing for thin film fabrication. These DNA–CTMA complexes resulted in the formation of self-assembled supramolecular films. Additionally, the molecular weight can be tailored to suit the application through sonication. It revealed that DNA–CTMA complexes were thermostable up to 230◦C. UV–VIS absorption shows that these thin films have high transparency from 350 to about 1,700nm. Due to its nature of large band gap and large dielectric constant, thin films of DNA–CTMA has been successfully used in multiple applications such as organic light emitting diodes (OLED), a cladding and host material in nonlinear optical devices, and organic field-effect transistors (OFET). Using this DNA based biopolymers as a gate dielectric layer, OFET devices were fabricated that exhibits current–voltage characteristics with low voltages as compared with using other polymer-based dielectrics. Using a thin film of DNA–CTMA based biopolymer as the gate insulator and pentacene as the organic semiconductor, we have demonstrated a bio-organicFET or BioFET in which the current was modulated over three orders of magnitude using gate voltages less than 10V. Given the possibility to functionalise the DNA film customised for specific purposes viz. biosensing, DNA–CTMA with its unique structural, optical and electronic properties results in many applications that are extremely interesting.

T.B. Singh (B) and N.S. Sariciftci Linz Institute of Organic Solar Cells (LIOS), Institute of physical chemistry, Johannes Kepler

University, A 4040 Linz, Austria e-mail: birendra.singh@CSIRO.Au; serdar.sariciftci@jku.at

J.G. Grote Air Force Research Laboratory, Materials and Manufacturing Directorate, AFRL/MLPS, Wright-Patterson Air Force Base, OH 45433-7707, USA

T.B. Singh et al.

Keywords Bioelectric phenomena · BioFET · BioLED · Biomolecular electronics · OFET · OLED · Organic electronics · Photonic devices · Plastic electronics

Contents

1 Introduction 2 DNA–CTMA as Optoelectronic Material 3 DNA–CTMA Films in Nonlinear Optics 4 DNA–CTMA in Organic Light Emitting Diodes 5 DNA–CTMA in Organic Field Effect Transistors 6 Dielectric Spectroscopy of DNA–CTMA Thin Films 7 Transient Response of BioFETs 8 Summary and Outlook References

Abbreviations

Alq3 Tris-(8-hydroxyquinoline)aluminum BCP 2,9-Dimethyl-4,7-diphenyl-1,10-phenanthroline

BioFET Bio-organic field-effect transistors BioLED Bio-organic light emitting diodes CTMA Hexadecyltrimethylammoniumchloride EBL Electron blocking layer EIL Electron injection layer ETL Electron transport layer HBL Hole blocking layer

IDrain,Sat Saturated drain current LCD Liquid crystal displays

NPB (N,N′-Bis(naphthalene-1-yl)-N,N′-bis(phenyl)benzidine)

PCBM 1-(3-Methoxycarbonyl)propyl-1-phenyl(6]C61 PEDOT [Poly(3,4-ethylenedioxythiophene)]

PSS Poly(4-styrenesulfonate) T Temperature

VDrain Drain voltage VGate Gate voltage Vt Threshold voltage

1 Introduction

The progress made in the field of organic electronics in the last two decades have resulted in the demonstration of prototype devices such as a 4.7-in. QVGA active matrix display containing 76,800 organic transistors [1], mechanical sensors [2]

Bio-Organic Optoelectronic Devices Using DNA and chemical sensors [3]. Devices such as organic light emitting diodes (OLEDs), which is a part of display technology is now used in consumer electronics in place of LCD (see w.sony.com). All these have been possible with the availability of a variety of organic materials, conducting polymers, insulators, semiconductors and metals. Apart from conventional organic materials, biomaterials are of particular interest. Biomaterials often show unusual properties which are not easily replicated in conventional organic or inorganic materials. In addition, natural biomaterials are from renewable resources and are inherently biodegradable. Among natural biodegradable materials, the science community has shown interest in DNA for various reasons, such as potential use of DNA assembly in molecular electronic devices [4], nanoscale robotics [5] and DNA-based computation [6].

