Nafion-stabilized black phosphorus nanosheets-maltosyl-β-cyclodextrin as a chiral sensor for tryptophan enantiomers

In this work, we have fabricated nafion (NF) stabilized black phosphorus nanosheets (BPNSs) and 6-O-α-maltosyl-β-cyclodextrin (G2-β-CD) composite (BPNSs-G2-β-CD) as novel electrochemical sensoring platform for chiral recognition of tryptophan (Trp) enantiomers. BPNSs-G2-β-CD composite modified glassy carbon electrode (BPNSs-G2-β-CD/GCE) was further coated with NF which served as a protective film to immobilize BPNSs-G2-β-CD on the electrode surface to achieve high stability. Under the optimum conditions, the oxidation peak current ratio of L-Trp to D-Trp (I_L/I_D) and the difference between the peak potential (ΔEp = E_D - E_L) were observed to be 1.49 and 20 mV at NF/BPNSs-G2-β-CD/GCE by square wave voltammetry (SWV). In addition, a linear calibration curve could be obtained for peak current versus Trp enantiomers in the concentration range 0.01-1.00 mM with detection limits of 1.07 μM and 1.71 μM for L-Trp and D-Trp (signal-to-noise ratio of 3, S/N = 3), respectively. The chiral recognition mechanism was also proposed, and the intermolecular hydrogen bonding interactions as well as the hydrophobic-cavity-triggered embedding effect dominated the effective chiral recognition. Moreover, the proposed NF/BPNSs-G2-β-CD/GCE showed excellent stability, good reproducibility and anti-interference capability. Therefore, the designed chiral sensor is expected to be practically applied for the sensitive recognition of Trp enantiomers in real samples.