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Nanoplastics (NPLs), of which polystyrene (PS) plastics are typical representatives, are of global concern as emerging contaminants, especially the leakage of NPLs into drinking water, which is directly related to human health. To onsite visually assess the extent of NPLs contamination in drinking water in a rapid and non-destructive manner, this work extends the application of the highly sensitive response to pH of mercaptoundecanoic acid (MUA)-functionalized gold nanoparticles (Au NPs). Further, a visual sensing method based on the binding of alkyl chains to PS NPLs with hydrophobic force to suppress pH-induced aggregation of functionalized nanoparticles was constructed. Particularly, the designed analytical strategy is a significant renewal of the first strategy for the visual detection of PS NPLs, featuring non-destructive, fast response (∼30 s), high selectivity, and detection limit (26 μg/L). Importantly, it can reliably distinguish the more hazardous PS NPLs of smaller particle size (<100 nm). Moreover, visualization-based detection observes the color change of the reaction solution from dark purple to wine red. The employment of a smartphone installed App to read the color three-channel value R further ensures the credibility of the analysis results. The proposed visual analysis strategy will provide a promising new avenue for efficient detection of surface hydrophobic NPLs and further evaluation of their particle size or shape. • This is the novel method for visual detection of PS nanoplastics. • It is able to rapidly visualize the sieving of PS nanoplastics smaller than 100 nm. • It is expected to develop test kits for testing nanoplastics in drinking water. • Provides the basis for visual detection of nanoplastics in complex environments. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • FeOx overcome single crystal phases generally suffering from serious agglomeration and poor electrical conductivity. • The synergistic effect between the electrocatalytic property and the polycrystalline structure of FeOx was verified. • Hybrid FeOx with variable oxidation states remarkably facilitate the efficient redox charge transfer. Abstract Investigations on interplay between sensing platform performance and crystal phase of material are the new beginning of designing advanced bioanalytical systems. Herein, FeO x nanoparticles (NPs, ∼100 nm), including superfine magnetic (Fe 3 O 4) and hematite (α-Fe 2 O 3) nanocrystals in single particles, have been employed to verify the synergistic effect between the electrocatalytic property and the polycrystalline structure of the materials. Moreover, this strategy overcomes that single crystal phases generally suffer from serious agglomeration and poor electrical conductivity. More importantly, hybrid metal oxides (e.g., α-Fe 2 O 3 /Fe 3 O 4) with variable oxidation states remarkably facilitate the efficient redox charge transfer. Taking the detection of Flutamide (FLT) in prostate cancer cells (VCaP cells) as example, the dynamic ranges of the oxidation states from the different crystal phases were integrated into a single electrochemical sensor interface. Furthermore, good selectivity, accuracy, satisfactory sensitivity (769.1 μA mM−1 cm-2) and low detection limits (46.6 nM) were achieved. Going beyond the conventional single-crystal phase-driven electrochemical sensing, the elaborate of polycrystalline structure in a single particle may open a new approach for the design of outstanding electrode materials, which not only can significantly improve the performance of sensing platforms, but also can be used to rationally design the material properties according to the applications. [ABSTRACT FROM AUTHOR]

Copper nanoparticles modified nitrogen doped reduced graphene oxide 3-D superstructure was successively prepared via a two-step reaction. Polydopamine was used as nitrogen source for the fabrication of nitrogen doped reduced graphene oxide and reducing agent for in-situ reduction of CuCl 2 . After calcination under nitrogen protection, the conductivity, electron transfer ability and electrocatalytic activity of nanocomposites were substantially improved. The enhanced redox property could be attributed to the difference in the electronegativity of carbon and nitrogen atoms of the 3-D superstructure. By using this composite material, an electrochemical sensor was constructed for the detection of dihydroxybenzene isomers, which exhibited excellent sensitivity (with limit of detection at 81–131 nmol L −1 levels), wide linear ranges (0.5–720 μmol L −1 ) and good selectivity. Hence it was directly applied for the simultaneous determination of dihydroxybenzene isomers in contaminated samples (e.g., waste waters). [ABSTRACT FROM AUTHOR]

In suit and dynamic reaction monitoring platform for chiral cysteine. • A customizable optoelectronically functionally coupled microelectrode was designed. • A novel chiral sensor based on microelectrode breaks the traditional template for electrochemical analysis. • The first developed a platform for EC-SERS studies the electrochemical reaction mechanism of cysteine enantiomers. • The proposed method provides ultra-high sensitivity and low detection limits for the detection of D-Cys. A novel concept for the development of chiral sensor is proposed based on electrochemical phase transformation of silver nanoparticles (Ag NPs), which is shown for in situ photoelectric cooperative analysis mode. To demonstrate this, self-assembled Ag NPs on gold microelectrode (Ag-Au ME) serve as the sensing platform for chiral cysteine (D/L-Cys) detection. Through differences in the specific binding force, the system was validated with efficient synergistic electrochemical redox reactions and complexation of D/L-Cys with silver ions, and a novel sensing mode was developed based on the shift of oxidation peak potential of silver ions. In the proposed assay procedure, the simple principle of electrochemical phase transformation of Ag NPs, which can be monitored by electrochemical-surface enhanced Raman scattering (EC-SERS), was used as an in situ , rapid, dynamic analysis strategy for improving the detection sensitivity. Moreover, the proposed assay strategy with satisfactory sensitivity up to 74.88 μA μM−1 cm−2 was achieved, the limit of detection (LOD) is reduced to nanomolar level (8.7 nM) for D-Cys. Going beyond the conventional chiral biosensing, more importantly, the elaborate dynamic coupling of multiple mechanisms in a micro/nanoscale interface may provide a new approach for future highly sensitive biosensing. [ABSTRACT FROM AUTHOR]

A new, sensitive, and rapid spectrophotometric method for selective determination of nanomolar levels of dissolved organic phosphorus (DOP) and inorganic phosphorus (DIP) in seawater was proposed. The microsphere of Fe 3 O 4 @SiO 2 @TiO 2 (FST) was surface modified with lysine (FST-Lys) and used as solid phase adsorbent, photocatalyst, and sensor. After surface modification with lysine, the zeta potential vs pH curve for FST could be reversed and then 98.1% of DIP anions in the seawater could be specifically adsorbed by electric attraction onto FST-Lys (1.2 mg/mL) at the pH value of natural seawater (8.1–8.3) after only stirring for 30 min. The adsorbed DIP could be eluted with hydrochloric acid solution (pH 4.0) for electric repulsion. Therefore, acid hydrolysis of DOP could be inhibited and its influence on the determination of DIP could be avoided. DIP could be determined spectrophotometrically and selectively by phosphomolybdenum blue method. After UV irradiation, DOP was photodegraded by FST-Lys into DIP, the total concentration of dissolved phosphorus (i.e., DIP and DOP) could be determined, and then the concentration of DOP could be calculated. FST-Lys could be easily recycled by applying an external magnetic field while maintaining the adsorption and catalytic activity without significant decrease even after running 10 times. The proposed method with high sensitivity (detection limit of 1.42 nmol/L), wide linear range (3.0–1200 nmol/L), and selective determination was successfully applied for in situ measure of DIP and DOP in South China Sea and the Taiwan Channel. [ABSTRACT FROM AUTHOR]