A novel antimicrobial nanohybrid based on near-infrared (NIR) photothermal conversion is designed for bacteria capture, separation, and sterilization (killing). Positively charged magnetic reduced graphene oxide with modification by polyethylenimine (rGO–Fe₃O₄–PEI) is prepared and then loaded with core–shell–shell Au–Ag–Au nanorods to construct the nanohybrid rGO–Fe₃O₄–Au–Ag–Au. NIR laser irradiation melts the outer Au shell and exposes the inner Ag shell, which facilitates controlled release of the silver shell. The nanohybrids combine physical photothermal sterilization as a result of the outer Au shell with the antibacterial effect of the inner Ag shell. In addition, the nanohybrid exhibits high heat conductivity because of the rGO and rapid magnetic-separation capability that is attributable to Fe₃O₄. The nanohybrid provides a significant improvement of bactericidal efficiency with respect to bare Au–Ag–Au nanorods and facilitates the isolation of bacteria from sample matrixes. A concentration of 25 μg mL⁻¹ of nanohybrid causes 100 % capture and separation of Escherichia coli O157:H7 (1×10⁸ cfu mL⁻¹) from an aqueous medium in 10 min. In addition, it causes a 22 °C temperature rise for the surrounding solution under NIR irradiation (785 nm, 50 mW cm⁻²) for 10 min. With magnetic separation, 30 μg mL⁻¹ of nanohybrid results in a 100 % killing rate for E. coli O157:H7 cells. The facile bacteria separation and photothermal sterilization is potentially feasible for environmental and/or clinical treatment.

A novel adsorbent was developed by coating yttrium hydroxide precipitate layer on cellulose fibre. This material takes up ca. 98% of 5 µg·L⁻¹ As(III) and As(V) at low pH (pH<7), while a favorable selectivity for As(V) was achieved within pH 11–12. In practice, a mini-column packed with Y(OH)₃ precipitate layer coated cellulose fibre particles was incorporated into a sequential injection system for selective uptake of arsenate at pH 11.5. The retained arsenate was afterwards recovered with 50 µL of 0.8 mol·L⁻¹ NaOH solution as eluent, followed by hydride generation in a reaction medium of 2.0 mol·L⁻¹ HCl and 1.0% NaBH₄ solution (W/V, in 0.5% NaOH) after pre-reduction of arsenate to arsenite by KI-ascorbic acid (5%, W/V), with detection by atomic fluorescence spectrometry. Total inorganic arsenic was quantitatively taken up at pH 6.0 by following the same procedure and arsenic speciation was performed by difference. With a sample volume of 1.0 mL, an enrichment factor of 16.4 was derived with a detection limit of 17 ng·L⁻¹ within a linear range of 0.05–2.0 µg·L⁻¹. A relative standard deviation (RSD) of 2.6% (0.5 µg·L⁻¹, n=11) was achieved. The procedure was validated by analyzing arsenic in a certified reference material GBW 09101 (human hair), and speciation of inorganic arsenic in natural water samples. The entire process requires no organic solvents, thus Y(OH)₃ coated cellulose fibre provides a green adsorbent.