Molecularly imprinted film based on chitosan-GQDs using citric acid as a crosslinker for creatinine adsorption and detection by FTIR-ATR

A molecularly imprinted polymer (MIP) film based on 3.5% w / v chitosan and graphene quantum dots (GQDs), crosslinked with citric acid (0.25% w / v ), was developed for the selective adsorption and detection of creatinine. Citric acid functioned both as a green crosslinker and as the GQD precursor, enabling an environmentally friendly fabrication route. The structural and morphological features of the MIP film were confirmed using AFM, SEM, FTIR-ATR, and UV–vis spectroscopy, while complete template removal was achieved through DI-water washing assisted by ultrasonication. Kinetic studies revealed rapid adsorption behavior, reaching equilibrium within 40–60 min, with a maximum adsorption capacity (Qₑ) of 12.5 mg g −1 . The MIP exhibited optimal binding at physiological conditions (pH 7, 37 °C), governed by synergistic electrostatic interactions, hydrogen bonding, and π–π interactions. Quantification based on the FTIR-ATR, ΔAbsorbance at 1375 cm −1 demonstrated high analytical sensitivity, achieving a limit of detection of 4.2 nM and a broad linear range from 0.1 nM to 10 μM (R 2 = 0.9873). The sensor showed strong selectivity against common interferents (urea, glucose, NHS), maintaining accurate responses even at 10-fold excess concentrations. Application to synthetic urine yielded a recovery of 90.3% using the standard addition method. • Eco-friendly MIP film was prepared using chitosan, GQDs, and citric acid. • The film shows high selectivity for creatinine over common biological compounds. • Nanomolar-level sensitivity was achieved with fast adsorption at neutral pH. • The film accurately detects creatinine in synthetic urine samples. • A promising biosensor for improving clinical creatinine detection methods.