Dual-role boron and oxidized phosphorus in collectively constructing the signal-amplified bio-carbon electroanalysis platforms for simultaneous recognition of sulfite and nitrite in aquaculture

Abstract

Developing the signal-amplified yet low-cost electrochemical analysis platforms for determination of sulfite and nitrite in aquaculture water is still a challenging but significant task. Herein, an attractive boron and phosphorus co-modified bio-carbon (BP-bioC) sensitive material synthesized via ultrasonic impregnation with cotton stalk and boric acid/phosphorus acid and followed pyrolysis is reported for simultaneously discriminating sulfite and nitrite through differential-pulse-mode voltammetric signals. The physico-chemical characterizations and electrochemical characterizations suggest that under optimized mass ratio of H₃BO₃/H₃PO₄ (0.2), the resultant BP-0.2-bioC possesses the faster electron-transfer kinetics and lower impedance as compared to the pristine phosphorus-modified bio-carbon (P-bioC), which is profited from the critically metallic-role boron (C₃B). Also, the higher electrocatalytic activity is observed thanks to non-metallic role of boron (C₂BO/CBO₂) which promotes more electroactive oxidized phosphorus (C₃P=O) configurations by phosphorus-boron Frustrated Lewis Pairs, in turn generating the unique phosphorus-frustrated-boron active site pairs (C₃B-C₃P=O). More strikingly, the evolution of wettability in the presence of boron ensures the availability of electroactive site pairs during electrochemical sensing process. These combined advantages impart the electrochemical sensing platforms (BP-0.2-bioC/ESPs) the enhanced electroanalytical properties towards sulfite and nitrite with limit of detection (LOD) low to 34.71 μM and 2.10 μM, respectively, which enable to compare favorably with certain metal-based sensing platforms reported. DFT calculations conclude that the combined active pairs of C₃P=O and C₃B show the best electrocatalytic activity towards sulfite and nitrite, respectively. This contribution provides guidance for deliberately devising ultrasensitive bio-carbon based electroanalysis platforms concerned sulfite and nitrite in aquaculture waterbodies or related aquacultural products.