Dual-Modulated Heterojunctions for Anti-Interference Sensing of Heavy Metals in Seawater

Abstract

Trace analyte detection in a complex environment such as in seawater is usually challenging for classic redox-based electrochemical sensors since the matrix effect of high salinity and various interfering species with similar redox properties can generate false positive/negative signals, thus impacting the sensitivity and specificity of the sensors. In this work, unlike redox-based approaches, we propose a novel sensing mode that relies on dual-modulated interfacial energy barriers of heterojunctions. By constructing the hierarchical structure of Ni/TiO2/porous-reduced graphene oxide/chitosan (CS), we introduce interfacial energy barriers of Schottky junctions into the electrochemical sensors for Cu2+. Most importantly, we found that two factors, light and the electrostatic interactions between the heterojunctions and Cu2+, can be coupled to regulate the height of the interfacial energy barrier and at last exponentially magnify the sensing signals in response to Cu2+. Since the electrostatic interaction is inert to redox, the proposed sensor is robust against most interfering species even in seawater. Illumination further enhances its sensitivity by 6.23 times and endows it a limit of detection of 0.22 nM. Such a dual-modulated sensing mode is also valid in other heterojunctions such as in the p–n junctions of Ni/NiO/MoS2/CS, demonstrating its potential in more universal applications.

Synergistic Signal Amplification-Initiated Innovative Self-Powered Photoelectrochemical Aptasensing: An Ingenious Photocathode Activated by the High-Light-Harvesting Photoanode

“…Among them, n-type photoactive materials could produce an evident photocurrent response for anodic PEC sensors, while the absorption of reductive molecules on the PEC sensing interface can cause an unreal signal response, leading to the poor specificity of such sensors in the detection of trace analytes in a complex environment. 3 Fortunately, for cathodic PEC analysis based on p-type semiconductors with holes as the main carriers, the flow of photoelectrons from the cathode interface to a species in solution endows its good anti-interference ability. 4 However, the low photoelectric conversion efficiency of the p-type semiconductor results in a relatively small PEC response, limiting the linear detection range and detection sensitivity of the cathodic PEC sensors.…”

“…Photoelectrochemical (PEC) analysis has attracted extensive attention due to its quick response, simple operation, high specificity, and sensitivity. , For designing PEC sensors with super sensitivity, photoactive material is the key, which can be generally divided into n-type and p-type ones according to their photoelectric properties. Among them, n-type photoactive materials could produce an evident photocurrent response for anodic PEC sensors, while the absorption of reductive molecules on the PEC sensing interface can cause an unreal signal response, leading to the poor specificity of such sensors in the detection of trace analytes in a complex environment . Fortunately, for cathodic PEC analysis based on p-type semiconductors with holes as the main carriers, the flow of photoelectrons from the cathode interface to a species in solution endows its good anti-interference ability .…”

Target-Controlled Redox Reaction and Ru(II) Release of a Smart Metal–Organic Framework Nanomaterial for Highly Sensitive Ratiometric Homogeneous Electroanalysis of Cadmium(II)

“…In recent years, the electrochemical technology has aroused intense attention in the detection of Cd 2+ , which is characterized by high sensitivity, fast response, and low cost. − As for the developed electrochemical sensing method for Cd 2+ , there are generally two common patterns. , One is the traditional nanomaterial-based anodic stripping voltammetry technology (ASV), which involves two steps: electrodeposition and reoxidation. ,− For instance, Sun et al prepared a graphdiyne/graphene nanohybrid-modified electrode to achieve the ASV detection of Cd 2+ upon the electrodeposition of 300 s at 1.2 V, which enables Cd 2+ to be reduced to Cd 0 ; similarly, Guo and his colleagues prepared a Co-TIC4R-I electrode to achieve sensitive ASV detection of Cd 2+ after 300 s electrodeposition at −1.0 V. The other pattern is the biosensors by using various biorecognition elements and introducing electroactive probes (e.g., ferrocene and thionine). , For instance, Yuan’s group assembled a Pd@Cu@Pt/DNA-ferrocene-modified electrode for the electrochemical detection of Hg 2+ ; herein, the ferrocene molecule was adopted as an electroactive probe. There is no doubt that these electrochemical methods can achieve sensitive detection for Cd 2+ ; however, suitable electrode modification processes and modifiers are generally inevitable for these methods, which are relatively complex and easily pose negative effects on the sensing activity of materials, disturbing the sensitivity, stability, and reproducibility of the sensing assay; in addition, modifiers may fall off from the electrode surface easily.…”