TY - JOUR
T1 - Transient photoresponse of nitrogen-doped ultrananocrystalline diamond electrodes in saline solution
AU - Ahnood, Arman
AU - Simonov, Alexandr
AU - Laird, Jamie Stuart
AU - Maturana, Matias I.
AU - Ganesan, Kumaravelu
AU - Stacey, Alastair
AU - Ibbotson, Michael R.
AU - Spiccia, Leone
AU - Prawer, Steven
PY - 2016/3/7
Y1 - 2016/3/7
N2 - Beyond conventional electrically-driven neuronal stimulation methods, there is a growing interest in optically-driven approaches. In recent years, nitrogen-doped ultrananocrystalline diamond (N-UNCD) has emerged as a strong material candidate for use in electrically-driven stimulation electrodes. This work investigates the electrochemical activity of N-UNCD in response to pulsed illumination, to assess its potential for use as an optically-driven stimulation electrode. Whilst N-UNCD in the as-grown state exhibits a weak photoresponse, the oxygen plasma treated film exhibits two orders of magnitude enhancement in its sub-bandgap open circuit photovoltage response. The enhancement is attributed to the formation of a dense network of oxygen-terminated diamond nanocrystals at the N-UNCD surface. Electrically connected to the N-UNCD bulk via sub-surface graphitic grain boundaries, these diamond nanocrystals introduce a semiconducting barrier between the sub-surface graphitic semimetal and the electrolyte solution, leading to a photovoltage under irradiation with wavelengths of λ = 450 nm and shorter. Within the safe optical exposure limit of 2 mW mm-2, charge injection capacity of 0.01 mC cm-2 is achieved using a 15 × 15 μm electrode, meeting the requirements for extracellular and intercellular stimulation. The nanoscale nature of processes presented here along with the diamond's biocompatibility and biostability open an avenue for the use of oxygen treated N-UNCD as optically driven stimulating electrodes.
AB - Beyond conventional electrically-driven neuronal stimulation methods, there is a growing interest in optically-driven approaches. In recent years, nitrogen-doped ultrananocrystalline diamond (N-UNCD) has emerged as a strong material candidate for use in electrically-driven stimulation electrodes. This work investigates the electrochemical activity of N-UNCD in response to pulsed illumination, to assess its potential for use as an optically-driven stimulation electrode. Whilst N-UNCD in the as-grown state exhibits a weak photoresponse, the oxygen plasma treated film exhibits two orders of magnitude enhancement in its sub-bandgap open circuit photovoltage response. The enhancement is attributed to the formation of a dense network of oxygen-terminated diamond nanocrystals at the N-UNCD surface. Electrically connected to the N-UNCD bulk via sub-surface graphitic grain boundaries, these diamond nanocrystals introduce a semiconducting barrier between the sub-surface graphitic semimetal and the electrolyte solution, leading to a photovoltage under irradiation with wavelengths of λ = 450 nm and shorter. Within the safe optical exposure limit of 2 mW mm-2, charge injection capacity of 0.01 mC cm-2 is achieved using a 15 × 15 μm electrode, meeting the requirements for extracellular and intercellular stimulation. The nanoscale nature of processes presented here along with the diamond's biocompatibility and biostability open an avenue for the use of oxygen treated N-UNCD as optically driven stimulating electrodes.
UR - http://www.scopus.com/inward/record.url?scp=84962483455&partnerID=8YFLogxK
UR - http://scitation.aip.org/docserver/fulltext/aip/journal/apl/108/10/1.4942976.pdf?expires=1479442708&id=id&accname=2121251&checksum=13B619C297945024278D8E242F65A685
U2 - 10.1063/1.4942976
DO - 10.1063/1.4942976
M3 - Article
AN - SCOPUS:84962483455
VL - 108
SP - 1
EP - 5
JO - Applied Physics Letters
JF - Applied Physics Letters
SN - 0003-6951
IS - 10
M1 - 104103
ER -