Helical Assembly of Flavin Mononucleotides on Carbon Nanotubes as Multimodal Near-IR Hg(II)-Selective Probes

Rapid Determination of Mercury Ions in Environmental Water Based on an N-Rich Covalent Organic Framework Potential Sensor

In this article, an N-rich covalent organic framework (COFTFPB-TZT) was successfully synthesized using 4,4′,4′-(1,3,5-triazine-2,4,6-triyl) trianiline (TZT), and 4-[3,5-bis (4-formyl-phenyl) phenyl] benzaldehyde (TFPB). The as-prepared COFTFPB-TZT possesses irregular cotton wool patches with a large specific surface area. A novel selective electrode based on COFTFPB-TZT was used for the determination of Mercury ions. The abundance of N atoms in COFTFPB-TZT provides more coordination sites for Hg2+ adsorption, resulting in a change in the surface membrane potential of the electrode to selectively recognize Hg2+. Under optimal experimental conditions, the ion-selective electrode shows a good potential response to Hg2+, with a linear range of 1.0 × 10−9∼1.0 × 10−4, a Nernst response slope of 30.32 ± 0.2 mV/-PC at 25°C and a detection limit of 4.5 pM. At the same time, the mercury-ion electrode shows a fast response time of 10 s and good reproducibility and stability. The selectivity coefficients for Fe2+, Zn2+, As3+, Cr6+, Cu2+, Cr3+, Al3+, Pb2+, NH4+, Ag+, Ba2+, Mg2+, Na+, and K+ are found to be small, indicating no interference in the detection system. The proposed method can be successfully applied to the determination of Hg2+ in 3 typical environmental water samples, with a recovery rate of 98.6–101.8%. In comparison with the spectrophotometric method utilizing dithizone, the proposed method is simple and fast and holds great potential application prospects in environmental water quality monitoring and other fields.

Recent Advances in Structure Separation of Single-Wall Carbon Nanotubes and Their Application in Optics, Electronics, and Optoelectronics

Structural control of single-wall carbon nanotubes (SWCNTs) with uniform properties is critical not only for their property modulation and functional design but also for applications in electronics, optics, and optoelectronics. To achieve this goal, various separation techniques have been developed in the past 20 years through which separation of high-purity semiconducting/metallic SWCNTs, single-chirality species, and even their enantiomers have been achieved. This progress has promoted the property modulation of SWCNTs and the development of SWCNT-based optoelectronic devices. Here, the recent advances in the structure separation of SWCNTs are reviewed, from metallic/semiconducting SWCNTs, to single-chirality species, and to enantiomers by several typical separation techniques and the application of the corresponding sorted SWCNTs. Based on the separation procedure, efficiency, and scalability, as well as, the separable SWCNT species, purity, and quantity, the advantages and disadvantages of various separation techniques are compared. Combined with the requirements of SWCNT application, the challenges, prospects, and development direction of structure separation are further discussed.

Carbon nanotube sorting due to commensurate molecular wrapping

Single-walled carbon nanotubes (SWCNTs) can be sorted by their structural parameters using organic molecules and polymers: some of which, demonstrating a profound affinity only for specific nanotubes, form dense coatings on them. Here, analyzing well-known examples of flavin group molecules and those of 2,4-dichlorophenoxyacetic acid, we show for the first time that successful formation of the considered coatings depends on the ability of molecules to wrap around the SWCNT in a commensurate way. Commensurability provides a decrease in the free energy of the resulting bilayer system and makes the coating much more stable. Concurrently, it strongly relates the nanotube chiral vector with the geometric characteristics of the adhering molecules, which leads to revealed selection rules. If they are not satisfied, the deposition of molecules does not occur or is insignificant. The proposed theory unambiguously explains known experimental results on the formation of spiral wrappings of SWCNTs by flavin group molecules and points out other organic molecules and polymers suitable for effective CNT sorting.

Advanced biomedical applications of carbon nanotube

With advances in nanotechnology, the applications of nanomaterial are developing widely and greatly. The characteristic properties of carbon nanotubes (CNTs) make them the most selective candidate for various multi-functional applications. The greater surface area of the CNTs in addition to the capability to manipulate the surfaces and dimensions has provided greater potential for this nanomaterial. The CNTs possess greater potential for applications in biomedicine due to their vital electrical, chemical, thermal, and mechanical properties. The unique properties of CNT are exploited for numerous applications in the biomedical field. They are useful in both therapeutic and diagnostic applications. They form novel carrier systems which are also capable of site-specific delivery of therapeutic agents. In addition, CNTs are of potential application in biosensing. Many recently reported advanced systems of CNT could be exploited for their immense potential in biomedicine in the future.