To date, various analytical methods have been proposed for the determination of 4-NP in water, including chromatography, electrochemical detection, chemiluminescence detection, and fluorescence monitoring. Thus, the development of sensitive and selective methods for the detection of 4-NP is of particular importance. Indeed, the US Environmental Protection Agency (EPA) has listed 4-NP as a priority pollutant and has specified a maximum permitted limit of 60 ng/mL 4-NP in drinking water. In particular, 4-nitrophenol (4-NP) is one of the most toxic substituted nitrophenols, being both carcinogenic and genotoxic to humans and wildlife even at very low concentrations. Nitrophenols are among the most abundant environmental contaminants due to their widespread use in the production of herbicides, pesticides, synthetic dyes, and pharmaceuticals. Furthermore, the simplicity, reliability, high selectivity, and high sensitivity of the developed sensor demonstrate that the combination of MIPs and ratiometric fluorescence allows the preparation of excellent fluorescent sensors for the detection of trace or ultra-trace analytes. The probe was then applied in the detection of 4-NP and exhibited good linearity between 0.051 and 13.7 μg/mL, in addition to a low detection limit of 0.026 μg/mL. The morphology, chemical structure, and optical properties of the resulting molecularly imprinted dual-emission fluorescent probe were characterized by transmission electron microscopy and spectroscopic analysis. The nanohybrids were further modified by anchoring a molecularly imprinted polymer (MIP) layer on the ratiometric fluorescent sensor through a facile sol–gel polymerization method. This sensor was synthesized by linking organosilane-functionalized CDs to silica-coated CdSe quantum dots 2) via Si–O bonds. This sensor was functioned by the transfer of fluorescence resonance energy between photoluminescent carbon dots (CDs) and 4-NP. Thus, we herein fabricated a novel molecularly imprinted core-shell nanohybrid as a ratiometric fluorescent sensor for the highly sensitive and selective detection of 4-NP. 127 ( 2005) 7480.4-Nitrophenol (4-NP) is a priority pollutant in water and is both carcinogenic and genotoxic to humans and wildlife even at very low concentrations. These results indicate that the water-soluble QDs coated by PP and PD oligomers have potential applications in cellular imaging and biosensor. In addition, they have tunable surface charges and show excellent colloidal stability over a relatively broad pH range ( 2 − 1 3 ), in high salt concentration, and even after thermal treatment at 100 ∘ C. The water-soluble QDs have relatively small hydrodynamic size (10 − 12 nm), and importantly, retain high fluorescence quantum yields (up to 45%) compared with that of the originally hydrophobic QDs (49%). The resulting water-soluble QDs have been characterized by ultraviolet-visible (UV-Vis), fluorescence, Fourier transform infrared (FTIR) spectroscopy as well as transmission electron microscopy (TEM) and dynamic light scattering (DLS) techniques. Meanwhile, the carboxyl groups (from PP) and mPEG segment (from PD) can render QDs water-soluble, and the free carboxylic groups can possibly be used for the further bioconjugation. The obtained oligomers with multi-thiol groups could bind strongly to the surface atoms of QDs. Pentaerythritol tetrakis 3-mercaptopropionate (PTMP) grafted poly(acryl acid) (PAA) ionic hydrophilic oligomer PAA-PTMP (PP) and dihydrolipoic acid (DHLA) grafted methoxypoly(ethylene glycol) (mPEG) nonionic hydrophilic oligomer mPEG-DHLA (PD) have been designed, synthesized and used as co-capping ligands in water-solubilization of hydrophobic quantum dots (QDs) via ligand exchange.
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