Proton-Functionalized Two-Dimensional Graphitic Carbon Nitride Nanosheet: An Excellent Metal-/Label-Free Biosensing Platform

• Published in: Small (Weinheim an der Bergstrasse, Germany) Vol. 10; no. 12; pp. 2382 - 2389
• Main Authors: Ma, Tian Yi, Tang, Youhong, Dai, Sheng, Qiao, Shi Zhang
• Format: Journal Article
• Language: English
• Published: Germany Blackwell Publishing Ltd 25-06-2014; Wiley Subscription Services, Inc
• Subjects: Animals; biosensing; Biosensing Techniques - instrumentation; Biosensing Techniques - methods; Carbon nitride; Charging; Coated Materials, Biocompatible - chemical synthesis; Coated Materials, Biocompatible - chemistry; Exfoliation; Fluorescence; Graphite - chemistry; heparin; Heparin - analysis; Heparin - blood; Heparins; Humans; Limit of Detection; Materials Testing; Metals; nanosheets; Nanostructure; Nanostructures - chemistry; Nanotechnology; Nitriles - chemical synthesis; Nitriles - chemistry; Platforms; Protons; Swine; Two dimensional; heparin; biosensing; carbon nitride; fluorescence; nanosheets
• ISSN: 1613-6810; 1613-6829
• DOI: 10.1002/smll.201303827

Ultrathin graphitic carbon nitride (g‐C3N4) nanosheets, due to their interesting two‐dimensional graphene‐like structure and unique physicochemical properties, have attracted great research attention recently. Here, a new approachis developed to prepare, for the first time, proton‐functionalized ultrathin g‐C3N4 nanosheets by sonication‐exfoliation of bulk g‐C3N4 under an acid condition. This method not only reduces the exfoliation time from more than 10 h to 2 h, but also endows the nanosheets with positive charges. Besides retaining the properties of g‐C3N4, the obtained nanosheets with the thickness of 2–4 nm (i.e., 6–12 atomic monolayers) also exhibit large specific surface area of 305 m2 g−1, enhanced fluorescence intensity, and excellent water dispersion stability due to their surface protonation and ultrathin morphology. The well‐dispersed protonated g‐C3N4 nanosheets are able to interact with negatively charged heparin, which results in the quenching of g‐C3N4 fluorescence. A highly sensitive and highly selective heparin sensing platform based on protonated g‐C3N4 nanosheets is established. This metal‐free and fluorophore label‐free system can reach the lowest heparin detection limit of 18 ng mL−1.
Proton‐functionalized g‐C3N4 ultrathin nanosheets with positively charged surface are synthesized by liquid exfoliating acidified bulk g‐C3N4. The obtained g‐C3N4 nanosheets with 6–12 atomic monolayers and large surface area up to 305 m2 g−1 exhibit outstanding sensitivity and selectivity in the fluorescence‐quenching sensing of heparin under both ideal and physiological conditions.