Surface Active Carbon Quantum Dot (CQD)-Modified NiWO ₄ Nanocomposite for Electrochemical Detection of Serotonin

Serotonin is one of the crucial neurotransmitters that plays a vital role in human physiology and normally exists in human serum in the 200 nM to 1.1 μM range along with a wide variety of interfering agents. This makes it a quite challenging task to detect serotonin in an efficient, electrochemical way at ambient temperature in a relatively low concentration (nanomolar) of abundance. So, this work is focused on developing an enzyme-less electrochemical sensing platform that can detect serotonin with a very low limit of detection (LOD) in a highly sensitive and selective way. For this purpose, carbon quantum dots (CQDs), one of the advanced carbonaceous materials, were prepared from a natural source (corn seeds) and applied to make a nanocomposite sensing platform with an electrochemically deposited NiWO 4 thin film on FTO-coated glass substrate. The prepared materials were thoroughly characterized by using sophisticated instrumentation techniques. The fabricated NiWO 4 /CQD nanocomposite thin film was then subjected to detailed electrochemical probing toward serotonin sensing. Fascinatingly, the developed sensor prototype yielded an LOD of 134.0 nM without compromising the sensitivity (16.9 μA μM –1 cm –2 ), which makes it well capable for detecting serotonin that is present in human serum in the nM to μM order.