High-Stability All-Solid-State Potentiometric Sensor Based On Single-Walled Carbon Nanotubes

Carbon nanotube is a one-dimensional nanomaterial discovered by Dr.Iijima in 1991,its structure is a seamless columnar morphology with a very high aspect ratio.The radial dimension is nanoscale,and the axial dimension is micron.The length and the diameter ratio reaches 102?107.Classified by the number of graphene layers in the photo layer,it can be divided into single-walled carbon nanotubes and multi-walled carbon nanotubes.Single-walled carbon nanotubes can be thought of as a single-layer sheet-shaped graphite sheet with a curved diameter,and the tube diameter is generally between 1 and 2 nm.Multi-walled carbon nanotubes can be understood as a set of single-walled carbon nanotubes with different diameters,the distance between layers is about 0.34 nmSingle-walled carbon nanotubes are a versatile additive with excellent electronic,mechanical,and mechanical properties.It can enhance the conductivity of the material,and the addition of a very small amount of single-walled carbon nanotubes can significantly improve the performance of the material.Because of its good electrical conductivity,this article takes the improvement of the stability,sensitivity,and response performance of all-solid-state potentiometric sensors as the starting point,and studies several high-stability all-solid-state potentiometric sensors based on single-wall carbon nanotube materials.1.All-solid-state polymer membrane calcium ion selective electrode based on single-wall carbon nanotube and conductive adhesionCurrently,nanomaterial-based all-solid-state ion-selective electrodes(ASS-ISEs)have become attractive tools for ion sensing in environmental and biological applications However,nanomaterial solid contact can easily fall off from the electrode surface owing to the poor adhesion.This poses serious limits to the wide use of these sensors.Herein,we report a general and facile method for robust fabrication of nanomaterial-based ASS-ISEs.It is based on the silver-based conductive adhesion(CA)with excellent electronic conductivity and strong adhesion ability as the binder to construct nanomaterial-based solid contact.The solid contact Ca2+-ISE based on singlewalled carbon nanotubes(SWCNTs)is chosen as a model.The proposed electrode based on CASWCNTs shows linear response in the concentration range of 10-6?10-3 M with a slope of 25.96±0.36 mV/decade and a detection limit of 1.7×10-7 M.In addition,the CA-SWCNT-based Ca2+-ISE exhibits an improved potential stability and reduced water film compared to the coated-wire ISE.Above all,experiments also show that the CA-SWCNT-based electrode exhibits the nearly same electrochemical characteristics with the classical only SWCNT-based electrode in term of resistance,capacitance and potential stability.We believe that CA-nanomaterial-based solid contacts provide an appealing substitute for traditional solid contacts based on nanomaterials2.All-solid-state plasticizer-free polymeric membrane ion-selectivel electrode for detection of inorganic ions based on single-wall carbon nanotube and conductive adhesion as solid contactTraditional ion-selective electrodes use PVC and plasticizer as the sensitive membrane substrate.When measuring the ion concentration using the electrode,the entrapment of a large amount of plasticizer and various other membrane components in the polymer leads to exudation and leaching;consequently,several problems arisesthe sensor lifetime is reduced and the exuded plasticizer is often toxic,causing short-term or long-term toxic response.In this paper,methyl methacrylate and 2-ethylhexyl acrylate(MMA-2-EHA)were used to polymerize a new polymer-sensitive film matrix to replace polyvinyl chloride(PVC)and plasticizer.Studies have shown that the polymerized new plasticizer-free polymer film can be used in ion selective electrodes instead of traditional polymer films.The new plasticizer-free polymer membrane electrode has a stable Nernst response,with a linear range of 1.0×10-6 to 1.0×10-3 M and a detection limit of 3.7×10-7 M.And the electrode has excellent resistance to the interference of CO2,O2 and light.In addition,no water layer is formed between the sensitive film and the solid contact conductive layer,and the new synthetic film shows high hydrophobicity.This research system provides a new type of sensitive membrane,which is a new method that can improve the traditional solid-contact ion-selective electrode sensitive membrane,laying a foundation for the further development of ion-selective electrodes3.All-solid-state plasticizer-free polymeric membrane ion-selectivel electrode for detection of neutral organic speciesPolymeric membrane potentiometric sensors based on molecularly imprinted polymers(MIPs)as the receptors have been successfully developed for detection of various organic and biological species.However,it should be noted that all of the polymeric membrane matrices of these sensors developed so far are the plasticized poly(vinyl chloride)(PVC)membranes.Such plasticized PVC membrane sensors are usually suffered from several problems such as plasticizer leaching,inflammatory response and weak membrane adhesion ability.These may pose serious limits to their wide applications,especially in the fabrication of the miniaturized sensors and in-vivo measurements.Hence,for the first time,we describe a novel plasticizer-free MIP-based potentiometric sensor.A new copolymer,methyl methacrylate and 2-ethylhexyl acrylate(MMA-2-EHA),is synthesized and used as the sensing membrane matrix.By using neutral bisphenol A(BPA)as a model,the proposed plasticizer-free MIP sensor shows an excellent sensitivity and a good selectivity with a detection limit of 32 nM.Additionally,the proposed MMA-2-EHA-based MIP membrane exhibits lower cytotoxicity,higher hydrophobicity and better MIP dispersion ability compared to the classical plasticized PVC-based MIP sensing membrane.We believed that the new copolymer membrane-based MIP sensor can provide an appealing substitute for the traditional PVC membrane sensor in the development of polymeric membrane-based electrochemical and optical MIP sensors.