This article reviews the development of electrochemical biosensors, incorporating magnetic particles, for detecting biomolecules (nucleic acids and proteins) and cells. Magnetic particles (MPs) of micro-and nanoscale, mimicking the size of molecules in nature, possess interesting characteristics that facilitate the purification and detection of biomolecules in a wide range of samples. In particular, the high surface area and the paramagnetic or superparamagnetic properties of these tiny particles provide an attractive technology platform for the design of electrochemical biosensors. Examples of electrochemistry-based approaches to achieve the separation and detection of bioentities utilizing MPs are described. Emphasis is placed on the strategies to incorporate the electrochemical labels to the MPs and the methods to achieve the dual function of electrochemical detection and magnetic separation. The protocols to make MPs as labels in biological sensors are also discussed.

Pure water production by solar distillation under no light concentration is attracting ever greater attention in the rural area with electricity limit due to its constant energy input. Meanwhile, the polluted raw water in these areas also lacks effective decontamination treatment. Rather than relying on external steps for decontamination process, photothermal materials with pollutant removal ability would have better water cleaning performance. Here, we designed a multifunctional photothermal material based on a copper mesh with abundant CuO nanowires. This CuO nanowire mesh exhibited a high solar absorption of 93% and superhydrophilicity for water transport, contributing to a high solar vapor efficiency of 84.4% under onesun illumination. Besides, the CuO nanowires possessed a great catalytic ability for the degradation of contaminants in raw water. Moreover, the diffusion inhibition test showed a clear antimicrobial effect of the CuO nanowire mesh on the bacteria. Hence, the as-prepared multifunctional CuO nanowire mesh allows for the incorporation of solar evaporation, pollutant degradation, and antibacterial action, which holds great application potential in the pure water production in solar distillation.

A novel, sensitive electrochemical DNA hybridization detection assay, using silver nanoparticles as the oligonucleotide labeling tag, is described. The assay relies on the hybridization of the target DNA with the silver nanoparticle-oligonucleotide DNA probe, followed by the release of the silver metal atoms anchored on the hybrids by oxidative metal dissolution and the indirect determination of the solubilized Ag(I) ions by anodic stripping voltammetry (ASV) at a carbon fiber ultramicroelectrode. The influence of the relevant experimental variables, including the surface coverage of the target oligonucleotide, the duration of the silver dissolution steps and the parameters of the electrochemical stripping measurement of the silver(I) ions, is examined and optimized. The combination of the remarkable sensitivity of the stripping metal analysis at the microelectrode with the large number of silver(I) ions released from each DNA hybrid allows detection at levels as low as 0.5 pmol L(-1) of the target oligonucleotides.

Solar distillation is emerging as a robust and energy-effective tool for water purification and freshwater production. However, many water sources contain harmful volatile organic compounds (VOCs), which can evaporate through the photothermal evaporators and be collected together with distilled water, or even be enriched in the distilled water. In view of the penetration of volatile organic compounds, herein, we rationally demonstrate a dual-scale porous, photothermal/ photocatalytic, flexible membrane for intercepting volatile organic compounds during solar distillation, which is based on a mesoporous oxygen-vacancy-rich TiO 2−x nanofibrous membrane (m-TiO 2−x NFM). The dual-scale porous structure was constructed by micrometer-sized interconnected tortuous pores formed by the accumulation of m-TiO 2−x nanofibers and nanometer-sized pores in the m-TiO 2−x individual nanofibers. Consequently, the membrane can sustainably in situ intercept VOCs by providing more photocatalytic reactive sites for collision (mainly by mesopores) and longer tortuous channels for prolonging VOC retention (mainly by micrometer-sized pores); thus, it results in less than 5% of phenol residual in distilled water. As a proof of concept, when the m-TiO 2−x NFM is employed to purify practical river water in an evaporation prototype under real solar irradiation, complex volatile natural organic contaminants can be effectively intercepted and the produced distilled water meets the drinking water standards of China. This development will promote the application prospects of solar distillation.