Magnetic field enabled spin-state reconfiguration for highly sensitive paper-based photoelectrochemical bioanalysis

Efficient carrier separation plays an utterly pivotal role in enhancing the sensitivity of photoelectrochemical (PEC) analysis. Here we report a concise yet powerful strategy of electron spin polarization induced by magnetic stimulation, to effectively modulate the efficiency of charge separation in a paper-based PEC (mu-PEC) sensing system. The electronic configuration of the sulfur-defected CdIn2S4/FeOOH photoactive matrix and ferromagnetic ZnFe2O4 signal label were regulated via the electron parallel alignment along with spin state flip and reconstruction at particular active sites under external magnetic field, significantly facilitating the separation of photoinduced carriers. As a proof-of-concept application, the magnetic-triggerable spin-state reconfiguration coupled with enzymatic catalytic precipitation reaction was developed for detection of chlorpyrifos with a wide linear range of 10-2.5-106 ng mL-1 and low detection limit of 0.67 pg mL-1. This work provides the basis for understanding the role of magnetic stimulus in tailoring charge separation and constructing a universal strategy for high performance mu-PEC bioanalysis.