Possibility of Combining Carbon Dots and Liquid Exfoliated Graphene as a Carbon-Based Light Addressable Potentiometric Sensor

Abstract

A light addressable potentiometric sensor (LAPS) is a versatile sensing platform for bioassay. However, the lack of carbon-based LAPS (C-LAPS) is a bottleneck for its sustainable development in a carbon electronic era. Herein, a study of C-LAPS based on the combinations of carbon dots (CDs) and liquid exfoliated graphene (LEG) is presented. Devices of C-LAPS are first fabricated by self-assembling the hydrothermally synthesized CDs and the cosolvent ultrasonic delaminated LEG on poly(diallyldimethylammonium chloride) (PDDA)-modified indium tin oxide (ITO) glasses. According to the stacking orders of CDs and LEG, C-LAPS are named as CDs/LEG@PDDA/ITO and LEG/CDs@PDDA/ITO. Then, their electronic and photoelectronic features are measured and compared with the pure CD-and pure LEG-decorated ITO electrodes. Furthermore, working mechanisms are proposed by means of the classical theories of energy band bending and built-in electric field at the heterojunction of CDs and LEG. The resemblances of CDs/LEG@PDDA/ITO-based C-LAPS with Si-based LAPS (Si-LAPS) are confirmed from the points of view of production and separation of the photogenerated carriers, the formation of photocurrent, and the distinction with LEG/CDs@PDDA/ITO. Finally, its feasibility for biological application is justified by using the immune reaction of 5-methylcytosine (5mC) and its antibody (anti-5mC) as a proof of concept. The improved linear responses are evidenced by the comparisons with Si-LAPS' results. Conclusively, the proposed C-LAPS is believed to be a candidate for traditional semiconductor-based LAPS, with the merit of solutionprocessable. Meanwhile, the theoretical deductions about C-LAPS' principle can also pave the way for developing similar carbonbased sensors.

Multifunctional N-Doped Carbon Dots for Bimodal Detection of Bilirubin and Vitamin B12, Living Cell Imaging, and Fluorescent Ink

“…Three vibration peaks at 1780, 1706, and 1667 cm –1 were attributed to the carbonyl group (carboxylic acid and amide CO) and C–N bond, respectively. , The characteristic absorption band at 1538 cm –1 indicates N–H bending. The IR peaks at 1448, 1394 (bimodal peak), 1266, 1185, and 1100 cm –1 stand for the CC aromatic frame; N–H, C–O, and C–NH–C asymmetric stretching vibrations; and the C–O–C group at the edge sites of NCD. − Moreover, the peaks at 2980–2924 cm –1 refer to the C–H stretching vibration.…”

N-Doped Carbon Dots for Visual Recognition of 4-Nitroaniline and Use in Fluorescent Inks

“…Two nanodots exhibit prominent peaks in the 3436–3209 cm –1 range for −OH/–NH 2 functional groups and the 1691–1596 cm –1 range for carbonyl functionalities arising from −COOH and OC–NH. The N functionality, i.e., C–N and CN stretching vibrations appear at 1464 to 1417 cm –1 , respectively, and the peaks from 1265 to 1033 cm –1 appear because of C–O, C–O–C, and C–NH–C bonds. − Thus, both XPS study and FTIR spectral analysis hold good agreement about the edge functionality of NCDs. For more endorsement about the structural composition, Raman analysis was conducted (Figure S1d).…”

Light-Addressable Potentiometric Sensors in Microfluidics

“…The possible solution to this problem may rely on the improvement of the peripheral circuits and data processing algorithms. In summary, it is necessary to further improve the spatial resolution, measurement speed, and accuracy of the LAPS to promote the wide applications of the microchannel analysis system in many fields such as biomedicine ( Welden et al, 2021 ), food safety, and environmental protection ( Tu et al, 2018 ; Tong et al, 2020 ; Li et al, 2021 ).…”