[en] Highlights: • A competitive colorimetric aptasensor was developed for saxitoxin detection. • HCR products was used to facilitate the colorimetric transduction by AuNPs nanozyme. • Magnetic separation contributed to reduce the background signals. • The aptasensor provided high sensitivity towards saxitoxin determination. • The innovation can be referred for other small molecules and toxins. Saxitoxin (STX) is a small molecule toxin (Mw. ca. 299 g/mol) with high acute toxicity, and it has urgent need of facile analytical methods. Herein, a competitive colorimetric aptasensor was developed for highly sensitive detection of STX. An anti-STX aptamer was hybridized with a complementary strand on the magnetic beads and was competitively bound by STX. The supernatant containing the aptamer binding to STX was obtained by magnetic separation, which could trigger hybridization chain reaction (HCR) to generate rigid double stranded DNAs (dsDNAs) with sticky end and variable length. These HCR-dsDNAs were found to be able to facilitate significant enhancement on the peroxidase-like catalytic capability of AuNPs nanozyme towards 3,3,5,5-tetramethylbenzidine (TMB). The concentration of STX was responded in a “turn on” mode, based on the amplified colorimetric transduction thereof. The aptasensor realized high sensitivity, with a limit of detection (LOD) as low as 42.46 pM. Moreover, a wide linear detection range of 78.13–2500 pM, good selectivity, as well as good recovery rates of 106.2–113.5% when analyzing STX in real shellfish samples were obtained. This strategy could be referred to develop robust aptasensors for simple and highly sensitive detection of other small molecules and toxins.

[en] Thorium, as an important natural radioactive element, is receiving an ever-increasing interest as nuclear fuel alternatives to uranium in nuclear power industry. In view of the extensive application, the development of reliable methods for the monitoring, and the recovery of Th from environmental and geological samples are of particular significance. Herein, a novel sorbent of Th(Ⅳ), phosphonate-functionalized mesoporous silica (NP10), was synthesized, and the adsorption of Th(Ⅳ) from aqueous solution using NP10 was studied in batch processes under varying operation conditions of pH, temperature, adsorption time and Th(Ⅳ) concentration. The experimental results show that the adsorption of Th (Ⅳ) by NP10 is ultra-fast, and the sorption process reaches equilibrium after about 30 min. The adsorption process can be well described by the Langmuir equation and the maximum sorption capacity is estimated to 149 mg/g at temperature of (14±1)℃. When the adsorption temperature is up to 40℃, the maximum sorption capacity reaches 192 mg/g. It is also found that the adsorption percentage of Th(Ⅳ) by NP10 increases rapidly with pH from 0.9 to 4, whereas ionic strength shows no obvious effect on the adsorption. Moreover, the adsorption percentage of Th(Ⅳ) by NP10 increases with the mass of NP10 until almost complete adsorption (>97%). (authors)

[en] Highlights: • MWCNT/NiO-Fe₃O₄ heterotrimers are firstly successfully fabricated. • Significant interfacial polarization is generated. • Effective electromagnetic adsorption band covers a frequency range of 3.5–18 GHz. • Attenuating 75% electrical field and 50% magnetic field of 50 Hz power frequency is achieved. Severe electromagnetic (EM) interference pollution as the fourth pollution has posed an ever increasing threat to human health and environment. These dangers have created an urgent need for the development of EM absorbers to address this issue. Herein, nanosized NiO and Fe₃O₄ particles were decorated along multiwalled carbon nanotubes (MWCNT) to achieve high-performance attenuation of EM waves of 2–18 GHz and a power frequency of 50 Hz. The hybrid nanotubes were prepared by an electroless nickel plating-oxidization process to form MWCNT/NiO, then followed by a polyol approach to produce triple-component MWCNT/NiO-Fe₃O₄ hybrid nanotubes. The microstructure of the hybrid was characterized by transmission electron microscopy, X-ray diffraction and vector network analysis. It was found that the multi-component structure endows the MWCNT/NiO-Fe₃O₄ hybrid nanotubes with an effective EM absorption band (RL < −10 dB) covering a frequency range of 3.5–18 GHz. As well, the MWCNT/NiO-Fe₃O₄ hybrid nanotubes had the ability to attenuate 75% of the electrical field and 50% of the magnetic field of a 50 Hz power frequency.