The molecular structure of DNA (double helix) consists of two inter-twined spirals of sugar and phosphate molecules linked by hydrogen-bonded base pairs (see Fig.1). The phosphate backbone is negatively charged with H+ or Na + to balance the neutrality. The width of the double helix is about two nanometres and the length of the DNA molecule depends on the number of base pairs (about a third of a nanometre per base pair). For practical use, natural DNA, derived from salmon milt, which is normally a waste product of the salmon-fishing industry is attractive

Base Base

Base

Base Phosphate

Sugar

Adenine

Thymine Guanine

Cytosine

Fig. 1 Phosphate–sugar backbone of single strand DNA. The phosphate back bone is negatively charged with H+ or Na+ to balance the neutrality. In the early years scientists had already known the phosphate backbone and sugar groups, also the four base groups, adenine, thymine, guanine, cytosine

T.B. Singh et al.

(see Figs.2 and 3). Although there is a wealth of knowledge on the nature of the transport properties of synthetic DNA, in this chapter we shall focus only on DNA materials derived from salmon milt. The reader may also pay attention to the fact that there is an ongoing debate on the insulating [7–12], semiconducting [13,14] as well as highly conducting[15] and even superconductingnature [16] of the transport in DNA molecules.

meat and roe are ediblemilt & roe sacs as a waste productmilt & roe sacs as a waste productmilt & roe sacs as a waste productmilt & roe sacs as a waste product

Fig. 2 Illustration of salmon as an edible meat and as a source of natural biomaterials (salmon DNA)

Frozen milt & roe sacs Homogenization

Enzyme treatment Protein elimination

DNA dissolutionActive carbon treatmentFiltrationFreeze Dried Purified DNA

Mw = 500,0–6,500,0,Purity = 96%, Protein Content = 1-2%

Mw = 500,0–6,500,0, Purity = 96%, Protein Content = 1-2%

Fig. 3 Illustration of purifying steps of salmon DNA from its frozen milt and roe sacs

Bio-Organic Optoelectronic Devices Using DNA 2 DNA–CTMA as Optoelectronic Material

The DNA used for research in optoelectronic devices was purified DNA provided by the Chitose Institute of Science and Technology (CIST) [17,18]. The processing steps involved are summarised in Figs.2 and 3. The starting point was marine-based DNA, first isolated from frozen salmon milt and roe sacs through a homogenisation process. It then went through an enzymatic treatment to degrade the proteins by protease. Resulting freeze dried purified DNA has molecular weight ranging from 500,0 to 8,0,0Da with purity as high as 96% and protein content of 1–2%. The average molecular weight of DNA provided by CIST is, on average, greater than 8,0,0Da. If necessary, the molecular weight of DNA supplied by CIST can be tailored and cut using an ultrasonic procedure [19] which gives rise to lower molecular weight of 200,000Da depending the sonication energy as shown in Fig.4. It was found that the purified DNA was soluble only in water, the resulting films are too water sensitive and have insufficient mechanical strength, so are not compatible with typically fabrication processes used for polymer based devices. It has also been observed that many particulates are present in the DNA films. Therefore, additional processing steps are performed to render DNA more suitable for device fabrication with better film quality. From the knowledge of stoichiometric combination of an anionic polyelectrolyte with a cationic surfactant, it has been shown that DNA which is an anionic polyelectrolyte could be quantitatively precipitated with cationic surfactant in water [20]. This processing was accomplished by precipitating the purified DNA in water with a cationic surfactant complex, hexadecyltrimethylammonium chloride (CTMA), by an ion exchange reaction [19,21–25] (see Fig.5). This surfactant was selected for the following reasons [17]. First, cationic surfactants having longer (>16) alkyl chains are water-insoluble, and chains shorter than

C16 might induce poor mechanical property of the materials. Second, DNA complexes made with longer alkyl chains might damage the double helix structure of

DNA as the strong association and aggregation among alkyl chains might break the hydrogen bonds of the nucleobase pairs. The third reason is that these surfactants are commercially available. The resulting DNA–lipid complex became water insoluble

Fig. 4 Molecular weight of DNA as a function of total sonication energy. The DNA was sonicated on ice in 10s long pulses with a 20s rest period between pulses to prevent overheating of the sample. (Reproduced with permission from American Institute of Physics, and [19]) Sonication Energy (kJ)

Molecular Weight

8,0,0 Da (12,0 base pairs)

145,0 Da (220 base pairs)

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Base

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