A versatile platform for colorimetric, fluorescence and photothermal multi-mode glyphosate sensing by carbon dots anchoring ferrocene metal-organic framework nanosheet

Concerns regarding pesticide residues have driven attempts to exploit accurate, prompt and straightforward approaches for food safety pre-warning. Herein, a nanozyme-mediated versatile platform with multiplex signal response (colorimetric, fluorescence and temperature) was proposed for visual, sensitive and portable detection of glyphosate (GLP). The platform was constructed based on a N-CDs/FMOF-Zr nanosensor that prepared by in situ anchoring nitrogen-doped carbon dots onto zirconium-based ferrocene metal-organic framework nanosheets. The N-CDs/FMOF-Zr possessed excellent peroxidase (POD)-like activity and thus could oxide colorless 3, 3′, 5, 5′-tetramethylbenzidine (TMB) into a blue oxidized TMB (oxTMB) in presence of H2O2. Intriguingly, owing to the blocking effect triggered by multiple interaction between GLP and N-CDs/FMOF-Zr, its POD-like activity of the latter was remarkably suppressed, which can modulate the transformation of TMB into oxTMB, generating tri-signal responses of fluorescence enhancement, absorbance and temperature decrease. More significantly, the temperature mode can be facilely realized by a portable home-made mini-photothermal device and handheld thermometers. The proposed multimodal sensing was capable of providing sensitive results by fluorescence mode and simultaneously realized visual/portable testing by colorimetric and photothermal channels. Consequently, it exhibited more adaptability for practical applications, which can satisfy different testing requirements according to sensitivity and available instruments/meters, presenting a new horizon for exploiting multifunctional sensors.