Observation of Six Orders of Magnitude Photoconductivity in DNA-MoS₂ Hydrogel Nano-Biocomposite

The advancement of bio-optoelectronic materials promises innovative systems and devices that can enable advanced optical bio-sensing, imaging, diagnostics, and treatment technologies. The materials choice and integration approach of an appropriate nanomaterial into a biomaterial matrix remains an open question towards achieving highly photoconductive nano-biocomposite materials. A nano-biocomposite film with ultrahigh photoconductivity remains elusive and critical for bio-optoelectronic applications. A uniform, well-connected, high-concentration nanomaterial network in the biological matrix remains challenging to achieve high photoconductivity. Wafer-scale continuous nano-biocomposite film without surface deformations and cracks play another major obstacle. In recent years, deoxyribonucleic acid (DNA) has emerged as a promising material for the development of hydrogels. However, natural DNA hydrogels are weak in mechanical strength and electrical conductivity due to their negatively charged phosphate backbone. However, poor charge transport and limited device performance were often observed due to an inadequate integration approach of 2D nanomaterials (such as MoS₂) in the DNA matrix. An appropriate integration approach of the well-connected MoS₂ network with a high concentration in the DNA matrix is deemed necessary for high-performance DNA-MoS₂ nano-biocomposites. Here we observed ultrahigh photoconductivity in DNA-MoS₂ nano-biocomposite film by incorporating a high-concentration, well-percolated, and uniform MoS₂ network in the ss-DNA matrix. This was achieved by utilizing DNA-MoS₂ hydrogel formation, which resulted in crack-free, wafer-scale DNA-MoS₂ nano-biocomposite films. Ultra-high photocurrent (5.5 mA at 1 V) with a record-high on/off ratio (1.3×10⁶) was observed, five orders of magnitude higher than conventional biomaterials (~10¹) reported so far. The incorporation of the Wely semimetal (Bismuth) as an electrical contact exhibited ultrahigh photoresponsivity (2.6×10⁵ A/W). Such high photoconductivity in DNA-MoS₂ nano-biocomposite could bridge the gap between biology, electronics, and optics for innovative biomedicine, bioengineering, and neuroscience applications.<br/><br/>Reference:<br/>Samanth Kokkiligadda, Ashok Mondal, Soong Ho Um, Sung Ha Park*, Chandan Biswas*, Observation of ultrahigh photoconductivity in DNA-MoS₂ nano-biocomposite, <b><i>Advanced Materials</i></b><b>, </b>2024, 2400124. DOI: https://doi.org/10.1002/adma.202400124, 15 March 2024